A negative pressure distillation process

Abstract

This invention discloses a negative pressure distillation process, relating to the field of negative pressure distillation technology, comprising the following steps: starting the distillation column and feeding the raw liquid into the distillation column through a feed pipe for heating and evaporation; alternately connecting a first negative pressure container and a second negative pressure container to the distillation column for negative pressure evacuation; transporting the steam extracted by the first and second pumps to a condenser in a mixing container for condensation and collecting the condensed liquid phase; collecting the azeotrope of water and the raw liquid obtained from preliminary distillation and dehydrating it through a permeate membrane. This invention, by alternately starting and stopping the first pump, the second control valve, the second pump, and the first control valve, allows the first and second negative pressure containers to alternately connect to the distillation column for negative pressure evacuation. This eliminates the need for the distillation column to be directly connected to other equipment via an evacuation pump, avoiding the efficiency problem caused by steam backflow due to negative pressure. Simultaneously, it allows for better control of the negative pressure within the distillation column.

Description

Technical Field

[0001] This invention relates to the field of negative pressure distillation technology, and more specifically to a negative pressure distillation process. Background Technology

[0002] Distillation is a separation process that utilizes the different volatility of components in a mixture to separate them. Commonly used equipment includes plate distillation columns and packed distillation columns. The principle and equipment flow of precision distillation are the same as those of ordinary distillation, except that the relative volatility of the components in the system to be separated is relatively low (<1.05~1.10), therefore, high-efficiency precision packing is used to achieve the separation and purification of the components to be separated. Distillation is usually carried out in a distillation column, where the gas and liquid phases come into countercurrent contact, and interphase heat and mass transfer occurs. The more volatile components in the liquid phase enter the gas phase, and the less volatile components in the gas phase transfer to the liquid phase. Thus, almost pure more volatile components are obtained at the top of the column, and almost pure less volatile components are obtained at the bottom. The feed liquid is added from the middle of the column. The section of the column above the feed inlet further concentrates the more volatile components in the rising vapor and is called the rectification section; the section of the column below the feed inlet extracts the more volatile components from the descending liquid and is called the stripping section. The vapor drawn from the top of the column is condensed, with a portion of the condensate returning to the distillation column as reflux, and the remaining distillate becoming the top product. The liquid drawn from the bottom of the column is partially vaporized in the reboiler, with the vapor rising up the column, and the remaining liquid becoming the bottom product. The ratio of the amount of liquid refluxed from the top of the column to the amount of top product is called the reflux ratio. Its magnitude affects the separation efficiency and energy consumption of the distillation operation. For materials with high boiling points, negative pressure distillation must be used to lower the temperature during separation and prevent material decomposition; for heat-sensitive materials that decompose at their boiling point for extended periods, negative pressure distillation is also necessary.

[0003] In existing negative pressure distillation, a closed tank is usually used to maintain a certain negative pressure before operation. However, with the generation of steam, the gas pressure will change, and the closed tank is not conducive to the extraction of steam. Summary of the Invention

[0004] The purpose of this invention is to provide a negative pressure distillation process to overcome the above-mentioned shortcomings in the prior art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a negative pressure distillation process, comprising the following steps:

[0006] Step 1: Start the distillation column and feed the raw liquid into the distillation column through the feed pipe for heating and evaporation;

[0007] Step 2: Install two sets of containers at the top of the distillation column, namely a first negative pressure container and a second negative pressure container. Install a first control valve and a second control valve on the first and second negative pressure containers, extending their pipes into the distillation column. Install a first pump and a second pump above the first and second negative pressure containers, respectively, to extract the air inside the containers. The first and second pumps are connected to a mixing container. When steam is generated in the distillation column, first open the first control valve and the second pump, then close the second control valve and the first pump. This allows the steam in the second negative pressure container to be extracted and transferred to the mixing container, creating a negative pressure in the second negative pressure container. Then, open the second control valve and the first pump, and close the first control valve. The first and second pumps utilize the negative pressure in the second negative pressure container to draw steam from the distillation column, creating a negative pressure inside the column. Simultaneously, steam from the first negative pressure container is drawn into the mixing container by the first pump, creating a negative pressure in the first negative pressure container. Then, the first control valve and the second pump are opened, and the second control valve and the first pump are closed, allowing the first negative pressure container to draw steam from the distillation column, creating a negative pressure inside the column. Steam is also drawn from the second negative pressure container, creating a negative pressure inside it. This cycle repeats, allowing the first and second negative pressure containers to alternately connect to the distillation column for negative pressure extraction. This eliminates the need for the distillation column to be directly connected to other equipment via a vacuum pump, avoiding the efficiency issues caused by steam backflow due to negative pressure. Furthermore, it allows for better control of the negative pressure within the distillation column.

[0008] Step 3: The mixing container delivers the steam drawn by the first and second pumps to the condenser for condensation, and collects the condensed liquid phase;

[0009] Step 4: Collect the azeotrope of water and original solution obtained from the initial distillation, remove the metal molecules contained therein by deionization, and then dehydrate it through a permeation membrane.

[0010] Preferably, in step one, a sprayer is installed at one end of the feed pipe inside the distillation column to spray the raw liquid into the distillation column for evaporation, thereby increasing the evaporation rate.

[0011] Preferably, the liquid phase in the distillation column is transported through a pipeline to a secondary distillation heater for secondary heating and evaporation. The evaporated vapor enters the distillation column, and the liquid phase obtained from the evaporation is an azeotrope of water and the original liquid.

[0012] Preferably, the feed pipe passes through a preheater and is then led into the distillation column. The preheater is a resistance heater, and the heating resistors are arranged around the feed pipe to preheat the raw liquid transported in the feed pipe, thereby accelerating its evaporation efficiency in the distillation column.

[0013] Preferably, the temperature for negative pressure evaporation and negative pressure distillation is 150-180℃, and the pressure is 12-15KPa(A).

[0014] The technical effects and advantages provided by the present invention in the above technical solution are as follows:

[0015] This invention utilizes two sets of containers at the top of a distillation column and alternately controls the start and stop of the first pump, the second control valve, and the second pump, as well as the first control valve. This allows the first and second negative pressure containers to be connected to the distillation column in turn for negative pressure evacuation. Consequently, the distillation column can be separated from other equipment directly by the evacuation pump, avoiding the problem of steam backflow affecting efficiency. At the same time, it allows for better control of the negative pressure within the distillation column. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0017] Figure 1 This is a diagram of the distillation equipment used in this invention.

[0018] Explanation of reference numerals in the attached figures:

[0019] 1. Distillation column; 2. Feed pipe; 3. Condenser; 4. Secondary distillation heater; 5. Preheater;

[0020] A1, First pump; A2, Second pump; C1, First negative pressure vessel; C2, Second negative pressure vessel; S1, First control valve; S2, Second control valve; D, Mixing vessel. Detailed Implementation

[0021] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0022] Example

[0023] This invention provides, for example Figure 1 The negative pressure distillation process shown includes the following steps:

[0024] Step 1: Start distillation column 1 and feed the raw liquid into distillation column 1 through feed pipe 2 for heating and evaporation;

[0025] Step 2: Add two sets of containers to the top of distillation column 1, namely a first negative pressure container C1 and a second negative pressure container C2. Install a first control valve S1 and a second control valve S2 on the first negative pressure container C1 and the second negative pressure container C2, so that the pipes of the first control valve S1 and the second control valve S2 extend into distillation column 1. Install a first pump A1 and a second pump A2 above the first negative pressure container C1 and the second negative pressure container C2, respectively, to extract the air inside the first negative pressure container C1 and the second negative pressure container C2. The first pump A1 and the second pump A2 are connected to the mixing container D. When steam is generated in distillation column 1, first open the first control valve S1 and the second pump A2, and close the second control valve S2 and the first pump A1, so that the steam in the second negative pressure container C2 is extracted and transported to the mixing container D, so that negative pressure is formed in the second negative pressure container C2. Then open the second control valve S2 and the first pump A1. The first control valve S1 and the second pump A2 are closed. Using the negative pressure in the second negative pressure container C2, steam is drawn from the distillation column 1, creating a negative pressure inside the column. Simultaneously, the steam in the first negative pressure container C1 is drawn by the first pump A1 into the mixing container D, creating a negative pressure in the first negative pressure container C1. Then, the first control valve S1 and the second pump A2 are opened, and the second control valve S2 and the first pump A1 are closed, allowing the first negative pressure container C1 to draw steam from the distillation column 1, creating a negative pressure inside the column. Steam in the second negative pressure container C2 is also drawn away, creating a negative pressure inside the second negative pressure container C2. This cycle repeats, allowing the first and second negative pressure containers C1 and C2 to alternately connect to the distillation column 1 for negative pressure extraction. This allows the distillation column 1 to avoid direct connection to other equipment via the extraction pump, preventing efficiency issues caused by steam backflow due to negative pressure. Furthermore, it allows for better control of the negative pressure within the distillation column 1.

[0026] Step 3: The mixing container D transports the steam drawn by the first pump A1 and the second pump A2 to the condenser 3 for condensation and collects the condensed liquid phase.

[0027] Step 4: Collect the azeotrope of water and original solution obtained from the initial distillation, remove the metal molecules contained therein by deionization, and then dehydrate it through a permeation membrane.

[0028] Furthermore, in the above technical solution, in step one, a sprayer is installed at one end of the feed pipe 2 inside the distillation column 1, and the raw liquid is sprayed into the distillation column 1 for evaporation through the sprayer to improve the evaporation rate.

[0029] Furthermore, in the above technical solution, the liquid phase in the distillation column 1 is transported to the secondary distillation heater 4 via a pipeline for secondary heating and evaporation. The evaporated vapor enters the distillation column 1, and the liquid phase obtained by evaporation is an azeotrope of water and the original liquid.

[0030] Furthermore, in the above technical solution, the feed pipe 2 passes through the preheater 5 and is led into the distillation column 1. The preheater 5 is a resistance heater, and the heating resistor is arranged around the feed pipe 2 to preheat the raw liquid transported in the feed pipe 2, thereby accelerating its evaporation efficiency in the distillation column 1.

[0031] Furthermore, in the above technical solution, the temperature of negative pressure evaporation and negative pressure distillation is 150-180℃, and the pressure is 12-15KPa(A);

[0032] Working principle: By using two sets of containers at the top of distillation column 1, namely the first negative pressure container C1 and the second negative pressure container C2, when steam is generated in distillation column 1, the first control valve S1 and the second pump A2 are opened first, and the second control valve S2 and the first pump A1 are closed, so that the steam in the second negative pressure container C2 is drawn away and sent to the mixing container D, creating a negative pressure in the second negative pressure container C2. Then, the second control valve S2 and the first pump A1 are opened, and the first control valve S1 and the second pump A2 are closed. Using the original negative pressure in the second negative pressure container C2, steam is drawn from distillation column 1, creating a negative pressure inside distillation column 1 as well. At this time, the steam in the first negative pressure container C1 is drawn by the first pump A1 to the mixing container D, so that the steam in the first negative pressure container C1 is drawn away and sent to the mixing container D, creating a negative pressure inside distillation column 1 as well. A negative pressure is formed in the first negative pressure container C1. Then, the first control valve S1 and the second pump A2 are opened, and the second control valve S2 and the first pump A1 are closed. This allows the first negative pressure container C1 to draw steam from the distillation column 1, creating a negative pressure inside the distillation column 1. Steam is also drawn from the second negative pressure container C2, creating a negative pressure inside the second negative pressure container C2. This cycle is repeated, with the first pump A1, the second control valve S2, the second pump A2, and the first control valve S1 being turned on and off in turn. This allows the first negative pressure container C1 and the second negative pressure container C2 to be connected to the distillation column 1 for negative pressure extraction. This allows the distillation column 1 to avoid being directly connected to other equipment via the extraction pump, thus avoiding the problem of steam backflow affecting efficiency. At the same time, it allows for better control of the negative pressure inside the distillation column 1.

[0033] The foregoing has only described certain exemplary embodiments of the present invention by way of illustration. Undoubtedly, those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the foregoing drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A negative pressure distillation process, characterized in that, Includes the following steps: Step 1: Start the distillation column (1) and feed the raw liquid into the distillation column (1) through the feed pipe (2) for heating and evaporation; Step 2: Add two sets of containers to the top of the distillation column (1), namely the first negative pressure container (C1) and the second negative pressure container (C2), and install the first control valve (S1) and the second control valve (S2) on the first negative pressure container (C1) and the second negative pressure container (C2), so that the pipes of the first control valve (S1) and the second control valve (S2) extend into the distillation column (1), and install the first pump (A1) and the second pump (A2) above the first negative pressure container (C1) and the second negative pressure container (C2) respectively to extract the internal air of the first negative pressure container (C1) and the second negative pressure container (C2). When steam is generated in the distillation column (1), first open the first control valve (S1) and the second pump (A2), and close the second control valve (S2) and the first pump (A1) so that the steam in the second negative pressure container (C2) is extracted and transported to the mixing container (D), so that a negative pressure is formed in the second negative pressure container (C2). Then, the second control valve (S2) and the first pump (A1) are opened, and the first control valve (S1) and the second pump (A2) are closed. Using the negative pressure in the original second negative pressure container (C2), steam is drawn from the distillation column (1), so that a negative pressure is also formed inside the distillation column (1). At this time, the steam in the first negative pressure container (C1) is drawn into the mixing container (D) by the first pump (A1), so that a negative pressure is formed in the first negative pressure container (C1). Then, the first control valve (S2) is opened again. The control valve (S1) and the second pump (A2) are closed, so that the first negative pressure container (C1) draws steam from the distillation column (1) to form a negative pressure in the distillation column (1), and the steam in the second negative pressure container (C2) is drawn away to form a negative pressure in the second negative pressure container (C2). This cycle is repeated so that the first negative pressure container (C1) and the second negative pressure container (C2) are connected to the distillation column (1) in turn to perform negative pressure gas extraction. Step 3: The mixing container (D) delivers the steam drawn by the first pump (A1) and the second pump (A2) to the condenser (3) for condensation and collects the condensed liquid phase; Step 4: Collect the azeotrope of water and original solution obtained from the initial distillation, remove the metal molecules contained therein by deionization, and then dehydrate it through a permeation membrane. In step one, a sprayer is installed at one end of the feed pipe (2) inside the distillation column (1) to spray the raw liquid into the distillation column (1) for evaporation. The liquid phase in the distillation column (1) is transported through a pipeline to the secondary distillation heater (4) for secondary heating and evaporation, and the evaporated steam enters the distillation column (1); The feed pipe (2) passes through the preheater (5) and is then led into the distillation column (1). The preheater (5) is a resistance heater, and the heating resistor is arranged around the feed pipe (2) to preheat the raw liquid transported in the feed pipe (2).

2. The negative pressure distillation process according to claim 1, characterized in that: The liquid phase obtained by secondary heating and evaporation is an azeotrope of water and the original liquid.

3. The negative pressure distillation process according to claim 1, characterized in that: The temperature for the negative pressure evaporation and negative pressure distillation is 150-180℃, and the pressure is 12-15KPa(A).

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