Discussion on the steam system of catalytic cracking units!
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I hope everyone can share the actual situation of their own devices for discussion; well, I’ll start by offering my own perspective first. Experience with catalytic steam systems I have worked on: 1. Steam generation section: Both the slurry tank and the waste heat boiler generate superheated steam at 1.0 MPa; the regenerator does not have any external heating facilities ； 2. Steam utilization section: The entire device uses 1.0 MPa superheated steam, with no staged usage. The turbine is a 1.0 MPa condensing type ； Stirring steam, lifting steam, and purging all use 1.0 MPa steam. Regarding the current situation, I think there are the following improvement measures: 1. The quality of the steam generated should be improved; currently, most factories produce steam at 3.5 MPa, and from an energy efficiency perspective, it is more economical to generate steam of higher quality. However, the various drum vessels need to be modified. 2. The turbine should be of back-pressure type, as it has low energy consumption. But the turbine needs to be replaced. 3. Use steam in a staged manner; some of the steam used for stripping and atomization does not require a pressure of 1.0 MPa. This allows the pressure of the 1.0 MPa steam to be reduced, the medium-pressure turbine can use less steam, and energy can be saved as well. 4. Install an upper flow control orifice plate on the distillation tower to prevent coking and reduce the amount of steam. If there is a diesel hydrogenation unit, the diesel stripping steam can be stopped. 5. Change the purge steam to industrial air for the valve.
With 300,000 tons of catalyst, the remaining boiler produces 6 cubic meters of steam; the two slurry steam generators produce 5 cubic meters each. Usually one of them is in use, while 20 cubic meters of steam are obtained from external sources. Some of the saturated steam is superheated in the superheating section of the remaining boiler to produce superheated steam for use in reactions (there is also distillation stripping steam). The turbine is supplied with superheated steam for power generation.
Our plant’s catalytic units are equipped with external heat extraction systems, internal heat extraction systems, and waste heat boilers. There are three steam drums, which exchange heat respectively with the external heat extraction system, the oil slurry, and the flue gas. The saturated steam from these three steam drums is then divided into two streams: one stream is sent to the internal heat extraction system, while the other stream goes to the waste heat boiler for superheating. The steam produced by us is medium-pressure steam at 3.5 MPA, which is used for the compressors and main fans. The steam at 1 MPA coming from the compressors and main fans is either fed into the pipeline network or used internally.
Our plant’s catalytic unit has a capacity of 500,000 units, and it is equipped with external heat extraction systems, waste heat boilers, startup boilers, oil slurry steam generators, etc.; each of these systems has its own steam drum. The steam we produce is medium-pressure steam at 3.5 MPA, which is used for backpressure turbines. The condensate, at 1 MPA, is fed into the low-pressure steam network.
Two units: 800,000 tons for catalytic cracking – 80 tons of heat extraction from outside – 20 tons of oil slurry – 30 tons remaining in the boiler – 10 kilograms of steam produced. One unit: 400,000 tons for catalytic cracking – 30 tons of heat extraction from outside – 10 tons of oil slurry – 10 tons remaining in the boiler – 10 kilograms of steam produced: lol
It primarily produces 3.5MPA steam, with 1.0MPA steam as a by-product.