CN102580493B - Flue gas demercuration system and method based on discharge and activation of halogen materials - Google Patents

Abstract

The invention discloses a flue gas mercury removal system and method based on discharge activation of halogen substances, including a pretreatment device, a dust removal device, and an absorption device for sequentially processing the flue gas. A halogen substance activation device is provided, and the halogen substance activation device is provided with a nozzle and a discharge reactor. The halogen group substance activating device injects the halogen group substance into the flue gas, and activates the halogen group substance through high-voltage discharge, and converts the elemental mercury in the flue gas into oxidized mercury and particulate mercury, and performs dust removal and Absorption and removal of oxidized mercury and particulate mercury. The invention can effectively utilize the existing flue gas purification device, reduce the cost of mercury removal, and simultaneously improve the efficiency of mercury removal and dust removal.

Description

A flue gas mercury removal system and method based on discharge activation of halogen substances

technical field

The invention belongs to the technical field of environmental protection/exhaust gas purification, and in particular relates to a flue gas mercury removal system and method for oxidizing and removing gaseous mercury into easily removable forms by activating halogen substances through electric discharge.

Background technique

Mercury (Hg) pollutants are highly volatile and stable in nature, and can affect the human nervous system and kidney function, as well as pollute soil and water. Mercury in the gaseous state has three forms: elemental mercury Hg ⁰ (gas state), oxidized mercury Hg ²⁺ (gas state), and particle-attached mercury Hg ^p (solid state). Hg ⁰ is highly volatile, not easily soluble in water, and is extremely difficult to remove in industrial processes, while Hg ²⁺ and Hg ^p can be removed in the flue gas dedusting device and flue gas desulfurization (FGD) downstream of the flue gas outlet. Mercury in fossil fuels will be released into the atmosphere in the gas phase during the combustion process.

my country has a complete set of dust removal, desulfurization, and denitrification equipment. The existing flue gas purification system usually includes pretreatment devices such as heat exchangers, as well as dust removal devices and absorption devices. As shown in Figure 1, the flue gas is discharged from the boiler 1, and is processed by the pretreatment device 2, the dust removal device 5 and the absorption device 8 in sequence. The dust removal device 5 in the figure is an electrostatic precipitator. In the electrostatic precipitator, dust, oxidized mercury, and particulate mercury can be charged and collected under the action of high-voltage corona, and discharged from the ash hopper 7 of the electrostatic precipitator. After dedusting, the flue gas enters the absorption device 8, which is the desulfurization absorption tower shown in the figure. The residual oxidized and particulate mercury in the flue gas is absorbed in the absorption tower and discharged together with the absorption by-products. The flue gas after mercury removal passes through the mist eliminator 9 and is discharged from the chimney 10. It can be seen that the existing flue gas purification system can only remove oxidized mercury and particle-attached mercury, but cannot remove gaseous elemental mercury.

However, the main type of coal burned in China is lignite, and the mercury produced by lignite is mainly elemental Hg ⁰ . Therefore, the removal of gaseous mercury still focuses on the form conversion of elemental mercury and the development of low-priced oxidants. How to use the existing flue gas dedusting system to effectively remove gaseous mercury and improve the efficiency of mercury removal is a problem that needs to be solved at present.

Contents of the invention

The purpose of the present invention is to solve the problem of effectively removing gaseous mercury in flue gas, and to provide a flue gas mercury removal system and method with high efficiency and low cost, which uses electric discharge to activate halogen substances, oxidizes and removes gaseous mercury , can effectively remove mercury in flue gas.

A flue gas mercury removal system based on discharge activation of halogen substances, including a pretreatment device for sequentially treating flue gas, a dust removal device, an absorption device, and a halogen substance arranged between the pretreatment device and the dust removal device Activation device, the halogen group substance activation device includes a housing, and flues located at both ends of the housing, a discharge reactor is arranged in the housing, and the flue in the discharge reactor or in front of it There is a nozzle inside.

The discharge reactor can adopt the discharge forms such as dielectric barrier discharge, glow discharge or corona discharge; the discharge reactor is connected with a high-voltage power supply for its power supply, and the high-voltage power supply is positive and negative pulse high-voltage power supply or high-frequency AC High-voltage power supply or AC-DC superimposed high-voltage power supply or DC superimposed positive and negative pulse high-voltage power supply or DC high-voltage power supply.

The discharge reactor adopts a dielectric barrier discharge reactor, and the dielectric barrier reactor includes a high voltage electrode and a ground electrode, and the high voltage electrode and the ground electrode are separated by a dielectric layer. The dielectric barrier discharge reactor is a plate-type dielectric barrier discharge reactor, the ground electrode, the dielectric layer and the high voltage pole are flat plates, the high voltage pole is attached to the medium layer flat plate, and the ground electrode flat plate and the medium layer flat plate are placed in parallel. There is a gap between the ground electrode plate and the dielectric layer plate for the flue gas to pass through and discharge. The ground plate can be arranged in double layers, cooling pipes are arranged in the layers, and cooling water or cooling air is arranged for heat dissipation. The plate-and-plate dielectric barrier reactor can be used for horizontal and vertical air flow, etc., and is convenient for direct modification in the flue.

Preferably, the dielectric barrier discharge reactor is a coil-type dielectric barrier discharge reactor, the ground electrode and the dielectric layer are attached together to form a channel for flue gas to pass through, and the ground electrode is located on the outer layer of the channel, so The dielectric layer is located in the inner layer of the channel, and the high voltage pole line is located at the central axis of the channel formed by the ground electrode and the dielectric layer. Cooling pipes may be arranged outside the discharge reactor or in the medium layer, and cooling water or cooling air may be arranged for cooling the discharge reactor. The coil-type dielectric barrier reactor has a compact structure and is mostly used in a vertical air flow flue, and can also be used in a horizontal air flow when the gas velocity is relatively high.

The discharge reactor can also be a corona discharge reactor, which is composed of a high voltage electrode and a plurality of ground electrodes, the high voltage electrode is located between the ground electrodes, and there is a discharge gap between the high voltage electrode and the ground electrode, the preferred discharge gap is 200mm .

A method for removing mercury from flue gas based on discharge-activated halogen substances, comprising the steps of:

(1) Mix halogenated substances with mercury-containing flue gas;

(2) Under the condition of aerobic gas, the halogen group substances are activated by high-voltage discharge, so that the elemental mercury in the flue gas is formed into oxidized mercury and particle-attached mercury;

(3) Dust removal and absorption to remove oxidized mercury and particle-attached mercury.

The principle of demercurization of activated halogen species in the present invention is: when discharge occurs in gas or liquid, highly chemically active free radicals (OH, H, O, N, etc.) and other active substances (O ₃ , H ₂ O ₂ , etc.). These active substances can carry out chemical reactions with industrial application value that are difficult to realize by conventional chemical techniques, thereby efficiently activating halogen substances and converting them into halogen simple substances, halogen intermediates and atoms. The activated halogen substances are easy to combine with mercury, so that the elemental mercury is converted into an oxidized state and a particle-attached state, which is captured and removed by the downstream removal device.

The high-voltage voltage used in the present invention is generally above 10kV, and the current is above tens of milliamps. The high-voltage discharge can be in the form of dielectric barrier discharge, glow discharge or corona discharge.

After the mercury-containing flue gas is treated by the halogen substance activation device, it can be further removed by the dust removal device or the absorption device alone, or it can be removed by the dust removal device and the absorption device successively. The dust removal device can be an electric dust collector, filter dust collector, wet dust collector, mechanical dust collector or other dust removal equipment. The absorption device can be packed tower, turbulent ball tower, sieve tray tower, spray absorber, fixed bed adsorber, moving bed adsorber, ebullating bed adsorber or other absorption/adsorption equipment.

The halogen substances in the present invention are simple halogens and halogen salts, such as simple chlorine Cl ₂ , simple bromine Br ₂ , simple iodine I ₂ , sodium chloride NaCl, sodium bromide NaBr, sodium iodide NaI, calcium bromide CaBr ₂ , etc. ; The injection of halogen substances can be in gaseous, liquid, solid or mixed state;

The oxygen-containing gas in the present invention is oxygen, air, flue gas, or gas containing SO ₂ , NH ₃ , and NO _x .

Compared with conventional environmental protection technologies, the flue gas mercury removal system and method based on discharge-activated halogen substances provided by the present invention can produce the following beneficial effects:

1) In the flue gas mercury removal system of the present invention, a halogen substance activation device is installed between the pretreatment device and the dust removal device in the existing flue gas purification system to effectively remove gaseous mercury, and it can also directly replace the existing flue gas pipeline Transformation was carried out to effectively utilize the existing flue gas purification system to reduce the cost of mercury removal;

2) The flue gas mercury removal method of the present invention can effectively remove mercury-containing flue gas by converting gaseous mercury in mercury-containing flue gas into oxidized mercury and particulate mercury by activating halogen substances through high-voltage discharge The gaseous mercury in the system improves the mercury removal efficiency.

Description of drawings

Fig. 1 is the schematic diagram of prior art flue gas purification system;

Fig. 2 is a schematic structural diagram of a flue gas mercury removal system based on discharge-activated halogen substances in the present invention;

Fig. 3 is a structural diagram of a plate-type dielectric barrier discharge halogen substance activation device;

Fig. 4 is the structural diagram of wire barrel type dielectric barrier discharge reactor;

Fig. 5 is a structural diagram of a corona discharge reactor.

Detailed ways

As shown in Figure 2, the mercury removal system based on the discharge activation of halogen substances in the present invention includes a pretreatment device 2, a dust removal device 5, and an absorption device 8 that sequentially treat the flue gas. There is a halogen substance activation device 3 . The dust removal device power supply 6 supplies power to the dust removal device 5, and the dust removal device 5 is also provided with a dust removal ash hopper 7.

The mercury-containing flue gas passes through a pretreatment device 2 such as a heat exchanger and then enters a halogen substance activation device 3, which adds halogen substances to the flue gas and mixes with the flue gas. The halogen substance activation device 3 efficiently activates the halogen substance under the condition of oxygen-containing gas, fully mixes and reacts with the halogen substance in the flue gas, and generates halogen element, halogen atom, etc. Halogen simple substances and atoms combine with elemental mercury in flue gas to form oxidized mercury such as mercury halide and particulate mercury. Subsequently, the flue gas enters the dust removal device 5, and the dust, oxidized mercury, and particulate mercury can all be removed, and are discharged from the dust hopper 7 of the dust collector. The flue gas after dedusting enters the absorption device 8, and the residual oxidized and particulate mercury in the flue gas is absorbed in the absorption device 8 and discharged together with the absorption by-products. The flue gas after mercury removal is discharged from the chimney through after-treatment devices such as mist eliminators.

The halogen group substance activation device 3 efficiently activates the halogen group substance through high-voltage discharge, wherein the discharge reaction can be in the form of dielectric barrier discharge, glow discharge or corona discharge discharge. Embodiments of the present invention use dielectric barrier discharge reactor and corona discharge The reactor is used to further illustrate the present invention.

As shown in Figure 3, it is a structural diagram of the plate-type dielectric barrier discharge halogen substance activation device of the present invention, including a housing 18 and flues 12a and 12b positioned at both ends of the housing 18; The reactor 11 is provided with a nozzle 16 in the flue 12a located in front of the discharge reactor 11 . The discharge reactor power supply 4 supplies power to the discharge reactor 11 . The discharge reactor 11 is composed of a high voltage electrode 13 , a ground electrode 14 , and a dielectric layer 15 , and the high voltage electrode 13 and the ground electrode 14 are separated by the dielectric layer 15 .

The discharge reactor 11 as shown in the figure is a plate-type dielectric barrier discharger. The high-voltage pole 13 is attached to the dielectric layer 15 plate, and the ground electrode 14 plate is placed in parallel with the dielectric layer 15 plate. The ground electrode 14 plate and the dielectric layer 15 There is a gap between the plates, the discharge gap is preferably 100mm, for the flue gas to pass through. A lower ash hopper 17 can also be provided for recovering halogenated substances, and it can also be used as a storage tank. However, when the halogen substance activation device 3 is arranged in the gas pipeline, the gas flow rate is relatively high, and the ash hopper may not be arranged.

The grounding plate 14 can be arranged as double layers, and cooling pipes are arranged in the middle, and cooling water or cooling air is arranged, and the cooling part at the grounding plate is used as a part of the heat exchanger to reduce heat loss.

It can be seen from the figure that multiple sets of discharge reactors 11 can be arranged in parallel, series or series-parallel in the halogen substance activating device 3, and multiple sets of discharge reactors 11 constitute a discharge reaction zone for activating halogen substances.

After the flue gas containing mercury enters the halogen substance activation device 3 from the flue 12a at the front end of the dielectric barrier discharge reactor 11, the nozzle 16 sprays the halogen substance into the flue gas. The dielectric barrier discharge reactor 11 performs high-voltage discharge, thereby efficiently activating halogen substances and converting them into halogen simple substances, halogen intermediates and atoms. The activated halogen substances are easy to combine with mercury, transforming elemental mercury into oxidized and particle-attached mercury. Then the flue gas is discharged from the flue 12b at the rear end of the dielectric barrier discharge reactor 11 to the downstream dust removal and absorption device to remove oxidized mercury and particulate mercury.

As shown in Figure 4, it is another embodiment of the discharge reactor of the present invention: a wire barrel type dielectric barrier discharge reactor, consisting of a high voltage pole 13, a ground pole 14, and a dielectric plate 15, wherein the ground pole 14 and the dielectric layer 15 Attached together to form a cylindrical channel for the passage of smoke, the high-voltage pole 13 is a high-voltage pole line, located on the central axis of the cylindrical channel formed by the ground electrode 14 and the dielectric layer 15 . Wherein the ground electrode 14 is located on the outer layer of the channel, and the dielectric layer 15 is located on the inner layer of the channel. The discharge reactor power supply 4 supplies power to the discharge reactor 11 . It can be seen from the figure that multiple sets of discharge reactors 11 can be arranged in the halogen substance activating device 3 , and the multiple sets of discharge reactors 11 constitute a discharge reaction zone for activating the halogen substances. Cooling pipes can be arranged outside the discharge reactor 11, and cooling water or cooling air can be arranged for cooling to reduce heat loss. Since the gas flow rate in the general gas pipeline is about 10-15m/s, there is generally no ash accumulation, and no ash hopper can be arranged.

After the mercury-containing flue gas is mixed with the halogen substances, it enters the channel formed by the discharge reactor 11, and the discharge reactor performs high-voltage discharge, thereby efficiently activating the halogen substances and converting them into halogen elements, halogen intermediates and atoms. The activated halogen substances are easy to combine with mercury, transforming elemental mercury into oxidized and particle-attached mercury. After passing through the discharge reactor, the flue gas is discharged to the downstream dust removal and absorption device to remove oxidized mercury and particulate mercury.

The mercury removal device with this structure can realize the oxidation of more than 60% of elemental mercury, and the energy consumption level is about 72Wh/m ³ . For the purpose of compact arrangement, it is also possible to change the cylindrical shape into a regular hexagonal shape, etc.

As shown in Figure 5, it is another embodiment of the discharge reactor of the present invention: a corona discharge reactor, made up of a high voltage pole 13 and a grounding pole plate 14, a high voltage pole line 13 is positioned between two grounding pole plates 14, and a high voltage pole There is a discharge gap between 13 and the ground electrode 14, and the preferred discharge gap is 200mm. The discharge reactor power supply 4 supplies power to the discharge reactor 11 . It can be seen from the figure that multiple sets of discharge reactors 11 can be arranged in the halogen substance activation device 3 , and multiple sets of discharge reactors 11 constitute a discharge reaction zone to activate the halogen substances. This embodiment can directly modify the existing flue, and arrange the high voltage pole 13 and the grounding plate 14 in the flue. Since the gas flow rate in the general gas pipeline is about 10-15m/s, there is generally no ash accumulation, and no ash hopper can be arranged.

This type of corona discharge reactor generally adopts positive polarity discharge, and the discharge peak voltage is 10-100kV. Short pulse or DC superimposed AC high-voltage power supply can be used to obtain better activation effect. The voltage rise time is generally tens of nanoseconds to tens of microseconds. Taking the above method to treat flue gas as an example, when the mercury content in the flue gas is 13μg/ ^m3 , when the concentration of Br ₂ added to the boiler exceeds 4ppm, mercury The net removal rate can reach 64%, and the total mercury control rate can reach 80%.

The invention can be used for flue gas demercuration of various boilers or incinerators.

Claims (6)

1. the flue gas mercury removal system based on discharge activation halogen family material, comprise pretreatment unit (2), dust arrester (5), the absorption plant (8) successively flue gas processed, it is characterized in that: between described pretreatment unit (2) and dust arrester (5), be provided with halogen family material activating apparatus (3); Described halogen family material activating apparatus (3) comprising:

Housing (18) and the flue that is positioned at described housing (18) two ends; In described housing (18), be provided with discharge reactor (11), at the flue (12a) that is positioned at housing (18) front end, be provided with nozzle (16);

Described halogen family material activating apparatus (3) is thrown in halogen family material by nozzle (16) in flue gas, halogen family material is mixed with flue gas, under aerobic gas condition, described halogen family material activating apparatus (3) activates halogen family material by electrion, makes elemental mercury in mercury fume form oxidation state mercury and particle adheres to mercury;

Described halogen family material is halogen simple substance or halogen;

Dust arrester (5), absorption plant (8) carry out dedusting and absorbing and removing oxidation state mercury and particle to the mercury fume after processing and adhere to mercury.

2. flue gas mercury removal system as claimed in claim 1, it is characterized in that: described discharge reactor (11) is dielectric barrier discharge reactor, described dielectric impedance reactor comprises high-pressure stage (13) and earthing pole (14), and described high-pressure stage (13) separates by dielectric layer (15) with earthing pole (14) is middle.

3. flue gas mercury removal system as claimed in claim 2, it is characterized in that: described dielectric barrier discharge reactor is the board-like dielectric barrier discharge reactor of plate, described earthing pole (14) and dielectric layer (15) and high-pressure stage (13) are dull and stereotyped, high-pressure stage (13) is attached on dielectric layer (15), earthing pole (14) and the parallel placement of dielectric layer (15), leave space between described earthing pole (14) and dielectric layer (15).

4. flue gas mercury removal system as claimed in claim 2, it is characterized in that: described dielectric barrier discharge reactor is line cartridge type dielectric barrier discharge reactor, described earthing pole (14) and dielectric layer (15) are attached together formation passage, described earthing pole (14) is positioned at the skin of passage, described dielectric layer (15) is positioned at the internal layer of passage, described high-pressure stage (13) is high pressure polar curve, is positioned at the place, axis that described earthing pole (14) and dielectric layer (15) form passage.

5. flue gas mercury removal system as claimed in claim 1, it is characterized in that: described discharge reactor (11) is corona discharge reactor, by high-pressure stage (13) and a plurality of earthing poles (14), formed, high-pressure stage (13) is positioned between earthing pole (14), between described high-pressure stage (13) and earthing pole (14), leaves discharging gap.

6. the flue gas mercury removal system as described in claim 2-5 any one claim, is characterized in that: the external discharge reactor power supply (4) of described discharge reactor (11) is high voltage source.

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