Rectifying Tower Top Waste Heat Self-Driven Pressure-Enhancing Power-Saving Device

Abstract

The present invention discloses a waste heat self-driven pressurization power-saving device for the top of a distillation column, which includes a self-driven pressurization system, a quality improvement heating system, a cooling system and a control system. The self-driven pressurization system includes an organic working fluid evaporator, an organic working fluid condenser, a turbine expander and a working fluid pressurization pump. The quality improvement heating system includes a centrifugal compressor and a reboiler at the bottom of the column. The cooling system serves as the cold end of the self-driven pressurization system and includes an organic working fluid condenser. The control system includes a controller, and the controller adjusts the distribution ratio of the gaseous product at the top of the distillation column to the self-driven pressurization system and the quality improvement heating system. The present invention cancels the traditional voltage compressor, replaces the traditional electric pressurization system with a self-driven pressurization system, and greatly reduces the power consumption through the energy conversion process.

Description

Technical Field

[0001] The present invention relates to the technical field of waste heat utilization of rectification towers in the petrochemical industry, and specifically to a waste heat self-driven pressurization and power-saving device for the top of a rectification tower. Background Technique

[0002] A rectification tower is a component separation, mass transfer and heat transfer device widely used in the petrochemical production process. The temperature and pressure of the gaseous product at the top of the rectification tower are relatively low, but it contains a large amount of latent heat. After pressurizing, increasing the temperature and improving the quality of the gaseous product at the top of the tower, it can be used as the heating heat source for the tower kettle. By utilizing the latent heat of the gaseous product at the top of the tower, the consumption of new steam can be reduced. Traditional utilization technologies all use voltage compression to pressurize, increase the temperature and improve the quality of the gaseous product at the top of the tower, and a large amount of electric energy needs to be consumed while utilizing the latent heat of the gaseous product at the top of the tower. Reducing the power consumption while utilizing waste heat has become an urgent problem to be solved in the waste heat utilization industry. Summary of the Invention

[0003] The purpose of the present invention is to provide a waste heat self-driven pressurization and power-saving device for the top of a rectification tower, which adopts a self-driven pressurization system combining a turboexpander and a centrifugal compressor, cancels the traditional voltage compressor, and greatly reduces the power consumption through the energy conversion process.

[0004] To achieve the above purpose, the present invention provides the following technical solutions:

[0005] The waste heat self-driven pressurization device for the top of a rectification tower includes a self-driven pressurization system, a quality improvement and heating system, a cooling system and a control system. The self-driven pressurization system includes an organic working fluid evaporator, an organic working fluid condenser, a turboexpander and a working fluid pressurization pump. The quality improvement and heating system includes a centrifugal compressor and a tower kettle reboiler. The cooling system serves as the cold end of the self-driven pressurization system and includes an organic working fluid condenser. The control system includes a controller, and the controller adjusts the distribution ratio of the gaseous product at the top of the rectification tower to the self-driven pressurization system and the quality improvement and heating system.

[0006] The centrifugal compressor, turboexpander, organic working fluid evaporator, working fluid pressurization pump and organic working fluid condenser are connected to form an ORC organic Rankine cycle system. The ORC organic Rankine cycle system absorbs the low-grade waste heat at the top of the rectification tower to drive the turboexpander to drive the centrifugal compressor to pressurize and improve the quality of the low-pressure steam.

[0007] The self-driven pressurization system, quality improvement and heating system, cooling system and control system are combined to form three functional routes: a heating gas route, a pressurized gas route and an organic working fluid loop. The heating gas route and the pressurized gas route are connected through the organic working fluid loop, and the gas flow rates of the heating gas route and the pressurized gas route are adjusted by the controller to achieve thermal balance.

[0008] The heating gas line is successively connected in series with a centrifugal compressor and a reboiler at the bottom of the column, and the pressurizing gas line is successively connected in series with an organic working fluid evaporator, a liquid storage tank and a top product transfer pump; the organic working fluid loop is successively connected in series with an organic working fluid condenser, a working fluid pressurizing pump, an organic working fluid evaporator and a turbine expander.

[0009] The centrifugal compressor in the heating gas line is connected to the turbine expander in the organic working fluid loop through a coupling, and the organic working fluid evaporator in the pressurizing gas line is connected to the turbine expander in the organic working fluid loop.

[0010] Further, the organic working fluid loop is filled with an organic working fluid, and the organic working fluid adopts a low-boiling-point environmentally friendly working fluid, preferably pentafluoropropane R245fa.

[0011] The self-driven pressurization system can be divided into four processes according to the change of the state of the organic working fluid: the constant-pressure evaporation process in the organic working fluid evaporator, the constant-pressure condensation process in the organic working fluid condenser, the adiabatic expansion process in the turbine expander, and the adiabatic compression process in the working fluid pressurizing pump.

[0012] Electric control valves are arranged at the inlets of the centrifugal compressor and the turbine expander, and the intake air volume is controlled by a controller.

[0013] A connecting pipe is arranged between the organic working fluid evaporator and the organic working fluid condenser as a start-up bypass. During start-up and warm-up, the gaseous organic working fluid does not enter the turbine expander but directly enters the organic working fluid condenser for condensation.

[0014] The cold side of the organic working fluid condenser passes through circulating cooling water, which serves as a cold source to absorb the heat released by the condensation of the organic working fluid in the organic working fluid condenser.

[0015] A pipeline and a connected air extractor are arranged at the outlet of the gaseous product at the top of the organic working fluid evaporator. A flow negative pressure is established by the air extractor at the initial stage of start-up, and the outlet of the air extractor is connected to the upper part of the distillation column.

[0016] Further, the turbine expander and the centrifugal compressor are connected through a coupling and adopt a coaxial connection method. The turbine expander converts part of the thermal energy of the gaseous product at the top of the column into mechanical energy, and the centrifugal compressor converts the mechanical energy into part of the thermal energy of the gaseous product at the top of the column.

[0017] Further, a reboiler at the bottom of the column is arranged between the centrifugal compressor and the distillation column, and the reboiler at the bottom of the column is also connected with a bottom product transfer pump. The gaseous product is compressed in the centrifugal compressor, and the gaseous product with increased pressure and temperature enters the reboiler at the bottom of the column. The gaseous product condenses into a liquid in the reboiler at the bottom of the column and enters the distillation column as a reflux liquid.

[0018] The quality-improving heating system heats the reboiler at the bottom of the column by using part of the gaseous product at the top of the rectifying column as the heat source after pressurizing, temperature-raising and quality-improving by a centrifugal compressor.

[0019] The organic working fluid evaporator is also connected to a liquid storage tank through a pipeline, and the liquid storage tank is then connected to a top product transfer pump. The gaseous product condenses into a liquid in the organic working fluid evaporator and then enters the liquid storage tank. The liquid substance at the bottom of the liquid storage tank enters the top product transfer pump and is output as the top product after pressurization.

[0020] The waste heat self-driven pressurization and power-saving device at the top of the rectifying column of the present invention can also be a waste heat self-driven pressurization and power-saving device at the top of a stripping column, and the technical solution is also applicable to a stripping column.

[0021] Compared with the prior art, the beneficial effects of the present invention are:

[0022] The waste heat self-driven pressurization and power-saving device at the top of the rectifying column of the present invention adopts a self-driven pressurization system combining a turbine expander and a centrifugal compressor, cancels the traditional voltage compressor, and greatly reduces the power consumption through the conversion process of heat energy → mechanical energy → mechanical energy → heat energy.

[0023] For the waste heat self-driven pressurization and power-saving device at the top of the rectifying column of the present invention, by controlling the intake parameters of the turbine expander and the centrifugal compressor, the heat balance can be achieved online. According to the heat balance, the distribution ratio of the gaseous product at the top of the rectifying column to the self-driven pressurization system and the quality-improving heating system is accurately controlled. Brief Description of the Drawings

[0024] Figure 1 It is a structural schematic diagram of the present invention.

[0025] In the figure: 1. Rectifying column; 2. Reboiler at the bottom of the column; 3. Liquid storage tank; 4. Top product transfer pump; 5. Bottom product transfer pump; 6. Controller; 7. Centrifugal compressor; 8. Coupling; 9. Turbine expander; 10. Organic working fluid evaporator; 11. Working fluid pressurizing pump; 12. Organic working fluid condenser; 13. Air extractor. Detailed Embodiments

[0026] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0027] Please refer to Figure 1 , the present invention provides a technical solution:

[0028] The waste heat self-driven pressurization device at the top of the distillation column includes a self-driven pressurization system, a quality improvement heating system, a cooling system and a control system. The self-driven pressurization system includes an organic working fluid evaporator 10, an organic working fluid condenser 12, a turbine expander 9 and a working fluid booster pump 11. The quality improvement heating system includes a centrifugal compressor 7 and a reboiler 2 at the bottom of the column. The cooling system, as the cold end of the self-driven pressurization system, includes an organic working fluid condenser 12. The control system includes a controller 6, which adjusts the distribution ratio of the gaseous product at the top of the distillation column 1 to the self-driven pressurization system and the quality improvement heating system.

[0029] The heating gas line is successively connected in series with a centrifugal compressor 7 and a reboiler 2 at the bottom of the column. The pressurized gas line is successively connected in series with an organic working fluid evaporator 10, a liquid storage tank 3 and a top product transfer pump 4. The organic working fluid loop is successively connected in series with an organic working fluid condenser 12, a working fluid booster pump 11, an organic working fluid evaporator 10 and a turbine expander 9.

[0030] The centrifugal compressor 7 in the heating gas line is connected to the turbine expander 9 in the organic working fluid loop through a coupling 8. The organic working fluid evaporator 10 in the pressurized gas line is connected to the turbine expander 9 in the organic working fluid loop.

[0031] A reboiler 2 at the bottom of the column is arranged between the centrifugal compressor 7 and the distillation column 1. A branch of the reboiler 2 at the bottom of the column is also connected to a bottom product transfer pump 5. The gaseous product is compressed in the centrifugal compressor 7, and the gaseous product with increased pressure and temperature enters the reboiler 2 at the bottom of the column, where the gaseous product condenses into a liquid and then enters the distillation column 1 as a reflux liquid.

[0032] The organic working fluid evaporator 10 is also connected to the liquid storage tank 3 through a pipeline, and the liquid storage tank 3 is then connected to the top product transfer pump 4. The gaseous product condenses into a liquid in the organic working fluid evaporator 10 and then enters the liquid storage tank 3. The liquid substance at the bottom of the liquid storage tank 3 enters the top product transfer pump 4 and is output as the top product after pressurization.

[0033] A pipeline and a connected air extractor 13 are arranged at the outlet of the gaseous product at the top of the organic working fluid evaporator 10. A flow negative pressure is established by the air extractor 13 at the initial startup stage, and the outlet of the air extractor 13 is connected to the upper part of the distillation column 1.

[0034] The centrifugal compressor 7, the turbine expander 9, the organic working fluid evaporator 10, the working fluid booster pump 11 and the organic working fluid condenser 12 are connected to form an ORC organic Rankine cycle system. The ORC organic Rankine cycle system absorbs the low-grade waste heat at the top of the distillation column to drive the turbine expander 9 to drive the centrifugal compressor 7 to pressurize and improve the quality of the low-pressure steam.

[0035] The self-driven supercharging system, quality-improving heating system, cooling system and control system of the present invention form three functional routes in combination: the heating gas route, the supercharging gas route and the organic working fluid loop. The heating gas route and the supercharging gas route are connected through the organic working fluid loop, and the gas flow rates of the heating gas route and the supercharging gas route are adjusted by the controller 6 to achieve thermal balance.

[0036] Supercharging gas route: A part of the gaseous product at the top of the distillation column 1 enters the organic working fluid evaporator 10, where the gaseous product condenses into a liquid state and then enters the liquid storage tank 3. The liquid substance at the bottom of the liquid storage tank 3 enters the top product delivery pump 4, and after being pressurized, it is output as the top product.

[0037] Heating gas route: A part of the gaseous product at the top of the distillation column 1 enters the centrifugal compressor 7, where the gaseous product is compressed. The gaseous product with increased pressure and temperature enters the reboiler 2 at the bottom of the column, and the gaseous product condenses into a liquid state in the reboiler 2 at the bottom of the column and enters the distillation column 1 as reflux liquid.

[0038] Organic working fluid loop: The liquid organic working fluid enters the working fluid pressurizing pump 11 at the bottom of the organic working fluid condenser 12. After being pressurized by the working fluid pressurizing pump 11, it enters the organic working fluid evaporator 10. The liquid organic working fluid absorbs heat and evaporates into a gaseous state in the organic working fluid evaporator 10. The gaseous organic working fluid enters the turbine expander 9 to expand and do work. The gaseous organic working fluid with reduced pressure and temperature enters the organic working fluid condenser 12 and condenses into a liquid state. The liquid organic working fluid re-enters the working fluid pump 11 from the bottom of the organic working fluid condenser 12 and circulates continuously in this way.

[0039] The gaseous product at the top of the distillation column 1 is divided into two paths and enters the supercharging gas route and the heating gas route respectively. The gas flow rates of the two paths are determined according to the thermal balance calculation and are precisely adjusted through the controller 6.

[0040] The turbine expander 9 and the centrifugal compressor 7 are connected by a coupling 8. The mechanical work output by the turbine expander 9 is converted from the latent heat of the gaseous product at the top of the distillation column 1 absorbed by the organic working fluid. The input work of the centrifugal compressor 7 is provided by the turbine expander 9, and the output work is converted into the thermal energy of the gaseous product at the top of the distillation column 1.

[0041] The organic working fluid uses the low-boiling-point environmentally friendly working fluid pentafluoropropane R245fa.

[0042] The cold side of the organic working fluid condenser 12 passes through circulating cooling water, which serves as a cold source to absorb the heat released by the condensation of the organic working fluid in the organic working fluid condenser 12.

[0043] A connecting pipe is provided between the organic working fluid evaporator 10 and the organic working fluid condenser 12 as a start-up bypass. During start-up and warm-up, the gaseous organic working fluid does not enter the turbine expander 9 but directly enters the organic working fluid condenser 12 for condensation.

[0044] The rectifying column top waste heat self-driven pressurization power-saving device of the present invention adopts a self-driven pressurization system combining a turbine expander and a centrifugal compressor, eliminates the traditional voltage compressor, and greatly reduces the power consumption through the conversion process of heat energy → mechanical energy → mechanical energy → heat energy.

[0045] The rectifying column top waste heat self-driven pressurization power-saving device of the present invention can also be a stripping column top waste heat self-driven pressurization power-saving device, and the technical solution is also applicable to the stripping column.

[0046] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. The waste heat self-driven pressurization and power-saving device at the top of the rectification column is characterized in that, It includes a self-driven supercharging system, a quality-improving heating system, a cooling system and a control system. The self-driven supercharging system includes an organic working fluid evaporator, an organic working fluid condenser, a turbine expander and a working fluid pressurizing pump. The quality-improving heating system includes a centrifugal compressor and a reboiler at the bottom of the column. The cooling system serves as the cold end of the self-driven supercharging system and includes an organic working fluid condenser. The control system includes a controller, and the controller adjusts the distribution ratio of the gaseous product at the top of the distillation column to the self-driven supercharging system and the quality-improving heating system. The centrifugal compressor, the turbine expander, the organic working fluid evaporator, the working fluid pressurizing pump and the organic working fluid condenser are connected to form an ORC organic Rankine cycle system. The ORC organic Rankine cycle system absorbs the low-grade waste heat at the top of the distillation column to drive the turbine expander to drive the centrifugal compressor to boost the quality of the low-pressure steam. The self-driven supercharging system, the quality-improving heating system, the cooling system and the control system are combined to form three functional routes: a heating gas route, a supercharging gas route and an organic working fluid loop. The heating gas route and the supercharging gas route are connected through the organic working fluid loop. The gas flow rates of the heating gas route and the supercharging gas route are adjusted by the controller to achieve thermal balance. The heating gas route is successively connected in series with a centrifugal compressor and a reboiler at the bottom of the column. The supercharging gas route is successively connected in series with an organic working fluid evaporator, a liquid storage tank and a top product transfer pump. The organic working fluid loop is successively connected in series with an organic working fluid condenser, a working fluid pressurizing pump, an organic working fluid evaporator and a turbine expander. The centrifugal compressor in the heating gas route is connected to the turbine expander in the organic working fluid loop through a coupling. The organic working fluid evaporator in the supercharging gas route is connected to the turbine expander in the organic working fluid loop. The self-driven supercharging system can be divided into four processes according to the state change of the organic working fluid: a constant-pressure evaporation process in the organic working fluid evaporator, a constant-pressure condensation process in the organic working fluid condenser, an adiabatic expansion process in the turbine expander, and an adiabatic compression process in the working fluid pressurizing pump.

2. The waste heat self-driven pressurization power-saving device at the top of the rectifying column according to claim 1, wherein: The organic working fluid loop is filled with an organic working fluid, and the organic working fluid uses the low-boiling-point environmentally friendly working fluid pentafluoropropane R245fa.

3. The rectifying column top waste heat self-driven pressurization power-saving device according to claim 1, characterized in that: Electrically adjustable valves are provided at the inlets of the centrifugal compressor and the turbine expander, and the intake air volume is controlled by the controller.

4. The rectifying column top waste heat self-driven pressurization power-saving device according to claim 1, characterized in that A connecting pipe is provided between the organic working fluid evaporator and the organic working fluid condenser as a starting bypass.

5. The waste heat self-driven pressurization and power-saving device at the top of the rectifying column according to claim 1, characterized in that, The cold side of the organic working fluid condenser passes through circulating cooling water, which serves as a cold source to absorb the heat released by the condensation of the organic working fluid in the organic working fluid condenser.

6. The waste heat self-driven pressurization and power-saving device at the top of the distillation column according to claim 1, wherein A pipeline and a connected air extractor are provided at the outlet of the gaseous product at the top of the organic working fluid evaporator.

7. The waste heat self-driven pressurization and power-saving device at the top of the distillation column according to claim 1, characterized in that The turbine expander and the centrifugal compressor are connected by a coupling and adopt a coaxial connection method. The turbine expander converts part of the thermal energy of the gaseous product at the top of the column into mechanical energy, and the centrifugal compressor converts the mechanical energy into part of the thermal energy of the gaseous product at the top of the column.

8. The waste heat self-driven pressurization and power-saving device at the top of the rectification column according to claim 1, characterized in that, A reboiler at the bottom of the column is provided between the centrifugal compressor and the distillation column, and the reboiler at the bottom of the column is also connected to a bottom product transfer pump.

9. The waste heat self-driven pressurization and power-saving device at the top of the rectifying column according to claim 1, characterized in that, The organic working fluid evaporator is connected to the liquid storage tank through a pipeline, and the liquid storage tank is then connected to the top product transfer pump.

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