Experimental and simulation study on preheating pulverized coal and air flow by a heat exchanger using thermal oil

Abstract Utility boilers consume a lot of fuel oil during the startup and low-load operation, which leads to the rise of power generation costs and environmental pollution problems. A finned shell-and-tube heat exchanger is proposed to preheat pulverized coal and air flow using thermal oil. Pilot-scale heat exchange tests were carried out to study the effects of the oil temperature, air temperature, air velocity, oil flow rate, coal-air ratio on the preheating performance and resistance properties of the system. Meanwhile, Computational fluid dynamic (CFD) numerical simulations were conducted. The tests verified the technical feasibility of the heat exchanger using thermal oil to preheat the primary air. The proposed preheating process is conducive to environmental protection and energy-saving. The test results show that when the coal-to-air ratio is 0.15, the 190 ℃ of thermal oil can preheat the pulverized coal and air flow from 65.2 ℃ to above 115 ℃. This preheating process will improve the ignition performance of the pulverized coal and air flow, which is favorable for startup and stable operation of the pulverized coal boiler, particularly when the boiler load is low.