What is the role of a terminator?
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In single-stage counter-current regeneration of catalytic cracking units: 1. When a terminator is injected into the upper part of the riser, the reaction temperature is maintained at 510 degrees. 2. When no terminator is injected into the upper part of the riser, the reaction temperature is also kept at 510 degrees. What is the difference between these two scenarios, given that the reaction temperature remains the same in both cases? Are the secondary reactions that occur in 1 and 2 the same?
It’s different; the reaction temperature you’re referring to, which is controlled at 510 degrees, refers to the temperature at the exit of the lift pipe. When a terminator is injected into the lift pipe, the reaction temperature is 510 degrees. Compared to the case where no terminator is injected, the amount of catalyst that circulates differs – it is higher in the former case, and the reaction rate is faster as well. Therefore, the secondary reactions occur more frequently in case 1 than in case 2.
My view is exactly the opposite of yours: when a terminator is added, at the same reaction temperature, although the oil-to-terminator ratio is higher than without it, the secondary reaction is not necessarily greater; otherwise, there would be no point in adding a terminator. At the same reaction temperature, when the terminator is added, the ratio of terminator to oil increases, the cracking reaction intensifies, and the target product increases. Coke and dry gas show little or no increase, which means that the secondary reaction results in virtually no increase. This is the purpose, or rather the function, of the termination agent; I’m not sure if that’s correct.
I agree with what was said on the third floor: the terminator serves to reduce secondary reactions, thereby lowering the amount of coke produced as well as the output of dry gas.
I agree with the suggestion from the 3rd floor; we use acidic water as a terminator here
Agree with the third floor. The terminator is used to control the extent of the reaction by lowering the temperature, thereby reducing secondary reactions.
I think it varies depending on the manufacturing process used by different factories. We use the MIP process here, so there is a second reaction zone. The point where the terminator is injected is at the exit of the riser (the first reaction zone) and at the entrance of the second reaction zone. This helps to reduce the flow rates of both the oil-gas mixture and the catalyst, thereby lowering the heavy space velocity. It also allows for temperature control, which helps to suppress secondary cracking reactions and promotes isomerization and hydrogen transfer reactions. As a result, the content of isoparaffins and aromatics in the gasoline increases, raising its octane rating.
The outlet temperature of the riser is the main parameter for catalyst adjustment; for the same outlet temperature, the bottom temperature of the riser also needs to be taken into consideration.
I believe the riser should be divided into three sections. Considering the reaction time, the first section is the pre-rising section (from the bottom of the riser to the feed nozzle), the second section is the feeding section (from the feed nozzle to the terminator nozzle), and the third section is the secondary reaction section (from the terminator nozzle to the outlet of the riser). 1. If a terminator is added and the outlet temperature is 510 degrees, then the reaction temperature in the feed section is high, resulting in a greater degree of reaction. The reaction time in this section accounts for 2/3 of the total residence time in the riser; there is not enough time for a secondary reaction to occur. By the time the material reaches the third section, a terminator is needed to lower the reaction temperature in order to suppress (but not completely prevent) the occurrence of a secondary reaction. 2. If no terminator is added and the outlet temperature is 510 degrees, the temperature in the second reaction stage will be lower than that in Scheme 1; as a result, the degree of reaction will be relatively small, and it is possible that the desired product (under the assumption that its properties are the same as those of the raw materials in Scheme 1) will have a lower concentration. A secondary reaction will also occur upon reaching the third stage. I don’t think the two options proposed on the first floor are comparable. Comparisons should be made under conditions of the same oil-to-agent ratio (i.e., the same temperature for the second-stage reaction) and the same properties of the raw materials; the secondary reaction is smaller when a terminator is added compared to when no terminator is used. This post was last edited by mxtao123 on 2009-2-21 08:28.]
I have reservations about the 3rd floor; I agree with the view on the 10th floor. Everyone is right about the role of the terminator, but it needs to be explained clearly. After adding the terminator, the outlet temperature is 510 degrees; without it, it would be above 510 degrees. Under these conditions, the role of the terminator is to reduce secondary reactions ； However, when compared with the secondary reaction situation for 2, it can only be said that the primary reaction depth for 1 is definitely greater than that for 2, and the reagent-to-oil ratio for 1 is also definitely higher than that for 2; at the same riser outlet temperature, the secondary reaction depth for 1 should be greater than that for 2.