Catalyst Gauzes
JSC Krastsvetmet produces gauzes of the following types:
«NitroLok»
This type of catalyst gauze has been designed for plants requiring special strength and operating flexibility.
An extra strength of knitted structure is obtained due to reducing central loop and creating a more uniform structure, which results in 40% strength improving. The advantage of NitroLok over the other catalyst types is that it retains its elongation properties while being resistant to movement during the initial displacement stages. The catalyst gauze retains its developed structure. This is distinctly beneficial for the plants where unscheduled shutdowns accompanied by sharp pressure falls are possible.
This type of gauze is used in high and medium pressure plants.
Nitrolok can be supplied as single, pairs of gauzes, pads of 3 or more gauzes mounted in the burner.
NitroLok gauzes can be also used in prussic acid production plants.
«ProLok»
This structure type was specially designed for the low pressure plants. The use of standard types of knitted catalyst can allow NH3 by-pass and subsequent formation of ammonium nitrate. This is because of the open area of the catalyst. Thus in the woven type of gauzes it is about 65%, in traditional knitted ones it is about 74%, while the ProLok structure has been developed with a 55% reduced open area. Typically atmospheric pressure plants use between 3 and 4 catalyst gauzes although some reactors only use one gauze. It is therefore critical that the surface reaction is almost instantaneous to prevent the possibility of ammonia by-pass.
The application of ProLok Type catalyst gauze allows to reach this condition with optimal performance.
«HiLok»
The operating conditions in the high pressure nitric acid plants sufficiently differ from those of medium and low pressure. These conditions result in higher gas velocity, shorter campaign length, lower ammonia conversion and higher metal losses. HiLok has been designed to minimize the above negative factors in HP plants.
HiLok gauzes are usually effectively used in combination with Nitro-Lok gauzes. HiLok gause is mounted in the pack as first layer. Due to a deeper developed structure HiLok catalyst improves conversion by increasing gas interaction per a unit of catalytic reactor cross-sectional area. This is achieved by linear gas flow velocity reduction and a greater catalyst contact surface. Total metal losses depend on pressure, temperature and linear gas flow velocity. As HiLok gauze lowers gas velocity metal losses reduces too. Thus ammonium conversion into nitrogen oxides increases, with extended catalyst campaign.
