The present invention is generally directed to improved processes for the preparation of various phosphorus oxides and phosphoric acid. Phosphorus oxides prepared in accordance with the present invention include phosphorus (III) oxides (e.g., tetraphosphorus hexaoxide (P.sub.4O.sub.6)). Phosphorus (III) oxides such as P.sub.4O.sub.6 are useful products and are also useful as precursors in preparation of other products, including phosphorous acid (H.sub.3PO.sub.3) and other phosphorus-containing chemicals. Certain aspects of this invention are also directed to using various byproducts formed during P.sub.4O.sub.6 production as precursors for the formation of phosphoric acid (H.sub.3PO.sub.4) and P.sub.2O.sub.5. In particular, the present invention is directed to improved processes for the preparation of phosphorus (III) oxides (e.g., P.sub.4O.sub.6) suitable for use in the preparation of phospho-herbicides such N-(phosphonomethyl)glycine (glyphosate) and precursors thereof (e.g., N-(phosphonomethyl)iminodiacetic acid (PMIDA)). The present invention is thus further directed to preparation of these compounds.

The invention relates to a process for the combined recycling of phosphate and nitrogen from sewage sludge. The core task of the invention consists of the recycling of phosphorous from sewage sludge ash and the reaction of phosphorous with nitrogen from the vapors of the sewage sludge drying and the manure to form NP fertilizer diammonium phosphate.

Phosphorus pentoxide production with fluorine management includes collecting phosphorus from kiln off gas as phosphoric acid containing fluorine and reacting the fluorine in the phosphoric acid with reactive silica to yield fluorosilicic acid. The fluorosilicic acid is removed from the collected phosphoric acid. Fluorine management includes discharging from the kiln a residue containing processed agglomerates and heating the discharged, processed agglomerates and releasing fluorine therefrom. The released fluorine is reacted with reactive silica to yield fluorosilicic acid and the fluorosilicic acid is collected. Fluorine management includes forming a reducing kiln bed with feed agglomerates below a reducing freeboard. Kiln off gas is generated containing phosphorus in the form of elemental phosphorus a) oxidized outside of the kiln to phosphorus pentoxide and collected as phosphoric acid, b) collected as elemental phosphorus, or c) both.

Processes for enhancing filtration rate and/or clarification of phosphoric acid produced by the wet process and containing suspended insoluble particulates by adding to one or more stage of the wet process phosphoric acid production stream an effective amount of a reagent including polymeric microparticles characterized as being anionic or amphoteric and having a weight average molecular weight of greater than 60 Million daltons are provided herein.

A method and process system of comprehensively utilizing high-temperature slag balls exiting a rotary kiln in a kiln process for producing phosphoric acid, comprising a rotary kiln, a cooling device and a dryer for composite green pellets in a kiln process for producing phosphoric acid, wherein the cooling device comprises at least two cooling stages; the high-temperature slag balls are first conveyed to the cooling device, then the cooling device carries slag balls successively to multiple cooling stages by the movement of a trolley, each cooling stage introduces cold air for cooling, a part of the hot air after cooling is sent to the cavity of the rotary kiln, and the other part thereof is sent to the dryer for composite green pellets in the kiln process for producing phosphoric acid for drying.

A method and process system of comprehensively utilizing high-temperature slag balls exiting a rotary kiln in a kiln process for producing phosphoric acid, comprising a rotary kiln, a cooling device and a dryer for composite green pellets in a kiln process for producing phosphoric acid, wherein the cooling device comprises at least two cooling stages; the high-temperature slag balls are first conveyed to the cooling device, then the cooling device carries slag balls successively to multiple cooling stages by the movement of a trolley, each cooling stage introduces cold air for cooling, a part of the hot air after cooling is sent to the cavity of the rotary kiln, and the other part thereof is sent to the dryer for composite green pellets in the kiln process for producing phosphoric acid for drying.

Disclosed is a method for phosphorus absorption by hydration and fluorine recovery for a fume exiting a kiln in a kiln process for the production of phosphoric acid, comprising the following steps: a fume containing P.sub.2O.sub.5 and fluorine exiting a kiln is introduced into a hydration tower, the fume performs heat and mass transfer with the spraying liquid, with most of the phosphoric acid produced being absorbed into the spraying liquid; the phosphoric acid solution falling from the spraying finally enters the acid solution circulating and spraying system; the fume discharged from a fume outlet then passes through a phosphoric acid mist capturing tower and a mist removing and separating tower successively, such that the phosphoric acid mist entrained in the fume exiting the hydration tower is further captured.

Disclosed is a method for phosphorus absorption by hydration and fluorine recovery for a fume exiting a kiln in a kiln process for the production of phosphoric acid, comprising the following steps: a fume containing P.sub.2O.sub.5 and fluorine exiting a kiln is introduced into a hydration tower, the fume performs heat and mass transfer with the spraying liquid, with most of the phosphoric acid produced being absorbed into the spraying liquid; the phosphoric acid solution falling from the spraying finally enters the acid solution circulating and spraying system; the fume discharged from a fume outlet then passes through a phosphoric acid mist capturing tower and a mist removing and separating tower successively, such that the phosphoric acid mist entrained in the fume exiting the hydration tower is further captured.

A total heat energy recovery system for furnace-process phosphoric acid is disclosed by the present disclosure. The system comprises a phosphorus burning tower, a hydration tower, an absorption tower, a Venturi tube, a demister, an induced draft fan, a deaerator, an economizer, a dilute acid circulating tank, a phosphoric acid pump, and a feedwater pump. In consideration of the whole process system, fresh soft water is deoxidized after being heated by an upper head of the phosphorus burning tower and a gas guide tube, and the deoxidized water is then pumped into the economizer by a high-pressure pump to recover the heat of the hydration tower and then enters a steam pocket of the phosphorus burning tower to generate medium-high pressure steam. Therefore, unified recovery of the heat of a furnace-process phosphoric acid device is achieved, the medium-high pressure steam is generated, the effective energy is improved.

A total heat energy recovery system for furnace-process phosphoric acid is disclosed by the present disclosure. The system comprises a phosphorus burning tower, a hydration tower, an absorption tower, a Venturi tube, a demister, an induced draft fan, a deaerator, an economizer, a dilute acid circulating tank, a phosphoric acid pump, and a feedwater pump. In consideration of the whole process system, fresh soft water is deoxidized after being heated by an upper head of the phosphorus burning tower and a gas guide tube, and the deoxidized water is then pumped into the economizer by a high-pressure pump to recover the heat of the hydration tower and then enters a steam pocket of the phosphorus burning tower to generate medium-high pressure steam. Therefore, unified recovery of the heat of a furnace-process phosphoric acid device is achieved, the medium-high pressure steam is generated, the effective energy is improved.