STUDY ON PRODUCING LIQUID CO₂ FROM BIOMASS-FIRED BOILERS AS A REPLACEMENT FOR FOSSIL FUELS

Abstract

Liquid carbon dioxide (CO₂) is widely used in industry and daily life. CO₂ is primarily produced from fermentation processes (such as in beer, wine, soft drink, and ethanol production) or from the direct combustion of diesel fuel (DO), natural gas (NG), nitrogen fertilizer production, and from the calcination of limestone (CaCO₃). Currently, in Vietnam, the supply of CO₂ to the market does not meet actual demand. To help increase supply, the research team proposes an additional solution for producing liquid CO₂ from biomass-fired boilers. The main result presented in this paper is the design and fabrication of an industrial-scale liquid CO₂ production system from the flue gas of a biomass-fired boiler. The CO₂ recovery system has a capacity of 50 tons of liquid CO₂ per day and night. Flue gas flow into the system is 22,000–25,000 m³/h, with an inlet gas temperature of 42–45°C. The MEA flow rate is 65–70 m³/h, the absorber column operates at 42–45°C, and the stripper column at 115–125°C. Steam is supplied at a pressure of 3 bar(a) and a flow rate of 6–7 tons/hour. The amount of steam consumed per ton of CO₂ produced is approximately 2.8–3.2 tons. The system meets the criteria for “green” CO₂ production, helps reduce greenhouse gas emissions, and is capable of meeting the future demand for liquid CO₂. This system can be applied to large-scale biomass-fired boilers.