System for preparing nano calcium carbonate from cement kiln bypass vent ash

Abstract

The utility model belongs to the technical field of energy conservation and environmental protection, and relates to a system for preparing nano calcium carbonate from cement kiln bypass vent ash, which comprises a flue gas heat exchanger, a gas-solid separation tower, a water washing tower, a first reaction tower, a neutralizing tower, a liquid-solid separation tower I, a second reaction tower, a liquid-solid separation tower II and a drying tower, liquid outlets of the water washing tower, the first reaction tower, the neutralizing tower, the first liquid-solid separation tower, the second reaction tower and the second liquid-solid separation tower are sequentially connected to a liquid inlet of a next device, and a solid outlet of the second liquid-solid separation tower is connected to an inlet of the drying tower and used for conveying separated solid substances. And bypass exhaust flue gas is input into an inlet of the flue gas heat exchanger. According to the utility model, the nano calcium carbonate product with higher economic value is obtained, and the waste heat of the bypass exhaust flue gas is utilized, so that the energy is saved.

Description

Technical Field

[0001] This utility model belongs to the field of energy-saving and environmental protection technology, and relates to a system for preparing nano-calcium carbonate from cement kiln bypass venting ash. Background Technology

[0002] The bypass ventilation system of a cement kiln releases a portion of high-temperature flue gas (containing some hot raw materials) from the kiln tail flue or other nearby areas. This high-temperature flue gas, at approximately 1200°C, is rapidly mixed with air in a collector box, reducing its temperature to 200-350°C. The hot raw materials are then collected using a cyclone dust collector or baghouse dust collector; this collected hot raw materials are called bypass ventilation ash. Bypass ventilation ash is a complex, high-alkali, high-chlorine material, and therefore can only be added in small quantities to cement as an admixture. However, its production is increasing year by year, making comprehensive utilization more difficult. Simultaneously, the high-temperature flue gas needs to be mixed with air to lower its temperature, but this method fails to effectively utilize the waste heat of the flue gas, resulting in a significant amount of heat being wasted. Even if the bypass ventilation ash is mineralized, the resulting product can only be used as a cement admixture or desulfurizer, with low added value. Compared to conventional mineralized products, nano-calcium carbonate is widely used in structural reinforcement, plastics and rubber production, coatings, papermaking, and other chemical, environmental, and energy fields, offering broad applications and high economic efficiency. Therefore, how to effectively convert bypass vent ash into nano-calcium carbonate while utilizing the waste heat of flue gas is a technical problem that existing technologies need to solve. Utility Model Content

[0003] The purpose of this invention is to provide a system for preparing nano-calcium carbonate from bypass vent ash in cement kilns, in order to solve the technical problems of existing technologies that make it difficult to effectively convert bypass vent ash into nano-calcium carbonate and do not make full use of the waste heat of flue gas.

[0004] The aforementioned system for preparing nano-calcium carbonate from bypass vent ash in a cement kiln includes a flue gas heat exchanger, a gas-solid separation tower, a water washing tower, a first reaction tower, a neutralization tower, a first liquid-solid separation tower, a second reaction tower, a second liquid-solid separation tower, and a drying tower. Starting from the water washing tower, the liquid outlets of the water washing tower, the first reaction tower, the neutralization tower, the first liquid-solid separation tower, the second reaction tower, and the second liquid-solid separation tower are sequentially connected to the liquid inlet of the next tower. The solid outlet of the second liquid-solid separation tower is connected to the inlet of the drying tower to transport the separated solid material. The inlet of the flue gas heat exchanger receives bypass vent ash, and the outlet of the flue gas heat exchanger is connected to the gas inlet of the gas-solid separation tower. The gas outlet of the gas-solid separation tower is connected to the gas inlet of the water washing tower, and the gas outlet of the water washing tower is connected to the gas inlet of the second reaction tower. The heat exchange medium outlet of the flue gas heat exchanger is connected to the drying tower via a pipeline for heating the drying tower. The first reaction tower also has an acid inlet, and the neutralization tower also has a raw material inlet.

[0005] Preferably, the gas inlets of both the water washing tower and the second reaction tower are located at the bottom, and the gas inlet of the second reaction tower is connected to a bubbler, through which flue gas is input from the bottom.

[0006] Preferably, the acid inlet is used to add hydrochloric acid, and the amount of acid added is excessive; the raw material inlet is used to add raw material to neutralize the acid solution.

[0007] Preferably, the liquid-solid separation tower is equipped with a solid outlet for discharging acid-insoluble substances.

[0008] Preferably, the flue gas heat exchanger reduces the temperature of the bypass vent gas to 200-350°C through the heat exchange medium, and the drying tower dries the gas through the heat exchange medium that has been heated after heat exchange, with the drying temperature of the drying tower maintained at 60-100°C.

[0009] Preferably, the liquid outlet of the liquid-solid separation tower two can be connected to the water washing tower through a circulation pipeline.

[0010] This invention has the following advantages: It utilizes the bypass vent ash (mainly composed of CaO) from a cement kiln, employing a deep calcium ion extraction process to extract calcium ions from the ash. These ions are then reacted with CO2 from the cement kiln flue gas to generate nano-calcium carbonate. After liquid-solid separation, the heat from the bypass vent flue gas is used to dry the nano-calcium carbonate, ultimately yielding the nano-calcium carbonate product. This process not only yields a high-value nano-calcium carbonate product but also utilizes the waste heat from the bypass vent flue gas, saving energy and achieving a significant energy-saving and environmentally friendly effect. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the structure of a system for preparing nano-calcium carbonate from cement kiln bypass venting ash according to the present invention.

[0012] The reference numerals in the attached figures are as follows: 1. Flue gas heat exchanger, 2. Gas-solid separation tower, 3. Water washing tower, 4. First reaction tower, 5. Neutralization tower, 6. Liquid-solid separation tower one, 7. Second reaction tower, 8. Liquid-solid separation tower two, 9. Drying tower. Detailed Implementation

[0013] The following detailed description of the embodiments, with reference to the accompanying drawings, will further illustrate the specific implementation of this utility model, in order to help those skilled in the art to have a more complete, accurate, and in-depth understanding of the inventive concept and technical solution of this utility model.

[0014] like Figure 1As shown, this utility model provides a system for preparing nano-calcium carbonate from bypass vent ash of a cement kiln, including a flue gas heat exchanger 1, a gas-solid separation tower 2, a water washing tower 3, a first reaction tower 4, a neutralization tower 5, a liquid-solid separation tower 1 6, a second reaction tower 7, a liquid-solid separation tower 2 8, and a drying tower 9. Starting from the water washing tower 3, the liquid outlets of the water washing tower 3, the first reaction tower 4, the neutralization tower 5, the liquid-solid separation tower 1 6, the second reaction tower 7, and the liquid-solid separation tower 2 8 are sequentially connected to the liquid inlet of the next device. The solid outlet of the liquid-solid separation tower 2 8 is connected to the inlet of the drying tower 9. The flue gas heat exchanger 1 is used to transport the separated solid materials. The inlet of the flue gas heat exchanger 1 is connected to the bypass exhaust flue gas. The outlet of the flue gas heat exchanger 1 is connected to the gas inlet of the gas-solid separation tower 2. The gas outlet of the gas-solid separation tower 2 is connected to the gas inlet of the water washing tower 3. The gas outlet of the water washing tower 3 is connected to the gas inlet of the second reaction tower 7. The heat exchange medium outlet of the flue gas heat exchanger 1 is connected to the drying tower 9 through a pipeline for heating the drying tower 9. The first reaction tower 4 is also provided with an acid inlet. The neutralization tower 5 is also provided with a raw material inlet.

[0015] Both the water washing tower 3 and the second reaction tower 7 have their gas inlets located at the bottom. The gas inlet in the second reaction tower 7 is connected to a bubbler, and the flue gas is input from the bottom through the bubbler. This allows the gas to fully contact the liquid, increasing the gas's residence time in the device. At the same time, the bubbler also creates a bubbling effect in the reaction tank of the second reaction tower 7, thereby increasing the reaction speed.

[0016] The acid inlet is used to add hydrochloric acid, and the amount of acid added is excessive. The raw material inlet is used to add raw material to neutralize the acid solution. In the first reaction tower 4, in order to ensure that the CaO in the bypass vent ash can be neutralized... 2+ To ensure complete extraction, it is crucial to add a slight excess of acid. This requires neutralization of the excess acid, as it would significantly impact the reaction of carbon dioxide dissolving in water to form carbonic acid. Therefore, a neutralization tower 5 should be installed, and raw material composed of calcium carbonate should be added to react with the excess acid and achieve neutralization.

[0017] The liquid-solid separation tower 6 is equipped with a solid outlet for outputting acid-insoluble substances, and the separated solids can be used as admixtures in cement production.

[0018] The flue gas heat exchanger 1 reduces the temperature of the bypass vent gas to 200-350℃ through the heat exchange medium, and the drying tower 9 dries the gas through the heated heat exchange medium, maintaining the drying temperature of the drying tower 9 at 60-100℃. This fully recovers and utilizes the waste heat of the bypass vent gas, which can reach temperatures of up to 1200℃.

[0019] The liquid outlet of the liquid-solid separation tower 8 can be connected to the water washing tower 3 through a circulation pipeline for filtrate recovery and reuse, and continue to circulate to prepare nano-calcium carbonate.

[0020] The working process of this utility model is as follows: The temperature of the bypass flue gas is about 1200℃. This system uses a flue gas heat exchanger 1 to exchange heat with the high-temperature flue gas. The heat extracted after heat exchange is used to dry the nano-calcium carbonate separated in the subsequent process.

[0021] The bypass vent gas from the flue gas heat exchanger 1 first passes through a gas-solid separator to separate the bypass vent ash from the flue gas. The flue gas then passes through a water scrubbing tower 3 to remove chloride ions, sulfur dioxide, and some carbon dioxide and other acidic gases from the flue gas, and obtain an acidic solution, which is used for further processing.

[0022] The acidic solution from the previous unit, lacking sufficient acidity, could not react with the bypass vent ash. Therefore, hydrochloric acid was added to the system to adjust the solution to a specific pH value. At this point, the bypass vent ash separated by the gas-solid separator was added, and the reaction occurred in the first reaction tower 4: CaO + RCl →

[0023] CaCl2 + R2O, thus converting Ca... 2+ It is extracted and used in the next process.

[0024] Next, a portion of cement raw meal, whose main component is CaCO3, is added to neutralization tower 5 to neutralize the excess acid.

[0025] After the reaction in neutralization tower 5 has proceeded for a period of time, the resulting liquid-solid mixture is subjected to liquid-solid separation to obtain a solution rich in Ca. 2+ A neutral solution is used as a raw material for preparing nano-calcium carbonate. The separated solids can be used as an admixture in cement production.

[0026] Rich in Ca 2+ The solution reacts with the scrubbed flue gas in the second reaction tower 7 to produce nano-calcium carbonate. The reaction process is as follows: CO2(g) → CO2(l), CO2(l) + OH- - →H2O(l)+CO3 2- Ca 2+ +CO3 2- →CaCO3.

[0027] The calcium carbonate slurry obtained from the reaction enters the next unit, the liquid-solid separation tower. The separated nano-calcium carbonate then enters drying tower 9, where it is dried using heat obtained from heat exchange at a temperature maintained between 60-100℃. The filtrate is reused to continue the production of nano-calcium carbonate.

[0028] In this invention, the mass ratio of the bypass vent ash to the hydrochloric acid is 7:5-7. When a certain amount of aqueous solution is added, the Ca content is ensured. 2+ With H + The concentration ratio is 1:2.5-4, and a further preferred concentration ratio is 1:2.5-3, to ensure that the Ca in the bypass vent ash can be effectively neutralized. 2+ All the reaction is extracted; the reaction temperature for generating nano-calcium carbonate is 30-60℃, and a more preferred reaction temperature is 40-45℃; the flue gas is introduced from the bottom in a bubbling manner. The calcium carbonate after filtration and separation is dried at a temperature of 60-100℃. The drying time is 1-5 hours.

[0029] The present invention has been described above by way of example with reference to the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-described manner. Any non-substantial improvements made by adopting the inventive concept and technical solution of the present invention, or the direct application of the inventive concept and technical solution of the present invention to other occasions without modification, are all within the protection scope of the present invention.

Claims

1. A system for preparing nano-calcium carbonate from cement kiln bypass vent ash, characterized in that: The system includes a flue gas heat exchanger (1), a gas-solid separation tower (2), a water washing tower (3), a first reaction tower (4), a neutralization tower (5), a liquid-solid separation tower one (6), a second reaction tower (7), a liquid-solid separation tower two (8), and a drying tower (9). Starting from the water washing tower (3), the liquid outlets of the water washing tower (3), the first reaction tower (4), the neutralization tower (5), the liquid-solid separation tower one (6), the second reaction tower (7), and the liquid-solid separation tower two (8) are sequentially connected to the liquid inlet of the next device. The solid outlet of the liquid-solid separation tower two (8) is connected to the inlet of the drying tower (9) to transport the separated solids. Solid material, the inlet of the flue gas heat exchanger (1) is connected to the bypass exhaust flue gas, the outlet of the flue gas heat exchanger (1) is connected to the gas inlet of the gas-solid separation tower (2), the gas outlet of the gas-solid separation tower (2) is connected to the gas inlet of the water washing tower (3), the gas outlet of the water washing tower (3) is connected to the gas inlet of the second reaction tower (7), the heat exchange medium outlet of the flue gas heat exchanger (1) is connected to the drying tower (9) through a pipeline for heating the drying tower (9), the first reaction tower (4) is also provided with an acid inlet, and the neutralization tower (5) is also provided with a raw material inlet.

2. The system for preparing nano-calcium carbonate from cement kiln bypass vent ash according to claim 1, characterized in that: The gas inlets of the water washing tower (3) and the second reaction tower (7) are both located at the bottom. The gas inlet of the second reaction tower (7) is connected to a bubbler, and the flue gas is input from the bottom through the bubbler.

3. The system for preparing nano-calcium carbonate from cement kiln bypass vent ash according to claim 1, characterized in that: The acid inlet is used to add hydrochloric acid, and the amount of acid added is excessive. The raw material inlet is used to add raw material to neutralize the acid solution.

4. The system for preparing nano-calcium carbonate from cement kiln bypass vent ash according to claim 1, characterized in that: The liquid-solid separation tower (6) is equipped with a solid outlet for outputting insoluble substances from the acid solution.

5. The system for preparing nano-calcium carbonate from cement kiln bypass vent ash according to claim 1, characterized in that: The liquid outlet of the liquid-solid separation tower 2 (8) can be connected to the water washing tower (3) through a circulation pipeline.

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