天然气-煤共气化制备合成气热态模拟

天然气-煤共气化制备通用合成气技术是基于天然气蒸汽转化法和煤气化过程开发的新工艺，通过技术原理分析，可以直接制备出H₂/CO在1.0～2.0之间可调的粗合成气.应用移动床反应器进行热态模拟实验，主要研究了不同操作参数对火焰区温度及合成气有效成分(H₂＋CO)和H₂/CO的影响.结果表明：天然气与氧气在同一位置喷入反应器，控制喷吹参数H₂O/CH₄/O₂以及流量，在气化炉炉温不低于1000 ℃的条件下，煤或焦炭中挥发分基本裂解，可以直接制备出H₂/CO在1.0～2.0之间，有效成分大于90.0%，残留的CH₄小于2.0%的粗合成气.     

生物质超临界气化制氢产物高压吸收法分离的气液相平衡分析

通过高压吸收法可以将生物质超临界水气化制氢的气体产物中的CO₂与H₂分离.基于修正的UNIFAC模型、SRK状态方程以及MHV2混合规则，建立了生物质超临界气化制氢产物高压吸收法分离的气液相平衡的计算模型，讨论了CO₂与H₂分离过程中压力和温度等参数对分离效果的影响.计算结果表明：随着分离器中压力的升高，气相产物中H2的摩尔分数增加，CO₂摩尔分数迅速下降，气相中H₂的收率不断降低；随着温度升高，气相产物中H₂的摩尔分数减小，CO₂摩尔分数上升，气相中H₂的收率增加；然而，高压吸收的方法不能将气体产物中的CO、CH₄、C₂H₄、C₂H₆与H₂分离.     

煤与天然气气流床共气化制合成气试验研究

为提高煤、天然气资源综合利用效率,优化合成气成分,进行了煤与天然气气流床共气化技术研究。介绍了煤与天然气气流床共气化的试验装置及工艺流程,考察了气化温度、压力、水煤浆浓度、CH4与煤比对共气化反应的影响。结果表明,气化温度和CH4与煤比是共气化反应的主要影响因素,较高的气化温度对共气化反应有利,气化温度为1 350℃时,共气化指标较好,有效气体积分数大于90%;随着CH4与煤比的增大,合成气n(H2)/n(CO)增高。CH4与煤比为0.9 m3/kg时,合成气中n(H2)/n(CO)约1.2。根据后续合成工艺要求,通过调节气化温度和CH4与煤比,可获得n(H2)/n(CO)在0.8~2.0的合成气。     

基于NiO载氧体的煤化学链燃烧实验

采用流化床反应器并以水蒸气作为气化-流化介质,研究了以NiO为载氧体在800～960℃内的煤化学链燃烧反应特性。实验结果表明,载氧体与煤气化产物在反应器温度高于900℃体现了高的反应活性。随着流化床反应器温度的提高,气体产物中CO₂的体积浓度(干基)呈单调递增;CO、H₂、CH₄的体积浓度(干基)呈单调递减;煤中碳转化为CO₂的比率逐渐递增,碳的残余率逐渐递减。反应器出口气体CO₂、CO、H₂、CH₄的生成率随反应时间呈单峰特性,H₂生成率的峰值远小于CO的峰值;且随反应器温度升高,CO₂生成率升高,CO、H₂、CH₄的生成率降低。反应温度高于900℃时,流化床反应器NiO载氧体煤化学链燃烧在9 min之内就基本完成,CO₂含量高于92%。     

煤种对煤与天然气共气化过程的影响

以移动床为反应器,进行煤与天然气共气化热态模拟实验,对无烟煤、瘦煤、肥煤与焦炭进行了对比研究,考察了煤种在不同喷吹参数H2O/CH4/O2时对高温火焰区温度、合成气有效成分H2+CO和H2/CO、以及CH4与水蒸汽转化率的影响. 结果表明,相对于焦炭,煤为原料时,高温火焰区温度略高,粗合成气有效成分H2+CO体积含量较高,且H2/CO更接近于热力学平衡值. 通过不同煤种的实验,可以直接制备H2/CO在1~2之间可调、有效成分H2+CO体积含量大于92%、残留CH4小于2%的粗合成气,CH4转化率超过90%,水蒸汽转化率高达75%. 煤种中高灰分含量有利于煤与天然气共气化过程.     

气体与煤表面吸附作用的量子化学研究

选用褐煤、次烟煤、高挥发分烟煤、低挥发分烟煤和无烟煤5种煤表面结构模型,采用量子化学半经验方法INDO,从分子水平描述了CO、O₂、H₂O(g)、CO₂、CH₄和H₂等6种气体在煤表面的吸附作用,计算了气体在煤表面的吸附能、吸附距离、吸附作用键级和净电荷变化等微观参数,用Morse函数拟合了气体与煤表面的结合能曲线,得到了气体吸附作用强弱次序为：CO和O₂最强,H₂O和CO₂次之,CH₄和H₂最弱。     

H2对CO气相催化偶联制草酸二乙酯反应的失活机理

重点研究了氢气（H₂）对一氧化碳（CO）催化偶联反应制草酸二乙酯的影响,分别考察了不同H₂浓度、不同温度和不同空时条件下加入H₂对CO偶联反应的影响,结果发现H₂的加入使反应过程中CO转化率、草酸二乙酯选择性和空时收率明显下降,且在实验条件范围内,通入H₂浓度越高、反应温度越高,催化剂活性下降越快.研究得出,H₂气氛下CO偶联反应失活动力学方程为：-da/dt=k_dc^0.65_H2.进一步分析失活动力学方程可知,加氢反应过程中,H₂和CO吸附在同一个活性中心上,H₂在活性中心上的吸附抑制了CO在催化剂上的吸附,从而使得CO催化偶联反应生成草酸二乙酯的速率下降,导致加氢后CO转化率、草酸二乙酯选择性和空时收率降低.     

煤-天然气气流床共气化新技术研究

煤-天然气气流床共气化技术是实现不同工艺优势互补的高效能源综合转化技术。通过建立煤-天然气共气化试验装置,研究气化温度、气化压力、天然气/煤、水煤浆浓度对煤-天然气共气化主要指标的影响。通过分析合成气中主要气体组成、氢碳比(H2/CO)以及CH4含量变化,优选煤-天然气共气化试验条件,最后进行煤-天然气共气化优化试验。结果表明,煤-天然气共气化较合适的反应条件为:气化温度1 300~1 400℃,天然气/煤0.75~1.50 Nm3/kg,水煤浆浓度58%~61%。以西湾煤为原料,在制浆浓度59%,入炉煤量18 kg/h,天然气/煤0.94 Nm3/kg,气化温度1 350℃、气化压力0.5 MPa的条件下,煤-天然气共气化试验装置生产的合成气产量为46.06 Nm3/h,H2+CO含量为88.64%,CH4含量为0.66%,H2/CO为1.23。说明煤-天然气气流床共气化技术是一项高效的气化技术,该技术的开发有利于实现煤与天然气共气化技术的大规模工业化应用。     

天然气-煤共气化制备合成气新工艺

天然气-煤共气化新工艺是基于天然气蒸气转化法和煤气化工艺进行耦合发展起来的新型工艺.本文分析了该工艺的技术原理,理论上可以直接制备H2/CO为1～2可调节的合成气;详细地介绍了天然气-煤共气化新工艺的主反应设备合成气制备炉的结构及工艺流程,通过对该工艺过程的热力学和动力学分析得出工艺的最优工艺参数,通过试验可以直接制备出H2/CO为1～1.5、可调节的合成气,从而证明该工艺过程的可行性,并指出天然气-煤共气化新工艺是一项值得开发的新型合成气制备技术.     

锯木屑在超临界水中气化制氢过程的主要影响因素

以锯木屑混合羧甲基纤维素钠（CMC）为反应原料,利用连续管流反应器,在反应器外壁面温度稳定在650 ℃条件下,对反应压力在17.5～30 MPa,反应停留时间在14.4～50 s,浓度范围为4%～9%（质量分数）的湿生物质浆液进行了超临界水气化制氢实验研究,讨论了气化过程的主要参数压力、温度、反应停留时间以及物料浓度对气化结果的影响.锯木屑在超临界水中接近完全气化,生成气体产物的主要成分是H₂、CH₄、CO、CO₂以及少量的C₂H₄和C₂H₆,气化产物中的H2含量可以超过40%.同时,实现了气化反应液体产物的循环利用.     

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.     

Effect of operating parameters on methanation reaction for the production of synthetic natural gas

Concerns about the depletion and increasing price of natural gas are generating interest in the technology of synthetic natural gas (SNG) production. SNG can be produced by the methanation reaction of synthesis gas obtained from coal gasification; this methanation reaction is the crucial procedure for economical production of SNG. We investigated the effect of operating parameters such as the reaction temperature, pressure, and feed compositions (H₂/CO and CO₂/CO ratios) on the performance of the methanation reaction by equilibrium model calculations and dynamic numerical model simulations. The performance of the methanation reaction was estimated from the CO conversion, CO to CH₄ conversion, and CH₄ mole fraction in the product gas. In general, a lower temperature and/or higher pressure are favorable for the enhancement of the methanation reaction performance. However, the performance becomes poor at low temperatures below 300 °C and high pressures above 15 atm because of limitations in the reaction kinetics. The smaller the amount of CO₂ in the feed, the better the performance, and an additional H₂ supply is essential to increase the methanation reaction performance fully.     

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.     

Low temperature catalytic steam gasification of HyperCoal to produce H2 and synthesis gas

HyperCoal is an ultra clean coal with ash content <0.05 wt%. Catalytic steam gasification of HyperCoal was carried out with K₂CO₃ at 775–650 °C for production of H₂ rich gas and synthesis gas. The catalytic gasification of HyperCoal showed nearly four times higher gasification rate than raw coal. The major gases evolved were H₂: 63 vol%, CO: 6 vol% and CO₂: 30 vol%. Catalyst was recycled for four times without any significant rate loss. The partial pressure of steam was varied from 0.5 atm to 0.05 atm in order to investigate the effect of steam pressure on H₂/CO ratio. The H₂/CO ratio decreased from 9.5 at 0.5 atm to 1.9 at 0.05 atm. No significant decrease in gasification rate was observed due to change in partial pressure of steam. Gasification rate decreased with decreasing temperature and become very slow at 650 °C. The preliminary results showed that HyperCoal, an ash less coal, could be a potential hydrocarbon resource for H₂ and synthesis gas production at low temperature by catalytic steam gasification process.     

入口气体组成对天然气重整工作温度的影响

重整催化剂是影响重整制氢系统造价和寿命的重要因素。由于在所需重整温度下容易烧结积炭,廉价的Ni系催化剂在分布式中小型重整反应器中的应用受到了限制。为了使Ni系催化剂在不易发生烧结积炭的温度下工作,分析了在一定原料CH4空速和转化率下入口气体组成对重整工作温度的影响,并探讨了在原料气中导入循环气来改变重整入口气体组成的方法。结果表明：Ni系催化剂在导入一定组成和流量比的循环气与不导入循环气时相比,一定原料CH4空速和转化率下的重整工作温度大幅降低。据此,提出了一种用于燃料电池电站氢源系统的重整制氢工艺流程,其特征是将部分燃料电池阳极出口气作为循环气与原料气混合后导入重整反应器,使天然气重整工作温度大幅降低。     

高温烟气中煤焦气化行为

针对高温烟气中煤焦的气化行为，本文采用FactSage 6.1计算了煤焦在高温烟气下的高温反应特性，并利用热重分析仪分析了煤焦气化行为。通过沉降炉实验进一步研究了不同温度、气体配比、粒径条件下气体产物的动态析出特性，同时计算了评价指标α、β、LHV值。结果表明：随着温度的升高，气体产物H₂和CO的含量增加，β、α、LHV值增大，CH₄和CO₂的含量下降。在温度为1200℃时，β、α值分别由CO₂/CO比为10∶70时的10.80%、5.21%增加到CO₂/CO比为50∶30时的24.71%、41.06%。同时，随着CO₂/CO比值的增大，高温烟气对煤焦气化反应抑制减弱。通过对比反应温度和粒径对煤焦气化反应的影响，得出反应温度远大于粒径对煤焦气化反应的影响。通过实验验证了向高温烟气中喷吹煤焦制备高品质可燃气体方法的可行性。     

Synthesis gas production using steam hydrogasification and steam reforming

Experimental work has been carried out on the mixed reforming reaction, i.e., simultaneous steam and CO₂ reforming of methane under a wide range of feed compositions and four different reaction temperatures from 700 °C to 850 °C using a commercial steam reforming catalyst. The experiments were conducted for a CO₂/CH₄ ratio from 0 to 2 and a steam to methane ratio from 3 to 5. The effect of CO₂/CH₄ ratio on the exit H₂/CO ratio and the conversions of the reactants indicate that the dry reforming reaction is dominant under increased carbon dioxide in the feed. Steam reforming of typical steam hydrogasification product gas consisting of CO, H₂ and CO₂ in addition to steam and methane has also been investigated. The H₂/CO ratio of the product synthesis gas varies from 4.3 to 3.7 and from 4.8 to 4.1 depending on the feed composition and reaction temperature. The CO/CO₂ ratios of the synthesis gas varied from 1.9 to 2.9 and 2.0 to 3.3. The results are compared with simulation results obtained through the Aspen Plus process simulation tool. The results demonstrate that a coupled steam hydrogasification and reforming process can generate a synthesis gas with a flexible H₂/CO ratio from carbon-containing feedstocks.