Problems with the pressing machine
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We use a process for producing methanol from coke oven gas. In terms of design, there is a DN100 pipeline at the outlet of the coke press that leads directly to the gas holder through a self-regulating valve; the pipeline after the valve has a diameter of DN250. The self-regulating valve adjusts the outlet pressure of the compressor automatically, based on the pressure reading from the gauge at the outlet of the coke press. There is also a quick-shut valve at the inlet to the desulfurization unit; once interlock activation occurs, this quick-shut valve closes. Can this pipeline be used to return 37,000 NM3/h of gas to the gas holder without causing pressure buildup in the compressor? What is the maximum allowable flow rate for coke oven gas? Please ask fellow sailors for help.
What is the pressure at the compressor outlet? If 5 MPa can be achieved, it’s almost sufficient for a DN100 pipeline. The DN250 size behind the valve is a bit small; it should be at least DN350 or larger. It is also necessary to consider the overall configuration of the pipeline, such as the type of self-regulating valve and the length of the pipeline. In such a situation similar to direct venting, the flow rate can be very high, and normal flow rate calculations cannot be applied.
The outlet pressure of the compressor is 2.4 MPa, and that of the gas tank is 4000 Pa. Based on a rough calculation, the flow velocity is likely to exceed 50 m/s – is this within the allowable limits per the standards?
Bro, I personally think this design is not acceptable. In the event that the valve fails or there is internal leakage, it could wash away the water seal in the gas tank, allowing the tank to become connected to the atmosphere – which is extremely dangerous. Please be careful!
As I mentioned earlier, in situations similar to direct venting, the flow rate can be very high, and normal flow rate calculations cannot be applied. Values over 50 m/s are also possible. Connecting the pipeline behind the valve directly to the air receiver is better than connecting it directly to the compressor outlet, as it results in a shorter pipeline and easier management.
We are from Tianyi Design; there is no such pipeline. I’m not sure if your compressor has a final return line. Also, how is the quick-cut valve for desulfurization interlocked? If the valve used for desulfurization isn’t fully closed, then a DN250 pipe should be sufficient.
1. Compressors are generally designed as one in one, or four in one. It won’t reach the gas holder. 2. Determine the purpose of designing this pipeline. 3. Safety first; a pipeline flow rate of 50 m/s is not acceptable. 4. The operation of gas cabinets is unsafe; it is extremely dangerous
Thank you to the user above for the answer. This pipe is used to regulate the air supply volume of the compressor; there is a quick-cut valve for precision desulfurization, which closes simultaneously during the oxygen cutout sequence action, thereby maintaining the temperature and pressure in the system for precision desulfurization. Compressors also come in four-stage and single-stage types. But that’s how design institutes design things. I just don’t know whether, due to the rapid operation of the quick-cut valve, it’s not possible to stop the compressor in time; with the fluid flowing back to the inlet of the gas tank through this pipe at such a fast speed, could static electricity be generated? Can the compressor be shut down?
I think in the situation you described, it would be more appropriate to install an interlocked vent valve on the main pipe at the outlet of the coke oven gas compressor.
This design reduces the waste of feed gas, but it is not advisable from a safety perspective, nor is it necessary.
Going back to floor 8: we have also installed quick-cut valves for precise desulfurization after the compressor. We use external venting, with a vent pipe of DN150; they are activated via interlock, and the results are satisfactory.
Suggestions； Add a DN100 vent operation right after the quick cut valve. Consider putting it into use later.