EP3898518A1 - Systèmes et méthodes de traitement de désulfuration de gaz de combustion et de flux de déchets métallifères pour récupérer des matériaux à valeur ajoutée - Google Patents

Systèmes et méthodes de traitement de désulfuration de gaz de combustion et de flux de déchets métallifères pour récupérer des matériaux à valeur ajoutée

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Publication number
EP3898518A1
EP3898518A1 EP20744889.5A EP20744889A EP3898518A1 EP 3898518 A1 EP3898518 A1 EP 3898518A1 EP 20744889 A EP20744889 A EP 20744889A EP 3898518 A1 EP3898518 A1 EP 3898518A1
Authority
EP
European Patent Office
Prior art keywords
ash
component
feedstock
predetermined
reactor
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP20744889.5A
Other languages
German (de)
English (en)
Other versions
EP3898518A4 (fr
Inventor
Lucien M. PAPOUCHADO
Barry E. Scheetz
Joseph D. Preston
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Elixsys Inc
Original Assignee
Elixsys Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from US16/749,860 external-priority patent/US11148956B2/en
Application filed by Elixsys Inc filed Critical Elixsys Inc
Priority claimed from PCT/US2020/015102 external-priority patent/WO2020154699A1/fr
Publication of EP3898518A1 publication Critical patent/EP3898518A1/fr
Publication of EP3898518A4 publication Critical patent/EP3898518A4/fr
Pending legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B7/00—Working up raw materials other than ores, e.g. scrap, to produce non-ferrous metals and compounds thereof; Methods of a general interest or applied to the winning of more than two metals
    • C22B7/006—Wet processes
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/50—Carbon dioxide
    • C01B32/55—Solidifying
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/113—Silicon oxides; Hydrates thereof
    • C01B33/12—Silica; Hydrates thereof, e.g. lepidoic silicic acid
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
    • C01D3/00—Halides of sodium, potassium or alkali metals in general
    • C01D3/04—Chlorides
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F11/00—Compounds of calcium, strontium, or barium
    • C01F11/18—Carbonates
    • C01F11/181—Preparation of calcium carbonate by carbonation of aqueous solutions and characterised by control of the carbonation conditions
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F17/00—Compounds of rare earth metals
    • C01F17/20—Compounds containing only rare earth metals as the metal element
    • C01F17/206—Compounds containing only rare earth metals as the metal element oxide or hydroxide being the only anion
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F5/00—Compounds of magnesium
    • C01F5/02—Magnesia
    • C01F5/06—Magnesia by thermal decomposition of magnesium compounds
    • C01F5/08—Magnesia by thermal decomposition of magnesium compounds by calcining magnesium hydroxide
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F5/00—Compounds of magnesium
    • C01F5/14—Magnesium hydroxide
    • C01F5/22—Magnesium hydroxide from magnesium compounds with alkali hydroxides or alkaline- earth oxides or hydroxides
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F7/00—Compounds of aluminium
    • C01F7/02—Aluminium oxide; Aluminium hydroxide; Aluminates
    • C01F7/34—Preparation of aluminium hydroxide by precipitation from solutions containing aluminium salts
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F7/00—Compounds of aluminium
    • C01F7/02—Aluminium oxide; Aluminium hydroxide; Aluminates
    • C01F7/44—Dehydration of aluminium oxide or hydroxide, i.e. all conversions of one form into another involving a loss of water
    • C01F7/441—Dehydration of aluminium oxide or hydroxide, i.e. all conversions of one form into another involving a loss of water by calcination
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G49/00—Compounds of iron
    • C01G49/02—Oxides; Hydroxides
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G49/00—Compounds of iron
    • C01G49/02—Oxides; Hydroxides
    • C01G49/06—Ferric oxide [Fe2O3]
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B3/00—Extraction of metal compounds from ores or concentrates by wet processes
    • C22B3/02—Apparatus therefor
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B3/00—Extraction of metal compounds from ores or concentrates by wet processes
    • C22B3/20—Treatment or purification of solutions, e.g. obtained by leaching
    • C22B3/44—Treatment or purification of solutions, e.g. obtained by leaching by chemical processes
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B59/00—Obtaining rare earth metals
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/20—Recycling

Definitions

  • This disclosure relates generally to chemical processing of Coal Combustion Products (CCP) to produce value-added, marketable products while simultaneously minimizing or eliminating a resultant waste stream.
  • CCP Coal Combustion Products
  • Coal combustion products comprise fly ash (fine particulates collected in electrostatic precipitators), a lime or limestone absorption spray tower to separate out sulfur oxide (SO x ) gases, and bottom ash remaining behind after coal combustion.
  • the lime or limestone in the absorption bed reacts with the SO x gases resulting in calcium sulfite (hannabeckite, CaSO 3 .0.5H 2 O).
  • the calcium sulfite is often oxidized to calcium sulfate, which is referred to as flue gas desulfurization (FGD) gypsum.
  • FGD flue gas desulfurization
  • the calcium sulfite/sulfate byproduct is separate from the other byproducts while in others it is mixed in with the ash.
  • FGD gypsum conversion comprises reacting flue gas desulfurization (FGD) gypsum (calcium sulfate) feedstock, in either batch or continuous mode, with ammonium carbonate reagent to produce commercial products wherein the commercial products comprise ammonium sulfate and calcium carbonate.
  • Ash conversion comprises a leach process followed by a precipitation process to selectively precipitate components at predetermined pHs resulting in metal hydroxides which may be optionally converted to oxides or carbonates. The processes may be controlled by use of one or more processors.
  • Figure 1 depicts a system and method for combining an FGD gypsum conversion process with an ash conversion process.
  • Figure 2 depicts an embodiment of a production plant for implementing an FGD gypsum conversion process.
  • Figure 3 is a table showing the composition of an FGD gypsum feedstock used in preliminary testing.
  • Figure 4 depicts a particle size distribution analysis for the FGD gypsum feedstock used in preliminary testing.
  • Figure 5 depicts kinetic data for varying reagent additions in preliminary testing of the FGD gypsum conversion process.
  • Figure 6 depicts crystallized ammonium sulfate product assays for ammonium sulfate product generated in preliminary testing of the FGD conversion process.
  • Figure 7 depicts example test conditions and results from preliminary testing of the FGD conversion process.
  • Figure 8 depicts calculated final product generated in preliminary testing of the FGD conversion process.
  • Figure 9 depicts a schematic of a pilot production plant operating in continuous mode.
  • Figure 10 depicts calculated gypsum conversion with changing conditions in the pilot production plant depicted in Figure 8.
  • Figure 11 depicts discharge sulfur assays from the pilot production plant depicted in Figure 9.
  • Figure 12 depicts exemplary ammonium sulfate and calcium carbonate products produced by the pilot production plant depicted in Figure 9.
  • Figure 13 depicts a composition of an ammonium sulfate product produced by the pilot production plant depicted in Figure 9.
  • Figure 14 depicts an embodiment of a calcium sulfite oxidation process added to Figure 2 to treat the FGD gypsum feedstock prior to feeding into the FGD gypsum conversion process.
  • Figure 15 depicts an embodiment of an acid dissolution calcium carbonate whitening process.
  • Figure 16 depicts a whitened calcium carbonate product produced by the calcium carbonate whitening process depicted in Figure 15.
  • Figure 17 depicts an example embodiment of a process for using a catalyst to separate impurities from calcium carbonate product produced by the FGD conversion process.
  • Figure 18 depicts a lime embodiment of an ash conversion system and process.
  • Figure 19 is a continuation of the Figure 18 flowsheet.
  • Figure 20 depicts a caustic embodiment of an ash conversion system and process.
  • Figure 21 is a continuation of the Figure 20 flowsheet.
  • Figure 22 is a table depicting the major earth forming oxides of a class F and a class C ash feedstock used in preliminary testing of the ash conversion process.
  • Figure 23 is a table depicting the major, minor, and trace elemental composition of the class F and class C ash feedstocks used in preliminary testing of the ash conversion process.
  • Figure 24 is a table depicting mineralogical composition of the class F and class C ash feedstocks used in preliminary testing of the ash conversion process.
  • Figure 25 is a table depicting leaching results of class F and class C ash feedstocks using 3: 1 hydrochloric acid to nitric acid.
  • Figure 26 is a table depicting leaching results of class F and class C ash using sulfuric acid and sodium fluoride.
  • Figure 27 is a table depicting leaching results of class F and class C ash feedstock using sulfuric acid and calcium fluoride.
  • Figure 28 is a table depicting leaching results of class F and class C ash feedstock using hydrochloric acid in two stages starting with hydrochloric acid to pH 1.5 followed by 11% hydrochloric acid.
  • Figure 29 is a table depicting leaching results of class F and class C ash feedstock using hydrochloric acid in two stages starting with hydrochloric acid to pH 1.5 followed by 30% hydrochloric acid.
  • Figure 30 is a table depicting leaching results of class C ash feedstock using 30% hydrochloric acid for 24 hours on the residue after leaching in Figure 29.
  • Figure 31 graphically depicts 11% versus 30% hydrochloric acid leachates for class C ash feedstock.
  • Figure 32 graphically depicts 11% versus 30% hydrochloric acid leachates for class F ash feedstock.
  • Figure 33 graphically depicts elemental composition of 11% versus 30% hydrochloric acid residues for class C ash and class F ash feedstocks from Figures 28 and 29 leaches.
  • Figure 34 depicts X-ray Diffraction (XRD) mineralogical compositions of class C and class F leach residues resulting from Figures 28 and 29 leaches.
  • XRD X-ray Diffraction
  • Figure 35 is a flowsheet depicting a two-stage leach embodiment.
  • Figure 36 is a chart depicting cumulative precipitation percent versus pulp pH for class C ash feedstock.
  • Figure 37 is a chart depicting the cumulative precipitation of rare earth elements versus pulp pH for class C ash feedstock.
  • Figure 38 is a table depicting the percent composition of precipitate hydroxides at different pHs for class C ash feedstock.
  • Figure 39 is a chart depicting percent elements precipitated at pH 3 for class C ash feedstock.
  • Figure 40 is a chart depicting percent elements precipitated at pH 4 for class C ash feedstock.
  • Figure 41 is a chart depicting percent elements precipitated at pH 5-8 for class C ash feedstock.
  • Figure 42 is a chart depicting percent elements precipitated at pH 5-8 for class C ash feedstock with aluminum removed to show the smaller percentage more clearly.
  • Figure 43 is a chart depicting percent elements precipitated at pH 9 for class C ash feedstock.
  • Figure 44 is a chart depicting percent elements precipitated at pH 10 for class C ash feedstock.
  • Figure 45 is a chart depicting percent elements precipitated at pH 2.5 for class C ash feedstock.
  • Figure 46 is a table depicting cations and anion for the sodium chloride final stream anions for class C ash feedstock.
  • Figure 47 is a chart depicting cumulative precipitations versus pH for calcium carbonate and calcium hydroxide for class C ash feedstock.
  • Figure 48 is a table showing results from lime precipitation testing.
  • Figure 49 depicts an optional process embodiment for refining a silica product.
  • Figure 50 depicts another optional process embodiment for refining a silica product.
  • Headings are for organizational purposes only and are not intended to be limiting. Embodiments described under the various headings herein are interoperable with embodiments under other headings.
  • FIG. 1 depicts an ash conversion process 1800 combined with an FGD gypsum conversion process 200 (FIG. 2).
  • the depicted ash conversion process 1800 may be the lime embodiment 1800a (FIGS. 18 and 19) or the caustic embodiment 1800b (FIGS. 20 and 21) or variations thereof as disclosed herein.
  • FGD gypsum feedstock that is mixed with ash is processed in the FGD gypsum conversion process 200 resulting in an ammonium sulfate product and a calcium carbonate product that is mixed with ash.
  • the calcium carbonate and the FGD are insoluble and are separated in the fdtration process.
  • the calcium carbonate product that is mixed with ash is processed through the ash conversion process 1800 resulting in the ash conversion process products as disclosed herein.
  • the calcium carbonate, mixed with ash, from dryer 225 (FIG. 2) in the FGD gypsum conversion process proceeds to leach tank 1810 (FIGS. 18 and 20) in the ash conversion process.
  • FIG. 2 depicts an embodiment of a production plant 200 for implementing an FGD gypsum conversion process resulting in at least two commercial products.
  • FGD gypsum (calcium sulfate) feedstock is fed, either in batch or continuous mode, into a reactor cascade 205 (comprising reactors 210, 211, 212, and 213) with ammonium carbonate reagent, which may be synthesized from ammonia and carbon dioxide gases or supplied as a powder.
  • the FGD gypsum feedstock may be fed to the system using a quantitative powder feeder or a gravimetric feeder optionally coupled to a screw feeder (not shown).
  • the FGD gypsum feedstock is in powder form. In embodiments where the FGD gypsum feedstock is moist it may require drying prior to feeding to avoid blockages in the feeder. In some embodiments, the FGD gypsum feedstock may be dried to 7% by weight or less moisture content.
  • the number of reactors in the reactor cascade 205 may vary depending on throughput required, the size and type of reactors, and the reaction time needed. In some embodiments, there may be between three and five reactors. As an example, for a two-hour reaction with four reactors having total volume V, the scaled total volume needed would be 4/3 V for three reactors and 2V for two reactors. The same rule applies when increasing the number of reactors. In some embodiments, the size of the reactors 210, 211, 212, and 213 may be reduced using weirs.
  • the one or more reactors 210, 211, 212, and 213 may be connected in overflow mode (material overflows from the top of a reactor to the next reactor) or underflow mode (material flows from the bottom of a reactor to the next reactor), or material may be transferred using one or more pumps between the one or more reactors.
  • the one or more reactors 210, 211, 212, and 213 may be continuously stirred tank reactors (CSTRs), stirred tank reactors, and/or in-line (located in a transfer line) reactors.
  • the first reactor 210 may be a small, high intensity reactor to thoroughly mix the FGD gypsum feedstock and reagent, followed by two to three (larger, in some embodiments) reactors 211, 212, and/or 213 to hold the mixture long enough for the reaction to reach completion (i.e. 99+% conversion of FGD gypsum feedstock) resulting in a reacted slurry.
  • the reactor cascade 205 vents ammonia gas from the ammonium carbonate reagent through vent 215a to the scrubber 217. Either water or between 0.01 to 0.1M sulfuric acid may be used in the scrubber 217.
  • ammonia from the vents 215a-e dissolves in water to yield ammonium hydroxide or, in the case of sulfuric acid, the ammonia reacts to form ammonium sulfate.
  • the ammonium hydroxide or ammonium sulfate from the scrubber 217 may optionally be recycled back into the reagent feed line into reactor 210, in some embodiments.
  • the reacted slurry is pumped, underflows, or overflows from the reactor cascade 205 into a filter 220 resulting in calcium carbonate residue and ammonium sulfate filtrate liquor. Wash water is pumped through filter 220 in the depicted embodiment. Ammonia off-gases from the filter 220 vent through vent 215c to scrubber 217.
  • filter 220 may be a drum filter or other similar continuous filter.
  • the calcium carbonate residue from filter 220 proceeds to dryer 225 to produce calcium carbonate product. In the depicted embodiment, dryer 225 vents through vent 215c ammonia to scrubber 217. In some embodiments, the calcium carbonate product may be further processed. Further processing options are discussed in the Examples.
  • ammonium sulfate (AS) filtrate liquor proceeds from filter 220 to evaporator 230 where water is evaporated from the ammonium sulfate liquor, and then to crystallizer 235 where ammonium sulfate crystals are produced in ammonium sulfate liquor (also referred to as processed liquor).
  • Centrifuge 240 separates the ammonium sulfate crystals from the ammonium sulfate liquor (processed liquor) resulting in separated ammonium sulfate crystals and saturated ammonium sulfate liquor.
  • Dryer 245 dries the separated ammonium sulfate crystals resulting in ammonium sulfate product.
  • the dryer 245 vents through vent 215e to scrubber 217.
  • saturated ammonium sulfate liquor is pumped from the centrifuge 240 back into the evaporator 230. Overheads or vapors coming off the top of the evaporator 230, containing excess ammonium carbonate reagent, may optionally proceed through a condenser 250 (evaporator condensate) to be recycled back into the reactor cascade 205 to react with the FGD gypsum feedstock thus reducing reagent demand and reducing waste streams.
  • water is pumped into the reactor cascade 205 and into the ammonia scrubber 217.
  • all off-gases, including water vapor and ammonia vent through vents 215a, 215b, 215c, 215d, 215e to ammonia scrubber 217.
  • the ammonium sulfate may be vacuum evaporated, the salt allowed to crystallize out, and the solid product is then fdtered using a solid/liquid separation device.
  • the conditions in the crystallizer 235 may be controlled to produce larger crystals which are more desirable in some markets.
  • the ammonium sulfate product may be greater than or equal to 99% pure.
  • the ammonium sulfate crystallization and the centrifuge separation processes may be continuous.
  • Filter 220 and centrifuge 235 are both solid/liquid separators and may be substituted by other solid/liquid separators in other embodiments.
  • a belt fdter may be used in place of filter 220 and a rotating drum filter may be used in place of the centrifuge 235.
  • a spray dryer may be used in place of the evaporator 230 and crystallizer 235. The spray dryer evaporates the water and forms small crystals all in one step. Continuous filtration systems other than those depicted in Figure 2 may be utilized in the process.
  • the equipment used in the process may be sized to fit the desired input/output. Material transfer between processes / equipment may be carried out with the use of pumps, etc.
  • ammonium carbonate reagent is synthesized using ammonia (NH 3 ) and carbon dioxide (C0 2 ) gases in flowing water.
  • the NH 3 and C0 2 gas are injected in the stoichiometric ratio of 2: 1 respectively.
  • the gases may be introduced sequentially using gas nozzles into a flowing water stream in either a batch process or a continuous process.
  • the gases are best fed sequentially with the NH 3 first followed by the C0 2 because NH 3 is more soluble in water than C0 2 and C0 2 is more soluble in ammonium hydroxide than in plain water. This order of gas introduction into the water has been found to reduce the chances of an ammonia gas release.
  • the order of gas introduction into the water may be reversed. Sequential feed of the NH 3 and C0 2 gases reduces chance of clogging in the gas nozzle; however, the NH 3 and C0 2 gases may be premixed, in some embodiments.
  • the NH 3 and C0 2 gases may be mixed with process water using a mixer 108 such as an in-line mixer or a reactor tank with mixer resulting in an ammonium carbonate reagent solution.
  • the gases may be fed directly into mixer 208.
  • the pH may optionally be monitored to ensure carbonate is formed (between pH 8.7 - 9.0), not bicarbonate.
  • Conductivity and/or the specific gravity may be monitored using an electric conductivity meter and a hydrometer, respectively, to determine the concentration of ammonium carbonate reagent formed. Both conductivity and specific gravity increase as the concentration of the ammonium carbonate formed in solution increases. For example, for a 15% concentration of ammonium carbonate in solution, the conductivity is 80-90 mS/cm (milli-siemens/centimeter).
  • the resulting ammonium carbonate reagent may be fed directly into reactor cascade 205.
  • the ammonium carbonate reagent is added in excess (more than stoichiometric) to ensure the reaction goes to completion (i.e. that all the FGD gypsum feedstock is reacted).
  • 140% stoichiometric addition of the ammonium carbonate reagent results in the reaction going to completion. If the reaction is not complete, then the calcium carbonate product is contaminated with FGD gypsum feedstock.
  • the ammonium sulfate and/or the calcium carbonate products may be agglomerated in an agglomerator to larger, more flowable particles to facilitate product application. In some embodiments, the particles are several millimeters in size.
  • the ammonium sulfate and/or calcium carbonate products may be further treated with coating agents, such as stearic acid and stearates, to improve their properties for specific markets, such as to reduce their moisture absorption.
  • the ammonium sulfate and/or calcium carbonate products may be treated with an additive to reduce the absorption of water.
  • the ammonium sulfate product produced by production plant 200 may be used as a solution.
  • the ammonium sulfate product is greater than 99% pure.
  • the ammonium sulfate solid product is fertilizer grade.
  • Ammonium sulfate is primarily used in the global fertilizer industry as a soil amendment to replenish depleted levels of nitrogen and sulfur to the soil. An additional use in the fertilizer industry is as an adjuvant for various insecticides, herbicides, and fungicides.
  • Ammonium sulfate may also be used in non-agricultural products and processes such as for flameproofmg of select materials, textile dyeing, a cattle feed supplement, and for certain water treatment processes.
  • the calcium carbonate product produced by production plant 200 is insoluble.
  • the calcium carbonate product may contain small amounts of impurities, such as carbon and iron, which may cause it to have a grey or tan color.
  • the calcium carbonate is 90-99% pure.
  • the calcium carbonate product may be further processed to obtain a higher purity white calcium carbonate product which typically has higher market value.
  • Calcium carbonate has a plethora of uses in many diverse industries including: the oil and gas industry as drilling fluid make-up to increase the fluid density, as an additive to control fluid loss to formation, and in oilfield cementing as a loss circulation material; the building materials and construction industry for roofing shingles, tiles, and cement, brick, and concrete block manufacture; and commercial applications such as industrial filler in the paper, paint, plastics, and rubber industries.
  • C0 2 gas may be provided from other processes, plants, or sources including naturally occurring or stored C0 2 gas which may be pumped from underground formations. Carbon capture is another potential environmental benefit of the processes described herein as C0 2 gas is converted to a solid carbonate compound.
  • one or more internal recycles may be incorporated to recover reagents resulting in near-zero waste stream which is of significant environmental benefit.
  • FGD gypsum feedstock from a typical coal power plant was used as the feedstock in preliminary testing.
  • the composition of the FGD gypsum feedstock used in preliminary testing of the FGD conversion process is depicted in Figure 3 and the particle size analysis of the FGD gypsum feedstock is shown in Figure 4.
  • Values shown“ ⁇ X” are below detection limits, where X is the detection limit of the equipment used in the analysis.
  • FGD gypsum feedstock samples were slurried in water at 19% by weight solids and reacted with 15% concentration ammonium carbonate reagent solution at ambient temperature and pressure. Higher solids samples can also be used with equivalent increases in the ammonium carbonate reagent. Higher temperatures are not desirable because the ammonium carbonate reagent is less stable at higher temperatures.
  • Kinetic data for varying reagent additions used in preliminary testing of the FGD conversion process shows that at 140%- 150% stoichiometric additions of reagents to reactants the reaction between FGD gypsum feedstock and ammonium carbonate worked well and after one to three hours, at atmospheric pressure and ambient temperature, produced ammonium sulfate > 99.9% in the liquor and 93-95% calcium carbonate product. When evaporated to dryness, the purity of the ammonium sulfate was > 99.7%.
  • Assays for the crystallized ammonium sulfate product produced in preliminary testing of the FGD conversion process are depicted in Figure 6. The assay results were 99.7% or 99.9% depending on the assay method. Values shown“ ⁇ X” are below detection limits, where X is the detection limit.
  • the FGD conversion process may be operated in a continuous mode. Continuous mode was demonstrated in a pilot production plant 900, depicted in Figure 9, operated at an FGD gypsum feedstock feed rate of lkg/hr.
  • Ammonium carbonate reagent was mixed by mixer 902 with water in vessel 905 to produce a 15% concentration ammonium carbonate solution that was pumped by pump 907 into the first reactor 910, operating in an overflow mode to three other reactors 911, 912, and 913, to provide sufficient reaction time for the conversion to go to completion.
  • material may be transferred between the reactors 910, 911, 912, and 913 using underflow, overflow, or a pump.
  • the FGD gypsum feedstock was fed as a powder from bin 920 using a screw feeder 925 to the first reactor in the reactor cascade 922, comprising reactors 910, 911, 912, and 913, where it was mixed with the ammonium carbonate solution.
  • the slurry is then kept in suspension by mixers 931, 932, and 933 in each reactor 911, 912, and 913 to allow sufficient time for the reaction to take place.
  • the slurry overflowed from reactor 913 into a continuous filter 940 (alternating between two pan filters) to remove the solid calcium carbonate product (which was then washed) and the resulting filtrate, ammonium sulfate liquor, was collected in tank 945.
  • the wash liquid was collected in tank 846.
  • the pilot production plant 900 depicted in Figure 9 was operated at a constant 20°C ⁇ 3°C and a pH ranging between 7.5 and 8.5 for 110 hours (over the course of five days) at the following conditions:
  • Condition 1A 150% of the stoichiometric quantity of reactants, Day 1-2
  • FIG. 9 depicts calculated gypsum conversion with changing conditions in pilot production plant 900 (FIG. 9).
  • Figure 11 depicts discharge sulfur assays from the pilot production plant 900 (FIG. 9). Referencing Figure 9, the majority of the conversion took place within the first two reactors 910, 911 ( ⁇ 1.5 hours for Conditions 1A and 3; and ⁇ 0.75 hours for Conditions IB and 4). The third and fourth reactors 912, 913 provided extra time to complete the reaction for the remaining gypsum.
  • the FGD conversion process can produce a high purity ammonium sulfate and a second product that is comprised of calcium carbonate and ash.
  • This product can be marketed as such, particularly to building material applications, or further processed in other separation schemes.
  • the processing system and methods for FGD gypsum feedstock that is mixed with ash is the same as that depicted in Figure 2; however, the calcium carbonate product may be lower purity than that generated from an FGD gypsum feedstock that is not mixed with ash.
  • FIG. 1 depicts a process where FGD feedstock mixed with ash can be processed in the FGD conversion process and the calcium carbonate mixed with ash can be processed in the ash conversion process depicted in Figures 18 through 21.
  • FGD gypsum feedstock contains levels of chloride that are too high for certain applications.
  • the excess chloride is removed from FGD gypsum feedstock through a process of water leaching, in some embodiments. Water leaching may be carried out at any temperature between room temperature (20°C) and boiling (100°C).
  • step 5 After the half hour agitation time, filter out the leached solids from step 4 and collect the filtrate, record filtration properties.
  • the fdtrate from the ammonium sulfate crystallization contains most of the chloride at 94.2%, the ammonium sulfate contained 5.2% and the calcium carbonate 0.6%.
  • Coal combustion products are comprised of fly ash (fine particulates from the combustion process collected in filters), a lime or limestone absorption bed to clean out sulfur dioxide (S0 2 ) gases, and bottom ash remaining behind after coal combustion.
  • the absorption bed is converted to calcium sulfate after absorption of SOx and oxidation of calcium sulfite to calcium sulfate.
  • the calcium sulfate is the FGD gypsum feedstock.
  • the FGD gypsum feedstock may be in the form of a calcium sulfite slurry.
  • an oxidation step may be required to convert calcium sulfite to calcium sulfate. While there are several well-established methods to oxidize calcium sulfite to calcium sulfate, none have been coupled to a more comprehensive conversion process. The conversion of calcium sulfite to calcium sulfate (gypsum) is a well-developed technology, which is widely practiced and generally understood. There are a number of oxidation methods that may be coupled to the FGD conversion process depicted in Figure 2.
  • Figure 14 depicts a modified production plant 200 (FIG. 2) with the addition of an oxidation step 1400 for calcium sulfite to calcium sulfate conversion prior to feeding into the FGD gypsum conversion process.
  • Oxidation with Oxygen The oxidation of calcium sulfite to calcium sulfate can be accelerated by using oxygen in place of air. Oxygen concentrations as low as 5% by volume may be effective. In another embodiment, a low concentration of a metal ion is added as a catalyst to the reaction. An example would be 5 to 10 ppm ferric ion, manganese(II), or cobalt(II).
  • Hydrogen Peroxide Oxidation Sulfur dioxide, and/or its aqueous byproduct sulfite, can be oxidized to sulfate with hydrogen peroxide. The reaction occurs over a wide pH range but is faster at lower pHs. This is conducted in an aqueous medium and involves the oxidation of dissolved sulfite ion with peroxide to convert to the more insoluble sulfate. Calcium peroxide may be used in place of hydrogen peroxide.
  • the calcium carbonate product produced by the FGD gypsum conversion process may comprise contaminants such as iron, carbon, and silicates. When such contaminants are present, the calcium carbonate may proceed through further processing to remove such contaminants resulting in a purer product.
  • the calcium carbonate product may be dissolved in dissolver 1502 in dilute acid (such as hydrochloric acid (HC1), nitric acid (HN0 3 ), or another acid forming a soluble calcium salt).
  • dilute acid such as hydrochloric acid (HC1), nitric acid (HN0 3 )
  • the carbon dioxide generated by equation 2 in dissolver 1502, in the depicted embodiment, may proceed to scrubber 1505 containing sodium hydroxide to form sodium carbonate.
  • the mixture resulting from equation 2 may then be filtered by filter 1510 with solid impurities proceeding to dryer 1515 and liquids proceeding to reactor 1520.
  • the dried solids may comprise carbon and silicates, in some embodiments.
  • hydrogen peroxide H 2 0 2
  • An amount of base such as calcium hydroxide (in depicted embodiment), sodium hydroxide, and/or sodium carbonate may also be added to reactor 1520 to raise the pH in the reactor to 3 or higher to precipitate ferric hydroxide.
  • the advantage of using calcium hydroxide is that the amount of high purity precipitated calcium carbonate produced is increased by the amount of calcium neutralizing agent used, thus improving process economics.
  • the amount of base added is the amount that is necessary to reach the desired pH value. This reaction with sodium hydroxide is shown in equation 3, below:
  • the slurry resulting from equation 3 in reactor 1520 may be fdtered with fdter 1525 to remove ferric hydroxide solids.
  • some carbon impurity may also fdter out with the ferric hydroxide.
  • the ferric hydroxide is transferred to calciner 1530 resulting in a ferric oxide product.
  • the fdtrate from fdter 1525 comprises a purified calcium chloride solution, or a mixed calcium and sodium chloride solution depending on the base used, which may then be combined with sodium carbonate, carbon dioxide, or another soluble carbonate, in reactor 1535 to produce precipitated calcium carbonate.
  • the mixture may proceed through filter 1540 to separate solids and liquids.
  • the solids may proceed through dryer 1545 to produce a white and high purity (>98%) precipitated calcium carbonate product.
  • the precipitation reaction with sodium carbonate is shown in equation 4.
  • the filtrate from filter 1540 may proceed through dryer 1555 to produce sodium chloride.
  • Figure 16 depicts a whitened calcium carbonate product generated by the calcium whitening process depicted in Figure 15.
  • a catalyst to delay the formation of calcium carbonate may be added to the reactor cascade 205 (FIG. 2) so that impurities (or impurities plus ash, in some embodiments) may be filtered out before the precipitate is formed.
  • the addition of a catalyst results in a fine white and high purity (>98%) precipitated calcium carbonate product.
  • FGD gypsum feedstock may comprise contaminants including carbon and/or fly ash, in some embodiments.
  • An example embodiment of a process for using a catalyst to separate impurities from calcium carbonate is depicted in Figure 17.
  • a quantity of a catalyst (0.5 - 7% by weight, in some embodiments) may be added to an FGD gypsum slurry mixture in a reactor 1610 wherein the FGD gypsum slurry mixture comprises a suspension in the range of 1% to 25% (4%, in some embodiments) weight by mass of FGD gypsum feedstock in water.
  • the catalyst is allowed to mix, by means of a stirring mechanism in some embodiments, with the slurry for several minutes (5-30 minutes, in some embodiments).
  • an ammonium hydroxide solution may be added to the reactor vessel 1710 resulting in 1: 1 ammonium hydroxide to slurry volumetric ratio. This addition of the ammonium hydroxide is immediately followed by the introduction of carbon dioxide gas at a rate of 4L/minute ⁇ lL/minute, in some embodiments.
  • the concentration of the ammonium hydroxide solution is chosen to be a concentration that will stoichiometrically react with all of the sulfate in the FGD gypsum slurry to form ammonium sulfate according to equation 5 :
  • the progress of the reaction can be followed by monitoring the pH which starts out at approximately 11.6 and with time drops to pH 7. At pH 7 all hydroxide has reacted and the solution is fdtered (immediately, in some embodiments) through a 0.45 to 0.7 micron fdter 1730. Filtration of the reacted FGD gypsum solution results in the separation of tramp fly ash and carbon from the resulting liquid comprising dissolved calcium carbonate and ammonium sulfate. The calcium carbonate in solution will separate from the ammonium sulfate solution in delay holding tank 1735 and can be collected by an additional fdtration step 1740 using a 0.45 to 0.7 micron. In some embodiments, one or more of the fdtration steps may be carried out using a filter composed of glass fibers.
  • the precipitation of calcium carbonate may be aided by seeding the solution with the desired crystalline form of calcium carbonate.
  • a small amount of product slurry may be recycled back to the reactor cascade 205 (FIG. 2).
  • the seeds may be calcite.
  • the CaC0 3 precipitate may be so fine it is nano-sized.
  • the solution containing the CaC0 3 may be heated to cause the CaC0 3 precipitate to coagulate to improve filtration. This process also allows a wider range of feedstocks such as FGD gypsum feedstock mixed with ash.
  • the solution passing filtration step 1740 contains the ammonium sulfate which can be harvested by various crystallization methods known in the art.
  • a catalyst is used to slow down the precipitation of calcium carbonate in order to allow the solution to be filtered. Some of the catalyst may remain in the ammonium sulfate solution and/or the crystallized product. The catalyst does not react with the reactants therefore it may be recaptured and/or recycled, in some embodiments.
  • the filtered ammonium sulfate solution may be returned to the beginning of the process to make up the FGD gypsum feedstock slurry.
  • the appropriate concentration of catalyst may remain in the recycled solution such that no further addition of the catalyst is necessary.
  • makeup catalyst may be added to the solution as needed.
  • the calcium carbonate whitening process with catalyst can also be performed in the production plant embodiment shown in Figure 2 with some modifications. For instance, referring to Figure 2, the calcium carbonate whitening process with catalyst may plug in in the place of filter 220. Reacted slurry from the reactor cascade 205 would proceed into reactor 1710 (FIG. 17) through the process depicted in Figure 17 with the liquor from filter 1640 (FIG.
  • the catalyst may be added to the reactor cascade directly and the reacted slurry with catalyst may proceed from the reactor cascade 205 to filter 1730 (FIG. 17) (i.e. reactor cascade 205 from Figure 2 replaces reactor 1710 in Figure 17).
  • Described herein are systems and methods for generating valuable products from coal ash with near-zero waste.
  • the systems and methods disclosed herein are unique in that they are the first demonstrated systems and methods that can convert coal ash feedstock (and other metal-bearing feedstocks) into marketable products of high value with near- zero waste.
  • the ash conversion process begins with a leach process.
  • a leach process in some embodiments, involved contacting, passing, and/or percolating an acid through a feedstock.
  • the leach process may be performed in one or more stages using one or more different acids or different concentrations of the same acids.
  • the leach process is performed in two- stages using different concentrations of hydrochloric acid.
  • elements and/or compounds in leachate resulting from the leach process in the ash conversion process may then be further separated by selective precipitation at one or more different pHs. pH adjustments may be made to the leachate using a base such as calcium hydroxide (lime) or sodium hydroxide (caustic), or both in separate steps. Potassium and ammonium hydroxides are other possible bases that may be utilized for pH adjustment of the leachate. After each precipitation, the precipitate is separated by filtration and the filtrate proceeds to the next pH adjustment and precipitation. In some embodiments, one or more of hydroxides of iron, aluminum, mischmetals (rare earth elements (REEs) and transition metals), magnesium, and calcium may be separated sequentially.
  • a base such as calcium hydroxide (lime) or sodium hydroxide (caustic), or both in separate steps. Potassium and ammonium hydroxides are other possible bases that may be utilized for pH adjustment of the leachate.
  • the precipitate is separated by filtration and the filtrate proceeds to the
  • the separations are quite clean and high purities (greater than 90%) may be obtained.
  • the final liquor at the end of the ash conversion process may comprise clean sodium chloride, resulting in near-zero waste streams.
  • Figures 18 through 21 depict embodiments of an ash conversion system and method for producing valuable products from an ash feedstock with near zero waste.
  • Figures 18 and 19 depict a lime embodiment of the ash conversion system and method and
  • Figures 20 and 21 depict a caustic embodiment of the ash conversion system and method.
  • the ash feedstock is powdered.
  • the ash feedstock is slurried.
  • FIGs 18 and 19 depict a lime embodiment 1800a of the ash conversion system and method for producing valuable products from an ash feedstock with near-zero waste.
  • ash feedstock is first floated with water in flotation tank 1805 to remove microspheres which can be marketed as a product.
  • microspheres make up 1-2% of the ash feedstock.
  • the remainder of the ash feedstock, with optional solids recycle from a silica fusion process depicted in Figure 50 proceeds to leach tank 1810 in leach process 1811.
  • Leaching may be completed in one or two stages using one or more different acids or different concentrations of the same acids resulting in leached ash feedstock.
  • leaching is performed in two-stages with hydrochloric acid (HC1) of differing concentrations.
  • HC1 hydrochloric acid
  • the leached ash feedstock is separated in solid/liquid separator 1815 resulting in solids, comprising silica and other impurities in some embodiments, and liquor.
  • the solids may proceed to either Figure 49 or Figure 50 for further processing.
  • the liquor from solid/liquid separator 1815, along with optional liquor recycle from Figure 49 proceeds to a pH adjustment tank 1820 where pH is adjusted to precipitate particular components.
  • the pH is first adjusted to pH 1 using calcium carbonate (CaC0 3 ) then to between pH 2.5 to 3 using calcium hydroxide (Ca(OH) 2 or lime).
  • Hydrogen peroxide (H 2 0 2 ) may also be added to the pH adjustment tank 1820 to convert ferrous iron to ferric iron.
  • the pH adjusted solution from pH adjustment tank 1820 proceeds to solid/liquid separator 1825 resulting in solids comprising predominantly iron hydroxide (Fe(OH) 3 ) precipitate and liquor.
  • Fe(OH) 3 may be marketed as-is or calcined in an oven 1830 (at 300°C, in some embodiments) with air circulation to iron oxide (alpha-Fe 2 0 3 ).
  • the liquor from solid/liquid separator 1825 proceeds to a second pH adjustment tank 1835 where the pH is adjusted to pH 4 using Ca(OH) 2 , in the depicted embodiment.
  • the pH adjusted solution from pH adjustment tank 1835 proceeds to solid/liquid separator 1840 resulting in solids comprising predominantly aluminum hydroxide (Al(OH) 3 ) and liquor.
  • the Al(OH) 3 can be marketed as-is or calcined in an oven 1845 (at 250°C, in some embodiments) to alumina (A1 2 0 3 ).
  • the liquor from solid/liquid separator 1840 proceeds to a third pH adjustment tank 1850 where the pH is adjusted to pH 8 using Ca(OH) 2 , in the depicted embodiment.
  • the pH adjusted solution from pH adjustment tank 1850 proceeds to Figure 19.
  • FIG. 19 is a continuation of Figure 18.
  • the pH adjusted solution from the third pH adjustment tank 1850 proceeds to solid/liquid separator 1855 resulting in solids comprising predominantly rare earth hydroxides and some transition metals.
  • the transition metals and rare earth hydroxides may be sold as-is or may proceed to further separation / processing disclosed in more detail under the Products heading.
  • the liquor from solid/liquid separator 1855 proceeds to a fourth pH adjustment tank 1865 where the pH is adjusted to pH 10.5 to 11 using Ca(OH) 2 , in the depicted embodiment.
  • the pH adjusted solution from pH adjustment tank 1865 proceeds to solid/liquid separator 1870 resulting in solids comprising predominantly magnesium hydroxide (Mg(OH) 2 ) and liquor.
  • Mg(OH) 2 magnesium hydroxide
  • the Mg(OH) 2 may be marketed as-is or may be calcined in an oven 1875 (at 250°C, in some embodiments) to magnesium oxide (MgO).
  • the liquor from solid/liquid separator 1870, which contains calcium ions, proceeds to precipitation tank 1880 where a stoichiometric amount of sodium carbonate (Na 2 C0 3 ) is added to precipitate calcium carbonate.
  • the solution from the precipitation tank 1880 proceeds to solid/liquid separator 1885 resulting in solid calcium carbonate (CaC0 3 ) and a liquor.
  • the total calcium carbonate produced is the sum of the calcium in the ash feed plus the lime reagent (Ca(OH) 2 ) used for pH adjustment.
  • the liquor from solid/liquid separator 1885 proceeds to an acid neutralization tank 1890 where the hydroxides used in the solid/liquid separation steps (1815, 1825, 1840 FIG. 18 and 1855, 1870, 1885 FIG. 19) are neutralized to pH 7 with HC1.
  • the final product is sodium chloride (NaCl) and may be marketed as a solution (brine) or the NaCl salt may be crystallized out of the solution using a crystallizer or spray dryer (not depicted).
  • the caustic embodiment 100b (FIGS. 20 and 21) of the ash conversion process comprises essentially the same steps and equipment as the lime embodiment 100a (FIGS. 18 and 19) of the ash conversion process with the primary difference being in the reagent used in pH adjustment steps.
  • caustic (NaOH) is used in place of lime (Ca(OH) 2 in the pH adjustment steps.
  • the NaOH may be 20%.
  • FIGS 20 and 21 depict a caustic embodiment 1800b of the ash conversion system and method for producing valuable products from an ash feedstock with near-zero waste.
  • ash feedstock is first floated with water in flotation tank 1805 to remove microspheres which can be marketed as a product.
  • microspheres make up 1-2% of the ash feedstock.
  • the remainder of the ash feedstock, with optional solids recycle from a silica fusion process depicted in Figure 50 proceeds to leach tank 1810 in leach process 1811.
  • Leaching may be completed in one or two stages using one or more different acids or different concentrations of the same acids resulting in leached ash feedstock.
  • leaching is performed in two-stages with hydrochloric acid (HC1) of differing concentrations.
  • HC1 hydrochloric acid
  • the leached ash feedstock is separated in solid/liquid separator 1815 resulting in solids, comprising silica and other impurities in some embodiments, and liquor.
  • the solids may proceed to either Figure 49 or Figure 50 for further processing.
  • the liquor from solid/liquid separator 1815, along with optional liquor recycle from Figure 49 proceeds to a pH adjustment tank 1820 where pH is adjusted to precipitate particular components.
  • the pH is adjust to 2.5-3 using sodium hydroxide (NaOH or caustic).
  • Hydrogen peroxide (H 2 0 2 ) may also be added to the pH adjustment tank 1820 to convert ferrous iron to ferric iron.
  • the pH adjusted solution from pH adjustment tank 1820 proceeds to solid/liquid separator 1825 resulting in solids comprising predominantly iron hydroxide (Fe(OH) 3 ) precipitate and liquor.
  • Fe(OH) 3 may be marketed as-is or calcined in an oven 1830 (at 300°C, in some embodiments) with air circulation to iron oxide (alpha-Fe 2 0 3 ).
  • the liquor from solid/liquid separator 1825 proceeds to a second pH adjustment tank 1835 where the pH is adjusted to pH 4 using NaOH, in the depicted embodiment.
  • the pH adjusted solution from pH adjustment tank 1835 proceeds to solid/liquid separator 1840 resulting in solids comprising predominantly aluminum hydroxide (Al(OH) 3 ) and liquor.
  • the Al(OH) 3 can be marketed as-is or calcined in an oven 1845 (at 250°C, in some embodiments) to alumina (A1 2 0 3 ).
  • the liquor from solid/liquid separator 1840 proceeds to a third pH adjustment tank 1850 where the pH is adjusted to pH 8 using NaOH, in the depicted embodiment.
  • the pH adjusted solution from pH adjustment tank 1850 proceeds to Figure 21.
  • FIG. 21 is a continuation of Figure 20.
  • the pH adjusted solution from the third pH adjustment tank 1850 proceeds to solid/liquid separator 1855 resulting in solids comprising predominantly rare earth hydroxides and some transition metals.
  • the transition metals and rare earth hydroxides may be sold as-is or may proceed to further separation / processing disclosed in more detail under the Products heading.
  • the liquor from solid/liquid separator 1855 proceeds to a fourth pH adjustment tank 1865 where the pH is adjusted to pH 10.5 to 11 using NaOH, in the depicted embodiment.
  • the pH adjusted solution from pH adjustment tank 1865 proceeds to solid/liquid separator 1870 resulting in solids comprising predominantly magnesium hydroxide (Mg(OH) 2 ) and liquor.
  • Mg(OH) 2 magnesium hydroxide
  • the Mg(OH) 2 may be marketed as-is or may be calcined in an oven 1875 (at 250°C, in some embodiments) to magnesium oxide (MgO).
  • the liquor from solid/liquid separator 1870 proceeds to a fifth pH adjustment tank 1880 where the pH is adjusted to between 12.5-13 using NaOH, in the depicted embodiment.
  • the pH adjusted solution from pH adjustment tank 1880 proceeds to solid/liquid separator 1885 resulting in solid calcium hydroxide (Ca(OH) 2 ) and liquor.
  • sodium carbonate may be added to the liquor from 1885 to precipitate traces of barium and strontium before neutralization in tank 1890.
  • the Ca(OH) 2 may be converted to calcium carbonate (CaC0 3 ) with the addition of C0 2 .
  • the liquor from solid/liquid separator 1885 proceeds to an acid neutralization tank 1890 where the hydroxides used in the solid/liquid separation steps (1815, 1825, 1840 FIG. 20 and 1855, 1870, 1885 FIG. 21) are neutralized to pH 7 with HC1.
  • the final product is sodium chloride (NaCl) and may be marketed as a solution (brine) or the NaCl salt may be crystallized out of the solution using a crystallizer or spray dryer (not depicted).
  • the final calcium precipitation is not performed, and the final product is a sodium chloride/calcium chloride blend.
  • the solid/liquid separators depicted in Figures 18 through 21 may be any one or more of centrifuges, disc, pan, belt, or drum filters, or other solid/liquid separators. To help coagulation of the precipitate and ease filtration, techniques such as heating or seeding with recycled product (10-30%) could be used. Calcine temperatures may be between 250°C and 300°C. Material transfer between processes / equipment may be carried out with the use of pumps, etc.
  • the ash conversion systems and methods disclosed herein are capable of being applied to waste streams other than coal ash such as red mud waste from the bauxite (comprising Fe 2 0 3 , A1 2 0 3 , Si0 2 , CaO, Na 2 0, TiO, K 2 0 and MgO) in the synthesis of aluminum, slag from the steel furnaces (comprising CaO, Si0 2 , A1 2 0 3 , FeO, and MgO), municipal incinerator solid waste, acid mine drainage, mine tailings, and other metal bearing waste streams, because of their similar compositions.
  • Some variations in type and composition of feedstock may require additional or fewer processing steps.
  • feedstock may require grinding to reduce particle size prior to processing in the ash conversion process.
  • the feedstock may be in powder form wherein powder is a bulk solid composed of many very fine particles.
  • feedstock may need to be dispersed in slurry prior to processing in the ash conversion process.
  • the feedstock may be a slurry of metal-bearing solids suspended in liquid.
  • the products are generally 1) silica, 2) ferric oxide, 3) aluminum oxide, 4) a mixture of REE and transition elements that are concentrated between 20 to 100-fold from the original coal ash, 5) magnesium oxide, 6) calcium carbonate, and 7) sodium chloride.
  • the oxides originally precipitate as hydroxides and may optionally be marketed as such.
  • the hydroxides may be converted to carbonates using reactants such as carbon dioxide.
  • manganese may be precipitated between the REEs and the magnesium at a pH of 9.
  • the leach residue from solid/liquid separator 1815 is predominantly amorphous and crystalline silica, technical grade, which has commercial applications.
  • Commercial applications for the silica product include: as additives in tires, elastomers, and plastics; in the construction industry as an anti-caking agent; for sand casting for manufacture of metallic components; and for use in glassmaking and ceramics. The value improves with higher purity, smaller particle size, and larger surface areas.
  • the silica also contains some aluminum silicate such as fibrous mullite or high aspect ratio mullite. This mullite could have its own intrinsic high value for uses in high temperature applications as in ceramic-in -ceramic fiber reinforcements for ceramic engines.
  • Ferric oxide is used primarily as a pigment in paints, glazes, coatings, colored concrete, mulches, mordant, coating for magnetic recording tapes, the manufacturing of polishing compounds and as an abrasive for glass, precious metals, and diamonds.
  • Aluminum hydroxide is often used as a feedstock for the manufacture of other aluminum compounds and in the manufacture of abrasives, water-proofing, water treatment, and as a filter medium. Additional uses include the manufacture of aluminosilicate glass, a high melting point glass used in cooking utensils and in the production of fire clay, pottery, and printing ink. Aluminum oxide is often used in glass, water purification, paint, and as a filler in plastics and cosmetics.
  • Magnesium hydroxide is used in the waste water treatment process; as a flame or fire retardant filler; as a fuel additive to treat heavy fuel oils; as well as in the ceramic glazing process.
  • Magnesium oxide is used as an anticaking agent in foods, in ceramics to improve toughness, and in optics.
  • Magnesium carbonate is used in fireproofing, a smoke suppressant in plastics, and a reinforcing agent in rubber.
  • Calcium carbonate has a plethora of uses in many diverse industries including: the oil and gas industry as drilling fluid make-up to increase the fluid density, as an additive to control fluid loss to formation, the oilfield cementing industry as a loss circulation material; the building materials and construction industry for roofing shingles, tiles, cement, brick, and concrete block manufacture; and commercial applications such as industrial filler in the paper, paint, plastics, and rubber industries.
  • Sodium chloride solution is used in a myriad of industrial applications. It is used in the chlor- alkali process, the process to produce chlorine and sodium hydroxide (see Examples for more detail). It is also widely used as a de-icing and anti-icing agent in winter climate road applications and as a dust suppressant in many mining operations. Crystallization of sodium chloride solution will produce dry sodium chloride crystals, commonly referred to as salt. Sodium chloride crystals are used across oil and gas exploration activities as an additive to drilling fluids as well as cementing operations, in the pulp and paper industry as a bleaching product for wood pulp, in the water softening industry, swimming pool chemical industry as pool salt and in a great number of other industrial applications.
  • Class F ash feedstock from Northern Appalachian coal and class C ash feedstock from Powder River Basin Coal were used in preliminary testing of the ash conversion process to ensure wide applicability.
  • Class C ash feedstock contains more calcium and less silica while class F ash feedstock contains less calcium and more silica and is more difficult to acid leach.
  • Figures 22 through 24 depict the compositions (elemental composition as well as mineral compounds by XRD) of the class F and class C ash feedstocks used in preliminary testing of the ash conversion process.
  • Displacement wash three times with 70 mL water. Displacement washing may be done two to four times in water. 8. Collect the combined wash liquors, record fdtration properties (time, color, paper type, etc.), determine weight, specific gravity, pH, and ORP.
  • Figure 25 is a table depicting leach test results of class F and class C ash feedstocks using 3: 1 6N hydrochloric acid (HC1) to 6N nitric acid (HN0 3 ) for 6 hours.
  • Figure 25 indicates good leaching results but the reaction was very vigorous and NOx fumes were liberated.
  • the 6N aqua regia was found to be effective for the more difficult to dissolve class F ash feedstock; however, the aqua regia adds nitrate to the final sodium chloride product of the ash conversion process which is not ideal because it results in a sodium chloride / sodium nitrate mixture which is more difficult to market than sodium chloride.
  • Figure 26 is a table depicting leach test results of class F and class C ash feedstocks using 6N sulfuric acid (H 2 S0 4 ) and 0.006N sodium fluoride (NaF). This reaction forms insoluble sulfates with calcium so it remains with the insoluble silica. Class F ash feedstock dissolution was poor.
  • Figure 27 is a table depicting leach test results of class F and class C ash feedstocks using 6N sulfuric acid (H 2 S0 4 ) and 0.05% calcium fluoride (CaF 2 ). This testing had similar results to Figure 26 (6N sulfuric acid and 0.006N sodium fluoride).
  • Figure 28 is a table depicting leach test results of class F and class C ash feedstocks using HC1 to pH 1.5 in a first stage then 11% HC1 in a second stage.
  • the dissolution of the class C ash feedstock was excellent but class F ash feedstock did not perform as well.
  • Most of the calcium dissolves in the first stage at pH 1.5. There is improved dissolution at the higher acid concentration for the other major elements. Dissolution continued to improve with time.
  • Figure 29 is a table depicting leach test results of class F and class C ash feedstocks using HC1 to pH 1.5 in a first stage then 30% HC1 in a second stage.
  • the class F ash feedstock had much better dissolution at 30% HC1 in the second stage compared to the 11% HC1 in Figure 11.
  • the class C ash feedstock dissolution on the other hand, only improved slightly compared to the 11% HC1 second stage in Figure 28.
  • the class F ash feedstock showed that the leaching improved with time.
  • Figure 30 is a table depicting leach test results for continuing the second-stage (30% HC1) leach of Figure 29 for class C ash feedstock for 24 hours.
  • the longer leach test time improved dissolution for all elements and results in improved quality of silica residue.
  • Figure 35 depicts a two-stage leach process 3500. This process may replace the single stage leach process 1811 depicted in Figures 18 and 20.
  • ash feedstock enters a first leach tank 3510 where it is leached with acid resulting in a first leachate.
  • the first leachate proceeds to solid/liquid separator 3515 resulting in a liquor which proceeds to precipitation steps and a residue.
  • the residue proceeds to a second leach tank 3520 resulting in a second leachate.
  • the second leachate proceeds to solid/liquid separator 3525 resulting in a silica residue or product and a liquor.
  • the liquor from solid/liquid separator 3525 is routed back to the first leach tank 3510.
  • the acid used in the first leach tank 3510 is HC1 to pH 1.5. In some embodiments, the acid in the second leach tank is 11 %-30% HC1.
  • X-ray Diffraction (XRD) patterns together with elemental analysis showed the final residues from the preliminary leach tests were primarily amorphous silica with minor amounts of crystalline silica, silicates (mullite), barite, phosphates, and titanates. The final residues from preliminary leach tests were grey in color due to a carbon impurity. Depending on the composition of the ash feedstock, residues may not have carbon impurities or may comprise other impurities.
  • the silica residue may be calcined at 600°C or higher to bum off all the carbon resulting in an off-white silica product with potentially improved market value over silica containing carbon impurities. These final residues can be further purified by an additional leaching in 30% HC1 for 24 hours.
  • the leachate may be combined with the other leachates and recycled through the ash conversion process, in some embodiments.
  • One adjustment that may be made prior to the first precipitation is to add hydrogen peroxide to oxidize ferrous ion to ferric ion.
  • the sequence of precipitates is: Fe, Al, REEs and transition metals, Mg, and Ca for ash feedstock.
  • Precipitation testing identified target pHs (also referred to herein as pH cuts) at which one or more certain elements precipitated out of the leachate into the residue.
  • Figure 36 is a chart depicting cumulative precipitation percent versus pulp pH for class C ash.
  • the liquor is filtered to separate a product and the filtrate is then subjected to the next pH condition.
  • the precipitates for iron and aluminum are difficult to filter with simple vacuum filtration but that is facilitated by high speed centrifugation.
  • Another approach is to seed the precipitation with 10-30% recycled product to produce more easily filterable solids (precipitate). Iron is best separated at pH 2.5 to 3 to minimize the amount of aluminum purities, and aluminum is then precipitated at pH 4.
  • Figure 37 The precipitation of some of the rare earths is shown in Figure 37. As can be seen, scandium precipitates with iron while most of the other REEs precipitate between pH 5 and pH 9. At pH 9, manganese may also be precipitated. Magnesium can be separated at pH 10.5-11 and calcium at pH 13.
  • Figure 38 is a table depicting the percent composition of precipitate hydroxides at different pHs resulting from precipitation testing.
  • the final liquor is a clean sodium chloride solution containing traces of strontium and barium when using sodium hydroxide as the base. It can be further purified by adding sodium carbonate and precipitating high value strontium and barium carbonates. At the end of this process, a marketable sodium chloride solution remains that can be marketed as a brine or dried to the salt. It should be noted that barium as the sulfate is mostly insoluble in the lixiviant so most of it is in the residue.
  • Figures 39 through 45 depict the percent elements precipitated at each pH cut for class C ash feedstock.
  • Figure 39 depicts percent elements precipitated at pH 3.
  • Figure 40 depicts percent elements precipitated at pH 4.
  • Figure 41 depicts percent elements precipitated at pH 5-8.
  • Figure 42 depicts percent elements precipitated at pH 5-8 with aluminum removed to show the smaller percentages more clearly.
  • Figure 43 depicts percent elements precipitated at pH 9.
  • Figure 44 depicts percent element precipitated at pH 10.
  • Figure 45 depicts percent elements precipitated at pH 2.5.
  • the iron purity shown precipitated at pH 3 can be improved to 92.5% by carrying out the precipitation at pH 2.5.
  • the percent element precipitated at pH 13 is >99% calcium.
  • the remaining liquor is not a waste stream but a sodium chloride solution containing traces of strontium and barium. These can be precipitated with sodium carbonate to isolate high value products.
  • the concentrations are 151 ppm strontium and 2 ppm barium. Since the solution is at pH 13, the excess hydroxide must be neutralized with HC1 to pH 7 for the final product.
  • the final product waste composition of the sodium chloride is shown in Figure 46.
  • This final sodium chloride product is an important aspect of this disclosure which processes ash with minimal waste which differentiates it from previous attempts to separate products from CCP. For every 1 ton of ash feedstock this flowsheet generates 0.8 tons of NaCl. There is a market for this product as a solution or as a dried solid.
  • An alternative process embodiment is the use of calcium carbonate (CaC0 3 ) and calcium hydroxide (Ca(OH) 2 ) for the precipitation.
  • Calcium carbonate can be used at the lower pHs up to pH 1 but then Ca(OH) 2 is used exclusively after that through the precipitation steps in the ash conversion process.
  • Figure 47 shows the precipitation as a function of pH for this reagent.
  • Figure 48 shows the elemental composition of all the precipitated products from Ca(OH) 2 precipitation testing.
  • the final calcium precipitation is not performed, and the final product is a sodium chloride/calcium chloride blend.
  • the residue after the leach process 1811 is silica which may comprise up to 20% impurities comprising primarily aluminum and carbon and occasionally barium in the test examples.
  • impurities may be removed by at least one of calcining, caustic fusion and filtration. Carbon impurities, for instance, may be removed by calcining at 600°C or higher.
  • the sodium silicate formed from the fusion is dissolved in water and the mixture filtered to remove any insoluble impurities.
  • the solids may be recycled back to the front end of the process or to acid leaching (FIGS. 18 and 20, leach tank 1810).
  • the filtrate is treated with HC1 to drop the pH to at least 1 and precipitate silicic acid (H 4 Si0 4 ).
  • the silicic acid may be filtered and then calcined, or spray dried then calcined, to convert it a high purity (greater than 99%), high value amorphous silica powder.
  • the silica powder has a BET - N2 surface area of greater than 160m 2 /g which has numerous applications as an additive in tires, elastomers, plastics, and rubber products.
  • the fdtrate is an acidic solution of sodium chloride containing some elements such as aluminum and may be recycled back to the precipitation start of the process (FIGS. 18 and 20, pH adjustment tank 1820).
  • Figures 49 and 50 depict two options for further processing of a silica product as optional continuations of Figures 18 and 20.
  • Figure 49 depicts an acid dissolution process 4900 and
  • Figure 50 depicts a sodium hydroxide fusion process 5000.
  • residue silica and silicates from solid/liquid separation 1815 proceed to dissolution tank 4905.
  • 30% hydrochloric acid (HC1) is applied for 24 hours in dissolution tank 4905.
  • the liquor proceeds to solid/liquid separator 4910 resulting in solids and a liquor.
  • the solids comprise carbon
  • the solids proceed to an oven 4915 for carbon bumoff.
  • the solids are heated in oven 4915 for 6 hours at a minimum of 600°C resulting in a purified silica (Si0 2 ) product.
  • the liquor from solid/liquid separator 4910 may be recycled to the pH adjustment tank 1820 (FIGS. 18 and 20).
  • the solids are primarily silicic acid (H 4 Si0 4 ) precipitate which may proceed to at least one of oven 5020, at 250°C in the depicted embodiment, and spray calcination 5025 resulting in a high purity (greater than 99%) amorphous Si0 2 product.
  • the Si0 2 product may be powdered, in some embodiments. Spray drying may preserve the small, submicron in some embodiments, particle size and prevent agglomeration.
  • the liquor proceeds to precipitation tank 5030. In the depicted embodiment, 1M NaOH is added to the precipitation tank 5030 to raise pH above 7. The liquor proceeds to solid/liquid separation 5035.
  • the solids are primarily aluminum hydroxide (Al(OH) 3 ) which may be marketed as-is or calcined in oven 5040, at 250°C in the depicted embodiment, resulting in an alumina (A1 2 0 3 ) product.
  • the final liquor is sodium chloride (NaCl) which can be marketed as a product.
  • Iron hydroxide is first precipitated together with scandium and other heavy elements.
  • Aluminum hydroxide is precipitated next with some iron impurity and other minor elements.
  • the iron hydroxide and the aluminum hydroxide are both around 90% pure but are contaminated with a small amount of the other product. These products may be further purified by first dissolving them in excess NaOH at 90°C.
  • the aluminum hydroxide dissolves to form a soluble aluminate which can then be separated from the iron hydroxide. After the solid-liquid separation, the aluminum can be reprecipitated by adding acid to get back to the insoluble hydroxide.
  • minor levels of manganese may be separately precipitated in either the caustic or the lime flowsheets at a pH of 9.
  • the major impurity is magnesium.
  • sodium carbonate can be added to separate barium and strontium carbonates before the final liquor is neutralized to yield sodium chloride.
  • rare earth elements (REEs) and transition metals may be separated from each other using ion exchange, solvent extraction, adsorption, or a combination thereof.
  • the process may concentrate REEs and transition metals (also referred to as mischmetals) from 20 to 100-fold.
  • Mischmetals are mixed metal alloys of rare-earth elements. Cerium mischmetal is a cerium rich misch and rare-earth mischmetal is rare earth rich.
  • rare-earth mischmetal comprises at least one of cerium, lanthanum, and neodymium.
  • a typical composition includes approximately 55% cerium, 25% lanthanum, and 15-18% neodymium with other rare earth metals following.
  • the mischmetals may be marketed as is to vendors specializing in separating these products or treated as a separate process.
  • Some embodiments use the well-established technology of a chlor-alkali plant to convert sodium chloride rich final product from Figure 19 and/or 21 to sodium hydroxide, hydrogen, and chlorine. Hydrogen and chlorine are then combined to produce HC1 gas which is then dissolved in water to produce hydrochloric acid.
  • hydrochloric acid is used as the leaching agent in Figures 18 and/or 20 and sodium hydroxide can be used directly in the caustic flowsheet embodiment 1800b (FIGS.
  • the CaC0 3 product is high purity (>99%).
  • Some embodiments use a side stream from a fossil fuel plant gaseous discharge containing carbon dioxide (C0 2 ) to use directly in the process thereby saving a significant reagent cost in purchased C0 2 gas and at the same time achieving an environmental benefit by capturing a greenhouse gas into commercial products (carbonates).
  • C0 2 carbon dioxide
  • One of the reactions used to capture the C0 2 is by absorbing it in sodium hydroxide from the chlor-alkali plant to form sodium carbonate, which is used as a process reagent, in some embodiments.
  • the acid-base reaction is rapid and one of the ways the reaction can be monitored is by tracking the pH from the higher sodium hydroxide value to the lower sodium carbonate value, in some embodiments.
  • This conversion can be done in a batch mode or a continuous mode through pipes with one or more C0 2 entry points to react with the caustic to quantitatively produce sodium carbonate and save the cost of another purchased reagent.
  • C0 2 may be provided from other processes, plants, or sources.
  • naturally occurring or stored C0 2 may be pumped from underground formations. Any use of carbon dioxide could be beneficially used for carbon sequestration from a slip stream off of a coal power plant exhaust.
  • one or more processors may be used to control and manage one more aspects of the systems and methods disclosed herein.
  • the feedstock is a powder that comprises metal-bearing components and sulfur components.
  • the feedstock may be loaded into a first reactor to begin processing.
  • a processor is configured to operate a processing sequence comprising at least one of a dissolution process and a precipitation process wherein the dissolution process and/or precipitation process take place in one or more reactors.
  • the processor may be configured to perform one or more of the following steps: using a first dissolution process, wherein the first dissolution process comprises using a leach process performed by at least one of contacting, passing, and percolating an acid through the powder feedstock and collecting a leachate formed in a second reactor; responsive to collecting the leachate, use a sequential selective precipitation process at a predetermined pH to sequentially precipitate components, wherein a first predetermined pH is used to precipitate a first component from the leachate; responsive to precipitating the first component, separate by filtration the first component, and collect the first filtrate in at least one of the second reactor and a third reactor; responsive to collecting the first filtrate, use a base component to adjust the first filtrate to a second predetermined pH; using the sequential precipitation process at the second predetermined pH, precipitate a second component, separate by filtration the second component and generate a second filtrate; and using the sequential precipitation process to separate additional components based on the predetermined pHs of the component of interest.
  • the steps may be
  • the systems and methods described above can use dedicated processor systems, micro controllers, programmable logic devices, or microprocessors that perform some or all of the communication operations. Some of the operations described above may be implemented in software and other operations may be implemented in hardware. [188] The various operations of methods described above may be performed by any suitable means capable of performing the operations, such as various hardware and/or software component(s), circuits, and/or module(s).
  • DSP digital signal processor
  • ASIC application specific integrated circuit
  • FPGA field programmable gate array signal
  • PLD programmable logic device
  • a hardware processor may be a microprocessor, commercially available processor, controller, microcontroller, or state machine.
  • a processor may also be implemented as a combination of two computing components, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.
  • the functions described may be implemented in software, firmware, or any combination thereof executing on a hardware processor. If implemented in software, the functions may be stored as one or more executable instructions or code on a non-transitory computer-readable storage medium.
  • a computer-readable storage media may be any available media that can be accessed by a processor.
  • such computer-readable storage media can comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to store executable instructions or other program code or data structures and that can be accessed by a processor.
  • Disk and disc includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk and Blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media.
  • Certain aspects of the present disclosure may comprise a computer program product for performing the operations presented herein.
  • a computer program product may comprise a computer readable storage medium having instructions stored (and/or encoded) thereon, the instructions being executable by one or more processors to perform the operations described herein.
  • Software or instructions may be transmitted over a transmission medium.
  • a transmission medium For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of transmission medium.
  • DSL digital subscriber line
  • modules and/or other appropriate means for performing the methods and techniques described herein can be downloaded and/or otherwise obtained by a user terminal and/or base station as applicable.
  • a user terminal and/or base station can be coupled to a server to facilitate the transfer of means for performing the methods described herein.
  • various methods described herein can be provided via storage means (e.g., RAM, ROM, a physical storage medium such as a compact disc (CD) or floppy disk, etc.), such that a terminal and/or base station can obtain the various methods upon coupling or providing the storage means to the device.
  • storage means e.g., RAM, ROM, a physical storage medium such as a compact disc (CD) or floppy disk, etc.
  • Batch Process A batch process operates in separate discrete operations that are connected in a stepwise fashion with the materials processed being fed in batches.
  • Catalyst is an agent that can either accelerate or decelerate a chemical reaction without reacting with the reactants or products.
  • Continuous Process A continuous process is designed to operate without interruptions.
  • the materials being processed either bulk dry or fluids, are continuously in motion undergoing chemical reactions or subject to mechanical or heat treatment.
  • REEs are any of a group of chemically similar metallic elements comprising the lanthanide series and (usually) scandium and yttrium.
  • Transition elements are any of the set of metallic elements occupying a central block (Groups IVB-VIII, IB, and IIB, or 4-12) in the periodic table, e.g., manganese, chromium, and copper.

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Abstract

L'invention concerne des systèmes et des méthodes de traitement de charges d'alimentation de gypse de FGD et de charges d'alimentation de cendres, soit séparément, soit ensemble. La conversion de gypse de FGD comprend la réaction d'une charge d'alimentation de gypse (sulfate de calcium) de désulfuration de gaz de combustion (FGD), dans un mode discontinu ou continu, avec un réactif de carbonate d'ammonium pour produire des produits commerciaux, les produits commerciaux comprenant du sulfate d'ammonium et du carbonate de calcium. La conversion de cendres comprend un procédé de lixiviation suivi d'un procédé de précipitation pour précipiter sélectivement des composants à des pH prédéterminés, ce qui permet d'obtenir des hydroxydes métalliques qui peuvent être éventuellement convertis en oxydes ou carbonates. Les procédés peuvent être contrôlés par l'utilisation d'un ou de plusieurs processeurs.
EP20744889.5A 2019-01-24 2020-01-24 Systèmes et méthodes de traitement de désulfuration de gaz de combustion et de flux de déchets métallifères pour récupérer des matériaux à valeur ajoutée Pending EP3898518A4 (fr)

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US201962796549P 2019-01-24 2019-01-24
US201962796550P 2019-01-24 2019-01-24
US201962796541P 2019-01-24 2019-01-24
US201962810066P 2019-02-25 2019-02-25
US201962824523P 2019-03-27 2019-03-27
US201962878542P 2019-07-25 2019-07-25
US16/749,860 US11148956B2 (en) 2019-01-24 2020-01-22 Systems and methods to treat flue gas desulfurization waste to produce ammonium sulfate and calcium carbonate products
PCT/US2020/015102 WO2020154699A1 (fr) 2019-01-24 2020-01-24 Systèmes et méthodes de traitement de désulfuration de gaz de combustion et de flux de déchets métallifères pour récupérer des matériaux à valeur ajoutée

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