贵宾会员zhuh提供----火电厂入厂煤与入炉煤热值差大的原因分析及对策
龚丽华，张国金，王应高，赵静
(华北电力科学研究院有限责任公司，北京100045)
[摘 要] 控制好火电厂入厂煤与入炉煤热值差(简称燃煤热值差)对降低发电成本、促进电厂安全稳定运行有着积极的意义。分析了使热值差超标的原因，具体包括:煤质均匀性的影响;计算热值差的入厂煤和入炉煤不是同一批次;入炉煤热值计算未调整到入厂煤全水的同期值;煤长时问存放发牛氧化的影响;入厂煤与入炉煤采样、制样、化验(简称采制化)过程中的偏差超过允许值。提出了采样过程、制样过程、热值测量过程的热值差检查分析方法，包括来煤粒度、采样机出料粒度、缩分器、热量计标定过程等检查。
[关键词] 火电厂,入厂煤,入炉煤,热值差
Reasons Analysis and Countermeasure of Caloric Value Differences Between Coal as Received and Coal as Fired
in Thermal Power Plant
GONG Li-hua, ZHANG Guo-jin, WANG Ying-gao, ZHAO Jing
(North China ELectric Power Research Institute Co., Ltd., Beijing 100045, China )
ABSTRACT： Controlling the caloric value differences between coal as received and coal as fired well is positive to reduce the
electricity generation cost and to insure the power plant safe and stable operation. The reasons of difference of caloric value exceeding
standard have been analyzed, which include the influence of coal uniformity, the coal as received and coal as fired used to calculated
difference of caloric valueare not the same batch, the coal as fired caloric value calculation has not been adjusted to the same period of coal
as received, coal has been oxidized after a long time stocking, and the overrange deviation of coal during sampling, sampling preparation and
lab test overranging. Then the analytical methods in the process of sampling, sampling preparation and caloric value measurement have been
proposed, including the inspections of the particle size of supplied coal, sampling machine discharge, reduction device and process of
calorimeter calibration.
KEY WORDS: thermal power plant; coal as received; coal as fired; the difference of caloric value
引言
火电厂燃煤热值差是经济性评价及燃煤管理的重要指标。电力行业一流火力发电厂考核标准(电综
【1997】577 号文附件1)对热值差作出了规定，要求入厂煤与入炉煤低位热值差小于502 J/g。在实际生产中，有的电厂达不到这一指标，热值差大，一方面影响燃煤成本;另一方面影响煤耗计算。控制好热值差，
对有效控制燃煤成本、促进电力安全生产、节能降耗都有积极意义。目前关于热值差超标原因分析的文献
仅局限于某几个方面的分析〔1-2〕，本文全面、系统地分析了热值差超标的原因，并提出了相应的检查分析办法。
1 影响热值差的因素
1.1 煤质均匀性
对燃用均匀、单一的煤种，比较容易达到热值差指标。如某厂燃用神华煤(煤质均匀性较好)，同一列火车机采20 个子样平均干基灰分A d=10.27%，人采20 个子样平均干基灰分A d=10.20% ,两者灰分0.070%，说明煤质均匀不容易造成采样偏差，人采与机采同样具有代表性。
对燃用煤质非常不均匀的煤种，如某电厂，同车厢机采20 个子样，灰分最小为36.45% ,最大为60.89%，
极差24.44%。对于这种情况，如果按常规采样方法采样，不增加子样个数，采样代表性就很差。
1.2 计算热值差的入厂煤和入炉煤批次
如果以月计算热值差，首先应保证每月入炉煤燃用的是当月的入厂煤，否则当月的热值差就没有可比性，此时可累计为3 个月的热值差进行比较。
1.3 入炉煤热值计算未调整到入厂煤全水的同期值
建议用人厂煤和入炉煤干基高位发热量计算热值差或入炉煤低位热值应以调整到同期入厂煤全水后的热值计[入炉煤调整后的每月加权平均低位热值=人炉煤每月加权平均低位热值x(100 一入厂煤每月加权平均全水)/(100-入炉煤每月加权平均全水)]。
1.4 煤长时间存放发生氧化
为防比煤长时问存放发生氧化影响热值，应加强煤场管理，防止煤场自燃，及时烧旧存新。据统计，无烟煤筒仓存放半年热量损失1%；烟煤筒仓存放半年热量损失1%~3%；褐煤筒仓存放半年热量损失6%。
1%灰分影响热值0.229~0.429 MJ/kg；1%全水分影响热值0.138~0.335 MJ/kg。
1.5 入厂煤与入炉煤采制化过程偏差超过允许值
为了分析产生较大热值差的原因，需弄清煤质检测偏差的主要来源。要从一批煤中(几千吨或上万吨)采取少量煤样(几百千克)，经过制样程序制成数量较少(仅约100g )、粒度小于0.2 mm 的试样供化验使用，