本文關(guān)鍵詞： 濕法脫硫 pH值 物性 傳質(zhì)系數(shù)　出處：《青島科技大學》2017年碩士論文　論文類型：學位論文

【摘要】：在眾多脫硫方法中,PDS法因具有堿耗低、硫容大、硫泡沫顆粒大、易分離、不堵塔等特點,已廣泛應(yīng)用于煤氣行業(yè)、氮肥行業(yè)和焦化脫硫等其他相關(guān)行業(yè),并取得了顯著的脫硫效果。影響脫硫效果的因素有很多,其中最重要的是體系的pH值。PDS脫硫工藝以Na_2CO_3-NaHCO_3緩沖液為吸收劑來吸收H_2S和穩(wěn)定體系的pH值,但由于存在副反應(yīng)及吸收CO_2的現(xiàn)象,需要定期向脫硫液中補充Na_2CO_3,以維持體系pH值的穩(wěn)定。在實際生產(chǎn)中,往往依靠經(jīng)驗進行調(diào)節(jié),缺乏理論指導(dǎo)。本論文通過進行一系列的實驗,系統(tǒng)地研究了脫硫液的性質(zhì)及其對氣液傳質(zhì)過程的影響,以期指導(dǎo)生產(chǎn)。PDS法脫硫的吸收液是Na_2CO_3和NaHCO_3組成的緩沖液,它能在一定程度上穩(wěn)定溶液的pH值,為了研究緩沖液的組成對pH值的影響,本文配制了不同濃度的Na_2CO_3-NaHCO_3溶液,考查其pH值的變化規(guī)律,并研究了緩沖液的性質(zhì)。然后固定溶液的pH值(8.5),考查Na_2CO_3和NaHCO_3的配比關(guān)系及對物性(密度、粘度和表面張力)的影響,為研究氣液傳質(zhì)過程奠定了基礎(chǔ)。脫硫過程中存在副反應(yīng),生成NaSCN、Na_2S_2O_3、Na_2SO_3和Na_2SO_4等副鹽,打破了Na_2CO_3和NaHCO_3的平衡關(guān)系,脫硫液中的副鹽對物性和NaHCO_3的溶解度產(chǎn)生一定影響。吸收液的pH值隨著副鹽含量的增加而降低,隨著副鹽含量的增加,吸收液的密度、粘度和表面張力都有增大的趨勢,但增大的程度不一樣,其中粘度變化最大。隨著副鹽含量的增加,NaHCO_3溶解度減小,溫度對溶解度也有一定的影響,基本上呈現(xiàn)溫度降低,溶解度下降的規(guī)律。為防止發(fā)生NaHCO_3析出現(xiàn)象,本文給出了實際運行中的密度操作區(qū)間及密度上限的計算公式,這一區(qū)間隨副鹽含量增加而減小。生產(chǎn)中應(yīng)對脫硫液密度(或副鹽含量)和NaHCO_3含量進行同時監(jiān)測。通過在自制填料塔內(nèi)模擬脫硫過程,并結(jié)合響應(yīng)曲面設(shè)計方法發(fā)現(xiàn):在實驗范圍內(nèi),Na_2CO_3濃度對總傳質(zhì)系數(shù)K_Ga的影響極為顯著,這是因為Na_2CO_3濃度的變化改變了體系的pH值,從而改變了化學吸收的速率。體系中的副鹽也會影響溶液的pH值,通過研究Na_2CO_3和副鹽含量對K_Ga的影響發(fā)現(xiàn)總體積傳質(zhì)系數(shù)K_Ga的變化存在一個敏感區(qū)。將三組實驗數(shù)據(jù)進行對比發(fā)現(xiàn)Na_2CO_3和副鹽對K_Ga的影響主要是通過影響體系的pH值來實現(xiàn)的。采用雙膜理論對濕法脫硫的吸收過程進行了描述,研究了氣液傳質(zhì)過程中物質(zhì)傳遞的機理,并提出了該過程的數(shù)學模型。本文采用Onda(恩田)等人的關(guān)聯(lián)式,分別計算了氣相傳質(zhì)系數(shù)kG和液相傳質(zhì)系數(shù)kL,結(jié)果表明,Na_2CO_3和副鹽通過改變體系的物性改變了kL而對kG并不產(chǎn)生影響,而且從kL的的數(shù)值上看,k L的變化量并不大。同時還計算了相應(yīng)的二級反應(yīng)速率常數(shù)k2,結(jié)果顯示,隨著體系pH值的增大,k2的變化規(guī)律與K_Ga的大致相同,說明Na_2CO_3和副鹽是通過改變體系的k2來改變總體積傳質(zhì)系數(shù)K_Ga的。
[Abstract]:Among the desulfurization method, PDS method has low alkali consumption, high sulfur content, sulfur foam particles, easy separation, no blocking tower and other characteristics, has been widely used in gas industry, fertilizer industry and Coking Desulfurization and other related industries, and has achieved remarkable desulfurization effect. There are many factors affecting the desulfurization effect among them, the most important is the pH value of the system of.PDS desulfurization process with Na_2CO_3-NaHCO_3 buffer as absorbent to absorb H_2S and stabilize the pH value of the system, but due to the presence of side reactions and CO_2 absorption phenomenon, need to be regularly to the desulfurization liquid Na_2CO_3, in order to maintain the pH value of the system stability. In the actual production, often rely on the experience of regulation, lack of theoretical guidance. This thesis through a series of experiments, systematically studied the properties of desulfurization liquid and its influence on the mass transfer process, in order to guide the production of.PDS desulfurization absorption liquid is Na_2CO_3 and NaHC O_3 buffer composition, it can stabilize the solution to a certain extent, the value of pH, in order to study the composition of the buffer effect on pH values, this paper prepared different concentrations of Na_2CO_3-NaHCO_3 solution, the variation of pH value, and study the properties of the buffer. Then fixed solution pH value (8.5 the effects of Na_2CO_3 and NaHCO_3), and ratio on physical properties (density, viscosity and surface tension) influence, laid the foundation for the research on the gas-liquid mass transfer process. The existence of side reaction, the desulfurization process to generate NaSCN, Na_2S_2O_3, Na_2SO_3 and Na_2SO_4 - salt, broke the balance between Na_2CO_3 and NaHCO_3, have a certain impact the solubility of by-product salt in desulfurizing liquid on physical properties and NaHCO_3. The pH value of absorption liquid decreased with increasing salt content on the side, with the increase of the content of secondary salt absorption liquid, density, viscosity and surface tension have a tendency to increase, but the increase of the 紼嬪害涓嶄竴鏍，

本文編號：1539112