Catalyst Cleaning and Handling
On a few occasions plants will experience unplanned plant shutdowns or problems with a filter damage etc which can result in contamination on the gauzes in the form of base metals, ceramic or sometimes organic material such as carbon etc which can be removed by the following washing process:
1. Wash the catalyst in demineralised water.
2. Pickle in Hydrochloric Acid (20-30%) for approximately 2 hours (Time will be dependent on degree of contamination). On no account should aqua-regia be used i.e. HNO3/HCl mixture.
3. Wash in demineralised water.
4. If the catalyst has organic (oil) contamination it should be placed in a bath of solvent leg acetone).
5. Dry the gauzes.
6. Flame using a hydrogen torch (ensure that no oxygen mixes with the hydrogen).
Sometimes this may not be sufficient to achieve the required conversion efficiency and depending on the design of the gauze pack it could be possible to turn the pack over if the majority of the contamination is on the top gauzes.
Also, occasionally during abnormal operation holes in the gauzes can result from blow backs etc, and depending on the severity of these holes the gauzes can be patched using a similar material. Johnson Matthey will endeavour to provide customers with appropriate patches within 3 days and these patches can then be welded to the catalyst pack by hammer welding.