The reformer exchanger uses high temperature process heat exiting the secondary reformer (or exiting an auto-thermal reformer) to produce syngas by reforming an additional flow of natural gas and steam. In this way additional reforming capacity is realized by utilizing heat available in the existing unit that was previously used for steam generation. As the process gas heat is used for hydrogen production instead of steam generation the hydrocarbon consumption and steam export per unit hydrogen produced is reduced (Haldor Topsoe, 2011; Singh and Price, 2011). Figure below shows the KRES heat exchanger used for increasing the front-end production. The use of a heat exchanger reformer can provide a low cost retrofit solution to ammonia plants that have either an expensive, limited or uncertain supply of natural gas, but have alternative energy sources available.
Another example of heat exchanger reformer is the Haldor Topsoe Exchange Reformer (HTER-p). The operating conditions of the HTER-p can be adjusted independently of the primary reformer to get the optimum performance of the whole reforming unit. About 20% of the natural gas feed can be reformed in this heat exchanger reformer and in this way by-pass the primary reformer. By introducing the HTER-p technology, an increase in reforming capacity of 25% can be achieved. The capacity increase could also be translated into an unchanged capacity and a correspondingly smaller load on the primary reformer (Haldor Topsoe, 2007).
The use of the heat exchanger reformer for capacity increase can be implemented as a retrofit in existing ammonia plants.
The adoption of the KRES technology in an Indian plant (CFCL) increased syngas production by 30% and improved the efficiency of the ammonia plant. It also improved the performance of the old reformed gas waste heat boiler by reducing its inlet temperature and thus reduced the thermal and mechanical stresses. Also shift converter conditions were improved because of the lower boiler outlet temperatures (Singh and Price, 2011).
The HTER-p is in commercial operation at a synthesis gas plant in South Africa since 2003, where it is placed downstream of an auto-thermal reformer. The revamp with the HTER-p resulted in a capacity increase of 33% (Haldor Topsoe, 2007).