【Weekly Topic】Discussion on Issues in the Installation of Sulfur Recovery Units
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In accordance with the requirements of the \"Emission Standards for Pollutants in the Petroleum Refining Industry\" GB31570-2015: \"The capacity of the sulfur recovery unit shall be such that, in the event of a failure in one such unit, acidic gases are not released into the acidic gas flare.\" The current situation is that sulfur recovery units are configured in multiple series; does this mean that the sulfur recovery capacity of each series must ensure that if one series stops operating, the remaining series must be able to maintain full capacity operation for the entire plant, rather than operating at reduced capacity? With this design, the maximum operating flexibility for sulfur recovery in this series is 140%, while under normal operation it operates at 70% capacity. Is it reasonable to set it this way?
It can meet the operational needs of the entire plant! Acidic gas emissions!
The typical design flexibility for sulfur recovery is 30–110%. Assuming that both units operate at 70% capacity under normal conditions, if one unit fails, the other takes over its function. To avoid overloading the single operating unit, the preceding units generally adopt measures to reduce their output.
Is it okay to increase the sulfur recovery scale to ensure that the load does not decrease ahead?
The device can be made as large as possible, but as its size increases, the minimum processing capacity also rises, making it difficult to maintain operation at low loads or during startup.
This problem certainly exists; then, how should the appropriate operational flexibility of the sulfur recovery unit be set?
Personal understanding: The lower limit of operational flexibility for sulfur units is generally set at 30%； When choosing the upper limit, consider two factors: one is the ability of the flexible upper limit to handle the volume of acidic gas generated when the sulfur content in the crude oil processed by the entire plant is at its highest level ； Another consideration is that when a single series stops operating, the upper limit of the remaining series can keep the entire plant at a low load level that is sufficient for operation ； The highest limit I’ve seen is 130%.
Firstly, I think the 140% you assumed doesn’t exist; a load factor of 30%-140% is not feasible from a design perspective. Raising the upper limit to 140% in numerical terms means that the lower limit could be 50% or 60%, resulting in an increase in scale. With two sets of sulfur, the problem you described exists and is difficult to resolve; if the scale is increased, it’s hard to maintain a low load, and it’s likely that one of the sets will not be able to operate continuously or will require supplemental fuel gas to function. If the sulfur production volume is high, having three columns provides more flexibility, though the investment required will be greater. For example, two sets of 10w can be divided into 8+8+4/5/6, 7+7+6/7, 8+6+6, and so on. But if the production capacity is low, for example 40,000 tons per year, then using three sets of 20,000 tons each is not economical; it also takes up more space. In my opinion, it’s better to use two sets with a capacity of 30,000 tons each. But three sets of 20,000 lines, I think that’s not entirely impossible either.
If the elastic range is too large, will it have any significant impact on the operation of the equipment and systems?
This question might be better answered by a designer, as it is a more specialized one. Forceful answer: lol: The range of flexibility is too wide, making it difficult to choose the appropriate device. Such as pumps, heat exchangers, tower internals, etc. To meet the high elastic limit, a larger margin is provided; during low-load operation, it is difficult for the moving equipment to remain operational, excessive heat transfer may occur, liquid leakage might happen inside the tower, and so on.
Forceful answer: The load is too low, making it difficult to control the wind; the reactor temperature cannot be maintained, the control valves fail to function properly, and there is leakage from the tower (copying from the moderator)