第三章：详细工艺描述.ppt

In a typical reagent preparation system, limestone that will be used for the day is sent to the ball mill for grinding. Water is added at this point to make a slurry. The ground product is then sent to the classifier for sizing. The smaller fraction is sent to a storage tank to be used in the FGD process. The larger fraction is sent back to the ball mill for additional grinding. This figure shows a two-step dewatering process in which hydroclones are used for the first or primary step and a horizontal belt filter is used for the second step. A dewatering systems such as the one pictured is very common in FGD systems that are producing a byproduct gypsum for resale. Bypass reheat is a common way to reheat the treated flue gas if high overall SO2 removal is not required. The reheat of the treated gas is accomplished by bypassing a portion, typically 10 to 15%, of the hot inlet gas around the scrubber and mixing it with the cooler treated gas downstream of the scrubber. Of course, the bypassed gas is untreated so overall SO2 removal efficiency is limited to the portion of gas that is treated. These figures illustrate two types of gas-gas heat exchangers used for re-heating the treated flue gas. Since gas is not exchanged between the inlet and outlet, this design will not affect the overall removal efficiency of the system. 除雾器布置 氧化风系统 宜采用罗茨风机 也可采用离心风机 设置：1+1或2+1 功能: 提供将吸收的SO2氧化成硫酸盐所必须的氧气 硫酸根及钙将沉淀以产生石膏副产物 氧化空气通常引入反应槽. 这被称作“就地氧化” 石灰石吸收剂制备系统 功能: 接收及贮存大量石灰石 将石灰石研磨到合适颗粒尺寸 由研磨石灰石及液体配制浆液 贮存石灰石浆液 根据需要将石灰石浆液输送到 FGD 系统 石灰石吸收剂制备流程图 固体脱水及处置系统 功能: 从浆液分离固体 产生可再利用或抛弃的固体副产物 水返回 FGD 系统 脱水通常有二个步骤: 一级脱水 – 水力旋流器或浓缩池 二级脱水 – 过滤机或离心机 有些工艺 (如：DCFS, JBR)只有一个脱水步骤 典型脱水流程图 一级脱水 浓缩吸收塔排出浆液，固体含量从18-25%到45–55% 可为水力旋流器或浓缩池 FGD 浓缩池 FGD 水力旋流器族 FGD水力旋流器族 二级脱水 设计产生固体滤饼，水份含量低于约10%（重量） 二种类型过滤机可采用: 水平皮带 鼓 离心机也可采用 FGD 离心机 鼓式过滤机 水平皮带过滤机给料端 水平皮带过滤机排料端 烟气再热 功能: 改善污染物扩散 减少烟囱可见烟羽 避免下游烟道腐蚀 避免烟囱液滴 “下雨” 普通 FGD 再热设计 普通 FGD 再热设计(续) 回转式 GGH 再生式 GGH 烟气换热器 要 求 。高传热性能 。低能耗 。低压力降 。低泄露率