CN1207084C

CN1207084C - Method of flue gas desulfurization by through steam to toransport materiel

Info

Publication number: CN1207084C
Application number: CN 02129383
Authority: CN
Inventors: 张凡; 陈复; 姚允升; 石应杰; 王红梅; 林军; 王凡
Original assignee: Chinese Research Academy of Environmental Sciences
Current assignee: Chinese Research Academy of Environmental Sciences
Priority date: 2002-09-06
Filing date: 2002-09-06
Publication date: 2005-06-22
Anticipated expiration: 2022-09-06
Also published as: CN1480245A

Abstract

The present invention relates to a method of smoke gas desulphurization by using steam for conveying materials. A desulphurization agent (CaO) and desulphurization ash materials are conveyed into a desulphurization tower by a venturi conveyer by making use of high-pressure steam generated by a boiler. When the materials are conveyed by the steam, CaO is converted into wet Ca (OH) 2, and alkali oxide in the desulphurization ash is converted into alkali hydroxide. Consequently, the utilization ratio of Ca in the desulphurization agent is improved; the alkali substances in the desulphurization ash are fully utilized; simultaneously, a high pressure fan required for conveying by means of wind force is saved; the work of electric power consumption and equipment maintenance is reduced. Simultaneously, after the flue gas is humidified, the moisture content of the smoke gas is increased within a certain range; the electrical conduction performance of dust is improved; the smoke temperature is reduced; the specific resistance of smoke dust is improved. The method of the present invention has an obvious function to improve the dust removing efficiency of a dust remover. The alkali performance of the desulphurization agent and the desulphurization ash is activated through steam conveying; that the desulphurization efficiency can reach 80% to 95% under the condition that Ca/S is less than 1 is realized.

Description

Flue gas desulfurization method for conveying materials by using steam

Technical Field

The invention relates to the technical field of boiler flue gas desulfurization in atmospheric environmental pollution treatment, is mainly applicable to the application technology in the flue gas desulfurization of various industrial and power station boilers taking high, medium and low-sulfur coal and the like as fuels, and is a flue gas desulfurization method for conveying materials by using steam

Background

Currently, flue gas desulfurization is the main means for controlling sulfur dioxide, and common methods include wet method, dry method and semi-dry method. Wherein the desulfurizer commonly used in the wet method is CaCO₃The common desulfurizer used in the dry and semi-dry methods is quicklime (CaO), and the conveying mode of the desulfurizer in the dry and semi-dry methods is mostly high-pressure air conveying, which needs to consume a large amount of electric energy to cause continuous noise pollution, and the high calcium-sulfur ratio causes overhigh cost of the desulfurizer. When in use, the high pressure fan conveys CaO into the desulfurizing tower through the Venturi conveyor, the CaO and SO in the flue gas₂Chemical reaction is carried out to generate solid CaSO₃To remove SO in the flue gas₂The purpose of (1). To react with SO₂The reaction is sufficient and CaO is usually in excess, so there is a large amount of unreacted CaO in the desulphurised ash. The excessive CaO increases the desulfurization cost, so the reduction of the consumption of CaO and the improvement of the utilization rate of calcium are important problems to be solved in the flue gas desulfurization. There are two general approaches: (1) the high-pressure fan is used for inputting a large amount of desulfurization ash into the desulfurizing tower for circulating desulfurization for many times through the Venturi conveyer SO as to increase CaO and SO₂The contact opportunity of (2) improves the utilization efficiency of CaO; (2) the activity of alkaline substances in the desulfurizer (CaO) and the (desulfurized fly ash) is improved to the maximum extent, and the dosage of the desulfurizer is reduced.

Disclosure of Invention

The invention aims to provide a flue gas desulfurization method for conveying materials by using steam, which has the advantages of simple process, lower cost and better desulfurization effect, and simultaneously increases the moisture content of flue gas in a certain range after the flue gas is humidified, improves the electric conductivity of dust, reduces the temperature of the flue gas, and has obvious effects of improving the specific resistance of the flue gas and improving the dust removal efficiency of a dust remover.

In order to achieve the purpose, the invention adopts the following design scheme:

a flue gas desulfurization method for conveying materials by using steam is characterized in that: conveying a desulfurizer (CaO) and a desulfurized ash material into a desulfurizing tower by high-pressure steam through a Venturi conveyor, and changing the CaO into alkaline Ca (OH) while conveying the material by the steam₂And changing the basic oxides in the desulfurized fly ash into basic hydroxides.

The steam temperature is 150-270 ℃, and the steam pressure is 5-10 Kg/cm²。

The desulfurized ash refers to the tower bottom ash output from the bottom of the desulfurization tower.

The desulfurization ash refers to tower bottom ash output from the bottom of the desulfurization tower and dust removed from the bottom of the dust remover.

The invention belongs to a second mode, namely, the activity of alkaline substances in a desulfurizer (CaO) and (desulfurized fly ash) is improved to the maximum extent, and the dosage of the desulfurizer is reduced.

In desulfurization ashThe main component of unused CaO is fly ash, and although the components in the fly ash are greatly changed, the average content of basic oxides such as calcium, magnesium, potassium, sodium and the like is more than 10 percent. The alkaline substance in the fly ash is burnt at high temperature of a boiler furnace, belonging to the over-burnt alkaline substances, such as CaO, and the CaO which is not over-burnt can quickly generate Ca (OH) in water₂The excessive burning of CaO in water takes 30 to 50 minutes to generate Ca (OH)₂Therefore, the activity of the overburnt alkaline substance in the fly ash and the overburnt CaO in the desulfurizer needs to be rapidly activated, so that the using amount of the desulfurizer can be effectively reduced.

The desulfurizing agent and the desulfurization ash (fly ash) are conveyed by steam, and simultaneously the following reactions occur:

as can be seen from the above reaction, under steam conditions, the fly ash releases many alkaline substances mainly comprising calcium, and the alkaline substances and SO in the flue gas₂The reaction is rapidly carried out to generate sulfite, so that the method has practical significance in the desulfurization process and can improve the desulfurization effect.

The invention has the advantages that:

the steam conveying desulfurizer and desulfurized ash in the flue gas desulfurization has the following advantages:

(1) the utilization rate of calcium is improved: CaO, in particular over-burnt CaO, is conveyed by steam under the action of steamTo Ca (OH)₂Activating the alkaline matter in the desulfurized fly ash, converting the desulfurizer and the over-burnt alkaline metal oxides (calcium, magnesium, iron, sodium, potassium and titanium) in the desulfurized fly ash into corresponding hydroxides, improving the utilization rate of Ca, and leading the mole number of CaO in the desulfurizer and the SO in the flue gas to be equal to each other₂The ratio of the total mole number is less than 1(Ca/S is less than 1), and the desulfurization efficiency can reach 80-95%.

(2) The technology is feasible: through the continuous operation of more than 2000 hours demonstration engineering, the system desulfurization efficiency is stable, steam participates in the reaction while conveying materials, the reaction time in the desulfurization tower is reduced, the water injection quantity in the tower is obviously reduced, and the scaling phenomenon of a wet wall and the tower bottom is thoroughly solved.

(3) And (3) economic and cost-effective: the high-pressure fan and supporting facilities of the air conveying equipment are reduced, the power consumption and the equipment maintenance work are reduced, the investment and the operating cost are reduced, meanwhile, the process flow is simplified, the system noise is reduced, and the working environment is improved.

(4) Since fly ash is a waste of coal-fired boilers,its use in flue gas desulfurization would be attractive both in economic and environmental benefits.

(5) After the flue gas is humidified, the moisture content of the flue gas is increased in a certain range, the dust conductivity is improved, the flue gas temperature is reduced, and the flue gas humidifying device has obvious effects of improving the specific resistance of the flue gas and improving the dust removal efficiency of a dust remover.

Drawings

FIG. 1 is a flow chart of the semi-dry semi-wet flue gas desulfurization steam delivery process of the present invention.

FIG. 2 is a schematic diagram of a Venturi conveyor for conveying desulfurizing agent and desulfurized ash, which are main devices for steam conveying.

Detailed Description

Example 1:

referring to fig. 1 and 2: through 35tThe test run of 2160 hours of the boiler flue gas desulfurization demonstration project of/h obtains better test effect, the steam comes from the coal-fired boiler itself, send into the Venturi conveyer through the heat-insulating steam pipeline, the steam temperature is 210 ℃, the steam pressure is 6Kg/cm²The steam pipeline is provided with a flowmeter and a pressure gauge for metering and adjusting the flow and pressure of the steam.

The flue gas generated by the boiler enters the desulfurizing tower from the top, reacts with the desulfurizing agent conveyed by steam, the desulfurized ash and the water mist sprayed in the tower in the desulfurizing tower, the reacted flue gas enters the dust remover from the bottom of the tower, and the dedusted flue gas is discharged from the chimney.

As can be seen from fig. 1, there are three applications of steam delivery: the method is respectively used for conveying the bottom ash of the desulfurizing tower, the ash discharged from a dust remover and the fresh desulfurizing agent (CaO).

Steam 1: the desulfurization ash collected at the bottom of the desulfurization tower is sent into a flue by a Venturi conveyor 3 in a manner of conveying by a steamer, and SO in the flue gas₂Carrying out desulfurization reaction with the desulfurization ash in a flue;

steam 2: the desulfurization ash collected under the dust remover is blown into the top of the desulfurization tower by a Venturi conveyor 3 in a manner of conveying by a steamer, and enters the desulfurization tower together with the flue gas for desulfurization reaction;

and (3) steam: fresh desulfurizer (CaO) is blown into a flue at the top of the desulfurization tower by a Venturi conveyor 3 in a manner of conveying by a steamer and enters the desulfurization tower together with flue gas for desulfurization reaction.

As can be seen from FIG. 2, the desulfurizing agent and the desulfurized ash stored in the storage bin 1 are fed to the upper part of the steam Venturi conveyor 3 by the gravity and the system negative pressure through the high vacuum quantitative feeder 2, the steam 6 metered by the steam flowmeter enters the Venturi conveyor 3 from the left end, is mixed with the desulfurizing agent (ash) from the upper part, and is blown out from the Venturi outlet to enter the desulfurizing tower 4. When the system is preheated and started, steam condensate water is generated and is discharged from the ball valve 5 at the lower end of the venturi conveyor 3, and when the negative pressure of the system is adjusted, a small amount of powder is accumulated at the bottom of the venturi and is also discharged from the ball valve 5 at the lower end of the venturi conveyor.

Example 2:

the conditions of the implementation are the same as above, wherein the steam temperature is 150 ℃, and the steam pressure is 5Kg/cm²。

Example 3:

the conditions of the implementation are the same as above, wherein the steam temperature is 270 ℃, and the steam pressure is 10Kg/cm²。

Claims

1. A flue gas desulfurization method for conveying materials by using steam is characterized in that: the desulfurizer CaO and the desulfurized ash are conveyed into a desulfurizing tower by high-pressure steam through a Venturi conveyor, and the CaO is changed into alkaline Ca (OH) while the materials are conveyed by the steam₂And changing the basic oxides in the desulfurized fly ash into basic hydroxides.

2. The flue gas desulfurization method according to claim 1, characterized in that: the steam temperature is 150-270 ℃, and the steam pressure is 5-10 Kg/cm²。

3. The flue gas desulfurization method according to claim 1 or 2, characterized in that: the desulfurized ash refers to the tower bottom ash output from the bottom of the desulfurization tower.

4. The flue gas desulfurization method according to claim 1 or 2, characterized in that: the desulfurization ash refers to tower bottom ash output from the bottom of the desulfurization tower and dust removed from the bottom of the dust remover.