K-/Ca-/Fe-化合物对煤焦催化气化作用特性

为考察不同催化剂（K-/Ca-/Fe-化合物）的催化特性,在STA 449F3同步热分析仪上开展了小龙潭（XLT）褐煤、府谷（FG）烟煤和高平（GP）无烟煤等3种不同煤阶煤焦催化气化实验研究。研究发现,与原煤焦的气化过程相比,添加不同种类的催化剂后,3种煤焦的初始气化温度有不同程度的降低,最大可达200 ℃左右;其中催化剂的活性排序为：K2CO3>Na2CO3> KCl>Fe(NO3)3>CaO。碱金属类催化剂良好的催化作用源于其受热条件下流动性好,从而能很好地分布于C基质表面,而Fe-,Ca-催化剂由于其具有更高的熔融温度,流动性较差,更多的还是体现在煤孔隙结构变化对气化反应速率的影响。     

Catalysis of gasification of coal-derived cokes and chars

Calcium is the most important in-situ catalyst for gasification of US coal chars in O₂, CO₂ and H₂O. It is a poor catalyst for gasification of chars by H₂. Potassium and sodium added to low-rank coals by ion exchange and high-rank coals by impregnation are excellent catalysts for char gasification in O₂, CO₂ and H₂O. Carbon monoxide inhibits catalysis of the CH₂O reaction by calcium, potassium and sodium; H₂ inhibits catalysis by calcium. Thus injection of synthesis gas into the gasifier will inhibit the CH₂O reaction. Iron is not an important catalyst for the gasification of chars in O₂, CO₂ and H₂O, because it is invariably in the oxidized state. Carbon monoxide disproportionates to deposit carbon from a dry synthesis gas mixture (3 vol H₂ + 1 vol CO) over potassium-, sodium- and iron-loaded lignite char and a raw bituminous coal char, high in pyrite, at 1123 K and 0.1 MPa pressure. The carbon is highly reactive, with the injection of 2.7 kPa H₂O to the synthesis gas resulting in net carbon gasification. The effect of traces of sulphur in the gas stream on catalysis of gasification or carbon-forming reactions by calcium, potassium, or sodium is not well understood at present. Traces of sulphur do, however, inhibit catalysis by iron.     

Steam gasification of German hard coal using alkaline catalysts: Effects of carbon burn-off and ash content

Laboratory-scale experiments were performed on chars from German hard coals with potassium carbonate addition. The steam gasification rate at 4 MPa and 700 °C as a function of the amount of catalyst added is described for a low-and high-ash char. From the burn-off behaviour the reaction order relative to carbon was determined. For the low-ash char a uniform reaction order was found but the high-ash char indicated a complex interaction of catalytic gasification, catalyst deactivation, and the development of the reacting surface.     

Application of K2CO3 catalysts in the coal gasification process using nuclear heat

Conventional gasification processes use coal not only as feedstock to be gasified but also for supply of energy for reaction heat, steam production, and other purposes. With a nuclear high temperature reactor (HTR) as a source for process heat, it is possible to transform the whole of the coal feed into gas. This concept offers advantages over existing gasification processes: saving of coal, as more gas can be produced from coal; less emission of pollutants, as the HTR is used for the production of steam and electricity instead of a coal-fired boiler; and a lower production cost for the gas. However, the process has the disadvantage that the temperature is limited to the outlet temperature (950 °C max) of the helium cooling gas of the HTR. Therefore the possibility of catalytic steam gasification was examined. Model calculations based on experimental results show that use of 3–4 wt% relative to coal of K²CO³ catalyst increases the throughput of a large scale nuclear gasification plant by ≈65%, while gas production costs decrease by ≈15%. Corrosion by catalysts is not significant at low concentration (< 5 wt%) and low temperature (< 900 °C).     

黑液气化技术发展历程及趋势

碱回收炉是回收黑液中能源与化学品的主要设备,其能源利用率较低且存在爆炸危险,黑液气化技术是一种较有前景的替代方案。在回顾黑液低温与高温气化工艺发展历程的基础上,从能源和化学品回收的角度对比已实现商业化的Chemrec气流床高温气化工艺和MTCI流化床低温气化工艺。总结黑液气化技术存在的主要障碍,判断其发展的重要趋势。根据我国造纸工业现状,认为如果成功应用黑液气化技术将大幅提高黑液的能源利用率和碱回收水平。     

生物质合成气发酵制取燃料乙醇研究进展

随着能源危机的日益严重,开发能够代替化石能源的可再生清洁能源已成为研究热点。燃料乙醇是一种很有应用潜力的替代能源,利用生物质合成气发酵是一种生产燃料乙醇的新技术。文章对该技术的生产工艺优势、生物质气化技术发展现状、生物质合成气发酵生产乙醇微生物、发酵基本过程和代谢机理及产业化进展进行了阐述,并提出了该领域面临的问题和建议。     

黑液气化研究现状及进展

黑液气化回收技术是在碱回收技术的基础上增加气化炉和燃气涡轮机,形成高效的能量回收系统。采用黑液气化回收技术的产电量是传统碱回收产电量的2.5倍,同时能使发电厂的净CO2排放量下降。该技术在制浆造纸行业已经得到初步应用。文章对黑液气化技术及其应用进展进行了论述。     

污泥煤浆气化制氢工艺研究

介绍污水处理厂剩余污泥与煤制成污泥煤浆进行气化制氢的方法和流程,分析其经济性和可靠性。研究发现,污泥煤浆气化出口合成气有效气约为80%,冷煤气效率约为72%,合成气产出率约为86%。污泥煤浆制氢能耗约为20.5GJ/1000m3H2,污泥添加量每增加5%,单位制氢能耗增加1.5%。采用污泥煤浆制氢,主要原料成本约920元/1000m3H2,且随着污泥添加量的增加,制氢成本下降。采用污泥制氢能处理到非常难于处理的废弃物,具有很好的经济效益和环境效益。     

煤粉燃烧中NO_x的预测:模型开发及Fluent实现

开发了新的煤粉燃烧NO_x预测模型,模型考虑了热力型,快速型和燃料型NO_x的生成以及已生成NO_x的异相,均相还原。通过不同煤种的大量热解实验建立了燃料N在挥发分,焦炭中分配比例的经验公式。为解决欠氧还原区NO_x均相还原的定量描述问题,提出以CO,H_2浓度来间接表征气相碳氢化合物含量的方法。利用Fluent提供的用户自定义函数(UDF)接口,加入焦炭与CO_2,H_2O的气化反应,准确计算CO,H_2在燃烧全过程的衍化规律。编写程序将NO_x模型以UDF的形式嵌入Fluent中,实现新的NO_x模型与先进湍流,辐射换热模型的耦合计算。与原有模型相比,新的NO_x预测模型可以自适应不同燃烧条件(常规燃烧,空气分级燃烧)下NO_x迥异的生成与还原特点,从而有助于评判不同结构设计,运行条件对NO_x排放的影响。     

Reactive intermediate in the alkali-carbonate-catalysed gasification of coal char

Based on results from a variety of experimental measurements, a detailed mechanism is postulated for the action of the inorganic catalyst in char gasification. In this mechanism, a catalyst such as potassium carbonate in contact with char undergoes a chemical and physical transformation to form a molten potassium oxide film that covers the char surface. This film serves as an oxygen transfer medium between the gaseous reactant (H₂O or CO₂) and the char. At the catalyst/char interface, an oxidation-reduction reaction occurs and the anions in the catalyst react with the oxidized char to form a phenolate-type functional group that subsequently splits out CO. The anions are replenished by reaction between the oxidizing gas (H₂O or CO₂) and the oxide at the gas/catalyst interface. Net transport of oxygen from gas to char occurs by diffusion of the species in the molten catalyst film.