Increasing the reliability of biomass solid fuel combustion using a combined regenerative heat exchanger as an indirect burner

In this study, an indirect burner system for solid biomass fuel is designed. The design is motivated by the need to solve the problem related to a direct burner system, such as slagging and high pollutant emissions due to the high-temperature burning process. Therefore, the utilization of an indirect burner is expected to improve the reliability of the solid biomass combustion process. It also can be used to reduce coal consumption by using an indirect burner where the working fluid reaches a relatively higher temperature before entering the boiler. The design used the first principle method for creating the regenerator heat exchanger. The regenerator consists of a mantle and coil heat exchanger. The test used solid biomass fuel for the combustion process where the working fluid first enters the mantle heat exchanger and then the coil heat exchanger. As a result, the mantle absorbs sufficient heat losses from the combustion chamber with the highest temperature increment of 19 °C. The warm water from the mantle then flows to the coil arrangement within the combustion chamber. As a result, the highest temperature of the coil is 84.5 °C. The heat transfer rate for the coil and mantle is 57.2–85.6 and 124.9–141.5 W. The key finding is that the combined regenerative heat exchanger can deliver a higher transfer rate. This can be achieved since the heat exchanger utilizes the same flow distribution, increasing the mean temperature differences at the inlet. Thus, it can produce an average heat transfer rate of 210.5 W. Therefore, energy consumption for coal or other fossil fuels can be reduced significantly. The data can be used for further improvement of the existing boiler system and help to increase the thermal efficiency of the system.