CN113941238A

CN113941238A - Integrated control method for low-temperature smoke pollutants

Info

Publication number: CN113941238A
Application number: CN202110300086.XA
Authority: CN
Inventors: 孙德帅; 刘鹏; 方龙; 张晓东; 陈照军; 巩玉苹
Original assignee: Shandong Zhenghan Environmental Protection Equipment Co ltd; Qingdao University
Current assignee: Shandong Zhenghan Environmental Protection Equipment Co ltd; Qingdao University
Priority date: 2021-03-22
Filing date: 2021-03-22
Publication date: 2022-01-18

Abstract

The invention relates to a low-temperature flue gas pollutant integrated control method, which comprises the steps that flue gas flows through an agglomeration chamber, a bag-type dust collector, a desulfurizing tower, an oxidation reactor and an absorption tower in sequence, and is discharged through a chimney after reaching a draught fan. The combination of the existing dust removal technology and the oxidation technology is fully utilized, the auxiliary effect of an agglomeration agent is utilized to pre-oxidize mercury in the flue gas, the conversion of mercury element to mercury particle is strengthened, and the dust removal and mercury removal synergistic effect is carried out by utilizing a bag-type dust remover; the sulfur dioxide in the flue gas is removed in the desulfurizing tower for one time, the residual gaseous pollutants are subjected to gas-liquid oxidation reaction in the oxidation reactor, and the synergistic effect of desulfurization, denitration and demercuration is carried out in the absorption tower through the ultramicro bubble enhanced oxidation process to complete the purification of the flue gas. Compared with the prior art, the removing method provided by the invention is easy to modify the existing flue gas equipment, the installation and modification cost is low, and the flue gas can meet the emission requirement after being treated.

Description

Integrated control method for low-temperature smoke pollutants

Technical Field

The invention belongs to the technical field of flue gas purification, and particularly relates to an integrated control method for dust removal, desulfurization, denitration and demercuration in low-temperature flue gas.

Background

Sulfur oxides (mainly SO) are produced during combustion₂) Pollutants such as nitrogen oxides (NOx), trace heavy metals and fine particulate matters; after being oxidized in the air, the acid gas contacts with water to form an acid substance, and acid rain is formed in the atmospheric precipitation process; in addition, the nitrogen oxide is easy to combine with hydrocarbon to form secondary pollution of photochemical smog; the discharge of trace heavy metals is ignored for a long time, but the mercury discharged by fire coal exceeds 1000 tons/year, the mercury is retained in the atmosphere for a long time, migrates for a long distance, is difficult to degrade in the natural environment, and finally accumulates in the food chain; various pollutants are easily accumulated on the surface of the fine particles, and can cause serious damage to the respiratory system, the cardiovascular system and the nervous system of a human body after entering the human body through the mouth and the nose, so that the fine particles are one of the pollutants which cause the most serious damage to the human body. The national standard of the emission Standard of atmospheric pollutants for thermal power plants (GB 13223-³，SO₂The discharge concentration is 50 mg/m³The nitrogen oxide emission concentration is 100 mg/m³Of mercuryThe discharge was 0.03 mg/m³. In 2014, the ultra-low emission requirements, such as smoke dust and SO, are also provided₂And the emission concentration of nitrogen oxides is not higher than 5 mg/m³，35 mg/m³And 50 mg/m³. The purification treatment of flue gases has therefore always been a problem that the combustion industry must face.

In the existing flue gas purification technology at home and abroad, a combined treatment technology is mainly adopted, and dust removal, desulfurization and denitration are usually completed by adopting independent systems aiming at a single pollutant target. Technologies such as lime-gypsum wet desulphurization and selective catalytic reduction denitration (SCR) are used for limiting the emission of acidic gas pollutants, and electrostatic or cloth bag dust removal Equipment (ESP) is used for capturing fly ash. Although the technologies are applied to large-scale commercial application, the removal effect is greatly different, the desulfurization effect can reach more than 95 percent, the denitration efficiency is generally maintained at 50-60 percent, the electrostatic dust collection and the bag type dust collection become main control methods of smoke dust, and the 10 mg/m can be reached under better operation conditions³. And this kind of pollutant treatment scheme of grading still has many defects, in order to meet the emission requirement, the coal fired boiler needs to be equipped with many flue gas treatment facilities at least simultaneously, the flue gas treatment procedure is long, equipment area is big, the treatment effect of preorder is showing the operation influence of follow-up equipment, causes the equipment complexity to increase, the efficiency reduces, the running cost is high. In addition, with the continuous improvement of the environmental protection requirement, the requirement for the emission of mercury in the flue gas also urgently needs to provide an effective solution. Therefore, the search for new desulfurization, denitrification and demercuration technologies has been an important issue for researchers.

Patent 20191068341.4 discloses a method for desulfurization and denitrification by catalytic oxidation of SO by microwave coupling with ultraviolet rays₂NO is mixed with oxygen and nitrogen, and SO is removed by pre-absorption₂Then the liquid phase composite oxidant is catalyzed and activated in the photocatalytic reactor to generate a plurality of free radicals to oxidize NO, and the NO is absorbed and purified by a subsequent absorption device. Microwave and ultraviolet coupling to enhance removal of nitrogen oxides is effective, but removal of heavy metals in flue gas is not known.

Patent 201710918454.0 discloses a system for simultaneously desulfurizing, denitrating and demercurating ozone and microwave-excited magnetically separable catalyst, which uses ozone to remove SO in flue₂NO and Hg⁰Pre-oxidation, activating peroxide in microwave reactor with magnetically separable catalyst to remove residual SO₂NO and Hg⁰And NO produced by pre-oxidation₂And SO₃And finally oxidized to sulfuric acid, nitric acid and Hg²⁺Washing the gas mixture by a spray tower to realize SO₂NO and Hg⁰Is completely removed. Although this method can achieve a higher removal efficiency, the stability, high energy consumption of the ozone generator during high-dose ozone operation is a problem that must be faced; in addition, although the expensive microwave reactor can be heated efficiently, the effect of long-term continuous operation needs to be improved, so that the industrial application of the method is still limited.

Therefore, a new integrated control method for dedusting, desulfurizing, denitrating and demercurating is sought in exploration, a simple flue gas treatment system can be effectively reduced, the investment of treatment equipment is effectively reduced, and the integrated purification requirement of multiple pollutants in flue gas of small and medium boilers is met.

Disclosure of Invention

Aiming at the characteristic of low exhaust gas temperature of an industrial boiler, the invention fully utilizes the synergistic effect of a dust removal system, combines an agglomeration technology with an oxidation technology, strengthens the preoxidation of element mercury in the flue gas through an agglomeration agent, combines the effective removal effect of a bag-type dust remover, and realizes the ultra-low emission of the flue gas by cooperating with the low-temperature oxidation technology to synchronously desulfurize, denitrate and demercuate.

In order to achieve the purpose, the technical scheme of the invention for synergistically removing the low-temperature flue gas pollutants comprises that flue gas sequentially flows through an agglomeration chamber, a bag-type dust remover, a desulfurizing tower, an oxidation reactor and an absorption tower, and is discharged through a chimney after reaching an induced draft fan. Pre-oxidizing mercury in the flue gas by using an agglomeration agent in an agglomeration chamber to strengthen mercury element (Hg)⁰) To particulate mercury (Hg)^p) The bag-type dust remover is utilized for dust removal and mercury removal synergistic effect; SO in flue gas in desulfurizing tower₂To carry outAnd (3) removing for the first time, wherein the residual gaseous pollutants are subjected to oxidation reaction in a liquid phase of an oxidation reactor, so that the water solubility of the pollutants is improved, and further, the synergistic effect of desulfurization, denitrification and demercuration is carried out in an absorption tower, and the purification of the flue gas is completed.

The reunion chamber is provided with a double-fluid nozzle which is a reunion agent spraying inlet, and a matrix type sloping plate vortex sheet group is arranged in the reunion chamber. The solution of the agglomeration agent is stored in a storage tank and enters a two-fluid nozzle through an air compressor to form liquid drops which enter an agglomeration chamber. The flue gas contacts the liquid drops of the agglomerating agent in a countercurrent mode.

The bag-type dust collector adopts a low-pressure pulse dust collector, and PTFE needles are covered with membrane filter materials; the desulfurizing tower adopts a liquid column tower, double-layer spraying and double-layer demister.

The oxidation reactor adopts a bubble column reactor, an oxidant circulates through a pump, and an ultramicro bubble inlet is arranged on the reactor; the absorption tower adopts a liquid column tower, a double-layer spray and a double-layer demister.

The above-mentioned agglomerating agent is an aqueous solution, including nonionic surfactant, macromolecular thickening agent, ammonium bromide, imidazole bromide salt, ammonium citrate and EDTA formed mixture, its solution concentration is 0.1-10 g/L, pH value is 4.5-8.5. Atomized liquid drops with the particle size of 20-80 mu m are formed by a two-fluid nozzle and sprayed into an agglomeration chamber, and the spray flow is 5-30 g/Nm³。

The oxidant in the oxidation reactor is aqueous solution, and comprises one or a mixture of two of hydrogen peroxide, sodium persulfate, sodium chlorite and a high manganese acid agent, the concentration of the solution is 1-25 g/L, and the pH value is 4.5-8.5.

The ultramicro bubble generator adopts oxygen water solution, wherein the oxygen input is 2-10L/min, and the water input is 20-30L/min.

The absorbent in the absorption tower is water solution comprising one or two of sodium sulfite, ammonium sulfite and sodium pyrosulfite, the concentration of the solution is 1-10%, and the pH value is 8.0-9.5.

In the integrated control method of low-temperature smoke pollutants, the dust-containing smoke generated by boiler combustion isThe aggregation chamber has collision effect with the high-speed sprayed aggregation agent liquid drops to absorb the aggregation agent solution, collision aggregation is formed under the blocking effect of the inclined plate vortex sheet, the particle size of particulate matters in smoke is increased, and Hg in smoke is simultaneously generated⁰After the catalyst is chemically reacted with a complexing component and an oxidizing component in an agglomerating agent, the catalyst is further adsorbed by fine particles to form Hg^pEffectively reduces the Hg in the smoke⁰Content (c); the agglomerated flue gas enters a bag-type dust collector, and particulate matters in the flue gas are effectively intercepted by the dust collector to form primary purified flue gas; the first-stage purified flue gas enters a desulfurizing tower to remove SO under the action of lime slurry₂Simultaneously to the mercury ions (Hg) in the flue gas²⁺) Forcibly removing to form secondary purified flue gas; the second-stage purified flue gas enters an oxidation reactor, oxidant solution is activated by ultramicro bubbles to form free radicals with high activity, and the free radicals and gas pollutants quickly complete oxidation reaction in a gas-liquid contact mode, so that NO and Hg in the flue gas⁰By oxidation to readily soluble NO₂，Hg²⁺Entering an absorption tower; and (3) purifying the nitrogen oxides and the mercury in the absorption tower by using alkaline sodium bisulfite and the like as an absorbent to form a three-stage purified gas, and introducing the purified gas into a chimney to be discharged into the atmosphere after passing through a draught fan. And (3) combining the residual liquid oxidant in the oxidation reactor with the absorption liquid in the absorption tower, and performing harmless treatment after dehydration.

Compared with the prior art, the low-temperature flue gas pollutant integrated control method disclosed by the invention fully utilizes the combination of the existing dust removal technology and the oxidation technology, flue gas agglomeration equipment is additionally arranged in the flue, agglomeration of fine particles is promoted by using an agglomeration agent, the pre-oxidation effect on pollutants in the flue gas is realized, the rapid oxidation reaction of the pollutants is carried out in an oxidation reactor, and the absorption and removal of the pollutants are promoted. The method has reasonable design, is easy to modify the existing flue gas equipment, has lower installation and modification cost, can meet the emission requirement after the flue gas is treated, and is convenient for the purification and use of small and medium boilers.

Description of the drawings:

FIG. 1 is a schematic diagram of an integrated contaminant control process.

FIG. 2 is a schematic view of the structure of an agglomeration chamber according to the present invention.

The method for removing the low-temperature smoke pollutants in a synergistic manner is described by combining the attached figure 1, wherein the smoke generated by boiler combustion is cooled, and the temperature of the smoke is not higher than 150 DEG^oC, entering an agglomeration chamber (1), starting an agglomeration agent storage tank (6), spraying the agglomeration agent into the agglomeration chamber (1) through a compressor and a double-fluid nozzle, and allowing the flue gas to stay in the agglomeration chamber for 3-5 s; the effluent smoke enters a bag-type dust remover (2) for primary dust removal and purification; the method comprises the steps that first-stage purified flue gas enters a desulfurizing tower (3), limestone slurry (8) is started for desulfurization, desulfurized second-stage purified flue gas enters an oxidation reactor (4), an ultramicro bubble generator (7) is started, generated ultramicro bubbles enter the oxidation reactor (4), an oxidant (9) is initiated to form a free radical oxidant, the oxidation reaction time is 3-8s, the flue gas enters an absorption tower (5), absorption liquid (10) is started for absorption, and the absorbed third-stage purified flue gas is discharged through a chimney after passing through an induced draft fan.

The inner components of the agglomeration chamber used in the method for removing the low-temperature flue gas pollutants synergistically are described with reference to the attached figure 2, and the agglomeration chamber (1) is internally provided with the inner components which are an inclined baffle plate (11) and a partition plate (12). Wherein the acute angle included angle of the residual smoke flow direction of the inclined baffle plate (11) is 30^oThe distance is 4-20 cm. The distance between the separation plates is 40-80 cm.

Detailed Description

Example 1

Particulate matter, SO in flue gas₂、NO、Hg⁰The concentration is 15 g/Nm respectively³2000ppm, 400ppm and 50. mu.g/Nm³Flue gas temperature 110^oC, enabling the flue gas to sequentially flow through the agglomeration chamber (1), starting an agglomeration agent storage tank (6), spraying the flue gas into the agglomeration chamber (1) through a compressor and a double-fluid nozzle, and enabling the flue gas to stay in the agglomeration chamber for 3-5 s; the effluent smoke enters a bag-type dust remover (2) for primary dust removal and purification; the method comprises the steps that first-stage purified flue gas enters a desulfurizing tower (3), limestone slurry (8) is started for desulfurization, second-stage purified flue gas after desulfurization enters an oxidation reactor (4), an ultramicro bubble generator (7) is started, ultramicro bubbles enter the oxidation reactor (4), an oxidant (9) is initiated to form an oxidation reaction, and the oxidation reaction is carried outThe reaction time is 3-8s, the flue gas enters the absorption tower (5), and the absorption liquid (10) is started for absorption. Wherein the agglomerant storage tank (6) is prepared from a mixture consisting of Tween 80, kappa-carrageenan, ammonium bromide, 1-butyl-3-methylimidazole bromine salt, ammonium citrate and EDTA into 1 g/L aqueous solution, and the pH value is adjusted to 5.8. Starting a compressor, forming atomized liquid drops with the particle size of 50 mu m through a two-fluid nozzle, and spraying the atomized liquid drops into an agglomeration chamber, wherein the spray flow rate is 15 g/Nm³. The oxidation reactor (4) adopts a mixture of hydrogen peroxide and a permanganate agent with a molar ratio of 10:1 to prepare 6 g/L aqueous solution, the pH value is adjusted to 5.5, and the atomization flow rate is 40 g/Nm³. The oxygen inlet amount of the ultramicro bubble generator (7) is 5L/min, and the water inlet amount is 20L/min. The result of the small test treatment is that the concentration of the particulate matters in the clean flue gas is 4.5 mg/Nm³，SO₂Concentration of 30ppm, NO concentration of 45ppm, Hg⁰The concentration was 13. mu.g/Nm³And the emission requirement is met.

Example 2

Particulate matter, SO in flue gas₂、NO、Hg⁰The concentration is 25 g/Nm respectively³2000ppm, 400ppm and 70. mu.g/Nm³Flue gas temperature 105^oC, enabling the flue gas to sequentially flow through the agglomeration chamber (1), starting an agglomeration agent storage tank (6), spraying the flue gas into the agglomeration chamber (1) through a compressor and a double-fluid nozzle, and enabling the flue gas to stay in the agglomeration chamber for 3-5 s; the effluent smoke enters a bag-type dust remover (2) for primary dust removal and purification; the method comprises the steps that first-stage purified flue gas enters a desulfurizing tower (3), limestone slurry (8) is started for desulfurization, second-stage purified flue gas after desulfurization enters an oxidation reactor (4), an ultramicro bubble generator (7) is started, ultramicro bubbles enter the oxidation reactor (4), an oxidant (9) is initiated to form an oxidation reaction, the oxidation reaction time is 3-8s, the flue gas enters an absorption tower (5), and absorption liquid (10) is started for absorption. Wherein the agglomerant storage tank (6) is prepared by mixing Tween 80, guar gum, ammonium chloride, 1-aminoethyl-3-methylimidazole bromine salt, ammonium citrate and EDTA to obtain 1 g/L aqueous solution, and adjusting the pH value to 6.2. Starting a compressor, forming atomized liquid drops with the particle size of 50 mu m through a two-fluid nozzle, and spraying the atomized liquid drops into an agglomeration chamber, wherein the spray flow rate is 15 g/Nm³. Oxygen gasThe chemical reactor (4) adopts a mixture of hydrogen peroxide and sodium persulfate with a molar ratio of 5:3, the mixture is prepared into 10 g/L aqueous solution, the pH value is adjusted to 6.5, and the atomization flow rate is 60 g/Nm³. The oxygen inlet amount of the ultramicro bubble generator (7) is 5L/min, and the water inlet amount is 20L/min. The result of the small test treatment is that the concentration of the particulate matters in the clean flue gas is 5.0 mg/Nm³，SO₂Concentration 39ppm, NO concentration 23 ppm, Hg⁰The concentration was 10. mu.g/Nm³And the emission requirement is met.

Example 3

Particulate matter, SO in flue gas₂、NO 、Hg⁰The concentration is 25 g/Nm respectively³1450 ppm, 500ppm and 64. mu.g/Nm³Flue gas temperature 110^oC, enabling the flue gas to sequentially flow through the agglomeration chamber (1), starting an agglomeration agent storage tank (6), spraying the flue gas into the agglomeration chamber (1) through a compressor and a double-fluid nozzle, and enabling the flue gas to stay in the agglomeration chamber for 3-5 s; the effluent smoke enters a bag-type dust remover (2) for primary dust removal and purification; the method comprises the steps that first-stage purified flue gas enters a desulfurizing tower (3), limestone slurry (8) is started for desulfurization, second-stage purified flue gas after desulfurization enters an oxidation reactor (4), an ultramicro bubble generator (7) is started, ultramicro bubbles enter the oxidation reactor (4), an oxidant (9) is initiated to form an oxidation reaction, the oxidation reaction time is 3-8s, the flue gas enters an absorption tower (5), and absorption liquid (10) is started for absorption. Wherein the agglomerant storage tank (6) is prepared from a mixture consisting of Tween 80, carrageenan, ammonium bromide, 1-butyl-3-methylimidazole bromine salt, ammonium citrate and EDTA into 1 g/L aqueous solution, and the pH value is adjusted to 5.8. Starting a compressor, forming atomized liquid drops with the particle size of 50 mu m through a two-fluid nozzle, and spraying the atomized liquid drops into an agglomeration chamber, wherein the spray flow rate is 15 g/Nm³. The oxidation reactor (4) adopts a mixture of hydrogen peroxide and sodium persulfate with a molar ratio of 5:3, and is prepared into 10 g/L aqueous solution, the pH value is adjusted to 6.0, and the atomization flow rate is 40 g/Nm³. The oxygen inlet amount of the ultramicro bubble generator (7) is 5L/min, and the water inlet amount is 20L/min. The result of the small test treatment is that the concentration of the particulate matters in the clean flue gas is 4.5 mg/Nm³，SO₂Concentration 23 ppm, NO concentration 35 ppm, Hg⁰At a concentration of 10μg/Nm³And the requirement of ultra-low emission is met.

Claims

1. The integrated control method of the low-temperature smoke pollutants comprises the steps that smoke sequentially flows through an agglomeration chamber, a bag-type dust remover, a desulfurizing tower, an oxidation reactor and an absorption tower, and is discharged through a chimney after reaching a draught fan; wherein a matrix type sloping plate vortex group is arranged in the reunion chamber; the oxidation reaction is enhanced by the ultramicro bubbles in the oxidation reactor.

2. The integrated control method for low-temperature flue gas pollutants according to claim 1, characterized in that the agglomerating agent sprayed into the agglomeration chamber is an aqueous solution comprising a mixture of a nonionic surfactant, a high-molecular thickener, ammonium bromide, imidazole bromide, ammonium citrate and EDTA, the concentration of the solution is 0.1-10 g/L, the pH value is 4.5-8.5, and the spray flow rate is 5-30 g/Nm³。

3. The integrated control method for low-temperature flue gas pollutants according to claim 1, characterized in that gas-liquid phase oxidation reaction is carried out in the oxidation reactor.

4. The integrated control method for low-temperature flue gas pollutants according to claim 1, wherein the oxidant in the oxidation atomizer is an aqueous solution comprising one or a mixture of two of hydrogen peroxide, sodium persulfate, sodium chlorite and a high manganese acid agent, the concentration of the solution is 1-25 g/L, and the pH value is 4.5-8.5.