Experimental Study On The Performances Of Catalytic Reforming With Dimethyl-ether

Reductions in fuel consumption and engine emissions are two major objectives in engine development. DME is an excellent alternative fuel for vehicle in China because its raw material accords with the energy structure. DME fuel mixed with hydrogen will be helpful to improve engine performance and reduce engine emissions. REGR (Reformed EGR) is an effective way to fulfill the target of energy saving and emission reduction. The process and performances of DME catalytic reforming reaction was studied in this thesis, which made a solid foundation for on-board DME reforming system and optimized the DME engine performances.1 The stream catalytic reforming of DME was studied. Other parameters were kept invariant, the influence of several factors on the performance were researched and analyzed, which included DME flow, operation temperature, catalyst charge, catalyst species, mass proportion of catalyst CNZ-1 and catalyst HZSM-1 and reduction time. Results showed that: under normal pressure, when DME flow increases, the yield of hydrogen increases at the beginning and then decreases; When operation temperature is within the scope of 250℃to 500℃, the production rate of hydrogen increases with the increasing of temperature, the maximum conversion rate of DME almost reaches one hundred percent; the volume fraction of carbon monoxide decreases with the decreasing of reaction temperature; although using more catalyst have no influences on hydrogen production rate under the test conditions, it can improve the conversion rate of DME effectively; compared with CNZ-1/HZSM-5, 1% Pd/γ-Al2O3 has a higher selectivity of CO, But CNZ-1/HZSM-5 has a higher selectivity of CO2; the concentration of hydrogen rises along with the mass proportion of CNZ-1/HZSM-5 between 250℃and 300 ℃; Reduction could increase the whole activity of catalyst and H2 concentration and DME conversion, but not very obvious.2 The CO2 catalytic reforming of DME was studied. Other parameters were kept invariant, the influence of several factors on the performance were researched and analyzed, which included operation temperature and catalyst charge. Results showed that: temperature has a big influence on DME reforming reaction; concentration of hydrogen and carbon monoxide increased quickly when reaction temperature increased, but concentration of hydrogen and carbon monoxide almost kept the same when reaction temperature beyond 350℃due to lacking of reactants; and the average level of hydrogen and carbon monoxide concentration is 46%; increasing catalyst charge made DME conversion go up subsitantially, the maximum of DME and CO conversion was 87.4 percent and 88 percent separately; concentration of hydrogen made from DME steam reforming was 30% more than that made from DME carbon dioxide reforming, which is in accord with the theoretical results.3 The energy saving rate of DME catalytic reforming was analyzed. DME steam reforming has the hightest energy saving rate among all the DME reforming way. Theoretically, its energy saving rate can reach 20.6 percent, and we got 14.6 percent in our study. The energy saving rate of DME reforming reaction mainly depends on DME conversion, the higher DME conversion rate it is, the more heat it needs in the reaction, the higher the energy saving rate it is.It also depends on the ratio of carbon monoxide concentration to hydrogen concentration: the bigger the ratio is, the bigger the whole heat value is, the higher the energy saving rate is. The study laid a solid foundation for both the reformed EGR technology and high efficiency & ultra-low emission engine technology.