Cost Minimization Model for Heat Recovery for Hydrogen Production from Biomass Steam Gasification

With the current energy and environmental crisis, hydrogen economy has now gained a positive outlook. This alternative form of energy becomes more attractive when produced from a sustainable source such as biomass, especially for an agricultural country such as Malaysia. However, the thermochemical conversion of biomass into hydrogen can be energy intensive due to its endothermic nature. In this work, a simple linear mathematical problem (LP) has been developed to design a heat integrated flowsheet for an energy efficient hydrogen production from oil palm empty fruit bunch via steam gasification with in situ CO2 capture. The LP transshipment model targets to minimize the utility cost by considering the heat content of process streams at a fixed number of temperature intervals. Three constrained matches are imposed for the synthesized flowsheet for the hydrogen production with hot and cold utility requirements of 1420 hJ/h and 832 kJ/h respectively. The proposed model is able to predict a minimum utility cost of US$ 8.76/ kJ h. The minimum of heat load for hot and cold utilities solved are 631.20 kJ/h and 0.743 kJ/h respectively. This gives an energy savings of approximately 55% in hot utilities and 98% in cold utilities. Furthermore, the production cost of hydrogen is predicted to decrease from US$ 1.91 to 1.80 per kg of H2 via the optimization approach. A result comparison is made with a previous heat integration work on the flowsheet that was based on pinch analysis.