Phosphorus is one of the most important macronutrients in fertilizers. To cater for the worlds growing demand for fertilizers, producers all over the world expand their production capacity and modernise their existing processing facilities to enhance the effectiveness of their processes, e.g. the dehumidification of the production waste.
(ed. WoMaMarcel - 06/4/2017)
Extending the Filter Belt Service Life
As a rule, the up to 105°C hot phosphogypsum slurry is spread onto the belt with a cake thickness of about 30 mm and a moisture content of about 80%. In a continuous process, the vacuum belt filter dewaters the gypsum slurry down to a residual moisture content of 15 - 20%.
The producers regularly check that the target dryness is being maintained. If the residual moisture is too high, the respective equipment operator reduces the belt speed in order to increase the moisture being extracted under negative pressure. However, because the aim is to achieve the highest possible throughput of gypsum, the belts have to run at the maximum permissible speed for effective dewatering. The process therefore puts heavy demands on the mechanical, thermal and chemical resistance of the filter belt being used.
Product penetration through the belt in the seam zone is another challenge, as it can lead to irreparable damage to the vacuum pumps as well as destroy the filter belt through abrasion on its bottom side – an issue that may cause a several months downtime for vacuum belt filters.
The Vacubelt 3354 type filter belt offers a solution to this problem. The woven polyester belt is manufactures with a special version of GKDs patented PAD seam 5, which significantly reduces product penetration, as the PAD seam is extremely flat and ensures extra grip and easy handling for the company’s process belts.
In a hot melting procedure, a special pad is melted into the belt mesh and pressed together with specially formed seam staples. Hastelloy steel staples ensure the required corrosion resistance of the seams in such an aggressive environment. Thus, the special seam version helps to significantly extend the service life of the vacuum filter system.
Utilisation in all Fields of Fertilizer Production
Due to their versatility Vacubelt filter belts are used by the fertilizer industry in more than just phosphoric acid production. They also demonstrate their outstanding efficiency in the potash fertilizer sector in the dewatering of the salt solution. Here, rock salt is separated from the potassium chloride to be used for the fertilizer. High temperatures and corrosive media are characteristic of the process conditions the filter belts have to withstand during dewatering of the salt. Filter belts of the type Vacubelt 5060 with a pore size of 490 µm are deployed here because – also in this application – the single-layer construction excels through its longer service life and its optimal dewatering efficiency.