In the recent times the refinery sector is facing a major challenge in coping up with the change in gasoline and diesel fuel specification, which is a trend that is set to continue. Moreover, the market for bottom of the barrel products has declined and given birth to the requirement of investing in the conversion processes. The changes within refineries to meet these demands, particularly investment in hydro-treating and hydro-cracking processes, have increased the requirement for volume and purity of hydrogen.
The latest approach adopted by the industry in order to sustain and confront the present situation is to maximise the recovery of hydrogen from refinery gas streams. This calls for huge investment in Hydrogen Purification Units or Hydrogen Gas Plants.
Hydrogen Gas Plants employs the well-known and widely accepted 'Steam Reforming Technology' for hydrogen generation. The commonly used refinery feedstocks (raw material required for any industrial process) are naphtha, natural gas and LPG. However, some alternative hydrocarbon feedstocks such as methanol are also considered at a large scale. Hydrogen Plants units basically operate according to PSA (Pressure Swing Adsorption) technology.
Hydrogen Gas Plant Process
As discussed earlier, the most commonly used method of hydrogen production is the steam reforming process. The main process consists of the reaction of steam with a hydrocarbon over a catalyst at around 750-800°C temperature, in order to form hydrogen and carbon oxides. The whole process starts with :-
- Purification of the raw material, in which
toxins, like, sulphur and chloride are removed ensuring maximum life
of the downstream steam reforming and other catalysts.
- Steam Reformation, is the next step which can
also be stated as the essence of the working process of a Hydrogen
Gas Plant involves the main hydrogen-producing reaction.
[There exists numerous process designs for the 'Steam Reforming Reaction'. The conventional design is 'High Pressure & High Temperature Process Design', which is basically used by refineries to generate Hydrogen. Another design is the 'Low Pressure Design, which is also rich in carbon-di-oxide and is primarily used for direct reduction plants.]
- High Temperature Shift and Low Temperature Shift,
the third step consists of the reaction of Carbon monoxide with the
steam in two phases, namely high temperature and low temperature.
This reaction results in carbon dioxide and additional hydrogen.
- The Purification Process, this is the final step which produces 99.99% product hydrogen and an-offgas by using Pressure Swing Absorption unit (PSA).