Process Intensification Characteristic Study On Methanol Steam Reforming For Hydrogen Production

Environmental pollution and energy crisis problems are increasingly serious, andthe development of new energy has become an effective way to solve this problem.Hydrogen energy is recognized as an ideal future energy because it is efficient andenvironmentally friendly. More and more researchers have been attracted by thedevelopment of hydrogen technologies. Methanol steam reforming (MSR) has become ahot topic area since methanol can be reformed at a relative low temperature. And alsosmall amount of CO and high hydrogen content could be obtained in the products.However, convensional heterogeneous catalytic packed bed usually suffers from severelimitations of mass and heat transfer. It usually results in "cold spot" in the endothermicreforming reaction. These disadvantages limit reformers to a low efficiency of catalystutilization. So process intensification research of MSR is significant for industrialapplication of hydrogen technologies. This study started from the packed bed. Andpacked tubular reactor and microreactor of different configuration have beenmanufactured for studying the effect of reactor configuration on the MSR processintensification. Different catalyst distributions have been manufactured through varyingdilution ratio for studying the effect of catalyst distributions and catlyst coating on theMSR process intensification in the microreactor. The temperature profiles have beenobtained through directly measuring the temperature in the catalyst bed. The effects oftemperature distribution and weakening cold spot on the MSR process intensificationhave been studied for the fisrt time. CuO/ZnO/Al2O3coating was obtained by sol-gelmethod. The performance of MSR on this coating was studied to analyze the effect ofMSR process intensification. For MSR application in thermoelectric power generation,a microreactor which can produce the hydrogen and electrical energy simultaneouslywas designed. Factors of intensifying hydrogen production were studied with numericalanalysis. The main works and innovations can be list as follows:①T he packed tubular reactor of catalyst particle was used to study the effect ofparticle diameter on the MSR process intensification. And the optimal particle diameterwas obtained. The MSR performance of tubular reactor was studied with the optimalparticle diameter. It was shown that the methanol conversion increased with reducedparticle diameter and higher temperature. Methanol conversion and Co contentdecreased with higher space velocity. And the hydrogen producttion rate increased firstly and then reduced. When the inlet temperature was543K and space velocity was1.37h-1, the highest hydrogen production rate was11.9ml/min.②Microreactor of integrated functions was used to intensify the MSR. And thetemperature distribution, together with the factors of the temperature distribution, wasanalysised. At all the inlet temperatures, temperature in the catalyst bed first rised andthen decreased along the axial. Mismatch of the rate of heat consumed and suppliedresulted in "cold spot". The maximum "cold spot" gradient increased with higher inlettemperature, it occured near the inlet and reduced along the axial. Uneven reactantsdistribution led to the uneven temperature distribution on both sides of the axis. Themethanol conversion of microreactor is higher than that of the tubular reactor since themicroreactor could supply higher specific surface area and had lower heat and massdiffusion resistance. When the inlet temperature was543K and space velocity was0.95h-1, the methanol conversion was5.46%higher than that of the tubular reactor. A singlerate model was obtained after kinetics experiments. The kinetics can be as the following:r100.67300.3707SR3.7210exp106976.RT PCH3OHPH2O③A plate-type was designed to inspect the temperature profile of reactor axis. Andalso packed beds of different catalyst distribtion were designed to study the effect ofcatalyst distribution on the MSR process intensification. The cold spot was found on allthe beds. The lowest cold spot gradient of3K was obtained on the catalyst distributionA bed, and the highest one of10K was obtained on the catalyst distribuion B bed. Thelowest cold spot temperature gradient is obtained on gradientcatalyst distribution type A.The maximum cold spot temperature gradient is obtained on gradientcatalystdistribution type B. It has been experimentally verified that reducing cold spottemperature gradients contributes to the improvement of the catalytic hydrogenproduction. The highest methanol conversion and hydrogen production rate respectivelywere93.1%and161.3ml/min. The highest methanol conversion and hydrogenproduction rate were obtained respectively on the gradientcatalyst distribution type Aand the lowest ones were obtained on the gradientcatalyst distribution type B.④CuO/ZnO/Al2O3coating was obtained by sol-gel method. The MSRintensification effect on this coating in microreactor was studied through comparing thepacked bed. It was found that the cold spot area shrinked, the methanol and hydorgenproduction rate incresed. At constant catlyst, the cold spot gradient was the lowest, themethanol conversion and hydrogen production rate were the highest on the coating bed I. However, the cold spot gradient was the maximum on coating-bed Ⅲ. The Methanolconversion and hydrogen production rate were the lowest on the coating bed III. Thehighest methanol conversion of96.26%was acquired on coating-bedⅠ, and it was9.25%and8.01%higher than coating-bed Ⅱ and coating-bed Ⅲ respectively. Whenthe inlet space velocity was0.96h-1, the methanol conversion of coating-bed was5.29%higher than the packed-bed.⑤C old spray wasused to deposit CuO/ZnO/Al2O3coating on Al substrate. Themicrostructure showed the surface area of coating was broadened than the substratesurface area, this was advantageous catalytic reaction. The MSR experiments werecarried out to study the performance of this coating. Comparative experiment showedthat Methanol conversion and hydrogen production rate was higher than that the tubularreactor. In the stability experiment, it was found that Methanol conversion decreasedand then was kept stable. That was because the catalyst particles with weak bindingforce drew down, leaving the only the coating of high strength with the substrate.⑥A micro-thermoelectric-generator based on MSR heated by methanol catalyticcombustion was designed. The numerical results showed that this microreactor ofthermoelectric-generator could produce hydrogen and electricity at the same time. Themain factors of steam reforming and catalytic combustion respectively were inlettemperature and inlet velocity. The temperature difference between steam reformingchannel and catalytic combustion channel was mainly affected by the thermalconductivity of thermoelectric-generator. To enhance thermal conductivity ofthermoelectric-generator was advantageous for the uniform temperature distribution andimprovment of methanol reforming efficiency.