CN1154263A

CN1154263A - Method and equipment for desulfurizing flue gas by circulation and fluidization

Info

Publication number: CN1154263A
Application number: CN 96100084
Authority: CN
Inventors: 彭斯干; 胡方荪; 唐崇武; 梁汉桥
Original assignee: Shenzhen Jingyuan Environmental Protection Technology Co Ltd; ZHONGNAN ELECTRIC POWER PRODUCTION DESIGN INST MINISTRY OF ELECTRIC POWER
Current assignee: Shenzhen Jingyuan Environmental Protection Technology Co Ltd; ZHONGNAN ELECTRIC POWER PRODUCTION DESIGN INST MINISTRY OF ELECTRIC POWER
Priority date: 1996-01-11
Filing date: 1996-01-11
Publication date: 1997-07-16
Anticipated expiration: 2016-01-11
Also published as: CN1087645C

Abstract

The hot flue gas is passed through a desulfurizing tower with a velocity of 3-12 m/s for 1-10 seconds, and contacts with the absorbent or cycling reactant which is entering the desulfurizing tower, and react to form mixtures and compounds which enter the dust eliminator with the flue gas. The dust eliminator is connected with the desulfurizing tower. Most of the solid reactants collected in the dust eliminator are sent back to the desulfurizing tower for reuse. The flue gas purified by the dust eliminator may further pass through a dust eliminator then exhaust to the atmosphere.

Description

Flue gas circulating fluidized method desulfurization process and device

The invention relates to a flue gas circulating fluidized method desulfurization method and a desulfurization device thereof, belonging to the technical field of environmental protection of industrial flue gas purification, being applicable to the desulfurization of industrial flue gas such as coal and flue gas discharged by an oil-fired boiler, in particular to the desulfurization of flue gas discharged by combustion equipment of a thermal power plant. The process belongs to the field of desulfurizing technology.

The existing semi-dry type flue gas desulfurization method is mainly a rotary spraying method and is characterized in that: flue gas enters from the lower part of the desulfurization tower, and lime slurry enters from the upper part and is sprayed on a high-speed rotating wheel to atomize the lime slurry. SO in atomized lime slurry and flue gas₂And directly discharging waste residues generated after the reaction from the bottom of the tower. The disadvantages of this method are: 1. the utilization rate of the absorbent is low, and the calcium-sulfur ratio is high, namely the lime consumption is large; 2. the desulfurization efficiency is relatively low; 3. the lime slurry is sprayed into a mist shape by the high-speed rotating wheel, and the lime slurry and reaction products are very easy to adhere to the inner wall of the tower to form scale, so that the volume in the tower is influenced, the tower body is corroded, and the maintenance cost is increased; 4. the spraying wheel is a vulnerable part and is expensive, and the rotating speed of the wheel is high, so that the spraying wheel is difficult to be made into a large size, and the scale of the desulfurizing tower is influenced. The other semi-dry desulfurizing method is biphase flow spraying method, which uses compressed air and lime slurry to enter the tower simultaneously to realize atomization without rotating wheel, the flue gas and the lime slurry flow relatively, and the waste slag is discharged from the bottom of the tower directly. The above methods all have the problem that the absorbent channel is easy to block because the requirement on the granularity of the absorbent is high.

The invention aims to: the method overcomes the defects of the method and provides a semi-dry abandon process, namely a flue gas circulating fluidized desulfurization method and a desulfurization device thereof, so as to improve the desulfurization efficiency, greatly reduce the system manufacturing cost and the operation and maintenance cost, and improve the system reliability to ensure the quality of the atmospheric environment.

The method of the invention is realized by the following steps: the hot flue gas discharged from industrial equipment is passed through Venturi-shaped desulfurizing tower at the speed of 3-12m/s for 1-10 seconds, and contacted with fluidized absorbent and cyclically-used reactant in the desulfurizing tower, then these mixtures or compounds are fed into dust-removing equipment connected with desulfurizing tower together with flue gas; the dust remover sends most of the collected solid reactants to the desulfurizing tower again for recycling; the flue gas dedusted by the deduster can be discharged into the atmosphere after being dedusted again or directly discharged into the atmosphere.

The principle of the technical scheme of the method is as follows:

the hot flue gas enters the vertical Venturi desulfurization tower from the lower part or the upper part of the vertical Venturi desulfurization tower, and contacts and mixes with fluidized solid particles consisting of calcium hydroxide and recycled reactants. Fresh lime slurry can be directly sprayed into the desulfurizing tower by a double-phase flow nozzle, and the water in the lime slurry humidifies flue gas to improve SO₂The removal rate of (3). Because the system has a relatively high flue gas flow velocity (which can be 7.5m/s generally), the system is convenient for flowing and conveying the particles in the desulfurizing tower and simultaneously promoting SO₂And the reaction of the particulate matter. The spent solids and fly ash are carried out of the top of the desulfurization tower and collected in a dust separator (typically a cyclone) connected to the desulfurization tower. Most of the solids collected by the dust collector are recycled to the desulfurization tower, so that the residual absorbent in the solids can be fully utilized, and the solids can be humidified again, thereby providing more reaction surface area. The residual solids in the flue gas, such as fly ash, etc., can be removed by a downstream dust collector, typically an electric dust collector or a bag-type dust collector.

In the method of the invention, the chemical reaction process and the corresponding reaction formula of the reactants are as follows:

1, lime slurry: calcium hydroxide slurry was formed from quicklime digested with water:

2 the lime slurry enters a desulfurizing tower (is sprayed into the desulfurizing tower by a double-phase flow nozzle) and reacts with the flue gas with the temperature of about 130 ℃ in the tower, and the reaction formula is as follows:

compared with other semi-dry process technologies, the invention has the advantages that:

1 the solid reactant returned by the dust remover is recycled, so that the concentration of solid particles in the desulfurizing tower is very high and can be generally as high as 500-1500 g/Nm³This concentration is 50-100 times the concentration in a typical spray drying process. Meanwhile, as the solid particles in the desulfurizing tower are rapidly dried in the fluidizing process, the scaling problem which usually occurs in the common spray drying process can be avoided in the tower.

2 because of the quite long contact time of the flue gas and the reactant of the absorbent, the contact time is obtained by depending on that the lime particles pass through the desulfurizing tower for hundreds of times of circulation, thereby greatly improving the utilization rate of the absorbent.

The recycled reactant 3 has the advantages that the surface of the recycled reactant is continuously coated with a new absorbent, and the activity of the product of the fly ash and the lime slurry in a hot state is enhanced, so that the capability of absorbing sulfur dioxide is greatly improved compared with that of a pure lime slurry absorbent.

4 the system has simple structure, low cost, low operation and maintenance cost and high desulfurization efficiency.

Compared with a wet limestone/gypsum method, the method has the main advantages that:

1) the scale formation and corrosion are reduced, and the equipment investment and maintenance cost are reduced; this is because the reducing liquid contacts the flue gas and rarely contacts the walls of the system. Therefore, equipment such as a slurry tank can be made of low carbon steel without using a rust-proof lining.

2) The invention has the advantages of small dosage of washing liquid, small number of pumps and low energy consumption. The product of the present invention can be treated with a conventional fly ash system due to drying, and a dewatering system is not required.

3) The flue gas discharged by the system of the invention does not need to be reheated, thereby reducing the manufacturing cost and energy consumption.

The method and the desulfurization device thereof are further described by combining the drawings and the examples as follows:

FIG. 1 is a schematic diagram of the apparatus and process flow of the process of the present invention.

FIG. 2 is a schematic view of a desulfurization unit of the present invention.

The device names included in the figure are: 1 combustion equipment (e.g. boilers); 2, a desulfurizing tower; 3 an absorbent inlet; 4, recycling and conveying the reactant; 5 dust collectors (such as cyclone dust collectors); 6 dust remover (such as electric dust remover); 7, a fan; 8, a chimney; 9 a flue gas channel; 10 a flue gas inlet; 11 a desulfurized flue gas discharge channel; 12 a flue gas outlet; 13 a slag discharge channel; 14 a circulating reactant channel; 15 a reactant inlet; 16 slag discharge ports; 17 a nozzle; 18 compressed air inlet.

The process of the invention, the flow diagram of which shows, is that hot flue gases are discharged fromthe combustion device (1), can be pressurized and accelerated to be sent to the desulfurization tower (2), the reactant in the desulfurization tower being the SO to be removed from the flue gases₂Solid fly ash (carried over from the fuel), and lime slurry, i.e. calcium hydroxide, sprayed into the desulfurization tower through an absorbent inlet (3), and the remaining reactants, which are collected by a dust collector (5) and returned to the desulfurization tower (2) through a reactant recycling conveyor (4). The speed of the flue gas flowing through the desulfurizing tower can be 3m/s, and the time of the flue gas flowing through the desulfurizing tower is 10 seconds; or 12m/s, and the flowing time is 1 second; most preferably, the velocity is 7.5m/s and the flow time is 3 seconds. The flue gas enters the tower from the lower part or the upper part of a vertically arranged Venturi desulfurization tower, and the lime slurry and the circulating reactant simultaneously enter the tower to participate in the reaction. The calcium-to-sulfur ratio (Ca/S) of the desulfurization system is 1.2 to 1.4, and may be 1.3. At this time, the desulfurization rate can reach 90 percent. When the calcium-sulfur ratio is 1.0, the desulfurization efficiency can reach more than 75 percent. A two-phase flow nozzle is arranged at the center of the tower, so that the absorbent liquid drops are dispersed in a good water mist form, and the reactants are fully reacted in the tower. The dust remover (5) into which the flue gas discharged from the desulfurizing tower (2) enters can be a cyclone dust remover; associated with the dust remover isAn electric dust collector or a bag-type dust collector for further dust removal. To further illustrate the present invention, the following is further exemplified:

flue gas flow 100 ten thousand Nm³/h

The flue gas temperature (outlet of air preheater) is 136 DEG C

Time of flue gas flowing through the tower: 3S

Velocity of flue gas flowing through the tower: 7.5m/s

A dust remover: the first stage is a cyclone dust collector, and the second stage is an electric dust collector;

calcium to sulfur ratio (Ca/s): 1.3

The effect is as follows: the desulfurization rate is as high as more than 90%.

The invention relates to a desulphurization device of a desulphurization method by a circulating fluidization method, which has the technical scheme that: it comprises a desulfurizing tower (2); the desulfurizing tower is provided with a flue gas inlet (10), an absorbent inlet (3) and a desulfurized flue gas discharge channel (11); it is characterized in that the desulfurizing tower is also provided with an input port (15) for the recycled reactant to enter the tower; the inlet (15) and the absorbent inlet (3) are positioned near the flue gas inlet (10); the desulfurized flue gas discharge channel (11) is connected with the dust remover (5); the slag discharge channel (13) of the dust remover is communicated with a conveying device (4) which can send slag materials into the tower as a circulating reactant for recycling.

In fig. 2: the absorbent inlet (3) and the compressed air inlet (18) may share a nozzle (17) which may be located at the flue gas inlet (10) of the desulfurization tower (2).

The device of the invention has the advantages that: the absorbent has high utilization rate, high desulfurization efficiency, no scale formation in the tower, reliable operation, no need of special operation and management, and low requirement on the absorbent, thereby having low cost and operation cost.

Claims

A flue gas circulating fluidized method desulfurization method is characterized in that hot flue gas passes through a desulfurization tower at the speed of 3-12m/s and the time of 1-10 seconds, and contacts, mixes and reacts with a sulfur dioxide absorbent and a reactant entering the desulfurization tower, and the generated mixture or reactant enters a dust remover connected with the desulfurization tower along with the flue gas; the dust remover repeatedly sends the collected solid mixture or reactant to the desulfurizing tower for recycling; the flue gas purified by the dust remover can be discharged into the atmosphere after being dedusted again or directly discharged into the atmosphere.
2, the desulfurization process of claim 1, wherein the reactant in the desulfurization tower is SO in flue gas₂The solid fly ash and the absorbent injected into the desulfurization tower can be lime slurry, i.e., calcium hydroxide, and the recycled reactants which are collected by the dust collector and returned to the desulfurization tower.
The desulfurization method according to claim 1, wherein the velocity of the flue gas flowing through the desulfurization tower is 3m/s, and the time of the flue gas flowing through the tower is 10 seconds; or 12m/s, and the flowing time is 1 second; the optimum speed is 7.5m/s and the flow time is 3 seconds.
The desulfurization method according to claim 1, wherein the flue gas enters the tower from the lower part or the upper part of a vertically arranged Venturi desulfurization tower, and the lime slurry and the recycled reactant enter the tower simultaneously to react.
The method according to claim 1, wherein the calcium-sulfur ratio of the reactants in the desulfurization tower is 1.2 to 1.4, and the corresponding desulfurization efficiency is 70 to 95%.
A desulfurization method according to any one of the preceding claims, characterized in that the dust collector into which the flue gas discharged from the desulfurization tower enters can be a cyclone dust collector, and the dust collector connected thereto for further dust collection can be an electric dust collector or a bag-type dust collector.
A desulfurization device of a desulfurization method by a circulating fluidized method comprises a desulfurization tower (2); the desulfurizing tower is provided with a flue gas inlet (10), an absorbent inlet (3) and a desulfurized flue gas discharge channel (11); it is characterized in that the desulfurizing tower is also provided with an input port (15) for the recycled reactant to enter the tower; the inlet (15) and the absorbent inlet (3) are positioned near the flue gas inlet (10); the desulfurized flue gas discharge channel (11) is connected with the dust remover (5); the slag discharge channel (13) of the dust remover is communicated with a conveying device (4) which can send slag materials into the tower as a circulating reactant for recycling.
An apparatus according to claim 7, characterized in that the absorbent inlet (3) and the compressed air inlet (18) share a nozzle (17) which is located at the flue gas inlet (10) of the desulfurization tower (2).