CN101254392B - Energy-saving sodium sulfite circulating desulfurization device and method - Google Patents

Abstract

The invention relates to an energy-saving sodium sulfite circulating desulfurization device and method. The desulfurization device includes a desulfurization tower, first and second absorption liquid circulation tanks, the top of the desulfurization tower communicates with the chimney, the lower part of the desulfurization tower communicates with the top of the washing and cooling tower, and the bottom of the washing and cooling tower communicates with the top of the washing and cooling tower. The circulating water washing tank is connected, which is characterized in that: the washing and cooling tower is connected with the heat exchanger, and the heat exchanger is connected with the decomposition jacket reactor and then connected with the flue; the second absorption liquid circulation tank is connected with the serpentine tube in the heat exchanger Communication, the serpentine tube communicates with the reaction chamber of the decomposed jacketed reactor; the lower part of the decomposed jacketed reactor communicates with the centrifuge. The desulfurization steps are as follows: preparing initial absorption liquid, cooling flue gas, absorbing sulfur dioxide, decomposing sodium bisulfite, and recycling sodium sulfite. The residual heat of the flue gas is fully utilized, and the initial absorbent is converted into a recycled absorbent, which reduces operating costs and is beneficial to environmental protection.

Description

Energy-saving sodium sulfite circulating desulfurization device and method

technical field

The invention relates to a flue gas desulfurization method, in particular to an energy-saving sodium sulfite circulating desulfurization device and method. the

Background technique

In China, coal burning accounts for more than 70% of the primary energy. Because coal contains sulfur, a large amount of SO ₂ is produced after combustion, which causes serious air pollution. Therefore, the task of flue gas desulfurization is very heavy. At present, flue gas desulfurization treatment is the most effective method to reduce SO ₂ emission and acid rain formation, and the wet flue gas desulfurization technology that has been successfully operated is dominated by calcium method. The calcium method uses calcium carbonate (ie limestone) as the absorbent, and its chemical reaction is as follows:

CaCO ₃ +SO ₂ +1/2H ₂ O＝CaSO ₃ ·1/2H ₂ O+CO ₂ ↑

2CaSO ₃ ·1/2H ₂ O+3H ₂ O＝2CaSO ₄ ·2H ₂ O

Calcium carbonate (that is, limestone) is a substance with very low water solubility. When used as an absorbent, it is pulverized into a 300-mesh powder, and it is implemented with water to form a slurry. Due to the presence of solid substances, the requirements for spray equipment and conveying equipment are high. The product CaSO ₃ after absorbing SO ₂ and the CaSO ₄ produced after oxidation are substances with low solubility, which are easy to block pipelines and equipment. Therefore, although the calcium method has the advantages of low calcium carbonate price, mature technology, and high desulfurization efficiency, it has the disadvantages of relatively complicated processes and equipment, large capital investment, and high operating costs. In terms of economic benefits, it is still in a state of loss. In order to reduce the loss, the power plant has to take measures to increase the price of electricity. Therefore, it is a long-standing objective demand to seek a flue gas desulfurization method that can reduce environmental pollution and significantly reduce operating costs. CN1660474A discloses an invention patent application titled "wet flue gas desulfurization process", which can treat the acid gas (SO ₂ ) in the flue gas after the combustion of sulfur-containing fuels. The principle is to achieve the purpose of purifying the flue gas by reacting the alkaline desulfurizer-sodium sulfite solution with the sulfur dioxide in the flue gas, and the sodium sulfite solution can be regenerated and recycled. The wet flue gas desulfurization process has the advantages of no fouling in the absorption system, no blockage of pipelines and equipment, high desulfurization efficiency, low liquid-gas ratio, and low operating cost of the entire system. However, when regenerating sodium sulfite, a certain concentration of milk of lime is used, and the neutralization reaction generates NaSO ₃ and precipitates CaSO ₃ and CaSO ₄ . It is necessary to recycle the regenerated sodium sulfite after separation and treatment, and the resulting precipitate things are processed. In addition, the utilization of the waste heat of the flue gas is not sufficient.

Contents of the invention

The object of the present invention is to provide an energy-saving sodium sulfite cycle desulfurization device and method, the supporting equipment of the device is not easy to block, can ensure smooth flow, easy maintenance and repair; the method is to use the waste heat of the flue gas as the energy required for the regeneration of the absorbent , the desulfurization efficiency is high, the products after the reaction can be used conveniently, the pollution to the environment is small, and the operation cost can be significantly reduced. the

The energy-saving sodium sulfite circulating desulfurization device of the present invention comprises a desulfurization tower, a first absorption liquid circulation tank and a second absorption liquid circulation tank arranged outside the desulfurization tower, and the interior of the desulfurization tower is divided into upper, middle and The lower three areas; the upper area inside the desulfurization tower is provided with the first spray nozzle communicated with the first absorption liquid circulation tank, and the bottom of the upper area is communicated with the first absorption liquid circulation tank; the middle area inside the desulfurization tower is provided with The second spray head communicated with the second absorption liquid circulation tank, the bottom of the middle zone communicates with the second absorption liquid circulation tank; the bottom of the first absorption liquid circulation tank communicates with the second absorption liquid circulation tank; the flue gas at the top of the desulfurization tower The outlet is communicated with the chimney, the flue gas inlet at the lower part of the desulfurization tower is communicated with the flue gas outlet at the top of the washing and cooling tower, the bottom of the washing and cooling tower is communicated with the circulating water washing tank, and the third nozzle connected with the circulating water washing tank is located in the washing and cooling tower. upper part; characterized in that:

a. The flue gas inlet at the lower part of the washing and cooling tower communicates with at least one flue gas outlet at the bottom of the heat exchanger, and the flue gas inlet at the upper part of the heat exchanger communicates with the flue gas outlet on the side of the decomposed jacket reaction kettle. The flue gas inlet on the side of the kettle communicates with the flue;

b. The outlet at the lower part of the second absorption liquid circulation tank communicates with the serpentine tube in the heat exchanger, and the outlet of the serpentine tube communicates with the reaction chamber of the decomposed jacketed reactor; the top of the reactor chamber of the decomposed jacketed reactor The outlet communicates with the inlet of the condenser, and the outlet of the condenser communicates with the inlet of the gas-water separator;

c. The lower part of the decomposed jacketed reactor communicates with a centrifuge, and the outlet of the centrifuge communicates with the reaction chamber of the decomposed jacketed reactor. the

The decomposed jacketed reactor of the energy-saving sodium sulfite circulating desulfurization device includes: a reaction chamber, a column tube connected to the reaction room at one end, a discharge hopper connected to the other end of the column tube, and a tube connected to the side of the reaction chamber and the column tube. Jacket; the flue gas inlet on the jacket communicates with the flue, and the lower end of the discharge hopper communicates with the centrifuge. The structure of the "decomposed jacketed reactor" used in the present invention is basically the same as the ZL200520009573.7 utility model patent, except that tubes are added in the reactor body to enhance the heat exchange effect, and it still maintains the convenience of installation and disassembly and easy maintenance. Features, when a lot of dust in the flue gas is deposited in the jacket, the jacket can be easily removed to remove the dust to ensure the heat exchange effect. the

In the energy-saving sodium sulfite circulating desulfurization device, the flue gas inlet at the lower part of the washing and cooling tower communicates with the flue gas outlets at the bottom of the two heat exchangers, and the flue gas inlets at the upper parts of the two heat exchangers are connected to the two decomposition jackets respectively. The flue gas outlets on the side of the reactor are connected, and the flue gas inlets at the lower part of the two decomposition jacketed reactors are respectively connected to the flue;

The outlets at the lower part of the second absorption liquid circulation tank communicate with the serpentine tubes in the two heat exchangers respectively, and the outlets of the two serpentine tubes respectively communicate with the reaction chambers of the two decomposed jacketed reactors; The outlets at the top of the reaction chamber of the sleeve reactor communicate with the inlets of the condenser respectively, and the outlets of the condenser communicate with the inlets of the gas-water separator;

The lower discharge hoppers of the two decomposed jacketed reactors communicate with a centrifuge respectively, and the outlets of the two centrifuges communicate with the reaction chambers of the two decomposed jacketed reactors respectively. the

In this scheme, two heat exchangers and two decomposed jacketed reactors are set up. In addition to rapidly reducing the temperature of the flue gas, the other can continue to work when one decomposed jacketed reactor is overhauled, so as to Keep the desulfurization going on continuously. the

The energy-saving type sodium sulfite circulation desulfurization method of the present invention is carried out on the energy-saving type sodium sulfite circulation desulfurization device, and its steps are as follows:

The first step is to prepare the initial absorption liquid: the initial absorption agent is Na ₂ CO ₃ , add soft water (ion-free water) into the first absorption liquid circulation tank, and gradually add Na ₂ CO ₃ under stirring to make it in the solution The weight percentage concentration is 8-18%. After fully dissolving, add 0.05% antioxidant by weight of the solution and stir evenly;

The second step is to circulate the initial absorption liquid: turn on the circulation pumps of the first absorption liquid circulation tank and the second absorption liquid circulation tank, so that the absorption liquid is sprayed into the upper part of the desulfurization tower through the first nozzle connected to the first absorption liquid circulation tank. area, and return to the first absorption liquid circulation tank from the bottom of the upper area, and the _Na2CO3 solution flows into the second absorption liquid circulation tank from the _bottom of the first absorption liquid circulation tank; The second nozzle connected to the circulation tank sprays into the middle zone inside the desulfurization tower, and returns to the second absorption liquid circulation tank from the bottom of the middle zone;

The third step, flue gas cooling: the flue gas discharged from the flue with a temperature of about 180°C enters the jacket and the tubes for heat exchange from the flue gas inlet on the side of the "decomposition jacketed reactor"; after the temperature drops The flue gas enters the heat exchanger from the flue gas outlet of the "decomposition jacketed reactor" for heat exchange again, and the flue gas whose temperature is lowered again is discharged from the flue gas outlet of the heat exchanger, and is discharged from the flue gas at the lower part of the washing cooling tower. The air inlet enters it; the water in the washing water circulation tank is sprayed down from the upper part of the washing cooling tower through the water pump to further reduce the temperature of the flue gas to below 60°C;

The fourth step is to absorb sulfur dioxide: the flue gas whose temperature drops below 60°C is discharged from the flue gas outlet at the top of the washing and cooling tower, and then enters the lower area from the flue gas inlet at the lower part of the desulfurization tower. Distribution, evenly enters the middle zone of the desulfurization tower from the brim of each riser pipe on the first interval, and contacts with the absorption liquid sprayed by the second nozzle installed on the upper part of the middle zone, and part of the _SO2 in the flue gas is absorbed; The flue gas enters the upper area of the desulfurization tower from the brims of the risers on the second interval, and contacts with the absorption liquid sprayed by the first spray nozzle on the upper part of the upper area, and most of the remaining _SO2 in the flue gas is absorbed , and then, the flue gas exits from the top of the desulfurization tower into the chimney for discharge; the following chemical reactions occur:

Na ₂ CO ₃ +SO ₂ ＝Na ₂ SO ₃ +CO ₂ ↑

The sodium sulfite obtained by the reaction reacts with the _SO in the flue gas as follows:

Na ₂ SO ₃ +SO ₂ +H ₂ O＝2NaHSO ₃

The fifth step is to decompose sodium bisulfite: the sodium bisulfite solution generated by the reaction between the absorption liquid and the sulfur dioxide in the flue gas is pumped from the second absorption liquid circulation tank into the serpentine tube in the heat exchanger through the water pump, and is preheated After entering the reaction chamber of the decomposing jacketed reactor, and then heated by the flue gas in the jacket of the decomposing jacketed reactor and between the tubes, the decomposition occurs as follows:

2NaHSO ₃ → Na ₂ SO ₃ +SO ₂ ↑+H ₂ O

The 6th step, the sulfur dioxide in the separation water vapor: the _SO2 that the 5th step decomposes generates discharges from the reaction chamber outlet on the decomposition type jacket reactor top, then enters condenser cooling, makes SO _most of the gas The water vapor is condensed into water, then, it is discharged from the outlet of the condenser, and enters the gas-water separator, after the gas-water separation, the SO ₂ gas is sent to liquefaction treatment as a chemical raw material;

The seventh step is to recycle sodium sulfite: the Na ₂ SO ₃ and H ₂ O generated by the decomposition in the fifth step are discharged from the hopper at the lower part of the decomposition jacketed reactor to the centrifuge for separation; the centrifuge is separated to obtain Na ₂ SO ₃ The solid is added to the first absorption liquid circulation tank for recycling as a circulating absorbent;

The eighth step, separation and filtrate treatment: pump the remaining filtrate containing NaHSO ₃ , Na ₂ SO ₃ and Na ₂ SO ₄ in the seventh step into the reaction chamber of the decomposed jacketed reactor to make the NaHSO ₃ Decomposition; when the content of Na ₂ SO ₄ in the separated filtrate reaches 5%, send the separated filtrate to freeze crystallization to separate the by-product Na ₂ SO ₄ .

In the energy-saving sodium sulfite circulating desulfurization method, the initial absorbent is NaOH, and the first step is to prepare the initial absorption liquid: add soft water to the first absorption liquid circulation tank, and gradually add NaOH under stirring, so that the weight in the solution is The percentage concentration is 7-14%. After fully dissolving, add 0.05% antioxidant by solution weight and stir evenly; the following chemical reaction occurs:

2NaOH+SO ₂ →Na ₂ SO ₃ +H ₂ O

The sodium sulfite obtained by the reaction reacts with the _SO in the flue gas as follows:

Na ₂ SO ₃ +SO ₂ +H ₂ O＝2NaHSO ₃

The remaining steps are the same as the previous method. the

In the energy-saving sodium sulfite cycle desulfurization method, the antioxidant added to the absorption liquid is p-phenylenediamine or hydroquinone. Due to oxidation, a small part of Na ₂ SO ₃ is oxidized to Na ₂ SO ₄ , and the effect of adding antioxidants is to reduce the oxidation rate to below 5%, thereby reducing the supplementary amount of the initial absorbent and reducing the cost.

In the energy-saving sodium sulfite circulating desulfurization method, when the circulating absorbent is lost during desulfurization, it is necessary to replenish the initial absorbent Na ₂ CO ₃ or NaOH in time to maintain the desulfurization capacity of the absorbing liquid.

Compared with the prior art, the present invention has the following advantages: the waste heat of the flue gas is fully utilized, the product after the reaction between the initial absorbent and sulfur dioxide is converted into a circulating absorbent for use, and the by-products obtained after desulfurization are easy to use and can be used as Commodities are sold, thereby greatly reducing the operating cost of desulfurization; the initial absorbent, circulating absorbent and by-products are all water-soluble substances, which will not cause equipment blockage during the process and ensure smooth flow; the desulfurization efficiency is high, Generally, it can reach more than 95%, which is beneficial to environmental protection. the

Description of drawings

Figure 1 is a schematic diagram of an energy-saving sodium sulfite circulating desulfurization device. the

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings. the

Embodiment 1: Sodium carbonate is used as the initial absorbent, and the flue gas is desulfurized by an energy-saving sodium sulfite circulating desulfurization device. the

Referring to Figure 1, the interior of the desulfurization tower 1 of the energy-saving sodium sulfite circulating desulfurization device is divided into upper, middle and lower areas by two intervals, and the first absorption liquid circulation tank 2 and the second absorption liquid circulation tank 3 are located in the desulfurization tower outside, the bottom of the upper area of the desulfurization tower communicates with the first absorption liquid circulation tank, the bottom of the middle area of the desulfurization tower communicates with the second absorption liquid circulation tank, and the bottom of the first absorption liquid circulation tank communicates with the second absorption liquid circulation tank; The first nozzle 2-1 connected to the first absorption liquid circulation tank is installed on the upper part of the upper area inside the desulfurization tower, and the second nozzle 3-1 connected to the second absorption liquid circulation tank is installed on the upper part of the middle area inside the desulfurization tower; The flue gas inlet at the lower part of the desulfurization tower communicates with the flue gas outlet at the top of the washing and cooling tower 4, and the flue gas outlet at the top of the desulfurization tower communicates with the chimney, and the desulfurized flue gas is discharged from the chimney;

The bottom of the washing and cooling tower 4 communicates with the circulating water washing tank 5, and the third nozzle 5-1 communicating with the circulating water washing tank is installed on the upper part of the washing and cooling tower; The flue gas outlets of the two heat exchangers are connected to each other, the flue gas inlets on the upper part of the two heat exchangers are respectively connected to the flue gas outlets on the upper side of the two decomposed jacketed reactors 7, and the flue gas inlets on the lower sides of the two decomposed jacketed reactors are respectively communicated with the flue;

The outlets at the lower part of the second absorption liquid circulation tank 3 communicate with the serpentine tubes in the two heat exchangers 6 respectively, and the outlets of the two serpentine tubes communicate with the reaction chambers 7-1 of the two decomposed jacketed reactors 7 respectively The outlets at the top of the reaction chamber of the two decomposable jacketed reactors 7 communicate with the inlet of the condenser 8 respectively, and the outlet of the condenser communicates with the inlet of the gas-water separator 9; the sulfur dioxide gas separated is sent to liquefaction as chemical raw materials;

The reaction chamber 7-1 of the decomposed jacketed reactor is connected to one end of the tube 7-2, the discharge hopper 7-3 is connected to the other end of the tube, and the jacket 7-1 connected to the outside of the reaction chamber and the tube 4 The flue gas inlet communicates with the flue;

The lower end of the discharge hopper is communicated with the centrifuge 10, and the sodium sulfite solid obtained by separation of the centrifuge is used as a circulating absorbent and returned to the first absorption liquid circulation tank 2 for recycling;

The separated liquid is returned from the outlet of the centrifuge to the reaction chamber 7-1 of the decomposing jacketed reactor to continue decomposing. the

The desulfurization steps are as follows:

The first step is to prepare the initial absorption liquid: the initial absorption agent is Na ₂ CO ₃ , add soft water (ion-free water) into the first absorption liquid circulation tank 2, and gradually add Na ₂ CO ₃ under stirring to make it in the solution The weight percent concentration is 8%. After fully dissolving, add 0.05% of the solution weight antioxidant—p-phenylenediamine, and stir evenly;

The second step is to circulate the initial absorption liquid: turn on the circulation pumps of the first absorption liquid circulation tank 2 and the second absorption liquid circulation tank 3, and spray the absorption liquid through the first nozzle 2-1 communicating with the first absorption liquid circulation tank The upper area inside the desulfurization tower 1, so as to absorb the sulfur dioxide in the flue gas, and then return to the first absorption liquid circulation tank from the bottom of the upper area, and flow into the second absorption liquid circulation tank from the bottom of the first absorption liquid circulation tank Simultaneously, the absorption liquid is sprayed into the middle zone of the desulfurization tower 1 through the second spray nozzle 3-1 communicated with the second absorption liquid circulation tank, so as to absorb the sulfur dioxide in the flue gas, and then return to the first zone from the bottom of the middle zone Two absorption liquid circulation tank;

The third step is to cool down the flue gas: the flue gas discharged from the flue with a temperature of about 180°C enters the jacket and the tubes for heat exchange from the flue gas inlets on the sides of the two "decomposition jacketed reactors" respectively; The flue gas after the temperature drop enters the two heat exchangers 6 from the flue gas outlets of the two "decomposition jacketed reactors" for heat exchange again. The outlet is discharged and enters from the flue gas inlet at the lower part of the washing cooling tower 4; the water in the washing water circulation tank 5 is sprayed down from the upper part of the washing cooling tower by the water pump through the nozzle 5-1 to further reduce the temperature of the flue gas. to below 60°C;

The fourth step is to absorb sulfur dioxide: the flue gas whose temperature drops below 60°C is discharged from the flue gas outlet at the top of the washing and cooling tower 4, and then enters the lower area from the flue gas inlet at the lower part of the desulfurization tower 1, and the flue gas in this area Carry out reasonable distribution, evenly enter the middle area of the desulfurization tower from the brim of each riser pipe on the first interval, and contact with the absorption liquid sprayed by the second spray nozzle located at the upper part of the middle area, and part of the _SO2 in the flue gas is absorbed Absorption; the flue gas enters the upper area of the desulfurization tower from the brims of the air risers on the second interval, and contacts with the absorption liquid sprayed by the first nozzle 2-1 located on the upper part of the upper area, and the remaining SO ₂ in the flue gas Most of it is absorbed, and then enters the chimney from the flue gas outlet at the top of the desulfurization tower; the following chemical reactions occur:

Na ₂ CO ₃ +SO ₂ ＝Na ₂ SO ₃ +CO ₂ t

The sodium sulfite obtained by the reaction reacts with the _SO in the flue gas as follows:

Na ₂ SO ₃ +SO ₂ +H ₂ O＝2NaHSO ₃

The fifth step is to decompose sodium bisulfite: the sodium bisulfite solution generated by the reaction of the absorption liquid and the sulfur dioxide in the flue gas is pumped from the second absorption liquid circulation tank 3 into the serpentine tubes in the two heat exchangers 6 , after preheating, respectively enter the reaction chambers of two decomposed jacketed reactors 7, and then heat the flue gas in the jacket of the decomposed jacketed reactor and between the tubes, and the decomposition reaction takes place as follows:

2NaHSO ₃ →Na ₂ SO ₃ +SO ₂ ↑+H ₂ O

The sixth step is to separate the sulfur dioxide in the water vapor: the _SO2 generated by the decomposition in the fifth step is discharged from the outlet of the reaction chamber at the top of the decomposition jacketed reactor, and then enters the condenser 8 for cooling, so that most of the water vapor in the _SO2 gas Condensate into water, then, discharge from the outlet of the condenser, enter the gas-water separator 9, after the gas-water separation, the _SO2 gas is sent to liquefaction treatment, as chemical raw material;

The seventh step is to recycle sodium sulfite: the Na ₂ SO ₃ and H ₂ O produced by the decomposition in the fifth step are discharged from the discharge hopper 7-3 at the lower part of the decomposition jacket reactor to the centrifuge 10 for separation; the centrifuge is separated to obtain Na ₂ The solid of SO ₃ is added to the first absorption liquid circulation tank 2 to be recycled as a circulating absorbent;

The eighth step, separation and filtrate treatment: the filtrate left in the seventh step contains NaHSO ₃ , Na ₂ SO ₃ and Na ₂ SO ₄ , and is pumped into the reaction chamber of the decomposed jacketed reactor 7 to make the NaHSO ₃ Decomposition; when the content of Na ₂ SO ₄ in the separated filtrate reaches 5%, send the separated filtrate to freeze crystallization to separate the by-product Na ₂ SO ₄ .

Embodiment 2: Sodium carbonate is used as the initial absorbent, and the flue gas is desulfurized by an energy-saving sodium sulfite circulating desulfurization device. the

The first step is to prepare the initial absorption liquid: the initial absorption agent is Na ₂ CO ₃ , add soft water (ion-free water) into the first absorption liquid circulation tank 2, and gradually add Na ₂ CO ₃ under stirring to make it in the solution The weight percent concentration is 16%. After fully dissolving, add 0.05% of the solution weight antioxidant-p-phenylenediamine, and stir evenly; the rest of the steps are the same as in Example 1.

Embodiment 3: Sodium carbonate is used as the initial absorbent, and the flue gas is desulfurized by an energy-saving sodium sulfite circulating desulfurization device. the

The first step is to prepare the initial absorption liquid: the initial absorption agent is Na ₂ CO ₃ , add soft water (ion-free water) into the first absorption liquid circulation tank 2, and gradually add Na ₂ CO ₃ under stirring to make it in the solution The concentration by weight is 18%. After fully dissolving, add 0.05% antioxidant-hydroquinone by weight of the solution and stir evenly; the rest of the steps are the same as in Example 1.

Embodiment 4: NaOH is used as the initial absorbent, and the flue gas is desulfurized by an energy-saving sodium sulfite circulating desulfurization device. the

The first step is to prepare the initial absorption liquid: the initial absorption agent is NaOH, soft water (ion-free water) is added in the first absorption liquid circulation tank 2, and NaOH is gradually added under stirring so that the concentration by weight in the solution is 7 After fully dissolving, adjust to a saturated solution at room temperature, then add 0.05% of the solution weight antioxidant—p-phenylenediamine, stir evenly; the following chemical reactions occur:

2NaOH+SO ₂ →Na ₂ SO ₃ +H ₂ O

The sodium sulfite obtained by the reaction reacts with the _SO in the flue gas as follows:

Na ₂ SO ₃ +SO ₂ +H ₂ O＝2NaHSO ₃

The remaining steps are the same as in Embodiment 1. the

Embodiment 5: NaOH is used as the initial absorbent, and the flue gas is desulfurized by an energy-saving sodium sulfite circulating desulfurization device. the

The first step is to prepare the initial absorption liquid: the initial absorption agent is NaOH, soft water (ion-free water) is added in the first absorption liquid circulation tank 2, NaOH is gradually added under stirring, so that the weight percent concentration in the solution is 12.5 %, after fully dissolved, then add 0.05% of the solution weight antioxidant - p-phenylenediamine, stir well; the following chemical reaction occurs:

2NaOH+SO ₂ →Na ₂ SO ₃ +H ₂ O

The sodium sulfite obtained from the reaction is used as a circulating absorbent to react with _SO in the flue gas as follows:

Na ₂ SO ₃ +SO ₂ +H ₂ O＝2NaHSO ₃

The remaining steps are the same as in Embodiment 1. the

Embodiment 6: NaOH is used as the initial absorbent, and the flue gas is desulfurized by an energy-saving sodium sulfite circulating desulfurization device. the

The first step is to prepare the initial absorption liquid: the initial absorption agent is NaOH, soft water (ion-free water) is added in the first absorption liquid circulation tank 2, NaOH is gradually added under stirring, so that the weight percent concentration in the solution is 14 %, after fully dissolving, then add 0.05% of the solution weight antioxidant—hydroquinone, stir evenly; the following chemical reaction occurs:

2NaOH+SO ₂ →Na ₂ SO ₃ +H ₂ O

The sodium sulfite obtained by the reaction reacts with the _SO in the flue gas as follows:

Na ₂ SO ₃ +SO ₂ +H ₂ O＝2NaHSO ₃

The remaining steps are the same as in Embodiment 1. the

The present invention can use one heat exchanger and one decomposed jacketed reactor, or multiple heat exchangers and multiple decomposed jacketed reactors according to the amount of actual flue gas, which can be deduced from the above examples Go out a plurality of embodiments, do not enumerate one by one.

Claims (7)

1. Energy-saving sodium sulfite circulating desulfurization device, including a desulfurization tower (1), a first absorption liquid circulation tank (2) and a second absorption liquid circulation tank (3) located outside the desulfurization tower, the interior of the desulfurization tower is divided by two It is divided into upper, middle and lower areas; the upper area inside the desulfurization tower is provided with a first spray head (2-1) connected to the first absorption liquid circulation tank, and the bottom of the upper area is connected to the first absorption liquid circulation tank. communicated; the middle zone inside the desulfurization tower is provided with a second nozzle (3-1) communicated with the second absorption liquid circulation tank, and the bottom of the middle zone communicates with the second absorption liquid circulation tank; the first absorption liquid circulation tank The bottom is connected with the second absorption liquid circulation tank; the flue gas outlet at the top of the desulfurization tower is connected with the chimney, the flue gas inlet at the lower part of the desulfurization tower is connected with the flue gas outlet at the top of the washing cooling tower (4), and the bottom of the washing cooling tower is connected with the circulating water washing The tank (5) communicates, and the third nozzle (5-1) communicated with the circulating water washing tank is arranged on the upper part of the washing and cooling tower; it is characterized in that: a. The flue gas inlet at the lower part of the washing and cooling tower (4) communicates with at least one flue gas outlet at the bottom of the heat exchanger (6), and the flue gas inlet at the upper part of the heat exchanger communicates with the flue gas at the side of the decomposed jacketed reactor (7). The gas outlet is connected, and the flue gas inlet on the side of the decomposition jacket reactor is connected to the flue; b. The outlet at the bottom of the second absorption liquid circulation tank (3) communicates with the serpentine tube in the heat exchanger (6), and the outlet of the serpentine tube communicates with the reaction chamber of the decomposed jacketed reactor (7); The outlet at the reaction chamber top of the jacket reactor (7) communicates with the inlet of the condenser (8), and the outlet of the condenser communicates with the inlet of the gas-water separator (9); c. The lower part of the decomposed jacketed reactor (7) communicates with a centrifuge (10), and the outlet of the centrifuge communicates with the reaction chamber of the decomposed jacketed reactor (7). 2. energy-saving type sodium sulfite circulation desulfurization device according to claim 1, is characterized in that: described decomposing jacketed reactor (7) comprises reaction chamber (7-1), the row tube that one end is connected with reaction chamber ( 7-2), the hopper (7-3) connected to the other end of the tube, the jacket (7-4) connected to the reaction chamber and the side of the tube; the flue gas inlet on the jacket communicates with the flue, The lower end of the discharge hopper communicates with the centrifuge (10). 3. The energy-saving sodium sulfite circulating desulfurization device according to claim 1 or 2, characterized in that: the flue gas inlet at the bottom of the washing cooling tower (4) communicates with the flue gas outlet at the bottom of the two heat exchangers (6), and the two The flue gas inlets on the upper part of the heat exchanger communicate with the flue gas outlets on the sides of the two decomposed jacketed reactors (7) respectively, and the flue gas inlets on the lower parts of the two decomposed jacketed reactors communicate with the flue respectively; The outlets at the bottom of the second absorption liquid circulation tank (3) communicate with the serpentine tubes in the two heat exchangers (6) respectively, and the outlets of the two serpentine tubes are respectively connected with the outlets of the two decomposed jacketed reactors (7). The reaction chamber is communicated; the outlets at the top of the reaction chamber of the two decomposable jacketed reactors (7) communicate with the inlet of the condenser (8) respectively, and the outlet of the condenser communicates with the inlet of the gas-water separator (9); The discharge hoppers (7-3) at the bottom of the two decomposed jacketed reactors (7) communicate with a centrifuge (10) respectively, and the outlets of the two centrifuges are connected to the two decomposed jacketed reactors (7) respectively. ) The reaction chamber (7-1) communicates. 4. energy-saving type sodium sulfite circulation desulfurization method is carried out on the energy-saving type sodium sulfite circulation desulfurization device described in claim 1, and its steps are as follows: The first step is to prepare the initial absorption liquid: the initial absorption agent is Na ₂ CO ₃ , add soft water into the first absorption liquid circulation tank (2), and gradually add Na ₂ CO ₃ under stirring to make the weight percentage in the solution The concentration is 8-18%. After fully dissolving, add 0.05% antioxidant by solution weight and stir well; The second step is to circulate the initial absorption liquid: open the circulation pumps of the first absorption liquid circulation tank (2) and the second absorption liquid circulation tank (3), and make the absorption liquid pass through the first nozzle ( 2-1) Spray into the upper area inside the desulfurization tower (1), return to the first absorption liquid circulation tank from the bottom of the upper area, and flow into the second absorption liquid circulation tank from the bottom of the first absorption liquid circulation tank; The absorption liquid is sprayed into the middle zone inside the desulfurization tower (1) through the second nozzle (3-1) communicated with the second absorption liquid circulation tank, and returns to the second absorption liquid circulation tank from the bottom of the middle zone; The third step, flue gas cooling: the flue gas discharged from the flue with a temperature of about 180°C enters the jacket and the tubes for heat exchange from the flue gas inlet on the side of the "decomposition jacketed reactor"; after the temperature drops The flue gas enters the heat exchanger (6) from the flue gas outlet of the "decomposition jacketed reactor" for heat exchange again, and the flue gas after the temperature is lowered again is discharged from the flue gas outlet of the heat exchanger, and is discharged from the washing cooling tower (4) The flue gas inlet of the lower part enters it; the water in the washing water circulation tank (5) is sprayed down from the upper part of the washing cooling tower through the water pump from the nozzle (5-1), further reducing the temperature of the flue gas to 60 Below ℃; The fourth step is to absorb sulfur dioxide: the flue gas whose temperature drops below 60°C is discharged from the flue gas outlet at the top of the washing and cooling tower (4), and then enters the lower area from the flue gas inlet at the lower part of the desulfurization tower (1), and the flue gas The gas is reasonably distributed in this area, and evenly enters the middle area of the desulfurization tower from the brim of the riser pipe on the first interval, and contacts with the absorption liquid sprayed by the second spray head (3-1) arranged at the upper part of the middle area, Part of the _SO2 in the flue gas is absorbed; the flue gas enters the upper area of the desulfurization tower from the brim of the riser pipe on the second interval, and is sprayed with the absorbing liquid sprayed by the first nozzle (2-1) arranged on the upper part of the upper area. contact, most of the remaining _SO2 in the flue gas is absorbed, and then enters the chimney from the flue gas outlet at the top of the desulfurization tower to be discharged; the following chemical reactions occur: Na ₂ CO ₃ +SO ₂ ＝Na ₂ SO ₃ +CO ₂ ↑ The sodium sulfite obtained by the reaction reacts with the _SO in the flue gas as follows: Na ₂ SO ₃ +SO ₂ +H ₂ O＝2NaHSO ₃ The fifth step is to decompose sodium bisulfite: the sodium bisulfite solution generated by the reaction of the absorption liquid and the sulfur dioxide in the flue gas is pumped from the second absorption liquid circulation tank (3) into the snake in the heat exchanger (6) through the water pump. After being preheated, it enters the reaction chamber of the decomposed jacketed reactor (7), and then is heated by the flue gas in the jacket of the decomposed jacketed reactor (7) and between the tubes, and decomposes as follows: 2NaHSO ₃ →Na ₂ SO ₃ +SO ₂ ↑+H ₂ O The sixth step is to separate the sulfur dioxide in the water vapor: the _SO2 generated by the decomposition of the fifth step is discharged from the outlet of the reaction chamber at the top of the decomposition jacket reactor, and then enters the condenser (8) for cooling, so that most of the _SO2 gas The water vapor is condensed into water, then, it is discharged from the outlet of the condenser, and enters the gas-water separator (9), after the gas-water separation, the _SO2 gas is sent to liquefaction treatment as a chemical raw material; The seventh step is to recycle sodium sulfite: the _Na2SO3 and _H2O generated by the _{decomposition} of the fifth step are discharged to the centrifuge (10) from the discharge hopper (7-3) at the lower part of the decomposition jacket reactor for separation; The solid obtained by mechanical separation of Na ₂ SO ₃ is added to the first absorption liquid circulation tank (2) for recycling; The eighth step, separate the filtrate treatment: pump the remaining filtrate containing NaHSO ₃ , Na ₂ SO ₃ and Na ₂ SO ₄ in the seventh step into the reaction chamber of the decomposed jacketed reactor (7), and make it The NaHSO ₃ decomposes; when the content of Na ₂ SO ₄ in the separated filtrate reaches 5%, the separated filtrate is sent to freeze crystallization, and the by-product Na ₂ SO ₄ is separated. 5. the energy-saving sodium sulfite circulation desulfurization method according to claim 4, is characterized in that: the first step, preparation initial absorption liquid: initial absorption agent is NaOH, soft water is added in the first absorption liquid circulation tank (2), in Gradually add NaOH under stirring so that the weight percent concentration in the solution is 7-14%. After fully dissolving, add 0.05% of the solution weight antioxidant and stir evenly; the following chemical reaction occurs: 2NaOH+SO ₂ →Na ₂ SO ₃ +H ₂ O The sodium sulfite obtained by the reaction reacts with the _SO in the flue gas as follows: Na ₂ SO ₃ +SO ₂ +H ₂ O＝2NaHSO ₃ 6. The energy-saving sodium sulfite circulating desulfurization method according to claim 4 or 5, characterized in that: the antioxidant added to the absorption liquid is p-phenylenediamine or hydroquinone. 7. The energy-saving sodium sulfite circulating desulfurization method according to claim 4 or 5, characterized in that: when the circulating absorbent is lost during desulfurization, it is necessary to replenish the initial absorbent Na ₂ CO ₃ or NaOH in time.