Method for adjusting temperature fluctuations in gasoline hydrogenation reaction
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The main factors causing fluctuations in the temperature of gasoline hydrogenation reactions are: 1. Changes in feed volume and feed composition; 2. Changes in the amount of recycle hydrogen, the amount of cold hydrogen, and system pressure; 3. Instrumentation control failures; 4. Fluctuations in the outlet temperature of the heater (caused by factors such as gas feed); 5. Decreased heat exchange efficiency of the heat exchangers; 6. Human operational factors, with the first four being the most significant. Cause analysis: Changes in factors such as the feed rate directly lead to significant variations in the temperature of the refined oil and the raw material after passing through the heat exchanger, as well as in the temperature of the circulating hydrogen and the temperature at the furnace outlet. Consequently, the temperature at the reactor inlet also changes. Due to delays in regulation, the temperature of the cold hydrogen changes as well, ultimately resulting in fluctuations in the reactor outlet temperature. The temperature at the reaction outlet, in turn, affects the temperature after heat exchange, thus creating a vicious cycle; it can be observed that the reaction temperature curve always fluctuates up and down. Adjustment methods: 1. Stabilize the feed – maintain a constant output from the compressor as well as a constant amount of gas. 2. Keep the valve position for cold hydrogen stable, ensuring that the temperature does not rise; do not adjust this valve, as any change in its position will cause variations in the amount of circulating hydrogen in the entire system (in the area ahead of the cold hydrogen bed), which in turn will affect the heat level and indirectly influence the temperature after heat exchange, making it difficult to achieve stability. 3. Control the reactor inlet temperature by adjusting the opening degree of the bypass valve connected to the heat exchanger for the refined oil and the raw material (when the temperature fluctuates, observe the changes in the valve position in automatic mode, select the intermediate value, hold it steady for a while to monitor the changes in the reactor inlet temperature, and then make adjustments. Be sure not to adjust the valve frequently; it must remain at a stable value before further adjustments can be made). 4. During the adjustment process, close attention should be paid to the changes in temperature at the reactor outlet and furnace outlet, and adjustments should be made accordingly; temperature increases or decreases should only be carried out after the reaction temperature curve stabilizes.
You’re right; these are roughly the factors that affect the temperature of the refined CAT. Generally, temperature control is carried out while keeping the reaction feed constant. The flow rate of gas in the reactor and the opening degree of the cold hydrogen valve are the main means used to achieve optimal energy savings by using the minimum amount of gas along with an appropriate opening degree for cold hydrogen. As for the heat exchange between the refined oil coming out of the reactor and the raw material, this is also a common method of temperature regulation in refining units. Each adjustment should be made in small steps, as it takes some time for the temperature to change; this can be determined by observing changes in the temperature of the raw material at the inlet. It’s also important to pay attention to the temperature of the refined oil as it moves to the subsequent high-temperature processing stages, in order to avoid overheating. Provided that overheating is avoided, the temperature can be set as high as possible, which can also help save energy. In daily operations, it’s necessary to explore these aspects further, as much of what is described in textbooks only covers one aspect of the issue. I hope this can help you.