PRELIMINARY DESIGN OF CO2 HYDROGENATION PLANT TO PRODUCE METHANOL FROM CO2 EFFLUENT OF SUBANG GAS PROCESSING FACILITY

Abstract

Methanol (CH3OH) is the main building block of petrochemical derivatives and is an important material to synthesize other chemicals. In general, methanol is produced from natural gas by reforming the gas with steam and then converting and distilling the synthesis gas mixture to produce pure methanol. The existing process uses syngas as feedstock so that it produces a lot of CO2 emissions, to overcome that a more environmentally friendly process is needed. CO2 hydrogenation is a solution to overcome this because it can help reduce CO2 emissions produced by Pertamina EP Subang Field Gas Facility. This utilization is expected to be able to encourage the implementation of CCUS in the oil and gas and petrochemical sectors. The reason methanol is chosen is because the market demand in Indonesia has increased significantly, but this is inversely proportional to the production of methanol in the country, so the government in 2021 imported 390,000 tons of methanol to meet domestic supply. This creates a big opportunity to establish a methanol plant in Indonesia. The methanol plant is planned to operate 330 days/year and 24 hours/day with a production capacity of 80,000 tons/year of methanol. Production of methanol through CO2 hydrogenation process requires 17,209 kg/hour of gas CO2 obtained from CO2 removal unit Pertamina EP Subang as raw material with a composition of 98.86% of CO2 with the remaining 1.14% are impurities and requires hydrogen gas of 2366.14 kg/hour supplied from PT Aneka Gas Industri through the pipeline. The catalyst used for the CO2 hydrogenation process is Cu/Zn/Al/Zr. In general, the stages of the methanol production process are as follows: 1) CO2 reacts with hydrogen in a multitube catalytic reactor, 2) separation between liquid and gas phases in a flash separator, 3) stripping of methanol and COx using gas hydrogen in the stripper, 4) COx that has been recovered by H2 gas will become a recycle stream, and 5) separation between product and water in distillation column. In steady state conditions, production support units or utility units require a total of 75,758.11 kg/h to meet the needs of steam generators, water for cooling, and chilled water (refrigerant) as follows: 1717.15 kg/h, 13757.58 kg/h, and 60283.38 kg/h. Electricity demand of 465.43 kW is generated from the generator. The plant is planned to be established in Subang Regency, West Java, an industrial area with raw material-oriented considerations. The plant area is about 5 hectares. The calculation of the economic evaluation gives a fixed capital of $ 23,491,569.34 and working capital of $ 3,523,735.40. At 100% production capacity, ROI before tax 192.59%, ROI after tax 173.51%, POT before tax 0.8 year, POT after tax 1.38 year, BEP 2.05%, SDP 0.19%, and IRR 64%. In terms of the environment, the construction of this plant can reduce CO2 emissions produced by Pertamina EP Subang byxiii 166174.36 tons/year. To save energy, we use a preheater unit before entering the reactor, this unit utilizes the heat flow from the downstream of the reactor to raise the temperature of the upstream reactor to the optimum temperature of the reactor 250°C, the heat that can be stored using this system is 26931460.45 kJ/h. The CO2 hydrogenation reaction has a CO2 conversion (per pass) of 17.20%, this number is small when compared to syngas process conversion, but it is hoped that the development of this process research will continue to be more optimal, because this process has a major impact on CO2 reduction. In terms of safety, the use of plotting maximizes simulation in the catastrophic incident of a toxic area of vapor cloud, flammable area of vapor cloud, and blast area of vapor cloud explosion. There are three equipments that are considered to have a high degree of danger, namely: reactor, distillation column, and methanol tank. In the reactor, the farthest thermal radiation is 75 meters with a number of 10 kW. In the distillation column, the toxic exposure area is as far as 1.5 km with a number of 7200 ppm, the farthest flammable exposure is 400 meters with a number of 4300 ppm, and the blast exposure area can reach 45 meters with a number of 8 psi. In methanol tanks, the toxic exposure area is as far as 2 km with a number of 7200 ppm, the farthest flammable exposure is 0.75 km a number of 4300 ppm, and the blast area exposure is up to 100 meters with a number of 8 psi.