Hydrogen Testing

Hydrogen is widely used in cooking, water heating, space heating, electricity generation, welding and cutting, and the synthesis and purification of other chemical materials. Hydrogen is present in air with several contaminants. The most widely occuring contaminants in hydrogen are oxygen, argon, nitrogen along with traces of water vapor, electrolyte and solid particulates.

Hydrogen gas is an ideal gas for high capacity turbine generators. Efficiency of turbine generators is linked directly to hydrogen purity. Hence, continuous, highly accurate hydrogen monitoring is vital for generator efficiency, for generator safety and for lowering operating costs per megawatt.

Hydrogen is purified according to personal and industrial needs. Purified hydrogen can be obtained in a number of ways.

Scrubbers for Particulate and KOH Removal
Hydrogen gas can be purified from particulates and KOH by simply scrubbing and passing through a water column.

Catalytic Recombination Purifier to Remove O2 Impurity
In the process the hydrogen and oxygen gases are recombined in a ratio of 2:1. The process is accomplished at room temperature and as the percentage of oxygen impurity increases so does the rewuired catalyst temperature. The catalyst used are platinum group metals that are placed on alumina surface and these are contained in a section of pipe through which hydrogen gas flows.

Palladium Silver Membrane Purifier

Ultra pure hydrogen can be obtained by diffusion through palladium alloys. Paladium is extremely permeable to hydrogen. The process involves the following steps:

• Adsorption - The accumulation of solid, liquid or gases on the surface of a solid or liquid.
  
  
• Dissociation - The separation of an electrolyte into ions of opposite charges.
  
  
• Ionization - The formation of or separation into ions by heat, electrical discharge, radiation, or chemical reaction; electrolytic dissociation.
  
  
• Diffusion - The process whereby particles of liquids, gases, or solids intermingle as the result of their spontaneous movement caused by thermal agitation and in dissolved substances move from a region of higher to one of lower concentration.
  
  
• Reassociation - The formation of ions together.
  
  
• Desorption - The process of removing the adsorbed particles from the solid or liquid surface.

Operating conditions required for palladium alloy membranes include temperature of approximately 200 to 800°C and differential pressure across the membrane of 3 to 12 bar. This is a very attractive and the most expensive method for simultaneously removing water and oxygen from hydrogen.

Hydrogen Dryers for Removing Moisture

Water contamination of hydrogen can be reduced by:

• Coalescers - Designed to cause combining of smaller aerosols into larger droplets, susceptible to the effects of gravity. Small particles are removed by diffusion, larger one by interception mechanism and the largest sized particles are removed by direct inertial impacting.
  
  
• Refrigeration Dryers - These cool the gas and dry it by condensation to a low dew point. These dryers use electric motor compressors and refrigeration fluids and the working of the dryer is based upon Joule Thompson expansion scheme.
  
  
• Desiccant Dryer - These dryers absorb water vapor from gas by contact with a chemical substance. The most common desiccant used is Drierite. Using a desiccant the color changes when water vapor is absorbed and the desiccant is later dried by heating.