Feasibility study of a spouted bed gasification plant

We have studied the feasibility of building a biomass gasification plant with an innovative spouted bed reactor for distributed energy production. The process was simulated using a thermodynamic approach (concentrated parameter model) using LIBPF, a C++ process modelling library. A nominal size of about 100 kW total thermal power was chosen.     

Elaboration of PIM feedstocks with 316L fine stainless steel powders for the processing of micro-components

The paper is concerned with the way to prepare feedstocks for powder injection moulding of fine stainless steel powders. The way to prepare adequate feedstocks is described, and injection moulding experiments are determined. The effects of powder volume loading, as well as mixing conditions are investigated and the results indicate that powder loading, injection moulding conditions and sintering kinetics largely influence the resulting shrinkage after sintering. Finally, the modelling and associated numerical simulations are used the help process design.     

Simulation and energy consumption analysis of a propane plus recovery plant from natural gas

This paper deals with the investigation of a cryogenic plant for the recovery of propane plus compounds from natural gas. The commercially available software ASPEN Plus® has been used to simulate the process, and to investigate the effect of the main operating variables on the efficiency of propane plus recovery and on the energy required by the various pieces of equipment of the plant. With respect to the base case considered, the optimized plant allows to reduce the heat required up to 25%; besides, the refrigeration required can be reduced up to 60%, without significantly affecting the propane plus recovery.     

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)

Fixed bed biomass gasification is a promising technology to produce heat and power from a renewable energy source. A twin-fire fixed bed gasifier based CHP plant was realized in the year 2003 in Wr. Neustadt, Austria. Wood chips are used as fuel, which are dried and sieved before being gasified to a low calorific gas of about 5.8 MJ/Nm³_dry. Before the clean gas is fed into a gas engine a cyclone and a RME (rapemethylester)/H₂O quench system followed by a wet electrostatic precipitator (ESP) is used for gas cleaning. The CHP plant has a fuel power of 2 MW_th and an electric output of 550 kW_el. As scale up and optimization tool a hot test rig with a capacity of 125 kW_th was built. Basic parameters like the type of wood chips, power and air distribution were varied to investigate the effect on gas composition, tar content in the producer gas and carbon content in the ash. Additionally a temperature profile over the height of the 125 kW hot test rig was measured. Furthermore, the results from the hot test rig are discussed and compared with the results from the 2 MW_th demonstration plant.     

Hydrogen production by steam gasification of polypropylene with various nickel catalysts

Several nickel-based catalysts (Ni/Al₂O₃, Ni/MgO, Ni/CeO₂, Ni/ZSM-5, Ni-Al, Ni-Mg-Al and Ni/CeO₂/Al₂O₃) have been prepared and investigated for their suitability for the production of hydrogen from the two-stage pyrolysis–gasification of polypropylene. Experiments were conducted at a pyrolysis temperature of 500 °C and gasification temperature was kept constant at 800 °C with a catalyst/polypropylene ratio of 0.5. Fresh and reacted catalysts were characterized using a variety of methods, including, thermogravimetric analysis, scanning electron microscopy with energy dispersive X-ray spectrometry and transmission electron microscopy. The results showed that Ni/Al₂O₃ was deactivated by two types of carbons (monoatomic carbons and filamentous carbons) with a total coke deposition of 11.2 wt.% after reaction, although it showed to be an effective catalyst for the production of hydrogen with a production of 26.7 wt.% of the theoretical yield of hydrogen from that available in the polypropylene. The Ni/MgO catalyst showed low catalytic activity for H₂ production, which might be due to the formation of monoatomic carbons on the surface of the catalyst, blocking the access of gaseous products to the catalyst. Ni-Al (1:2) and Ni-Mg-Al (1:1:2) catalysts prepared by co-precipitation showed good catalytic abilities in terms of both H₂ production and prevention of coke formation. The ZSM-5 zeolite with higher surface area was also shown to be a good support for the nickel-based catalyst, since, the Ni/ZSM-5 catalyst showed a high rate of hydrogen production (44.3 wt.% of theoretical) from the pyrolysis–gasification of polypropylene.     

Effect of operating conditions on gas components in the partial coal gasification with air/steam

With increasing environmental considerations and stricter regulations, coal gasification, especially partial coal gasification, is considered to be a more attractive technology than conventional combustion. Partial coal gasification was conducted in detail under various experimental conditions in a lab-scale fluidized bed to study the factors that affected gas components and heating value, including fluidized air flow rate, coal feed rate, and steam feed rate, gasification temperature, static bed height, coal type and catalyst type. The experiment results indicate that gasification temperature is the key factor that affects components and the heating value of gas is in direct proportion to gasification temperature. There exists a suitable range of fluidized air flow rate, coal feed rate, steam feed rate and static bed height, which show more complex effect on gas components. High rank bitumite coal is much more suitable for gasification than low rank bitumite coal. The concentrations of H₂, CO and CH₄ of bitumite coal are more than those of anthracite coal. Compounds of alkali/alkaline-earth metals, such as Ca, Na, K etc., enhance the gasification rate considerably. The catalytical effects of Na₂CO₃ and K₂CO₃ are more efficient than that of CaCO₃. This work was presented at the 6 ^th Korea-China Workshop on Clean Energy Technology held at Busan, Korea, July 4–7, 2006.     

The study of reactions influencing the biomass steam gasification process☆

Steam gasification studies were carried out in an atmospheric fluidised bed. The gasifier was operated over a temperature range of 700-900 °C whilst varying a steam/biomass ratio from 0.4 to 0.85 w/w. Three types of forestry biomass were studied: Pinus pinaster (softwood), Eucalyptus globulus and holm-oak (hardwood). The energy conversion, gas composition, higher heating value and gas yields were determined and correlated with temperature, steam/biomass ratio, and species of biomass used. The results obtained seemed to suggest that the operating conditions were optimised for a gasification temperature around 830 °C and a steam/biomass ratio of 0.6-0.7 w/w, because a gas richer in hydrogen and poorer in hydrocarbons and tars was produced. These conditions also favoured greater energy and carbon conversions, as well the gas yield. The main objective of the present work was to determine what reactions were dominant within the operation limits of experimental parameters studied and what was the effect of biomass type on the gasification process. As biomass wastes usually have a problem of availability because of seasonal variations, this work analysed the possibility of replacing one biomass species by another, without altering the gas quality obtained.     

ASPEN PLUS在顺酐回收工艺模拟中的应用

应用化工流程模拟软件ASPEN PLUS对顺酐溶剂回收工艺进行模拟。使用经K-D混合规则修正了的Soave-Redlich-Kwong方程进行热力学计算,并对数据库中缺失的物性参数进行补充以获得更准确的模拟结果。通过灵敏度分析,得到最优的操作参数:吸收剂入塔最优温度40～45℃,顺酐混合气入塔最优温度48～56℃,吸收剂循环流量24 214 kg/h。根据分析优化结果对原工艺提出改造方案,经过模拟计算预测,改造后的工艺与原工艺相比可以节省能量5 501.948 MJ/h,同时减少一个换热器的建造和维护费用。     

Simulation study on the gasification process of Ningdong coal with iron-based oxygen carrier

Chemical looping gasification (CLG) of Ningdong coal by using Fe₂O₃ as the oxygen carriers (OCs) was studied, and the gasification characteristics were obtained. A computation fluid dynamics (CFD) model based on Eulerian‐-Lagrangian multiphase framework was established, and a numerical simulation the coal chemical looping gasification processes in fuel reactor (FR) was investigated. In addition, the heterogeneous reactions, homogeneous reactions and Fe₂O₃ oxygen carriers' reduction reactions were considered in the gasification process. The characteristics of gas flow and gasification in the FR were analyzed and it was found that the experiment results were consistent with the simulation values. The results show that when the O/C mole rate was 0.5:1, the gasification temperature was 900 ℃ and the water vapor volume flow rate was 2.2 ml·min^-1, the mole fraction of syngas reached a maximum value of the experimental result and simulation value were 71.5% and 70.2%, respectively. When the O/C mole rate was 0.5:1, the gasification temperature was 900 ℃, and the water vapor volume flow was 1.8 ml·min^-1; the gasification efficiency reached the maximum value was 62.2%, and the maximum carbon conversion rate was 84.0%.     

大型煤制天然气项目气化技术方案的主要特点和技术优势的探讨

介绍了粉煤气化和碎煤气化两种工艺技术特点,并探讨了两种工艺组合在大型煤制合成天然气项目中应用前景。     

Modelling of an IGCC plant with carbon capture for 2020

Currently several industrial scale IGCC - carbon capture demonstration plants are being planned. Thermodynamic simulations are a useful tool to investigate the optimal plant configuration. In order to demonstrate the potential of the next generation of IGCC with CCS a thermodynamic model was developed using conventional but improved technology. The plant concept was verified and simulated for a generic hard coal and lignite. The simulation showed a net efficiency (LHV) of 38.5% and 41.9% for hard coal and lignite, respectively.The results are consistent with current studies but also indicate that major simulations were too optimistic. The auxiliary demand of an IGCC plant with carbon capture can be expected with 21 to 24% based on gross output. The drop in efficiency compared to the none-capture case is estimated with roughly 11 to 12%-points. During a sensitivity study the impact of process changes on plant efficiency and economics is evaluated. Releasing the captured CO₂ without compression is found to be economically favourable at CO₂ prices below 15 €/t and electricity prices above 100 €/MWh. Further the impact of carbon capture rate is quantified and an efficiency potential is indicated for lower CO₂ quality.     

Process analysis for polygeneration of Fischer-Tropsch liquids and power with CO2 capture based on coal gasification

This paper designs four cases to investigate the performances of the polygeneration processes, which depend on the commercially ready technology to convert coal to liquid fuels (CTL) and electricity with CO₂ sequestration. With Excel-Aspen Plus based models, mass and energy conversion are calculated in detail. The simulation shows that the thermal efficiency is down with the synfuels yield decrease though the electricity generation is increased. It also suggests that the largest low heat value (LHV) loss of coal occurs in the gasification unit. From the comparison of the four cases, prominent differences of coal energy transition appear in water-gas shift (WGS) units, Fischer-Tropsch (FT) synthesis and combined cycle processes. CO₂ capture and vent are discussed and the results show that the vent amount of CO₂ increases with the increase of percentage of the syngas going to produce electricity. The results also show that the ratio of carbon captured to total carbon increases from 58% to 93% which is an important contribution to cutting down the greenhouse gas vent.     

Experimental studies on gasification of the Shenmu coal char with CO2 at elevated pressures

The gasification rates of Shenmu coal chars with CO₂ were experimentally studied with a pressurized thermo- gravimetric analyzer (PTGA). Shenmu coal is a typical Chinese coal, and the coal char was prepared by a fixed-bed reactor in nitrogen at 900 °C. The experiments were carried out in the dynamic heating segments from 750 °C to 1,000 °C, and the reaction pressure increased from 0.1MPa to 3.1MPa with pure CO₂. The external diffusion resistances were minimized by increasing the flow rates and decreasing the thickness of sample layer before the test, to ensure the reactions were under kinetic control. The results show that the gasification rates increase proportionally to the 0.1 power of the CO₂ partial pressure. The unreacted-core shrinking model was applied to predict the reaction rate by changing the molar fraction of CO₂ at 0.6Mpa and 1.6Mpa total pressures, which showed a good match with experimental data. This work was presented at the 6 ^th Korea-China Workshop on Clean Energy Technology held at Busan, Korea, July 4–7, 2006.     

The effect of coal particle size on pyrolysis and steam gasification

For future power generation from coal, one preferred option in the UK is the air-blown gasification cycle (ABGC). In this system coal particles sized up to 3 mm, perhaps up to 6 mm in a commercial plant, are pyrolysed and then gasified in air/steam in a spouted bed reactor. As this range of coal particle sizes is large it is of interest to investigate the importance of particle size for those two processes. In particular the relation between the coal and the char particle size distribution was investigated to assess the error involved in assuming the coal size distribution at the on-set of gasification. Different coal size fractions underwent different changes on pyrolysis. Smaller coal particles were more likely to produce char particles larger than themselves, larger coal particles had a greater tendency to fragment. However, for the sizes investigated in this study ranging from 0.5 to 2.8 mm, the pyrolysis and gasification behaviour was found not to vary significantly with particle size. The coal size fractions showed similar char yields, irrespective of the different char size distributions resulting from pyrolysis. Testing the reactivity of the chars in air and CO₂ did not reveal significant differences between size fractions of the char, nor did partial gasification in steam in the spouted bed reactor. From the work undertaken, it can be concluded that pyrolysis and gasification within the range of particle sizes investigated are relatively insensitive to particle size.     

基于湿法气化的褐煤液化分级转化技术

分析了褐煤液化理论及影响因素,结合湿法气化技术,提出褐煤部分液化、液化残渣气化的分级转化技术,探索褐煤综合化、洁净化、集成化的利用途径。分析表明,褐煤具有较高的加氢液化活性,通过气化与液化技术结合,能够实现褐煤的高效利用。     

基于流程模拟软件平台的化工计算教材编写

为了适应化工流程模拟软件应用日益普及的现状,我们编写了以强化训练学生计算能力为目标的《化工计算与软件应用》教材。本文分析了传统化工计算教材内容的不足,阐明了选用流程模拟软件作为化工计算主要工具的必要性,介绍了新教材编写过程中内容组织、章节安排、编写风格的考虑,对新教材教学方式的变革提出了意见。本教材在校内使用两年来效果明显,学生应用化工流程模拟软件进行工艺设计的能力大幅增强。     

ASPEN Plus在工业精馏塔故障诊断与参数寻优中的应用

通过在生产实践中应用ASPEN Plus软件模拟实际生产过程，对实际操作中可能存在的故障进行了诊断；在系列化过程模拟与优化的基础上，以理论计算为指导，针对性地提出了操作参数调整方案及精馏塔内构件的维护策略。实际运行结果表明，以最小的成本投入获得了最佳改造效果，故障诊断与参数寻优是成功的。     

Gasification of municipal solid waste in a pilot plant and its impact on environment

Municipal solid waste from three cities was gasified in a 3 ton/day capacity gasification/melting pilot plant based on Thermoselect at a temperature of around 1,200 °C using double inverse diffusion flame burner. The synthesis gas (syngas) obtained from gasification contains 25–34% CO and 28–38% of H₂. The high heating value of syngas was in the range of 10.88–14.65MJ/Nm³. Volatile organic compounds like furan, dioxin, and other organics in gaseous and liquid phase were effectively destroyed because of the high temperature of the high temperature reactor and shock cooling of syngas. Pollutants in exhaust gases were also found to be satisfying the Korean emission standard. Leaching concentration of heavy metals in the melted slag (vitrified mineral aggregate), fly ash, and treated water was much less than the Korean regulatory limit values due to high melting temperature (1,600 °C). The vitrified slag was of dark brown color. The glassy and amorphous nature of the vitrified mineral aggregate was further confirmed from SEM micrograph and XRD spectra of slag. The vitrified mineral aggregate could be used as natural raw material in cement and construction industry.     

The effect of steam temperature on the economics of a cogeneration power plant

Using steady-state simulation, we have evaluated the effect of boiler superheat and reheat temperatures on the economics of the utility section of a Bayer Alumina Plant. These economics were compared with those of a steam plant which purchased power. Under this study's nominal economic conditions, producing steam and purchasing electricity was the cheaper option. A sensitivity analysis showed that the cogeneration plant became the better choice when the local cost of electricity rose above 10C/kWh. The plant economics improved monotonically with superheat temperature as did the thermo-dynamic efficiency. However, for reheat, the plant economics did not improve monotonically with temperature even though the thermodynamic eficiency did; thus improvement in the thermodynamic efficiency does not always yield improved economics.     

Effect of iron on the gasification of Victorian brown coal with steam:enhancement of hydrogen production

This paper reports the significant enhancement of hydrogen production during the gasification of Victorian brown coal with steam using iron as a catalyst. Iron was loaded into the acid-washed Loy Yang brown coal using ferric chloride aqueous solution. Gasification experiments were carried out using a quartz reactor at a fast particle heating rate. The yield of char was determined by directly weighing the reactor before and after each experiment. Gases were analysed using a GC with dual columns. The overall gasification rate of a char increases greatly in the presence of iron. The transformation of iron species during pyrolysis and gasification was examined using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results show that both reduced-iron (α-Fe and γ-Fe) and magnetite (Fe₃O₄) highly dispersed in a char can catalyse the gasification of the char with steam. In particular, the char from iron-loaded coal samples gives much higher yields of H₂ than a char from the acid-washed coal under similar conditions. The mechanism for the enhancement of hydrogen production in the presence of iron is discussed.