Method for mass production of phosphoric acid with rotary kiln

An improved method for mass producing phosphoric acid with a rotary kiln, comprising the following steps:

• (1) pretreating raw materials carbonaceous reductant, phosphate ore and silica respectively with a carbonaceous reductant pretreatment system, a phosphate ore pretreatment system and a silica pretreatment system;
• a process procedure of the carbonaceous reductant pretreating system comprises:
• crushing the carbonaceous reductant to below 30 mm in granularity by a single-stage crushing device, and then
• delivering the crushed material to a carbonaceous reductant intermediate bin which delivers the crushed material to an ore grinding device via a weighing and feeding device for grinding;
• after the ore grinding device grinds the fed material to a granularity meeting a process requirement, collecting the powder material by a combined dust collector comprised of a cyclone powder-collecting device and a pouch powder-collecting device;
• and
• delivering the powder material to the carbonaceous reductant powder storage bin;
• wherein hot air is replenished constantly via a configured hot air furnace during grinding so as to remove moisture entrained in the powder material;
• and/or,
• a process procedure of the phosphate ore pretreating system comprises:
• crushing the phosphate ore to below 30 mm in granularity by a single-stage crushing device;
• and then
• delivering the crushed material to a phosphate ore intermediate bin which delivers the crushed material to an ore grinding device via a weighing and feeding device for grinding;
• after the ore grinding device grinds the fed material to a granularity meeting a process requirement, collecting the powder material by a combined dust collector comprised of a cyclone powder-collecting device and a pouch powder-collecting device;
• and
• delivering the powder material to a homogenization silo;
• wherein hot air is replenished constantly via a configured hot air furnace during grinding so as to remove moisture entrained in the powder material;
• and/or,
• a process procedure of the silica pretreating system comprises:
• crushing silica to below 30 mm in granularity by a single-stage crushing device or a dual-stage one-closed-loop crushing device, and then
• delivering the crushed material to a silica intermediate bin which delivers the crushed material to an ore grinding device via a weighing and feeding device for grinding;
• after the ore grinding device grinds the fed material to a granularity meeting a process requirement, collecting the powder material by a combined dust collector comprised of a cyclone powder-collecting device and a pouch powder-collecting device;
• and
• delivering the powder material to a silica powder storage bin;
• wherein hot air is replenished constantly via a configured hot air furnace during grinding so as to remove moisture entrained in the powder material;
• (2) mixing the carbonaceous reductant powder, phosphate ore powder and silica powder obtained in step (1) and a binding agent according to a proportional requirement,
• feeding the mixed material into a pelleting machine for pelleting treatment, and
• obtaining inner balls upon completion of the pelleting;
• (3) mixing the carbonaceous reductant powder and silica power obtained in step (1) and a binding agent according to proportional requirements to obtain a cladding material;
• screening the inner balls obtained in step (2) to obtain inner balls with a granularity meeting the process requirement,
• feeding screened inner balls into another pelleting machine for cladding treatment,
• introducing the cladding material in said another pelleting machine;
• obtaining composite green pellets upon completion of the cladding treatment;
• delivering the composite green pellets into a dryer for drying and solidification to obtain the composite pellets;
• (4) introducing the composite pellets obtained in step (3) into a cavity of the rotary kiln;
• reducing the composite pellets in the rotary kiln by the carbonaceous reductant at a high temperature to generate kiln fume,
• wherein an outlet flue is arranged in a way that the fume exiting the kiln at the kiln tail of the rotary kiln does not deviate much in a movement direction upon entering the outlet flue, thereby preventing metaphosphoric acid in the fume exiting the kiln from generating centrifugal physical settlement at the tail of the rotary kiln so that the metaphosphoric acid in the kiln gas directly enters a subsequent hydration tower along with the fume exiting the kiln;
• (5) introducing the fume exiting the kiln containing P2O5 and fluorine into the hydration tower;
• bringing the fume exiting the kiln in sufficient contact with a concentrated phosphoric acid solution sprayed downwardly in a way of reverse-flow for mass transfer and heat transfer, wherein P2O5 in the fume is subjected to chemical reaction with water in the sprayed concentrated phosphoric acid solution to produce phosphoric acid.