Thermodynamic evaluation of integrated gasification combined cycle: Comparison between high‐ash and low‐ash coals

In the present study, a coal‐integrated gasification combined cycle power plant is simulated. A high‐ash coal and low‐ash coal are considered to compare the performance of the plant. The combined cycle is in typical commercial size with 450 MW capacity. The feeds are Tabas and Illinois #6 coals which approximately contain more than 30% and 10% ash and have higher heating values of 22.7 MJ/kg and 26.8 MJ/kg, respectively. Energy and exergy analyses are done by aspen plus ^® and ees , respectively. Energy analysis shows that the overall efficiencies of power plants using high‐ash and low‐ash coals are 33% and 28%, respectively. The result shows that in high‐ash case, 52 kg/s coal, 10 kg/s water, and 1050 kg/s air and in low‐ash case, 48 kg/s coal and 820 kg/s air are required for providing mentioned power, approximately. Exergy analysis shows that maximum exergy destruction is in heat recovery steam generator unit. Investigating the emissions shows that high percent of ash in the coal composition has slight effects on the IGCC pollution. Finally, from thermodynamic viewpoint, it is concluded that the high‐ash coal, like the conventional one, can be used as thermally efficient and environmentally compatible feed of IGCCs. Copyright © 2016 John Wiley & Sons, Ltd.     

Experimental investigation of a multi‐stage air‐steam gasification process for hydrogen enriched gas production

To achieve hydrogen‐rich and low‐tar producer gas, multi‐stage air‐blown and air‐steam gasification processes were studied in this research. Results showed that the tar content from multi‐stage air‐blown and air‐steam gasification were lower, compared to the average value of that from downdraft gasification. In the cases of air supplies of 80, 100 l min^?1 and 100, 100 l min^?1 with steam, hydrogen yields were increased by 40.71 and 41.62%, respectively, compared to that without steam. These were about 1.6 times of hydrogen flow rate of the base case (S/B = 0). However, it was found that too much steam added to the process was disadvantageous. The equilibrium model was also applied to predict the hydrogen production and the composition of producer gas obtained from the multi‐stage air‐blown and air‐steam gasification processes. The predicted result showed a better match for the case of multi‐stage air‐blown gasification process. Copyright © 2010 John Wiley & Sons, Ltd.     

水煤浆气化制氢的气化压力选择

为确定最适合水煤浆制氢装置的气化压力,以石油焦为原料,采用单喷嘴水煤浆气化技术,在20万m~3/h制氢规模下,对4.0和6.5 MPa两种不同气化压力下的装置配置、技术经济指标、消耗、投资进行综合对比。结果表明,4.0 MPa压力等级下的气化装置和净化装置均出现系列数增加或设备结构尺寸变大的情况,导致投资增加;系列数的增加还会导致备用率降低,在线率和装置可靠性下降,不利于连续稳定供氢;4.0 MPa压力等级低,装置消耗增加,尤其对于低温甲醇洗单元,冷量消耗将大幅增加。因此,针对20万m~3/h制氢规模,6.5 MPa气化压力下的装置在投资、消耗、占地、在线率、可靠性以及操作和维修的复杂性、生产成本等方面均优于4.0 MPa气化压力,在选择气化压力时应优先考虑6.5 MPa压力等级。     

CO2 gasification characteristics of nascent pyrolyzed particles from coals and oil shale

In this work, the co‐pyrolysis characteristics of oil shale with two typical coals, bitumite and lignite, and the co‐gasification characteristics of the mixture pyrolyzed fuels were studied via thermo‐gravimetric analysis. The individual fuels and mixture fuels were first pyrolysis in N₂ atmosphere to specified temperature (450, 550, and 620 °C) at the heating rate of 20, 30 and 40 °C/min, respectively, and then maintained at the given temperature for 20 min before converted to CO₂ ambient to conduct the CO₂ gasification tests. The kinetic behavior and effects of both fuel types and pyrolysis temperature were investigated. The shoulder peak at around 550 °C observed in the derivative of weight loss derivative thermogravimetry analysis (DTG) curve during the pyrolysis of oil shale has confirmed the existence of specific reactions of oil shale at around 550 °C that leads to a sharp trough in the differential curves of co‐pyrolysis with coals and the unusual change in activation energies of gasification. In isothermal pyrolysis stage, oil shale lost its vast majority of organic matters at the temperature lower than 550 °C. The escape of pyrolysis gas and liquids in the coals is much harder than that in oil shale. The interaction between oil shale and bitumite was too weak to discriminate both in the pyrolysis and CO₂ gasification process. The variation of the particle surface structure caused by the releasing of volatile gases is strongly affected by the reaction rate and temperature. Quick volatile decomposition and gas releasing lead to the increase of surface area, decrease of the average pore diameter as well as the uniformization of the pore structure, while the higher temperature results in the blockade and merging of fine pores. The two factors lead to the greatest mass loss rate in the pyrolyzed particles obtained at 550 °C in temperature programmed CO₂ gasification stage. Two model‐free methods, Friedman method and Flynn–Wall–Ozawa method, were used to extract kinetic parameters from the experimentally determined pyrolyzed fuel conversions. The volatile contend has a significant influence on the fixed carbon conversion during the partially pyrolyzed particles' CO₂ gasification. In this study, significant interactions existed in co‐thermal utilization, both pyrolysis and CO₂ gasification, of oil shale and lignite. It is therefore surmised that co‐gasification of pyrolyzed lignite and oil shale may represent a feasible, practical route to high‐efficiency utilization of these fuels. Copyright © 2017 John Wiley & Sons, Ltd.     

Polygeneration of hydrogen and power based on coal gasification integrated with a dual chemical looping process: Thermodynamic investigation

This paper assesses, from a thermodynamic perspective, the conversion of coal to power and hydrogen through gasification simultaneously with a dual chemical looping processes, namely chemical looping air separation (CLAS) and water–gas shift with calcium looping CO₂ absorption (WGS-CaL). CLAS offers an advantage over other mature technologies in that it can significantly reduce its capital cost. WGS-CaL is an efficient method for hydrogen production and CO₂ capture. The three major factors, oxygen to coal (O/C), steam to coal (S/C) and CaO to coal (Ca/C) were analyzed. Moreover, the comparisons of this suggested process and the traditional processes including integrated gasification combined cycle (IGCC), integrated gasification combined cycle with carbon capture and storage (IGCC-CCS) and integrated gasification combined cycle with calcium-based chemical looping (IGCC-CaL) were discussed. And, the exergy destruction analysis of this suggested process has also been calculated.     

Moving bed syngas conditioning: Modelling

This paper presents a modelling approach for simulating tars and particulate (dust) removal in a moving bed heat exchange filter (MBHEF) in order to satisfy gas requirements of end-use syngas applications: engines and turbines. The two-dimension, adiabatic, steady-state proposed model accounts for two-phase (gas and solid) and neglects conduction and mass diffusion. Tars condensation is modelled through representative tar class lumps: phenol (class 2), naphthalene (class 4), pyrene (class 5). The model also considers tar concentration influence on the tar dew point. The filtration model is taken from literature. A sensitivity analysis is performed varying the particle size and the superficial gas velocity. Maps of temperature and tars abatement efficiency are presented. The simulation results indicate the feasibility of the use a MBHEF as tars removal equipment benefiting its advantages against others gas-cleaning methods with acceptable pollutant removal efficiencies, ranging 88–94% for ranges studied. Results also point out low gas velocities (0.5-1 m/s) and high particle size (400–700 μm) for reducing operational costs in MBHEFs with compact size.     

低压投煤技术在壳牌煤气化装置中的应用

壳牌煤气化装置低压投煤开车技术要求开工烧嘴在较低热负荷情况下的运行时间尽可能短,且气化炉压力在0.1～0.5 MPa（原设计为0.8～1.0 MPa）时就投用煤烧嘴,并通过煤烧嘴的运行来为气化炉升温升压,直至装置满负荷运行。分析了壳牌煤气化装置采用高压投煤开车存在的主要问题及其原因;对比了高压投煤和低压投煤的运行情况;...     

Hydrothermal catalytic production of fuels and chemicals from aquatic biomass

One of the promising avenues for biomass processing is the use of water as a reaction medium for wet or aquatic biomass. This review focuses on the hydrothermal catalytic production of fuels and chemicals from aquatic biomass. Two different regimes for conversion of aquatic biomass in hydrothermal conditions are discussed in detail. The first is hydrothermal liquefaction, and the second is hydrothermal gasification. The goals of these processes are to produce liquid‐fuel‐range hydrocarbons and methane or hydrogen, respectively. The catalytic upgrading of biocrude resulting from noncatalytic liquefaction and the stability and degradation of catalysts in high temperature water are also discussed. The review concludes with a brief discussion of the outlook for and opportunities within the field of hydrothermal catalytic valorization of biomass. Copyright © 2012 Society of Chemical Industry     

基于生物质–太阳能气化的多联产系统模拟及分析

提出一种基于太阳能–生物质气化技术并用于生产甲醇和发电的多联产系统。利用塔式集热镜场聚焦产生的800~1 200℃高温热源来驱动塔式太阳能气化反应器中的生物质气化反应,产生的合成气经压缩后送至甲醇合成塔,而未反应的合成气送至燃气–蒸汽联合循环系统中用于发电。对该系统进行了热力学分析,同时研究各参数包括水蒸气流量和气化温度对系统性能产生的影响。结果表明,调整水蒸气流量和气化温度将改变合成气的组分,影响到系统的甲醇产量和发电功率,当水蒸气流量为50 kg/s时系统效率达到最高值49.48%。随着水蒸气流量和气化温度增加,太阳能热份额逐步提高,系统相对节省率同步下降,同时系统的生物质节省率维持在50%左右。研究成果为高效利用新疆等西部地区丰富的太阳能和生物质资源提供了新途径。     

油气开采企业开展深层煤炭地下气化业务的前景分析

我国主要含油气盆地深层煤炭资源蕴藏量丰富,但长期以来未能得到有效开发利用。煤炭地下气化技术（UCG）属于煤炭资源清洁高效开发和利用的范畴,符合国家“能源革命”的相关要求,国内外的发展经验已经初步证实,UCG在技术、经济和市场方面均是可行的。分析结果认为,油气企业在推动深层UCG发展的进程中具有很大的优势,具体表现在以下方面：①国家政策层面大力支持UCG工业化;②油气开采企业具有一定的资源优势;③油气开采企业具有明显的工程技术优势;④油气开采企业具有类似的生产控制经验;⑤油气开采企业具有市场保障优势和天然气替代效益驱动;⑥油气开采企业具有利用深层UCG建设地下储气库的综合优势。综合宏观的国际形势及UCG业务发展所面临的困难,提出了对我国深层UCG可持续发展的建议：可以由油气开采企业牵头,煤炭开采企业和燃气发电企业参与,集中各家优势力量,实现互利共赢。结论认为,发展深层UCG业务可以将原来无法开发利用的深层煤炭资源转化为现实的、长期的清洁能源供应,这将有力推动中国“能源独立”的进程。