Method for deeply removing and purifying halide in flue gas

Abstract

The embodiment of the invention provides a method for deeply removing and purifying halide in flue gas. The method for deeply removing and purifying the halide in the flue gas comprises the following steps: step 1, carrying out dust removal and cooling treatment on the flue gas containing the halide to obtain flue gas A; step 2, feeding the obtained flue gas A into a multi-stage stepped cooling spray tower for cooling treatment to obtain low-temperature flue gas C with the temperature of minus zero; 3, the low-temperature flue gas C is fed into a low-temperature adsorption tower for adsorption treatment, and regenerated gas C containing nitrogen and sulfur is obtained after purification and regeneration. Therefore, the method for deeply removing and purifying the halide in the flue gas has the advantages that the energy consumption is reduced, the adsorption efficiency of the halide in the flue gas is improved, and the construction cost is low.

Description

Technical Field

[0001] The invention relates to the technical field of flue gas treatment, and in particular to a method for deep removal and purification of halides in flue gas. Background Art

[0002] The large amount of pollutants produced by coal-fired flue gas is one of the important factors that endanger the atmospheric environment and human health. Coal-fired flue gas pollutants can be divided into two categories: main pollutants and other pollutants according to their emission and degree of harm. my country is faced with the problem of how to remove SO3, NOx, halides and heavy metals from flue gas.

[0003] In the related art, ammonia is sprayed into the activated coke bed layer, so that a denitrification rate of 70-80% can be achieved through catalytic reduction. The high-temperature flue gas is cooled to about 200°C through a cooling tower and then directly passed into a flue gas purification tower for high-temperature adsorption purification. However, high-temperature adsorption not only has the problem of large adsorbent consumption, but also has the problem of poor adsorption effect on halides in the flue gas. Summary of the invention

[0004] The present invention is based on the inventor's discovery and understanding of the following facts and problems:

[0005] In order to overcome the problems in high-temperature adsorption, the related technology proposes flue gas low-temperature adsorption technology, which is to cool the flue gas to a low temperature flue gas below room temperature, and then remove the pollutant components in the flue gas by adsorption. Low-temperature pollutant integrated removal technology (abbreviated as COAP technology) is a comprehensive flue gas pollutant treatment technology based on the principle of flue gas low-temperature adsorption. After the flue gas to be purified is cooled to a low temperature in the sub-zero temperature range, it enters the low-temperature adsorption tower and is adsorbed and purified by adsorbent. NO in the flue gas x It can be deeply adsorbed and removed at low temperatures. The saturated adsorbent is regenerated to generate a large amount of nitrogen-sulfur regeneration gas. In low-temperature adsorption, the adsorption capacity of the adsorbent is increased exponentially in a low-temperature environment, which greatly improves the adsorption purification rate compared to conventional high-temperature flue gas adsorption, and can achieve near-zero flue gas emissions. However, the inventors have realized through research that, compared with conventional high-temperature adsorption, in the low-temperature adsorption process, the diffusion rate of low-temperature flue gas is lower than that of high-temperature flue gas, which greatly increases the residence time of low-temperature flue gas in the purification tower, resulting in the problem of long purification time, which in turn affects the flue gas purification efficiency.

[0006] The present invention aims to solve one of the technical problems in the related art at least to a certain extent. To this end, an embodiment of the present invention provides a method for deep removal and purification of halides in flue gas. The method for deep removal and purification of halides in flue gas has the advantage of improving adsorption efficiency.

[0007] The method for deep removal and purification of halides in flue gas according to the embodiment of the present invention comprises the following steps:

[0008] Step 1, dust removal and cooling of flue gas containing halides to obtain flue gas A;

[0009] Step 2: The obtained flue gas A is subjected to a water washing process to remove the acidic substances soluble in water to obtain flue gas B, and the acid-containing wastewater generated by the water washing process is sent to an alkaline washing process for neutralization reaction to obtain halide salts;

[0010] Step 3, sending the obtained flue gas B into a multi-stage step cooling spray tower for cooling treatment to obtain low-temperature flue gas C with a temperature below zero;

[0011] Step 4: sending the low-temperature flue gas C to a low-temperature adsorption tower for adsorption treatment to obtain purified and regenerated nitrogen-sulfur regeneration gas D.

[0012] The method for deep removal and purification of halides in flue gas of the embodiment of the present invention sequentially passes through dust removal, water washing and cooling, step cooling spray and low temperature adsorption and other processes, wherein dust removal and water washing and cooling can remove dust from flue gas, and through the adsorption of adsorbent materials, deep removal, low temperature adsorption, adsorption at low temperature, the final removal efficiency can reach 98%, and there is the advantage of high adsorption efficiency. At the same time, through the step-by-step cooling treatment, the flue gas temperature is gradually cooled from about 80°C to about -80°C, and when the temperature is graded, when the total temperature of the cooling is constant, the temperature difference between each stage is reduced, which helps to realize the gradient utilization of cold capacity, reduces energy consumption and improves cooling efficiency.

[0013] In addition, the method for deep removal and purification of halides in flue gas according to the embodiment of the present invention eliminates the need for economizers, air preheaters and electrostatic precipitators, which has the advantage of low construction cost in terms of overall equipment construction and application efficiency.

[0014] Therefore, the method for deep removal and purification of halides in flue gas according to the embodiment of the present invention has the advantages of reducing energy consumption, improving the adsorption efficiency of halides in flue gas and low construction cost.

[0015] In some embodiments, in step 1, the flue gas is first sent to a dust collector for dust removal, and then the dust-removed flue gas is passed into an air premixer for cooling. The temperature of the flue gas A at the outlet of the air premixer is below 80°.

[0016] In some embodiments, the flue gas A is sequentially passed into the first-stage cooling component, the second-stage cooling component, the third-stage cooling component and the fourth-stage cooling component of the multi-stage cascade cooling spray tower to obtain a low-temperature flue gas C with a temperature of -80°C to -15°C.

[0017] In some embodiments, the first-stage cooling component cools the flue gas A after alkali solution washing from 70°C to 80°C to 40°C to 44°C; the second-stage cooling component cools the flue gas to 10°C to 15°C; the third-stage cooling component cools the flue gas to -10°C to 0°C; the fourth-stage cooling component cools the flue gas to -80°C to -15°C.

[0018] In some embodiments, in step 3, the temperature of the adsorption treatment is -80°C to -15°C.

[0019] In some embodiments, at least two low-temperature adsorption towers are provided. When one of the low-temperature adsorption towers is saturated with adsorption, the flue gas is switched to another low-temperature adsorption tower for adsorption treatment, and the two low-temperature adsorption towers are alternately treated in sequence.

[0020] In some embodiments, the low-temperature adsorption tower is a moving bed adsorption tower.

[0021] In some embodiments, the saturated adsorbent in the low-temperature adsorption tower is regenerated by heating or vacuum suction.

[0022] In some embodiments, in step 3, the adsorbent used in the adsorption treatment is a low-temperature flue gas adsorbent, which is spherical or cylindrical and includes a breathable outer shell and a plurality of adsorbent particles contained in the breathable outer shell or a plurality of adsorbent particles coated with a breathable membrane. The breathable outer shell is provided with air holes for allowing low-temperature flue gas to enter and exit. The diameter of the adsorbent particles is 1 mm to 10 mm, and the diameter of the adsorbent is 10 mm to 100 mm.

[0023] In some embodiments, in step 1, the flue gas includes NO x :70mg / N m 3 ~80mg / N m 3 ; SO3: 25mg / m 3 ~35mg / Nm 3 ; Dust: 175~200mg / Nm 3 , Mercury: 1.50μg / Nm 3 ~3.00μg / Nm 3 HCl: 1.2 μg / m 3 ~1.9μg / Nm 3 . BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a flow chart of a method for deep removal and purification of halides in flue gas according to an embodiment of the present invention. DETAILED DESCRIPTION

[0025] Embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to be used to explain the present invention, but should not be understood as limiting the present invention.

[0026] Reference below Figure 1 The method for deep removal and purification of halides in flue gas according to an embodiment of the present invention is described.

[0027] The method for deep removal and purification of halides in flue gas according to the embodiment of the present invention comprises the following steps:

[0028] Step 1, dust removal and cooling of flue gas containing halides to obtain flue gas A;

[0029] Step 2: The obtained flue gas A is subjected to a water washing process to remove the acidic substances soluble in water to obtain flue gas B, and the acid-containing wastewater generated by the water washing process is sent to an alkaline washing process for neutralization reaction to obtain halide salts;

[0030] Step 3, sending the obtained flue gas B into a multi-stage step cooling spray tower for cooling treatment to obtain low-temperature flue gas C with a temperature below zero;

[0031] Step 4: sending the low-temperature flue gas C to a low-temperature adsorption tower for adsorption treatment to obtain purified and regenerated nitrogen-sulfur regeneration gas D.

[0032] The method for deep removal and purification of halides in flue gas of the embodiment of the present invention sequentially comprises the processes of dust removal, cooling treatment, step cooling spray and low-temperature adsorption, wherein the dust removal and cooling treatment can remove dust from the flue gas, and low-temperature adsorption is performed through the adsorption effect of the adsorption material. The adsorption is performed at low temperature, and the final removal efficiency of halides and heavy metals can reach 98%, which has the advantage of high adsorption efficiency.

[0033] At the same time, the flue gas B is subjected to a step-by-step cooling treatment, and the flue gas temperature is gradually reduced from about 80°C to about -80°C. Moreover, during the graded cooling, when the total cooling temperature is constant, the temperature difference between each stage is reduced, which helps to realize the gradient utilization of cooling capacity, reduce energy consumption, and improve cooling efficiency.

[0034] In addition, the method for deep removal and purification of halides in flue gas in the embodiment of the present invention eliminates the need for economizer and electrostatic precipitator to treat flue gas, so the overall construction cost and application cost of the equipment can be reduced.

[0035] Therefore, the method for deep removal and purification of halides in flue gas according to the embodiment of the present invention has the advantages of reducing energy consumption, improving the adsorption efficiency of halides in flue gas and low construction cost.

[0036] Table 1 Pilot platform verification results

[0037]

[0038] Table 1 shows that the mercury content before water washing is 1.94 μg / m 3 At the outlet of the spray tower, the mercury content was reduced to 0.04 μg / m 3 After passing through the adsorption tower outlet, the mercury content was reduced to 0.02 μg / Nm 3 , the removal rate reached 99%.

[0039] Table 1 shows that the HCl content before water washing is 1.52 μg / m 3 At the outlet of the spray tower, the mercury content was reduced to 0.03 μg / m 3 After passing through the adsorption tower outlet, the mercury content was reduced to 0.02 μg / Nm 3 , the removal rate reaches 98.7%. It can be seen from the above treatment results that the treatment method according to the present invention can achieve a high removal rate of sulfur-containing pollutants and heavy metals in flue gas, meeting the national requirements for pollutant emissions. At the same time, its treatment operation is simple and low-cost.

[0040] In addition, sulfides and nitrides (SO3 and NO x ) for further adsorption and conversion, pending further utilization of the sulfides therein.

[0041] In step 1, the flue gas is first sent to a dust collector for dust removal, and then the dust-removed flue gas is passed into an air premixer for cooling. The temperature of the flue gas A at the outlet of the air premixer is below 80°.

[0042] The method for deep removal and purification of halides in flue gas in the embodiment of the present invention cools the flue gas by first passing it into an air premixer. The air premixer has the advantages of improved heat exchange efficiency and low energy consumption.

[0043] The flue gas A is sequentially passed into the first-stage cooling component, the second-stage cooling component, the third-stage cooling component and the fourth-stage cooling component of the multi-stage cascade cooling spray tower to obtain low-temperature flue gas C with a temperature of -80°C to -15°C.

[0044] It can be understood that the multi-stage cascade cooling spray tower includes a primary cooling component, a secondary cooling component, a tertiary cooling component and a quaternary cooling component.

[0045] The method for deep removal and purification of halides in flue gas of the embodiment of the present invention can reduce the temperature difference between each temperature reduction by using a primary cooling component, a secondary cooling component, a tertiary cooling component and a quaternary cooling component to cool the flue gas, thereby avoiding the problem of poor heat exchange effect and high energy consumption caused by large temperature difference of step cooling. Therefore, setting a four-stage cooling component is helpful to further realize the utilization of cooling gradient and improve the cooling efficiency of the equipment.

[0046] In addition, the flue gas is cooled to -80℃ to -15℃, because the adsorption efficiency of the adsorbent is positively correlated with its temperature, that is, during adsorption, the lower the temperature of the flue gas and the higher the adsorption efficiency of the adsorbent. However, if the temperature of the adsorbent is set too low, the temperature of the heat exchange medium that needs to be set will be set too low, and the cost of producing a heat exchange medium with a lower temperature will be higher. Therefore, reasonable settings can be made according to the requirements of the adsorption efficiency of different adsorbents, taking into account the adsorption efficiency and cost of the adsorbent.

[0047] Furthermore, the flue gas is cooled to -20°C to -15°C, and the nitrogen oxides in the flue gas undergo low-temperature oxidation and adsorption on the surface of adsorbents such as activated carbon, oxidizing the difficult-to-adsorb nitric oxide gas into easily adsorbed nitrogen dioxide gas, which can achieve an adsorption capacity increase of hundreds of times. In addition, the adsorption capacity of sulfur dioxide, carbon dioxide, halides, etc. is also increased exponentially under low temperature conditions. The method for deep removal and purification of halides in flue gas of an embodiment of the present invention absorbs flue gas at low temperatures, which can increase sulfur dioxide, carbon dioxide, halides, etc. in the flue gas exponentially. In particular, for nitric oxide gas that is difficult to adsorb, the treatment efficiency increases exponentially.

[0048] Specifically, the first-stage cooling component cools the flue gas from 70°C to 80°C to 40°C to 50°C; the second-stage cooling component cools the flue gas to 10°C to 15°C; the third-stage cooling component cools the flue gas to -10°C to 0°C; the fourth-stage cooling component cools the flue gas to -80°C to -15°C.

[0049] More preferably, the four-stage cooling assembly cools the flue gas to -20°C to -15°C, and the nitrogen oxides in the flue gas undergo low-temperature oxidation and adsorption on the surface of adsorbents such as activated carbon, oxidizing the difficult-to-adsorb nitric oxide gas into easily adsorbed nitrogen dioxide gas, which can achieve a hundreds-fold increase in adsorption capacity. In addition, the adsorption capacity of sulfur dioxide, carbon dioxide, and halides is also multiplied in a low-temperature environment.

[0050] Furthermore, the primary cooling assembly can be sprayed, and the spray liquid used can be tap water or filtered lake water, river water, etc. This helps to reduce the cost of cooling. The secondary cooling assembly, the tertiary cooling assembly, and the quaternary cooling assembly can be cooled by a multi-stage compression refrigerator.

[0051] In the step 3, the temperature of the adsorption treatment is -80°C to -15°C.

[0052] The low-temperature adsorption tower can be a moving bed adsorption tower. The use of a moving bed adsorption tower can avoid the problem of poor flue gas adsorption effect due to adsorption saturation of the adsorbent. This helps to improve the adsorption efficiency of flue gas.

[0053] The method for deep removal and purification of halides in flue gas in the embodiment of the present invention can ensure that the temperature of the flue gas is not increased during adsorption by setting the temperature of the adsorption treatment to -80°C to -15°C, so that the flue gas can be adsorbed at a low temperature, which helps to maintain the adsorption capacity of the adsorbent, thereby facilitating improving the flue gas adsorption effect.

[0054] There are two low-temperature adsorption towers. When the first low-temperature adsorption tower is saturated with adsorption, the flue gas is switched to the second low-temperature adsorption tower for adsorption treatment, and the two low-temperature adsorption towers are alternately treated in sequence.

[0055] The method for deep removal and purification of halides in flue gas of the embodiment of the present invention can facilitate continuous adsorption of flue gas by setting up two low-temperature adsorption towers, thereby preventing the problem of poor adsorption effect due to adsorbent saturation.

[0056] The saturated adsorbent in the low-temperature adsorption tower is regenerated by heating or vacuum suction, which is conducive to the regeneration of the adsorbent and reduces the cost of flue gas treatment to a certain extent.

[0057] In step 3, the low-temperature flue gas adsorbent is spherical or cylindrical and includes a breathable outer shell and a plurality of adsorbent particles contained in the breathable outer shell or a plurality of adsorbent particles coated with a breathable membrane. The breathable outer shell is provided with air holes for allowing low-temperature flue gas to enter and exit. The diameter of the adsorbent particles is 1 mm to 10 mm, and the diameter of the adsorbent is 10 mm to 100 mm.

[0058] The method for deep removal and purification of halides in flue gas of the embodiment of the present invention is to install the adsorbent in a breathable shell to form adsorbent particles, and to provide the adsorbent cylinder with air holes, through which the flue gas can enter the adsorbent cylinder, and the flue gas can pass through the gaps between adjacent adsorbents and / or the holes of the adsorbent itself, thereby further reducing direct collisions, friction and wear between adsorbents, and the generation of dust, and also increasing the contact area between the flue gas and the adsorbent, and improving the air permeability of the adsorbent.

[0059] In step 1, the flue gas includes NO x :70mg / Nm 3 ~80mg / Nm 3 ; SO3: 25mg / m 3 ~35mg / N m 3 ; Dust: 175~200mg / Nm 3 , Mercury: 1.50μg / Nm 3 ~3.00μg / Nm 3 HCl: 1.2 μg / m 3 ~1.9μg / Nm 3 .

[0060] Furthermore, the method for recycling the nitrogen-sulfur regeneration gas D comprises the following steps:

[0061] The nitrogen-sulfur regeneration gas is oxidized with ozone in an oxidation tower and sprayed with water to obtain acid solution; ammonia water, the acid solution in the oxidation tower and the residual gas are introduced into a reactor with ammonia water to react to obtain a nitric-sulfur-ammonia solution; the nitric-sulfur-ammonia solution is sequentially subjected to solid-liquid separation and drying to obtain a nitric-sulfur-ammonia product.

[0062] In the description of the present invention, it is to be understood that the terms “center”, “longitudinal”, “lateral”, “length”, “width”, “thickness”, “up”, “down”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inside”, “outside”, “clockwise”, “counterclockwise”, “axial”, “radial”, “circumferential”, etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0063] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0064] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral one; it can be a mechanical connection, an electrical connection, or communication with each other; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0065] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0066] In the present invention, the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" etc. mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the described specific features, structures, materials or characteristics may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0067] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A method for deep removal and purification of halides in flue gas, characterized in that: include: Step 1, dust removal and cooling of flue gas containing halides to obtain flue gas A; Step 2: The obtained flue gas A is subjected to a water washing process to remove the acidic substances soluble in water to obtain flue gas B, and the acid-containing wastewater generated by the water washing process is sent to an alkaline washing process for neutralization reaction to obtain halide salts; Step 3, sending the obtained flue gas B into a multi-stage step cooling spray tower for cooling treatment to obtain low-temperature flue gas C with a temperature below zero; Step 4: sending the low-temperature flue gas C to a low-temperature adsorption tower for adsorption treatment to obtain purified and regenerated nitrogen-sulfur regeneration gas D.

2. The method for deep removal and purification of halides in flue gas according to claim 1, characterized in that: In step 1, the flue gas is first sent to a dust collector for dust removal, and then the dust-removed flue gas is passed into an air premixer for cooling. The temperature of the flue gas A at the outlet of the air premixer is below 80°.

3. The method for deep removal and purification of halides in flue gas according to claim 1, characterized in that: The flue gas A is sequentially passed into the first-stage cooling component, the second-stage cooling component, the third-stage cooling component and the fourth-stage cooling component of the multi-stage cascade cooling spray tower to obtain low-temperature flue gas C with a temperature of -80°C to -15°C.

4. The method for deep removal and purification of halides in flue gas according to claim 3, characterized in that: The primary cooling component cools the flue gas A after washing with alkali solution from 70°C to 80°C to 40°C to 44°C; The secondary cooling assembly cools the flue gas to 10°C to 15°C; The three-stage cooling assembly cools the flue gas to -10°C to 0°C; The four-stage cooling assembly cools the flue gas to -80°C to -15°C.

5. The method for deep removal and purification of halides in flue gas according to claim 1, characterized in that: In the step 3, the temperature of the adsorption treatment is -80°C to -15°C.

6. The method for deep removal and purification of halides in flue gas according to claim 1, characterized in that: At least two low-temperature adsorption towers are provided. When one of the low-temperature adsorption towers is saturated with adsorption, the flue gas is switched to another low-temperature adsorption tower for adsorption treatment, and the two low-temperature adsorption towers are alternately treated in sequence.

7. The method for deep removal and purification of halides in flue gas according to claim 6, characterized in that: The low-temperature adsorption tower adopts a moving bed adsorption tower.

8. The method for deep removal and purification of halides in flue gas according to claim 6, characterized in that: The saturated adsorbent in the low-temperature adsorption tower is regenerated by heating or vacuum suction.

9. The method for deep removal and purification of halides in flue gas according to claim 1, characterized in that: In step 3, the adsorbent used in the adsorption treatment is a low-temperature flue gas adsorbent, which is spherical or cylindrical and includes a breathable outer shell and a plurality of adsorbent particles contained in the breathable outer shell or a plurality of adsorbent particles coated with a breathable membrane. The breathable outer shell is provided with air holes for the low-temperature flue gas to enter and exit. The diameter of the adsorbent particles is 1 mm to 10 mm, and the diameter of the adsorbent is 10 mm to 100 mm.

10. The method for deep removal and purification of halides in flue gas according to claim 1, characterized in that: In the flue gas, in step 1, the flue gas includes NO x :70mg / Nm 3 ~80mg / Nm 3 ; SO3: 25mg / m 3 ~35mg / N m 3 ; Dust: 175~200mg / Nm 3 , Mercury: 1.50μg / Nm 3 ~3.00μg / Nm 3 ; HCl:1.2μg / m 3 ~1.9μg / Nm 3 。

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