Methods for phosphate processing

Abstract

Embodiments described herein provide systems and methods for phosphate processing systems having integrated subsystems, such as a phosphoric acid plant, a precipitation system, a crystallizer system, a flushing system, a granulation system, a pond water system, an organic matter removal system, and / or an exhaust treatment system. Such subsystems can be integrated with each other by using one or more output streams from one or more subsystems as one or more input streams for one or more subsystems. In some embodiments, for example, a phosphate processing system can produce phosphoric acid, a fertilizer containing struvite, a fertilizer using the struvite recovered, a composition containing magnesium or fluoride using the magnesium or fluoride recovered, and other components using phosphoric acid collected from phosphoric acid and gypsum compositions or using sludge collected from waste streams.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Application No. 62 / 916,584, filed on October 17, 2019, and entitled SYSTEMS AND METHODS FOR PHOSPHATE PROCESSING, which is hereby incorporated by reference for all purposes. For the United States of America, this application claims the benefit under 35 U.S.C. §119 of U.S. Application No. 62 / 916,584, filed on October 17, 2019, and entitled SYSTEMS AND METHODS FOR PHOSPHATE PROCESSING. Technical Field

[0003] Some embodiments of the present invention generally relate to systems and methods for processing phosphates, and more particularly to the integration of processing systems for phosphates. Background Art

[0004] Phosphoric acid can be produced by the "wet process," which involves reacting naturally occurring phosphate rock with an inorganic acid such as sulfuric acid, phosphoric acid, or nitric acid. In addition to phosphoric acid, a solid precipitate forms as a by-product. If sulfuric acid is used as the digesting acid, the precipitate will contain gypsum (primarily calcium sulfate) as its main component. Such a precipitate is known as "phosphogypsum."

[0005] Phosphoric acid is typically separated from the insoluble gypsum precipitate by filtration. The gypsum is removed as a filter cake. Considerable amounts of phosphoric acid can be trapped in the filter cake. This trapped phosphoric acid constitutes a significant portion of the phosphate yield lost during production.

[0006] Phosphate rock is typically produced by mining (i.e., removing phosphate ore from the ground) followed by a beneficiation process to separate sand and clay to remove impurities. Phosphate rock contains varying amounts of impurities. One impurity often found in phosphate rock is dolomite, a source of magnesium oxide (MgO). Magnesium is one of the least desirable impurities in phosphate rock. The presence of Mg causes difficulties in flotation and phosphoric acid production processes. For example, magnesium ions form precipitates in the reaction mixture. A reaction mixture containing a large amount of magnesium precipitate may clog the filter medium. The filtration rate of the reaction mixture used to recover the phosphoric acid product is also low. Separating phosphoric acid from such a reaction mixture is difficult and expensive.

[0007] It is generally desirable to avoid such low-grade phosphate rocks containing high magnesium contents. However, avoiding such low-grade phosphate rocks is not always feasible, and it is desirable to have economically viable methods for processing such low-grade phosphate rocks. Therefore, it is desirable to have cost-effective methods for using these low-grade phosphate rocks to produce useful end products, and more particularly, to not require first purifying these low-grade rocks to remove magnesium impurities prior to product production.

[0008] The wet process for the production of phosphoric acid generates large amounts of contaminated water. This contaminated water is typically discharged. This discharged water is often referred to as "pond water."

[0009] Pond water can also include water discharged from gypsum piles and other water used in and around phosphoric acid plants, freshwater fume scrubbers (e.g., for cleaning or washing), as well as phosphoric acid spills or leaks within the plant. Pond water is highly acidic. It contains a dilute mixture of phosphoric acid, sulfuric acid, and fluosilicic acid. Pond water is often saturated with gypsum and contains other ions found in phosphate rocks. The accumulation of pond water is harmful to the environment. It requires significant cost to treat the pond water before it can be safely discharged.

[0010] There is an existing method for treating pond water and / or for reclaiming valuable products from pond water. One of such methods is called double lime treatment. The method relates to adding a calcium compound (e.g., CaCO 3 , Ca (OH) 2 or CaO) to the pond water in two stages so that phosphate and other impurities are precipitated to produce purified water. Another existing method is reverse osmosis. Reverse osmosis relates to applying an external pressure that exceeds the osmotic pressure of the water component of the salt solution in contact with a semipermeable membrane. This forces some water to pass through the membrane in the opposite direction, while other components in the solution do not pass through the membrane, resulting in a stream of purified water and a stream of increased salt content that will be discarded or returned to the storage pond.

[0011] Ideally, collected pond water is continuously recycled into the phosphoric acid production plant for reuse, for example, as a source of water for phosphoric acid, for washing gypsum filter cake, for gas scrubbing, for slurrying produced gypsum, and for other purposes that do not require fresh water. An efficiently operated phosphoric acid plant achieves a balance between water input and water evaporation, so that virtually all contaminated water is directed for reuse within the plant. This eliminates the need to treat and discharge contaminated pond water as long as the plant continues to operate.

[0012] There is a need for methods to make the production of phosphoric acid more efficient, more environmentally sustainable and / or more economically viable. In particular, there is a need for efficient methods to process low-grade phosphate rocks that contain significant amounts of magnesium. Summary of the Invention

[0013] The present invention has many aspects. Some of these aspects exploit synergies between different processes that can be applied to process phosphate-containing materials to produce useful products. These synergies can be exploited individually or in any combination. The present invention can be applied to the processing of phosphate pond water, but can also be applied to the processing of phosphate sources.

[0014] The processes that can be synergistically combined as described herein include:

[0015] Production of phosphoric acid;

[0016] Production of granular fertilizers;

[0017] Removal of dissolved materials from pond water or other solutions by sedimentation;

[0018] crystallization of struvite, struvite analogs or other phosphorus-containing compounds;

[0019] Making fertilizers (in some embodiments by producing homogenous granules, for example, using the methods and compositions described in U.S. Patent No. 9,878,960, entitled “Slow and fast release fertilizer composition and methods for making same,” the entire contents of which are incorporated herein by reference); and / or

[0020] Mining of phosphate rock.

[0021] Some aspects of the present invention provide improvements to apparatus and methods for processing phosphate-containing materials, including:

[0022] Production of phosphoric acid;

[0023] Production of granular fertilizers;

[0024] Production of monoammonium phosphate (MAP), diammonium phosphate (DAP) and / or struvite;

[0025] Removal of dissolved materials from pond water or other solutions by sedimentation;

[0026] crystallization of struvite, struvite analogs or other magnesium phosphate-containing compounds;

[0027] Making fertilizers (in some embodiments by producing homogenous granules, for example, using the methods and compositions described in U.S. Patent No. 9,878,960, entitled “Slow and fast release fertilizer composition and methods for making same,” the entire contents of which are incorporated herein by reference); and / or

[0028] Mining of phosphate rock.

[0029] In some embodiments, struvite is produced in combination with processing phosphate rock to obtain phosphoric acid. Such embodiments can advantageously use phosphate rock with a high Mg content as a raw material. In such embodiments, a relatively high water content can be maintained in the process liquid being processed to produce phosphoric acid. This, in turn, facilitates the introduction / use of fresh water for flushing the gypsum filter cake to achieve increased phosphate production while maintaining a negative water balance in the process (i.e., the process tends to consume more water on input than it produces on output).

[0030] In some embodiments, phosphoric acid is produced in a system that also includes a granulation unit (which can, for example, produce a granular material containing struvite). Such embodiments can use sewage sludge, a byproduct of phosphoric acid production, as input to the granulation unit, and / or integrate the treatment of granulation unit dust discharge / scrubber water in the pond water treatment system clarifier with pond water treatment, and / or use the treated water stream for washing gypsum filter cake to increase phosphoric acid production. This can be accomplished while maintaining an overall negative water balance.

[0031] One aspect of the present invention provides a phosphate processing system. The phosphate processing system involves synergistically combining some or all of the above-described processes to increase final product recovery while reducing the environmental impact and costs associated with hazardous waste generated by fertilizer production. The phosphate processing system of the present invention ideally operates with a negative water balance to avoid handling and discharging contaminated pond water.

[0032] Some embodiments of the phosphate processing system produce phosphoric acid from low-grade phosphate rock. Low-grade phosphate rock contains high magnesium content, which is generally undesirable in phosphoric acid and fertilizer production. Embodiments of the system use such low-grade phosphate rock to produce phosphoric acid. Increased water input can be used in phosphoric acid production to produce more dilute phosphoric acid. The dilute phosphoric acid product alleviates some of the challenges surrounding filtering the reaction mixture in the presence of magnesium precipitates. Embodiments of the phosphate processing system are directed to producing struvite-based fertilizers from the dilute phosphoric acid product. The magnesium contained in the low-grade phosphate rock can be used as a magnesium source in a fertilizer pelletizing process. Excess water contained in the dilute phosphoric acid product can be used as a water source in the fertilizer pelletizing process. The fertilizer pelletizing process can be directed to the production of struvite-containing fertilizers.

[0033] Some embodiments of phosphate processing systems relate to improving the recovery of phosphoric acid from byproducts. One process for recovering phosphoric acid begins by rinsing or washing the gypsum filter cake produced by separating the gypsum byproduct from the phosphoric acid. In some embodiments, the gypsum filter cake is rinsed with fresh water to recover phosphoric acid trapped in the filter cake. In some embodiments, the gypsum filter cake is rinsed with treated water. The treated water can be water purified from pond water. Pond water collects excess water discharged from a phosphoric acid plant. The pond water purification process produces a purified water stream and a sludge stream containing phosphate as a byproduct. Some embodiments involve recycling the sludge to the phosphoric acid plant for recovery of phosphoric acid trapped in the sludge.

[0034] Some embodiments of the phosphate processing system relate to combining an exhaust treatment system with a phosphoric acid plant and a granulation system. The exhaust treatment system includes a process for removing solid particles and vapors generated during the granulation process. The removed solid particles can be recovered and recycled for the granulation process. Alternatively, the removed solid particles can be crystallized to recover phosphorus, for example in the form of a phosphate-containing product such as struvite. The struvite can be fed to the granulation system for the manufacture of a struvite-based fertilizer.

[0035] In some embodiments, a method for producing phosphoric acid is provided, the method comprising receiving phosphate sludge from a phosphogypsum processing system; processing the sludge in a phosphoric acid plant to produce phosphoric acid; and optionally producing a composition having phosphoric acid and magnesium above a threshold value.

[0036] In some embodiments, a method for producing phosphoric acid and struvite is provided, the method comprising receiving a phosphate source comprising magnesium; processing the phosphate source; producing phosphoric acid from the phosphate source; and crystallizing struvite using magnesium from the phosphate source.

[0037] In some embodiments, a method for producing phosphoric acid and struvite is provided, the method comprising receiving a phosphate source comprising magnesium; processing the phosphate source to produce phosphoric acid; and pelletizing a struvite-containing fertilizer using the magnesium.

[0038] In some embodiments, a method for crystallizing struvite is provided, the method comprising receiving organic waste comprising a phosphate-containing material; dissolving phosphate from the organic waste using partially treated pond water; removing organic matter from the organophosphate-containing material to form a phosphate-containing solution; and crystallizing struvite using the phosphate-containing solution.

[0039] In some embodiments, a method for pelletizing a struvite-containing fertilizer is provided, comprising receiving an effluent from a precipitated phosphorus-containing solution; crystallizing struvite from the effluent; receiving phosphoric acid from a phosphoric acid plant; and pelletizing the struvite-containing fertilizer using the struvite and the phosphoric acid.

[0040] In some embodiments, a method for separating phosphoric acid from a gypsum-containing composition is provided, the method comprising receiving an aqueous phosphate solution recovered from treated phosphogypsum pond water having a phosphate content below a threshold value; flushing the gypsum-containing composition with the aqueous phosphate solution to produce an output stream; and collecting the phosphoric acid from the output stream.

[0041] In some embodiments, a method for extracting phosphate from organic waste is provided, the method using partially treated phosphogypsum pond water and using it to crystallize struvite.

[0042] In some embodiments, a method for pelletizing to produce fertilizer is provided, the method comprising receiving phosphoric acid produced as a byproduct from sludge produced when treating phosphogypsum pond water.

[0043] In some embodiments, methods are provided for concentrating a stream using membranes for nanofiltration or reverse osmosis to provide an output stream concentrated in one or more components for use in the system.

[0044] Other aspects and embodiments will become apparent by reference to the accompanying drawings and by study of the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] The embodiments are illustrated in the figures of the accompanying drawings. It is intended that the embodiments and figures disclosed herein be considered illustrative rather than restrictive.

[0046] Embodiments will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0047] Figure 1 is a schematic diagram of an example phosphate processing system according to some embodiments; and

[0048] Figure 2 is a schematic diagram of an example phosphate processing system, according to some embodiments.

[0049] Figure 3 It shows Figure 2 Schematic diagram of selected processes in an example phosphate processing system.

[0050] Figure 4 It shows Figure 2 Schematic diagram of selected processes in an example phosphate processing system.

[0051] Figure 5 It shows Figure 2 Schematic diagram of selected processes in an example phosphate processing system.

[0052] Figure 6 It shows Figure 2Schematic diagram of selected processes in an example phosphate processing system.

[0053] Figure 7 It shows Figure 2 Schematic diagram of selected processes in an example phosphate processing system. Detailed Description of the Invention

[0055] Throughout the following description, specific details are set forth to provide a more thorough understanding to those skilled in the art. Accordingly, the description and drawings are to be regarded in an illustrative rather than a restrictive sense.

[0056] In some embodiments, an integrated system for processing phosphate is provided that includes one or more component subsystems. This disclosure describes example integrated systems in a manner that explains the various synergies and improvements to be described. However, some of the inventions described herein can be implemented using only one or more portions of the described integrated systems.

[0057] In some embodiments, certain component subsystems may be omitted. In some embodiments, certain other component subsystems may be included. In some embodiments, subsystems may be arranged to be related to each other, integrated, and / or selected in different ways.

[0058] For example, an integrated system for processing phosphates may include some or all of the following:

[0059] systems for producing phosphoric acid (e.g. from phosphate rock, phosphate pond water, wastewater, etc.),

[0060] systems for the production of gypsum (e.g. as a waste stream or as a precipitate in the production of phosphoric acid),

[0061] Systems for precipitating materials (e.g., for collecting phosphate-containing materials and / or other materials from pond water, process water, wastewater, or other sources),

[0062] systems for flushing materials (e.g., flushing gypsum produced as a by-product of the reaction between phosphate rock and sulfuric acid in a phosphoric acid reactor to collect the associated phosphoric acid),

[0063] crystallizers for crystallizing compounds (e.g., struvite crystallization from input sources such as: pond water, process water, wastewater, exhaust gas streams from exhaust gas scrubber treatment, from fertilizer granulation or co-granulation or phosphoric acid production),

[0064] Systems for granulating or co-granulating materials (e.g. to produce fertilizers using phosphoric acid and other materials),

[0065] • A combination of any two or more of these subsystems or other systems.

[0066] These and other systems can be integrated in various ways, for example, by using the output of one (or some) system as an input to other systems. Such integration can help reduce or mitigate the environmental impacts that may result from mining phosphate rock, handling phosphates, processing phosphates, producing fertilizers from phosphate-containing materials, and other industrial processes. For example, integration can reduce the amount of freshwater used or contaminated by reusing wastewater output from some subsystems as input to other subsystems.

[0067] Where appropriate, integration can include using output streams from one subsystem as input streams in other subsystems. In some embodiments, one or more subsystems of the phosphate processing system mitigate the environmental impact of the phosphoric acid plant by reusing one or more constituent components of its output streams (e.g., struvite, phosphorus, phosphates, phosphoric acid, magnesium, fluoride, gypsum, organic materials, water) and / or by reducing the amount or concentration of phosphorus-containing materials in its output streams (e.g., mitigating the impact of any output stream produced by the phosphoric acid plant that has a high concentration of phosphoric acid).

[0068] Throughout this description, "stream" means a flow of material. A subsystem may receive one or more streams as input and may produce one or more streams as output. A stream may carry matter in any state. For example, a flow of any of the following materials may be referred to as a "stream": phosphoric acid, phosphate rock, phosphate rock immersed in solution, gypsum with phosphoric acid associated therewith, effluent, treated or partially treated wastewater or process water, acidic solution, slurry, sludge, co-granulated composition, fines, desiccant, fertilizer, organic waste stream (manure, food waste, biomass, etc.), etc.

[0069] Throughout this description, the term "co-granulation" includes the production of homogeneous granules, and "co-granulated" materials or compositions include homogeneous granules. Homogeneous granules can be granules or compositions that are homogeneous, substantially homogeneous, or homogeneous with respect to one or more constituent components (e.g., gypsum, struvite, magnesium, fluoride, etc.).

[0070] Figure 1 is a schematic diagram of an example phosphate processing system 100 according to some embodiments. As shown, phosphate processing system 100 includes a phosphoric acid plant 110, a precipitation system 120 (in some embodiments, a treatment system), a crystallizer system 130, a rinse system 140, a pelletizing system 150, a pond water system 160, an organics removal system 170, and an exhaust gas treatment system 180. As described above, one or more of these subsystems may be optionally omitted and / or one or more other systems may be optionally included.

[0071] Figure 1Example paths are shown for conveying streams output by systems included in the phosphate processing system 100 to inputs of systems included in the phosphate processing system 100 (eg, to the same system, such as in a feedback loop; to a different system).

[0072] Figure 2 is a schematic diagram of an example phosphate processing system 100, according to some embodiments. Phosphate processing system 100 includes a phosphoric acid plant 110, a precipitation system 120, a crystallizer system 130, a gypsum flushing system 140, a granulation system 150, pond water (or process water / cooling water system) (e.g., an aqueous phosphate solution), an organics removal system 170, and / or an exhaust gas treatment system 180. In other embodiments, one or more systems and / or steps are omitted from and / or added to phosphate processing system 100.

[0073] Figures 3 to 7 Detailed depiction of selected synergies within the phosphate processing system 100. The phosphate processing system 100 relies on a synergistic combination of processes to provide one or more of the following:

[0074] Production of phosphoric acid and / or fertilizers from low-grade phosphate rock containing high levels of magnesium, with sufficiently high yield and purity of the final product;

[0075] Recovery of struvite from crystallization of reaction by-products and / or other waste products generated within the plant for use in a pelletizing process to produce struvite-based fertilizers;

[0076] Increase phosphoric acid production by recycling by-products from various streams into the phosphoric acid plant; and

[0077] Maintain a negative water balance within the device.

[0078] Reference Figure 3 , one embodiment of the phosphate processing system 100 combines the phosphoric acid plant 110 with the granulation system 150 to produce a fertilizer product 152. In some embodiments, low-grade phosphate rock 116 is used as a raw material for producing phosphoric acid 112. The low-grade phosphate rock 116 may contain elevated amounts of dolomite (MgO) (and / or other magnesium sources). Magnesium is generally considered one of the most undesirable impurities in phosphoric acid production. For example, elevated magnesium content increases the viscosity of the liquid phase in the reaction medium and reduces the kinetics and crystal growth of gypsum. It also promotes the formation of insoluble complex mineral phases, which can lead to equipment fouling problems and significant losses of phosphorus.

[0079] To alleviate these problems, a more dilute phosphoric acid product 112 having a higher water content can be produced. The more dilute phosphoric acid product 112 can be produced, for example, by utilizing increased water input or a reduced evaporation concentration of the phosphoric acid product 112. The increased water input can come from any suitable source, such as undried phosphate rock, wet grinding of phosphate rock, use of dilute sulfuric acid, or input of fresh or processed water.

[0080] The dilute phosphoric acid product 112 can be supplied as a feedstock to a reactor or granulator for crystallization of struvite, another magnesium-containing material (eg, MAP or DAP), or a mixture thereof.

[0081] Struvite is a compound having the formula: NH4MgPO4·6H2O. Crystallizing struvite from the dilute phosphoric acid product removes magnesium. Crystallizing struvite from the dilute phosphoric acid product also removes water, which increases the concentration of the dilute phosphoric acid product 112. Producing more dilute phosphoric acid (e.g., less than 54 wt% PO5) can facilitate the use of lower-grade phosphate ores. Using more dilute phosphoric acid to form struvite helps the overall process have a negative or neutral water balance (despite providing more dilute phosphoric acid) because water is consumed in the production of struvite. Providing an overall process with a negative or neutral water balance can advantageously reduce or eliminate the production of wastewater and / or the need to treat the wastewater.

[0082] In cases where phosphoric acid 112 contains a significant amount of Mg, the Mg in phosphoric acid 112 can contribute to the Mg required for struvite production (and thus reduce the need for other Mg sources).

[0083] In some embodiments, phosphoric acid 112 contains greater than 0.5%, greater than 1%, greater than 3%, or greater than 5% MgO. In some embodiments, phosphoric acid 112 contains Mg at a concentration such that the molar ratio of Mg:P in phosphoric acid 112 is in the range of 1:25 to 1:2, or 1:7 to 1:2, or 1:6 to 1:3, or the amount of Mg is high enough such that the molar ratio of Mg:P in phosphoric acid 112 is greater than 1:15, or 1:7, or 1:5, or 1:4.

[0084] The resulting struvite can be used, for example, in the production of fertilizers. Figure 1 The processing system can use the magnesium in low-grade phosphate rock 116 as a source of magnesium in fertilizer while avoiding the problems typically caused by excessive magnesium.

[0085] In some embodiments, granulation system 150 receives the supply of ammonia (for example, as gas or cryogenic liquid) and extra magnesium source. Phosphoric acid 112 can be sprayed into the drum wherein spraying ammonia. Extra magnesium can be added as powder or slurry of magnesium source. Phosphoric acid 112 and the Mg comprised in ammonia and phosphoric acid 112 and extra Mg react to produce struvite and / or other compounds comprising ammonium, phosphate and magnesium. Optionally, some ammonia can contact with phosphoric acid 112 before phosphoric acid 112 is introduced into granulator. This neutralizes or partially neutralizes phosphoric acid 112.

[0086] When the granulator is running, solids can be separated and classified by size. Solids within a desired size range can be removed (for example, for use as fertilizer or fertilizer components). Fines can be recycled back to the granulator. Solid particles larger than the desired size range can be crushed and recycled back to the granulator.

[0087] Figure 4 An embodiment of a phosphate processing system 100 is shown that incorporates a flushing system 140 with Figure 3 The synergistic effect (i.e., the combination of phosphoric acid plant 110 and granulation system 150) is combined to produce fertilizer product 152. A flushing system 140 operates to flush gypsum filter cake 118 generated during the filtration of the products of phosphoric acid production (i.e., phosphoric acid 112 and gypsum byproduct). Gypsum filter cake 118 contains trapped phosphoric acid. Flushing gypsum filter cake 118 recovers the trapped phosphoric acid. The flushing water, mixed with the phosphoric acid, can be returned to the phosphoric acid plant 110, where it can be recovered. The flushing water helps keep the process liquid in the phosphoric acid plant sufficiently dilute to avoid at least some of the problems described above.

[0088] In some embodiments, fresh water is directed to a flushing system 140 to wash the gypsum filter cake 118. It is generally undesirable to introduce fresh water further into the phosphoric acid plant due to the need to further treat or discharge any excess contaminated water from the plant. However, in embodiments where it is desired to produce a dilute phosphoric acid product 112 (e.g., Figure 3 As shown in the production of struvite-based fertilizers using low-grade phosphate rock, the introduction of fresh water increases the production of phosphoric acid while maintaining an overall negative water balance within the plant.

[0089] In some embodiments, the flushing system 140 flushes the gypsum filter cake 118 in several stages. The flushing system can be a countercurrent flushing system, in which the gypsum filter cake 118 is flushed two or more times with water that has been used in other stages of the flushing system 140, and finally with fresh water. For example, if the flushing system 140 has four stages, fresh water can be supplied in the fourth stage to flush the gypsum filter cake 118, the water can be collected and supplied in the third stage to flush the gypsum filter cake 118, the water can be collected again and supplied in the second stage to flush the gypsum filter cake 118, and the water can be collected again and supplied in the first stage to flush the gypsum filter cake 118. The flushing water (now containing phosphoric acid that has been washed out of the gypsum filter cake 118) can then be returned to the phosphoric acid plant 110 and / or mixed into the phosphoric acid 112.

[0090] When fresh water is used to flush gypsum filter cake 118, significantly more phosphoric acid trapped in gypsum filter cake 118 can be captured than if pond water, which already contains a significant amount of phosphate, were used for flushing. However, where flushing system 140 is included in a system that includes struvite production (e.g., in pelletizing system 150), the flushing water can be consumed in struvite production and thus produce no (or less) water that requires treatment before it can be released into the environment.

[0091] Figure 5 Another example process combination for improving phosphoric acid recovery is shown. When fluoride, phosphate, and gypsum are precipitated from pond water in precipitation system 120, a precipitated solids stream (i.e., sludge 124) is produced as a byproduct. Sludge 124 may include a mixture of phosphate, precipitated impurities, unreacted calcium compounds, and water. Sludge 124 is recycled to phosphoric acid plant 110 for use in phosphoric acid production, thereby increasing the overall yield of phosphoric acid in its production.

[0092] In some embodiments, sludge 124 is produced in a multi-stage process, wherein different stages produce sludges having different compositions. Sludge 124 can be selected from sludges having a desired composition for recycling to phosphoric acid plant 110. For example, sludge 124 can be selected to contain more phosphate than other sludges that can be obtained in a multi-stage precipitation process and / or sludge 124 can be selected to contain less fluoride than other sludges that can be obtained in a multi-stage precipitation process.

[0093] Collecting and recycling the phosphate-containing sludge 124 may increase the production of phosphoric acid and / or fertilizer for a given input of phosphate rock.

[0094] like Figure 6 As shown, another aspect of the present invention provides a phosphate processing system 100 that integrates a pond water system 160 and a precipitation system 120 with a phosphate processing system 100. Figure 4 The synergistic effect (i.e., the flushing system 140 is combined with the phosphoric acid plant 110 and the granulation system 150) is combined to produce fertilizer 152. In this embodiment, the treated water is directed to the flushing system 140 to wash the gypsum filter cake 118 (with the gypsum filter cake 118). Figure 4 The implementation scheme using fresh water varies.

[0095] Figure 6 The process uses contaminated water (i.e., pond water) discharged from phosphoric acid production at phosphoric acid plant 110. The pond water is purified in precipitation system 120 (or first in reverse osmosis (RO) and / or nanofiltration (NF) system 162 and then purified in precipitation system 120). The purified water can be used, for example, to rinse gypsum filter cake 118 to recover retained phosphoric acid 112. This increases the yield of phosphoric acid 112 that is input to granulation system 150 for fertilizer production.

[0096] Treated water 121 may be used for a variety of purposes, including as rinse water supplied to flush system 140 , as water used to dilute phosphoric acid 112 , and / or discharged to the environment.

[0097] By treating pond water (e.g. Figure 6 ) and recycling of sludge 124 (e.g. Figure 5 (shown) combination, which can consume pond water while leaving a reduced amount of sludge, thereby alleviating the significant environmental problems caused by pond water. For example, instead of increasing the amount of pond water associated with phosphoric acid plant 110, Figure 5 and Figure 6 The combined elements of the apparatus can, over time, reduce the amount of pond water associated with the phosphoric acid plant 110. This can provide significant environmental benefits, as pond water is typically highly acidic and presents disposal issues.

[0098] Figure 7 The exhaust gas treatment system 180 is shown in combination with the phosphoric acid plant 110 and the granulation system 150. The exhaust gas treatment system 180 includes one or more processes configured to remove dust generated during fertilizer granulation. One example of such a process is the use of a scrubber. For example, a wet scrubber can be used to dissolve or suspend dust in water and recover the dust as a low concentration solution or suspension in water. The scrubber solution or suspension contains fines 182. In some embodiments, the fines 182 are crystallized in a crystallizer to recover phosphorus, for example, in the form of a product 132 containing phosphates. One such by-product may be struvite. In some embodiments, the fines 182 are recycled to the granulation system 150. The fines 182 may contain source material that can be used in the granulation process.

[0099] Examples of source materials that can be recovered from the fines 182 include urea and ammonium nitrate. The fines 182 can first be dehydrated in an evaporation step 184 and then fed to a mixing device (e.g., a kneader mill 186) in fertilizer granulation.

[0100] Figure 2 Various synergistic effects are shown. Figure 2 Will Figures 3 to 7 The various synergistic effects described in are combined in a phosphate processing plant. Figure 2 Also included in phosphate processing plants Figures 3 to 7 Other processes not specifically discussed in . In some embodiments, the phosphate processing system 100 provides for integration of the process water treatment systems (pretreatment, struvite crystallization, and membrane treatment / polishing, e.g., at the precipitation system 120, crystallizer system 130, and RO / NF system 162, respectively) with the gypsum filter flushing (e.g., at the flushing system 140). In some embodiments, using clean (e.g., low phosphate content) water from the membrane treatment steps (e.g., water produced at 162) to provide fresh water makeup to the gypsum filter (e.g., when flushing gypsum at 140) allows for a higher percentage of phosphoric acid to be removed / recovered from the gypsum by-product.

[0101] As another example, in some embodiments, the phosphate processing system 100 provides for integration of a process water treatment system and an emission control system associated with phosphoric acid granulation (e.g., at the exhaust gas treatment system 180) to produce a granular fertilizer product. The granular fertilizer product can be monoammonium phosphate (MAP), diammonium phosphate (DAP), triple superphosphate (TSP), struvite, or struvite co-granulated with MAP, DAP, or TSP and / or other nutrients / trace element nutrient components. The presence of a water treatment system in these embodiments can allow for greater flexibility in using higher water volumes in the emission control scrubber system, allowing for easier operation, less scale formation, and lower emissions to the atmosphere.

[0102] As another example, in some embodiments, the phosphate processing system 100 provides for reusing high-phosphate (e.g., P2O5 content >5%, >10%, >15%, >20%, >25%, >30%, >35%, >40%, >45%, >50%) sludge from any one or more of the process water treatment and / or precipitation stages as a replacement or supplement for phosphate rock input to the phosphoric acid manufacturing process. For example, the phosphoric acid plant 110 may receive sludge from Figure 2 sludge from one or more of the systems shown in (where present) and may be used to produce phosphoric acid 112 and / or gypsum.

[0103] As another example, in some embodiments, the phosphate processing system 100 uses high-magnesium phosphate rock (e.g., at 114) to produce a phosphoric acid product (e.g., phosphoric acid 112) with an elevated magnesium product. This can allow for the production of struvite fertilizer or a fertilizer co-granulated with struvite and MAP / DAP / TSP in a granulation plant (e.g., granulation system 150), reducing the need to add an external / purchased magnesium source. In some embodiments, this has the dual benefit of allowing the use of otherwise discarded or "lower-grade" phosphate rock while reducing or eliminating the cost of a magnesium source for the struvite component of the produced fertilizer. This can allow for a dedicated phosphoric acid plant and granulation system for processing phosphate rock with elevated magnesium content and producing struvite fertilizer, wherein the struvite and MAP / DAP / TSP are co-granulated into a fertilizer product. The process line can also employ or use struvite recovered from process water treatment and / or from animal waste.

[0104] As another example, in some embodiments, the phosphate processing system 100 utilizes the acidity in the pretreated process water (e.g., an acidic solution) after precipitation to acidify animal waste (e.g., poultry manure, pig manure, cattle manure) to dissolve the phosphate contained in the animal waste. In some embodiments, this enables the recovery of phosphate in a form suitable for use as fertilizer. This can allow the use of animal waste to increase the pH of the pretreated process water instead of using purchased chemicals (e.g., limestone, lime, caustic soda), while using process water instead of purchased chemicals (e.g., sulfuric acid, phosphoric acid, hydrochloric acid) to acidify and extract the phosphate from the animal waste. The remaining parts of the plant (struvite crystallizer, granulator) can then be used to convert the phosphate extracted from the animal waste into a fertilizer product, such as at the granulation system 150.

[0105] Phosphoric acid plant

[0106] In some embodiments, phosphoric acid plant 110 produces phosphoric acid 112. Phosphoric acid plant 110 uses one or more phosphate sources as input streams. For example, the input streams may include phosphate rock 114 (e.g., high-grade phosphate rock, low-grade phosphate rock 116, and / or a combination thereof) and / or phosphate-containing fluids (e.g., aqueous phosphate solutions, pond water, process water, cooling water, slurries), or processed fluids (e.g., after concentration, dilution, or other processing of the fluid). As other examples, phosphoric acid plant 110 may use phosphate-containing compounds, such as a calcium phosphate source or magnesium phosphate.

[0107] For example, phosphoric acid plant 110 may produce phosphoric acid 112 and gypsum (eg, calcium sulfate) by reacting sulfuric acid with a phosphate source.

[0108] In some embodiments, phosphoric acid plant 110 is configured to use both a source containing magnesium at a level above a threshold amount (e.g., a source with a high level of magnesium) and a source containing magnesium at a level below a second threshold amount (e.g., a source with a low level of magnesium).

[0109] High-grade phosphates (e.g., in rock) can include phosphorus-containing components, such as phosphates (e.g., calcium phosphates), and in some embodiments, can include sulfur-containing components, such as sulfates (e.g., calcium sulfates). For example, phosphoric acid plant 110 can receive high-grade phosphate rock or concentrated phosphate rock ore having above a threshold amount of calcium phosphate or phosphates (e.g., typically 27% to 39% P2O5 or greater than 23% P2O5) and having impurities such as silica, fluoride, sulfates, carbonates (e.g., 1% to 3%), iron, aluminum (e.g., <5% to 6% combined iron and aluminum oxide), and magnesium (e.g., typically trace amounts to 3% MgO, mostly above 0.2% or 0.3% (e.g., typically 0.4% to 0.9% in Florida, 0.5% in Morocco, and typically up to 3% in Chinese rocks), below a threshold amount (e.g., typically less than ~5% combined Fe2O3, Al2O3, and MgO).

[0110] Low-grade phosphate (e.g., in rock) can include a phosphorus-containing component, such as phosphorus (e.g., calcium phosphate), a magnesium-containing component, and / or one or more other substances (e.g., iron, aluminum). In some embodiments, phosphoric acid plant 110 receives and / or uses low-grade phosphate rock to produce phosphoric acid. The low-grade phosphate rock can contain magnesium above a threshold amount, for example, having greater than 3% MgO.

[0111] Any magnesium in a low-grade phosphate composition (e.g., in the case of a rock composition) may adversely affect its use in phosphoric acid plant 110 to produce phosphoric acid because, for example, the magnesium may cause phosphoric acid plant 110 to become inefficient, cause accumulation in various mechanical components, stick machinery or plant equipment, increase the viscosity of the fluid, adversely affect phosphoric acid production, adversely affect the pelletizing characteristics of ammoniated phosphate fertilizer made from the phosphoric acid, and / or undesirably affect one or more chemical reactions.

[0112] Magnesium impurities are generally considered undesirable in phosphate rock, which can be used for phosphoric acid production. Therefore, in some embodiments, depending on the equipment type and process conditions, the phosphoric acid plant 110 generally maintains a MgO:PO ratio of less than 0.03 in phosphoric acid (e.g., 112) produced from phosphate rock or other phosphate-containing inputs (e.g., sludge 124) to minimize these operational issues.

[0113] However, the production of struvite or other magnesium-containing compounds (e.g., at the crystallizer system 130, at the pelletizing system 150) requires magnesium. In some embodiments, low-grade phosphate (e.g., low-grade phosphate rock, a phosphate source containing magnesium impurities) is provided to the phosphoric acid unit 110 along with sulfuric acid, and the phosphoric acid unit 110 produces phosphoric acid 112, gypsum, and / or one or more other output streams containing magnesium (e.g., aqueous phosphate solutions, such as pond water). These output streams can be supplied to the crystallizer system 130 or the pelletizing system 150 to supply some or all of the magnesium required to produce struvite, or a fertilizer co-granulated with struvite and MAP / DAP / TSP, or other desired magnesium-containing products.

[0114] In some embodiments, phosphoric acid plant 110 selects, receives, and / or uses low-grade phosphate containing 0.4% to 10% magnesium oxide (MgO). For example, phosphoric acid plant 110 can selectively extract phosphate rock formations based on the amount of magnesium in the phosphate rock. For example, phosphate rock with a magnesium content above a threshold can be avoided.

[0115] As another example, the phosphoric acid plant 110 can select ores with different magnesium contents and use a mixture thereof to produce an input source of phosphate rock with a total magnesium content within a desired range. The phosphate rock can be used to produce phosphoric acid with an elevated magnesium content and / or a magnesium-containing output. For example, the magnesium-containing output can be provided to the crystallizer and / or pelletizing system 150 and used to produce struvite or a fertilizer co-granulated with struvite and MAP / DAP / TSP, or other magnesium-containing materials. This process can promote the extension of the useful life of the phosphate rock mass and any environmental issues caused by the discard of large amounts of low-grade phosphate rock, as well as reduce the demand for imported / purchased magnesium-containing materials / reagents (e.g., magnesium oxide, magnesium chloride or magnesium sulfate, magnesium hydroxide, magnesium carbonate, or dolomitic lime for producing magnesium-containing products or struvite).

[0116] In some embodiments, one or more streams produced by phosphoric acid plant 110 are provided to a granulator system, and the granulator system produces a phosphate-containing material (e.g., granules), such as struvite or a struvite analog. In some embodiments, using one or more streams produced by phosphoric acid plant 110 from low-grade phosphate (e.g., low-grade phosphate rock) with a granulator system can reduce the amount of magnesium (and / or other materials in some embodiments) that needs to be added separately to produce a desired product (e.g., struvite or a struvite analog). This may be because one or more streams produced by phosphoric acid plant 110 contain magnesium (and / or other materials in some embodiments), and in some embodiments, the granulator can use such streams to facilitate the production of a desired product, such as magnesium-containing struvite or a struvite analog, rather than allowing such streams to become waste. This can result in advantages in, for example, efficiency, cost, environmental impact, recycling, the amount of material required, and / or the amount of pollutants or contaminated water generated.

[0117] In some embodiments, phosphoric acid plant 110 receives one or more streams containing magnesium levels above a threshold, such as high-magnesium rock (e.g., low-grade phosphate rock). In some embodiments, phosphoric acid plant 110 uses it to produce phosphoric acid having magnesium impurity levels above a threshold and / or phosphoric acid having a concentration below a threshold.

[0118] Phosphoric acid plant 110 can produce a phosphoric acid stream having one or more components at concentrations below a threshold value to help avoid or reduce scaling that may result from the presence of magnesium in amounts greater than would typically be expected from phosphoric acid production alone. In some embodiments, phosphoric acid plant 110 provides one or more streams containing magnesium above a threshold value (e.g., a phosphoric acid stream containing magnesium impurities) to granulation system 150. Granulation system 150 can then use this stream to produce one or more products that can be beneficial for promoting crop growth and / or fertilizer use (e.g., nutrient release or absorption characteristics, pH, dissolution, other fertilizer properties), such as magnesium-containing fertilizer 152. This can be advantageous for producing one or more products (e.g., fertilizer 152) (e.g., by co-granulation). In some embodiments, lower concentrations of phosphoric acid can be effectively used to produce struvite-based fertilizers in a granulation plant compared to MAP / DAP granulation, because struvite fertilizer production can absorb significant amounts of water from the phosphoric acid to form water of crystallization in the struvite. This feature can enable the phosphoric acid plant 110 to operate at lower phosphoric acid concentrations using less evaporator heat without negatively impacting the operating efficiency of the downstream pelletizing plant. For example, in some embodiments, phosphoric acid production (e.g., at the phosphoric acid plant 110) can be operated at a concentration of less than 54% P2O5, or less than 40% P2O5. In some embodiments, phosphoric acid production (e.g., at the phosphoric acid plant 110) can be operated at a concentration of less than 52%, 50%, 48%, 46%, 44%, 42%, 38%, 35%, 30%, 25%, 20%, 15%, 10%, or 5%.

[0119] In some embodiments, phosphoric acid plant 110 can be unexpectedly used in this manner to advantageously produce phosphoric acid using a phosphorus source containing magnesium above a threshold (e.g., high-magnesium rock). The presence of more magnesium than usual in phosphoric acid plant 110 can reduce the efficiency of phosphoric acid plant 110. However, this can be more than offset by the efficiency gains and / or environmental benefits that arise when magnesium is used in downstream processes. In some embodiments, phosphoric acid plant 110 produces phosphoric acid using a high-magnesium source, which can reduce production costs and allow the use of rock reserves that would otherwise be unusable or uneconomical, thereby mitigating or reducing the environmental impact of phosphoric acid production.

[0120] In some embodiments, the phosphoric acid plant 110 can produce an output stream comprising an acid (e.g., phosphoric acid) and having 1% magnesium and provide it to the granulation plant. This can be a large amount for the granulation plant. For example, the granulation plant can produce an output stream having 3.5% magnesium and can use the output stream from the phosphoric acid plant 110 to produce it.

[0121] In some embodiments, a source having high levels of magnesium / phosphorus is used by the pelletizing system 150 to produce struvite and / or is used in a chemical drying process, for example, as described in U.S. Pat. No. 9,334,166, entitled "METHODS AND COMPOSITIONS FOR CHEMICALDRYING AND PRODUCING STRUVITE," the entire contents of which are incorporated herein by reference, or is used for co-granulation of struvite with MAP, DAP, and / or TSP, for example, as described in U.S. Pat. No. 9,878,960. In contrast, high-magnesium phosphate sources may tend to produce soft or sticky granular materials in other systems for producing ammonium phosphate (e.g., MAP / DAP), resulting in off-spec products or operational challenges, as well as the use of higher concentrations of phosphoric acid (e.g., 54% P2O5 or the like) in granular ammoniated phosphate production due to the lack of chemical drying characteristics of struvite production.

[0122] In some embodiments, pelletizing system 150 allows for co-pelleting with a high magnesium phosphate source from phosphoric acid plant 110, and this may provide additional options to expand the available mineral resources of deposits having elevated magnesium content.

[0123] In other phosphoric acid production processes, elevated magnesium levels can lead to increased viscosity of the produced phosphoric acid, resulting in reduced efficiency in filtering phosphoric acid from the gypsum byproduct, as well as increased scaling and maintenance of downstream evaporation processes and pipelines. In some embodiments, phosphate processing system 100, for example, at phosphoric acid unit 110, can mitigate these issues by producing a more dilute phosphoric acid product (e.g., with a higher water content) (e.g., 112) than is optimal for ammoniated phosphate granulation. In some embodiments, the dilute phosphoric acid product can be more effectively used to produce struvite-containing fertilizers due to the water of crystallization absorbed by the product.

[0124] In some embodiments, phosphoric acid plant 110 receives phosphate rock 114 that has been mined and / or processed, applies one or more processing steps, and outputs phosphoric acid 112. In some embodiments, phosphoric acid plant 110 may react ground phosphate rock (e.g., ground in a wet ball mill) with sulfuric acid in a phosphoric acid reactor, thereby producing a phosphoric acid solution (e.g., 112) and a gypsum precipitate. In some embodiments, the mixture of phosphoric acid solution and gypsum is then filtered to separate the dilute phosphoric acid from the gypsum byproduct, and the gypsum filter cake is then flushed with water (or more typically pond water / process water) countercurrently to flush as much phosphoric acid as possible from the gypsum byproduct, for example, at flushing system 140. In some embodiments, the gypsum is then slurried in process water and pumped to a gypsum disposal site, such as a gypsum stockpile system. In some embodiments, the phosphoric acid solution (e.g., 112) is then evaporated in turn to produce phosphoric acid of the desired concentration for downstream granulation or other uses.

[0125] Example embodiments will now be described. In some embodiments, phosphoric acid plant 110 is provided with phosphoric acid material, phosphate-containing material, phosphate rock, high-grade phosphate (e.g., high-grade phosphate rock), and / or low-grade phosphate (e.g., low-grade phosphate rock), and phosphoric acid plant 110 produces phosphoric acid 112, gypsum, and / or one or more other output streams (e.g., an aqueous phosphate solution, such as pond water). This can facilitate the production of phosphoric acid 112 (e.g., for use in fertilizer or for pelleting), the recycling of any residual phosphorus-containing material (e.g., attached to or associated with gypsum) or other residual material through filtration / washing system 140, and / or the recycling of any residual phosphorus-containing material (e.g., in one or more output streams, such as any stream added to pond water or the aqueous phosphate solution) or other material through precipitation system 120, and / or other processing (e.g., by concentration, filtration, or other processes described herein at 164).

[0126] In some embodiments, phosphoric acid plant 110 produces one or more output streams comprising gypsum. As an example, gypsum comprises calcium sulfate.

[0127] In some embodiments, a certain amount of phosphoric acid or other materials becomes associated (e.g., physically attached) with the gypsum. Significant amounts of phosphoric acid may be lost in this manner. Flushing the gypsum with fresh water is generally considered impractical because using fresh water for flushing contaminates the fresh water and may result in an increase in the amount of process water that must be stored and / or treated, potentially violating environmental laws, and may result in increased dilution of the recovered phosphoric acid, necessitating further evaporative concentration downstream.

[0128] In some embodiments, the phosphate processing system 100 allows for the gypsum (e.g., gypsum at the flushing system 140) to be flushed in a practical manner at the flushing system 140. This allows for the substantial reuse of the streams flushed and separated from the gypsum. For example, in some embodiments, one or more output streams of the system 100 are provided to the gypsum flushing system 140. For example, in some embodiments, gypsum and any phosphoric acid associated with the gypsum are provided to the gypsum flushing system 140. After the gypsum is flushed, the stream containing phosphoric acid flushed from the gypsum can be returned to a point in the system 100 where the phosphoric acid can be recovered and / or used. In this manner, large amounts of phosphoric acid can be recovered.

[0129] Plaster flushing system

[0130] In some embodiments, the gypsum flushing system 140 is configured to flush a quantity of gypsum (e.g., a composition comprising gypsum) and collect a quantity of phosphoric acid from the gypsum using a flushing fluid received from one or more other systems included in the phosphate processing system 100, such as the phosphoric acid plant 110. For example, in some embodiments, the flushing fluid is one or more output streams from the phosphoric acid plant 110 and / or one or more streams from an aqueous phosphate solution, such as pond water. The flushing fluid can include an amount of one or more components below a threshold value, wherein the components and / or the threshold value can be suitable for use by the flushing system 140, for example, to separate the components.

[0131] In some embodiments, the gypsum flushing system 140 is configured to reuse water from one or more other systems of the phosphate processing system 100 to substantially separate one or more components from a stream (e.g., an output stream). For example, in some embodiments, the stream comprises gypsum and phosphoric acid, and the gypsum flushing system 140 applies a flushing fluid (e.g., an aqueous phosphate brine, pond water, output from one or more systems in the phosphate processing system 100) to produce a stream comprising phosphoric acid. For example, one or more processing steps may be applied to the stream and / or any intermediate streams produced. In some embodiments, the gypsum flushing system 140 allows for the recovery of phosphoric acid from a waste stream comprising gypsum. This can reduce the amount of phosphoric acid that is lost along with the by-product gypsum and sent to a waste storage system, such as a gypsum dump.

[0132] In some embodiments, the gypsum flushing system 140 receives a slurry comprising gypsum. For example, the slurry can be produced by the phosphoric acid plant 110 using sulfuric acid and phosphate rock during phosphoric acid production. For example, in some embodiments, the gypsum flushing system 140 receives a slurry comprising gypsum and washes it with water to flush out the phosphoric acid. This process can leave residual phosphoric acid associated with the gypsum. The residual phosphoric acid can form a waste stream and / or be provided to the flushing system 140 for further processing (e.g., for collecting additional phosphoric acid, such as all or a portion of the residual phosphoric acid). In some embodiments, the gypsum flushing system 140 applies one or more washing steps to the input stream (e.g., to the gypsum-containing slurry). For example, the gypsum flushing system 140 can use pond water as an initial flushing fluid and clean water as a final flushing fluid. This can promote the reduction of impurities in the recovered product (e.g., recovered acid) compared to applying only a flushing fluid as pond water. The gypsum flushing system 140 can use pond water as the flushing fluid in one or more steps (e.g., where the pond water has different chemical compositions in one or more different steps) to alleviate water balance difficulties, such as adding more fresh water to the phosphoric acid plant system than is lost to evaporation, resulting in the accumulation of large amounts of wastewater / process water / pond water to be stored or treated.

[0133] pond water

[0134] In some embodiments, pond water (e.g., phosphate brine solution, phosphogypsum pond water, etc.) contains a certain amount of phosphate and / or phosphoric acid and / or phosphorus. The pond water can be generated by one or more systems of the phosphate processing system 100, for example, as an output and / or waste product. For example, the pond water can be a sludge or slurry. The pond water may be the result of a historical industrial operation. The system 100 can process the pond water while recovering useful components such as struvite, MAP, phosphoric acid, gypsum, calcium fluoride, fluorosilicates, hydrofluoric acid, silicon hexafluoride, uranium, etc. from the pond water.

[0135] In some embodiments, the pond water is derived from one or more output streams from phosphoric acid plant 110. For example, the pond water may be a phosphogypsum pond derived from a waste stream containing gypsum produced by phosphoric acid plant 110. For example, the waste stream may be formed from one or more input streams to phosphoric acid plant 110 (e.g., from aqueous phosphate solution, pond water, phosphate rock 114, low-grade phosphate rock 116, etc.).

[0136] In some embodiments, pond water system 160 is input to a treatment system that receives and / or processes pond water. In some embodiments, pond water system 160 receives output streams from other portions of system 100, such as one or more output streams from exhaust gas treatment system 180 and / or from granulation system 150. For example, pond water system 160 can receive a suspension containing struvite particles and / or sludge containing fines, which can be generated by granulation system 150 during the process of producing fertilizer 152 and / or generated by exhaust gas treatment system 180 after collecting any waste (e.g., hot gases containing struvite, fines, dust) from granulation system 150.

[0137] Example embodiments will now be described that may integrate the pond water system 160 with the exhaust gas treatment system 180 and, in some embodiments, the granulation system 150. In some embodiments, the exhaust gas treatment system 180 captures, washes, collects, thickens, separates, and / or otherwise processes fines, exhaust gases, and dust containing useful materials (e.g., struvite, ammonium phosphate), other materials containing phosphate, magnesium, and / or ammonium, etc., flowing in a gas (e.g., a gas flow system that directs one or more output streams from one or more systems of the phosphate processing system 100). For example, the exhaust treatment system 180 can use an exhaust fan to collect exhaust gases, fine powders, and dust to use an exhaust fan to draw in contaminated air from various processes of a granulation device (granulation drum, dryer, cooler, screener, conveyor belt, storage bin, grinder, feed tank or hopper, etc.) and direct the contaminated air to an air pollution device that separates solid particles from the air (e.g., a cyclone separator, a filter, a bag filter house, a scrubber), or an air pollution device that removes exhaust gases from the air (e.g., a scrubber, a condenser, etc.).

[0138] In some embodiments, the exhaust gas treatment system 180 includes an air pollution control process that collects dry powder that can be directly reused in the granulation process from the air flow. In other cases, a wet scrubber collects and concentrates exhaust gases such as ammonia and fine dust into a scrubber fluid that can be converted into a slurry. In some embodiments, the slurry may need to be regularly discharged and supplemented with fresh liquid (e.g., typically water and / or an acid such as phosphoric acid, sulfuric acid, or an alkali such as sodium hydroxide). The scrubber slurry discharge stream can be directly reused (if the water balance allows) in the granulation process (e.g., at the granulation system 150), or must be disposed of and / or treated, for example, sent to the pond water system 160 for disposal or advantageously treated in a stage of the pond water treatment system, which can capture, concentrate, and / or recycle the desired components of the scrubber slurry discharge and return it to the granulation process (e.g., at the granulation system 150) in a more desired form. In some embodiments, the scrubber blowdown slurry can be sent to a struvite fines clarifier to precipitate and concentrate the fine struvite dust particles from a struvite granulation or co-granulation device, wherein the precipitated solid can be dehydrated and returned to the granulation device for reuse. Soluble phosphate, ammonia or ammonium phosphate dust can be returned to the pond water treatment system to reclaim ammonia and phosphate components as struvite. In some embodiments, the flow rate of the blowdown stream is minimum, but the concentration is high, which can allow the blowdown stream to minimize the impact on the design / capacity of the pond water treatment system, but can be used to reclaim the component of the economically significant amount in the blowdown, and clean water is provided back to the scrubber system with relatively high volume. This can make it possible to better wash the exhaust gases from the granulation device and reduce the discharge to the environment.

[0139] The pond water system can facilitate reuse of particles (e.g., struvite); reduce waste generated by one or more systems of the phosphate processing system 100; and / or reduce the amount of material used in one or more steps and / or processes of one or more systems in the phosphate production system 100.

[0140] In some embodiments, the pond water is reused by one or more systems of the phosphate processing system 100. In some embodiments, the pond water is reused by the phosphoric acid plant 110.

[0141] For example, in some embodiments, the use of pond water facilitates the recycling, reuse, and / or recovery of one or more components (e.g., components that might otherwise be produced as an output stream from one or more systems of the phosphate processing system 100 and / or discarded as waste). For example, the pond water can mitigate negative environmental impacts. For example, the phosphoric acid plant 110 can produce a waste output stream that contains less than a threshold amount of phosphoric acid (e.g., less than an amount that can be used by the pelletizing system 150 and / or in the production of fertilizer 152).

[0142] The pond water may receive a waste output stream from the phosphoric acid plant 110. For example, the pond water may be produced as an input stream and / or directed to the precipitation system 120 to precipitate calcium phosphate using phosphoric acid contained in the waste stream.

[0143] In some embodiments, pond water is received by precipitation system 120, and precipitation system 120 causes precipitation of one or more components and forms sludge 124 or slurry. For example, sludge 124 or slurry can be composed of one or more precipitated components suspended in a solution. In some embodiments, sludge 124 is provided to phosphoric acid plant 110, and one or more precipitated components are used by phosphoric acid plant 110 to produce phosphoric acid.

[0144] In some embodiments, an input stream derived from pond water can be provided to phosphoric acid plant 110 to produce higher grade phosphoric acid (e.g., phosphoric acid with lower impurities). For example, this can occur if one or more of the sludges generated from processing the pond water contains phosphates and a lower concentration of impurities than the phosphate rock being processed by phosphoric acid plant 110. In this case, higher purity phosphoric acid, such as for food or industrial chemical grade products, can be produced more cost-effectively.

[0145] In some embodiments, the slurry and / or sludge precipitated from the pond water may contain elevated levels of phosphate (i.e., >10% PO) and may form an input stream to the phosphoric acid plant 110. In some embodiments, the phosphoric acid plant 110 receives the slurry or sludge, e.g., high-phosphate sludge, as a substitute for or supplement to phosphate rock.

[0146] In some embodiments, one or more streams from one or more systems included in the phosphate processing system 100 are concentrated, for example, at 164. This can facilitate reducing the cost of transporting pond water to a treatment / storage location. In some embodiments, if the concentration of one or more components in the pond water decreases over time (e.g., years), the pond water system 160 concentrates the remaining pond water. Concentration using nanofiltration or reverse osmosis can be used to produce a concentrate stream and a clean water permeate stream that can be discharged to a receiving environment or reused for other purposes such as flushing gypsum (e.g., at flushing system 140).

[0147] In some embodiments, the pond water system 160 uses nanofiltration and / or reverse osmosis to concentrate the stream of one or more components. In some embodiments, one or more output streams after the nanofiltration and / or reverse osmosis process at 162 are provided to the precipitation system 120. In some embodiments, the performance of the nanofiltration process and / or reverse osmosis process is based on charge balance and / or solubility (e.g., reverse osmosis is less effective than nanofiltration).

[0148] In some embodiments, pond water (e.g., phosphogypsum ponds) and / or treated pond water is provided as one or more input streams to precipitation system 120. For example, pond water from a location remote from phosphate processing system 100 can be concentrated by a process that can involve collecting the concentrate by a membrane filtration system. The concentrated pond water can then be delivered to a location in system 100 and used as an input stream in one or more subsystems of system 100.

[0149] Sedimentation system

[0150] In some embodiments, precipitation system 120 receives one or more input streams such as fluids (e.g., aqueous phosphate solutions, pond water, slurries). For example, the fluid may be phosphogypsum pond water generated by phosphoric acid plant 110. As another example, the fluid may be a concentrate stream or a stream derived from process pond water.

[0151] In some embodiments, the precipitation system 120 produces one or more precipitants, for example, from one or more input streams. In some embodiments, the one or more input streams are derived from one or more output streams of one or more systems of the phosphate processing system 100. In some embodiments, the one or more precipitants may form one or more output streams of the precipitation system 120, for example, which are used to obtain one or more inputs to one or more systems of the phosphate processing system 100. For example, one or more output streams (e.g., containing precipitants), such as sludge 124, gypsum 126, and / or fluoride-containing components 128 or fluorosilicates, may be provided from the precipitation system 120 to the phosphoric acid plant 110 (see, for example, U.S. Patent Application No. 14 / 240,701, published as U.S. Publication No. 2014 / 0231359, entitled "TREATMENT OF PHOSPHATE-CONTAINING WASTEWATER WITH FLUOROSILICATE AND PHOSPHATE RECOVERY," the entire contents of which are incorporated herein by reference).

[0152] In some embodiments, precipitation system 120 receives one or more input streams such as fluids (e.g., aqueous phosphate solutions, pond water, slurries). For example, the fluid may be phosphogypsum pond water generated by phosphoric acid plant 110. As another example, the fluid may be a concentrate stream or a stream derived from process pond water.

[0153] In some embodiments, the precipitation system 120 adds an alkali (limestone, lime, caustic, ammonia, etc.) to increase the pH of the pond water, and this can result in the sequential precipitation of components of the pond water including silica, fluoride, phosphate, calcium, and trace metals (including heavy metals). This is described, for example, in U.S. Patent Application No. 13 / 698,129 (U.S. Patent No. 10,196,289, entitled "TREATMENT OF PHOSPHATE-CONTAINING WASTEWATER"), the entire contents of which are incorporated herein by reference, and in U.S. Patent Application No. 14 / 240,701 (U.S. Publication No. 2014 / 0231359). Some precipitated solids (e.g., sludge produced as described in U.S. Patent No. 10,196,289 and U.S. Publication No. 2014 / 0231359) may contain high levels of phosphate compounds, particularly calcium phosphate and / or struvite, and low levels of impurities such as heavy metals or radioactive components, which can be settled, dewatered, or otherwise concentrated and subsequently reused as a substitute for phosphate rock in the phosphoric acid plant 110. This can provide improvements in efficiency, environmental impact, and cost, for example, by allowing the reuse of waste streams (e.g., pond water, aqueous phosphate solution, etc.) after precipitation of the components to produce one or more output streams having a desired composition (e.g., a stream having a greater concentration or amount per volume of a certain precipitant or precipitants than in the input stream to the precipitation system 120; a stream having a lower concentration or amount per volume of a certain type or types of components (e.g., those that may have formed the precipitant); etc.). Specifically, sludge or precipitated solids that may be produced as a byproduct from the phosphate processing system 100 or from the systems described in U.S. Patent No. 1,0196,289 and U.S. Publication No. 2014 / 0231359 may be used in phosphoric acid plant 110 as a substitute for phosphate rock, for example, to produce phosphoric acid 112 .

[0154] In some embodiments, the precipitation system 120 produces one or more precipitants, for example, from one or more input streams. In some embodiments, the one or more input streams are derived from one or more output streams of one or more systems of the phosphate processing system 100. In some embodiments, the one or more precipitants can form one or more output streams of the precipitation system 120, for example, to obtain one or more inputs to one or more systems of the phosphate processing system 100. For example, one or more output streams (e.g., containing precipitants), such as sludge 124, gypsum 126, and / or fluoride-containing components 128 or fluorosilicates, can be provided from the precipitation system 120 to the phosphoric acid plant 110 (see, for example, U.S. Patent Application No. 14 / 240,701, published as U.S. Publication No. 2014 / 0231359, entitled "TREATMENT OF PHOSPHATE-CONTAINING WASTEWATER WITH FLUOROSILICATE AND PHOSPHATE RECOVERY," the entire contents of which are incorporated herein by reference).

[0155] In some embodiments, precipitation system 120 processes one or more input streams to produce one or more precipitation agents and / or one or more effluent streams 122. For example, precipitation system 120 can add alkali (e.g., from limestone, lime, ammonia, caustic soda, etc.) to one or more input streams to produce a slurry. As another example, precipitation system 120 can add brine (e.g., concentrated salt solution) and / or another solution to one or more input streams to increase pH to above a threshold level to produce (e.g., precipitate) calcium phosphate and / or gypsum. As another example, precipitation system 120 can add solution or material to one or more input streams and reduce or increase pH to above a threshold level to produce one or more streams. For example, these one or more streams can be used as input streams in a precipitation process.

[0156] In some embodiments, precipitation system 120 produces an effluent stream 122 by precipitating one or more precipitants (e.g., calcium fluoride, fluorosilicates, calcium phosphates, gypsum, silica polymers, precipitants in slurries) from one or more input fluid streams in one or more precipitation steps.

[0157] For example, the precipitation system 120 can precipitate one or more precipitants in the input fluid stream and separate one or more of these precipitants from the input fluid stream to produce an effluent stream 122. For example, separation can be performed by filtration, sedimentation, osmosis, selective binding of components, and / or one or more reactions. The one or more effluent streams 122 can contain components with reduced concentrations and / or altered compositions compared to one or more of the one or more input fluid streams. For example, the precipitation system 120 can produce an effluent stream 122 comprising reduced amounts or concentrations of phosphate ions and calcium ions; a precipitant stream comprising precipitated calcium phosphate; and / or an acidic output stream (e.g., comprising phosphoric acid).

[0158] In some embodiments, the precipitation system 120 produces a sludge output stream, a gypsum output stream, and / or a fluoride output stream 128. These may include calcium phosphate precipitates, calcium fluoride precipitates, and / or fluorosilicate precipitates (e.g., sodium fluorosilicate) having a PO concentration exceeding 10% (in some embodiments, exceeding 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or 95%).

[0159] In some embodiments, one or more output streams from precipitation system 120 are provided to flushing system 140 or crystallizer system 130.

[0160] Crystallizer system

[0161] In some embodiments, the crystallizer system 130 causes crystallization of one or more components received from one or more output streams generated by the phosphate processing system 100. For example, in some embodiments, the crystallizer system 130 can receive one or more effluent streams 122, such as from the precipitation system 120. The one or more effluent streams 122 can be produced after the one or more components have been precipitated from solution by the precipitation system 120. In some embodiments, one or more additional components are added to the one or more effluent streams 122 before they are processed through the crystallizer. For example, the added components can promote or improve crystallization.

[0162] In some embodiments, a crystallizer receives one or more streams (e.g., from one or more systems of phosphate processing system 100 or such streams after processing) and causes one or more components in the one or more streams to crystallize. For example, in some embodiments, a crystallizer receives a stream of phosphorus-containing material (e.g., effluent from precipitation system 120, a phosphate-containing stream from organic removal system 170, a phosphoric acid-containing stream from flushing system 140 and / or phosphoric acid unit 110), processes such a stream, and causes struvite crystallization or precipitation. In some embodiments, the stream is processed by adding one or more components, such as seed crystals (e.g., small crystalline materials) to promote crystallization, acid and / or base to adjust pH, magnesium or ammonia or phosphate sources, and / or catalysts.

[0163] In some embodiments, one or more components are added to the crystallizer to improve, promote, or influence crystallization and can be obtained from one or more other streams from the systems included in the phosphate processing system 100. For example, the precipitation system 120, the phosphoric acid unit 110, the flushing system 140, the granulation unit, or the exhaust treatment system 180, and / or other systems can generate one or more streams from organic materials such as animal manure or poultry manure and / or other components. In some embodiments, one or more streams are processed, for example, by diluting one or more components, concentrating one or more components, precipitating one or more components, adjusting their pH, adjusting their temperature, and / or adding, removing, increasing, and / or decreasing one or more components. For example, one or more streams containing organic phosphate-containing materials 172 (e.g., manure) are combined with one or more streams from the precipitation system 120 (e.g., one or more output streams that are acidic solutions) and processed through the organic matter removal system 170. In some embodiments, the organic removal system 170 modifies, reduces, removes, and / or increases the amount of one or more organic-related materials from one or more streams. For example, the organic removal system 170 can remove an amount of organic material from one or more streams that can be formed from the output stream of the precipitation system 120 and manure (e.g., a material containing organophosphates).

[0164] In some embodiments, the crystallizer receives fines from the pelletizing system 150 and / or exhaust gas treatment.

[0165] Co-granulation system

[0166] In some embodiments, the granulation system 150 receives P, N, and Mg (e.g., as phosphoric acid, ammonia, and MgO) and produces a co-granulated (e.g., homogeneous granular) composition, such as a fertilizer containing struvite. For example, in some embodiments, the granulation system 150 receives phosphoric acid (e.g., from the phosphoric acid plant 110), struvite from the crystallization system or dehydration system 184, and / or struvite and / or phosphate and ammonium phosphate compounds from the exhaust gas treatment system 180. In some embodiments, the granulation system 150 also receives other components from one or more streams generated by one or more systems of the phosphate processing system 100.

[0167] In some embodiments, granulation system 150 processes and / or granulates these components and produces fertilizer 152. For example, in some embodiments, granulation system 150 can granulate phosphoric acid 112 from phosphoric acid plant 110, struvite from a crystallizer (e.g., struvite produced by the crystallizer and / or struvite concentrated or dehydrated from exhaust fines from the exhaust system), and a magnesium-containing product produced by phosphoric acid plant 110 from a magnesium-containing phosphate source (e.g., low-grade phosphate rock 116). For example, granulation system 150 can then produce fertilizer 152 from such granulation. Granulation system 150 can produce a struvite-based fertilizer, for example, using a chemical drying process, or can produce a co-granulated struvite product with a water-soluble phosphate source, such as MAP / DAP / TSP, optionally with additional nutrients or trace elements.

[0168] In some embodiments, the pelletizing system 150 generates exhaust gas, e.g., struvite particles contained in the gas or hot gas. In some embodiments, the pelletizing system 150 provides the exhaust gas to the exhaust gas treatment system 180. In some embodiments, the exhaust gas treatment system 180 extracts and / or separates fertilizer particles from any exhaust gas received. For example, the exhaust gas treatment system 180 can use an output stream from one or more systems of the phosphate processing system 100 (e.g., pond water or a solution containing one or more types of particles (e.g., struvite) in an amount below a threshold) to scrub the exhaust gas. This can facilitate water recycling, capture or increase production of one or more components (e.g., struvite, phosphate, ammonia), and / or provide environmental improvements.

[0169] In some embodiments, the exhaust treatment system 180 produces fines 182, which can include components with a changed composition compared to one or more input streams to the exhaust treatment system 180. For example, the fines 182 can be a composition of struvite particles with an increased amount per volume. In some embodiments, the fines 182 are provided to a dehydration system 184 for further processing. For example, the dehydration system 184 can dehydrate the fines and produce a dry composition of struvite particles. One or more output streams from the dehydration system 184 can be combined with one or more output streams from the crystallizer (e.g., phosphate-containing particles 132) and provided to one or more systems in the phosphate processing system 100. This can promote the recapture or increased production of one or more types of particles from one or more different systems in the phosphate processing system 100. For example, one or more streams from different systems can be combined to produce a composition with an increased amount per volume (e.g., increased concentration) of one or more components. This can facilitate further processing, such as detection, measurement, and / or reuse, of one or more components because their amount may be above a threshold that may facilitate or allow such detection, measurement, and / or reuse, such as in granulation system 150 .

[0170] For example, in some embodiments, the fines 182 dewatered at the dewatering system 184 can be combined with any struvite granules 132 produced by the crystallizer and provided to a kneading mill 186 (or other mixing device) for processing in a granulation device, or directly to a granulation device for incorporation into granular fertilizer. In some embodiments, the kneading mill 186 provides one or more processed output streams to the granulation system 150. This can facilitate the recovery of one or more components (e.g., phosphate-containing granules) for reuse by the granulation system 150 to produce, for example, fertilizer 152.

[0171] In some embodiments, a scrubber water blowdown process (e.g., scrubber liquid purge) is implemented by the phosphate processing system 100. For example, as more solids are added to the scrubber, the scrubber liquid may be concentrated over time, and the liquid may be occasionally (or continuously) purged from the scrubber to maintain a reasonable solids concentration in the scrubber. Scrubber efficiency (ability to remove particulates, etc.) may be affected by the solids concentration.

[0172] In some embodiments, the dewatering system 184 applies a dewatering step to the scrubber water blowdown process and facilitates the recovery of a slurry of dust or solids or fines (e.g., struvite dust, fertilizer dust, etc.) that may be captured in the scrubber. This can facilitate the concentration or reconcentration of one or more components or dust or solids or fines (e.g., struvite) and facilitates providing a concentrated stream to the granulation system 150. The granulation system 150 can thereby use recycled or recollected dust or solids or fines and reduce the amount of one or more components that may be added during one or more granulation steps, such as the step of producing fertilizer 152. For example, this process can also facilitate reducing the water load on one or more granulators and reducing the energy that can be used for the drying process.

[0173] In some embodiments, the granulation system 150 receives, uses, and / or adds sulfur (e.g., elemental sulfur), sulfate, zinc, boron, and / or one or more other components. For example, one or more components can be co-granulated with struvite or a phosphorus-containing component to produce fertilizer 152. As another embodiment, trace element nutrients and / or macronutrient nutrients can be co-granulated with one or more other components, such as a phosphate-containing component (e.g., struvite, dittmarite, MAP / DAP / TSP). In some embodiments, the granulation system 150 produces compositions having different release rates relative to each other and / or relative to one or more constituent components in each composition. For example, the granulation system 150 can produce fertilizers with fast and slow release of phosphate, where the phosphate is a component of different compositions and / or is arranged, dispersed, or granulated in a specific manner. In some embodiments, the granulation system 150 uses one or more components received and / or sourced from one or more input streams from one or more systems included in the phosphate processing system 100.

[0174] In some embodiments, the granulation system 150 is integrated with the pond water system 160. For example, the struvite granulation / co-granulation equipment can be integrated with the pond water treatment process. This can provide multiple advantages. For example, in some embodiments, the granulation system 150 generates a slurry of captured struvite fertilizer dust in water or an acidic solution and returns it to the pond water system 160. The pond water system 160 can then use this slurry in the struvite recovery step of the phosphogypsum treatment process. For example, the pond water system 160 can generate and / or separate struvite, phosphorus-containing materials, phosphoric acid, gypsum, magnesium, fluoride, calcium phosphate, calcium-containing materials, sulfuric acid, and / or other components in one or more streams. This can facilitate the reduction of any evaporation capacity of the granulator and / or eliminate bottlenecks.

[0175] For example, in some embodiments, the slurry that can otherwise be sent to the granulator can be sent to the pond water system 160 instead and the pond water system 160 can process the slurry. For example, the pond water system 160 can accommodate the stream from the air pollution control equipment and capture and thicken the struvite fine powder from the wastewater. In some embodiments, wet struvite dust or powder is incorporated into the product at the granulation system 150. The integration of the granulation system 150 and the pond water system 160 can provide advantages such as: alleviate environmental impact, improve the output of one or more components, reduce the use of any additional amount of one or more components, promote the recycling and / or reuse of one or more components, produce one or more streams (for example, compositions) of the composition with desired amount, ratio, state and / or one or more components. For example, capturing magnesium in the waste stream can promote the production of struvite fertilizer with magnesium.

[0176] In some embodiments, the granulation system 150 receives one or more streams from the phosphoric acid plant 110 that contain magnesium above a threshold amount. The one or more streams can be generated by the phosphoric acid plant 110 from a source (e.g., phosphate rock containing high levels of magnesium impurities) that contains magnesium above a second threshold amount. In this way, the phosphoric acid plant 110 can help reduce the amount of magnesium from another source that can be added to produce a product such as a fertilizer.

[0177] In some embodiments, the granulation system 150 heats and / or cools the reaction intermediates during one or more processing (e.g., granulation) steps. In some embodiments, the granulation system 150 selects a temperature based on one or more intermediates, the desired product, the desired form, the desired processing steps, or other reaction characteristics. For example, the granulation system 150 can increase the temperature of the reaction above a threshold amount (e.g., above an amount that can be used in the process of manufacturing different fertilizers), and the increased temperature can promote the production of the product and / or promote the drying of one or more intermediates and / or products. For example, this can allow for the absorption of water. Heat can also affect the amount of power used by the granulation system 150. The temperature selection can advantageously reduce costs and / or environmental impacts. For example, the granulation device can be operated to maintain the temperature of the components below approximately 55°C or 60°C to produce a struvite-based fertilizer, or operated at a temperature above 60°C (e.g., above 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, etc.) to produce a magnesia-based fertilizer.

[0178] mud

[0179] In some embodiments, the sludge or slurry is generated by phosphate processing system 100. For example, in some embodiments, sludge 124 is generated by pond water system 160. As another example, in some embodiments, sludge 124 is generated by precipitation system 120 (e.g., as one or more precipitation components suspended in solution), by organics removal system 170, by steps or systems included in phosphate processing system 100, and / or one or more output streams from any one or more thereof.

[0180] In some embodiments, sludge (e.g., sludge produced by the systems included in the phosphate processing system 100) is reused. For example, processed sludge from phosphogypsum pond water treatment technology can be reused as a source of calcium phosphate to replace the original phosphate rock in the phosphoric acid plant 110.

[0181] For example, in some embodiments, the input to the phosphoric acid plant 110 can include a sludge composition (e.g., sludge from the calcium phosphate precipitation stage of phosphogypsum pond water treatment) that is similar in composition to phosphate rock (e.g., calcium phosphate with a certain amount of Si / F impurities). In some embodiments, the phosphoric acid plant 110 reuses the sludge to produce phosphoric acid. In some embodiments, the sludge is incorporated into the phosphoric acid production step. Phosphoric acid can be used in situ in the granulation step. This can provide advantages, for example, when installed at an operating phosphoric acid plant or at a shutdown point where an existing abandoned phosphoric acid production system can be repurposed.

[0182] In some embodiments, the sludge is directly reused at an existing phosphoric acid production site, incorporated as a phosphoric acid production step, and used to produce phosphoric acid for integration with chemical dry granulation (e.g., see U.S. Pat. No. 9,334,166), or with co-granulation technology (e.g., see U.S. Pat. No. 9,878,960), or used to produce granular phosphate fertilizers such as MAP / DAP / TSP in a granulation step in situ or elsewhere. This can be particularly attractive, for example, when installed at an operating phosphoric acid complex or at a decommissioned site where existing abandoned phosphoric acid production and granulation assets can be repurposed.

[0183] In some embodiments, sludge and / or slurry is generated by the granulation system 150. For example, in some embodiments, a treatment system (e.g., air pollution control system, exhaust gas treatment) generates a slurry of captured fertilizer dust in water or an acidic solution. This can be generated from one or more output streams from the granulation system 150, such as one or more waste output streams.

[0184] In some embodiments, the slurry is provided to a struvite recovery step in a phosphogypsum pond water treatment system. This can provide several advantages, such as reducing or eliminating bottlenecks in any evaporation capacity of the granulation system 150 (e.g., a granulation unit). For example, the slurry can be reused with pond water and / or incorporated into pond water for reuse in one or more systems in the phosphate processing system 100, such as, for example, crystallizing struvite and / or other components at a crystallizer, or precipitating struvite and / or one or more other components at a precipitation system 120, according to some embodiments. In some embodiments, the struvite granulation / co-granulation facility is integrated with the pond water treatment process.

[0185] In some embodiments, the pond water treatment system includes steps for capturing and / or thickening fines (e.g., struvite fines, fines 182) from one or more output streams (e.g., wastewater, output stream from pelletizing system 150, output stream from exhaust gas treatment system 180). In some embodiments, the pond water treatment system can readily accommodate streams from air pollution control equipment (e.g., air pollution treatment systems).

[0186] As another example, in some embodiments, a slurry (e.g., produced by the pelletizing system 150 and / or by the exhaust gas treatment system 180) is provided to the pelletizing system 150 and the slurry (e.g., wet struvite or fertilizer dust) is incorporated (directly or indirectly) into the product produced by the pelletizing system 150. This can facilitate increasing the yield of the product (e.g., the yield of struvite or fertilizer-containing product per unit amount of struvite or fertilizer that can be input into the system). For example, this can reduce the amount of struvite or fertilizer lost by the pelletizing system 150 (e.g., not incorporated into the product), for example, by allowing the capture and / or reuse of struvite or fertilizer in the form of dust, waste, granules, suspended matter, sludge, and / or slurry. In some embodiments, the sludge / slurry (e.g., containing struvite or fertilizer granules) can be provided to one or more systems of the phosphate processing system 100 for processing (e.g., precipitated by the precipitation system 120, crystallized as struvite in a crystallizer, concentrated in a concentration system, etc.) and one or more resulting streams can be provided to the granulation system 150.

[0187] In some embodiments, sludge from the pond water treatment system or sedimentation system 120 is used to produce industrial or food-grade phosphoric acid, for example, at a phosphate processing system 100 that can include an integrated mining / fertilizer / phosphogypsum / technology and / or food-grade acid process. In some embodiments, one or more processing steps are applied to the sludge to produce one or more components. For example, such components can be separated or mixed. Such components can be used by one or more systems included in the phosphate processing system 100. For example, in some embodiments, the phosphoric acid plant 110 receives sludge having lower impurities than phosphate rock to produce phosphoric acid having lower impurities.

[0188] In some embodiments, the precipitation process produces calcium fluoride. For example, the precipitation process can produce calcium fluoride in which the amount of calcium fluoride is above a threshold (e.g., at a concentration above a threshold) and / or has one or more specific properties (e.g., at a purity above a threshold). For example, this can facilitate the production, collection, and / or reuse of calcium fluoride from waste streams generated by the precipitation process.

[0189] In some embodiments, precipitation system 120 produces sodium fluorosilicate sludge. Sodium fluorosilicate can be a source of fluoride and can be used for drinking water treatment or as a source of silicon dioxide, for example, for solar panel manufacturing. The generation of this sludge can provide advantages, for example, promote fluoride production to remove silicon dioxide from pond water to be treated, reduce the possibility of silica gel formation, alleviate environmental impact, and / or improve product yield and / or purity. For example, this sludge can be used to produce and / or separate sodium fluorosilicate with a purity of 98%, 96% to 99%, higher than 90%, higher than 80%, higher than 70%, higher than 60% and / or higher than 50%. In some embodiments, precipitation system 120 provides phosphate and fluorosilicate recovery, for example, using U.S. application No. 14 / 240,701 (U.S. Publication No. 2014 / 0231359).

[0190] In some embodiments, one or more systems in the phosphate processing system 100 produce calcium fluoride (e.g., in a sludge stream), and in some embodiments, the production of the stream containing calcium fluoride is optimized (e.g., the amount, composition, form, pH, production location, chemical composition of the stream). For example, in some embodiments, one or more systems (e.g., precipitation system 120) produce calcium fluoride. This can facilitate the reuse of the sludge containing calcium fluoride.

[0191] In some embodiments, the sludge stream from the precipitation system 120 having an elevated calcium phosphate content is provided back to the ball mill and / or directly to the phosphoric acid reactor 110, for example, where the water balance is at a threshold value (e.g., within a threshold range between the various systems included in the phosphate processing system 100). This can help reduce the volume of sludge to be disposed of from the pond water treatment system or the precipitation system 120. For example, sludge with high calcium phosphate can be processed in a ball mill along with phosphate rock and, in turn, fed back to the phosphoric acid reactor 110 to produce phosphoric acid.

[0192] In some embodiments, the heat generated in system 100 is used to remove water from struvite to produce calcite and the calcite is fed to a pelletizing system to make fertilizer. Using calcite instead of struvite can produce a fertilizer with higher nutrients per unit weight.

[0193] An example phosphate processing system 100 will now be described according to some embodiments.

[0194] In this embodiment, the phosphate processing system 100 combines input and output streams from various systems included in the phosphate processing system 100. For example, such streams using treated pond water from the pond water treatment system include cooling water tower makeup / blowdown, vacuum pump seal water input / output, and the various streams listed below. In various embodiments, one or more streams may be omitted. Unless otherwise noted, the following values ​​are related to an approximately 1,000 TPD PO process rate and are expressed as gallons of water per minute as a function of PO production. The various streams that use water included in the phosphate processing system 100 will now be described. The various values ​​are specified and therefore may vary, as in the same embodiment or different embodiments.

[0195] sulfuric acid

[0196] Fresh water can be added to the sulfuric acid column at 65 GPM or 80 GPM (e.g., sulfuric acid plant with HRS). The heat recovery system can vary the amount of dilution water.

[0197] There may be cooling tower feed: for 1,000TPD P2O5 (in) 2800TPD H2SO4: 1,231GPM = Total In

[0198] Cooling tower blowdown may occur: (Outflow) minus drift = 822.542 GPM; Blowdown = 408.473 GPM for 3 concentration cycles. Drift plus blowdown equals total flow in. Blowdown equals total flow in divided by concentration cycles.

[0199] Boiler Makeup: Smaller stream, used for facilities with condensate recovery systems. This is optionally included.

[0200] phosphoric acid

[0201] There may be water supplied to the ball mill: (Inlet) Total slurry 261.2 GPM. Inlet water in the rock may be 83.2 GPM. Water for the ball mill may be 178 GPM.

[0202] There may be a reactor barometric condenser: (in / out) 3054 GPM in / 2652 out. Most of the primary "out" may be reused in cloth wash.

[0203] There may be water evaporating from the reactor: (out) 15.78 GPM (if considered separately from the atmospheric water flow)

[0204] Reactor scrubber water flow may be present: (in / out) 485 GPM

[0205] Reactor Vacuum Pump Seal Water: (In) 30 GPM may be present. This is omitted in some embodiments of the phosphate processing system 100.

[0206] There may be filter cake wash water for gypsum filter: (inlet) 667GPM

[0207] Filter cloth wash and sluice water can be provided to the slurry stream and in gypsum transport: (Output) 556 GPM (filter cloth wash). 1618.2 GPM (sluice water).

[0208] There may be a filter disc fresh water spray: (In) Minimal volume from a very fine spray.

[0209] A flat filter table may be present. Vacuum pump seal water: (inlet) 20 GPM

[0210] Evaporator pressure condenser supply: (in / out) 12,758.5GPM (in); 12,990.9GPM (out)

[0211] There may be water evaporated from the evaporator: (out) 1000 TPD*(1 / .28)-(1 / .52)=1648 tons=274.5 GPM (if considered separately from the barometric water flow).

[0212] There may be a small stream of hydrosilicic acid make-up water which may be present. This is omitted in some embodiments of the phosphate processing system 100.

[0213] Granulation

[0214] There may be a pond water scrubber: pond water flow (in / out) to the downstream system and tail gas scrubber may be 1,320 GPM (in) and 1,350 GPM (out). In some embodiments, the pelletizing system 150 is a negative user.

[0215] There may be a fresh water / closed loop scrubber system: (inlet) 10 GPM to 20 GPM. For example, there may be a velocity of approximately 10 feet per second and a maximum flow of 55 GPM.

[0216] Phosphate-gypsum system

[0217] In some embodiments, in a plant operating at normal heat load (eg, phosphoric acid plant 110), rainfall over time equals evaporation. When the plant is shut down and loses heat load, the balance can shift toward excess water accumulation.

[0218] There may be various wash water streams: this may be a smaller stream. This is optional in some embodiments.

[0219] There may be a fill and seal water flow: this may be a smaller flow. This is optional in some embodiments.

[0220] There may be a drinking water stream / septic water stream: this may be a smaller stream. This is optional in some embodiments.

[0221] There may be evaporation / condensation in addition to the rain pond and cooling pond: this may be a smaller stream. This is optional in some embodiments.

[0222] In some embodiments, the various streams are inputs and / or outputs between the various systems included in phosphoric acid plant 110 , as described in the examples below.

[0223]

[0224] Explanation of terms

[0225] Throughout the description and claims, unless the context clearly requires otherwise:

[0226] "comprise", "comprising", etc. should be interpreted in an inclusive sense as opposed to an exclusive or exhaustive sense; that is, in the sense of "including but not limited to";

[0227] Unless otherwise stated, the amounts of chemical substances (e.g., P2O5, MgO, Mg, etc.) expressed in % are by weight. Unless otherwise stated, the ratios of the amounts of chemical substances are by weight;

[0228] "Connect," "couple," or any variation thereof, means any connection or coupling between two or more elements, whether direct or indirect; the connection or coupling between elements may be physical, logical, or a combination thereof;

[0229] "Herein," "above," "below," and words of similar import when used in describing this specification will refer to this specification as a whole and not to any particular portions of this specification;

[0230] • "or" with respect to a list of two or more items encompasses all of the following interpretations of the word: any item in the list, all items in the list, and any combination of items in the list;

[0231] The singular form also includes the meaning of any appropriate plural form.

[0232] The use of directional words such as "vertical," "lateral," "horizontal," "upward," "downward," "forward," "backward," "inward," "outward," "left," "right," "front," "backward," "top," "bottom," "below," "above," "below," and the like, if any, in this specification and any appended claims depends on the specific orientation of the device being described and illustrated. The subject matter described herein can assume various alternative orientations. Accordingly, these directional terms are not strictly limiting and should not be construed narrowly.

[0233] Although processes or blocks are presented in a given order, alternative examples may perform routines with steps or employ systems with blocks in a different order, and some processes or blocks may be deleted, moved, added, subdivided, combined, and / or modified to provide alternatives or sub-combinations. Each of these processes or blocks may be implemented in a variety of different ways. Furthermore, although processes or blocks are sometimes shown as being performed serially, these processes or blocks may alternatively be performed in parallel or may be performed at different times.

[0234] Where reference is made above to a component (e.g., a subsystem, an assembly, a device, etc.), unless otherwise specified, reference to the component (including reference to a "device") should be interpreted as including any component that performs the function of the component (i.e., is functionally equivalent) as an equivalent to the component, including components that are not structurally equivalent to the disclosed structure that performs the function in the exemplary embodiments illustrated by the invention.

[0235] For purposes of illustration, specific examples of systems, methods, and apparatus have been described herein. These are merely examples. The techniques provided herein may be applied to systems other than the exemplary systems described above. In the practice of the invention, many changes, modifications, additions, omissions, and permutations are possible. The present invention includes variations of the described embodiments that will be apparent to those skilled in the art, including variations obtained by: replacing features, elements, and / or actions with equivalent features, elements, and / or actions; mixing and matching features, elements, and / or actions from different embodiments; combining features, elements, and / or actions from the embodiments described herein with features, elements, and / or actions of other technologies; and / or omitting features, elements, and / or actions from combinations of the described embodiments.

[0236] Various features are described herein as being present in "some embodiments". Such features are not mandatory and may not be present in all embodiments. Embodiments of the invention may include zero, any one, or any combination of two or more of such features. This is limited to the extent that one of such features is incompatible with another of such features, in the sense that it would be impossible for one of ordinary skill in the art to construct an actual embodiment in which such incompatible features are combined. Thus, a description that "some embodiments" have feature A and that "some embodiments" have feature B should be interpreted as an explicit indication that the inventors also contemplate embodiments in which features A and B are combined (even if A and B are described in different sentences, paragraphs or parts of the disclosure and / or in different claims) (unless the description states otherwise or features A and B are fundamentally incompatible).

[0237] Any embodiment previously described or otherwise described in this application may be described or otherwise described as having more than one feature, arrangement of features, or combination of features. However, it is also contemplated that other embodiments may have only any one or more of those features, arrangements, and / or combinations. For example, where an embodiment is described or otherwise described as having features A, B, C, and D, even if not explicitly described or described, another embodiment may have only features A and C. As another example, another embodiment may have any combination of A, C, and D, including, for example, features A, C, D, and L. Furthermore, it is also contemplated that other embodiments may have one or more or all of the features described or otherwise described for one or more other embodiments. For example, if a first embodiment is described or otherwise described as having features E, F, G, and H, and a second embodiment is described or otherwise described as having features I, J, and K, then even if not explicitly described or described, another embodiment may have only features F, G, and J. As another example, another embodiment may have features F, G, J, and M.

[0238] It is therefore intended that the appended claims and claims hereafter introduced be interpreted to include all such modifications, permutations, additions, omissions, and sub-combinations that can reasonably be inferred. The scope of the claims should not be limited by the preferred embodiments described in the examples, but should be given the broadest interpretation consistent with the entire specification.

Claims

1. A method for processing phosphate rock, the method comprising the following steps: reacting phosphate rock with acid in a phosphoric acid plant to produce a filter cake by-product and a phosphoric acid product; discharging from the phosphoric acid plant an output stream comprising the aqueous phosphate solution obtained from the reaction step; supplying the phosphoric acid product to a granulation system; pelletizing a phosphate-containing fertilizer product using the phosphoric acid product in the pelletizing system, wherein the phosphoric acid plant and the pelletizing system are collectively operated at a negative water balance; Also includes: supplying a flushing fluid to the filter cake byproduct to obtain a filtrate comprising phosphoric acid; and recycling the filtrate to the phosphoric acid unit for use in the reaction step, The flushing fluid comprises fresh water, wherein an amount of the fresh water supplied to the flushing system as the flushing fluid is equal to or less than an amount of water consumed in producing struvite.

2. The method of claim 1, wherein the pelletizing system produces struvite as the phosphate-containing fertilizer product.

3. The method of claim 1 , further comprising purifying the aqueous phosphate solution at a precipitation system to generate one or more of a treated water stream, a sludge stream, and an effluent stream.

4. The method of claim 3, further comprising recycling the sludge stream or a portion of the sludge containing elevated phosphate content to the phosphoric acid plant for use in the reaction step.

5. The method of claim 3, wherein the flushing fluid comprises the treated water stream resulting from a purification step.

6. The method according to any one of claims 1 to 5, further comprising the steps of: collecting exhaust gases containing solid particles from an air stream released from the pelletizing step at an exhaust treatment system; and processing the exhaust gas to separate the solid particles; and The solid particles are supplied to one or more of the pelletizing system, crystallizer, and pond water treatment system. 7 . The method according to claim 6 , further comprising feeding the separated solid particles to a fine dust clarifier to separate fine dust particles. 8 . The method of claim 7 , further comprising dehydrating the fine dust particles to concentrate the dust particles.

9. The method of claim 7, further comprising recycling the dust particles into the granulation system for the granulation step.

10. The method of claim 6, wherein the processing step comprises mixing a scrubber fluid with the exhaust gas to produce a scrubber slurry comprising the solid particles.

11. The method according to any one of claims 7 to 9, further comprising supplying the separated fine dust particles to the crystallizer for producing phosphate-containing particles from the separated dust particles.

12. The method of claim 3, further comprising supplying the effluent stream generated by the purification step to a crystallizer for producing phosphate-containing particles from the effluent stream.

13. The method according to claim 6, further comprising: Accepts organic waste containing phosphate-containing materials; removing organic matter from the organic waste to form a phosphate-containing solution; and The phosphate-containing solution is supplied to one or more of the granulation system and the phosphoric acid plant.

14. The method according to claim 13, wherein the phosphate-containing solution is supplied to the crystallizer for crystallizing phosphate-containing particles from the solution.

15. The method of claim 13 or 14, wherein the organic waste comprises animal manure and / or poultry manure.

16. The method of claim 14, further comprising supplying the crystallized phosphate-containing particles to the granulation system for use in a granulation step to produce the phosphate-containing fertilizer product.

17. The method of claim 16, wherein the phosphate-containing particles comprise struvite.

18. The method of any one of claims 1 to 5, wherein the phosphate rock comprises a magnesium source at a concentration greater than a threshold value.

19. The method of claim 18, wherein the threshold value is 3% by weight of the total mineral content of the phosphate rock when expressed as MgO.

20. The method of claim 18, wherein the threshold value is 5% by weight of the total mineral content of the phosphate rock when expressed as MgO.

21. The method of any one of claims 1 to 5, wherein the concentration of the phosphoric acid product is below a threshold amount.

22. The method of claim 21, wherein the concentration of the phosphoric acid is less than 54 wt%.

23. The method of claim 21, wherein the concentration of the phosphoric acid is less than 40 wt%.

24. The method of any one of claims 3 to 5, further comprising concentrating the aqueous phosphate solution at a membrane filtration system to produce a concentrate stream and a clean water permeate stream.

25. The method of claim 24, wherein the membrane filtration system comprises nanofiltration and / or reverse osmosis.

26. The method of claim 24, wherein the flushing fluid used in the flushing step comprises the clean water permeate stream.

27. The method of claim 25, wherein the flushing fluid used in the flushing step comprises the clean water permeate stream.

28. The method of claim 24, wherein the concentrate stream is supplied to the precipitation system for purification.

29. The method of claim 25, wherein the concentrate stream is supplied to the precipitation system for purification.

30. The method of any one of claims 1 to 5, wherein the acid comprises sulfuric acid and the filter cake by-product comprises gypsum.

31. The method of any one of claims 3 to 5, wherein the purification of the aqueous phosphate solution at the precipitation system also generates a source of fluoride and / or gypsum.

32. The method of claim 6, further comprising: heating the struvite produced in the crystallizer to produce magnesia phosphate; and The schist is supplied to the granulation system to produce a schist-based fertilizer in the granulation step.

33. The method of claim 32, further comprising co-granulating the produced struvite and / or magnesia with any one of monoammonium phosphate (MAP), diammonium phosphate (DAP) and / or triple superphosphate (TSP) to produce the phosphate-containing fertilizer product.

34. The method of any one of claims 1 to 5, further comprising supplying one or more trace and macronutrients to the pelletizing system to produce the phosphate-containing fertilizer product.

35. The process according to any one of claims 1 to 5, wherein the granulation step is maintained at a temperature below 60°C.

36. The process according to any one of claims 1 to 5, wherein the granulation step is maintained at a temperature above 60°C.

37. The process of any one of claims 1 to 5, wherein the phosphoric acid comprises magnesium at a concentration such that the molar ratio of Mg:P in the phosphoric acid product is in the range of 1:25 to 1:

2.

38. The process of any one of claims 1 to 5, wherein the phosphoric acid comprises magnesium at a concentration such that the molar ratio of Mg:P in the phosphoric acid product is in the range of 1:7 to 1:

2.

39. The process of any one of claims 1 to 5, wherein the phosphoric acid comprises magnesium at a concentration such that the molar ratio of Mg:P in the phosphoric acid product is in the range of 1:6 to 1:

3.

40. The process of any one of claims 1 to 5, wherein the phosphoric acid comprises magnesium at a concentration such that the molar ratio of Mg:P in the phosphoric acid product is greater than 1:

15.

41. The method of any one of claims 1 to 5, further comprising delivering a source of ammonia to the granulation system.

42. The method of any one of claims 1 to 5, wherein the pelletizing system uses a source of magnesium from the phosphate rock to produce the phosphate-containing fertilizer product.

43. The method of any one of claims 1 to 5, further comprising supplying additional magnesium to the granulation system via a delivery system for producing the phosphate-containing fertilizer product.

44. The method of claim 6, wherein the crystallizer is a fluidized bed crystallizer.

45. A method of processing phosphate rock, the method comprising the steps of: reacting phosphate rock with an acid in a phosphoric acid plant to produce a filter cake byproduct and a phosphoric acid product, wherein the phosphate rock comprises a magnesium source at a concentration greater than a threshold value; discharging from the phosphoric acid plant an output stream comprising the aqueous phosphate solution obtained from the reaction step; purifying the aqueous phosphate brine at a pond water treatment system to produce a treated water stream and a sludge stream; supplying a flushing fluid to the filter cake byproduct to obtain a filtrate comprising phosphoric acid; recycling the filtrate to the phosphoric acid unit for use in the reaction step; supplying the phosphoric acid product to a granulator; granulating a fertilizer product in the granulator using the phosphoric acid product from the phosphate rock and the magnesium source, wherein the phosphoric acid unit and the granulator are operated together with a negative water balance; Also includes: supplying a flushing fluid to the filter cake byproduct to obtain a filtrate comprising phosphoric acid; and recycling the filtrate to the phosphoric acid unit for use in the reaction step, The flushing fluid is fresh water, wherein the amount of fresh water supplied to the flushing system as the flushing fluid is equal to or less than the amount of water consumed in producing struvite.

Images