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Steam reforming

The most common feedstock for the hydrogen production is natural gas other feedstocks as naphtha or LNG are also used.

The generation of hydrogen by steam reforming can be outlined as follows.

A hydrocarbon feedstock is treated and purified mainly from sulphur compounds and olefins, mixed with steam (molar ratio between steam and carbon can be between 2.5-3.2) and fed into a fired tubular reformer.

The reaction of steam reforming can be summarized as follows:

CH4 + H2O ‹—› 3H2 + CO

CO + H2O ‹—› H2 + CO2

The first reaction is strongly endothermic and it is necessary to heat the stream in a furnace in which are inserted a catalytic pipe where on catalyst happen the reaction.

The second reaction is exothermic and consist of one or more shift stages where the carbon monoxide is converted to carbon dioxide by catalyst to give carbon dioxide and hydrogen.

After the shift stage the gas, after recovering energy, is cooled at 25-30°C and purified in the PSA section the is shown in the enclosed supervision page

The Pressure Swing Adsorption purification unit work using three layers of adsorbents one for water (activated alumina) one for CH4 and CO2 (activated carbon) and final one for N2 and CO (molecular sieve). The PSA vessels number can be 3-6. The regeneration is made depressurizing and purging the vessels.

The off gas coming from the purification is fed to the furnaces burner to recovery energy.

To increase the performances of the plants can be added the pre-reformer section and secondary reformer section using oxygen.

To reduce the input of heat and to obtain an acceptable conversion rate a large heat recovery system is used.

The working temperature of the steam reforming is typically 815-840°C at the pressure of 18-30 bar.

From the steam reforming plant it is possible to recovery carbon dioxide using a hot potassium process.

The recovered carbon dioxide has a very high purity and the increasing of hydrogen yield pays the working cost of the recovery unit excluding the compression and liquefaction costs.

The main specification of the our steam reforming are: