Connecting structure of upper tower body and lower tower body of carbonization tower

Abstract

The utility model discloses a connecting structure of an upper tower body and a lower tower body of a carbonization tower, and relates to the technical field of main equipment carbonization towers for producing sodium carbonate by an ammonia-alkali method. The back-mixing ring is additionally arranged at the connecting position of the upper tower body and the lower tower body, inlet air at the upper section rises to the upper part of the tower plate from sieve holes of the back-mixing sieve plate, carbonized liquid from the upper part flows to the lower part of the back-mixing sieve plate from the primary back-mixing liquid discharging pipe, and the carbonized liquid at the lower part of the back-mixing sieve plate flows to the lower half part of the cooling section through the liquid discharging pipe at the center of the liquid collecting cone; part of the carbonization liquid reaching a certain carbonization degree rises to the upper part of the back-mixing sieve plate from the liquid-phase back-mixing holes under the action of the upper-section inlet gas and the lower-section residual gas, and continues to be subjected to primary mixing and carbonation reaction with the carbonization liquid from the upper part, so that the carbonization degree of the upper-section carbonization liquid is improved again, and the carbonization degree difference between the upper-section carbonization liquid and the cooling carbonization liquid at the top of the lower section is reduced; the temperature difference is reduced, and the effects of reducing fine grains, reducing generation of secondary crystal nucleuses and reducing the too large temperature difference between the upper carbonization liquid and the lower carbonization liquid in the cooling section are achieved.

Description

Technical Field

[0001] The utility model relates to the technical field of carbonization towers, in particular to an upper and lower tower body connection structure of a carbonization tower. Background Art

[0002] The carbonization tower is the main equipment used in the carbonization process of soda ash (sodium carbonate) production. Its function is to use the ammonia brine of the Solvay process or the ammonia mother liquor of the Hou alkali process to absorb carbon dioxide to produce sodium bicarbonate, which is then sent to calcination and decomposed into sodium carbonate (i.e. soda ash). The carbonization process is an exothermic process, and the large amount of heat released needs to be removed from the tower in time. Therefore, the structural requirements of the carbonization tower must meet the requirements of the processes such as carbon dioxide absorption, sodium bicarbonate crystallization, and cooling.

[0003] Commonly used carbonization equipment is generally designed in three sections, about 20~30m high, with a daily output of about 200~300 tons / day. The tower is equipped with mushroom cap-shaped tower plates or sieve plate-type tower plates. The tower is divided into three sections from top to bottom, forming three reaction areas: ① Absorption zone: in the upper part of the tower, the solution absorbs carbon dioxide, and no crystals are precipitated; ② Generation zone: in the middle of the tower, sodium bicarbonate crystals begin to precipitate from about 2 / 3 of the tower height, and continue to absorb carbon dioxide to make the crystals grow; ③ Cooling zone: in the lower part of the tower, while absorbing carbon dioxide, cooling is carried out, so that the crystals generated in the middle continue to grow. The suspension containing crystals is taken out from the bottom of the tower and sent to the next process for solid-liquid separation, and the tail gas after absorption is discharged from the top of the tower.

[0004] In 2019, China National Salt Kunshan Co., Ltd. applied for a utility model patent with announcement number CN210457498U and name "Multi-stage external natural circulation cooling large carbonization tower", which provides a design idea for a large carbonization tower with multi-stage cooling and external natural circulation cooling. The tower body is divided into three sections: upper section, middle section and lower section. In actual production, it is only used in joint alkali production. High-concentration conversion gas enters from the bottom of the lower section. However, in the ammonia-soda process production, due to the existence of low-concentration kiln gas, the application of this design carbonization tower type in the ammonia-soda process cannot be met, so it has not been used in actual production. Utility Model Content

[0005] In order to solve the above technical problems, the utility model provides a connection structure of the upper and lower tower bodies of a carbonization tower, which reduces the temperature difference of liquid in the upper and lower tower bodies and reduces the excessive generation of secondary crystal nuclei.

[0006] To achieve this technical purpose, the utility model adopts the following scheme:

[0007] The connecting structure of the upper and lower tower bodies of the carbonization tower includes a back-mixing ring, which is connected between the upper and lower tower bodies and plays the role of gas redistribution and reducing the temperature difference of liquid in the upper and lower sections.

[0008] Compared with the prior art, the beneficial effects of the device of the utility model are:

[0009] The utility model adds a return mixing circle at the reducer connection position of the upper and lower tower bodies, spanning the upper and lower tower bodies. The main function of the return mixing circle is to cool the carbonized liquid with a higher temperature (temperature 65℃~70℃) in the upper tower body by mixing with the upper section air intake with a lower temperature. The carbonized liquid in this circle exchanges heat with the lower section carbonized liquid (temperature 44℃~46℃) through the liquid collecting cone and the partition wall. A part of the carbonized liquid reaches the return mixing screen plate through the agitation of the upper section air intake, thereby effectively reducing the temperature of the circle of carbonized liquid. When the cooled carbonized liquid flows to the lower section tower body, the liquid temperature difference is reduced, thereby reducing the excessive generation of secondary crystal nuclei. In addition, the back-mixing circle also acts as a gas distributor for the upper air intake and the lower residual gas; the upper air intake rises from the sieve holes of the back-mixing screen plate to the upper part of the tower plate, and the carbonized liquid coming down from the upper part flows from the primary back-mixing lower liquid pipe to the lower part of the back-mixing screen plate, and some of the carbonized liquid with a better carbonization degree in the lower part of the back-mixing screen plate flows to the lower tower body through the primary back-mixing lower liquid pipe in the center of the liquid collecting cone, and some of the carbonized liquid that has not reached a certain carbonization degree rises from the liquid phase back-mixing pipe arranged on the back-mixing screen plate to the upper part of the back-mixing screen plate under the action of the upper air intake and the lower residual gas, and continues to be primarily mixed and carbonated with the carbonized liquid coming down from the upper part, so that the carbonization degree of the upper carbonized liquid is once again improved, thereby reducing the carbonization degree difference with the carbonized liquid cooled at the top of the lower section, and reducing the temperature difference at the same time, which plays a role in reducing fine crystals, reducing the formation of secondary crystal nuclei, and reducing the excessive temperature difference between the upper carbonized liquid and the carbonized liquid in the lower cooling section.

[0010] After adding the back-mixing loop, the conversion rate of the alkali solution can reach 76.8% (the theoretical maximum conversion rate is 78.8%, and the currently recorded maximum conversion rate of the alkali solution carbonized by the ammonia-soda process is 76%, which is disclosed in the patent announcement No. CN210457498U), which is 0.8% higher than the recorded maximum conversion rate. Every 0.1% increase in the carbonization conversion rate can save 19 to 20 kilograms of raw salt. This application provides a more energy-saving equipment for energy-saving in the production of soda ash by the ammonia-soda process and has been put into production.

[0011] Preferably, the back-mixing circle includes a back-mixing screen plate, a primary back-mixing liquid lower pipe, a liquid collecting cone and a lower section residual gas guide pipe; the back-mixing screen plate is fixed and laid flat in the tower, and a back-mixing liquid flow channel is provided on the back-mixing screen plate; the primary back-mixing liquid lower pipe is inserted on the back-mixing screen plate, and the liquid collecting cone is located below the back-mixing screen plate and the primary back-mixing liquid lower pipe, the tower wall below the liquid collecting cone is connected to the lower end of the lower section residual gas guide pipe, and the upper end of the lower section residual gas guide pipe is connected to the side wall of the tower body below the back-mixing screen plate.

[0012] Preferably, sieve holes are provided on the back-mixing sieve plate and connected to a liquid-phase back-mixing tube, the liquid-phase back-mixing tube is extended to below the back-mixing sieve plate, and the sieve holes and the liquid-phase back-mixing tube together constitute a back-mixing liquid flow channel.

[0013] Preferably, the upper end of the primary back-mixing downpipe is higher than the back-mixing sieve plate.

[0014] Preferably, an upper gas inlet is provided on the tower wall below the back-mixing sieve plate, and a lower edge of the upper gas inlet is higher than a lower edge of a back-mixing pipe on the back-mixing sieve plate. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic diagram of the structure in the back-mixing circle provided by the utility model;

[0016] Figure 2 A top view of the back-mixing screen plate provided by the utility model;

[0017] Figure 3 The overall schematic diagram of the ultra-large carbonization tower with three sections of different diameters and graded cooling provided by the utility model;

[0018] Figure 4 A schematic diagram of the structure of the liquid retaining tower plate in the upper tower body provided by the utility model;

[0019] Figure 5 A top view of the liquid retaining tower plate provided by the utility model;

[0020] Figure 6 A schematic diagram of the air bag screen plate provided by the utility model;

[0021] Figure 7 A schematic diagram of the structure of the lower tower body provided by the utility model;

[0022] Figure 8 A schematic diagram of the structure of the annular sieve plate provided by the utility model;

[0023] The markings in the figure are: 1. liquid retaining plate; 101. ammonia-salt water inlet; 102. neutralizing water inlet; 103. gas outlet; 2. liquid retaining sieve plate; 201. inter-plate downpipe; 3. airbag sieve plate; 301. airbag baffle; 4. back-mixing circle; 401. back-mixing sieve plate; 402. liquid phase back-mixing pipe; 403. primary back-mixing downpipe; 404. liquid collecting cone; 405. lower section residual gas guide pipe; 406. upper section gas inlet; 5. cooler; 6. redistribution cone; 601. primary back-mixing downpipe; 602. secondary back-mixing downpipe; 603. tertiary back-mixing downpipe; 7. middle section gas inlet; 8. lower section gas inlet; 9. alkali solution outlet; 10. annular sieve plate; 11. cooler liquid inlet; 12. cooler liquid outlet. DETAILED DESCRIPTION

[0024] In order to fully understand the purpose, features and effects of the present invention, the present invention is described in detail through the following specific implementation methods, but the present invention is not limited thereto.

[0025] like Figure 1 and Figure 2As shown, the utility model provides a connection structure of the upper and lower tower bodies of a carbonization tower. In order to avoid excessive temperature difference between the liquid discharged from the bottom of the upper tower body and the liquid at the top of the cooling section of the lower tower body, a return mixing circle 4 is arranged at the diameter-changing position where the bottom of the upper tower body and the top of the lower tower body are connected. The return mixing circle 4 includes a return mixing screen plate 401, a primary return mixing lower liquid pipe 403, a liquid phase return mixing pipe 402, a liquid collecting cone 404, an upper gas inlet 406 and a lower residual gas guide pipe 405. The return mixing screen plate 401 is provided with a liquid phase return mixing pipe 402 while arranging ordinary sieve holes. The hole pipe of the liquid phase return mixing pipe 402 extends to a certain distance below the return mixing screen plate 401 as a return mixing liquid flow channel. A primary return mixing lower liquid pipe 403 is inserted in the center of the return mixing screen plate 401. The upper end of the primary return mixing lower liquid pipe 403 is higher than the return mixing screen plate 401 by a certain distance, and the lower end of the primary return mixing lower liquid pipe 403 extends downward to a certain position above the liquid collecting cone 404. A liquid collecting cone 404 (similar to a funnel structure) is fixed below the back-mixing sieve plate 401 (upper end of the lower tower body), and the tower wall below the upper edge of the liquid collecting cone 404 is connected to the lower end of the lower residual gas guide pipe 405, and the upper end of the lower residual gas guide pipe 405 is connected to the tower wall of the upper tower body below the back-mixing sieve plate 401, so that the residual gas of the lower tower body flows to the lower part of the back-mixing sieve plate 401 through the lower residual gas guide pipe 405, and the residual gas rises to the lower part of the upper tower body through the common sieve holes of the back-mixing sieve plate 401. An upper gas inlet 406 is provided on the tower wall of the lower tower body below the back-mixing sieve plate.

[0026] The above-mentioned carbonization tower upper and lower tower body connection structure is applied to the carbonization tower used in the ammonia-soda process, specifically:

[0027] like Figure 3 As shown, a three-stage air inlet graded cooling super-large carbonization tower with different diameters is divided into an upper tower body and a lower tower body with different diameters, and the diameter of the upper tower body is significantly larger than the diameter of the lower tower body.

[0028] like Figure 4 and Figure 5 As shown, the top cap of the upper tower body is provided with an air outlet 103, and a liquid retaining plate 1 is fixed at the top of the space inside the upper tower body to prevent the tail gas from carrying liquid into the air outlet pipe and causing material loss. The liquid retaining plate 1 is fixed at the center of the upper tower body in an umbrella-shaped cone surface, and a neutralization water inlet 102 is provided on the upper tower body side wall on one side of the liquid retaining plate 1, and an ammonia salt water inlet 101 is provided on the upper tower body side wall on the opposite side of the neutralization water inlet 102.

[0029] Several layers of sieve plates with different opening rates are fixed in the upper tower body, so that there is both a liquid continuous phase and a gas continuous phase in a section of the tower body, so that the absorption of the dioxide tower and the generation of sodium bicarbonate nuclei are completed in the upper tower body. Specifically, the upper part of the upper tower body is evenly distributed with liquid retaining sieve plates 2, and each liquid retaining sieve plate 2 is equipped with an inter-plate lower liquid pipe 201, the upper end of the inter-plate lower liquid pipe 201 is higher than the upper surface of the liquid retaining sieve plate 2 by a certain distance of 200mm, and the lower end of the inter-plate lower liquid pipe 201 extends to a certain height (100mm from the lower sieve plate) of the lower surface of the upper liquid layer of the next layer of liquid retaining sieve plate 2, and the inter-plate lower liquid pipe 201 on the upper and lower connected liquid retaining sieve plates 2 is staggered, and the gas and liquid in this part of the tower are arranged in layers, which belongs to the gas continuous phase, and the liquid height on the liquid retaining sieve plate 2 is only the height of the upper part of the inter-plate lower liquid pipe 201 higher than the liquid retaining sieve plate 2. Several layers of airbag sieve plates 3 are evenly distributed in the lower part of the upper tower body. This part is a liquid continuous phase. Evenly distributed airbag baffles 301 are fixed on the lower surface of the airbag sieve plate 3. The lower edge of the airbag baffle 301 is higher than the lower edge of the lower liquid pipe of the airbag sieve plate 3. The gas in the tower rises from the bottom to the bottom of the airbag sieve plate 3. Due to the design of the sieve hole gas flow rate, the gas cannot pass through the sieve hole all at once. An airbag area with a certain pressure is formed between the baffles below the airbag sieve plate 3, which plays a role in reinforcing the strength of the sieve plate, and also plays a role in evenly distributing the gas and stabilizing the gas flow of each sieve hole. Figure 6 shown.

[0030] like Figure 7 As shown, the lower tower body is the cooling zone, the tower diameter is 4000mm, and a three-stage equal-height tubular cooler 5 is used. The upper port is the cooler liquid inlet 11, and the lower port is the cooler liquid outlet 12. In order to make the carbonized liquid evenly distributed during cooling, 4 coolers 5 are set on the tower ring at the same height. The coolant of the cooler 5 can use the same medium and different media as the coolant. In order to adjust the cooling capacity and cooling area, a middle-layer water outlet process is set. The lower section coolant uses circulating water or direct current water as the coolant, and the middle and upper sections use seawater as the coolant.

[0031] A redistribution cone 6 is set in the space of the lower tower body between each section of the cooler 5, and each level of tower liquid back-mixing down-liquid pipe is added in conjunction with the redistribution cone 6 (from top to bottom, the first-level back-mixing down-liquid pipe 601, the second-level back-mixing down-liquid pipe 602 and the third-level back-mixing down-liquid pipe 603), and the upper ends of the added tower liquid back-mixing down-liquid pipes are connected to a liquid collecting bucket, and the top tower liquid back-mixing down-liquid pipe uses the liquid collecting cone of the back-mixing circle as the liquid collecting bucket. The length of the tower liquid back-mixing down-liquid pipe is extended to 2 / 3 of the height below the liquid inlet of each section of the cooler 5, thereby effectively increasing the residence time of the carbonized liquid in the carbonization tower, extending the growth time of the sodium bicarbonate crystals, and obtaining larger crystals. A layer of redistribution cone 6 is also set at the bottom of the lower tower body.

[0032] In order to make up for the loss of carbon dioxide absorbed by the lower section of the carbonized liquid crystal growth, a middle section gas inlet 7 and an annular sieve plate 10 (such as Figure 8 As shown in the figure, and the redistribution cone, so that the reaction in the tower is more balanced. The middle section air intake should not be too much, and 1~2 middle section air inlets 7 are set. A plurality of lower section air inlets 8 and alkali solution outlets 9 are evenly distributed at the bottom of the lower tower body. The lower section air inlet 8 is located at the lower part of the cone surface of the bottom redistribution cone, and the lower section air inlet 8 is evenly distributed in the same layer of the tower circle; the alkali solution outlet 9 is a certain distance away from the bottom redistribution cone. In order to form an effective air bag under the lower section annular sieve plate 10, which is more conducive to the full reaction of carbon dioxide gas and carbonized liquid, the middle section air intake uses kiln gas with a relatively low carbon dioxide concentration as the gas source, and the lower section air intake uses a calcining furnace with a high carbon dioxide concentration.

[0033] Carbonization method:

[0034] In order to adapt to the use of low-concentration kiln gas in the production of soda ash by the ammonia-soda process, the utility model sets three sections of air intake in the tower body, selects kiln gas with relatively low carbon dioxide concentration as the upper and middle sections of air intake, and furnace gas with higher carbon dioxide concentration as the lower section of air intake. Preferably, the kiln gas containing 35% to 45% carbon dioxide produced by calcining limestone in the lime kiln used for the upper section of the air intake. The kiln gas containing 35% to 45% carbon dioxide is used for the middle section of the air intake, which can effectively ensure the formation of the lower air bag of the lower annular sieve plate 10, so that the carbon dioxide in the gas further reacts with the carbonized liquid, and at the same time, the gas generates an upward force to overcome gravity for the smaller sodium bicarbonate crystal particles, thereby completing the self-circulation of the finer crystals in the carbonized liquid with the different temperature differences of the carbonized liquid into each section of the cooler for cooling, so that the crystals are further enlarged, and the larger particles of sodium bicarbonate crystals are obtained by repeating this process and discharged from the alkali outlet pipe at the bottom of the tower.

[0035] The furnace gas and kiln gas containing carbon dioxide enter the carbonization tower from the bottom and middle of the carbonization tower, and come into countercurrent contact with the ammonia salt water (or neutralized water) entering from the top from bottom to top through the multi-layer tower plate distribution in the carbonization tower, producing a chemical reaction. The overall reaction equation is:

[0036] NaCl+NH3+CO2+H2O=NaHCO3+NH4Cl+Q, the generated sodium bicarbonate suspension flows out from the alkali outlet at the bottom of the tower, the reaction heat Q is removed through the heat exchange of the cooler partition, and at the same time, the sodium bicarbonate crystals gradually grow from top to bottom, and the reaction waste gas and residual gas are discharged from the top of the tower to the ammonia tower to recover ammonia and carbon dioxide.

[0037] The upper intake air enters the tower from the bottom back-mixing circle 4 of the upper tower body, and enters the upper tower body after being distributed by the back-mixing screen plate 401, which not only serves as a carbon dioxide supplement but also provides back-mixing power for the carbonized liquid. Specifically, the upper air intake rises from the sieve holes of the back-mixing screen plate 401 to the upper part of the back-mixing screen plate 401, and the carbonized liquid coming down from the upper part flows from the primary back-mixing downcomer 403 to the lower part of the back-mixing screen plate 401. Part of the carbonized liquid in the lower part of the back-mixing screen plate 401 flows by gravity to the lower tower body cooling section through the liquid collecting cone 404 and the primary back-mixing downcomer 601. Part of the carbonized liquid that has reached a certain degree of carbonization rises from the liquid phase back-mixing tube 402 provided on the back-mixing screen plate 401 to the upper part of the back-mixing screen plate 401 under the action of the upper air intake and the lower residual gas, and continues to be primarily mixed and carbonated with the carbonized liquid flowing down from the upper tower body, so that the carbonization degree of the upper carbonized liquid is once again improved, thereby reducing the difference in carbonization degree with the carbonized liquid cooled at the top of the lower section, and reducing the temperature difference at the same time, which plays a role in reducing fine crystals, reducing the formation of secondary crystal nuclei, and reducing the excessive temperature difference between the upper carbonized liquid and the carbonized liquid in the lower cooling section.

[0038] In order to form an effective air bag at the bottom of the lower annular sieve plate 10, which is more conducive to the full reaction of carbon dioxide gas and carbonized liquid, the middle section air intake uses kiln gas with a relatively low carbon dioxide concentration as the gas source, and the lower section air intake uses calcining furnace gas with a high carbon dioxide concentration as the gas source. Preferably, the lower section air intake uses calcining furnace gas with a carbon dioxide concentration of 90% to 97%.

[0039] In the field application case, in order to better obtain the sodium bicarbonate crystal nucleus and increase the residence time of the upper carbonized liquid, the upper tower body diameter is increased without increasing the tower body too high. The upper tower body diameter is 4900mm, which effectively solves the above problems. By modifying the tower ring in the upper tower body and reasonably arranging the sieve hole layout, the gas-liquid contact and mass transfer are more sufficient.

[0040] The utility model uses seawater and fresh water (circulating water or direct current water) as cooling liquids, fresh water is used for the bottom cooler to ensure a qualified alkali outlet temperature, seawater with a higher temperature is used for the middle and upper coolers, the two coolants are used in series, and a direct return water main pipe flow is added to the outlet pipe of the middle cooler. The outlet water flow of the middle layer can be selected or adjusted according to the processing capacity of the carbonization tower, the cooling capacity of the upper cooler is reduced, thereby reducing the higher temperature difference caused by the high-temperature carbonization liquid coming down from the upper tower body, thereby avoiding the generation of more fine crystals.

[0041] The lower section air intake uses furnace gas with a higher concentration as the gas source. When high-concentration carbon dioxide gas enters the tower, the reaction is more violent. In addition, due to the large tower diameter, when the gas enters the tower through one air inlet, it is easy to have a biased flow. Therefore, the utility model optimizes the uniform distribution of the lower section gas inlet. Four lower section gas inlets are arranged on the tower body at the same height, and a gas distributor is arranged inside the tower.

[0042] The key to forming the airbag lies in the design of the sieve holes and the amount of air intake. Because the tower body diameter is too large, the uniform distribution and mixing of gas and liquid in the tower is the key point. This patent optimizes and transforms the inner parts of the tower body to more effectively distribute gas and liquid, so that the reaction is uniform, and better sodium bicarbonate crystals can be produced. The carbonization conversion rate can reach 76.8%, the sedimentation time can be as low as 100~130S, the carbon dioxide content in the tail gas is reduced to less than 2%, the alkali production cycle is extended to 96 hours, and the daily output can reach 400~700 tons.

[0043] Finally, it should be noted that the above-listed examples are only preferred embodiments of the present invention. Of course, those skilled in the art can make changes and modifications to the present invention. If these modifications and modifications fall within the scope of the claims of the present invention and their equivalent technologies, they should be considered to be within the scope of protection of the present invention.

Claims

1. A carbonization tower upper and lower tower body connection structure, characterized in that: It includes a back-mixing circle, which is connected between the upper and lower tower bodies and plays the role of gas redistribution and reducing the temperature difference of liquid in the upper and lower sections; The back-mixing circle includes a back-mixing screen plate, a primary back-mixing liquid pipe, a liquid collecting cone and a lower residual gas guide pipe. The back-mixing screen plate is fixed and laid flat in the tower, and a back-mixing liquid flow channel is provided on the back-mixing screen plate. A primary back-mixing liquid down pipe is inserted on the back-mixing screen plate, and a liquid collecting cone is located below the back-mixing screen plate and the primary back-mixing liquid down pipe. The tower wall below the liquid collecting cone is connected to the lower end of the lower section residual gas guide pipe, and the upper end of the lower section residual gas guide pipe is connected to the side wall of the tower body below the back-mixing screen plate.

2. The upper and lower tower body connection structure of the carbonization tower according to claim 1 is characterized in that: The back-mixing screen plate is provided with sieve holes, and is connected with a liquid phase back-mixing pipe, the liquid phase back-mixing pipe is extended to the bottom of the back-mixing screen plate, and the sieve holes and the liquid phase back-mixing pipe together form a back-mixing liquid flow channel.

3. The upper and lower tower body connection structure of the carbonization tower according to claim 1 is characterized in that: The upper end of the primary back-mixing downpipe is higher than the back-mixing screen plate.

4. The upper and lower tower body connection structure of the carbonization tower according to claim 1, characterized in that: An upper gas inlet is arranged on the tower wall below the back-mixing sieve plate, and a lower edge of the upper gas inlet is higher than a lower edge of a back-mixing pipe on the back-mixing sieve plate.

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