Key safety aspects of the catalytic reforming process

A catalytic reforming unit generally consists of three main parts: feedstock pretreatment, catalytic reforming reaction, and stabilization and fractionation. 　　The raw material is the gasoline fraction with a initial boiling point of 150°C (180°C); it first passes through a pre-distillation column, from which the fraction with a boiling point of 60–130°C is selected as the feedstock for reforming. It is then mixed with hydrogen, and through pre-hydrogenation, the sulfur, nitrogen, oxygen, olefins, and metal impurities in the feedstock are converted respectively into hydrogen sulfide, ammonia, water, saturated hydrocarbons, and the metal impurities are absorbed by the catalyst, thereby ensuring that the subsequent reforming catalyst is not damaged. The catalyst used for pre-hydrogenation is cobalt molybdate or nickel molybdate with alumina as the support. Pre-hydrogenation is an exothermic reaction, so the reaction temperature cannot be too high; it is generally controlled at 320–370°C for cobalt aluminate or 280–340°C for nickel molybdate. The pressure is roughly 2.0–5.0 MPa. A fixed-bed reactor is used. 　　In domestic catalytic reforming, three fixed-bed reactors are generally used in series, or four reactors can be employed, with three of them in operation and one undergoing regeneration to restore catalyst activity. Some units are equipped with a hydrogenation reactor at the back, aimed at converting the unsaturated hydrocarbons in the reformed oil into saturated hydrocarbons to ensure the quality of the final aromatic products. The 3 main reforming reactors operate at temperatures in the range of 480–500°C, as the primary dehydrogenation reaction is a strong endothermic reaction; heat must be supplied to maintain the reaction temperature. The operating pressure is generally greater than 2.0 MPa. Therefore, the 3 reactors must be operated in series, with attached components such as thermocouple tubes and catalyst outlet tubes between them. Whether it is a reactor or a regenerator, insulation measures must be employed to strictly control the temperature. To monitor the wall temperature, color-changing paint is often applied to the exterior of the reactor; once the temperature exceeds the specified limit, this is indicated by a change in color. For platinum reforming, the reaction unit includes a hydrorefining reactor, and due to high temperatures, hydrogen corrosion, and pressure, high-quality materials are required. 　　When loading and unloading the catalyst, care must be taken to prevent it from breaking or becoming contaminated. When removing the unrenewed carbon-containing catalyst, measures should be taken to avoid spontaneous combustion and resulting temperature damage. 　　The heating furnace is the source of heat; during the catalytic reforming process, the reactions of reforming and pre-hydrogenation require large furnaces to provide the necessary reaction heat. Therefore, the safety and stability of the heating furnace are very important. Furthermore, the heat required for feed addition during the process, as well as for the bottom heater and reboiler, often needs to be supplied by a heat carrier heating furnace. It is necessary to prevent local overheating and decomposition of the heat carrier during use, as well as to avoid the entry of low-boiling-point substances such as water, which could lead to vaporization-induced overpressure explosions. The combustion furnace must ensure normal combustion and timely adjustment. The level of the outlet temperature of the heating furnace is a condition for stabilizing the inlet temperature of the reactor; however, changes in furnace temperature are related to many factors, such as the flow rate and pressure of the fuel oil, as well as the quality of the fuel. To stabilize the furnace temperature and ensure the safe operation of the entire system, the heating furnace should be equipped with an automatic control system. 　　In a catalytic reforming unit, important process parameters such as temperature, pressure, flow rate, and liquid level should all be equipped with alarms.