洁净煤技术

2019, (04) 1-7

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中低温热解煤气热量清洁利用技术途径分析与策略建议
Approach analysis and strategy suggestions for clean utilization technology of medium and low temperature pyrolysis gas heat

王岩;白效言;袁殷;
WANG Yan,BAI Xiaoyan,YUAN Yin

摘要(Abstract):

高温含焦油热解煤气携带大量显热与潜热,该部分热量高效回收利用对于整个工艺系统能效提升至关重要。为促进中低温热解过程余热资源高效回收利用,分析了激冷工艺、废热锅炉余热利用等中低温热解煤气冷却与余热利用方式的主要技术特点及不足;阐述了初冷器上段余热回收、循环氨水余热回收、上升管余热回收等高温热解煤气热量利用技术现状与特点。分析了含焦油高温热解煤气冷凝过程中焦油黏附问题、低温低压煤气热量捕捉与高效利用等中低温热解煤气热量回收利用过程中的主要技术难点。基于该技术难点及前期相变换热技术研究积累,以含焦油热解煤气冷凝-传热特性为科学基础,提出了热解煤气分级冷凝与相变换热相耦合的能量梯级回收利用一体化技术。即以焦油蒸汽不同组分露点差异与析出特性为基础,形成基于温度梯度的热解煤气分级冷凝工艺技术,逐级回收热解煤气所含热量,并实现不同馏程焦油产物在线分质回收;同时耦合复合相变换热技术,换热介质与热解煤气分级逆流换热,针对性回收热解煤气显热及低品位热解煤气潜热,实现含油热解煤气分级冷凝与热量梯级回收利用一体化,从而达到热解系统热效率与产品品质提升的双重效果。以100万t/a流化床热解工艺为例,提出了中低温热解煤气热量回收技术路线并进行了热量衡算。结果表明:该技术路线中低温热解煤气热量利用率可达到81. 17%,初步显示了其可行性。高效回收利用热解过程中的余热资源将是资源节约、环境友好热解产业发展的主要方向和潜力所在。
High temperature tar-containing pyrolysis gas carries a large amount of sensible heat and latent heat,and the efficient heat recycling of this part is crucial for the energy efficiency improvement of the whole process.In order to promote the efficient recycling of residual heat resources in the medium and low temperature pyrolysis process,this paper reviewed the main technical characteristics and shortcomings of the cooling and waste heat utilization methods of medium and low temperature pyrolysis gas,such as waste heat utilization from chilling process and exhaust heat boiler.This paper also summarized the research status and characteristics of high-temperature pyrolysis gas heat utilization technology,including waste heat recovery in the upper part of the primary cooler,circulating aqueous ammonia and upward pipes.The main technical difficulties in the process of heat recycle from medium and low temperature pyrolysis gas,such as tar adhesion happened in condensation process of tar-containing high temperature pyrolysis gas,low-temperature and low-pressure gas heat capture and efficient utilization,were also analyzed.Based on the technical limitations and the phase-change heat transfer technologies,took the condensation-heat transfer characteristics of tar-containing pyrolysis gas as the scientific basis,an integrated technology coupling pyrolysis gas multi-stage condensation and phase-change heat transfer for energy cascade recovery and utilization was proposed.Based on the dew point difference and precipitation characteristics from different components of tar steam,such technology forms a temperature gradient-based classifying and condensation process of pyrolysis gas,recycles the heat contained in pyrolysis gas step by step,and realizes on-line quality recovery of tar products in different distillation ranges.At the same time,it takes advantages of coupling and composites phase-change heat transfer technology,the heat transferring medium and pyrolysis gas implementes classifying and counterflow heat transfer,purposefully recycled sensible heat from pyrolysis gas and latent heat from low-grade pyrolysis gas,to achieve the integration of grading condensation and heat cascade recycling of oil-containing pyrolysis gas,thereby to achieve the dual effects of heat efficiency and product quality improvement of the pyrolysis system.Taking 1 million t/a fluidized bed pyrolysis process as an example,the heat recovery technical route of medium and low temperature pyrolysis gas was proposed,and the heat balance was calculated.The results indicate that an 81.17% heat utilization rate of medium and low temperature pyrolysis gas could be achieved in this technical route,which shows its feasibility initially.The efficient recycling of residual heat resources in the pyrolysis process will be the main direction and potential of resource-saving and environment-friendly pyrolysis industry development.

关键词(KeyWords): 中低温热解;煤气余热;分级冷凝;相变换热
medium and low temperature pyrolysis;gas waste heat;multi-stage condensation;phase-change heat transfer

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作者(Author): 王岩;白效言;袁殷;
WANG Yan,BAI Xiaoyan,YUAN Yin

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