Pyramid E&C offers cost-effective, small-scale modular hydrogen plants capable of producing hydrogen using natural gas and other hydrocarbon feedstock. The process scheme consists of a methane steam reformer and a sift conversion reactor.
The process comprises of following steps:
- Gas Treatment and Compression
- Shift Conversion
- Hydrogen Purification
Natural gas is pre-treated to remove liquids, water and acid gases. If battery limit pressure is low than feed gas is compressed and preheated in the waste heat section of the reformer. After preheating gas is feed to hydrogenator where the organic sulfur compounds are converted into H2S. H2S is removed by adsorption of it on solid bed scavenger. Purified hydrogen gas is used for hydrogenation of sulfur compounds.
Treated gas is prereformed in pre-reformer. Mixture of natural gas and steam is preheated in waste heat recovery section and sent to prereformer resulting in stable and mild operating conditions for steam reformer. Pre-reformed gases are further preheated and sent to main reformer. Here, conversion of hydrocarbons to hydrogen, carbon monoxide and carbon dioxide takes place over a reforming catalyst. Product gas from the reformer is cooled by producing steam before entering the shift converter.
CH4+H2O -> CO+3H2
CH4+2H2O -> CO2+4H2
The cooled gas from the reformer sent over the shift catalyst to lower the concentration of carbon monoxide in the gas and increase the yield of hydrogen. The water gas shift (WGS) reactor converts carbon mono oxide and steam to hydrogen and carbon dioxide.
The gas from shift converter is cooled further to ambient temperature before entering the PSA unit
High purity hydrogen product is obtained in Pressure Swing Adsorption (PSA) Unit. At high pressures off gases are adsorbed on adsorbent and pure H2 is obtained in main gas stream. Off-gases are released during low pressure cycle. The off-gases from the PSA unit are used in the reformer as fuel supplemented with natural gas fuel. In PSA unit the high purity can be easily reached at relatively low cost. Minimum four PSA columns are provided depending on capacity of the plant. The waste gas that normally contains a lot of combustible gases is sent to the reformer to be combusted and generate heat for the reforming.