本文關(guān)鍵詞： 濕法脫硫 汞 石膏 pH 值 金屬離子　出處：《華中科技大學》2015年碩士論文　論文類型：學位論文

【摘要】：燃煤過程汞排放是主要的大氣汞排放來源,對人類健康和環(huán)境存在潛在的風險。難捕捉的元素態(tài)汞(Hg0)的脫除成為燃煤電站汞減排的瓶頸問題,濕法脫硫系統(tǒng)雖然可以高效脫除燃煤煙氣中SO2和氧化態(tài)汞(Hg2+),但又存在Hg2+被還原成Hg0的再釋放現(xiàn)象,增加燃煤電站汞減排的難度。為提高燃煤電站和濕法脫硫系統(tǒng)的脫汞效率,本文實驗研究了濕法脫硫及其副產(chǎn)品加工過程汞再釋放及遷移規(guī)律。首先采用單因素分析方法研究了pH對Hg0再釋放的作用機理。脫硫清液p H值在3.0-8.0時,pH越高Hg0再釋放越難發(fā)生。pH值低于4.0時,亞硫酸氫根與氧化態(tài)汞生成的亞硫酸汞和亞硫酸氫汞易分解,造成Hg0大量釋放。pH值上升使亞硫酸根增加,其會與亞硫酸汞生成更穩(wěn)定的Hg(SO3)22-,減少Hg0再釋放。采用數(shù)學擬合方法得到的亞硫酸鹽濃度、pH、時間與Hg0釋放率的定量關(guān)系式能初步預測Hg0再釋放。為了深入研究金屬離子對Hg0再釋放的作用,結(jié)合熱力學理論探討了金屬離子及其與亞硫酸鹽協(xié)同對Hg0再釋放的作用。堿性環(huán)境時Fe2+、Mn2+和Co2+能使Hg0再釋放,酸性環(huán)境時Fe2+能使Hg0再釋放。堿性環(huán)境和酸性環(huán)境時Mn2+、Co2+、Ni2+與亞硫酸鹽的協(xié)同作用顯著促進了Hg0再釋放。本文通過實驗探究了濕法脫硫系統(tǒng)三相汞遷移特性和煅燒過程中石膏汞釋放規(guī)律。二氧化碳、氧氣和硝酸根增加氣相汞比例,減少固相和液相汞比例。亞硫酸鈣和氯離子抑制汞向氣相遷移,氯離子大幅增加液相汞比例。添加劑TMT、DTCR和Na HS明顯減少氣相和液相的汞比例,增加固相汞比例,其富集汞到石膏的能力依次減弱,使煅燒后的石膏剩余汞含量升高。Na HS、TMT和DTCR添加后石膏汞熱穩(wěn)定性依次減小,分別使石膏中形成HgS、Hg3(TMT)2和Hg(DTCR)2。程序升溫實驗中,Hg3(TMT)2和Hg(DTCR)2的分解溫度為170℃-290℃和110℃-270℃,峰值溫度為235℃和198℃。
[Abstract]:Mercury emission from coal combustion process is the main source of mercury emission in the atmosphere, which has potential risks to human health and environment. The removal of elemental mercury (Hg0) from coal-fired power plants has become the bottleneck of mercury emission reduction in coal-fired power plants. Although the wet desulfurization system can efficiently remove SO2 and Hg2 (oxidized mercury) from coal-fired flue gas, there is a rerelease phenomenon in which Hg2 is reduced to Hg0. In order to improve the efficiency of mercury removal in coal-fired power plants and wet desulfurization systems, it is difficult to reduce mercury emissions in coal-fired power stations. In this paper, the rerelease and migration of mercury in wet desulfurization and by-product process were studied experimentally. Firstly, the mechanism of pH on Hg0 rerelease was studied by single factor analysis. H values ranged from 3.0 to 8.0. The higher the pH is, the more difficult the rerelease of Hg0 is. When the pH value is lower than 4. 0, the mercurous sulfite and mercurous hydrogen sulfate produced by H2SO4 and mercuric oxide are easily decomposed. The increase of pH value of Hg0 resulted in the increase of sulfite radical, which together with mercurous sulfate produced a more stable HgCSO3 (22-). To reduce the rerelease of Hg0, the concentration of sulfite and pH were obtained by mathematical fitting method. The quantitative relationship between time and Hg0 release rate can predict the rerelease of Hg0. In order to study the effect of metal ions on the rerelease of Hg0. Combined with thermodynamic theory, the effect of metal ions and their coordination with sulfite on the rerelease of Hg0 was discussed. In alkaline environment, Hg0 can be rereleased by Fe2 limn 2 and Co2. Fe2 can rerelease Hg0 in acidic environment and Mn2 CO2 in alkaline environment and acidic environment. The synergistic effect of Ni2 and sulfite significantly promoted the rerelease of Hg0. In this paper, the characteristics of three-phase mercury migration in wet desulphurization system and the rules of mercury release from gypsum during calcination were investigated. Oxygen and nitrate increase the proportion of mercury in gas phase and decrease the ratio of mercury in solid phase and liquid phase. Calcium sulfite and chloride ions inhibit the migration of mercury to gas phase, and chlorine ion significantly increases the proportion of mercury in liquid phase. Additive TMT. DTCR and NaHS obviously reduced the proportion of mercury in gas phase and liquid phase, increased the proportion of mercury in solid phase, its ability to enrich mercury to gypsum decreased in turn, and the residual mercury content of calcined gypsum increased .NaHS. After the addition of TMT and DTCR, the thermal stability of gypsum mercury decreased in turn, which resulted in the formation of HgSN Hg3 TMT2 and HgGN DTCR2 in gypsum, respectively. The decomposition temperatures of Hg3(TMT)2 and Hg(DTCR)2 are 170 鈩，

本文編號：1477785