APPROPRIATE CHARACTERISTICES FOR THE PERFORMANCE OF A PROTOTYPE STEAM BOILER WITH AUTOMATIC FLUID-FLOW AND TEMPERATURE CONTROL IN THE STEAM HYDROGASIFICATION PROCESS

Abstract

This research aims to design and construct a steam boiler equipped with an automatic flow and temperature control system for the Steam Hydrogasification process. The study also investigates the operating principles of a water-tube boiler (Water-Tube Boiler), in which water flows inside the tubes while hot gases generated by combustion flow around the outside of the tubes. Heat is transferred from the hot gases to the water, causing the water to boil and be converted into steam. The steam generator is designed as a compact water-tube system with vertically arranged and stacked tubes, providing a high steam-production capacity relative to the system weight. A preliminary experimental study was conducted to evaluate the performance of the steam boiler equipped with an automatic flow and temperature control system for the Steam Hydrogasification process. The system consists of a heat-exchanger assembly comprising vertically stacked tubes arranged in two layers: 22 tubes in the inner layer and 28 tubes in the outer layer, for a total of 50 tubes. Each tube is made of seamless stainless steel, with an internal diameter of 12.6 mm, a tube wall thickness of 2.3 mm, and a vertical tube height of 580 mm. The combustion chamber is equipped with one gas burner, and Liquefied Petroleum Gas (LPG) is used as the fuel for the experiments. The experiments investigated the thermal efficiency and heat transfer characteristics occurring within the steam boiler furnace to determine the optimum operating conditions of the steam boiler equipped with an automatic flow and temperature control system for the Steam Hydrogasification process. The system features vertically stacked tubes heated by a gas burner. The study also examined the air supply rate and recorded the air preheating temperature before the air entered the steam boiler. These data were used to determine the optimum operating conditions of the vertically stacked water-tube steam generator. In addition, the thermal efficiency resulting from the incorporation of porous materials was analyzed to improve the thermal performance of the steam-generation system, thereby achieving the highest possible efficiency and suitable operating conditions for the process. The experimental results showed that the optimum excess air levels for the vertically stacked water-tube steam generator were investigated at 0%, 5%, 10%, 15%, and 20%. The test conducted at an excess air level of 15% achieved the highest thermal efficiency of 65.75%.The study also investigated the effect of incorporating porous materials on the thermal efficiency of the vertically stacked water-tube steam generator, with the aim of increasing its thermal efficiency. The porous materials used were steel hex nuts in sizes M8, M10, and M12, with 8 kg of each size tested. The results showed that the M8 porous material at 8 kg was the most suitable for practical use and increased the thermal efficiency to 80.98%. It was also capable of retaining heat for a longer period compared with the system without porous material. In contrast, the M10 and M12 porous materials had larger gaps between the individual pieces, resulting in a smaller effective surface area for heat absorption. This consequently affected the thermal efficiency and steam production rate of the system