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Author: Wang Deshi Abstract: By modifying the gas nozzles of the four cylindrical furnaces in the catalytic reforming unit, and applying high-temperature radiant coatings to the radiation chambers of H102 and H103, the furnace temperature and flue gas temperature were effectively reduced, gas consumption was decreased, and the thermal efficiency of the furnaces was improved； The radiation chamber lining of the reformation three-in-one furnace was replaced, effectively reducing the surface temperature of the furnace wall. Keywords: catalytic reforming unit ； Heating furnace ； There are issues with the modification of l. 1.1 The original hydrogen burners cannot meet the requirements for burning gas. In June 1999, considering that hydrogen would not be available in sufficient quantities after the catalytic reforming unit started operating, we collaborated with the Equipment Research Institute of Luoyang Petrochemical Engineering Company to design and develop a new SUG series of hydrogen-enriched gas burners. The 70 burners in those 7 heating furnaces were modified, which effectively solved the problem of what to do with the excess hydrogen. In March 2001, our plant’s 800,000 t/year catalytic diesel hydrogenation unit was put into operation. Due to a shortage of hydrogen, all the reforming heaters were switched to using gas from the pipeline system. The nozzles originally designed for using hydrogen could no longer meet the production requirements, resulting in issues such as long flames, weak combustion, easy flame failure, and easy extinguishment – problems that severely affected the safe operation of the unit. 1.2 Increased load on cylinder furnace H103: Due to adjustments in the pretreatment process, the load on furnace H103 has increased. In October 2001, after the pre-hydrogenation load was increased to 80 t/h, the temperature in furnace H103 rose to 780°C, and the gas flow rate far exceeded the design value. This led to limitations in the temperature increase at the bottom of the stripping tower, severely affecting the plant’s processing capacity. 1.3 High surface temperature of the furnace wall in the radiation chamber of the three-in-one heating furnace: The lower part of the lining in this furnace’s radiation chamber is made of refractory bricks, while the upper part consists of multiple layers of ceramic fiber blocks, which are fixed to the furnace wall using insulation pins. Due to cracks in the refractory brick wall, the ceramic fiber layer came loose and cracked, and the insulation nails became exposed, resulting in a surface temperature of 70–120°C at the lower part of the furnace wall, 60–70°C at the upper part, and around 190°C in the area surrounding the explosion-proof doors and manholes. 2 Modification Status 2.1 Modification of the gas nozzles In May 2002, we modified the nozzles of four cylindrical furnaces. By changing the size and direction of the nozzle opening, the angle between the gas flow and the air flow is increased; moreover, a flame stabilizer is added to the nozzle tip to reduce the gas flow velocity and enhance mixing with the air. After operation began, the flame length decreased significantly, eliminating the problem of a flame without a stable base and being easily extinguished. This resolved the issues of incomplete combustion and susceptibility to flash explosions in H101, **improving the operational flexibility of the furnace; combustion could proceed properly at pressures ranging from 0.03 to 0.125 MPa behind the gas valve, and the processing capacity of H103 increased markedly. 2.2 Renovation of the lining in the radiation chamber of the three-in-one heating furnace: In May 2002, we replaced the lining in the radiation chamber of this three-in-one furnace. All the existing ceramic fiber blocks, refractory bricks, and insulation nails were removed; the furnace walls were manually rust-removed, and “Z”-shaped insulation nails were rewelded in a square pattern. Ordinary aluminum (high-alumina) fiber cotton was fed into a spraying machine and sent to the nozzle through cotton delivery pipes, while the binder was also sent to the nozzle via a high-pressure pump. The binder and fiber cotton mixed in the air were then sprayed onto the furnace body. After the lining surface was restored, a surface curing agent was sprayed on it. Among them, for the furnace wall insulation nails below 2m in height, the height is 160mm with a spacing of 3000mm×300mm; the sprayed fiber cotton consists of a 160mm thick ordinary aluminum layer plus a 50mm thick high-alumina layer ； For furnace wall insulation nails over 2m in height, the height is 140mm with a spacing of 350mm×350mm. The coating consists of a 140mm thick ordinary aluminum layer plus a 50mm thick high-alumina layer, and a stainless steel wire mesh is tied between the two layers. The entire spraying process is carried out from top to bottom, layer by layer; the total volume of work is 105 m3, and the construction period is 9 days. 2.3 Application of high-temperature radiation coating in the H102 and H103 radiation chambers: Due to the increased load on H102 and H103, in order to further improve their processing capacity, we applied high-temperature radiation coating to the inner surfaces of these chambers. This increased the blackness of the furnace walls, enhanced radiation heat transfer within the furnace, reduced the exhaust temperature, decreased gas consumption, and improved the furnace’s thermal efficiency. 3 Comparison before and after the renovation and benefit analysis The gas consumption of the heating furnace is closely related to the operating conditions of the furnace, its load, as well as the gas pressure and composition. For easier comparison, we selected operation data from April 25, 2002 (before the renovation) and September 7, 2002 (after the renovation), when the pre-hydrogenation feed rate was 68 t/h and the operating conditions, gas pressure, and composition were similar, as shown in Table 1. Table 1 Comparison of Data Before and After the Renovation of Four Heating Furnaces 3.1 Comparison of H101 Before and After Renovation As can be seen from Table 1, after the renovation, the temperature difference between the inlet and outlet of H101 increased from 6°C to 20°C; the load on the furnace increased, and the furnace temperature rose by 43°C. The temperature at the bottom of the furnace and the exhaust gas temperature remained relatively unchanged, while the gas consumption decreased by 17 Nm3/h. This shows that after replacing the gas gun, the combustion condition improved, and the furnace’s processing capacity and thermal efficiency increased. Assuming a gas density of 0.746 kg/Nm3 (the same value will be used throughout), 11,000 cubic meters of gas can be saved each year, which is equivalent to 160,000 yuan in value. The entire investment can be recovered in 2 months. 3.2 Comparison before and after the modification of H102: As shown in Table 1, after the modification, the furnace temperature of H102 decreased by 14°C, the bottom temperature of the furnace dropped by 47°C, the flue gas temperature fell by 8°C, and the gas consumption was reduced by 36 Nm3/h. This shows that after replacing the gas burner, the combustion conditions improved: the temperature at the center of the flame increased, while the temperature at the bottom of the furnace decreased significantly. After applying high-temperature radiant coatings to the radiation chamber, the efficiency of radiant heat transfer was enhanced, resulting in a significant reduction in the furnace temperature, exhaust gas temperature, and gas consumption. 235 tons of gas can be saved each year, equivalent to 350,000 yuan. The entire investment can be recovered in 2 months. 3.3 Comparison before and after the modification of H103: As shown in Table 1, after the modification, the temperature difference between the inlet and outlet of H103 increased from 14°C to 21°C. The furnace load increased, while the temperature in the furnace chamber remained relatively unchanged. The temperature at the furnace bottom decreased by 44°C, the flue gas temperature dropped by 9°C, and the gas consumption was reduced by 49 Nm3/h. 320 tons of gas can be saved each year, which is equivalent to 480,000 yuan in value. Since this furnace is equipped with four gas nozzles, the entire investment can be recovered in just over a month. 3.4 Comparison before and after the modification of H204: As can be seen from Table 1, after the modification of H204, the inlet and outlet temperatures of the furnace as well as the temperature difference between them increased slightly. With the feed rate remaining unchanged, the temperature in the furnace chamber, the temperature at the furnace bottom, and the flue gas temperature also increased slightly. This was due to an increase in the furnace load, while the gas consumption decreased by 28 Nm3/h. This shows that after replacing the gas gun, the combustion condition improved, and the furnace’s processing capacity and thermal efficiency increased. 183 tons of gas can be saved each year, equivalent to 270,000 yuan, and the entire investment can be recovered within just one month. 3.5 Comparison before and after the renovation of the three-in-one furnace lining: After the renovation of the radiation chamber lining of the reforming three-in-one heating furnace, the temperature at various points on the furnace surface decreased significantly, eliminating the problem of local overheating. The average surface temperature of the furnace wall dropped from 81.91°C to 60.81°C, a reduction of 21.1°C, achieving the desired outcome. Reducing the surface temperature of the furnace body from 80°C to below 60°C reduces surface heat loss by more than 1%, which is equivalent to an increase in the efficiency of the heating furnace of more than 1%. Before the renovation of the three-in-one furnace lining, the fuel gas consumption was 4500 Nm3/h; after the renovation, 45 Nm3/h of fuel gas can be saved. This results in a yearly savings of 294 tons of fuel gas, equivalent to 294,000 yuan, and the entire investment can be recovered within 2 years. Furthermore, the modification of the furnace lining reduced the furnace temperature, increased the furnace’s processing capacity, eliminated hot spots on the furnace walls, and prevented further cracking and collapse of the refractory brick walls, ensuring the safe, stable, and long-term operation of the furnace. 4 Conclusion: After the modification of the gas nozzles in the four cylindrical furnaces in Workshop 6, the fuel conditions of the furnaces were significantly improved. The furnace temperature, bottom temperature, and flue gas temperature all decreased, while the processing capacity of the furnaces increased; moreover, the amount of gas used was markedly reduced. After the renovation of the radiation chamber lining in the three-in-one heating furnace, the external surface temperature of the furnace wall decreased significantly. The renovation of the heating furnace has yielded significant results: it eliminated potential hazards, reduced the energy consumption of the facility, and improved the furnace’s thermal efficiency.