5P Engineering - Crio & Eng

C.E.O. Aldo SalmoiraghiOur C.E.O. Mr. Aldo Salmoiraghi is at your disposal for any question you can have.

Please contact him at address: a.salmoiraghi@5pengineering.it

POX Partial oxidation unit

The most common feedstock for the hydrogen POX production is natural gas. The chemical mechanisms involved in the controlled oxidation of hydrocarbons are extremely complex.
The following transformations are considered in this case:

CH4 + 3/2O2 CO +2H2O
CO + H2O H2 + CO2
CH4 C(g) + 2H2

The first reaction is strongly exothermic and exentropic . It is virtually complete and also serves to reach the temperature required for the operation.
The second reaction depends on an equilibrium which shifts in the desired direction at low temperature that is incompatible with the partial oxidation that creates a high reaction temperature (1.100°C).

This effect is corrected by catalytic conversion of CO after having cooled the gas.

The third conversion favoured by the high temperature is the main side reaction. To a certain degree, the presence of CO2 and water helps to offset these harmful effects.
It is important to avoid the production of carbon black choosing the right O2/ CH4 ratio that corresponds to 2.5-2.7 volume ratio of air/ CH4 .
The catalyst used for this reaction is Nickel base.

One important parameter is the natural gas quality that can respect the following specifications :

  • Olefins contents less than 2%
  • Sulphur content less Than 20 ppm
  • Oil vapour free
  • Dew point less than –20°C

The approximate composition of the gas that must be purified is 40% N2, 40% H2 and 20% CO+CO2.

After the shift stage the gas is cooled at 25-30°C and purified in the VSA section.

The Vaccum 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 VSA vessels number can be 3. The regeneration is made depressurizing under vacuum and purging the vessels. The off gas coming from the purification is fed to the furnaces burner to recovery energy.

The main specification of the our POX plants are:

Production purity


99.5-99.9 %


> 10 ppm


> 10 ppm




Nominal Capacity of plant

50-200 Nmc/h


Yield Nmc CH4/Nmc H2



* excluding He, Ar