Increase in the efficiency of preparing specially pure hydrogen from methane in a high-temperature converter-membrane equipment system

Abstract

The possibility is analyzed of preparing specially pure hydrogen (SPH) in a high-temperature converter-membrane equipment system drawing on model representations developed previously using heat-resistant palladium alloys. Dependences are calculated for the parameters of membrane separation of methane steam catalytic conversion products on membrane area with different ratios of C H 2 O /C CH 4 in the starting material. The high efficiency of preparing SPH is demonstrated, i.e., of the order of 1.28 m 3 per cubic meter of starting gas.Previously in membrane equipment and units for preparing specially pure hydrogen (SPH) there has mainly been use of palladium alloyed with silver distinguished by high hydrogen permeability. In Russia, the most extensively used alloy has been type V-1 [1] with the optimum combination of physical, mechanical, engineering, and operating properties. The majority of large test-industrial membrane equipment and units for producing SPH of 100-2100 m 3 /h [2] are fitted with membranes of this alloy. With membrane separation of hydrogen containing gas atmospheres that do not interact chemically, such as the products of ammonia dissociation [3] and technical-grade hydrogen after furnaces for "light" annealing of electrical engineering steels [4], use of alloy V-1 has made it possible to resolve practical problems quite effectively.In order to prepare SPH with use of natural gas as a starting material, consisting almost solely of methane, it is normal to carry out prior high-temperature vapor catalytic conversion of methane at 800-900°C with preparation of a multicomponent gas mixture (H 2 , H 2 O, CO 2 , CO, CH 4 ). Nickel applied to a porous ceramic carrier (for example Al 2 O 3 ) with a high internal surface is used as the active component of the conversion catalyst.Under conditions providing absence of carbon deposition, the ratio between the components given above for the gas phase is determined by two reversible chemical reactions:With the use of alloy V-1, direct membrane separation of methane conversion products is not sufficiently effective both with absence [5] and with presence [6] of a methane conversion catalyst in the high-pressure chamber of the membrane equipment. The reason for the low efficiency of SPH preparation from natural gas is connected with the limitation for the membrane material working temperature (600°C).

Calculating the main parameters of a membrane reformer with a production rate of 40 m3/h designed for producing highly pure hydrogen from natural gas

“…=4.12 m 2 for MR Note that this method for estimating the probability of carbon deposition from the gas phase offers the same results as the method of C-H-O ternary diagrams [6][7][8].…”

“…A sufficiently large number of publications deal with the development of this promising technique of HPH production, some of them [1][2][3][4][5][6][7][8][9][10] being mentioned in the Reference. The results reported in [10] are of the greatest interest, namely, the results of testing (~ 3000 hours) of a steadystate experimental-industrial unit with a maximum production rate of 40 m 3 H 2 /h, based on a membrane reformer (MR), designed for producing highly pure (99.999 %) hydrogen from natural gas (NG).…”

Major ways of enhancing efficiency and economy of membrane method of special-purity hydrogen production from natural gas

“…An additional methane conversion catalyst was put in the high-pressure chamber (HPC) of the membrane apparatus. Thus, the compact HTC-HTMA system [13], shown schematically in Fig. 2, was built around version a of the HTMU flow scheme.…”

Special-purity hydrogen production from methane in a high-temperature converter–membrane apparatus system combined with a carbon monoxide conversion catalyzer

“…The high-temperature converter−high-temperature membrane apparatus (HTC−HTMA) system (investigated earlier by mathematical modeling) with a catalyzer for methane conversion in the high-pressure chamber (HPC) of the membrane apparatus allows high-purity hydrogen production at 800°C with high technoeconomic indices [6], which is associated with more exhaustive extraction of hydrogen from methane conversion products by shifting chemical equilibriums (1, 2) to the right.…”