Method and device for co-production of ethylene glycol and formic acid byproduct diethylene glycol

Abstract

The invention discloses a method and a device for co-production of ethylene glycol and formic acid as a byproduct diethylene glycol. According to the method, an ethylene glycol reaction solution is firstly subjected to vacuum dehydration and concentration, a formic acid aqueous solution is obtained at the tower top, high-concentration ethylene glycol is obtained at a tower kettle and enters a formic acid recovery tower, most formic acid is extracted from the tower top, a tower kettle solution enters a diethylene glycol alcohol recovery tower, the diethylene glycol recovery tower adopts a thermal coupling dividing wall tower, and ethylene glycol and light components are extracted from the tower top; diethylene glycol is extracted from a side line, heavy components (heavy alcohol and non-volatile salts) are treated as wastes, and materials are discharged from a tower kettle. And extracting from the top of the diethylene glycol recovery tower, and neutralizing in a neutralizing tank. The neutralized material enters an ethylene glycol refining tower, and qualified ethylene glycol is extracted from a side line after a small amount of water and components lighter than ethylene glycol are extracted from the tower top. The recovered formic acid aqueous solution enters a formic acid recovery section to be purified, and is purified through a pressurization rectifying tower and a decompression rectifying tower in sequence. And the recovered diethylene glycol enters a diethylene glycol recovery tower for purification.

Description

Technical Field

[0001] The invention relates to the technical field of ethylene glycol refining, and more specifically to a method and device for co-producing ethylene glycol with formic acid and by-producing diethylene glycol. Background Art

[0002] At present, the main method for producing ethylene glycol is the hydration of ethylene oxide, and its production process mainly involves first producing and refining ethylene oxide, and then synthesizing ethylene glycol with ethylene oxide and hydration and refining it. This process requires two catalysts to catalyze the reaction and two steps of purification and refining, which is complex, costly and has a low yield.

[0003] Currently, there is a new process for preparing ethylene glycol from ethylene in one step. In this process, ethylene glycol is directly prepared by reacting ethylene and hydrogen peroxide in the presence of a catalyst. The reaction liquid obtained has many by-products, including a large amount of formic acid. It is of great significance to develop a separation process for this system. While separating and purifying ethylene glycol, formic acid is recovered and purified, thereby achieving the co-production of ethylene glycol and formic acid and recovering the by-product diethylene glycol. Since the system has many equipment and many work sections, the present invention also designs a heat integration method, which is of great significance for saving energy.

[0004] This system has many new impurities that are different from those in the ethylene oxide process, such as formic acid, diethylene glycol, ethylene glycol formate, polyethylene glycol, etc. There are also acetic acid, 1,3-dioxane-2-methanol, etc., which are impurities that are also produced in the ethylene oxide process.

[0005] Therefore, how to provide a method and device for removing impurities in the above system to produce ethylene glycol and formic acid and produce diethylene glycol as a by-product is a technical problem that those skilled in the art urgently need to solve. Summary of the invention

[0006] The purpose of the present invention is to purify ethylene glycol on the one hand and to recover a large amount of formic acid as another product on the other hand to achieve co-production. At the same time, there is a recyclable diethylene glycol product in the system. For the above purposes, a co-production method with simple operation, high yield and good separation effect is designed, and heat is coupled and reused to design a heat integration system.

[0007] In order to achieve the above object, the present invention adopts the following technical solution:

[0008] A method for producing ethylene glycol and formic acid with diethylene glycol as a byproduct, comprising the following steps:

[0009] (1) The liquid phase material in the ethylene glycol synthesis system is sent to a dehydration and concentration tower, and a formic acid-containing aqueous solution is produced from the top of the dehydration and concentration tower. After most of the water is produced, the bottom liquid enters a formic acid recovery tower;

[0010] (2) Formic acid is extracted from the top of the formic acid recovery tower, and the bottom solution enters the diethylene glycol recovery tower;

[0011] (3) Ethylene glycol and light components are produced from the top of the diethylene glycol recovery tower, diethylene glycol is produced from the side line, and the heavy components in the bottom of the tower are discharged as waste;

[0012] (4) The top of the diethylene glycol recovery tower is taken out and enters the neutralization tank to adjust the pH. The neutralized material enters the ethylene glycol refining tower;

[0013] (5) Water and components lighter than ethylene glycol are produced from the top of the tower, qualified ethylene glycol is produced from the side line, and waste water is discharged from the bottom of the tower.

[0014] Preferably, the above method further comprises: the formic acid in step (2) enters a formic acid pressure separation tower and a formic acid pressure reduction separation tower in sequence for purification.

[0015] Preferably, the above method further comprises: the diethylene glycol in step (3) enters a diethylene glycol refining tower for purification.

[0016] The liquid phase material in the ethylene glycol synthesis system in the process of the present invention is mainly composed of ethylene glycol, water, diethylene glycol, formic acid, 1,3-dioxane-2-methanol, ethylene glycol monoformate and polyethylene glycol. Calculated by percentage, ethylene glycol accounts for 15-20%, water accounts for 60-64%, formic acid accounts for 15-20%, 1,3-dioxane-2-methanol accounts for 2-5%, ethylene glycol monoformate accounts for 2-5%, and polyethylene glycol accounts for 1-5%.

[0017] Preferably, the top extraction (shell side) of the formic acid pressurized separation tower provides heat to the side feed (tube side) of the dehydration concentration tower and the side feed (tube side) of the formic acid recovery tower through the first coupled heat exchanger; the side feed of the dehydration concentration tower and the side feed of the formic acid recovery tower are fed through different tube sides;

[0018] The top discharge (tube side) and side line extraction (tube side) of the diethylene glycol recovery tower provide heat to the side line feed (shell side) of the formic acid vacuum separation tower through the second coupling heat exchanger; the top discharge and side line extraction of the diethylene glycol recovery tower go through different tube sides;

[0019] The top extraction (tube side) of the diethylene glycol refining tower is used to supply heat to the side feed (shell side) of the formic acid pressurized separation tower through the third coupled heat exchanger.

[0020] Preferably, the vacuum degree of the dehydration and concentration tower in step (1) is controlled at 0.085-0.095 MPa, the tower top temperature is controlled at 30-40°C, and the tower bottom temperature is controlled at 40-80°C;

[0021] The vacuum degree of the formic acid recovery tower in step (2) is controlled at 0.085-0.095 MPa, the tower top temperature is controlled at 40-50°C, and the tower bottom temperature is controlled at 80-110°C;

[0022] The vacuum degree of the diethylene glycol recovery tower in step (3) is controlled at 0.095-0.01 MPa, the top outlet temperature is controlled at 100-110°C, the side outlet temperature is controlled at 110-130°C, and the bottom temperature is controlled at 150-200°C;

[0023] The pH adjustment in step (4) is to use 20-30wt% NaOH to adjust the pH to 7.5-9.5;

[0024] In step (5), the vacuum degree of the ethylene glycol refining tower is controlled at 0.095-0.1 MPa, the tower top temperature is controlled at 40-90°C, the side line extraction temperature is controlled at 100-110°C, and the tower bottom temperature is controlled at 110-150°C.

[0025] Operating under optimal conditions can effectively inhibit the occurrence of side reactions during the distillation process, and the resulting product recovery rate is high. In this system, the number of plates required to separate formic acid into trace amounts simply by distillation is high. The use of neutralization can effectively reduce the cost of equipment and hydrolyze trace esters in the system. 20-30wt% NaOH is a concentration close to saturation, which reduces the introduction of water.

[0026] Preferably, water is produced from the top of the formic acid pressure separation tower, and the bottom components enter the formic acid pressure reduction separation tower, formic acid is produced from the top of the formic acid pressure reduction separation tower, and the bottom liquid is a mixture of water, formic acid, and ethylene glycol;

[0027] The absolute pressure of the formic acid pressurized separation tower is 0.2-0.3 MPa, the tower top temperature is controlled at 100-120°C, and the tower bottom temperature is controlled at 120-140°C;

[0028] The vacuum degree of the formic acid vacuum separation tower is controlled at 0.02-0.05 MPa, the tower top temperature is controlled at 60-70°C, and the tower bottom temperature is controlled at 80-90°C.

[0029] The beneficial effects brought about by the above-mentioned optimization include: formic acid and water form the highest azeotrope, which is significantly affected by pressure in the absolute pressure range of 0.02-0.1 MPa, and the azeotrope composition fluctuation is relatively stable after the absolute pressure of 0.2 MPa. Under the optimal conditions, the proportion of formic acid in the azeotrope composition is larger during pressurized distillation and smaller during decompression, while saving operating costs.

[0030] Preferably, the ethylene glycol extracted from the top of the diethylene glycol refining tower enters the neutralization tank, and the diethylene glycol is extracted from the bottom of the tower;

[0031] The vacuum degree of the diethylene glycol refining tower is controlled at 0.085-0.095 MPa, the tower top temperature is controlled at 110-120°C, and the tower bottom temperature is controlled at 180-200°C.

[0032] Under the optimal conditions, while recovering qualified diethylene glycol, ethylene glycol is effectively recovered and enters the neutralization tank, and the concentration of the recovered ethylene glycol is similar to that produced from the top of the diethylene glycol recovery tower.

[0033] Another object of the present invention is to provide a device for producing ethylene glycol and formic acid as a by-product of diethylene glycol, comprising: an ethylene glycol refining section, a formic acid refining section, and a diethylene glycol refining section;

[0034] The ethylene glycol refining section includes a dehydration concentration tower, a formic acid recovery tower, a diethylene glycol recovery tower, a neutralization tank, and an ethylene glycol refining tower which are connected in sequence;

[0035] The formic acid refining section comprises a formic acid pressure separation tower and a formic acid pressure reduction separation tower connected to each other;

[0036] The diethylene glycol refining section includes a diethylene glycol refining tower;

[0037] The formic acid recovery tower is connected to the formic acid pressurized separation tower;

[0038] The diethylene glycol recovery tower is connected to the diethylene glycol refining tower;

[0039] The diethylene glycol refining tower is also connected to the neutralization tank.

[0040] Preferably, the above device further comprises: a coupled heat exchanger unit, the coupled heat exchanger unit comprising: a first coupled heat exchanger, a second coupled heat exchanger and a third coupled heat exchanger;

[0041] The top of the formic acid pressure separation tower is connected to the shell side of the first coupled heat exchanger, and the side line of the dehydration concentration tower and the side line of the formic acid recovery tower are respectively connected to the tube side of the first coupled heat exchanger;

[0042] The top and the side line of the diethylene glycol recovery tower are respectively connected to the tube side of the second coupled heat exchanger, and the side line of the formic acid vacuum separation tower is connected to the tube side of the second heat exchanger;

[0043] The top of the diethylene glycol refining tower is connected to the tube side of the third coupled heat exchanger, and the side line of the formic acid pressurized separation tower is connected to the shell side of the third coupled heat exchanger.

[0044] The present invention adopts a waste heat recycling process to save steam and circulating water consumption. In the coupling system designed by the invention, the temperature difference between materials is utilized to reuse energy through the coupling heat exchanger. The energy loss of all coupling heat exchangers is planned to be 10%. The temperature of the ethylene glycol refining tower, the diethylene glycol recovery tower, and the diethylene glycol refining tower kettle is high, so high-grade steam is used for direct heating. The material produced from the top of the diethylene glycol refining tower is heat-exchanged with the material entering the formic acid vacuum refining tower through the coupling heat exchanger. The heating load of the formic acid vacuum refining tower is designed to be 0.3-0.5 times the production requirement.

[0045] The top and side-line extraction of the diethylene glycol recovery tower are used to heat the materials of the formic acid pressure refining tower through a coupled heat exchanger. The heating load of the formic acid pressure refining tower is designed to be 0.3-0.5 times the production requirement. The top extraction of the formic acid pressure refining tower is heat exchanged with the materials of the vacuum concentration tower and the formic acid recovery tower through a coupled heat exchanger. The vacuum concentration tower and the formic acid recovery tower kettle reboiler are designed according to production. However, after the production enters a stable state, the reboiler operates at 0.2-0.4 times the production, and the remaining heat is provided by the coupled heat exchanger. The extraction temperature of the top of the concentration and formic acid recovery tower is relatively low, and no recovery is performed. To ensure the cleanliness of the product, the product is directly condensed and enters the storage tank, and no heat recovery is performed.

[0046] Preferably, the diethylene glycol recovery tower and the ethylene glycol refining tower are thermally coupled dividing wall towers.

[0047] Preferably, the dehydration and concentration tower is provided with 50-70 plates, and the distance between the feed inlet and the bottom of the tower is 22-42 plates;

[0048] The formic acid recovery tower is provided with 60-80 plates, and the distance between the feed port and the bottom of the tower is 45-65 plates;

[0049] The diethylene glycol recovery tower is provided with 35-50 plates, the distance between the feed port and the bottom of the tower is 15-30 plates, and the distance between the side line extraction and the bottom of the tower is 10-20 plates;

[0050] The ethylene glycol refining tower is provided with 63-73 plates, the distance between the feed port and the bottom of the tower is 34-44 plates, and the distance between the side line outlet and the bottom of the tower is 40-50 plates;

[0051] The formic acid pressure separation tower is provided with 40-60 plates, and the distance between the feed port and the bottom of the tower is 27-47 plates; the formic acid pressure reduction separation tower is provided with 36-50 plates, and the distance between the feed port and the bottom of the tower is 25-39 plates;

[0052] The diethylene glycol refining tower is provided with 10-20 plates, and the distance between the feed port and the bottom of the tower is 5-15 plates;

[0053] It can be seen from the above technical solution that compared with the prior art, the present invention has the following beneficial effects:

[0054] 1. Water and formic acid form the highest azeotrope, dehydration is performed first, and then formic acid is recovered. During the decompression dehydration process, the temperature is controlled as low as possible to effectively reduce the occurrence of side reactions (esterification reaction, etc.).

[0055] 2. The top of the diethylene glycol recovery tower is taken out and enters the ethylene glycol refining tower after being treated with alkali in the neutralization tank. The ethylene glycol product standard requires a very low formic acid content. If distillation is used for removal, the equipment cost is extremely high. Therefore, 20-30wt% NaOH solution is used for treatment at this time to avoid high equipment costs. The pH is controlled between 7.5-9.5. NaOH can inhibit formic acid from mixing into the product, irreversibly hydrolyze the generated esters, and inhibit the generation of aldehydes, thereby meeting the product standards. At the same time, a small amount of polyethylene glycol in the ethylene glycol reaction solution can also be eliminated through the pH effect.

[0056] 3. The diethylene glycol recovery tower and the ethylene glycol refining tower adopt the side line extraction of the dividing tower, which collects the heat on the one hand and saves the equipment required for the conventional two-tower separation of three components on the other hand (that is, the side line extraction of one dividing tower is equivalent to the conventional two-tower separation).

[0057] 4. The three coupled heat exchangers recover most of the waste heat in the system, saving heat energy consumption and condenser load.

[0058] 5. The process of the present invention has the characteristics of simple flow, low operation difficulty and good separation effect, which reduces the equipment investment cost and recycles the available components in the system, thereby reducing costs and increasing profits. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0060] Figure 1 This is a schematic diagram of the structure of the ethylene glycol refining section;

[0061] Figure 2 It is a schematic diagram of the structure of formic acid refining section;

[0062] Figure 3 It is a structural schematic diagram of the diethylene glycol refining section;

[0063] Figure 4Schematic diagram of the structure of the coupled heat exchanger unit, wherein EC1 is the first coupled heat exchanger; EC2 is the second coupled heat exchanger; EC3 is the third coupled heat exchanger;

[0064] Among them, in the figure:

[0065] 1-dehydration concentration tower; 2-formic acid recovery tower; 3-diethylene glycol recovery tower; 4-neutralization tank; 5-ethylene glycol refining tower; 6-formic acid pressure separation tower; 7-formic acid pressure reduction separation tower; 8-diethylene glycol refining tower. DETAILED DESCRIPTION

[0066] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0067] Example 1

[0068] This embodiment provides a device for producing ethylene glycol and formic acid as a by-product of diethylene glycol, comprising: an ethylene glycol refining section, a formic acid refining section, and a diethylene glycol refining section;

[0069] The ethylene glycol refining section includes a dehydration concentration tower 1, a formic acid recovery tower 2, a diethylene glycol recovery tower 3, a neutralization tank 4, and an ethylene glycol refining tower 5 which are connected in sequence;

[0070] The formic acid refining section includes a formic acid pressure separation tower 6 and a formic acid pressure reduction separation tower 7 connected to each other;

[0071] The diethylene glycol refining section includes a diethylene glycol refining tower 8;

[0072] The formic acid recovery tower 2 is connected to the formic acid pressurized separation tower 6;

[0073] The diethylene glycol recovery tower 3 is connected to the diethylene glycol refining tower 8;

[0074] The diethylene glycol refining tower 8 is also connected to the neutralization tank 4 .

[0075] In this embodiment, the above device further comprises: a coupled heat exchanger unit, the coupled heat exchanger unit comprising: a first coupled heat exchanger EC1, a second coupled heat exchanger EC2 and a third coupled heat exchanger EC3;

[0076] The top of the formic acid pressure separation tower 6 is connected to the shell side of the first coupled heat exchanger EC1, and the side line of the dehydration concentration tower 1 and the side line of the formic acid recovery tower 2 are respectively connected to the tube side of the first coupled heat exchanger EC1;

[0077] The top and side line of the diethylene glycol recovery tower 3 are respectively connected to the tube side of the second coupled heat exchanger EC2, and the side line of the formic acid vacuum separation tower 7 is connected to the tube side of the second heat exchanger EC2;

[0078] The top of the diethylene glycol refining tower 8 is connected to the tube side of the third coupled heat exchanger EC3, and the side line of the formic acid pressurized separation tower 6 is connected to the shell side of the third coupled heat exchanger EC3.

[0079] The diethylene glycol recovery tower 3 and the ethylene glycol refining tower 5 are thermally coupled dividing wall towers;

[0080] The dehydration and concentration tower 1 is provided with 60 plates, and the distance between the feed inlet and the bottom of the tower is 35 plates;

[0081] The number of plates of formic acid recovery tower 2 is 70, and the distance between the feed inlet and the bottom of the tower is 50 plates;

[0082] The number of plates of the diethylene glycol recovery tower 3 is 45, the distance between the feed port and the bottom of the tower is 20 plates, and the distance between the side line extraction and the bottom of the tower is 15 plates;

[0083] The ethylene glycol refining tower 5 is provided with 70 plates, the distance between the feed port and the bottom of the tower is 40 plates, and the distance between the side line outlet and the bottom of the tower is 46 plates;

[0084] The formic acid pressure separation tower 6 is provided with 55 plates, and the distance between the feed port and the bottom of the tower is 42 plates; the formic acid pressure reduction separation tower 7 is provided with 40 plates, and the distance between the feed port and the bottom of the tower is 35 plates;

[0085] The diethylene glycol refining tower 8 is provided with 15 plates, and the distance between the feed inlet and the bottom of the tower is 10 plates.

[0086] Example 2

[0087] This embodiment provides a method for co-producing ethylene glycol with formic acid and producing diethylene glycol as a by-product, comprising the following steps:

[0088] (1) The liquid phase material in the ethylene glycol synthesis system is sent to the dehydration and concentration tower 1, and the formic acid aqueous solution is produced from the top of the dehydration and concentration tower 1. After most of the water is produced, the bottom liquid enters the formic acid recovery tower 2;

[0089] (2) Formic acid is extracted from the top of formic acid recovery tower 2, and the formic acid enters formic acid pressure separation tower 6 and formic acid pressure reduction separation tower 7 for purification, and the bottom solution enters diethylene glycol alcohol recovery tower 3;

[0090] (3) Ethylene glycol and light components are extracted from the top of diethylene glycol recovery tower 3, diethylene glycol is extracted from the side line, and diethylene glycol enters diethylene glycol refining tower 8 for purification, and the heavy components in the bottom of the tower are discharged as waste;

[0091] (4) The top of the diethylene glycol recovery tower 3 is taken out and enters the neutralization tank 4 to adjust the pH. The neutralized material enters the ethylene glycol refining tower 5;

[0092] (5) Water and components lighter than ethylene glycol are produced from the top of ethylene glycol refining tower 5, qualified ethylene glycol is produced from the side line, and waste water is discharged from the bottom of the tower.

[0093] In this embodiment, the liquid phase materials in the ethylene glycol synthesis system are calculated by percentage, wherein ethylene glycol accounts for 15%, water accounts for 65%, formic acid accounts for 15%, 1,3-dioxane-2-methanol accounts for 2%, ethylene glycol monoformate accounts for 2%, and polyethylene glycol accounts for 1%.

[0094] Liquid material flow rate is 1000kg / h, product ethylene glycol flow rate is 150kg / h, and the content is greater than 99.9%. Diethylene glycol flow rate is 34kg / h, and the content is greater than 99%. Formic acid product flow rate is 140kg / h, and the content is greater than 99%;

[0095] In step (1), the vacuum degree of the dehydration concentration tower is controlled at 0.09 MPa, the tower top temperature is controlled at 30-40°C, and the tower bottom temperature is controlled at 50-60°C;

[0096] In step (2), the vacuum degree of the formic acid recovery tower is controlled at 0.09 MPa, the tower top temperature is controlled at 40-45° C., and the tower bottom temperature is controlled at 100-110° C.;

[0097] In step (3), the vacuum degree of the diethylene glycol recovery tower is controlled at 0.098 MPa, the top outlet temperature is controlled at 100-110°C, the side outlet temperature is controlled at 120-130°C, and the bottom temperature is controlled at 160-180°C;

[0098] In step (4), the pH is adjusted to 8.5 using 25 wt% NaOH;

[0099] In step (5), the vacuum degree of the ethylene glycol refining tower is controlled at 0.098 MPa, the tower top temperature is controlled at 60-80°C, the side line extraction temperature is controlled at 100-110°C, and the tower bottom temperature is controlled at 130-140°C.

[0100] Water is produced from the top of the formic acid pressure separation tower, and the bottom components enter the formic acid pressure reduction separation tower. Formic acid is produced from the top of the formic acid pressure reduction separation tower, and the bottom liquid is a mixture of water, formic acid, and ethylene glycol.

[0101] The absolute pressure of the formic acid pressurized separation tower is 0.25MPa, the tower top temperature is controlled at 125-130℃, and the tower bottom temperature is controlled at 135-140℃;

[0102] The vacuum degree of the formic acid decompression separation tower is controlled at 0.05MPa, the tower top temperature is controlled at 60-70℃, and the tower bottom temperature is controlled at 80-90℃;

[0103] The ethylene glycol produced from the top of the diethylene glycol refining tower enters the neutralization tank, and the diethylene glycol is produced from the bottom of the tower;

[0104] The vacuum degree of the diethylene glycol refining tower is controlled at 0.09MPa, the tower top temperature is controlled at 125-130℃, and the tower bottom temperature is controlled at 175-180℃;

[0105] In the above steps, the top extraction (shell side) of the formic acid pressure separation tower 6 is used to heat the side feed (tube side) of the dehydration concentration tower 1 and the side feed (tube side) of the formic acid recovery tower 2 through the first coupling heat exchanger EC1; the side feed of the dehydration concentration tower 1 and the side feed of the formic acid recovery tower 2 are fed through different tube sides;

[0106] The top discharge (tube side) and side line extraction (tube side) of the diethylene glycol recovery tower 3 are used to heat the side line feed (shell side) of the formic acid vacuum separation tower 7 through the second coupling heat exchanger EC2; the top discharge and side line extraction of the diethylene glycol recovery tower 3 are carried out in different tube sides;

[0107] The top extraction (tube side) of the diethylene glycol refining tower 8 is used to provide heat for the side feed (shell side) of the formic acid pressure separation tower 6 through the third coupled heat exchanger EC3.

[0108] Example 3

[0109] This embodiment provides a method for co-producing ethylene glycol with formic acid and producing diethylene glycol as a by-product, comprising the following steps:

[0110] (1) The liquid phase material in the ethylene glycol synthesis system is sent to the dehydration and concentration tower 1, and the formic acid aqueous solution is produced from the top of the dehydration and concentration tower 1. After most of the water is produced, the bottom liquid enters the formic acid recovery tower 2;

[0111] (2) Formic acid is extracted from the top of formic acid recovery tower 2, and the formic acid enters formic acid pressure separation tower 6 and formic acid pressure reduction separation tower 7 for purification, and the bottom solution enters diethylene glycol alcohol recovery tower 3;

[0112] (3) Ethylene glycol and light components are extracted from the top of diethylene glycol recovery tower 3, diethylene glycol is extracted from the side line, and diethylene glycol enters diethylene glycol refining tower 8 for purification, and the heavy components in the bottom of the tower are discharged as waste;

[0113] (4) The top of the diethylene glycol recovery tower 3 is taken out and enters the neutralization tank 4 to adjust the pH. The neutralized material enters the ethylene glycol refining tower 5;

[0114] (5) Water and components lighter than ethylene glycol are produced from the top of ethylene glycol refining tower 5, qualified ethylene glycol is produced from the side line, and waste water is discharged from the bottom of the tower.

[0115] In this embodiment, the liquid phase materials in the ethylene glycol synthesis system are calculated by percentage, wherein ethylene glycol accounts for 15%, water accounts for 64%, formic acid accounts for 15%, 1,3-dioxane-2-methanol accounts for 3%, ethylene glycol monoformate accounts for 2%, and polyethylene glycol accounts for 1%.

[0116] Liquid material flow rate is 1000kg / h, product ethylene glycol flow rate is 192kg / h, and the content is greater than 99.9%. Diethylene glycol flow rate is 38kg / h, and the content is greater than 99%. Formic acid product flow rate is 150kg / h, and the content is greater than 99%;

[0117] In step (1), the vacuum degree of the dehydration concentration tower is controlled at 0.095 MPa, the tower top temperature is controlled at 30-40°C, and the tower bottom temperature is controlled at 50-60°C;

[0118] In step (2), the vacuum degree of the formic acid recovery tower is controlled at 0.095 MPa, the tower top temperature is controlled at 40-45° C., and the tower bottom temperature is controlled at 100-110° C.;

[0119] In step (3), the vacuum degree of the diethylene glycol recovery tower is controlled at 0.01 MPa, the top outlet temperature is controlled at 100-110°C, the side outlet temperature is controlled at 120-130°C, and the bottom temperature is controlled at 160-180°C;

[0120] In step (4), the pH is adjusted to 9.5 using 30 wt% NaOH;

[0121] In step (5), the vacuum degree of the ethylene glycol refining tower is controlled at 0.1 MPa, the tower top temperature is controlled at 60-80°C, the side line extraction temperature is controlled at 100-110°C, and the tower bottom temperature is controlled at 130-140°C.

[0122] Water is produced from the top of the formic acid pressure separation tower, and the bottom components enter the formic acid pressure reduction separation tower. Formic acid is produced from the top of the formic acid pressure reduction separation tower, and the bottom liquid is a mixture of water, formic acid, and ethylene glycol.

[0123] The absolute pressure of the formic acid pressurized separation tower is 0.3MPa, the tower top temperature is controlled at 125-130℃, and the tower bottom temperature is controlled at 135-140℃;

[0124] The vacuum degree of the formic acid decompression separation tower is controlled at 0.05MPa, the tower top temperature is controlled at 60-70℃, and the tower bottom temperature is controlled at 80-90℃;

[0125] The ethylene glycol produced from the top of the diethylene glycol refining tower enters the neutralization tank, and the diethylene glycol is produced from the bottom of the tower;

[0126] The vacuum degree of the diethylene glycol refining tower is controlled at 0.095MPa, the tower top temperature is controlled at 125-130℃, and the tower bottom temperature is controlled at 175-180℃;

[0127] In the above steps, the top extraction (shell side) of the formic acid pressure separation tower 6 is used to heat the side feed (tube side) of the dehydration concentration tower 1 and the side feed (tube side) of the formic acid recovery tower 2 through the first coupling heat exchanger EC1; the side feed of the dehydration concentration tower 1 and the side feed of the formic acid recovery tower 2 are fed through different tube sides;

[0128] The top discharge (tube side) and side line extraction (tube side) of the diethylene glycol recovery tower 3 are used to heat the side line feed (shell side) of the formic acid vacuum separation tower 7 through the second coupling heat exchanger EC2; the top discharge and side line extraction of the diethylene glycol recovery tower 3 are carried out in different tube sides;

[0129] The top extraction (tube side) of the diethylene glycol refining tower 8 is used to provide heat for the side feed (shell side) of the formic acid pressure separation tower 6 through the third coupled heat exchanger EC3.

[0130] Example 4

[0131] This embodiment provides a method for co-producing ethylene glycol with formic acid and producing diethylene glycol as a by-product, comprising the following steps:

[0132] (1) The liquid phase material in the ethylene glycol synthesis system is sent to the dehydration and concentration tower 1, and the formic acid aqueous solution is produced from the top of the dehydration and concentration tower 1. After most of the water is produced, the bottom liquid enters the formic acid recovery tower 2;

[0133] (2) Formic acid is extracted from the top of formic acid recovery tower 2, and the formic acid enters formic acid pressure separation tower 6 and formic acid pressure reduction separation tower 7 for purification, and the bottom solution enters diethylene glycol alcohol recovery tower 3;

[0134] (3) Ethylene glycol and light components are extracted from the top of diethylene glycol recovery tower 3, diethylene glycol is extracted from the side line, and diethylene glycol enters diethylene glycol refining tower 8 for purification, and the heavy components in the bottom of the tower are discharged as waste;

[0135] (4) The top of the diethylene glycol recovery tower 3 is taken out and enters the neutralization tank 4 to adjust the pH. The neutralized material enters the ethylene glycol refining tower 5;

[0136] (5) Water and components lighter than ethylene glycol are produced from the top of ethylene glycol refining tower 5, qualified ethylene glycol is produced from the side line, and waste water is discharged from the bottom of the tower.

[0137] In this embodiment, the liquid phase materials in the ethylene glycol synthesis system are calculated by percentage, wherein ethylene glycol accounts for 15%, water accounts for 61%, formic acid accounts for 15%, 1,3-dioxane-2-methanol accounts for 3%, ethylene glycol monoformate accounts for 3%, and polyethylene glycol accounts for 3%.

[0138] Liquid material flow rate is 1000kg / h, product ethylene glycol flow rate is 170kg / h, and the content is greater than 99.9%. Diethylene glycol flow rate is 36kg / h, and the content is greater than 99%. Formic acid product flow rate is 145kg / h, and the content is greater than 99%;

[0139] In step (1), the vacuum degree of the dehydration concentration tower is controlled at 0.085 MPa, the tower top temperature is controlled at 30-40°C, and the tower bottom temperature is controlled at 50-60°C;

[0140] In step (2), the vacuum degree of the formic acid recovery tower is controlled at 0.085 MPa, the tower top temperature is controlled at 40-45° C., and the tower bottom temperature is controlled at 100-110° C.;

[0141] In step (3), the vacuum degree of the diethylene glycol recovery tower is controlled at 0.095 MPa, the top outlet temperature is controlled at 100-110°C, the side outlet temperature is controlled at 120-130°C, and the bottom temperature is controlled at 160-180°C;

[0142] In step (4), the pH is adjusted to 8.5 using 25 wt% NaOH;

[0143] In step (5), the vacuum degree of the ethylene glycol refining tower is controlled at 0.095 MPa, the tower top temperature is controlled at 60-80°C, the side line extraction temperature is controlled at 100-110°C, and the tower bottom temperature is controlled at 130-140°C.

[0144] Water is produced from the top of the formic acid pressure separation tower, and the bottom components enter the formic acid pressure reduction separation tower. Formic acid is produced from the top of the formic acid pressure reduction separation tower, and the bottom liquid is a mixture of water, formic acid, and ethylene glycol.

[0145] The absolute pressure of the formic acid pressurized separation tower is 0.2MPa, the tower top temperature is controlled at 125-130℃, and the tower bottom temperature is controlled at 135-140℃;

[0146] The vacuum degree of the formic acid decompression separation tower is controlled at 0.02MPa, the tower top temperature is controlled at 60-70℃, and the tower bottom temperature is controlled at 80-90℃;

[0147] The ethylene glycol produced from the top of the diethylene glycol refining tower enters the neutralization tank, and the diethylene glycol is produced from the bottom of the tower;

[0148] The vacuum degree of the diethylene glycol refining tower is controlled at 0.085MPa, the tower top temperature is controlled at 125-130℃, and the tower bottom temperature is controlled at 175-180℃;

[0149] In the above steps, the top extraction (shell side) of the formic acid pressure separation tower 6 is used to heat the side feed (tube side) of the dehydration concentration tower 1 and the side feed (tube side) of the formic acid recovery tower 2 through the first coupling heat exchanger EC1; the side feed of the dehydration concentration tower 1 and the side feed of the formic acid recovery tower 2 are fed through different tube sides;

[0150] The top discharge (tube side) and side line extraction (tube side) of the diethylene glycol recovery tower 3 are used to heat the side line feed (shell side) of the formic acid vacuum separation tower 7 through the second coupling heat exchanger EC2; the top discharge and side line extraction of the diethylene glycol recovery tower 3 are carried out in different tube sides;

[0151] The top extraction (tube side) of the diethylene glycol refining tower 8 is used to provide heat for the side feed (shell side) of the formic acid pressure separation tower 6 through the third coupled heat exchanger EC3.

[0152] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0153] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for co-producing formic acid with ethylene glycol and producing diethylene glycol as a by-product, characterized in that: The following steps are involved: (1) The liquid phase material in the ethylene glycol synthesis system is sent to the dehydration and concentration tower. After 80-90% of the water is extracted from the top of the dehydration and concentration tower, the bottom liquid enters the formic acid recovery tower; (2) Formic acid is extracted from the top of the formic acid recovery tower, and the bottom solution enters the diethylene glycol alcohol recovery tower; (3) Ethylene glycol and light components are produced from the top of the diethylene glycol recovery tower, diethylene glycol is produced from the side line, and the heavy components in the bottom of the tower are discharged as waste; (4) The top of the diethylene glycol recovery tower is taken out and enters the neutralization tank to adjust the pH. The neutralized material enters the ethylene glycol refining tower; (5) Water and components lighter than ethylene glycol are produced from the top of the tower, qualified ethylene glycol is produced from the side line, and waste water is discharged from the bottom of the tower.

2. The method for co-producing formic acid with ethylene glycol as a by-product according to claim 1, characterized in that: Also includes: The formic acid in step (2) enters the formic acid pressure separation tower and the formic acid pressure reduction separation tower in sequence for purification; The diethylene glycol described in step (3) enters a diethylene glycol refining tower for purification.

3. The method for co-producing formic acid with ethylene glycol as a by-product according to claim 2, characterized in that: The top of the formic acid pressure separation tower is extracted to provide heat for the side feed of the dehydration concentration tower and the side feed of the formic acid recovery tower through the first coupled heat exchanger; The top discharge and side line extraction of the diethylene glycol recovery tower are used to supply heat to the side line feed of the formic acid vacuum separation tower through a second coupled heat exchanger; The overhead extraction of the diethylene glycol refining tower is used to supply heat to the side feed of the formic acid pressurized separation tower through the third coupled heat exchanger.

4. The method for co-producing formic acid with ethylene glycol and by-producing diethylene glycol according to claim 3, characterized in that: The vacuum degree of the dehydration and concentration tower in step (1) is controlled at 0.085-0.095 MPa, the tower top temperature is controlled at 30-40°C, and the tower bottom temperature is controlled at 40-80°C; The vacuum degree of the formic acid recovery tower in step (2) is controlled at 0.085-0.095 MPa, the tower top temperature is controlled at 40-50°C, and the tower bottom temperature is controlled at 80-110°C; The vacuum degree of the diethylene glycol recovery tower in step (3) is controlled at 0.095-0.01 MPa, the top outlet temperature is controlled at 100-110°C, the side outlet temperature is controlled at 110-130°C, and the bottom temperature is controlled at 120-200°C; The pH adjustment in step (4) is to use 20-30wt% NaOH to adjust the pH to 7.5-9.5; In step (5), the vacuum degree of the ethylene glycol refining tower is controlled at 0.095-0.1 MPa, the tower top temperature is controlled at 40-90°C, the side line extraction temperature is controlled at 100-110°C, and the tower bottom temperature is controlled at 110-150°C.

5. The method for co-producing formic acid with ethylene glycol as a by-product according to claim 3, characterized in that: The formic acid pressure separation tower produces water from the top, and the bottom components enter the formic acid pressure separation tower. Formic acid is produced from the top of the formic acid pressure separation tower, and the bottom liquid is re-sent to the formic acid pressure separation tower. The operating pressure of the formic acid pressurized separation tower is 0.2-0.3 MPa absolute pressure, the tower top temperature is controlled at 100-120°C, and the tower bottom temperature is controlled at 120-140°C; The vacuum degree of the formic acid vacuum separation tower is controlled at 0.02-0.05 MPa, the tower top temperature is controlled at 60-70°C, and the tower bottom temperature is controlled at 80-90°C.

6. The method for co-producing formic acid with ethylene glycol as a by-product according to claim 3, characterized in that: The diethylene glycol refining tower produces ethylene glycol from the top and enters the neutralization tank, and the diethylene glycol is produced from the bottom of the tower; The vacuum degree of the diethylene glycol refining tower is controlled at 0.085-0.095 MPa, the tower top temperature is controlled at 110-120°C, and the tower bottom temperature is controlled at 180-200°C.

7. A device for producing ethylene glycol and formic acid as a by-product of diethylene glycol, characterized in that: include: Ethylene glycol refining section, formic acid refining section, diethylene glycol refining section; The ethylene glycol refining section includes a dehydration concentration tower, a formic acid recovery tower, a diethylene glycol recovery tower, a neutralization tank, and an ethylene glycol refining tower which are connected in sequence; The formic acid refining section comprises a formic acid pressure separation tower and a formic acid pressure reduction separation tower connected to each other; The diethylene glycol refining section includes a diethylene glycol refining tower; The formic acid recovery tower is connected to the formic acid pressurized separation tower; The diethylene glycol recovery tower is connected to the diethylene glycol refining tower; The diethylene glycol refining tower is also connected to the neutralization tank.

8. The device for producing ethylene glycol and formic acid as a by-product of diethylene glycol according to claim 7, characterized in that: Also includes: A coupled heat exchanger unit, the coupled heat exchanger unit comprising: a first coupled heat exchanger, a second coupled heat exchanger and a third coupled heat exchanger; The top of the formic acid pressure separation tower is connected to the shell side of the first coupled heat exchanger, and the side line of the dehydration concentration tower and the side line of the formic acid recovery tower are respectively connected to the tube side of the first coupled heat exchanger; The top and the side line of the diethylene glycol recovery tower are respectively connected to the tube side of the second coupled heat exchanger, and the side line of the formic acid vacuum separation tower is connected to the tube side of the second heat exchanger; The top of the diethylene glycol refining tower is connected to the tube side of the third coupled heat exchanger, and the side line of the formic acid pressurized separation tower is connected to the shell side of the third coupled heat exchanger.

9. The device for producing ethylene glycol and formic acid as a by-product of diethylene glycol according to claim 7, characterized in that: The diethylene glycol recovery tower and the ethylene glycol refining tower are thermally coupled dividing wall towers.

10. The device for producing ethylene glycol and formic acid as a by-product of diethylene glycol according to claim 7, characterized in that: The dehydration and concentration tower is provided with 50-70 plates, and the distance between the feed inlet and the bottom of the tower is 22-42 plates; The formic acid recovery tower is provided with 60-80 plates, and the distance between the feed port and the bottom of the tower is 45-65 plates; The diethylene glycol recovery tower is provided with 35-50 plates, the distance between the feed port and the bottom of the tower is 15-30 plates, and the distance between the side line extraction and the bottom of the tower is 10-20 plates; The ethylene glycol refining tower is provided with 63-73 plates, the distance between the feed port and the bottom of the tower is 34-44 plates, and the distance between the side line outlet and the bottom of the tower is 40-50 plates; The formic acid pressure separation tower is provided with 40-60 plates, and the distance between the feed port and the bottom of the tower is 27-47 plates; the formic acid pressure reduction separation tower is provided with 36-50 plates, and the distance between the feed port and the bottom of the tower is 25-39 plates; The diethylene glycol refining tower is provided with 10-20 plates, and the distance between the feed inlet and the bottom of the tower is 5-15 plates.

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