本文選題：制氫 + 甲烷��； 參考：《浙江大學(xué)》2017年博士論文

【摘要】：氫氣是重要的石油化工原料,也是未來的清潔能源載體。以納米氧化鈣作為CO2反應(yīng)吸附劑的反應(yīng)吸附強化甲烷蒸汽重整(Reactive Sorption Enhanced Reforming,簡稱ReSER)制氫是一種高效的制氫技術(shù),相比于傳統(tǒng)的甲烷蒸汽重整制氫,ReSER制氫技術(shù)具有降低反應(yīng)溫度,提高甲烷轉(zhuǎn)化率和氫氣濃度,以及縮短流程等優(yōu)勢。在ReSER制氫反應(yīng)體系中,納米氧化鈣與C02的反應(yīng)特性是其對甲烷蒸汽重整制氫的強化作用的關(guān)鍵。因此,研究提高納米氧化鈣的CO2吸附性能,以及吸附性能與制氫反應(yīng)強化作用之間關(guān)系,對ReSER制氫技術(shù)的工業(yè)化應(yīng)用具有重要理論和實際意義。首先,本文以商用納米氧化鈣為例,就其碳酸化反應(yīng)性能對甲烷蒸汽重整制氫的強化作用進行理論分析。結(jié)合固定床反應(yīng)器中ReSER制氫的“三傳一反”特點,首次以COMSOLMultiphysics軟件作為計算平臺,建立了本文的模擬計算方法,并對納米氧化鈣CO2吸附性能與強化作用之間的關(guān)系進行計算。結(jié)果表明:在ReSER制氫反應(yīng)體系中,提高吸附劑的CO2吸附速率有利于提高對制氫反應(yīng)的強化作用,但兩者之間并非線性相關(guān),且強化作用存在上限。納米氧化鈣的吸附容量對甲烷蒸汽重整的影響主要體現(xiàn)在強化作用時間的長短,吸附容量越大,強化作用時間越長。其次,本文首次提出采用碳球模板法制備不同球徑的籠狀納米氧化鈣,用于ReSER制氫的C02反應(yīng)吸附脫除,并研究其吸附性能。結(jié)果表明:籠狀納米氧化鈣的吸附速率和吸附容量都要高于平均粒徑70納米的商用納米氧化鈣。優(yōu)選的籠狀納米氧化鈣球徑為1.62 μm,在碳酸化反應(yīng)溫度為600 ℃時能達到理論最大吸附容量0.786 gCO2/gCaO。為了提高籠狀納米氧化鈣的循環(huán)吸附穩(wěn)定性,本文采用鋯添加制備了鋯改性的籠狀納米氧化鈣基吸附劑。研究表明:優(yōu)選的樣品Ca/Zr摩爾比為5,其在30次循環(huán)之后氧化鈣轉(zhuǎn)化率保持在76%,而未經(jīng)鋯改性的籠狀納米氧化鈣在30次循環(huán)之后轉(zhuǎn)化率只有20%。另外,與制備得到的Mg和Al改性的籠狀納米氧化鈣循環(huán)穩(wěn)定性對比,發(fā)現(xiàn)鋯改性的籠狀納米氧化鈣具有更好的循環(huán)穩(wěn)定性,且鋯改性和籠狀結(jié)構(gòu)在提高吸附劑循環(huán)穩(wěn)定性中起顯著協(xié)同作用。此外,本文根據(jù)籠狀納米鈣基吸附劑的碳酸化反應(yīng)特性,提出了適用于區(qū)分籠狀納米鈣基吸附劑碳酸化反應(yīng)快、慢段的新判據(jù),并采用Boltzmann方程擬合了籠狀吸附劑在快速反應(yīng)段的動力學(xué)方程。結(jié)果表明:動力學(xué)方程平均相對誤差為5.78%,具有較好的精度,得到反應(yīng)活化能為26.661 kJ/mol,較商用納米氧化鈣低3.54 kJ/mol,且籠狀納米鈣基吸附劑的最大吸附速率是商用納米氧化鈣的1.44 倍。最后,本文將鋯改性籠狀納米鈣基吸附劑用于強化甲烷蒸汽重整制氫反應(yīng),結(jié)合“三傳一反”對反應(yīng)進行模擬計算。經(jīng)實驗驗證,模型計算得到的甲烷轉(zhuǎn)化率誤差為5.15%。實驗證明:鋯改性籠狀納米鈣基吸附劑較商用納米氧化鈣有更高的制氫強化作用,尤其是在650℃,壓力為5bar,水碳摩爾比等于3.5,空速為700 h-1的情況下,籠狀納米鈣基吸附劑的強化因子是商用納米氧化鈣的2.02倍。對不同反應(yīng)條件下的強化作用模擬計算發(fā)現(xiàn),水碳摩爾比的提高有利于相同反應(yīng)條件下甲烷轉(zhuǎn)化率和產(chǎn)物氫氣摩爾分率的提高。在水碳摩爾比為4,反應(yīng)溫度650 ℃,常壓條件下甲烷轉(zhuǎn)化率最高可達99.8%,氫氣摩爾分率最高可達到99.9%。壓力的增高并不利于甲烷轉(zhuǎn)化率和氫氣純度的提高,要在高壓反應(yīng)條件下取得較好的反應(yīng)效果可以提高反應(yīng)溫度或增加水碳摩爾比。不同水碳摩爾比條件下的強化因子響應(yīng)面均呈凸形曲面,當水碳摩爾比為3,反應(yīng)溫度為611 ℃,壓力為5bar時強化因子達到最大為67.2%。為了了解納米氧化鈣碳酸化反應(yīng)性能對甲烷蒸汽重整以及變換反應(yīng)的強化作用規(guī)律和影響過程,本文首次采用COMSOL Multiphysics軟件對反應(yīng)吸附強化作用的過程進行模擬計算,得到了床層軸向上各組分濃度和溫度在反應(yīng)過程中的變化情況。發(fā)現(xiàn)了強化作用峰面的存在與變化規(guī)律,認為其形成與移動取決于氧化鈣碳酸化反應(yīng)轉(zhuǎn)化率的變化,且強化作用也主要集中于這個峰面內(nèi)。通過對管內(nèi)軸向溫度隨時間變化情況的分析,發(fā)現(xiàn)了入口段的低溫區(qū)現(xiàn)象和高溫峰的移動現(xiàn)象。
[Abstract]:Hydrogen is an important petrochemical raw material and a clean energy carrier in the future. The reaction adsorption enhanced methane steam reforming (Reactive Sorption Enhanced Reforming, abbreviated for short) using nano calcium oxide as a CO2 reaction adsorbent is a highly efficient hydrogen production technology. Compared to the traditional methane steam reforming and hydrogen production, ReSER hydrogen production technology is used. In the ReSER hydrogen production system, the reaction characteristics of nano calcium oxide and C02 are the key to the strengthening of methane steam reforming and hydrogen production in the ReSER hydrogen production system. Therefore, the adsorption properties of nano calcium oxide and the adsorption properties and hydrogen production are studied. The relationship between the strengthening effect and the industrial application of ReSER hydrogen production technology is of great theoretical and practical significance. First, in this paper, the commercial nano calcium oxide is used as an example to analyze the strengthening effect of the carbonation reaction on the steam reforming of methane, and the "three transmission and one inverse" characteristic of the ReSER hydrogen production in the fixed bed reactor. The simulation calculation method was established for the first time using COMSOLMultiphysics software as the calculation platform. The relationship between the adsorption properties of nano calcium oxide CO2 and the strengthening effect was calculated. The results showed that in the reaction system of ReSER hydrogen production, the enhancement of the adsorption rate of adsorbents was beneficial to the enhancement of the hydrogen production reaction, but both of them were enhanced. The influence of the adsorption capacity of nano calcium oxide on the steam reforming of methane is mainly reflected in the length of the strengthening time, the larger the adsorption capacity and the longer the strengthening time. Secondly, the carbon sphere template method is the first time to prepare the cage like nano calcium oxide with different ball sizes, which is used for ReSE. The adsorption and adsorption properties of R hydrogen are removed by C02 reaction, and the adsorption capacity is studied. The results show that the adsorption rate and adsorption capacity of caged nano calcium oxide are higher than that of commercial nano calcium oxide with the average particle size of 70 nanometers. The optimum cage like nano calcium oxide ball diameter is 1.62 mu m, and the maximum adsorption capacity can reach the theoretical maximum adsorption capacity of 0.7 when the carbonation reaction temperature is 600. 86 gCO2/gCaO. in order to improve the cyclic adsorption stability of caged nano calcium oxide, zirconium modified caged nano calcium oxide adsorbent was prepared by zirconium addition. The study showed that the optimized sample Ca/Zr molar ratio was 5, and the conversion of calcium oxide was kept at 76% after 30 cycles, while the non zirconium modified caged nano calcium oxide was 30 times without zirconium modification. After the cycle, the conversion rate is only 20%.. Compared with the stability of the caged nanocrystalline calcium oxide cyclic stability obtained by Mg and Al modification, it is found that the caged nano calcium oxide modified by zirconium has better cycling stability, and the zirconium modification and the cage like structure play a significant role in improving the stability of the adsorbent cycle. The characteristics of carbonation reaction of mica calcium based adsorbents are presented. A new criterion is proposed to distinguish the fast and slow stages of carbonation reaction of caged nano calcium based adsorbents. The kinetic equation of the cage like adsorbent in the rapid reaction section is fitted by Boltzmann equation. The results show that the average relative error of the kinetic equation is 5.78%, and the accuracy is better. The activation energy is 26.661 kJ/mol, 3.54 kJ/mol lower than commercial nano calcium oxide, and the maximum adsorption rate of caged nano calcium based adsorbents is 1.44 times as much as that of commercial nano calcium oxide. Finally, the zirconium modified cage like nano calcium adsorbent is used to strengthen the reaction of methane steam reforming and hydrogen production, combined with the "three trans" reaction to the reaction. It is proved by the experiment that the error of the methane conversion rate calculated by the model is 5.15%. experiment. It is proved that the zirconium modified cage like nano calcium adsorbent has a higher hydrogen production strengthening effect than the commercial nano calcium oxide, especially at 650 C, the pressure is 5bar, the water carbon mole ratio is equal to 3.5, the air velocity is 700 H-1, and the cage like nano calcium adsorbent is used. The enhancement factor is 2.02 times that of the commercial nanometer calcium oxide. The simulation calculation of the strengthening effect under different reaction conditions shows that the increase of the ratio of water carbon mole is beneficial to the increase of methane conversion and the molar fraction of hydrogen under the same reaction conditions. The ratio of the molar ratio of water to carbon is 4, the reaction temperature is 650, and the maximum methane conversion can reach 99. under the condition of atmospheric pressure. 8%, the increase of the maximum hydrogen molar fraction can reach the increase of 99.9%. pressure, which is not conducive to the increase of methane conversion and hydrogen purity. A better reaction effect under the condition of high pressure reaction can increase the reaction temperature or increase the ratio of water carbon mole. The response surface of the intensifying factor under the condition of different water carbon mole ratio is convex surface, when the water carbon friction is in the condition of water carbon mole ratio. The reaction temperature is 3, the reaction temperature is 611, the strengthening factor reaches the maximum when the pressure is 5bar is 67.2%., in order to understand the strengthening law and the influence process of the methane steam reforming and the transformation reaction of the nanometer calcium oxide acidification reaction, this paper uses the COMSOL Multiphysics software for the first time to simulate the process of the reaction adsorption strengthening. The variation of the concentration and temperature of each component in the axial direction of the bed was obtained. The existence and variation of the peak surface was found. It was found that its formation and movement depended on the change of the conversion rate of calcium oxide carbonation, and the intensifying effect was mainly concentrated in the peak surface. The phenomenon of low temperature zone and Gao Wenfeng's moving phenomenon were found in the analysis of the variation.

【學(xué)位授予單位】：浙江大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2017
【分類號】：TQ116.2;TQ424

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