Fly ash injection dechlorination system based on mechanochemical modification

Abstract

The invention discloses a fly ash injection dechlorination system based on mechanochemical modification, which comprises a boiler body and a component arranged in the boiler body for dechlorination, and is characterized in that an electric dust remover body is arranged in the middle of the boiler body, and a desulfurization tower and a wet electric dust remover are sequentially arranged behind the boiler body; an adsorbent spraying device, a spraying pipeline, a ball mill and a feeding tank are arranged outside the boiler body, a feeding port of the ball mill is in through connection with an ash hopper and the feeding tank, and the ash hopper is installed below the electric dust remover body and used for collecting coal ash. The fly ash jet dechlorination system based on mechanochemical modification not only can absorb hydrogen chloride in flue gas, but also can modify and reuse fly ash, so that the concentration of hydrogen chloride in the flue gas before entering a desulfurization tower is reduced, and the amount of desulfurization wastewater is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of pollutant control in coal-fired power plants, in particular to a fly ash injection dechlorination system based on mechanochemical modification. Background Art

[0002] The gypsum wet desulfurization process of limestone is widely used in the flue gas desulfurization treatment process of domestic coal-fired power plants due to its high desulfurization efficiency, stable equipment operation and good reliability. Fly ash, as a by-product of coal-fired power plants, is considered to be a potential adsorbent due to its low cost advantages and wide sources. By adding fly ash and lime milk to the ball mill, the fly ash is mechanochemically modified, and the modified fly ash is sprayed into the flue, which can effectively remove hydrogen chloride in the flue gas. my country's power plants are paying more and more attention to zero discharge of desulfurization wastewater, but operating costs are currently the main problem. Therefore, the development of a new dechlorination technology that is safe, environmentally friendly, economical and efficient is of great significance to achieving the goal of zero discharge of desulfurization wastewater in power plants.

[0003] The invention with announcement number CN110294461B discloses an adjustable sulfuric acid dechlorination process and a dechlorination tower. Waste chlorine gas passes through a wire mesh demister with compressed air to remove entrained foam, is discharged from the gas outlet N4, and is treated by a chlorine-containing tail gas absorption system; the dechlorinated sulfuric acid flows into the bottom of the tower and is transported to a sulfuric acid storage tank for storage through a dechlorination tower discharge pump. The process route is simple, and the treatment capacity of waste sulfuric acid of a single set of equipment is improved; the total chlorine removal rate can reach up to 98.6%; the waste sulfuric acid treatment capacity is flexible, and refined control is achieved.

[0004] The invention with the announcement number CN108310938A discloses a method and system for controlling the discharge of desulfurization wastewater by dechlorination. Before wet desulfurization, the gaseous chlorine in the flue gas is removed by acid-base neutralization reaction, and the amount of alkaline absorbent sprayed is aimed at removing almost all the chlorine. The chlorine-containing particles generated after the reaction are removed by the dust collector, and there is no need to discharge wastewater to the outside, fully realizing the active zero discharge of desulfurization wastewater. Moreover, this scheme is a "two-stage dechlorination", which can meet the requirements of the chlorine content index, so that complete dechlorination can meet the actual industrial application.

[0005] However, the high concentration of chloride ions in the flue gas causes the limestone solution to be inhibited. Desulfurization wastewater containing heavy metals, high salt content, and high suspended solids must be discharged regularly to ensure the stability of the system and the flue gas desulfurization efficiency. This desulfurization wastewater is difficult to treat and will cause secondary pollution to the environment if discharged directly.

[0006] Therefore, we proposed a fly ash injection dechlorination system based on mechanochemical modification to solve the above problems. Summary of the invention

[0007] The purpose of the present invention is to provide a fly ash injection dechlorination system based on mechanochemical modification. In order to solve the problem that the concentration of chloride ions in the existing flue gas is too high, resulting in the inhibition of limestone solution, it is necessary to regularly discharge desulfurization wastewater containing heavy metals, high salt content and high suspended matter to ensure the stability of the system and the flue gas desulfurization efficiency. This desulfurization wastewater is difficult to treat and will cause secondary pollution to the environment if discharged directly.

[0008] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: a fly ash injection dechlorination system based on mechanochemical modification, comprising a boiler body, and components arranged inside the boiler body for dechlorination, an electrostatic precipitator body, which is installed in the middle of the boiler body, and a desulfurization tower and a wet electrostatic precipitator are installed in sequence behind the boiler body, an adsorbent injection device, an injection pipeline, a ball mill and a feeding tank are arranged outside the boiler body, the feed port of the ball mill is respectively connected with the ash hopper and the feeding tank, and the ash hopper is installed below the electrostatic precipitator body for collecting fly ash.

[0009] Preferably, the components for dechlorination include a superheater, an economizer body, a denitrification device, an air preheater, and a low-temperature economizer which are sequentially arranged inside the boiler body, and an exhaust chimney is arranged at the rear end of the boiler body to discharge the cleaned flue gas.

[0010] Preferably, the adsorbent injection device is connected to the discharge port of the ball mill so as to spray the modified fly ash into the denitrification device.

[0011] Preferably, the ball mill cylinder is installed in a horizontal manner, and is connected to a transmission mechanism driven by a motor through a gear ring on the ball mill cylinder. The motor drives the ball mill to rotate, and the two ends of the ball mill are a feed port and a discharge port respectively.

[0012] Preferably, the discharge port of the ball mill is provided with a screen, and the screen allows fine ash with a particle size of less than or equal to 10 μm to pass through.

[0013] Preferably, the ball mill uses 50 mm steel balls as grinding media, and grinding aids and mineral powder are added to the ball mill with a filling rate of 40%. The fly ash and alkaline agent are fully ground by rotating the drum so that they can pass through the screen of the ball mill to obtain a modified fly ash dechlorination adsorbent.

[0014] Preferably, the adsorbent injection device is communicated with the discharge port of the ball mill, and a powder conveying device is provided outside the adsorbent injection device, which uses high-temperature gas for conveying to control the conveying amount of the modified fly ash.

[0015] Preferably, the feeding tank is filled with an alkaline agent, and the alkaline agent and fly ash in the ash hopper enter the ball mill.

[0016] Preferably, the feeding tank is connected to the feed port of the ball mill, and the alkaline agent stored in the feeding tank is lime milk, and a chemical metering device is installed inside the feeding tank to control the delivery amount of lime milk.

[0017] Preferably, the end of the injection pipe away from the adsorbent injection device is installed in the flue inside the boiler body, and the injection pipe inside the boiler body is located between the economizer body and the denitrification device, and nozzles are arranged at equal angles at the end of the injection pipe, and the injection direction of the nozzle is opposite to the flue gas flow direction.

[0018] Compared with the prior art, the beneficial effects of the present invention are: the fly ash injection dechlorination system based on mechanochemical modification can not only absorb hydrogen chloride in flue gas, but also modify and reuse fly ash, so as to reduce the concentration of hydrogen chloride in flue gas before entering the desulfurization tower, thereby reducing the amount of desulfurization wastewater. The specific contents are as follows:

[0019] 1. The fly ash obtained from the electrostatic precipitator body can be mechanochemically modified to greatly increase the specific surface area of ​​the fly ash, so that the chloride generated by the reaction is easy to adhere to the surface of the modified fly ash, thereby achieving the adsorption and removal of hydrogen chloride.

[0020] 2. The modified fly ash containing alkaline substances is sprayed into the flue through the injection pipe arranged between the economizer body and the denitrification device, and can react with the hydrogen chloride in the flue gas, thereby realizing the adsorption and removal of the hydrogen chloride in the flue gas.

[0021] 3. Use limestone and gypsum as alkaline absorbents to absorb SO2 in flue gas through chemical reaction. Since hydrogen chloride in flue gas is removed, the gypsum in the desulfurization tower will not be inhibited, which can ensure the quality of gypsum and reduce the discharge of desulfurization wastewater. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the overall process of the present invention.

[0023] In the figure: 1. Boiler body; 2. Superheater; 3. Economizer body; 4. Denitrification device; 5. Air preheater; 6. Low-temperature economizer; 7. Electrostatic precipitator body; 8. Desulfurization tower; 9. Wet electrostatic precipitator; 10. Exhaust chimney; 11. Adsorbent injection device; 12. Ball mill; 13. Feeding tank; 14. Ash hopper; 15. Injection pipe. DETAILED DESCRIPTION

[0024] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the implementation regulations described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] See also Figure 1 , the present invention provides the following technical solutions:

[0026] Embodiment 1: In order to solve the problems existing in the existing flue gas desulfurization processing operation, this embodiment adopts the following technical scheme, a dechlorination system based on mechanochemical modified fly ash injection, including a boiler body 1, and components arranged inside the boiler body 1 for dechlorination, the components for dechlorination include a superheater 2, an economizer body 3, a denitrification device 4, an air preheater 5, and a low-temperature economizer 6 arranged in sequence inside the boiler body 1, and an exhaust chimney 10 is arranged at the rear end of the boiler body 1 to discharge the cleaned flue gas, an electrostatic precipitator body 7, which is installed in the middle of the boiler body 1, and a desulfurization tower 8 and a wet electrostatic precipitator 9 are installed in sequence behind the boiler body 1.

[0027] An adsorbent injection device 11, an injection pipe 15, a ball mill 12 and a feeding tank 13 are arranged outside the boiler body 1; the feed port of the ball mill 12 is respectively connected with the ash hopper 14 and the feeding tank 13, and the ash hopper 14 is installed under the electrostatic precipitator body 7 for collecting fly ash; the adsorbent injection device 11 is connected with the discharge port of the ball mill 12 so as to spray the modified fly ash into the denitrification device 4.

[0028] The flue gas generated by the combustion of pulverized coal in the boiler body 1 passes through the superheater 2, the economizer body 3, the denitrification device 4, the air preheater 5, and the low-temperature economizer 6 in sequence. The superheater 2 can increase the steam temperature and improve the thermal energy utilization rate. The economizer body 3 and the low-temperature economizer 6 can absorb the waste heat of the flue gas and reduce energy loss. The denitrification device 4 uses a catalyst and ammonia to remove NO in the flue gas. X The air preheater 5 enables the flue gas to preheat the air to a certain temperature through the internal heat sink, which can improve the heat exchange performance of the boiler and reduce energy consumption.

[0029] Then the flue gas is separated into gas and solid in the electrostatic precipitator body 7, so that the fly ash is collected in the ash hopper 14, and is ground into the ball mill 12 together with the lime milk in the feeding tank 13, and is sucked into the adsorbent injection device 11, and is sprayed into the flue through the injection pipe 15. Finally, the flue gas coming out of the electrostatic precipitator body 7 enters the desulfurization tower 8 and the wet electrostatic precipitator 9 in turn, and the obtained clean flue gas is discharged into the environment through the exhaust chimney 10.

[0030] The ash hopper 14 is connected to the feed port of the ball mill 12. The collected fly ash and the lime milk in the feeding tank 13 are ground by the ball mill 12, enter the adsorbent injection device 11, and then are sprayed into the flue inside the boiler body 1 through the injection pipe 15; according to the actual conditions of the unit, the injection position can also be selected before the denitrification device 4, after the denitrification device 4, after the air preheater 5, and before the wet desulfurization.

[0031] Embodiment 2: In order to solve the problems existing in the processing of existing flue gas desulfurization, this embodiment adopts the following technical scheme: the cylinder of the ball mill 12 is installed in a horizontal manner, and is connected to the transmission mechanism driven by the motor through the gear ring on the cylinder of the ball mill 12. The motor drives the ball mill 12 to rotate, and the two ends of the ball mill 12 are respectively a feed port and a discharge port; the discharge port of the ball mill 12 is provided with a screen, and the screen allows fine ash with a particle size of less than or equal to 10μm to pass through; 50mm steel balls are used as grinding media in the ball mill 12, and grinding aids and mineral powder are added to the ball mill 12, with a filling rate of 40%. The fly ash and alkaline agent are fully ground by rotating the drum so that they can pass through the screen of the ball mill 12 to obtain a modified fly ash dechlorination adsorbent; the adsorbent injection device 11 is connected to the discharge port of the ball mill 12, and a powder conveying device is provided outside the adsorbent injection device 11, which uses high-temperature gas for conveying to control the conveying amount of the modified fly ash.

[0032] After the modified fly ash is ground, the specific surface area of ​​the fly ash is increased, so that the area and probability of hydrogen chloride contacting with alkaline substances (such as calcium hydroxide) on the fly ash surface are larger, so that the chloride generated by the reaction is easy to adhere to the surface of the modified fly ash, and the hydrogen chloride is adsorbed and removed. After absorbing the hydrogen chloride in the flue gas, the modified fly ash finally enters the electrostatic precipitator body 7 in the form of chloride salt for dust removal.

[0033] During the operation of the ball mill 12, the length of the grinding time is a factor that affects the fly ash removal effect. Too short or too long a time cannot achieve the best fly ash removal effect. The grinding time of the ball mill 12 is 10min-30min, which can not only ensure a relatively good removal effect of the modified fly ash, but also save electricity.

[0034] Embodiment 3: In order to solve the problems existing in the existing flue gas desulfurization processing operation, this embodiment adopts the following technical scheme: the feeding tank 13 is filled with an alkaline agent, and the alkaline agent and the fly ash in the ash hopper 14 enter the ball mill 12; the feeding tank 13 is connected to the feed port of the ball mill 12, and the alkaline agent stored in the feeding tank 13 is lime milk, and the feeding tank 13 is equipped with a chemical metering device to control the delivery amount of lime milk; the injection pipe 15 is installed in the flue inside the boiler body 1 at one end away from the adsorbent injection device 11, and the injection pipe 15 inside the boiler body 1 is located between the economizer body 3 and the denitrification device 4, and nozzles are arranged at equal angles at the end of the injection pipe 15, and the injection direction of the nozzle is opposite to the flue gas flow direction, so as to increase the contact area between the injected modified fly ash and the flue gas.

[0035] The material of the feeding tank 13 is an organic polymer material or stainless steel material that is resistant to high temperature, high pressure and corrosion. The adsorbent injection device 11 is provided with a powder conveying device inside, which can control the conveying amount of the modified fly ash by adjusting the pneumatic conveying, and use high-temperature air as a carrier to convey the ground fly ash, so that the ground fly ash has a certain temperature when entering the flue, thereby improving the chemical reaction energy and adsorption energy of the modified fly ash.

[0036] The flue gas separated from the electrostatic precipitator body 7 enters the desulfurization tower 8, which adopts the limestone and gypsum wet desulfurization technology, that is, limestone and gypsum are used as alkaline absorbents to absorb SO2 in the flue gas through chemical reactions. Since the hydrogen chloride in the flue gas is removed, the gypsum in the desulfurization tower 8 will not be inhibited, which can ensure the quality of the gypsum, resulting in a reduction in the discharge of desulfurization wastewater.

[0037] The desulfurized flue gas discharged from the desulfurization tower 8 is dried and purified in the wet electrostatic precipitator 9 , and then the clean flue gas is discharged from the exhaust chimney 10 .

[0038] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A fly ash injection dechlorination system based on mechanochemical modification, comprising a boiler body (1), and a component arranged inside the boiler body (1) for dechlorination, characterized in that: An electrostatic precipitator body (7) is installed in the middle of the boiler body (1), and a desulfurization tower (8) and a wet electrostatic precipitator (9) are installed in sequence behind the boiler body (1). An adsorbent injection device (11), an injection pipeline (15), a ball mill (12) and a feeding tank (13) are arranged outside the boiler body (1). The feed port of the ball mill (12) is connected to the ash hopper (14) and the feeding tank (13) respectively. The ash hopper (14) is installed below the electrostatic precipitator body (7) for collecting fly ash.

2. A fly ash injection dechlorination system based on mechanochemical modification according to claim 1, characterized in that: The components for performing the dechlorination work include a superheater (2), an economizer body (3), a denitrification device (4), an air preheater (5), and a low-temperature economizer (6) which are sequentially arranged inside the boiler body (1), and an exhaust chimney (10) is arranged at the rear end of the boiler body (1) so as to discharge the cleaned flue gas.

3. The fly ash injection dechlorination system based on mechanochemical modification according to claim 1 is characterized in that: The adsorbent injection device (11) is connected to the discharge port of the ball mill (12) so as to inject the modified fly ash into the denitration device (4).

4. A fly ash injection dechlorination system based on mechanochemical modification according to claim 3, characterized in that: The cylinder of the ball mill (12) is installed in a horizontal manner and is connected to a transmission mechanism driven by a motor through a gear ring on the cylinder of the ball mill (12). The motor drives the ball mill (12) to rotate. The two ends of the ball mill (12) are respectively a feed port and a discharge port.

5. A fly ash injection dechlorination system based on mechanochemical modification according to claim 4, characterized in that: The discharge port of the ball mill (12) is provided with a screen, and the screen allows fine ash with a particle size of less than or equal to 10 μm to pass through.

6. A fly ash injection dechlorination system based on mechanochemical modification according to claim 5, characterized in that: The ball mill (12) uses 50 mm steel balls as grinding media, and grinding aids and mineral powder are added to the ball mill (12) with a filling rate of 40%. The fly ash and alkaline agent are fully ground by the rotation of the drum so that they can pass through the screen of the ball mill (12) to obtain a modified fly ash dechlorination adsorbent.

7. The fly ash injection dechlorination system based on mechanochemical modification according to claim 1 is characterized in that: The adsorbent injection device (11) is communicated with the discharge port of the ball mill (12), and a powder conveying device is arranged outside the adsorbent injection device (11).

8. The fly ash injection dechlorination system based on mechanochemical modification according to claim 1 is characterized in that: The feeding tank (13) is filled with an alkaline agent, and the alkaline agent and fly ash in the ash hopper (14) enter the ball mill (12).

9. A fly ash injection dechlorination system based on mechanochemical modification according to claim 8, characterized in that: The feeding tank (13) is connected to the feeding port of the ball mill (12), and the alkaline agent stored in the feeding tank (13) is lime milk. A chemical metering device is installed inside the feeding tank (13) to control the delivery amount of lime milk.

10. The fly ash injection dechlorination system based on mechanochemical modification according to claim 1, characterized in that: The end of the injection pipe (15) away from the adsorbent injection device (11) is installed in the flue inside the boiler body (1), and the injection pipe (15) inside the boiler body (1) is located between the economizer body (3) and the denitrification device (4), and nozzles are arranged at equal angles at the end of the injection pipe (15), and the injection direction of the nozzle is opposite to the direction of the flue gas flow.

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