Regarding steam-sealed purging, what are the design temperatures and scheme settings for the plant’s flare network?
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To reduce pollution emissions during purging, it is required that purging be carried out in a closed system when the plant is shut down; that is, after steam purging, the liquid goes into a sealed underground sludge tank, while the gas phase is sent to a flare. The condensate in the underground sludge tank needs to be pumped to a dehydration unit in the sludge tank area. Have the underground sludge system and the above-ground flare system been designed to handle this condition of purging in a closed system during shutdown? For example: 1. The flare system is designed for a temperature of 250°C (usually 100°C). 2. The underground sewage oil system is designed for a maximum temperature of 250°C. 3. The tanks used for storing and transporting sewage oil are also designed for 250°C. If the above solutions cannot be implemented (for instance, if it’s not possible to select the right pumps, if there is no space for thermal expansion in the underground sewage oil pipelines, or if anti-corrosion measures cannot be applied, etc.), is it necessary to install additional flushing and cooling facilities on the flare system, such as coolers? How do those systems that require sealed flushing handle this situation?
Doesn’t this technology provider offer guidelines?
Go and check the Environmental Impact Assessment report and the approval document for the environmental impact assessment; the answers to the questions you raised should be available there, otherwise the assessment cannot be approved.
The torch line is to be designed for 200°C. The emergency pressure relief in the hydrogenation unit reactor can exceed this temperature; it was discussed previously to use a cooler after the safety valve before sending the fluid to the flare.
The hydrogenation unit releases pressure at the top of the high-pressure section, where it has already been cooled; the temperature there should be at most 100°C
When the old units were designed, such strict environmental requirements were not taken into account. We used to vent the oil back to the top of the tower and then blow it into the flare system; after 24 hours, we switched to venting it from the top of the tower. We didn’t consider whether the flare system could handle that amount of flow
A design temperature of 250 degrees Celsius for the storage tank is inappropriate; this is not done in such cases.
When entering the underground sludge oil system, different temperature requirements apply for the inlet of light and heavy sludge oil tanks. When gas enters the flare system, the temperature must take into account the limitations set by the inlet temperature of the gas holder compressor. In short, the delivery medium should be arranged according to the external system conditions of the device.
In many cases nowadays, when performing sealed purging, large amounts of steam from the system are directed into the flare system, which can easily lead to the formation of liquid pockets (where liquid accumulates at certain points and gradually blocks the pipes), resulting in blocked pathways and pressure buildup within the system! The separation of oil, gas, and liquid is not adequate!