典型燃烧源细颗粒物及气态污染物排放规律研究

No standard method has been currently released for PM2.5 (i.e., particles with an aerodynamic diameter of ≤2.5 μm) collection from stationary sources in China. Only filterable particulate matter is considered in the existing monitoring standards of particulate matter, without considering condensable particulate matter that is in the vapor phase under stack temperature conditions and condense into liquid or solid after emitted from the stack. That underestimate the emissions of particulate matter emitted from combustion sources. This paper try to set up sampling systems for field monitoring of filterable PM2.5 and condensable PM2.5 simultaneously, and apply these systems in two aspects of studies: (1) Carry out the field measurements of particulate matter emissions from major sources, and obtain the emission characteristics of filterable PM2.5, condensable PM2.5, and chemical components before and after the denitration, dust-removal, and desulfurization facilities, respectively. Study the laws of function between PM2.5 emissions and removal technology of pollutants. (2) Study the migration and variation laws of gaseous pollutants including SO2, NH3, NOX, and HCl in the flue gas. Clarify the interaction between PM2.5 and gaseous pollutants in the process of the removal of gaseous pollutants, revealing the emission characteristics of PM2.5 emitted from combustion sources. The research results of this project are expected to answer some important scientific problems such as whether “wet desulphurization” is the main reason leading to the atmospheric haze or not, which has been widely discussed recently. The results will be of great importance to the improvement of a PM2.5 high-resolution emissions inventory, targeted control of combustion source emissions, and the improvement of atmospheric environment quality quickly and effectively.

目前我国尚无固定源PM2.5采样标准方法，现有的颗粒物监测标准仅针对可过滤颗粒物，未考虑烟道温度状态下为气态、离开烟道后凝结成为液态或固态的可凝结颗粒物，低估了燃烧源颗粒物排放。本研究拟搭建可同时用于可过滤PM2.5和可凝结PM2.5现场监测的采样系统，并应用于以下两个方面的研究：（1）开展重点源颗粒物排放现场实测，获取脱硝、除尘、脱硫设施前后可过滤、可凝结PM2.5及化学组分的排放特征，研究PM2.5排放与污染物脱除工艺间的作用规律；（2）研究SO2、NH3、NOX和HCl等气态污染物在烟气中的迁移变化规律，阐明污染物脱除过程中PM2.5与气态污染物的相互作用，揭示燃烧源PM2.5排放规律。本项目的研究成果有望回答近期陷入广泛讨论的“湿法脱硫”是否是造成大气雾霾的主要原因等重要科学问题，并对高分辨率PM2.5排放清单完善、有针对性地控制燃烧源排放和快速有效改善大气环境质量具有重要意义。

目前我国尚无固定源PM2.5采样标准方法，现有的颗粒物监测标准仅针对可过滤颗粒物，未考虑烟道温度状态下为气态、离开烟道后凝结成为液态或固态的可凝结颗粒物，低估了燃烧源颗粒物排放。本研究搭建可同时用于可过滤PM2.5和可凝结PM2.5现场监测的采样系统，开展重点源颗粒物排放现场实测，获取可过滤、可凝结PM2.5及化学组分的排放特征，研究SO2、NH3、NOX和HCl等气态污染物在烟气中的迁移变化规律，阐明污染物脱除过程中PM2.5与气态污染物的相互作用，揭示燃烧源PM2.5排放规律。冷凝法测得的CPM质量浓度均显著高于稀释间接法和稀释直接法测量结果，且与固定源类型无关。冷凝液吸收SO2、HCl和NH3等可溶性气体并转化为SO42–、Cl–和NH4+是导致冷凝法高估CPM的主要原因。冷凝法造成的CPM和水溶性离子浓度正偏差在高可溶性气体浓度状态下更大，如燃煤电厂烟气脱硫入口的SO2和HCl。稀释间接法模拟了烟气从烟囱排放进入大气环境中快速稀释、降温、均相或非均相成核形成CPM的过程，且不存在冷凝水吸收气体等干扰，测得的结果更接近真实排放，被看作是更合适的固定源CPM测量方法。燃煤电厂烟气湿法脱硫和湿式电除尘器对CPM有去除作用，SO3、HNO3、NH3和HCl等气态前体物通过冷凝或者化学反应形成CPM，SO42–、Cl–、NH4+和NO3–是脱硫入口CPM中水溶性离子中的重要组分。脱硫出口和总排口的气态前体物浓度降低，稀释间接法结果显示SO3非均相冷凝在已有的颗粒物表面，水溶性离子主要以SO42–为主。焦化厂CPM中水溶性离子主要以Cl-和K+为主，主要来自煤和铁矿石在高炉炼铁过程中生成的KCl和HCl；烧结厂CPM中水溶性离子主要为Cl-，来自钢铁烧结原料在高温下产生的HCl气体。垃圾焚烧发电厂的CPM中水溶性离子以Cl–和NH4+为主，主要来自垃圾焚烧过程中产生的HCl和脱硝过程中的氨逃逸。研究结果对于提升我国燃烧源排放监测技术水平、推进相关技术的国产化、有针对性地控制燃烧源排放和快速有效改善大气环境质量具有重要意义。