Chương này tập trung chủ yếu vào lượng khí thải sulfur dioxide, vì họ là nguồn lớn nhất của lượng khí thải lưu huỳnh và đóng góp chính để mưa axit. Các hình thức khác của khí thải lưu huỳnh, bao gồm H2S, SO3, và sương mù axít sulfuric sẽ được thảo luận. Và, bởi vì một số SO2 của công nghệ kiểm soát trực tiếp áp dụng đối với HCl kiểm soát, sẽ được thảo luận ngắn gọn phát thải HCl cũng Bởi đến nay các nguồn phát thải lưu huỳnh lớn nhất là từ đốt than để tạo. | 18 Control of SOx This chapter focuses primarily on sulfur dioxide emissions because they are the largest source of sulfur emissions and the primary contributor to acid rain. Other forms of sulfur emissions including H2S SO3 and sulfuric acid mist will be discussed. And because some of the SO2 control technologies are directly applicable to HCl control there will be brief discussion of HCl emissions as well. By far the largest source of sulfur emissions is from burning coal to generate electricity. An approximate distribution of sources that generate SO2 is presented in Figure . The declining trend in SO2 emissions which is largely as a result of efforts to control SO2 as a source of acid rain is plotted in Figure . Note in particular the sharp decline that occurred in 1995 which was a direct result of implementing the Phase I acid rain controls to comply with Title IV of the Clean Air Act Amendments. Sulfur occurs naturally in fuels. In coal it is bound as iron pyrite FeS2 mineral sulfates elemental sulfur and in organic compounds and mercaptans. High sulfur coals typically contain 2 to 5 sulfur. Low sulfur coals have less than 1 sulfur. Besides burning coal sources of sulfur emissions include petroleum refining oil and gas production sulfur and sulfuric acid manufacturing ore smelting waste incineration and petroleum coke calcining. Sulfur emissions as a source of air pollution can be avoided by using processes that remove sulfur from coal before it is burned. Washing coal removes some of the mineral sulfur sometimes as much as 30 to 50 of sulfur in coal. But washing can be a relatively costly process and research continues for froth flotation magnetically enhanced washing sonic enhancement chemical oxidation and selective agglomeration. H2S control H2S is a common pollutant in oil and natural-gas processing facilities. Many facilities have sulfur recovery units that convert H2S to elemental sulfur using the Claus process. A simplified flow diagram .
