CN102675265B - Method of refining furfural through six-tower continuous rectification - Google Patents

Abstract

The invention discloses a method of refining furfural through six-tower continuous rectification. A process of the method comprises the following steps of: flowing furfural steam through a steam generator and a primary tower reboiler and then feeding into a primary tower; obtaining furfural water azeotrope on the top of the tower; condensing to split phase; reflowing the water phase; feeding aldehyde phase into a washing tower; removing acidic substances in the material by the washing tower; returning the furfural solution on the top of the tower to a primary tower feed tank; feeding output at the bottom of the tower into a light component removal tower; removing light component impurities by the light component removal tower; feeding the furfural liquid at the bottom of the tower into a dehydrating tower; obtaining furfural water azeotrope on the top of the dehydrating tower; condensing to split phase and reflowing; feeding coarse furfural produced at the bottom of the tower into a refining tower; obtaining a furfural product on the top of the refining tower; feeding high boiling point aldehyde mud at the bottom of the tower into a stripping tower; recovering the furfural from the aldehyde mud in the stripping tower; returning furfural solution on the top of the stripping tower to the primary tower feed tank; and treating the aldehyde residue at the bottom of the tower to serve as a boiler fuel. The method has the advantages of high furfural product purity, high yield, low energy consumption and low pollution.

Description

Method for refining furfural by six-tower continuous distillation

technical field

The invention belongs to furfural refining technology, in particular to a six-tower continuous rectification method for refining furfural.

Background technique

The scientific name of furfural is furan formaldehyde. It is an important chemical raw material and has a wide range of uses in industry. It can be used as a selective solvent for separating unsaturated aliphatic compounds from saturated aliphatic compounds, and it is also a raw material for the production of various furan compounds. Its downstream products cover many industries such as petrochemical, synthetic resin, food, medicine and synthetic fiber. It is made by hydrolyzing corncobs, bagasse and other plant stalks in an acidic solution. During the production process, saturated steam is introduced into the bottom of the hydrolysis pot to obtain aldehyde vapor containing 4% to 10% furfural. At the same time, acetic acid, By-products such as methanol and acetone.

There are various furfural continuous refining processes in the world. A complete process should include three basic processes: concentration and preliminary purification of furfural contained in the stock solution; removal of low-boiling impurities and recovery of furfural; removal of high-boiling impurities and recovery of furfural. These three processes are mainly realized by distillation devices such as initial distillation tower (including composite initial distillation tower), light removal tower, dehydration tower and refining tower. However, many processes do not fully take into account the integrity of the above process. The refining process of furfural is also constantly developing, from the initial simple distillation and batch rectification to three-column continuous distillation, four-column continuous distillation and five-column continuous distillation. The main device of the five-tower refining process is composed of an initial distillation tower, a delightening tower, a water washing tower, a dehydration tower and a refining tower, in which the aldehyde-water azeotrope is extracted from the top of the initial distillation tower, and the organic acid contained in furfural is removed by the water washing tower. , eliminating the previous alkali neutralization process before entering the dehydration tower, and avoiding the sodium acetate contained in the furfural product, which is not clean. out. In the five-tower continuous distillation, the furfural vapor is condensed and then enters the initial distillation tower, which does not make full use of heat energy; and the process is to remove light first and then wash with water, and the bottom material of the light removal tower needs to return to the initial distillation tower and then evaporate; at the same time, the aldehyde sludge at the bottom of the tower is refined It contains about 10% furfural, which is not processed in the five-tower continuous distillation process. If it is directly used as fuel, it will not only waste part of the furfural but also pollute the surrounding environment.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies of the prior art, to provide a six-tower continuous rectification method for furfural purification, the technology of the present invention can be used to obtain a purity of more than 99% from aldehyde vapor containing 4% to 10% aldehyde furfural, and has the advantages of high product yield, low energy consumption, and little pollution.

The present invention is realized by following technical scheme, a kind of method for furfural by continuous rectification of six towers, the device that this method adopts comprises initial distillation tower, water washing tower, light removal tower, dehydration tower, refining tower and A stripper, characterized by the following processes:

1) The furfural vapor from the hydrolysis kettle with a pressure of 0.6~0.8MPa, a temperature of 153~172°C, and a furfural mass content of 4%~10% first enters the steam generator, and after heat exchange, the furfural vapor-liquid mixture enters the initial distillation After the tower reboiler and condenser, the initial distillation tower is added from the middle and upper part of the initial distillation tower. The initial distillation tower is operated under normal pressure and the temperature at the top of the tower is 92~103°C. The furfural water produced from the top of the tower is totally Boiling matter, after condensation, the upper water phase in the phase-separation tank of the initial distillation tower is refluxed to the initial distillation tower, and the furfural phase in the lower layer of the phase-separation tank of the initial distillation tower is sent to the water washing tower, and the residue produced from the bottom of the initial distillation tower Liquid to water treatment system;

2) The furfural phase from the phase separation tank of the initial distillation tower enters the water washing tower from the upper part of the water washing tower. The water washing tower is operated under the conditions of normal pressure and temperature of 33~48°C, and a part of the acid-containing furfural solution produced from the top of the water washing tower is returned The phase separation tank of the primary distillation tower, and the rest is returned to the feed tank of the primary distillation tower, and the furfural solution produced from the bottom of the washing tower is sent to the light removal tower;

3) The furfural solution from the bottom of the water washing tower and the light component condensate from the condenser of the primary distillation tower and the furfural steam condenser enter the light removal tower from the middle of the light removal tower. Operate at a temperature of 39-62°C, enrich and recover light components including methanol and acetone at the top of the light removal tower, and send the furfural solution at the bottom of the light removal tower to the dehydration tower;

4) The furfural solution from the bottom of the light removal tower enters the dehydration tower from the middle of the dehydration tower. The dehydration tower is operated at a pressure of 5~25KPa and an operating temperature of 35~68°C at the top of the tower. The fraction distilled from the top of the tower is condensed and enters dehydration The phase separation tank of the tower, the aldehyde phase in the lower layer of the phase separation tank of the dehydration tower flows back into the dehydration tower, the water phase in the upper layer of the phase separation tank of the dehydration tower returns to the feed tank of the primary distillation tower, and the crude furfural at the bottom of the dehydration tower is sent to the refining tower;

5) The crude furfural from the bottom of the dehydration tower enters the refining tower from the middle and upper part of the refining tower. The refining tower is operated at a pressure of 5~25KPa and an operating temperature of 62~97°C at the top of the tower. The purity of the purified tower top is over 99%. The furfural product, the aldehyde sludge produced at the bottom of the refining tower is sent to the stripping tower;

6) The aldehyde sludge from the bottom of the refining tower enters the stripping tower from the upper part of the stripping tower, and the steam from the steam generator enters the stripping tower from the bottom of the stripping tower. It is operated under the condition of 110~146°C. The furfural vapor produced at the top of the stripping tower is condensed and then returned to the feed tank of the primary distillation tower. The aldehyde residue produced at the bottom of the stripping tower is used as boiler fuel after treatment.

Advantage of the present invention and beneficial effect are:

1. In the present invention, the aldehyde vapor first passes through the steam generator, and the generated water vapor provides a heat source for the subsequent rectification process, and also serves as a source of steam for the stripping tower. The aldehyde vapor then enters the reboiler of the initial distillation tower, making full use of the material heat, reducing energy consumption.

2. The present invention adopts the delightening process after washing with water to remove the acidic substances in the material, avoiding the side reaction of furfural under the action of acid in the lightening tower, reducing the yield of furfural and reducing the corrosion of equipment; the original five The continuous rectification of the column is to remove the light first and then wash with water. The bottom material of the light removal tower needs to be returned to the initial distillation tower and then evaporated. The design of this process is more energy-saving. And the condenser of the initial distillation tower adopts the separation condensation measure, and the non-condensable gas condensate is directly sent to the light removal tower.

3. The present invention adds a stripping tower, reclaims the furfural in the aldehyde mud at the bottom of the refining tower, improves the yield of furfural, reduces the furfural content in the waste water, and the aldehyde residue at the bottom of the stripping tower is used as boiler fuel after being treated. Solved the pollution problem of aldehyde mud.

Description of drawings

Figure 1 is a schematic diagram of the existing five-tower process for furfural purification.

Fig. 2 is the schematic flow chart of the six-tower continuous rectification refining furfural process of the present invention.

Among them, 1-furfural steam condenser, 2-primary distillation tower feed tank, 3-steam generator, 4-primary distillation tower reboiler, 5-primary distillation tower, 6-primary distillation tower condenser, 7-primary distillation tower Distillation tower phase separation tank, 8-water washing tower, 9-tail gas condenser, 10-light removal tower, 11-light component tank, 12-dehydration tower, 13-dehydration tower phase separation tank, 14-refining tower, 15- Refined furfural product tank, 16-stripping tower.

Detailed ways

Example 1:

The vapor pressure of furfural is 0.6MPa, the temperature is 158.6℃, its mass composition is methanol 0.1%, formic acid 1%, acetic acid 2%, methylfurfural 2.5%, furfural 8%, water 86.3%, acetone content 400mg/L, the raw material is first The 0.4MPa water vapor is generated by the steam generator as the steam source of the stripping tower; the aldehyde vapor is then heat-exchanged with the reboiler of the initial distillation tower, and the temperature drops to 90°C, and then fed from the middle and upper part of the initial distillation tower. Operated under normal pressure, the temperature at the top of the tower is 97.4°C. The furfural water azeotrope produced at the top of the initial distillation tower is condensed, and the upper water phase in the phase separation tank of the initial distillation tower is refluxed to the initial distillation tower. The furfural phase in the middle and lower layer of the phase tank is sent to the water washing tower, and the raffinate produced from the bottom of the primary distillation tower is sent to the water treatment system; the water washing tower is under normal pressure and the temperature is 40°C, and a part of the acid-containing furfural solution is produced at the top of the tower Return to the phase-separation tank of the initial distillation tower, and return the rest to the feed tank of the initial distillation tower, and send the furfural solution produced from the bottom of the washing tower to the light removal tower; the light removal tower is operated at normal pressure, the temperature at the top of the tower is 50 ° C, and the reflux ratio is 10. The top of the light removal tower enriches and recovers light components including methanol and acetone, and the furfural solution at the bottom of the light removal tower is sent to the dehydration tower; the operating pressure of the dehydration tower is 15KPa, and the temperature at the top of the tower is 52°C. The distillate from the top is condensed and enters the phase separation tank of the dehydration tower. The aldehyde phase in the lower layer of the phase separation tank of the dehydration tower flows back into the dehydration tower. into the refining tower; the operating pressure of the refining tower is 10KPa, and the tower top temperature is 70°C. In the refined furfural product obtained at the top of the tower, the acetic acid content is 127 mg/L, the formic acid content is 93 mg/L, and the methanol content is 12 mg/L. The water content is 0.037%, the content of methylfurfural is 0.5%, the content of furfural is 99.4%, and the yield of furfural is 96.3%. Enter 0.4MPa water vapor, the tower operates under normal pressure, the operating temperature at the top of the tower is 124°C, the furfural vapor produced at the top of the stripping tower returns to the feed tank of the primary distillation tower after condensation, and the aldehyde produced at the bottom of the stripping tower The slag is treated as boiler fuel.

Example 2:

The furfural vapor pressure is 0.7MPa, the temperature is 164.7°C, and its mass composition is methanol 0.1%, formic acid 1.4%, acetic acid 2.5%, methylfurfural 3%, furfural 6.8%, water 86.1%, acetone content 385mg/L, other processes Condition is identical with embodiment 1, and the product that refining tower top obtains is composed of: acetic acid content 144mg/L, formic acid content 108 mg/L, methanol content 28mg/L, water content 0.03%, methyl furfural content is 0.7%, furfural The content is 99.2%, and the yield of furfural is 96.1%.

Example 3:

The vapor pressure of furfural is 0.6MPa, the temperature is 158°C, and its mass composition is 0.6% formic acid, 1.5% acetic acid, 2% methylfurfural, 7.3% furfural, 88.4% water, 412mg/L acetone, and 871mg/L methanol. Other processing conditions are identical with embodiment 1, and the product that refining tower tower top obtains consists of: acetic acid content 102 mg/L, formic acid content 135 mg/L, methanol content 10 mg/L, water content 0.042%, methyl furfural content is 0.3 %, the furfural content is 99.6%, and the furfural yield is 97.1%.

Example 4:

The vapor pressure of furfural is 0.75MPa, the temperature is 167.5°C, and its mass composition is 0.4% formic acid, 1.1% acetic acid, 2.8% methylfurfural, 4.6% furfural, 91% water, 233mg/L acetone, and 611mg/L methanol. Other processing conditions are identical with embodiment 1, and the product that refining tower tower top obtains consists of: acetic acid content 119mg/L, formic acid content 126 mg/L, methanol content 17mg/L, water content 0.04%, methyl furfural content is 0.6% , the furfural content is 99.3%, and the furfural yield is 96.3%.

Claims (1)

1. six tower continuous rectifications are refined a method for furfural, and the device that the method adopts comprises primary tower, water wash column, lightness-removing column, dehydration tower, treating tower and the stripping tower connecting successively, and its feature comprises following process:

1) from pressure in hydrolysis kettle, be 0.6 ~ 0.8MPa, temperature is 153 ~ 172 ℃, furfural mass content is that first 4% ~ 10% furfural vapour enter vapour generator, through heat exchange, furfural liquid-vapor mixture enters after primary tower reboiler and condenser again, from primary tower middle and upper part, add primary tower, this primary tower under normal pressure and tower top temperature be 92 ~ 103 ℃ and operate, furfural water azeotrope by this tower top output, through condensation, upper strata water in primary tower phase separation tank is back to primary tower, in primary tower phase separation tank, the furfural of lower floor is sent into water wash column mutually, by the raffinate of output at the bottom of this primary tower treatment system of anhydrating,

2) furfural from primary tower phase separation tank enters water wash column from water wash column top, this water wash column is to operate under 33 ~ 48 ℃ of conditions at normal pressure and temperature, by washing tower top output, containing a sour furfural solution part, return to primary tower phase separation tank, rest part returns to primary tower charging stock tank, by the furfural solution of output at the bottom of water wash column, sends into lightness-removing column;

3) from the furfural solution at the bottom of water wash column and come from primary tower condenser and the light constituent lime set of furfural vapour condenser, by lightness-removing column middle part, enter this lightness-removing column, this lightness-removing column is 39 ~ 62 ℃ in normal pressure and tower top temperature and operates, the light constituent that comprises methyl alcohol and acetone in this lightness-removing column top enriching and recovering, sends into dehydration tower at this lightness-removing column bottom furfural solution;

4) from the furfural solution at the bottom of lightness-removing column, from dehydration tower middle part, enter dehydration tower, this dehydration tower is 35 ~ 68 ℃ of conditional operations at pressure 5 ~ 25KPa and tower top service temperature, from this tower top, distillate cut and enter dehydration tower phase separation tank through condensation, dehydration tower phase separation tank lower floor aldehyde refluxes mutually and enters dehydration tower, dehydration tower phase separation tank upper strata water turns back to primary tower charging stock tank, and at the bottom of dehydration tower tower, chaff aldehyde is sent into treating tower;

5) from the chaff aldehyde at the bottom of dehydration tower, by treating tower middle and upper part, enter treating tower, this treating tower is that 5 ~ 25KPa and tower top service temperature are to operate under 62 ~ 97 ℃ of conditions at pressure, it is more than 99% furfural product that refining tower top obtains purity, and at the bottom for the treatment of tower, output aldehyde mud is sent into stripping tower;

6) the aldehyde mud from output at the bottom for the treatment of tower enters stripping tower from stripping tower top, water vapor from vapour generator enters stripping tower from stripping tower bottom, this stripping tower is to operate under the condition of 110 ~ 146 ℃ in normal pressure and tower top service temperature, the furfural steam of stripping tower top output returns to primary tower charging stock tank after condensation, and the aldehyde slag of stripping tower bottom output is after treatment as boiler oil.