THE CHALMERS GASIFIER

ASSESSMENT OF THE MASS AND ENERGY FLOWS IN THE CHALMERS GASIFIER Anton Larsson 1,2*, Martin Seemann 1,3, Henrik Thunman 1,4 1 Division of Energy Technology, Chalmers University of Technology, SE-412 96 Göteborg, Sweden, Tel. +46 (0)317721000 Fax. +46 (0)317723592 2 anton.larsson@chalmers.se, 3 martin.seemann@chalmers.se, 4 henrik.thunman@chalmers.se *corresponding author Abstract This work assesses the performance of the Chalmers gasifier using wood pellets as fuel and steam as fluidization medium. The Chalmers gasifier is an indirect bubbling fluidized bed gasifier in the size of 2-4 MW th connected to 12 MW circulating fluidized bed. The focus of the work has been on how the conversion of char effects the performance of the gasifier. The char conversion was altered by changing bed temperature in the gasifier and two temperature cases are presented here. Char conversion increased with temperature from 1% mass to 25% mass and at the same time the chemical efficiency increased from 60% to 70% based on lower heating value of dry fuel. Unconverted char is burnt in the combustor to produce heat that should coincide with the internal heat demand of the system. The different contributions to the internal heat demand are investigated and approaches to reduce this demand and increase the performance of the gasifier are discussed. Keywords: Gasification, Biomass conversion 1. Introduction Biomass gasification has in recent years experienced an increasing interest, with dual fluidized bed systems as one of the most promising reactor systems. At Chalmers, a dual fluidized bed gasifier has been built by redirecting the circulating bed material flow from a 12 MW Circulating Fluidized Bed (CFB) boiler [1] through one particle seal to a new reactor followed by a second particle seal before it is returned back to the original boiler, see Fig 1. The two particle seals and the new reactor are fluidized with steam. This reactor is, here on, referred to as the Chalmers gasifier and is able to gasify between 2-4 MW biomass. In this setup the heat for the gasification process is transported from the combustor via the bed material and a high-calorific as well as a nitrogen-poor product gas is produced. The Chalmers gasifier and the potential of the concept of retrofitting fluidized bed boilers with a biomass gasifier are presented elsewhere, e.g. Thunman et.al [2] and Seemann and Thunman [3]. Several dual fluidized bed boilers exist around the world with the gasifier in Güssing [4] being the most famous example. The major difference between Chalmers gasifier and these other installations is the amount of biomass added to the combustor for heat production. This enables a much more flexible process and allows investigations of the gasification process in a broader operating range as the heat balance for the operation always can be fulfilled. In the present work the heat and mass balances and the performance of the Chalmers gasifier are presented for two different operating temperatures using wood pellets as fuel. The various in- and outgoing flows are quantified and possible adjustments to optimize the system are discussed. The energy flows are illustrated based on the thermal and chemical energy of the mass flows of the

Chalmers gasifier. The approach applied for the illustration is similar to the one proposed by Niklasson et al [5]. The aim of this work was to estimate the char conversion and internal heat demand of the process to investigate how the performance could be improved. 2. Theory The mass and energy flows through the gasifier are investigated to describe the conversion of the fuel. From the measurements made of the considered flows of the gasifier, sufficient information was obtained to fulfill the mass balance through a system of equations. 2.1 Mass balance The in and the outgoing flows for the mass balance of the Chalmers gasifier are summarized in Fig 2. The available measurement data and the values that can be estimated are the following: 1. Raw gas: The raw gas is the desired product from the gasifier and the information required for the heat and mass balance are the composition of the permanents gases and of the condensables (water and tar) as well as the mass flow. To analyze the composition of the raw gas, a slip stream of gas is extracted from the main flow. The permanent gases are separated from the condensable compounds by lowering the temperature from 450 o C to around 7 o C in a scrubber, where isopropanol is used as scrubbing agent. After the scrubber the gas is further cooled down to -2 o C. The condensable compounds are collected and measured gravimetrically. Sequentially the amount of dry gas is measured with a volume meter. The fraction of condensables in the raw gas is then calculated. The concentrations of permanent gases H2, CO, CO2, CH4, C2H2, C2H4, C2H6 and N2 in the dry gas are measured with a micro Gas Chromatograph (GC). The condensable compounds consist mainly of water. However, a non negligible part consists of higher hydrocarbons, which usually are referred to as tar. The amount of tar is measured by solid phase absorption (SPA) [6], where a defined volume of raw gas is extracted and the tar is absorbed on a solid absorber. Thereafter, the absorbed tar is analyzed with a GC to get an estimate of the total amount as well as the composition of the tar. For the mass flow of the raw gas only a rough estimate is available. This is calculated from the increase in the concentration of nitrogen generated by an injection of a known amount of nitrogen. However, this estimate has been shown to be rather uncertain and, therefore, the mass flow presented in this work is calculated from the mass balance across the gasifier. Figure 1. Illustration of the system setup before (to the left) and after the reconstruction (to the right).

2. Char: A fraction of the char will leave the gasifier unconverted and follow the bed material to the combustor. To close the mass balance the amount and composition of the char need to be estimated. The mass flow of char is in this work calculated from the mass balance. In the Chalmers gasifier the calculated flow can be compared with the out flowing fraction of char leaving the gasifier obtained by extracting bed samples from the second loop seal. The composition of the char can be analyzed from extracted samples. However, it is quite stable at the investigated temperatures and thus, the composition used in this work are taken from literature data [7]. 3. Leakage: To avoid raw gas to penetrate by diffusion into the solid fuel feeding system, there is a need to have a counter flow of gas, a flow that will enter and dilute the raw gas. If the end use of the raw gas is biofuel production, this gas should be free of nitrogen; e. g. carbon dioxide could be used. Further, the gas should also be used to evacuate the air between the fuel particles higher up in the fuel feeding system. In the Chalmers gasifier an operation with carbon dioxide are not economically feasible and instead dry flue gases are used. However, as the main purpose of the Chalmers gasifier is to be a research unit for the gasification process a dilution of the product gas with nitrogen has no significant influence for the addressed research questions. During the experimental runs presented in this work, one of the rotary valves was slightly damaged resulting in an unwanted and uncontrolled smaller leakage of air into the gasifier. Hence, the name leakage is used for the associated flow. The relation between the air and flue gases in the leakage flow is estimated to 4:1. The mass flow of leakage is derived from the mass balance. 4. Steam: During the experiments the gasifier and the two particle seals are fluidized with pure steam and the mass flow to the three units are measured separately. However, the steam flow to each particle seal could either go into the gasifier or back to the boiler. Therefore, a dedicated experiment with nitrogen used as tracer was conducted. This indicates that the steam follows the bed material and consequently it is assumed that all steam entering the first particle seal goes to the gasifier and all steam entering the second seal goes into the boiler. 5. Fuel feed: The mass flow of the fuel fed to the gasifier is calculated from the continuously measured mass decrease of the fuel silo and the composition of the fuel is given form a standard fuel analysis. In summary, to fulfill the mass balance of Chalmers gasifier all necessary compositions are known, together with the mass flow of fuel and steam. The mass flows of raw gas, char and leakage though, are unknown. However, enough information is available to calculate these flows from the following described system of equations. The overall mass balance of the gasifier is defined as: (1) or based on each of the elemental components, i=c, H, O and N: (2)

where m is the mass flow per kg of dry fuel and Y is the mass fraction. The index fuel stands for fuel as received, steam in for the steam feed to the gasifier, leak for leakage, raw for raw gas, tar for tar and char out for unconverted char leaving the gasifier. Further, as both the composition and mass flows are known for the fuel and steam, these can be lumped together to a single flow in the calculations. The unknown mass flows can then be expressed by the mass fraction of leakage,, and the mass fraction of char, : (3) (4) (5) where the index fuel and steam stands for fuel and steam lumped together. Applying Eqs (3-5), Eq 2 can be rewritten as: (6) Figure 2. In- and output flows Chalmers gasifier Figure 3. Elemental composition of lumped in- and outputs

This gives two input flow terms, left hand side Eq 6, and two output flow terms, right hand side Eq 6. In Fig 3 typical elemental compositions for each of these four terms are illustrated. When applying Eq 6 for each of the ingoing elements (C, H, O and N) a system of four equations, with two unknowns is achieved hence, the system is over defined. The system of equations is solved by the least square method, yielding the 1 and 2 values for each investigated case. As the system of equations is over defined the influence of the errors in the individual measurements and estimates can be reduced and the resulting values of 1 and 2 correspond to the mathematically most correct solution. The resulting mass flows are, thereafter, given by the known mass flow of fuel and steam together with Eqs (1) and (6): (7) 2.2 Energy Flows When the mass flows are known, the energy flows through the gasifier can be estimated from the inand outgoing temperatures and lower heating value of gas, liquids and solids. The energy flows are given by: 1. Raw gas: (8) with i =H 2,CO,CO 2,CH 4,C 2 H 2,C 2 H 4,C 2 H 6,N 2,H 2 O and tar. And for dry raw gas:, (9) with i =H 2,CO,CO 2,CH 4,C 2 H 2,C 2 H 4,C 2 H 6 and N 2 2. Char: (10) 3. Leakage: (11) 4. Steam: The energy stored in the fluidizing steam, Q steam in, and heat needed to raise the temperature of the ingoing steam to the raw gas temperature inside the gasifier Q steam,gasif : (12)

(13) 5. Fuel: The energy stored in the fuel, Q fuel, and the energy required to evaporate and heat the fuel moisture, Q moisture, is given by: (14) (15) Where Q is the energy flow, LHV is the lower heating value, T is the temperature, c p is the specific heat capacity and H is enthalpy. The index char,heat stands for the sensible heat in char, steam,gasif for steam inside the gasifier, fuel,dry for dry fuel and evap for evaporation. Following properties have been used to estimate the energy flows: Enthalpy of permanent gases and the steam is calculated from polynomial correlations [8]. The specific heat capacity of the tar estimated to be equal to the one of Benzene: 1.0 kj/kgk. The heating value of all the tars was estimated to be the same as the average heating value of identified tar compounds in the measured tar samples: 39.5 MJ/kg tars. Heating value of the fuel from fuel analysis is presented in Table 2, and specific heat of the dry fuel was calculated according to [9]: Char was assumed to have the properties of graphite and the heating value was calculated from the enthalpy of formation to 32.8 MJ/kg. Specific heat capacity [9]: The char is assumed to leave the gasifier at the same temperature as the bed material. To evaluate the performance and efficiency of a dual fluidized bed gasifier critical parameters are the required energy for heating, drying and devolatilization of the fuel. This is the minimum amount of heat that needs to be transported to the gasifier by the circulating bed material. In addition, there is a need for heat to raise the temperature of the fluidizing media and, if the system shall be optimized for gas production, heat to gasify the part of the char not needed in the combustor for heat production. The additional heat for the gasification reaction C+H 2 O CO+H 2 is given by: (16) (17) (18) where n char is the amount of mol char gasified, T bed is the average temperature of the bed and h reaction is the change in the enthalpy of formation. In order to evaluate the overall efficiency of the process the heat requirement of the combustor also needs to be taken into account. The heat demand required to heat the char and air in the combustor is calculated as: (19)

where is the air to fuel ratio. The index flue stands for flue gas, comb for combustion and air for combustion air. The heat needed for the combustor is in present work estimated by the energy needed to heat the combustion air from 25 o C to the outlet temperature of the combustor. The air to fuel ratio is set to 1.2. The total heat demand to the process is given by: (20) The heat needed to be transported from the combustor to the gasifier is given by: (21) which also is given by: (22) where Q pyro includes the energy needed to heat and convert the volatile part of the dry fuel. By setting Eqs 21 22 equal to each other Q pyro can be estimated. The theoretical max of the chemical efficiency for a standalone gasifier, ɳ max standalone, is estimated by assuming: The fuel is dried externally, the air to the combustor is preheated to the temperature out of the combustor, the steam is preheated to the temperature of the bed in the gasifier, no heat loss and the tar is burnt for heat production in the combustor: (23) (24) where need,min stand for the minimum internal heat demand. The optimized char conversion is given by: (25) For a gasifier with an abundance of heat available from the combustor, essentially all of the char could be converted. The maximal chemical efficiency of the fuel fed to the gasifier, ɳ max,gasif, is then given by: (26) 3. Experimental conditions In this work two operating conditions representing a high and a low gasification temperature has been evaluated. The operational parameters for the two cases are summarized in Table 1. The temperature was changed while the other parameters were kept as stable as possible. Wood pellets (Ø8mm) with a fuel analysis according to Table 2 were used as fuel in both cases.

Table 1. Summary of operational parameters Operational parameters Case: Low T Case: High T Mass flow fuel 387 (kg/h) 384 (kg/h) Mass flow steam 253 (kg/h) 253 (kg/h) Average bed temperature 777 ( o C) 831 ( o C) Raw gas outlet temperature 718 ( o C) 766 ( o C) Bed material Silica sand Silica sand Circulating flow of bed material ~11000 (kg/h) ~14000 (kg/h) Combustor, max temperature 832 ( o C) 871 ( o C) Table 2. Fuel composition by proximate and ultimate analysis Moisture (as received) Char (dry) Volatiles (dry) Ash (dry) Proximate, % mass 7.3 18.6 80.9 0.5 Carbon (daf*) Hydrogen (daf*) Oxygen (daf*) Others Ultimate, % mass 50 6 43,4 Negligible *daf stands for dry ash free 4. Results and Discussion The mass balance was used to calculate the mass flow of raw gas, char and leakage as presented in Table 3. These mass flows have been used for the calculation of the char conversion and for the analysis of the fuel conversion. The composition of the gas is affected by the temperature and in Fig 4 the gas composition, yield of gas per kg of dry fuel and the lower heating value of the gas normalized by the lower heating value of the fuel is presented. On molar basis small differences can be seen with a minor increase of H 2 and CO 2 at higher temperature as a consequence of the water gas shift reaction. On the basis of kg per kg dry fuel an increase of the gas yield can be seen at higher temperature. The increase is due to the more extensive gasification of char at higher temperatures, also indicated by an increase of CO and CO 2, and due to more water gas shift reaction. Further, by looking at the lower heating value of the gas species an increase of the hydrogen can be seen as well. It can also be noticed that roughly half of the energy in the product gas is stored as methane and light hydrocarbons. Only rough estimates of the tar content, 30g/Nm 3, are available for the two cases. Figure 4. Composition of dry gas for low T case (to the left) and high T case (to the right) based on molar ratio Bar 1, mass ratio Bar 2 (kg/kg dry fuel) and Energy Bar 3 (MJ/MJ dry fuel).

The fuel conversion can be described through the energy stored in the fuel and gas at the different stages of the fuel conversion. In Fig 5 the stored energy for the high and the low temperature cases are illustrated, where stored energy is represented by the sum of the lower heating value and sensible heat of the fuel and the gas, normalized by the lower heating value of the fuel at reference condition (25 o C), in accordance to [5]. The conversion process is divided into ten steps where the initial point (1) represents the fuel at ambient temperature (25 o C). Step 1-2; the fuel is heated to 100 o C. Step 2-3; evaporation of the fuel moisture. Step 3-4; fuel and evaporated moisture are heated to the temperature at which the steam is injected. Step 4-5; heat stored in the steam injected as fluidization media (heat of evaporation plus the sensible heat of the steam at injection temperature per MJ of dry fuel). Step 5-6; fuel, evaporated moisture and steam are heated to the temperature at which the gas leaves the gasifier, during this step the fuel is devolatilized and at the late stage some of the char is gasified. Step 6-7; the char leaves the gasifier at bed temperature. Note: this temperature is slightly higher than the temperature at which the gas leaves the gasifier (the temperature shown in Fig 5). Step 7-8; recoverable heat without risk for condensation of tars on heat transfer surfaces. Step 8-9; sensible heat which possible can be recovered, but the level of recovery will depend on the composition and the amount of tars in the raw gas. Step 9-10; represent the chemically energy stored in the tars (9 to t) and sensible heat of the tar and the steam (t to 10). Both the tars and the water will condense in a wide temperature range, here, for illustration, the condensation takes place at a single temperature. Step 10-11; sensible heat in dry gas from condensation to reference temperature. Figure 5. Thermal and chemical energy in the fuel and gas during the fuel conversion. The high T case had a bed temperature of 830 o C and a raw gas temperature of 766 o C. The low T case had a bed temperature of 780 o C and a raw gas temperature of 718 o C.

Table 3. The mass flows calculated through the mass balance as well as the resulting char conversion. Case: Low T Case: High T Raw gas 625 (kg/h) 640 (kg/h) Raw gas, dry 306 (kg/h) 335 (kg/h) Char 65 (kg/h) 50 (kg/h) Leakage 55 (kg/h) 55 (kg/h) Char conversion 1% 25% The final position point 11 represents the resulting energy chemically stored in the dry raw gas at reference temperature. The bars to the right in Fig 5 represent the chemical energy stored in the raw gas, char and tar leaving the gasifier respectively. The bar representing char includes both the sensible heat and the chemically stored energy as both is utilized on the combustion side of the system. The differences between the high and low temperature cases, which can be observed already after position 5 in Fig 5, raise a number of questions: How does the chemical efficiency change with the temperature in the gasifier, Point 11 and, is this change related to the gas composition and yield? What is the explanation for the difference in the slope between point 5 and 6 for the two cases? Does the energy in the unconverted char (point 7 - point 6) meet the internal heat demand ((point 6 point 1) (point 5 point 4) or Eq 22) for the two cases? How does the water consumption change and is the difference equivalent to the amount of water consumed by char gasification? Chemical efficiency: In Fig 6 the chemical efficiency calculated on dry fuel basis for the High T and Low T cases (the two cases presented in Fig 5 are highlighted by filled dots). It can be seen that the chemical efficiency increase with temperature which is a result of the increased gas yield shown in Fig 4. An enhancement of the water gas shift decrease the efficiency slightly as it is an exothermic reaction. Figure 6. Chemical efficiency based on lower heating value of dry fuel for different temperatures. The filled markers are the Low T and High T cases treated in present work; and the unfilled markers represent additional measurements.

Difference in the slope: For the High T case a higher energy level is reached at point 6 implying that more heat has been stored up in the gas, see Fig 7 which is a close up of point 6 in Fig 6. The main explanations for this are; the gas is heated to a higher temperature and more char is gasified. The gasification reaction is endothermic and consumes heat from the bed according to Eq 18. These effects explain the difference with a deviation of less than 1% of the lower heating value of the fuel. Further, aspects such as increase of heat transfer through radiation from the bed to the gas, heat loss from the reactor, more water gas shift reaction and other gas phase reaction have minor effect on the difference between these two points. Unconverted char and heat demand: In Fig 8 the energy stored in the char is compared with the internal (Eq 20) and external (Eq 12) heat demand of the process. For the low T case it can be seen that much more energy is transported as unconverted char to the combustor than what is needed to cover the internal heat demand. For the high T case the internal heat demand is greater than the energy in the unconverted char. However, if the tar (quantified in Fig 5) is entered into the combustor for heat production the high T case would be more or less balanced. It can also be seen that the heat needed to convert the fuel (Eq 22) or (point 6 point 1) (point 5 point 4) in Fig 5 increases for the high T case, as a result of the gasification reactions. The decreased amount of char also results in a decreased heat demand for the combustion air (Eq 19). In Fig 8 it is also possible to see the considerable amount of heat required for production of steam used in the process (Eq 12) and heat needed in the gasifier to raise the temperature of the steam (Eq 13). The external heat demand should preferably be covered by heat exchanging with flue gas from the combustor and raw gas from the gasifier. Water consumption: In Fig 9, the amount of water added to the gasifier as moisture, steam in volatiles and fluidization steam is compared with the measured amount of steam in the raw gas. Water is one of the products of the volatiles and literature data [7] show that the amount of water produced varies between 5-20% mass of the ingoing dry fuel. To quantify the potential steam amount from the volatiles a value of 15% mass is assumed. Further, in Fig 9 it can be seen how the amount of steam in the raw gas decreases with higher temperature. However, the amount of consumed water is considerably smaller than the amount added to the process. Most of the condense water could be reused to produce the steam but the remaining part should be entered to the combustor and that is another reason to minimize the water fed to the gasifier. The decrease of water in the raw gas between the two cases is equivalent to a certain quantity of char gasified. An estimate is that the measured decrease of water between the two cases answers for more than 60% mass of the difference in amount of char converted. The remaining reduction of the char can have several explanations, such as inaccuracies in the measurements. Another explanation could be a reduced amount of primary produced char as a result of the higher temperature. Figs 8 and 9 reveal possibilities to optimize the process for gas production by reducing the amount of steam and thus, decreasing the internal heat demand. A lower heat demand allows more char to be gasified which in turn increases the chemical efficiency. Other alternatives to reduce the internal heat demand are: predrying of the fuel, preheating the fluidizing steam of the gasifier to a higher temperature and preheating of the air to the combustor. By doing so the process could be further optimized for gas production.

Figure 7. A close up in of Fig 5 where the points 6a and 6b represents point 6 for the Low T and High T cases respectively. The line from 6a to I represents the heating of the gas from the low to the high temperature. The line between I-II represents the increase in energy stored in the gas due to gasification of char (Eq 18). Figure 8. The chemical energy stored in char (bar 1) compared with internal (bar 2) and external (bar 3) heat demand Eqs 8-15, 18-22 for the low (to the left) and the high (to the right) temperature case. The dotted line represents the energy stored in the fixed carbon given by the proximate analysis. Figure 9. The measured amount of water in the raw gas (H 2 O in ) compared to the water inputs to the process (H 2 O out ).

Example: In a standalone gasifier (where no additional fuel is fed to the combustor) optimized for gas production, the internal heat demand should be minimized. Assuming dried fuel, preheated combustion air to a temperature close to the flue gas temperature, preheated steam to the temperature of the bed in the gasifier and that tar is burnt in the combustor, the maximum chemical efficiency can be estimated, Eqs 23-24. The optimal char conversion for this case, given by Eq 25, is around 70% mass. The maximum chemical efficiency, using the reactor temperatures of the high temperature case, is estimated to around 90 % based on the lower heating value of the dry fuel. Another situation occurs if the gasifier is linked to a combustor producing additional heat as in the system at Chalmers. As plenty of additional heat is then available in the gasifier it is then possible to gasify more or less all of the fuel. This would mean that some of the heat from the combustor will be stored as chemical energy in the gas and a chemical efficiency even over 100%, based the fuel fed to the gasifier, can in principal be obtained for a high temperature case, Eq 26. 5. Conclusions The mass and energy flows of the Chalmers gasifier are quantified in this work. Further, the conversion of the fuel in the gasifier is determined for two different temperature cases. The difference between the cases raised a number of questions from which the following was concluded: The chemical efficiency as well as the gas yield increase with temperature. The increase is due to char conversion; at the low temperature only around 1% mass char was converted, while around 25% mass was converted during the high temperature case. This increase in char conversion results in an increase of the chemical efficiency from 60% to 70% on dry fuel basis. The difference in the energy level between the two cases is well described by the additional heat stored in the raw gas due to the higher temperature and the endothermic gasification reaction of the char. The energy remaining in the unconverted char was compared to the internal heat demand of the process. For the low temperature case more energy is available for heat production than the internal heat demand; thereby indicating that more char could be gasified while still having a stable process. For the high temperature case there is less unconverted char, lower heat demand to the combustor and higher heat demand from the increased gasification reaction. Assuming that the tars can be burnt in the combustor the high temperature case is nearly balanced. The measured amount of water in the raw gas decreased with temperature which concurs well with the trend of increased gasification of the char. Further, the amount of steam added to the process is much larger than the amount needed for the char conversion. Thus, if the amount of steam per kilo of fuel could be reduced both the internal and external heat demands would be decreased. Comparing the energy stored in the char with the internal heat demand the following conclusions can be drawn about optimizing the process for gas production: The maximum chemical efficiency that could be reached in theory for standalone gasifier is estimated to 90% on dry fuel basis. The maximum chemical efficiency of the fuel fed to the gasifier in a system where additional fuel is fed to the combustor is estimated to over 100% as heat from the combustor is stored up in the gas though the gasification of char.

6. References Conference Proceedings: [1] Leckner, B., et al. Boundary layers-first measurements in the 12 MW CFB research plant at Chalmers University. 1991. Conference Proceedings: [2] Thunman, H., et al., A cost effective concept for generation of heat, electricity and transport fuel from biomass in fluidized bed boilers using existing energy infrastructure. 2007, Proceedings of the 15th European Biomass Conference & Exhibition - From research to market Deployment, Berlin, Germany, 7-11 May 2007. Conference Proceedings: [3] Seemann, M. and H. Thunman. The new Chalmers research-gasifier. in the 20th International Conference on Fluidized Bed Combustion. 2009. Conference Proceedings: [4] Hofbauer, H. Scale up of fluidized bed gasifiers from laboratory scale to commercial plants: steam gasification of solid biomass in a dual fluidized bed system. 2006. Thesis for the degree of doctor of philosophy: [5] Niklasson, F., HeatBalance Modeling of a Stationary Fluidized-Bed Furnace Burning Biomass, in Department of Energy Conversion. 2004, Chalmers University of Technology. Jurnal publication: [6] Brage, C., et al., Use of amino phase adsorbent for biomass tar sampling and separation. Fuel, 1997. 76(2): p. 137-142. Conference Proceedings: [7] Neves, D., et al., A Database on Biomass Pyrolysis for Gasification Applications, in 17 th European Biomass Conference & Exhibition. 2009: Hamburg. Online database: [8] Linstrom, P.J., W.G. Mallard, and (eds.), NIST Chemistry WebBook. Jurnal publication: [9] Thunman, H., et al., Composition of volatile gases and thermochemical properties of wood for modeling of fixed or fluidized beds. Energy and Fuels, 2001. 15(6): p. 1488-1497. 7. Acknowledgements This work has been support by Akademiska Hus, Göteborg Energi, METSO and the Swedsih Energy Agency. Claes Breitholtz, Rustan Marberg, Fredrik Lind and the staff at the Chalmers power station is acknowledged for their contribution to successful experiments. Further, Nicolas Berguerand and Mikael Israelsson are also acknowledged for their support in this work.