Methanol feed stoichiometry

Figure 2.12 Voltages of the individual cells in a 30-cell DMFC stack at 14 Voperated at 60 °C with a 0.5 M methanol solution feed at 125 ml min at the anode and with 0.76atm dry air feed at 7.35 SLPM at the cathode. At a stack current of 6.1 A, the corresponding methanol and air feed actual stoichiometries are 2.8 and 2.0, respectively.

Autothermal reforming of methanol, also known as Oxidative Methanol Reforming (OMR), is one such method. This process is distinguished from steam reforming of methanol by the co-feeding of oxygen to the reactor system. The stoichiometry of the reaction at an oxygen/methanol ratio of 0.25 is shown in Equation 1. 

Unexpectedly, however, Voc depends on stoichiometry with the growth of A, Voc increases (Figure 4.26(b)). At A = oo, the cell open-circuit voltage reaches the value where E < 100 mV is the voltage loss under open-circuit conditions (see below). The effect of V(,c lowering due to methanol crossover (mixed potential) is well known in DMFC studies. The model above allows us to explain the dependence of OCV on feed molecule stoichiometry A. 

The liquid level in the base of column C3 is controlled by manipulating bottoms flow-rates. In column C2, the base level is controlled by manipulating the fresh feed of methanol, as shown in Figure 5.13. This exactly balances the stoichiometry in the entire plantwide system by appropriately adjusting the addition of fresh methanol as it is consumed in the TAME reaction. Remember that the downstream methanol is set by two flow controllers (methanol flow to the reactor and to Cl). This means that increasing methanol fresh feed flow produces an immediate decrease in the flowrate of bottoms from C2. Thus there is an instantaneous effect on the base level. 

The feed is composed of two streams. The first stream is a hydrocarbon stream that contains 30 mol % isobutene and 70 mol % 1-butene. The second stream, consisting of pure methanol, is in 5 per cent molar excess of the reaction stoichiometry. The hydrocarbon feed rate is 1000 kg h . Both streams are at 30°C and 1500 kPa. The reactor inlet temperature should be controlled at 70°C. The reactor outlet temperature will be higher than the inlet, since the reaction is exothermic and a considerable amount of heat is released. This has the effect of limiting the conversion of isobutene in the reactor. The reactor product should be cooled to around 40°C so that a second reaction stage can increase the isobutene conversion to around 99 per cent. The reactor pressure drop is 140 kPa, and the pressure drops through the exchangers are 70 kPa. The exchanger volumes can be estimated at 0.1 m each. 

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