Facility and method for purifying flue gas and recovering secondary raw materials

Abstract

The invention relates to a plant and a method for purifying flue gases from industrial emissions and / or for recovering and reconverting sulfur oxides and / or nitrogen oxides and / or carbon dioxide contained in the flue gases. The method comprises by means of one or more aqueous solutions selected from the group comprising:-a solution having an acidic pH of between 0.5 and 1; -a solution having a pH between 3 and 5, a pH of about 4; a-Ca (OH) 2 or CaCl2 or calcium acetate solution; -a solution having a pH of between 8 and 9.

Description

Background Art

[0001] The concentration of greenhouse gases in the atmosphere has been gradually increasing in recent decades, which has had consequences observable today at the climate level.

[0002] The Paris Climate Conference in 2015 proposed an agreement aiming to keep the increase in the global average temperature within 2 °C above the pre-industrial level as a long-term goal.

[0003] Industries and energy sectors covered by the EU Emissions Trading System (ETS) must make greater efforts to increase the reduction of CO2 emissions with strong environmental impacts from 43% to 61% compared to 2005 by 2030.

[0004] The physical and chemical properties of the atmosphere and the earth's sphere determine the earth's climate conditions and affect the survival of organisms. Air pollutants can be defined as any substance that directly or indirectly changes and disrupts its natural balance when introduced into the atmosphere (Bond R., Straub, C, Prober R.: “CRC Handbook of Environmental Control”, vol. I: Air Pollution, CRC Press Inc., Boca Raton Florida, 4th print, 1980).

[0005] According to the source of pollutants, two main categories of pollutants can be identified: anthropogenic pollutants, i.e., pollutants manufactured by humans, and natural pollutants.

[0006] Pollutants can also be classified as primary pollutants and secondary pollutants. Primary pollutants are released into the environment as they are and as a result of a certain process (such as CO, CO2, NOx, SOx), and secondary pollutants are formed in the atmosphere through chemical-physical reactions (such as photochemical smog) (Lund, R.: “Industrial Pollution Control Handbook”, chapter 9 - “Research programs for air and water pollution control”, Mc Graw-Hill, 1971).

[0007] According to the state of matter, air pollutants are classified as gaseous pollutants or particulate pollutants. Examples of gaseous pollutants are nitrogen oxides (NO, NO2), sulfur oxides (SO2, SO3), carbon monoxide (CO), carbon dioxide (CO2), hydrogen sulfide (H2S), hydrogen fluoride (HF), hydrogen chloride (HCI), ammonium compounds (NH4), and hydrocarbons. Particulate pollutants include various powders, fumes, and mists.

[0008] Combustion is an exothermic oxidation of reducing substances by oxygen, which usually refers to the oxygen contained in the air. The oxidizable chemical classes of fuels are carbon, hydrogen, sulfur, small amounts of nitrogen, and compounds containing these substances. For complete combustion, they are converted into CO2, H2O, SOx (SO2 + SO3), and partially into NOx (NO + NO2).

[0009] Particularly in the case of the ceramic industry, emissions from firing furnaces are the most relevant and the most complex to control. These high-temperature emissions basically include:

[0010] — Powders of mixtures and enamels dragged by the circulating air flow in the furnace during the firing of enamel products;

[0011] — Gaseous or particulate products resulting from reactions or transformations (degradation, collapse of clay materials such as, evaporation and distillation, sublimation) occurring within or between certain components of the supports or enamels. Such pollutants include fluorine, chlorine, ammonium, boron, sulfur, lead and other metals, organic substances, etc.;

[0012] — Combustion products: carbon dioxide and nitrogen oxides (and of course water vapor), especially when it is assumed that the fuel used is natural gas.

[0013] In the prior art, the flue gas is treated with powdered lime. However, this treatment does not allow the retention of sulfur and nitrogen oxides except for the residual amounts.

[0014] Therefore, there is an urgent need for an economically sustainable and efficient method to purify industrial flue gas and recover and recycle its components. Summary of the Invention

[0015] The object of the present invention is to provide a facility and method for purifying industrial flue gas emissions and / or recovering and recycling sulfur oxides and / or nitrogen oxides and / or carbon dioxide contained in the flue gas.

[0016] Such flue gas is, for example, the flue gas generated during combustion, gasification, or chemical processes. In one embodiment, they refer to the flue gas generated by a blast furnace (such as a blast furnace for processing ceramics).

[0017] Operating in an aqueous solution under mild conditions and with low energy requirements, the method according to the present invention surprisingly produces high-purity precipitated calcium carbonate (PCC) and / or high-purity sodium bicarbonate and / or calcium sulfate and / or calcium bisulfite and / or calcium nitrate.

[0018] Furthermore, the method according to the present invention reduces odors, volatile organic compounds (VOCs), and heavy metals without the need for a post-combustion burner.

[0019] The method according to the present invention not only produces no CO2 emissions, but also consumes the CO2 contained in the flue gas.

[0020] As described and claimed below, the present invention achieves these and other objects. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1: Schematic diagram of an embodiment of the method according to the present invention. (A) Purification of flue gas; (B, C) Re-conversion of sulfur oxides and / or nitrogen oxides and / or carbon dioxide.

[0022] Figure 2 : Schematic diagram of an embodiment of the purification device.

[0023] Figure 3 : Schematic diagram of an embodiment of the capture reactor.

[0024] Figure 4 : Analysis of calcium carbonate and calcium sulfate obtained by the method according to the present invention. Calcium sulfate: (A) Microcrystals, scanning electron microscope (SEM) photograph; (B) EDS microanalysis spectrum. Calcium carbonate precipitated after the capture liquid 3: (C) Microcrystals, SEM photograph; (D) EDS microanalysis spectrum. Calcium carbonate precipitated from CaCl2: (E) Microcrystals, SEM photograph; (F) EDS microanalysis spectrum.

[0025] Figure 5 : X-ray analysis spectra of (A) calcium carbonate and (B) calcium sulfate obtained by the method according to the present invention.

[0026] Figure 6 : FT-IR spectra, comparison of (A) calcium carbonate and (B) calcium sulfate obtained by the method according to the present invention (upper figure) with their respective reference spectra (lower figure). DETAILED DESCRIPTION

[0027] The present invention first relates to a method for purifying flue gas containing pollutants, with reference to Figure 1A the figures, the method comprising the following steps:

[0028] - Providing a purification device including a purification chamber;

[0029] - Supplying the flue gas to be purified into the purification chamber;

[0030] - Transporting an aqueous solution into the purification chamber;

[0031] - Recovering the aqueous solution and electro-oxidizing the aqueous solution with titanium and / or graphite electrodes;

[0032] - Recovering the electro-oxidized aqueous solution and optionally recycling the aqueous solution;

[0033] - Recover the purified flue gas.

[0034] Conveniently, the aqueous solution fed into the purification chamber intercepts the flue gas to be purified to reduce the organic and / or inorganic compounds present therein.

[0035] In one embodiment, the flue gas to be purified passes through a heat exchanger before entering the purification chamber to recover the excess heat.

[0036] In one embodiment, the heat generated during the electrooxidation step is also conveniently recovered.

[0037] In one embodiment, during the electrooxidation step, in a strongly acidic environment with a pH in the range of 0.5 to 1 created to dissolve SO3 in water and form H2SO4, the oxidation capacity of the system is enhanced, resulting in the oxidation of metals precipitating as oxides, the oxidation of soluble COD (chemical oxygen demand), the oxidation of organic substances accompanied by the formation of CO2, and the oxidation of nitrogen-containing substances to N2. This process is particularly suitable for oxidizing hazardous organic molecules such as VOC, BTEX, IPA, aniline.

[0038] When the flue gas to be treated does not have a high content of SOx, these pollutants are conveniently removed by delivering an acidic aqueous solution into the purification chamber and / or extending the residence time of the aqueous solution in the electrooxidation step.

[0039] In one embodiment, the aqueous solution is water.

[0040] In one embodiment, the aqueous solution is atomized in the purification chamber.

[0041] After the electrooxidation step, the water used for atomization in the purification chamber is conveniently reintroduced into the purification chamber.

[0042] During the process, the dissolution of SO3 in water causes an increase in the solution density. Conveniently, when the density exceeds a value in the range of 1.2 kg / m 3 to 1.3 kg / m 3 range, the water leaving the electrooxidation step is no longer recycled but is preferably used as an aqueous solution with a pH between 0.5 and 1 for subsequent recovery and reconversion steps. Subsequently, the volume of water is replenished with fresh water in the purification chamber.

[0043] In one embodiment, the method further includes recovering and reconverting the sulfur oxides and / or nitrogen oxides and / or carbon dioxide contained in the flue gas.

[0044] In this embodiment, the flue gas containing pollutants passes through one or more aqueous solutions before or after being treated by the purification device. After each pass through the aqueous solution, partially treated flue gas and / or aqueous solution is obtained, in which the reaction products precipitate and / or dissolve.

[0045] The aqueous solution is selected from the group comprising:

[0046] - A solution with an acidic pH between 0.5 and 1;

[0047] - A solution with a pH between 3 and 5, approximately pH 4;

[0048] - A Ca(OH)₂ solution with a pH greater than 10;

[0049] - A CaCl₂ solution with a pH less than 10;

[0050] - A calcium acetate solution;

[0051] - A solution with a pH between 8 and 9.

[0052] The method comprises passing the flue gas through one or more of such aqueous solutions; optionally, the partially treated flue gas and / or the aqueous solution pass through the same aqueous solution more than once.

[0053] The reactions occurring during the passing process are exothermic reactions controlled by kinetics rather than thermodynamics, and prompt the immediate obtaining of high-purity PCC and / or high-purity sodium bicarbonate and / or calcium sulfate and / or calcium bisulfite and / or calcium nitrate.

[0054] Advantageously, the passing process occurs in a reactor called a trap. Advantageously, the trap further comprises a layer 21 of packing bodies 22 having a random geometry, made of, for example, ceramics, PP, or PVC. Advantageously, the layer of packing bodies slows down the flow, enables greater contact with water, breaks the preferential flow of the gas, and forces it into a zigzag path.

[0055] In one embodiment, in order to recover sulfur oxides by converting them into bisulfites, the flue gas is introduced into an aqueous solution called an acidic capture liquid and / or into an aqueous solution called a desulfurization capture liquid before or after being exposed to the purification method. The acidic capture liquid is water with a pH between 0.5 and 1, allowing the passage of SO₃ solution, and the desulfurization capture liquid is water with a pH between 3 and 5, allowing the passage of SO₂ solution.

[0056] In one embodiment, in order to recover nitrogen oxides and / or CO₂ for subsequent use or convert them into carbonates, the flue gas is introduced into an aqueous solution called a calcium capture liquid before or after being exposed to the purification method. The calcium capture liquid is optionally selected from a Ca(OH)₂ solution, a CaCl₂ solution, and a calcium acetate solution to precipitate carbonates and / or bring nitrates into solution.

[0057] Optionally, a solution that dissolves nitrates and / or precipitates carbonates is passed through an acidic aqueous solution with a pH between 0.5 and 5, thereby causing the formation of pure CO2, which can be used, for example, for food purposes.

[0058] In a preferred form, the method includes Figure 1B one or more of the steps shown in the flowchart.

[0059] In this embodiment, the flue gas to be treated is introduced into an aqueous solution with a pH between 0.5 and 1 (i.e., acidic capture liquid 1) before or after being exposed to the purification method, and / or is introduced into an aqueous solution called desulfurization capture liquid 2 (the aqueous solution is water with a pH between 3 and 5), and / or is introduced into an aqueous solution called calcium capture liquid 3 (the aqueous solution is optionally selected from Ca(OH)2 solution, CaCl2 solution, calcium acetate solution).

[0060] When passing through acidic capture liquid 1, the SO3 contained in the flue gas reacts to form soluble sulfate H2SO4. The aqueous solution dissolved with this bisulfite and the pretreated flue gas are optionally exposed to subsequent steps.

[0061] When passing through desulfurization capture liquid 2, the SO2 contained in the flue gas reacts to form soluble bisulfite HSO3 - . The aqueous solution dissolved with this bisulfite and the pretreated flue gas are optionally exposed to subsequent steps.

[0062] To recover carbonates and nitrates, the flue gas and / or the flue gas pretreated in desulfurization capture liquid 2 is passed through calcium capture liquid 3.

[0063] When passing through calcium capture liquid 3, the CO2 contained in the flue gas that is insoluble in the acidic environment encountered in the previous steps of this method reacts with the calcium salt present in the solution and immediately precipitates, producing calcium carbonate with impurities. In the same calcium capture liquid 3, nitrogen oxides also pass through the aqueous solution in the form of nitrates. The aqueous solution containing this carbonate and nitrate and the pretreated flue gas are optionally exposed to subsequent steps.

[0064] To completely recover CO2, the pretreated flue gas leaving calcium capture liquid 3 is optionally re-fed back into the same calcium capture liquid 3.

[0065] The carbonates and nitrates from calcium capture liquid 3 are transported to an acidic aqueous solution with a pH between 0.5 and 1, also called acidic capture liquid 1, where gypsum CaSO4×2(H2O) is formed. The CO2 generated in this method is conveniently recovered for subsequent use. The nitrates remain in the solution.

[0066] Additionally or alternatively, carbonates and nitrates from the calcium capture liquid 3 are conveyed to another desulfurization capture liquid (i.e., desulfurization capture liquid 2’), where the bisulfite obtained in the first step is also conveniently introduced into an aqueous solution with a pH between 3 and 5. The reaction results in the precipitation of sulfite, facilitating its recovery for later use. The nitrates remain in the solution.

[0067] Optionally, the CO2 generated by passing through an acidic solution and a desulfurization capture liquid is conveyed to another calcium solution (i.e., calcium capture liquid 3’). Thus, the obtained CO2 is pure and forms calcium carbonate of high purity. The nitrates remain in the solution.

[0068] Optionally, the CO2 generated by passing through an acidic solution and a desulfurization capture liquid is conveyed to an alkaline solution with a pH between 8 and 9 (referred to as alkaline capture liquid 4). In the alkaline environment, the introduced pure CO2 reacts to form bicarbonate of high purity. The nitrates remain in the solution.

[0069] In one embodiment, with reference to Figure 1C , the flue gas to be purified and the flue gas from which oxides and carbon dioxide are re-converted are introduced into a first acidic capture liquid (which is an aqueous solution with a pH between 0.5 and 1, preferably a pH of about 1) after passing through a heat exchanger to recover its heat.

[0070] In the first capture liquid, SO3 passes into the solution to form sulfates. When the concentration of sulfates increases and can be verified by measuring the density of the solution contained in the first capture liquid, the solution is passed into reactor 1, where calcium carbonate is added at a controlled T and pH, promoting the formation of gypsum, which precipitates and releases CO2. The CO2 obtained therefrom is pure CO2 from this reaction; therefore, it is directly sent to the CO2 storage tank.

[0071] When the sulfate-bearing water in reactor 1 passes through, the volume of this aqueous solution in the first capture liquid is conveniently maintained by adding fresh water.

[0072] The flue gas enters from the first capture liquid into a second capture liquid, which is the desulfurization capture liquid and has a pH between 3 and 5, preferably a pH of 4. The desulfurization capture liquid allows SO2 to enter the solution, and all components other than SO2 enter the next step. In a preferred manner, the desulfurized flue gas passes through an adsorber and a CO2 desorber, from which pure CO2 is sent through the CO2 storage tank.

[0073] The CO2 adsorber / desorber is conveniently arranged to reduce the volume of the flue gas to be treated and use simpler facilities. For example, the operating conditions include a gas flow rate of about 40,000 m 3 / h entering the facility. By passing through the CO2 adsorber / desorber, the following method reduces the volume, reducing the volume of the flue gas to be treated to only the volume of CO2.

[0074] CO2 is introduced into the calcium trap (reactor 3), resulting in the formation of calcium carbonate, which is introduced into the calcium carbonate storage container. Subsequently, the solution is filtered to recover pure calcium carbonate and the water that can be conveniently reintroduced into the system.

[0075] When the concentration of SO2 in the second capture liquid increases, the solution enters reactor 2, where, at controlled T and pH, the addition of calcium carbonate results in the formation of sulfite, which precipitates and is recovered in a convenient manner, releasing CO2. The CO2 thus obtained is pure CO2 from this reaction; therefore, this CO2 is sent directly to the CO2 storage tank.

[0076] Conveniently, the reactor uses some of the calcium carbonate obtained from re-conversion to neutralize sulfuric acid and sodium bisulfite, producing CO2 due to the low pH. This allows an additional CO2 purification step, as well as the precipitation of commercially valuable salts such as gypsum and calcium sulfite. In addition, the recovery of calcium nitrate is allowed.

[0077] The present invention also relates to a facility for purifying industrial flue gas emissions, the flue gas including pollutants, with reference to Figure 2 , the facility comprising:

[0078] - A purification device 1 including a double purification chamber 10, the double purification chamber 10 being at least composed of a first hollow body 2 and a second hollow body 3 that are fluidly connected to each other, wherein:

[0079] ○ The first hollow body 2 includes a water collection lower zone 11, an upper zone 12, an outlet port 13 arranged at the bottom of the lower zone, an inlet 4 for the flue gas to be purified, and an outlet 5 for the purified flue gas located at the top of the upper zone 12, wherein, under operating conditions, the outlet port 13 is located below the water level of the water occupying the lower zone;

[0080] ○ The second hollow body 3 includes titanium and / or graphite electrodes.

[0081] In one embodiment, the first hollow body 2 of the purification chamber 10 is a demister.

[0082] In one embodiment, the first hollow body 2 of the purification chamber 10 further includes a layer 21 of packing bodies 22 having a random geometry, for example made of ceramic, PP, or PVC. Advantageously, this layer of packing bodies slows down the flow, enables greater contact with water, breaks the preferential flow of the gas, and forces it into a zigzag path.

[0083] The first hollow body 2 also includes a nozzle 6 located therein, which is used to atomize the aqueous solution therein.

[0084] A pump P-1 is conveniently arranged to allow the necessary flow of the fluid.

[0085] In one embodiment, there is provided a facility for recovering and re-converting sulfur oxides and / or nitrogen oxides and / or carbon dioxide contained in industrial flue gas. The facility includes at least one, two, three, four, five, six or seven capture reactors, wherein the capture reactors are fluidly connected to each other independently, and the term "fluidly connected to each other independently" means that some capture reactors are fluidly connected to one or more other capture reactors, forming a network. This fluid connection is understood to convey an aqueous solution from one capture reactor to the next, or to convey flue gas from one capture reactor to the next.

[0086] Each of the one or more capture reactors includes a lower zone conveniently filled with an aqueous solution selected from the group consisting of:

[0087] - A solution with an acidic pH between 0.5 and 1, for an acidic capture reactor;

[0088] - A solution with a pH between 3 and 5, approximately pH 4, for a desulfurization capture reactor;

[0089] - A Ca(OH)₂ solution, for a calcium capture reactor;

[0090] - A CaCl₂ solution, for a calcium capture reactor;

[0091] - A calcium acetate solution, for a calcium capture reactor;

[0092] - A solution with a pH between 8 and 9, for an alkaline capture reactor.

[0093] Referring Figure 3 , the one or more capture reactors 30 include: at least one inlet port 31 for flue gas and / or at least one inlet port 32 for the aqueous solution; optionally, at least one outlet port for the treated flue gas and at least one discharge port 33 leading to the lower zone 34. The flow is conveniently managed using a pump P-6.

[0094] In one embodiment, the one or more capture reactors are mist eliminators.

[0095] In one embodiment, the facility includes a calcium capture reactor and an acidic capture reactor downstream of the capture reactor.

[0096] In one embodiment, the facility includes a desulfurization capture reactor, an acidic capture reactor, and a calcium capture reactor.

[0097] In one embodiment, the facility includes two desulfurization capture reactors, one acidic capture reactor, and two calcium capture reactors.

[0098] In one embodiment, the facility includes two desulfurization capture reactors, an acid capture reactor, two calcium capture reactors, and an alkaline capture reactor.

[0099] In one embodiment, the first desulfurization capture reactor is in downstream fluid connection with the second desulfurization capture reactor, the first calcium capture reactor, and optionally the alkaline capture reactor.

[0100] In one embodiment, the first calcium capture reactor is in downstream fluid connection with the second desulfurization capture reactor and the acid capture reactor.

[0101] In one embodiment, the acid capture reactor is in downstream fluid connection with the second calcium capture reactor and optionally the alkaline capture reactor.

[0102] In one embodiment, sensors are provided on some or all of the inlet ports and / or outlet ports of the capture reactors.

[0103] For example, with reference to the first calcium capture reactor, the flue gas exiting the calcium capture reactor is only re-circulated back to the same calcium capture reactor when the sensor detects that the amount of CO2 exceeds a defined threshold.

[0104] In one embodiment, the present invention relates to a facility comprising:

[0105] - A facility for purifying industrial emission flue gas;

[0106] - A facility for recovering and re-converting sulfur oxides and / or nitrogen oxides and / or carbon dioxide contained in the same flue gas.

[0107] In one embodiment, the facility comprises:

[0108] - A purification device 1 comprising a double purification chamber, the double purification chamber being at least composed of a first hollow body 2 and a second hollow body 3 which are in fluid connection with each other, wherein

[0109] — The first hollow body 2 includes a water collection lower zone, an upper zone, and an outlet port disposed at the bottom of the lower zone

[0110] 13, an inlet 4 for the flue gas to be purified, and an outlet 5 for the purified flue gas located at the top of the upper zone 12;

[0111] — The second hollow body 3 includes titanium and / or graphite electrodes;

[0112] - A re-conversion device, at least including an acid capture liquid, a desulfurization capture liquid, and a calcium capture liquid.

[0113] The method according to the invention allows the active ingredient recovered from the outlet of the capture reactor to be dissolved or suspended in water. In one embodiment, after any precipitation, the active ingredient is conveniently recovered by filtration according to the prior art. In one embodiment, the filtrate is dried to provide the active ingredient in powder form.

[0114] Conveniently, this drying is carried out using the heat recovered from the flue gas by means of a heat exchanger before and during the purification treatment.

[0115] After filtration, the water is recovered and can be reintroduced into the process.

[0116] In its different embodiments, the installation and method according to the invention offer significant advantages, thus providing a new method in which industrial waste products that are not only inexpensive and polluting, and which involve costly proper disposal, are used as starting materials, and also reducing the highly energy-intensive processes usually required to produce raw materials such as high-purity calcium carbonate.

[0117] The installation and method according to the invention achieve the purification of industrial flue gas in a convenient manner, thus introducing into the environment flue gas that contains no polluting components and mainly contains oxygen, while also conveniently reusing nitrates, sulfites, and calcium sulfate.

[0118] For example, nitrates are conveniently used in agriculture, such as in fertilizer production.

[0119] In addition, calcium sulfate is used in the construction industry to make gypsum. In agriculture, calcium sulfate is used as a fertilizer that can provide calcium to the roots. Calcium sulfate is also useful in the correction of alkaline soils and promotes the entry of air and water into the ground. In the food industry, calcium sulfate is known as E516 and is used for flour treatment. In medicine, calcium sulfate is used as an excipient in tablet production; in dentistry, it is used as a base for making dental impressions, dentures, and restorations.

[0120] Calcium carbonate without impurities forms a valuable raw material. In fact, the precipitated calcium carbonate is a very fine white powder, which is used as a filler in cosmetics, improves the adhesion of the powder, regulates the density, and has water-absorbing capacity. In addition, due to its high purity, it can be used to obtain food-grade CO2.

[0121] The following examples are only for better illustrating the invention and should not be construed as limiting the invention in any way. The scope of the invention is defined by the following claims.

[0122] Examples

[0123] Example 1: Facilities and methods for recovering and re-converting sulfur oxides, nitrogen oxides, and carbon dioxide contained in industrial flue gas .

[0124] The flue gas to be treated is conveyed to a first reactor, which is a desulfurization capture reactor.

[0125] The desulfurization capture reactor includes a lower zone, an inlet port for the flue gas, an outlet port for the treated flue gas, and a discharge opening leading to the lower zone.

[0126] In one embodiment, the desulfurization capture reactor is a demister.

[0127] The lower zone contains water, and its pH is adjusted to between 3 and 5 by adding NaOH, which is necessary due to the severe acidification occurring due to the formation of hydrogen sulfide in the desulfurization capture liquid.

[0128] Alternatively, the pH is adjusted to the range of 3 to 5 by adding KOH, resulting in the formation of KHSO3. Alternatively, by adding Ca(OH)2, resulting in the formation of CaSO3.

[0129] In the desulfurization capture reactor, bisulfite is formed, which enters the aqueous solution.

[0130] The aqueous solution in which the formed bisulfite is dissolved is recovered through the discharge opening. The treated flue gas leaves through the outlet port.

[0131] The flue gas leaving the desulfurization capture reactor is conveyed to a second reactor, which is a calcium capture reactor.

[0132] The calcium capture reactor includes a lower zone, an inlet port for the flue gas, an outlet port for the treated flue gas, and one or preferably two discharges leading to the lower zone.

[0133] In one embodiment, the desulfurization capture reactor is a demister.

[0134] In two separate experiments, two different aqueous solutions were used for the calcium capture reactor.

[0135] In the first experiment, Ca(OH)2 with a pH greater than 11 was contained in the lower zone, which was conveniently obtained by dissolving CaO in water.

[0136] In the second experiment, CaCl2 with a pH less than 10 was contained in the lower zone.

[0137] In both cases, carbonates and nitrates precipitate in the calcium capture reactor and enter the aqueous solution.

[0138] The aqueous solution containing carbonates and nitrates is recovered through one of the discharges. The treated flue gas leaves through the outlet port.

[0139] In one embodiment, the carbonate and nitrate recovered from one of the open discharge ports on the calcium capture reactor are transported to a buffer reactor that serves as a reservoir.

[0140] The carbonate and nitrate leaving the calcium capture reactor are transported to a reactor, which is an acid capture reactor.

[0141] The acid capture reactor includes a lower zone, two inlet ports, and one outlet port.

[0142] Water with a pH between 0.5 and 1 is contained in the lower zone. Conveniently, the acidic water is water recovered from the purification process, in which the dissolution of SO3 results in the formation of H2SO4.

[0143] Calcium sulfate and nitrate are formed and conveniently recovered in the acid capture reactor. The calcium sulfate thus obtained is characterized, and the results are shown in Example 2 below.

[0144] In one embodiment, the facility includes another desulfurization capture reactor. In the second desulfurization capture reactor having the characteristics of the desulfurization capture reactor already described, an aqueous solution of bisulfite is transported out from the discharge port of the first desulfurization capture reactor. The aqueous solution is water with a density reaching 1.2 to 1.3, and the carbonate and nitrate leave from the discharge port of the calcium capture reactor or come out from the buffer reactor. In this another desulfurization capture reactor, the carbonate reacts with the bisulfite to form calcium sulfite and CO2.

[0145] The water-soluble nitrate does not contaminate the precipitated powder. Conveniently, the nitrate is recovered when it reaches a significant concentration in water.

[0146] In one embodiment, the facility includes another calcium capture reactor. In this second calcium capture reactor, CO2 is transported out from the discharge port of the acid capture reactor and / or the second desulfurization capture reactor.

[0147] The CO2 is pure CO2, and when it is introduced into another calcium capture reactor, it causes the precipitation of calcium carbonate lacking impurities. The calcium carbonate obtained using the calcium capture liquid mentioned in Experiment 1 or Experiment 2 is characterized. The results are shown in Example 2.

[0148] In one embodiment, the facility includes an alkaline capture reactor. An aqueous solution with a pH between 8 and 9 is contained in the alkaline capture reactor. In a preferred form, the pH is maintained by adding NaOH or alternatively by adding KOH. In the alkaline capture reactor, CO2 is transported out from the discharge port of the acid capture reactor and / or the second desulfurization capture reactor. In this alkaline capture reactor, high-purity sodium bicarbonate or potassium bicarbonate is formed.

[0149] The aqueous solution level including calcium sulfate, high-purity calcium carbonate, and high-purity bicarbonate recovered by the facility is filtered, and the powder is dried.

[0150] The nitrate in the solution is also conveniently recovered.

[0151] Surprisingly, the facility and the method implemented using the facility achieve high-purity calcium carbonate, high-purity bicarbonate, and nitrate from industrial flue gas emissions, along with an exothermic reaction.

[0152] Example 2: Analysis of calcium carbonate and calcium sulfate obtained by the method according to the present invention

[0153] The calcium carbonate sample obtained in Example 1 and the calcium sulfate sample obtained in Example 1 were analyzed under a scanning electron microscope, where the calcium carbonate was precipitated from Ca(OH)2 with a pH greater than 11 or from CaCl2 with a pH less than 10.

[0154] For calcium carbonate, the results obtained show that depending on the calcium salt used for precipitation, there is control over the morphology and size of the obtained particles.

[0155] Figure 4 A shows that the calcium sulfate particles obtained by precipitation in an acidic solution are uniform with each other and have a regular rod-like morphology.

[0156] The spectrum (4B) obtained by EDS microanalysis shows the high purity obtained.

[0157] Figure 4 C shows that the calcium carbonate particles obtained by precipitation in Ca(OH)2 have a regular and uniform morphology.

[0158] The spectrum (4D) obtained by EDS microanalysis shows the high purity obtained.

[0159] Figure 4 E shows that the calcium carbonate particles obtained by precipitation from CaCl2 have a uniform spherical regular morphology, which is beneficial for their flow aid properties.

[0160] The spectrum (4F) obtained by EDS microanalysis shows that the sample also obtains high purity.

[0161] The structures of the calcium carbonate sample obtained by precipitation from Ca(OH)2 and the calcium sulfate sample were analyzed by X-ray. The obtained spectra are shown in Figure 5 A and Figure 5 B, where several characteristic peaks of these elements can be well identified.

[0162] The peak lists are listed in Table 1 and Table 2 respectively.

[0163] Table 1: Peaks of X-ray diffraction analysis of calcium carbonate obtained by precipitation from Ca(OH)2 using the method according to the present invention.

[0164]

[0165] Table 2: Peaks of X-ray diffraction analysis of calcium sulfate leaving the acidic capture liquid using the method according to the present invention.

[0166]

[0167]

[0168]

[0169] Finally, FT-IR spectra of the same calcium carbonate sample and calcium sulfate sample were obtained to study their structures.

[0170] The results are shown in Figure 6 Figures A and B.

[0171] In both cases, the spectra were compared with those of substances present in the database. The comparison clearly shows that the precipitate obtained from the method is exactly the indicated compound.

[0172] Example 3: Heat recovery

[0173] The following Table 3 shows the KW recovered by transferring the 110 °C flue gas from the chimney through the heat exchanger.

[0174] Table 3

[0175]

[0176] In an exemplary case, the 400 KW / h recovered is used for the operation of the CO2 desorption column, and the remainder is used to facilitate the drying of the crystals formed downstream of the facility reactor.

[0177] Example 4: Passage through the purification chamber

[0178] Table 4 shows the reaction data of the gas in the purification chamber. In the case shown, only SO3 and Nox are soluble, while SO2 and CO2 remain insoluble and enter the next desulfurization capture liquid. The absorption of SO3 in water is thermodynamically favorable, as can be clearly seen from deltaG and log(K).

[0179] Table 4

[0180]

[0181]

[0182] When the density of the solution in the purification chamber reaches 1.2 g / cm 3 to 1.3 g / cm 3 it is electro-oxidized to oxidize organic and inorganic substances such as heavy metals.

[0183] Example 5: Passage through the desulfurization capture liquid

[0184] In the desulfurization capture liquid (operated at 35 °C and pH 4), only SO2 is soluble, and the presence of sodium makes the absorption in water thermodynamically favorable, as shown in Table 5 below.

[0185] Table 5

[0186]

[0187] Due to the acidic pH, CO2 remains insoluble and stays in the flue gas, which is then subjected to CO2 absorption treatment.

[0188] When the density of the aqueous solution in the desulfurization capture liquid reaches 1.1 g / cm 3 the solution is sent to Reactor 2, where, with the addition of calcium carbonate, sulfite precipitates and CO2 is released. The reaction parameters are summarized in Table 5-II.

[0189] Table 5-II

[0190]

[0191] Example 6: CO2 adsorbent / desorbent

[0192] The CO2 present in the flue gas leaving the desulfurization capture liquid is adsorbed by a 20% potassium carbonate solution in the adsorption tower. The carbonate is converted to potassium bicarbonate at room temperature and a pH between 7 and 8. Then the CO2 is released into the desorption tower, where the bicarbonate returns to the carbonate, operating under hot conditions (85 °C, 0.4 bar). The released CO2 is stored in a storage tank at a pressure of 32 bar. The reaction parameters are summarized in Table 6.

[0193] Table 6

[0194]

[0195] Example 7: Calcium carbonate precipitation

[0196] The collected CO2 is transported to a reactor where it diffuses in the form of microbubbles. There is a 20% sand (lime) suspension with a pH of 12 present. Under these conditions, CO2 is soluble and reacts spontaneously, resulting in the precipitation of calcium carbonate. The reaction parameters are summarized in Table 7.

[0197] Table 7

[0198]

Claims

1. A method for purifying flue gas, the method recovering and re-converting sulfur oxides and / or nitrogen oxides and / or carbon dioxide contained in the flue gas, wherein, The method includes: - providing a purification device including a purification chamber; - supplying the flue gas to be purified into the purification chamber; - transporting an aqueous solution into the purification chamber; - recovering the aqueous solution and electro-oxidizing the aqueous solution with a titanium and / or graphite electrode; - recovering the electro-oxidized aqueous solution and optionally recycling the electro-oxidized aqueous solution; - recovering the purified flue gas, characterized in that the purified flue gas is further passed through one or more aqueous solutions selected from the group consisting of: - a solution with an acidic pH between 0.5 and 1, called an acidic capture liquid; - a solution with a pH between 3 and 5 and a pH of approximately 4, called a desulfurization capture liquid; - a Ca(OH)2 or CaCl2 or calcium acetate solution, called a calcium capture liquid; - a solution with a pH between 8 and 9, called an alkaline capture liquid.

2. The method according to claim 1, wherein The flue gas is introduced into the solution with a pH between 3 and 5, i.e., the desulfurization capture liquid, to form bisulfite.

3. The method according to claim 1 or 2, wherein, The flue gas is introduced into the Ca(OH)2 or CaCl2 or calcium acetate solution, i.e., the calcium capture liquid, to precipitate carbonates and / or bring nitrates into the solution.

4. The method according to claim 3, wherein, The carbonates precipitated in the calcium capture liquid solution are transported to an acidic aqueous solution to form calcium sulfate and CO2.

5. The method according to claim 1, wherein The flue gas is introduced into the desulfurization capture liquid to obtain bisulfite, and the flue gas is introduced into the calcium capture liquid to obtain carbonates and nitrates. The carbonates and the bisulfite are transported to another desulfurization capture liquid to obtain pure CO2.

6. The method according to any one of claims 1 to 5, wherein The CO2 generated in the process is transported to another calcium capture liquid solution to precipitate high-purity calcium carbonate.

7. The method according to any one of claims 1 to 6, wherein The CO2 generated in the process is transported to the alkaline capture liquid solution to precipitate high-purity bicarbonate.

8. The method according to any one of claims 1 to 7, wherein, The active ingredients obtained as a precipitate in water are filtered and optionally dried.

9. A facility for purifying industrial emission flue gas and for recovering and re-converting sulfur oxides and / or nitrogen oxides and / or carbon dioxide contained in the flue gas, the facility comprising: - a purification device (1) including a double purification chamber (10), the double purification chamber (10) being at least composed of a first hollow body (2) and a second hollow body (3) that are fluidly connected to each other, wherein: ○ The first hollow body (2) includes a water collection lower region (11), an upper region (12), an outlet port (13) arranged at the bottom of the lower region, an inlet (4) for the flue gas to be purified, and an outlet (5) for the purified flue gas located at the top of the upper region (12), wherein, under operating conditions, the outlet port (13) is located below the water level of the water occupying the lower region; ○ The second hollow body (3) includes a titanium and / or graphite electrode; - At least one, two, three, four, five, six or seven capture reactors (30), wherein the capture reactors (30) are in fluid communication with each other independently, and wherein each of one or more of the capture reactors includes a lower section (34) conveniently filled with an aqueous solution, at least one inlet port (31) for the flue gas and / or at least one inlet port (32) for the aqueous solution; optionally, at least one outlet port for the treated flue gas and at least one discharge port (33) from the lower section.

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