Rectification column for separating by-product crude methanol from coal-to-methanol

Abstract

This invention relates to the field of coal-to-methanol production equipment technology, and more particularly to a distillation column for separating crude methanol by-products from coal-to-methanol production. The column includes a pre-distillation column, a pressurized distillation column, and an atmospheric distillation column. An energy-saving control device is installed between the pressurized and atmospheric distillation columns. The power control device controls the steam output of the pressurized distillation column, and then valve two controls the liquid phase distribution to the atmospheric distillation column, thereby achieving equilibrium and effectively saving energy. A temperature compensation device is installed between the pressurized distillation column and the reboiler. This device includes a heat storage body installed on pipeline two, with an insulation layer outside the heat storage body. A temperature sensor is installed near the end of the heat storage body. The heat storage body can store heat when the steam flow is high, thus stabilizing the power of the reboiler and providing a buffer time for delayed feedback control, ensuring stable operation of the three columns.

Description

Technical Field

[0001] This invention relates to the field of coal-to-methanol production equipment technology, and in particular to a distillation column for separating crude alcohol as a byproduct of coal-to-methanol production. Background Technology

[0002] Distillation is the equipment used for methanol purification in the coal-to-methanol process. Typically, three distillation towers are used: a pre-distillation tower, a pressurized distillation tower, and an atmospheric distillation tower. The pre-distillation tower removes light components such as dimethyl ether, while the pressurized and atmospheric distillation towers are used to extract methanol. Distillation is a major energy-consuming step in coal-to-methanol production. To save energy, those skilled in the art have developed a three-tower system based on the two-tower design. The three-tower system effectively saves energy. The pressurized distillation tower is connected to a reboiler, and the atmospheric distillation tower is connected to a reboiler and a condenser. The steam outlet of the pressurized distillation tower is connected to the reboiler via pipeline 2. The pre-distillation tower is connected to a condenser and a preheater, and the reboiler is connected to the preheater. The methanol vapor extracted from the pressurized distillation tower sequentially provides heat to the reboiler and the preheater, thereby achieving energy savings.

[0003] To further improve the energy utilization rate of distillation columns, researchers in this field mainly focus on adjusting the parameters of the three columns and further expanding the three-column system. Adjusting the parameters of the three columns refers to adjusting the temperature, pressure, flow rate, and other parameters of the pre-distillation column, pressurized distillation column, and atmospheric distillation column, which is achieved by constructing a database and building a data model. Further expanding the three columns involves obtaining distillation columns with various pressures, achieving energy saving through tiered settings. Adjusting the parameters of the three columns is more cost-effective and has higher precision. However, adjusting the parameters of the three columns is based on data feedback from monitoring nodes, which has a long delay time and requires long-term data collection to obtain an optimized model, thereby achieving effective energy saving. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a distillation column for separating crude alcohol from coal-to-methanol by-products by means of temperature compensation and flow control to achieve energy saving.

[0005] This invention is achieved through the following technical solution: a distillation column for separating crude alcohol as a byproduct of coal-to-methanol production, comprising a pre-distillation column, a pressurized distillation column, and an atmospheric distillation column. The pressurized distillation column is connected to a reboiler, and the atmospheric distillation column is connected to a reboiler and a condenser. The vapor outlet of the pressurized distillation column is connected to the reboiler via a pipeline. The pre-distillation column is connected to a condenser and a preheater, and the reboiler is connected to the preheater. An energy-saving control device is provided between the pressurized distillation column and the atmospheric distillation column. The energy-saving control device includes a power control device connected to the reboiler and a valve connected to the liquid phase inlet of the atmospheric distillation column.

[0006] The power of the reboiler can be controlled by the power control device, thereby controlling the steam output of the pressurized distillation column;

[0007] Valve 2 can control the flow rate of liquid phase delivered from the pressurized distillation column to the atmospheric distillation column;

[0008] A temperature compensation device is provided between the pressurized distillation column and the second reboiler. The temperature compensation device includes a heat storage body installed on the second pipeline. The heat storage body is provided with a heat insulation layer. A temperature sensor is installed near the end of the heat storage body.

[0009] Furthermore, the reboiler is a steam-type reboiler, and the power control device is a valve connected to the steam inlet of the reboiler, wherein the valve is an electrically controlled valve.

[0010] Furthermore, the heat storage body is provided with multiple airflow channels, and the second pipeline is connected to a heat exchange tube bundle that cooperates with the airflow channels.

[0011] Furthermore, the temperature compensation device is an underground temperature compensation device, including a foundation pit. The bottom and side walls of the foundation pit are provided with a waterproof support layer. A waterproof isolation layer is provided inside the waterproof support layer. The waterproof isolation layer includes a water-removing overhead layer connected to the waterproof support layer. The water-removing overhead layer is connected to an air compressor. A dry sand layer is provided between the water-removing overhead layer and the heat insulation layer.

[0012] Furthermore, a detection pipe is provided at the outlet end of the air compressor, and an outlet air temperature sensor and an outlet air humidity sensor are installed on the detection pipe. Multiple foundation pits are provided between the pressurized distillation column and the atmospheric distillation column, and a maintenance well is provided between two adjacent foundation pits. A spare pipe cavity is provided at the bottom of the foundation pit, and a spare pipe is provided in the spare pipe cavity. The spare pipe and the heat exchange tube bundle are connected in the maintenance well through a maintenance valve group, which is configured to control the switching between the spare pipe and the heat storage body through the maintenance valve group.

[0013] Furthermore, a pile foundation is provided at the bottom of the waterproof support layer, and an anti-settlement raft is provided on the side of the waterproof support layer.

[0014] Furthermore, the preheater is connected to a methanol vapor precooling device, which is connected to condenser two.

[0015] The beneficial effects of this invention are as follows: A distillation column for separating crude methanol by-products from coal-to-methanol production includes a pre-distillation column, a pressurized distillation column, and an atmospheric distillation column. An energy-saving control device is installed between the pressurized and atmospheric distillation columns. This energy-saving control device includes a power control device connected to a reboiler and a valve connected to the liquid inlet of the atmospheric distillation column. The power control device controls the power of the reboiler, thereby controlling the steam output of the pressurized distillation column. The valve controls the flow rate of liquid phase supplied from the pressurized distillation column to the atmospheric distillation column. When the power of the reboiler is high, the steam output of the pressurized distillation column is high; correspondingly, the power of the reboiler is also high, and the atmospheric distillation column... The distillation column produces a large amount of vapor. To achieve equilibrium, the steam output of the pressurized distillation column is controlled by a power control device. Then, the liquid phase output to the atmospheric distillation column is controlled by valve two, thereby achieving equilibrium and effectively saving energy. A temperature compensation device is installed between the pressurized distillation column and the reboiler. The temperature compensation device includes a heat storage body installed on pipeline two. The heat storage body is covered with a heat insulation layer. A temperature sensor two is installed near the end of the heat storage body. The heat storage body can store heat when the steam flow is high, thereby making the power of the reboiler relatively stable, providing a buffer time for the lagging feedback control, and ensuring the stable operation of the three columns. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the connection relationship of the three towers in Example 1;

[0017] Figure 2 This is a schematic cross-sectional view of the heat storage body in Example 1;

[0018] Figure 3 This is a schematic diagram of the condenser structure in Example 1;

[0019] Figure 4 This is a schematic diagram of the cross-section of the heat storage body in Example 2;

[0020] Figure 5 This is a schematic diagram of the maintenance well structure in Example 2;

[0021] Figure 6 This is a top view of the water removal overhead layer in Example 2.

[0022] 1. Pre-distillation column; 2. Condenser I; 201. Condensing coil; 3. Vent tank; 4. Vent pipe; 5. Preheater; 6. Reboiler III; 7. Pressurized distillation column; 8. Reboiler I; 9. Valve I; 10. Atmospheric distillation column; 11. Valve II; 12. Reboiler II;

[0023] 13. Temperature compensation device; 1301. Insulation layer; 1302. Heat storage body; 1303. Heat exchange tube bundle; 1304. Distribution plate; 1305. Temperature sensor one; 1306. Temperature sensor two; 1307. Water removal overhead layer; 1308. Waterproof isolation layer; 1309. Cover plate; 1310. Waterproof support layer; 1311. Upper anti-settlement raft; 1312. Lower anti-settlement raft; 13 14. Precast support base; 1315. Support beam; 1316. Spare pipe; 1317. Liquid phase pipe; 1318. Pile foundation; 1319. Spare pipe cavity; 1320. Foundation pit; 1321. Inspection well; 1322. Positioning groove; 1323. T-junction; 1324. Flange; 1325. Valve three; 1326. Valve four; 1327. Valve five; 1328. Base plate; 1329. Support rib;

[0024] 14. Bottom vent pipe of the tower; 15. Condenser II; 16. Methanol storage tank; 17. Pipeline II. Detailed Implementation

[0025] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] Example 1

[0028] like Figure 1-3 As shown, a distillation column for separating crude alcohol as a byproduct of coal-to-methanol production includes a pre-distillation column 1, a pressurized distillation column 7, and an atmospheric distillation column 10. The pre-distillation column 1 is connected to a reboiler 3 6, a condenser 1 2, and a preheater 5. The condenser 1 2 is connected to a venting tank 3, and then to a venting pipe 4. Non-condensable gases are discharged after being cleaned by the venting tank 3. The pressurized distillation column 7 is connected to a reboiler 1 8, and the atmospheric distillation column 10 is connected to a reboiler 2 12 and a condenser 2 15. The steam outlet of the pressurized distillation column 7 is connected to the reboiler 2 12 through a pipe 2 17, and the reboiler 2 12 is connected to the preheater 5, thereby achieving energy saving.

[0029] An energy-saving control device is installed between the pressurized distillation column 7 and the atmospheric distillation column 10. The energy-saving control device includes a power control device connected to the reboiler 8 and a valve 11 connected to the liquid phase inlet of the atmospheric distillation column 10. In this embodiment, the reboiler 8 and the reboiler 6 are steam-type reboilers, which provide a heat source through a steam source. The power control device is a valve 9 connected to the steam inlet of the reboiler 8. The valve 9 is an electrically controlled valve that can control the opening degree, thereby controlling the steam flow rate of the reboiler 8, and thus controlling the steam output of the pressurized distillation column 7. The flow rate of the liquid phase delivered from the pressurized distillation column 7 to the atmospheric distillation column 10 can be controlled through the valve 11.

[0030] A temperature compensation device 13 is installed between the pressurized distillation column 7 and the reboiler 2 12. The temperature compensation device 13 includes a heat storage body 1302 installed on the pipeline 2 17. The heat storage body 1302 is wrapped with a heat insulation layer 1301, and the heat insulation layer 1301 is covered with a steel shell. A temperature sensor 2 1306 is installed near the end of the heat storage body 1302. Specifically, the heat storage body 1302 is made of precast refractory bricks, with a length of 800-1000mm and a weight controlled at 100-150Kg. It consists of 4-5 sets connected in series through pipelines, which have good heat storage stability. The heat storage body 1302 has multiple pre-formed airflow channels. The pipeline 2 17 is connected to a heat exchange tube bundle 1303 that matches the airflow channels. During use, in order to ensure sealing performance, the pipeline 2 17 is connected to the heat exchange tube bundle 1303 through a distribution plate 1304. The heat exchange tube bundle 1303 is made of steel pipe.

[0031] During operation, the opening degrees of valves 1-9 and 2-11 are controlled according to design values. The raw material flows into the pre-distillation column 1 through the preheater 5, where light components are removed. It then flows into the pressurized distillation column 7. The liquid phase passes through the pressurized distillation column 7, where methanol is collected. A portion of the liquid phase is pumped from the bottom of the pressurized distillation column 7 into the atmospheric distillation column 10, where methanol is collected. The flow rate of the liquid phase entering the atmospheric distillation column 10 is controlled by adjusting the opening degree of valve 2-11. During operation, the temperature of the heat storage body 1302 is detected by temperature sensor 2-1306. When the temperature of the heat storage body 1302 is lower than the preset range, the steam output from the pressurized distillation column 7 is insufficient, the reboiler 1-8 needs to be heated, and the atmospheric distillation column 10 needs to reduce the liquid phase inflow or increase the temperature of the reboiler 2-12. In this case, emergency measures are taken, such as raising the valve 1-9. The opening degree of valve 11 is reduced, thereby rapidly increasing the methanol vapor output of pressurized distillation column 7 while ensuring sufficient gas-liquid reaction in atmospheric distillation column 7. When the methanol vapor output in pressurized distillation column 7 increases, it flows through temperature compensation device 13, thereby increasing the temperature of heat storage body 1302. After reaching the preset value, the opening values ​​of valve 19 and valve 21 are restored. Due to the heat storage effect of heat storage body 1302, the impact of the sudden increase in methanol vapor output in reboiler 212 on atmospheric distillation column 10 is weakened, and the purity of methanol extracted from atmospheric distillation column 10 is guaranteed. To ensure control accuracy, temperature sensor 1305 is also installed on heat storage body 1302. Temperature sensor 1305 and temperature sensor 21306 are distributed at intervals, thereby enabling the acquisition of temperature at different locations and avoiding detection errors caused by the failure of a single temperature sensor.

[0032] During use, it was found that the methanol vapor generated by the pressurized distillation column 7 still had a high temperature after passing through the reboiler 8 and preheater 5. It needed to be cooled before flowing into the methanol storage tank 16. The steam outlet of the preheater 5 is connected to a methanol vapor precooling device, which is a condenser. Since the condenser 2 is connected to the pre-distillation column 1 and the working load of the condenser 2 is relatively small, it is considered to use the condenser 2 as the methanol vapor precooling device. The condenser 2 includes multiple sets of condensing coils 201. In this embodiment, there are three sets. One set is used as the methanol vapor precooling device. Two sets are used to condense the vapor phase of the pre-distillation column 1, which can effectively utilize the space. The methanol vapor precooling device is connected to the condenser 15. After mixing with the methanol vapor of the atmospheric distillation column 10, it is condensed and enters the methanol storage tank 16.

[0033] The bottom of the atmospheric distillation column 10 is connected to the bottom vent pipe 14 to discharge high-boiling-point materials.

[0034] Example 2

[0035] like Figure 4-6As shown, a distillation column for separating crude alcohol as a byproduct of coal-to-methanol production differs from Example 1 in that the temperature compensation device 13 is a buried temperature compensation device 13, including a foundation pit 1320. The foundation pit 1320 is excavated between the pressurized distillation column 7 and the atmospheric distillation column 10. A waterproof support layer 1310 is constructed on the bottom and side walls of the foundation pit 1320. The waterproof support layer 1310 is made of waterproof mortar, which has good waterproof effect and structural strength. Installing the temperature compensation device 13 underground saves space, makes it easier to fix, and improves the insulation effect. A waterproof isolation layer 1308 is constructed inside the waterproof support layer 1310. The waterproof isolation layer 1308 includes a water-removing overhead layer 1307 connected to the waterproof support layer 1310. In this embodiment, except... The water-removing overhead layer 1307 includes a substrate 1328, which is a precast plate or a steel plate. Supporting ribs 1329 are machined on the outer side of the substrate 1328, thus forming a cavity between the substrate 1328 and the waterproof support layer 1310. The water-removing overhead layer 1307 is connected to an air compressor. The air compressor blows air outwards, extracting the gas from the cavity for testing. A detection pipe is installed at the outlet of the air compressor, and an outlet air temperature sensor and an outlet air humidity sensor are installed on the detection pipe to detect the temperature and humidity values ​​within the pit 1320. A dry sand layer, composed of quartz sand or resin sand, is laid between the water-removing overhead layer 1307 and the steel shell. Since the insulation layer 1301 contains a heat storage body 1302 and a heat exchange tube bundle 1303, it releases heat, causing the dry sand layer to dry. The dry sand removes water vapor. When some moisture seeps in from the outside, it can be absorbed by the dry sand, thus forming an isolation layer to protect the steel shell and the insulation layer 1301. Four to five foundation pits 1320 are distributed between the pressurized distillation column 7 and the atmospheric distillation column 10. A maintenance well 1321 is constructed between two adjacent foundation pits 1320. A spare pipe cavity 1319 is constructed at the bottom of each foundation pit 1320. A spare pipe 1316 is laid in the spare pipe cavity 1319 through a prefabricated support base 1314. The spare pipe 1316 and the heat exchange tube bundle 1303 are connected in the maintenance well 1321 through a maintenance valve assembly. This assembly allows for control of the switching between the spare pipe 1316 and the heat storage body 1302. Specifically, the valve assembly includes a tee 132... 3. The tee 1323 is connected to the two heat exchange tube bundles 1303 and the spare pipe 1316 through valves 1325, 1326, and 1327 respectively. The connection uses flange 1324 for easy disassembly and maintenance. When the outlet air temperature sensor and outlet air humidity sensor detect abnormalities, maintenance is carried out. When the heat storage body 1302 needs to be replaced, the corresponding heat storage body 1302 can be isolated by operating the valve. The dry sand layer can be pumped out to lift out the steel shell and heat storage body 1302 assembly. To avoid interference, the dry sand layer is refilled after the replacement is completed. A positioning groove 1322 is processed on the isolation wall between the maintenance well 1321 and the foundation pit 1320. The upper end of the positioning groove 1322 is open, so that the connecting pipe can pass through.

[0036] The bottom of the waterproof support layer 1310 has a pile foundation 1318. The side of the waterproof support layer 1310 is integrally formed with an anti-settlement raft slab. Specifically, the anti-settlement raft slab is divided into an upper anti-settlement raft slab 1311 and a lower anti-settlement raft slab 1312. The lower raft slab can effectively ensure the anti-settlement effect. The upper anti-settlement raft slab 1311 is also used to form a maintenance support base. Maintenance and hoisting tools can walk on the upper surface of the upper anti-settlement raft slab 1311. A cover plate 1309 is laid on the upper end of the foundation pit and the maintenance well. The cover plate 1309 is sealed with the foundation pit 1320 and the maintenance well 1321 through a sealing strip or mortar for waterproofing.

[0037] In this embodiment, the lower surface of the spare tube cavity 1319 is arc-shaped. The spare tube cavity 1319 and the foundation pit 1320 are isolated by a support beam 1315. The upper end of the support beam is supported by a prefabricated support seat 1314 to support the steel shell and the heat insulation layer 1301. A spare tube 1316 is installed in the middle of the spare tube cavity 1319. Liquid phase tubes 1317 are laid on both sides of the spare tube 1316. This allows for the underground installation of the liquid phase tubes 1317 between the pressurized distillation column 7 and the atmospheric distillation column 10, which is convenient for installation and can be protected.

[0038] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A distillation column for separating crude alcohol as a byproduct of coal-to-methanol production, comprising a pre-distillation column, a pressurized distillation column, and an atmospheric distillation column, wherein the pressurized distillation column is connected to a reboiler, the atmospheric distillation column is connected to a reboiler and a condenser, the vapor outlet of the pressurized distillation column is connected to the reboiler via a pipeline, the pre-distillation column is connected to a condenser and a preheater, and the reboiler is connected to the preheater, characterized in that... An energy-saving control device is installed between the pressurized distillation column and the atmospheric distillation column. The energy-saving control device includes a power control device connected to the reboiler and a valve connected to the liquid inlet of the atmospheric distillation column. The power of the reboiler can be controlled by the power control device, thereby controlling the steam output of the pressurized distillation column; Valve 2 can control the flow rate of liquid phase delivered from the pressurized distillation column to the atmospheric distillation column; The reboiler is a steam-type reboiler, and the power control device is a valve connected to the steam inlet of the reboiler, which is an electrically controlled valve. A temperature compensation device is installed between the pressurized distillation column and the second reboiler. The temperature compensation device includes a heat storage element installed on the second pipeline, an insulation layer installed outside the heat storage element, and a temperature sensor second installed near the end of the heat storage element. The heat storage body is provided with multiple airflow channels, and the second pipeline is connected to a heat exchange tube bundle that cooperates with the airflow channels. Temperature sensor 2 detects the temperature of the heat storage body. When the temperature of the heat storage body is lower than the preset range, the steam output of the pressurized distillation column is insufficient, and the reboiler 1 itself needs to increase its temperature. The atmospheric distillation column needs to reduce the liquid phase inflow or increase the temperature of reboiler 2. At this time, emergency measures are taken: the opening of valve 1 is increased and the opening of valve 2 is decreased, so that the methanol vapor output of the pressurized distillation column can be increased rapidly, while ensuring that the gas-liquid reaction in the atmospheric column is sufficient. After the methanol vapor output in the pressurized distillation column increases, it flows through the temperature compensation device, which in turn increases the temperature of the heat storage body. After reaching the preset value, the opening values ​​of valve 1 and valve 2 are restored. Due to the heat storage effect of the heat storage body, the impact of the sudden increase in methanol vapor output of reboiler 2 on the atmospheric distillation column is weakened, and the purity of the methanol collected from the atmospheric distillation column is guaranteed. Temperature sensor 1 is also installed on the heat storage body. Temperature sensor 1 and temperature sensor 2 are distributed at intervals, so that the temperature at different locations can be collected.

2. The distillation column for separating crude alcohol as a byproduct of coal-to-methanol production according to claim 1, characterized in that, The temperature compensation device is an underground temperature compensation device, including a foundation pit. The bottom and side walls of the foundation pit are provided with a waterproof support layer. A waterproof isolation layer is provided inside the waterproof support layer. The waterproof isolation layer includes a water-removing overhead layer connected to the waterproof support layer. The water-removing overhead layer is connected to an air compressor. A dry sand layer is provided between the water-removing overhead layer and the heat insulation layer.

3. The distillation column for separating crude alcohol as a byproduct of coal-to-methanol production according to claim 2, characterized in that, The air compressor is equipped with a detection pipe at its outlet end, and the detection pipe is equipped with an outlet air temperature sensor and an outlet air humidity sensor. Multiple foundation pits are set between the pressurized distillation column and the atmospheric distillation column, and a maintenance well is set between two adjacent foundation pits. A spare pipe cavity is set at the bottom of the foundation pit, and a spare pipe is set in the spare pipe cavity. The spare pipe and the heat exchange tube bundle are connected in the maintenance well through a maintenance valve group, which is configured to control the switching between the spare pipe and the heat storage body through the maintenance valve group.

4. The distillation column for separating crude alcohol as a byproduct of coal-to-methanol production according to claim 2, characterized in that, The bottom of the waterproof support layer is provided with pile foundation, and the side of the waterproof support layer is provided with anti-settlement raft.

5. The distillation column for separating crude alcohol as a byproduct of coal-to-methanol production according to claim 1, characterized in that, The preheater is connected to a methanol vapor precooling device, which is connected to condenser two.

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