部分煤气化空气预热燃煤联合循环发电系统(PGACC)技术方案研究

部分煤气化空气预热燃煤联合循环发电系统是一种把煤气化技术，常压流化技术与联合循环结合起来的洁净煤发电技术，它通过将压气机排气在常压流化床锅炉中进行预热，同时利用气化炉内的高温煤气使蒸汽过热，从而提高循环效率，它的发电效率比较高，系统比较简单，是一种新的洁净煤发电技术的选择。文章采用ASPEN PLUS软件对部分煤气化空气预热燃煤联合循环方案改造老电厂的多种技术方案进行计算并对技术方案作了初步研究。     

煤的部分空气气化联合循环发电系统特性研究

煤的部分空气气化联合循环发电是一种把煤气化技术和循环流化床技术结合起来的洁净煤发电技术。文章通过对三种方案的计算，得出了碳的转化率与运行温度、煤气热值、气化效率、系统效率之间的关系，证实了碳的转化率对系统运行有重要的影响，同时和其他气化方式下联合循环发电系统进行比较分析，证实煤的空气部分气化联合循环系统是一高效低污染、技术简单、投资小、见效快的发电系统。     

气化参数对高温空气气化的影响

介绍了生物质高温空气气化思想和系统的工作原理及其过程，并就气化参数对生物质高温空气气化的影响进行了深入的分析，结畏发现：随蒸汽消耗率的增加气化温度降低，而气化所得的煤气热值增大；气化温度随氮碳比的增大而升高，而气化所得的煤气热值却随氮碳比的增加而降低；煤气热值随气化温度的增加而增大，但是增加量不大。     

联合循环发电技术及其余热锅炉

燃气-蒸汽联合循环发电技术可实现化学能梯级利用,具有很高的效率。余热锅炉处于燃气轮机和蒸汽轮机之间,对联合循环系统效率产生重要影响。本文概述了燃气-蒸汽联合循环发电技术的原理和组成,重点介绍了余热锅炉的结构和热力性能等方面的特点,并对影响余热锅炉性能的有关因素进行了阐述。最后,对余热锅炉的研究方向进行了讨论。     

煤转化为洁净燃料技术

正煤的气化技术,有常压气化和加压气化2种,它是在常压或加压条件下,保持一定温度,通过气化剂(空气、氧气和蒸汽)与煤炭反应生成煤气,煤气中主要成分是一氧化碳、氢气、甲烷等可燃气体。用空气和蒸汽做气化剂,煤气热值低;用氧气做气化剂,煤气热值高。煤在气化中可脱硫除氮,排去灰渣,因此,煤气就是洁净燃料了。     

温度对中试规模的喷动流化床煤部分气化行为的影响

在构建的热输入2MW的中试规模加压喷动流化床部分气化试验装置上,对徐州烟煤的加压部分气化行为进行了研究.重点考察了气化温度对煤气成分、煤气热值、碳转化率和煤气产率等气化指标的影响.研究结果表明,煤气各组分的浓度,特别是甲烷浓度对气化温度非常敏感,碳转化率和煤气产率随温度的升高而增加,在试验的温度区间内,温度对煤气热值影响不大.部分气化炉所产生的煤气和半焦的热值均满足第二代增压流化床联合循环发电系统的要求.     

市政污泥循环流化床气化特性的模拟研究

运用Aspen Plus分析软件对市政污泥进行循环流化床气化模拟计算,分析了空气当量比、预热空气温度和污泥含水率对污泥气化特性的影响。结果表明：空气当量比对气化特性影响较大,在选定的污泥含水率下,最佳空气当量比在0.3左右;预热空气温度的提高可以提高气化温度和燃气热值;随着污泥含水率的升高,气体产物中CO₂、CH₄含量升高,燃气热值和气化温度明显降低,在流化床气化反应时干污泥含水率不宜高于20%。模拟研究结果可为污泥气化耦合燃煤发电工程方案提供一定的数据支撑和依据。     

低热值煤气火力发电技术应用进展

通过对比分析4种煤气发电技术的应用场景和技术特性，探究钢铁厂煤气的最佳利用路径，最大限度地实现能量的分级回收、梯级利用和协同发电。余热回收加汽轮机发电技术(HTG)最优回收了煤气的高温余热，但产出的低压饱和蒸汽发电效率较低。燃气锅炉加汽轮机发电技术(BTG)简单高效，提高了锅炉初参数，一次再热，极大地提高了发电效率，但所燃烧煤气热值不能低于5 400 k J/m3。燃气轮机联合循环发电技术(CCPP)发电效率高，但初期投资大，适用于大型钢铁厂，机组选型要求高，需根据特定的使用工况确定。余压透平发电技术(TRT)仅利用煤气的压力能和热能，同时对煤气进行预处理，后续可通过BTG、CCPP进一步利用余热。     

整体煤气化燃气—蒸汽联合循环机组

整体煤气化蒸汽燃气联合循环机组（Integrated Gasification Combined-Cycle），简称IGCC发电技术，是煤气化和蒸汽联合循环的结合，是当今国际上正在兴起的先进的洁净煤（CCT）发电技术，其具有高效、低污染、节水、综合利用串高等优点。它由两大部分组成，即煤的气化与净化部分和燃气-蒸汽联合循环发电部分。     

燃气-蒸汽联合循环系统设计与蒸汽系统参数分析研究

研究了蒸汽系统的参数选择对联合循环部件及总体性能的影响，通过对单压、双压和三压三种蒸汽系统参数配置方案的设计计算和分析。初步得到了联合循环热力系统合理设计的一些基本原则，研究结果对联合循环系统的总体优化设计具有一定的参考价值。     

Effect of supplementary firing options on cycle performance and CO2 emissions of an IGCC power generation system

Supplementary firing is adopted in combined‐cycle power plants to reheat low‐temperature gas turbine exhaust before entering into the heat recovery steam generator. In an effort to identify suitable supplementary firing options in an integrated gasification combined‐cycle (IGCC) power plant configuration, so as to use coal effectively, the performance is compared for three different supplementary firing options. The comparison identifies the better of the supplementary firing options based on higher efficiency and work output per unit mass of coal and lower CO₂ emissions. The three supplementary firing options with the corresponding fuel used for the supplementary firing are: (i) partial gasification with char, (ii) full gasification with coal and (iii) full gasification with syngas. The performance of the IGCC system with these three options is compared with an option of the IGCC system without supplementary firing. Each supplementary firing option also involves pre‐heating of the air entering the gas turbine combustion chamber in the gas cycle and reheating of the low‐pressure steam in the steam cycle. The effects on coal consumption and CO₂ emissions are analysed by varying the operating conditions such as pressure ratio, gas turbine inlet temperature, air pre‐heat and supplementary firing temperature. The results indicate that more work output is produced per unit mass of coal when there is no supplementary firing. Among the supplementary firing options, the full gasification with syngas option produces the highest work output per unit mass of coal, and the partial gasification with char option emits the lowest amount of CO₂ per unit mass of coal. Based on the analysis, the most advantageous option for low specific coal consumption and CO₂ emissions is the supplementary firing case having full gasification with syngas as the fuel. Copyright © 2008 John Wiley & Sons, Ltd.     

Thermodynamic Analysis and Conceptual Design for Partial Coal Gasification Air Preheating Coal-fired Combined Cycle

The partial coal gasification air pre-heating coal-fired combined cycle (PGACC) is a cleaning coal power system, which integrates the coal gasification technology, circulating fluidized bed technology, and combined cycle technology. It has high efficiency and simple construction, and is a new selection of the cleaning coal power systems. A thermodynamic analysis of the PGACC is carried out. The effects of coal gasifying rate, pre-heating air temperature, and coal gas temperature on the performances of the power system are studied. In order to repower the power plant rated 100 MW by using the PGACC, a conceptual design is suggested. The computational results show that the PGACC is feasible for modernizing the old steam power plants and building the new cleaning power plants.     

Optimization of a combined heat and power system based gasification of municipal solid waste of Urmia University student dormitories via ANOVA and taguchi approaches

Municipal solid waste (MSW) of Urmia University student dormitories was utilized to trigger a co-generation system. The combined heat and power system consisted of a gasifier, a micro gas turbine, an organic Rankine cycle, a heat exchanger, and a domestic heat recovery. The system performance was validated by comparing the results with experimental results available in the literature. Air, steam, and oxygen were considered as different gasification mediums. Hydrogen content in the case of the steam medium was higher at all gasification temperatures and low moisture contents. However, hydrogen content of the system based oxygen medium was higher at high moisture contents. The system performances from power generation and hot water flow rate viewpoints were assessed versus the MSW flow rate, gasification temperature, pressure ratio, and turbine inlet temperature. Taguchi approach was employed to optimize the generated power in air, steam, and oxygen medium cases. The optimum conditions were the same for all cases. The optimum powers were 281.1 kW, 279.4 kW, and 266.9 kW for the system based steam, air, and oxygen gasifying agents, respectively.     

High-temperature air and steam gasification of densified biofuels

An experimental study was carried out to investigate gasification of densified biofuels using highly preheated air and steam as a gasifying agent. Preheat of air and steam is realised by means of the newly developed high-cycle regenerative air/steam preheater. Use of highly preheated feed gas provides additional energy into the gasification process, which enhances the thermal decomposition of the gasified solids. For the same type of feedstock the operating parameters, temperature, composition and amount of gasifying agent, were varied over a wide range. Results of experiments conducted in a high-temperature air/steam fixed bed updraft gasifier show the capability of this technology of maximising the gaseous product yield as a result of the high heating rates involved, and the efficient tar reduction. Increase of the feed gas temperature reduces production of tars, soot and char residue as well as increases heating value of the dry fuel gas produced. Overall, it has been seen that the yield and the lower heating value of the dry fuel gas increase with increasing temperature.     

Distributed gasification and power generation from solid wastes

A small-scale gasification system for solid wastes has been developed and tested. In this innovative system, known as the STAR-MEET system, a fixed-bed pyrolyzer combined with a high temperature steam/air reformer is employed. From the experimental results using wood chips and polyolefin sheets as feedstocks, it has been demonstrated that injection of high temperature steam/air mixture into the pyrolysis gas can effectively decomposes tar components in the pyrolysis gas into CO and H₂, resulting in an almost tar-free, clean product gas. A 900 °C class compact metallic heat exchanger has been successfully developed, which serves as the high temperature steam/air generator for the STAR-MEET system. Finally, power generation experiments using a complete STAR-MEET plant have been successfully carried out. These results demonstrate small-scale gasification and power generation system using solid wastes is quite feasible.     

The effect of air preheating in a biomass CFB gasifier using ASPEN Plus simulation

In the context of climate change, efficiency and energy security, biomass gasification is likely to play an important role. Circulating fluidised bed (CFB) technology was selected for the current study. The objective of this research is to develop a computer model of a CFB biomass gasifier that can predict gasifier performance under various operating conditions. An original model was developed using ASPEN Plus. The model is based on Gibbs free energy minimisation. The restricted equilibrium method was used to calibrate it against experimental data. This was achieved by specifying the temperature approach for the gasification reactions. The model predicts syn-gas composition, conversion efficiency and heating values in good agreement with experimental data. Operating parameters were varied over a wide range. Parameters such as equivalence ratio (ER), temperature, air preheating, biomass moisture and steam injection were found to influence syn-gas composition, heating value, and conversion efficiency. The results indicate an ER and temperature range over which hydrogen (H₂) and carbon monoxide (CO) are maximised, which in turn ensures a high heating value and cold gas efficiency (CGE). Gas heating value was found to decrease with ER. Air preheating increases H₂ and CO production, which increases gas heating value and CGE. Air preheating is more effective at low ERs. A critical air temperature exists after which additional preheating has little influence. Steam has better reactivity than fuel bound moisture. Increasing moisture degrades performance therefore the input fuel should be pre-dried. Steam injection should be employed if a H₂ rich syn-gas is desired.     

Energy and exergy analyses of the oxidation and gasification of carbon

Exergy losses in gasification and combustion of solid carbon are compared by conceptually dividing the processes into several subprocesses: instantaneous chemical reaction, heat transfer from reaction products to reactants (internal thermal energy exchange) and product mixing. Gasification is more efficient than combustion because exergy losses due to internal thermal energy exchange are reduced from 14–16 to 5–7% of expended exergy, while the chemical reactions are relatively efficient for both processes. The losses due to internal thermal energy exchange may be reduced by replacing air with oxygen, although this introduces additional process losses for separation of oxygen from air, or alternatively, preheating of air by heat exchange with product gas. For oxygen-blown gasification of fuels with high calorific value, such as solid carbon, it is advisable to moderate the temperature by introduction of steam. At optimum gasification temperatures in the ranges of 1100–1200 K (for atmospheric pressure) and 1200–1300 K (for 10 bar pressure), up to 75% of the chemical exergy contained in solid carbon can be preserved in the chemical exergy of carbon monoxide and hydrogen.     

Parametric analysis of a coal based combined cycle power plant

In the present paper thermodynamic analyses, i.e. both energy and exergy analyses have been conducted for a coal based combined cycle power plant, which consists of pressurized circulating fluidized bed (PCFB) partial gasification unit and an atmospheric circulating fluidized bed (ACFB) char combustion unit. Dual pressure steam cycle is considered for the bottoming cycle to reduce irreversibilities during heat transfer from gas to water/steam. The effect of operating variables such as pressure ratio, gas turbine inlet temperature on the performance of combined cycle power plant has been investigated. The pressure ratio and maximum temperature (gas turbine inlet temperature) are identified as the dominant parameters having impact on the combined cycle plant performance. The work output of the topping cycle is found to increase with pressure ratio, while for the bottoming cycle it decreases. However, for the same gas turbine inlet temperature the overall work output of the combined cycle plant increases up to a certain pressure ratio, and thereafter not much increase is observed. The entropy generation, the irreversibilities in each component of the combined cycle and the exergy destruction/losses are also estimated. Copyright © 2005 John Wiley & Sons, Ltd.     

提高燃气轮机联合循环电站性能的优化方法

天然气联合循环机组因启停快、运行灵活性好、热效率高、排放清洁、建造周期短而倍受中国市场青睐.围绕如何通过燃气轮机进气系统、主机参数匹配、汽轮机冷端等参数优化来提高联合循环热效率是国内外学者研究的热点.以配有目前市场上最高性能等级燃气轮机的联合循环为研究对象,建立了以提高联合循环热效率为目标的热力计算和分析模型,提出了各段蒸汽压力及温度参数优化匹配方法,并进一步分析、讨论了燃料预热对联合循环热效率的影响.在综合考虑余热锅炉换热温差、汽轮机结构设计等制约因素下得到了一组蒸汽循环的优化参数配置.计算结果表明,相比直接沿用上一代蒸汽循环参数,使用该优化参数配置可大幅度提高联合循环效率,并且使用燃料预热可使循环性能得到进一步改善.     

Improvement of part load efficiency of a combined cycle power plant provisioning ancillary services

According to the type of ancillary service provisioned, operation mode of a power plant may change to part load operation. In this contribution, part load operation is understood as delivering a lower power output than possible at given ambient temperature because of gas turbine power output control. If it is economically justified, a power plant may operate in the part load mode for longer time. Part load performance of a newly built 80 MW combined cycle in Slovakia was studied in order to assess the possibilities for fuel savings. Based on online monitoring data three possibilities were identified: condensate preheating by activation of the currently idle hot water section; change in steam condensing pressure regulation strategy; and the most important gas turbine inlet air preheating. It may seem to be in contradiction with the well proven concept of gas turbine inlet air cooling, which has however been developed for boosting the gas turbine cycles in full load operation. On the contrary, in a combined cycle in the part load operation mode, elevated inlet air temperature does not affect the part load operation of gas turbines but it causes more high pressure steam to be raised in HRSG, which leads to higher steam turbine power output. As a result, less fuel needs to be combusted in gas turbines in order to achieve the requested combined cycle’s power output. By simultaneous application of all three proposals, more than a 2% decrease in the power plant’s natural gas consumption can be achieved with only minor capital expenses needed.