CN1631493A - A wet flue gas desulfurization method and device thereof - Google Patents

Abstract

The invention unfurls a kind of way of taking off the sulphur by wet smoke and its equipment. The way uses the alkaline object from coal burnt to take off the sulphur. The equipment involves: removing dusk machine of wet smoke, removing mist machine of taking off water, and also include pond for taking off the alkaline object, water pond and the pond of taking off the sulphur. In the removing dusk machine of wet smoke, there are chemical reaction between smoke and the liquid for taking off the sulphur, taking off the pollution of the sulphur into acid water, used for recycling. The smoke is brought to the air after taking off the mist. Start smoke-water separated machine at certain times to prevent the system wearing knot, eject the dusk water after removing them. The way and the equipment have the strong function between liquid and air, using little water and eject little too, large field to use, eject dusk while taking off the sulphur, cost little when separating and investing.

Description

A wet flue gas desulfurization method and device thereof

Technical field:

The invention relates to the technical field of flue gas desulfurization applicable to large and medium-sized coal-fired industrial boilers, in particular to a wet-type flue gas desulfurization method and device for large and medium-sized coal-fired industrial boilers.

Background technique:

As we all know, there are many ways to remove sulfur dioxide in coal-fired flue gas, including limestone/lime-gypsum method, double alkali method, flue gas circulating fluidized bed method and other flue gas desulfurization technologies. In these methods, limestone (CaCO ₃ ), lime (CaO), caustic soda (NaOH) and other desulfurization agents are prepared into desulfurization liquid, which is injected into the desulfurization reactor to react with sulfur dioxide in the flue gas to generate sulfite and sulfate and remove them. For this reason, these methods all need to set up a set of desulfurization agent preparation, storage, transportation, and desulfurization by-product collection and removal devices in the desulfurization process system, so that the complete desulfurization system is huge and there are many supporting equipment. In addition, desulfurization agents need to be purchased. Cause system equipment investment and operating costs to increase.

Invention content:

The purpose of the present invention is to provide a wet flue gas desulfurization method and its device which use the alkaline waste discharged by the coal-fired boiler itself as a desulfurizer to remove sulfur dioxide carried in the coal-fired flue gas, and the method has strong gas-liquid mass transfer , Desulfurization liquid recycling, small water consumption, wide application range, low investment and operating costs, while desulfurization can also remove fine dust.

In order to achieve the above object, the technical solution adopted in the present invention is: a wet flue gas desulfurization method:

1) Dissolve the alkaline substances in the coal slag and form a cycle of slag flushing water: the slag flushing water is drawn from the rear of the alkaline substance dissolution tank through the slag flushing pump, so that the ash generated after the coal combustion in the boiler is washed with the slag flushing water Together, they flow into the dissolution tank of alkaline substances, and mix and merge with the acid gray water discharged from the wet flue gas desulfurization dust collector. circulation of slag water;

2) Primary filtration: the above-mentioned mixture of ash water and acidic ash water flows into the sump after being filtered;

3) Mixing: the above solution merges with the alkaline sewage discharged from the boiler in the sump;

4) Secondary filtration: the combined solution flows into the desulfurization liquid pool after filtering to further filter out fine particles to form a desulfurization liquid;

5) Flue gas desulfurization: the above-mentioned desulfurization liquid enters the wet type flue gas desulfurization dust collector, and chemically reacts with the flue gas discharged from the coal-fired boiler entering the device to remove sulfur dioxide pollutants;

6) Desulfurization liquid circulation: After the above-mentioned desulfurization liquid desulfurizes the flue gas, the acid gray water produced flows into the front end of the alkaline substance dissolution tank to form a desulfurization liquid circulation;

7) Flue gas dehydration and defogging: the desulfurized flue gas is dehydrated and defogged by the demister demister, and then discharged into the atmosphere;

8) Timing gray water separation: regularly inject the solution in the sump into the gray water separator, and the separated water is discharged from the outlet pipe at the top of the gray water separator for reuse; the slurry flows from the mud hopper into the alkaline substance dissolution tank, and the system supplement Appropriate amount of water to form a circulation of external drainage;

The alkalinity of boiler alkaline sewage is 8mmol/L-20mmol/L, and the pH value is 10-12;

The concentration of suspended solids in the water separated by the gray water separator is less than or equal to 100mg/L;

Timed gray water separation time is 1-24 hours.

A device for realizing a wet flue gas desulfurization method, the device includes a wet flue gas desulfurization dust collector, a dehydration demister, and a gray water separator, and the device also includes an alkaline substance dissolution pool, a water collection pool, and a desulfurization liquid pool; coal-fired The flue gas discharged from the boiler enters the entrance of the wet flue gas desulfurization dust collector; the flue gas outlet of the wet flue gas desulfurization dust collector is connected to the entrance of the dehydration demister; the outlet of the dehydration demister is connected to the chimney through the induced draft fan; the alkaline substance dissolution tank , water collection pool and desulfurization liquid pool are concrete masonry pools respectively; the alkaline substance dissolution pool is connected to the outlet of the lower part of the flue gas desulfurization dust collector; the first filter grid is set between the alkaline substance dissolution pool and the water collection pool; the water collection pool A second filter grid is set between the desulfurization liquid pool; the sump pool is connected to the alkaline sewage outlet discharged from the boiler; the sump pool is connected to the inlet of the gray water separator by a mortar liquid pump; a mud bucket is set at the bottom of the gray water separator, and the mud bucket is connected to the alkali Dissolution tank for alkaline substances; a water outlet pipe is set on the top of the gray water separator to connect to the dissolution tank for alkaline substances; the desulfurization liquid pool is connected to the water distribution system of the wet flue gas desulfurization dust collector by the desulfurization liquid circulating pump.

The working principle of the wet flue gas desulfurization method and device provided by the present invention: in the ash generated after the coal is burned in the boiler, calcium oxide (CaO), magnesium oxide (MgO), sodium oxide ( _Na2O ), potassium oxide The content range of basic metal oxides such as (K ₂ O) is very wide. Under certain conditions (mainly controlling the pH value of the leaching solution and the contact time with the ash) the above-mentioned basic substances can be dissolved and have a neutral and acidic substances; iron oxide (Fe ₂ O ₃ ) and aluminum oxide (Al ₂ O ₃ ) in ash are amphoteric compounds, and they can be dissolved under acidic conditions to neutralize acidic substances. In addition, the boiler feed water contains a large amount of carbonate hardness. In order to prevent these salts in the feed water from causing fouling on the heating surface of the boiler during boiler operation and affecting the safe and economical operation of the boiler, the boiler feed water needs to be treated with sodium ion exchange in advance. The hardness of the feed water (mainly calcium salts and magnesium salts), that is, the Ca ²⁺ and Mg ²⁺ in the calcium and magnesium compounds that are easy to form scales are replaced by Na ⁺ ions in the exchanger and transformed into sodium bicarbonate that does not form scales (NaHCO ₃ ), which is decomposed into sodium carbonate (Na ₂ CO ₃ ) or soda ash in the boiler furnace water, and is an ideal desulfurizer. It reacts as follows:

In sodium ion exchange:

After heating in the furnace:

In order to prevent the calcium and magnesium products in the boiler water from sticking to the heating surface inside the boiler in the form of scale, forcing it to crystallize out in the boiler boiler water and form dispersed slag precipitation, the alkalinity in the boiler water must be kept at 8 mmol /L-20mmol/L, the pH value is 10-12, in order to maintain this value, the process operated by the boiler must be discharged periodically. So boiler blowdown water is also a cheap desulfurizer.

The process flow of the wet flue gas desulfurization method provided by the present invention is: the ash generated after the coal is burned in the boiler flows into the alkaline substance dissolution pool together with the slag water under the impact of the slag water, and is combined with the wet flue gas desulfurization dust collector The discharged acidic gray water is mixed, and most of the ash is gradually deposited in the alkaline substance dissolution tank during the time of flowing through the alkaline substance dissolution tank, and under the dual action of acidic gray water and hydraulic agitation, the alkali in the ash The alkaline substances are gradually dissolved out, and then, the mixed gray water flows from the tail of the alkaline substance dissolution tank through the first filter grid into the sump, while the fine particles in the mixed gray water are removed, the alkaline substances in the ash residue are further removed Dissolution: In the sump, the gray water is mixed with the alkaline sewage discharged from the boiler, and when it flows through the second filter grid, the fine particles are further removed, and the desulfurization liquid is prepared into the desulfurization liquid pool that flows into the water circulation system. The desulfurization liquid is pumped into the wet flue gas desulfurization dust collector through the desulfurization liquid circulation pump. In this device, the desulfurization liquid passes through the three-stage water distribution system and the tray group, and fully mixes and contacts with the flue gas flowing in from the boiler. After desulfurization, the clean After the flue gas is dehydrated and defogged, it is discharged into the atmosphere by the induced draft fan and the chimney; the acid gray water produced after the removal of sulfur dioxide in the flue gas flows into the front end of the alkaline substance dissolution tank to form a cycle of desulfurization liquid; the gray water separator , once every 1-24 hours, the mixed gray water is introduced into the sump through the mortar pump. After the mixed gray water passes through the coagulation zone, sedimentation zone and filtration zone in the device, it is reused and an appropriate amount of clean water is added; a small part of the concentrated mortar is reused. It flows through the front of the alkaline substance dissolution tank to form an external drainage cycle.

It can be seen from the above working principle that, compared with the existing wet flue gas desulfurization method and device, the present invention has the following beneficial effects:

1) The desulfurization effect is good, and fine dust can be removed at the same time:

Since the wet flue gas desulfurization and dust collector adopted in the present invention has a three-stage water distribution system and a tray group, the flue gas and the desulfurization liquid are fully contacted, thereby achieving the effect of good gas-liquid mass transfer performance, high desulfurization efficiency, and removal of fine particles dust.

2) Reduce environmental pollution:

The present invention is provided with a plurality of ponds to form a plurality of water circulation systems inside, which reduces the discharge of waste, that is, reduces the pollution to the environment.

3) Low cost:

In the present invention, the alkaline substances in the waste discharged from the boiler combustion——the ash are dissolved and combined with the waste water discharged from the boiler to be used as desulfurization liquid. This method of treating waste with waste reduces the investment of equipment and its operation cost , In addition, due to the recycling of water, while saving resources, it also reduces costs.

Description of drawings:

Figure 1: Schematic diagram of a waste-to-waste wet flue gas desulfurization device.

Detailed ways:

The present invention adopts the wet flue gas desulfurization method and device that the coal-fired boiler itself discharges alkaline substances, and is equipped with a boiler with an evaporation capacity of 35t/h to treat boiler flue gas with a flue gas volume of 100,000m ³ /h.

As shown in the figure: the desulfurization method is:

1) Dissolving the alkaline substances in the coal slag, and forming a cycle of slag washing water: the slag washing water is drawn from the rear of the alkaline substance dissolution tank 14 through the slag washing pump 13, so that the ash generated after the coal combustion in the boiler is flushed The slag water flows into the alkaline substance dissolution tank 14 together, and is mixed with the acid gray water discharged from the wet flue gas desulfurization dust collector 2. At the same time, a cycle of flushing slag water is formed;

2) Primary filtration: the above-mentioned mixture of ash water and acidic ash water flows into the sump 16 after being filtered;

3) Mixing: the above solution merges with the alkaline sewage discharged from the boiler in the sump 16;

4) Secondary filtration: the merged solution flows into the desulfurization liquid pool 19 after further filtering out fine particles to form a desulfurization liquid;

5) Flue gas desulfurization: the above-mentioned desulfurization liquid enters the wet type flue gas desulfurization dust collector 2, and chemically reacts with the flue gas 1 discharged from the coal-fired boiler entering the device to remove sulfur dioxide pollutants;

6) Desulfurization liquid circulation: after the above-mentioned desulfurization liquid desulfurizes the flue gas, the acid gray water produced flows into the front end of the alkaline substance dissolution tank 14 to form a desulfurization liquid circulation;

7) Flue gas dehydration and defogging: the desulfurized flue gas is discharged into the atmosphere after being dehydrated and defogged by the demister 9;

8) Regular gray water separation: every 8 hours, inject the solution in the sump 16 into the gray water separator 22, and the separated water, in which the concentration of suspended matter is less than or equal to 100 mg/L, is discharged from the outlet pipe 12 at the top of the gray water separator , re-use, and add an appropriate amount of clear water; the slurry flows from the mud bucket 7 into the alkaline substance dissolution tank 14, forming a circulation of external drainage.

The alkalinity of boiler alkaline sewage 17 is 10mmol/L, and the pH value is 10.5.

A device for realizing the wet flue gas desulfurization method, including wet flue gas desulfurization dust collector 2, dehydration demister 9, ash water separator 22, alkaline substance dissolution pool 14, water collection pool 16 and desulfurization liquid pool 19; coal-fired boiler discharge The flue gas 1 enters the entrance of the wet flue gas desulfurization dust collector 2; the flue gas outlet of the wet flue gas desulfurization dust collector 2 is connected to the entrance of the dehydration demister 9 through a pipe; the outlet of the dehydration demister 9 is connected to the chimney through the induced draft fan 10 11. Alkaline substance dissolution pool 14, sump pool 16 and desulfurization liquid pool 19 are pools made of concrete masonry, which are integrated together and divided into three independent and interconnected water holding tanks by three water walls and two filter grids. space; the alkaline substance dissolution pool 14 is connected to the outlet 8 of the lower part of the flue gas desulfurization dust collector; the first filter grid 15 is set between the alkaline substance dissolution pool 14 and the water collection pool 16; between the water collection pool 16 and the desulfurization liquid pool 19 The second filter grid 18 is set; the sump 16 is connected to the alkaline sewage outlet 17 discharged from the boiler through pipelines; the sump 16 is connected to the entrance of the gray water separator 22 by the gray slurry pump 21 and the pipeline; The outlet pipe 12 is connected to the alkaline substance dissolution pool 14; the desulfurization liquid pool 19 is connected to the water distribution systems 3, 4, and 5 of the wet flue gas desulfurization and dust collector 2 by the desulfurization liquid circulation pump 20.

Among them: the wet flue gas desulfurization dust collector 2 adopts the patent applied by our institute (application number is 2004200481440.6), with a diameter of 2.5 meters and a total height of 13.6 meters; the dehydration demister 9 adopts the patent applied by our institute (application number is 03245346.9) , is a corrugated folded plate group type; gray water separator 22 adopts the patent (application number is 200420047915. Pool 19 is respectively 5 meters * 5 meters * 5 meters.

The flue gas 1 discharged from the coal-fired boiler enters the wet compound flue gas desulfurization and dust collector 2 with a diameter of 2.5 meters and a total height of 13.6 meters through the flue. The device is equipped with a first-stage water distribution system 3 and a second-stage Level water distribution system 4, third level water distribution system 5 and tray group 6, when the flue gas flows through the above areas, it is fully mixed and contacted with the desulfurization liquid dissolved and collected by the boiler alkaline substances, the sulfur dioxide in the flue gas and Calcium, magnesium and other ions in the desulfurization liquid react chemically, and the generated desulfurization by-products such as sulfate and sulfite are discharged from the outlet 8 at the lower part of the flue gas desulfurization dust collector along with the water flow, and enter the water circulation system. When the boiler burns medium-low sulfur coal, the concentration of sulfur dioxide in the flue gas after desulfurization can reach below the limit value specified in GB13271 "Emission Standard of Air Pollutants for Boilers". The desulfurized flue gas passes into the dehydration demister 9 with a resistance of only about 100 Pa and a mist removal efficiency of 97-99%.

When the ash generated after coal combustion in the boiler flows into the alkaline substance dissolution tank 14 and merges with the acid ash water discharged from the desulfurization dust collector, under the dual action of acid ash water and hydraulic agitation, the alkaline substances in the ash are gradually dissolved Dissolution, large particles of ash and slag are deposited in the alkaline substance dissolution pool 14, and then flow into the sump 16 after the first filter grid 15 removes the fine ash and slag particles, merge with the alkaline sewage 17 discharged from the boiler, and then flow After passing through the second filter grid 18, it flows into the desulfurization liquid pool 19 after further filtering out fine particles.

The desulfurization liquid circulation pump 20 draws the desulfurization liquid from one side of the desulfurization liquid pool, and pumps it into the wet compound flue gas desulfurization dust collector, thereby realizing the flow of the flue gas desulfurization process.

In the present invention, in order to prevent the fouling phenomenon caused by the concentration of desulfurization by-products in the water circulation system, the gray water separator 22 and the gray slurry liquid pump 21 are set up, and the water is pumped in from one side of the sump every 8 hours. , the concentration of suspended matter in the water can be lower than 100mg/L, and it is discharged out of the system from the outlet pipe 12 at the top of the gray water separator to reduce the concentration of desulfurization by-products in the water and prevent scaling. The concentrated slurry is discharged from the mud hopper 7 and flows into the alkaline substance dissolution tank 14 .

It can be seen from the above working principle that compared with the existing wet flue gas desulfurization methods and devices, the present invention has strong gas-liquid mass transfer, desulfurization liquid recycling, small water consumption, wide application range, low investment and operating costs , It can also remove fine smoke and dust while desulfurizing.

Claims (5)

1. A wet flue gas desulfurization method, characterized in that: 1) Dissolving the alkaline substances in the coal slag, and forming a cycle of slag washing water: the slag washing water is drawn from the rear of the alkaline substance dissolution pool (14) through the slag washing pump (13), so that the coal generated after the combustion of coal in the boiler The ash and slag flow into the alkaline substance dissolution tank (14) together with the slag flushing water, and are mixed with the acid ash water discharged from the wet flue gas desulfurization dust collector (2). Alkaline substances in the solution are gradually dissolved, and at the same time, a cycle of washing slag water is formed; 2) Primary filtration: the above-mentioned mixture of ash water and acidic ash water flows into the sump (16) after being filtered; 3) Mixing: the above solution merges with the alkaline sewage discharged from the boiler in the sump (16); 4) Secondary filtration: the combined solution flows into the desulfurization liquid pool (19) after further filtering out fine particles to form a desulfurization liquid; 5) Flue gas desulfurization: the above-mentioned desulfurization liquid enters the wet type flue gas desulfurization dust collector (2), and chemically reacts with the flue gas (1) discharged from the coal-fired boiler entering the device to remove sulfur dioxide pollutants; 6) Desulfurization liquid circulation: after the above-mentioned desulfurization liquid desulfurizes the flue gas, the acid gray water produced flows into the front end of the alkaline substance dissolution tank (14) to form a desulfurization liquid circulation; 7) Flue gas dehydration and defogging: the desulfurized flue gas is discharged into the atmosphere after being dehydrated and defogged by the demister (9); 8) Regular grey-water separation: regularly inject the solution in the sump (16) into the grey-water separator (22), and the separated water is discharged from the outlet pipe (12) at the top of the grey-water separator for reuse, and the slurry is discharged from the mud hopper ( 7) Flow into the alkaline substance dissolution tank (14), and at the same time, the system replenishes an appropriate amount of clear water; forming a circulation of external drainage. 2. The wet flue gas desulfurization method according to claim 1, characterized in that: the alkalinity of the boiler alkaline sewage is 8mmol/L-20mmol/L, and the pH value is 10-12. 3. The wet flue gas desulfurization method according to claim 1, characterized in that the concentration of suspended solids in the water separated by the gray water separator (22) is less than or equal to 100 mg/L. 4. The wet flue gas desulfurization method according to claim 1, characterized in that: the time for the timing gray-water separation is 1-24 hours. 5. A device for realizing the wet flue gas desulfurization method according to claim 1, the device comprises a wet flue gas desulfurization dust collector (2), a dehydration demister (9), and an ash-water separator (22), characterized in In that: the device also includes an alkaline substance dissolution pool (14), a water collection pool (16) and a desulfurization liquid pool (19); the flue gas (1) discharged from the coal-fired boiler enters the wet flue gas desulfurization dust collector (2) The inlet of the wet flue gas desulfurization dust collector (2) is connected to the inlet of the dehydration demister (9); the outlet of the dehydration demister (9) is connected to the chimney (11) through the induced draft fan (10) ); the alkaline substance dissolution pool (14), the sump (16) and the desulfurization liquid pool (19) are respectively pools of concrete masonry; the alkaline substance dissolution pool (14) is connected to the lower part of the flue gas desulfurization dust collector The discharge port (8); the first filter grid (15) is set between the alkaline substance dissolution pool (14) and the sump (16); The second filter grid (18) is arranged between; the alkaline sewage outlet (17) that the described sump (16) is connected to the boiler discharge; the described sump (16) is connected to the gray water separator ( 22) inlet; the bottom of the gray water separator (22) is provided with a mud bucket (7), and the mud bucket (7) is connected to the alkaline substance stripping tank (14); at the top of the gray water separator (22), an outlet pipe ( 12), connected to the alkaline substance dissolution pool (14); the desulfurization liquid pool (19) is connected to the water distribution system (3), (4) of the wet flue gas desulfurization dust collector (2) by the desulfurization liquid circulation pump (20) , (5).