Sodium carbonate drying and cooling system

Abstract

The utility model provides a sodium carbonate drying and cooling system which comprises a fluidized bed, the fluidized bed comprises a drying section, a sodium carbonate hydrate wet filter cake is heated to a process temperature in the drying section, water vapor is separated, and dried sodium carbonate is obtained; a cooling section in which the dried sodium carbonate is cooled to obtain a sodium carbonate product; the drying section further comprises a first-stage closed circulating air unit used for separating solids in the tail gas generated by the first drying section and a second-stage closed circulating air unit used for separating and recycling solids and moisture in the tail gas generated by the second drying section and heating the tail gas. And the cooling section comprises a tail gas dust removal unit for separating and recovering solids entrained in the tail gas of the cooling section. According to the system, sodium carbonate products are effectively recovered, water vapor in tail gas is efficiently recovered, and the tail gas emission is remarkably reduced; the system disclosed by the utility model is simple in process flow and low in equipment investment and operation cost.

Description

Technical Field

[0001] The utility model relates to the technical field of soda ash production, in particular to a soda ash drying and cooling system. Background Art

[0002] In the soda ash preparation process, the crystallized sodium carbonate usually exists in the form of hydrates, such as sodium carbonate monohydrate and sodium carbonate decahydrate, and then is dehydrated and dried to obtain a soda ash product that is convenient for storage and transportation. Among them, the crystallized sodium carbonate is generally dehydrated by a centrifuge to obtain a sodium carbonate monohydrate filter cake containing about 3-7% of free water, and then soda ash is obtained after drying and cooling.

[0003] The existing process often uses a fluidized bed or a combination of a calciner and a cool soda ash machine for drying and cooling the sodium carbonate monohydrate filter cake. For example, Figure 1 shows a schematic structural diagram of a fluidized bed soda ash drying and cooling system in the prior art. The generated tail gas needs to be dust-removed before being discharged. Since the gas volume required in the drying and cooling processes is large, the gas volume of the tail gas discharged after dust removal is also large. In addition, the tail gas contains a large amount of saturated water and free water, resulting in a large amount of "white smoke" composed of small droplets when the tail gas contacts cold air at the discharge port. It should be noted that the droplets generated by the tail gas discharge in the existing process contain alkali, which is likely to cause corrosion of nearby equipment and product loss, and the water vapor contained in the tail gas is not recycled. In addition, the dust removal equipment has a high investment and high operating costs. Summary of the Utility Model

[0004] Aiming at the deficiencies in the prior art, the utility model discloses a soda ash drying and cooling system, which fully recovers sodium carbonate products and water vapor through multiple tail gas circulations, and can also perform collaborative drying through a closed tail gas circulation, simplifying the process flow and reducing equipment investment.

[0005] To achieve the above technical purposes, the utility model proposes a soda ash drying and cooling system, which includes a fluidized bed. The fluidized bed includes: a drying section, including a first drying section and a second drying section; the wet sodium carbonate monohydrate filter cake is heated to the process temperature in the drying section, water vapor is separated, and dried sodium carbonate is obtained; a cooling section, where the dried sodium carbonate is cooled in the cooling section to obtain a soda ash product.

[0006] Among them, the drying section further includes a primary closed-loop air unit and a secondary closed-loop air unit; the primary closed-loop air unit is connected to the tail gas outlet of the first drying section and the fluidizing gas inlet of the second drying section; the primary closed-loop air unit includes a first dust removal device for separating solids in the tail gas generated by the first drying section; the secondary closed-loop air unit is connected to the tail gas outlet of the second drying section and the fluidizing gas inlet of the first drying section; the secondary closed-loop air unit includes a second dust removal device, a condensation device and a heater for separating and recovering solids and moisture in the tail gas generated by the second drying section, and heating the tail gas; the cooling section includes a tail gas dust removal unit connected to the tail gas outlet of the cooling section for separating and recovering solids entrained in the tail gas of the cooling section.

[0007] In the above technical solution, the effective recovery of soda ash products is achieved by setting up multiple tail gas circulations. Specifically: matching the technological process in which the wet filter cake of sodium carbonate monohydrate is gradually dried in the first drying section and the second drying section of the fluidized bed and cooled in the cooling section, the present invention sets 1) a first dust removal device for separating and recovering sodium carbonate entrained in the tail gas of the first drying section, 2) a second dust removal device and a condensation device for recovering sodium carbonate entrained in the tail gas of the second drying section, and in addition 3) a tail gas dust removal unit is also set in the cooling section for separating and recovering sodium carbonate entrained in the tail gas of the cooling section; among them, the sodium carbonate recovered by the first dust removal device and the second dust removal device is returned to the drying section, and the sodium carbonate recovered by the tail gas dust removal unit is used as a product. Thus, the soda ash product in the corresponding tail gas is recovered at appropriate links in the technological process, which not only improves the process efficiency and yield, but also reduces the investment in dust removal equipment, reduces the alkali content in the tail gas to protect the environment, and reduces the process cost.

[0008] Furthermore, in the above technical solution, a technical feature of recovering water vapor and significantly reducing tail gas emissions is also set. Specifically: a condensation device is set in the secondary closed-loop air unit for recovering water vapor in the tail gas of the second drying section. It should be noted that the present invention concentrates the water vapor contained in the wet filter cake of the feed sodium carbonate monohydrate in the tail gas of the second drying section through the primary closed-loop air unit, and by setting a device for condensing and recovering water vapor in the secondary closed-loop air unit, most of the water contained in the wet filter cake of the feed sodium carbonate monohydrate can be recovered, thereby significantly reducing the overall process gas emissions.

[0009] In summary, the above technical solution can improve the process efficiency and yield, significantly reduce tail gas emissions and recover water vapor, reduce equipment investment and save energy consumption. The embodiments and comparative examples of the present invention show the effects of the soda ash drying and cooling system of the present invention.

[0010] Compared with the prior art, the beneficial effects of the present utility model are as follows: The soda ash drying and cooling system of the present utility model realizes the effective recovery of soda ash products by setting multiple tail gas circulations, simultaneously efficiently recovers the water vapor in the tail gas and significantly reduces the tail gas emissions; reduces the process energy consumption through the coordinated cooperation of the closed-loop circulation of the tail gas in two drying sections; the process flow of the soda ash drying and cooling system of the present utility model is simple, and the equipment investment and operation costs are low. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The accompanying drawings forming a part of this application are used to provide a further understanding of the present utility model. The schematic embodiments of the present utility model and their descriptions are used to explain the present utility model and do not constitute an improper limitation to the present utility model. In the drawings:

[0012] Figure 1 is a schematic structural diagram of a soda ash drying and cooling system in the prior art;

[0013] Figure 2 is a schematic structural diagram of the integrated soda ash drying and cooling system shown in Embodiment 1;

[0014] Figure 3 is a schematic structural diagram of a split soda ash drying and cooling system shown in Embodiment 2;

[0015] Figure 4 is a schematic structural diagram of another split soda ash drying and cooling system shown in Embodiment 3;

[0016] Among them, the above-mentioned accompanying drawings include the following reference numerals:

[0017] 11 - First drying section, 11 - 1 Primary closed-loop circulation air unit, 11 - 2 First dust removal device, 11 - 3 First fan, 12 - Second drying section, 12 - 1 Secondary closed-loop circulation air unit, 12 - 2 Second dust removal device, 12 - 3 Condensing device, 12 - 4 Second fan, 12 - 5 Heater, 12 - 6 First branch, 12 - 7 Second branch;

[0018] 2 - Cooling section, 21 - Tail gas dust removal unit, 22 - Third dust removal device, 23 - Third fan, 24 - Third branch, 25 - Fourth branch, 26 - Tail gas exhaust pipeline, 27 - Fourth fan, 28 - Fifth branch. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0019] For the convenience of understanding the present utility model, the present utility model will be described more comprehensively below, and preferred embodiments of the present utility model are given. However, it should be understood that these embodiments are only for more detailed description and should not be construed as limiting the present utility model in any form, that is, it is not intended to limit the protection scope of the present utility model.

[0020] It should be noted that unless otherwise defined, the technical terms used in the following embodiments have the same meanings as commonly understood by those skilled in the art to which the present utility model belongs. The test reagents used in the following embodiments are all conventional biochemical reagents unless otherwise specified; the experimental methods are all conventional methods unless otherwise specified.

[0021] Unless otherwise defined, the technical terms used in the following embodiments have the same meanings as commonly understood by those skilled in the art to which the present utility model belongs. In this embodiment, relational terms such as "first", "second", "primary", "secondary", etc. are only used to distinguish one component with the same name from another, and do not necessarily require or imply any such actual relationship or order between these components. Features defined with "first", "second", "primary", "secondary", etc. may explicitly or implicitly include one or more of such features.

[0022] Embodiment 1

[0023] The present utility model provides a soda ash drying and cooling system, as Figure 2 shown. The system includes a fluidized bed, and the fluidized bed includes: a drying section, including a first drying section 11 and a second drying section 12; the monohydrate sodium carbonate wet filter cake is heated to the process temperature in the drying section, water vapor is separated, and dry sodium carbonate is obtained; a cooling section 2, the dry sodium carbonate is cooled in the cooling section 2 to obtain a soda ash product; wherein, the drying section further includes a primary closed-circuit air unit 11-1 and a secondary closed-circuit air unit 12-1; the primary closed-circuit air unit 11-1 connects the tail gas outlet of the first drying section 11 and the fluidizing gas inlet of the second drying section 12; the primary closed-circuit air unit 11-1 includes a first dust removal device 11-2 for separating solids in the tail gas generated by the first drying section 11; the secondary closed-circuit air unit 12-1 connects the tail gas outlet of the second drying section 12 and the fluidizing gas inlet of the first drying section 11; the secondary closed-circuit air unit 12-1 includes a second dust removal device 12-2, a condensation device 12-3, and a heater 12-5 for separating and recovering solids and moisture in the tail gas generated by the second drying section 12, and heating the tail gas; the cooling section 2 includes a tail gas dust removal unit 21, and the tail gas dust removal unit connects the tail gas outlet of the cooling section 2 for separating and recovering solids entrained in the tail gas of the cooling section 2.

[0024] Among them, the process temperature reached by heating the sodium carbonate monohydrate wet filter cake in the drying section in this embodiment is not limited, and those skilled in the art can set it according to specific working conditions. For example, 130-150°C can be selected, which does not limit the protection scope of the present invention. In addition, the temperature reached by cooling the dried sodium carbonate in the cooling section in this embodiment is also not limited, and those skilled in the art can set it according to specific working conditions. For example, considering the requirements of subsequent packaging and transportation, it can be cooled to below 80°C or other appropriate temperatures, which does not limit the protection scope of the present invention.

[0025] In a further example of the present invention, the connection mode and structure of the first-stage closed-circuit air unit 11-1 are optimized. Optionally, the first-stage closed-circuit air unit 11-1 is sequentially provided with a first dust removal device 11-2 and a first fan 11-3. After the first drying section 11 tail gas is dust-removed and pressurized, it is used as fluidizing gas to input the second drying section 12 to continue drying sodium carbonate.

[0026] In a further example of the present invention, the connection mode and structure of the second-stage closed-circuit air unit 12-1 are optimized. Optionally, the second-stage closed-circuit air unit (12-1) is sequentially provided with a second dust removal device 12-2, a condensation device 12-3, a second fan 12-4, and a heater 12-5. Thus, after the tail gas of the second drying section 12 is separated and the solid is recovered in the second dust removal device 12-2, the dust-like solid and water vapor are further recovered in the condensation device 12-3, thereby greatly reducing the volume of the tail gas of the overall process flow; the air after dust removal and water vapor recovery is compressed by the second fan 12-4 and heated by the heater 12-5 and then used as fluidizing gas to input the second dryer for drying the newly fed sodium carbonate monohydrate wet filter cake.

[0027] In a further example of the present invention, the structure of the second-stage closed-circuit air unit 12-1 is optimized. Optionally, a first branch 12-6 for exhausting tail gas is provided on the pipeline connecting the second fan 12-4 and the heater 12-5, so as to adjust the amount of fluidizing gas input to the first drying section 11 and reduce energy consumption. Optionally, a second branch for inputting air is provided on the pipeline connecting the condensation device 12-3 and the second fan 12-4.

[0028] In a further example of the present invention, the structure of the condensation device 12-3 is optimized. Optionally, the condensation device 12-3 includes a spray cooling tower and a condenser, or includes an electrostatic precipitator and a condenser, which can simultaneously achieve the effect of further removing solids and condensing and recovering water vapor therein.

[0029] In a further example of the present utility model, the structures of the first dust removal device 11-2 and the second dust removal device 12-2 are optimized. Optionally, the first dust removal device 11-2 and / or the second dust removal device 12-2 is a cyclone separator, so as to efficiently separate dust or particulate solids in the tail gases of the first drying section 11 and the second drying section 12. Optionally, multiple stages of cyclone separators are provided, so as to achieve a better solid separation effect through the cooperation of multiple stages of cyclone separators.

[0030] In a further example of the present utility model, the connection mode and structure of the tail gas dust removal unit 21 are optimized. Optionally, the tail gas dust removal unit 21 includes a third dust removal device 22 and a third fan 23. After the tail gas of the cooling section 2 is separated and recovered of solids by the third dust removal device 22, it enters the third fan 23 for compression and then is input into the cooling section 2 as fluidizing gas. Optionally, the third dust removal device 22 includes a bag filter, or includes a cyclone dust collector and a bag filter, which can more thoroughly recover the solids in the tail gas of the cooling section 2 and prevent environmental pollution caused by the inclusion of soda ash in the tail gas.

[0031] In a further example of the present utility model, the structure of the tail gas dust removal unit 21 is optimized. Optionally, a third branch 24 for inputting gas is provided on the pipeline connecting the third dust removal device 22 and the third fan 23, so as to partially supplement and / or replace air to the system of the present utility model, keep the air humidity inside the system relatively low, and improve the operability of the system.

[0032] In a further example of the present utility model, the outlet of the third fan (23) is connected to the fluidizing gas inlet of the cooling section (2), or directly connected to the tail gas exhaust pipeline (26). After the solid soda ash entrained in the tail gas of the cooling section 2 is recovered by the tail gas dust removal unit 21, this part of the tail gas can be circulated to the inlet of the cooling section 2 to reduce the amount of tail gas discharged, or directly discharged.

[0033] In a further example of the present utility model, the connection mode between the drying section and the cooling section 2 is optimized. Optionally, the drying section and the cooling section 2 are integrated or split devices, and those skilled in the art can select a suitable device according to the actual working conditions for the drying and cooling of sodium carbonate monohydrate. The technical solutions formed thereby are all within the protection scope of the present utility model.

[0034] Embodiment 2

[0035] Based on the soda ash drying and cooling system shown in Embodiment 1, as Figure 3As shown, the soda ash drying and cooling system is a split type, and the drying section and the cooling section 2 of the fluidized bed are split type. In this embodiment, the structure of the tail gas dust removal unit 21 is optimized. Specifically, when recycling the tail gas of the cooling section 2, a fourth branch 25 for discharging the tail gas is provided on the pipeline connecting the outlet of the third fan 23 and the fluidizing gas inlet of the cooling section 2. By partially discharging the tail gas, new air is supplemented and replaced, so as to keep the humidity of the air in the overall system appropriate.

[0036] Embodiment 3

[0037] Based on the soda ash drying and cooling system shown in Embodiment 1, as Figure 4 shown, the soda ash drying and cooling system is a split type, and the drying section and the cooling section 2 of the fluidized bed are split type; in this embodiment, the structure of the tail gas dust removal unit 21 is optimized.

[0038] Specifically, the outlet of the third fan 23 is directly connected to the tail gas discharge pipeline 26, and the tail gas after the solid is recovered by the third dust removal device 22 is directly discharged. In order to supplement the fluidizing gas of the cooling section, a fifth branch 28 for inputting air can be optionally provided, and the newly input air is compressed by the fourth fan 27 and then input into the fluidizing gas inlet of the cooling section 2.

[0039] Embodiment 4

[0040] Based on the soda ash drying and cooling system shown in Embodiment 1, this embodiment shows a soda ash drying and cooling process under a working condition. It should be noted that this embodiment is only a better display and does not limit the protection scope of the present invention thereby.

[0041] Specifically, taking a 500,000-ton / year soda ash drying system as an example, as Figure 2 , calculated based on the feed of monohydrate sodium carbonate filter cake with 5% water content, the tail gas exhaust temperature of the first branch 12-6 is 50°C, and the tail gas emission is 0.68 - 1.4 t / h. It includes a water vapor emission loss of 0.06 - 0.12 t / h, and the condensation device 12-3 recovers and utilizes about 19 t / h of water.

[0042] Comparative Example 1

[0043] This comparative example shows the soda ash drying and cooling process using the Figure 1 existing technology shown. Specifically, taking a 500,000-ton / year soda ash drying system as an example, as Figure 1 , calculated based on the feed of monohydrate sodium carbonate filter cake with 5% water content, the tail gas emission is 89.6 t / h, and the water vapor emission loss is 7.9 t / h.

[0044] It should be noted that the above content is a further detailed description of the present utility model in combination with specific implementation manners, and it cannot be determined that the specific implementation of the present utility model is only limited to these descriptions; the size data of this embodiment does not necessarily limit the technical solution, but only shows one specific working condition. For those of ordinary skill in the technical field to which the present utility model belongs, without departing from the concept of the present utility model, several simple improvements and retouches can still be made, and all should be regarded as belonging to the protection scope of the present utility model.

Claims

1. A soda ash drying and cooling system, characterized in that: The system includes a fluidized bed comprising: A drying section, comprising a first drying section (11) and a second drying section (12); the sodium carbonate monohydrate wet cake is heated to a process temperature in the drying section, water vapor is separated and dry sodium carbonate is obtained; A cooling section (2), wherein the dried sodium carbonate is cooled in the cooling section (2) to obtain a soda ash product; in, The drying section also includes a primary closed circulation air unit (11-1) and a secondary closed circulation air unit (12-1); The first-stage closed circulation air unit (11-1) is connected to the tail gas outlet of the first drying section (11) and the fluidizing gas inlet of the second drying section (12); the first-stage closed circulation air unit (11-1) comprises a first dust removal device (11-2) for separating solids in the tail gas generated by the first drying section (11); The secondary closed circulation air unit (12-1) is connected to the tail gas outlet of the second drying section (12) and the fluidizing gas inlet of the first drying section (11); the secondary closed circulation air unit (12-1) comprises a second dust removal device (12-2), a condensing device (12-3) and a heater (12-5), which are used to separate and recover solids and moisture in the tail gas generated by the second drying section (12), and to heat the tail gas; The cooling section (2) comprises a tail gas dust removal unit (21), which is connected to the tail gas outlet of the cooling section (2) and is used to separate and recover solids entrained in the tail gas of the cooling section (2).

2. The soda ash drying and cooling system according to claim 1, characterized in that: The first-stage closed-cycle air unit (11-1) is provided with a first dust removal device (11-2) and a first fan (11-3) in sequence; And / or, the two-stage closed-cycle air unit (12-1) is provided with a second dust removal device (12-2), a condensing device (12-3), a second fan (12-4), and a heater (12-5) in sequence.

3. The soda ash drying and cooling system according to claim 2, characterized in that: A first branch (12-6) for discharging exhaust gas is provided on the pipeline connecting the second fan (12-4) and the heater (12-5); And / or, a second branch for inputting air is provided on the pipeline connecting the condensing device (12-3) and the second fan (12-4).

4. The soda ash drying and cooling system according to any one of claims 1 to 3, characterized in that: The condensing device (12-3) includes a spray cooling tower and a condenser, or includes an electrostatic precipitator and a condenser.

5. The soda ash drying and cooling system according to claim 1, characterized in that: The first dust removal device (11-2) and / or the second dust removal device (12-2) is a cyclone separator.

6. The soda ash drying and cooling system according to claim 1, characterized in that: The tail gas dust removal unit (21) comprises a third dust removal device (22) and a third fan (23).

7. The soda ash drying and cooling system according to claim 6, characterized in that: A third branch (24) for inputting gas is arranged on the pipeline connecting the third dust removal device (22) and the third fan (23).

8. The soda ash drying and cooling system according to claim 6, characterized in that: The outlet of the third fan (23) is connected to the fluidizing gas inlet of the cooling section (2), or is directly connected to the tail gas exhaust pipeline (26).

9. The soda ash drying and cooling system according to claim 8, characterized in that: A fourth branch (25) for discharging tail gas is provided on the pipeline connecting the outlet of the third fan (23) and the fluidizing gas inlet of the cooling section (2).

10. The soda ash drying and cooling system according to claim 1, characterized in that: The drying section and cooling section (2) are integrated or split equipment.

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