油水煤浆在新型气化炉内气化过程的数值模拟

在多喷嘴入口新型水煤浆气化炉内对油水煤浆(COW)的气化过程进行了数值模拟计算研究,分析了气化炉内的温度分布、各种气化产物浓度分布规律。数值模拟计算结果证明,同浓度的油水煤浆气化与普通水煤浆气化相比,气化炉内平均温度略有上升,碳转化率提高1.81%,气化炉出口粗煤气中有效气(CO H2)含量提高10.58%,CO2和H2O浓度大幅下降,水分解率大大提高,气化效果明显优于普通水煤浆。     

煤质对水煤浆气化性能的影响研究

煤质与气流床气化炉的匹配性至关重要,其不但影响气化炉的运行条件,也影响气化性能。本文选择了10种来自新疆和陕西北部的煤样进行了工业分析、元素分析、灰组成分析、灰熔点分析以及成浆性测试,并筛选出适合水煤浆气化的煤样。同时借助Aspen Plus软件对适合水煤浆气化的煤样在相同的煤浆浓度、碳转化率及操作压力条件下开展煤质对水煤浆气化性能影响的模拟分析。结果表明煤中灰含量越高,冷煤气效率和有效气含量越低,比氧耗和比煤耗越高;煤中O/C质量比和H/C质量比的增加也会导致冷煤气效率和有效气含量降低,比氧耗和比煤耗增加。因此从水煤浆气化经济性考虑,建议水煤浆气化煤质灰含量小于9.0wt%,煤中O/C质量比小于0.173,H/C质量比小于0.065。     

石油焦水煤浆在新型气化炉内气化过程的数值计算

对石油焦水煤浆(PCCWS)在多喷嘴新型水煤浆气化炉内的气化过程进行了数值计算,考察了气化炉内的温度分布、各种气化产物浓度分布规律.结果表明:同浓度的石油焦水煤浆气化与普通水煤浆气化相比,气化炉内平均温度略有上升,碳转化率提高,气化炉出口粗煤气中有效气(CO H2)含量提高7.91%,CO2和H2O浓度大幅下降,水分解率大大提高;石油焦水煤浆气化可以节约氧气约6%,气化效果明显优于普通水煤浆.     

气流床煤气化装置稳态模拟及优化分析

煤气化过程是煤中有机质在一定温度、压力及气化剂(如蒸汽、空气或氧气等)等条件下发生一系列复杂化学反应,将固体煤转化成粗合成气,同时副产蒸汽、焦油、灰渣等产品的过程。以工业化运行气流床粉煤气化及水煤浆气化装置为研究对象,采用Aspen Plus流程模拟软件,建立与实际工况吻合的气化装置稳态模拟模型。通过使用该模型,研究了氧煤比、加入烧嘴水蒸气量、煤浆浓度、激冷水量、气化压力等工艺参数对煤气化反应性能的影响,结果表明:水煤浆气化有效气含量随氧煤比降低先增加后减少,随煤浆浓度增加而增加;粉煤气化有效气含量随氧煤比降低而增加,H2含量随蒸汽量增加而增加;气化压力对煤气化合成气组成影响较小;降低激冷水量有利于提高合成气水汽比及变换装置副产蒸汽量,并可降低激冷水泵和洗涤塔低压灰水泵功率。运用稳态模拟模型指导生产装置操作优化,每年可实现经济效益507.51万元。     

氧煤比对气流床煤气化过程的影响

为研究氧煤比对气流床煤气化炉气化过程的影响,对某厂运行的Texaco气化炉进行了数值模拟研究。利用所建立的数学模型,分析了Texaco气化炉内的气化过程,以及氧煤比对炉内温度、气相成分及炉膛出口合成气成分的影响规律。结果表明:Texaco气化炉内下行火焰的长度约占气化炉高度的1/3,炉膛上部火焰高度区域内气相温度及主要成分浓度的变化梯度最大,而在炉膛下部气相成分及温度的变化均不明显;随着氧煤比的增大(0.95~1.10),气化炉出口合成气有效成分(H2+CO)浓度逐渐降低,CO2和H2O的浓度及气化炉内气相温度逐渐升高;在保证顺利排渣和合适的出口合成气成分的条件下,存在一个最佳氧煤比。     

气化参数对IGCC系统中气化炉性能的影响

首先单独对气化炉出口合成气成分含量进行核算,计算结果与文献基本吻合.然后建立200 MW级整体煤气化联合循环(IGCC)系统模型,对基本参数下的IGCC系统进行计算,得出整个系统的性能参数.最后对不同气化参数温度、水煤浆浓度、氧气浓度、O/C比的气化炉性能及其整个IGCC系统效率进行比较,分析不同气化条件下的合成气成分体积含量、冷煤气效率、有效气(CO+H2)体积含量、比氧耗、比煤耗及整个IGCC系统效率的变化.结果表明:提高水煤浆的浓度,有利于提高气化炉的冷煤气效率;气化温度对IGCC系统性能影响较大;提高氧气浓度有利于提高气化冷气效率和系统的效率,本系统对应的最佳O/C比为1.02左右.     

炭化气氛对黑液煤浆及不同煤种气化反应特性的影响

煤气化前阶段的炭化气氛(温度、时间)影响到煤焦的气化反应特性.采用不同的炭化温度和炭化时间制备了黑液水煤浆、普通水煤浆以及其他5种煤的焦样,得到了各种煤焦气化反应的碳转化率;同时,通过扫描电子显微镜分析手段鉴别焦炭表面孔隙分布情况.试验结果表明,相同炭化气氛下得到的7种不同煤焦中,黄陵煤焦的气化活性最高,说明煤化程度越高反应性越低;由于黑液中有机物和无机物钠盐的影响,黑液水煤浆焦的气化特性高于普通水煤浆焦和新汶煤焦.煤焦的气化反应性,不仅与煤阶有关,还和煤焦中含氧官能团和无机化合物的含量有关,同时煤浆中外在添加的无机物组分也影响到煤焦的气化活性.     

新疆沙尔湖煤气化过程影响因素研究

应用Aspen Plus模拟软件建立了新疆沙尔湖煤气流床气化过程的计算模型,并对新疆沙尔湖煤的气化过程进行模拟计算。以粗合成气中(H2+CO)摩尔分数和有效气产量最高为目标函数,研究了主要参数对气化结果的影响,确定出最佳气化工艺条件。     

煤粉加压气化炉操作参数对气化特性的影响

采用基于平衡态模型的气流床气化炉煤气组分预测程序,分析研究了气化压力、氧煤比以及蒸汽煤比等操作参数对气化温度、煤气组分、碳转化率和气化效率的影响规律。研究结果表明:气化压力对气化特性指标影响甚微,而氧煤比和蒸汽煤比的影响较为显著。随氧煤比的增加,气化温度升高,碳转化率升高,气化效率先升高再降低,CO浓度先增加后降低。CH_4的体积浓度可用于预测气化温度。在蒸汽煤比较低时,提高蒸汽煤比可增加H_2的浓度,提高碳转换率和气化效率,但进一步提高蒸汽煤比仅会降低气化炉内的气化温度,提高H_2O和CO_2浓度。对于所研究的煤种,合理的氧煤比应在0.7左右,合理的蒸汽煤比在0.1左右。     

水煤浆流经局部管件的阻力特性研究进展

水煤浆流经局部管件阻力特性的研究对水煤浆管道输送的工业应用和设计有重要意义。论文对水煤浆流经局部管件的阻力特性的研究方法进行了较为全面的阐述，包含了其影响因素、实验方法、数值模拟及实验结果分析等方面的一些研究进展。与此同时，笔者也对局部管件的几何定义、压差分析及阻力特性参数等方面提出一些新的观点，并对局部管件中水煤浆的阻力特性研究作了几点展望。     

Sensitivity and safety boundary Analysis of Opposed Multi-Burner Coal Water Slurry Gasification System

Taking the opposed multi-burner (OMB) coal water slurry (CWS) gasification system as the simulation object, based on the gasification process flow-path and the flow field distribution characteristics in the gasifier, the model of CWS gasification system is established by using the chemical simulation software UniSim Design, the simulation results are in good agreement with the industrial data. On this basis, the Morris method is used to analyze the sensitivity of gasification parameters, and the response surface between coal gasification performance index and sensitive parameters is constructed by using the response surface method. The sensitivity of different gasification parameters and the impact of key sensitive parameter interactions on gasification performance indicators is investigated. The results show that the gasification parameters have different sensitivities for different responses. When the operating temperature range of the gasifier is limited to 1212°C to 1400°C and the syngas water-gas ratio is in the range of 1.0 to 1.4, there is a safe boundary for oxygen-coal ratio and CWS concentration. In actual production, the relevant parameters should be avoided to deviate from the safety region. This article provides a reference for the safe and stable operation of actual industrial production.     

Study of pyrolysis of brown coal and gasification of coal‐water slurry using the ReaxFF reactive force field

Based on the Wender coal model, the processes of brown coal pyrolysis and coal‐water slurry (CWS) gasification were studied by molecular dynamics simulations with the ReaxFF reactive force field. To examine the pyrolysis/gasification process and the initiation mechanism of brown coal and its CWS, some large‐scale reactive systems containing different numbers of brown coal and water were built in this work. A relatively high simulation temperature, which was proven reasonable in other studies, was used to control the simulation within an acceptable period of time. The products and the change of potential energy of the systems were analyzed. The related initial reaction mechanisms and factors were discussed. It was found that the pyrolysis of brown coal began with the rupture of bridge bonds, closely followed by the separation of some functional groups such as carboxyl, methoxyl, and methyl. Then, gas products were generated from the reactions between small intermediate structures. Some mechanisms of CO and H₂ generation were discussed in the article. It was observed that temperature significantly enhanced the reactions in the brown coal pyrolysis process and the yields of gas products. For the gasification of CWS, it was observed that the reaction started from the pyrolysis of coal, and then water reacted with the fragments. The effects of temperature and mass fraction were taken into consideration. It was found that gas products were hardly generated and the consumption of water was relatively less at low temperatures and that rising temperature could significantly enhance gas yield and water consumption. There was an inflection point in the curve of water consumption when the temperature is greater than 3000 K. The mass fraction could not affect the gasification process as great as temperature. However, an appropriate amount of water could enhance the yield of gas products and the CWS with 70% mass fraction could provide enough water for H₂ and CO generation. Some of the important reactions and intermediate structures agreed with other experimental data from the literature.     

Development of a high‐temperature two‐stage entrained flow gasifier model for the process of biomass gasification and syngas formation

This paper presents development of the Mitsubishi Heavy Industries (MHI) gasifier utilizing an analogy between a model with coal feedstock and the model with torrefied woody biomass. A computational fluid dynamics (CFD) model was primarily developed for coal gasification, and the simulation results were validated with similar published work and experimental measurements. The model was extended for the woody biomass to predict the gasifier performance under the gasification process. The results were used to compare the effect of fuel type on the gasifier performance and gaseous product compositions. The second‐level injection nozzles were modified tangentially, and the flow characteristics, species yields, and temperature were evaluated. The possibility of reducing the gasifier length from 13 to 8 m is also evaluated for different total length. The results revealed that using woody biomass leads to a decrease in the mole fraction of CO and H₂ at the gasifier outlet compared with coal. An opposite trend was observed for CO₂ and CH₄ compositions. The contributions of modified second‐level nozzles to the total gas composition and exit temperature only account for less than 3%. Reducing the gasifier length from 13 to 8 m increased the exit temperature from 1289 to 1340 K, but the changes in the exit gas composition were less than 2%. The new design of the MHI gasifier can reduce the investment costs by reducing the gasifier length as well as using biomass instead of coal.     

Modeling biomass gasification in circulating fluidized beds

Detailed review of existing models resulted in the development of a new mathematical model to study biomass gasification in a circulating fluidized bed. Hydrodynamics as well as chemical reaction kinetics were considered to predict the overall performance of a biomass gasification process. The fluidized bed was divided into two distinct sections: a) a dense region at the bottom of the bed where biomass undergoes mainly heterogeneous reactions and b) a dilute region at the top where most of homogeneous reactions occur in gas phase. Each section was divided into a number of small cells, over which mass and energy balances were applied. A number of homogeneous and heterogeneous reactions were considered in the model. Mass transfer resistance was considered negligible since the reactions were under kinetic control due to good gas–solid mixing. The model is capable of predicting the bed temperature distribution along the gasifier, the concentration and distribution of each species in the vertical direction of the bed, the composition and heating value of produced gas, the gasification efficiency, the overall carbon conversion and the produced gas production rate. The modeling and simulation results were in good agreement with published data.     

High temperature steam-only gasification of woody biomass

We have studied a high temperature steam gasification process to generate hydrogen-rich fuel gas from woody biomass. In this study, the performance of the gasification system which employs only high temperature steam exceeding 1200 K as the gasifying agent was evaluated in a 1.2 ton/day-scale demonstration plant. A numerical analysis was also carried out to analyze the experimental results. Both the steam temperature and the molar ratio of steam to carbon (S/C ratio) affected the reaction temperature which strongly affects the gasified gas composition. The H₂ fraction in the produced gas was 35–55 vol.% at the outlet of the gasifier. Under the experimental conditions, S/C ratio had a significant effect on the gas composition through the dominant reaction, water–gas shift reaction. The tar concentration in the produced gas from the high temperature steam gasification process was higher than that from the oxygen-blown gasification processes. The highest cold gas efficiency was 60.4%. However, the gross cold gas efficiency was 35%, which considers the heat supplied by high temperature steam. The ideal cold gas efficiency of the whole system with heat recovery processes was 71%.     

Experimental study on non-woody biomass gasification in a downdraft gasifier

The current paper concerns the process of non-woody biomass gasification, particularly about releasing processes of detrimental elements. The gasification of corn straw was carried out in a downdraft fixed bed gasifier under atmospheric pressure, using air as an oxidizer. The effects of the operating conditions on gasification performance in terms of the temperature profiles of the gasifier, the composition distribution of the producer gas and the release of sulphur and chlorine compounds during gasification of corn straw were investigated. Besides, the gasification characteristics were evaluated in terms of low heating value (LHV), gas yield, gasification efficiency and tar concentration in the raw gas.     

Effect of the type of gasifying agent on gas composition in a bubbling fluidized bed reactor

It is commonly accepted that gasification of coal has a high potential for a more sustainable and clean way of coal utilization. In recent years, research and development in coal gasification areas are mainly focused on the synthetic raw gas production, raw gas cleaning and, utilization of synthesis gas for different areas such as electricity, liquid fuels and chemicals productions within the concept of poly-generation applications. The most important parameter in the design phase of the gasification process is the quality of the synthetic raw gas that depends on various parameters such as gasifier reactor itself, type of gasification agent and operational conditions. In this work, coal gasification has been investigated in a laboratory scale atmospheric pressure bubbling fluidized bed reactor, with a focus on the influence of the gasification agents on the gas composition in the synthesis raw gas. Several tests were performed at continuous coal feeding of several kg/h. Gas quality (contents in H₂, CO, CO₂, CH₄, O₂) was analyzed by using online gas analyzer through experiments. Coal was crushed to a size below 1 mm. It was found that the gas produced through experiments had a maximum energy content of 5.28 MJ/Nm³ at a bed temperature of approximately 800 °C, with the equivalence ratio at 0.23 based on air as a gasification agent for the coal feedstock. Furthermore, with the addition of steam, the yield of hydrogen increases in the synthesis gas with respect to the water–gas shift reaction. It was also found that the gas produced through experiments had a maximum energy content of 9.21 MJ/Nm³ at a bed temperature range of approximately 800–950 °C, with the equivalence ratio at 0.21 based on steam and oxygen mixtures as gasification agents for the coal feedstock. The influence of gasification agents, operational conditions of gasifier, etc. on the quality of synthetic raw gas, gas production efficiency of gasifier and coal conversion ratio are discussed in details.     

Development and demonstration plant operation of an opposed multi-burner coal-water slurry gasification technology

The features of the opposed multi-burner (OMB) gasification technology, the method and process of the research, and the operation results of a pilot plant and demonstration plants have been introduced. The operation results of the demonstration plants show that when Beisu coal was used as feedstock, the OMB CWS gasification process at Yankuang Cathy Coal Co. Ltd had a higher carbon conversion of 3%, a lower specific oxygen consumption of about 8%, and a lower specific carbon consumption of 2%–3% than that of Texaco CWS gasification at the Lunan Fertilizer Plant. When Shenfu coal was used as feedstock, the OMB CWS gasification process at Hua-lu Heng-sheng Chemical Co. Ltd had a higher carbon conversion of more than 3%, a lower specific oxygen consumption of about 2%, and a lower specific coal consumption of about 8% than that of the Texaco CWS gasification process at Shanghai Coking & Chemical Corporation. The OMB CWS gasification technology is proven by industrial experience to have a high product yield, low oxygen and coal consumption and robust and safe operation.