Modeling and Simulation of Interconnected CFB-boiler and Fast Pyrolysis

Modeling and Simulation of Interconnected CFB-boiler and Fast Pyrolysis Processes Control Design Case

Yrj Majanne* Jani Laine**

Jyri Kaivosoja*** Petri Kykk **

*Tampere University of Technology, Department of Automation Science and Engineering, P.O. Box 692, FI-33101 Tampere, Finland (e-mail:[email protected])

** Metso Power, P.O.Box 109, FI-33101 Tampere, Finland (e-mails: [email protected] [email protected] )

*** Metso Automation, P.O.Box 237, FI-33101, Tampere, Finland (e-mail: [email protected])

Abstract: The fast pyrolysis process is developed to produce liquid bio oil from biomass. In the discussed process the required thermal energy is extracted from a circulating fluidized bed boiler (CFB) as hot sand fed into the pyrolysis reactor. Residual char and uncondensed gases from the pyrolysis process are fed back and combusted in the boiler. Thus, the pyrolysis and the boiler processes are interconnected together both via energy and mass balances. Dynamic simulation is used to analyze how start ups, stops, and disturbances in the pyrolysis process effect on the operation of the boiler. According to the results of the analysis the boiler control system is modified to be able to stabilize the operation of the boiler with the interconnected pyrolysis process. The trouble free operation of the boiler must be guaranteed during all possible situations of the pyrolysis process. This project is a part of a R&D project by Metso Power where fast pyrolysis process is developed and commercialized as a new liquid bio fuel production process which can be integrated e.g. as a part of a paper mill. Keywords: Dynamic simulation, CFB boilers, Fast Pyrolysis, Interconnected systems, Boiler control.

1. INTRODUCTION

Fuels produced from renewable energy sources are seen as a part of the solution to reduce CO2 emissions and the replacement of fossil fuels. Pyrolysis is a promising process for conversion of solid biomass to liquid bio fuels.

This paper introduces an integrated process concept, where the pyrolysis process is connected together with a fluidized bed boiler. The concept is developed by Metso Corporation and Technical Research Centre of Finland, VTT. Heat required for the pyrolysis process is extracted as hot sand from the fluidized bed boiler. The charcoal remained from the pyrolyzed biomass and non-condensable pyrolysis gases are fed back to the boiler to be combusted. Thus, both the energy and the mass balances of the boiler and the pyrolysis processes are connected with each other.

In the pyrolysis process the volatile components are extracted from biomass by heating up the solid matter in an oxygen free atmosphere. After the extraction the gaseous pyrolysis product is condensed into a liquid phase. This pyrolysis oil can be used directly to replace heavy fuel oil in industrial processes or as a raw material for upgrading processes to synthesize new hydrocarbon compounds, (Sipil et al., 2007), (Calabria et al., 2005). Research and development of pyrolysis process is surveyed by Bridgwater (1999) and Bridgwater & Peacocke (2000).

Modelling of the pyrolysis process is based on the first principal models of heat and mass transfer and experimental

results about the reaction kinetics. The applied heat transfer model is based on the model presented in Saastamoinen, 2006. The pyrolyzer model used in the study is based on the reactor model developed in a research project with Metso Power described in (Kaivosoja, 2008) and (Kaivosoja and Majanne, 2009).

There is a lot of research work going on about the modelling of combustion of different type of fuels in different type of combustors, e.g. (Scala & Palatino, 2002) and (Galgano et al. 2005). However, the combustion models developed there are seldom connected with the dynamic heat transfer models for water-steam cycle of a boiler. In the dynamic boiler models the combustion process and phenomena in the furnace have often been left for a minor consideration. The heat power released in the furnace is often presented as a simple low order transfer function describing the dynamics caused by the fuel transportation, combustion speed and heat storage of steely heat exchangers bodies. With this kind of approach it is not possible to represent the interconnections between the boiler and the pyrolysis processes, where mass and energy are transported between the two processes effecting on the fuel power and combustion parameters in the furnace.

The boiler model used in the study is based on the circulating fluidized bed boiler model developed in a research project with Metso Power, (Kykk, 2007) and (Majanne and Kykk, 2009). The simulation models are built and run in Matlab/Simulink environment. A moderately complicated combustion model is connected with the water-steam cycle

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model resulting a dynamic boiler model taking account also physical phenomena of the fluidized bed combustion.

The topic of this paper is a simulation study about the dynamic interactions between the two interconnected processes. The final goal is to use the analysis results for process design in order to decouple these two processes from each other and also to develop process control structures for improved disturbance rejection.

The structure of this paper is as follows: Section 2 presents the structure and the operation of the integrated pyrolysis process. Section 3 presents the applied boiler control system and the simulation results. Section 4 concludes the paper.

2. INTEGRATED PYROLYSIS PROCESS

The structure of the pyrolysis process integrated with a circulating fluidized bed (CFB) boiler is shown in Fig. 1.

Fig. 1 The structure of the integrated pyrolysis process. (Kaivosoja and Majanne, 2009)

2.1 Fast Pyrolysis

The function of the pyrolysis process is to produce a maximum amount of condensable organic pyrolysis gas from the biomass fed into the reactor. In the operation point producing maximum oil yield the process is endothermic. Typically 60 70% of the mass of biomass (dry base) is converted to bio-oil, 10 20% to non-condensable gases and 10 20 % char residue. The heat value of the bio oil varies from 13 to 18 MJ/kg and it consists of organic compounds (app 90%) and pyrolysis water (app. 10%). The energy yield of bio-oil is about 50 60% of the energy content of dry biomass.

Heat required for the pyrolysis reactions is introduced to the reactor as hot sand extracted from the fluidized bed boiler. Besides carrying heat power to the process, hot sand particles also improve the heat transfer efficiency from the reactor atmosphere to the biomass. Hot sand and biomass are fed into the reactor together with an inert fluidization gas at the bottom of the reactor. During the turbulent pneumatic transportation in the reactor biomass decomposes into four main components: condensable organic gas, non-condensable gas, water, and charcoal.

The best bio-oil yield is obtained with a high heating rate at reaction temperatures around 500 C (app. 1 sec.) and with short vapour residence time before condensation (typically less than 2 seconds). This type of process is called a fast pyrolysis process. The characteristic features of the fast pyrolysis process usually require small particle size of biomass and rapid condensing of pyrolysis vapours.

On the top of the reactor solids (sand and charcoal) are separated from gases in a cyclone. From the cyclone solids flow through a loop seal to the furnace of the CFB boiler. In the furnace the char coal is combusted and sand and ash are mixed with the boiler bed.

From the cyclone hot pyrolysis gases flow to the condenser, where gas is quenched by cooled pyrolysis oil spray. Condensable components of the gas condense into liquid pyrolysis oil. Non-condensable gases are recirculated as an oxygen free fluidization gas for the reactor. Excessive gas is blown to the CFB boiler to be combusted.

The structure of the dynamic simulation model is depicted in fig. 2. Pyrolysis reactor has been divided into four blocks. The structure of each reactor block is identical. Symbols inside the elements represent the state variables (see Table 1.) of the dynamic model.

Fig. 2 The block diagram of the fast pyrolysis process model. (Kaivosoja and Majanne, 2009)

Biomass

Pyrolysis gas

Fluidizationgas

Condenser

Fluidization gascompressor

Pyrolysis reactor

Circulating Fluidized Bed B

oiler

Cyclone

Cooler

Loopseal

Primary air

Char,

Sand

Non-condensed pyrolysis gas

Boiler Fuel

Combustion gas

Pyrolysis oil

Non-condensedpyrolysis gas

Aerationgas

Cyclone

Condensate

pumpSand

Loopseal

Biomass

Pyrolysis gas

Fluidizationgas

Condenser

Fluidization gascompressor

Pyrolysis reactor

Circulating Fluidized Bed B

oiler

Cyclone

Cooler

Loopseal

Primary air

Char,

Sand

Non-condensed pyrolysis gas

Boiler Fuel

Combustion gas

Pyrolysis oil

Non-condensedpyrolysis gas

Aerationgas

Cyclone

Condensate

pumpSand

Loopseal

Condenser model

totm

,i inx

,n inT

,i kx

,n kT

Pyrolysis reactor model

Cyclone and loopseal model

gasmscrT

oilm

totm gasm

solidm

loopsealT

oilm

fluidgasm

,4ix

,4nT

( )i gasx

gasT

k = elementi = componentn = phase

gasT

cwT

cwm

k = 1

k = 2

k = 3

k = 4

,i kx

,n kT

,i kx

,n kT

,i kx

,n kT

Condenser model

totm

,i inx

,n inT

,i kx

,n kT

Pyrolysis reactor model

Cyclone and loopseal model

gasmscrT

oilm

totm gasm

solidm

loopsealT

oilm

fluidgasm

,4ix

,4nT

( )i gasx

gasT

k = elementi = componentn = phase

gasT

cwT

cwm

k = 1

k = 2

k = 3

k = 4

,i kx

,n kT

,i kx

,n kT

,i kx

,n kT


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Substances flowing in the pyrolysis process have been divided into three phases: sand, biomass, and gas. These phases are divided into ten components presented in a table 1. Dashed arrow represents evaporation of moisture during drying of biomass and solid arrows represent pyrolysis of active material into pyrolysis products.

Table 1. Phases and components.

Total modelled mass flow totm is supposed to be equal in all the elements of the reactor. It can be calculated as a sum of sand, biomass and fluidization gas feeds.

Mass balances of the components xi of the active material mact and pyrolysis products in the block k are:

,, , , 1 , ,i ktot k tot k i k i k i v act kdxm m x x y k mdt . (1) The reaction rates of the pyrolysis reactions are defined by the Arrhenius expression:

e uE R Tvk A . (2)

Calculation of experimental kinetic parameters A and E are presented in Lehto (2007). Parameters yi define the composition of the pyrolysis products. Values vary with reaction temperature according to Bridgwater (1999). Values of yi are between zero and one, and their sum must be exactly one.

According to Milosavljevic (1996), the reaction enthalpy qpyr of pyrolysis reactions can be expressed as a function of char yield ychar:

538 2000pyr charq y . (3) More detailed description of the process and dynamic model equations are presented in (Kaivosoja and Majanne,2009)

2.2 Circulating Fluidized Bed Boiler

A dynamic model of the CFB boiler consists of an air-flue gas process consisting of air preheaters, furnace, and heat exchangers and a water-steam process consisting of water preheaters (economizers), drum, evaporator, superheaters,

and attemperators. In addition steam pressure, steam temperature, and feed water control loops are included in the model. The model is based on the mass, energy, and momentum balances together with physical behaviour of heat transfer, reaction kinetics etc. The structure of the CFB furnace is represented in Fig. 3. In the model the furnace is divided into nine blocks.

Fig. 3. CFB boiler structure (Majanne and Kykk, 2009).

In the CFB boiler combustion takes place in a fluidized sand bed circulating around the furnace hot loop. Bed sand and fuel comprise a solid matter suspension. Combustion and heat transfer efficiencies depend on the mass of the circulating bed and the local suspension density in the furnace.

The suspension density varies as a function of the height in the furnace and the amount of the fluidizing air. The fluidizing air flow is a nonlinear function of the boiler load. Static suspension density profile as a function of the furnace height h is described by an experimental equation

h f h , (4) where (h) is a suspension density at height h, is a scaling factor and f(h) is the fitting function for the density profile (Breitholtz et al, 2001).

, , ,tot below aboveKh ah Khsusp x susp exit susp exitf h e e e , (5) where susp,x is the suspension density at the bottom of the furnace, susp,exit is the suspension density at the top of the furnace, htot is furnace height, a and K adjusting parameters for the density profile below and above point h, h below and habove furnace heights below and above point h. Values for susp,x, susp,exit, a, and K were determined by the process experiments as a function of primary air mass flow.

Inert fluidization gasxfluidgas,k

Moisture (steam)xsteam,k

Pyrolysis water (steam)xpyroH2O,k

Non-condensable pyrolysis gasxnoncond,k

Organic condensable pyrolysis gasxcond,k

Tgas,k

Charxchar,k

Active raw materialxact,k

Moisture (water)xwater,k

Ashxash,k

Tbio,k

Sandxsand,kTsand,k

Component i

Mass fraction xof component i in element k

Temperature Tof phase nin element k

Inert fluidization gasxfluidgas,k

Moisture (steam)xsteam,k

Pyrolysis water (steam)xpyroH2O,k

Non-condensable pyrolysis gasxnoncond,k

Organic condensable pyrolysis gasxcond,k

Tgas,k

Charxchar,k

Active raw materialxact,k

Moisture (water)xwater,k

Ashxash,k

Tbio,k

Sandxsand,kTsand,k

Component i

Mass fraction xof component i in element k

Temperature Tof phase nin element k

Primary air

Secondary airFuel feed1

2

3

4

5

6

7

8

9

Flue gas

Cyclone

Solidsreturn

leg


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During the transients caused by the change of the primary air flow the dynamics of the change of the density profile is determined as

1, , ,d h t h t f h tdt , (6) where is a time constant. The combustion model is suitable for different types of fuels. The quality of the fuel is parameterized by the elemental composition of the fuel, moisture, proportion of volatile matter, ash content, upper heat value of charcoal, and upper heat value of dry fuel. The combustion model describes the vaporization and combustion of volatile mater and combustion of charcoal.

Combustion of volatile matter is modelled by an experimental equation

, , 2,Nvol

vol k vol vol k O km k y x , (7) where mvol,k is the amount of reactive volatile components in element k, kvol is a reaction speed, yvol,k is a mass proportion of volatile matter, xO2,k is a mole fraction of oxygen in element k, and Nvol is an order of the reaction.

Combustion of charcoal is divided into combustion of big and fine particles. Big particles are attritted into fine ones due to the grinding effect between solid particles in the fluidized bed. Combustion of big particles is constrained by diffusion of oxygen and combustion of fine particles is constrained by reaction speed (Borman, 1998). Combustion speed tc for big particles is

2

23c c

ci O

dtD Sh

, (8)

where c is a char density, dc is a particle diameter, Di is a molecular diffusion coefficient from oxygen to nitrogen, O2() is oxygen density far from the particle surface, and Sh is Sherwood number.

For fine particles combustion speed tcf is

21,5f f

cfc O

dt

k

, (9)

where f is fine char density, df is fine char particle diameter, kc is kinetic reaction speed factor determined by Eq. (2).

Solid matter and flue gases are separated from each other in the cyclone. Hot flue gases are flown further to the convective heat transfer section consisting of evaporators, superheaters and preheaters.

Solid matter consisting of bed sand, ash and unburned fuel is returned back to the bottom of the furnace via cyclone and a loop seal. The function of the loop seal is to prevent counter current gas flow through the return leg to the cyclone. Block diagrams of the flue gas and water side models are shown in figs. 4 and 5. More detailed description of the process and the dynamic simulation is presented in (Majanne and Kykk, 2009).

Fig. 4 The block diagram of the CFB boiler flue gas side model.

Fig. 5 The block diagram of the CFB boiler water side model.

2.3 Interconnections of Engaged Processes

The pyrolysis and the boiler processes are connected together by mass and energy balances. Thermal energy required by the pyrolysis reaction is extracted from the boiler process as app. 800C hot sand taken from the return leg of the furnace hot loop. In the pyrolysis reactor the required amount of hot sand is mixed with biomass to maintain the optimal 500C temperature in the reactor.

Sand and char are returned from the reactor to the boiler. This return flow effects on the energy and mass balances of the boiler. Returned sand is cooling the furnace because sand temperature is app. 400C below the furnace temperature. On the other hand the returned charcoal has a high energy content, app. 32 MJ/kg, effecting on the released thermal power in the furnace. Approximately 40 % of the energy content of the pyrolyzed biomass is contained in the remaining charcoal. It should also be taken into account that in case of some disturbance in the pyrolysis process all the biomass fed in the reactor might go unprocessed through the reactor to the boiler.

After the reactor pyrolysis gases are condensed into a liquid phase in the condenser. Some light hydrocarbon compounds of the pyrolysis gas are non-condensable in the process

ELEMENT 1

Fuel (amount +properties)

Refractorytemperature

Recirculationgas

ELEMENTS 2 - 9

O2 +flue gases

Volatiles,charcoal

Elementtemp.

Mixingof sand

CYCLONE

Heat powerto wall

Heat powerto wall andradiationsuperheaters

O2 +flue gases

Volatilescharcoal

Element 9 temp.

Sandflow

Heat powerto wall

FLUE GASDUCT

AIRPREHEATER

LOOP SEALSand temperature

Sand flow

Primary air

Secondary air

Cyclone temperature

Sand flow


Refractoryand tubetemperature

Tubetemperature

Heat powerto preheater

Flue gase flow

Flue gase tempConvective superheaters

and economizer tubetemperatures

Heat power to conv.superheaters and

economizer

DRUM

EVAPORATOR,REFRACTED WALL

EVAPORATOR,NONREFRACTED

WALL

FEED WATERPREHEATER

Down comer flow

Drum water enthalpy

Water-steammixture enthalpy


Steam quality

Tubetemperature

Water-steammixture enthalpy

Water-steammixture density

Steam quality

Feed water flow

Feed water enthalpy

Heat power

TubetemperatureFeed water flowFeed water enthalpy

Drumpressure

Steam flow to primarysuperheater


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atmosphere, e.g. CO, CO2, C2H6(ethane) and C2H4(ethylene). This non-condensable gas fraction is recirculated and used as an oxygen free fluidizing gas for the reactor (Fig. 1). However, those non-condensable gases are produced all the time while running the process and the excessive amount of gases is fed into the furnace of the boiler. This gas has combustible components effecting on the energy balance of the boiler. Gas flow effects also on the mass balance of the flue gas flow of the boiler. Disturbances in the returned gas flow effect on the convective heat transfer, furnace pressure and further to the combustion air flow. Furnace pressure measurements are typically connected with the boiler safety automation and because of this connection, disturbances in the furnace pressure may lead to boiler shut down.

3. BOILER CONTROL

The operation of the integrated pyrolysis process system must be designed so that start ups, shut downs and disturbances in the pyrolysis process will not cause major problems in the operation of the boiler. The boiler process is anyway the main process generating heat and power for the customers on-line. Thermal power of the pyrolyzer must be scaled with the thermal power of the boiler so that disturbances originated from the pyrolyzer can be stabilized by the boiler control system. Normal start ups and shut downs of the pyrolyzer can be operated smoothly so that the boiler control system can easily compensate these disturbances. The two worst cases are the tripping of the pyrolyzer running full load and if the biomass is blown unprocessed through the pyrolyzer into the boiler.

The function of the combustion control is to feed a required amount of fuel and combustion air into the boiler furnace. The required fuel power is determined by the boiler master controller according to the generated power or steam pressure demand. The controllable part of the fuel power is fed into the furnace by the fuel feeders and the rest is coming from the pyrolysis process. The required combustion air flow is calculated from the total fuel flow into the boiler and trimmed by a flue gas oxygen content controller.

In order to stabilize the operation of the boiler measurements from the pyrolysis process must be included to the boiler control scheme. Operation state of the pyrolyzer must be connected with the boiler fuel feed, combustion air, steam temperature, and furnace pressure controls. The easiest way to include the interactions between the pyrolyzer and the boiler is to apply filtered feed forward signals from the biomass feed of the pyrolyzer and non-condensable gas flow to the boiler controls. The ideal transfer function Gff_ideal for the feed forward control is

_d

ff idealp

GG

G

, (10)

where Gd is the disturbance transfer function from the fuel power coming from the pyrolyzer to the boiler power and Gp is the transfer function from the boiler fuel feed to the boiler power. In the following simulations only static feed forward transfer function is applied because the dynamics of the fuel flows from the pyrolyzer and from the fuel feeding system to the boiler are very similar and fast compared with the

dynamics of the heat transfer process from the furnace to the evaporator.

In case of the pyrolyzer trip the heat power released by the charcoal and non-condensable gases must be replaced by the primary fuel feed as quickly as possible. By adding the feed forward signals to the power control loop, speed of the primary fuel feeders can be increased immediately after the pyrolyzer fuel feed is stopped. Feed forward signals are applied also in the steam temperature and furnace pressure controls.

Fig. 6 shows open loop responses from the pyrolyzer trip to the generated steam power in three cases, where the thermal capacity of the pyrolyzer is 1/3, 2/3 and 1/1 of the thermal power of the boiler. The controllable fuel feed to the boiler is kept constant during the simulation runs.

Fig. 6. Effect of the pyrolyzer thermal capacity compared with the boiler capacity to the generated steam power during the pyrolyzer trip.

Fig. 7 shows the closed loop responses from the pyrolyzer trip to the generated steam power with the same three different size pyrolyzers. Combustion control loop with feed forward signals from the biomass feed to the pyrolyzer and non-condensable gas flow to the furnace stabilizes generated disturbances quite satisfactorily.

Fig. 7. Effect of the pyrolyzer size to controlled steam power during the pyrolyzer trip.

50 60 70 80 90 100 110 120 130 140 150 16060

70

80

90

100Steam power

%

Time, min

1/1 2/3 1/3

50 55 60 65 70 75 80 85 90 95 10096

97

98

99

100Steam power

%

Time, min

1/12/31/3


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Fig. 8 shows the performance of the feed forward compensation in the steam pressure control during the trip of the pyrolyzer. The thermal capacity of the pyrolyzer is 1/3 of the thermal power of the boiler. The first case depicts the control response with no feed forward compensation. In the second case the feed forward information is connected to the controller and the maximum rate of the change of the fuel feed is limited to 10%/min. In the third case the rate of the change of the fuel feed is unlimited.

Fig. 8. Performance of the power control loop of the boiler without feed forward information (- - - -), with feed forward and limited rate of change of fuel feed (____), and with feed forward and unlimited rate of change of fuel feed (----).

4. CONCLUSIONS

Fast pyrolysis is a novel process for converting solid bio mass to liquid form to replace heavy fuel oil or as a raw material for refinery processes to produce higher value bio fuels like bio diesel. Dynamic simulation has been used to help designers to evaluate different options in process structures and control principles of this new process. A very important point of view is how this new process interacts with the interconnected power boiler. The primary function of the power boiler is, however, power generation, not to run pyrolysis process. The important issues to be considered are the disturbance propagation from the pyrolyzer to the boiler and the requirements for the operation range of the boiler to produce enough hot sand for the pyrolysis process. Optimal scaling of the power ratio between the pyrolyzer and the boiler is required to result stable operation of the boiler and maximum yield of the bio-oil.

This paper presented some results gained in the research project with Metso Power and Tampere University of Technology. This project is a part of the long term research work dealing with dynamic modelling of different type of fluidized bed boilers and new processes for production of bio energy.

5. REFERENCES

Borman, G.L. & Ragland, K,W. (1998). Combustion engineering. Singabore 1998, McGraw-Hill Inc. 613 p.

Breitholtz, A., Leckner, B. & Baskakov, A.P. (2001). Wall average heat transfer in CFB boilers. Powder Technology 120(2001), pp. 41-48.

Bridgwater, A.V. (1999). Principles and practice of biomass fast pyrolysis processes for liquids. Journal of Analytical and Applied Pyrolysis, 51(12):322.

Bridgwater, A.V. and Peacocke G.V.C. (2000). Fast pyrolysis processes for biomass. Renewable and Sustainable Energy Reviews, 4(1):173.

Calabria, R., Chiarello, F., De Bellis, V., Massoli, P. (2005). Combustion Fundamentals of Pyrolysis Oil Based Fuels, Instituto Motori CNR, Napoli, Italy.

Galgano, A., Salatino, P., Crescitelli, S., Scala, F. & Maffettone, P.L. (2005). A model of the dynamics of a fluidized bed combustor burning biomass. Combustion and flame Vol.140, No.4, pp. 271284.

Kaivosoja J. (2008) Modeling and Control of Pyrolysis Process Integrated with Circulating Fluidized Bed Boiler. Master of Science Thesis (in Finnish), Tampere University of Technology, Institute of Automation and Control. Tampere 2008

Kaivosoja J and Majanne Y. (2009) Dynamic Modeling and Simulation of Fast Pyrolysis Process Integrated with Circulating Fluidized Bed Boiler. Proceedings of IFAC Symposium on Power Plants and Power Systems Control, 5-8.7.2009, Tampere, Finland

Kykk P. (2007) Dynamic modeling of the circulating fluidized bed boiler. Master of Science Thesis (in Finnish), Tampere University of Technology, Institute of Automation and Control. Tampere 2007

Lehto, J. (2007). Development and Characterization of Test Reactor with Results of Its Application to Pyrolysis Kinetics of Peat and Biomass Fuels, Dissertation, Tampere University of Technology, Publication 665.

Majanne, Y. and Kykk, P. (2009) Dynamic model of the circulating fluidized bed boiler. Proceedings of IFAC Symposium on Power Plants and Power Systems Control, 5-8.7.2009, Tampere, Finland.

Milosavljevic, I., Oja, V., Suuberg, E.M. (1996). Thermal effects in Cellulose Pyrolysis: Relationship to Char Formation Processes, Industrial & Engineering Chemistry Research, 35(1996), 653-662.

Saastamoinen, J.J. (2006). Simplified model for calculation of devolatilization in fluidized beds, Fuel 85, 23882395.

Scala, F. & Salatino, P. (2002). Modelling fluidized bed combustion of high-volatile solid fuels. Chemical engineering science, Vol. 57, pp. 1175-1196.

Sipil, E., Vasara, P., Solantausta, Y., Sipil, K. (2007). Feasibility and market potential of pyrolysis oils in European pulp and paper industry, Proceedings of the 15th European Bioenergy Conference and Exhibition, Berlin.

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N

+1

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Feed forward control with limited rate of changeFeed forward control with unlimited rate of changeControl with no feed forward


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Modeling and Simulation of Interconnected CFB-boiler and Fast Pyrolysis

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