CN101721906B - Method for enhancing activity of calcium sulfite slurry in wet flue gas denitration technique - Google Patents
Method for enhancing activity of calcium sulfite slurry in wet flue gas denitration technique Download PDFInfo
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- CN101721906B CN101721906B CN2010100395332A CN201010039533A CN101721906B CN 101721906 B CN101721906 B CN 101721906B CN 2010100395332 A CN2010100395332 A CN 2010100395332A CN 201010039533 A CN201010039533 A CN 201010039533A CN 101721906 B CN101721906 B CN 101721906B
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- calcium sulfite
- flue gas
- additive
- denitration
- oxidation
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Abstract
The invention discloses a method for enhancing the activity of calcium sulfite slurry in a wet flue gas denitration technique, which utilizes the calcium sulfite slurry to absorb nitric oxide; and the calcium sulfite slurry is added with additive which can be soluble sulfate or soluble magnesium salt. The added additive leads the solubility of calcium sulfite to be obviously improved, and enhances the activity of the slurry, thus not only greatly improving the denitration efficiency, but also being beneficial to the oxidation of the calcium sulfite. The method enhances the denitration feasibility of the calcium sulfite, saves the cost of forced oxidation in the desulphurization process, and realizes the organic combination between wet desulphurization and wet denitration.
Description
Technical field
The present invention relates to the air pollution control technique field, specifically relate to a kind of active method of wet flue gas denitration technique Central Asia calcium sulfate slurries that strengthens.
Background technology
The selective catalytic reduction technology of the main method of denitrating flue gas (SCR), SNCR technology (SNCR), wet process complex absorption techniques, oxidation-absorption techniques etc.Wherein oxidation-absorption denitration technology is owing to its investment, operating cost are lower, and denitration efficiency is high, and is better to the adaptability of the coal and the type of furnace, and receives increasing concern.They are to utilize gas phase or liquid-phase oxidation with flue gas nitrogen oxide NO
xThe middle less nitric oxide NO of solubility is oxidized to the nitrogen oxide of high valence state, and then with the absorption liquid of alkalescence, oxidisability or reproducibility it is absorbed.
Publication number is that the Chinese invention patent of CN1768902, CN101352644, CN101385942 and CN101352645 discloses a kind of ozone oxidation and denitration method of boiler flue gas, a kind of wet flue gas denitration technique, liquid-phase oxidation-absorption two-stage wet method flue-gas denitration technology and flue gas catalytic oxidation denitration technique and catalyst thereof that reclaims nitrite respectively.They all be with alkali lye as absorbent, absorb through the nitrogen oxide of oxidation to a certain degree.But nitric oxide partly or entirely is oxidized to NO
2The time, alkali lye is not high to the efficient of nox adsorption.
Publication number is the method that the Chinese invention patent of CN101053750 has proposed a kind of flue gas combined desulfurization and denitration, and the reducing substances sodium sulfite that utilizes the sweetening process generation is as absorbent, and absorbing through the nitrogen oxide after the photocatalytic conversion is NO
2This method denitration efficiency is very high.But because sodium sulfite very easily by the dioxygen oxidation in the flue gas, even add oxidation retarder bigger additive decrementation is arranged still, and the price of absorbent own is more expensive, has influenced the economy of this method.
Therefore, it is most important as far as oxidation-absorption denitration technology to seek a kind of absorbent of Cheap highly effective.And the accessory substance calcium sulfite in the calcium base wet-process sulfur removal technology is exactly a kind of potential desirable absorbent.It and sodium sulfite are similar, also can with NO
2Thereby the purpose that redox reaction reaches denitration takes place.In the sweetening process, in order to prevent secondary pollution and, generally to adopt means such as forced oxidation that calcium sulfite further is oxidized to gypsum to its recycling.If as the denitration absorbent, can not only save the cost of material in the denitrification process, and NO with it
2Can quicken its conversion greatly, thereby reduce the operating cost in the sweetening process to gypsum.But the solubility of calcium sulfite is very low, and denitration efficiency and gypsum oxidation rate are very limited, and therefore managing to improve its activity is to use the key of its denitration.
Summary of the invention
The present invention utilizes the calcium sulfite absorbing NOx, and a kind of method that strengthens the calcium sulfite slurry activity is provided, and improves the problem that calcium sulfite solubility further improves denitration efficiency and calcium sulfite oxidation speed thereby solve.
A kind of active method of wet flue gas denitration technique Central Asia calcium sulfate slurries that strengthens is utilized calcium sulfite slurries absorbing NOx; In the calcium sulfite slurries, add additive, described additive is soluble sulphate or solubility magnesium salts.
Described soluble sulphate refers to that anion is the solubility salt of sulfate ion, comprises sodium sulphate, potassium sulfate etc.;
Described solubility magnesium salts refers to that cation is the solubility salt of magnesium ion, comprises magnesium sulfate, magnesium nitrate, magnesium chloride etc.
Described additive is most preferably used magnesium sulfate.
In the calcium sulfite slurries gross weight behind the interpolation additive, additive concentration is 0.5～10%, and the calcium sulfite concentration of slurry is 0.05～5%; The calcium sulfite slurry pH value is 4～9 behind the interpolation additive, NO in the flue gas after the increment of calcium sulfite and the oxidation
2Mol ratio be 3-15.
Denitrification process can carry out in absorbers such as spray column, rotating stream tray scrubber, bubble tower, sieve-plate tower.The nitrogen oxide that utilizes the calcium sulfite slurries to absorb is the nitrogen dioxide through generating behind the complete oxidation.
Basic principle:
When absorbing nitrogen dioxide with the calcium sulfite slurries, nitrogen dioxide can be absorbed through two kinds of approach: a kind of is the hydrolysis of nitrogen dioxide, shown in reaction (1); Another kind is and calcium sulfite generation redox reaction, shown in reaction (2).Wherein the speed of hydrolysis is limited, during denitration mainly by the SO that dissociates in the calcium sulfite especially liquid phase
3 2-Play a role.After nitrogen oxide is absorbed by the calcium sulfite slurries, with the form entering liquid phase of nitrous acid and nitric acid.A calcium sulfite part is directly by the nitrogen dioxide oxidation, and the radical reaction that another part is induced through nitrogen dioxide is generated calcium sulfate by the dioxygen oxidation in the flue gas.
2NO
2+CaSO
3+H
2O＝2NO
2 -+CaSO
4+2H
+ (2)
But generally, the denitration efficiency of calcium sulfite slurries is not high.Main cause is that the solubility of calcium sulfite is very low, generally only about 0.5mmol/L, participates in the SO that dissociates of denitration reaction
3 2-Concentration is very limited.Research shows, NO
2With SO
3 2-Reaction pair SO
3 2-Be rapid first-order reaction, so low excessively SO in the calcium sulfite slurries
3 2-Concentration can serious limited reactions speed.On the contrary, the SO that dissociates
3 2-Concentration is high more, and absorption rate is fast more, especially under the low concentration absorption rate with SO
3 2-The increase of concentration and improve very fastly.Meanwhile, the oxidation rate of calcium sulfite and the SO that dissociates
3 2-Concentration and NO
2Absorption rate relevant, SO
3 2-Concentration is high more, NO
2Absorption rate fast more, its conversion rate to gypsum is also fast more.Therefore manage to improve SO
3 2-Concentration all has great practical significance to improving denitration efficiency and calcium sulfite oxidation speed.
The soluble sulphate additive can significantly improve the SO that dissociates in the calcium sulfite slurries
3 2-Concentration.Reason is that after a certain amount of sulfate added calcium sulfite slurries system, sulfate radical can combine to generate the also very low calcium sulfate of solubility with the part calcium ion, thereby promoted SO
3 2-Release.Shown in reaction (3).
In addition, the adding of solubility magnesium salts also can be played the effect that is similar to sulfate.Reason is, Mg
2+Ability and SO
3 2-Be combined into a kind of ion pair MgSO of solubility
3 0At absorption of N O
2The time, MgSO
3 0Ion pair and SO
3 2-Effect closely similar, therefore improve its concentration and also help NO
2Absorb and calcium sulfite oxidation.Shown in reaction (4) and reaction (5).
Mg
2++CaSO
3＝Ca
2++MgSO
3 0 (4)
2NO
2+MgSO
3 0+H
2O＝2NO
2 -+MgSO
4+2H
+ (5)
In the absorption process, additive concentration is regulated between 0.5～10%, and corresponding calcium sulfite concentration of slurry is controlled between 0.05～5%.Slurry pH value can pass through Ca (OH)
2, alkaline matter such as CaO regulates, be stabilized between 4～9.NO in the flue gas after the increment of calcium sulfite and the oxidation
2Mol ratio be 3-15.So both guaranteed the absorption efficiency of nitrogen oxide, and also helped calcium sulfite and be completely oxidized to gypsum.
The adding of additive is significantly improved the solubility of calcium sulfite, has strengthened the activity of slurries, has not only significantly improved denitration efficiency, and helps the oxidation of calcium sulfite.Additive can not pass through reaction consumes in this process.Under general flue gas condition, the amount of the calcium sulfite that sweetening process generates can satisfy the needs of wet method denitration; Through the consumption of control additive, the wet method denitrification process also can all be oxidized to gypsum with calcium sulfite.This method has strengthened the feasibility of utilizing the calcium sulfite denitration, has practiced thrift the cost of forced oxidation in the sweetening process, has realized the combination of wet desulphurization and wet method denitration.
Description of drawings
Fig. 1 is a process flow diagram of the present invention.
The specific embodiment
As shown in Figure 1, send in the oxidation reactor 2 by blower fan 1 through the flue gas that contains nitrogen oxide after dedusting, the desulfurization, NO all is oxidized to NO therein
2, getting into absorption tower 3 afterwards, the flue gas after the absorption is through chimney 7 dischargings.Absorbent and additive add from circulatory pool 4; Being conveyed into absorption tower 3 by circulating pump 5 absorbs; Slurries after absorbing are fully sent into solid-liquid separation system 6 by the circulatory pool bottom; Obtain the mixed solution of gypsum and nitrite, nitrate and portions additive after the separation respectively, obtain nitrite, nitrate product and additive solids respectively behind the separation of mixed solution process, the crystal system 8, additive supplies to recycle.
Embodiment 1: the denitration of magnesium sulfate activation calcium sulfite slurries
From lime-gypsum method desulphurization system, extract the calcium sulfite slurries, add MgSO
4As additive, the concentration of calcium sulfite is 2% in the calcium sulfite slurries behind the interpolation additive, and the concentration of additive is 8%, regulates pH and is about 5, makes the denitration absorbent behind the mixing.Flue gas after desulfurization mixes with the high-concentrated ozone of ozone generator preparation, and the amount that ozone is sent into is according to the NO concentration of surveying in the flue gas, according to O
3/ NO mol ratio is about 1 dynamically adjustment, with the whole oxidations of NO.Flue gas after the oxidation gets into the absorption tower, is absorbed agent and absorbs, and denitration efficiency is between 85～90%.
Embodiment 2: the denitration of sodium sulphate activation calcium sulfite slurries
From lime-gypsum method desulphurization system, extract the calcium sulfite slurries, add Na
2SO
4As additive, the concentration of calcium sulfite is 5% in the calcium sulfite slurries behind the interpolation additive, and the concentration of additive is 5%, regulates pH and is about 8, makes the denitration absorbent behind the mixing.Flue gas after the desulfurization is sent into oxidizing tower earlier, and by liquor natrii hypochloritis's oxidation of 0.1mol/L, oxidation efficiency is 80%.Flue gas after the oxidation gets into the absorption tower again, is absorbed by the denitration absorbent, and total denitration efficiency is more than 75%.
Embodiment 3: the denitration of magnesium chloride activation calcium sulfite slurries
From lime-gypsum method desulphurization system, extract the calcium sulfite slurries, add MgCl
2As additive, the concentration of calcium sulfite is 1% in the calcium sulfite slurries behind the interpolation additive, and the concentration of additive is 2%, regulates pH and is about 7, makes the denitration absorbent behind the mixing.Flue gas behind the desulfurization and dedusting is sent into catalyst oxidation reactor earlier, utilizes ferrimanganic mixed oxide catalytic oxidation NO, and 200 ℃ of following oxidation efficiencies are 90%.Flue gas after the oxidation gets into the absorption tower again, is absorbed by the denitration absorbent, and total denitration efficiency is about 80%.
Embodiment 4: the denitration of magnesium sulfate activation calcium sulfite slurries
From lime-gypsum method desulphurization system, extract the calcium sulfite slurries, add MgSO
4As additive, the concentration of calcium sulfite is 0.1% in the calcium sulfite slurries behind the interpolation additive, and the concentration of additive is 1%, regulates pH and is about 9, makes the denitration absorbent behind the mixing.Flue gas after desulfurization mixes with the high-concentrated ozone of ozone generator preparation, and the amount that ozone is sent into is according to the NO concentration of surveying in the flue gas, according to O
3/ NO mol ratio is about 1 dynamically adjustment, with the whole oxidations of NO.Flue gas after the oxidation gets into the absorption tower, is absorbed agent and absorbs, and denitration efficiency is more than 70%.
Claims (2)
1. one kind strengthens the active method of wet flue gas denitration technique Central Asia calcium sulfate slurries, utilizes calcium sulfite slurries absorbing NOx; It is characterized in that: in the calcium sulfite slurries, add additive, described additive is soluble sulphate or solubility magnesium salts; In the calcium sulfite slurries gross weight behind the interpolation additive, described additive concentration is 0.5～10%, and the calcium sulfite concentration of slurry is 0.1～5%, and the calcium sulfite slurry pH value is 4～9 behind the interpolation additive, NO in the flue gas after the increment of calcium sulfite and the oxidation
2Mol ratio be 3-15.
2. the method for claim 1, it is characterized in that: described additive is a magnesium sulfate.
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