System and method for continuously producing modified calcium hydroxide for dechlorination

Abstract

The invention relates to the field of preparation of dechlorinating agents, and discloses a system and a method for continuously producing modified calcium hydroxide for dechlorination. The system adopts an aqueous solution containing ethanol and triethanolamine as a digestion solution, and the prepared modified calcium hydroxide has large specific surface area and controllable particle size; the system is provided with a device for recovering and separating ethanol and triethanolamine in steam generated by the digestion reaction, and the recovered ethanol and triethanolamine return to the corresponding storage tanks for continuous use, so that the production cost is effectively reduced, the raw material feeding frequency is reduced, and the production continuity of the system is improved. When the system is used for preparing modified calcium hydroxide, high-quality modified calcium hydroxide can be prepared from quicklime raw materials with lower quality, and the system shows better dechlorination performance and selectivity and has better economic benefits.

Description

Technical Field

[0001] The invention relates to the field of dechlorination agent preparation, and in particular to a system and method for continuously producing modified calcium hydroxide for dechlorination. Background Art

[0002] The largest source of wastewater in coal-fired power plants comes from the desulfurization wastewater of the limestone-gypsum wet desulfurization system. The HCl gas released by coal combustion is absorbed by the desulfurization slurry in the desulfurization tower, generating desulfurization wastewater with a high chloride ion concentration, which will cause equipment corrosion, slurry poisoning, reduce the utilization rate of desulfurizers and desulfurization efficiency, affect the quality of desulfurization byproduct gypsum, increase the energy consumption of the desulfurization system, and affect the safe and stable operation of the desulfurization device. Regular discharge is required to reduce the impact on the normal operation of the desulfurization equipment. The chloride ions in the desulfurization wastewater mainly come from chlorine compounds in the flue gas. Therefore, an effective way to reduce the chloride ion concentration of the desulfurization system and reduce wastewater discharge is to reduce the chlorine-containing substances in the flue gas from entering the desulfurization tower. Flue gas dechlorination is required to reduce the concentration of chlorine-containing substances from the source. Flue gas injection adsorbent dechlorination technology can achieve desulfurization wastewater reduction.

[0003] At present, the direct removal of hydrogen chloride in flue gas mainly relies on the direct contact of the dechlorinating agent with the flue gas, which reacts with the hydrogen chloride in the flue gas to generate harmless products to achieve flue gas dechlorination. Calcium hydroxide is an economical and efficient adsorbent for dry dechlorination. Calcium hydroxide is sprayed into the reactor with a nozzle. The calcium hydroxide particles directly contact the acidic gas in the flue gas, and an acid-base neutralization reaction occurs to achieve the purpose of dechlorination, generating harmless neutral salt particles, which then enter the downstream dust removal equipment for removal. It has the characteristics of simple process flow, easy operation, no waste liquid, small flue gas temperature drop, and low cost. However, the sulfur dioxide content in flue gas is dozens of times higher than that of hydrogen chloride, and its competitive reaction will greatly affect the removal efficiency of hydrogen chloride. Calcium hydroxide needs to be modified to improve the dechlorination efficiency and selectivity. Summary of the invention

[0004] The purpose of the present invention is to overcome the problems of poor effect and complicated process of calcium hydroxide dechlorination agent in the prior art, and provide a system for continuously producing modified calcium hydroxide for dechlorination and its application. The system is provided with a recovery and separation device for digestion solution components, which can respectively recover ethanol and triethanolamine as effective components of the digestion solution, save digestion solution raw materials and reduce the frequency of feeding; ethanol and triethanolamine storage tanks are independently provided, which can accurately control the proportion of each raw material when preparing the digestion solution, which is beneficial to control the digestion reaction process and obtain modified calcium hydroxide with stable quality; a wet ball mill is used for digestion reaction, and the reaction time and the particle size of the material after the reaction are completed can be controlled by adjusting the steel ball particle size and the ball mill speed. The system is used to prepare modified calcium hydroxide, and the digestion solution with ethanol and triethanolamine as effective components can obtain modified calcium hydroxide with stable quality, good dechlorination effect and selectivity, and can achieve continuous production, which is beneficial to industrial application.

[0005] In order to achieve the above object, the present invention provides a system for continuously producing modified calcium hydroxide for dechlorination, which comprises a quicklime powder bin, a digestion solution storage tank, a wet ball mill, a conveying fan, a modified calcium hydroxide powder bin, a bubbling tower, a distillation device, an ethanol storage tank and a triethanolamine storage tank; Among them, the quicklime powder bin 1 is used to store quicklime powder and control the amount of quicklime powder supplied to the wet ball mill, the ethanol storage tank and the triethanolamine storage tank are used to supply a controllable amount of ethanol and triethanolamine solution to the digestion solution storage tank to form a digestion solution, the digestion solution storage tank is used to store the digestion solution and supply the digestion solution required for the digestion reaction to the wet ball mill, the wet ball mill is used to carry out the digestion reaction and control the particle size of the material after the digestion reaction, the conveying fan is used to provide the wind force required for conveying the modified calcium hydroxide after the digestion reaction to the modified calcium hydroxide powder bin, the bubbling tower 6 is used to absorb the ethanol and triethanolamine carried by the dust generated by the digestion reaction in the wet ball mill, the distillation device is used to distill the absorption liquid after the bubbling tower absorbs ethanol and triethanolamine and separate ethanol and triethanolamine, and the separated ethanol and triethanolamine are respectively sent to the corresponding ethanol storage tank and triethanolamine storage tank for recycling.

[0006] Preferably, the quicklime powder bin is provided with a level meter, a variable frequency air lock feeder, a belt scale, a rotary scraper and an industrial frequency rotary feeder for weighing and accurately controlling the amount of quicklime powder supplied to the wet ball mill.

[0007] Preferably, the ethanol storage tank is provided with an ethanol level meter, an ethanol adding pump and an ethanol flow meter, and the triethanolamine storage tank is provided with a triethanolamine level meter, a triethanolamine adding pump and a triethanolamine flow meter, for controlling the amount of ethanol and triethanolamine supplied to the digestion solution storage tank.

[0008] Preferably, the digestion solution storage tank is provided with a digestion solution level meter, a digestion solution pump and a digestion solution flow meter for controlling the amount of digestion solution supplied to the wet ball mill.

[0009] Preferably, the wet ball mill is provided with a bag dust collector, a branch valve, a post-digestion feeder and an ejector. The bag dust collector is used to remove dust carried in the steam generated by the digestion reaction. The post-digestion feeder is used to control the feeding speed and send the digested modified calcium hydroxide out of the wet ball mill through the branch valve. The ejector is used to use the wind power provided by the conveying fan to transport the modified calcium hydroxide to the modified calcium hydroxide powder bin.

[0010] Preferably, the wet ball mill (3) uses steel balls for grinding.

[0011] Preferably, with the total mass of the steel balls being 100 parts by weight, the amount of steel balls with a diameter of 50 mm is 19-25 parts by weight, the amount of steel balls with a diameter of 40 mm is 44-50 parts by weight, the amount of steel balls with a diameter of 30 mm is 22-26 parts by weight, and the amount of steel balls with a diameter of 25 mm is 0-10 parts by weight.

[0012] The second aspect of the present invention provides a method for continuously producing modified calcium hydroxide for dechlorination, which is carried out in the aforementioned system and comprises the following steps: (S1) mixing ethanol, triethanolamine and water in a digestion solution storage tank to obtain a digestion solution, and then mixing and ball-milling the digestion solution and quicklime powder in the wet ball mill to perform a digestion reaction; (S2) The dust-containing steam generated by the digestion reaction is dedusted, and then the ethanol and triethanolamine in the dedusted steam are recovered using an absorbing agent in the bubbling tower (6). The absorbing agent containing ethanol and triethanolamine is then distilled in the distillation device, and the obtained ethanol and triethanolamine are subsequently transported to the ethanol storage tank and the triethanolamine storage tank, respectively.

[0013] Preferably, in the digestion solution, the content of ethanol is 35-45wt%, and the content of triethanolamine is 0.1-2wt%.

[0014] Preferably, the mass ratio of the quicklime powder to the digestion solution is 1.8-2.5:1.

[0015] Preferably, the digestion reaction conditions include: temperature of 100-150° C., time of 10-15 min, and rotation speed of the wet ball mill 3 of 30-45 rpm.

[0016] Preferably, the absorption agent is ethanol and / or triethanolamine.

[0017] Preferably, the distillation treatment is carried out in two stages, and the conditions of the distillation treatment include: a temperature of 73-83°C and a time of 120-180 min for distilling out ethanol; a temperature of 95-105°C and a time of 180-240 min for distilling out water.

[0018] According to the system of the present invention, by setting up a recovery and separation device, ethanol and triethanolamine as effective components of the digestion solution can be separated and recovered, thereby saving the raw materials of the digestion solution and reducing the frequency of adding materials, thereby ensuring the continuity of the production process; independent ethanol and triethanolamine storage tanks are provided, which can accurately control the proportion of each raw material when preparing the digestion solution, which is beneficial to controlling the digestion reaction process and obtaining modified calcium hydroxide with stable quality; a wet ball mill is used for the digestion reaction, and the reaction time and the particle size of the material after the reaction are completed can be controlled by adjusting the particle size of the steel balls and the rotation speed of the ball mill.

[0019] According to the method of the present invention, modified calcium hydroxide is prepared, and the digestion solution with ethanol and triethanolamine as effective components can obtain modified calcium hydroxide with stable quality, good dechlorination effect and selectivity, and can realize automatic continuous production with high controllability, which is conducive to industrial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The present invention is a schematic diagram of a system for continuously producing modified calcium hydroxide for dechlorination.

[0021] Description of Reference Numerals 1. Quicklime powder silo; 1-1. Ash conveying pipeline; 1-2. Silo top dust collector; 1-3. Dust removal fan; 1-4. Material level meter; 1-5. Gasification plate; 1-6. Gate valve; 1-7. Frequency conversion air lock feeder; 1-8. Belt scale; 1-9. Rotary scraper; 1-10. Power frequency rotary feeder; 2. Digestion solution storage tank; 2-1. Digestion solution level meter; 2-2. Digestion solution pump; 2-3. Digestion solution flow meter; 2-4. Digestion solution concentration meter; 2-5. Deionized water flow meter; 3. Wet ball mill; 3-1. Bag dust collector; 3-2. Fan; 3-3. Thermometer; 3-4, bypass valve; 3-5, feeder; 3-6, plug valve; 3-7, ejector; 4, conveying fan; 5, modified calcium hydroxide powder silo; 5-1, gasification plate; 5-2, silo top dust collector; 5-3, fan; 5-4, level meter; 5-5, electric discharge valve; 5-6, feeder; 6, bubbling tower; 7, distillation device; 8, ethanol storage tank; 8-1, ethanol level meter; 8-2, ethanol adding pump; 8-3, ethanol flow meter; 9, triethanolamine storage tank; 9-1, triethanolamine level meter; 9-2, triethanolamine adding pump; 9-3, triethanolamine flow meter. DETAILED DESCRIPTION

[0022] The specific embodiments of the present invention are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0023] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0024] In the description of this application, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating relative importance or implicitly indicating the number of technical features indicated. Therefore, unless otherwise specified, features defined as "first" and "second" may explicitly or implicitly include one or more of the features; "plurality" means two or more. The term "including" and any variation thereof means non-exclusive inclusion, and one or more other features, integers, steps, operations, units, components and / or combinations thereof may exist or be added.

[0025] In the description of the present application, the term "include" and any variation thereof means non-exclusive inclusion, and one or more other features, integers, steps, operations, units, components and / or combinations thereof may exist or be added. Terms indicating orientation or positional relationships such as "center", "lateral", "upper", "lower", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc. are described based on the orientation or relative positional relationships shown in the drawings, and are only simplified descriptions for the convenience of describing the present application, rather than indicating that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limiting the present application.

[0026] In addition, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be internally connected between two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0027] like Figure 1As shown, the system for continuously producing modified calcium hydroxide for dechlorination of the present invention comprises a quicklime powder bin 1, a digestion solution storage tank 2, a wet ball mill 3, a conveying fan 4, a modified calcium hydroxide powder bin 5, a bubbling tower 6, a distillation device 7, an ethanol storage tank 8 and a triethanolamine storage tank 9; Among them, the quicklime powder bin 1 is used to store quicklime powder and control the amount of quicklime powder supplied to the wet ball mill 3, the ethanol storage tank 8 and the triethanolamine storage tank 9 are used to supply a controllable amount of ethanol and triethanolamine solution to the digestion solution storage tank 2 to form a digestion solution, the digestion solution storage tank 2 is used to store the digestion solution and supply the digestion solution required for the digestion reaction to the wet ball mill 3, the wet ball mill 3 is used to carry out the digestion reaction and control the particle size of the material after the digestion reaction, the conveying fan 4 is used to provide the wind force required for conveying the modified calcium hydroxide after the digestion reaction to the modified calcium hydroxide powder bin 5, the bubbling tower 6 is used to absorb the ethanol and triethanolamine carried by the dust generated by the digestion reaction in the wet ball mill 3, the distillation device 7 is used to distill the absorption liquid after the bubbling tower 6 absorbs ethanol and triethanolamine and separate ethanol and triethanolamine, and the separated ethanol and triethanolamine are respectively sent to the corresponding ethanol storage tank 8 and triethanolamine storage tank 9 for recycling.

[0028] In the system described in the present invention, preferably, the quicklime powder bin 1 is provided with a level meter 1-4, a variable frequency air lock feeder 1-7, a belt scale 1-8, a rotary scraper 1-9 and an industrial frequency rotary feeder 1-10, which are used to weigh and accurately control the amount of quicklime powder supplied to the wet ball mill 3.

[0029] In the system described in the present invention, preferably, the quicklime powder silo 1 is also provided with an ash conveying pipeline 1-1, a silo top dust collector 1-2, a dust removal fan 1-3, a gasification plate 1-5, and a gate valve 1-6. The ash conveying pipeline 1-1 is used to receive quicklime powder input from the outside, the silo top dust collector 1-2 and the dust removal fan 1-3 are used to prevent dust from overflowing during quicklime storage, the gasification plate 1-5 is used to prevent powder from caking and facilitate unimpeded material discharge, and the gate valve 1-6 is arranged at the bottom of the quicklime powder silo 1 to control the discharge speed of quicklime powder.

[0030] In a specific embodiment of the present invention, quicklime powder transported from the outside is sent to the quicklime powder bin 1 for storage through the ash conveying pipeline 1-1. When unloading is required, the discharge of quicklime powder is controlled by the gate valve 1-6 and the variable frequency air lock feeder 1-7. The stock of quicklime powder in the quicklime powder bin 1 is monitored by the level meter 1-4 for timely replenishment. The discharged quicklime powder is weighed by the belt scale 1-8 to allocate the amount of digestion solution accordingly, and then the weighed quicklime powder is sent to the wet ball mill 3 by the rotary scraper 1-9 and the industrial frequency rotary feeder 1-10.

[0031] In the system described in the present invention, preferably, the ethanol storage tank 8 is provided with an ethanol level meter 8-1, an ethanol adding pump 8-2 and an ethanol flow meter 8-3, and the triethanolamine storage tank 9 is provided with a triethanolamine level meter 9-1, a triethanolamine adding pump 9-2 and a triethanolamine flow meter 9-3, which are used to control the amount of ethanol and triethanolamine supplied to the digestion solution storage tank 2.

[0032] In the system described in the present invention, preferably, the digestion solution storage tank 2 is provided with a digestion solution level meter 2 - 1 , a digestion solution pump 2 - 2 and a digestion solution flow meter 2 - 3 for controlling the amount of digestion solution supplied to the wet ball mill 3 .

[0033] In the system described in the present invention, preferably, the digestion solution storage tank 2 is also provided with a digestion solution concentration meter 2-4 to detect the concentration of ethanol and triethanolamine in the digestion solution in real time to ensure the stability of the digestion reaction.

[0034] In a specific embodiment of the present invention, the calculated amounts of ethanol and triethanolamine are mixed in the digestion solution storage tank 2 to obtain a digestion solution, and the digestion solution is supplied to the wet ball mill 3 through the digestion solution level meter 2-1 and the digestion solution pump 2-2 according to the amount of quicklime powder obtained by weighing.

[0035] In the system described in the present invention, preferably, the wet ball mill 3 is provided with a bag dust collector 3-1, a fan 3-2, a branch valve 3-4, a post-digestion feeder 3-5 and an ejector 3-7. The bag dust collector 3-1 is exhausted by the fan 3-2 to extract and remove the dust carried in the steam generated by the digestion reaction. The post-digestion feeder 3-5 is used to control the feeding speed and send the digested modified calcium hydroxide out of the wet ball mill 3 through one of the branch valves 3-4, and the other branch valve 3-4 is used for standby in case of accidents. The ejector 3-7 is used to use the wind power provided by the conveying fan 4 to transport the modified calcium hydroxide to the modified calcium hydroxide powder bin 5.

[0036] In the system described in the present invention, preferably, the wet ball mill 3 uses steel balls, and the reaction time and the particle size of the material after the reaction are controlled by adjusting the particle size of the steel balls and the rotation speed of the ball mill.

[0037] In the system described in the present invention, preferably, the total mass of the steel balls is 100 parts by weight, the amount of steel balls with a diameter of 50 mm is 19-25 parts by weight, the amount of steel balls with a diameter of 40 mm is 44-50 parts by weight, the amount of steel balls with a diameter of 30 mm is 22-26 parts by weight, and the amount of steel balls with a diameter of 25 mm is 0-10 parts by weight. More preferably, the total mass of the steel balls is 100 parts by weight, the amount of steel balls with a diameter of 50 mm is 19-23 parts by weight, the amount of steel balls with a diameter of 40 mm is 44-48 parts by weight, the amount of steel balls with a diameter of 30 mm is 23-25 ​​parts by weight, and the amount of steel balls with a diameter of 25 mm is 4-9 parts by weight. In the present invention, by adopting the above-mentioned ball milling conditions, modified calcium hydroxide with a particle size of 50-70 μm can be obtained, which is more suitable for use as a solid-phase flue gas dechlorination agent.

[0038] According to the system of the present invention, by setting up a recovery and separation device, ethanol and triethanolamine as effective components of the digestion solution can be separated and recovered, thereby saving the raw materials of the digestion solution and reducing the frequency of adding materials, thereby ensuring the continuity of the production process; independent ethanol and triethanolamine storage tanks are provided, which can accurately control the proportion of each raw material when preparing the digestion solution, which is beneficial to controlling the digestion reaction process and obtaining modified calcium hydroxide with stable quality; a wet ball mill is used for the digestion reaction, and the reaction time and the particle size of the material after the reaction are completed can be controlled by adjusting the steel ball particle size and the ball mill speed, so that the product is more suitable as a solid-phase flue gas dechlorination agent for spraying.

[0039] The method for continuously producing modified calcium hydroxide for dechlorination according to the present invention is carried out in the aforementioned system and comprises the following steps: (S1) mixing ethanol, triethanolamine and water in a digestion solution storage tank 2 to obtain a digestion solution, and then mixing and ball-milling the digestion solution with quicklime powder in the wet ball mill 3 to perform a digestion reaction; (S2) The dust-containing steam generated by the digestion reaction is dedusted, and then the ethanol and triethanolamine in the dedusted steam are recovered using an absorbing agent in the bubbling tower (6). The absorbing agent containing ethanol and triethanolamine is then distilled in the distillation device 7, and the obtained ethanol and triethanolamine are subsequently transported to the ethanol storage tank 8 and the triethanolamine storage tank 9, respectively.

[0040] In the method of the present invention, preferably, in the digestion solution, the content of ethanol is 35-45wt%, and the content of triethanolamine is 0.1-2wt%. More preferably, the content of ethanol is 38-43wt%, and the content of triethanolamine is 0.5-1.5wt%. Most preferably, the content of ethanol is 39-42wt%, and the content of triethanolamine is 0.8-1.3wt%. In the present invention, the digestion solution obtained by the above-mentioned dosage configuration can effectively modify the surface properties of calcium hydroxide after digestion, increase the specific surface area, reduce the competitive adsorption of sulfur dioxide in flue gas, increase the selective adsorption of hydrogen chloride in flue gas, and is conducive to the overall improvement of dechlorination performance.

[0041] In the method of the present invention, preferably, the mass ratio of the quicklime powder to the digestion solution is 1.8-2.5: 1, more preferably 1.9-2.4: 1, and most preferably 2-2.3: 1. In the present invention, the above ratio can be used to save the amount of digestion solution as much as possible and reduce production costs while ensuring the acquisition of high-quality modified calcium hydroxide and the conversion rate.

[0042] In the method described in the present invention, preferably, the conditions of the digestion reaction include: a temperature of 100-150°C, a time of 10-15min, and a rotation speed of the wet ball mill 3 of 30-45rpm. More preferably, the conditions of the digestion reaction include: a temperature of 110-145°C, a time of 10-15min, and a rotation speed of the wet ball mill 3 of 32-43rpm. Most preferably, the conditions of the digestion reaction include: a temperature of 110-130°C, a time of 11-14min, and a rotation speed of the wet ball mill 3 of 35-42rpm. In the present invention, by adopting the above-mentioned digestion reaction conditions, high-quality modified calcium hydroxide can be obtained, and the modified calcium hydroxide can be prevented from agglomerating. The prepared modified calcium hydroxide has a particle size of 50-70μm, which is conducive to its application as a flue gas dechlorination agent.

[0043] In the method of the present invention, preferably, the absorption agent is ethanol and / or triethanolamine. In the present invention, for cost considerations, using ethanol as the absorption agent is beneficial to saving costs and is more suitable for industrial production.

[0044] In the method of the present invention, preferably, the distillation treatment is carried out in two stages, and the conditions of the distillation treatment include: a temperature of 73-83°C and a time of 120-180 min for distilling out ethanol; a temperature of 95-105°C and a time of 180-240 min for distilling out water. More preferably, the conditions of the distillation treatment include: a temperature of 76-82°C and a time of 110-160 min for distilling out ethanol; a temperature of 97-103°C and a time of 170-220 min for distilling out water.

[0045] In a specific embodiment, the method for continuously producing modified calcium hydroxide for dechlorination of the present invention is as follows Figure 1 The system shown in the figure includes the following steps: (1) The quicklime powder transported from the outside is transported to the quicklime powder silo 1 by pneumatic conveying through the ash conveying pipeline 1-2. The quicklime powder silo 1 is provided with a silo top dust collector 1-2 and a dust removal fan 1-3 to prevent dust leakage, a gasification plate 1-5 to prevent powder from caking, and a level meter 1-4 to detect the quicklime powder reserve; then the quicklime dust in the quicklime powder silo 1 is sent to the belt scale 1-8 for weighing by the variable frequency air lock feeder 1-7 through the gate valve 1-6, and then sent to the wet ball mill 3 by the rotary scraper 1-9 and the industrial frequency rotary feeder 1-10; (2) The ethanol and triethanolamine in the ethanol storage tank 8 and the triethanolamine storage tank 9 are transported to the digestion solution storage tank 2 through the ethanol adding pump 8-2 and the triethanolamine adding pump 9-2 to mix and obtain a digestion solution, and the amount of ethanol and triethanolamine is controlled by the ethanol flow meter 8-3 and the triethanolamine flow meter 9-3, so that the ethanol content in the digestion solution is 35-45wt%, and the triethanolamine content is 0.1-2wt%; the digestion solution storage tank 2 is provided with a digestion solution level meter 2-1 for monitoring the storage amount of the digestion solution and a digestion solution concentration meter for monitoring the concentrations of ethanol and triethanolamine in the digestion solution; (3) The digestion solution is transported to the wet ball mill 3 through the digestion solution pump 2-2, mixed with the quicklime powder for digestion reaction, and the amount of the digestion solution is controlled by the digestion solution flow meter 2-3, so that the mass ratio of the quicklime powder to the digestion solution is 1.8-2.5:1; the wet ball mill 3 uses steel balls for grinding, and the total mass of the steel balls is 100 parts by weight, the amount of steel balls with a diameter of 50 mm is 19-25 parts by weight, the amount of steel balls with a diameter of 40 mm is 44-50 parts by weight, the amount of steel balls with a diameter of 30 mm is 22-26 parts by weight, and the amount of steel balls with a diameter of 25 mm is 0-10 parts by weight; the conditions of the digestion reaction include: temperature of 100-150°C, time of 10-15 min, and rotation speed of the wet ball mill 3 of 30-45 rpm; (4) The modified calcium hydroxide obtained by the digestion reaction is discharged from the wet ball mill 3 through the bypass valve 3-4, and then transported to the modified calcium hydroxide powder bin 5 through the transport fan 4 and the ejector 3-7; (5) The dust-containing steam generated by the digestion reaction is dedusted by the bag filter 3-1 on the upper part of the wet ball mill 3, and then the dedusted steam is passed through the absorbing agent in the bubbling tower 6 to absorb the ethanol and triethanolamine carried by the steam. The absorbed absorbing agent is then transported to the distillation device 7 to separate and recover the ethanol and triethanolamine, and the recovered ethanol and triethanolamine are respectively returned to the ethanol storage tank 8 and the triethanolamine storage tank 9 for continued use.

[0046] According to the method described in the present invention, the digestion solution with ethanol and triethanolamine as effective components can obtain modified calcium hydroxide with stable quality, good dechlorination effect and selectivity. The modified calcium hydroxide has a high specific surface area and a suitable particle size, and stable quality. When used to remove hydrogen chloride in flue gas, it shows a high dechlorination efficiency and selectivity. In the presence of a high concentration of interfering sulfur dioxide, the adsorption selectivity of hydrogen chloride can reach 99.5%, which is convenient for the subsequent treatment of flue gas to achieve wet desulfurization wastewater reduction and gypsum quality improvement. Using the method of the present invention, 1.31 tons of modified calcium hydroxide can be synthesized per ton of pure quicklime, and automatic and continuous production can be achieved, with high controllability, which is conducive to industrial application.

[0047] The following examples further illustrate the system for continuously producing modified calcium hydroxide for dechlorination and its application. The examples are implemented based on the technical solution of the present invention, and detailed implementation methods and specific operation processes are given, but the protection scope of the present invention is not limited to the following examples.

[0048] The experimental methods in the following examples, unless otherwise specified, are all conventional methods in the art. The experimental materials used in the following examples, unless otherwise specified, are all commercially available.

[0049] Example 1 (1) The quicklime powder transported from outside is transported to the quicklime powder bin 1 through the ash conveying pipeline 1-2 by pneumatic conveying, and then the quicklime dust in the quicklime powder bin 1 is sent to the belt scale 1-8 for weighing by the variable frequency air lock feeder 1-7 through the gate valve 1-6, and then sent to the wet ball mill 3 by the rotary scraper 1-9 and the industrial frequency rotary feeder 1-10; (2) The ethanol and triethanolamine in the ethanol storage tank 8 and the triethanolamine storage tank 9 are transported to the digestion solution storage tank 2 through the ethanol adding pump 8-2 and the triethanolamine adding pump 9-2 to mix and obtain a digestion solution, and the amounts of ethanol and triethanolamine are controlled through the ethanol flow meter 8-3 and the triethanolamine flow meter 9-3 so that the ethanol content in the digestion solution is 40wt% and the triethanolamine content is 1wt%; (3) The digestion solution is transported to the wet ball mill 3 through the digestion solution pump 2-2 (the total mass of the steel balls is 100 parts by weight, the amount of steel balls with a diameter of 50 mm is 21 parts by weight, the amount of steel balls with a diameter of 40 mm is 46 parts by weight, the amount of steel balls with a diameter of 30 mm is 24 parts by weight, and the amount of steel balls with a diameter of 25 mm is 8 parts by weight, and the rotation speed is 39 rpm), mixed with the quicklime powder, and digested at 120°C for 14 minutes. The amount of the digestion solution is controlled by the digestion solution flow meter 2-3 so that the mass ratio of the quicklime powder to the digestion solution is 1.8-2.5:1; (4) The modified calcium hydroxide obtained by the digestion reaction is discharged from the wet ball mill 3 through the bypass valve 3-4, and then transported to the modified calcium hydroxide powder bin 5 through the conveying fan 4 and the ejector 3-7. The obtained modified calcium hydroxide is recorded as A1; (5) The dust-containing steam generated by the digestion reaction is dedusted by the bag filter 3-1 on the upper part of the wet ball mill 3, and then the dedusted steam is passed through the absorbing agent in the bubbling tower 6 to absorb the ethanol and triethanolamine carried by the steam. The absorbed absorbing agent is then transported to the distillation device 7 to separate and recover the ethanol and triethanolamine, and the recovered ethanol and triethanolamine are respectively returned to the ethanol storage tank 8 and the triethanolamine storage tank 9 for continued use.

[0050] Example 2 The method described in Example 1 was adopted, except that the total mass of the steel balls was 100 parts by weight, the amount of steel balls with a diameter of 50 mm was 24 parts by weight, the amount of steel balls with a diameter of 40 mm was 49 parts by weight, the amount of steel balls with a diameter of 30 mm was 26 parts by weight, the rotation speed was 35 rpm, the digestion reaction was carried out at 140°C for 13 min, and the obtained modified calcium hydroxide was recorded as A2.

[0051] Example 3 The method described in Example 1 was adopted, except that the total mass of the steel balls was 100 parts by weight, the amount of steel balls with a diameter of 50 mm was 24 parts by weight, the amount of steel balls with a diameter of 40 mm was 49 parts by weight, the amount of steel balls with a diameter of 30 mm was 26 parts by weight, the rotation speed was 40 rpm, the digestion reaction was carried out at 150° C. for 110 min, and the obtained modified calcium hydroxide was recorded as A3.

[0052] Example 4 The method described in Example 1 was adopted, except that the content of ethanol in the digestion solution was 42wt%, the content of triethanolamine was 1.3wt%, and the obtained modified calcium hydroxide was recorded as A4.

[0053] Example 5 The method described in Example 1 was adopted, except that the content of ethanol in the digestion solution was 39wt%, the content of triethanolamine was 0.9wt%, and the obtained modified calcium hydroxide was recorded as A5.

[0054] Comparative Example 1 The method described in Example 1 was adopted, except that the digestion reaction was carried out at 170° C. and the obtained modified calcium hydroxide was recorded as D1.

[0055] Comparative Example 2 The method described in Example 1 was adopted, except that the ethanol content in the digestion solution was 40wt%, no triethanolamine was added, and the obtained modified calcium hydroxide was recorded as D2.

[0056] Test Example 1 The average particle size of the modified calcium hydroxides A1-A5 and D1-D2 prepared in Examples 1-5 and Comparative Examples 1-2 was measured using a particle size analyzer; The specific surface areas of the modified calcium hydroxides A1-A5 and D1-D2 prepared in Examples 1-5 and Comparative Examples 1-2 were tested by the BET method; The results are shown in Table 1: Table 1

[0057] As can be seen from Table 1, the modified calcium hydroxide prepared by the method of the present invention has a larger specific surface area and a smaller particle size than the modified calcium hydroxide obtained by digesting the digestion solution without adding triethanolamine, which is more conducive to the application in flue gas dechlorination and improves the dechlorination performance; by premixing the digestion solution, setting multiple flow meters and weighing the raw materials, the reaction process is effectively controlled, the reaction temperature is controlled below 150°C, and agglomeration caused by excessively violent reaction is avoided, which is conducive to obtaining high-quality modified calcium hydroxide with a smaller average particle size.

[0058] Test Example 2 The dechlorination efficiency and selectivity of the modified calcium hydroxides A1-A5 and D1-D2 prepared in Examples 1-5 and Comparative Examples 1-2 were tested by the following method: the modified calcium hydroxide was sprayed into the flue gas dechlorination device of the boiler system, the concentrations of hydrogen chloride and sulfur dioxide in the flue gas to be treated were both 150 ppm, the concentrations of hydrogen chloride and sulfur dioxide at the tail gas outlet were recorded, and the amounts of hydrogen chloride and sulfur dioxide absorbed were calculated, the percentage of the amount of hydrogen chloride absorbed to the total amount of hydrogen chloride in the flue gas was taken as the dechlorination efficiency, and the percentage of the amount of hydrogen chloride absorbed to the total amount of hydrogen chloride and sulfur dioxide absorbed was taken as the dechlorination selectivity; The specific test conditions and results are shown in Table 2: Table 2

[0059] As can be seen from Table 2, the modified calcium hydroxide prepared by the method of the present invention, under the same test conditions, shows better dechlorination efficiency than the modified calcium hydroxide obtained by digestion solution without adding triethanolamine and the modified calcium hydroxide obtained by digestion at a higher temperature, which is consistent with the average particle size and specific surface area data obtained by the test. Even under the interference of the same concentration of sulfur dioxide, the dechlorination selectivity is generally higher than 99%, showing good dechlorination selectivity.

[0060] The system for continuously producing modified calcium hydroxide for dechlorination disclosed by the present invention adopts ethanol and triethanolamine to synthesize modified calcium hydroxide, has high product conversion rate and stable quality, and can synthesize 1.31 tons of calcium hydroxide per ton of pure quicklime powder; the obtained modified calcium hydroxide has good dechlorination efficiency and selectivity; by setting a recovery and separation device for effective components of the digestion solution, the separation and recovery of ethanol and triethanolamine are realized, and the ethanol and triethanolamine are directly returned to the corresponding raw material storage tank for continued use, thereby reducing the frequency of raw material feeding, having better production continuity, and saving production cost; the modified calcium hydroxide prepared by the present invention uses relatively low-quality quicklime powder as raw material, with a cost of about 400 yuan / ton, ethanol cost of about 8,000 yuan / ton, and triethanolamine cost of 8,000 yuan / ton, so that a product of good quality can be obtained, and taking a sales price of 1,000 yuan / ton as an example, the profit of each ton of modified calcium hydroxide is about 600 yuan, which has good economic benefits.

[0061] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A system for continuously producing modified calcium hydroxide for dechlorination, characterized in that: The system comprises a quicklime powder bin (1), a digestion solution storage tank (2), a wet ball mill (3), a conveying fan (4), a modified calcium hydroxide powder bin (5), a bubbling tower (6), a distillation device (7), an ethanol storage tank (8) and a triethanolamine storage tank (9); The quicklime powder bin (1) is used to store quicklime powder and control the amount of quicklime powder supplied to the wet ball mill (3); the ethanol storage tank (8) and the triethanolamine storage tank (9) are used to supply a controllable amount of ethanol and triethanolamine solution to the digestion solution storage tank (2) to form a digestion solution; the digestion solution storage tank (2) is used to store the digestion solution and supply the digestion solution required for the digestion reaction to the wet ball mill (3); the wet ball mill (3) is used to perform a digestion reaction and control the particle size of the material after the digestion reaction; The conveying fan (4) is used to provide the wind force required for conveying the modified calcium hydroxide after the digestion reaction to the modified calcium hydroxide powder bin (5); the bubbling tower (6) is used to absorb ethanol and triethanolamine carried by the dust generated by the digestion reaction in the wet ball mill (3); the distillation device (7) is used to distill the absorption liquid after the bubbling tower (6) absorbs ethanol and triethanolamine and separate ethanol and triethanolamine, and respectively convey the separated ethanol and triethanolamine to the corresponding ethanol storage tank (8) and triethanolamine storage tank (9) for recycling.

2. The system according to claim 1, characterized in that The quicklime powder bin (1) is provided with a material level meter (1-4), a variable frequency air lock feeder (1-7), a belt scale (1-8), a rotary scraper (1-9) and an industrial frequency rotary feeder (1-10), which are used to weigh and accurately control the amount of quicklime powder supplied to the wet ball mill (3).

3. The system according to claim 1, characterized in that The ethanol storage tank (8) is provided with an ethanol level meter (8-1), an ethanol liquid adding pump (8-2) and an ethanol flow meter (8-3), and the triethanolamine storage tank (9) is provided with a triethanolamine level meter (9-1), a triethanolamine liquid adding pump (9-2) and a triethanolamine flow meter (9-3), which are used to control the amount of ethanol and triethanolamine supplied to the digestion solution storage tank (2).

4. The system according to claim 1, characterized in that The digestion solution storage tank (2) is provided with a digestion solution level meter (2-1), a digestion solution pump (2-2) and a digestion solution flow meter (2-3), which are used to control the amount of digestion solution supplied to the wet ball mill (3).

5. The system according to claim 1, characterized in that The wet ball mill (3) is provided with a bag dust collector (3-1), a branch valve (3-4), a post-digestion feeder (3-5) and an ejector (3-7). The bag dust collector (3-1) is used to remove dust carried in the steam generated by the digestion reaction. The post-digestion feeder (3-5) is used to control the feeding speed and send the digested modified calcium hydroxide out of the wet ball mill (3) through the branch valve (3-4). The ejector (3-7) is used to use the wind power provided by the conveying fan (4) to transport the modified calcium hydroxide to the modified calcium hydroxide powder bin (5).

6. The system according to claim 1, characterized in that The wet ball mill (3) uses steel balls for grinding; Preferably, with the total mass of the steel balls being 100 parts by weight, the amount of steel balls with a diameter of 50 mm is 19-25 parts by weight, the amount of steel balls with a diameter of 40 mm is 44-50 parts by weight, the amount of steel balls with a diameter of 30 mm is 22-26 parts by weight, and the amount of steel balls with a diameter of 25 mm is 0-10 parts by weight.

7. A method for continuously producing modified calcium hydroxide for dechlorination, characterized in that: The method is carried out in a system as claimed in any one of claims 1 to 6, comprising the following steps: (S1) mixing ethanol, triethanolamine and water in a digestion solution storage tank (2) to obtain a digestion solution, and then mixing and ball-milling the digestion solution with quicklime powder in the wet ball mill (3) to perform a digestion reaction; (S2) The dust-containing steam generated by the digestion reaction is dedusted, and then the ethanol and triethanolamine in the dedusted steam are recovered using an absorption agent in the bubbling tower (6). The absorption agent containing ethanol and triethanolamine is then distilled in the distillation device (7), and the obtained ethanol and triethanolamine are subsequently transported to the ethanol storage tank (8) and the triethanolamine storage tank (9), respectively.

8. The method according to claim 7, characterized in that In the digestion solution, the content of ethanol is 35-45wt%, and the content of triethanolamine is 0.1-2wt%.

9. The method according to claim 7, characterized in that: The mass ratio of the quicklime powder to the digestion solution is 1.8-2.5:

1.

10. The method according to claim 7, characterized in that The digestion reaction conditions include: temperature of 100-150° C., time of 10-15 min, and rotation speed of the wet ball mill 3 of 30-45 rpm.

11. The method according to claim 7, characterized in that The absorption agent is ethanol and / or triethanolamine.

12. The method according to claim 7, characterized in that The distillation treatment is carried out in two stages, and the conditions of the distillation treatment include: a temperature of 73-83° C. and a time of 120-180 min for distilling out ethanol; a temperature of 95-105° C. and a time of 180-240 min for distilling out water.

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