摘要
生物质高温空气气化技术是燃料利用和能源供应领域内的一项高新技术,对缓解能源危机和改善环境质量具有重要意义,在日本、美国、西欧等一些发达国家已受到学术界和工业界的高度重视。由于我国在这方面的研究工作刚刚起步,一方面对高温空气气化过程本身缺乏足够的研究,另一方面还没有一个较完善的可用于高温空气气化研究的实验系统。为提高我国高温空气气化技术的研究水平,早日形成我国自主的知识产权,以迎接加入WTO后的挑战,有必要着手开展有关研究工作。
作为“十五”863计划项目“生物质气化发电优化系统及其示范工程”的子课题—“生物质高温气化技术研究”的前期工作,本文主要进行了如下工作:
1 收集并阅读了大量的中外文献,阐述了中外高温空气气化研究和技术的发展动态。
2 为认识生物质高温空气气化过程,并为工艺过程设计及实验装置设计提供理论指导,对生物质高温空气气化进行了理论探讨,将生物质高温气化分为不完全燃烧与高温干馏阶段和高温气化阶段,并对各阶段的理论计算进行了分析。
3 为了设计生物质高温空气气化系统实验装置及编制生物质高温空气气化工艺过程的计算机程序,首先以无烟煤为原料对高温空气气化工艺过程作了手工设计计算,计算结果为:气化温度为1537℃、气化效率为93.8%、合成燃气热值为6746kJ/Nm~3、系统热效率为43.8%、燃烧室的燃烧温度为1575℃、蓄热体的流通截面积为0.02m~2、蓄热体的高度为0.23m。然后采用Visual C++编制了高温空气气化工艺过程的计算机程序,并运用该程序进行了如下两类工作:(1)取高温空气温度为1100℃,对无烟煤气化工艺进行了计算,其结果与手工计算完全一致,验证了该程序的正确性;同样地对木块、垃圾分别进行计算,木块的计算结果为:气化温度为1338℃、气化效率为81%、合成燃气热值为5692kJ/Nm~3、系统热效率为42.3%、燃烧室的燃烧温度为1386℃、蓄热体的流通截面积为0.023m~2、蓄热体的高度为0.38m;垃圾的计算结果为:气化温度为1269℃、气化效率为82.1%、合成燃气热值为6153kJ/Nm~3、系统热效率为50%、燃烧室的燃烧温度为1386℃、蓄热体的流通截面积为0.045m~2、蓄热体的高度为0.38m。(2)对高温空气气化的主要影响因素进行了分析,结果指出:对于确定的氮碳比,蒸汽消耗率增加气化温度降低,气化所得的煤气热值增大;对于确定的蒸汽消耗率,气化温度随氮碳比的增大而升高,然而气化所得的煤气热值却随氮碳比的增加而降低;对于确定的蒸汽消耗率、氮碳比,煤气热值随气化温度的增加而增加,但是增加量不大。
4 高温空气发生器是我校“生物质高温空气气化技术研究”课题组正在研制的实验研究系统的关键部件之一,其主要功能是产生温度为800~1500℃的空气。作者按照给定的设计参数结合上述工艺计算的结果,设计了以高温低氧弥散燃烧为核心技术的高温空气发生器,绘制了全套工程图纸,并自始至终参加了该装置的建造过程。
5 高温空气发生器呈对称结构,其中一侧进行燃烧,另一侧产生高温空气,形成的高温空气必须分成两部分,一部分流向发生器的另一侧用作助燃剂,另一部分流向气化器用作气化剂。为掌握高温空气发生器内空气流量的分配特性及送出空气的压力大小,在高温空气发生器实验装置上进行了冷态实验。结果表明,通过冷端调节就可以实现分流的目的,即:对于确定的排烟机开度,可以调
Gasification from Biomass Using High Temperature Air is a new technology developed in the fields of fuel utilization and energy supply. The great attention has been paid on the new technology in many countries such as Japan、 the United States and some developed countries in west Europe because of its great significance considering the increasingly serious energy crisis and environmental pollution. However, as the relevant study in China is just at the initial stage, there is neither enough research on the process of HTAG (High Temperature Air Gasification) nor perfect experimental system. In order to improve the study level and form independent property right of information concerned, it is very necessary to set about the revelent study work to meet the challenge of joining the WTO.As the first-phase work of the "Research on Gasification from Biomass Using High Temperature Air Technology", subproject of "863 Program"—Optimization System and Demonstration Project of Gasification and Power Generation from Biomass", the author carried out the mainly research work as follows:(1) Many pieces of Chinese and foreign literatures are collected and read, and the development dynamic of HTAG in China and foreign countries is stated.(2) In order to comprehend the process of HTAG and to provide academic directions for the design of process and experimental devices, the author conducted theoretical analysis and divided it into two phases: One of them is the imperfect combustion and high temperature carbonization phase and the other is the high temperature gasification phase. Each phase was analyzed and calculated theoretically.(3) For the purpose of designing experimental device and compiling the computer program, firstly, the author made manual design calculation on the HTAG of the anthracite coal in detail. The results show: the gasification temperature is 1537℃; gasification efficiency is 93.8%; caloric value of syngas is 6746kJ/Nm~3; thermal efficiency of system is 43.8%; combustion temperature in the combustion chamber is 1575℃; Circulation section area of the regenerator is 0.02m~2; height of the regenerator is 0.23m. Then, the process of HTAG has been programmed with Visual C++. The computer program was applied on the following work: ① Supposing the air temperature is 1100℃, the computer calculation results coincide with the manual results completely, which validates the correctness of the program; In the same way, both the charcoal and garbage are calculated respectively. For the block, the gasification temperature is 1338℃; gasification efficiency is 81%; caloric value of syngas is 5692kJ/Nm~3; thermal efficiency of system is 42.3%; combustion temperature in the combustion chamber is 1386℃; Circulation section area of the regenerator is 0.023m~2; height of the regenerator is 0.38m. Similarly, for the garbage, the gasification temperature is 1269℃; gasification efficiency is 82.1%; caloric value of syngas is 6153kJ/Nm~3; thermal efficiency of system is 50%; combustion temperature in the combustion chamber is 1386℃; Circulation section area of the regenerator is 0.045m~2; height of the regenerator is 0.38m. ②The main factors dominating the HTAG process were analyzed. As a results, the calculation results indicate: when steam consumption rate is raised, gasification temperature decreases and caloric value of syngas increases; when the rate of nitrogen and carbon is enhanced, gasification temperature goes up while the caloric value of syngas drops; caloric value of syngas increases a little when gasification temperature increases.(4) As one of the key components of the experimental system being developed by the study group on "Research on Technology of Gasification from Biomass Using High Temperature Air" in CSU, the primary function of the high temperature air generator is to produce high temperature air of 800~1500℃.
According to the related design parameters and the calculation results, the high temperature air generator was designed whose core technology is the high temperature air combustion with low oxygen concentration. At the same time, the author drew up the whole engineering drawings and took part in the construct process all the time.(5) The structure of the high temperature air generator is symmetrical. One side is used for combustion and the other side is used to produce high temperature air. The high temperature air is divided into two parts; one is used for combustion of syngas to heat up the other side honeycomb and the other is extracted toward the gasifier. With the aim to grasping the distribution performance of the air flow rate inside the generator and the outlet pressure at the shunting, the author carried out cold-state experiment on the high temperature air generator. The results show that cold-end regulation can realize flow distribution, that is to say, on condition that the switching value of fume blower is definite, adjusting the switching value of air blower can regulate shunting outlet flow rate; Similarly, if the switching value of air blower is definite, adjusting the switching value of fume blower can regulate shunting outlet flow rate; the total range of the divided flow is between -0.012 and 0.102Nm3/s. For a certain switching value of shunt baffle, shunting outlet pressure enhances with the decrease of the switching value of fume blower and with the increase of that of air blower. The range of regulation is between -50 and 210Pa.In the end, the author put forward a series of proposals on further research work.
引文
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