Autothermic Reforming by Super-Adiacatic Combustion in Porous Media

通过数值模拟和实验对多孔介质中超绝热燃烧自热重整进行了研究。甲烷、空气和蒸汽的混合物被引入海绵状多孔介质中，流动方向以一定的间隔交替。气相燃烧和重整反应都发生在多孔介质的中间，多孔介质由堇青石陶瓷制成，并具有用于重整反应的镍催化剂层。在产物气体通过多孔介质的过程中，流动的气体焓被多孔介质储存起来。在反转时，混合物在进入反应区之前被预热，就像流经多孔介质一样。采用往复流系统，发生过焓燃烧；因此，可燃性极限被扩展到燃料丰富的一侧。因此，供应的一部分甲烷被用于放热反应，即与氧的燃烧反应，而剩余的p…更多的art被转化为氢气；这里发生了产氢的吸热反应。对于往复流超绝热燃烧系统，通过热再循环将可燃性极限扩展到5左右的等效比。最显著的特点是甲烷转化率，即甲烷到氢气的转化率，在相当大的等效比范围内达到90%以上，产物气的出口温度与进口温度几乎相同。即燃烧反应热有效转化为生产氢气的反应热，流动的气体焓有效再循环，提高混合物温度。随着当量比的增大，由于多孔催化剂中温度的降低，甲烷转化率降低。在这种情况下，为了避免碳在催化剂表面沉积，需要提供大量的蒸汽。当蒸汽流量与甲烷流量之比为7时，在转炉进出口之间，碳的质量守恒在5%以内。此外，本文提出的重整系统的空间速度为2600(/h)，远高于常规管式重整器的500（/h）。因此，本文提出的重整体系具有很大的潜力，可以减少重整器的规模，并通过燃烧过程产生一些有价值的物种。少

Autothermic reforming by super-adiabatic combustion in porous medium was investigated through numerical simulation and experiment. A mixture of methane, air and steam is introduced into a spongelike porous medium, where the flow direction is alternated at a regular interval. Both gas-phase combustion and reforming reaction occur around the middle of the porous medium which is made of a cordierite ceramics with a nickel catalyst layer for the reforming reaction. During the period when the product gases pass through the porous medium, the flowing gas enthalpy is stored by the porous medium. Upon reversal, the mixture is preheated before entering the reaction zone, as flowing through the porous medium. By using the reciprocating-flow system, the excess enthalpy combustion occurs ; as a result, the flammability limit is extended to the fuelrich side. Consequently, a part of the methane supplied is consumed for exothermic reaction, i.e., combustion reaction with oxygen, while the residual p … More art is converted into the hydrogen ; where the endothermic reaction for the production of hydrogen occurs.For the reciprocating-flow super-adiabatic combustion system, the flammability limit is extended to the equivalence ratio of about 5 by the heat recirculation. The most striking feature is that the methane conversion, i.e., the conversion ratio from methane to hydrogen, reaches the value above 90 % over a wide range of the equivalence ratio, and the exit temperature of the product gas is almost the same as that of the inlet temperalure. That is, the combustion reaction heat is effectively converted into the reaction heat for the production of hydrogen, and the flowing gas enthalpy is effectively recirculated to increase the temperature of the mixture. With increasing equivalence ratio, the methane conversion decreases because of the decrease in the temperature in the porous catalyst. In this case, to avoid the deposition of the carbon on the catalyst surface, the large amount of steam is supplied. For the ratio of the steam flow rate to the methane flow rate of 7, the mass of carbon is conserved within 5% between the inlet and outlet of the reformer. Furthermore, the reforming system proposed here has a much higher space velocity of 2600(/h)than that of 500(/h)for conventional tubular reformers. Consequently, the reforming system proposed here has a high potential to reduce the scale of the reformer and to produce some valuable species through the combustion process. Less