Comparison of Pea Coal Combustion in a Novel Burner With Separated Primary and Secondary Air With Combustion in a Typical Retort Burner

Abstract Pea coal remains a significant fuel source for heating residential and public buildings, particularly in areas without access to centralized heating or gas networks. Recently, there has been growing interest in upgrading heating systems to modern automatic pea coal boilers. To address the need for more environmentally friendly solutions, efforts were directed toward designing pea coal burner that produces lower emissions of CO, NOX, and particulates compared to traditional retort burners. A new burner design using integrated in-burner secondary air (ISA) technology was developed. This innovative approach separates combustion air into primary and secondary streams. The air distribution is controlled by adjustable apertures operated via cables. Primary air is delivered to the base of the burner, directly to the fuel bed, facilitating coal pyrolysis and partial combustion. Secondary air is supplied to the top of the burner to burn off the gases generated during the process. Combustion tests were conducted with two types of pea coal using the ISA burner: uncertified (out-of-class) coal and certified pea coal. These tests were carried out at Klimosz, a company equipped with a specialized laboratory featuring a test stand with a boiler, measurement tools, and data recording equipment. Identical fuel and air settings were used for all tests. For comparison, a typical retort burner was also tested under the same conditions. Each test lasted several hours, during which key parameters were measured, including CO, NOX, O2, CO2, exhaust gas temperature, excess air coefficient, and particulate levels. Visual documentation of the combustion process was also collected. The results showed that the ISA burner outperformed the retort burner in terms of emissions. It emitted almost eight times less CO and reduced NOX emissions by over 25%. Particulate matter emissions from the ISA burner were comparable to those of the retort burner. However, when using uncertified coal, coking occurred, leading to sintering on the furnace surface and hindering combustion efficiency.