【摘要】：超低濃度甲烷廣泛存在于礦井抽采的煤層氣和化工廢氣中,它的濃度通常隨著開采條件的變化而波動(dòng),通常其體積濃度不超過(guò)3%,熱值很低,利用難度較大。在我國(guó)煤炭開采過(guò)程中,大量超低濃度甲烷不經(jīng)處理直接排放到外界環(huán)境中,不僅污染環(huán)境而且浪費(fèi)資源,因此,研究利用超低濃度甲烷具有節(jié)能和環(huán)保雙重意義。流態(tài)化燃燒技術(shù)具有燃料適應(yīng)性廣、熱容量大等優(yōu)點(diǎn),適用于低熱值氣體的燃燒利用,當(dāng)超低濃度甲烷流化床內(nèi)催化燃燒時(shí),反映其流態(tài)化催化燃燒特點(diǎn)的反應(yīng)模型需要進(jìn)一步研究和建立。針對(duì)此問(wèn)題,本文根據(jù)超低濃度在鼓泡流化床中催化燃燒特點(diǎn),建立分區(qū)模型并進(jìn)行耦合,并采用實(shí)驗(yàn)研究和理論分析相結(jié)合的方法研究了0.15~3 vol.%超低濃度甲烷在以0.5%Pd/Al2O3作為催化劑顆粒床料的鼓泡流化床反應(yīng)器中催化燃燒特性并對(duì)反應(yīng)模型進(jìn)行了驗(yàn)證,最后通過(guò)模型計(jì)算,對(duì)甲烷在流化床反應(yīng)器的變化進(jìn)行了預(yù)測(cè)。基于超低濃度甲烷在鼓泡流化床催化燃燒特性,在流化床流動(dòng)、反應(yīng)和質(zhì)量平衡的基礎(chǔ)上,根據(jù)氣固兩相流理論,在密相區(qū)與稀相區(qū)分別建立反應(yīng)模型,在密相區(qū)中考慮了氣泡相與乳化相之間的傳質(zhì)以及甲烷在催化顆粒表面的催化反應(yīng);在稀相區(qū),根據(jù)超低濃度甲烷燃燒的特點(diǎn),又進(jìn)一步劃分為飛濺顆粒區(qū)和均相反應(yīng)區(qū),并分別建立反應(yīng)模型。采用實(shí)驗(yàn)研究的方法對(duì)所建立的反應(yīng)模型在不同工況下進(jìn)行了驗(yàn)證,考察了床層溫度、進(jìn)氣濃度、流化風(fēng)速以及靜態(tài)床層高度等因素對(duì)低濃度甲烷流態(tài)化催化燃燒的影響,并與常見流態(tài)化反應(yīng)模型活塞流、混合流及K-L反應(yīng)模型進(jìn)行了對(duì)比分析,研究表明本文建立的反應(yīng)模型與實(shí)驗(yàn)數(shù)據(jù)吻合較好,誤差在5%以內(nèi)。同時(shí)研究發(fā)現(xiàn),床層溫度增加到650℃時(shí),甲烷的轉(zhuǎn)化率可達(dá)100%,減小甲烷進(jìn)氣濃度和流化風(fēng)速以及增加床層溫度均可提高低濃度甲烷的轉(zhuǎn)化率,并使反應(yīng)向著床層下方移動(dòng);甲烷在密相區(qū)床層的反應(yīng)主要發(fā)生在乳化相,氣泡相甲烷濃度的變化主要是通過(guò)氣泡相和乳化相間的傳質(zhì)來(lái)實(shí)現(xiàn)。本文根據(jù)超低濃度甲烷在鼓泡流態(tài)化燃燒反應(yīng)不同區(qū)域的特點(diǎn),建立了催化燃燒的反應(yīng)模型,并對(duì)反應(yīng)模型進(jìn)行了實(shí)驗(yàn)驗(yàn)證,考察了操作條件等對(duì)低濃度甲烷流態(tài)化催化燃燒的影響規(guī)律,研究結(jié)果可為低熱值氣體的高效利用與轉(zhuǎn)化提供理論支撐與依據(jù)。
[Abstract]:Ultra-low concentration methane widely exists in coalbed methane and chemical waste gas extracted from mine, its concentration usually fluctuates with the change of mining conditions, usually its volume concentration is not more than 3, the calorific value is very low, and it is difficult to use. In the process of coal mining in China, a large amount of ultra-low concentration methane is discharged directly into the outside environment without treatment, which not only pollutes the environment but also wastes resources. Therefore, it is of dual significance to study the utilization of ultra-low concentration methane for energy saving and environmental protection. Fluidized combustion technology has the advantages of wide fuel adaptability and large thermal capacity. It is suitable for the combustion and utilization of low calorific gas. The reaction model reflecting the characteristics of fluidized catalytic combustion needs further study and establishment. According to the catalytic combustion characteristics of ultra-low concentration in bubbling fluidized bed, a zonal model is established and coupled. The catalytic combustion characteristics of 0.15m3 vol.% ultra-low concentration methane in a bubbling fluidized bed reactor with 0.5%Pd/Al2O3 as catalyst particle bed material were studied by means of experimental study and theoretical analysis, and the reaction model was verified. Finally, the change of methane in fluidized bed reactor was predicted by model calculation. Based on the catalytic combustion characteristics of ultra-low concentration methane in bubbling fluidized bed and on the basis of fluidized bed flow, reaction and mass balance, the reaction models in dense phase region and dilute phase region were established according to the gas-solid two-phase flow theory. The mass transfer between the bubble phase and the emulsified phase and the catalytic reaction of methane on the surface of the catalytic particle are considered in the dense phase region, and in the dilute phase region, according to the combustion characteristics of the ultra-low concentration methane, it is further divided into the splash particle region and the homogeneous reaction region. Reaction models were established. The effects of bed temperature, inlet air concentration, fluidization velocity and static bed height on the fluidized catalytic combustion of low concentration methane were investigated. The results are compared with the piston flow, mixed flow and K-L reaction model. The results show that the reaction model is in good agreement with the experimental data, and the error is less than 5%. At the same time, it is found that when the bed temperature increases to 650 鈩，

本文編號(hào)：2215281