CN1088392C

CN1088392C - Dry absorbent smoke desulfuration process

Info

Publication number: CN1088392C
Application number: CN98111735A
Authority: CN
Inventors: 王晋宁; 陈德放
Original assignee: Individual
Current assignee: Individual
Priority date: 1998-12-24
Filing date: 1998-12-24
Publication date: 2002-07-31
Anticipated expiration: 2018-12-24
Also published as: CN1229691A

Abstract

The present invention discloses a method for desulfurizing fume by a dry absorbent. High-voltage static generation equipment is used for generating a high-voltage static corona zone in charge powder spraying equipment, absorbent granules passing through the zone have the same kind of electric charge, and then, the absorbent with the electric charge is sprayed in the proper position of a fume channel. The absorbent reacts with SO2 in the fume to generate granular substances which are removed by dust removing equipment. Because the absorbent used for the method has the same kind of electric charge, the absorbent is uniformly distributed in the fume, and activity is high. Thereby, the removal rate of the SO2 can be effectively improved, and desulfurization efficiency reaches 70 to 80%. The present invention has the advantages of equipment investment saving, small occupation area, little electric consumption, no reduced thermal boiler efficiency without production stop during maintenance, long service life, etc.

Description

Dry absorbent flue gas desulfurization method

The invention belongs to the technical field of environmental protection, and particularly relates to a dry-type absorbent flue gas desulfurization method. At present, it is popular at home and abroadMature flue gas desulfurization processes are wet and semi-dry processes. Although the two desulfurization methods can achieve the purpose of desulfurization, the popularization and the application of the two desulfurization methods are limited due to the following reasons: (1) the investment of the desulphurization device is high, and the investment accounts for 8-25% of the total investment of the power station; (2) the occupied area is large, and the occupied area of a desulfurizing device used by one 220t/h boiler reaches 1500m²(ii) a (3) The power consumption is high, and the power consumption is about 3-7% of that of the power station; (4) because the desulphurization device is a part of the boiler smoke exhaust system, the normal operation of the boiler is influenced once the desulphurization device fails; (5) because the procedures of temperature reduction, desulfurization and temperature rise and smoke exhaust are adopted, the thermal efficiency of the boiler is reduced, and the like. Although the existing dry-method desulfurization technology is greatly improved compared with the two methods, no dry-method flue gas desulfurization device which can be used for engineering maturity exists so far. The traditional dry flue gas desulfurization technique is to spray alkaline absorbent (generally CaO or Ca (OH)) into the flue gas₂) Absorbent and SO in flue gas₂Chemical reaction is carried out to generate sulfite (CaSO)₃And a small amount of CaSO₄) Thereby achieving the aim of desulfurization. However, no obvious development is available in recent two thirty years, and the main reason that the traditional dry desulfurization technology is slow in development is that the desulfurization efficiency always lingers about 20% due to the following two technical problems which are not solved.

1. The gas/solid contact time is long and the reaction speed is slow.

The temperature of the boiler flue gas is usually less than 200 ℃, under which conditions the sorbent and SO are present₂Only slow sulfitation reactions can be generated, the gas/solid contact time is at least 4 seconds, and the flow speed of the flue gas is generally 10-15m/s, which means that the flue gas needs at least 40-60m of flue before entering the dust removal equipment, which is unrealistic in terms of floor space, capital investment, flue gas temperature reduction and the like.

2. The sorbent is not uniformly distributed in the flue gas.

Even if the conditions of gas/solid contact time and reaction temperature are satisfied, it is difficult to uniformly suspend and distribute the absorbent in the flue gas and the SO₂The reaction occurs due to the extremely small particle sizeThe absorbent is gathered together again after entering the flue to form larger particles, so that the specific surface area of the absorbent is greatly reduced, the activity is reduced, and the desulfurization efficiency is greatly reduced. Moreover, the absorbent rapidly falls to the bottom of the flue due to the increase of the particle size and the increase of the self-weight. In addition, it is difficult to ensure that the sorbent is uniformly diffused in the flue, no matter where it is sprayed, the sorbent is collected on either side of the flue, or only in the center of the flue. For the above reasons, the conventional dry desulfurization technology is difficult to be popularized and applied in industry.

The invention aims to provide a novel flue gas desulfurization method, which can ensure that an absorbent is uniformly distributed in flue gas and has high reaction speed, thereby greatly improving the desulfurization efficiency and having small occupied area and less investment.

The purpose of the invention is realized by the following technical scheme: a dry absorbent fume desulfurizing apparatus is designed, and a high-voltage electrostatic generating device is used to generate a high-voltage electrostatic corona region in a charging and dusting device, when the absorbent passes through the region, the same electrostatic charges are carried, and then the absorbent with charges (usually Ca (OH) is sprayed into the proper position in the flue₂) Absorbent and SO in flue gas₂A chemical reaction is carried out to generate GaSO₃And a small amount of CaSO₄The granular substances are removed by the subsequent dust removing equipment, and the reaction formula is as follows;

since flue gas also contains small amounts of oxygen and moisture, the following reactions may also occur:

when the absorbent is sprayed into the flue gas through the spray pipe, the absorbent particles are mutually repelled due to the same electrostatic charge, and rapidly diffused in the flue gas to be in a uniformly distributed suspension state, and each absorbent particle is fully exposed in the flue gas, SO that the absorbent and SO₂The chance of the reaction is greatly increased and,thereby greatly improving the desulfurization efficiency. The activity of the absorbent is greatly improved after the absorbent is charged, and the absorbent and SO are reduced₂The gas/solid contact time required for the reaction is generally 2 seconds to complete the sulfitation reaction, thereby effectively increasing the SO₂The removal rate of (3). In addition, the charged absorbent particles can adsorb fine dust particles on the surfaces of the absorbent particles to form larger particles, so that the average particle size of the dust in the flue gas is increased, and the removal efficiency of the dust removal equipment on the fine dust particles can be improved.

The invention has the following positive effects:

1. the desulfurization efficiency is high. When SO in flue gas₂The concentration is 2000mg/Nm³In the above process, the desulfurization efficiency of the dry-type absorbent flue gas desulfurization device reaches 70-80%;

2. the occupied area is small. The dry absorbent flue gas desulfurization device occupies 1/20-1/15 of wet and semi-dry desulfurization devices. For example, a dry absorbent flue gas desulfurization device for 220t/h boiler desulfurization has the floor area of only 100m²Left and right;

3. the investment is saved. The investment of the dry-type absorbent flue gas desulfurization device accounts for about 4 percent of the total investment of the power station;

4. the power consumption is low. The power consumption of the dry-type absorbent flue gas desulfurization device is only about 0.2 percent of the generated energy;

5. the heat efficiency of the boiler is not reduced, the exhaust gas temperature is not reduced, and the normal operation of the boiler is not influenced no matter the desulphurization device is operated or overhauled;

6. the service life of the equipment is long. Because no mechanical rotating part is arranged in the powder spraying equipment, and Ca (OH)₂Has a small specific gravity and thus has a long life.

7. Can be used in combination with various dust-removing equipment (electric dust remover, bag-type dust remover, water film dust remover, etc.).

The invention is further described with reference to the following examples and figures: FIG. 1 is a flow diagram of a dry absorbent flue gas desulfurization process. As shown in figure 1, the invention comprises a storage feeding unit, a charging and powder spraying unit and a computer control unit.

1. A storage and feeding unit: mainly comprises an absorbent storage device 6 and a feeding device 7. The storage device 6 is used for storing the absorbent and has a volume which is generally dimensioned for a dosage of 1 to 2 days. The feeding device 7 should select a motor with stepless speed regulation to regulate the feeding amount.

2. The charging and powder spraying unit: the unit should include a high voltage static electricity generating device 8, a gas-powder mixing device 10, a high voltage blower 5, etc. The feeding device 7 feeds the absorbent into the gas-powder mixing device 10 so that the absorbent has a suitable transport ratio with respect to air. The powder spraying device 9 is in a circular tubular shape, and a high-voltage electrostatic corona area is formed in a certain area in the powder spraying device 9 through the high-voltage electrostatic generating device 8. The sorbent carries a high-pressure electrostatic charge as it passes through the zone and is then sprayed into the flue gas with the SO₂The reaction takes place. However, care must be taken that the corona region is not discharged, otherwise the electric field strength is destroyed or weakened, and the charging effect of the corona region is eliminated or weakened. The high-voltage static electricity generating equipment 8 can generate high voltage of 0-70KV, the power is less than or equal to 300W, and a voltage signal is output so as to be convenient for a computer to monitor. The equipment can automatically reduce the working voltage when the discharge phenomenon appears in the corona area so as to prevent the charging effect of the corona area from disappearing or weakening. The gas-powder mixing apparatus 10 is similar to a pulverized coal mixer of a pulverizing system of a pulverized coal boiler, when air passes through the apparatus at a high speedThe narrow part of the device can generate certain negative pressure, so that the absorbent can smoothly flow out of the feeding device. 7 enter a powder spraying device 9.

3. The computer control unit: to ensure that the computer works reliably, an industrial control computer should be used. Installing high-precision SO at proper positions at two ends of spray inlet of dry-type absorbent flue gas desulfurization device₂On-line instrument 11 for continuously monitoring SO in flue gas₂Original concentration, and SO after desulfurization₂The concentration and the measurement result are input to the computer 12 at any time. According to a pre-programmed program, first, the computer 12 is based on SO₂On-line instrument 11 for measuring SO₂The spraying amount of the absorbent is automatically set according to the original concentration, and then the SO after desulfurization is carried out₂Concentration, automatically adjusting the spraying amount of the absorbent.

In addition to the above control method, a relatively simple and inexpensive control method can be adopted. If the operating load of the boiler is not changed greatly and the sulfur content and the low calorific value of the same batch of coal are stable, the low calorific value and the sulfur content of the boiler fuel can be input into a computer, and then the injection amount of the absorbent is adjusted through the load change of the boiler 1. If the load of the boiler 1 or the coal type changes, the input values can be changed at any time in the computer control system. Furthermore, all devices can be controlled and monitored by a computer.

4. A desulfurization absorbent: theoretically, alkaline substances can be used as desulfurization absorbents. However, since the desulfurization is performed by a dry method, an alkaline liquid should be excluded. Calcium-based alkaline materials should be the preferred absorbents from the standpoint of desulfurization effectiveness and economy. Constructional Ca (OH)₂Since CaO has a low purity and excessive water is added during digestion, Ca (OH) is generated₂Not only the purity is lower, but also the surface area is smaller, and the requirement of desulfurization is difficult to meet. The device is Ca (OH)₂The requirements are as follows:

the purity is more than or equal to 90 percent; the grain diameter is less than or equal to 50 mu m; the water content is less than or equal to 1 percent; specific surface area is more than or equal to 15m/gCa (OH)₂。

The invention can use Ca (OH)₂As the absorbent, the caustic sludge produced in the production process of soda ash and the carbide slag produced in the production process of acetylene gas can be used as the absorbent, wherein the physical and chemical properties of the carbide slag are more suitable for being used as the absorbent.

The flue gas generated by the boiler 1 in operation is sent to a chimney 4 through a draught fan 3 and then discharged into the atmosphere after being dedusted by a dry-type absorbent fluegas desulfurization device and dedusting equipment 2. Desulfurization product CaSO₃And a small amount of CaSO₄Stable chemical property, difficult water solubility, and no secondary pollution.

Claims

1. A dry-type absorbent flue gas desulfurization method is technically characterized in that: a high-voltage electrostatic corona area is generated in the charging powder spraying equipment by utilizing high-voltage electrostatic generating equipment,the absorbent particles passing through the region are charged with the same kind of charges, and then the absorbent with the charges is sprayed into the proper position of the flue, and the absorbent is uniformly distributed in the flue gas under the action of the charges and is mixed with SO in the flue gas₂Reaction to generate CaSO₃And a small amount of CaSO₄The particulate matter being then removed by dust-removing equipment, i.e.

。

2. The flue gas desulfurization method according to claim 1, characterized in that: the spraying amount of the desulfurization absorbent can adopt SO₂On-line instrument for continuously monitoring SO in flue gas₂Original concentration and desulfurized SO₂The concentration of the fuel is automatically set by a computer, or parameters such as low-level calorific value, sulfur content and the like of the boiler fuel are firstly input into the computer and automatically controlled by the computer.

3. The desulfurization method according to claim 1 or 2, characterized in that: the absorbent used may be Ca (OH)₂Carbide slag or caustic sludge.