PROJECT REPORT-RAHUL

JAMADOBA COAL PREPARATION PLANT, JHARIA DIVISION INDIAN SCHOOL OF MINES, DHANBAD

A PROJECT REPORT ON

PERFORMANCE ANALYSIS OF DENSE MEDIA CYCLONE

JAMADOBA COAL PREPARATION PLANT

JHARIA DIVISION

DURATION -8TH JUNE -20TH JULY 2015

UNDER GUIDANCE OF- SUBMITTED BY-

SHRI MANISH KUMAR RAHUL SINGH -2012JE1320

(SENIOR MANAGER, JCPP) Mineral Engg. (B.tech+M.tech)

FUEL AND MINERAL ENGINEERING DEPARTMENT INDIAN SCHOOL OF MINES DHANBAD


TATA STEEL-PIONEER IN STEEL MANUFACTURING

ACKNOWLEDGEMENT

I wish to acknowledge the fuel and Mineral Engineering Department for giving the opportunity to conduct this Industrial training Project. I also acknowledge the support of Assistant Prof. Shri Pankaj kumar Jain (AP and Training-in charge) for this Industrial training Project. I hereby, take this opportunity to express my gratitude to all the people who have helped me in successfully completing my Industrial training project at Tata Steel, Jharia Division I express my gratitude to MR.SANJAY SINGH, (General Manager), Tata Steel Jharia Division for giving this opportunity to me. I wish to acknowledge the support of Mr G.S TIWARI (Training –in charge) JCPP I am highly indebted to Mr. PARTHA DAS, (Head JCPP), Tata Steel Jharia Division, for providing adequate facilities and guidance to complete my Industrial training Project. I wish to acknowledge the support of SHRI MANISH KUMAR (Senior Manager, JCPP) for this Industrial training Project I wish to acknowledge the support of SHRI MAHESH KUMAR ( Manager, JCPP) for this Industrial training Project I acknowledge the wonderful support of individuals numerous to mention by name-they

allowed us uninhibited access to their database for the success of the this Industrial training

Project



SUMMARY

At JCPP coal from BCCL mines and Jharia division mines is been washed at ash 18%. The feed

coal of size-1000mm contain ash 30-37% which is first introduced to CHP section where sizing

and de-shaling is done in rotary breaker, from there it introduced to impact crusher and

scalping of feed take place. Finally feed coal of size-15mm is introduced to De-sliming screen of

0.5mm aperture, where+0.5mm is introduced to DM cyclone and -0.5mm is introduced to FF

section. DM cyclone separate clean coal at yield of 52.47% with an ash of 18-21% and reject

coal at yield of 23.28% with an ash of 50-60%.

Optimization of DM cyclone should be done and new digital techniques should be introduced

improve DM cyclone efficiency, proper visual checking of screen should be done so that it can

be checked that the oversize or undersize fraction is not exceeding it standard value, Moreover

proper checking of cyclone pressure should also be done in order to improve cyclone efficiency.

The magnetite media should have atleast 90% of -325mesh size fraction in media, it should be

checked in regular interval that so that proper size distribution.

2



CONTENTS

1.0 CHAPTER ONE –INTRODUCTON

1.1 Introduction to Tata Steel and Jharia division.

1.2 About Jamadoba coal preparation plant (JCPP).

1.3 Quality Performance Report

1.4 Process Flow sheet

1.5 Process Description

1.6 Major Failure and Prevention

2.0 CHAPTER TWO- DENSE MEDIA CYCLONE

2.1 Introduction to DMC

2.2 Design and Separation Mechanism

2.3 Common Problem in DMC

2.4 Parameter effecting DMC performance

2.5 Performance Evolution

2.5.1 Efficiency of Separation

2.5.3 Major Failure Mode, Potential Cause and Prevention

2. 6 Separating Media

2.6.1 Major Losses

2.7 Dense Media cyclone Development and Different Models.

3.0 CONCLUSION

4.0 RECOMMENDATION

5.0 REFERENCE

3



1.0 CHAPTER ONE - INTRODUCTION

1.1 INTRODUCTION TO TATA STEEL AND JHARIA DIVISON

TATA STEEL

Envisioned by the great patriot, Jamsetji Tata, and founded in 1907, Asia's first integrated private

sector steel company, Tata Steel Group is among the top-ten global steel companies with an annual

crude steel capacity of over 29 million tonnes per annum. It is now the world's second-most

geographically-diversified steel producer, with operations in 26 countries and a commercial presence

in over 50 countries. The Tata Steel Group, with a turnover of Rs. 1, 48,614 crores in FY 14, has over

80,000 employees across five continents and is a Fortune 500 company Tata Steel founded India’s

first industrial city, now Jamshedpur, where it established India’s first integrated steel plant in 1907.

The Jamshedpur Works currently comprises of a 9.7 mtpa crude steel production facility and a variety

of finishing mills.Two new Greenfield steel projects are planned in the states of Jharkhand and

Chhattisgarh. Kalinganagar project is underway, it is set to augment production capacity by 3 MnTPA

in the first phase. Mines and collieries in India give the Company a distinct advantage in raw material sourcing. Iron Ore mines are located at Noamundi (Jharkhand) and Joda (Odisha) both located within a distance of 150 km from Jamshedpur. The Company’s captive coal mines are located at Jharia and West Bokaro (Jharkhand) JHARIA DIVISION

Tata Steel is mining and beneficiating coal from Jharia Division since 1909. The division produces steel grade prime coking coal and clean it by beneficiation process at its two washeries – one at Jamadoba group and the other at Bhelatand group, supplying clean coal to Jamshedpur plant for coke making. The division comprises of five collieries, each nearly 100 years old spread over 5507.81 acres of leasehold areas in two locations 20km apart, namely Jamadoba group with Jamadoba Digwadih and 6&7 Pits collieries and Sijua group with Sijua, Malkera and Bhelatand collieries in it. The country’s Jharia collieries have extractable reserves of prime coking coal at depths of more than 600 metres.



FIG. NO. 1 – GEOLOGICAL MAP OF JHARIA DIVISION KEY FEATURES OF JHARIA DIVISION

First Underground Mines Certified to QMS (ISO 9001:2008), EMS (ISO 14001:2004) and OHSAS (18001:2007).

Safety, low manpower productivity, escalating wage cost & deteriorating underground geo- mining conditions with depth are the challenges. Not amenable to high level of mechanization and uniqueness in geo-mining condition

Facilities like Electronically Operated Koppe Winders, which is first time being used at coal mines in the country, using SDLs in depillaring first time in India for loading of coal, Programmable Logic Controllers (PLC) based coal beneficiation plant, Heavy Dense media Cyclones, Tailing dewatering plant, Rotary breaker, Online monitoring of coal ash through Ash Analyzer, Captive10MW Fluidized Bed Power Plant that uses washery rejects for power generation are specially implemented in this division.



1.2 ABOUT JAMADOBA COAL PREPARATION PLANT (JCPP)

The need for beneficiation occurs because the coal coming from the collieries has high ash percentage (30%-37%) but the coke sinter and iron plant at Jamshedpur needs coal of 17.5% ash for metallurgical purpose. In JCPP, the beneficiation of coal from underground mines coming from Jamadoba collieries, Digwadih collieries and 6-7 pits is done. Apart from this, coal from mines of BCCL are also washed during the process of beneficiation four products are generated. The reject is sent to the power plant where as the tailings are handled as ‘secondary products’ The Jharia division consists of two coal preparation plant known as Jamadoba Coal Preparation Plant (JCPP), and Bhelatand Coal preparation plant,(BCPP) located in Dhanbad district, which were commissioned in year 1952 and 1995 respectively,. Out of the total raw Coal, 80% of the coal is treated through Dense media cyclone and 20 % through the Froth Flotation operation

1.3 QUALITY PERFORMAMNCE REPORT (AVERAGE)

PLANT OPERATIONAL HOURS

SHIFT PLANT OPERATIONAL HOURS

RAW COAL FEED

DMC FF TONNES A 7:00 7:00 1120 B 7:50 7:50 1273 C 8:00 8:00 1434 TOATL(AVG.) 22.50 22.50 3827

PRODUCTION AND QUALITY SUMMARY

RAW COAL

COMP. CLEAN COAL

TAILING REJECT

TONNES 3827 1995 891 1056 ASH% 32.03 18.19 41.35 51.65 MOISTURE% 6.087 10.18 6.67 YIELD% 52.13 23.28 27.59 CUM. TONNES 59986 31484 11856 18444 CUM. YIELD 52.49 19.76 30.75 CUM. ASH% 33.31 18.18 43.57 53.92 CUM. MOISTURE %

5.11 10.05 6.52



SIZE DISTRIBUTION OF RAW COAL , COMPOSITE CLEAN AND REJECT COAL

SIZE RAW COAL

COMPOSITE CLEAN

COAL DMC CLEAN

COAL DMC REJECTS

WT% ASH% WT% ASH% WT% ASH% WT% ASH%

+20mm

+15mm 4.55 46.25 1.92 21.70 2.56 22.95 5.99 61.72

+ 13 mm 6.91 43.60 3.48 21.38 4.72 21.49 11.29 58.24

+ 10 mm 8.45 40.88 8.03 22.13 13.17 21.95 7.88 56.61

+ 6 mm 19.76 38.94 14.03 21.95 16.53 20.49 28.01 56.12

+ 3 mm 15.49 38.10 13.01 20.28 23.91 20.20 22.01 54.00

+ 1 mm 18.01 35.50 21.66 19.17 30.77 19.23 21.33 54.36

+ 0.5 mm 8.36 30.14 7.30 15.40 7.83 17.63 3.26 51.43

- 0.5 mm 18.46 26.59 30.60 13.84 0.52 17.15 0.25 45.23

Total 100.00 35.99 100.00 18.16 100.00 20.09 100.00 55.71

0.00

20.00

40.00

60.00

80.00

100.00

120.00

+20mm +15mm + 13 mm + 10 mm + 6 mm + 3 mm + 1 mm + 0.5 mm - 0.5 mm Total

RAW COAL WT% RAW COAL ASH% COMPOSITE CLEAN COAL WT% COMPOSITE CLEAN COAL ASH%



1.4 PROCESS FLOWSHEET 1.3.1 Dry process

RAW COAL; SIZE -1000mm Ash; 30-37%

ROTARY DISCARD

-75mm size, Ash; 30-37%

SCALPING

-15mm size, Ash; 30-37%

1.3.2 WET PROCESS

-15mm +0.5mm - 0.5mm

Ash; 30-37% Ash; 20-23%

ROTARY BREAKER

IMPACT CRUSHER

DESLIMING SCREEN

DENSE MEDIA CIRCUIT FLOTATION CIRCUIT

COARSE CLEAN COAL ASH 19-21%

FINE CLEAN COAL

ASH 12-14%

TAILING

ASH 40-45%

REJECT COAL ASH 50-60%

CLEAN COAL, ASH %18-19 METTALURGICAL COAL

REJECT COAL, ASH 40-50%, THERMAL POWER PLANT

SCREEN



GRIZZLY

C4 C5 ROTARY BREAKER ROTARY DISCARD

C2 C106

C3 BC5

SILO1 TO 6 C2 BC2 PAJAMA CHUTE BC5

C6 BC1

CHP SC2 (15mm) CHP SC1

BC6

BC3

BC10 IMPACT CRUSHER

-15mm, Ash- 30-37%

ROM &FEED TO MAIN PALNT

DISTRIBUTER

O/F & U/F

DS SC 207-1 DS SC 207-2 DS SC 207-3 DS SC207-4 FEED TO CELL

+0.5mm FROTH

-0.5mm FEED TO FF SECTION FLOTATION CELL TAILING

MAGNETIC MEDIA+WATER FEED TO DMC CELL-1 &CELL-2(STANDBY) DERRICK SCREEN

MIXER BOX FEED TO BIRD EFFLUENT

208-1 208-2 208-3 208-4 C308

BIRD CENTRIFUGE

DMC 209-1 DMC 209-2 DMC 209-3 DMC 209-4 C309

CSS 211-1 CSS 211-2 CSS211-3 CSS 211-4-

C248 SCREEN BOWL Ash40-45%

RS 215-1 RS215-2 CENTRIFUGE

C213 CLEAN COAL (Ash-18-19%)

C15 FTS & BF REJECT Ash 50-60% REJECT COAL C403 C403A OUTSIDE STOCK

OVERALL FLOWSHEET OF PLANT REJECT BUNKER CLEAN COAL BUNKER C406 C406A

OPEN CAST

MINES STOCK

YARD

UNDERGROUND

ROM

TANK

200K

HEAD

BOX CONDITIONER

THICKNER

HIGH RATE

THICKNER

REJECT

STOCK

TAILING

STOCK



1.4 PROCESS DESCRIPTION

The whole Jamadoba coal preparation plant consists of three sections which are as follows: 1. Coal Handling Plant (CHP) 2. Coarse Coal Circuit

3. Fine Coal Circuit

1. COAL HANDLING PLANT (CHP)

In this unit, the coal received from the collieries by means of conveyor belts and trucks undergo primary crushing in a rotary breaker. It produces coal of -75mm which are then stored in bunker. There are six bunkers each of 100 ton capacity. The coals from the bunker go to scalping screens. There are two scalping screens. The undersize of the screens i.e. -15 mm is feed of the main plant where as the oversize undergoes

secondary cruising in the impactor. The product from the impactor is recirculates back to the screens.

TRUCK DUMP HOPPER:-

The run of mine coal with segments less than 1000 mm in size is dumped from a truck dump hopper or a belt network to a belt conveyer. The coal processed in Jamadoba Washery comes from Jamadoba, 6 & 7 pits and Digwadih (with ash percentage of 24 to 27%).

The truck sample is held in a triangular kiln known as ‘tippler’. The raw coal passes through the screens in the tippler and then goes to rotary breaker

ROTARY BREAKER:-

Rotary Breakers are used to break the coal to a predetermined size and remove rock. It is mostly used by the coal washery plants. From here coal segments less than 75 mm in dimensions are allowed to pass to primary scalping screen. The rest goes to the stone bunker.

The rotary principle has the advantage of very low fines production because

undersize coal is immediately screened out. The residual contaminants will get

segregated by the Rotary Breaker which operates on the principle that coal being

lighter will break and get segregated by centrifugal force of the rotary breaker and

pass through the screen inside the Rotary Breaker. Hard stone and shale will not

break under same speed and centrifugal force and hence will be discharged through

the reject chute of the Rotary Breaker.

Length of rotary breaker = 11 feet

Diameter of rotary breaker = 12 feet

Speed of rotary breaker =16.49 rpm (approx.)

Motor speed = 985 rpm Motor drive = 100 h p V-belt = D 328



FIG NO.2 TOP VIEW OF ROTARY BREAKER

SILOS:-

From here the coal moves on to the steel bunkers also known as silos which are used as a raw coal section.

STONE BUNKER:-

The stone bunker is the place where the segments with larger dimensions than 75

mm are deposited and this in turns derives it to dump yard .The stones or rejects of

rotary bunker is collected more or less manually

IMPACT HAMMER CRUSHER:-

Impact hammer crushers are hammer mills that are particularly used for primary and secondary crushing of feed materials from mining and pit and quarry industries. Reversible impact hammer mill for crushing of medium-hard rock and ore.

After entering the crushing radius of the rotor, the feeding material is grasped by the beater heads and crushed by being thrown against the beater head respectively the impact wall. A second crushing process is carried out in the lower section between the rotor and the impact wall. The impact hammer crusher is resistant to foreign matters entering the mechanism, due to the flexible suspension of the beater arms on the rotor. The adjustment of the impact walls also functions as a compensation for wear and tear.

Advantages:-

High and constant capacity High level of operational safety Long lifetime Easy replacement of wear and spare parts Resistance to foreign matters High reduction ratio



DESLIMING SCREEN:-

In -15x20 mm sized coal, water is seeped through at a very high speed into it. The mixture of coal and water runs through the distributer bands and falls on de-sliming screens and separates the particles on the basis of size. Thus the particle is separated into -15+0.5 mm and -0.5 mm sized coal.

The undersize (of size -0.5mm) is sent to the fines section or fine coal circuit.

The oversize (of size-15+0.5mm) coarse coal circuit

2. COARSE COAL CIRCUIT

There are mainly three section in coarse coal circuit

DISTRIBUTION AND DESLIMING SECTION

CYCLONE SECTION

MEDIA RECOVERY SECTION

1. DISTRIBUTION AND DESLIMING SECTION

In this section coal feed coming from CHP section is allowed to fall in a distribution box

with water through conveyer and the slurry is distributed to four de-sliming screen.

There are four de-sliming screen named as 207-1, 207-2, 207-3, 207-4.

Aperture of each de-sliming screen is 0.5mm

CHP -15mm

WATER CONVEYER BELT

DS SCREEN 207-1 DS SCREEN 207-2 DS SCREEN 207-3 DS SCREEN 207-4

-0.5mm -0.5mm -0.5 mm

+0.5mm MIXER BOX TOWARD FINE COAL CIRCUIT

DISRIBUTION

BOX

MIXER BOX 208-1

MIXER BOX 208-4

MIXER BOX 208-3

MIXER BOX 208-2



CYCLONE SECTION

In Cyclone section there are four dense media cyclone named as DMC 209-1,

DMC 209-2, DMC 209-3, DMC 209-4. The coal feed coming from de-sliming screen

(+0.5mm) in allowed to fall in mixer box where fresh separating media (Magnetite ) in

mix with coal and a mixer is prepared which is gravity fed to DMC cyclone. The overflow

(size -15+0.5 mm) is now sent to four Mixer Boxes. In the mixer boxes the coal is mixed with

a media made up of Fe3O4 (Magnetite) suspension in water. This mixture is now sent into

four Dense Media Cyclones (DMC) where separation takes place at specific gravity of about

1.50. The overflow is composed of particles of specific gravity less than 1.50while the

underflow is made up of particles of specific gravity more than 1.50. The overflow is now of

ash content of about 18-19% and is considered as Washed Coal. The underflow is high in ash

content, about 45-55%. The underflow is thus considered to be Reject.

DENSE MEDIA CYCLONE

Dense medium cyclones are the conical dynamic dense medium separators

developed by Dutch State Mines in 1940s. These units are mainly used for

coal cleaning applications. Geometrically DM cyclones are similar to

hydrocyclone and generally use magnetite as a media to separate lights from

heavies.

DM Cyclone operation is very simple and gained popularity many folds over

conventional techniques for treating particularly intermediate size coal i.e. -50

+0.50 mm

FIG.NO.3 CYCLONE AT JCPP FIG.NO.4 CROSS SECTION VIEW OF CYCLONE



MEDIA MEDIA MEDIA MEDIA

DMC 209-1 DMC 209-2 DMC 209-3 DMC 209-4

CLEAN COAL CLEAN COAL CLEAN COAL CLEAN COAL

REJECT COAL REJECT COAL REJECT COAL REJECT COAL

FLOWSHEET NO. 3 FEED TO DMC AND DMC PRODUCT

MEDIA RECOVERY CIRCUIT

Media from clean coal and reject coal is recoverd first using media recocery sieve bend

of aperture 0.5mm . There are four sieve bend for clean coal ( CCS 211-1, CSS 211-2,

CSS 211-3, CSS 211-4 ) and two for reject coal (RS 215-1, RS 215-2). The diute media is

then collected to receiver tank 1 and 2 , from receiver tank it is passed over primary

magnetic separator where magnetic media is separated from effluent and the

separated media is collected in Dense tank (FTS & BF ). The effluent from Primary

separator is collected to Dilute tank.

KEY FEATURES OF MEDIA RECOVERY CIRCUIT

Media recovery system greatly reduces the required magnetic separator

capacity. Also, the extremely fine magnetite particles are more effectively

recovered.

The dilute media is classified in a low pressure cyclone.

MIXER BOX 208-1

MIXER BOX 208-2

MIXER BOX 208-3

MIXER BOX 208-4



The coarse magnetite in the underflow is fed to a magnetic separetor which

concentrates the magnetite and removes the nonmagnetic. This magnetite

concentrate also flows to the static thickner.

The magnetite particles settle rapidly to the bottom of the thickner because their high

magnetic charge causes them to form strong flocs. This thickned magnetite is then fed

to the medium sump at a rate generally determined by an automatic mediam specific

gravity control system.

The thickner overflow, which contain only a few grams of magnetite per gallonn, is used

for rising the cyclone products.

The concentration of magnetite in the dilute medium may become high enough to

couse the cyclone classifier to act as a dense medim cyclone. Low specific gravity coal

particles then report to the cyclone classifier overflow, settle to the bottom of the

thickner, and discharge with the thickner overflow.

High concentration of the material lowers the specific gravity of the thickner underflow,

which in turn may cause difficulty in maintaining the specific gravity of the dense

medium.



DMC CLEAN COAL DMC CLEAN COAL DMC CLEAN COAL DMC CLEAN COAL

DMC REJECT COAL DMC REJECT COAL DMC REJECT COAL DMC REJECT COAL

c

DILUTE MAGNETIC MEDIA DILUTE MAGNETIC MEDIA

B

BIRD CENTIFUGE CLEAN COAL

PRIMARY MAGNETIC SEPARATOR

DENSE TANK (FTS) DENSE TANK (BF)

DILUTE TANK

FLOWSHEET NO.4 MEDIA RECOVERY CIRCUIT

CSS 211-1 CSS 211-4 CSS 211-3 CSS 211-2

REJECT SCREEN

RS 215-1

REJECT SCREEN

RS 215-2

RECEIVER TANK I RECEIVER TANK II

MAINS STANDBY



3.0 FINE COAL CIRCUIT

The fines section coal of below 0.5mm, which comes from the underflow of de-sliming screen, is processed. It consists of three Water only Cyclones and two Froth Flotation cells. Recently cyclones have been stopped in action and only flotation cells are taken into process for the purpose of beneficiation. Input to fines circuit is the underflow of de-sliming screen (207-1, 2, 3, 4). The fines coming from underflow of de-sliming screen has size –0.5mm and of ash percentage 21%-24%.

The underflow of de-sliming screens is taken first to 200k tank sump from where it is pumped to head box. From head box the slurry is taken to two conditioners which take it to two flotation cell (A & B) each containing 4 compartments Presently the quantity of collector and frother added is 20cc/min and 200cc/min respectively. The slurry in flotation chambers is agitated with the help of a rotor-stator assembly and air is flown as per requirement. The froth formed is collected out continuously with the help of paddles and is taken into froth launder from where it is taken to centrifuge for the process of dewatering. The tailings are taken out by automatic valve or manual valve and are taken to tailing thickener.

In the thickener the tailings got settled down owing to the principle of sedimentation and are taken out through pump and are sent to tailing ponds from where after settling, tailings are taken out and sent through trucks. The overflow of tailing thickener is clarified water which is further reused in the plant.

The froth from flotation cell is sent to screen bowl centrifuge (manufactured by Bird) for the dewatering purpose. It consists of a horizontal revolving shell or bowl inside which a screw conveyor of similar section rotates in the same direction at a slightly lower speed. The feed pulp is admitted to bowl through the centre tube of revolving screw conveyor. On leaving the feed pipe the slurry is immediately subjected to high centrifugal force causing the solids to settle on the inner surface of the bowl at a rate which depends on the rotational speed employed. Here the bowl is revolved at speed 1000 rpm. The product of the centrifuge is the dry clean coal (ash=14.5%), effluent and port. The clean coal obtained here has moisture

around 20%. It has been found that effluent carries ultra-fines of low ash content.. The clean coal obtained from screen bowl centrifuge is mixed with the clean coal coming

from main plant. The ash percentage of composite coal is 18.0% which is then sent to

Jamshedpur



STUDY OF DIFFERENT UNITS OF FINES CIRCUIT

1. Head box:-

The underflow of de-sliming screens of size -0.5mm is taken first to 200k tank sump from where it is pumped to head box. Head Box has three chambers. The feed is falling from the pipe on the middle chamber and the two chambers are there to provide feed to both the flotation panels A and B. Each flotation panel contains 4 flotation cells.

2. Water only cyclone:- From the main feed pipe coming from the 200k tank sump, a valve is there and from there another pipe is placed to supply feed to the water only cyclone. The under flow of cyclone is taken to the conditioning tank of flotation cells of A. The overflow of the cyclone is taken directly to the froth launder of the flotation cell A. There are 3 cyclones out of which one was running but recently cyclones have been stopped in action and only flotation cells are taken into process for the purpose of beneficiation.

3. Conditioning tank:- ` Both the flotation panels A & B consisting four flotation cells, each panel is having two

different conditioning tanks for the feed. In conditioning tank feed is allowed to mix with reagent i.e. collector. Collector is added in conditioning tank and provided with sufficient conditioning time which is very important for flotation. Conditioning tank is also having an agitator for the proper mixing of feed and collector. Collector used here is diesel and its dosage is 200ml/min. Main function of collector is to promote contact between coal particles and air bubbles by forming a thin layer/coating over the particle to be floated

4. Flotation cell In JCPP, Mechanical flotation machines are used with two parallel flotation banks A & B, each of four flotation cells. Flotation cell gets feed from the feed launder. Flotation cell consists of agitator rotating at certain rpm and air introduction pipe which gets into agitator by a hollow pipe and air is introduced at the bottom of the cell and distributed with agitator forming suspension. Volume of the cell is 8.5m3. Air is controlled depending upon the product quality.

5. Screen bowl centrifuge:- The froth from flotation cell is sent to screen bowl centrifuge (manufactured by Bird) for the dewatering purpose. It consists of a horizontal revolving shell or bowl inside which a screw conveyor of similar section rotates in the same direction at a slightly lower speed. The feed pulp is admitted to bowl through the center tube of revolving screw conveyor. On leaving the feed pipe the slurry is immediately subjected to high centrifugal force causing the solids to settle on the inner surface of the bowl at a rate which depends on the rotational speed employed.

6. High rate thickener:- Effluent and port of Bird centrifuge which mainly contains ultra-fines (-300mesh) are sent to high rate thickener. The thickener is used to increase the concentration of suspension by sedimentation, accompanied by the formation of clear liquid. The underflow of HRT is sent back to centrifuge for



dewatering. The diameter of HRT is 12m and flocculants are used to increase the sedimentation of particles. One of the problems is that sedimentation of particles in HRT is not effective and ultra-fines are coming in overflow.

7. Tailing thickener:- Tailings from the flotation cells are taken to tailing thickener where they got settled down.

These tailings are then taken to tailing ponds from where, after settling, are taken through

trucks for selling. The overflow of thickener is clarified water which is taken to 302 tank and

reused as process water in the main plant.



1.5 MAJOR FAILURES AND PREVENTION

1. COAL HANDLING PLANT (CHP)

COAL PREPARATION (CRUSHING AND STACKING)

Product (output) characteristics requirements

Potential failure mode

Potential effect of failure

Potential cause

Prevention

+15mm size fraction <4.5%

+15mm size fraction > 4.5%

Lower clean coal yield

Woven wire screen cloth panel damaged

Visual checking at De-sliming screens

Identification of the shift wise coal stacked in silos

Mix up of underground coal and opencast coal

misplacement Tripper position not as per the coal received & stacking the different coal in same silo

Manually as and when coal changes

-0.5mm size fraction <20%

-0.5mm size fraction >20%


Crusher gap setting = 25mm

Checking gap by measuring linear length of adjusting bolt

DE-SLIMMING OPERATION




Potential cause Prevention

-0.5mm size fraction < 2.0 % in DM cyclone

-0.5mm size fraction > 2.0 % in DM cyclone

Lower clean yield coal

Non uniform feeding of coal throughout the screens Unequal distribution of coal in all the streams Improper water spray in screens

Visual checking at de-sliming screens

+0.5mm < 11% in feed FF cell

+0.5mm > 11% in feed FF cell


Non uniform feeding of coal throughout the screens Unequal distribution of coal in all the streams

Visual checking at de-sliming screens Measurement by filler gauge



2. COARSE COAL SECTION




Potential cause Prevention

Misplacement of clean coal in rejects < 0.5 %



Specific gravity of media in DM cyclone not as per coal blend Unequal distribution of coal in all the streams Cyclone pressure < 0.6 Kg /cm2 Cyclone Vortex Finder > 210 mm Cyclone nozzles > 190mm Feed rate > 170 TPH

DCS continuous Monitoring & Automatic correction Visual checking at de-sliming screens Measurement by pressure gauge Measurement by measuring scales Measurement by measuring scales Continuous monitoring by weightometer & manual correction

Rejects Ash > 48 %

Rejects Ash < 48 %


Specific gravity of media in DM cyclone not as per coal blend Unequal distribution of coal in all the streams Cyclone pressure < 0.6 Kg /cm2

DCS continuous Monitoring & Automatic correction Visual checking at desliming screens Measurement by pressure gauge



3.0 FINE COAL SECTION

FINE COAL BENIFICIATION




Potential cause

Prevention

Loss of magnetite in rejects < 2kg/t

Coarse clean coal ash > 19.8% Loss of magnetite in rejects > 2kg/t

High clean coal ash High CPT of clean coal

Cyclone nozzle > 190mm Improper profile of primary & secondary sprays

Measurement by measuring scales Visual checking at product screens

Fines clean coal ash = 13.2 – 15.2 %

Fines clean coal; ash > 15.2 %


Frother & collector dozing not as per coal blend Gap between rotor & stator > 70mm Tailing gate level as per SOP

Manually Measurement by measuring scales Manually

Tailing ash > 44.0 %

Tailing ash < 44 %


Gap between rotor & stator > 70mm

Measurement by measuring scales

CLEAN COAL DE-WATERING




Potential cause

Prevention

Coarse clean coal moisture < 6.0 %

Coarse clean coal moisture > 6.0 %

High clean coal dispatch moisture

Coarse coal centrifuge basket aperture > 0.7mm

Measurement by filler gauge

fines clean coal moisture < 24.0 %

fines clean coal moisture > 24.0 %

High clean coal dispatch moisture

Pool depth of SCBC > 3.5mm

Manually



2.0 CHAPTER TWO- DENSE MEDIA CYCLONE

2.1 INTRODUCTION

Dense medium cyclones are the conical dynamic dense medium separators developed by Dutch State Mines in 1940s. These units are mainly used for coal cleaning applications. Geometrically DM cyclones are similar to hydrocyclone and generally use magnetite as a media to separate lights from heavies. DMC yclone operation is very simple and gained popularity many folds over conventional techniques for treating particularly intermediate size coal i.e. -50 +0.50mm. Due to the high tonnage, a small increase in DMC efficiency can have a large impact on plant profitability

At tata steel , Jamadoab or any other plant Dense media cyclone (DMC) treats 80% of the wahsery feed and hence feed rate of the washery can be increased when proper arrangement are made to increase the feed rate to DM cyclone.

80% of the feed is washed by DM cyclone (-15 +0.5 mm ) coal doesn’t responed well to gravity separation process due to the presence of high NGM in the coarse coal feed, hence the Ep (Ecart propabale) for the DM cyclone operation is also high.

In Jamadoba there are four DM cyclone named as DMC209-1 , DMC209-2, DMC209-3, DMC209-4.Earlier terminology was that two cyclone (DMC209-1, DMC209-2) were considered as FTS section and two( DMC209-3, DMC209-4) were considered as BF section.

There are four sieve bend named as CSS 211-1, CSS 211-2, CSS 211-3, CSS 211-4 used to recover the magnetic media from the cyclone product that ‘s clean coal , and there are two screen named as RS 215-1,RS 215-2 for Recovery of magnetic media from reject coal.

SOME ADVANTAGES OF DMC PROCESS OVER OTHER BENEFICIATION PROCESS

DMS have the ability to make sharp separations at any required relative density within the range normally required for coal preparation (and other minerals). A high degree of efficiency can be achieved even in the presence of high percentages of near density material (minerals/coal within ±0.1 relative density units of the cut point).

The rate of separation is much higher the any other bath, Fe> 500*g

The relative density and thereby the cut point, can be changed at will and fairly quickly to meet varying requirements.

A wide range of sizes (+0.1mm – 150mm) can be handled (each size range in different units), Through put capacity is much higher than any other bath



WASHING OF COAL AT SIZE (-13 +.5 mm) IS MORE ECONOMICAL BECAUSE-

Lower capital and operating costs in size reduction

Dewatering is easy

Material handling and transportation at this size is very easy.

Lesser environmental problems for tailing disposal

2.2 DESIGN AND SEPARATION MECHANISM

The constructional features of a cyclone washers are essentially the same as that as a

cyclone thickener or cyclone classifier. The only difference lies in the mode of operation and

the use of medium for separation.

A cyclone washer consists of a cylindrical part with a tangential feed inlet and a cover plate

with a central outlet pipe at the top. A cone is fitted at the bottom of the cylinder having

suitable aperture at the apex. Over the cover plate there is a chamber with an outlet pipe.

In a typical dense media cyclone, the mixture of medium and raw coal enters tangentially

near the top of the cylindrical section, thus forming a strong vertical flow. The refuse moves

along th e wall of the cyclone and is discharged through the underflow orifice. The washed

coal moves towards the longitudinal axis of the cyclone and passes through the vortex

finder to the overflow chamber. The washed coal is discharged from this chamber, usually a

tangential outlet.

The lighter particles reverse its path and move towards the longitudinal axis of the cyclone

and pass through the vortex tinder as a clean coal.

In a cyclone washer, the force responsible for separation or sorting is the centrifugal which

is many times (50-100) greater than the gravitational force that effects separation of small

or fine particles in conventional washers including jigs and heavy medium units.

The effect of viscosity in the required separation of small or fines particles in the

conventional baths is eliminated to larger extent in cyclone washers. Thus the application of

centrifugal force in a cyclone washers makes it possible to efficiently treat coal down to a

bottom size of 0.5mm.



OPERATING PRINCIPLE AND RESPONSIBLE FORCES

The buoyant forces acting on the coal particles cause them to rise the surface, the impurity

particles, being heavier than the liquid they displace, sink to the bottom.

The magnitude of the gravitational and buoyant forces that separate the particles is a

primary consideration because it governs the velocity with which the particles separate,

which in turn determines the capacity of the separating vessel.

In a static baths the net forces is written as Fg = (Mp-Mt)g

Where Fg= gravitational force, Mp= mass of particle,Mt= mass of fluid displaced by particle,

and g= acceleration of gravity

For float particels Fg will have a negative value

For sink particles Fg will have a positive value

In a cyclone specific gravity separation results primarily from application and utilization of

similar forces. However, the acceleration of gravity is substituted by a centrifugal

acceleration. Thus the equation changes to

Fc=(Mp – Mt)V2/R

Where Fc=centrifugal , V= tangential velocity and R= radius of cyclone

In a typical cyclone the centrifugal force acting on a particle in the inlet region is about 20

times greater than the gravitational force in a static bath , In the conical section of the

cyclone, V is further increased according to the relationship Vr1/2=constant

At the apex of the cyclone the acceleration increases to over 200 times greater than gravity.

Thus the forces tending to separate the coal and impurity particles are much greater in

cyclone than in other baths

GENERAL FLOW PATTERN OF THE MEDIUM IN A CYCLONE

It consist of a descending vortex that originates at the inlet and progresses through the

cyclone to the underflow outlet. As the descending vortex passes down the cyclone, the

part of the fluid peels off toward the center of the cyclone to form an ascending vortex.

The ascending vortex, in turn surrounds a cylindrical air core that encircles the entire

longitudinal axis of the cyclone.

An additional factor that influence the separation is the progressive increase in specific

gravity of the medium as it descend towards the apex. This increase occurs because of

the centrifugal force also tend to force the medium particles toward the cyclone wall.

Therefore, they are preferentially caught in the descending vortex resulting in



progressively higher concentration of medium particles as the apex is approached. As

might be expected, then, the specific gravity of the medium flowing through the

underflow orifice is higher than the specific gravity of the circulating medium.

Conversely, the specific gravity of the medium passing through the overflow orifice is

less.

FIG. NO.5 IDEALIZED FLOW PATTERN OF MEDIUM IN DM CYCLONE



FIG. NO.6 A 510mm DM CYCLONE

At jamadoba coal washery the DM cyclone is gravity feeding low pressure cyclone So advantages of gravity feed cyclone

Degradation was minimized as in pump feed cyclone a lot of degradation of the coal particles took place inside the pump

Fluctuation in feed rate were avoided as due to fairly wide fluctuation in the delivery rate of feed pump, the pressure could not be properly maintained , this lead to the design and installation of a different setup in which feed was delivered from the overhead tank from which the pulp gravitated to the cyclone below at constant pressure

Segregation of coal particles was mostly eliminated.

Continuous operation was ensured.

CYCLONEWISE SPECIFIC GRAVITY/LINE GRAVITY

CYCLONES OVERFLOW UNDERFLOW LINE GRAVITY

DMC 209-1 1.320 1.808 FTS 1.393

DMC 209-2 1.312 1.787

DMC 209-3 1.352 1.705 BF 1.410

DMC 209-4 1.349 1.731



2.3 COMMON PROBLEM IN DMC Field studies indicate that the most common troubles encountered in dense

Medium cyclone circuits include:

Clean coal vortex overload, Excessive particle retention, Improper specific gravity cut-point

1. CLEAN COAL VORTEX OVERLOAD

The vortex finder of a dense medium cyclone is somewhat analogous to the overflow lip of a dense medium vessel. In a vessel, a minimum depth of overflow of 7-10cm must be maintained to ensure that the largest size particles of clean coal can be hydraulically carried into the clean product. Likewise, an adequate flow of medium containing the proper amount of medium particles must pass through the vortex finder of a DMC in order to carry out the coal particles. If the flow of medium to the overflow is too low, then the excess clean coal cannot be carried through the vortex finder and will instead report to refuse. This problem is common in DMCs operated with too large an apex or too low of an inlet pressure.

2. EXCESSIVE PARTICLE RETENTION

The centrifugal field within a DMC causes magnetite to classify and preferentially report to underflow. The classification causes the underflow SG to be higher than that of the feed and the overflow SG to be lower than that of the feed. As a result, middlings particles that have a density between that of the feed SG and overflow SG tend to remain in the cyclone for a longer period of time than particles outside this density range. Retention is normally associated with only the coarsest particles and rarely occurs for particles finer than about 15 mm. The retention of coarser middlings may even improve the separation by breaking middlings into smaller particles that are better liberated and easier to discharge. However, particle retention can be a serious problem when middlings particles enter the cyclone at a faster rate than they can be removed. The excessive build-up of middlings eventually leads to a sudden surge to the underflow that clears the accumulated load of retained material. Unfortunately, the surge also tends to carry out a portion of low-density clean coal to the refuse stream.

3. IMPROPER SPECIFIC GRAVITY CUT-POINT

Dense medium cyclones are frequently installed in banks of two or more parallel units in order to achieve the production requirements of a given plant. For all practical purposes, the maximum yield from such a circuit can only be achieved when all of the DMCs are operated at the same specific gravity cut-points. This optimization principle is valid regardless of the desired quality of the total clean coal product or the ratios of different coals passed through the circuit.



2.4 PARAMETER AFFECTING DMC PERFORMANCE A systematic study was conducted to find out the influence of the following variables on the performance of the cyclone; Aperture of overflow and underflow nozzles and their ratio Length of the vertex finder tube. Feed pressure Apex angle of the cone Size- grading of the feed Coal Pulp ratio Specific gravity of separation 1. APERTURE OF OVERFLOW AND UNDERFLOW NOZZLES AND THEIR RATIO

The size variation of the opening and underflow openings influenced the separation most significantly, It become apparent from the study that by adjusting the opening of the either of the nozzles, the yield from nill to nearly 100%. However, an optimum ratio of their combination gave maximum efficiency in separation. For a 75mm cyclone washer the optimum ratio is 1:5

INFLUENCE OF SIZE OF CLEANS NOZZLE

Dia. Of Clean nozzles

9.5 13 15.9 19.1

Clean wt% 35.8 61.3 81.6 91.4

Clean Ash % 7.2 10.8 13.4 16.2

Feed Ash% 19.4 20.3 18.6 19.2

Sp. Gr. of separation

1.358 1.442 1.450 1.590

INFLUENCE OF SIZE OF REJECT NOZZLE

Reject nozzle Dia (mm)

7.9 9.5 11.1 13

Clean Wt% 84.7 67.4 48.2 39.7

Clean Ash% 19.4 15.9 12.2 10.5

Reject Wt% 15.3 32.6 51.8 60.3

Reject Ash % 56.1 49.3 42.6 39.5

Feed Ash % 25.1 26.8 27.9 27.9

Sp. Gr. Of separation

1.650 1.600 1.470 1.440



2. LENTH OF VERTEX FINDER

Cyclones have been constructed with many different inlet configuration: round, square, rectangular, inclined, parabolic, cycloidal, etc. Each style has its supporters. The overflow pipe, commonly called the vortex finder, usually discharges into an overflow chamber. A tangential exit pipe from this chamber is preferred because it reduces undesirable back pressure on the cyclone.

3. FEED PRESSURE

Dense media cyclones will operate with inlet pressures as low as 6-8 psi, but pressures of 20 psi and higher are used. About 10-14 psi is perhaps a good average. It is generally not advisable to operate at inlet pressure as low as 6-8 psi because the recovery of low specific gravity material and the rejection of impurity is noticeably improved at higher pressure, especially for the finer sizes. The pressure can be developed by two methods which are governed by the point where the de-slimed raw coal enters the cyclone plant

The simplest, from a materials handling standpoint, is to simply feed the coal directly into the medium sump. The mixture is then pumped to the cyclone.

In an alternative method, the medium is pumped to a head tank, which is about 15-30 (4.57-6.1m) above the cyclone inlet, where the coal is added. The method is especially applicable for friable coals, because degradation in the medium pump is eliminated, although an elevator may be required to raise the coal to the head tank level.

With the both methods, it is important that the medium flow impinge on the incoming feed. Also, if the raw coal is fed to the medium sump, the coal-medium mixture should be directed by a feed tube to the strong suction currents at the bottom of the medium sump. Otherwise, rafting of the fee coal may cause difficulty.

4. APEX ANGLE OF CONE A cone angle of about 200 appears to be standard, but a few investigator advocate larger cone angles. Many test in US Bureau of Mines pilot plants, however, indicates that occasionally the performance of cyclones with larger cone angles were equal, but never superior, to those with 200.

5. SIZE GRADING OF FEED COAL The size distribution play an important role in deciding the performance of the DM cyclone. The feed should not contain over size fraction, it should be limited to <2% and the undersize should also be limited to 2% for effective separation. At JCPP the feed distribution after going through primary process is follows



FEED TO CYCLONE

De-sliming Screen 207-1

From the above plot as the size decrease the ash % also decreases so for an effective separation to take place in DM cyclone the oversize i.e +15mm should be <4% and undersize i.e -0.5mm should also be <2%. As in the given case for de-sliming screen 207-3, 207-4 the oversize fraction is >4%, hence there should be possibility of bad performance of DM cyclone and more misplacement.

0

10

20

30

40

50

60

70

80

90

100

SIZE + 20mm

+ 15mm

+ 13mm

+ 10mm

+ 6 mm + 3 mm + 1 mm + 0.5mm

- 0.5mm

Total

Wt% 0 4.18 9.18 7.30 28.91 21.52 22.23 5.74 0.95 100.00

Ash% 0 48.19 44.40 42.61 36.52 34.93 37.12 33.38 37.21 37.79

207-1 207-2 207-3 207-4

SIZE WT% ASH% WT% ASH% WT% ASH% WT% ASH%

+ 20 mm

+ 15 mm 4.18 48.19 3.95 47.54 4.28 51.25 6.11 49.09

+ 13 mm 9.18 44.40 9.10 45.53 9.12 48.52 10.23 45.33

+ 10 mm 7.30 42.61 8.59 40.11 9.63 40.54 8.76 45.24

+ 6 mm 28.91 36.52 25.55 37.37 32.48 37.60 29.84 36.75

+ 3 mm 21.52 34.93 22.84 36.71 21.44 36.15 19.99 35.19

+ 1 mm 22.23 37.12 24.07 34.25 19.62 34.14 20.42 35.34

+ 0.5 mm 5.74 33.38 5.38 34.52 3.09 27.70 4.28 35.00

- 0.5 mm 0.95 37.21 0.52 29.10 0.34 26.11 0.38 29.55

Total 100.00 37.79 100.00 37.65 100.00 38.13 100.00 38.42



6. PULP RATIO

A medium to coal ratio of about 5:1 is recommended. A ratio as low as 3:1 can be used, but with some sacrifice in performance. Performance is not improved by using ratios higher than 5:1, and such dilute feeds involve a number of disadvantages. Pumping and maintenance costs are both increased, and if the drainage screen are heavily loaded, the loss of magnetic media may increase because the load on the magnetic separators will be greater. For a 150mm cyclone washer

Pulp Ratio 6:1 4.75:1 3.25:1 3:1

Sp. Gr of separation

1.486 1.487 1.527 1.542

Ecart probable 0.020 0.026 0.042 0.042

NGM 43.4 44.2 48.5 50.0

Capacity of washer(kg/hr)

70.9 87.7 197.3 270.9

7. SPECIFIC GRAVITY OF SEPARATION

For all practical purposes, the maximum yield from such a circuit can only be achieved when all of the DMCs are operated at the same specific gravity cut-points. This optimization principle is valid regardless of the desired quality of the total clean coal product or the ratios of different coals passed through the circuit.

Specific gravity of separation

1.486 1.487 1.527 1.542

Ecart probable 0.020 0.026 0.042 0.042



2.5 PERFOMANCE EVOLUTION

Performance evolution of DM cyclone can be done by determining the efficiency of separation Misplacement of particles, Major failure mode. Misplacement can be defined in the term of misplaced clean coal in reject coal due to improper separation in DM cyclone.

2.5.1 EFFICIENCY OF SEPARATION

In continuous production process, however, conditions are usually for away from the

ideal and particles can be misplaced to wrong product for a variety of reasons. The

dominant effect is that of the density distribution of feed. Very dense or very light

particles will settle through the medium and report to appropriate product quickly but

particles of density close to that of medium will move more slowly and may not reach

the right product in the time available for separation

Other factors also play a role in determining the efficiency of separation

Fine particles generally separate less efficiently than coarse again because of

their slower settling rates. So fines fraction should be <2%

Observation of De-sliming screen shown below

207-1 207-2 207-3 207-4

SIZE WT% ASH% WT% ASH% WT% ASH% WT% ASH%

-0.5MM 1.82 31.26 0.44 32.47 0.43 29.15 0.72 28.22

As in the above observation it is clear that the size fraction -0.5mm is less

than 2%

The properties of medium, the design and condition of separating vessel, the

feed condition, particularly feed rate, will all influence the separation

For an effective separation the size distribution of magnetic media should

contain at least 90% size fraction of -325mesh.

The efficiency of separation can be represented by the slope of partition or tromp

curve, first introduce by K.F. Tromp (1937). It describe the separating efficiency for the

separator whatever the quality of feed and can be used for estimation of performance

and comparison between separators



PARTITION CURVE

Partition curve relates the partition coefficient or partition number, i.e. the

percentage of the feed material of a particular specific gravity which reports

to either the sinks product or the float product (generally for coal), to

specific gravity.

The ideal partition curve reflects a perfect separation in which all particles

having a density higher than the separating density report to sinks and those

lighter report to floats. There is no misplaced material.

The partition curve for a real separation shows that efficiency is highest for

particles of density far from the operating density and decrease for particles

approaching the operating density.

The partition curve for an operating dense medium vessel can be

determined by sampling the sink and float products and performing heavy

liquid test to determine the amount of material in each density fraction. The

range of liquid densities applied must envelope the working density of the

dense medium unit. The result of heavy liquid test on samples of float and

sink from a vessel separating coal(floats) from shale (sinks) are shown in

table

FLOAT AND SINK ANALYSIS OF CYCLONE PRODUCT AT JCPP

FLOAT & SINK FLOAT & SINK

215-1 &2 207-1 TO 4

Sp-Gr WT% ASH% Sp-Gr WT% ASH%

Ft-1.30 0.00 Ft-1.30 1.82 3.42

Ft-1.40 0.37 10.20 Ft-1.40 10.30 10.19

Ft-1.50 0.88 17.24 Ft-1.50 19.73 17.42

Sk-1.50 98.76 56.27 Sk-1.50 68.16 46.07

TOTAL 100.00 55.76 TOTAL 100.00 35.95

WHERE 215-1 & 215-2 REPRESENT SINK FLOAT OF REJECT COAL

AND 207-1, 207-2, 207-3, 207-4 REPRESENT SINK-FLOAT ANALYSIS OF

CYCLONE FEED.

The above highlighted part shows that when separation done at 1.50

specific gravity we are misplacing 1.25% clean coal where matters a lot to

plant economic.



REPRESENT SINK FLOAT OF REJECT COAL

REPRESENT SINK-FLOAT ANALYSIS OF CYCLONE FEED.

0.00

20.00

40.00

60.00

80.00

100.00

Ft-1.30 Ft-1.40 Ft-1.50 Sk-1.50 TOTAL

WT% 0.00 0.37 0.88 98.76 100.00

ASH% 10.20 17.24 56.27 55.76

FLOAT & SINK-REJECT COAL

WT%

ASH%

0.00

20.00

40.00

60.00

80.00

100.00

Ft-1.30 Ft-1.40 Ft-1.50 Sk-1.50 TOTAL

WT% 1.82 10.30 19.73 68.16 100.00

ASH% 3.42 10.19 17.42 46.07 35.95

Chart Title

WT% ASH%



PARTITION CUVRE FOR REAL AND IDEAL CONDITION

MISPLACEMENT OF PARTICLES

Misplacement is define as the particles of density close to that of medium will move

more slowly and may not reach the right product in the time available for

separation, Dominant factor for misplacement is density distribution of feed.

Area between the two curve is called the “error” and is a measure of the degree of

misplacement of particles to the wrong product

Many partition curves give a reasonable straight-line relationship between the

distribution of 25 and 75%, and slope of line between these distributions is used

show efficiency of the process.

The probable error of separation or Ecart probable (Ep) is defined as half the

difference between the density where 75% is recovered to sinks and that at which

25% is recovered to sinks

EP= (d75-d25)/2d50

The density at which 50% of the particle report to sinks is shown as the effective

density of separation which may not be exactly the same as medium density,

particularly for centrifugal separators, in which the separating density is generally

higher than the medium density.

Lower the Ep, the nearer to the vertical is the line between 25 and 75% and the

more efficient is the separation.

An ideal separation has a vertical line with an Ep = 0 whereas in the practice the Ep

usually lies in the range the range 0.01-0.10.

The Ep is not commonly used as a method of assessing the efficiency of separation

in units such as table, spirals, cones, etc. due to many variable (wash water, table

slope, speed, etc.) which can affect the separation efficiency. It is however, ideally

suited to the relatively simple and reproducible DMS process



MISPLACEMENT OF CLEAN COAL TO REJECT AT 1.50 SPECIFIC GRAVITY AT JCPP IS

SHOWN BELOW

CLEAN COAL MISPLACEMENT

FLOAT AT 1.50 20/06/2015 21/06/2015

A B C A B C

FTS WT% 2.70 2.80 3.20 11.00 8.00 2.10

ASH% 19.71 20.87 19.62 19.15 18.80 17.54

BF WT% 0.35 1.40 1.80 6.6 5.50 0.60

ASH% 21.99 21.78 20.28 21.17 30.55 18.38

AVERAGE WT% 1.52 2.10 2.50 8.80 6.75 1.35

ASH% 20.85 21.33 19.95 20.16 19.82 17.96

As per required product characterization misplacement should be less 0.5% but we

see in both FTS and BF section misplacement is more than 0.5%, due improper

feed distribution to all stream , cyclone pressure >0.6 kg/cm3

FTS has more misplacement than BF because

Improper distribution of feed to FTS section.

Fines more to FTS i.e >2% due damaged PU panel of 207-1, 207-2

de-sliming screen



2.5.2 MAJOR FAILURE MODE, POTENTIAL CAUSE AND PREVENTION

MISPLACEMENT OF PARTICLE AND EFFICIENCY OF SEPARTION

ANALYSIS OF REJECT ASH %




Potential cause / mechanism of failure

Current process controls detection / prevention

Rejects Ash > 48 %

Rejects Ash < 48 %


Specific gravity of media in DM cyclone not as per coal blend Unequal distribution of coal in all the streams Cyclone pressure < 0.6 Kg /cm2

DCS continuous Monitoring & Automatic correction Visual checking at de-sliming screens Measurement by pressure gauge




Potential cause / mechanism of failure

Current process controls detection / prevention

-0.5mm size fraction < 2 % in DM cyclone

-0.5mm size fraction > 2 % in DM cyclone


Non uniform feeding of coal throughout the screens Unequal distribution of coal in all the streams Improper water spray in screens

Visual checking at de-sliming screens




Specific gravity of media in DM cyclone not as per coal blend Unequal distribution of coal in all the streams Cyclone pressure < 0.6 Kg /cm2 Cyclone Vortex Finder > 210 mm Cyclone nozzles > 190mm Feed rate > 170 TPH

DCS continuous Monitoring & Automatic correction Visual checking at de-sliming screens Measurement by pressure gauge Measurement by measuring scales Measurement by measuring scales Continuous monitoring by weightometer% manual correction



2.7 SEPARATING MEDIA

Media from clean coal and reject coal is recovered first using media recovery sieve bend of

aperture 0.5mm. There are four sieve bend for clean coal (CCS 211-1, CSS 211-2, CSS 211-3,

CSS 211-4) and two for reject coal (RS 215-1, RS 215-2). The dilute media is then collected

to receiver tank 1 and 2 , from receiver tank it is passed over primary magnetic separator

where magnetic media is separated from effluent and the separated media is collected in Dense tank (FTS & BF ). The effluent from Primary separator is collected to dilute tank

KEY FEATURES OF MAGNETIC SEPARATION CIRCUIT

Media recovery system greatly reduces the required magnetic separator capacity. Also, the extremely fine magnetite particles are more effectively recovered.

The dilute media is classified in a low pressure cyclone.

The coarse magnetite in the underflow is fed to a magnetic separetor which concentrates the magnetite and removes the nonmagnetic. This magnetite concentrate also flows to the static thickner.

The magnetite particles settle rapidly to the bottom of the thickner because their High magnetic charge causes them to form strong flocs. This thickened magnetite is then fed to the medium sump at a rate generally determined by an automatic mediam specific gravity control system.

The thickner overflow, which contain only a few grams of magnetite per gallonn, is used for rising the cyclone products.

The concentration of magnetite in the dilute medium may become high enough to couse the cyclone classifier to act as a dense medim cyclone. Low specific gravity coal particles then report to the cyclone classifier overflow, settle to the bottom of the thickner, and discharge with the thickner overflow.

High concentration of the material lowers the specific gravity of the thickner underflow, which in turn may cause difficulty in maintaining the specific gravity of the dense medium.

MAGNETITE SCREEN ANALYSIS IN MEDIA CIRCUIT AT JCPP

Magnetite Content % Magnetite Screen analysis in Media Circuit

FTS BF FTS BF

94.00 94.00 +325 MESH 18.09 15.96

-325 MESH 81.91 84.04



2.7.1 MAJOR LOSSES

MAGNETITE LOSS IN COARSE CLEAN SCREEN AND REJECT SCREEN

Magnetite Loss

Clean Coal Screen (GM/KG)

Reject Screen (GM/KG)

211-1 211-2 211-3 211-4 Average 215-1 215-2 Average

0.017 0.03 0.01 0.05 0.03 0.03 0.04 0.04

ASH% 19.38 20.69 20.88 20.71 20.42 57.62 53.61 55.62

MAGNETITE LOSS IN PRIMARYY SEPARATION

PRIMARY SEPARATOR

Magnetite Loss

Primary Separator U/F (gm/Lt)

FTS BF Average 0.237 0.073 0.155

MAGNETITE LOSS IN COARSER BIRD EFFLUENTS

Magnetite loss in coarser bird effluents (gm/Lt) 0.039



2.8 DENSE MEDIA CYCLONE DEVELOPMENT AND DIFFERENT MODEL

DSM (Dutch state mines) recorded many principle guidelines for DM cyclones which are used to this day. The Guidelines are summarised in table DSM DM cyclone selection guidelines vs. current trends

PARAMETERS DSM

RECOMMENDATIONS

CURRENT

MANUFACTURING

TRENDS

CYCLONE DIAMETER(DC) <800mm UPTO 1500mm

INLET SIZE(DI) 0.2*DC 0.20, 0.25, 0.30* DC

VORTEX FINDER(DO) 0.43*DC 0.43-0.53* DC

SPIGOT OR APEX (DU) 0.3* DC 0.3-0.4* DC

BARREL LENGTH 0.5* DC 0.5 to 2.5* DC

CONE ANGLE 200 200

CYCLONE FEED

PRESSURE

9* DC 6 DC to 18 DC

LAMINAR SPIRAL FEED CHAMBER DM CYCLONE DESIGN All equipment and resources were provided by Weir Minerals Africa. A material

survey on the current installed DM cyclones indicated that +92% Alumina ceramic tiles lasted about 1.5 times as long as 27% Cr cast iron.

Silicon Carbide was excellent in high wear applications like spigots, but if the entire cyclone was cast in Silicon Carbide, the impact of the slurry caused the Silicon feed chamber to crack when pump fed.

The market survey was comprehensive and included the DM cyclone installation sizes of 72 different operations across Southern Africa. After the market survey, it was concluded that +92% Alumina tiles were the most cost effective material of construction for DM cyclones. The 27% Cr Cast iron cyclones are almost exclusively used in diamond operation

The operating principle was to reduce the turbulence when feeding the cyclone in order to increase the residence time of the particles in the classification zone and, as a result, increase efficiency by reducing the misplaced particles.

This required the design and fabrication of radius-moulded tiles to follow the exact profile of the Cavex feed chamber whilst using +92% Alumina tiled

ceramics instead of the traditional natural rubber moulds.



3.0 CONCLUSION DMS plays a significant role in the global coal industry, This R&D project established that almost all coal plants use DMS in order to produce saleable yields. The most common DMS separating vessel was a DM cyclone. Dense medium cyclones are playing vital role in Indian coal preparation plants and optimising the performance of DM cyclone is imperative for the washeries. DM cyclone operation can be tuned to achieve optimum result, by manipulating operating and design variables. Systematic investigation in the operating plants and use of suitable mathematical models can significantly improve the performance of the dense medium cyclones. At JCPP clean coal of ash 18% is supplied at yield of 53.76%, where as tailing with ash of 41.54% at a yield of 23.28 and reject of ash 51.26% with a yield of 27.57% is done, Misplacement of clean coal to reject is about 2% is observed, to avoid misplacement it is required to have visual checking of de-sliming screen , pressure of cyclone at regular interval.



4.0 RECOMMENDATIONS

At JCPP the misplacement of clean coal to reject coal is about 2% which value to a larger extent , so it is required to stop misplacing clean coal of high value to reject, For which proper checking of aperture of PU panel of all de-sliming screen should be done at regular interval so that fine fraction to DMC should not exceed 2%(-0.5mm) and moreover avoiding oversize(+0.5mm) fraction to go Flotation cell. Measurement of cyclone pressure in regular interval should be done.



5.0 REFERENCE

GEOLOGICAL SECTION OF JCPP STUDIES ON COAL PREPARATION IN INDIA(CFRI) COAL PREPARATION BY LEONARD DEVELOPMENT AND EVALUATION OF A DENSE MEDIA CYCLONE FOR THE SOUTHERN AFRICAN

MINERAL AND COAL INDUSTRIES https://www.google.co.in/ https://scholar.google.co.in/ WILL’S MINERAL PROCESSING TECHNOLOGY

https://www.google.co.in/

https://scholar.google.co.in/

PROJECT REPORT-RAHUL

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