Experimental Investigation of Coal and Biomass Mixtures in a Traveling Grate Commercial Steam Boiler

An industrial steam boiler is a steam-generating device made of steel, designed as a closed chamber with a capacity of over 1,000 liters and a pressure exceeding six times atmospheric pressure. The steam produced is used in various industries, including electricity generation, drying processes, sterilization, and pasteurization. Boilers are classified into three types: fire-tube boilers, water-tube boilers, and hybrid boilers. They can operate using various fuels, such as liquid fuels (e.g., diesel oil, heavy oil), gaseous fuels (e.g., LPG, NGV), and solid fuels (e.g., coal, biomass). An analysis of fuel combustion in boilers reveals notable variations in emissions, pollution levels, heat cost per unit, and steam quality. This study focused on a traveling grate water-tube boiler powered by bituminous coal, which is popular due to its advantages: compact size, ease of installation and maintenance, moderate heat output, and lower heat cost compared to other types. However, it has some drawbacks, including difficulties in maintaining consistent heat levels, which can lead to uneven temperatures and unstable steam pressure. Additionally, adjusting the fuel feed rate is slow, causing delayed responses, and the combustion process generates smoke and sulfur dioxide gas. The aim of this research was to improve traditional solid-fuel boilers by enabling them to use mixed fuels, specifically converting them to boilers that utilize a coal-biomass powder blend. The biomass component, which uses readily available agricultural residues, was incorporated to address the limitations of solid fuels. The results showed that pure coal fuel provided an efficiency of 63.01%, while the coal-biomass blend achieved an efficiency of 78.2%. Toxic gas emissions were reduced by 8%, and the use of the coal-biomass mix saved 52.675 kilograms of fuel per hour, resulting in an annual fuel cost reduction of 16,565,871 THB.