Candle Filters can be used in the dry process (electric furnace) described below; the phosphate rock is sintered or nodulized to facilitate escape of phosphorus vapours in the furnace and to prevent the blowing over of dust. After sintering, the material is sized and the fines retuned to the sintering machine. Coke and sand are added and the materials charged to the electric furnace. The temperature of the furnace is approximatively 2400 ºF.
The gas containing P and CO are withdrawn with a fan. In some plants, air is admitted here and P is burned directly to P2O5 with large wastage of CO. In the two step method gases are cooled and the condensed P is collected under water and transported in tank cars to consumption centres where it is burned. This method permits using CO as fuel.
REACTION: P4 + 5O2 – 2P2O5
P2O2 + 3H2O – 2H3PO4
H3PO4 and P2O5 mists are entrained from the downstream spraying tower, and possible solids entrained also.
Mist Load up to 70,000 mg/m3
1st stage irrigated meshpad (demister or co-knit coalescer)
2nd stage ‘Becofil’ Candle Filters Type F(2) TGW15 or B14W glass fibre in a PP or SS316L structure.
Check for chloride or fluoride attack – if so use de-ionized water for process or PP structure; Also other fibre material may be used, e.g. PP13.5 Polypropylene.
Product Loading Stations transfer Phosphorous to (railway) wagons, and this generates both P4 dust and P2O5 vapours, which escape into the atmosphere.
Phosphorous Rock and Phosphoric Acid particles come from the air around the product transportation & loading operation many times per day and also during the frequent wagon cleaning operation.
Localised operator pollution
‘Becoflex’ BF Series rotary brush scrubber in 316L Stainless Steel handling typically 600 – 1200 m3/hr.
The rotating brush acts as a fan impeller and draws the air from the source of the contamination into the fan volute. There the extraction air is sprayed with recirculated water at the spinning brush section. This scrubs out the mist and solid particles, with no risk of blockage.