CN101879404A - A resource-based flue gas desulfurization and denitrification method - Google Patents

Abstract

The present invention relates to a resource-based flue gas desulfurization and denitrification method, which comprises sequentially: passing the flue gas of _SO2 and _NOx into a desulfurization tower, and in the desulfurization tower, _SO2 is absorbed by a desulfurizer (lean liquid); absorbing The desulfurization agent (rich liquid) after SO ₂ is desorbed by the multi-effect evaporator to release SO ₂ gas, which is compressed into liquid SO ₂ after being condensed and dried. The flue gas after desulfurization enters the denitrification tower and is sprayed with ozone gas from the ozone generator. After the NO in the flue gas is oxidized, it is absorbed by the denitration agent to form nitrate; the nitrate in the solution crystallizes out after reaching a certain concentration, and after Filter and dry to obtain nitrate products. The invention turns waste into wealth, recovers _SO2 and NOx in the flue gas with liquid _SO2 and nitrate products with higher added value, and realizes resource utilization and value maximization in the desulfurization and denitrification process. Adopting the technical scheme of the invention can obtain very high desulfurization and denitrification rates, the desulfurization rate is greater than 96%, the denitrification rate is greater than 90%, and the purity of the nitrate product is greater than 96%. The desulfurization and denitrification process of the present invention is simple, low in investment, low in operating cost of desulfurization and denitrification, and avoids the problems of high cost, by-products being a mixture of sulfuric acid (salt) and nitric acid (salt), and low added value in the existing desulfurization and denitrification process.

Description

A resource-based flue gas desulfurization and denitrification method

technical field

The invention relates to a resource-based flue gas desulfurization and denitrification method, in particular to a method for removing NO and _SO2 in flue gas and realizing resource utilization respectively.

Background technique

my country is a big coal-burning country, and coal accounts for 75% of the total primary energy consumption. The massive consumption of energy has caused serious air pollution, the most prominent of which is the acid rain hazard caused by SO ₂ and NO _x emissions, as well as the ozone layer destruction and photochemical smog caused by NO _x . According to the "First National Pollution Source Survey Bulletin" published by the Ministry of Environmental Protection on February 6, 2010, in 2007, my country's sulfur dioxide emissions were 23.20 million tons, smoke and dust 11.6664 million tons, and nitrogen oxides 17.977 million tons. The task is daunting. At present, my country's total sulfur dioxide emissions rank first in the world, and the economic losses caused by acid rain and sulfur dioxide pollution are more than 100 billion yuan per year. In recent years, the country has successively issued a number of measures aimed at strongly promoting the reduction of SO ₂ emissions and policies and regulations to alleviate the growth momentum of sulfur dioxide emissions. Thermal power plants have taken active actions, or built FGD devices, or replaced clean fuels, or adopted clean combustion technologies, or Shutting down, shutting down old and small units initially curbed the total amount of SO ₂ emissions that had skyrocketed over the years. However, nitrogen oxides are increasingly prominent. As we all know, nitrogen oxides are more harmful than sulfur dioxide, and even deeper and wider. The future acid rain pollution in my country will develop from sulfuric acid to sulfuric acid/nitric acid compound. It is extremely urgent to control the emission of SO ₂ and nitrogen oxides.

At present, desulfurization and denitrification are placed in the same important position in our country. The existing mainstream technology has many advantages and can meet the requirements of environmental protection, but the disadvantages are high investment and operation costs, desulfurization by-products such as calcium sulfate, etc. The value is low, and it even brings secondary pollution problems. Denitrification is a worthless by-product N ₂ , but consumes a large amount of reducing agent ammonia and expensive catalysts. Therefore, the development of low-investment, low-cost combined desulfurization and denitrification technology is the development direction of new technologies for coal-fired pollutant control.

In the 21st century, the world has entered the era of knowledge economy and sustainable development, which requires the establishment of a unity of opposites between development and the environment. With the development of human beings, many resources are facing the point of reduction or even exhaustion. It has become the social responsibility of contemporary scientific and technological workers to make full and reasonable use of resources or even waste resources. Theoretically, there is no waste in any production process, only underutilized resources. The same is true for air pollution. SO ₂ and NO _x , currently known as one of the main air pollutants, are two important and urgently needed resources in our country. SO ₂ is a necessary raw material for the production of sulfuric acid, and sulfuric acid is a necessary raw material for the production of fertilizers. It is known as the "mother of industry and father of agriculture". Similarly, NO _x is also a necessary raw material for the production of nitric acid, and nitric acid is an important raw material for the production of nitrogen, phosphorus and potassium compound fertilizers, and is also an important raw material for industries such as chemical industry, military industry, and civil explosives. Therefore, it is of great significance to carry out research on SO ₂ and NO _x pollution control and recovery technology to reduce the harm of acid rain and promote the rational use of resources!

There are three main types of desulfurization and denitrification technologies in the prior art:

(1) desulfurization technology (lower nitrogen oxide removal rate in this technology): as lime-gypsum method (CN1281747), wet ammonia method desulfurization technology (CN1226459), seawater desulfurization technology (CN1262145), double alkali desulfurization technology ( CN1475298), semi-dry desulfurization technology (CN101249380), circulating fluidized bed desulfurization technology (CN1401411), electron beam desulfurization technology (Environmental Protection, 2004(9): 15-18), etc.

(II) Denitrification technology: including selective catalytic reduction (SCR), such as US 4221768, US4101238, US4048112; and selective non-catalytic reduction (NCSR), such as CN1817415, CN101244361.

(III) Simultaneous desulfurization and denitration technology: such as CN1454700, CN1147416, CN1843574, CN1923341, CN101053747, CN101337152, CN101485957, CN101352648, CN101306308, CN1311052, CN101053750, etc.

In technology (I), desulfurization is mainly used, and the denitrification rate is generally low. Lime-gypsum method is currently the most used technology in domestic desulfurization technology. It has high desulfurization efficiency and can produce gypsum as a by-product. Compared with gypsum, there are still subtle differences, such as color and luster, heavy metal content, etc. Therefore, domestic desulfurization gypsum is not used much, and most of the desulfurization gypsum is being piled up. With the construction of a large number of desulfurization projects in thermal power plants in my country, the discharge of desulfurization gypsum has increased sharply. How to deal with this part of gypsum will also be a very important issue. If it is discarded and stockpiled, it is necessary to build a special slag yard, which not only requires a huge investment , Occupying a large amount of land, it is also easy to cause dust and groundwater pollution to the surrounding environment, and the operating cost of gypsum treatment is also very high. Ammonia desulfurization is a resource-based desulfurization technology that recovers sulfur dioxide in the flue gas to produce ammonium sulfate fertilizer. However, the use of ammonium sulfate as a fertilizer has certain limitations. Long-term use will cause soil compaction, and under flooding conditions, the soil will Severe hypoxia, after the application of ammonium sulfate, the sulfate ions in it will be reduced to sulfide, and the excessive accumulation of sulfide concentration will cause the plant root system to suffer and die. Ammonium sulfate fertilizer is better used in saline-alkali land. Therefore, if a large number of desulfurization projects adopt the ammonia method, it may cause sales problems of ammonium sulfate fertilizer. Other desulfurization technologies are relatively seldom used in industry at present.

In technology (II), the denitrification efficiency of SCR is higher than that of NCSR, and the denitrification efficiency of SCR can reach more than 80%. Most of the technologies used in denitrification devices are SCR. However, the main disadvantage of the SCR method is that the catalyst is easily poisoned, and there are problems such as ammonia leakage, investment costs, and high operating costs. According to (China Electric Power, 2006, 39(3): 86-89), the cost of removing 1-ton of NOx by using the SCR method has reached more than 9,800 yuan! High operating costs will hinder the enthusiasm of enterprises to denitrify, and researchers at home and abroad are exploring new denitrification technologies.

In technology (III), it refers to the technology of simultaneously removing SO ₂ and NOx in the flue gas by the same method in one process, that is to say, regardless of whether the product after desulfurization and denitrification is useful or not, the product also contains SO ₃ ^- /SO ₄ ^- or NO ₂ ^- /NO ₃ ^- is a mixture. CN1454700 uses microwave radiation to the adsorption sensitizer layer composed of Ni, Fe, Co, Mn metal or metal oxide, _SO2 in the flue gas is reduced to sulfur, NOx is reduced to _N2 , but the process device is complex , there are microwave leakage problems, etc. CN1147416 discloses the technology of using _TiO2 to adsorb _SO2 and NOx in flue gas. The saturated _TiO2 is regenerated by immersing in dilute sulfuric acid, but this method does not clarify the _SO2 and NOx adsorbed in _TiO2 during its regeneration process. As we all know, dilute sulfuric acid solution will not react with SO ₂ and NOx. CN1843574 discloses the use of sodium chlorite and additives to form an absorbent solution to oxidize SO ₂ in the flue gas to SO ₄ ^- , oxidize NO to NO ₃ ^- , and then react with ammonia water to form a mixture of ammonium sulfate and ammonium nitrate; but the The consumption of sodium chlorite in the technology is large, and the pH value of the absorbent is low, which is highly corrosive to the equipment. CN1923341 discloses a method for simultaneously oxidizing _SO2 and NO by using ozone, using the oxidizing properties of ozone to oxidize _SO2 to _SO3 and NO to _NO2 or _NO3 , and then absorb and crystallize with lye to form sulfate and nitrous acid A mixture of salts and nitrates, but this mixture is of little use unless it is separated. CN101053747 oxidizes _SO2 and NO in the flue gas by hydrogen peroxide or ozone, then absorbs it with ammonia water, and finally forms a mixture of ammonium sulfate and ammonium nitrate, which is used as a fertilizer. Although the final desulfurization and denitrification by-products in this technology can be used as fertilizers, the added value is relatively low. CN101337152 uses ozone to oxidize _SO2 and NO in the flue gas, then absorbs it with water, and finally forms a dilute solution of sulfuric acid and nitric acid, and separates them by chemical methods to form a single product of sulfuric acid and nitric acid. However, this technology does not specify how to separate the mixed acid of sulfuric acid and nitric acid. Workers in the chemical field know that it is very difficult to separate the mixed solution of sulfuric acid and nitric acid, and the formation of dilute acid solution in the desulfurization equipment is harmful to The corrosiveness of the equipment is very large, and the equipment investment and maintenance costs will be very large. CN101485957 discloses that desulfurization and denitrification are carried out in two devices, and SO in the flue gas is absorbed by lye, and sulfite is oxidized into sulfate with ozone in the liquid phase _; The NO is oxidized and then absorbed with lye to form a nitrite/nitrate mixture. Although this technology separates desulfurization and denitrification in two devices and realizes the separation of sulfur resources and nitrogen resources, the cost of deoxidizing sulfite with ozone is much higher than that of air oxidation. CN101352648 then uses cobalamin complex solution to absorb NO, divalent metal oxide or carbonate alkaline desulfurizer to absorb SO _The method realizes simultaneous desulfurization and denitrification. This is a pure method for removing SO ₂ and NOx, and has not been able to realize resource utilization. CN101306308 is similar to CN101352648, knowledge replaces cobalamin complex solution with ferrous ammonium complex solution. CN1311052 discloses that the complex formed by divalent cobalt and ammonia is used to oxidize NO into NO ₂ , and then react with ammonia water to generate ammonium nitrite, and SO ₂ in the flue gas reacts with ammonia to generate ammonium sulfite, which is absorbed in the liquid phase Oxidized to ammonium sulfate, forming a mixture of ammonium sulfate and ammonium nitrite/ammonium nitrate to achieve the purpose of desulfurization and denitrification. Like CN101053747, the by-products of desulfurization and denitrification can only be used as chemical fertilizers with low added value. CN101053750 discloses that under the action of photocatalyst TiO ₂ , NO in flue gas is oxidized to NO ₂ by ultraviolet light irradiation, and NO ₂ is reduced to N ₂ by sodium sulfite. The statement that NO ₂ is reduced to N ₂ is debatable, because in the patent document, there is no reaction of NO ₂ and sodium sulfite to generate N ₂ in the relevant reaction equation. In the aforementioned desulfurization and denitrification patents, most of them are NO ₂ Absorbed by lye, forming nitrite/nitrate, which mixes with sulfite formed after _SO2 absorption.

China is a sulfur-deficient country. Every year, a large amount of sulfur needs to be imported from abroad to prepare SO ₂ or sulfuric acid, and China is a country with a large SO ₂ emission. Most of the existing desulfurization technologies absorb SO ₂ to form solid waste. Gypsum, a small amount of desulfurization technology produces ammonium sulfate with low fertilizer efficiency. At the same time, in the desulfurization and denitrification process, most of the _SO2 and NOx in the flue gas are absorbed to form a mixture of sulfate and nitrate, which makes it difficult to form high value-added resource products.

To sum up, there are still deficiencies in the existing desulfurization and denitrification process, and the desulfurization and denitrification technology needs to be further improved.

Contents of the invention

The purpose of the present invention is to overcome the defects of the prior art and provide a resource-based desulfurization and denitrification technology that can remove SO ₂ and NOx from flue gas and recover SO ₂ and NOx.

The technical scheme that realizes the object of the present invention:

The inventor believes that in order to recover SO ₂ , the method of absorbent absorption and desorption can be used to remove SO ₂ from flue gas and prepare liquid SO ₂ , so as to realize resource management of SO ₂ in flue gas and maximize value . The method of absorbing _SO2 with sodium sulfite solution is also called the Wellman-Lord method, and its principle is:

Absorption process: Na ₂ SO ₃ +SO ₂ +H ₂ O→2NaHSO ₃

Desorption process:

Side reaction: Na ₂ SO ₃ +1/2 O ₂ →Na ₂ SO ₄

However, the main reasons why the sodium sulfite absorption and desorption method is difficult to popularize are: (1) high alkali consumption: because a part of sodium sulfite is oxidized into sodium sulfate and loses absorption capacity, the oxidation rate is about 10%, so it is necessary to supplement alkali such as soda ash to supplement Lost sodium sulfite:

Na ₂ CO ₃ +SO ₂ →Na ₂ SO ₃ +CO ₂

In this way, 0.3 tons of soda ash will be supplemented for every ₁ ton of SO recovered. (2) High steam consumption. The desorption process needs to be heated by steam, and about 10 tons of water need to be evaporated for every ton of _SO2 desorbed. If a single-effect evaporator is used, 11 tons of steam will be consumed, and if a double-effect evaporator is used, about 7 tons of steam will be consumed. . The high cost of desulfurization limits the popularization and application of this method.

In view of the fact that there is a part of oxygen in the flue gas and sodium sulfite is easy to oxidize, the inventor found through a large number of experiments that the addition of high-efficiency antioxidants can effectively inhibit the oxidation of sodium sulfate, and the oxidation rate of sodium sulfite can be reduced to below 1.5%, thereby greatly reducing Alkali consumption. Aiming at the problem of high steam consumption when the original sodium sulfite method desorbs SO ₂ , the secondary steam from the second-effect evaporator is used after being pressurized and heated to reduce the consumption of fresh steam to below 3 tons/ton of SO ₂ .

Since more than 95% of NOx in the flue gas is NO, and NO is difficult to dissolve in water, it is difficult to absorb it with absorbents, so NO is oxidized to _NO2 and then absorbed with lye, so as to achieve the purpose of denitrification. The reaction mechanism of NO oxidation by ozone _O3 is very complicated, and it is still lack of in-depth research. The main reactions are:

O ₃ +NO→NO ₂ +O ₂

NO ₂ +O ₃ →NO ₃ +O ₂

NO ₃ +NO ₂ →2N ₂ O ₅

Absorbed with lye, nitrates can be formed. Therefore, the flue gas after removing SO ₂ enters the denitrification tower, O ₃ gas is passed into the lower part of the tower, and lye is sprayed into the upper part of the tower for absorption, and the denitrification rate can reach more than 90%. The nitrate in the solution can be crystallized after accumulating to a certain concentration, and the nitrate product with high purity can be obtained after filtration and drying, so as to realize the resource utilization of the denitrification process.

The waste gas desulfurization and denitrification method of resource utilization in the present invention comprises the following steps:

(1) The flue gas from the boiler enters the desulfurization tower from the lower part, and the absorbent is sprayed from the upper part of the desulfurization tower, and in the desulfurization tower, the absorbent sodium sulfite reacts with _SO2 to generate sodium bisulfite.

(2) In the step (1), the rich liquid at the bottom of the desulfurization tower enters the first-effect evaporator after exchanging heat with the lean liquid from the multi-effect evaporator, and after heating and vaporizing, the gas phase containing SO enters the _second -effect evaporator for heating; After the gas phase of the first-effect evaporator is pressurized by the compressor, it enters the first-effect evaporator together with the fresh steam.

(3) The vapor condensed water and _SO2 mixture of the evaporator in step (2) enters the gas-liquid separation tank, and after the gas phase is condensed by the condenser, it is compressed by a compressor to obtain a liquid _SO2 product, which enters the storage tank. The liquid is mixed with the lean liquid from the second effect and then enters the desulfurization tower for recycling after heat exchange with the rich liquid.

(4) _The flue gas from the top of the tower in step (1) enters the denitrification tower, and the O ₃ from the ozone generator also enters the denitrification tower. In the desulfurization tower, NO is oxidized by O ₃ to NO The denitration agent sprayed into the upper part absorbs and forms nitrate.

(5) When the nitrate in the absorption solution in step (4) reaches a certain concentration, it will crystallize out, and the nitrate with higher purity can be obtained by filtering.

(6) The filtrate obtained by filtering in step (5) is returned to the upper part of the denitrification tower together with the added denitrification agent.

Wherein, in said desulfurization absorbent sodium sulfite solution, add high-efficiency antioxidant, said antioxidant is composed of hydroquinone, catechol, resorcinol, tert-butyl phthalate which are easily soluble in water One or two or two of phenol, α-naphthol, β-naphthol, p-phenylenediamine, methyl-p-phenylenediamine, sodium thiosulfate, sodium sulfide, sodium dithionite, and thiourea dioxide For the above mixture composition, the concentration of said antioxidant is 0.001%-0.5%.

Said denitration agent is one of sodium carbonate, potassium carbonate, ammonium carbonate, ammonium bicarbonate, sodium bicarbonate, potassium bicarbonate, sodium hydroxide, potassium hydroxide, liquid ammonia or ammonia water.

Said desulfurization tower is a spray tower, plate tower or packed tower.

Said denitrification tower is a spray tower, plate tower or packed tower.

The liquid SO ₂ can be obtained by adopting the above technical scheme, the desulfurization rate can reach more than 96%, the denitrification rate can reach more than 90%, and the nitrate content can be more than 96%.

Description of drawings

Figure 1 is a schematic flow chart of a method for desulfurization and denitrification of waste gas from resources.

Some symbols in Figure 1 are explained as follows:

3-Desulfurization tower, 5-Ozone generator, 7-Denitrification tower, 11-Filter, 17-Lean-rich liquid heat exchanger, 23-First effect evaporator, 26-First effect gas-liquid separator, 30- Second-effect evaporator, 36-second-effect gas-liquid separator, 40-condensate gas-liquid separator, 44-SO ₂ gas condenser, 48-liquid SO ₂ storage tank.

Detailed ways

Referring to accompanying drawing 1, the present invention is realized like this:

The flue gas from the boiler fan enters the lower part of the desulfurization tower 3 from the pipe 1, and the lean liquid from the rich-poor heat exchanger 17-sodium sulfite (containing a small amount of sodium bisulfite) absorbing liquid (containing antioxidant) enters the desulfurization tower from the pipe 2 The upper part of 3. The rich liquid-sodium bisulfite solution (containing a small amount of sodium bisulfite) at the bottom of the desulfurization tower 3 enters the heat exchanger 17 from the pipe 16, and enters the first effect evaporator 23 from the pipe 18 through the pump 21 after being heated by the lean liquid from the pipe 19 , the heat source of the first effect evaporator 23 is the live steam from the pipe 24 and the secondary steam from the compressor 38 . After the rich liquid is heated and vaporized by the first effect evaporator 23, it enters the first effect gas-liquid separator 26, and the gas phase enters the second effect evaporator 30 from the pipe 27 as a heat source, and most of the liquid enters from the pipe 28 and circulates through the pump 21. The first effect evaporator 23 , a part of the liquid enters the second effect evaporator 30 from the pipe 29 through the pump 32 . The condensate in the first effect evaporator 23 enters the condensate gas-liquid separator 40 from the pipe 34 . After the rich liquid in the second effect evaporator 30 is vaporized, the gas enters the second effect gas-liquid separator 36 from the pipe 31, and after the gas-liquid separation, the gas phase enters the first effect evaporator 23 from the pipe 37 through the compressor 38 In this process, most of the liquid is circulated into the second effect evaporator 30 from the pipe 42 through the pump 32, and a part of the liquid is drawn out from the pipe 39 through the pump 20 as lean liquid. The condensed liquid in the second effect evaporator 30 enters the condensed liquid gas-liquid separator 40 from the pipe 35, and the gaseous SO ₂ enters the condenser 44 from the pipe 43. After the condenser, it is compressed into liquid SO ₂ by the compressor 46 from the pipe 45, From pipe 47 into storage tank 48 . The liquid in the condensate gas-liquid separator 40 is mixed with the liquid from the pipe 39 from the pipe 41 and extracted by the pump 20 .

The flue gas after removing _SO2 comes out from the top of the desulfurization tower 3, enters the lower part of the denitrification tower 7 from the pipe 4, O3 from the ozone generator 5 enters the pipe ₄ from the pipe 6, and the circulating denitration agent flows from the pipe 15 to the bottom of the denitrification tower 7. 9 supplementary denitrification agent mixed together into the upper part of the denitrification tower 7. Inside the denitrification tower, NO is oxidized to NO ₂ and N ₂ O ₅ , absorbed by the denitrification agent to form nitrate and dissolved in water. When the concentration of nitrate reaches a certain level, it can be crystallized and precipitated. It enters from the bottom of the denitrification tower 7 through the pipe 10. The filter 11 is used for solid-liquid separation, and the solid is discharged from the pipe 12. After drying, the nitrate product with a purity of more than 95% can be obtained. The filtrate is pumped into the upper part of the denitrification tower 7 from the pipe 13 by the pump 14 through the pipe 15, and is recycled. The flue gas after denitration is discharged from the top of the denitration tower through the pipe 8 into the chimney of the boiler.

In this way, the flue gas containing SO ₂ and NOx is treated, the liquid SO ₂ and nitrate products are recovered, and the waste is turned into a single useful product instead of a mixture of sulfur and nitrogen, which maximizes the value of the waste gas desulfurization and denitrification process. Greatly reduce the cost of desulfurization and denitrification.

Below by embodiment this is done further elaboration, and its purpose is only to better understand content of the present invention. Therefore, the examples given do not limit the protection scope of the present invention:

Example 1

Flue gas conditions: 15000Nm ³ /h, SO ₂ concentration 2000ppm (5714mg/Nm ³ ), NO concentration 460ppm (616mg/Nm ³ ), temperature 150°C.

Absorption liquid (poor liquid) composition: sodium sulfite 16.78%, sodium bisulfite 11.45%, antioxidant hydroquinone 0.03%, sodium sulfide 0.02%.

The flue gas enters the desulfurization tower (the desulfurization tower is a corrugated structured packing tower), and the lean liquid is sprayed into the tower from the upper part of the tower with a flow rate of 2t/h. After desulfurization, the composition of the rich liquid at the bottom of the desulfurization tower is: 8.69% sodium sulfite and 23.37% sodium bisulfite. The content of SO ₂ in the flue gas at the top outlet of the tower is 190 mg/Nm ³ , and the desulfurization rate is 96.6%.

After the rich liquid is desorbed by the second-effect evaporator, SO ₂ is released, and after condensation and compression, 82.8kg/h of liquid SO ₂ is obtained. The solution after desorption is the barren solution, and the composition is the same as above.

The flue gas after removing SO ₂ enters the denitrification tower, which is a spray tower, and 14.8kg/h O ₃ is produced from the ozone generator into the flue gas, and 5% ammonia solution 500kg/h is sprayed from the upper part of the denitrification tower h. After denitration, the NO concentration in the flue gas discharged from the top of the denitration tower is 49 mg/Nm ³ , and the denitration rate is 92%. After the ammonium nitrate produced has accumulated to a certain concentration, it crystallizes out from the denitrification tower and is filtered and dried to obtain 23.4kg/h of ammonium nitrate with a content of 96.5%.

Example 2

Flue gas conditions: 54200Nm ³ /h, SO ₂ concentration 1560ppm (4457mg/Nm ³ ), NO concentration 650ppm (875mg/Nm ³ ), temperature 140°C.

The composition of the absorption liquid (poor liquid): 13.58% of sodium sulfite, 5.6% of sodium bisulfite, 0.01% of antioxidant methyl-p-phenylenediamine, and 0.03% of sodium dithionite.

The flue gas enters the desulfurization tower (desulphurization tower spray tower), and the lean liquid is sprayed into the tower from the upper part of the tower with a flow rate of 5.5t/h. After desulfurization, the composition of the rich liquid at the bottom of the desulfurization tower is: 5.6% sodium sulfite and 24.96% sodium bisulfite. The content of SO ₂ in the flue gas at the top outlet of the tower is 89 mg/Nm ³ , and the desulfurization rate is 98.0%.

After the rich liquid is desorbed by the second-effect evaporator, SO ₂ is released, and after condensation and compression, 236kg/h of liquid SO ₂ is obtained. The desorbed solution is the barren solution.

The flue gas after removing SO ₂ enters the denitration tower, which is a guided floating valve tower with 3 trays inside, and 84.7kg/h O ₃ produced from the ozone generator enters the flue gas, and is sprayed from the upper part of the denitrification tower. Inject 5% KOH solution 2600kg/h. After denitration, the NO concentration in the flue gas discharged from the top of the denitration tower is 61.2 mg/Nm ³ , and the denitration rate is 93.0%. After the produced potassium nitrate accumulates to a certain concentration, it crystallizes out from the bottom of the denitrification tower, and is filtered and dried to obtain 148.6kg/h of potassium nitrate product with a content of 97.5%.

Claims (9)

1. the flue gas desulfurization and denitration method of a resource is characterized in that, this method comprises the steps:

(1) will contain SO ₂Enter desulfurizing tower with the flue gas of NOx, in desulfurizing tower, contact with desulfurizing agent (lean solution);

(2) desulfurizing agent (rich solution) that obtains in the step (1) is carried out desorb through multi-effect evaporator;

(3) SO that desorb in the step (2) is obtained ₂Gas is compressed into liquid SO after the condensation drying ₂

(4) flue gas through desulfurization enters denitrating tower in the step (1), sprays into ozone, and flue gas contacts with the denitrfying agent that cat head gets off;

(5) nitrate in step (4) solution reaches the finite concentration post crystallization and comes out, after filtration, after the drying, obtain the higher nitrate product of purity.

2. the method for claim 1 is characterized in that, wherein said desulfurizing agent is made up of the aqueous solution of sodium sulfite, niter cake and high-efficiency anti-oxidant.

3. method as claimed in claim 2, it is characterized in that wherein said high-efficiency anti-oxidant is to be made up of a kind of in hydroquinones soluble in water, catechol, resorcinol, tert-butyl catechol, alpha-Naphthol, betanaphthol, p-phenylenediamine (PPD), dimethyl-p-phenylenediamine, sodium thiosulfate, vulcanized sodium, sodium dithionate, the thiourea dioxide or two or more mixture.

4. method as claimed in claim 2 is characterized in that, wherein said antioxidant concentration is 0.001%～0.5%.

5. the method for claim 1 is characterized in that, wherein said ozone amount is 0.5～1.5 times of NO molal quantity.

6. the method for claim 1 is characterized in that, wherein said denitrfying agent is a kind of in sodium carbonate, potash, ammonium carbonate, carbonic hydroammonium, sodium acid carbonate, saleratus, NaOH, potassium hydroxide, liquefied ammonia or the ammoniacal liquor.

7. as any described method in the claim 1～6, it is characterized in that the flue gas desulfurization and denitration method of said resource comprises the steps:

Enter the bottom of desulfurizing tower (3) from the flue gas of boiler fan from pipe (1), enter the top of desulfurizing tower (3) from lean solution-sodium sulfite (containing a small amount of sodium hydrogensulfite) absorption liquid (containing antioxidant) of rich or poor heat exchanger (17) from pipe (2).Rich solution-the solution of sodium bisulfite (containing a small amount of sodium sulfite) of desulfurizing tower (3) bottom enters heat exchanger (17) from pipe (16), by from entering first single-effect evaporator (23) from pipe (18) through pump (21) after the heating of lean solution of pipe (19), the thermal source of first single-effect evaporator (23) be from the live steam of managing (24) with from the indirect steam of compressor (38).After rich solution is vaporized by first single-effect evaporator (23) heating, enter first and imitate gas-liquid separator (26), gas phase enters second single-effect evaporator (30) from pipe (27) as thermal source, the liquid major part then enters first single-effect evaporator (23) from pipe (28) through pump (21) circulation, and a part of liquid enters second single-effect evaporator (30) through pump (32) from pipe (29).Condensate liquid in first single-effect evaporator (23) enters the condensate liquid gas-liquid separator (40) from pipe (34).After rich solution in second single-effect evaporator (30) is vaporized, gas enters second from pipe (31) and imitates the gas-liquid separator (36), after gas-liquid separation, gas phase enters first single-effect evaporator (23) from pipe (37) compressed machine (38), the liquid major part then enters second single-effect evaporator (30) through pump (32) circulation from pipe (42), and a part of liquid is extracted out through pump (20) from pipe (39) as lean solution.Condensate liquid in second single-effect evaporator (30) enters the condensate liquid gas-liquid separator (40) gas phase SO from pipe (35) ₂After (43) enter condenser (44) condenser from pipe, be compressed into liquid SO by compressor (46) from pipe (45) ₂, enter the storage tank 48 from pipe (47).Liquid in the condensate liquid gas-liquid separator (40) mixes from pipe (41) and from the liquid of managing (39), extracts out through pump (20).

Through removing SO ₂Flue gas come out from the top of desulfurizing tower (3), enter the bottom of denitrating tower (7) from pipe (4), from the O of ozone generator (5) ₃Enter pipe (4) from pipe (6), the denitrfying agent of circulation is mixed from pipe (15) and from the additional denitrfying agent of managing (9) and enters the top of denitrating tower (7).In denitrating tower inside, NO is oxidized to NO ₂And N ₂O ₅, it is soluble in water to be absorbed formation nitrate by denitrfying agent, when nitrate concentration reaches one regularly, can crystallization separate out, enter filter (11) from the bottom of denitrating tower (7) from pipe (10) and carry out Separation of Solid and Liquid, solid is discharged by pipe (12), and drying can get the nitrate product of purity more than 95%.Filtrate pumps into the top of denitrating tower (7) by pump (14) through pipe (15) from pipe (13), recycles.Enter the chimney of boiler from pipe (8) from the top of denitrating tower through the flue gas after the denitration.

8. the method for claim 1 is characterized in that, wherein said desulfurizing tower is spray column, plate column or packed tower.

9. the method for claim 1 is characterized in that, wherein said denitrating tower is spray column, plate column or packed tower.

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