CN105617831A - Flue gas low-temperature denitration and semi-dry desulfurization process - Google Patents

Abstract

The invention relates to a flue gas low-temperature denitration and semi-dry desulfurization process, which comprises the following steps of (1) feeding tail gas into a low-temperature SCR (Selective Catalytic Reduction) reactor, and reducing NOx in the tail gas to be N2 and H2O; (2) feeding gas obtained in the step (1) into a semi-dry desulfurization reaction system, spraying an absorbing agent into the reaction system to desulfurize, and removing acid gas in the tail gas; (3) feeding gas obtained in the step (2) into a dust collection device, thoroughly removing dust in the tail gas, and discharging obtained cleaned gas into atmosphere. The tail gas comprises NOx, SO2, SO3, HCl and the like, and the tail gas temperature is 100 to 260 DEG C. The process provided by the invention can be widely applied to treating the tail gas containing the NOx and the SO2 produced by enterprises such as electric power, steel and petrochemical industry; after treatment, in the cleaned tail gas, the SO2 is less than or equal to 35mg/Nm<3>, the NOx is less than or equal to 50mg/Nm<3>,and the dust is less than or equal to 5mg/Nm<3>; the conversion rate of the SO2 is larger than or equal to 97 percent, and the conversion rate of the NOx is larger than or equal to 85 percent.

Description

A kind of flue gas low-temperature denitration semi-dry desulfurizing process

Technical field

The present invention relates to a kind of tail gas treatment process, particularly relate to a kind of flue gas low-temperature denitration semi-dry desulfurizing process.

Background technology

The SO that industrial process produces₂And NO_x, the atmospheric pollution and the acid rain problem that bring are extremely serious, and living environment and health to the mankind cause great injury, therefore control SO₂And NO_xIt is imperative to pollute.

Owing to flue gas containing SO simultaneously₂And NO_x, therefore developed the Technology of some simultaneous SO_2 and NO removal, such as activated carbon method, SNOX technique, SNRB technique, NOXSO technique and electronic beam method etc. But desulfurization and denitrification integral technology is ripe not enough at present, and applicable industryization can not be fully achieved. Therefore current, major part power plant, Industrial Boiler still adopt independent desulfurization denitration method.

The method of independent denitration and independent desulfurization is of a great variety. Wherein sulfur method mainly has wet method, dry method and semidry method. Wet desulphurization is the sulfur method that coal-burning power plant is the most ripe, and wet desulfurizing process mainly has limestone/gypsum method, ammonia process, magnesium processes, Sea water respiratory distress syndrome etc. But wet desulphurization yet suffers from a series of problem, such as wet desulfurization system is complicated, floor space is big, equipment corrosion is serious, produce a large amount of waste liquid to be difficult to process and cause secondary pollution etc., and study and show that wet desulphurization is also cause one of reason that haze phenomenon is serious. And the existing occupation of land of semi-dry desulfurizing process less, investment operating cost feature low, free of contamination, higher desulfurization degree can be obtained again when calcium sulfur ratio is moderate, therefore at present semi-dry desulphurization technology receives much concern.

SCR (SCR) technology is the major technique of China's station boiler denitration. Currently commercially Application comparison is the middle temperature catalyst that running temperature is in 320-450 DEG C widely. The position difference laid according to SCR device is classified, and SCR technique can be divided into high ash section, low ash section and afterbody and arrange three types. Ash-rich technological requirement catalyst is applicable to medium temperature condition, has stronger antiblocking ability, has stronger alkali resistant metal toxicity, anti-SO₂Toxicity etc. Low ash catalyst uses medium temperature condition, remains that have anti-SO₂Toxicity. High ash section and the section denitration of low ash require that catalyst has good antiblocking ability and anti-SO₂Toxicity is higher to catalyst requirement. Catalyst can be made from high dust and SO although afterbody is arranged₂Murder by poisoning, it is prevented that catalyst poisoning, but use in temperature catalyst need reheating to waste a large amount of energy consumption. Therefore low-temperature smoke air SCR denitrating system need to be developed in pole, reduces the heating link of flue gas, is substantially reduced energy resource consumption and systematic running cost use, decreases equipment investment scale.

Owing to wet desulphurization conventional at present and denitration processing method, its equipment investment and operating cost are high, produce secondary pollution after fume treatment, and make haze phenomenon day by day serious. Thus how to find and a kind of can obtain higher denitrification efficiency and reduce investment and the process technique of secondary environmental pollution is current problem demanding prompt solution.

Summary of the invention

For the defect that prior art exists when tail gas desulfurization denitration processes, the invention provides a kind of flue gas low-temperature denitration semi-dry desulfurizing process, its technique is simple, energy consumption is low, non-secondary pollution, cleaning of off-gas can qualified discharge, there is certain economic benefit.

For reaching this purpose, present invention employs techniques below scheme:

The invention provides a kind of flue gas low-temperature denitration semi-dry desulfurizing process, comprise the following steps:

(1) tail gas enters low-temperature SCR reactor, with by the NO in tail gas_xIt is reduced to N₂And H₂O;

(2) gas that obtains in step (1) is sent in semi-dry desulphurization response system, and in response system, spray into absorbent carry out desulfurization, with by the acid gas removal in tail gas;

(3) being sent in dust arrester by the gas obtained in step (2), thoroughly to be removed by the dust in tail gas, the purification gas obtained enters air.

The present invention adopts novel low temperature SCR denitration catalyst, by the NO in tail gas_xIt is converted into N₂And H₂O, the low-temperature denitration catalyst of selection can greatly reduce equipment investment and operating cost; Adopt advanced semi-dry desulfurizing process to replace ripe Wet Limestone Desulfurization technique, not only can simplified system flow process, save equipment investment, reduce floor space, and secondary pollution will not be produced, the CaSO that desulfurization produces₃Can also use as construction material. Therefore this technique is compared with traditional desulfurizing and denitrifying process, reduces investment, it is to avoid secondary pollution, has considerable economic benefit, it is ensured that the tail gas after process meets up-to-date discharge standard.

In the present invention, step (1) described tail gas includes NO_x��SO₂��SO₃With HCl etc.

Preferably, the inlet temperature of the described low-temperature SCR reactor of step (1) is 100-260 DEG C, can be such as 100 DEG C, 110 DEG C, 120 DEG C, 130 DEG C, 140 DEG C, 150 DEG C, 160 DEG C, 170 DEG C, 180 DEG C, 190 DEG C, 200 DEG C, 210 DEG C, 220 DEG C, 230 DEG C, 240 DEG C, 250 DEG C, 260 DEG C, outlet temperature is 102-280 DEG C, can be such as 102 DEG C, 110 DEG C, 120 DEG C, 130 DEG C, 140 DEG C, 150 DEG C, 160 DEG C, 170 DEG C, 180 DEG C, 190 DEG C, 200 DEG C, 210 DEG C, 220 DEG C, 230 DEG C, 240 DEG C, 250 DEG C, 260 DEG C, 270 DEG C, 280 DEG C.

Preferably, the described low-temperature SCR reactor of step (1) adopts fixed bed catalytic reactor.

Preferably, the denitrating catalyst adopted in the described low-temperature SCR reactor of step (1) is the catalyst containing rare earth metal active component.

Preferably, step (1) described rare earth metal is the mixture of any one or at least two in scandium, yttrium, lanthanum, cerium or praseodymium, the wherein typical but mixture of certain non-limiting examples is: the mixture of scandium and yttrium, the mixture of lanthanum and cerium, the mixture of yttrium, lanthanum and cerium, the mixture of scandium, yttrium, lanthanum, cerium and praseodymium.

Preferably, the reducing agent that step (1) described reduction is used is NH₃, it would however also be possible to employ other reducing agents.

In the present invention, the described semi-dry desulphurization response system of step (2) includes desulfurization reactor; The semi-dry desulphurization reaction of the present invention carries out in desulfurization reactor.

Preferably, the inlet temperature of described desulfurization reactor is 100-280 DEG C, it can be such as 100 DEG C, 110 DEG C, 120 DEG C, 130 DEG C, 140 DEG C, 150 DEG C, 160 DEG C, 170 DEG C, 180 DEG C, 190 DEG C, 200 DEG C, 210 DEG C, 220 DEG C, 230 DEG C, 240 DEG C, 250 DEG C, 260 DEG C, 270 DEG C, 280 DEG C, outlet temperature is 40-120 DEG C, for instance can be 40 DEG C, 50 DEG C, 60 DEG C, 70 DEG C, 80 DEG C, 90 DEG C, 100 DEG C, 105 DEG C, 110 DEG C, 120 DEG C.

Preferably, in the process of described desulfurization, Ca/S is 1-1.5, for instance calcium sulfur ratio can be 1:1,1:1.1,1:1.15,1:1.2,1:1.25,1:1.3,1:1.35,1:1.4,1:1.45,1:1.5.

Preferably, described absorbent is the Calx through digestive appartus digestion process.

Preferably, described absorbent is to spray into desulfurization reactor with spray pattern; Described absorbent sprays into the temperature of desulfurization reactor and is 40-120 DEG C, for instance can be 40 DEG C, 50 DEG C, 60 DEG C, 70 DEG C, 80 DEG C, 90 DEG C, 100 DEG C, 110 DEG C, 120 DEG C.

In the present invention, step (3) described dust arrester is sack cleaner, electric cleaner or electrostatic fabric filter.

As the preferred technical solution of the present invention, described technique comprises the steps:

(1) tail gas enters low-temperature SCR reactor, the NO in tail gas_xAt reducing agent NH₃Existence under, be converted into N₂And H₂O; The inlet temperature of described low-temperature SCR reactor is 100-260 DEG C, and outlet temperature is 102-280 DEG C; Described low-temperature SCR reactor adopts fixed bed catalytic reactor; The denitrating catalyst adopted in described low-temperature SCR reactor is the catalyst containing rare earth metal active component;

(2) gas that obtains in step (1) is sent in semi-dry desulphurization reactor, and in reactor, spray into absorbent carry out desulfurization, with by the SO in tail gas₂��SO₃Remove with HCl; The inlet temperature of described desulfurization reactor is 100-280 DEG C, and outlet temperature is 40-120 DEG C; In the process of described desulfurization, Ca/S (calcium sulfur ratio) is 1-1.5; Described absorbent is the Calx through digestive appartus digestion process; Described absorbent is to spray into desulfurization reactor with spray pattern; Described absorbent sprays into the temperature of desulfurization reactor and is 40-120 DEG C;

(3) being sent in cleaner unit by the gas obtained in step (2), thoroughly to be removed by the dust in tail gas, the purification gas obtained enters air; Described cleaner unit is sack cleaner, electric cleaner or electrostatic fabric filter.

Compared with prior art, the present invention at least has the advantages that

The present invention adopts novel low temperature SCR denitration catalyst, by the NO in tail gas_xIt is converted into N₂And H₂O, it is possible to greatly reduce equipment investment and operating cost; Adopt advanced semi-dry desulfurizing process to replace ripe Wet Limestone Desulfurization technique, not only can simplified system flow process, save equipment investment and reduce floor space, and secondary pollution will not be produced, the CaSO that desulfurization produces₃Can also use as construction material. Therefore this technique is compared with traditional desulfurizing and denitrifying process, reduces investment, it is to avoid secondary pollution, has considerable economic benefit, it is ensured that the tail gas after process meets up-to-date discharge standard.

Technology process is simple, energy consumption is low, non-secondary pollution, SO for the low-temperature denitration of the present invention and semi-dry desulphurization process₂And NO_xConversion ratio is high, wherein SO₂Conversion ratio >=97%; NO_xConversion ratio >=85%; Tail gas SO after processed by the invention₂��35mg/Nm³, NO_x��50mg/Nm³, dust��5mg/Nm³; Can qualified discharge.

Accompanying drawing explanation

Fig. 1 is low-temp tail gas denitration of the present invention and semi-dry desulphurization processing technological flow figure;

Wherein: 1-low-temperature SCR reactor; 2-desulfurization reactor; 3-cleaner unit; 4-digestive appartus; 5-lime silo; 6-ash feed bin.

Detailed description of the invention

Below in conjunction with the drawings and specific embodiments, the present invention is expanded on further. These embodiments are interpreted as being merely to illustrate the present invention rather than limiting the scope of the invention. After having read the content that the present invention records, the present invention can be made various change or amendment by those skilled in the art, and these equivalence changes and modification fall into the scope of the claims in the present invention equally.

As it is shown in figure 1, the processing technological flow of tail gas is in following example of the present invention: tail gas enters low-temperature SCR reactor 1, the NO in tail gas_xIt is converted into nontoxic N₂And H₂O, then through semi-dry desulphurization reactor 2, the quick lime in lime silo 5 enters reactor 2 after digestive appartus 4 digests and contacts with tail gas and react, with by the SO in tail gas₂��SO₃, the acid gas removal such as HCl, then through cleaner unit 3, the dust in tail gas is thoroughly removed, the purification gas obtained enters air, and the Desulphurization bottom reactor 2 and bottom cleaner unit 3 enters ash feed bin 6.

Following example of the present invention use the waste gas data that certain device discharges, after measured shown in the table composed as follows 1 of this tail gas.

Table 1

Title	Unit	Numerical value
			Total tolerance	Nm3/h	213000
CO2	V%	11.57
			N2	V%	67.96
H2O	V%	18.60
			O2	V%	1.87
SO2	mg/Nm3	1300
			NOx	mg/Nm3	300
Particulate matter	mg/Nm3	��20

Embodiment 1

As shown in Figure 1, tail gas is introduced into low-temperature SCR reactor, adopts scandium, yttrium active constituent catalyst, and entrance temperature of charge controls at 120 DEG C, outlet temperature controls at 123 DEG C, entering back into semi-dry desulphurization reactor, entrance temperature of charge controls at 123 DEG C, and outlet temperature controls at 50 DEG C, finally enter and discharge after cleaner unit processes, it is 80 DEG C that absorbent Calx sprays into the temperature of semi-dry desulphurization reactor, and desulphurization system Ca/S is 1.1, and operating pressure controls at 20kPa.

After measured, in cleaning of off-gas, other constituent contents are: SO₂��35mg/Nm³, NO_x��50mg/Nm³, dust��5mg/Nm³; Wherein SO₂Conversion ratio >=97%, NO_xConversion ratio >=85%.

Embodiment 2

As shown in Figure 1, tail gas is introduced into low-temperature SCR reactor, adopts lanthanum, cerium active constituent catalyst, and entrance temperature of charge controls at 190 DEG C, outlet temperature controls at 193 DEG C, entering back into semi-dry desulphurization reactor, entrance temperature of charge controls at 193 DEG C, and outlet temperature controls at 100 DEG C, finally enter and discharge after cleaner unit processes, it is 70 DEG C that absorbent Calx sprays into the temperature of semi-dry desulphurization reactor, and desulphurization system Ca/S is 1.2, and operating pressure controls at 20kPa.

After measured, in cleaning of off-gas, other constituent contents are: SO₂��35mg/Nm³, NO_x��50mg/Nm³, dust��5mg/Nm³; Wherein SO₂Conversion ratio >=98%, NO_xConversion ratio >=87%.

Embodiment 3

As shown in Figure 1, tail gas is introduced into low-temperature SCR reactor, adopts cerium, praseodymium active constituent catalyst, and entrance temperature of charge controls at 150 DEG C, outlet temperature controls at 153 DEG C, entering back into semi-dry desulphurization reactor, entrance temperature of charge controls at 153 DEG C, and outlet temperature controls at 80 DEG C, finally enter and discharge after cleaner unit processes, it is 80 DEG C that absorbent sprays into the temperature of semi-dry desulphurization reactor, and desulphurization system Ca/S is 1.3, and operating pressure controls at 20kPa.

After measured, in cleaning of off-gas, other constituent contents are: SO₂��35mg/Nm³, NO_x��50mg/Nm³, dust��5mg/Nm³; Wherein SO₂Conversion ratio >=98%, NO_xConversion ratio >=90%.

Embodiment 4

As shown in Figure 1, tail gas is introduced into low-temperature SCR reactor, adopts yttrium, lanthanum active constituent catalyst, and entrance temperature of charge controls at 170 DEG C, outlet temperature controls at 173 DEG C, entering back into semi-dry desulphurization reactor, entrance temperature of charge controls at 173 DEG C, and outlet temperature controls at 90 DEG C, finally enter and discharge after cleaner unit processes, it is 80 DEG C that absorbent sprays into the temperature of semi-dry desulphurization reactor, and desulphurization system Ca/S is 1.4, and operating pressure controls at 20kPa.

After measured, in cleaning of off-gas, other constituent contents are: SO₂��35mg/Nm³, NO_x��50mg/Nm³, dust��5mg/Nm³; Wherein SO₂Conversion ratio >=98.5%, NO_xConversion ratio >=92%.

Applicant states, the present invention illustrates detailed process equipment and the technological process of the present invention by above-described embodiment, but the invention is not limited in above-mentioned detailed process equipment and technological process, namely do not mean that the present invention has to rely on above-mentioned detailed process equipment and technological process could be implemented. The equivalence of each raw material of product of the present invention, it will be clearly understood that any improvement in the present invention, is replaced and the interpolation of auxiliary element, concrete way choice etc. by person of ordinary skill in the field, all falls within protection scope of the present invention and open scope.

Claims (5)

1. a flue gas low-temperature denitration semi-dry desulfurizing process, it is characterised in that comprise the following steps:

(1) tail gas enters low-temperature SCR reactor, with by the NO in tail gas_xIt is reduced to N₂And H₂O;

(2) gas that obtains in step (1) is sent in semi-dry desulphurization response system, and in response system, spray into absorbent carry out desulfurization, with by the acid gas removal in tail gas;

(3) being sent in dust arrester by the gas obtained in step (2), thoroughly to be removed by the dust in tail gas, the purification gas obtained enters air.

2. technique according to claim 1, it is characterised in that in step (1), described tail gas includes NO_x��SO₂��SO₃And HCl;

Preferably, the inlet temperature of described low-temperature SCR reactor is 100-260 DEG C, and outlet temperature is 102-280 DEG C;

Preferably, described low-temperature SCR reactor adopts fixed bed catalytic reactor;

Preferably, the denitrating catalyst adopted in described low-temperature SCR reactor is the catalyst containing rare earth metal active component;

Preferably, described rare earth metal is the mixture of any one or at least two in scandium, yttrium, lanthanum, cerium or praseodymium;

Preferably, the reducing agent that described reduction is used is NH₃��

3. technique according to claim 1 and 2, it is characterised in that in step (2), described semi-dry desulphurization response system includes desulfurization reactor;

Preferably, the inlet temperature of described desulfurization reactor is 100-280 DEG C, and outlet temperature is 40-120 DEG C;

Preferably, in the process of described desulfurization, Ca/S is 1-1.5;

Preferably, described absorbent is the Calx through digestive appartus digestion process;

Preferably, described absorbent is to spray into desulfurization reactor with spray pattern; Described absorbent sprays into the temperature of desulfurization reactor and is 40-120 DEG C.

4. the technique according to any one of claim 1-3, it is characterised in that in step (3), described dust arrester is sack cleaner, electric cleaner or electrostatic fabric filter.

5. the technique according to any one of claim 1-4, it is characterised in that described technique comprises the steps:

(1) tail gas enters low-temperature SCR reactor, the NO in tail gas_xAt reducing agent NH₃Existence under, be converted into N₂And H₂O; The inlet temperature of described low-temperature SCR reactor is 100-260 DEG C, and outlet temperature is 102-280 DEG C; Described low-temperature SCR reactor adopts fixed bed catalytic reactor; The denitrating catalyst adopted in described low-temperature SCR reactor is the catalyst containing rare earth metal active component;

(2) gas that obtains in step (1) is sent in semi-dry desulphurization reactor, and in reactor, spray into absorbent carry out desulfurization, with by the SO in tail gas₂��SO₃Remove with HCl; The inlet temperature of described desulfurization reactor is 100-280 DEG C, and outlet temperature is 40-120 DEG C; In the process of described desulfurization, Ca/S (calcium sulfur ratio) is 1-1.5; Described absorbent is the Calx through digestive appartus digestion process; Described absorbent is to spray into desulfurization reactor with spray pattern; Described absorbent sprays into the temperature of desulfurization reactor and is 40-120 DEG C;

(3) being sent in cleaner unit by the gas obtained in step (2), thoroughly to be removed by the dust in tail gas, the purification gas obtained enters air; Described cleaner unit is sack cleaner, electric cleaner or electrostatic fabric filter.