Method for electrochemical redox regeneration of desulfurization solution in wet desulfurization

Abstract

The application discloses a kind of wet desulfurization desulfurization liquid electrochemical oxidation reduction regeneration methods, it is related to desulfurization liquid regeneration technical field.The application includes the following steps: S1: obtaining desulfurization liquid using wet desulfurization;S2: build inert electrode group;S3: install inert electrode group in the lower part of wet desulfurization spray tower;S4: the anode plate in inert electrode group is connected with the positive connection of direct current power supply, the cathode of electrode assembly is connected with direct current power supply negative pole.The application is closed loop operation by desulfurization liquid electrochemical oxidation reduction regeneration method, there is no waste gas emission, compared with air aeration oxidation regeneration, electrochemical oxidation reduction regeneration is more energy-saving, and belongs to the environment-friendly process, avoid the energy consumption of regeneration process, noise, desulfurization liquid generates a large amount of foam.

Description

Technical Field

[0001] This invention relates to the field of desulfurization liquid regeneration technology, specifically to an electrochemical oxidation-reduction regeneration method for wet desulfurization liquid. Background Technology

[0002] Existing desulfurization liquid regeneration methods use aeration to blow air in, which requires large investment in desulfurization liquid regeneration equipment, occupies a large area, consumes a lot of energy and generates a lot of noise during the regeneration process, and produces a lot of foam in the desulfurization liquid, which affects the sedimentation of sulfur particles. The large amount of excess air in the solution can degrade chelating agents and activators, further increasing the cost of desulfurization agents. Therefore, a new solution is needed to address the above problems. Summary of the Invention

[0003] The purpose of this invention is to provide an electrochemical oxidation-reduction regeneration method for wet desulfurization liquid to solve the problems mentioned in the background art.

[0004] To achieve the above objectives, the present invention provides the following technical solution: an electrochemical oxidation-reduction regeneration method for wet desulfurization liquid, comprising the following steps:

[0005] S1: Desulfurization liquid is obtained by wet desulfurization;

[0006] S2: Construct an inert electrode assembly;

[0007] S3: Install an inert electrode assembly at the bottom of the wet desulfurization spray tower;

[0008] S4: Connect the anode plate in the inert electrode assembly to the positive terminal of the DC power supply, and connect the cathode of the electrode assembly to the negative terminal of the DC power supply.

[0009] S5: When the electrode assembly is energized, under the influence of the electric field and potential energy, electrons migrate from the anode region to the cathode. The area near the anode exhibits oxidizing properties, while the cathode region is enriched with electrons and exhibits reducing properties.

[0010] Hydrogen ions generated during the desulfurization process gain electrons in the cathode region and are reduced to generate hydrogen gas.

[0011] 2H+(L)+2e→H2(g);

[0012] The ferrous ions generated during the desulfurization process lose electrons in the anode region and are oxidized into ferric ions (Fe3+).

[0013] Fe2+(L)-e→Fe3+(L);

[0014] Under the influence of electrical energy, the desulfurization liquid undergoes an electrochemical reaction, which reduces and regenerates the desulfurization liquid.

[0015] Preferably, the construction of the inert electrode assembly includes at least the following steps:

[0016] A. A porous foam mesh is placed between every two layers of electrode plates to facilitate solution flow and hydrogen escape;

[0017] B. Stack the electrode plates and the spacers layer by layer to form an inert electrode assembly.

[0018] Preferably, the substrate of the electrode plate in the inert electrode assembly is a high-purity titanium plate, and the outer side of the substrate is coated with PT, the thickness of which is 0.3-10μm.

[0019] Preferably, the process of obtaining desulfurization liquid using wet desulfurization includes at least the following steps:

[0020] H2S + 1 / 2O2 → H2O + S;

[0021] The complexed iron desulfurization catalyst utilizes the redox properties of complexed iron ions in aqueous solution to enable a gas-liquid phase contact reaction between hydrogen sulfide gas and aqueous solution containing complexed iron catalyst. This gas-liquid phase contact reaction first passes through an alkaline complexed iron solution. During gas-liquid phase contact, hydrogen sulfide in the raw gas is absorbed into the aqueous solution through acid-base chemical absorption.

[0022] In alkaline solution, the solubility and absorption rate of hydrogen sulfide are increased. The oxidizing property of the trivalent ferric complex ions is used to oxidize the hydrogen sulfide to elemental sulfur, and the trivalent ferric complex ions are reduced to divalent ferrous complex ions. The absorption and oxidation reaction equation of the ferric complex aqueous solution is as follows:

[0023] Aqueous solution absorbs H2S gas:

[0024] H₂S(g) + H₂O(L) ⇌ H₂S(L) + H₂O(L)

[0025] In the formula: (g) — gas phase, (L) — liquid phase;

[0026] H2S ionization:

[0027] H₂S(L)H⁺(L)+HS⁻(L)

[0028] Ferrous iron (Fe3+) oxidizes divalent sulfur:

[0029] HS-(L)+2Fe3+(L)→2Fe2+(L)+H+(L)+S↓

[0030] Overall reaction equation for absorption oxidation:

[0031] H2S(g)+2Fe3+(L)→2H+(L)+S↓+2Fe2+(L).

[0032] Compared with the prior art, the beneficial effects of the present invention are:

[0033] This invention utilizes an electrochemical oxidation-reduction regeneration method for desulfurization liquid, which operates in a closed loop with no waste gas emissions. Compared to air aeration oxidation regeneration, electrochemical oxidation-reduction regeneration is more energy-efficient and environmentally friendly, avoiding high energy consumption, noise, and excessive foaming of the desulfurization liquid during the regeneration process. Attached Figure Description

[0034] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 This is a schematic diagram of the electrochemical oxidation-reduction desulfurization liquid regeneration method of the present invention;

[0036] Figure 2 This is a schematic diagram of the inert electrode assembly of the present invention. Detailed Implementation

[0037] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0038] Example 1:

[0039] Please see Figure 1-2 An electrochemical oxidation-reduction regeneration method for wet desulfurization liquid includes the following steps:

[0040] S1: Desulfurization liquid is obtained by wet desulfurization;

[0041] S2: Construct an inert electrode assembly;

[0042] S3: Install an inert electrode assembly at the bottom of the wet desulfurization spray tower;

[0043] S4: Connect the anode plate in the inert electrode assembly to the positive terminal of the DC power supply, and connect the cathode of the electrode assembly to the negative terminal of the DC power supply.

[0044] S5: When the electrode assembly is energized, under the influence of the electric field and potential energy, electrons migrate from the anode region to the cathode. The area near the anode exhibits oxidizing properties, while the cathode region is enriched with electrons and exhibits reducing properties.

[0045] Hydrogen ions generated during the desulfurization process gain electrons in the cathode region and are reduced to generate hydrogen gas.

[0046] 2H+(L)+2e→H2(g);

[0047] The ferrous ions generated during the desulfurization process lose electrons in the anode region and are oxidized into ferric ions (Fe3+).

[0048] Fe2+(L)-e→Fe3+(L);

[0049] Under the influence of electrical energy, the desulfurization liquid undergoes an electrochemical reaction, which reduces and regenerates the desulfurization liquid.

[0050] Setting up an inert electrode assembly includes at least the following steps:

[0051] A. A porous foam mesh is placed between every two layers of electrode plates to facilitate solution flow and hydrogen escape;

[0052] B. Stack the electrode plates and the spacers layer by layer to form an inert electrode assembly;

[0053] The substrate of the electrode plate in the inert electrode assembly is a high-purity titanium plate, and the outer side of the substrate is coated with PT, with a coating thickness of 0.3-10μm.

[0054] Obtaining desulfurized liquid using wet desulfurization includes at least the following steps:

[0055] H2S + 1 / 2O2 → H2O + S;

[0056] The complexed iron desulfurization catalyst utilizes the redox properties of complexed iron ions in aqueous solution to enable a gas-liquid phase contact reaction between hydrogen sulfide gas and aqueous solution containing complexed iron catalyst. This gas-liquid phase contact reaction first passes through an alkaline complexed iron solution. During gas-liquid phase contact, hydrogen sulfide in the raw gas is absorbed into the aqueous solution through acid-base chemical absorption.

[0057] In alkaline solution, the solubility and absorption rate of hydrogen sulfide are increased. The oxidizing property of the trivalent ferric complex ions is used to oxidize the hydrogen sulfide to elemental sulfur, and the trivalent ferric complex ions are reduced to divalent ferrous complex ions. The absorption and oxidation reaction equation of the ferric complex aqueous solution is as follows:

[0058] Aqueous solution absorbs H2S gas:

[0059] H₂S(g) + H₂O(L) ⇌ H₂S(L) + H₂O(L)

[0060] In the formula: (g) — gas phase, (L) — liquid phase;

[0061] H2S ionization:

[0062] H₂S(L)H⁺(L)+HS⁻(L)

[0063] Ferrous iron (Fe3+) oxidizes divalent sulfur:

[0064] HS-(L)+2Fe3+(L)→2Fe2+(L)+H+(L)+S↓

[0065] Overall reaction equation for absorption oxidation:

[0066] H2S(g)+2Fe3+(L)→2H+(L)+S↓+2Fe2+(L).

[0067] Comparative Example 1:

[0068] This comparative example provides a commonly used desulfurization liquid regeneration method process compared to the above embodiment 1;

[0069] Ferric ions (Fe3+) oxidize divalent sulfur to form elemental sulfur molecules, reducing the ferric ions to ferrous ions (Fe2+). Since ferrous ions lose their strong oxidizing properties, the desulfurization reaction becomes discontinuous. To ensure the continuous and normal operation of the desulfurization process, the desulfurization liquid must be oxidized and regenerated, causing the ferrous ions to lose an electron and generate ferric ions (Fe3+).

[0070] A general-purpose rich liquid pump transports desulfurization liquid containing ferrous ions to the desulfurization liquid regeneration tower.

[0071] Air is blown into the regeneration tower using a Roots aerator. The oxygen in the air dissolves in the solution, and the divalent ferrous ion solution reacts with the dissolved oxygen, oxidizing the divalent ferrous ions in the desulfurization solution into trivalent ferric ions.

[0072] The regeneration and reduction reaction equation for the divalent ferrous ion complex solution is as follows:

[0073] Divalent ferrous ion complex solution absorbs oxygen:

[0074] 1 / 2O2(g)+H2O(L)→1 / 2O2(L)+H2O(L)

[0075] Regeneration reaction of divalent ferrous ions (Fe2+):

[0076] 1 / 2O2(L)+H2O(L)+2Fe2+(L)→2OH-(L)+2Fe3+(L)

[0077] Overall reaction equation for regeneration and reduction:

[0078] 1 / 2O2(g)+H2O(L)+2Fe2+(L)→2OH-(L)+2Fe3+(L)

[0079] In the overall reaction, the role of the ferric ions (Fe3+) is to release electrons generated in the absorption reaction into the regeneration reaction. Since the production of each elemental sulfur molecule requires the consumption of two ferric ions, the formation of one elemental sulfur molecule during the reaction requires the loss of two electrons by the divalent sulfur. In other words, to form one elemental sulfur molecule, the desulfurization solution needs to provide two ferric ions to acquire the two electrons from the divalent sulfur.

[0080] By comparing Comparative Example 1 with Example 1, it can be seen that...

[0081] The environmental assessment of the desulfurization liquid regeneration process in Comparative Example 1 is as follows:

[0082] Under standard conditions, the solubility of oxygen in water is 14.64 mg / L. At 35℃, the saturated dissolved oxygen content is 6.85 mg / L. Experiments show that the solubility of oxygen in an alkaline complexed iron desulfurization solution at 35℃ is 1.7 mg / L. Since the solubility of oxygen in the desulfurization solution is very low, the utilization rate of oxygen during air regeneration is very low. Therefore, to complete the regeneration of the complexed iron desulfurization solution, a large amount of air needs to be blown into the regeneration tower, resulting in relatively loud noise from the aeration blower.

[0083] The air aeration regeneration method is an open-loop system. Most of the air blown into the regeneration tower, except for a small amount of oxygen dissolved in the solution, needs to be discharged from the tower. The discharged air is then drawn by an induced draft fan to a waste gas purification device, where it is purified to meet emission standards.

[0084] Based on current operational calculations, removing 1 mol H2S(g) requires approximately 50 m3 / h of air to be blown in during the regeneration of the desulfurization liquid, and 2 mol Fe2+ ions are oxidized into 2 mol Fe3+ ions. Including the circulation and transportation by the rich liquid pump and the exhaust gas purification treatment by the induced draft fan, the total energy consumption for the regeneration process is approximately 10350 kJ on average.

[0085] Using aeration to introduce air results in large investment and a large footprint for desulfurization liquid regeneration equipment. The regeneration process is energy-intensive, noisy, and produces a large amount of foam in the desulfurization liquid, affecting the settling of sulfur particles. Excess air in the solution can degrade chelating agents and activators, further increasing the cost of desulfurization reagents.

[0086] The environmental assessment of electrochemical oxidation-reduction regeneration in Example 1, section 3, is as follows:

[0087] From the reaction H₂S(g) + 2Fe³⁺(L) → 2H⁺(L) + S↓ + 2Fe²⁺(L), it can be seen that removing 1 mole of Fe³⁺ ions from H₂S requires 2 moles of Fe³⁺. The resulting product is 1 mole of elemental S, 2 moles of H⁺ ions, and 2 moles of Fe²⁺ ions.

[0088] From the ionic reaction equations 2H+(L) + 2e → H2(g) and Fe2+(L) - e → Fe3+(L), it can be seen that under the action of electrical energy, two moles of Fe2+ ions migrate two moles of electrons from the anode to the cathode. Two moles of H+ ions gain electrons at the cathode, producing one mole of hydrogen gas. Simultaneously, the two moles of Fe2+ ions at the anode lose electrons to generate two Fe3+ ions. The Fe2+ ions are oxidized to Fe3+ ions, and the desulfurization solution is regenerated.

[0089] Removing 1 mol of H2S(g) requires 2 mol of Fe3+ ions, and regenerating the desulfurization solution requires oxidizing 2 mol of Fe3+ ions into 2 mol of Fe2+ ions;

[0090] The third ionization energy of iron is 2957 kJ / mol. 2 mol of Fe2+ ions lose 2 × 6.022 × 1023 electrons to ionize into 2 mol of Fe3+ ions, which requires an ionization energy of 5914 kJ.

[0091] 2 mol of H+ ions gain 2 × 6.022 × 1023 electrons to generate 1 mol of H2(g). The H2(g) enters the biogas, adding 1 mol of heat energy to the biogas. The calorific value of hydrogen is 143 kJ / g, and 1 mol of H2(g) has a total of 286 kJ / mol.

[0092] The wet desulfurization of complexed iron and the electrochemical oxidation-reduction regeneration method of the desulfurization liquid are closed-loop operations with no waste gas emissions. Compared with the air aeration oxidation regeneration in Comparative Example 1, the electrochemical oxidation-reduction regeneration used in Example 1 is an energy-saving and environmentally friendly process.

[0093] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A method for electrochemical oxidation-reduction regeneration of desulfurization liquid in wet desulfurization, characterized in that: Includes the following steps: S1: Desulfurization liquid is obtained by wet desulfurization; S2: Construct an inert electrode assembly; The construction of the inert electrode assembly includes at least the following steps: A. A porous foam mesh is placed between every two layers of electrode plates; B. Stack the electrode plates and the spacers layer by layer to form an inert electrode assembly; The substrate of the electrode plate in the inert electrode assembly is a high-purity titanium plate, and the outer side of the substrate is coated with PT, the thickness of which is 0.3-10μm. S3: Install an inert electrode assembly at the bottom of the wet desulfurization spray tower; S4: Connect the anode plate in the inert electrode assembly to the positive terminal of the DC power supply, and connect the cathode of the electrode assembly to the negative terminal of the DC power supply. S5: When the electrode assembly is energized, under the influence of the electric field and potential energy, electrons migrate from the anode region to the cathode. The area near the anode exhibits oxidizing properties, while the cathode region is enriched with electrons and exhibits reducing properties. Hydrogen ions generated during the desulfurization process gain electrons in the cathode region and are reduced to generate hydrogen gas. 2H + (L)+2e - →H2(g); The ferrous ions generated during the desulfurization process lose electrons in the anode region and are oxidized into ferric ions (Fe3+). Fe 2+ (L)-e - →Fe 3+ (L); Under the influence of electrical energy, the desulfurization liquid undergoes an electrochemical reaction, which reduces and regenerates the desulfurization liquid. The process of obtaining desulfurized liquid using wet desulfurization includes at least the following steps: H2S + 1 / 2O2 → H2O + S; The complexed iron desulfurization catalyst utilizes the redox properties of complexed iron ions in aqueous solution to enable a gas-liquid phase contact reaction between hydrogen sulfide gas and aqueous solution containing complexed iron catalyst. This gas-liquid phase contact reaction first passes through an alkaline complexed iron solution. During gas-liquid phase contact, hydrogen sulfide in the raw gas is absorbed into the aqueous solution through acid-base chemical absorption. In alkaline solution, the solubility and absorption rate of hydrogen sulfide are increased. The oxidizing property of ferric ions (trivalent complex ions) is used to oxidize hydrogen sulfide into elemental sulfur. The ferric ions are reduced to ferrous ions (divalent complex ions). The absorption and oxidation reaction equation of the ferric ion aqueous solution is as follows: Aqueous solution absorbs H2S gas: H2S(g)+H2O(L) H2S(L)+H2O(L) In the formula: (g) — gas phase, (L) — liquid phase; H2S ionization: H2S(L) H + (L)+HS - (L) Ferric ions (Fe) 3+ Divalent sulfur oxides: HS - (L)+2Fe 3+ (L)→2Fe 2+ (L)+H + (L)+S↓ Overall reaction equation for absorption oxidation: H2S(g)+2Fe 3+ (L)→2H + (L)+S↓+2Fe 2+ (L)。

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