Energy-saving phenol rectifying tower based on intermediate reboiling

Abstract

The utility model discloses an energy-saving rectifying phenol tower based on intermediate reboiling, which comprises a phenol tower body, a tower kettle of the phenol tower body is communicated with a tower kettle reboiler, an intermediate reboiler is communicated between the lower part of a feeding pipeline of the phenol tower body and the upper part of a tower bottom extraction pipeline, and the tower top of the phenol tower body is sequentially communicated with a tower top condenser and a condensate tank. And a feeding heat exchanger is communicated between the tower bottom extraction pipeline and the feeding pipeline of the phenol tower body. According to the energy-saving rectifying phenol tower based on intermediate reboiling, a part of the tower kettle reboiler with large thermal load is loaded to the intermediate reboiler in an intermediate reboiling manner, so that the requirement on the steam specification is reduced, the aims of saving energy, reducing consumption and reducing the operation cost are fulfilled, the size of equipment is reduced, and the production cost is reduced. And the application under the large flow load is effectively expanded.

Description

Technical Field

[0001] The utility model belongs to the technical field of phenolic ammonia wastewater treatment devices, and particularly relates to an energy-saving rectifying phenolic tower based on intermediate reboiling. Background Art

[0002] High-concentration phenolic ammonia pollutant wastewater has complex components, high phenolic concentration, large water volume and is difficult to be biochemically treated. In particular, phenolic substances are toxic to water sources, aquatic organisms and crops. At present, the phenolic substances in wastewater such as coal gasification sewage and semi-coke wastewater have complex components, mainly unit phenols and polyhydric phenols, with a content as high as 5000 - 15000 mg / L. At this concentration, the recovery technology of phenolic ammonia mainly adopts the Lurgi phenolic ammonia wastewater treatment process and the phenolic ammonia wastewater treatment process of South China University of Technology. Both of these two processes use the method of solvent extraction followed by rectification to recover the solvent. Among them, the phenolic ammonia wastewater treatment process of South China University of Technology adopts the method of first deacidifying and deammoniating, then extracting and finally recovering the extractant, with good overall performance and being widely used. However, this technology also has deficiencies in the treatment of phenols, mainly including:

[0003] (1) When recovering phenols by the method of first extracting and then rectifying, since the bottom of the phenolic tower for solvent recovery mainly contains phenols, and the boiling point of phenols is relatively high, the bottom temperature is above 200 °C, and the heat load at the bottom of the tower is large, requiring a relatively high specification of bottom steam.

[0004] (2) With the increase in the wastewater treatment volume, the volume of the bottom reboiler will increase. When it is greater than a certain amount, the volume of the bottom reboiler is too large, causing certain difficulties in equipment layout and operation.

[0005] (3) The steam specification required for the phenolic tower is high, with high energy consumption and low energy utilization efficiency, resulting in a relatively high operating cost of the device.

[0006] The utility model aims to solve the problems of high energy consumption and high operating cost of the rectifying system in the process of recovering high-phenol-concentration wastewater by using extraction and rectification methods, and overcome the shortcomings and deficiencies of the original rectifying system. Content of the Utility Model

[0007] The purpose of the utility model is to provide an energy-saving rectifying phenolic tower based on intermediate reboiling, which solves the problem of high energy consumption of the phenolic tower caused by high requirements for the bottom reboiler in the prior art.

[0008] The technical solution adopted by the utility model is: an energy-saving rectifying phenolic tower based on intermediate reboiling, including a phenolic tower body. The bottom of the phenolic tower body is connected to a bottom reboiler. Between the lower part of the feed pipeline of the phenolic tower body and the upper part of the bottom product pipeline, an intermediate reboiler is connected. The top of the phenolic tower body is sequentially connected to a top condenser and a condensate tank. Between the bottom product pipeline of the phenolic tower body and the feed pipeline, a feed heat exchanger is connected.

[0009] The characteristics of the present utility model also lie in that

[0010] The reboiler at the bottom of the tower is connected to a heat source through a pipeline, and the heat source is medium-pressure saturated steam at 250 °C.

[0011] The intermediate reboiler is connected to a heat source through a pipeline, and the heat source is low-pressure saturated steam at 200 °C.

[0012] The bottom end of the condensate tank is connected to the top of the phenol tower body through a condensate return pump.

[0013] A bottom product pump is connected between the bottom product pipeline of the phenol tower body and the feed heat exchanger.

[0014] The beneficial effects of the present utility model are as follows: The energy-saving rectifying phenol tower based on intermediate reboiling of the present utility model divides a part of the load of the reboiler at the bottom of the tower with a large heat load to the intermediate reboiler through the way of intermediate reboiling, reduces the requirements for steam specifications, achieves the purpose of energy conservation and consumption reduction and reduces the operating cost, and reduces the volume of the equipment, effectively expanding the application under large flow loads. Description of the Drawings

[0015] Figure 1 It is a schematic structural diagram of the energy-saving rectifying phenol tower based on intermediate reboiling of the present utility model.

[0016] In the figure, 1. Feed heat exchanger, 2. Phenol tower body, 3. Top condenser, 4. Intermediate reboiler, 5. Reboiler at the bottom of the tower, 6. Bottom product pump, 7. Condensate tank, 8. Condensate return pump. Detailed Description of the Preferred Embodiment

[0017] The present utility model will be described in detail below with reference to the drawings and the specific embodiments.

[0018] The present utility model provides an energy-saving rectifying phenol tower based on intermediate reboiling. As Figure 1 shown, it includes a phenol tower body 2. The bottom of the phenol tower body 2 is connected to a reboiler 5 at the bottom of the tower. The reboiler 5 at the bottom of the tower is connected to medium-pressure (2.5 - 6 MPa) saturated steam at 250 °C as a heat source through a pipeline. An intermediate reboiler 4 is connected between the lower part of the feed pipeline of the phenol tower body 2 and the upper part of the bottom product pipeline. The intermediate reboiler 4 is connected to low-pressure (less than 2.5 MPa) saturated steam at 200 °C as a heat source through a pipeline. The top of the phenol tower body 2 is sequentially connected to a top condenser 3 and a condensate tank 7. The bottom end of the condensate tank 7 is connected to the top of the phenol tower body 2 through a condensate return pump 8. A feed heat exchanger 1 is connected between the bottom product pipeline of the phenol tower body 2 and the feed pipeline. A bottom product pump 6 is connected between the bottom product pipeline of the phenol tower body 2 and the feed heat exchanger 1.

[0019] The energy-saving rectifying phenol tower based on intermediate reboiling provided by the present utility model has the following technological process:

[0020] (1) The feed containing phenol and extractant is preheated to 90 °C by the feed heat exchanger 1 and then enters the phenol tower body 2. The phenol tower body 2 operates under atmospheric pressure. The extractant is taken out from the top of the tower, and phenol is taken out from the bottom of the tower. The commonly used extractant at present is mainly methyl isobutyl ketone. The top temperature of the tower is 110 - 120 °C, and the bottom temperature of the tower is 195 - 210 °C. Moreover, as the polyhydric phenol at the bottom of the tower increases, the bottom temperature of the tower will also increase accordingly;

[0021] (2) The extractant vapor taken out from the top of the phenol tower body 2 is condensed to 40 - 50 °C by the top condenser 3 and then enters the condensate tank 7. Part of the condensate is returned to the phenol tower body 2 by the condensate reflux pump 8, and part of the extractant is taken out for recovery;

[0022] (3) The bottom of the phenol tower body 2 is equipped with a kettle reboiler 5. The temperature of the kettle inlet heat exchanger is 195 - 210 °C, and the heat source is medium-pressure saturated steam at 250 °C;

[0023] (4) An intermediate reboiler 4 is connected through a pipeline below the feed of the phenol tower body 2 and above the bottom take-out. The temperature of the intermediate material inlet heat exchanger is 180 - 185 °C, and the heat source is low-pressure saturated steam at 200 °C;

[0024] (5) The bottom material of the phenol tower body 2 is taken out as crude phenol product by the bottom take-out pump 6. This hot stream can be used as a preheater for raw materials and exchange heat with cold stream raw materials.

[0025] By the above method, the energy-saving rectifying phenol tower based on intermediate reboiling of the present utility model, through the way of intermediate reboiling, distributes part of the load of the kettle reboiler 5 with a large heat load to the intermediate reboiler 4, reduces the requirement for steam specifications, achieves the purpose of energy conservation and consumption reduction, reduces the operation cost, and reduces the volume of the equipment, effectively expanding the application under large flow load. The specific features are as follows:

[0026] (1) The energy-saving rectifying phenol tower based on intermediate reboiling provided by the present utility model reduces the requirement for steam specifications and achieves the purpose of energy conservation and consumption reduction.

[0027] (2) The present utility model ingeniously distributes part of the load of the kettle reboiler 5 with a large heat load to the intermediate reboiler 4, reducing the volume of the equipment.

[0028] (3) The present utility model uses the kettle reboiler 5 and the intermediate reboiler 4 simultaneously for the phenol tower rectification system. During the start-up process of the device, the kettle material can be heated in time, the reflux of the phenol tower is established in advance, and the phenol tower product is qualified in advance, shortening the start-up time.

[0029] (4) The bottoms product of the phenol column is heat-exchanged with the feed, saving energy consumption and reducing the investment cost of equipment.

[0030] (5) Through the distillation energy-saving system based on intermediate reboiling, the technical application of solvent recovery by rectification after extraction is extended, the reversibility of the separation process is improved, the energy utilization efficiency is increased, and the operating cost is reduced. With a feed scale of 25 m 3 / h for the phenol column, the annual operating cost can be saved by about more than 2.1 million yuan. With a feed scale of 100 m 3 / h for the phenol column, the annual operating cost can be saved by about more than 8.4 million yuan, achieving the goal of energy conservation and consumption reduction and obtaining good economic benefits.

[0031] Example 1

[0032] The phenol in the phenol-ammonia wastewater is contained in the extractant after previous extraction. To recycle and reuse the extractant, the energy-saving rectifying phenol column of this utility model is adopted. The feed of 25 m 3 / h containing phenol and the extractant is preheated to 90 °C by the feed heat exchanger 1 and then enters the phenol column body 2. The specific composition of the feed is shown in Table 1 below:

[0033] Table 1 Process parameters and inlet and outlet compositions of different examples and comparative examples

[0034]

[0035] The phenol column body 2 operates at atmospheric pressure, the top temperature is 110 - 120 °C, and the bottom temperature is 195 - 210 °C. In addition, the bottom temperature will further increase with the increase in the content of polyphenols in the feed components.

[0036] The extractant steam at 110 - 125 °C extracted from the top of the phenol column body 2 is condensed to 40 - 50 °C by the top condenser 3 and then enters the condensate tank 7. Part of the condensate is returned to the phenol column body 2 by the condensate reflux pump 8, and part of it is extracted for extractant recovery, with the content of the extractant > 95%;

[0037] The bottom of the phenol column body 2 is equipped with a bottom reboiler 5. The temperature of the bottom entering the reboiler is 195 - 210 °C, and the heat source is medium-pressure saturated steam at 250 °C, with a steam consumption of 3136.66 kg / h;

[0038] An intermediate reboiler 4 is connected by a pipeline below the feed of the phenol column body 2 and above the bottom draw. The temperature of the intermediate material entering the reboiler is 180 - 185 °C, and the heat source is low-pressure saturated steam at 200 °C, with a steam consumption of 2575.17 kg / h;

[0039] The bottoms of the phenol column body 2 are pumped by the bottom draw pump 6 to send the crude phenol to the feed heat exchanger 1 for heat exchange with the raw material and then used as the crude phenol product.

[0040] Comparative Example 2

[0041] To make a detailed comparison with the case without the intermediate reboiler 4, the installation of the intermediate reboiler 4 is cancelled in this Comparative Example 2, and the operating parameters in this Comparative Example 2 are the same as those in Example 1. See the attached table for specific operating parameters.

[0042] Example 3

[0043] Adjust the feed flow rate to 100 m 3 / h. The treatment method of Example 3 is the same as that of Example 1.

[0044] Comparative Example 4

[0045] Adjust the feed flow rate to 100 m 3 / h. The treatment method of Comparative Example 4 is the same as that of Comparative Example 2.

Claims

1. An energy-saving phenol distillation tower based on intermediate reboiling, characterized in that: The invention comprises a phenol tower body (2), wherein the tower kettle of the phenol tower body (2) is connected to a tower kettle reboiler (5), an intermediate reboiler (4) is connected between the lower part of the feed pipeline of the phenol tower body (2) and the upper part of the tower bottom extraction pipeline, the top of the phenol tower body (2) is connected to a tower top condenser (3) and a condensate tank (7) in sequence, and a feed heat exchanger (1) is connected between the tower bottom extraction pipeline and the feed pipeline of the phenol tower body (2).

2. The energy-saving phenol distillation tower based on intermediate reboiling according to claim 1, characterized in that: The tower bottom reboiler (5) is connected to a heat source via a pipeline, and the heat source is medium-pressure saturated steam at 250°C.

3. The energy-saving phenol distillation tower based on intermediate reboiling according to claim 1, characterized in that: The intermediate reboiler (4) is connected to a heat source through a pipeline, and the heat source is low-pressure saturated steam at 200°C.

4. The energy-saving phenol distillation tower based on intermediate reboiling according to claim 1, characterized in that: The bottom end of the condensate tank (7) is connected to the top of the phenol tower body (2) via a condensate reflux pump (8).

5. The energy-saving phenol distillation tower based on intermediate reboiling according to claim 1, characterized in that: A bottom extraction pump (6) is connected between the bottom extraction pipeline of the phenol tower body (2) and the feed heat exchanger (1).

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