Phosphorus production methods and systems and methods for producing a reduction product
A phosphorus production method can include reducing feed containing phosphate ore and providing a silica ratio from 0.3 to 0.7 in a reaction chamber from 1250 to 1380° C. Less than 20% of the phosphate remains in the residue. Another phosphorus production method includes continuously moving a reducing bed through the reaction chamber with the feed agglomerates substantially stable while in the reducing bed. Reaction chamber temperature can be from 1250 to 1380° C. A phosphorus production system includes a barrier wall segmenting the reaction chamber into a reduction zone differentiated from a preheat zone. The bed floor is configured to move continuously from the preheat zone to the reduction zone during operation. A method for producing a reduction product includes exothermically oxidizing reduction/oxidation products in the reaction chamber, thereby adding heat to the reducing bed from the freeboard as a second heat source.
1 . A method for producing a reduction product comprising:
forming a reducing bed containing feed agglomerates in a reaction chamber by heating the feed agglomerates, the reaction chamber including:
a barrier wall segmenting the reaction chamber into a reduction zone differentiated from a preheat zone; and
one or more over-bed air and/or oxygen ports above the reducing bed in the reduction zone, but not in the preheat zone;
delivering over-bed air and/or oxygen to the reduction zone through the one or more ports, but not delivering over-bed air and not delivering over-bed oxygen to the preheat zone;
the feed agglomerates including a core initially containing an oxidizing agent and a reducing agent;
continuously moving the reducing bed through the reaction chamber with the feed agglomerates substantially stable while in the reducing bed;
maintaining a temperature in the reduction zone along at least a portion of the reducing bed partly by adding heat from a direct or indirect first heat source;
maintaining the temperature in the preheat zone by adding heat from an indirect third heat source;
generating gaseous products that enter a freeboard over the reducing bed from a reduction-oxidation reaction occurring in the reducing bed, the gaseous products containing a reduction product from reduction of the oxidizing agent and an incompletely oxidized oxidation product from oxidation of the reducing agent;
exothermically oxidizing the reduction product in the freeboard while still in the reduction zone and exothermically further oxidizing the incompletely oxidized oxidation product in the freeboard while still in the reduction zone, thereby adding heat to the reducing bed from the freeboard as a direct second heat source to reach the temperature in the reduction zone;
collecting oxidized reduction product and/or remaining, unoxidized reduction product, if any, from an off gas from the reaction chamber; and
removing from the reaction chamber a residue containing processed agglomerates.
2 . The method of claim 1 , wherein the reducing bed is formed on a rotating hearth-like bed floor in the reaction chamber.
3 . The method of claim 1 , wherein the feed agglomerates further include a protective coating on the core, the coating containing carbonaceous material particles.
4 . The method of claim 1 , wherein the reducing agent is carbon, the reduction-oxidation reaction is a carbo-thermal reduction reaction, the incompletely oxidized oxidation product is carbon monoxide, and the carbon monoxide is exothermically further oxidized to form carbon dioxide.
5 . The method of claim 4 , wherein the oxidizing agent is phosphate comprised by phosphate ore, the reduction product is phosphorus, and the phosphorus in the reaction chamber is exothermically oxidized to form phosphorus pentoxide.
6 . The method of claim 5 , wherein the core initially provides a formula weight ratio of silicon dioxide to calcium oxide plus magnesium oxide higher than 1.6.
7 . The method of claim 5 , wherein the heating of the feed agglomerates comprises heating the feed agglomerates at the reaction chamber temperature, the heating occurring under a reducing freeboard at least until after a carbo-thermal reduction reaction begins, which forms the reducing bed.
8 . The method of claim 5 , wherein the core initially provides a phosphate content of greater than 13 weight % calculated as P 2 O 5 .
9 . The method of claim 5 , wherein the temperature in the reaction chamber along at least the portion of the reducing bed ranges from 1250 to 1380° C. without exceeding 1380° C. in all of the reaction chamber.
10 . The method of claim 9 , wherein, for any reaction chamber temperatures exceeding 1180° C., the reducing bed is exposed to such temperatures for less than 60 minutes.
11 . The method of claim 9 , wherein the feed agglomerates are heated for 30 minutes to less than 60 minutes at the reaction chamber temperature.
12 . The method of claim 9 , further comprising melting at least a portion of the core in at least some of the agglomerates heated at the reaction chamber temperature.
13 . The method of claim 9 , wherein the temperature in all of the reaction chamber ranges from 1250 to 1380° C.
14 . The method of claim 13 , wherein the reaction chamber occupies the entirety of a space bounded by a roof, an inner sidewall, an outer sidewall, and a floor of a rotary hearth furnace.
15 . The method of claim 14 , wherein the reaction chamber is annular.
16 . The method of claim 9 , wherein the core initially provides a formula weight ratio of silicon dioxide to calcium oxide plus magnesium oxide ranging from 0.3 to 0.7.
17 . The method of claim 16 , wherein less than 20% of the phosphate initially in the feed agglomerates remains in the residue.
18 . The method of claim 16 , wherein the phosphate ore contains silicon dioxide and the core initially does not contain supplemental silicon dioxide in addition to the silicon dioxide in the phosphate ore.
19 . The method of claim 16 , wherein the processed agglomerates contain phosphate ore residue and calcium silicate and exhibit pozzolanic properties suitable for supplementary cementitious material at least when ground to a particle size of approximately 45 micrometers.
20 . A method for producing a reduction product comprising:
forming a reducing bed containing feed agglomerates in a reaction chamber by heating the feed agglomerates, the reaction chamber including:
a barrier wall segmenting the reaction chamber into a reduction zone differentiated from a preheat zone;
a bed floor at a bottom of the reaction chamber;
one or more direct-fired burners in the reduction zone, but not in the preheat zone;
one or more over-bed air and/or oxygen ports above the bed floor in the reduction zone, but not in the preheat zone; and
one or more indirect heating sources in the preheat zone;
the feed agglomerates including a core initially containing an oxidizing agent and a reducing agent;
continuously moving the reducing bed on the bed floor through the reaction chamber from the preheat zone to the reduction zone with the feed agglomerates substantially stable on the bed floor while in the reducing bed and at least while in the reduction zone;
maintaining a temperature in the reduction zone along at least a portion of the reducing bed partly by adding heat from the one or more direct-fired burners;
maintaining the temperature in the preheat zone by adding heat from the one or more indirect heating sources;
generating gaseous products that enter a freeboard over the reducing bed from a reduction-oxidation reaction occurring in the reducing bed, the gaseous products containing a reduction product from reduction of the oxidizing agent and an incompletely oxidized oxidation product from oxidation of the reducing agent;
exothermically oxidizing the reduction product in the freeboard while still in the reduction zone and exothermically further oxidizing the incompletely oxidized oxidation product in the freeboard while still in the reduction zone, thereby adding heat to the reducing bed from the freeboard as a direct second heat source to reach the temperature in the reduction zone;
collecting oxidized reduction product and/or remaining, unoxidized reduction product, if any, from an off gas from the reaction chamber; and
removing from the reaction chamber a residue containing processed agglomerates.
21 . The method of claim 20 , further comprising maintaining a reducing freeboard in the preheat zone during a carbo-thermal reduction reaction among feed agglomerates on the bed floor.
22 . The method of claim 20 , wherein the bed floor is a rotating bed floor.
23 . The method of claim 20 , wherein the one or more indirect heating sources comprise electric heating elements and/or radiant tube burners.
24 . The method of claim 20 , wherein:
the reaction chamber further comprises a second barrier wall further segmenting the reaction chamber into a cooling zone differentiated from the reduction zone; and
the method further comprises continuously moving the bed floor through the reaction chamber from the reduction zone to the cooling zone, the cooling zone lacking the direct-fired burners, the over-bed air and oxygen ports, and the indirect heating sources.
25 . The method of claim 24 , wherein:
the bed floor is a rotating bed floor and the reaction chamber further comprises a third barrier wall further segmenting the reaction chamber and differentiating the cooling zone from the preheat zone; and
the method further comprises continuously moving the bed floor through the reaction chamber from the cooling zone to the preheat zone.
26 . The method of claim 1 , wherein the oxidizing agent is not a metal oxide.