Hydrogen production rate decreases
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Recently, at our company, the hydrogen production volume from 5,000 cubic meters of natural gas has decreased, while the consumption of natural gas has increased. We suspected that there was an error in the flow meter; after calibrating it, the deviation was found to be within normal limits. After thorough analysis, it was determined that the change was caused by alterations in the composition of the natural gas. A comparison of the natural gas components showed that the methane content in natural gas increased from 91% to 98%. An increase in methane content leads to a decrease in ethane and propane levels. The hydrogen production rate per unit volume is lower for methane compared to ethane and propane, and the difference is significant: 1 cubic meter of methane, when completely converted to steam, can produce 4 cubic meters of hydrogen, while 1 cubic meter of ethane, when completely converted, can produce 7 cubic meters of hydrogen, and 1 cubic meter of propane can produce 10 cubic meters of hydrogen. However, we are legally required not to change the composition of natural gas, so it cannot be altered.
It seems like the person upstairs said the exact opposite. Produce the same hydrogen. Methane has the lowest consumption. Therefore, as methane content increases, raw material consumption should decrease rather than increase. Personally, I think it’s the issue of a lower PSA yield that leads to increased raw material consumption.
The ideal natural gas for hydrogen production is one that consists entirely of methane.
Calculated on a volumetric flow basis, as the proportion of ethylene propylene in the feedstock decreases to produce the same amount of hydrogen, the volume of the feed gas needs to increase; however, on a weight basis, the amount of feedstock required is reduced.
CH4+2H2O=CO2+4H2; C2H6+4H2O=2CO2+7H2
If calculated by weight, 16 grams of methane produce 8 grams of hydrogen, while 30 grams of ethane produce 14 grams of hydrogen. Methane thus has a higher hydrogen production rate than ethane; therefore, when calculating by weight, a higher proportion of methane is present
We are billed based on traffic, so it’s rather disadvantageous for us
How accurate can you be in measuring the hydrogen content in the gas analyzed by PSA?
I think it’s a PSA issue; changes in the composition of the natural gas aren’t the fundamental problem. I’ve previously used natural gas rich in C2/C3 compounds for hydrogen production as well – it just has a higher calorific value, which allows for less fuel to be used, and it seems to have little impact on hydrogen production.
That is, for a given volume of raw material, the greater the carbon source, the higher the hydrogen production rate. The carbon source for methane is 1, ethane is 2, and propane is 3.