Issues with catalyst startup
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During the catalytic start-up of heavy oil, during the fluidization phase of the two reactors in the reaction unit, the pressure in the settler is generally adjusted using stripping steam and pre-lift steam, and is controlled through butterfly valves and flare valves. Throughout this phase of preparing for feeding while the reactors are in a fluidized state, it is very difficult to maintain a stable differential pressure between the two reactors, as the fluctuations are quite large. Do you have any good methods to ensure a stable differential pressure between these two reactors?
The pressure in the settler at this stage should be controlled by the disc valve ahead of the fractionation tower; the flare valve should remain open, but it should not be used for regulation. There should be no problem under normal circumstances.
Pressure control scheme during the startup of the settler: 1. During drying, use a double-acting slide valve and the settler’s vent valve for control； 2. From the removal of the large blind flange until fuel injection, it is controlled by the top of the tower butterfly valve ； 3. After fuel injection, control is achieved using the flare valve or compressor speed.
Pressure control scheme during the startup of the settler: from the removal of the large blind plate until fuel injection, gas is introduced to start the air compressor and it operates at low speed to regulate the reaction pressure； Until fuel injection begins, it is controlled by the speed of the air compressor, so there is no need to use a flare!
In my opinion, if pressure control was satisfactory during the startup phase, then if problems arise during the preparation for fluidizing the two reactors, it is necessary to analyze what exactly is causing these fluctuations. It should be relatively easy to control the pressure in the regenerator using double-acting slide valves; it’s worth checking whether there are significant changes in the opening degree of these valves. In the settler, only steam is present, and if the steam pressure and temperature remain constant, then the steam flow rate should also be stable. At this stage, distillation should be in the process of heating through circulation within the tower. It’s possible that pressure fluctuations are caused by excessive water in the distillation system, which vaporizes and affects pressure. It would be advisable to increase the flow rate during the bypass circulation in the distillation section in order to remove the water. Additionally, it’s best to compare the pressures at the top of the settler, the top and bottom of the distillation tower, as well as the inlet pressure of the compressor, to determine which pressure rises first. Generally, there is a lag of around ten to several dozen seconds between these pressures, as gases passing through the various containers require some time to adjust.
What was said on the 2nd floor is correct. Designate a person specifically to adjust the butterfly valve at the top of the fractionation tower in order to control the reaction pressure. Until the valve is fully open.
Personal understanding: Under normal circumstances, the pressure in the regenerator is easy to control; it’s mainly the pressure in the settler that matters. First, do not turn on the air cooling or water cooling for the oil-gas line, as this increases the vapor phase and raises the temperature. Second: Use the small valve used for the flare valve to control it; do not use a large one. Third: Use steam in combination. As for butterfly valves, it’s fine to use them or not. Also, the fluidization needs to be stable; otherwise, the temperature will be unstable, and the vaporization expansion of steam will also be unstable. :)
The settler pressure should be controlled and adjusted via the fractionator disc valve and the flare vent valve. Be sure to adjust frequently, with small increments. Always monitor the differential pressure between the two devices. After fuel injection, it is controlled by a pneumatic press.
Before starting up and changing the catalyst, it is feasible to control the settler using butterfly valves and flare valves. It mainly depends on the medium present in the fractionation system at this time. If no gas has been introduced into the fractionation tower, then the pressure in the settler is primarily supplied by steam. If the pressure is high, it may be due to non-condensable gases entering the reaction system; a low pressure is also possible. In such cases, it is necessary to increase the amount of steam used in the reaction and adjust the butterfly valves in order to control the reaction pressure. If gas needs to be charged, it must be adjusted by controlling the gas charging valve and the flare.
There’s no good solution other than frequent and careful adjustment; usually, a dedicated person is assigned to adjust the pressure at the start of operation.
We are urging the resumption of work; before removing the large blind flange, it is necessary to load the agent and carry out pre-fluidization. Only after ensuring normal fluidization should the blind flange be removed! Pressure control during pre-fluidization: The regenerator is controlled using a double-acting slide valve, while the pressure in the settler must be adjusted by a dedicated person at the vent valves of the oil and gas pipelines; steam is used as an auxiliary means for adjustment indoors! After switching to the fractionation tower, oil and gas butterfly valves are generally used; it is essential to adjust them frequently, but in small increments! ! At this time, if the pressure difference between the two vessels fluctuates too much, it can lead to leakage of the fluid into the distillation tower, and that would be a problem! ! ! Be sure to seize this opportunity! ! This post was last edited by chengkang on 2009-4-27 17:48]