Modeling Of The Nonlinear Physical Processes 3rmebrk.kz/journals/3714/32157.pdf · 2017. 9. 29. ·...

Modeling Of The Nonlinear Physical Processes 3

4 ISSN 1811-1165. Eurasian Physical Technical Journal, 2012, Vol.9, No.2(18)


UDC 517.957, 622.833.5

SIMULATION OF ROOF CAVING IN WHILE CONDUCTING EXCAVATION

MINING WORK

P.V. Makarov, E.P. Evtushenko, N.A. Bektemirov

Institute of Strength Physics and Materials Science of Siberian Branch Russian Academy of Sciences (ISPMS SB RAS)

2/4, pr. Akademicheskii, Tomsk, 634021, Russia, Phone: +7 (3822) 286875, e-mail: [email protected]

Peculiarities of geo-environment evolution as a nonlinear dynamic system with the self-organized

limiting feature are discussed. Calculations of the initial and subsequent roof cavings for different advancing

rates were fulfilled. Special attention was given to the study of unsteady nonequilibrium deformation process

in the roof at high face advancing rate. It is shown that other features of such systems are the existence of

calm zones in the area of looming crisis and peculiarities of slow dynamics of deformed systems can be sure

portents of the fact that the process of destruction epicenter formation is moving to become a superfast

catastrophic evolution stage.

Keywords: simulation, roof caving, rate, destruction, distribution.

Traditional criteria approach of phenomenological macroscopic mechanics is not capable in

principle to solve the problem of destruction prognosis, as it is based on macroscopic scale of

averaged description, while all solid objects and types of geo-medium are multi-scale systems. The

Evolution concept of destruction foundation [1] is an idea of hierarchical and multi-scale nature of

deformation process – basic ideas of Physical Mesomechanics and Nonlinear Dynamics [1-4].

Nonlinear Dynamics sheds a new light onto a problem of prognosis too, even when it "deprived us

of an illusion of a global predictability: we cannot forecast, starting from some horizon of

prognosis, the behavior of simple enough systems" [3]. Thus not so simple a question arises: what is

the horizon of prognosis for the process of destruction of a medium with a given rheology? Or in

other words: starting from which stage or scale can we answer the question, where and when will

the slow quasi-stationary phase of the heart of destruction formation come up to escalation at the

studied macroscopic scale?

We see a significant progress in the area of catastrophic events prediction, which includes the

problem of destruction. This progress is connected to a new concept of self-organized criticality of

nonlinear dynamic systems [5, 6], which contradicts seriously with traditional thinking, based on

which rare catastrophic phenomena were deemed accidental independent events, where the future is

not practically impacted by the past. Such approach leads to Gaussian statistics - normal Gaussian

distribution of probability for an independent accidental event.

The statistics of natural disasters – earthquakes, hurricanes, floods, technogenic catastrophes:

the destruction of different constructions, industrial explosions, as well as many other disasters -

crash at the stock-markets, information leaks, etc., as a rule, is subject to power law probability

distribution [3, 7].

Power law distribution is a fundamental property of evolution of the majority of multi-scale

hierarchical nonlinear systems, and in the event of loaded media it reflects their following most

important qualities: 1) formation of long space and time correlations in the evolving system, that

scope all hierarchy of scale; 2) self-similarity of destruction processes, stipulated by self-similar

character of accumulating the defects and damages in all hierarchy of scale; 3) migration of

deforming activity in a formed area of space and time correlation.

The other most important side of such nonlinear systems is the existence of slow dynamics

within, that is a dynamic correlated process, significantly slower than fast information exchange in a

dynamic system. In deforming solid objects and media the processes of locating deformation and

damage, forming of the deformation fronts of different scale, epicenters and different waves of

mailto:[email protected]


damage constitute the slow dynamics of nonlinear system in the process of deformation. And

information in these systems is transmitted via tension (voltage) waves distributed with the speed of

sound that exceeds the typical speed of slow dynamic processes by a lot [8].

Systems with such properties are called the systems with self-organized criticality [5, 6]. In

such systems any event, because long cause and effect relations appear, – will inevitably call the

next event, etc., provoking the avalanche of events, touching upon all hierarchy of scale, i.e. all

system as a whole. In other words, the fundamental property of the systems with self-organized

criticality is the fact that they evolve (speed) to critical condition by themselves [3]. Consequently,

the main danger of "power" catastrophes is not only in the fact that its probability is much higher,

than in Gaussian system, and it cannot be disregarded, but in the fact that the catastrophe in the

system with self-organized criticality is inevitable. Indeed, if the process of destruction is correlated

statistically in all hierarchy of scale up to the macroscopic scale of a sample, then it will inevitably

reach that macroscopic scale. This process is governed by nonlinear character of properties of a

dynamic system as a whole, which follows from nonlinear character of evolution of tense and

deforming condition (nonlinear equation of deformed solid objects' mechanics), nonlinear character

of rheology (nonlinear state of definitive equations, including kinetic equations of aggregating non-

elastic deformations and damages in a different scale and a nonlinear state of media durability

properties' degradation), nonlinear quality of positive and negative feedback. Consequently, in

critically self-organized systems one cannot single out statistically independent mesoscopic scales.

At this moment it is considered proven that deformed solid objects are truly dynamic nonlinear

systems showing properties of self-organized criticality. For geo-media, the widely known

Gutenberg-Richter and Omori laws reflect the relevant statistics of seismic events. Analysis of

destruction processes of laboratory samples [9], as well as of constructions [10] by the acoustic

emission method leads to the same universal dependence - Gutenberg-Richter and Omori laws.

A predictive model, - capable of describing the mechanism of forming the epicenter of the

future destruction, and, importantly, of predicting when and under what conditions the slow quasi-

stationary phase of evolution will turn into the superfast catastrophic regime, - can be only the

model that accounts for all most important properties of the loaded nonlinear media's evolution

process, including the characteristic properties of self-organized criticality. In ISPMS SB RAS the

evolutionary approach to modeling of solid objects and media's destruction is being developed [1,

2]. This approach describes the processes of self-organizing in the loaded geo-medium, locating

non-elastic deformations and damages in it, forming of block hierarchy; allows to model the slow

stages of evolution at any time, including geological, as well as the superfast catastrophic regimes

of evolution, - so-called acute regimes.

The proposed evolutionary concept of describing the deformation feedback to the loading of

solid objects is based on the ideas of nonlinear dynamics and dynamic equations of solid objects'

deforming mechanics. Such approach describes the destruction of solid objects and media (elastic

and brittle) as common mutual growth process of non-elastic (plastic) deformation, related damage,

degradation of medium durability, and, finally, macroscopic destruction, which happen upon a

catastrophic decline of local durability to zero. Therefore, numerical solutions demonstrate the

fundamental property of all evolutionary processes - the existence of two stages: 1) quasi-stationary

stage of relatively slow accumulation of changes in a nonlinear system; 2) catastrophic superfast

stage of evolution, when the events develop in an acute regime.

Based on the discussed model [1, 2] the calculations of a loaded and deformed condition of a

massif evolution over the mine in the field of gravity forces were carried out. The model takes into

account the internal friction, dilatancy, and accumulation of damages and degradation of geo-

medium's durability characteristics. The developed method of calculations allows solving practical

problems of mining stability under the timing factor more accurately and correctly. The developed

models of a damaged massif allow modeling the processes of damage accumulating and developing

of cracks of different sizes, as well as catastrophic collapse of rock.


Attention of this work is focused on the research of the three following important problems:

specifics and mechanism of forming the destruction centers in brittle and quasi-brittle media, study

of the destruction transition process from a slow quasi-stationary phase to a superfast catastrophic

regime, evaluation of risks, and a prospect of prognosis of possible catastrophic destruction of

massif elements with mining. Numerical solution is carried out in two-dimensional dynamic stage

for the condition of plain strain.

Equations system, solution method and detailed formulation of the problem were published

earlier [11]. The proposed approach allows describing the stages of slow preparatory phase of stress

strain state evolution, forming of destruction stages and superfast acute regime. Relevant times and

scale of these evolution stages are determined by nonlinear qualities of geo-medium on the relevant

scale. Thus in high speed of mining we have lengthy sections of hanging roof, so a nonequilibrium

destruction regime takes place. It is also shown that depending on the competition of negative

feedback, stabilizing the deformation process and evening out of inhomogeneous pieces in

parameter distribution, and positive feedback, caused by the degradation of loaded medium, the

scenario of medium evolution can change from a typical viscoplastic course to a brittle behavior.

Fig. 1 shows the results of the calculation of roof rock deformation at the moment when the

excavation reached 50 meters in length (calculation and excavation can continue). Different values

of damage accumulation parameters were chosen, which allowed the possibility to describe the

behavior of the geo-medium either as viscid (Fig. 1.a), or as brittle (Fig. 1.b), depending on the

medium property, as well as the specifics of loading.

a) b)

Fig. 1. The character of damage development in a massif over excavation (black horizontal line).

Grey shading shows average tension, thin lines - lines of nonelastic skidding (a), main cracks (b).

16 20 24 28

0,000000

0,000002

0,000004

0,000006

0,000008

0,000010

0,000012

ddt

t, дни

16 20 24 28

0,000000

0,000005

0,000010

0,000015

0,000020

t, дни

ddt

a) b)

Fig.2. The graph of nonelastic deformation speed in the roof monitoring.


The built graphs of monitoring the speed of nonelastic deformation (damage) in the chosen

points of the roof are shown in Fig. 2. One can see that in a case of a viscid feedback of a medium

(Fig. 2.a) nonelastic course in the roof is developing in waves, at the rate as excavation continues,

and creates even bigger tension and deformation in the caving roof. Roof caving in brittle geo-

medium (Fig. 2.b) is developing as a sequence of periodic catastrophes (extension of a main crack),

at the rate of continuing excavation; the period here is related to the character of excavation

movement and geo-medium properties, in part to the speed of accumulating damages in it.

Therefore, the obligatory stage of a geo-medium evolution is reflected in the model: the catastrophe

at the relevant scale. Physically, this regime means the burst of destruction from a minor scale to a

larger one, the increase of the destruction scale is always developing in the acute regime.

Fig. 3 shows the nature of growth of damage function D (0D1) for a main crack in the roof

over an excavated space (medium viscid-brittle). One can see that on Day 28 the slow quasi-

stationary phase of damage evolution D is replaced by a catastrophic regime (Fig. 3a).

Consequently, the yield strength degradation speed is also transformed into an acute regime (yield

strength Y=Y0(1–D), where D1,Y0) and, as a result, the roof collapse happens.

Fig. 3. The character of damage function growth in the roof.

The fundamental property of evolution is the existence of calm zones before a catastrophe.

This phenomenon is demonstrated in Fig. 3b. In numeric calculation of a problem of roof

collapsing, the damage accumulation speed monitoring in the nearest zone of a future catastrophic

event was executed. The processes of damage accumulation for accompanying cracks forming in

this area stopped still (curves 2, 3, 4 on Fig. 3b), and the accumulation of damage in the future main

break has peaked sharply (curve 1 on Fig. 3b).

Therefore, any macroscopic destruction is an obligatory catastrophic stage of a geo-medium

evolution - an acute regime at the relevant scale. Physically this regime means the plunge of

destruction from a minor scale to a larger one. Consequently, the increase of destruction scale is

always developing as a catastrophe in the acute regime, and all the processes of damage

accumulation and medium degradation in the area of preparation to a multi-scale event are stopping

still.

The developed method of calculations allows describing the first and subsequent roof cavings

for modern conditions of increasing pace of excavation movement and a non-equilibrium condition

of the rock in the bared roof.

4 8 12 16 20 24 28 t, дни

D

0

0.5

1

a


a)

b)

c)

d) e)

f)

Fig. 4. The modeling of a first (a,b,c) and secondary (d,e,f) roof collapses for different speeds of excavation

pace: 2m/24hrs (a,d), 4m/24hrs (b,e), 8m/24hrs (c,f). The accumulated damage of a geo-medium in conditional values

from 0 to 1 is reflected.

Fig.4 shows the results of roof caving modeling for different speeds of extending the

excavation shaft. For primary caving in the border conditions the model approximation for the roof

was used in the form of a beam created in the process of excavation, for the secondary one -

consoles (cantilevers). For slow speed of excavation, a larger damage accumulation in the roof geo-

medium is typical, and therefore, more viscid (lengthier in time) character of roof caving. This work

was supported by grant RFBR № 12-05-00503-а.

REFERENCES

1. Mathematical theory of evolution of loaded solids and media // Phys. Mesomech. – 2008. – V. 11, No. 5-6. -

213 p.

2. Makarov P.V. Evolutionary nature of structure formation in lithospheric material: universal principle for fractality of solids // Russian Geology and Geophysics. – 2007. V. 48, No. 7. - 558 p.

3. Akhromeeva T.S., Kurdyumov S.P., Malinetskiy G.G., Samarskiy A.A. Structures and Chaos in Nonlinear Media. – 2007. Fizmatlit, Moscow (in Russian).

4. Malinetskiy G.G., Potapov A.B. Modern Problems of Nonlinear Dynamics. - URSS, Moscow. - 2002 (in Russian).

5. Ananthakrishna G., Naronha S.J., Fressengeas C. and Kubin L.P. Crossover from chaotic to self-organized critical dynamic in jerky flow of single crystals // Phys. Rev. E. – 1999. – V. 60, No. 3. – P. 5455-5462.

6. Bramwell S., Holdsworth P., Pinton J.-F. Universality of rare fluctuations in turbulence and critical phenomena // Nature. – 1998. – V. 396. – P. 552-554.


7. Pisarenko V.F., Rodkin M.V. Heavy-tailed distributions: application to the analysis of accidents // Vichislitelnaja seismologija. – 2007. - V. 38. (in Russian).

8. Goldin S.V., Yushin V.I., Ruzich V.V., Smekalkin O.P. Slow motion - a myth or reality // Fizicheskie osnovy prognozirovanija razrushenija gornyh porod.- Krasnoyarsk. - 2002. (in Russian).

9. Panteleev I.A., Froustey C., Naimark O.B. Structural-scaling transitions and universality of statistics of fluctuations in metal plastic flow // Vychislitel'naja mehanika sploshnyh sred. – 2009. – V. 2. – № 3. (in Russian).

10. Prediction of cracking evolution in full scale structures by the b-value analysis and Yule statistics // Phys. Mesomech. – 2008. - V. 11, No. 5-6. – 260p.

11. Makarov P.V., Smolin I.Yu., Evtushenko E.P., Trubitsyn A.A., Trubitsyna N.V., Voroshilov S.P. Evolution scenarios of the rock mass over the opening // Fiz. Mezomekh. 2009. – V. 12, No. 1. - 65 p. (in Russian).

Article accepted for publication 07.08.2012

Heat Physics, Hydrodynamics, Energetic 9

UDC 53.097

THE INFLUENCE OF UNDERWATER SPARK DISCHARGE ON THE STRUCTURE OF

SHUBARKUL COAL

K.Kussaiynov, M.S.Duisenbayeva, G.K.Alpysova, E.T.Tanashev, A.Tolynbekov

Karaganda State University named after E.A. Buketov, 100026, Kazakhstan, Karaganda, Universitetskaya Str.28

Nowadays petroleum is the main source of organic raw materials. Its limited world reserves and

permanent increase in the cost of production due to involvement in exploitation more hard-to-reach fields

stimulates the development of new technologies for chemical processing of alternative organic raw

materials. Coal, world reserves of which are substantially larger than those of oil and gas, is considered in

the future as one of the basic raw materials for the production of motor fuels and organic synthesis products.

In this paper we propose to process Shubarkul coal using electric hydro-pulse technology. Application of

electric hydraulic technique brings substantial economic benefits and contributes to significantly reduce

harmful emissions into the environment or recycle harmful waste products. Study of influence of electric

hydraulic effects on heterogeneous media due to rising costs for energy and mineral resources, the

deterioration of the environmental situation is currently necessary and urgent.

Keywords: electric hydro-pulse plant, electric-hydraulic effect, shubarkul coal, coal-water fuel, electric discharge.

Kazakhstan has huge deposits of brown and hard coal of various metamorphism stages, which

are widely used mainly for production of coke used in the steel industry, and for energy purposes.

But these reserves of coal are not effectively used at present. So for the scientists, the age of

technological progress poses the problem of development of optimal processing technology and use

of coal. One of the efficient techniques of coal utilization is the process of obtaining motor and

boiler liquid fuels, energy and process gases, semi-synthetic resins, soil conditioners etc., from coal

[1]

Coal-water fuel (CWF) is a mixture (slurry) of finely ground coal and water. In some cases, the

suspension may include various additives (surfactants, stabilizers, etc.) that change the stability,

viscosity and other properties of the CWF. CWF can be used as a substitute for fuel oil, gas and

coal. The main advantages of CWF are reduction in fuel costs compared to those of fuel oil and gas,

as well as lower harmful emissions, particularly NOx and the technological ease-of-use of coal in a

liquid form. We propose a coal processing technology by using the electric hydro-pulse technique.

It is possible to grind coal to a certain fraction by means of an electric discharge in a fluid. [2.3]

The essence of this method is that inside a volume of liquid held in an open or closed vessel, a

specially formed electric pulse discharge of a certain form (spark, brush, etc.) is implemented.

Around the field of its formation there is super-high hydraulic pressure capable to perform useful

mechanical work and accompanied by a set of physical and chemical phenomena [4].

In the Laboratory of physics of pulse phenomena in heterogeneous media of the Chair of

engineering thermal physics named after Prof. Zh.S. Akylbaev at E.A. Buketov Karaganda State

University an electro-hydraulic plant for coal processing was installed.

The electric hydro-pulse plant is designed in the form of structural aggregates consisting of a

pulse voltage generator, a triggered spark gap, a cell, an ignition block, a voltage divider, a current

shunt and a control panel.

The scheme of the electric hydro-pulse plant and its separate units are shown in Figure 1.

The experimental stand works as follows. After switching on the control panel a control

voltage is applied and the generator produces high-voltage pulses of specified energy which are

transferred to the electrode system of the working cell area with the object of study through the

triggered spark gap and high-voltage power lines. [5]


Fig.1. Block diagram of the electric hydro-pulse plant.

The working cell of the electro-hydraulic plant for coal processing was also installed in the

Laboratory of physics of pulse phenomena in heterogeneous media.

There are two measuring electrodes inside the cell, one of them is fixed and the other is

attached to the micrometer screw to adjust the distance between the electrodes. Figure 2 shows a

general view of the cell designed for grinding coal. [6]

Fig.2. The working cell designed for grinding: 1- working cell cover, 2 - electrode of positive polarity,

3 – metal rod of negative polarity.

In the experiments the optimal parameters of coal grinding at different electrical parameters of

electric hydro-pulse plant were determined.

2

1

3

ELECTRO-HYDRAULIC PLANT

PULSE VOLTAGE

GENERATOR

TRIGGERED

SPARK GAP

CELL WITH THE

OBJECT OF STUDY

IGNITION UNIT

VOLTAGE DIVIDER

CURRENT SHUNT

CONTROL UNIT AND TEST INSTRUMENTS

CONTROL PANEL DELAYED-PULSE

GENERATOR


In Figure 3 (a, b, c) dependency graphs of the degree of grinding on the inter-electrode distance

for different capacitance of the capacitors are shown. Coal processing time t = 3 minutes, the coal

fraction of diameter d = 8 mm, distance of the triggered spark gap ld = 7 mm.

In Figure 3 (a) for the size of coal fraction d = 8 mm the distance between electrodes varied ld

= 7, 8, 9, 10 mm. The graph shows that at the inter-electrode distance ld = 7 mm and the capacitance

of the capacitor C = 0.25 μF the number of fractions of the diameter df


1

3

5

7

7 8 9 10

c)

Fig.3. Dependency graphs of the degree of grinding on the inter-electrode

distance for the capacitance of capacitors C = 0.25 (a), 0.5 (b), 0.75 (c) μF.

In Figure 3 (b) at the inter-electrode distance ld = 7 mm and the capacitance of the capacitor C

= 0.5 µF the number of fractions of the diameter df


UDC 536.33

NONDESTRUCTIVE TESTING FOR DIAGNOSTICS OF PIPELINES

B.R. Nussupbekov, D. Zh. Karabekova, S.S. Zhargakova, A.Zh. Beisenbek,

Karaganda State University named after E.A.Buketov, 100026, Kazakhstan, Karaganda, Universitetskaya Str.28, [email protected]

Thermal methods of nondestructive testing are widely used for the analysis of the thermal

insulation of underground pipelines. In heat methadone nondestructive testing, the thermal

energy is distributed in the test object. Temperature field of the object's surface is a source of

information on the characteristics of heat transfer. This article describes the modifications we

have developed some of the heat flux sensors. A common element of these devices is the battery

thermoelectric sensor special design, acting as a thermoelectric converter heat flow.

Keywords: heat flux, heat flux sensors, thermal radiation detectors, heat sensor metric.

Thermal methods of nondestructive testing are widely used for different kinds of protective

coatings for the analysis of the thermal insulation of underground pipelines, in oil and gas industry,

house-building, etc.

Violation of thermal insulation leads to a change of temperature on the surface of the coating.

Conclusion about the state of thermal insulation can be made on the basis of data of the surface

temperature of insulation and temperature field inside the studied object [1].

One of the main structural units of the automatic system for the experimental investigation of

thermal processes is a unit for the measurement of thermal processes [2]. Requirements for complex

sensors, built the block, are defined by the basic parameters of the processes investigation. The

basis of the unit contents specially designed heat flux sensors, heat detectors, which allow

measurements of local and average parameters of thermal processes under stationary and non-

stationary conditions.

Among the various applications of the heat flux sensors the control of the state of thermal

insulation of pipes with coolants has a special place. Such control can be done by measurement of

heat losses with primary thermoelectric converter heat flow, heat detector and electronic unit for

conversion of signal. The main lack of these devices is the dependence of their data from accidental

changes of the environment.

To solve the problems, we have developed several versions of the heat flux sensors, whose

indications are independent from changes in the environment [2, 3]. A common element of these

devices is the special designed battery of thermoelectric sensors, acting as a thermoelectric

converter heat flow. Thermoelectric sensor is designed as a finite cylinder, whose one base is the

work surface, and the second one has the thermal contact with the body of environmental

temperature. Built-in heaters can create heat flow through a thermoelectric sensor in the direction

perpendicular to its bases [3].

In one of the versions of the thermal flow sensor "active" junctions of thermoelectric converter

are in thermal contact with the receiving plate, and "passive" junctions contact with a heating

element, the temperature of which is controlled by temperature-dependent element. This design

allows you to combine the function of two heat-flow units in one. During the preparation of the

device the receiving plate is put in thermal contact with the test object in the place with absence of

defects in thermal insulation. Electrical current is passed through the heating element and its value

must be such that the signal at the output of the thermoelectric converter would be constant. This

means that the heating element generate a reference heat flaw through a thermoelectric converter

that is equal in magnitude and opposite in direction to heat flow from the test object in the field of

thermal insulation defects. In the investigation of possible defects in insulation the current through

the heating element is not regulated. This leads to a change in the signal at the output of the


thermoelectric converter of the heat flow. The magnitude of the changing allows appreciate the

degree of thermal insulation defects.

In another variation of the heat flux sensor the heating element is replaced with thermoelectric

refrigerator, "cold" junctions are embedded in the radiator, and "hot" one is in thermal contact with

the thermoelectric converter of a heat flow. Through the thermoelectric refrigerator the electric

current is passed with a value which gives the zero as the output signal of the thermoelectric

converter if the receiving plate is in contact with the investigated object in the absence of defects in

the thermal insulation. Thus, the heat flux that produced by the thermoelectric cooler in the

direction of a thermoelectric converter is reference one. With these data the heat fluxes in areas

where in thermal insulation defects have places are compared.

In the third modification of the heat flux sensor the heating element serves as a receiving plate

simultaneously. This modification implies the calibration method of substitution of the heat flow

from the investigated object by one from a heating element under passing an electric current trough

it.

The proposed devices can operate as with a single channel scheme so with a dual channel one.

Detecting anomalously high values of energy losses indicate the section of a pipeline with fully or

partially damaged thermal insulation or mechanical damage of the pipe material.

The aim of the investigation is to study the heat sensor operating for diagnostics of pipelines.

The main element of this heat sensor is the laminated sensitive element of battery type (Figure 1).

Heat flow through the protective film 1 goes to the sensor 2. The hot junctions of the thermal

batteries have thermal contact with a protective film and the cold junctions with thermal stabilizer 3.

In this case, the role of thermal stabilizer performs massive body transferred the heat flow through

the bottom of the housing 4 to the radiator 5. To eliminate the heat transfer from the flank surface

the sensor element is surrounded by a heat insulator 6. The entire system is closed with a conical

lateral surface 7.

Fig. 1. Schema of the heat sensor: 1 – protective film, 2 – sensor, 3 - thermal stabilizer, 4 - bottom of the body,

5 – radiator, 6 - heat insulator, 7 – flank surface, 8 - gauge coils.

As a model of a sensor element, let‟s consider homogeneous limited cylinder.

Let the function q (r, t) describes the dependence of the heat flux, directed on a base of the

cylinder, from the radius r and time t. The function ),,( tzrqv describes the dependence of the

power of internal sources (W/m2) from the radius r, the height z and time t. The heat exchange has

place between all the surface of the cylinder and the environment variable temperature Tc(r,z,t) due

to the Newton's law [4].


Fig.2. Schema of a sensor element.

The heat equation and boundary conditions in this case for a cylinder with radius R and height

1 will be next:

),,(),,(),,(1),,(1 2 tzrq

z

tzrT

T

tzrT

rrT

tzrT

a

v

(1)

zrflzrT ,,, (2)

tzRTtzRT

z

tzRTcR ,,),,(

,,

(3)

tlrTtlrTz

tlrTcl ,,,,

,,

(4)

torTtorTz

torTc ,,,,

,,0

(5)

where T*c(r,o,t) - the equivalent temperature of the environment:

0

,,,,,

trqtorTtorT cc

(6)

10,, R are the coefficients of heat transfer from the environment to the lateral surface of the

cylinder with the z = 0 and z = 1, respectively.

To solve the boundary problem (1) - (5) we will use the method of finite integral Hankel

transformations with respect to r:

rtzrTR

rrJtzT n

R

l

Ln

,,,, , (7)

where

R

rJ nl is the Bessel function of a zero order, μn are roots of the equation:


R

l

Bi

d

J

J

)(

)(

1

(8)

in which /RBi RR .

Then let‟s apply the finite neutral transformation of the general form o to the variable z:

dzzbKtzTtbu knkn ,,,,1

0

, (9)

where K (bk, z) is the core of the transformation. Let‟s put

zl

b

b

Biz

l

bzbK k

k

lkk sincos, , (10)

where Bil=α11/λ.

It is easy to show that the coefficients must satisfy the next equation:

0

0

2

BiBib

BiBibctgb

Lk

LkR

, (11)

where Bi0=α01/λ.

Inversion formulas for finite integral transformations (7) and (9) are, respectively:

1

1

0

2 ),(

,,),,(

kk

kknn

dzzbK

zbKtbutzT

, (12)

)(

,,2

),,(222

12

nlnR

nln

n

nJBi

R

rJ

tzTR

tzrT

. (13)

Making the transition from the image to the original formulas (12) and (13) we obtain the

desired expression

nlnR

knln

n

k

n JBi

zbKR

rJ

cR

tzrT

221 1

2

),()(4

),,(

l R

nlkn

R

rJzrft

l

b

Ra

0 0

2

2

2

2

,,exp

×

t

l

b

Ra

adrdzzbK kn

t

k 2

2

2

2

0

exp,

R

nlcb drR

rrJ

a

rqtorTKa

k

0 1

0,0

1

,,,

+

+

1

00

)(,,, nlRnl

R

Ckl RJdrR

rrJtlrTlbK

R

kvnc ddzzbKdrtzrqR

rrJtzRT

0

1 ),()),,()(),,( , (14)

where


k

ik

k

k

k

l

k b

BiBib

b

b

b

Bi

с

1222

sin22

sin11

1

. (15)

The solution (14) describes the temperature distribution in a limited solid cylinder with the

boundary conditions (2) - (5). Let‟s consider the special case solutions. Let

constTozrT c ),,( ,

cTtzrTtzr ),,(),,( ,

if the surface density of the absorbed radiation flux and internal sources of power q (r, z, t)

depend on time, they can be represented as:

tFqtq 0 )()( tFqtq vov

The expression for the excess temperature can be written as follows:

12

0

22

2

12

.4

,,k

nnR

nnk

т JBi

R

rJc

lR

dtzr

t

knk

n

k tl

b

Rd

l

zb

B

Bi

l

zb

02

2

2

2

0 expsincos

R l

n

R

lvnk

k

k drR

rrJFqdr

R

rrJ

l

zb

b

Bi

l

zbtFq

0 0 0

000

0 sincos)(

ddzl

zb

B

Bi

l

zb k

k

k

sincos 0

Consider the case of internal and external heating. When q(t) = 0, i.e. when internal (by

current) heating has place, the temperature field of the cylinder is described by:

1 1

22

0

0

04,,n k nRnk

nRk

BiJb

R

rJBic

cp

qvtzr

)(sincos2

sin2

sin 20 tPl

zb

b

Bi

l

zbb

b

Bib k

k

kk

k

k

,

where

dtl

b

RdFtP

t

kn

0

2

2

2

2

exp)()( .


When the external heating (radiation) has place, that is 0)( tqv , the excess temperature is

given by:

1 1

22

0

04

,,n k nRnk

nkk

BiJb

R

rJBic

lcp

qtzr

kik bBib sincos )(sincos0 tP

l

zb

b

Bi

l

zb k

k

k

.

Thus, the approach proposed in this paper has allowed to consider the temperature field of the

device sensor described here in the different cases of heating. This device can be used in the sensor

unit under automated experimental research of some particular processes.

For the purpose of testing of the method in the laboratory conditions the temperature field of

wooden shield with sizes 1500x2000x20 mm, heated by radiation from the opposite side of the

muffle furnace (t = 4000C), located from the shield at a distances of 2 m and 4 m. On the shield was

applied the grid with the step of 200 mm. The measurements were carried out at the nodes. The

dependence of the relative radiometer signal (the ratio of the current signal to the maximum one) in

respect to the coordinates of the grid is shown in Fig 3.

Fig.3. Dependence of relative signal of heat sensor on the coordinates.

On the horizontal axis are number of points from left to right. The numbers on the curves

correspond to the number of horizontal lines from the top to the bottom of the shield. The

measurements confirm the potential possibility to use the proposed heat sensor for realization of the

nondestructive heat control method.

REFERENCES

1. Antipov Y.N. Measurement of pulsed light. – Karaganda, 1981. – 94 p.

2. AS 27617 RK 1999. A device for measuring heat flow. Antipov Y.N, Karabekova D.Zh.

3. AS 37716 RK 2001. A device for measuring heat flow. Kussaiynov K. Gladkov V.E., Karabekova D.Zh.

4. Antipov Y.N., Karabekova D.Zh., Akhtanova M.K., Imanasova N.V. Instruments for measuring the energy

performance of thermal processes KSTU news Kaliningrad. - 2005.- № 7. p.241-245.



UDC 621.7

ELECTRO-PULSE TECHNOLOGY OF PRODUCTION HEAT EXCHANGERS

FOR EXTRACTING THE HEAT FROM THE GROUND AT SHALLOW DEPTHS

K.Kussaiynov, S.E.Sakipova, K.M.Turdybekov, B.A.Ahmadiev, N.N.Shuyushbaeva, J.A.Kuzhuhanova

Karaganda State University named after E.A.Buketov, Universitetskaia Str. 28, Karaganda, 100026, Kazakhstan,

[email protected]

The aim of the study is to develop scientific and practical bases of introducing energy-saving heat pump

technology to heat and cold supply of residential, public and industrial premises on the basis of alternative

and renewable energy sources. The heat exchanger of the heat pump is installed in the wells for groundwater

heat. A widely used method of getting well, canals - drilling. Electro drilling, in which electrical energy is

directly in the slaughter goes into mechanical work, breaking the rock, is a fundamentally new way of

drilling. For its implementation are electro drills of various types and modifications.

Keywords: electric pulse technology, heat pump, heat exchanger, drilling, heat from the ground at shallow depths.

Currently, search and active use of new alternative energy sources in many developed countries

of the world are accepted as vital, strategic resources necessary to ensure the future development of

their economies.

Modern development of power engineering in the Republic of Kazakhstan is characterized by a

cardinal restructuring of the fuel and energy complex. This is due to the increase in the price of

fossil fuel in the world market, the aggravation of environmental problems.

In these circumstances, the measures to save fuel and energy resources are a priority in the

long-term energy policy.

In the CIS countries, large heat and power plants and district heating stations with a heating

capacity of more than 50 Gcal/h are the sources of district heating for residential, public municipal

buildings and public utilities. One of the energy saving alternatives is to obtain thermal energy

using a heat pump, which makes it possible to use heat of the ground, underground water, water

bodies, natural water flows, etc. [1]

For a small heat pump with a capacity of about 10 kW, which can be used for individual

houses, the expense of an underground water flow of about 1-2 m3/h is required. For this purpose a

heat exchanger is used. Heat exchangers can be arranged horizontally or vertically [2].

A horizontal ground heat exchanger is usually arranged near the house at a shallow depth. The

use of horizontal ground heat exchangers is limited by the size of available sites.

Vertical ground heat exchangers permit the use of low-potential heat energy of the ground

mass lying below the "neutral zone" (10-20 m from the ground level). Vertical ground heat

exchanger systems do not require large area sites and do not depend on the intensity of solar

radiation incident on a surface. Vertical ground heat exchanger works effectively in virtually all

types of geological environments, except for ground with low thermal conductivity, such as dry

sand or dry gravel. Systems with vertical ground heat exchangers are widely spread.

Vertical ground heat exchanger systems can be used for heat and cold supply of buildings of

different sizes. For a small building just one heat exchanger is enough; large buildings may require

an entire unit of wells with vertical heat exchangers.

Coaxial vertical ground heat exchangers located outside the perimeter of the building are the

main heat exchanger element in the collecting system of low potential heat of the ground.

These heat exchangers are 8 wells with the depth from 32 to 35 meters each, arranged near the

house. [3]



To use the groundwater heat, the heat exchanger of the heat pump is installed in the wells. A

widely used method to make wells and canals is drilling. Nowadays there are many types of drilling

rigs widely used in Kazakhstan. The existing technologies for drilling wells of heat exchangers are

efficient in case of soft ground in the absence of hard rocks and stone plates. Drilling a well with the

diameter up to half a meter to the depth of 25 meters in the condition of the above mentioned

constraints can be difficult. The proposed technology would make it easy to overcome such

obstacles, destroying them by the impact of shock waves at high-voltage discharge in water. It

involves crushing and grinding of hard rock that allows efficient drilling wells to the required depth

in the short term.

The main advantages of this technology are: the uniqueness of the proposed innovative way of

drilling hard rocks is the ability to work within limited space (covered premises, cellars, etc.), that

is, in many cases, impossible with traditional mechanical methods of drilling hard formations due to

the bulkiness of the equipment used.

The electrohydraulic drilling when the electrical energy turns into mechanical work directly in

the bottom, thus destroying the rock, it is a fundamentally new way of drilling. For its

implementation various types and modifications of electro-hydraulic drills are designed.

Depending on the design and purpose of a drill, it may have two or more electrodes, they can

be fixed, rotating and perform vibration movement. The movement of the electrodes can be caused

either by an external source (an engine), or due to the energy of flowing water, or action force of the

electro-hydraulic shocks.

Suggested electro-hydraulic drills constructively are divided into four main groups.

First group: electro-hydraulic drills with a rotating central electrode – it is experimentally

proved that the drills of the continuous face of this type at a voltage of 70-100 kW and capacity 0,7-

1.0 mF can drill large wells with the diameter of up to 450-500mm. The rotation of the front edge of

the central electrode is carried out in various ways (for example, by an electric engine, turbine,

driven by drill water supported through the drill pipe, as well as by reaction of electro-hydraulic

shocks) [4]

Second group: electro-hydraulic drills with fixed central electrode. In the course of

investigation on the creation of a drill with a fixed central electrode dependence of breakdown

voltage in a liquid on the mass content of any mechanical impurities in it was revealed. The method

of the so-called "dirty face" was suggested, and drill of continuous face used for this technique was

created as well.

The third group: linear drills. If, figuratively speaking, we "flatten" the continuous or circular

face drill with a fixed central electrode, we will constructively obtain two types of linear drills.

Linear drills with water supply through the central electrode with a length of cut equal to 1-2 m, at a

voltage of 50-80 kV can form narrow slits and slots with the widths of up to 8-10 mm not only

along direct, but also any curved lines.

Fourth group: drills of this type can drill all the rocks, frozen ground, ice, salt; they can cut

wood, perform various underwater works - cut expansion gaps in concrete channels, holes for the

groove at the bottom of dams and drill wells with any longitudinal curvature that is achieved by

imparting the corresponding longitudinal curvature to the drill rod.

But they all are not brought to the industrial applications, only their principles are described.

All aforesaid made it necessary to carry out experiments to develop an electro-hydraulic

technology of preparation of ground ditches for industrial use. For this purpose we used an

experimental setup based on the electro-hydraulic effect.

Electro-hydraulic effect - is a transformation of the process of hydrodynamic vortex power to

mechanical energy. Electro-hydraulic effect is a high voltage electrical discharge in a liquid

medium. During the formation of an electric discharge in a liquid energy release occurs within a

relatively short period of time. A powerful high-voltage electric pulse with a steep leading front

causes a variety of physical phenomena. Such as the emergence of ultra-high hydraulic pulse


pressure, electromagnetic radiation in a wide range of frequencies up, under certain conditions, to x-

rays, the cavitations phenomenon. The electro-hydraulic discharge occurs upon the application of

pulse voltage of sufficient amplitude and duration to a liquid, resulting in evolving of an electric

breakdown [5].

To form the pulse with a short leading front voltage applied to the discharge gap in the liquid

we used the discharge gap in a gas – a gas discharger, and in order to generate certain pulse energy

an accumulating electrical capacitor was used. Once we developed and implemented into practice a

scheme of constructing electro-hydraulic setup, figure 1.

Fig.1. Scheme of electrohydraulic setup: kV - rectifier, Fg - forming a spark gap, W - working cell of the

electrohydraulic drilling, C - capacitance of the capacitor.

The laboratory equipment consists of the following units: control panel, a system protective

capacitor, an electric power supply, current limiter, automatic power off, a high voltage indicator,

commutation generator, high voltage rectifier of the transformer, power storage devices, the

protective system of the capacitor, residual voltage removing unit, protection system, a small

discharger, an electrode system. To carry out experiments on the destruction of stones in the drilling

process, a working cylindrical cell was made, the bottom of which has a hemispherical concave

shape (its thickness together with the insulating material is 13mm). To hold the electrode in the cell

body at the same position attachments are mounted. The negative electrode of the electro-hydraulic

setup is placed at the bottom of the cylindrical cell. In Figure 2 and Figure 3 the working cell of the

electro-hydraulic setup is shown.

Fig.2. Working cell for drilling.

Fig.3. Working cell, mounted on a stone.


The thickness of the stones used for the investigation in the laboratory of hydrodynamics and

heat and mass exchange, was different (h = 30mm, h = 40mm, h = 70mm). The best results were

obtained at a gap length of 9 mm in the discharger of the electro-hydraulic equipment.

As a result the experimental study, the optimal values of time and quantity of spark discharges

during the electrohydraulic drilling of stones, as well as the time when the cracking of the stone

took place in the drilling process were determined.

The experimental results of electrohydraulic drilling of stones with h = 30 mm, h = 40 mm are

shown in Figures 5 and 6.

Fig.5. Break of the stone after

drilling for 3 minutes (h = 30mm)

Fig.6. Break of the stone after

drilling for 5 minutes (h = 40mm)

Figure 7 shows that at the thickness of the of stone h = 30mm-40mm the number of discharges

prior to crushing was 150-200 impacts and for h = 70 mm it was 400-450 impacts. Drilling depth

depends on the number of impact discharges. At the maximum impact discharge, the rate of

increase in drilling depth grows. The reason is that at the impact discharge an increase in pressure

takes place, it causes the lump grinding on the surface of a stone. An increase in the impact of a

ЭГУ

Fig. 4. Scheme of the electro-hydraulic drilling: 1– electrode, 2 – cell, 3 – stone.


discharge leads to pressure growth, so at the maximum impact of an electric discharge the depth of

drilling is increased.

0

50

100

150

200

250

300

350

400

450

20 30 40 50 60 70

H, мм

n

Fig.7. Dependence of the number of impact discharges on the thickness of a

stone prior to crushing.

Figure 8 shows a graph of dependence of the impact discharges number on the length of time

of the drilling process

0

50

100

150

200

250

300

350

400

450

0 2 4 6 8

t, мин.

n

Fig.8. Dependence of the number of impact discharges on the time length at a

electro-hydraulic effect.

The dependence of the number of impact discharges on the length of time at a electro-hydraulic

effect was established. As it is shown in the graph, in the process of crushing of stone (h = 40 mm)

the number of spark discharges amounts to 50 impacts per minute, 150 impacts in two minutes, 200

impacts in three minutes, 350 impacts in seven minutes. It was found out that during the process of

drilling, the stone surface begins to grind and eventually the drilling depth increases, and

consequently this increases the frequency of electrical discharges.

REFERENCES

1. The Energy Strategy of the Republic of Kazakhstan for the period 2004-2015.- Astana.

2. Ray D., Mcmichael J. Heat Pumps. - Moscow: Energoatomizdat, 1982.-224 p.

3. Vasiliev G.P. The use of low-grade heat the soil surface layers of the earth to the refrigerant heat supply of

buildings // Thermal Engineering. - 1994. - № 2.- P.31-35.

4. Yutkin L.A. Electro effekt.- M.: Mashgiz, 1955. - 51 p.

5. Yutkin L.A. Electro-effect and its application in industry. - A: Engineering. - 1986. -253 p.



UDC 53.096

RECYCLING OF SILICON CARBIDE AND SILICON FROM WAFER SAWING SLURRY

T. Neesse1, J. Dueck1, E. Endres1, L. Jakob2

1FAU Busan, Republic of Korea, 2SiC Processing GmbH Hirschau, Germany [email protected]

In the production of silicon wafers for the photovoltaic industry a wafer saw cutting process is

employed to slice the mono- or polycrystalline ingots to wafers. For that, multi-wire sawing using SiC slurry

is the main slicing technology in photovoltaic (PV) and semiconductor (SC) industry. The cutting process

produces a large quantity of saw dust (kerf). Dependent on the wafer thickness and the diameter of the

cutting wire, the amount of sawing chips yields up to 30 – 50% of the ingot weight. This residue contains

mainly the abrasive SiC, the Si-abrasion and Fe with other metals coming from the saw wire in a suspension

of polyethylen glycol (PEG). They thus constitutes valuable materials which are well suited to be recycled to

the photovoltaic industry. A solution of the waste slurry problem is unfortunate, both from an economical

and environmental point of view. This paper reports on different concepts and own experiences related to Si

and SiC recycling.

Keywords: Si-Recycling, SiC-Recycling, Trichlorosilane, Hydrocyclone.

Introduction

Over 80 % of the global solar cell production requires the cutting of silicon blocks into wafers

[1]. For that, multi-wire sawing using SiC slurry is the main slicing technology in photovoltaic (PV)

and semiconductor (SC) industry. During sawing a large amount of slurry is produced, which

contains polyethylene glycol (PEG) as suspending fluid, silicon carbide (SiC), iron and silicon.

Much attention is paid to recycling of SiC and PEG to the sawing process. The base publication in

this direction is an article by Neesse [2], where the variants of SiC recycling from wafer sawing

slurries are reported.

These technologies have reached a high standard and are industrially applied.

On the other hand, Si –recycling from wafer sawing residues is much more difficult and

challenging and has been subject of a large European Project [3] (Recycling of Silicon Rejects,

2006) Methods for this are actually still in the development.

After reporting on SiC recycling in this paper options and limitations of physical Si-separation

processes are reported. High grade solar Si can be achieved applying combined physical and

chemical treatment considering a special chemical technology were Si is reacting with chlorinated

acid to trichlorosilane [4-6]. First experiences with this process are reported.

1. Recycling of SiC

The SiC- recycling technology should fulfil the following requirements:

Production of PEG and SiC of a quality, comparable with virgin material

User-friendly handling of the recycling products

Consideration of environmental aspects for the separated residues As can be seen from Fig.1, two variants are to consider: The “in-house” approach consists of

equipment that the semiconductor- manufacturer purchases, sometimes offered during the original

saw purchase, and runs in-line with their own slurry system. In the US these systems exist in many

wire sawing plants.

The alternative is outsourcing the SiC-recycling to a specialised recycling company. The

recycler can operate an on-site system using mobile equipment or requires the manufacturer to

transport the slurry to a stationary recycling plant (off-site-system).

Methods and technologies of new materials 25

Fig.1. In house-(a) and outsourced (b) SiC recycling [2].

Necessary steps of SiC recycling are the separation of liquid medium PEG by filtration and

separation of SiC as recycling products from the contaminants by hydroclassification. The

contaminants are fine dispersed Si, SiC and Fe.

As classifiers in the range with cut sizes of of about 10 µm Decanter centrifuges and

hydrocyclones are available. The decanter centrifuges spin at a high rotational speed and the

classification is accomplished because the particles settle with different settling rates dependent on

their size. Due to the fact that all particles (more or less) settle, the decanter is more a solid/liquid

separator than a classifier.

A marked portion of particles < 5mµ (contaminants) is misplaced and discharged together with

the coarse SiC-particles (recycling product). The remaining contaminants from even the most

elaborate decanter technologies are generally ~3-4%. The enrichment of fine particles in the

recycled SiC-product leads in the closed circuit to a deterioration of the suspension properties.

Under these conditions only 3 – 4 passes of the slurry through the sawing process can be carried

out. In this regard, the use of hydrocyclones deliver better results.

At present, the tendency seems to increase that semiconductor- manufacturers (because of

overall-cost improvement) replace the “in-house” system running their entire slurry volume with an

outsourced system. An enhanced outsourced system in a stationary plant prefers a multistage

technology. The market leader describes a plant scheme in Fig.2 consisting of following steps [2]:

1. Separation of PEG 2. Cleaning of PEG 3. Separation of SiC 4. Cleaning of SiC 5. Drying of SiC 6. Conditioning of SiC It is obvious that a multistage cleaning can approach the final SiC-product to zero-

contamination. Therefore, the number of passes of slurry through the sawing process is not limited.


Fig.2. Multistage technology of SiC processing [2].

Further, multi-stage systems show higher cost effectivity, if a well sophisticated process

sequence is found avoiding expensive centrifuges. Additionally, the specific costs per ton are

reduced due to the high throughput of a stationary plant.

Outsourced systems have to answer the demands of user- friendly handling of the recycled

products. Applied is the transport of wet SiC products which are discharged from hydroclassifier

without further drying and cleaning. The material must be reconstituted with carrier into slurry. This

means that the manufacturer is forced to install equipment to remix the slurry after the transport

because the solids will settle in the containment.

More appropriate are products separated into dry SiC powder and PEG. The manufacturer has

three options to receive SiC and PEG from the recycling plant:

1. Separated delivery of reclaimed SiC powder and reclaimed PEG. Slurry preparation by

adding of virgin material at the manufacturer.

2. Separated delivery of reclaimed SiC powder mixed with virgin SiC powder and of reclaimed

PEG mixed with fresh PEG (slurrying is performed at the manufacturer).

3. Delivery of a ready mixed slurry consisting of SiC (reclaimed and virgin) and PEG (

reclaimed and virgin ), In this case no slurry preparation at the manufacturer.

In the EU a tendency of increasing outsourcing the entire slurry preparation to the recycler can

be observed.

2. Recycling of Si

Concerning Si there are two concepts for the recycling: Production of a low grade metallurgical

Si or production of solar Si. The first variant can be achieved using only physical separation

processes.

High grade solar Si can be achieved applying combined physical and chemical treatment.


3. Physical separation of Silicon

The feed for the Si-recycling was dried filter cake with 24% moisture, as it occurs typically in

the SiC (Silicon carbide) recycling from the wafer production at a separation cut at 10 microns. As

further components after SiC were 9.5% iron, 31% elemental silicon and 1.8% polyethylene glycol

were determined. The initial particle size distribution of material after intense dispersing can be

found in Fig.3.

Fig.3. Volume fractions of particles in the SiC/Si suspension with enriched fine Si particles

As can be seen from Fig. 3, the material contains finest Si-abrasive in the range 0.1 – 0.3 µm

and coarser silicon carbide SiC. The gap between the fine and the coarse portion delivers an

advantage for the hydroclassification.

This material was used as a feed for a special 20mm-hydrocyclone, which operated in closed

circuit duration 60 min [7]. Because no fluid is discharged in the underflow, the suspension can be

kept indefinitely in the circuit as can be seen in Fig.4.

Fig.4. Scheme of the hydrocyclone test rig with closed circuit and attached

accumulation box for the underflow.


Fig. 5 and 6 show the final particle size distributions of the coarse product and of the overflow,

respectively.

Fig.5. The final volume fractions and cumulative particle size distributions in the coarse product of the

hydrocyclone.

Fig.6. The final volume fractions and cumulative particle size distributions in the fine product of the

hydrocyclone.

As can be seen, the overflow contains only particles < 0,3 µm. The chemical analysis of this

Silicon-concentrate have shown that Si contents 90 – 95 % may be achieved. Due to the high

specific surface the Si-particles are covered with silicon oxide and adsorbed metal ions of this

product . This indicates the limit of the physical Si-recycling. Even acid leaching did not deliver an

acceptable cleaning to produce high grade solar silicon.


5. Thermo-chemical separation of Silicon

The goal of these tests was to successfully perform the hydrochlorination of silicon metal in

waste filter cake and to recover a condensed sample of the product, trichlorosilane (TCS). By-

products of this reaction include also dichlorosilane and silicon tetrachloride. The reaction summary

is written below.

3 HCl (g) + Si (s) → SiHCl3 (g) + H2 (g) – 218 kJ/mol

Details on the chemistry of this reaction can be found for example in [4-6].

This equation requires gas to solids contact. Fluid bed treatment provides excellent solids-gas

contact and heat transfer. Hydrogen chloride is thereby used as the fluidizing gas stream in an

indirectly-heated fluid bed reactor with integrated filter head. The process gases used included only

anhydrous HCl and nitrogen. For each test, a quantity of starting solids was loaded, heated to

temperature under nitrogen, and reacted with HCl gas.

The starting material for these tests was in the form of solid dispersed filter cake, containing

silicon carbide (60-80%), iron (5-10%), and silicon metal (15-30%).

The process employed to accomplish the objectives of the testing involved the use of a fluid

bed reactor system, using nitrogen and hydrogen chloride as fluidizing gases. The solids bed was

loaded, fluidized on nitrogen, and heated to the operating temperature where the reactant gas, HCl,

was introduced either at 100% concentration or as a partial atmosphere in nitrogen.

6. Lab scale

The experiments were carried out at a flow apparatus [4], shown in Fig. 7. The test rig was

equipped with a glass-vibration reactor of about 35 ml volume. The reactor is equipped with a

rotating vibrator, which leads to a fluidized bed of the reactive silicon-containing material. The

experiments were carried out at atmospheric pressure and the specified reaction temperatures. HCl

was used undiluted. All experiments were executed with a HCl standard flow rate of 1.26 l / h

(room temperature). The reactor heating was an electrically operated radiant oven. The reaction

products were analyzed online by gas chromatography.

Fig 7. Test Rig for trichlorosilane (TCS)-Synthesis.


The gas chromatogram in Fig.8 indicates trichlorosilane (TCS) dichlorosilane (DCS), and

silicon tetrachloride (STC) as products of the reaction.

Product selectivities are dependent on the reaction conditions, especially temperature,

residence time and catalytic additions.

The use of Cu powder and CuCl as potential catalysts for accelerating the reaction and / or

influencing the selectivity has been tested. These additions have a marked effect on the reaction and

may even be a precondition for the technical usability of the TCS- reaction. Under appropriate

conditions (variation of T and catalyst) high HCl - recoveries of about 90% TCS, and on the other

hand even high selectivities of 90% can be achieved.

Fig. 8. Typical gas chromatogram of chlorination.

A typical run of completeness and selectivity of the reactions is shown in Fig. 9.

Fig 9. Typical run of completeness and selectivity of the reactions.


Figure 9 indicates that the reaction at the beginning is inhibited and starts at the reaction

temperature of > 330 0 C after 80 min, than developing with increasing completeness of the

reaction. The resason for the inhibition may be the blockage of the Si-surface by oxide layers [6].

7. Pilot scale

Referring to Fig. 10, a series of experiments were performed using a 6”-diameter fluid bed

reactor constructed entirely of high temperature alloys, with graphite gaskets for the flange

connections. The unit was equipped with a screw plate gas distributor and Fines Retention Filter

System. Nitrogen was used as blowback gas to clear filters. This vessel was submerged in an

electric indirectly heated fluidized Sand Bath. A custom manifold was constructed to meter both

nitrogen and hydrogen chloride.

Fig. 10. Pilot scale fluid bed system [8].

The hydrochlorination reaction is exothermic, increasing the temperature of the solids bed.

Total flow rate of gases were maintained to keep the solids bed fluidized. These bed temperatures

were controlled by limiting HCl in the fluidizing gas.

The reaction is exothermic and the rate of the reaction, once the activation energy is sufficient,

increases as the temperature is driven up according to Arrhenius equation. In perfect fluidization,

this additional heat is transferred evenly within the fluidized solids bed. Fluidizing gas enters the

reactor, is in contact with the solids bed, and exits the reactor through the filters. Also exiting the

filters is any additional blowback gas clearing the filters. Certain exothermic activity was seen

throughout the solids bed in the familiar trend seen in Fig.11. This is characterized by an increase in

the upper bed temperatures followed by a delayed, higher temperature increase in Bed Low. The

temperature profile indicates the strongly exothermic character of the reaction. To stabilize the

reaction, at high temperature gradients the dosage of HCL was down regulated.


Fig.11. Temperature Profiles and HCL Mass flow Rate [8].

A condenser was built to condense liquids and solids in the reactor off-gas generated during the

tests. The single stage condenser was cooled by solid carbon dioxide (dry ice) in a bath of ethylene

glycol, which held the condensate/vapor stream between -10°C to -20°C. The temperature is enough

to condense the compound of interest, trichlorosilane, as well as other by products of the reaction.

The solids bed was loaded, fluidized on nitrogen, and heated to the operating temperature where the

reactant gas, HCl, was introduced either at 100% concentration or as a partial atmosphere in

nitrogen.

The batch, which was deemed the most successful of the trials, exhibited a mass loss of 37.1%

the material loaded. If 10% was lost from iron hydrochlorination and 5% to volatiles, then a 22.1%

is likely lost due to silicon reaction. This mass loss falls well within the determined silicon content

of the feed.

Summary

In recent years the problem of recycling of SiC and PEG to the sawing process has achieved

substantial progress. The recycling of SiC from wafer sawing slurry is already used industrially.

High modern technology fulfills the following requirements:

a) PEG and SiC can be produced of a quality, comparable with virgin material, b) the recycling products can be user-friendly handled, c) environmental aspects for the separated residues are considered. An enhanced outsourced system in a stationary plant prefers a multistage technology. The

recycling plant consists of following steps: separation of PEG, cleaning of PEG, centrifugal

separation of SiC, cleaning of SiC, drying and conditioning of SiC.

However, Si –recycling from wafer sawing residues is much more difficult and challenging.

Methods for this are actually still in the development. Concerning Si there are two concepts for the

recycling:

a) Production of a low grade metallurgical Si or production of solar Si. This can be achieved using physical separation processes. The options and limitations of physical separation processes

are reported.


b) High grade solar Si can be produced applying combined physical and chemical treatment considering a special chemical technology were Si is reacting with chlorinated acid to

trichlorosilane.

REFERENCES

1. Moeller H.J.. Basic Mechanisms and Models of Multi-Wire Sawing. Advanced Engineering Materials 2004. -

V.6. - N 7. - P. 501-513.

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UDC 537.528, 621.7

GRINDING TECHNOLOGY OF SILICON METAL

B.R. Nusupbekov, A.K. Khassenov, A.Zh. Beisenbek

Karaganda State University named after E.A. Buketov, Universitetskaya str. 28, Karaganda, 100026, Kazakhstan,

[email protected]

In article is presented application silicon, and advantage him(it) in contrast with the other

semiconductor. The aims and purposes of processing of metallurgical silicon electrohydraulic way.

Proposed optimal processing parameters of the product. The Certain admixture other element in

composition metallurgical silicon processed электрогидравлическим way, and got given are compared to

product reduced in mechanical grinder. Processing metallurgical silicon on электрогидравлическим

installation does not require the greater expenses for reception powder silicon in necessary proportion

Keywords: electro-technology, metallurgical silicon.

There are many debates in the modern Kazakhstan's science about how to correctly call the

material containing 95 to 99% by weight of pure silicon. Some call it the Silicon metal, some

metallurgical, some of silicon. For the purposes of this review, we use the following terms:

Industrial silicon is a material with a silicon content of more than 95%, and suitable for use in

electronic and chemical industries.

Metallurgical silicon is a material with a silicon content of 50 to 95% and is used in the

production of aluminum, iron and steel. Since in most cases, used in metallurgy alloys contain

silicon except as iron, in this report we refer to as the silicon metal and ferrosilicon ferroalloys.

Silicon metal is a broad category that combines both technical and metallurgical silicon.

Silicon metal is brittle mineral gray, weak ties which prevents the use of the mechanical

properties, but which has been widely used as an alloy for steel and as the basis for the production

of silicone products and subsequent forms of silicon.

In an alloy with iron, silicon in the form of ferrosilicon is used for making acid-products, mainly

in metallurgy for deoxidation and alloying. There is a production of 50% x (the majority) and 75%-s

grades of ferrosilicon.

Industrial silicon is mainly used in the aluminum and chemical industries. Thus, about 54% of

the world's commercial silicon directed to manufacture aluminum-silicon alloys, in which the silicon

content is only about 6%. These alloys are used in the automobile industry, and the average content

of Al-Si alloy car ^ 1995-1999 year is 945 kg [1, 2].

To obtain further redistribution of silicon, namely polycrystalline and monocrystalline silicon,

used pure grade silicon, samples of which are shown in the figures. This type of silicon - Technical

KpeMHnq chemical quality, is divided into several classes: 441, 3303, 2202. The numbers in the

name refer to the number of grades of silicon impurities present in the material. So widespread

grade 553 should contain no more than 0.5% iron, 0.5% aluminum, 0.3% calcium.

According to studies of fossil fuels by 2020 can satisfy world energy only partially. The rest

of the energy demand can be met by renewable sources.

Among the solutions to environmental problems related to the depletion of fossil fuels, an

important place direction, based on the direct conversion of solar energy into electricity using solar

cells. This solution of the energy problem is very attractive to environmentally friendly, using

virtually inexhaustible source of energy, lack of long-term cycles of heating and rotating

machinery.

Many countries are working to develop the production of solar energy converters based on

silicon "solar" as the quality of material, favorable for photovoltaic cells (PEC), the physical-

chemical properties and high level of modern production technologies. However, the development of



this area is constrained by the high cost of the trichlorosilane process unit received power compared

to conventional energy sources.

In industry, silicon is obtained by restoring coke SiO2 melt at a temperature of about 1800 ° C

in electric arc furnaces. The purity of such silicon is about 99.9%. Because the need for the practical

use of higher purity silicon, the silicon is chlorinated. The formation of compounds of SiCl4 and

SiCl3H. These chlorides further purified in various ways from impurities and the final stage of

restoring pure hydrogen. It is also possible cleaning silicon due prior magnesium silicide Mg2Si.

Next of magnesium silicide with hydrochloric or acetic acid are volatile monosilane SiH4.

Monosilane further purified by distillation, sorption and other methods, and then decomposed into

silicon and hydrogen at a temperature of about 1000 ° C. The content of impurities in the product of

these methods is reduced to silicon 10-8-10-6% by weight. Currently, silicon is the basic material

for electronics. Monocrystalline silicon is used to mirror gas lasers [3].

Besides silicon is the leading modern semiconductor material, which is widely used in

electronics and electrical engineering for the manufacture of integrated circuits, diodes, transistors,

thyristors, solar cells, etc. In the first phase of development of microelectronic production as a raw

material used germanium (Ge). Currently, 98% of the total number of integrated circuits made of

silicon.

Raw material for the microelectronics industry is the electronic polycrystalline silicon, which is

then obtained from single-crystal ingots with the necessary physical properties.

The final silicon is a mirror on one side polished single-crystal plate of diameter 15 - 40 cm

and a thickness of 0.5 - 0.6 mm with different orientation of the surface.

Industrial silicon is used as an alloying component in steel production (eg, transformer steel)

and non-ferrous metal (silicon bronze). Ultra-pure silicon is used as a semiconductor. Over 90% of

solar cells made from silicon. At the moment, it is the optimal material for the conversion of

sunlight into electricity. Other materials have a low efficiency and high cost. Industrial uses solar

power silicon solar cells with an efficiency of 14-16%. In the experimental production of silicon

squeeze 26% efficiency, but the cost of laboratory samples is much higher production solar cells [4,

5].

Economically feasible to establish commercial silicon of high purity of at least 99.90%.

Production of such silicon is only possible if supequartzitic deposits with a minimum total content

on the main contaminants - boron, aluminum, phosphorus, iron, calcium, less than 40 ppm. Quartz

deposits of Kazakhstan meet such requirements for cleanliness and elemental composition and

quartzite reserves of more than 6.8 million tons.

Therefore, in the laboratory of hydrodynamics and heat transfer of Engineering Thermophysics

named after prof. Zh.S.Akylbaev of Karaganda State University named after E.A. Buketov

developed and assembled electrohydroimpulse installation, based on the use of pulsed shock wave

resulting from the spark discharge in a liquid for crushing and grinding of metallurgical silicon [6-

8].

In the experiments the initial diameter of the silicon particles averaged from m fineness

increases with specific energy input into the discharge channel, which is explained by the fact that

in the processed ore first formed a network of micro-cracks in the path of the shock wave, which

creates a continuous state of stress

Unlike mechanical crushers electro setting has no moving parts, much is made of conventional

structural steel, so the body is almost no wear at work. The main factors affecting the grinding

mechanism, are the intensity of the pulse pressure wave, its duration, the nature of energy input in

the discharge channel, the total length of the grinding process, high velocity fluid, formed as a result

of volume microcavitating

Experiments were conducted on electrohydropulse installation at different discharge energy,

distance between electrodes on the switching device (Figure 1), capacitance capacitor bank (Figure

2), and pulse repetition rate


Fig.1. The dependence of the degree of decomposition of silicon the size of the interelectrode distance.

Fig. 2. The dependence of the degree of decomposition of silicon capacity capacitor bank.

From these graphs it can be concluded that increasing the distance between electrodes and

capacitance capacitor bank large diameter particles are crushed intense and there is a general

pattern of an electric discharge in liquid. The data obtained allows to choose the optimal value of

the interelectrode distance requirefor playback experiments.

Below in Figures 3 and 4 it is shown the experimental results of the processing of silicon

metal electrohydroimpulse before and after exposure.

Fig.3. The experimental results of the processing of silicon metal before and after

electrohydroimpulse exposure and percentage of pure silicon.


Fig.4. The experimental results of the processing of silicon metal before and after

electrohydroimpulse exposure and percentage of items.

As can be seen from the figures, the content of impurities in the medium can be reduced by

applying electro-way. However, after a certain period of time, the percentage of Si treatment

increased from 99.73% to 99.94%, and the sulfur is reduced from 58 to -4 ppm, titanium from 45 to

9 ppm, manganese from 105 - up to 40 ppm, of boron 322 to 115 ppm, vanadium from 3 to 0 ppm;

barium 6 to 1 ppm.

Thus, the impact of implemented with an underwater spark discharge, lead to the destruction of

metallurgical silicon with subsequent reduction of alkaline and heavy non-ferrous metals and a

simultaneous increase in the elemental composition of silicon.

The results showed that, electrohydroimpulse method of grinding allows you to adjust size

distribution of the finished product with high selectivity. The proposed method and power

installation options are best suited to industrial environments, provides intensive crushing and

grinding of metallurgical silicon. These studies and the implementation of their results to the

enterprises will promote technical progress in the industry.

REFERENCES

1. Samsonov. G. V. Silicides and their use in engineering. Kiev, 1959. - 204 p.

2. Semiconductor silicon technology // under publish. E.S. Filkevich. - М.: Metalurgiya, 1992. – 408 p.

3. Katkov О.М. Smelting of silicon. Irkutsk: publishing house IPU, 1997, - 243 p.

4. Balagurov L.L. Porous silicon: Preparation, properties, areas of application // Materials Science. – 1998.

5. Nemchinova N.V. Belsky S.S., Krasin B.A. High-purity metallurgical silicon as a basic element for solar energy

/ / Success of modern natural science. - M., 2006 - № 4. -P. 56-57.

6. Yutkin L.А. Electrohydraulic effect and its application in industry. - A: Engineering, Leningrad Branch, 1986. –

253p.

7. Guly G.А. Scientific basis of the discharge-pulse technology / / SSR PCB Electrohydraulics. - Kiev: Nauka.

Dumka, 1990. - 280 p.

8. Nusupbekov B.R. Shaimerdenova G.M. Kusainova D.K. Dynamics of destruction and formation of structures in

the process of electroimpulse processing of silicium minerals. Eurasian Physical Technical Journal. – 2008. – Vol.5. –

№1(9). – P. 24-28. Article accepted for publication 09.07.2012


UDC 539.26 THE STUDY OF THE COMPOSITION OF THE NATURAL

NANOSTRUCTURED MATERIAL - CHRYSOTILE ASBESTOS

Medetov N.A.

Scientific Research Institution “Moscow State Institute of Electronic Technology - MIET”, [email protected]

The article discusses the properties of the natural nanostructured material - chrysotile asbestos. The

object of the research is produced at the minefield in Zhitikara, Kostanai region. Some areas for possible

applica

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