Chi Kai Hsien, Chang Shu Hao, Chang Moo Been
Research Center for Environmental Changes, Academia Sinica, Taipei 115, Taiwan.
Environ Sci Technol. 2007 Apr 1;41(7):2515-22. doi: 10.1021/es061665p.
Significant formation of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) has been observed in a typical Waelz process plant. In 2005, the Waelz plant investigated was equipped with a dust settling chamber (DSC), a venturi cooling tower, a cyclone (CY), and baghouse filter (BF). In early 2006 activated carbon injection (ACI) was adopted to reduce PCDD/F emissions from the plant investigated. Samplings of flue gases and ash were simultaneously conducted at different sampling points in the Waelz plantto evaluate removal efficiency and partitioning of PCDD/Fs between the gas phase and particulates. As the operating temperature of the dust settling chamber (DSC) is increased from 480 to 580 degrees C, the PCDD/F concentration measured at the DSC outlet decreases from 1220 to 394 ng-l-TEQ/Nm3. By applying ACI, the PCDD/F concentrations of stack gas decrease from 139-194 to 3.38 ng-l-TEQ/ Nm(3) (a reduction of 97.6-98.3%) while the PCDD/F concentration of reacted ash increases dramatically from 0.97 to 29.4 ng-l-TEQ/g, as the activated carbon injection rate is controlled at 40 kg/h. Additionally, ambient air PCDD/F concentrations were measured in the vicinity of this facility during different operating stages (shutdown, and operation with and without ACI). The ambient PCDD/F concentration measured downwind and 2.5 km from the Waelz plant decreases from 568 to 206 fg-I-TEQ/m(3) after ACI has been applied to collect the dioxins. Due to the high PCDD/F removal efficiency achieved with ACI + BF, about 24.3 and 3980 ng-l-TEQ/kg EAF-dust treated are discharged via stack gas and reacted ash, respectively, in this facility.
在一个典型的瓦尔斯法工厂中，已观察到多氯二苯并对二噁英和二苯并呋喃（PCDD/Fs）的大量生成。2005年，所调查的瓦尔斯法工厂配备了一个沉降室（DSC）、一个文丘里冷却塔、一个旋风分离器（CY）和布袋除尘器（BF）。2006年初，采用了活性炭喷射（ACI）来减少所调查工厂的PCDD/F排放。在瓦尔斯法工厂的不同采样点同时进行了烟气和灰分的采样，以评估PCDD/Fs的去除效率以及其在气相和颗粒物之间的分配情况。随着沉降室（DSC）的运行温度从480℃升高到580℃，在DSC出口处测得的PCDD/F浓度从1220 ng-TEQ/Nm³降至394 ng-TEQ/Nm³。通过应用ACI，当活性炭喷射速率控制在40 kg/h时，烟囱气体中的PCDD/F浓度从139 - 194 ng-TEQ/Nm³降至3.38 ng-TEQ/Nm³（降低了97.6 - 98.3%），而反应后灰分中的PCDD/F浓度则从0.97 ng-TEQ/g急剧增加到29.4 ng-TEQ/g。此外，在该设施的不同运行阶段（停机以及有和没有ACI的运行阶段）对设施附近的环境空气中的PCDD/F浓度进行了测量。在应用ACI收集二噁英后，在距瓦尔斯法工厂下风方向2.5公里处测得的环境PCDD/F浓度从568 fg-TEQ/m³降至206 fg-TEQ/m³。由于ACI + BF实现了较高的PCDD/F去除效率，在该设施中，分别通过烟囱气体和反应后灰分排放的经处理的电弧炉粉尘中的PCDD/F量约为24.3 ng-TEQ/kg和3980 ng-TEQ/kg。
