Experimental Study on Co-gasification of Wood Biomass and Post

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Experimental study on co-gasification of wood biomass and post-extraction rapeseed meal – rich-methane gasification Danuta Joanna Król, and Slawomir Poskrobko Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.6b02163 • Publication Date (Web): 10 Mar 2017 Downloaded from http://pubs.acs.org on March 11, 2017

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Experimental Study on Co-gasification of Wood Biomass and Post-extraction Rapeseed Meal – Rich-Methane Gasification

* **

Danuta Król*, Sławomir Poskrobko** Silesian University of Technology, Gliwice, Poland,

Białystok University of Technology, Białystok, Poland,

KEYWORDS : biomass, fuel beneficiation, gasification, rich-methane syngas. ABSTRACT: The paper presents laboratory research on a new manufacturing technology of high-methane synthesis gas from biofuels such as: pine wood biomass and post-extraction rapeseed meal. The study was conducted in the gasifier with a power of to 5kW. As a result were obtained: the content of CH4 in the syngas is from 5% to approx. 15%. The calorific value of the syngas (LHV), depending on the content of the preparation in the fuel (0-30%) varied from 4 MJ/Nm3 to 9MJ/Nm3. Exothermic balance of the gasification process was established for the following technological parameters: temperature over the grate T1= 800oC, the temperature in the fuel layer T2=450oC, the temperature over the fuel layer T3=850oC. **

Corresponding author: Sławomir Poskrobko, E-mail address: [email protected]

1. Introduction The prevalence of the use of synthesis gas generators in the power industry is limited by too low efficiency of conversion of chemical energy contained in the fuel into chemical energy of obtained post-processing gas (syngas). Biomass gasification technologies implemented for

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practical applications, which recently draw a lot of attention in the literature, are characterized by low efficiency, reaching the chemical efectiveness estimated at about 70%1-4. Lowefficiency conversions of biomass fuels in combustible gas are for the most widespread low pressure gasification technology, where the process is carried out in a fixed compact bed of fuel, with a cocurrent or countercurrent flow of gaseous products in relation to the movement of the fuel layer5-8. Slightly higher carbon conversion and conversion efficiency is obtained in a fluidized bed6-10. The predominant gaseous constituents, significantly influencing the caloric content of the synthesis gases in the above-mentioned technologies of biomass fuel gasification, are hydrogen (H2 = 10 - 50%)11-13 and carbon monoxide (CO = 10 - 25%)14-16. Yet the high proportion of H2 is obtained in secondary transformations during the gasification at high temperatures of approx. 1000°C - usually in a fluidized bed. The share of the CO is a result of the interconnection of oxidation and reduction zones, characteristic for the process, and secondary effects over a layer of fuel in the gas phase. In real conditions, an unstable equilibrium composition of gaseous products is set up. It changes during the atmospheric gasification. It depends on the process temperature and the flow rate of the gasifying agent through the fuel layer. Besides, the self-going of the process for which, the CO/CO2 equilibrium is determined, depends on the fuel properties (e.g. in case of biomass mainly on its moisture content, size of grain) and thermal conditions of the flow in the layer of fuel. CO/CO2 ratio indicates the efficiency of the gasification process. If the CO/CO2 >1, it means the dominance of the reduction processes in which gas with predominant share of gaseous combustible substances is obtained. Recent literature reports indicate that these processes may be carried out in many different ways (keeping in mind the high caloric content of synthesis gases). Taking into account the novelty of the gasification technology presented, based on the literature17, available technologies running on a laboratory scale are presented. Thanks to the innovations


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used, a synthesis gas with improved caloric properties than in applied industrial technologies was obtained. Table 1 shows the share of gaseous products of CH4, CO, CO2 in the synthesis gas obtained in the gasification of fuel mixtures - with the use of coal, biomass and plastic17. The high efficiency of the process was achieved thanks to the use of the above mentioned mixes of fuels and the use of new construction of the fluid gasifier e.g: gasification in fluidized circulating or bubble bed and in a double bed gasifier, and small dusty fractions of biomass in cyclone gasifiers. Gasification was carried out in the gasifier at 850°C. Another gasifying factor was air or air and steam. Gasification without catalysts is taken into account. Table 1 Producer gas composition in different technologies17 The most effective gasification technology in terms of methane yield, found out to be the gasification of the fuel mixture consisting of pine biomass, coal and plastic, using a gasification agent- steam and air (item 6 in Table 1 CH4 = ca. 30%) and gasification of rice husk, where CH4 = app. 10%. By the use of catalysts to enhance the reactivity of the components involved, the process yields highly effective18,19. The increase in caloric content of the synthesis gas is achieved by improving the construction of gasifying chambers (furnaces) e.g.: gasification in chambers with fluidized grate20, bilayer gasification21 gasification in cyclone chambers22. Despite extensive research material on the progress of new gasifier technologies (due to the low efficiency of fuel conversion into useful energy - in comparison with the combustion process), in practice, these technologies have not found widespread use. A little number of deployments is the evidence. An installation of fluidized bed gasifier which is the forburner of the dust boiler, working in the CHP Latchi (Finland) seems to be noteworthy23. Various organic fuel additives, e.g: gasification of biomass and coal with the addition of plastics, biomass gasification with resin pine biomass, may result in increased efficiency of the process, reflected in an increase in the content of combustible gases included in the


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synthesis gas (table 1). Fuel additives used, do not fulfill the role of catalysts, they are auxiliary fuel - a substrate involved in the processes of thermal decomposition of biomass occurring in the reaction chamber of the gasifier. The aim of this study is to identify opportunities (on the laboratory scale)of producing generator gas of average calorific value and high methane content, from wood biomass with the addition of rapeseed meal. As the calorific value of methane is significantly higher than the calorific value of CO and H2, thus directing the process to manufacture the generator gas with higher shares of methane (compared to commonly used technologies), seemed to be a desirable direction for the development of innovation in the gasification technology. Our earlier original studies24 on the combustion of coal with the addition of rapeseed meal have proven that its addition to the fuel promotes the formation of local reducing environment zones in the furnace grate of the boiler. Such property suggested the possibility of using meal in gasification process (where the reducing environment (oxygen deficiency) plays an important role in shaping the quality of gas product- in the direction of increasing the share of CH4) .Such orientation of the gasification process for methanation, by hydrogenation of gasification products CO, CO2 and C in the bed of fuel, makes for process innovation.

2. Materials The research of the gasification process were conducted for biofuels such as: wooden biomass and rapeseed meal. Table 2 provides a partial elemental compositions of tested materials related to dry mass and their LHV calorific value, which were calculated based on measurements of elemental composition of flammable substances and measured values of HHV combustion heats (enthalpy), dependent mainly on gram shares of elements such as carbon C and hydrogen H (and combustible sulfur). The fuel properties were marked according to PN-ISO: moisture PN-Z–15008-02:1993, ash (non-combustible parts) PN-ISO


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1171:2002, heat of combustion PN – ISO 1928 :2002, carbon, hydrogen, nitrogen, and sulfur by means of CHNS elemental analyzer, model 2400 series II, from Perkin Elmer, and chlorine PN-ISO 587/2000.

Table 2. Elemental composition of dry mass of surveyed fuels and its LHV calorific value (of dry, mass [%sm]). Post-extraction rapeseed meal is a waste from the production of rapeseed oil. In the combustible substance it contains amino acids, peptides, proteins, and as a result - a considerable proportion of nitrogen, so an element which in proper conditions of the combustion chamber, particularly in gasification, is released in the form of ammonia. Fat compounds contained in the rapeseed meal make the ignition temperature of the degassing substances higher than the conventional biomass materials, which results in time delay of the ignition. At the same time, the total time of thermal decomposition of the biopreparation [25,26] is longer than other fuels with the same high calorific value, comparable to wood biomass The requirement of trace amounts of alkali metals (Table 3) and a low chlorine content (Table 2) in a combustible material, allow for the use of the rapeseed meal at temperatures above 8000C, since it does not form the low-melting chlorides. A high sulfur content (Table 2) in the flammable substance rapeseed meal, also protects the fuel against the formation of lowmelting salts involving chlorine. The rapeseed meal can thus be used not only as a supplement to the coals, but it can be also successfully used in the process of their co-combustion or cogasification with agro biomass. Dispensed in suitable proportions, it also reduces the effects of high temperature corrosion being the result of alkali metal chlorides presence e.g. if agricultural waste is used as fuel. Table 3. Alkali metal concentration in preparation rapeseed meal


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3.

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Experimental

Biomass gasification studies were performed using the gas generator shown in Fig. 1. The maximum thermal efficiency of the gasifier was about 4 kW. Gasification was carried out in a fluidized compact bed, in an atmosphere of air shortage and continuous dosing of wood biomass mixed in different ratios with the product of rapeseed meal to the gasifier chamber. The ratio of the fuel stream (F) to the air (A) F/A = 0.76, where the efficiency of the gasifying agent - air A= 0.5 g/s, and. fuel i.e. wood biomass loading capacity. containing meal F=0.38g/s. In order to obtain synthesis gas having different contents of CH4, the share of the rapeseed meal in the fuel was graded from 5 to 30%. The ash was removed from the reactor chamber by controlling within a fan. The fan blew part of the ash through the chimney and the remaining ash was deposited in the lower section of the secondary combustion chamber. The initiation of the gasification process was carried out by means of resistance heating elements installed along the gasification chamber, and the air supply channel. In the initial phase of the process, a spontaneous combustion of fuel took place. Then, the start-up heating elements were turned off, and the chamber was heated up to a temperature of 900oC, burning biomass. At this temperature the tested fuels were dosed, and then gasification process was stabilized by adjusting the flow of air and fuel. Stabilization meant establishing proper process temperature, which in this case was T2= -900oC on the grate, T3 = 450-500oC in the fuel layer, T4 = 800-900oC above the fuel layer and T4 = 700oC in the convection zone and at the outburst of the reactor. (Fig. 8). The air flow was controlled by changing the blower motor speed, changing with the inverter the frequency of

current supplying the engine. The

installation was featured with a continuous measurement of mass flow rate of air.


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Identification of the mass flow of fuel was performed using the previously formed characteristics of the dispensing system equipped with a stepping motor. The measurement of the composition of the gas was made by the synthesis gas analyzer type GAS 3100 SYNGAS. The reaction chamber of the gasifier with a diameter of 80 mm and a length of 1800 mm was equipped with a perforated grate of perforation size i.e. diameter hole 4 mm, which was backfilled with fuel (biomass containing rapeseed meal). Through the openings in the grate, the air was supplied into the reaction chamber. The reactor is also adapted for use in a fluidized bed (BFB), and in a compact double layer6 The aim of the experiment was to determine optimal technological parameters for the process of identified fuels gasification i.e. the mixture of wood biomass and rapeseed meal. In order to identify the properties for the production of the reducing zone, the formulation rapeseed meal was dosed in the amount from 5% to 30%, referring to the weight of biomass. The results of the experiment are shown in the form of shares of the synthesis gas composition (CO, CH4, H2, CO2) and the oxygen share in the syngas. Identification of the adjustment process to the conditions set, was made by the indication of O2 share in the synthesis gas, for which the process happened automatically. Figure. 1. Laboratory test stand – fluidized bed gasifier, where: 1 – gasifier, 2 – combustion chamber and chimney channel, 3 – fuel tank and dosing system, 4 – air heater, 5 – air flow channel and fan, 6 – con-trol chimney draft, 7 – control panel, 8 – measurement of airflow 4. Results and discussion The test results of gasification of wood biomass with the addition of preparation rapeseed meal are shown in Fig. 2-5. In each succeeding attempt the preparation was added to wood biomass in amounts from 5% to 30% in relation to the biomass. The process took place at 800 - 850°C. Fig. 2 shows the percentages of each gaseous products of gasification (CO2, CO, CH4, H2) forming a synthesis gas. Combustible gas components, i.e. CO, H2 and CH4 were


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gradually rising with the increase of the share of rapeseed meal in the fuel, which contributed to an increase in the calorific value of the synthesis gas. The proportional increase in CO and CH4 was followed by an increase in the share of rapeseed meal in the fuel. The addition of rapeseed meal to wood biomass results in the formation of local reduction zones within the grains of fuel (it has to do with the presence of oil fractions). When the amount of grit in the fuel increases from 15% to 25%, a reduction zone expands. This results in a proportional increase of the gaseous forms of carbon (with insufficient oxygen and reduced) in the syngas: CO and CH4. In contrast, the amount of its oxidized form - CO2, decreases. The process achieves balance maintaining the CO/CO2 >1 ratio as shown in Fig. 4. In such conditions a proportional increase of CO and CH4 in the synthesis gas takes place, but a weakening growth in the share of H2 can be noted, as shown in Fig. 2. As regards to the participation of rapeseed meal 0-10% (Fig. 2), the increase of CO2 suggests rapid combustion of wood biomass. The addition of rapeseed meal in amounts up to 5% of the wood biomass (with the fuel to air ratio F/A = 0.76), does not particularly affect the process of its gasification in the direction of methanation. Under such conditions, the composition of the generator gas is dominated by CO2 - oxidizing zone is maintained Fig. 2. This is confirmed by the decreasing share of O2 in the gas. That means that oxygen in the gasifier reaction chamber (Fig. 3), was actively involved in oxidation reactions – the temperature in the bed was 500°C. Increasing the share of rapeseed meal in the fuel, increases the efficiency of the gasification process through an increase in the content of CO and CH4. The conversion of the fuel into gas takes place at a preferred ratio of CO/CO2 >1. Reduction nature of the process (CO/CO2 >1) stabilizes from approximately 20% of rapeseed meal share in the wood fuel. The growthof the meal share makes the O2 content in the gas increase (Fig. 3) and the temperature of the bed decreases, and is maintained at 450°C. A slight decrease in the temperature preserves the reductive nature of the process and improves the kinetic conditions of CO and CO2 hydrogenation, i.e.


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methanation (which will be discussed below). Temperature distribution in zone I (oxidative), II (reduction) and III (above the bed, in the cracked tars zone) is shown in Figure 4. Temperature distribution indicates that the process, principally in reducing layer (gasification layer) is run stably. Figure. 2. Synthesis gas composition in function of the rapeseed meal share in the fuel. The recorded changes of O2 (Fig. 3), depending on the meal share in the fuel, can be affected by inaccurate mixing of the meal with wood biomass. The quality of homogenization of fuel is significantly affected by the difference in the size of the particles and the density of wood biomass and meal. Wood biomass was in the form of pellets, and rapeseed meal is a loose material (Fig. 8). Fuel composed of ingredients - pelleted wood biomass with the addition of rapeseed meal, it was thoroughly mixed. However, due to the difference in weight of the two components, when dosing the fuel, the soybean is flaking. No homogenization of the fuel on the grid (changes of rapeseed meal content in the entire layer of fuel) causes variable temporary oxygen demand. In the absence of a homogeneous mixture on the grate of the reactor, from a practical point of view, this result (a difference of 0.3% O2 in the generator gas) we found very satisfactory. Figure. 3. The share of O2 in the synthesis gas for different shares of rapeseed meal. Figure 4. Temperature distribution in the reaction chamber of the gasifier, based on the proportion of rapeseed meal The presence of H2 in the generator gas (Fig.2) has its origins in the fact that this is hydrogen which is produced at high temperature (850°C) cracking zone (cracking occurs over the layer of fuel). Hydrogen formed in radical reactions H + H = H2 in the layer of fuel (at T=450°C), is almost exclusively involved in the methanation processes by hydrogenation of C, CO and


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CO2. It is a possible hypothesis, for which at this stage of research, there is no conclusive evidence. Figure. 5. Dependence CO/CO2 for the proces of CH4 formation. Figure. 6. Fuel characteristics of synthesis gases. HHV of synthesis gas for various gas shares of flammable components (CH4, H2, CO). The effect of CO/ CO2 ratio on the methane formation process was shown in Fig. 5. The process is disrupted by the changes in concentration of CO2 in the synthesis gas, so the most sensitive gas to oxygen, as indicated by the test results obtained. This graph also shows that, irrespective of the atmosphere in the gasification chamber of the reactor, the proportion of CH4 always increases with the addition of rapeseed meal. Fig. 6 shows the fuel characteristics of the obtained synthesis gas for various bulk quantity of fuel added to the formulation, the operation of which, naturally tends to produce a reducing atmosphere. The diagram has an essential technological meaning, as on its basis (for a given calorific value) the composition of the synthesis gas is estimated. Figure. 7. LHV of synthesis gases depending on the share of rapeseed meal in the fuel. Fig. 7 illustrates in turn the effect of the formulation rapeseed meal on the calorific value of the synthesis gas obtained in the gasification. It is worth noting that 30% share of the rapeseed meal in wood biomass increases the calorific value of gas of about three times. This has an impact on increasing the efficiency of chemical conversion

process of solid fuel into

generator gas, in relation to the gasification technology with a low share of CH4 in gas. Chemical conversion (chemical efficiency) is defined as the ratio of the calorific value of gas to the calorific value of the fuel (density of the generator gas obtained is 1.019 kg/m3 in standard conditions) LHV(g)/LHV(f). This factor indicates the development of the gasification technology. In the present case of the gasification of wood biomass with the extracted rapeseed meal, the ratio is LHV(g)/LHV(f) = 0.65 (30% addition of rapeseed meal), and


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referring to the quality of the gas in the literature29 LHV*(gas)/LHV*(fuel) = 0.29. Calorific value of the generator gas is calculated from 30. LHV(generator gas) =126[%CO]+108[%H2]+359[%CH4]+665[%CnHm]

[kJ/Nm3],

where: [%CO], [%H2], [%CH4], [%CnHm] – measured percentage share of the combustible components in the generator gas. Figure 8. Grain structure of fuel (a) - rapeseed meal, post-extraction, (b) - wood pellet 4.1. Methane formation mechanism A characteristic feature of the gasification process in a tubular reactor, where rich in methane synthesis gas is obtained, is temperature distribution in the reaction chamber of the gasifier, which fosters the methane creation processes. In areas: combustion (II)-T2= 900°C, gasification (III)-T3 = 450-500oC, cracked tars (IV)-T4 = 800-900oC (Figure 9). The temperature of the air gasification medium was (I) T1 = 20°C. Figure. 9. Scheme of the high methane gasification in the reactor The basis of the methane creative process of thermal decomposition of biomass is to maintain a stable temperature T3 = 450-500oC in the gasification zone and the temperature of 800900oC over the gasification zone (over a layer of fuel) permitting thermal cracking of heavy hydrocarbon pairs i.e. tar. Producing and maintaining a high temperature in zone IV is promoted by partial combustion of flammable condensable organic vapors e.g.: according to the kinetic model of Brydon27: CH1,522O0,0228 + 0,867O2 → CO + 0,761H2O

(1)

The remaining not burned pairs are cracked according to the reaction27: + where:

– stoichiometric coefficient.


,…..(2)

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In temperature conditions of the degassing zone (III) in the gas phase in the fuel layer occur, apart from conventional reactions typical for generator processes, exothermic methane forming Fischer – Tropsch, Sabatier - Senderens reactions28: CO + 3H2 ↔ CH4 + H2O

∆H = - 206,4 kJ/mol

(3)

The water forming in the reaction (3) also reacts with carbon monoxide according to the equation: CO + H2O ↔ CO2 + H2

∆H = -41,5 kJ/mol

(4)

As the concentration of CO in the reaction system is reducing, the reaction equilibrium shifts, and the reaction takes place in the opposite direction (from right to left). Carbon monoxide, which is forming, is the subject to methanation by the equation (3). By adding the reaction (4) extending from right to left to reaction (3) an equation of carbon dioxide methanation reaction (5) is obtained28: CO2 + H2 ↔ CO + H2O CO + 3H2 ↔ CH4 + H2O CO2 + 4H2 ↔ CH4 + 2H2O

∆H = -164,9 kJ/mol

(5)

Methane is also formed in methanisation reactions: 2CO + 2H2 → CH4 + CO2

∆H = - 254,1 kJ

CO + 4H2 → CH4 + 2H2O

(6) (7)

Methanation reactions such as CO and CO2 are exothermic reactions and run with reduced volume. Therefore, lowering the temperature and increasing the pressure favour the shift of the equilibrium to the increase of methane in equilibrium gas mixture. In the presented experiment the pressure was not increased and the temperature was maintained in the range T3 = 450 - 5000C. The effectiveness of the above reactions in zone III Fig.9 (at T3 = 450-500oC), shown in Fig. 10 indicate dependences making the equilibrium constant Kp dependent of the temperature,


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which is considered due to the simple way to speed the calculation according to the estimate Nernst equation, which provides good accuracy of the calculations in the gas phase:

(8) where: Q – thermal effect of reaction at standard conditions;

- the

difference between the number of moles of reaction products and numbers of moles of the starting materials

– contractual chemical constant. These are determined on the basis of

empirical equations of resilience curve of lg pj pairs:

,

(9)

where: rj – vapourisation heat (J/mol) with pressure p = 1.013 bar. The agreed chemical constant for mononuclear gases can take: i = 1.5, polynuclear i = 3. Figure.10. Logarithmic dependence of the equilibrium constant Kp of methanation reaction to temperature Figure 10 indicates that the above methanation reactions occur with high intensity at process temperatures in the gasification layer III. The results of the gasification experiment showed that the process was maintained within the specified temperature range, despite increasing the gasification air flow. In such cases, the temperature in the layer of fuel increased up to 500°C. The increase in the temperature was recorded over a layer of fuel to 1000°C with an increase in the share of O2 in the gaseous products of the process. Considering the methanation process one cannot overlook the reaction of carbon with hydrogen : C + H2 ↔ CH4

∆H = -73,7 kJ/mol

(10)

In this case the kinetics of the gasification is directed by the correlation of chemical and physical phenomena.


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The reaction substrate of gasification i.e. fuel (biomass and rapeseed meal), after the first step - degassing (which takes place at elevated temperature), changes its form (structure) and becomes a porous solid. Heterogeneous gasification reaction occurs at the interface of gas solid. Grains of gasified fuels are surrounded by a thin (film) coating. Through this coating the molecules of the gaseous reactants must firstly penetrate - oxygen, water vapor and which further diffuse into the pores. On the walls of the pores they react with carbon. The speed of heterogeneous gasification reaction depends therefore on the rate of chemical reaction and diffusion rate of gasifying agent into the pores of the fuel. However, in low reactive temperatures, at which the methanation process is carried out, the reaction equilibrium (10) is determined slowly. Environmental conditions of methanation reaction is influenced by the fuel composition. In addition to the main fuel - wood biomass, an important supplement is a biomass preparation rapeseed meal, with high (3760C) flashpoint. The composition of the rapeseed meal includes difficult to volatile oil fractions, affecting the increase in the ignition temperature of the preparation. The presence of the oil compounds in the form of vapor, isolates fuel particles from the oxygen, which forms the local, reductive reaction environment, conducive to the formation of the reduced form of carbon - CH4. The addition of rapeseed meal supports the methane forming process, because the meal is composed of approx. 4% of the fatty acids. These are primarily: linolenic acid, linoleic, erucic, oleic, eicosenoic, palmitic, stearic. In the temperature zone - in the layer of fuel T3 = 450-5000C – apart from the

gasification of fuel (wood biomass and rapeseed meal),

evaporation of the above mentioned fatty compounds takes place. In the gasification of biomass, in addition to gaseous products and solid residue, condensable substances are formed, mainly tar. In the cracking zone at a temperature of 850 –9000C , thermal cracking of fat vapor and condensing substances takes place. Cracking products are CO, CH4, H2, CO2.


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5. Conclusion The process of high- methane gasification of wood biomass with the addition of rapeseed meal was carried out at atmospheric pressure in the air, in a tubular reactor having a maximum power of 5 kW. Based on the obtained results, it was found that the post-extraction rapeseed meal added to wood biomass has increased the share of methane in the generator gas from 5 (without the addition of meal) to 14% (with 30% addition). Increasing the share of CH4 has increased the calorific value of gas from 4000 kJ/m3 (without the addition of rapeseed meal) to 9000 kJ/m3 (with 30% addition of rapeseed meal). As a result of adding rapeseed meal, we obtained a high conversion efficiency of fuel into gas LHV(g)/LHV(f) = 0.74. With the addition of rapeseed meal in the reaction chamber of the gasifier (in the layer of fuel), reductive process conditions, favorable to methanation reactions, were formed. In the reducing zone, low temperature of approx. 400-450oC remained. In this temperature range, exothermic methanation processes of C, CO and CO2 involving H2 were taking place. Preferred hydrogenation conditions in the existing process conditions justify the calculation of the equilibrium constants lgKp(CO + 3H2 → CH4 + H2O ) = 3 – 0.8, lgKp (CO2 + 4H2 → CH4 + 2H2O) = 4.1 – 1.2. The process of methane formation, in the present case, took also place above the layer of fuel (in the convection zone of the gasifier), wherein the pair of tars at a temperature of 800900oC underwent cracking. The high temperature in that part of the gasifier was maintained by partial combustion of high calorific tar vapors in the presence of oxygen, which has not reacted during the gasification in the fuel layer. The use of tubular reactors in the gasification processes makes it much easier to create and maintain a reduction zone in the reaction chamber of the reactor by adjusting the air blow. Maintaining the reduction zone allows methanogenic processes in the layer of fuel.


Energy & Fuels

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References (1) Kramreiter, R.; Url, M.; Kotik, J.; Hofbauer H.: Experimental investigation of a 125 kW twin-fire fixed bed gasification pilot plant and comparison to the results of a 2 MW combined heat and power plant (CHP). Fuel processing technology 2008, 89, 90 – 102. (2) Carvalho, M.M.O.; Cardoso, M.; Vakkilainen; E.K. Biomass gasification for natural gas substitution in iron ore pelletizing plants. Renewable Energy 2015, 8, 566 – 577. (3) Yoon, H.C.; Cooper, T.; Steinfeld A. Non-catalytic autothermal gasification of woody biomass. International journal of hydrogen energy 2011, 36, 7852 - 7860. (4) Šulc, J.; Štojdl, J.; Richter, M.; Popelka, J.; Svoboda, K.; Smetana, J.; Vacek, J.; Skoblja, S.; Buryan, B. Biomass waste gasification – Can be the two stage process suitable for tar reduction and power generation? Waste Management 2012, 32, 692 –700. (5) Saravanakumar, A.; Haridasan, T.M.; Reed, T.B.; Bai, R.K. Experimental investigations of long stick wood gasification in a bottom lit updraft fixed bed gasifier, Fuel Processing Technology 2007, 88, 617– 622. (6) Van de Steene, L.; Tagutchou, J.P.; Mermoud, F.; Martin, E.; Salvador, S. A new experimental Continuous Fixed Bed Reactor to characterise wood char gasification, Fuel 2010, 89, 3320 – 3329. (7) Gordillo, G.; Annamalai, K. Adiabatic fixed bed gasification of dairy biomass with air and steam, Fuel 2010, 89, 384–391. (8) Kern, S.; Pfeifer, C.; Hofbauer, H. Co-gasification of wood and lignite in a dual fluidized bed gasifier. Energy & Fuels 2013, 27, 919 − 931. (9) Ammendola, P.; Chirone, R.; Miccio, F.; Ruoppolo, G.; Scala, F. Devolatilization and Attrition Behavior of Fuel Pellets during Fluidized-Bed Gasification. Energy & Fuels 2011, 25, 1260 – 1266.


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Energy & Fuels

(10) Hanping, Ch.; Bin, L.; Haiping, Y.; Guolai, Y.; Shihong. Z. Experimental Investigation of Biomass Gasification in a Fluidized Bed Reactor, Energy & Fuels 2008, 22, 3493 – 3498. (11) Hamad, M.A.; Radwan, A.M.; Heggo, D.A.; Moustafa, T. Hydrogen rich gas production from catalytic gasification of biomass, Renewable Energy, 2016, 85, 1290 - 1300. (12) Luo, S.; Xiao, B.; Hu, Z.; Liu, S.; Guo, X.; He, M. Hydrogen-rich gas from catalytic steam gasification of biomass in a fixed bed reactor: Influence of temperature and steam on gasification performance, International journal of hydrogen energy 2009, 34, 2191 – 2194. (13). Sun, Y.; Li, R.; Yang, T., Kai X., He Y. Gasification of biomass to hydrogen-rich gas in fluidized beds using porous medium as bed material, International journal of hydrogen energy, 2013, 38,14208 – 14213. (14) Gunarathne, D,.S.; Mueller, A.; Fleck, S.; Kolb, T.; Chmielewski, J.K.; Yang, W.; Blasiak, W. Gasification Characteristics of Hydrothermal Carbonized Biomass in an Updraft Pilot-Scale Gasifier. Energy Fuels 2014, 28, 1992−2002 (15) Couto, N; Rouboa, A; Silvaa, V.; Monteiro, E.; Bouziane K.: Influence of the biomass gasification processes on the final composition of syngas. Energy Procedia, 2013, 36, 596 – 606. (16) Prasad, L.; Subbarao, P.M.V.; Subrahmanyam, J.P. Experimental investigation on gasification characteristic of high lignin biomass (Pongamia shells). Renewable Energy, 80, 2015, 415-423. (17) Zainal, Alimuddin Bin Zainal Alauddin; Lahijani, P.; Mohammadi, M.; Mohamed, A.R. Gasification of lignocellulosic biomass in fluidized beds for renewable energy development: A review. Renewable and Sustainable. Energy Reviews, 2010, 14, 2852 – 2862.


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(18) Osada, M.; Norihito Hiyoshi, N.; Sato, O.; Arai, K.; Shirai M. Reaction Pathway for Catalytic Gasification of Lignin in Presence of Sulfur in Supercritical Water Energy & Fuels 2007, 21, 1854-1858. (19) Zhu, W.; Song, W.; Lin, W. Catalytic gasification of char from co-pyrolysis of coal and biomass. Fuel Procesing Technology 2008, 89, 890-896. (20) Li, K.; Zhang, R.; Bi, J. Experimental study on syngas production by co – gasification of coal and biomass in fluidized bed, International Journal of hydrogen. Energy 2010, 35, 2722 – 2726. (21) Sudiro, M.; Zanella, C.; Bertucco, A; Bressan, L.; Fontana, M. Dual-Bed Gasification of Petcoke: Model Development and Validation. Energy Fuels 2010, 24, 1213–1221. (22) Guo, X.; Ciao, B.; Liu, S.; Hu, Z.; Luo, S.; He M. An experimental study on air gasification of biomass in a cyclone gasifier, International Journal of Hydrogen. Energy 2009, 34, 1265 – 1269. (23) Granatstain, D.L.; Case study on Lahden Lampovaima gasification project Kymiyarvi Power Statation, Lahti, Finland. November 2002. (24) Poskrobko, S; Król, D.; Łach, J. A primary method for reducing nitrogen oxides in coal combustion through addition of Bio-CONOx. Fuel Processing Technology 2012, 101, 58 - 63. (25) Król, D.; Poskrobko, S. Waste and fuel from waste.Part I Analysis of thermal decomposition. J Therm Anal Calorim 2012, 109, 619 – 628. (26) Poskrobko, S.; Król, D. Biofuels Part II. Thermogravimetric research of dry decomposition. J Therm Anal Calorim 2012, 109, 629 – 638. (27) Radmanesh, R.; Chaouki, J.; Guy, Ch. Biomass gasification in bubbling fluidized bed reactor: experiments and modeling. Environmental and energy engineering 2006, 52, 4258 - 4271.


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(28) Rönsch, S.; Schneider, J.; Matthischke, S.; Schlüter, M.; Götz, M.; Lefebvre, J; Prabhakaran, P.; Bajohr, S. Review on methanation – From fundamentals to current projects. Fuel, 2016, 166, 276 – 296. (29) Bhaduri S.; Contino F.; Jeanmart H.; Breuer E. The effects of biomass syngas composition, moisture, tar loading and operating conditions on the combustion of a tartolerant HCCI (Homogeneous Charge Compression Ignition) engine. Energy 2015 87, 289 – 302. (30) User manual gas analyser SYNGAS 3000.

Titles of figures: Figure. 1. Laboratory test stand – fluidized bed gasifier, where: 1 – gasifier, 2 – combustion chamber and chimney channel, 3 – fuel tank and dosing system, 4 – air heater, 5 – air flow channel and fan, 6 – con-trol chimney draft, 7 – control panel, 8 – measurement of airflow. Figure. 2. Synthesis gas composition in function of the rapeseed meal share in the fuel. Figure. 3. The share of O2 in the synthesis gas for different shares of rapeseed meal. Figure 4. Temperature distribution in the reaction chamber of the gasifier based on the proportion of rapeseed meal Figure. 5. Dependence CO/CO2 for the proces of CH4 formation. Figure. 6. Fuel characteristics of synthesis gases. HHV of synthesis gas for various gas shares of flammable components (CH4, H2, CO). Figure. 7. LHV of synthesis gases depending on the share of rapeseed meal in the fuel. Figure 8. Grain structure of fuel (a) - rapeseed meal, post-extraction, (b) - wood pellet Figure. 9. Scheme of the high methane gasification in the reactor (I - the air from the environment, II- zone of oxidation on the grid, III - gasification in the layer of fuel zone, IV combustion and cracked tars zone) Figure. 10. Logarithmic dependence of the equilibrium constant Kp of methanation reaction to temperature .


Energy & Fuels

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Titles of table: Table 1. Producer gas composition in different technologies 17 Table 2. Elemental composition of dry mass of surveyed fuels and its LHV calorific value Table 3. Alkali metal concentration in preparation rapeseed meal

Figures:

Fig.1


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% CH 4,H 2,CO,CO2 = f(% rapeseed meal)

% CH 4,H2,CO,CO2

25 20 CH4

15

H2 CO

10

CO2

5 0 0

10

20

30

% rapeseed meal

Fig.2

% O2 = f(% rapeseed meal) 0,9 0,8 0,7 0,6

% O2

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

0,5 0,4 0,3 0,2 0,1 0 0

3

6

9

12

15

18

21

% rapeseed meal

Fig.3


24

30

Energy & Fuels

T=f(% rapeseed meal)

900

0

temperature [ C]

1000

800

T2

700

T3 T4

600 500 400 0

5

10

15

20

25

30

% rapeseed meal Fig. 4 CO/CO2 = f(% CH4) 1,2 1,1 1

CO/CO2

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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0,9 0,8 0,7 0,6 0,5 4

6

8

10

12

% CH4

Fig.5


14

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% CH 4,H2,CO = f(LHV) 25 20 CH4

15

H2

10

CO

5 0 2500

4500

6500

8500

3

LHV[kJ/m ] Fig.6 LHV = f(% rapeseed meal) 9000 3

8000

LHV kJ/m

% CH 4,H2,CO

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

7000 6000 5000 4000 3000 0

5

10

15

20

% rapeseed meal

Fig.7


25

30

Energy & Fuels

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Fig.8

Fig.9

Fig.10 Table 1. No.

Biomass type

pine sawdust

Gasification technology cyclone air cyclone air

wood pelets

fluidized (FBF) air, steam

1 rice husks 2 3

CH4

Gaseous product vol% CO

10.26 - 2.02

21.31 - 13.57

1.58 – 2.42

17.27 – 19.29

10


21

CO2 19 - 18

12.14– 13.82 20

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Energy & Fuels

4

wood pelets

5

rice husks

6

7

fluidized air enrich O2

pine (20 wt%) carbon (40 wt%) plastic waste (20 wt%) wood dust

Table 2 Sample type Softwoo d pellets Rapesee d meal

8.1

28.5

9.2

fluidized air

2.9

19.9

14.45

fluidized steam+air

hydrocarbons 30 i 36

fluidized circulation air

6.9

not specified

not specified

16.7

15.6

A %

C %

H %

N %

S %

Cl %

O %

6.0

2.65

44.93

6.71

2.32

0.17

0.03

43.19

15581

8.76

7.05

49.30

6.96

6.76

1.38

0.01

35.59

16836

Moisture %

Table 3. Preparation rapeseed meal

Calcium Ca 226.4

Metal [ppm] Kalium K 227.4


Sodium Na 228.4

LHV kJ/kg

Experimental Study on Co-gasification of Wood Biomass and Post

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