Sulphuric acid has become extremely important as it is used to make hundreds of compounds used by a wide range of industries. The process for producing sulphuric acid include the extraction of sulphur, the conversion of sulphur to sulphur dioxide, conversion of sulphur dioxide to sulphur trioxide and finally the conversion of the sulphur trioxide to sulphuric acid. During the conversion of sulphur dioxide to sulphur trioxide, a cylindrical vessel is used which acts as a fixed bed reactor known as a sulphuric acid converter. These converters usually consists of four separate beds of catalyst (Vanadium oxide on silica) which is in the form of small pellets.
Screening the converter catalyst is very important as dust and scale that accumulates on the catalyst increases the production costs and limits the plant's capacity due to an increased pressure drop. Bidvest TMS Industrial Services have recently acquired a new screening unit that allows the screening of the catalyst to take place at a faster rate, with reduced catalyst breakages, increased safety, reduced catalyst dust and an overall more efficient catalyst change turnaround.
The catalyst is vacuumed out of the converter using a 6 inch vacuum hose to reduce breakages. The catalyst is vacuumed into a 2 m3 cyclone separator with 100 micron PTFE filter bags under continues air pulsation for dust suppression. A flapper valve system continuously feeds the catalyst out of the cyclone at a rate of 6-8 m3/hour into the screening unit. The screening unit was designed to increase the screening rate and decrease catalyst breakages. This is achieved through the asymmetric linear vibratory screening mechanism that consist of a higher frequency at the top section of the unit to allow the catalyst to be spread faster and evenly across the screens and a lower frequency at the bottom section to prevent screen over chute. The polyurethane screens also decreases the catalyst breakages and noise levels of the process. Catalyst dust is extracted at the bottom of the screening unit by means of an ogre. The screening unit has an adjustable screening angle to allow for the optimum screening rate to be achieved with the required screened catalyst sizes. The unit separates the ceramic balls from the catalyst and the catalyst from the fines in one process.
The unit that was designed for Bidvest TMS Industrial Services by Jean Visser at Highpoint Vacuum allows the screening of catalyst to be carried out in one process with multiple advantages compared to conventional methods used. The unit is a compact, easy to move and setup system that enables Bidvest TMS Industrial Services to execute catalyst changes and screening requirements efficiently and productively. The unit is also used to screen a variety of other catalysts used in reactors and plat-formers. By continuously improving our technologies and methods used, we as Bidvest TMS industrial Services pride ourselves as leaders in the catalyst handling industry.