Hydrogen production from natural gas
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Our company plans to build a natural gas hydrogen production plant with a capacity of 10,000 m3/h. The gas supply pressure is 7.5–8 MPa; after being reduced to a pressure of 3.0 MPa, which is the appropriate pressure for the hydrogen production unit, the gas enters the conversion furnace. In other words, without a natural gas compressor, how can the hydrogen production volume be adjusted in a timely manner when there are fluctuations in the hydrogenation system? Does anyone with expertise have a good solution? I hope for your advice.
Well, reduce the processing volume in a timely manner
If the hydrogenation unit reduces its output significantly and the valve in the new hydrogen compressor circuit opens, pressure will build up in the PSA system. Is it too late to reduce the feed rate of the natural gas feedstock at this point?
It depends on how you look at it; the PSA system won’t suddenly get clogged, and if allowed, some of the hydrogen can be vented. Seeing that the pressure in the new hydrogen tank has increased, reduce the processing volume slightly – there’s still time.
Implement sequential control to increase the PSA pressure by closing the valve for natural gas feedstock intake
The PSA will not hold back pressure; if there is an excess of hydrogen, a vent valve on the hydrogen pipeline will open automatically
PSA and the feed gas are equipped with automatic or cascade control; meanwhile, when the hydrogen consumption during hydrogenation is too low, some of the hydrogen can be returned to the inlet of the converter to facilitate its operation
The processes here are: desulfurization – conversion – shift – PSA decarburization – PSA hydrogen extraction； I want to make the operation of the hydrogen production unit more flexible while minimizing hydrogen waste. It is capable of keeping up with the rapid adjustments in hydrogenation units. Adjusting the amount of feed natural gas after detecting an increase in pressure in the new hydrogen buffer tank results in regulatory lag.
Will the return of hydrogen to the converter cause significant fluctuations in the converter’s operation, and is there a limit on the amount of hydrogen that can be returned?
The impact on PSA shouldn’t be very significant; it’s likely to have a greater effect on the new hydrogen tank. In this case, there’s nothing else to do but monitor the pressure regulation of the new hydrogen tank
What concerns me more is that without a compressor, what will provide the power for catalyst sulfidation and reduction at the start of operation?