An energy-saving BDO distillation process using acetylene aldehydes

Abstract

The present invention relates to the field of chemical industry, and discloses an energy-saving BDO distillation process of the acetylene-aldehyde process. The present invention sets a tower section in the middle of the concentration tower of the BDO of the acetylene-aldehyde process, and uses a heat pump or an energy integration scheme with a deweighting tower to recover the heat of the steam evaporated and use it as a heat source for material heating. The scheme of the present invention can achieve the purpose of saving both the steam in the tower bottom and the circulating water at the top of the tower; the technology is mature and reliable, the energy-saving and water-saving effects are significant, the investment payback period is short, the investment is small, and the energy-saving effect is good.

Description

Technical Field

[0001] The invention relates to the field of chemical industry, in particular to an energy-saving acetylene-aldehyde BDO distillation process. Background Art

[0002] BDO is the abbreviation of 1,4-butanediol, with the molecular formula of C4H10O2 and a relative molecular mass of 90.12. It is a colorless, viscous oily liquid with a pungent odor at room temperature and pressure. It is miscible with water, easily soluble in ethanol, acetone and ethylene glycol ether, slightly soluble in ether, and almost insoluble in solvents such as aliphatic hydrocarbons, aromatic hydrocarbons, and chlorinated hydrocarbons. It has strong hygroscopicity and is flammable. BDO is an important fine chemical product and an important raw material for the production of polybutylene terephthalate (PBT) engineering plastics and fibers, tetrahydrofuran (THF), γ-butyrolactone (GBL), polyurethane artificial leather, polyurethane elastomers, and polyurethane shoe sole glue.

[0003] The main technological methods for industrializing BDO include the acetylene aldehyde method, butadiene method, propylene oxide method and maleic anhydride method, among which the acetylene aldehyde method (Reppe method) is the main method for producing BDO. In the late 1990s, newly built or expanded BDO plants around the world were turning from the traditional Reppe method to newer and more economical processes using maleic anhydride, propylene oxide and butadiene as raw materials. In addition to BDO, the typical material composition of the BDO separation process of the acetylene aldehyde method also contains a large amount of water, salt, light components (low boiling substances) and heavy components (high boiling substances). Since the purity requirements of BDO products are relatively high (BDO wt% ≥ 99.5%), the above impurities must be removed.

[0004] CN207002609U discloses a 1,4-butanediol purification device, including a purification device body, a heating device is provided at the bottom of the purification device body, a liquid storage tank is provided at the top of the heating device, a liquid level gauge is provided at one side of the liquid storage tank, a reflux port is provided at the other side of the liquid storage tank, a liquid feed port is provided at the bottom of the reflux port, a reaction purification tank is provided at the top of the liquid storage tank, a reflux pipe is provided at one side of the reaction purification tank, a separation filter port is provided at the top of the reaction purification tank, and a purification liquid outlet is provided at the top of the separation filter port. The device is a 1,4-butanediol purification device, which can effectively solve the problems of the 1,4-butanediol purification device, and the device can effectively improve the working efficiency of the 1,4-butanediol purification, is convenient and simple to use, has an ideal purification effect, and has the function of recycling and purification, saves material costs, and is very convenient.

[0005] The main method for removing them is distillation, which usually consists of four distillation towers in series, namely, a concentration tower (also called a concentration tower), a desalination tower, a light removal tower (also called a low-boiling tower) and a heavy removal tower (also called a high-boiling tower). The four distillation towers all use steam as a heat source to heat the tower kettle reboiler and use circulating water as a cold source to cool the tower top material. For BDO units of different scales, the distillation process is different. For example, for a 100,000 tons / year BDO unit, the distillation process consists of the above four towers. For a 200,000 tons / year BDO unit, one more concentration tower and one desalination tower are usually added. The process is characterized by high energy consumption. For example, for a 200,000 tons / year BDO unit, the distillation process consumes about 80 tons / hour of steam and about 4,700 tons / hour of circulating water. Therefore, energy saving is an important research topic for the BDO distillation process. Regarding the energy saving problem of BDO distillation process, Zhang Fangxia (BDO project distillation workshop energy saving transformation research) has used pinch point technology to simulate the 80,000 tons / year BDO unit, Xie Jingwei et al. (BDO unit butanol waste liquid three-tower coupling separation process research) have conducted three-tower coupling separation process research on BDO unit butanol waste liquid, Xie Lanmei (1,4-butanediol production by-product n-butanol separation and purification process and simulation), Dang Huijuan (AspenPlus simulation of BDO unit light component replacement selection research), Liu Shaobo (BDO heavy component removal tower ASPENPLUS simulation and research) have studied the computer simulation method of BDO distillation process. More research on BDO units focuses on BDO product quality improvement and by-product recovery. Summary of the invention

[0006] In order to solve the above problems, the present invention provides an energy-saving acetylene-aldehyde BDO distillation process.

[0007] The technical solution of the present invention mainly considers the energy saving of the concentration tower and the deweighting tower, including saving the steam of the tower kettle reboiler and the circulating water of the tower top condenser.

[0008] The concentration tower was simulated by computer, and the simulation results were verified by actual field data, which can reflect the actual situation more accurately.

[0009] The energy integration scheme of the concentration tower and the deweighting tower is adopted; the deweighting tower and the concentration tower are energy integrated; for the concentration tower, the tower section scheme is adopted for design and transformation, the heat pump is removed, and the top steam of the deweighting tower is introduced into the shell side of the tower section through the material steam conduit as a heat source.

[0010] Furthermore, an energy-saving BDO distillation process using an acetylene aldehyde method is provided, and the scheme is as follows: an energy-saving BDO distillation process using an acetylene aldehyde method, wherein the BDO distillation process using an acetylene aldehyde method is composed of four distillation towers, namely, a concentration tower, a desalting tower, a lightness removal tower and a heavyness removal tower, connected in series; a tower section is added at the position of the stripping section of the concentration tower; the liquid phase material in the tower flows through the tube side, flows through the tower section from top to bottom, is heated and vaporized while flowing, and the gas phase flows upward; the gas phase at the top of the tower enters the heat pump through the gas phase pipeline at the top of the tower without being condensed by the condenser, and enters the shell side of the tower section as a heat source after being pressurized and heated, and is condensed into a liquid phase at the same time; the condensed liquid phase is depressurized and cooled by a throttle valve, and then enters the condenser for further cooling, a part of which is discharged from the tower through the discharge port as the material produced from the top of the tower, and the other part is returned to the top of the distillation tower through the reflux pipe as the reflux liquid.

[0011] The tower section is a shell and tube heat exchanger or a falling film evaporator.

[0012] As one of the multiple optional schemes, the acetylene-aldehyde method BDO distillation process is composed of four distillation towers, namely, a concentration tower, a desalting tower, a light-removing tower and a heavy-removing tower, which are connected in series, and is characterized in that: a small tower is added next to the concentration tower, and the small tower is used to replace the part below the tower section; a part of the liquid phase in the original concentration tower kettle flows from top to bottom through the small tower, and the gas phase in the small tower moves upward and enters the concentration tower from the kettle of the concentration tower.

[0013] The solution of adding a small tower is suitable for the transformation of existing devices.

[0014] As one of the multiple optional solutions, the acetylene aldehyde method BDO distillation process is composed of four distillation towers, namely, a concentration tower, a desalting tower, a light desalting tower and a heavy desalting tower, which are connected in series. The tower section solution also includes energy integration of the concentration tower and the heavy desalting tower. The top temperature of the heavy desalting tower is as high as 155° C., and energy integration with the concentration tower can be considered. The concentration tower is designed and modified by adopting a tower section solution, the heat pump is removed, and the top vapor of the heavy desalting tower is introduced into the shell side of the tower section through a material steam conduit as a heat source.

[0015] The deweighting tower is a vacuum tower. The vapor at the top of the tower is condensed and enters a storage tank. A vacuum pipeline is added above the storage tank.

[0016] The present invention discloses an energy-saving BDO distillation process using an acetylene-aldehyde method, which has the following substantial advantages:

[0017] 1. Simultaneous energy and water saving: The scheme of the present invention can save both the steam in the tower bottom and the circulating water at the top of the tower. The thermal insulation material of the material steam conduit used has the characteristic of small thermal conductivity, which minimizes heat loss.

[0018] 2. The technology is mature and reliable. Whether it is heat pump distillation, heat exchanger heat exchange, or falling film evaporator, they are all mature industrial technologies.

[0019] 3. Significant energy-saving and water-saving effects, short investment recovery period, low investment and good energy-saving effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 :Computer simulation flow chart of concentration tower.

[0021] Figure 2 :The temperature distribution of the concentration tower simulated by computer is shown in the figure.

[0022] Figure 3 :Tower section scheme flow chart.

[0023] Figure 4 :Flow chart of energy integration scheme of concentration tower and deweighting tower.

[0024] In the figure: 1, concentration tower; 2, tower section; 3, heat pump; 4, tower top gas phase pipeline; 5, throttle valve; 6, discharge port; 7, reflux pipe; 8, condenser; 9, deweighting tower.

[0025] Figure 5 : Add a small tower process.

[0026] 10---small tower, 11---reboiler, 12----small tower gas phase, 13----concentration tower liquid phase. DETAILED DESCRIPTION

[0027] A computer simulation was conducted on the concentration tower of the 100,000 tons / year acetylene-aldehyde method BDO distillation process. The simulation results were verified by actual field data and can reflect the actual situation more accurately. The simulation results of key parameters are shown in the following table.

[0028] Comparison of simulation results and field results of key parameters of BDO concentration column

[0029] project unit Analog value On-site value deviation / % illustrate Tower top temperature ℃ 115.1 111.9 2.9 Deviation caused by incomplete light component data Tower top pressure Bar 1.695 1.695 0 Settings Bottom temperature ℃ 158.9 162.9 2.5 Ignore the salt bias in the simulation Bottom pressure Bar 1.824 1.824 0 Settings

[0030] The temperature distribution of the concentration tower can be obtained in the simulation. It can be found that

[0031] (1) Although the temperature of the bottom of the concentration tower reaches about 160°C, it quickly drops to about 120°C after leaving the bottom reboiler;

[0032] (2) Although the condensation temperature at the top of the concentration tower is about 80°C, the temperature of the gas phase entering the condenser reaches about 110°C. In this way, the temperature difference between the top of the tower and most of the plates in the stripping section is only about 10°C. Therefore, it is possible to consider using heat pump distillation technology to save energy.

[0033] The invention will be further described below by means of specific embodiments:

[0034] Example 1

[0035] For the 100,000 tons / year acetylene-aldehyde BDO distillation process, the acetylene-aldehyde BDO distillation process is composed of four distillation towers in series, namely, a concentration tower, a desalting tower, a lightness removal tower and a heavyness removal tower. A tower section is added at the distillation section of the concentration tower. The liquid phase material in the tower goes through the tube side and flows through the tower section from top to bottom. It is heated and vaporized while flowing, and the gas phase goes upward; the top gas phase is not condensed by the condenser, but enters the heat pump through the top gas phase pipeline of the tower, and after being pressurized and heated, it enters the shell side of the tower section as a heat source and is condensed into a liquid phase at the same time; the condensed liquid phase is depressurized and cooled by a throttle valve, and then enters the condenser for further cooling. A part of it is discharged from the tower through the discharge port as the top produced material, and the other part is returned to the top of the distillation tower through the reflux pipe as the reflux liquid.

[0036] For a single concentration tower, the steam consumption is reduced from about 21t / h to about 0.4t / h, saving 20.6t / h of steam; the amount of circulating water saved is about 1000t / h. Cost: heat pump investment is required, and the power consumption increases by about 840kW.

[0037] Example 2

[0038] For the 200,000 tons / year acetylene-aldehyde BDO distillation process, the acetylene-aldehyde BDO distillation process is composed of four distillation towers, namely, a concentration tower, a desalting tower, a lightness removal tower and a heavyness removal tower, connected in series. As one of the multiple optional schemes, the acetylene-aldehyde BDO distillation process is composed of four distillation towers, namely, a concentration tower, a desalting tower, a lightness removal tower and a heavyness removal tower, connected in series, and is characterized in that: a small tower is added next to the concentration tower, and the small tower is used to replace the part below the tower section; a part of the liquid phase in the original concentration tower kettle flows through the small tower from top to bottom, and the gas phase in the small tower moves upward and enters the concentration tower from the kettle of the concentration tower.

[0039] For a single concentration tower, the steam consumption is reduced from about 21t / h to about 0.4t / h, saving 225t / h of steam; the amount of circulating water saved is about 1130t / h. Cost: heat pump investment is required, and the power consumption increases by about 70kW.

[0040] Example 3

[0041] For the 200,000 tons / year acetylene-aldehyde BDO distillation process, the acetylene-aldehyde BDO distillation process is composed of four distillation towers in series, namely, a concentration tower, a desalting tower, a lightness removal tower and a heavyness removal tower. The tower section scheme also includes energy integration of the concentration tower and the heavyness removal tower; energy integration of the heavyness removal tower and the concentration tower; and the tower section scheme design and transformation of the concentration tower, removing the heat pump, and introducing the top vapor of the heavyness removal tower into the shell side of the tower section through the material steam conduit as a heat source.

[0042] The deweighting tower is a vacuum tower. The vapor at the top of the tower is condensed and enters a storage tank. A vacuum pipeline is added above the storage tank.

[0043] The energy integration of the concentration tower and the de-weighting tower was used to implement the tower saving scheme to save energy on one concentration tower, and the other tower was distilled by heat pump. The energy saving effect of the former is: after integration, the steam consumption of the concentration tower is reduced from about 21t / h to about 4.1t / h, saving 16.9t / h of steam; the circulating water of the high boiling tower top condenser is also saved, saving about 1000t / h.

[0044] Investment: The main investment is only a section of shell and tube heat exchanger, with no additional operating costs.

[0045] Example 4

[0046] For the 100,000 tons / year acetylene-aldehyde BDO distillation process, the energy integration of the concentration tower and the deweighting tower can also be used to implement the tower section solution.

[0047] The BDO distillation process of the acetylene aldehyde method is composed of four distillation towers connected in series, namely, a concentration tower, a desalting tower, a light removal tower and a heavy removal tower. The tower section scheme also includes energy integration of the concentration tower and the heavy removal tower. The top temperature of the heavy removal tower is as high as 155° C., and energy integration with the concentration tower can be considered. The concentration tower is designed and modified by adopting a tower section scheme, the heat pump is removed, and the top vapor of the heavy removal tower is introduced into the shell side of the tower section through a material steam conduit as a heat source.

[0048] The deweighting tower is a vacuum tower. The vapor at the top of the tower is condensed and enters a storage tank. A vacuum pipeline is added above the storage tank.

[0049] However, the energy saving effect is greatly reduced compared with that of Example 2, and theoretically is only about 50% of that of Example 2. Investment: The main investment is only a section of shell and tube heat exchanger, and there is no additional operating cost.

Claims

1. An energy-saving BDO distillation process by an acetylene-aldehyde method, wherein the BDO distillation process by an acetylene-aldehyde method comprises four distillation towers, a concentration tower, a desalting tower, a light-removing tower and a heavy-removing tower, connected in series, and characterized in that: A tower section is added at the position of the stripping section of the concentration tower. The liquid phase material in the tower flows through the tube side from top to bottom through the tower section. It is heated and vaporized while flowing, and the gas phase moves upward; the gas phase at the top of the tower enters the heat pump through the gas phase pipeline at the top of the tower without being condensed by the condenser, and enters the shell side of the tower section as a heat source after being pressurized and heated, and condensed into a liquid phase at the same time; the condensed liquid phase is depressurized and cooled by a throttle valve, and then enters the condenser for further cooling. A part of it is discharged from the tower through the discharge port as the top produced material, and the other part is returned to the top of the distillation tower through the reflux pipe as reflux liquid; The tower section scheme also includes energy integration of the concentration tower and the deweighting tower; energy integration with the concentration tower; design and transformation of the concentration tower using the tower section scheme, removing the heat pump, and introducing the top steam of the deweighting tower into the shell side of the tower section through the material steam conduit as a heat source.

2. The energy-saving BDO distillation process according to claim 1, characterized in that: The tower section is a shell and tube heat exchanger or a falling film evaporator.

3. The energy-saving BDO distillation process according to claim 1, wherein the BDO distillation process comprises four distillation towers, namely, a concentration tower, a desalting tower, a light-removing tower and a heavy-removing tower, connected in series, and characterized in that: A small tower is added next to the concentration tower, and the small tower is used to replace the part below the tower section; a part of the liquid phase in the original concentration tower kettle flows from top to bottom through the small tower, and the gas phase in the small tower goes upward and enters the concentration tower from the concentration tower kettle.

4. The energy-saving BDO distillation process according to claim 3, characterized in that: The solution of adding a small tower is suitable for the transformation of existing devices.

5. The energy-saving BDO distillation process according to claim 1, characterized in that: The deweighting tower is a vacuum tower. The vapor at the top of the tower is condensed and enters a storage tank. A vacuum pipeline is added above the storage tank.

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