WO2004022205A1

WO2004022205A1 - Method and apparatus for eliminating and recovering s02 from fume

Info

Publication number: WO2004022205A1
Application number: PCT/CN2002/000819
Authority: WO
Inventors: Wende Xiao
Original assignee: East China University Of Science & Technology
Priority date: 2002-09-09
Filing date: 2002-11-18
Publication date: 2004-03-18
Also published as: AU2002349435A1; CN1408464A; CN1178735C

Abstract

The present invention provides a method and apparatus for eliminating and recovering S02 from fume, including the following steps: l ) firstly, the fume containing low sulphur reacts with aqueous solution of ammonia, producing ammonia sulfite solution, ammonia/sulphur=1.3-1.8 (molar ratio), gas/liquid=2000-5000 (volume ratio); 2) the oxidizing reaction between the ammonium sulfite and air produces ammonia sulfate solution; 3) the ammonia sulfate solution is contacted heat fume, then the water-vaporized ammonia sulfate solution is delivered to crystallizer to be processed into ammonia sulfate fertilizer. The apparatus includes a desulphurizing tower, the desulphurizing tower includes S02 adsorption section, ammonia sulfite oxidizing section, ammonia sulfate solution condensing section, scrubbing section and demisting section. The apparatus can be operated easily. The cost can be reduced 10-30%.The vapor consumption can be reduced 90%. The concentration of S02 of fume can be reduced less than 10-100ppm. The quality of ammonia sulfate meets national standard.

Description

Method and device for extracting and recovering S0 _{7 in} flue gas

The invention relates to a method and a device for desorbing and recovering SO ₂ in flue gas, in particular to a flue gas desulfurization method using ammonia as a raw material (including liquid ammonia, ammonia water and ammonium carbonate).

Background technique

When sulfur-containing minerals and fuels are burned, the exhaust gas contains so ₂ . The content of so _{2 in the} flue gas is usually low.

300-5000ppmv (1000-15000mg / standard cubic meter), but the amount of smoke is huge. In the case of coal-fired boilers, the steam scale ranges from IT / h to 2500T / h, the generating unit capacity is 6MW to 900MW, and the flue gas volume is from 10,000 Nm ³ / h to 2.5 million Nm ³ / h. Serious acid rain and S0 ₂ pollution. Therefore, 'desulfurization of flue gas and recovery of SO ₂ have received widespread attention.

The principle of flue gas desulfurization is the chemical reaction between an alkaline desulfurizer and an acidic SO ₂ gas. Typical desulfurizing agents are limestone (CaC0 ₃ ) and ammonia (N¾), forming two typical technology categories, which are called calcium method and ammonia method, respectively.

The calcium method generates a gypsum by-product, CaS0 ₄ .2H ₂ 0, at the same time as desulfurization, which can be used as a raw material for building materials, but it is generally not very useful and can only be discarded and stacked. Therefore, the calcium method is often called the abandonment method.

The ammonia method can co-produce a variety of products while desulfurizing, such as sulfuric acid and ammonium sulfate fertilizers. The desulfurization by-product of the ammonia method has greater application value than the calcium method. In addition, the ammonia desulfurizing agent ammonia comes from chemical fertilizers, and its desulfurization products also serve as chemical fertilizers, which do not cause additional ecological and environmental problems to nature. Therefore, the ammonia method is called the recycling method.

The ammonia desulfurization process usually includes two steps:

(1) So _{2 is} absorbed to form a mixed solution of ammonium sulfite and ammonium bisulfite. The reaction principle is:

S0 ₂ absorption:

NH _{3 is} dissolved: H ₃ + NH ₄ HS0 ₃ ― (NH ₄ ) ₂ S0 ₃

(When using ammonium carbonate as raw material, H ₄ HC0 ₃ + NH ₄ HS0 ₃ = (NH ₄ ) ₂ S0 ₃ + C0 ₂ + H ₂ 0)

The total response is:

S0 ₂ + xNH ₃ + H ₂ 0 = (NH ₄ ) _x H _2-x S0 ₃

The absorption solution contains NH ₄ HS0 ₃ and (NH ₄ ) ₂ S0 _3. The ratio of the two salts is controlled by the H ₃ / S0 ₂ ratio in the desulfurization process. In Chinese patent 99110643.6, N¾ / S0 ₂ = 1.2 — 1.4, the ratio of (NH ₄ ) ₂ S0 ₃ and N¾HS03 in the solution is 1 / 4-2 / 3.

The mixed solution of ammonium sulfite is a semi-finished product produced as a by-product of the desulfurization process, and it can also be directly used, for example, by adding After the ammonia was neutralized, an ammonium sulfite solution was obtained and sold as a liquid nitrogen fertilizer. Generally speaking, in the field of flue gas desulfurization of thermal power plants, ammonium sulfite needs to be processed into solid ammonium sulfide, which is convenient for storage, transportation and seasonal sales.

(2) Processing transformation of ammonium sulfite mixed solution

In Chinese patent 99110643.6, a method is disclosed that decomposes ammonium sulfite solution with sulfuric acid to obtain ammonium sulfate and SO ₂ gas. By blowing in air, an air mixture with a higher S0 ₂ concentration can be obtained, for example, the content of S0 ₂ is 7-15%, which is suitable for oxidation to S0 ₃ by a catalytic (V ₂ 0 ₅ / Si0 ₂ ) oxidation method. Sulfuric acid absorption gave 98.2% concentration of commercial grade concentrated sulfuric acid. Part of the sulfuric acid is used for the decomposition of ammonium sulfite, and part of it is sold as commercial sulfuric acid. Since the ammonia / sulfur ratio in ammonium sulfite is between 1.2 and 1.4, 30-40% of the recovered SO ₂ is produced in commercial sulfuric acid. The response is as follows:

(NH ₄ ) _x H _2- xS0 ₃ + H ₂ S0 ₄ = x (NH ₄ ) ₂ S0 ₄ + S0 ₂ + H ₂ 0 (1) S0 ₂ + 1/20 ₂ = S0 ₃ (2) S0 ₃ + H ₂ 0 = H ₂ S0 ₄ (3) China Electric Power, 2001] introduced another ammonium sulfite processing scheme, using phosphoric acid to decompose the ammonium sulfide solution to obtain ammonium dihydrogen phosphate and so ₂ . In this scheme, all of the so _{2 is} converted to sulfuric acid. Sulfuric acid is used in phosphoric acid production. This solution is especially applicable to the case where there is an ammonium phosphate fertilizer plant next to the thermal power plant.

The above-disclosed technology is particularly suitable for boiler flue gas containing sulfur, such as flue gas burning high sulfur coal or sintering machine flue gas of non-ferrous metal smelting plant. However, lower sulfur content for boiler flue gas, such as flue gas SO ₂ content is less than lOOOppmv, the sulfur content of coal-fired boilers corresponding to less than 1%, especially smaller boiler capacity, the total annual prolapse than S0 ₂ small. If a solution for producing sulfuric acid is used, the scale of the sulfuric acid plant is too small, the relative investment and energy consumption are high, and the economy is poor. Therefore, it is of great significance to develop and research the sulfur extraction and recycling in the flue gas with very low sulfur content.

Summary of the Invention

The technical problem to be solved by the present invention is to disclose a method and device for extracting and recovering SO ₂ in flue gas with low sulfur content, so as to overcome the defects existing in the prior art. '' The technical idea of the present invention is as follows: from the mixed solution of ammonium sulfite from the absorption process, after neutralization with ammonia, an ammonium sulfite solution is obtained:

(NH ₄ ) _x H _2-x S0 ₃ + (2-x) H ₃ = (NH ₄ ) ₂ S0 ₃

The ammonium sulfite solution is oxidized directly, and ammonium sulfate can be obtained:

(NH ₄ ) ₂ S0 ₃ + 1/20 ₂ = (NH ₄ ) ₂ S0 ₄ As far as the oxidation reaction of sulfite is concerned, it is easy to see. However, since the reaction has a unique relationship with the concentration of the salt of the solution (including ammonium sulfite and ammonium sulfate), the actual implementation process is difficult. In the literature

[Chemical Engineering Science, 2000] described this unique property. When the salt concentration is less than 0.5mol / L (about 5% (wt)), the oxidation rate of ammonium sulfite increases with its concentration, and when it exceeds this concentration, At the limit, the oxidation rate decreases with increasing concentration. At higher salt concentrations, the oxidation rate of ammonium sulfite is very low. Therefore, in the actual implementation process, traditional technology, such as the technology introduced in the document [S «p / i« r, 1995], the flue gas desulfurization obtained a 10-20% (wt) ammonium sulfite solution, the oxidation process is The compressed air is pressurized and oxidized, and the compressed air pressure is 0.5_0.8Mpa. The ammonium sulfate solution obtained after the oxidation is further subjected to three-effect evaporation, concentration, crystallization, and drying steps to obtain solid ammonium sulfate. The investment in this process is high, the power consumption and steam consumption are high, and the equipment requires high corrosion protection. Chinese invention patent ZL99113403.6 is also a method proposed to overcome this shortcoming. In this method, the upper limit of the concentration of ammonium sulfite mixed salt is not limited, and the normal operating concentration is 30-50% (wt), In this way, energy consumption is low and equipment investment is small. However, this method is more suitable for high-sulfur coal and / or large power plants. Accordingly, the inventor has proposed the following:

1. Control the concentration of ammonium sulfite, especially the lowest concentration of ammonium sulfite, generally between 0.1-5% (wt), preferably between 0.5-2.0%, to create the most favorable conditions for oxidation and reduce oxidation Energy consumption and investment;

2. Use the heat of the flue gas reasonably and use it for the concentration of dilute ammonium sulfate solution, so that the concentration of the ammonium sulfate solution reaches 30-50% (wt) without consuming additional energy (steam) _;

3. Construct a multi-functional desulfurization device, which is equivalent to being divided into multiple sections. It has ammonium sulfite oxidation function, ammonium sulfate solution concentration function, SO ₂ absorption function, water washing and defogging (沬) function. It is called a five-effect device ( Tower) (Five-Way Column, FWC).

The specific method includes the following steps:

(1). The low sulfur-containing flue gas is first reacted with an ammonium sulfite solution to form a mixed solution of ammonium sulfite and ammonium bisulfite, and the concentration of ammonium sulfite is controlled to be between 0.1 and 5% (wt), preferably In the range of 0.5-2.0%, in order to create the most favorable conditions for oxidation, reduce the energy consumption and investment of oxidation, and ensure high desulfurization efficiency, therefore, the ammonia / sulfur ratio = 1.3-1.8 (molar ratio), gas / liquid ratio It is 2000-5000 (volume ratio), and then ammonia is added to react to form ammonium sulfite solution. The ammonia includes liquid ammonia, ammonia water or / and ammonium carbonate;

(2) The ammonium sulfite solution is oxidized with air to obtain an ammonium sulfate solution. The pressure of the compressed air is generally 0.05-0.2Mpa (gauge pressure). The flow rate of the compressed air is 1 to 5 times the theoretical amount of ammonium sulfite oxidation. Commonly, it is 2 to 4 times. The residence time of the oxidation reaction is generally 1 to Between 3 hours, preferably around 2 hours. Under these conditions, the oxidation rate can be greater than 95%. The concentration of ammonium sulfate solution is generally 5-20% (wt).

(3). The ammonium sulfate solution generated in step (2) is in contact with hot flue gas with a temperature of 100-160 ° C. Through the process of heat and mass transfer, the temperature of the hot flue gas is reduced to 50-55 ° C and the humidity is increased to Near saturation humidity. While the water in the ammonium sulfate solution evaporates, the ammonium sulfate concentration can be increased to 40-50% (wt), sent to the ammonium sulfate crystallizer, and processed into commercial ammonium sulfate fertilizer.

(4) an aqueous solution of ammonia to be absorbed S0 ₂ the flue gas is washed with water, eluting the absorption liquid entrained in the flue gas, in particular ammonium sulfate, etc., in order to reduce product loss, while preventing into the reheater. The water flow of the washing is the flow required to maintain the water balance of the absorption system, which is related to the flue gas conditions, and is generally 5 to 20% of the absorption liquid flow.

(5) Defoaming the water-washed flue gas, the function of which is to remove the water droplets entrained in the flue gas. The removed flue gas can be evacuated directly.

According to the present invention, it is best to heat the flue gas after removing it, because the flue gas is basically a vapor saturated with water vapor. If it is not reheated and the temperature is increased, water dew will necessarily form on the flue and the inner wall of the chimney. Causes corrosion. In addition, the saturated smoke leaving the chimney will often form a "white dragon". Due to insufficient lifting degree, raindrops will be formed, which will cause acid rain pollution to the boiler plant area. Generally, the flue gas temperature after desulfurization is 48-50 ° C, and the saturated dew point is about 48 ° C. In order to solve the above problems, the flue gas temperature should be above 20 ° C above the dew point. Therefore, the reheated flue gas temperature should be greater than 70 ° C. The reheating heat source can come from the original flue gas, whose temperature is between 130-160 ° C. After the reheating, the desulfurized flue gas is sent to the chimney and exhausted after being pressurized.

The device for implementing the above method includes at least one desulfurization tower including a SO ₂ absorption section, an ammonium sulfite oxidation section, an ammonium sulfate solution concentration section, a water washing section and a defogging section;

An ammonium sulfate crystallization tank connected to the outlet of the concentrated ammonium sulfate solution at the lower part of the concentration section through a pipeline; an ammonium sulfate liquid-solid separator connected to the ammonium sulfate crystallization tank through a pipeline;

An ammonium sulfate solution circulation tank connected to the dilute ammonium sulfate outlet of the oxidation section and the mother liquid outlet of the separator through a pipeline;

A circulation pump connected to the circulation tank through a pipeline, and the outlet of the circulation pump is connected to the dilute ammonium sulfate solution inlet provided on the upper part of the ammonium sulfate solution concentration section;

An absorption liquid circulation pump connected through a pipeline to an absorption liquid outlet provided at the bottom of the oxidation section and an absorption liquid inlet provided at the upper portion of the absorption section;

An ammonium sulfate dryer connected to the liquid-solid separator via a line. The device of the invention works like this:

The flue gas containing so ₂ is reacted in the desulfurization tower with the absorption solution (mixed solution of ammonium sulfite) entering the desulfurization tower, so that the S0 ₂ in the flue gas generates an ammonium sulfite solution with a concentration of 0.1 to 5% (wt), The ammonium sulfite solution is then contacted with the air entering the desulfurization tower and is oxidized into an ammonium sulfate solution. The ammonium sulfate solution is contacted with the high temperature flue gas entering the desulfurization tower. The ammonium sulfate solution is concentrated by using the heat of the high temperature flue gas, and the concentrated sulfuric acid The ammonium solution is sent to an ammonium sulfate liquid-solid separator, and the separated solid ammonium sulfate is dried in an ammonium sulfate dryer to obtain a finished ammonium sulfate, which can be used as a general chemical fertilizer;

Prolapse S0 ₂ in the flue gas desulfurization tower in contact with the upper portion of the water entering, washed with water, and then by the demister provided at the top of the desulfurization column (Mo) demisting means (respiratory droplets), and finally, the purified flue gas desulfurization Discharge from the top of the tower.

The method and device of the present invention integrate the functions of SO ₂ absorption in flue gas, oxidation of ammonium sulfite, concentration of ammonium sulfate solution, water washing and defogging (沬), convenient operation, and the investment cost is the same as that of the prior art. Under the conditions of processing capacity, it can be reduced by 10 ~ 30%, and the energy consumption is low. The waste heat of high temperature flue gas is fully utilized, and the steam consumption can be reduced by 90%. In addition, the desulfurization efficiency is very high, in which the concentration of SO ₂ in the flue gas can be reduced to less than 10 to 100 ppm, and the quality of the obtained ammonium sulfate conforms to the national fertilizer grade standard, and the nitrogen content is 20.5 to 21%, which can be used as agricultural fertilizer .

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flowchart of the present invention.

Figure 2 shows the structure of the desulfurization tower.

FIG. 3 is a schematic diagram of a vertical partition plate and a horizontal partition plate.

detailed description

Referring to Figures 1 and 2, the device of the present invention includes:

A desulfurization tower 6 including an S0 ₂ absorption section 63, an ammonium sulfite oxidation section 61, an ammonium sulfate solution concentration section 62, a water washing section 64 and a demister section 65;

An ammonium sulfate crystallization tank 9 connected to the concentrated ammonium sulfate solution outlet 6201 provided at the lower portion of the liquid concentration section 62 through a pipeline 9;

An ammonium sulfate liquid-solid separator 13 connected to the ammonium sulfate crystallization tank 9 through a pipeline, and a centrifuge may be preferred;

An ammonium sulfate solution circulation tank 12 is connected to the dilute ammonium sulfate outlet 6101 of the oxidation section 61 and the mother liquid outlet 1301 of the separator 13 through pipelines, respectively; A circulation pump 10 connected to the circulation tank 12 through a pipeline, and the outlet of the circulation pump 10 is connected to the dilute ammonium sulfate solution inlet 6202 provided on the upper part of the ammonium sulfate solution concentration section 62;

• An absorption solution outlet 6301 provided at the lower portion of the absorption section 63 and an ammonium sulfite solution inlet 6102 of the oxidation section 61 are connected to the ammonium sulfite delivery line 5;

An absorption liquid circulation pump 7 connected to the absorption liquid outlet 6103 provided at the bottom of the oxidation section 61 and the absorption liquid inlet 6302 provided at the upper portion of the absorption section 63 through a pipeline, respectively; 7

An ammonium sulfate dryer 14 connected to the liquid-solid separator 13 through a pipeline may be preferably a fluidized bed dryer;

It can be seen from FIG. 1 that the present invention further includes:

A reheater 2 connected to the desulfurization tower 6 through a pipeline for raising the temperature of the purified flue gas; a filter 4 connected to the bottom of the desulfurization tower 6 through a pipeline for filtering ammonium sulfate; The drying fan 15 at the rear end of the dryer 14 and the outlet of the drying fan 15 are connected to the crystallization tank 9 so that the dryer 14 can be operated under negative pressure. The dried hot air enters the crystallization tank 9 and the fine ammonium sulfate particles entrained in the hot air are removed. Then enter the desulfurization tower 6. In this way, the present invention will not generate additional exhaust gas.

It can be seen from FIG. 2 that the desulfurization tower 6 mentioned above is a vertical tower, which includes an ammonium sulfite oxidation section 61, an ammonium sulfate concentration section 62, a S0 ₂ absorption section 63, a water washing section 64, and a demister from the bottom to the top. In the foam section 65, a flue gas inlet 66 is provided at the lower part of the desulfurization tower 6, a purge gas outlet 67 is provided at the top of the desulfurization tower 6, an air inlet 68 for oxidation is provided at the side of the oxidation section 61, and a process water inlet 69 is provided at The upper part of the water washing section 64; the mentioned oxidation section 61 is provided with a vertical partition plate 6104 and a horizontal partition plate 6105, as shown in FIG. The transverse partition plate 6105 is a sieve hole plate, the sieve holes are evenly distributed, and the sieve hole diameter d. = 5—15mm, opening ratio is 0.1 ~ 0.5%, one end of the vertical partition plate 6104 is provided with a channel hole 6106, so that the liquid flow path is ¾ serpentine, and the ammonium sulfite inlet 6102 is set on one side of the oxidation section 61, The dilute ammonium sulfate outlet 6101 is set on the other side. The ammonium sulfite enters the oxidation section 61 from one end, and leaves the tritium oxidation section 61 from the opposite end, so that the unoxidized ammonium sulfite solution and the oxidized ammonium sulfate solution are separated as much as possible. Back to mix. The flue gas inlet 66 is provided above the vertical partition plate 6104 and the horizontal partition plate 6105, and the oxidation air inlet 68 is provided below the horizontal partition plate 6105 of the oxidation section 61.

A first partition plate 6203 with a gas distribution device and a liquid collector is provided between the ammonium sulfate concentration section 62 and the oxidation section 61, and a dilute ammonium sulfate solution inlet 6202 is provided in the upper part of the concentration section 62. The ammonium sulfate solution An outlet 6201 is provided in the lower part of the concentration section 62, and an ammonia gas inlet 6204 is provided above the concentration section 62. A gas distribution device and a liquid are provided between the above-mentioned S0 ₂ absorption section 63 and the ammonium sulfate concentration section 62. The second partition plate 6303 of the collector and the absorption section 63 are filled with a vapor-liquid contact element 6304. The vapor-liquid contact element 6304 can be preferably a sieve plate type or a packing type. For example, in Chinese patent 99113403.6, a large-pore sieve plate is disclosed with a hole diameter of 10-25 mm and an opening ratio of 15-25%, which is particularly suitable for the situation of the present invention. Or it is preferred to use structured packing with a specification of 50-150m ² / m ^3. The filling height of the packing is generally 2-5m, and a suitable height is 3-4m. In addition, a large-pore screen is used, generally 2-5 pieces, suitably 3-4 pieces. An absorption liquid inlet 6302 is provided in the upper part of the absorption section 63, and an absorption liquid outlet 6301 containing ammonium sulfite is provided in the lower part of the absorption section 63. It is connected to the ammonium sulfite inlet 6102 of the oxidation section 61 through a connection line 5.

The washing section 64 is filled with polypropylene plate corrugated structured packing. The model can be 125 or 250m ² / m ³ , and the filling height is 0.3-0.6m.

The defogging section 65 is filled with 250-500m ² / m ³ structured corrugated packing with a degree of 0.3-0.6m. When the above-mentioned device is used to process low sulfur content flue gas, the operation steps are as follows:.

(1) The low sulfur-containing flue gas enters the desulfurization tower 6 from the flue gas inlet 66, passes through the first partition plate 6203, and enters the concentration section 62, and performs heat and mass exchange with the dilute ammonium sulfate solution from the ammonium sulfate solution circulation tank 12, The flue gas is cooled and humidified, and the dilute ammonium sulfate solution is concentrated. Then the flue gas passes through the second partition plate 6303 and enters the absorption section 63, and comes into countercurrent contact with the absorption liquid sprayed down from the top of the absorption section 63. S0 in the flue gas ₂ is absorbed, and ammonium sulfite is generated. The purified flue gas passes through the water washing section 64 and the defogging section 65, and then exits the desulfurization tower 6 and exchanges heat with the high temperature flue gas in the reheater 2. Empty by chimney;

(2) The concentrated ammonium sulfate solution enters the crystallization tank 9 for crystallization, and then is sent to the liquid-solid separator 13, the separated mother liquor is returned to the circulation tank 12, and the solid ammonium sulfate is dried in the dryer 14 to become a commercial fertilizer.

(3) The ammonium sulfite solution mentioned above enters the oxidation section 61 through the connection line 5 and undergoes an oxidation reaction with the air entering the oxidation section 61 to generate ammonium sulfate, which flows into the circulation tank 12 and is sent by the pump 10 to the concentration section 62.

Example 1

A 220T / h coal-fired thermoelectric boiler has a flue gas flow of 250,000 Nm ³ / hr, a S0 ₂ content of 1500mg / Nm ³ , a flue gas dust content of 80mg / Nm ³ , and a flue gas temperature of 140 ° C. The desulfurization tower 6 has a diameter of 6 m and a height of 28 m. The reheater 2 is of a heat pipe type. After the flue gas passes through the reheater 2, the temperature drops to 110 ° F. and enters the desulfurization tower 6. When Depart from the desulfurization tower, desulfurizing tail gas S0 ₂ content of 20mg / Nm ^_3, H ³ content lmg / Nm ^3, the water content through droplets of 96mg / Nm ^3.

The absorption section uses 100m ² / m ³ polypropylene structured porous plate corrugated packing, the absorption liquid flow rate is 100m ³ / hr, and the ammonium sulfate content is 7.5% (wt). When leaving the absorption section, the ammonium sulfite concentration is 0.6% (wt ). In the absorption section, the ammonia feed rate is 1.45 according to N / S, and the BP is 145 kg / hr. The amount of water added was 11.75 m ³ / r. The ammonium sulfate production was 780 kg / hr, of which the ammonium sulfate content was 97.8%, which was equivalent to a nitrogen content of 20.8%.

Example 2

A 670T / h thermal power unit, namely 200MW, burns coal with a sulfur content between 1.5-2.0%. The flue gas flow is 800,000 Nm ³ / hr, and the S0 ₂ content is 4200mg / Nm ³ . The device has 3 electric fields, the dust content of the flue gas is 200mg / Nm ³ , and the flue gas temperature is 145 ° F. The desulfurization tower 6 has a diameter of 10 m and 髙 is 30 m.

The reheater 2 is a rotary heat storage type. After the flue gas passes through the reheater, the temperature drops to 116 ° C and enters the desulfurization tower. Leaving the desulfurization tower, desulfurizing tail gas S0 ₂ content of 34mg / Nm ^_3, NH ³ content of lmg / Nm ^3, Shuimo content of 125mg / Nm

The absorption section was filled with 125m ² / m ³ polypropylene structured porous plate corrugated packing, the absorption liquid flow was 400m ³ / hr, and the ammonium sulfate content was 17.3% (wt). When leaving the absorption section, the ammonium sulfite concentration was 1.6% ( wt).

In the absorption section, the ammonia feed rate is N / S = 1.45, which is 1295 kg / hr. The amount of water added was controlled at 39.5 m ³ / hr. The output of ammonium sulfate is 7070 kg / hr, and the ammonium sulfate content is 98.0%, which is equivalent to the nitrogen content of 21.0%.

Claims

Rights request

1. A method for extracting and recovering so ₂ from flue gas, comprising the following steps:

(1) Low-sulfur-containing flue gas is first reacted with ammonium sulfite solution to generate a mixed solution of ammonium sulfite and ammonium bisulfite. The ammonia / sulfur ratio = 1.3 ~ 1.8 (molar ratio), and the gas / liquid ratio is 2000— 5000 (volume ratio), and then adding ammonia to generate ammonium sulfite solution, the ammonia includes liquid ammonia, ammonia water or / and ammonium carbonate;

(2) The produced ammonium sulfite solution is oxidized with air to obtain an ammonium sulfate solution. The pressure of the compressed air is 0.05_0.2Mpa. The flow rate of the compressed air is 1 to 5 times the theoretical amount of ammonium sulfite oxidation. Oxidation reaction Residence time is 1 ~ 3 hours;

(3) Step (2) The generated ammonium sulfate solution is in contact with hot flue gas, the evaporated ammonium sulfate solution is sent to an ammonium sulfate crystallizer, and processed into a commercial ammonium sulfate fertilizer;

(4) washing the flue gas after having absorbed SO ₂ by the aqueous ammonia solution;

(5) Defoaming the water-washed flue gas.

2. The method according to claim 1, wherein the flow rate of the compressed air is 2-4 times the theoretical amount required for the oxidation of ammonium sulfite, and the residence time of the oxidation reaction is 2 hours.

3. The method according to claim 1, wherein the flow rate of the water for washing is 5-20% of the flow rate of the absorption liquid.

The method according to any one of claims 1 to 3, characterized in that the flue gas after heating is heated.

5. The method according to claim 4, wherein the heat source for reheating is from raw flue gas.

6. The device for realizing the method according to any one of claims 1 to 5 at least comprises: · a device comprising a SO ₂ absorption section (63), an ammonium sulfite oxidation section (61), an ammonium sulfate solution concentration section (62), and a water washing section (64) and the desulfurization tower (6) of the demister section (65);

An ammonium sulfate crystallization tank (9) connected to the concentrated ammonium sulfate solution outlet (6201) provided at the lower part of the liquid concentration section (62) through a pipeline;

An ammonium sulfate liquid-solid separator (13) connected to the ammonium sulfate crystallizing tank (9) through a pipeline; an ammonium sulfate solution circulation tank (12), the circulation tank (12) passing through the pipeline and the oxidation section (61) respectively The dilute ammonium sulfate outlet (6101) is connected to the mother liquor outlet (1301) of the separator (13);

A circulation pump (10) connected to the circulation tank (12) through a pipeline, and the outlet of the circulation pump (10) It is connected to the dilute ammonium sulfate solution inlet (6202) provided at the upper part of the ammonium sulfate solution concentration section (62); one is connected to the absorbent liquid outlet (6301) and the oxidation section (61) of the ammonium sulfite solution at the lower part of the absorption section (63) The inlet (6102) is connected to the ammonium sulfite transfer line (5);

An absorption liquid circulation pump (7) connected to the absorption liquid outlet '(6103) provided at the bottom of the oxidation section (61) and the absorption liquid inlet (6302) provided at the upper portion of the absorption section (63) through pipelines;

An ammonium sulfate dryer (14) connected to the liquid-solid separator (13) via a line.

The device according to claim 6, characterized in that the ammonium sulfate liquid-solid separator (13) is a centrifuge.

The device according to claim 6, characterized in that the ammonium sulfate dryer (14) is a fluidized bed dryer.

The device according to claim 7, characterized in that the ammonium sulfate dryer (14) is a fluidized bed dryer.

The device according to claim 6, further comprising: a reheater (2) connected to the desulfurization tower (6) through a pipeline, for increasing the temperature of the purified flue gas.

The device according to claim 6, further comprising: a filter (4) connected to the bottom of the desulfurization tower (6) through a pipeline for filtering ammonium sulfate.

The device according to claim 6, further comprising: a drying fan (15) provided at the rear end of the dryer (14), and an outlet of the drying fan (15) is connected to the crystallization tank (9) to dry The subsequent hot air enters the crystallization tank (9) through the pipeline.

The device according to any one of claims 6 to 12, characterized in that the desulfurization tower (6) is a vertical tower, and includes an sulfite ammonium oxidation section (61) and sulfuric acid in order from bottom to top. ammonium concentration section (62), S0 ₂ absorption section (63), the water wash section (64) and the entrainment section (65), the flue gas inlet (66) disposed in the desulfurization tower

In the lower part of (6), the purified gas outlet (67) is set on the top of the desulfurization tower (6), the oxidation air inlet (68) is set on the side of the oxidation section (61), and the process water inlet (69) is set on the water washing section ( 64).

The device according to claim 13, characterized in that said oxidizing section (61) is provided with a vertical partition plate (6104) and a horizontal partition plate (6105), and the horizontal partition plate (6105) is a sieve Orifice plate, one end of the longitudinal partition plate (6104) is provided with a passage hole (6106), an ammonium sulfite inlet (6102) is provided on one side of the oxidation section (61), and a dilute ammonium sulfate outlet (6101) is provided on the other side The flue gas inlet (66) is disposed above the vertical partition plate (6104) and the horizontal partition plate (6105), and the oxidizing air inlet (68) is disposed at the oxidation section (61) and the horizontal partition plate (6105). Below.

15. The device according to claim 14, characterized in that the sieve holes are uniformly distributed, and the diameter of the sieve holes is d. = 5—15mm, opening ratio is 0.1 ~ 0.5%.

The device according to claim 13, characterized in that a first partition plate (a gas distribution device and a liquid collector) is provided between the ammonium sulfate concentration section (62) and the oxidation section (61). 6203), the dilute ammonium sulfate solution inlet (6202) is provided in the upper part of the concentration section (62), the ammonium sulfate solution outlet (6201) 'is provided in the lower part of the concentration section (62), and the ammonia gas inlet (6204) is provided in the concentration Above paragraph (62).

The device according to claim 13, characterized in that a second partition having a gas distribution device and a liquid collector is provided between the S0 ₂ absorption section (63) and the ammonium sulfate concentration section (62). The plate (6303), the absorption section (63) is filled with a vapor-liquid contact element (6304), and the absorption liquid inlet (6302) is arranged in the absorption section

(63) In the upper part, an absorption solution outlet (6301) containing ammonium sulfite is arranged in the lower part of the absorption section (63), and is connected to the ammonium sulfite inlet (6102) of the oxidation section (61) through a connecting line 5.

18. The device according to claim 17, characterized in that the vapor-liquid contact element (6304) is of a sieve plate type or a packing type.

19. The device according to claim 18, characterized in that the sieve plate type is a large-pore sieve plate disclosed in Chinese Patent No. 99113403.6, the hole diameter is 10-25 mm, and the opening ratio is 15-25%.

20. The device according to claim 17, wherein the packing type adopts a structured packing with a specification of 50 to 150 m ² / m ³ , and the filling height of the packing is 2 to 5 m.

The device according to claim 20, wherein the filling height of the filler is 3-4m.

22. The device according to claim 13, characterized in that the water washing section (64) is filled with a plate corrugated structured packing.

23. The device according to claim 22, wherein the plate corrugated structured packing model is 125 or 250m ² / m ³ , and the filling height is 0.3_0.6m.

24. The device according to claim 13, characterized in that the defogging section (65) is filled with a regular corrugated packing.

25. The device according to claim 24, wherein the height is 0.3-0.6m.