Heat-Integrated Processes for Endothermic Reactions

The intended purpose of heat-integrated processes for endothermic reactions is illustrated by the example of methane steam reforming for hydrogen generation, which is of high practical relevance [6] and features typical characteristics of the considered process class. The reaction is given by the following stoichiometric equation ... 

Fig. 1.2. Schematic flow configurations of heat-integrated processes for coupling endothermic and exothermic reactions, (a) Countercurrent flow of process streams, (b) Cocurrent flow of the process streams in the reactor stages and heat recovery in separate circuits.

Chemical-looping modifications of these processes open novel possibilities to address some of the main concerns associated with each of these processes as discussed below. The earliest CLR studies simply explored integration of CLC with a conventional reforming process [78,91-93]. For example, Ryden et al. [78] integrated the cran-bustion of the pressure-swing off-gas of a conventional SRM process to serve as the fuel for a CLC reducer reactor. This allows the capture of any carbon that was not cmiverted to CO in the reforming process itself via CO2 capture in the CLC step while providing some of the heat necessary for the endothermic reaction in the steam reformer. 

The majority of ethylbenzene (EB) processes produce EB for internal consumption within a coupled process that produces styrene monomer. The facility described here produces 80,000 tonne/yr of 99.8 mol% ethylbenzene that is totally consumed by an on-site styrene facility. As with most EB/styrene facilities, there is significant heat integration between the two plants. In order to decouple the operation of the two plants, the energy integration is achieved by the generation and consunption of steam within the two processes. The EB reaction is exothermic, so steam is produced, and the styrene reaction is endothermic, so energy is transferred in the form of steam. 

In addition to mass integration, the reforming process, Eqs. (1) and (2), which overall is endothermic, is energetically coupled to the exothermic oxidation reactions, Eqs. (3) and (4). Thus, the heat required for the generation of hydrogen is provided. 

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