Co-gasification Performance Research Articles

ANN model of co-gasification process in bubbling fluidized bed: Contribution ratio analysis

Co-gasification of coal and biomass in a bubbling fluidized bed may offer an effective and economical method to partially replace coal to produce hydrogen, thereby addressing the objectives of achieving a carbon dioxide emissions peak and carbon neutrality. An Artificial neural network (ANN) model was utilized to simulate the hydrogen and other performance of co-gasification in the bubbling fluidized bed. Five types of ANN architectures were tested, including FFBP, CFBP, EFBP, LR, and NARX. Five optimization algorithms were also applied, including L-M, GA, GD, GDX, and PSO, to identify the optimal model to give a more accurate predicate the hydrogen production. The input data were derived from the ultimate analysis of the mixed coal and biomass, the proximate analyzes of mixed coal and biomass, and the operational conditions. The output data consisted of gas composition, carbon conversion, gasification efficiency, total gas yield, syngas yield, low and high heating values of the gas. The LR-PSO with 6 hidden neurons (R2 = 0.9995 and MSE = 0.1357) outperformed other ANN types and optimization algorithms. To further understand the performance of co-gasification, the influences of biomass to coal ratio, equivalence ratio, steam to carbon ratio and temperature on ratio of H2 to CO and syngas yield were predicted. The highest ratio of H2 to CO for the work of Li et al. (2010) [26], Song et al. (2013) [27] and Valdés et al. (2015) [28] were 0.7, 1.2 and 0.88, respectively. And those for syngas yield were 0.85, 1.09 and 1.55 m3/kg, respectively. To reveal the important factor on the ratio of H2 to CO, a detailed analyzed of the contribution ratio was conducted. The most critical factor affecting co-gasification performance in the work of Song et al. (2013) [27] were identified as SC ratio and temperature, which was higher than those of W and ER. The effect of SC exceeded that of T at SC ratio of 0.4, while it came to a reverse at temperature above 700 °C. These findings may serve as a valuable tool for adjusting the various factors to achieve the desired performance in the co-gasification of coal and biomass.

Thermodynamic modeling and performance analysis on co-gasification of Chlorella vulgaris and petrochemical industrial sludge via Aspen plus combining with response surface methodology

The co-gasification process of Chlorella vulgaris (CV) and petrochemical industrial sludge (IS) was uncoupled and simulated by Aspen Plus. The co-gasification process was considered into drying, pyrolysis, partial oxidation, as well as reduction and reforming. Simulation results showed that, the interactions between IS and CV were found for the differences in CHO, and affected by the IS ratio and gasification temperature. Increasing the temperature could improve the CO content, and get optimal H2 at 700 °C, while decrease CO2 and CH4 contents, thus lead to a higher LHV (lower heating value) of syngas, CGE (cold gas efficiency), and syngas content, CO selection. The higher S/IS-CV (steam to IS-CV blends ratio) value favored H2 production but reduce CO content and CGE. As air equivalent ratio (ER) increased, the H2 content constantly reduced, while CO varied slightly when the ER was lower than 0.10. After the ER value was higher than 0.10, CO reduced and thereby decreasing co-gasification performance. When the drying degree of feedstock increased, the CO content continuously increased, leading to better co-gasification performances. The RSM results showed that the significance factors in the interactions are ER and drying degree, S/IS-CV and ER, gasification temperature and ER, and gasification temperature and ER, respectively for CGE, LHV, Csyngas, and SelCO.

Addition of torrefied algal biomass to improve land-based biomass gasification for hydrogen-rich gas production

Steam co-gasification of two kinds of biomass with different activities could generate synergetic effect on the fuel gas production. In this study, steam co-gasification of torrefied biochar from seaweed with land-based biomass, i.e., cedar wood and rice husk, was performed for the production of hydrogen(H2)-rich fuel gas, in which seaweed was torrefied at different temperatures (i.e., 200, 250 and 300 °C), and the performance of co-gasification was evaluated at three different gasification temperatures (i.e., 650, 700 and 750 °C) under atmospheric condition with three different steam flow rates (i.e., 0.05, 0.10 and 0.15 g/min) in a fixed bed reactor with a feed biomass and torrefied biochar weight ratio of 1:1. Taguchi's orthogonal array of L9 (34) was used to determine the importance of each parameter on the amount of H2 produced. It is found that the optimum parameters resulting in the highest H2 gas were the co-gasification cedarwood with the torrefied seaweed obtained at a torrefaction temperature of 300 °C at a co-gasification temperature of 750 °C with a steam flow rate of 0.10 g/min. Especially, at this condition, the produced H2 gas was nearly twice higher than that from cedarwood individual gasification and 11 % less tar produced than the calculated result.

Coarse-grained CFD-DEM simulation of coal and biomass co-gasification process in a fluidized bed reactor: Effects of particle size distribution and operating pressure

The co-gasification of coal and biomass through fluidized bed gasifier is a promising technology for the improvement of the utilization efficiency of fossil fuels and the development of renewable energy. In this work, a coarse-grained computational fluid dynamics-discrete element method (CFD-DEM) simulation is performed to investigate the co-gasification process in a bubbling fluidized bed gasifier. The effects of particle size distribution and operating pressure on the hydrodynamics, heat transfer, and co-gasification performance are analyzed. The results show that the increase of sand particle size distribution (PSD) width slightly affects the particle concentration distribution, particle residence time distribution, and co-gasification performance. The heat transfer rate of convection is an order of magnitude higher than those of conduction and radiation. At higher PSD width, the formation of the vertical solid temperature gradient at the bed bottom is attributed to the deteriorated solid mixing. As the operating pressure increases, the bed temperature decreases apparently. In addition, the variation of the convective heat transfer rate dominates the heat transfer efficiency as the operating pressure changes. The application of elevated operating pressure benefits to the thermal-chemical conversion of blend fuel since the char conversion reaction is accelerated.

Acceleration effect of BDO tar on coal water slurry during co-gasification

1,4-butanediol (BDO) is a general-purpose chemical feedstock. BDO tar is produced from the plant and is difficult to dispose of. This study has used the waste-coal-water-slurry (WCWS) technology to dispose of BDO tar and investigated the acceleration mechanism during co-gasification. The results show that the weight loss of BDO-tar-coal-water-slurry (BCWS) is more evident in the range of 200–300 °C because most of the organic constituents in BDO tar are lost. In the high-temperature field (>600 °C), the BCWS thermogravimetric (TG) curves migrate to the low-temperature zone, indicating that the co-gasification performance of the BCWS is significantly enhanced. The most distinct areas (“spotted area,” “rough area,” and “subsidence area”) exist on the surface of coal char by the alkali metal Na in BDO tar, which impedes the formation of defective carbon structures and amorphous carbon structures. Moreover, many defective and amorphous carbon emerged due to the tightly bound complexes with O and Na generated by the reaction between the unstable intermediate and the carbon matrix. BDO tar for BCWS co-gasification process is catalytic, suggesting that activation energy is lower than that of CWS.

Co-gasification of biomass and coal in a top-lit updraft fixed bed gasifier: Syngas composition and its interchangeability with natural gas for combustion applications

The co-gasification of biomass and coal is a promising approach for efficiently integrating the unique advantages of different gasification feedstock with syngas production. Additionally, syngas from the co-gasification of locally available biomass and coal could supplement the natural gas used in household and industrial burners. The top-lit updraft gasifier features a moving ignition front that starts at the top and propagates downward through the solids bed, while air enters from the bottom and the gas product flows upwards. This study assesses the co-gasification performance of palm kernel shell and high-volatile bituminous coal in a top-lit updraft fixed bed gasifier using 70, 85, and 100 vol% biomass and equivalence ratios ranging from 0.26 to 0.34. The results indicate that the ignition front propagates faster and is more uniform as the biomass volume increases. Micro GC analysis revealed that the H2/CO ratio remained in the range of 0.57–0.59, 0.49–0.51, and 0.42–0.46 for experiments with 70, 85, and 100 vol% biomass, respectively. A gas interchangeability analysis showed that syngas-natural gas blends with up to 15 vol% of syngas could combust in atmospheric natural gas burners without modifications. Thus, the top-lit updraft gasifier shows excellent potential for the co-gasification of coal and biomass. Further research on this technology should explore steam as a gasification agent to enhance the syngas energy content and continuous solids feeding.

Catalytic and inhibitory roles of K and Ca in the pyrolysis and CO2 or steam gasification of Erianthus, and their effects on co-gasification performance

Increasing biomass demand for domestic power production due to feed-in tariffs has led to the use of herbaceous perennial energy crops such as Erianthus arundinaceus (Erianthus) as a biomass resource. Erianthus (JES1) is obtained in a yield of approximately 14 t/ha on a dry basis in Nasu-shiobara, a temperate climate region of Japan and its standing-dead characteristics permit a small drying cost. In this study, the catalytic roles of Ca and K on the CO2 and steam gasification of Erianthus char were investigated using thermogravimetry-differential thermal analysis (TG-DTA), and the effect of blending Erianthus with timber waste on the co-gasification performance was elucidated. The obtained results showed that the loading of K into the demineralised char (DC) enhanced both the CO2 and steam gasification processes. In contrast, the loading of Ca on DC slightly inhibited CO2 gasification, while steam gasification was significantly inhibited. In the co-gasification of an Erianthus-blended timber waste feedstock, the conversion to gas and cold-gas efficiency was promoted in the case of an Erianthus blend ≤30% due to the presence of inorganic components, such as K, in the blended feedstock.

Parametric optimisation through the use of Box-Behnken design in the Co-gasification of oil palm trunk and frond for syngas production

Biomass co-gasification is among the most encouraging bio-conversion technologies used in the production of clean and sustainable fuel. This research work was performed on the co-gasification of oil palm trunk and frond to explore the mutual relation of input variables on syngas and optimize them for maximum syngas generation. Air was utilised as the agent of gasification, while a downdraft gratifier was used as the reactor. The operating variables are temperature (700–900 °C), blending ratio (20–80 wt%) and particle size (1.18–4 mm). Optimization was achieved through Response Surface Methodology, Box-Behnken design. The results showed that the operating variables influenced the results in increasing order of temperature, particle size, and blending ratio. Optimum syngas composition was obtained as 20.22 vol% H2, 24.86 vol% CO, and 13.78 vol% CH4 at a temperature of 900 °C, particle size of 2.59 mm and a blending ratio of 20OPT:80OPF.The optimized values resulted in a high syngas yield and co-gasification performance. Cost analysis of the optimum blend was carried out, and it was found that the operating cost played a significant role in the final syngas cost. It occupied about 49% of the production cost, while the capital and other cost occupied occupy 44% and 7% respectively.

Cogasification performance of deashed coal with various biomass

Cogasification of lignite and EPFB is present as a production of energy sources that aim to get a synergy effect. However, not all cogasification gives better product quality than fuel parent gasification. In this study, demineralization acted as lignite pre-treatment stage is achieved through HF leaching at 70°C for 4 hours. The mixing ratio varied by lignite to empty palm fruit bunches (EPFB) are 1: 2, 1: 1, and 2: 1 both for non-demineralized lignite (BLM) and lignite demineralized (BLD). The negative synergy effect of two combination is caused by the high content of silica and alumina from the empty palm fruit bunches (EPFB). The lignite demineralization cogasification produces a lower H2 yield than BLM because it also dissolves the mineral content which functions as a catalyst for cogasification synthesis.

Model development and thermodynamic analysis of biomass co-gasification using Aspen plus®

ABSTRACT Gasification is the process of producing syngas with acceptable heat value from a feedstock. Co-gasifying biomass and using syngas thus produced reduce the net CO2 emission as biomass is effectively CO2 neutral. An Aspen plus® model for co-gasification of Indian lignocellulosic biomass is developed and validated against available experimental results. Performance of co-gasification as obtained from this developed model is also assessed by energy and exergy efficiencies of the process. Variations of these two efficiencies with gasification parameters are also reported. Results show that best performance of gasification may be obtained for rice straw with sugarcane bagasse energetically and wheat straw with sugarcane bagasse exergetically. The methodology and results may help selecting Indian biomass for co-gasification with further experimental investigations to decide the suitable one(s).

Enhancement of performance and emission characteristics by co-gasification of biomass and coal using an entrained flow gasifier

Co-gasification of renewable biomass and coal is a promising technique to reduce greenhouse gas emission beside increasing gasification performance instead of individual coal gasification. In this study, the co-gasification performance of pine bark (PB) biomass and Barapukurian bituminous coal (BBC) have been assessed using a high-temperature entrained flow gasifier using CO2 reactant. Results show that increasing biomass concentration increases the carbon conversion, syngas quality and cold gas efficiency (CGE), while reduces emission. For example, an addition of 20% biomass with coal increased the carbon conversion by 21.5, 10.6 and 4.5%-point at temperatures of 1000, 1200 and 1400 °C compared to pure coal gasification. Similarly, increasing biomass ratio in the blend increased the yield of CO by 11–36 vol% under different temperatures. Also, the CGE, fragmentation index (FI=∑inFDo) and alkali and alkaline earth minerals in ash were increased with increasing biomass ratio in the blend. Overall, at least 50% of coal can be replaced with renewable biomass considering performance and emission characteristics, making the technology more sustainable.

Catalytic and noncatalytic gasification of wood–coconut shell blend under different operating conditions

The formation of tar during biomass gasification is a main barrier to establishing reliable gasification technologies. Different catalysts are being used for tar abatement from the biomass gasification. In this study, catalytic and noncatalytic cogasification of wood‐coconut shell blends was carried out in a downdraft gasifier. The effect of the operating parameters on syngas quality, performance of cogasification, and tar reduction was investigated. The biomass blending ratio (BR) was varied as W20:CS80, W50:CS50, and W80:CS20, equivalence ratio (ER) was varied from 0.19 to 0.35, gasification temperature from 700 to 900 °C and catalyst loading (CL) from 5 to 30%. Dolomite, limestone, and Portland cement were used as a catalyst. The results revealed that under noncatalytic conditions, the blend with higher proportion of coconut shells produces better syngas composition with higher HHV and lower tar content. The high ER reduced H2, tar formation, cold gas efficiency and gas yield. It also improved the carbonaceous gas species and carbon conversion efficiency. Increasing gasification temperature significantly improved the syngas quality, cogasification performance and reduced the tar content. The 30% CL significantly improved the gas composition content, gas yield, cold gas efficiency and reduced the tar content up to 52%. Better syngas quality and cogasification performance was possible with calcined cement catalyst whereas a reduction in tar content was observed in the presence of limestone. © 2018 American Institute of Chemical Engineers Environ Prog, 38: 688–698, 2019

Co-gasification of High-ash Sewage Sludge and Straw in a Bubbling Fluidized Bed with Oxygen-enriched Air

Abstract Gasification is a promising technology to utilize solid wastes. Co-gasification of high-ash sewage sludge and straw were studied in a fluidized bed using oxygen-enriched air. Several factors influencing co-gasification performance were investigated, including the blending ratio of straw (BR, 0–100 %), the oxygen percentage of enriched air (OP, 30.2–50 %) and the bed material type (high alumina bauxite, calcined dolomite and olivine). The results indicated that the proper increase in BR led to higher syngas yield and an increase in OP caused an increase in combustible gas components, both showing improvements for waste gasification. Correspondingly, the maximum cold gas efficiency was obtained at BR of 50 % and OP of 44.7 %, respectively. Additionally, calcined dolomite exhibited the maximum advantage in the reduction of heavy polycyclic aromatic hydrocarbons (PAHs), promoting the production of H2 and CO. The addition of high alumina bauxite was favored for improving syngas yield and gasification efficiency.

Effect of biomass type on the performance of cogasification of low rank coal with biomass at relatively low temperatures

Cogasification of low rank coal with three kinds of biomass, i.e., Japanese cedar, rice straw, and seaweed, at relatively low temperatures were performed in a fixed bed downdraft reactor. The effect of different biomass addition on the coal gasification performance was investigated by comparing the experimental char and gas yields with the calculated prediction data. Effect of the blending ratio was also investigated. It was found that the mixing of coal with biomass revealed a synergy effect. Biomass promoted the coal gasification rate, but the extent of promoting effect was depended on the characteristics of biomass themselves. Alkali and alkaline earth metal (AAEM) content played an important role in this synergy effect. Seaweed which contained high AAEM content promoted the coal gasification significantly. Structure of coal was also found to have great effect on the cogasification performance. The results indicated that cogasification of coal with biomass is feasible at relatively low temperatures.

Taguchi approach for co-gasification optimization of torrefied biomass and coal

This study employs the Taguchi method to approach the optimum co-gasification operation of torrefied biomass (eucalyptus) and coal in an entrained flow gasifier. The cold gas efficiency is adopted as the performance index of co-gasification. The influences of six parameters, namely, the biomass blending ratio, oxygen-to-fuel mass ratio (O/F ratio), biomass torrefaction temperature, gasification pressure, steam-to-fuel mass ratio (S/F ratio), and inlet temperature of the carrier gas, on the performance of co-gasification are considered. The analysis of the signal-to-noise ratio suggests that the O/F ratio is the most important factor in determining the performance and the appropriate O/F ratio is 0.7. The performance is also significantly affected by biomass along with torrefaction, where a torrefaction temperature of 300°C is sufficient to upgrade eucalyptus. According to the recommended operating conditions, the values of cold gas efficiency and carbon conversion at the optimum co-gasification are 80.99% and 94.51%, respectively.

Co-gasification performance of coal and petroleum coke blends in a pilot-scale pressurized entrained-flow gasifier

Co-gasification performance of coal and petroleum coke (petcoke) blends in a pilot-scale pressurized entrained-flow gasifier was studied experimentally. Two different coals, including a subbituminous coal (Coal A) and a bituminous coal (Coal B), individually blended with a petcoke in the gasifier were considered. The experimental results suggested that, when the petcoke was mixed with Coal A over 70%, the slagging problem, which could shorten the operational period due to high ash content in the coal, was improved. It was found that increasing O2/C tended to decrease the syngas concentration and better operational conditions of O2/C were between 0.6 and 0.65 Nm3 kg−1. For the blends of Coal B and the petcoke, the slagging problem was encountered no more, as a result of low ash content in both Coal B and the petcoke. The better co-gasification performance could be achieved if the blending ratio of the two fuels was 50%, perhaps resulting from the synergistic effect of the blends. With the aforementioned blending ratio, the optimal condition of O2/C was located at around 0.65 Nm3 kg−1. The co-gasification was also simulated using Aspen Plus. It revealed that the simulation could provide a useful insight into the practical operation of co-gasification. Copyright © 2011 John Wiley & Sons, Ltd.

Hydrogen production from co-gasification of coal and biomass in supercritical water by continuous flow thermal-catalytic reaction system

Hydrogen is a clean energy carrier. Converting abundant coal sources and green biomass energy into hydrogen effectively and without any pollution promotes environmental protection. The co-gasification performance of coal and a model compound of biomass, carboxymethylcellulose (CMC) in supercritical water (SCW), were investigated experimentally. The influences of temperature, pressure and concentration on hydrogen production from co-gasification of coal and CMC in SCW under the given conditions (20–25 MPa, 650°C, 15–30 s) are discussed in detail. The experimental results show that H2, CO2 and CH4 are the main gas products, and the molar fraction of hydrogen reaches in excess of 60%. The higher pressure and higher CMC content facilitate hydrogen production; production is decreased remarkably given a longer residence time.