Ammonium bisulfate formation and reduced load SCR operation
Ammonium bisulfate formation and reduced load SCR operation
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DOI：
10.1016/j.fuel.2017.05.081
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发表时间：
2017-10-15
期刊：
影响因子：
7.4
通讯作者：
Dunn-Rankin, Derek
中科院分区：
文献类型：
--
作者：
Muzio, Lawrence;Bogseth, Sean;Dunn-Rankin, Derek
燃煤电站锅炉使用的主要NOx控制方法是使用氨和尿素为基础的工艺。这些过程导致一些氨离开处理区，这些氨可以与燃煤烟气中的SO3/H_2SO_4反应生成硫酸氢铵(ABS)。这种ABS的形成可能会导致工厂运行问题的潜在平衡：在稀释空气不足以用于氨传输的情况下，在SCR NOx控制喷氨组件上沉积；在低负荷运行时，在催化剂表面沉积，降低催化剂活性；在空气预热器的冷端篮内沉积；减少这些影响需要准确地了解ABS形成温度作为烟气成分的函数。过去的五项关于ABS形成温度的研究显示出非常大的变化。本文对这些研究和新的实验数据进行了评述，以表明ABS的形成可以用最新的实验室工作来描述，ABS的形成温度可以用方程：P-NH3(ATM)*P-SO3(ATM)=2.97*10(13)*e((-54；(1)其中R是通用气体常数(1.987卡·K摩尔)，T是以开尔文(K)度为单位的烟气温度。随着可再生燃料来源的增加和天然气发电的增加，燃煤锅炉被要求在更宽的负荷范围内运行。使用上面的表达式，这项工作表明，ABS形成温度的普遍接受值名义上太高5%(14K或25华氏度)。虽然这一差异看起来很小，但从实践的角度来看，它可以节省大量的运营成本，因为大型燃煤电厂可以在低于催化剂供应商规定的SCR最低运行温度要求的最低负荷下运行，该最低运行温度基于先前工作中的ABS形成温度。(C)2017爱思唯尔有限公司。保留所有权利。
Primary NOx control methods used on coal fired utility boilers utilize ammonia- and urea-based processes. These processes result in some ammonia exiting the treatment zone, which can react with SO3/H2SO4 in the coal fired flue gas to form ammonium bisulfate (ABS). This ABS formation can lead to potential balance of plant operational issues:deposition on the SCR NOx control ammonia injection components in cases of insufficiently heated dilution air for ammonia transportdeposition on catalyst surfaces during low load operation, reducing catalyst activitydeposition in the cold end baskets of the air preheaterMitigating these impacts requires an accurate understanding of the ABS formation temperature as a function of flue gas composition. Five past studies of ABS formation temperature exhibit a very large variation. This paper provides a critical review of these studies, along with new experimental data, in order to show that ABS formation is best described by recent laboratory work, with the ABS formation temperature effectively described by the equation:P-NH3(atm) * P-SO3(atm) = 2.97 * 10(13) * e((-54; 950/RT)) (1)where R is the universal gas constant (1.987 cal K mol) and T is the flue gas temperature in degrees Kelvin (K)With the increase in renewable fuel sources and the increasing use of natural gas for electricity generation, coal fired boilers are called upon to operate over a broader load range. Using the above expression, this work shows that the generally accepted value for ABS formation temperature is nominally 5% (14 K or 25 degrees F) too high. While this difference may seem small, from a practical perspective it can represent substantial operating cost savings, as a large coal fired plant can operate at a lower minimum load than is currently required by the catalyst vendor's prescribed SCR minimum operating temperature based on ABS formation temperature from prior work. (C) 2017 Elsevier Ltd. All rights reserved.