上吸式生物质秸秆气化炉的设计与试验研究

设计一台上吸式生物质秸秆气化炉,并进行热解气化试验,分析不同气化剂量对炉内温度的影响以及温度和秸秆种类对产气成分的影响。试验结果表明：气化剂量对炉内温度及炉内温度对产气成分含量的影响均较大;秸秆种类也对产气的热值有较大的影响,稻草热解可燃气热值4．1MJ／m^3,油菜秆热解可燃气热值4．9MJ／m^3,玉米秆热解可燃气热值5．5MJ／m^3。     

Design and experimental study of pilot scale throat-less downdraft gasifier fed by rice husk and wood sawdust

In this work, pilot scale throat-less downdraft gasifier is fabricated and tested on rice husk and blend of rice husk-sawdust. The test aims to investigate effect of equivalence ratio on temperature profile, propagation front (flame propagation rate, bed movement rate, and effective propagation rate), and performance of the gasifier (composition of producer gas, heating value of producer gas, and thermal efficiency of the gasifier). Equivalence ratio investigated are 0.15, 0.20, and 0.25, while the blend ratio is 1:1 by mass. The results show that axial temperatures in the reactor surge faster with increasing equivalence ratio during the rice husk gasification and the blend gasification. Typically, flame propagation rate, bed movement rate, and effective propagation rate improve with rising equivalence ratio from 0.15 to 0.25. The best higher heating values and thermal efficiencies are obtained at equivalence ratio of 0.2 and 0.15 for the rice husk gasification and the blend gasification, respectively.     

生物质膜法富氧气化制气技术试验研究

利用膜法富氧制气与生物质热解气化技术相结合,在半工业试验的基础上,通过改变固定床气化试验台中的氧浓度等关键反应因素,研究子玉米秸秆在常压固定床气化炉中的气化特性,并总结出燃气热值及燃气主要成分随氧气浓度变化的主要规律.试验研究表明,膜法富氧气化技术是可行的,对改善生物质燃气组分和热值具有较好作用,可用于工程实践.     

Characteristics of cyclone gasification of rice husk

The gasification characteristics of the rice husk were studied in a cyclone gasifier using air as the gasifying medium to generate the fuel gas with available heating value and less tar content. The influence of equivalence ratio on temperature profiles, composition and low heating value of the produced gas, tar content, carbon conversion and cold gas efficiency was investigated. The equivalence ratios considered in this study were 0.20–0.32. The results show that the optimal equivalence ratio is 0.29 and the maximum temperature of gasification should be lower than 1000 °C. In order to optimize the performance of the cyclone gasifier, the main body of the gasifier was lengthened and air staged gasification was carried out. The low heating value of the produced gas, carbon conversion, cold gas efficiency and tar content are 4.72 MJ/Nm³, 57.5%, 37.3% and 1.85 g/Nm³, respectively.     

60kW两段式秸秆气化炉运行特性

研究了上海交通大学热能研究所研制的60kW两段式秸秆气化炉的运行特性.以秸秆为原料在该气化炉上实验,考察原料量、空气过量系数对气化炉生产能力和碳转化率以及气化效率的影响,并分析了气化气成分及热值.数据表明该气化炉各项参数均优于一般固定床气化炉:原料消耗量为100kg/h,ER=0.35时,秸秆气化气平均热值为6599.6010/m~3,产气率为1.88m~3/kg,碳转化率为91.3%,气化效率为84.6%.     

Comparison of green waste gasification performance in updraft and downdraft fixed bed gasifiers

This study aimed to investigate the gasification potential of municipal green waste in different fixed-bed gasifier configurations as updraft and downdraft. Both reactor systems were constructed from stainless-steel with a cyclone separator to increase synthesis gas yield and reduce tar production. Green waste collected from parks and gardens by Manisa Metropolitan Municipality, Turkey, was used in the experiments. After full-characterization of green waste, gasification experiments were performed above 700 °C to produce syngas with more than 40% (volumetric) H₂ and heating value around 12.54 MJ/Nm³. Dry air (DA) and pure oxygen (PO) were used as gasification agents. DA was applied with the flow-rates ranged between 0.4 and 0.05 L/min while the flow-rate of PO was 0.01 L/min. The maximum H₂ production as 45 vol% was obtained in downdraft reactor while it was about 51 vol% in updraft system. CH₄ production was obtained as higher value (app. 19 vol%) in downdraft reactor than that (13 vol%) in the updraft one. In the experiments with DA above 700 °C, the H₂/CO ratio varied between 1 and 3, and in the experiments with PO, it increased up to a maximum value of 4. The study has found a suitable set of gasification process parameters for two reactor systems. Therefore, the findings have been compared and discussed in detail.     

Exergy analysis of updraft and downdraft fixed bed gasification of village-level solid waste

The most commonly used for gasification of village-level solid waste is the fixed-bed gasifier, but there is no reasonable method to evaluate the gasification process. This paper attempts to find a gasifier that is most suitable for gasification of village-level solid wastes through exergy analysis method. Based on experimental data from literature, the exergy efficiencies and LHV(Low Heat Value) of product gas from updraft and downdraft fixed bed gasifier are studied in this paper. The results show that the updraft fixed bed gasifier has higher exergy efficiency, and the gas produced by the downdraft fixed bed gasifier has a higher heating value. Air gasification has higher exergy efficiency than steam gasification and pure oxygen gasification. The highest exergy efficiency at a gasification temperature of about 1000 °C and ER (Equivalence Ratio) value in the range of 0.33–0.36. The volatile content of gasification raw materials is higher, and the gasification efficiency is higher. Through the research of this paper, a new path to reasonably evaluate the gasification process is obtained.     

Assessment of low-rank coal and biomass co-pyrolysis system coupled with gasification

To utilize low-rank coal and biomass in a highly efficient and environmental-friendly manner, a co-pyrolysis system coupled with char gasification is investigated. This system has five main units, namely, the drying and mixing, pyrolysis, cooling and separation, combustion, and gasification units, which are simulated by ASPEN plus based on experimental data. Results show that 37% of the pyrolysis char is burned to supply heat for pyrolysis and drying processes based on cascade utilization of heat energy, whereas the rest is sent to a gasifier. The sensitivity analysis is performed to investigate the impacts of steam and O₂ injection on gas composition, gasification temperature, carbon conversion efficiency, heating value of gas during gasification, and gas production efficiency. The fractions of H₂, CH₄, CO, and CO₂ demonstrate diverse variation tendencies with an increasing equivalence ratio and steam-to-char (S/C) ratio. However, carbon conversion efficiency reaches its peak of 99.91% when the equivalence ratio is approximately 4 regardless of S/C ratio. An equivalence ratio of 4 and S/C ratio of 0.15 are used as decent examples to calculate the mass balance and to simulate the overall system. Results show that 1000 kg/h coal and 500 kg/h biomass can produce 285.83 m³/h pyrolysis gas and 2580.78 m³/h gasification gas with low heating values of 8.20 and 9.746 MJ/m³, respectively.     

Co-gasification between coal/sawdust and coal/wood pellet: A parametric study using response surface methodology

This study had compared raw biomass and pre-treated biomass co-gasified with coal with the aim of investigating the reliability of pre-treated biomass for enhancing gasification performance. Sawdust (SD) and wood pellet (palletisation form of sawdust - WP) and blends of these two feedstocks with sub-bituminous coal (CL), were gasified in an air atmosphere using an external heated fixed-bed downdraft gasifier system. Response surface methodology (RSM) incorporating the central composite design (CCD) was applied to assist the comparison of all operating variables. The three independent variables were investigated within a specific range of coal blending ratios from 25% to 75%, gasification temperature from 650 °C to 850 °C and equivalence ratio from 0.20 to 0.30 against the dependent variables, namely the H₂/CO ratio and higher heating value of the syngas (HHVsyngas). The results revealed the H₂/CO ratio and a higher heating value of the syngas of more than 1.585 and 6.072 MJ/Nm³, respectively. Findings also showed that the H₂/CO ratio in the syngas from CL/WP possessed a higher value than the CL/SD. In contrast, CL/SD possessed a higher heating value for syngas with about 1% difference compared to the CL/WP. Therefore, co-gasified coal with wood pellets could potentially be a substitute for sawdust.     

Hydrogen-rich gas production from biomass steam gasification in an updraft fixed-bed gasifier combined with a porous ceramic reformer

This paper investigates the hydrogen-rich gas produced from biomass employing an updraft gasifier with a continuous biomass feeder. A porous ceramic reformer was combined with the gasifier for producer gas reforming. The effects of gasifier temperature, equivalence ratio (ER), steam to biomass ratio (S/B), and porous ceramic reforming on the gas characteristic parameters (composition, density, yield, low heating value, and residence time, etc.) were investigated. The results show that hydrogen-rich syngas with a high calorific value was produced, in the range of 8.10–13.40 MJ/Nm³, and the hydrogen yield was in the range of 45.05–135.40 g H₂/kg biomass. A higher temperature favors the hydrogen production. With the increasing gasifier temperature varying from 800 to 950 °C, the hydrogen yield increased from 74.84 to 135.4 g H₂/kg biomass. The low heating values first increased and then decreased with the increased ER from 0 to 0.3. A steam/biomass ratio of 2.05 was found as the optimum in the all steam gasification runs. The effect of porous ceramic reforming showed the water-soluble tar produced in the porous ceramic reforming, the conversion ratio of total organic carbon (TOC) contents is between 22.61% and 50.23%, and the hydrogen concentration obviously higher than that without porous ceramic reforming.     

Thermodynamic optimization of biomass gasification for decentralized power generation and Fischer–Tropsch synthesis

In recent years, biomass gasification has emerged as a viable option for decentralized power generation, especially in developing countries. Another potential use of producer gas from biomass gasification is in terms of feedstock for Fischer–Tropsch (FT) synthesis – a process for manufacture of synthetic gasoline and diesel. This paper reports optimization of biomass gasification process for these two applications. Using the non–stoichometric equilibrium model (SOLGASMIX), we have assessed the outcome of gasification process for different combinations of operating conditions. Four key parameters have been used for optimization, viz. biomass type (saw dust, rice husk, bamboo dust), air or equivalence ratio (AR = 0, 0.2, 0.4, 0.6, 0.8 and 1), temperature of gasification (T = 400, 500, 600, 700, 800, 900 and 1000 °C), and gasification medium (air, air–steam 10% mole/mole mixture, air–steam 30%mole/mole mixture). Performance of the gasification process has been assessed with four measures, viz. molar content of H₂ and CO in the producer gas, H₂/CO molar ratio, LHV of producer gas and overall efficiency of gasifier. The optimum sets of operating conditions for gasifier for FT synthesis are: AR = 0.2–0.4, Temp = 800–1000 °C, and gasification medium as air. The optimum sets of operating conditions for decentralized power generation are: AR = 0.3–0.4, Temp = 700–800 °C with gasification medium being air. The thermodynamic model and methodology presented in this work also presents a general framework, which could be extended for optimization of biomass gasification for any other application.     

Promising components of waste-derived slurry fuels

The paper presents the results of experimental studies of energy (calorific value, ignition delay times and threshold ignition temperatures, duration and temperature of combustion) and environmental (CO₂, NO_x and SO_x emission) characteristics of fuel slurries based on pulverized wood (sawdust), agricultural (straw), and household (cardboard) waste. Wastewater from a sewage treatment plant served as a liquid medium for fuels. Petrochemical waste and heavy oil were additives to slurries. The focus is on obtaining the maximum efficiency ratio of slurry fuel, calculated taking into account environmental, cost, energy and fire safety parameters. All slurry fuels were compared with typical coal-water slurry for all the parameters studied. A comparison was also made between slurries and traditional boiler fuels (coal, fuel oil). The relative efficiency indicator for waste-based mixtures was varied in the range of 0.93–10.92. The lowest ignition costs can be expected when burning a mixture based on straw, cardboard and oil additive (ignition temperature is about 330 °C). The volumes of potential energy generated with the active involvement of industrial waste instead of traditional coal and oil combustion are forecasted. It is predicted that with the widespread use of waste-derived slurries, about 43% of coal and oil can be saved.     

下吸式生物质气化炉热力学平衡模型研究

建立下吸式生物质气化炉热力学平衡模型,该模型包括焦炭、焦油和气体,并用已公布的实验数据对模型进行验证,均方根（RMS）在1.304~3.814之间,结果表明该模型的预测值与实验数据吻合较好,可认为模型可靠。然后模拟棉秆在下吸式生物质气化炉中以空气和富氧气体2种气化氛围下,不同操作参数(当量比、预热温度和气化炉反应温度)下对棉秆气化的气体组分、热值和产率的影响。模拟结果表明：富氧气体为气化剂时,当量比从0.20增至0.35时,气体中N₂含量比空气显著下降,达10%以上,同时发现能提高气体中H₂和CO的含量和热值,热值比空气提高约20%。预热温度对气化成分变化影响有限,随预热温度从30 ℃变化到130 ℃,气体的平均热值从空气的5.2 MJ/m³提高到富氧气体的7.0 MJ/m³。随气化炉内反应温度从750 ℃升至1250 ℃,空气和富氧气体2种气化剂下的H₂和CO分别从20.94%、26.84%和21.77%、28.67%下降到4.06%、9.12%和10.49%、21.60%,导致气体的热值降低。     

Determination of reactor scaling factors for throatless rice husk gasifier

Four open core throatless batch fed rice husk gasifier reactors having internal diameters of 15.2, 20.3, 24.4 and 34.3 cm were designed and fabricated. Each reactor connected with gas cleaning unit was tested for its performance characteristics. On each reactor ten trial runs were conducted varying the air flow rate or specific gasification rate. Gas quality, gas production rate, gasification efficiency specific gasification rate, and equivalence ratio were determined for every run on each of the four reactors. It was found that for each reactor the gasifier performance was the best at a specific gasification rate of around 192.5 kg/h-m². Under the best operating conditions, the equivalence ratio was 0.40 and the gasification efficiency was around 65%. These parameters may be used for designing rice husk operated throatless gasifiers in the capacity range of 3–15 kW.     

玉米秸秆循环流化床热解气化试验

采用循环流化床气化中试装置对玉米秸秆进行了气化试验,分别在常温空气与250℃预热空气条件下,研究了空气当量比（ER）和原料含水率对气化特性的影响规律。结果表明：随着ER的增大,循环流化床气化炉内的反应温度升高,气化燃气中的CO₂含量增加,焦油与CO含量及燃气热值降低,气化效率随ER的增大呈先增大后减小的趋势;随着气化原料含水率的增加,循环流化床气化炉内的平均温度下降,燃气中的CO₂与H₂及焦油含量逐渐升高,CO含量下降,CH₄与C_nH_m含量均为先增加后减少。与常温空气工况相比,预热空气工况下的燃气热值与气化效率均有一定程度的提高。采用预热空气为气化介质,提高气化剂温度,可显著促进玉米秸秆的气化反应,提升气化效率。     

H2-enriched gaseous fuel production via co-gasification of an algae-plastic waste mixture using Aspen PLUS

Thermo-chemical conversion of biomass is a promising technological alternative for producing renewable fuel and reducing waste disposal. This simulation study includes the first attempt to perform co-gasification of algae-plastic waste for H₂-enriched gaseous fuel production. An Aspen Plus-based simulation model was developed to evaluate the influence of gasifier temperature and equivalence ratio on the syngas composition, heating value, and carbon conversion efficiency. Simulation results indicated that the rise in gasifier temperature favoured the H₂ and CO formation, and further, plastic loading enhanced H₂ production to a greater extent. It was observed that the product (H₂ and CO) yield decreased significantly with the rise of the equivalence ratio. At the same time, CO₂ formation increased due to more carbon conversion after enhancing O₂ content in the gasifier. It was also noticed that the synergy of biomass and plastic waste significantly enhanced H₂ content and improved heating value, leading to a produced energy-efficient gaseous product. It is inferred that H₂-enriched feedstock acts as an H₂ donor to the H₂ deficient biomass. Based on the findings, consistency in the simulation results was observed compared with the previous literature. Hence, a mixture of biomass and plastic waste favours obtaining an energy-efficient renewable fuel that could be utilized for different applications.     

Hydrogen production from steam gasification of corn straw catalyzed by blast furnace gas ash

A lab scale gasifier was built to perform the gasification experiment. The effects of temperature and steam flow on the process were investigated, and the effects of the addition of blast furnace gas ash (BFGA) on product composition, the value of H₂/(CO + CO₂), the lower heating value (LHV) of product gas, and productivity are summarized. The experimental results clearly indicate that the addition of BFGA in the steam gasification of corn straw pellets effectively enhances the ability of the downdraft gasifier to produce hydrogen-rich gas. Compared with the non-catalytic gasification process, the addition of BFGA promotes the formation of H₂, inhibits the generation of methane, CH₄, and other hydrocarbon gases, C_nH_m, and increases the H₂/(CO + CO₂) ratio. Unlike the process without the BFGA, the LHV of the product gas with BFGA increases with increasing temperature. When the water vapor volume was 0.75 kg/h, the gas production rate was the same at 850 °C with BFGA and at 950 °C without ash gas. The addition of BFGA clearly leads to a significant improvement in the ability of gasifiers to produce hydrogen-rich gas.     

Main performance analysis of kitchen waste gasification in a small-power horizontal plasma jet reactor

Plasma gasification technology has been demonstrated in recent studies as one of the most effective and environmentally friendly methods for solid waste treatment, which could be attractive for resource and energy recovery from kitchen waste. This study focuses on the effects of plasma gasification of kitchen waste replaced by 85% flour and 15% vegetables (Mass Fraction), including dimensionless operation parameters, ER (equivalence ratio), SFR (steam to feedstock ratio) and the gasification efficiency. The Horizontal plasma jet reactor is employed in the experiments. It is found that the influence of the equivalence ratio on syngas can be divided into positive and negative parts. And the steam injection is conducive to improving the yield of syngas, which mainly results from the heterogeneous water gas shift reaction. The optimal experimental parameters can be obtained at ER = 0.095 and SFR = 0.084. Besides, the maximum first and second efficiency of plasma gasification during these cases occurs in SFB = 0.084, accounting for 28.2% and 23.0%, respectively, which needs to study further to get improvement. The XRD and Raman spectra are applied to characterize the residual char, which may illustrate that the degree of graphitization is competing with a high yield of syngas during plasma gasification.     

Effect of the type of gasifying agent on gas composition in a bubbling fluidized bed reactor

It is commonly accepted that gasification of coal has a high potential for a more sustainable and clean way of coal utilization. In recent years, research and development in coal gasification areas are mainly focused on the synthetic raw gas production, raw gas cleaning and, utilization of synthesis gas for different areas such as electricity, liquid fuels and chemicals productions within the concept of poly-generation applications. The most important parameter in the design phase of the gasification process is the quality of the synthetic raw gas that depends on various parameters such as gasifier reactor itself, type of gasification agent and operational conditions. In this work, coal gasification has been investigated in a laboratory scale atmospheric pressure bubbling fluidized bed reactor, with a focus on the influence of the gasification agents on the gas composition in the synthesis raw gas. Several tests were performed at continuous coal feeding of several kg/h. Gas quality (contents in H₂, CO, CO₂, CH₄, O₂) was analyzed by using online gas analyzer through experiments. Coal was crushed to a size below 1 mm. It was found that the gas produced through experiments had a maximum energy content of 5.28 MJ/Nm³ at a bed temperature of approximately 800 °C, with the equivalence ratio at 0.23 based on air as a gasification agent for the coal feedstock. Furthermore, with the addition of steam, the yield of hydrogen increases in the synthesis gas with respect to the water–gas shift reaction. It was also found that the gas produced through experiments had a maximum energy content of 9.21 MJ/Nm³ at a bed temperature range of approximately 800–950 °C, with the equivalence ratio at 0.21 based on steam and oxygen mixtures as gasification agents for the coal feedstock. The influence of gasification agents, operational conditions of gasifier, etc. on the quality of synthetic raw gas, gas production efficiency of gasifier and coal conversion ratio are discussed in details.