Combining coal gasification and natural gas reforming for efficient polygeneration

A techno-economic analysis of several process systems to convert coal and natural gas to electricity, methanol, diesel, and gasoline is presented. For these polygeneration systems, a wide range of product portfolios and market conditions are considered, including the implementation of a CO₂ emissions tax policy and optional carbon capture and sequestration technology. A new strategy is proposed in which natural gas reforming is used to cool the gasifier, rather than steam generation. Simulations along with economic analyses show that this strategy provides increased energy efficiency and can be the optimal design choice in many market scenarios.     

Combining coal gasification, natural gas reforming, and solid oxide fuel cells for efficient polygeneration with CO2 capture and sequestration

Several polygeneration process systems are presented which convert natural gas and coal to gasoline, diesel, methanol, and electricity. By using solid oxide fuel cells as the primary electricity generator, the presented systems improve upon a recently introduced concept by which natural gas is reformed inside the radiant cooler of a gasifier. Simulations and techno-economic analyses performed for a wide range of process configurations and market conditions show that this strategy results in significant efficiency and profitability improvements when CO₂ capture and sequestration are employed. Market considerations for this analysis include variations in purchase prices of the coal and natural gas, sale prices of the products, and CO₂ emission tax rates.     

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。     

Simulation of partial oxidation of natural gas to synthesis gas using ASPEN PLUS

Conversion of natural gas to liquid fuels is a challenging issue. In SMDS process natural gas is first partially oxidized with pure oxygen to synthesis gas (a mixture of H₂ and CO) which is then converted to high quality liquid transportation fuels by utilizing a modernized version of the Fischer-Tropsch reaction. This paper presents a computer simulation of the first stage of the process, i.e. the synthesis gas production from natural gas. ASPEN PLUS equipped with a combustion databank was used for calculations. Concentrations of over 30 combustion species and radicals expected in the synthesis gas have been calculated at equilibrium and several non-equilibrium conditions. Using a sensitivity analysis tool, the relative feed flow rates and reactor parameters have been varied searching to maximize the CO/O₂ yield as well as to minimize the undesired nitrogen compounds in the product stream. The optimum reactor temperature for maximizing the CO mole fraction in the synthesis gas was also calculated.     

Comparative study of coal,natural gas,and coke-oven gas based methanol to olefins processes in China

Traditional olefins production mainly depends on oil. In view of the short supply of oil, feedstocks are expanded to coal, natural gas, coke-oven gas, and methanol in China. In this paper, a comparative study of alternative olefins production is conducted from aspects of techno-economic feasibility and environmental friendliness. Results show that coal-to-olefins has a significant cost advantage. However, it suffers from low energy efficiency and serious CO₂ emissions. To address these problems, this study proposes and analyses coal-to-olefins with CO₂ capture, coal and natural gas-to-olefins, and coal and coke-oven gas-to-olefins. The two co-feed systems ensure great reduction of CO₂ emissions and significant improving energy efficiency. They should be actively developed in regions with rich coal and gas. While in regions with rich coal and lean gas, coal-to-olefins with CO₂ capture should be developed in large scale. This paper also provides several suggestions on planning these olefins production routes in China.     

Co-pyrolysis characteristics of coal and natural gas

A co-pyrolysis experiment of coal and natural gas was investigated on a fixed-bed reactor. SEM was used to study the structure changes of the exterior surface of char prepared in this co-pyrolysis experiment, while GC was also utilized to analyze the associated gas. The result showed that, with increasing temperature, the coal char tended to agglomerate. GC and SEM results show that the CH₄ decomposition on the exterior surface of char was turned to filamentous char and extended around like coral. It was also proved that the co-pyrolysis of coal and natural gas promoted syngas production. A synergistic effect of coal and natural gas does exist during this process. This work was presented at the 6 ^th Korea-China Workshop on Clean Energy Technology held at Busan, Korea, July 4–7, 2006.     

Synthesis of zeolitic materials from natural clinker: A new alternative for recycling coal combustion by-products

In this study, we report an innovative process of zeolite synthesis through transforming of natural raw clinker (NRC) via (1) conventional hydrothermal alkaline activation and (2) alkaline fusion prior to hydrothermal reaction. Both methods were evaluated at 100 °C as a function of the alkaline agent, although in the first method other variables such as concentration of the activation solution and reaction time were selected, whereas in the second method similar ratios of alkaline activator/NRC and H₂O/alkali fused product during different reaction times were used. Experimental results indicate that the method, alkali activator, concentration and time have a strong effect on the type and degree of crystallinity of the synthesized zeolite. Low-silica sodium or potassium zeolitic materials were synthesized, which include Na-phillipsite, hydroxysodalite and hydroxycancrinite, K-chabazite, zeolite K-F, faujasite and zeolite Linde Type A. The use of a recycling process of NRC in zeolite synthesis could become an area of important interest and research, playing an active role in encouraging and promoting technological advances, research and technology transfer related to the use and disposal of mining wastes, remaining after the natural and spontaneous combustion of coal seams. NRC-based zeolites (NRCZs) synthesized under well-optimized experimental conditions could be used in applications for environmental waste treatment.     

Experimental study of synthesis gas production by coal and natural gas co-conversion process

A moving bed was used as the reactor in experiments to produce synthesis gas by coal and natural gas co-conversion process. The effects of coal types on the temperature in the flame zone, the ingredients and the H₂/CO ratio of synthesis gas, together with the methane and steam conversions were investigated by using coke, anthracite, lean and fat coals as the raw materials. By comparing the results between coals and coke, it can be seen that the temperatures in the flame zone and the content of the active compounds (H₂, CO) of coals are higher than those of coke. In addition, the H₂/CO ratio of synthesis gas closes to the calculated value by thermodynamic equilibrium. For the produced crude synthesis gas with coals by coal and natural gas co-conversion process, in which the H₂/CO ratio varies in 1.0–2.0, the content of the active compounds (H₂, CO) is more than 92%, and the residual methane is less than 2%, the methane and steam conversion rates are more than 90% and 75%, respectively. All these results demonstrated that the concept of coal and natural gas co-conversion process is positive and feasible.     

抽氢气及合成气工艺在合成氨装置的应用

介绍了抽氢气、合成气装置的工艺路线,技术特点,运行情况。该工艺在30万t／a年合成氨装置上的应用为国内首创,7．0MPa甲烷化工艺的工业化应用亦为国内首创。     

Combustion synthesis of perovskite-type catalysts for natural gas combustion

Combustion synthesis has been applied to LaMnO₃ production with a view to boosting its activity towards natural gas combustion by enhancing its specific surface area. With a highly exothermic and self-sustaining reaction, this oxide can be quickly prepared from an aqueous solution of metal nitrates (oxidisers) and urea (fuel).

The favourable conditions for LaMnO₃ formation were sought: only fuel-rich mixtures are effective, but carbonaceous deposits are formed when too much urea is used. In the field of operating conditions in which the combustion synthesis reaction takes place, the specific surface areas were not dramatically higher than those obtained with traditional methods; moreover, even short thermal treatments have been found to rapidly deactivate the catalysts by rapid sintering. With a view to tackling these problems, NH₄NO₃ was chosen as an additive for its low costs, highly exothermic decomposition and because it generates gaseous products only, without altering the proportion of the other elements in the catalysts. With ammonium nitrate, specific area was enhanced from 4 m²/g up to about 20 m²/g. A short thermal treatment at 900 °C partially deactivates also the NH₄NO₃-derived catalysts. It was found that NH₄NO₃-boosted mixtures produce materials whose activity, after a similar thermal treatment, behave practically as the perovskites obtained by the “citrates” method.

Combustion synthesis is though rather cheap—in terms of reactants employed—and quick, given that the process requires few minutes at low temperature without successive calcination. However, the main drawback of this method is that hazardous or polluting compounds are emitted during the synthesis (mainly NH₃ or NO_x).

The MgO introduction, which should act both as a structural promoter and as a sulphur poisoning limiting agent, has proved to be harmful: since MgO does not physically interpose between perovskite grains, it does not offer resistance to deactivation induced by high temperatures.     

移动床煤与天然气共气化制备合成气的工艺技术

煤与天然气共气化是基于天然气蒸汽转化和煤气化工艺耦合的一种新工艺.阐述了煤与天然气共气化制合成气的技术原理.实验研究表明合成气最佳出口温度为1000 ℃,氧气、水蒸气和天然气在同一位置进入反应器能有效降低火焰区温度;理论计算得到的合成气有效气体浓度（CO+H₂）大于95%.实验研究和理论计算结果都表明,煤与天然气共气化可以直接得到H₂/CO在1.0～1.5之间可以调节的合成气.     

Simulation of DME synthesis from coal syngas by kinetics model

DME (Dimethyl Ether) has emerged as a clean alternative fuel for diesel. There are largely two methods for DME synthesis. A direct method of DME synthesis has been recently developed that has a more compact process than the indirect method. However, the direct method of DME synthesis has not yet been optimized at the face of its performance: yield and production rate of DME. In this study it is developed a simulation model through a kinetics model of the ASPEN plus simulator, performed to detect operating characteristics of DME direct synthesis. An overall DME synthesis process is referenced by experimental data of 3 ton/day (TPD) coal gasification pilot plant located at IAE in Korea. Supplying condition of DME synthesis model is equivalently set to 80 N/m³ of syngas which is derived from a coal gasification plant. In the simulation it is assumed that the overall DME synthesis process proceeds with steadystate, vapor-solid reaction with DME catalyst. The physical properties of reactants are governed by Soave-Redlich-Kwong (SRK) EOS in this model. A reaction model of DME synthesis is considered that is applied with the LHHW (Langmuir-Hinshelwood Hougen Watson) equation as an adsorption-desorption model on the surface of the DME catalyst. After adjusting the kinetics of the DME synthesis reaction among reactants with experimental data, the kinetics of the governing reactions inner DME reactor are modified and coupled with the entire DME synthesis reaction. For validating simulation results of the DME synthesis model, the obtained simulation results are compared with experimental results: conversion ratio, DME yield and DME production rate. Then, a sensitivity analysis is performed by effects of operating variables such as pressure, temperature of the reactor, void fraction of catalyst and H₂/CO ratio of supplied syngas with modified model. According to simulation results, optimum operating conditions of DME reactor are obtained in the range of 265–275 °C and 60 kg/cm². And DME production rate has a maximum value in the range of 1–1.5 of H₂/CO ratio in the syngas composition.     

A new type of coal gas fueled chemical-looping combustion

A new type of coal gas fueled chemical-looping combustion is experimentally investigated by means of a fixed-bed reactor operated at elevated pressure. Chemical-looping combustion may be carried out in two successive reactions between two reactors, a reduction reactor (coal gas with metal oxides) and an oxidation reactor (reduced metal with oxygen in the air), which may lead to a breakthrough in clean coal technology by simultaneously allowing efficient use of energy and greenhouse gas control. We have experimentally examined the kinetic behavior between solid looping materials and coal gas in a high-pressure fixed bed reactor. On the basis of the development of suitable material and the good reactivity with the fixed bed reactor, we have identified that the coal gas fueled chemical-looping combustor has much better reactivity than natural gas combustors, and this phenomenon is completely different from direct combustion with natural gas. The promising results obtained here will be valuable for the design of a practical reactor.     

燃煤锅炉烟气氨法脱硫技术概况

介绍了氨法脱硫的原理、主要的脱硫工艺以及实际应用情况。实践表明,大型锅炉采用氨法脱硫效率高,投资省,用电量少,可生产硫酸或硫酸铵。烟气即使不降温,直接进入脱硫塔,也可达到较高的脱硫效率。通过对多种工艺的比较,为燃煤烟气脱硫技术的选择提供参考。     

Thermogravimetric study of coal and petroleum coke for co-gasification

As a preliminary study of gasification of coal and petroleum coke mixtures, thermogravimetric analyses were performed at various temperatures (1,100, 1,200, 1,300, and 1,400 °C) and the isothermal kinetics were analyzed and compared. The activation energies of coal, petroleum coke and coal/petroleum coke mixture were calculated by using both a shrinking core model and a modified volumetric model. The results showed that the activation energies for the anthracite and petroleum coke used in this study were 9.56 and 11.92 kcal/mol and reaction times were 15.8 and 27.0 min. In the case of mixed fuel, however, the activation energy (6.97 kcal/mol) and reaction time (17.0 min) were lower than the average value of the individual fuels, confirming that a synergistic effect was observed in the coprocessing of coal and petroleum coke. This work was presented at the 6 ^th Korea-China Workshop on Clean Energy Technology held at Busan, Korea, July 4–7, 2006.     

焦炉煤气合成天然气工业侧线试验

进行了焦炉煤气合成天然气全流程工业侧线试验,试验规模为焦炉煤气150m3/h,甲烷化工段试验历经1 000h,试验结果表明,M-849催化剂具有良好的甲烷化活性和选择性,并具有多次开停车后稳定性良好、耐短期超温的优良性能.采用补入水蒸汽、反应气不循环的二段绝热甲烷化工艺运行平稳、操作简单,出口气体组成达到设计指标.     

Metal sorbents for high temperature mercury capture from fuel gas

We have determined the Hg removal capacities of Pt and Pd supported on alumina at a range of different metal loadings from 2 to 9 wt% using Hg vapour in a simulated fuel gas feed. In the temperature range studied (204-388 °C) Pd proved far superior to Pt for Hg removal. The Hg removal capacity for both Pt and Pd increased with metal loading, though decreased with sorbent temperature. A shift in the 2θ position of the Pd XRD diffraction peak from 82.1 to 79.5 after Hg adsorption at 204 °C was consistent with the formation of a solid solution of Hg in Pd.     

天然气部分氧化制合成气的研究和实践

叙述了天然气部分氧化法制合成气的原理、国内外的开发和生产情况。并用模拟法进行了部分氧化工艺优化条件的研究，提出了这一方法的使用范围。     

管输节流降压过程中水合物形成研究

天然气管输节流降压过程中容易形成水合物,该物质会堵塞管道、阀门等,造成巨大损失。本文介绍了天然气水合物的形成机理、条件,探讨了水合物形成的平衡常数法、热力学模型计算方法,并介绍了目前常用的水合物防止方法。     

高硫烟煤取代重油制合成气工艺技术探讨

对Texaco气化、Shell气化和CFB气化技术进行了比较 ,并就Texaco气化工艺流程和气化压力的选择等进行了分析。着重阐述了Texaco气化气的变换、脱硫、脱碳和精炼等技术 ,建议在4 0MPa条件下 ,以高硫烟煤为原料 ,采用Texaco激冷流程进行气化 ,耐硫变换催化剂进行CO变换 ,NHD法脱硫脱碳 ,低温变换串甲烷化法精炼 ,并推荐了以高硫烟煤取代重油为原料制氨、氢气和甲醇等产品的技术改造工艺流程