Double-effect rectification-ethanol recovery energy-saving device

Abstract

The double-effect rectification-ethanol recovery energy-saving device comprises a first rectification tower, a second rectification tower and a membrane separation assembly, a tower top outlet of the first rectification tower is connected with an inlet of the membrane separation assembly, a tower kettle outlet of the first rectification tower is connected with an inlet of the second rectification tower, and a heat source of the first rectification tower is provided by a tower top gas-phase product of the second rectification tower. The tower kettle of the first rectifying tower is provided with a reboiler, and a gas-phase product outlet at the top of the second rectifying tower is connected with the reboiler to provide a heat source for the first rectifying tower; a gas-phase outlet of the reboiler is connected with the membrane separation assembly, and a liquid-phase outlet of the reboiler is connected with an inlet of the second rectifying tower. According to the device, only the second rectifying tower needs to be heated by steam provided by the outside, the first rectifying tower is heated by steam at the top of the second rectifying tower, product gas of the membrane separation assembly is used as a heat source to preheat mother liquor, internal heat of the whole system is recycled, and compared with a traditional single rectifying tower and membrane coupling device, energy consumption is saved by 42%.

Description

TECHNICAL FIELD

[0001] The utility model relates to the field of membrane separation technology, especially a double-effect rectification-ethanol recovery energy-saving device. BACKGROUND

[0002] High-purity ethanol is widely used in many fields, such as ultra-clean cleaning and drying in precision electronic component processing, ultra-clean cleaning of purifying equipment, scientific experiments, and important solvent in pharmaceutical and chemical industries. However, due to the existence of ethanol-water system, the ordinary azeotropic point (mass fraction of ethanol 95.6%), high-purity ethanol cannot be obtained by using ordinary rectification method.

[0003] Currently, the main methods for dehydrating ethanol include distillation, adsorption, and rectification-membrane coupling separation. Figure 1 As shown in the figure, the energy consumption is high by using the ordinary rectification tower membrane coupling process, especially in the large-scale dehydration of ethanol. SUMMARY

[0004] The utility model discloses a kind of devices for separating ethanol and water mixture with low energy consumption.

[0005] To achieve the purpose of the utility model, the technical solutions are as follows:

[0006] A double-effect rectification-ethanol recovery energy-saving device includes a first rectification tower, a second rectification tower, and a membrane separation assembly. The top outlet of the first rectification tower is connected to the inlet of the membrane separation assembly. The outlet of the bottom of the first rectification tower is connected to the inlet of the second rectification tower. The heat source of the first rectification tower is provided by the gas phase product at the top of the second rectification tower.

[0007] Further, the bottom of the first rectification tower is equipped with a reboiler. The gas phase product outlet at the top of the second rectification tower is connected to the reboiler, which provides heat for the first rectification tower. The gas phase outlet of the reboiler is connected to the membrane separation assembly, and the liquid phase outlet of the reboiler is connected to the inlet of the second rectification tower.

[0008] Further, the device is also equipped with a reflux tank and a reflux pump. The liquid phase outlet of the reboiler is connected to the reflux tank, the reflux pump in sequence, and the outlet of the reflux pump is connected to the inlet of the second rectification tower.

[0009] Further, the device is also equipped with a superheater. The outlet of the superheater is connected to the membrane separation assembly, and the inlet of the superheater is connected to the top outlet of the first rectification tower and the gas phase outlet of the reboiler, respectively.

[0010] Further, the top of the first rectification tower is also equipped with a condenser. The top outlet of the first rectification tower is connected to the inlet of the condenser. The outlet of the condenser is divided into two pipelines. One pipeline is connected to the top inlet of the first rectification tower, and the other pipeline is connected to the inlet of the superheater.

[0011] Further, the double-effect rectification-ethanol recovery energy-saving device is further provided with a preheater, a product outlet of the preheater is connected with an inlet of the first rectification tower; a permeation interception side outlet of the membrane separation assembly is connected with a heat source inlet of the preheater, and a heat source outlet of the preheater is connected with a product condenser, a product tank and a product pump in sequence.

[0012] Further, the first rectification tower operates at a pressure and a temperature lower than those of the second rectification tower.

[0013] Further, the membrane separation assembly is composed of one group or two groups or more than two groups of membrane assemblies; the membrane assemblies are selected from water-priority permeable membranes.

[0014] Compared with the prior art, the device has the following advantages: the device can obtain high-purity ethanol (ethanol≥99.5%) through the coupling of the differential pressure rectification of the first rectification tower and the second rectification tower and the membrane separation equipment, and is efficient and environmentally friendly.

[0015] The second rectification tower needs steam heating provided by the outside, the first rectification tower uses the steam at the top of the second rectification tower for heating, and the product gas of the membrane separation assembly is used as a heat source to preheat the mother liquor, so that the internal heat of the whole system is recycled and used, and compared with the traditional single rectification tower and membrane coupling device, the energy consumption is saved by 42%. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 It is a device structure schematic view of the prior art for separating alcohol.

[0017] Figure 2 It is a device structure schematic view of the device.

[0018] In the figure, 1 is the first rectification tower, 11 is the preheater, 12 is the partial condenser, 13 is the reflux tank, 14 is the reflux pump, 15 is the column still pump, 16 is the reboiler, 2 is the second rectification tower, 3 is the membrane separation assembly, 31 is the superheater, 35 is the heat compensator, 32 is the product condenser, 33 is the product tank, and 34 is the product pump. DETAILED DESCRIPTION

[0019] The technical solutions in the embodiments of the device will be clearly and completely described below with reference to the drawings in the embodiments of the device. Apparently, the described embodiments are only part of the embodiments of the device, rather than all the embodiments. Based on the embodiments in the device, all the other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the device.

[0020] In order to clearly describe the solutions of the device, the device is first described in the embodiments, and then the process principle is described.

[0021] As Figure 2 shown, a double-effect distillation-ethanol recovery energy-saving device, comprising a first distillation column 1, a second distillation column 2, a membrane separation assembly 3, wherein the first distillation column 1 top outlet is connected to the membrane separation assembly 3 inlet, the first distillation column 1 bottom outlet is connected to the second distillation column 2 inlet, and the heat source of the first distillation column 1 is provided by the second distillation column 2 top gas phase product. Further, the first distillation column 1 bottom is provided with a reboiler 16, the second distillation column 2 top gas phase product outlet is connected to the reboiler 16 to provide heat source for the first distillation column 1; the reboiler 16 gas phase outlet is connected to the membrane separation assembly 3, and the reboiler 16 liquid phase outlet is connected to the second distillation column 2 inlet.

[0022] As a specific embodiment, the double-effect distillation-ethanol recovery energy-saving device is further provided with a reflux tank 13 and a reflux pump 14, the reboiler 16 liquid phase outlet is sequentially connected to the reflux tank 13, the reflux pump 14, and the reflux pump 14 outlet is connected to the second distillation column 2 inlet.

[0023] The double-effect distillation-ethanol recovery energy-saving device is further provided with a superheater 31, the superheater 31 outlet is connected to the membrane separation assembly 3, and the superheater 31 inlet is respectively connected to the first distillation column 1 top outlet and the reboiler 16 gas phase outlet.

[0024] The first distillation column 1 top is further provided with a condenser 12, the first distillation column 1 top outlet is connected to the condenser 12 inlet, the condenser 12 outlet is divided into two pipelines, one pipeline is connected to the first distillation column 1 top inlet, and the other pipeline is connected to the superheater 31 inlet.

[0025] The double-effect distillation-ethanol recovery energy-saving device is further provided with a preheater 11, the preheater 11 product outlet is connected to the first distillation column 1 inlet. The membrane separation assembly 3 permeate interception side outlet is connected to the heat source inlet of the preheater 11, and the preheater 11 heat source outlet is sequentially connected to a finished product condenser 32, a finished product tank 33, and a finished product pump 34.

[0026] The first distillation column 1 bottom is further provided with a bottom pump 15, and the first distillation column 1 bottom liquid phase product is transported to the second distillation column 2 by the bottom pump 15.

[0027] The membrane separation assembly 3 can be composed of one or two or more groups of membrane assemblies. The membrane assembly can be selected from a group consisting of water-priority membranes, and the water-priority membranes are one or more of Na molecular sieve membranes, organic polymer membranes, hollow fiber membranes, and composite membranes. The membrane assembly can be combined in a way of series connection, parallel connection, or a combination of series connection and parallel connection to form the membrane separation assembly 3. As a preferred embodiment, the membrane separation assembly 3 removes water in a steam permeation mode. When connected in series, a heat supplement device 35 can be added between the membrane assemblies to prevent the to-be-separated gas from being liquefied.

[0028] The specific separation process of the device is as follows:

[0029] The ethanol-containing mother liquor is pumped from the raw material to the preheater 11 for preheating, and then sent to the first rectifying tower 1 for treatment. The first tower is operated under pressure (operating temperature 100-108°C, pressure 0.2-0.35 MPaG), and the condenser 12 at the top of the tower condenses part of the ethanol and water backflow, and part of the uncondensed gas phase enters the superheater 31, and then enters the membrane separation assembly 3 for further dehydration. The ethanol and water mixture at the bottom of the first rectifying tower 1 is transported to the second rectifying tower 2 for treatment.

[0030] The second rectifying tower 2 is continuously operated under pressure (operating temperature 128-137°C, pressure greater than or equal to 0.6 MPaG), and the vapor at the top of the tower is condensed after passing through the reboiler 16 of the first rectifying tower 1, part of which is condensed backflow to the reflux tank 13, and part of the uncondensed gas phase is decompressed and then enters the superheater 31, and then enters the membrane separation assembly 3 for further dehydration. The ethanol-containing waste water at the bottom is transported to the outside.

[0031] The operating parameters of the membrane separation assembly 3 are 110-130°C and 0.2-0.35 MPaG. The water in the raw material penetrates from the upstream side of the membrane assembly to the downstream side of the membrane, and the last stage of the membrane assembly on the upstream side obtains the finished product with the required water content, which is used as a heat source to heat the mother liquor in the preheater 11. The downstream side of the membrane adopts a vacuum pumping and condensing method to form a vapor pressure difference between the upstream and downstream sides of the membrane. The permeate vapor enters the condenser under the suction of the vacuum unit, and the condensed permeate is discharged.

[0032] The device is suitable for processing large-scale ethanol mother liquor containing water. The raw material treatment capacity of the first rectifying tower 1 can reach 5000 kg / h, and the raw material treatment capacity of the second rectifying tower 2 can reach 4050 kg / h. The heat recovered from the second rectifying tower 2 is used for heating the first rectifying tower 1, and the heat source of the finished product is used to preheat the mother liquor. This can reduce the heat consumption, and compared with the existing process, the steam consumption is reduced by about 42%. The high heat energy utilization effect is ensured.

[0033] It is obvious to those skilled in the art that the present application is not limited to the details of the above exemplary embodiments, and can be implemented in other specific forms without departing from the spirit or essential characteristics of the present application. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting, and the scope of the present application is defined by the appended claims rather than the above description, and therefore all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present application. Any reference signs in the claims should not be regarded as limiting the claims involved.

Claims

1. A double-effect rectification-ethanol recovery energy saving device, characterized in that: The device comprises a first rectifying tower (1), a second rectifying tower (2), and a membrane separation assembly (3), wherein the top outlet of the first rectifying tower (1) is connected to the inlet of the membrane separation assembly (3), the outlet of the bottom of the first rectifying tower (1) is connected to the inlet of the second rectifying tower (2), and the heat source of the first rectifying tower (1) is provided by the gaseous phase product at the top of the second rectifying tower (2).

2. The double-effect rectification-ethanol recovery energy saving device according to claim 1, characterized in that: The bottom of the first rectifying tower (1) is provided with a reboiler (16), the gaseous phase product outlet at the top of the second rectifying tower (2) is connected to the reboiler (16) to provide the heat source for the first rectifying tower (1), the gaseous phase outlet of the reboiler (16) is connected to the membrane separation assembly (3), and the liquid phase outlet of the reboiler (16) is connected to the inlet of the second rectifying tower (2).

3. The double-effect rectification-ethanol recovery energy saving device according to claim 2, characterized in that: The double-effect rectification-ethanol recovery energy-saving device is further provided with a reflux tank (13) and a reflux pump (14), the liquid phase outlet of the reboiler (16) is sequentially connected to the reflux tank (13), the reflux pump (14), and the outlet of the reflux pump (14) is connected to the inlet of the second rectifying tower (2).

4. The double-effect rectification-ethanol recovery energy saving device according to claim 3, characterized in that: The device is further provided with a superheater (31), the outlet of the superheater (31) is connected to the membrane separation assembly (3), and the inlet of the superheater (31) is respectively connected to the top outlet of the first rectifying tower (1) and the gaseous phase outlet of the reboiler (16).

5. The double-effect rectification-ethanol recovery energy saving device according to claim 4, characterized in that: The top of the first rectifying tower (1) is further provided with a partial condenser (12), the top outlet of the first rectifying tower (1) is connected to the inlet of the partial condenser (12), the outlet of the partial condenser (12) is divided into two pipelines, one of which is connected to the top inlet of the first rectifying tower (1), and the other of which is connected to the inlet of the superheater (31).

6. The double-effect rectification-ethanol recovery energy saving device according to claim 5, characterized in that: The device is further provided with a preheater (11), the product outlet of the preheater (11) is connected to the inlet of the first rectifying tower (1), the permeation interception side outlet of the membrane separation assembly (3) is connected to the heat source inlet of the preheater (11), and the heat source outlet of the preheater (11) is sequentially connected to a product condenser (32), a product tank (33), and a product pump (34).

7. The double-effect rectification-ethanol recovery energy saving device according to claim 1, characterized in that: The operating pressure and temperature of the first rectifying tower (1) are lower than the operating pressure and temperature of the second rectifying tower (2).

8. The double-effect rectification-ethanol recovery energy saving device according to claim 1, characterized in that: The membrane separation assembly (3) is composed of one group or two groups or more than two groups of membrane assemblies, and the membrane assemblies are selected from water-priority permeable membranes.

Images