Sieve plate type thin liquid distillation tower and application thereof

Abstract

The invention discloses a sieve plate type thin liquid distillation tower and application thereof. The distillation tower sequentially comprises a base, a bottom storage barrel, a middle distillation section and a top cooling water tank from bottom to top, wherein the middle distillation section is provided with a plurality of layers of sieve plates, each sieve plate is provided with a plurality of sieve holes, and a gap is formed between every two adjacent sieve plates; an air inlet is formed below the sieve plate on the lowermost layer and is used for introducing steam; and a liquid inlet is formed above the sieve plate on the uppermost layer and is used for introducing ammonia-containing condensate (or diluted liquid). The treatment capacity of the light liquid distillation tower is multiplied compared with that of a packed tower, the operation period is long, the light liquid distillation tower can continuously run for 2-3 years without being cleaned, and the problem of low distillation efficiency is effectively solved. On the premise of ensuring the production efficiency, the height of the tower can be reduced by about 8-10 meters, the production cost is greatly reduced, and the processing capacity is nearly two times that of a packed tower with the same tower diameter. The light liquid distillation tower disclosed by the invention meets higher environmental protection requirements, and meanwhile, the sodium carbonate production efficiency and economic benefits are also improved.

Description

Technical Field

[0001] This invention belongs to the field of distillation tower technology, specifically relating to a sieve plate distillation tower and its applications. Background Technology

[0002] In the soda ash production process, the distillation tower is mainly used to distill the ammonia-containing condensate, i.e., the distillate, to recover the ammonia and reduce the ammonia nitrogen concentration in the distillate to meet emission or reuse requirements. This process is not only environmentally friendly but also economical because the recovered ammonia and carbon dioxide can be used in other processes, reducing raw material waste.

[0003] In industrial production, the packing material in a distillation tower should have a large specific surface area and good porosity to avoid channeling and flow deviation, ensuring sufficient contact between the vapor and liquid phases and improving distillation efficiency. Furthermore, the tower design should also consider the expansion of the mother liquor and the fact that as production increases, the volume of distillate also increases, leading to reduced distillation efficiency and increased ammonia content in the waste distillate. Therefore, for large-scale soda ash plants, the distillation tower needs to be modified to meet higher production demands. Currently, all soda ash production plants use packed distillation towers, which require maintenance and packing replacement after a certain period of use. Specifically, existing distillation tower technologies suffer from the following problems:

[0004] 1. Reduced distillation efficiency

[0005] As production increases and the volume of distillate rises, uneven gas-liquid distribution and poor contact occur within the distillation tower, leading to reduced distillation efficiency. Furthermore, space constraints prevent further expansion of the distillation tower, further decreasing production efficiency and increasing energy consumption. Additionally, existing packed towers, using Pall ring packing, have short operating cycles, are prone to clogging, and require regular cleaning and packing replacement, resulting in high operating costs.

[0006] 2. Material corrosion

[0007] Severe corrosion of the liquid distributor inside the distillation tower causes uneven liquid distribution, resulting in flow deviation, increased tower pressure, and high steam consumption. The multi-section packing structure inside the tower also leads to scaling and narrowing of packing gaps after a certain period of use. Under these circumstances, it is necessary to modify the internal structure of the tower to improve the service life and production efficiency of the equipment.

[0008] 3. Energy waste

[0009] Excessive steam consumption is a serious problem during distillation. Poor liquid distribution in the distributor between the two packing layers in the lower layer of the column leads to uneven liquid distribution, resulting in ammonia-containing waste liquor, excessively high column pressure, and liquid carryover in the effluent. These problems not only affect production stability but also lead to energy waste. Summary of the Invention

[0010] To improve the above-mentioned technical problems, the present invention provides a sieve plate type distillation column, which includes, from bottom to top, a base, a bottom storage tank, an intermediate distillation section, and a top cooling water tank; wherein, the intermediate distillation section is provided with multiple sieve plates, each sieve plate is provided with multiple sieve holes, and there are gaps between adjacent sieve plates;

[0011] Each sieve plate is also equipped with a downcomer;

[0012] An air inlet is provided below the bottommost sieve plate for introducing steam;

[0013] An inlet is provided above the top sieve plate for introducing ammonia-containing condensate (or dilute liquid).

[0014] According to an embodiment of the present invention, the bottom storage tank is used to collect waste desalination liquid. Preferably, the ammonia nitrogen content in the waste desalination liquid is below 80 ppm.

[0015] According to an embodiment of the present invention, the spacing between adjacent sieve plates is 500-1200 mm, preferably 700-1000 mm.

[0016] According to an embodiment of the present invention, the sieve plate has at least 10 layers, for example, 10-40 layers.

[0017] According to an embodiment of the present invention, a plurality of sieve holes are evenly distributed on a sieve plate.

[0018] According to an embodiment of the present invention, any three sieve holes on the sieve plate are arranged in a triangular pattern.

[0019] According to an embodiment of the present invention, the sieve plates are all located between two column rings. The distillation column body of the present invention is made of HT200 cast iron. During the manufacturing of the column body, it cannot be manufactured as a single piece; it must be divided into multiple column rings, each of which is integrally cast and then connected together by flanges to form the entire column body.

[0020] According to an embodiment of the present invention, the sieve plate is made of stainless steel.

[0021] According to an embodiment of the present invention, the aperture of the sieve holes is 16–35 mm. Preferably, the opening ratio of the sieve holes is 6.5%–19.2%.

[0022] According to an embodiment of the present invention, the opening ratio of the downcomer is 8.7% to 24.6%. The working principle of the sieve plate is that an air cushion layer is formed at the bottom of the sieve plate, the liquid flows down from the downcomer, and the downcomer ensures that there is a certain liquid level at the top of the sieve plate, and the steam passes through the sieve holes to fully contact the liquid; that is, the sieve holes are for the steam to go upward, and the downcomer is for the liquid to flow downward.

[0023] According to an embodiment of the present invention, an inlet pipe is provided on the inlet. Preferably, the inlet pipe is an L-shaped inlet pipe.

[0024] According to an embodiment of the present invention, an air inlet pipe is provided on the air inlet.

[0025] According to an embodiment of the present invention, the cooling water tank is used for ammonia recovery. Preferably, the shell of the cooling water tank is made of HT200 cast iron, and the internal heat exchange tube bundle of the cooling water tank is made of S31603 stainless steel or TA2 titanium.

[0026] The present invention also provides a method for recovering ammonia, the method employing the above-described apparatus, the method comprising:

[0027] Steam is introduced through the air inlet; ammonia-containing condensate is introduced through the liquid inlet and flows down through the downcomer on the sieve plate. Steam flows up through the sieve holes on the sieve plate and comes into contact with the ammonia-containing condensate.

[0028] The desalinated wastewater after ammonia nitrogen removal is collected in the bottom storage tank;

[0029] Ammonia is recovered after being condensed in the top cooling water tank.

[0030] According to an embodiment of the present invention, the ammonia nitrogen content in the waste desalination liquid is below 80 ppm.

[0031] According to an embodiment of the present invention, the flow rate ratio of ammonia-containing condensate to steam is 1:200-500, for example, 1:400.

[0032] According to an embodiment of the present invention, the temperature of the upper part of the distillation column is 60-85°C.

[0033] According to an embodiment of the present invention, the steam temperature at the bottom of the distillation column is 190-210°C.

[0034] According to an embodiment of the present invention, the pressure at the top of the distillation column is -30 to -50 kPa.

[0035] According to an embodiment of the present invention, the outlet water pressure at the bottom of the distillation column is -15 to 50 kPa.

[0036] The present invention also provides the application of the above-described apparatus in the recovery of ammonia or carbon dioxide.

[0037] The beneficial effects of this invention are:

[0038] (1) The distillation tower of this invention has a significantly higher processing capacity than packed towers, a longer operating cycle (2-3 years without cleaning), and effectively solves the problem of low distillation efficiency. While ensuring production efficiency, the tower height can be reduced by approximately 8-10 meters, greatly reducing production costs, while the processing capacity is nearly twice that of a packed tower of the same diameter. The distillation tower of this invention meets higher environmental protection requirements and also improves the efficiency and economic benefits of soda ash production.

[0039] (2) The sieve plate of the present invention has the following advantages:

[0040] a) Low gas pressure drop and small liquid level difference on the plates. The gas-liquid flow path in a sieve-plate distillation column is relatively smooth, and the resistance encountered by the gas as it passes through the sieve holes is small, resulting in a relatively low gas pressure drop. Simultaneously, because the liquid layer is relatively evenly distributed on the plates, the liquid level difference on the plates is also small. These two characteristics help reduce energy consumption during the distillation process and improve overall energy efficiency.

[0041] b. High tray efficiency. The longer gas-liquid contact time and more thorough mixing in sieve tray distillation columns contribute to higher tray mass transfer efficiency. Furthermore, sieve tray distillation columns offer operational flexibility, maintaining high tray efficiency even when gas-liquid loads fluctuate.

[0042] (3) The present invention has a separate cooling water tank at the top of the tower, which can effectively solve the problem that the cooling system does not meet the production needs due to sharing a cooler with the mother liquor distillation.

[0043] (4) The internal components of the distillation tower of the present invention are all made of stainless steel, which effectively solves the problem of failure due to corrosion of components and prevents the adverse situation of increased tower pressure and increased energy consumption caused by corrosion and scaling of internal components. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of the structure of the distillation tower of the present invention;

[0045] Figure 2 This is a magnified view of point A;

[0046] Figure 3 This is a schematic diagram of the sieve plate structure;

[0047] The components include: 1. base; 2. bottom storage tank; 3. sieve plate; 4. top cooling water tank; 5. tower cover; and 6. tower ring. Detailed Implementation

[0048] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention, and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0049] Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available products or can be prepared by known methods.

[0050] Example 1

[0051] like Figure 1 As shown, the overall height H of the distillation tower for the third branch of Jiangsu Suyanjingshen Co., Ltd., which was manufactured and put into use by our company in 2021, is 30995mm; the tower diameter is 2730mm. A sieve plate type distillation tower includes, from bottom to top, a base 1, a bottom storage tank 2, an intermediate distillation section, a top cooling water tank 4, and a tower cover 5; wherein, the intermediate distillation section is provided with 22 layers of sieve plates 3, each sieve plate has multiple sieve holes, the multiple sieve holes are evenly distributed on the sieve plate, any three sieve holes on the sieve plate form a triangular shape, and the distance between adjacent sieve plates is 1000mm.

[0052] An air inlet is provided below the bottommost sieve plate, and an air inlet pipe is provided on the air inlet for introducing steam;

[0053] An inlet is provided above the top sieve plate, and an L-shaped inlet pipe is provided on the inlet for introducing ammonia-containing condensate.

[0054] The bottom storage tank is used to collect waste desalination liquid, in which the ammonia nitrogen content is below 80 ppm.

[0055] The sieve plate is located between the two tower rings.

[0056] The sieve plate is made of stainless steel.

[0057] The aperture of the sieve is 20-25 mm. Preferably, the opening ratio of the sieve is 15.5%-18.3%.

[0058] Each sieve plate is also equipped with a downcomer, with an opening ratio of 17.5% to 20.7%.

[0059] The cooling water tank recovers ammonia. The shell of the cooling water tank is made of HT200 cast iron, and the internal heat exchange tube bundle is made of S31603 stainless steel or TA2 titanium.

[0060] Application Example 1

[0061] The sieve plate distillation column described in Example 1 was used to treat distillate. Its parameters and distillate throughput are shown in Table 1 below:

[0062] Table 1

[0063] Parameter name Sieve plate distillation column <![CDATA[Inlet liquid flow rate m 3 / h]]> 74.44 Steam flow rate t / h 9～10 Tower temperature (upper part ℃) 66.4 Tower temperature (central °C) 96.46 PCD outlet temperature (°C) 56.2 Water outlet pressure (kPa) 47.7 Outlet pressure (kPa) -49.5 <![CDATA[Throughput m 3 / h]]> 90-110 ammonia nitrogen content in waste desalination liquid (ppm) <80ppm

[0064] Comparative Example 1

[0065] The difference between Comparative Example 1 and Example 1 is that Comparative Example 1 uses a packed tower with H = 39445 mm, that is, the sieve plate is replaced with Pall ring packing.

[0066] Table 2

[0067]

[0068]

[0069] The embodiments of the present invention have been described above by way of example. However, the scope of protection of the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made by those skilled in the art within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A sieve tray dilute liquid distillation column characterized by, The device comprises, from bottom to top, a base, a bottom tank, an intermediate distillation section, and a top cooling water tank. The intermediate distillation section is provided with multiple layers of sieve plates, each of which is provided with multiple sieve holes, and there is a gap between adjacent sieve plates. Each layer of sieve plate is further provided with a downcomer. An air inlet is arranged below the lowermost sieve plate for passing in steam.

2. The sieve tray dilute liquid distillation column of claim 1, wherein, An inlet for liquid is arranged above the uppermost sieve plate for passing in condensed liquid containing ammonia.

3. The sieve tray dilute liquid distillation column of claim 2, wherein, The bottom tank is used for collecting waste dilute liquid. The ammonia nitrogen content in the waste dilute liquid is less than 80 ppm. Preferably, the gap between adjacent sieve plates is 500-1200 mm.

4. The sieve tray dilute liquid distillation column of claim 1, wherein, Preferably, the sieve plates are at least 10 layers.

5. The sieve tray dilute liquid distillation column of claim 1, wherein, The multiple sieve holes are uniformly distributed on the sieve plate. The sieve plates are located between two tower rings.

6. The sieve tray dilute liquid distillation column of claim 1, wherein, Preferably, the sieve plates are made of stainless steel. The sieve hole diameter is 16-35 mm.

7. The sieve tray dilute liquid distillation column of claim 1, wherein, The sieve hole opening rate is 6.5%-19.2%.

8. The sieve tray dilute liquid distillation column of claim 1, wherein, The downcomer opening rate is 8.7%-24.6%. The cooling water tank is used for recovering ammonia.

9. A method of recovering ammonia, characterized by, Preferably, the shell of the cooling water tank is made of HT200 cast iron, and the internal heat exchange tube bundle of the cooling water tank is made of S31603 stainless steel or TA2 titanium. The method uses the device of any one of claims 1-8, and the method comprises: Passing in steam through the air inlet, passing in condensed liquid containing ammonia through the liquid inlet, and flowing downward through the downcomer on the sieve plate, and passing in steam from bottom to top through the sieve holes on the sieve plate and contacting with the condensed liquid containing ammonia; Collecting the waste dilute liquid after removal of ammonia nitrogen in the bottom tank; Recovering the condensed ammonia in the top cooling water tank.

10. Use of the device of any one of claims 1-8 in recovering ammonia water or carbon dioxide.

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