Seeking Technology For The Purification Of Chlorine Gas

A SpecialChem Client is seeking a technology for the purification of dry gaseous Chlorine to a minimum of 99.9%. The technological solution must be solvent-free.

Currently, the main production route for Chlorine is the following:

1. Electrolysis of brine in the so-called Chlor-Alkali process,
2. Drying of the gas,
3. Purification in 3 steps by liquefaction, cryogenic distillation and re-evaporation.

The 3-steps purification process is very energy intensive, and requires the use of solvents that SpecialChem Client wishes to remove from his manufacturing process as it implies storage management, waste treatment or exposure control.

The 97% to 99% incoming Chlorine dry gas only significant contamination is O₂ at a concentration of 1% to 3% in volume. It must be purified to a 99.9% grade. At least 98% of the Cl₂ present in the feed must be recovered.

Temperature and pressure can be adapted during the purification process to optimize the operation, but it is preferable if the maximum temperature anywhere in the process doesn’t exceed 100°C.

The solution must be very robust: compatible with chlorine chemistry and with a continuous industrial process at a flow rate of 15 tons/hour (typically).

The new solution will eventually be implemented as default in all chlorine production process lines of the SpecialChem Client, who manufactures 100 to 150 kilotons of chlorine per year within more than 2 production sites.

Gas separation by membrane has potentially several advantages compared to conventional purification processes, including reduced energy consumption and the absence of solvent management.

Purification of chlorine gas with membranes has been studied for more than 15 years and several scientific publications have been issued.

Various materials have been tested to form the membrane (including PTFE, glass or rubber) with some matrix modifications in order to meet the requirements. But no satisfactory solution has been found at this stage because of the lack of robustness / durability directly induced by the limited chemical resistance of the material employed in such an aggressive environment.

SpecialChem Client is interested in a technology that would design a suitable high performance membrane. For such a membrane the material must be proven to have:

• Sufficient durability (ideally 2 years), with cost consideration
• Selectivity to separate O₂ from Cl₂
• Permeability

The SpecialChem Client is not interested in Solvent extraction process as it could contaminate chlorine.

The SpecialChem Client is expecting solutions that could potentially be implemented in the mid-term (2-3 years). Sooner would be greatly appreciated.

The SpecialChem Client expects to replace a 3-steps purification process into a 1 (or 2) step. This should lead to a significant gain in overall operating costs. Elements supporting this would be appreciated.

• Concepts
• Proven concepts
• Ready to use solutions
• Partners

The SpecialChem Client has R&D laboratories and is ready to scale up a proven concept and develop an industrial solution.