The Coal-to-Gas RTO Waste Heat Boiler is designed for waste heat recovery from relatively clean hot flue gas sources such as RTO (Regenerative Thermal Oxidizers) and VOCs furnaces. It features a smoke tube arrangement with natural water circulation. The high-temperature flue gas flows through the horizontally arranged smoke tubes, scrubbing the tubes longitudinally, while the outer side of the tubes, shell, and tube sheets form the working medium side. Boiler feedwater is preheated in the economizer and mixed with saturated steam and water in the drum before circulating through the downpipes, absorbing heat, and returning to the drum as a steam-water mixture. The saturated steam exits the drum and enters the superheater, where it is further heated to produce superheated steam. The superheater outlet is equipped with a desuperheater to regulate the steam temperature to meet network requirements. The design effectively manages the significant flue gas temperature fluctuations typical of RTO furnaces, ensuring efficient and stable operation.