Flue gas flow issues
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Could everyone talk about the flue gas flow after the three spinners in catalytic cracking? In our system, after coming out of the third spinner, the gas enters the waste catalyst tank; from the top of this tank, the gas is sent to the fourth spinner for further treatment, after which it goes to the critical nozzle, while the waste catalyst returns to the waste catalyst tank. I heard that some manufacturers connect the three-spin outlet directly to the four-spin, eliminating the air inlet pipe from the waste agent tank to the four-spin. What are the advantages and disadvantages of each of these two piping methods? Please provide some answers.
Our factory’s process is similar to yours: the material coming out of the third spinner goes directly into the fourth spinner, while the gas from the catalyst waste tank enters directly at the bottom of the third selector before going into the fourth spinner. The advantage of this approach is that it reduces the amount of catalyst in the flue gases, preventing wear on the flue gas engines as well as on the nozzles located on the street-facing side.
The originally designed process was of the first type mentioned by the poster. However, since the three-spinners and the storage tank are on the same vertical line, and given the high temperature of the flue gases, a compensation device was installed between the outlet of the three-spinners and the storage tank in order to absorb the thermal expansion of these components. Yet due to the harsh operating conditions, leaks often occur. To address the leakage issue, the process was changed to the second method mentioned by the poster: the output from the three-spinners is directly fed into the four-spinner, and the pipelines are designed with a larger radius to accommodate expansion. Moreover, since the number of static sealing points is reduced, wear is decreased as well, which reduces the amount of maintenance required.
I have seen both processes, but I have never delved into the reasons behind them; I always thought that the centrifugation effects were different. Thanks for the explanation from the moderator.
I’ve learned it; although I know the process, I’m not sure why I understand it now. As the moderator mentioned, our process involves selecting one out of three options, after which it goes directly to the four-spin stage and then into the waste catalyst tank; the catalyst settles there while the flue gas proceeds to the flue gas critical nozzle. There have been no leaks in the equipment used in this process! !
Our process is the same as what you mentioned earlier. The advantage of using a waste catalyst tank is that the fine catalyst particles can settle in it, thereby reducing the concentration of these particles at the inlet to the four-rotor system. This reduces the amount of catalyst particles that reach the critical flow velocity nozzles, which is beneficial for the lifespan and performance of the four-rotor system. However, this does increase the workload related to equipment and maintenance, and wear and leakage are more likely to occur.