75 t/h循环流化床锅炉性能测试及基于Aspen Plus模拟研究

陈宝明,段钰锋,耿新泽,许一凡,赵士林,黄天放

(东南大学 能源与环境学院 能源热转换及其过程测控教育部重点实验室,江苏 南京 210096)

摘 要:为寻找循环流化床(CFB)燃煤锅炉机组热损失的原因,以额定负荷75 t/h CFB燃煤锅炉为试验平台,对其进行热力性能测试,为与实测法对比,利用Aspen Plus流程模拟软件对CFB锅炉进行建模计算,提出一种基于Aspen Plus模型法获得CFB锅炉热效率的新思路。试验选取低负荷、满负荷、高负荷3种运行工况,利用反平衡法通过热力计算求得各项热损失,探究不同运行工况参数对CFB锅炉热效率的影响,并分析了不同运行工况下,飞灰及炉渣中未燃尽碳(UBC)含量的分布规律。通过对CFB锅炉的煤热解、煤燃烧、气固分离和热交换4个子过程进行建模,利用现场稳定运行的锅炉各级换热设备进出口流股温度、压力、流量等数据,对满负荷(工况2)条件下锅炉各项热损失、锅炉热效率及炉膛出口烟气组分浓度进行计算。根据实测数据与模拟结果的比对,验证建模的准确性、可靠性。结果表明:模型法与实测法数据吻合良好,能够精准预测炉膛出口烟气的组成;通过对比锅炉各项热损失及热效率,发现排烟热损失q2实测结果为7.75%,模型结果为6.48%;固体未完全燃烧热损失q4实测结果为3.72%,模型结果为3.17%;二者相对误差较小,说明利用Aspen Plus建模可以对排烟热损失及固体未完全燃烧热损失进行较为精准的预测;模型计算得到的锅炉热效率为88.66%,实测锅炉热效率为87.426%,相对误差仅为1.41%,实测法和模型法对热效率及各项热损失的计算结果极为接近,验证了建模思路及方法的准确性和可靠性,也印证了基于Aspen Plus模型法计算CFB锅炉热效率的可行性;3种工况下锅炉运行存在排烟温度高、飞灰含碳量高、实际热效率偏低未达到锅炉设计值等问题;入炉煤燃烧后飞灰中的UBC含量较高,为13.28%~16.40%,炉渣中UBC含量较少,为2.92%~3.39%;3种工况下锅炉排烟热损失在7.64%~7.93%,固体未完全燃烧热损失在3.72%~4.69%,锅炉热效率在86.14%~87.43%,且η2>η3>η1。说明基于Aspen Plus对CFB锅炉建模进行锅炉热力计算可行、可靠。

关键词:循环流化床锅炉;性能测试;Aspen Plus;流程模拟;热损失;热效率

中图分类号:X511TK229.6

文献标志码:A

文章编号:1006-6772(2020)03-0052-08

收稿日期:2020-03-16;责任编辑:白娅娜

DOI:10.13226/j.issn.1006-6772.CFB20031601

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基金项目:国家重点研发计划资助项目(2016YFB0600203)

作者简介:陈宝明(1994—),男,安徽宿州人,硕士研究生,研究方向为模拟电厂热力系统的优化及提效。E-mail:403451708@qq.com。

通讯作者:段钰锋,教授,博士生导师,研究方向为洁净煤发电和大气污染控制。E-mail:yfduan@seu.edu.cn

引用格式:陈宝明,段钰锋,耿新泽,等.75 t/h循环流化床锅炉性能测试及基于Aspen Plus模拟研究[J].洁净煤技术,2020,26(3):52-59.

CHEN Baoming,DUAN Yufeng,GENG Xinze,et al.Performance test of 75 t/h CFB boiler and simulation study based on Aspen Plus[J].Clean Coal Technology,2020,26(3):52-59.

Performance test of 75 t/h CFB boiler and simulation study based on Aspen Plus

CHEN Baoming,DUAN Yufeng,GENG Xinze,XU Yifan,ZHAO Shilin,HUANG Tianfang

(Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education,School ofEnergy and Environment,Southeast University,Nanjing 210096,China)

Abstract:In order to find out the causes of heat loss of circulating fluidized bed(CFB) boiler unit,the thermal performance of CFB coal-fired boiler with rated load of 75 t/h was tested. In order to compare with the measured method,a new idea of obtaining the thermal efficiency of CFB boiler based on Aspen Plus model method was proposed,that is,by using Aspen Plus process simulation software to model and calculate CFB boiler. In the experiment,three operating conditions of low load,full load and high load were selected,and the heat losses was calculated by the anti-balance method,and then the effects of different operating conditions on the thermal efficiency of the CFB boiler were explored,the distribution of unburned carbon(UBC) in fly ash and slag under different operating conditions was analyzed. By modeling the four sub-processes of coal pyrolysis,coal combustion,flue gas-fly ash separation and heat exchange of CFB boiler,and based on the data of inlet and outlet flow unit temperature,pressure,flow rate,etc. in heat exchange equipment at all levels of the boiler,the heat loss,the heat efficiency and the concentration of flue gas at the outlet of the boiler were calculated under the condition of full load(working condition 2). The accuracy and reliability of the model were verified by comparing the measured data with the simulation results. The results show that the model method is in good agreement with the measured data and can accurately predict the composition of flue gas at furnace outlet. Through the comparison of the heat loss and thermal efficiency of boiler,it is found that the measured result of exhaust heat loss q2 is 7.75%,and the model result is 6.48%.The measured result of solid incomplete combustion q4 is 3.72% and the model result is 3.17%.The relative error between two methods is small,indicating that Aspen Plus modeling can be used to accurately predict the heat loss of smoke exhaust and the heat loss of incomplete solid combustion. The thermal efficiency of the boiler calculated by the model is 88.66%,the measured thermal efficiency of boiler is 87.426%,and the relative error is only 1.41%,the calculation results of thermal efficiency and heat loss is extremely close between the measured method and the model method,which can verify the veracity and reliability of the modeling idea and method,and the feasibility of CFB boiler thermal efficiency calculation based on Aspen Plus model is also verified. There are some problems in the operation of the boiler under the three operating conditions,such as high flue gas temperature,high carbon content of fly ash,and low actual thermal efficiency that does not reach the boiler design value. The content of UBC in fly ash after coal combustion is relatively high,ranging from 13.28% to 16.40%,while the content of UBC in slag is low,ranging from 2.92% to 3.39% under three operating conditions,the heat loss of boiler exhaust flue gas between 7.64%-7.93%,the heat loss of solid incomplete combustion between 3.72%-4.69%,the boiler thermal efficiency is between 86.14%-87.43%,in which η2>η3>η1.It shows that it is feasible and reliable to use Aspen Plus to model CFB boiler for thermal calculation.

Key words:CFB boiler;performance testing;Aspen Plus;process simulation;heat loss;thermal efficiency

0 引 言

循环流化床(CFB)锅炉燃烧技术具有燃料适应性广、燃烧效率高、污染物排放低以及负荷调节方便等优点,被广泛应用于电站锅炉,成为劣质煤商业化最成功的洁净煤燃烧技术[1-2]。但常规CFB电站存在部分炉型可靠性差、热利用率低、供电效率不足等缺点[3-4],因此,CFB锅炉热力性能测试对了解锅炉的实际运行状况、优化燃烧、提高锅炉热效率具有重要意义。目前,电站锅炉热效率计算标准有2种:DL/T 964—2018《循环流化床锅炉性能试验规程》和美国机械工程师协会颁布的ASME-PTC4—1998《锅炉性能试验规程》[5]。二者按照计算的标准分为输入-输出热量法(正平衡法)和热损失法(反平衡法)。反平衡法简单易行,数据可靠,测试结果可为锅炉的运行参数优化和提高锅炉效率提供有效参考[6-7]

针对锅炉性能测试的常规热平衡法具有周期较长、成本较大、诸多参数不易获取、核算繁琐且无法实时掌握锅炉热效率等缺点,采用相关软件对CFB锅炉进行流程模拟,可快捷获得锅炉工业试验条件下的运行参数。基于Aspen Plus强大的物性数据库和灵活且便于计算的单元模块,可方便灵活地模拟煤转化过程中