A novel trigeneration model using landfill gas upgrading process and waste heat recovery: Application of methanol, desalinated water, and oxygen production

Abstract

In this paper, an integrated process for coproduction of methanol (122500 kgh), desalinated water (40.56 m3h), and oxygen (13420 Nm3h) using landfill gas upgrading is presented. The process embraces negative carbon dioxide (CO2) emission framework, high thermodynamic efficiency, and low product cost. The proposed process consists of nine subsystems, which are utilized for heat recovery in addition to production of electricity and desalinated water. Results showed that the total energy and exergy efficiencies of the trigeneration system are 59.19% and 48%, respectively. According to the conducted analysis, the total exergy destruction rate equals 973291 kW in which the biogas upgrading unit has an 80% contribution. In addition, it is demonstrated that the combustor of the biogas upgrading unit is responsible for 57.96% of the total exergy destruction rate. Moreover, the sensitivity analysis illustrates that the increase in the H2CO2 ratio is an important factor in increasing the carbon efficiency and total energy efficiency, and decreasing the CO2 emission. From the environmental perspective, it is deduced that the total net emission of the proposed process is −0.6773 kgCO2kgMeOH, which is significantly lower than other methanol production technologies. Economic analysis is performed for the integrated structure and its results showed that the total annual cost and methanol production cost rate are 124,660,373 $ and 0.124 $kg, respectively. This value is 91.68% lower than the renewable methanol production technology.