【摘要】：甲烷氧化偶聯(lián)制乙烯工藝是最有希望工業(yè)化的甲烷直接轉(zhuǎn)化方法,但甲烷氧化偶聯(lián)反應(yīng)是強(qiáng)放熱反應(yīng),催化劑床層容易形成熱點(diǎn),工業(yè)裝置的溫度難以控制。僅采用實(shí)驗(yàn)的方法實(shí)現(xiàn)反應(yīng)器放大,會(huì)導(dǎo)致反應(yīng)器開(kāi)發(fā)成本高、周期長(zhǎng)。計(jì)算流體力學(xué)是在流場(chǎng)計(jì)算的基礎(chǔ)上,同時(shí)考慮流動(dòng)、傳熱、化學(xué)反應(yīng)等多物理化學(xué)現(xiàn)象間的耦合作用,可以準(zhǔn)確預(yù)測(cè)反應(yīng)器的特性,為反應(yīng)器的放大提供工藝數(shù)據(jù),降低開(kāi)發(fā)成本、縮短開(kāi)發(fā)周期。本文采用計(jì)算流體力學(xué)方法,利用修改參數(shù)后的Stansch反應(yīng)動(dòng)力學(xué)模型,首先建立了裝填Na2WO4-Mn/SiO_2顆粒催化劑的OCM固定床反應(yīng)器實(shí)驗(yàn)室裝置的計(jì)算模型,模擬了原料氣體流量為80ml/min常壓操作下顆粒固定床反應(yīng)器的反應(yīng)特性。通過(guò)對(duì)比顆粒催化劑固定床反應(yīng)器出口處CH_4轉(zhuǎn)化率、CO_2等產(chǎn)物選擇性的計(jì)算值與實(shí)驗(yàn)值,可以發(fā)現(xiàn),所有參數(shù)的計(jì)算值與實(shí)驗(yàn)值誤差范圍為±2%,二者吻合較好,模型可靠；通過(guò)分析反應(yīng)器的催化劑床層內(nèi)組分濃度、反應(yīng)溫度、側(cè)壁面熱通量、壓力、流體密度和流速等參數(shù)分布表明：在催化劑床層的進(jìn)口附近,OCM反應(yīng)較快,該區(qū)域的溫度稍高于其它區(qū)域,包圍該區(qū)域的反應(yīng)器壁面放熱較多,熱通量最大值為17500W/m~2；顆粒催化劑床層內(nèi)的OCM反應(yīng)為變?nèi)莘e反應(yīng),并且生成物總摩爾數(shù)大于反應(yīng)物總摩爾數(shù),導(dǎo)致流體速度沿流動(dòng)方向逐漸增加,密度逐漸減小。然后,模擬了裝填Na_3PO_4-Mn/SiO_2/堇菁石整體式催化劑固定床反應(yīng)器,采用與顆粒催化劑固定床反應(yīng)器計(jì)算結(jié)果類(lèi)似的處理辦法,分析計(jì)算結(jié)果。研究表明,反應(yīng)器出口處主要參數(shù)計(jì)算值與實(shí)驗(yàn)值的誤差范圍為±4%,模型可靠；由于邊界層、化學(xué)反應(yīng)和整體式催化劑結(jié)構(gòu)的影響,導(dǎo)致催化劑床層內(nèi)的流速沿內(nèi)壁面法向方向先升高再降低。裝填顆粒催化劑和整體式催化劑的兩段式固定床反應(yīng)器可以將這兩種催化劑的優(yōu)點(diǎn)互補(bǔ)。在上述計(jì)算的基礎(chǔ)上,模擬研究了兩段式固定床反應(yīng)器的反應(yīng)特性,并考察了反應(yīng)溫度和床層高度對(duì)反應(yīng)器特性的影響。計(jì)算結(jié)果表明：顆粒催化劑床層內(nèi)OCM反應(yīng)比整體式催化劑床層內(nèi)的劇烈；與顆粒催化劑床層相比,整體式催化劑床層在耗氧量較小的情況下,可以有效地提高C：產(chǎn)物選擇性和收率；反應(yīng)溫度通過(guò)影響反應(yīng)網(wǎng)絡(luò)內(nèi)各步反應(yīng)的速率,進(jìn)而影響各組分質(zhì)量分?jǐn)?shù)的分布,導(dǎo)致反應(yīng)溫度為800℃時(shí),C_2產(chǎn)物選擇性達(dá)到最優(yōu)值66.7%；當(dāng)整體式催化劑床層高度為50mm、位于上游的顆粒催化劑床層高度變化時(shí),由于顆粒催化劑床層出口處各組分的質(zhì)量分?jǐn)?shù)存在差異,改變了下游的整體式催化劑床層的進(jìn)口條件,最終導(dǎo)致C_2收率在顆粒催化劑床層高度為1 Omm達(dá)到最優(yōu)值21.8%。由于兩段式固定床反應(yīng)器內(nèi)整體式催化劑床層內(nèi)氧氣分壓較低,降低了整體式催化劑的活性,導(dǎo)致整體式催化劑無(wú)法發(fā)揮其高C：選擇性的優(yōu)勢(shì)。在兩段式固定床反應(yīng)器的兩段床層之間補(bǔ)充氧氣,可以有效提高C_2產(chǎn)物收率。本文在兩段式固定床反應(yīng)器模擬計(jì)算的基礎(chǔ)上,對(duì)中間補(bǔ)氧的兩段式固定床反應(yīng)器進(jìn)行模擬研究,并考察了補(bǔ)氧量和反應(yīng)溫度對(duì)反應(yīng)器特性的影響。計(jì)算結(jié)果表明：對(duì)于不同補(bǔ)氧量下的P_(10)M_(50)固定床反應(yīng)器,補(bǔ)充的氧氣促進(jìn)了整體式催化劑床層內(nèi)的OCM反應(yīng),導(dǎo)致反應(yīng)器出口處的C_2選擇性和收率隨補(bǔ)氧量的增加而逐漸升高；對(duì)于不同溫度下補(bǔ)氧量為15%的P_(10)M_(50)固定床反應(yīng)器,其整體式催化劑床層上的參數(shù)分布規(guī)律與無(wú)補(bǔ)氧的P_(10)M_(50)固定床反應(yīng)器內(nèi)整體式催化劑床層上的參數(shù)分布規(guī)律類(lèi)似。在上述模擬研究的基礎(chǔ)上,將兩段式固定床反應(yīng)器進(jìn)行放大,設(shè)計(jì)了乙烯產(chǎn)量為300ton/a的兩段式固定床反應(yīng)器的中試裝置,并采用與實(shí)驗(yàn)室小反應(yīng)器模擬中相同的數(shù)學(xué)模型對(duì)其進(jìn)行模擬,同時(shí)考察了冷卻劑流量和冷卻劑進(jìn)口溫度對(duì)反應(yīng)器特性的影響。通過(guò)分析列管式固定床中試反應(yīng)器內(nèi)冷卻劑流速、溫度和反應(yīng)氣體的組分質(zhì)量分?jǐn)?shù)以及壁面熱通量、對(duì)流換熱系數(shù)等反應(yīng)器的特性參數(shù)的分布,得到如下結(jié)論：顆粒催化劑床層溫度是決定C_2H_6產(chǎn)量的主要因素,而整體式催化劑床層溫度是決定C_2H_4產(chǎn)量的主要因素；當(dāng)冷卻劑流量為453ton/h,冷卻劑進(jìn)口溫度為790℃,原料氣體流量為594Nm~3/h,原料氣體進(jìn)口溫度為775℃,烷氧比為3時(shí),所設(shè)計(jì)的反應(yīng)器滿足設(shè)計(jì)要求。
[Abstract]:Based on the calculation of flow , heat transfer , chemical reaction and so on , it is possible to predict the characteristics of the reactor accurately and to reduce the development cost and shorten the development cycle .
By analyzing the concentration of components , the reaction temperature , the heat flux , pressure , fluid density and flow velocity in the catalyst bed of the reactor , it is shown that the OCM reaction is faster in the vicinity of the inlet of the catalyst bed , the temperature of the region is slightly higher than that of other regions , and the heat flux is more than 17500W / m ~ 2 .
The reaction of OCM in the bed of catalyst bed is variable volume reaction , and the total number of moles of product is greater than the total number of moles of reactants , resulting in a gradual increase in the velocity of the fluid along the flow direction and a gradual decrease in density . The results are analyzed by a similar approach to the calculation results of the fixed bed reactor of particulate catalyst . The results show that the error range of the main parameters at the outlet of the reactor and the experimental value is 鹵 4 % and the model is reliable ;
Due to the influence of boundary layer , chemical reaction and monolithic catalyst structure , the flow velocity in the catalyst bed is increased and then decreased in the direction of the inner wall surface method . The two - stage fixed bed reactor filled with granular catalyst and monolithic catalyst can complement the advantages of the two catalysts . On the basis of the above calculation , the reaction characteristics of the two - stage fixed bed reactor are simulated and the influence of reaction temperature and bed height on the characteristics of the reactor is studied .
Compared with the granular catalyst bed layer , the monolithic catalyst bed layer can effectively improve the selectivity and the yield of the product under the condition that the oxygen consumption is small ;
By influencing the rate of reaction in the reaction network , the reaction temperature affects the distribution of the mass fraction of each component , which results in the selectivity of the C _ 2 product reaching the optimum value 66.7 % when the reaction temperature is 800 鈩，

本文編號(hào)：2126207