熱水室中熱質(zhì)同時傳遞過程強化研究
發(fā)布時間：2019-05-17 02:37
【摘要】：氣流床煤氣化技術(shù)是煤炭清潔高效利用的核心技術(shù),是發(fā)展現(xiàn)代煤化工、IGCC發(fā)電等過程工業(yè)的基礎。黑水能量回收單元是氣流床煤氣化系統(tǒng)的核心過程之一,該單元運行好壞不僅影響到煤氣化系統(tǒng)的整體效率,也嚴重影響和制約氣化系統(tǒng)的安全、長周期、穩(wěn)定、優(yōu)質(zhì)運行。本文以黑水處理關(guān)鍵設備-蒸發(fā)熱水塔為研究對象,采用實驗和理論計算相結(jié)合的手段,對蒸發(fā)熱水塔中的熱水室內(nèi)兩相直接接觸的冷凝過程、不同接觸方式的傳熱強化和各種塔內(nèi)件上兩相的流體力學行為進行了研究。論文主要內(nèi)容如下:(1)在其他結(jié)構(gòu)參數(shù)相同的情況下,孔中心距減小,固閥塔板的傳熱效率略有增大,但增大幅度不明顯;當孔徑增大50%時,固閥塔板的傳熱效率增大25%;當開孔率減小60%時,固閥塔板的傳熱效率增大20%;固閥高度增大,固閥塔板的傳熱效率先快速減小,后維持穩(wěn)定不變;篩孔塔板的傳熱效率隨著孔徑增大50%而減小約10%,其余結(jié)構(gòu)參數(shù)如孔中心距和開孔率等對篩孔塔板的傳熱效率的影響作用不顯著。由于塔板上兩相接觸流型的不同,固閥塔板的傳熱效率均優(yōu)于篩孔塔板。穿流式固閥和篩孔塔板上進行的兩相直接接觸冷凝過程,傳熱單元數(shù)與兩相的流動參數(shù)間存在指數(shù)關(guān)系NTUl=a·FPb,其中,固閥塔板的擬合系數(shù)a=0.32-0.84,b=0.85-0.91,篩孔塔板的系數(shù)a=0.29-0.4,b=0.86-0.9,此模型可對工業(yè)裝置的塔板設計和選型提供理論指導。(2)以散堆拉西環(huán)填料為兩相接觸元件,考察了兩相在填料塔中的傳熱和傳質(zhì)過程。研究了兩相流體流量及填料堆積高度等參數(shù)對傳熱效率的影響。得到描述兩相間的傳熱單元數(shù)與流動參數(shù)的關(guān)系式如下,(?)該經(jīng)驗關(guān)系式與實驗數(shù)據(jù)的平均偏差為2%,可較準確地快速估算填料塔內(nèi)熱質(zhì)同時傳遞過程的傳熱單元數(shù)。(3)對不同塔板結(jié)構(gòu)的固閥塔內(nèi)流體流動行為開展了系統(tǒng)實驗研究,研究結(jié)果表明,在溢流式塔板上,隨著軸向高度的增大,固閥對于塔板上局部氣含率的影響逐漸減小,沿著徑向方向的氣含率分布趨于均勻,且液相流量對于局部氣含率的影響越來越顯著。而在穿流式塔板上,塔板中心區(qū)域的局部氣含率大于溢流式塔板,而靠近塔壁的邊緣區(qū)域,局部氣含率則小于溢流式塔板。兩種不同結(jié)構(gòu)的固閥塔板上的局部氣含率均呈現(xiàn)出塔板中心區(qū)域大,而塔板邊緣區(qū)域小的趨勢。在塔板的不同軸向高度上,穿流式塔板上沿不同徑向長度上氣泡速度均大于溢流式塔板。對于這兩種不同結(jié)構(gòu)的塔板,其氣泡速度的分布有相似的趨勢,即中心區(qū)域的氣泡速度大于塔壁附近區(qū)域;在塔板的中心區(qū)域,穿流塔板上的氣液比表面積大于溢流塔板,隨著徑向長度的增加,穿流塔板上的氣液比表面積逐漸減小,而溢流塔板上氣液比表面積隨徑向長度的變化則無明顯規(guī)律,呈現(xiàn)出波動性。(4)實驗研究了塔板型式和結(jié)構(gòu)參數(shù)對塔板壓降的影響特征,得出穿流式塔板的塔板壓降小于溢流式塔板。隨著孔中心距和開孔率的減小,穿流式塔板的壓降和清液層高度均增大,孔徑的增大,則使壓降和清液層高度增大;對清液層高度與塔板結(jié)構(gòu)參數(shù)和操作變量進行關(guān)聯(lián),擬合值與實驗測量值吻合良好。從最小能量原理出發(fā),推導了穿流(?)式塔板上氣體流過開孔面積分率的計算式(?)。由計算式可得,氣體流通分率正比于氣體流過閥孔的壓降與漏液區(qū)、鼓泡區(qū)靜態(tài)液層高度差的比值的立方根。計算結(jié)果表明,塔板上開孔區(qū)的氣體流通分率隨著孔中心距的減小而減小,并隨著孔徑和開孔率的增大而減小。且在各個塔板結(jié)構(gòu)變量中,孔徑對該氣體流通分率參數(shù)的影響最不顯著。
[Abstract]:The gas-flow bed coal gasification technology is the core technology of coal cleaning and high-efficiency utilization, and is the foundation of the development of modern coal chemical industry, IGCC power generation and other process industries. The black water energy recovery unit is one of the core processes of the air-flow bed coal gasification system. The operation of the unit not only affects the overall efficiency of the coal gasification system, but also seriously affects and restricts the safety, long-period, stable and high-quality operation of the gasification system. This paper deals with the condensation process of the two-phase direct contact of the hot water chamber in the steam-heating water tower by means of the combination of experiment and theoretical calculation, taking the key equipment of the black water treatment-the steam-heating water tower as the research object, using the combination of experiment and theoretical calculation. The heat transfer enhancement of different contact modes and the fluid mechanics behavior of two phases on the internal parts of the tower were studied. The main contents of the thesis are as follows: (1) In the case of the same structure parameters, the center distance of the hole is reduced, the heat transfer efficiency of the fixed valve tray is slightly increased, but the increase is not obvious; when the aperture is increased by 50%, the heat transfer efficiency of the fixed valve tray is increased by 25%; when the opening ratio is reduced by 60%, The heat transfer efficiency of the fixed valve tray is increased by 20%, the height of the solid valve is increased, the heat transfer efficiency of the fixed valve tray is rapidly reduced, the stability is maintained, and the heat transfer efficiency of the sieve tray tray is reduced by about 10% as the aperture is increased by 50%, The influence of the other structural parameters, such as the center distance of the hole and the opening ratio, on the heat transfer efficiency of the sieve tray tray is not significant. Since the two-phase contact flow pattern on the tray is different, the heat transfer efficiency of the fixed valve tray is better than that of the sieve tray. The two-phase direct contact condensation process is carried out on the flow-through fixed valve and the sieve plate tray, and the number of the heat transfer units and the flow parameters of the two-phase flow are the index relation NTUl = a. FPb, wherein the fitting coefficient a of the fixed valve plate is a = 0.32-0.84, b = 0.85-0.91, and the coefficient a of the sieve plate tray is 0.29-0.4, b = 0.86-0.9, The model can provide theoretical guidance for the design and selection of the tray of the industrial plant. (2) The heat transfer and mass transfer process of the two-phase in the packed column were investigated in the form of two-phase contact elements. The effect of two-phase fluid flow and packing height on heat transfer efficiency was studied. The relationship between the number of heat transfer units and the flow parameters that describe the two phases is as follows (? ) The average deviation of the empirical relation and the experimental data is 2%, and the number of heat transfer units in the heat transfer process of the internal heat of the packed column can be estimated more accurately. (3) The system experiment was carried out on the fluid flow behavior in the fixed valve column of the different tower plate structure. The results show that, with the increase of the axial height, the effect of the solid valve on the partial gas content on the tray decreases gradually with the increase of the axial height. The gas-containing rate distribution in the radial direction tends to be uniform, and the effect of the liquid-phase flow on the partial gas content is becoming more and more significant. And the partial gas holdup in the central region of the tray is higher than that of the overflow tray on the flow-through tray, and the partial gas content is less than that of the overflow tray. The partial gas holdup in the fixed-valve trays of the two different structures exhibited a large central area of the tray and a small trend in the edge area of the tray. At different axial heights of the trays, the velocity of the air bubbles on the flow-through trays along different radial lengths is larger than that of the overflow tray. for the trays of the two different structures, the distribution of the bubble velocity is similar, that is, the bubble velocity in the central region is larger than that in the vicinity of the tower wall; in the central region of the tray, the gas-liquid ratio surface area on the flow-through tray is larger than that of the overflow tray, and as the radial length increases, The gas-liquid ratio surface area of the flow-through tray is gradually reduced, while the gas-liquid ratio surface area on the overflow tray decreases with the change of the radial length. (4) The influence of the tray type and the structural parameters on the pressure drop of the tray was studied, and the pressure drop of the tray in the flow-through tray was less than that of the overflow tray. As the distance of the center of the hole and the aperture ratio are reduced, the pressure drop of the through-flow tray and the height of the clear liquid layer are both increased, and the pore diameter is increased, so that the pressure drop and the height of the clear liquid layer are increased; and the height of the clear liquid layer is associated with the parameters of the tower plate structure and the operating variable, and the fitting value is in good agreement with the experimental measurement value. From the principle of minimum energy, a flow-through (? ) The calculation formula (?) of the gas flow through the opening area fraction on the tray? And the gas flow rate is proportional to the cubic root of the ratio of the pressure drop and the leakage liquid area of the gas flowing through the valve hole and the height difference of the static liquid layer of the bubbling area. The results show that the gas flow rate of the open hole in the tray decreases with the decrease of the center distance of the hole, and decreases with the increase of the aperture and the aperture ratio. And in each column plate structure variable, the influence of the pore size on the gas flow rate parameter is least significant.
【學位授予單位】：華東理工大學
【學位級別】：博士
【學位授予年份】：2017
【分類號】：TQ545
本文編號：2478738
[Abstract]:The gas-flow bed coal gasification technology is the core technology of coal cleaning and high-efficiency utilization, and is the foundation of the development of modern coal chemical industry, IGCC power generation and other process industries. The black water energy recovery unit is one of the core processes of the air-flow bed coal gasification system. The operation of the unit not only affects the overall efficiency of the coal gasification system, but also seriously affects and restricts the safety, long-period, stable and high-quality operation of the gasification system. This paper deals with the condensation process of the two-phase direct contact of the hot water chamber in the steam-heating water tower by means of the combination of experiment and theoretical calculation, taking the key equipment of the black water treatment-the steam-heating water tower as the research object, using the combination of experiment and theoretical calculation. The heat transfer enhancement of different contact modes and the fluid mechanics behavior of two phases on the internal parts of the tower were studied. The main contents of the thesis are as follows: (1) In the case of the same structure parameters, the center distance of the hole is reduced, the heat transfer efficiency of the fixed valve tray is slightly increased, but the increase is not obvious; when the aperture is increased by 50%, the heat transfer efficiency of the fixed valve tray is increased by 25%; when the opening ratio is reduced by 60%, The heat transfer efficiency of the fixed valve tray is increased by 20%, the height of the solid valve is increased, the heat transfer efficiency of the fixed valve tray is rapidly reduced, the stability is maintained, and the heat transfer efficiency of the sieve tray tray is reduced by about 10% as the aperture is increased by 50%, The influence of the other structural parameters, such as the center distance of the hole and the opening ratio, on the heat transfer efficiency of the sieve tray tray is not significant. Since the two-phase contact flow pattern on the tray is different, the heat transfer efficiency of the fixed valve tray is better than that of the sieve tray. The two-phase direct contact condensation process is carried out on the flow-through fixed valve and the sieve plate tray, and the number of the heat transfer units and the flow parameters of the two-phase flow are the index relation NTUl = a. FPb, wherein the fitting coefficient a of the fixed valve plate is a = 0.32-0.84, b = 0.85-0.91, and the coefficient a of the sieve plate tray is 0.29-0.4, b = 0.86-0.9, The model can provide theoretical guidance for the design and selection of the tray of the industrial plant. (2) The heat transfer and mass transfer process of the two-phase in the packed column were investigated in the form of two-phase contact elements. The effect of two-phase fluid flow and packing height on heat transfer efficiency was studied. The relationship between the number of heat transfer units and the flow parameters that describe the two phases is as follows (? ) The average deviation of the empirical relation and the experimental data is 2%, and the number of heat transfer units in the heat transfer process of the internal heat of the packed column can be estimated more accurately. (3) The system experiment was carried out on the fluid flow behavior in the fixed valve column of the different tower plate structure. The results show that, with the increase of the axial height, the effect of the solid valve on the partial gas content on the tray decreases gradually with the increase of the axial height. The gas-containing rate distribution in the radial direction tends to be uniform, and the effect of the liquid-phase flow on the partial gas content is becoming more and more significant. And the partial gas holdup in the central region of the tray is higher than that of the overflow tray on the flow-through tray, and the partial gas content is less than that of the overflow tray. The partial gas holdup in the fixed-valve trays of the two different structures exhibited a large central area of the tray and a small trend in the edge area of the tray. At different axial heights of the trays, the velocity of the air bubbles on the flow-through trays along different radial lengths is larger than that of the overflow tray. for the trays of the two different structures, the distribution of the bubble velocity is similar, that is, the bubble velocity in the central region is larger than that in the vicinity of the tower wall; in the central region of the tray, the gas-liquid ratio surface area on the flow-through tray is larger than that of the overflow tray, and as the radial length increases, The gas-liquid ratio surface area of the flow-through tray is gradually reduced, while the gas-liquid ratio surface area on the overflow tray decreases with the change of the radial length. (4) The influence of the tray type and the structural parameters on the pressure drop of the tray was studied, and the pressure drop of the tray in the flow-through tray was less than that of the overflow tray. As the distance of the center of the hole and the aperture ratio are reduced, the pressure drop of the through-flow tray and the height of the clear liquid layer are both increased, and the pore diameter is increased, so that the pressure drop and the height of the clear liquid layer are increased; and the height of the clear liquid layer is associated with the parameters of the tower plate structure and the operating variable, and the fitting value is in good agreement with the experimental measurement value. From the principle of minimum energy, a flow-through (? ) The calculation formula (?) of the gas flow through the opening area fraction on the tray? And the gas flow rate is proportional to the cubic root of the ratio of the pressure drop and the leakage liquid area of the gas flowing through the valve hole and the height difference of the static liquid layer of the bubbling area. The results show that the gas flow rate of the open hole in the tray decreases with the decrease of the center distance of the hole, and decreases with the increase of the aperture and the aperture ratio. And in each column plate structure variable, the influence of the pore size on the gas flow rate parameter is least significant.
【學位授予單位】：華東理工大學
【學位級別】：博士
【學位授予年份】：2017
【分類號】：TQ545
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