Energy-saving system for ethanol rectification

Abstract

The utility model discloses an energy-saving system for ethanol rectification. The energy-saving system comprises a rectifying tower, a first-stage feed preheater, a second-stage feed preheater, a third-stage feed preheater, a tower top condenser, a heat pump compressor, a condensation reboiler and a reflux tank, the first-stage, second-stage and third-stage feed preheaters are sequentially connected with the rectifying tower; a tower top gas phase outlet of the rectifying tower is respectively communicated with a hot side inlet of the tower top condenser and an inlet of the heat pump compressor, an outlet of the heat pump compressor is communicated with a hot side inlet of the condensation reboiler, and a hot side outlet of the condensation reboiler is communicated with a heat source inlet of the three-stage feeding preheater; a tower kettle liquid extraction port of the rectifying tower is respectively communicated with a cold side inlet of the condensation reboiler and a heat source inlet of the secondary feeding preheater; a tower kettle liquid backflow port of the rectifying tower is communicated with a cold side outlet of the condensation reboiler; a first inlet of the reflux tank is communicated with a hot side outlet of the tower top condenser, and a liquid phase outlet of the reflux tank is respectively communicated with a tower top reflux inlet of the rectifying tower and a heat source inlet of the primary feeding preheater. The device can reduce the consumption of tower top cooling circulating water and tower kettle steam in the rectification process, and is economical and energy-saving.

Description

Technical Field

[0001] This utility model relates to chemical separation technology, and specifically to an energy-saving system for ethanol distillation. Background Technology

[0002] In industrial production, ethanol dehydration is typically required to obtain high-purity ethanol. Traditional ethanol distillation systems consume large amounts of steam and circulating water, resulting in high energy consumption. With the escalating energy crisis and increasingly stringent environmental regulations, reducing energy consumption and improving energy efficiency in the distillation process has become a key research focus for enterprises and research institutions.

[0003] Existing ethanol distillation systems have the following drawbacks:

[0004] 1) High energy consumption: Traditional distillation systems use a lot of steam as a heat source. With the transformation of the energy structure, the price of steam is getting more and more expensive, and the cost per ton of ethanol distillation is getting higher and higher, resulting in poor economic efficiency.

[0005] 2) Low energy efficiency: In traditional distillation processes, the overall energy efficiency of the system is low due to the low heat exchange efficiency;

[0006] 3) Complex process: In order to reduce the operating cost of the distillation system, some units also adopt double-effect distillation, which can reduce energy consumption to a certain extent. However, it is inevitable that the high-pressure tower bottom still needs to be supplied with high-grade steam to provide a heat source, and the top of the low-pressure tower needs to consume circulating water to remove heat. At the same time, it increases equipment investment compared with conventional distillation.

[0007] 4) Environmental pollution: The steam generated by the large-scale use of fossil fuels may lead to environmental pollution problems. Summary of the Invention

[0008] The technical problem to be solved by this utility model is to provide an energy-saving system for ethanol distillation, which can reduce energy consumption in the distillation process, improve the energy efficiency of distillation, and achieve economic and environmental protection effects.

[0009] An energy-saving system for ethanol distillation according to an embodiment of the present invention includes a distillation column, a primary feed preheater, a secondary feed preheater, a tertiary feed preheater, a top condenser, a heat pump compressor, a condenser-reboiler, and a reflux tank; the primary feed preheater, secondary feed preheater, tertiary feed preheater, and the feed inlet of the distillation column are connected in sequence; the vapor outlet at the top of the distillation column is connected to the hot side inlet of the top condenser and the inlet of the heat pump compressor, respectively; the outlet of the heat pump compressor is connected to the hot side inlet of the condenser-reboiler. The side inlet is connected, and the hot side outlet of the condenser-reboiler is connected to the heat source inlet of the third-stage feed preheater; the bottom liquid outlet of the distillation column is divided into two paths, one connected to the cold side inlet of the condenser-reboiler, and the other connected to the heat source inlet of the second-stage feed preheater; the bottom liquid reflux port of the distillation column is connected to the cold side outlet of the condenser-reboiler; the first inlet of the reflux tank is connected to the hot side outlet of the top condenser, and the liquid phase outlet of the reflux tank is connected to the top reflux port of the distillation column and the heat source inlet of the first-stage feed preheater, respectively.

[0010] This utility model has at least the following advantages and features:

[0011] 1. Reduce energy consumption in the distillation process. This embodiment of the invention employs heat pump distillation technology, directly compressing the overhead gas of the distillation column as the heat source for the reboiler in the bottom column, significantly reducing the consumption of reboiler steam and overhead condensate circulating water;

[0012] 2. Improve the energy efficiency of the distillation process. This embodiment of the invention utilizes the heat recovered by the heat pump compressor and the condenser-reboiler, as well as the waste heat from the top and bottom of the column, to preheat the feed, reducing the heat load on the bottom of the column and also reducing the consumption of circulating water required for product cooling; the heat pump compressor is driven by a permanent magnet synchronous motor with frequency conversion regulation, enabling energy-saving operation even under low load;

[0013] 3. Simplified equipment configuration and reduced maintenance costs. This embodiment of the invention employs a stripping process, reducing the need for a reboiler in the distillation column. Simultaneously, the heat pump distillation utilizes a single-tower process, simplifying equipment configuration.

[0014] 4. Reduce environmental pollution and promote green production. Heat pump compressors are driven by electric motors, resulting in lower costs and environmental friendliness. Attached Figure Description

[0015] Figure 1 A schematic diagram of an energy-saving system for ethanol distillation according to an embodiment of the present invention is shown. Detailed Implementation

[0016] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0017] Please refer to Figure 1An energy-saving system for ethanol distillation according to an embodiment of the present invention includes two main parts: a distillation unit and a heat pump unit. The distillation unit includes a distillation column T101, a first-stage feed preheater E103, a second-stage feed preheater E104, a third-stage feed preheater E105, a top condenser E102, and a reflux tank V101, etc. The heat pump unit includes a heat pump compressor C101 and a condenser-reboiler E101.

[0018] The feed inlets of the primary feed preheater E103, secondary feed preheater E104, tertiary feed preheater E105, and distillation column T101 are connected in sequence. That is, the outlet of the primary feed preheater E103 is connected to the inlet of the secondary feed preheater E104, the outlet of the secondary feed preheater E104 is connected to the inlet of the tertiary feed preheater E105, and the outlet of the tertiary feed preheater E105 is connected to the inlet of the distillation column T101.

[0019] The vapor outlet of distillation column T101 is connected to the hot-side inlet of the top condenser E102 and the inlet of the heat pump compressor C101. The outlet of heat pump compressor C101 is connected to the hot-side inlet of condenser-reboiler E101, and the hot-side outlet of condenser-reboiler E101 is connected to the heat source inlet of the tertiary feed preheater E105. The bottom liquid outlet of distillation column T101 is divided into two paths: one is connected to the cold-side inlet of condenser-reboiler E101, and the other is connected to the heat source inlet of the secondary feed preheater E104. The bottom liquid reflux outlet of distillation column T101 is connected to the cold-side outlet of condenser-reboiler E101.

[0020] In this embodiment, a valve S101 is installed on the connecting pipeline between the top vapor outlet of the distillation column T101 and the inlet of the heat pump compressor C101. When the heat pump unit fails, the shut-off valve S101 can be closed to switch back to the original distillation system. The top gas of the distillation column T101 can be condensed by the top condenser E102 and then enter the reflux tank V101, thereby ensuring that the system can operate normally.

[0021] Considering the initial equipment investment and subsequent operation and maintenance costs, the distillation column in this embodiment does not have a steam reboiler. Instead, it adopts stripping distillation. The reboiler of distillation column T101 is equipped with a low-pressure steam inlet 111. When the system is started up, low-pressure steam is directly introduced into the reboiler of distillation column T101 to heat the reboiler. When the heat pump unit is switched on, if the booster gas from the top of the column is insufficient to heat the reboiler, a small amount of steam can be added to provide sufficient heat.

[0022] The first inlet of the reflux tank V101 is connected to the hot-side outlet of the overhead condenser E102. The liquid outlet of the reflux tank V101 is connected to the overhead reflux port of the distillation column T101 and the heat source inlet of the first-stage feed preheater E103, respectively. Furthermore, the liquid outlet of the reflux tank V101 is also connected to the inlet of the heat pump compressor C101, so that the condensate from the reflux tank V101 can be used as the inlet spray of the heat pump compressor C101.

[0023] In this embodiment, the heat pump compressor C101 is driven by a variable frequency motor. The heat pump compressor C101 is a screw compressor.

[0024] In this embodiment, the heat source outlet of the primary feed preheater E103 is connected to the hot-side inlet of the top product cooler E107, and the hot-side outlet of the top product cooler E107 is connected to the top product storage tank. The heat source outlet of the secondary feed preheater E104 is connected to the hot-side inlet of the bottom liquid cooler E106, and the hot-side outlet of the bottom liquid cooler E106 is connected to the wastewater treatment system. The heat source outlet of the tertiary feed preheater E105 is connected to the second inlet of the reflux tank V101, and the vapor phase outlet of the reflux tank V101 is connected to the inlet of the heat pump compressor C101. The reflux tank V101 is used to flash-evaporate the condensate output from the tertiary feed preheater E105 and output the flash-evaporated vapor phase from the vapor phase outlet.

[0025] The distillation process of the energy-saving system for ethanol distillation according to embodiments of this utility model includes the following steps:

[0026] Dilute ethanol solution from the feed buffer tank is used as the feed for the distillation system. It is preheated in the primary, secondary, and tertiary feed preheaters via feed pump P101 before entering the distillation column T101 from the middle. The heat source for the primary feed preheater E103 is the top product from distillation column T101; the heat source for the secondary feed preheater E104 is the bottom liquid from distillation column T101; and the heat source for the tertiary feed preheater E105 is the high-temperature, high-pressure condensate from the outlet of the condenser-reboiler E101. The two product streams from the top and bottom of distillation column T101 exchange heat with the feed and are then cooled to 40°C using circulating water in the top product cooler E107 and the bottom liquid cooler E106 before being sent to the product storage tank and wastewater treatment system.

[0027] The overhead gas from distillation column T101 is pressurized by heat pump compressor C101 to improve its grade and then enters condenser-reboiler E101 to supply heat to the column bottom. Reflux liquid from the overhead reflux tank V101 is injected into the inlet of heat pump compressor C101. The discharge temperature of the compressor is controlled by the injection volume to achieve the saturation temperature at the outlet pressure, resulting in high-temperature, high-pressure saturated gas at the outlet of heat pump compressor C101.

[0028] After the high-temperature and high-pressure condensate has undergone heat exchange in the condenser-reboiler E101, it enters the three-stage feed preheater E105 to heat the feed and release part of the sensible heat before entering the reflux tank V101. The flash vapor phase returns to the inlet of the heat pump compressor C101 for further compression to provide more heat to the tower bottom.

[0029] The liquid phase output from the liquid phase outlet of the reflux tank V101 is divided into three outputs by the reflux pump P103: one part is used as the top reflux of the distillation column T101, another part is taken out as ethanol product after exchanging heat with the feed through the first-stage feed preheater E103, and a small part is used as the injection medium to enter the heat pump compressor C101 to cool the unit outlet.

[0030] The bottom liquid of distillation column T101 is heated in the secondary feed preheater E104 after being pumped out of the bottom by column bottom pump P102, and then fed to the wastewater treatment plant.

[0031] The distillation process of the energy-saving system according to the embodiments of this utility model has the following advantages:

[0032] 1. Compared with the prior art, the heat pump distillation process adopted in this embodiment of the utility model is more energy-efficient. By using heat pump technology to recover and reuse heat, the energy consumption of the device is greatly reduced.

[0033] 2. Compared with the prior art, the heat pump distillation process used in this embodiment of the utility model has higher energy efficiency, the heat exchange network is optimized by pinch technology, and the heat pump compressor is driven by a permanent magnet synchronous motor with frequency conversion regulation, making the distillation system more energy-efficient and heat exchange more efficient.

[0034] 3. Compared with the prior art, the heat pump distillation process adopted in this embodiment of the utility model is more economical and environmentally friendly. It is driven by an electric motor, which greatly reduces the use of fossil energy and is environmentally friendly. Although the initial investment of the equipment is increased, the operating cost is low and the long-term economic benefits are very considerable.

[0035] The following specific application example further illustrates the technical solution of this utility model, and the advantages of the embodiment of this utility model are illustrated by comparing the energy consumption and operating costs with those of traditional distillation processes.

[0036] Application Example 1

[0037] The following description is based on a heat pump distillation system with an annual output of 300,000 tons of finished ethanol. The feed conditions and separation requirements are shown in Table 1. The operating flexibility of the unit is 60% to 120%.

[0038] Table 1 Separation Requirements and Operating Parameters for Ethanol Heat Pump Distillation System

[0039]

[0040] Process description:

[0041] (1) The dilute ethanol solution from the raw material buffer tank is used as the raw material for the distillation system. After being pressurized by the feed pump P101 to overcome the pipe resistance and feed height, it is sent to the first, second and third stage feed preheaters to be preheated from room temperature to 87°C and then enters the distillation column T101 from the middle.

[0042] (2) The overhead gas of the distillation column T101 and a small amount of flash vapor from the outlet of the three-stage feed preheater E105 are pressurized to 490 kPaA by the heat pump compressor C101 and then enter the condenser reboiler E101 to supply heat to the column bottom. The outlet temperature of the heat pump compressor C101 is the saturation temperature corresponding to the outlet pressure, which is 126.5℃. Considering the 15℃ heat exchange temperature difference with the column bottom, the outlet temperature of the heat pump compressor C101 is controlled by injecting the overhead reflux liquid from the reflux tank V101 into the unit inlet.

[0043] (3) The high-temperature and high-pressure condensate that has been replaced in the condenser reboiler E101 enters the three-stage feed preheater E105 to heat the feed and release part of the sensible heat before entering the reflux tank V101. The flash vapor phase returns to the inlet of the heat pump compressor C101 for further compression to provide more heat to the tower bottom.

[0044] (4) The liquid phase output from the liquid phase outlet of the reflux tank V101 is divided into three outputs by the reflux pump P103: one part is used as the top reflux of the distillation column T101, one part is used as the ethanol product after exchanging heat with the feed through the first-stage feed preheater E103, and a small part is used as the spray medium to enter the heat pump compressor C101 to control the exhaust temperature.

[0045] (5) The bottom liquid of the distillation column T101 is heated to 66°C in the secondary feed preheater E104 after passing through the bottom liquid pump P102, and then cooled to 40°C by circulating water in the bottom liquid cooler E106 before being sent to the sewage treatment system.

[0046] (6) The top product of distillation column T101 is heated from room temperature to 40°C by the primary feed preheater E103 after the reflux pump P103. Then it is cooled to 40°C by circulating water in the top product cooler E107 and sent to the product storage tank.

[0047] The energy consumption and operating costs of this process are compared with those of the traditional distillation process when achieving the same separation requirements. The specifications, consumption and operating costs of the utilities are shown in Table 2.

[0048] Table 2 Comparison of Energy Consumption between Heat Pump Distillation and Conventional Distillation

[0049]

[0050] Note: The prices of various public works in this project are as follows: circulating water: 0.3 yuan / t, steam: 200 yuan / t, electricity: 0.6 yuan / kWh, calculated based on 8000 hours per year.

[0051] Comparison Results: When the two ethanol distillation processes achieve the same separation requirements, the operating cost of heat pump distillation is significantly lower than that of traditional distillation. Steam and circulating water consumption are greatly reduced, the heat pump compressor is rationally selected, and it can control the outlet temperature and produce by-product steam, effectively improving heat exchange efficiency. The permanent magnet synchronous motor driving the heat pump compressor has higher energy efficiency, and frequency conversion regulation saves labor and energy. The motor drive is economical and environmentally friendly. In terms of operating costs, the annual operating cost of the heat pump distillation system is approximately 14.88 million yuan, a 73.3% saving compared to the 55.79 million yuan of the traditional distillation process, demonstrating considerable economic benefits. This invention couples multiple energy-saving technologies, maximizing savings on operating costs. This technology has advantages in feasibility, energy saving, economy, and environmental protection, aligning with my country's overall development direction of resource utilization, energy conservation and emission reduction, and environmental protection, and has broad industrialization prospects.

[0052] This invention provides an energy-saving system for ethanol distillation, which exhibits significant energy-saving effects compared to traditional distillation processes. This provides a framework for energy-saving and consumption-reducing designs in processes such as bio-fermentation ethanol and coal-to-ethanol production. Those skilled in the art should understand that the above description is not intended to limit this invention. Any modifications, equivalent substitutions, recombinations, improvements, or alterations made within the principles of this invention should be included within the protection scope of this invention.

Claims

1. An energy-saving system for ethanol distillation, characterized in that, It includes a distillation column, a primary feed preheater, a secondary feed preheater, a tertiary feed preheater, a top condenser, a heat pump compressor, a condenser-reboiler, and a reflux tank; The primary feed preheater, the secondary feed preheater, the tertiary feed preheater, and the feed inlet of the distillation column are connected in sequence. The vapor outlet at the top of the distillation column is connected to the hot-side inlet of the top condenser and the inlet of the heat pump compressor, respectively. The outlet of the heat pump compressor is connected to the hot-side inlet of the condenser-reboiler, and the hot-side outlet of the condenser-reboiler is connected to the heat source inlet of the tertiary feed preheater. The liquid outlet at the bottom of the distillation column is divided into two paths: one path is connected to the cold-side inlet of the condenser-reboiler, and the other path is connected to the heat source inlet of the secondary feed preheater. The liquid reflux outlet at the bottom of the distillation column is connected to the cold-side outlet of the condenser-reboiler. The first inlet of the reflux tank is connected to the hot side outlet of the top condenser of the column, and the liquid phase outlet of the reflux tank is connected to the top reflux port of the distillation column and the heat source inlet of the first-stage feed preheater, respectively.

2. The energy-saving system for ethanol distillation according to claim 1, characterized in that, The liquid phase outlet of the reflux tank is connected to the inlet of the heat pump compressor so that the condensate from the reflux tank can be used as the inlet spray liquid for the heat pump compressor.

3. The energy-saving system for ethanol distillation according to claim 1 or 2, characterized in that, The heat pump compressor is a screw compressor.

4. The energy-saving system for ethanol distillation according to claim 1, characterized in that, The heat pump compressor is driven by a variable frequency motor.

5. The energy-saving system for ethanol distillation according to claim 1, characterized in that, The heat source outlet of the three-stage feed preheater is connected to the second inlet of the reflux tank, and the gas phase outlet of the reflux tank is connected to the inlet of the heat pump compressor. The reflux tank is used to flash evaporate the condensate output by the three-stage feed preheater and to output the flashed gas phase from the gas phase outlet.

6. The energy-saving system for ethanol distillation according to claim 1, characterized in that, A valve is installed on the connecting pipeline between the vapor outlet at the top of the distillation column and the inlet of the heat pump compressor.

7. The energy-saving system for ethanol distillation according to claim 1, characterized in that, The distillation column is equipped with a low-pressure steam inlet in its bottom.

8. The energy-saving system for ethanol distillation according to claim 1, characterized in that, The heat source outlet of the primary feed preheater is connected to the hot side inlet of the top product cooler, and the hot side outlet of the top product cooler is connected to the top product storage tank.

9. The energy-saving system for ethanol distillation according to claim 1, characterized in that, The heat source outlet of the secondary feed preheater is connected to the hot side inlet of the bottom liquid cooler, and the hot side outlet of the bottom liquid cooler is connected to the wastewater treatment system.

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