Co-gasification Of Biomass Research Articles

Co-gasification of biomass blends: Performance evaluation in circulating fluidized bed gasifier

An important aspect of the commercialization of biomass gasifiers is feedstock flexibility. The present study has dealt with performance assessment of a circulating fluidized bed gasifier (50 kWth) with binary blends of three biomasses, sawdust (SD), rice husk (RH) and bamboo dust (BD), as feedstock. The performance of gasification was assessed in respect of the specific yield of producer gas, its LHV, and tar content in addition to gasification efficiencies. Experiments were conducted with varying equivalence ratio (ER) from 0.19 to 0.35, and temperatures of 800°–900 °C. The blending of biomasses resulted in the enhancement of gasification performance due to synergistic effects. Minerals in the ash of RH catalyzed char and tar conversion leading to higher efficiencies. At ER = 0.35, maximum CGE = 62% and CCE = 98% were obtained for RH + BD blend. With increasing temperature, H2, CO content and net yield of producer gas increased with concurrent decreasing in tar. The highest LHV of producer gas (5.05 MJ/Nm3) was obtained for the RH + BD blend at ER = 0.19 and 800 °C. Maximum gas yield (1.72 Nm3/kg dry biomass) and minimum tar content (2.01 g/kg dry biomass) were obtained for SD + BD and RH + BD blends, respectively, at 800 °C and ER = 0.35.

Co-gasification of coal and empty fruit bunch in an entrained flow gasifier: A process simulation study

Co-gasification of coal and biomass is a proven method to improve gasification performance and a platform towards being independent of fossil fuel in power generation. Thus, this research was conducted to assess the feasibility of coal and EFB as fuels in co-gasification using Aspen HYSYS. A sequential model of an EFG was developed to predict the syngas composition and the optimum operating condition of the gasifier. The process was modelled with a set of five reactors to simulate various reaction zones of EFG in accordance with its hydrodynamics. The model considers devolatilization, char and volatile combustion, char gasification and water-gas shift reactions. The model prediction has exhibited excellent agreement with the experimental results. Three parameters of BR, Top and S/F were considered to account for their impacts on syngas composition in the process. The CE, CGE, PE and HHV were adopted as the indicators of process performance. The optimal values of BR, Top and S/F were 50%, 950°C and 0.75, respectively. While the value of CE reached above 90% and the maximum value of CGE, PE and HHV was obtained. This finding should be helpful in designing, operating, optimizing and controlling any co-gasification process especially in the entrained flow system.

Catalytic steam co-gasification of biomass and coal in a dual loop gasification system with olivine catalysts

A dual loop gasification system (DLG) has been previously proposed to facilitate tar destruction and H2-rich gas production in steam gasification of biomass. To sustain the process auto-thermal, however, additional fuel with higher carbon content has to be supplied. Co-gasification of biomass in conjunction with coal is a preferred option. Herein, the heat balance of the steam co-gasification of pine sawdust and Shenmu bituminous coal in the DLG has been analyzed to verify the feasibility of the process with the help of Aspen Plus. Upon which, the co-gasification experiments in the DLG have been investigated with olivine as both solid heat carriers and in-situ tar destruction catalysts. The simulation results show that the self-heating of the DLG in the co-gasification is achieved at the coal blending ratio of 28%, gasification circulation ratio of 19 and reforming circulation ratio of 20 when the gasifier temperature 800 °C, reforming temperature 850 °C, combustor temperature 920 °C and S/C 1.1. The co-gasification experiments indicate that the tar is efficiently destructed in the DLG at the optimized reformer temperature and with olivine catalysts.

Gasification of coal, Chenopodium Album biomass, and co-gasification of a coal-biomass mixture by thermogravimetric-gas analysis

Gasification studies were performed on sub-bituminous coal of the province Centro in Boyacá state of Colombia, vegetable biomass Chenopodium album (cenizo) and co-gasification of coal-biomass mixtures agglomerated with paraffin in a thermogravimetric analyzer. Biomass synergistically promoted thermochemical transformation of the coal was observed. Experimental results were compared to equilibrium composition simulations. Ash fusibility tests of the coal-biomass mixture were carried out, which allowed to clarify its behavior, such as dry or fluid ash according to own chemical composition, during the gasification process. The experimental tests allowed determining the differences in thermal decomposition, between coal, cenizo and coal-biomass blend, which are attributable to the physicochemical properties of each one solid fuel. During the tests, gas chromatography analyses were performed to establish the compositions of the syngas. The syngas obtained from biomass had the highest concentration of CO and the lowest H2; the coal and the coal-biomass mixture were slightly minor respectively. Concentrations of CH4, CO2 and C2H4 were similar between coal and biomass. This result is consistent with the higher calorific value of the coal syngas. The production of syngas from the coal-biomass mixture had the lowest contents of H2 and CO due to synergistic phenomena that occur with the fuel mixture. The co-gasification of the mixture gave the highest syngas production, carbon conversion, and thermal efficiency. These results indicate the viability of co-gasification of coal-Chenopodium album agglomerated mixtures. In gasification of non-agglomerated mixtures of coal-cenizo, the biomass can be burned directly without producing syngas.

High H2/CO ratio syngas production from chemical looping co-gasification of biomass and polyethylene with CaO/Fe2O3 oxygen carrier

Chemical looping co-gasification of pine wood and polyethylene with CaO/Fe2O3 oxygen carrier was preliminarily conducted in a fixed bed reactor and thermogravimetric analyzer (TGA). The effects of Fe2O3 /biomass mass ratio, temperature and steam/biomass mass ratio on the product distribution (syngas yield, H2/CO ratio and cold gas efficiency) during the pine wood chemical looping gasification were investigated. Results showed that the optimal product distribution was obtained at the gasification temperature of 850 °C with the Fe2O3/feedstock ratio of 0.25 and steam/biomass mass ratio of 0.25. The interactions of pine wood and polyethylene were further studied. It was found that the positive or even the synergetic effects existed, which resulted in the enhancement of syngas and hydrogen yield. The optimal addition of 75% polyethylene increased H2 yield from 0.62 Nm3/kg to 1.59 Nm3/kg compared to the pine wood chemical looping mono-gasification. Chemical looping co-gasification also improved the cold gas efficiency from 77.22% to 89.30% and H2/CO ratio from 1.54 to 1.88. The CaO/Fe2O3 mass ratio of 1.0 was sufficient to elevate the H2/CO ratio above 2. The maximum H2 yield of 1.73 Nm3/kg, cold gas efficiency of 92.23% and H2/CO ratio of 2.09 were finally obtained to meet the demand for the Fischer-Tropsch synthesis. The presence of synergetic effects on syngas and hydrogen yield from the fixed bed data but their absence from the TGA data revealed the interaction mechanism could be attributed to gas phase reformation and cracking reactions.

Numerical study of coal and woody biomass co-gasification in oxygen-fed gasifier

The use of biomass in the energy sector is associated with two important tasks: reducing the dependence of energy systems on expensive high-quality fuel, and increasing the environmental efficiency of thermal power plants (by processing carbon-containing waste and, in some cases, reducing harmful emissions). In addition to co-combusiton, other methods of fuels co-processing are possible, including co-gasification. The process of gasification of low-grade fuels can be unstable because of their low calorific value, often accompanied by the formation of tar products, so the addition of coal improves the efficiency of co-conversion. On the other hand, the high reactivity of biomass can contribute to the stabilization of combustion and gasification regimes of fuels with low-reactivity, such as coals with high degree of metamorphism or petcoke. In this paper, the process of pulverized fuel gasification is considered, and limitations on the efficiency associated with the melting of ash are investigated.

Integration of a selected district heating system with an installation for cogasification of coal and biomass

The article presents a topic related to generation of heat and power in small and medium size coal power units which are able to comply with the emission benchmark of 550 g of CO2/kWh through utilization of biomass. The concept for coal and biomass cogasification installation is based on GazEla reactor, which has been developed by Institute for Chemical Processing of Coal. Authors also present a discussion on issues related to technological scheme of the gasification unit which has been integrated with a selected district heating system. The system has been set up for generation of hot technological water and electrical power. Focal point of the installation is a fixed bed gasification reactor. For the system to provide means enabling cogeneration of heat and power, downstream from the generator a high-temperature gas dedusting system, a unit for recovery of heat from process gas coupled with separation of tar contaminants as well as a gas engine were proposed. A sorted chart presenting historical data for annual demand for heat together with the most important assumptions used during the analyses are discussed. Finally authors present results of calculations for the integrated unit that are further broadened by sensitivity analyses for change of gasification reactor’s efficiency, as well as engine’s efficiency for heat and power generation.

Investigation on improve ash fusion temperature (AFT) of low-AFT coal by biomass addition

The co-gasification of coal and biomass is of importance for coal clean conversion and biomass utilization on a large scale. To investigate the effecting behaviors of biomass on ash fusion characteristics of low ash-fusion-temperature (AFT) coal, the ash chemical properties of three materials (Shenmu coal (SM), chestnut shell (CS), and rice husk (RH)), the variations in SM mixed AFT with increasing CS or RH mass ratio and their mechanisms were explored through silicate-network structure theory, X-ray powder diffractometry, and FactSage software. The formations of anorthite, gehlenite and their eutectics caused SM with low AFT. An increased CS mass ratio led to the increasing contents of high melting-point (MP) kalsilite, lime and magnesia and the decreasing contents of low MP nepheline, olivine, and gehlenite, this made SM mixed AFTs increased gradually. Increasing high MP tridymite content led to SM mixed AFT mostly increased with increasing RH mass ratio. The temperature that all minerals changed into liquid phase based on FactSage calculation could reflect the AFT variation of samples.

Effect of fuel blend composition on hydrogen yield in co-gasification of coal and non-woody biomass

In this study, torrefaction of sunflower seed cake and hydrogen production from torrefied sunflower seed cake via steam gasification were investigated. Torrefaction experiments were performed at 250, 300 and 350 °C for different times (10–30 min). Torrefaction at 300 °C for 30 min was selected to be optimum condition, considering the mass yield and energy densification ratio. Steam gasification of lignite, raw- and torrefied biomass, and their blends at different ratios were conducted at downdraft fixed bed reactor. For comparison, gasification experiments with pyrochar obtained at 500 °C were also performed. The maximum hydrogen yield of 100 mol/kg fuel was obtained steam gasification of pyrochar. The hydrogen yields of 84 and 75 mol/kg fuel were obtained from lignite and torrefied biomass, respectively. Remarkable synergic effect exhibited in co-gasification of lignite with raw biomass or torrefied biomass at a blending ratio of 1:1. In co-gasification, the highest hydrogen yield of 110 mol/kg fuel was obtained from torrefied biomass-lignite (1:1) blend, while a hydrogen yield from pyrochar-lignite (1:1) blend was 98 mol/kg. The overall results showed that in co-gasification of lignite with biomass, the yields of hydrogen depend on the volatiles content of raw biomass/torrefied biomass, besides alkaline earth metals (AAEMs) content.

Fluidized bed air gasification of solid recovered fuel and woody biomass: Influence of experimental conditions on product gas and pollutant release

The aim of this work is to study the air gasification of solid recovered fuel (SRF), and to compare it to the gasification of woody biomass (beech wood sawdust, and waste wood). This study focuses on the influence of several operating parameters: temperature – between 800 and 910 °C –, O2/C ratio – between 0 (pyrolysis conditions) and 0.34, and addition of steam. Experiments are performed in a bubbling fluidized bed at 1.5 bar, with a solid feeding rate of 1–3 kg/h. The yield and composition of the product gas is particularly looked at, together with the repartition of carbon into the different types of products (gas species, tar molecules). Sulphur release to the gas phase is also investigated.Temperature has mainly an influence on H2 and CO yields, which is attributed to char gasification enhancement. The addition of steam in fluidising gas induces an increase in oxygenated gas species yields (CO + CO2), related to char gasification improvement. It does not have any reforming influence on light hydrocarbon and tar, with even a slight inhibiting effect. Woody biomass and SRF show significant differences in product yields, which are qualitatively explained by the initial elemental composition and material content of each type of fuel.From a process point of view, the conversion efficiency improvement by varying the gasification conditions for SRF is limited compared to the higher efficiency obtained with woody biomass. Co-gasification of biomass – possibly waste wood – and SRF, could be a way to improve the overall efficiency, and limit pollutant content.

A comprehensive mathematical model of a serial composite process for biomass and coal Co-gasification

A comprehensive mathematical model to simulate a serial composite process for biomass and coal co-gasification has been built. The process is divided into combustion stage and gasification stage in the same gasifier, it is a new process for the co-gasification of biomass and coal. The model is based on reaction kinetic, hydrodynamics, mass and energy balances, it is a one-dimensional, K-L three-phase, unsteady state model. The model is divided into two sub-models, one is the combustion sub-model, the other is the coal-biomass serial gasification sub-model. Combustion sub-model includes coal pyrolysis, dense phase combustion, and dilute phase combustion model. Gasification sub-model includes biomass pyrolysis, dense phase coal gasification, dense phase biomass gasification, and dilute phase gasification model. The model studies the effects of key parameters on gasification properties, including gasification temperature, S/B, B/C, and predicts the composition of product gas and gas calorific value along the reactor's axis at different time. The model predictions agree well with experimental results and can be used to study and optimize the operation of the process.

Co-pyrolysis and co-gasification of biomass and polyethylene: Thermal behaviors, volatile products and characteristics of their residues

Co-pyrolysis and co-gasification of biomass and plastics could be a promising method to alleviate environmental pollution and provide renewable energy. In this paper, co-pyrolysis and co-gasification of eucalyptus wood (EW) or rice straw (RS) with polyethylene (PE) were investigated by a thermogravimetric analyzer coupled with a Fourier transform infrared spectrometer (TG-FTIR) and a scanning electron microscope coupled with energy-dispersive spectroscopy (SEM/EDS). Results showed that the pyrolysis behaviors were characterized by two stages. The first stage was the decomposition of EW and RS, and the second stage primarily consisted of the degradation of PE. The gasification exhibited a third stage for the reaction of products with CO2. A synergistic effect was presented in the pyrolysis and gasification of biomass with PE, and it could have a positive effect on the decomposition of biomass. Compared to individual pyrolysis and gasification, co-pyrolysis and co-gasification generated no new substances, but the yield of some products was changed in these processes. In co-pyrolysis, the decomposition of biomass was promoted. In co-gasification, the production of CH4, CO and oxygenated compounds was inhibited, while the reaction to generate H2O was promoted. Gasification and the addition of PE both increased the carbon content and reduced the oxygen content of volatile products. Additionally, more metal elements could be deposited in residues when PE was added.

Pathway of biomass-potassium migration in co-gasification of coal and biomass

The migration pathway of potassium in biomass during coal/biomass co-gasification was studied both qualitatively and quantitatively. A reactor was employed to individually perform pyrolysis and gasification of two raw materials and their blends. An inductively coupled plasma mass spectrometry accurately measured the amount and occurrence of potassium in biomass migration. Results showed that about 58.6 wt% potassium in biomass existed in the water-soluble form. When the blends were pyrolyzed at above 500 °C, about 65.0 wt% potassium in biomass migrated to the coal char, 19.1 wt% potassium in biomass remained in the biomass char and 15.9 wt% potassium in gas phase. The migrated potassium salt in coal char still existed as a 75.4 wt% insoluble sulfate. Reaction temperature and the ratio of Al to Si from the minerals in coal are key issues for the redistribution of potassium in biomass. The water-soluble potassium in biomass helps to catalytic co-gasification.

Gasification of lignocellulosic biomass to produce syngas in a 50 kW downdraft reactor

Lignocellulosic biomass gasification shows a pronounced prospective to replace fossil fuels. In this study, the gasification of coconut shell with charcoal using a 50 kW downdraft reactor was investigated. The controlling parameter of temperature and pressure were used to verify the production of gas during the gasification process with air. The higher contents of cellulose and hemicellulose than lignin in the sample were found to gasify better, as evident from structural analysis. The gasifier produces a combustible gas with a H2, CO, CO2 and CH4 concentrations of 8.44, 15.38, 5.38 and 1.62 mol.% respectively, at a total flow of air of 30 m3 h−1. The results revealed that 30 wt% charcoal in the feedstock was effectively gasified to generate syngas comprising over 30 mol.% of syngas with a lower heating value of 3.27 MJ/Nm3. Thus, the co-gasification of lignocellulosic biomass with charcoal may contribute to affordable and environmentally friendly syngas energy.

Comparative analysis of biomass and coal based co-gasification processes with and without CO2 capture for HT-PEMFCs

With the seasonal availability and low energy density of biomass and the high environmental impact of coal, the co-gasification of biomass and coal is an alternative approach facilitating a trade-off between renewable and non-renewable resources. The aim of this study was to investigate hydrogen production from the co-gasification of biomass and coal integrated by means of the sorption-enhanced water gas shift reactor (G-SEWGS) for a high temperature proton exchange membrane fuel cell (HT-PEMFC). The effects of the gasifier temperature, the steam to fuel ratio (S/F ratio), and the equivalence ratio (ER) on the hydrogen production performance and environmental impact of the G-SEWGS were theoretically analysed and compared with the conventional gasifier integrated with the water gas shift reactor (G-WGS) and the sorption-enhanced gasifier integrated with the water gas shift reactor (SEG-WGS). As compared to the conventional water gas shift reactor, the addition of a CaO sorbent in the modified water gas shift reactor not only reduces the amount of the CO2 emission but also leads to an increase in the hydrogen concentration and hydrogen content. The G-SEWGS provides better performance in terms of its fuel processor efficiency and CO2 emission than the G-WGS and the SEG-WGS. Also, the problem of sulphur compound in the hydrogen-rich gas can be reduced by using of the sorption-enhanced water gas shift reactor (SEWGS). The best system exergy efficiency, which was around 22% for the power generation, was determined from the HT-PEMFC integrated with the G-SEWGS. The main exergy destruction of around 70% of the total loss was caused by hydrogen production processes.

Techno-economic analysis of electricity and heat production by co-gasification of coal, biomass and waste tyre in South Africa

South Africa has large deposit of coal that supports about 95% of electric power generation in the country. The fuel is fast depleting, though the current reserve may serve for the next century. However, the emissions from the coal projects huge threat to the environment. Similarly, the country has abundant solid wastes that can be co-gasified with coal to H2 enriched syngas for clean energy production. A 5 MW combined heat and power plant was studied using different coal-to-solid waste ratios of 1:1, 3:2, and 4:1 and economy of the plant was evaluated with feedstock costing (WFC) and without feedstock costing (WOFC). The lower heating value of the fuels, determined from a model equation was applied to estimate the annual feedstock requirement and the feed rate. Net Present Value (NPV), Internal Rate of Return (IRR), and Payback Period (PBP) were used to evaluate the viability of the power generation at the 10th, 11th, 17th and 18th year business periods. The predicted optimum period of the plant is the 10th year. The use of Coal + Pine saw-dust (PSD) blend of blend ratio 1:1, is the most attractive feedstock for the energy generation. A higher profit of about 13.82%, and 23.56% were estimated for the use of Coal + PSD as compared to the use of 100% Matla coal at WFC and WOFC, thus; enabling a savings of about 1,868.81 t feedstock per annum. The use of Coal + PSD blend of blend ratio 1:1 reduces the CO, CO2, SO2, and NOX emissions by 3.4%, 23.28%, 22.9%, and 0.55%, respectively.

A mechanism investigation of synergy behaviour variations during blended char co-gasification of biomass and different rank coals

Abstract Co-gasification reactivity of rice straw and bituminous coal/anthracite blended chars under CO2 atmosphere was evaluated using thermogravimetric analysis, and the influences of coal type and gasification temperature on synergy behaviour variations on co-gasification reactivity as carbon conversions increased were quantitatively studied. Furthermore, the chemical forms and concentrations of AAEM species at different co-gasification conversions were quantitatively analyzed for revealing co-gasification synergy mechanism. The results demonstrate that as conversions increased, synergy behaviour on co-gasification reactivity of rice straw-bituminous coal blends was shown as the weakened inhibition effect firstly and then the enhanced synergistic effect. Moreover, the inhibition effect on co-gasification reactivity of rice straw-bituminous coal blends was sustained up to higher conversion with the increment of gasification temperature. Differing from rice straw-bituminous coal blends, synergistic effect on co-gasification reactivity of rice straw-anthracite blends was obviously enhanced at early stage of co-gasification and started to slowly weaken after reaching the most significant synergistic effect at middle stage of co-gasification. Additionally, it was revealed that synergy behaviour variations on co-gasification reactivity of rice straw-bituminous coal blends were mainly attributed to the combination effects of active K and Ca transformation during co-gasification, while those of rice straw-anthracite blends indicated a good correlation with active K transformation during co-gasification.

Process Simulation of the Co-Gasification of Wood and Polymeric Materials in a Fixed Bed

The problem of waste processing remains of considerable current interest. Energy processing can become a method for its solution. For this purpose, the addition of higher grade fuel is frequently required in order to stabilize the process of thermal conversion. In this work, the effect of control parameters on the efficiency of the co-gasification of biomass (wood) and waste polymers in a dense layer was investigated. For this purpose, a mathematical model, which included blocks for describing drying, pyrolysis, and gasification processes for each particular component of a fuel mixture, was developed. The results of the calculation were compared with published data.

Energy analysis and techno-economic assessment of a co-gasification of woody biomass and animal manure, solid oxide fuel cells and micro gas turbine hybrid system

Co-gasification of woody biomass and animal manure is an effective technology to utilize animal manure. In this work, the thermodynamic and economic analysis of an integration of co-gasification of woody biomass and animal manure with solid oxide fuel cell (SOFC) and micro gas turbine is carried out. The overall thermodynamic performance of this combined heat and power (CHP) system is investigated by a mathematics model consisting of simple zero-dimensional model of SOFC and one-dimensional model of downdraft biomass gasifier. The net present value (NPV) method is adopted to investigate the economic feasible of the CHP system.The gasifier model includes two parts. The pyrolysis-oxidation zone includes pyrolysis zone and combustion zone, and a lumped capacitance method and chemical equilibrium are used to simulate the species in pyrolysis-oxidation zone, while one-dimensional kinetic model is adopted to analyze the performance of reduction zone, which considering geometrical dimensions of downdraft gasifier and actual char conversion process.Effects of three operating parameters such as air flow rate in gasifier, moisture content of blended fuel and mass fraction of woody biomass in blended fuel on overall performance of CHP system are evaluated. The results show that decreased mass fraction of animal manure and increased mass flow rate of gasification air have positive effect on conversion of char owing to higher reaction temperature. Entire conversion of char in gasifier and electrical efficiency of the CHP power system above 45% can be achieved on the condition that mass fraction of animal manure is less than 0.4, moisture content is less than 0.4 and mass flow rate of gasification air is more than 47 kg h−1 as the total mass flow rate of blended fuel equal to 28 kg h−1.Economic analysis shows that more woody biomass rather than animal mature in blend fuel is more economically attractive despite of the low cost of animal mature. The particular high initial capital investment of SOFC is the main part of the whole CHP system. In this work, the payback time is less than eight years. If the target cost less than 3000 €/kW for SOFC in a future year will be reached and the optimized operating parameter is adopted, the investment of a co-gasification of woody biomass and animal manure, SOFC and MGT hybrid system will be more competitive for the user.

Ash fusion characteristics during co-gasification of biomass and petroleum coke

In this study, the effect of biomass ash on petroleum coke ash fusibility was investigated at a reducing atmosphere. Some analytical methods, such as ash fusion temperatures (AFTs) analysis, X-ray diffraction (XRD), FactSage and scanning electron microscopy (SEM), were applied to determine the characteristics of ash fusion and transformation of mineral matters. The results indicated that AFTs were closely associated with ash mineral compositions. It was found that the formations of high melting point calcium silicate, vanadium trioxide and coulsonite resulted in the high AFTs of Yanqing petroleum coke (YQ). When blending with certain proportional pine sawdust (PS), corn stalk (CS), the AFTs of mixture could be decreased significantly. For PS addition, the formations of low-melting point calcium vanadium oxide should be responsible for the reduction of AFTs, whereas for CS addition the reason was ascribed to the formation of low-melting point leucite and the disappearance of high-melting V2O3.