工业炉窑物质流和能量流匹配的节能原理分析

Principle analysis of energy saving of matched material and energy flows in the industrial furnace and kiln

工业炉窑是我国的能耗大户,每年耗能约占全国总能耗的1/4。在能源日益紧缺、环境污染严重的今天,工业炉窑节能减排工作十分紧迫。工业炉窑的生产是不同设备、不同工序协同生产的一个过程,包含物质与能量在各个系统之间的转换与转移,因此工业炉窑的物质流和能量流分析是炉窑实现高能效和低排放的基础。一般的方法主要从炉窑的产品用能或余热利用角度来分析,未将工业炉窑作为一个系统,整体来考察物质流和能量流状况。基于节点计算法,从工业炉窑整体系统出发,建立一种工业炉窑物质流与能量流匹配的数学模型,获得了典型工业炉窑不同部位的能量收支情况;同时采用热力学第二定律的分析方法研究炉窑系统的损失,明确了炉窑节能的重点部位。采用该方法开展了3200 t/d典型水泥炉窑的物质流和能量流分析计算,结果表明,水泥炉窑的热量损失主要包含高温损失与低温损失,其中高温损失主要是炉窑壁面散热损失与煤粉未燃尽的碳热损失,分别占6.84%与1.95%,损失分别为4.17%与2.59%,有较大的节能潜力;低温热损失包含烟道尾部烟气的排烟热损失、出冷却机熟料带出的显热等,AQC炉和SP炉的热量损失各占3.06%和6.19%,损失分别为1.26%和1.45%,仍有利用价值。针对高温和低温热量损失的不同原因,对于炉窑的节能潜力进行了评估,提出采用先进保温、富氧煅烧、低温余热再利用等新技术,可进一步降低炉窑的煤耗;此外,也推荐了减少设备电耗的新技术,如采用高效风机以及永磁电机等,结合富余蒸汽拖动风机以及节能管控等技术,有望实现熟料烧成系统零电耗的目标。

Industrial furnace is a huge energy consumption industry in China,which accounts for about 1/4 of the total energy consumption in China every year.In the increa sin g shortage of energy and environmental pollution today,the energy saving and emission reduction is very urgent for the industrial furnaces and kilns.The production of industrial furnaces is a process of collaborative works of different equipments and processes,including the conversion and transfer of material and energy between various systems.Therefore,the analysis of material flow and energy flow for industrial furnaces and kilns is the basis of realizing high efficiency and low emission.The general method is mainly analyzed from the perspective of energy or waste heat utilization of the furnace products,and the industrial furnace is not regarded as a total system to investigate the material flow and energy flow status.In this paper,based on the node calculation method and starting from the whole system of industrial furnaces,a mathematical model of matching material flow and energy flow was established,and the energy balance of different parts of a typical industrial furnace was obtained.Meanwhile,the exergy loss of furnace system was studied by the sec ond law of thermodynamics,and the key parts of furnace energy saving were found.The material flow and energy flow of 3200 t/d typical cement kiln were analyzed and calculated by this method.The results show that the heat loss of cement kiln mainly includes high-temperature loss and low-temperature loss.The high-temperature loss is mainly the heat loss of the kiln′s walls and the carbon heat loss of unburned coal,accounting for 6.84%and 1.95%respectively,and corresponding to the loss of exergy as 4.17%and 2.59%respectively,which has a few energy-saving potential.The low-temperature heat loss includes the heat loss of flue gas at the tail of kiln and sensible heat from the clinker out of the cooler.The heat loss of AQC furnace and SP furnace accounts for 3.06%and 6.19%respectively,and corresponding to the loss of exergy as 1.26%and 1.45%respectively,which is still worthy of utilization.According to the different reasons for high temperature and low temperature heat loss,in this paper,the energy saving potential of furnace and kiln was evaluated and some new technologies,such as advanced heat insulation of furnace wall,oxygen enriched calcination,and low temperature waste heat utilization were proposed,which could further reduce the coal consumption of the kiln.In addition,some new technologies are recommended to reduce the electrical power consumption of the equipment,such as the use of high-efficiency fans and permanent magnet motors,combined with the technology of surplus steam-driven fan and energy-saving management,which is expected to achieve the goal of zero power consumption of clinker sin tering system.