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11.Hydrogen Production & Utilisation - Coggle Diagram
11.Hydrogen Production & Utilisation
Hydrogen Production
Hydrogen is needed for the conversion processing of heavy petroleum fractions into lighter products and for removing sulphur, nitrogen and metals from many petroleum fractions.
Hydrogen Production (Old scheme)
Steam reforming to produce synthesis gas, a mixture of hydrogen and carbon monoxide.
Conversion of CO to CO² with steam. This is done in two stages, a hightemperature shift converter (HTSC) and a low-temperature shift converter (LTSC).
The hydrogen rich gas is purified by a CO² removal unit where a hot potassium carbonate or amine solution absorbs the CO².
A methanator converts the remaining CO and CO² into methane and water.
Hydrogen Production (Newer scheme)
Steam reforming to produce synthesis gas, a mixture of hydrogen and carbon monoxide.
Conversion of CO to CO2 with steam. This is done in one-stage shift converter.
A pressure swing adsorption (PSA) unit is used to selectively separate CO2 through membranes, thus purifying the hydrogen rich product gas stream.
Steam Reforming Reactions
The catalyst is nickel on alumina support.
The feed of light hydrocarbons, mainly methane, is fed to the steam reforming reactor ,tubes filled with a nickel catalyst passing through a furnace.
High-Temperature Shift (HTS) Converter
Temperature affects shift converter operation in two ways: a higher temperature in- creases the catalyst activity and the reaction proceeds closer to equilibrium.
Low-Temperature Shift Converter
The product gas from HTSC is routed to a boiler feed water pre-heater. The gas temperature is reduced to 230 °C (446 °F).
Most of the CO is converted
Methanation
The purpose of the methanator is to convert the residual CO and CO² to methane according to the following reactions
Pressure Swing Adsorption (PSA)
The reformed gas from the shift converter which contains 65–70 vol% hydrogen can be purified by adsorption instead of amine treatment and methanation. The process produces a higher purity hydrogen stream (99.9%).
