How are the trip values for the coal slurry and oxygen in water-coal slurry gasification set? What is the purpose of setting these two?

https://wenku.baidu.com/view/0b7d01287375a417866f8f54.html I’m not sure if it will be useful

I think the purpose of setting up interlocks is mainly for safety reasons: too low a slurry flow, too high an oxygen flow, and overheating of the gasifier can cause damage to the equipment. Here, interlocks have been set for the slurry flow rate and the oxygen-to-coal ratio. The interlock for the slurry flow rate is in place to prevent the high-pressure slurry pump from stopping operation. The oxygen-coal ratio interlock is not activated because the ash content of the raw coal varies too much, preventing it from meeting the requirements of the production process; as a result, the oxygen-coal ratio interlock is bypassed.

The interlocks for coal slurry and oxygen are indeed implemented from a safety perspective, with the aim of preventing safety accidents. There have been cases in some plants where explosions occurred due to issues related to coal slurry and oxygen; these incidents stemmed from a failure to fully understand the purpose of such interlocks, which should be carefully studied.

By the way, I checked the SIS system again today and saw that there is also a interlock related to oxygen levels; it’s meant to prevent low oxygen levels from causing excessive slag formation that could block the pipes

I asked the engineer today, and he said that another reason why the oxygen-coal ratio is not adjusted is that the flow rate of the high-pressure coal slurry pump can be unstable, especially during startup; the oxygen-coal ratio changes significantly in such situations, and if interlocks are used, it’s easy for the system to shut down unexpectedly. :lol

The trip interlock for the slurry pump can incorporate the pump operation signal. The reason for setting a low slurry flow threshold seems not to be to monitor whether the slurry pump trips; a high oxygen flow level is understandable, but it’s unclear why such a low threshold is set for oxygen flow. It’s also unknown whether there is any relationship between the thresholds for low oxygen flow and low slurry flow

So what are the considerations behind setting the low values for the oxygen and slurry flow rates? The off-load values are all below the load during feeding – is this due to fluctuations in the slurry flow rate?

Generally, when raising the pressure, if proper adjustment of the oxygen-to-coal ratio is not made, the ratio will be low; while shutdown occurs when the ratio is high. According to this explanation, operations must be quite unstable

The slurry pump operation signal is also a separate interlock; the disappearance of this signal will likewise trigger a shutdown of the gasifier. There are approximately 17 items that should directly trigger interlocks for water-coal slurry gasification SIS; this number increases if indirect trips are also taken into account. Regardless of which company is responsible for the water-coal slurry gasification, none of these interlocks will be missing in the SIS; it’s just that each unit has its own considerations and actual conditions, so not all of them will be installed. In principle, this is not allowed; it’s fine as long as nothing goes wrong. In the event of an accident, these missing chains will serve as pieces of evidence. The purpose of all interlock settings is basically to trigger actions from a safety perspective. My opinion on the low-low slurry flow interlock is as follows: When the slurry operates at a low flow rate, cavities may form within the slurry pipelines and the burner channels, which can lead to unstable pressure differences in these pipelines and burners. This increases the risk of gas from the furnace entering the slurry pipelines ； My view on the low oxygen flow interlock is that it serves to prevent the furnace temperature from dropping too low, which could lead to blockages at the slag outlet and potentially a risk of overpressure in the combustion chamber. As a main operator for gasification, it is essential to have a thorough understanding of the procedures for increasing or decreasing load, as well as for raising or lowering pressure – these are the most fundamental skills that one must possess. During load addition and reduction, the slurry flow rate is not as stable as the oxygen flow rate. If cascade automatic control for the oxygen-to-coal ratio is implemented, the oxygen flow rate will fluctuate in response to changes in the slurry flow rate, thereby destabilizing the entire system. Therefore, when increasing or decreasing the load, it is best not to use this device; consider using it once things have stabilized. The same applies to the oxygen-coal ratio interlock. At this time, although the workload for manual operation is relatively high, it is much more stable and safer to operate manually rather than using automatic control. During pressure adjustment operations, due to changes in the pressure difference at the burner, the oxygen flow entering the furnace decreases when pressure is increased and increases when pressure is decreased; therefore, it is important to remember to adjust the oxygen flow as well during these operations, otherwise excessive oxygen levels may occur or an emergency shutdown could be triggered. However, at no time shall the slurry flow interlock or the oxygen flow interlock be disabled; this is a safety red line