燃料化学学报
燃料化學學報
연료화학학보
JOURNAL OF FUEL CHEMISTRY AND TECHNOLOGY
2011年
4期
251-257
,共7页
王保文%晏蓉%郑瑛%赵海波%郑楚光
王保文%晏蓉%鄭瑛%趙海波%鄭楚光
왕보문%안용%정영%조해파%정초광
化学链燃烧%煤基合成气%氧载体%CaSO4%热力学模拟
化學鏈燃燒%煤基閤成氣%氧載體%CaSO4%熱力學模擬
화학련연소%매기합성기%양재체%CaSO4%열역학모의
chemical looping combustion (CLC)%coal-derived syngas%oxygen carriers%CaSO4%thermodynamic simulation
相对于金属氧载体,CaSO4作为氧载体用于化学链燃烧,具有成本低、来源广泛和氧传递容量大等诸多优点,但是气相SO2以及各种固相硫沉积物对CaSO4用于化学链燃烧过程造成很大的障碍.基于热力学模拟,对CaSO4氧载体与以合成气为燃料的化学链燃烧进行了模拟研究,结果表明就CaSO4与合成气的反应而言,在燃料反应器中,100℃～400℃的低温反应条件下,主要发生的是合成气中CO和H2的甲烷化反应以及硫酸盐热化学还原反应,反应产物主要是H2S和CaCO3;在400℃～915℃,主要发生的是CO和H2与CaSO4的还原反应,还原产物是Cas和CO2;当反应温度高于915℃时,诸多副反应开始发生,反应物相除了CaS和CO2外,CaO等副产物开始出现;而在空气反应器中,在CaS的整个氧化过程中,CaS再生形成CaSO4的反应都是主要的,但是当空气过量系数ΦAR＜0.8时,CaSO4与CaS的固相反应以及CaS氧化形成CaO的两个副反应也同时起作用.在燃料反应器中,最优的反应条件是反应温度915℃、常压并严格控制CaSO4的加入量并确保CaSO4氧载体过量系数ΦFR～1;而在空气反应器中,提供充足的空气量对于CaS的氧化非常重要,空气过量系数ΦAR≥1不仅能确保CaS的充分氧化,而且还能避免CaS氧化过程中SO2的排放和CaO的产生.
相對于金屬氧載體,CaSO4作為氧載體用于化學鏈燃燒,具有成本低、來源廣汎和氧傳遞容量大等諸多優點,但是氣相SO2以及各種固相硫沉積物對CaSO4用于化學鏈燃燒過程造成很大的障礙.基于熱力學模擬,對CaSO4氧載體與以閤成氣為燃料的化學鏈燃燒進行瞭模擬研究,結果錶明就CaSO4與閤成氣的反應而言,在燃料反應器中,100℃～400℃的低溫反應條件下,主要髮生的是閤成氣中CO和H2的甲烷化反應以及硫痠鹽熱化學還原反應,反應產物主要是H2S和CaCO3;在400℃～915℃,主要髮生的是CO和H2與CaSO4的還原反應,還原產物是Cas和CO2;噹反應溫度高于915℃時,諸多副反應開始髮生,反應物相除瞭CaS和CO2外,CaO等副產物開始齣現;而在空氣反應器中,在CaS的整箇氧化過程中,CaS再生形成CaSO4的反應都是主要的,但是噹空氣過量繫數ΦAR＜0.8時,CaSO4與CaS的固相反應以及CaS氧化形成CaO的兩箇副反應也同時起作用.在燃料反應器中,最優的反應條件是反應溫度915℃、常壓併嚴格控製CaSO4的加入量併確保CaSO4氧載體過量繫數ΦFR～1;而在空氣反應器中,提供充足的空氣量對于CaS的氧化非常重要,空氣過量繫數ΦAR≥1不僅能確保CaS的充分氧化,而且還能避免CaS氧化過程中SO2的排放和CaO的產生.
상대우금속양재체,CaSO4작위양재체용우화학련연소,구유성본저、래원엄범화양전체용량대등제다우점,단시기상SO2이급각충고상류침적물대CaSO4용우화학련연소과정조성흔대적장애.기우열역학모의,대CaSO4양재체여이합성기위연료적화학련연소진행료모의연구,결과표명취CaSO4여합성기적반응이언,재연료반응기중,100℃～400℃적저온반응조건하,주요발생적시합성기중CO화H2적갑완화반응이급류산염열화학환원반응,반응산물주요시H2S화CaCO3;재400℃～915℃,주요발생적시CO화H2여CaSO4적환원반응,환원산물시Cas화CO2;당반응온도고우915℃시,제다부반응개시발생,반응물상제료CaS화CO2외,CaO등부산물개시출현;이재공기반응기중,재CaS적정개양화과정중,CaS재생형성CaSO4적반응도시주요적,단시당공기과량계수ΦAR＜0.8시,CaSO4여CaS적고상반응이급CaS양화형성CaO적량개부반응야동시기작용.재연료반응기중,최우적반응조건시반응온도915℃、상압병엄격공제CaSO4적가입량병학보CaSO4양재체과량계수ΦFR～1;이재공기반응기중,제공충족적공기량대우CaS적양화비상중요,공기과량계수ΦAR≥1불부능학보CaS적충분양화,이차환능피면CaS양화과정중SO2적배방화CaO적산생.
Compared to metal oxides, CaSO4 adopted as oxygen carrier (OC) in chemical looping combustion (CLC) presents several advantages such as low cost, easy availability and superior oxygen transfer capacity, whilst the SO2 emission and solid sulfur deposit in the process could be a big concern. In this study, thermodynamic simulations were conducted to investigate the sulfur distribution in a CLC system with CaSO4 as OC and syngas derived from coal as the fuel. Several findings were attained:(i) On the main products and reaction pathways in the fuel reactor (FR), at the low temperature of 100 ℃～400℃, the main sulfur species and carbon deposit were H2S and CaCO3 via the methanation of CO with H2 coupled with the shift reaction of CO with H2O(g) and the ensuing thermocbemical sulfate reduction (TSR). Then at 400 ℃～915 ℃, CaS and CO2 were the main products through the reaction of CaSO4 with H2 or CO, and both products increased with increasing FR temperature. Furthermore, at the FR temperature higher than 915 ℃, due to the initiation of the solid side reaction between CaS and CaSO4, the percentage of CaS declined. In contrary, the percentages of CaO, H2 and CO increased possibly due to the consumption of part of CaSO4 in the side reaction and thus not enough lattice oxygen available. In the air reactor(AR), the oxidization of CaS by air into CaSO4 was always dominant.Besides at ΦAR below 0.8, both the solid side reaction of CaSO4 with CaS and the oxidization of CaS into CaO were simultaneously in effect. (ii) In the FR, the optimized condition was suggested as at around 915 ℃, atmospheric condition and carefully controlled ΦFR around unity. (iii) In the AR, sufficient supply of air was important for the oxidization of CaS, and ΦAR≥ 1 would ensure the full oxidization of CaS into CaSO4 and prevent the emission of SO2 and formation of CaO as well. Overall, this study provided the most suitable conditions of using CaSO4 as OC in CLC of syngas with the minimal SO2 emissions and CaO formation.
