A furfural production system and process

Abstract

The invention discloses a furfural production system and process, comprising an acid mixer, a hydrolysis kettle, a first separator, a distillation tower, and a heat energy recovery system. The acid mixer is connected with the hydrolysis kettle and the first separator in sequence, the feed port of the acid mixer is respectively connected with a silo and a dilute acid tank, the heat energy recovery system comprises a heat exchanger, a second separator, a buffer, and a compressor, the heat exchanger is connected in series with the second separator, the buffer, and the compressor in sequence, the discharge port of the first separator is connected with the feed port of the distillation tower through the heat exchanger, the waste outlet of the distillation tower is connected with a wastewater pool, a second water pump, a preheater, and an evaporator in sequence, and the outlet of the evaporator is connected with the inlet of the hydrolysis kettle; the invention can fully recover the energy in the aldehyde vapor for recycling in furfural production, greatly improve the energy utilization rate of furfural production, and greatly reduce the steam consumption per ton of furfural production from more than 15 tons to less than 5 tons, and at the same time, by adding a material distributor of the hydrolysis kettle, the uniform distribution of the material is achieved, and the steam usage is effectively reduced.

Description

Technical Field

[0001] The invention relates to the technical field of furfural production, in particular to a furfural production system and process. Background Art

[0002] Furfural is an industrial chemical that can be extracted from various agricultural by-products, including corn cobs, oat and wheat bran, and sawdust; it is used as a raw material for organic synthesis and is also used in synthetic resins, varnishes, pesticides, pharmaceuticals, rubber and coatings.

[0003] At present, domestic furfural production mainly uses one-step hydrolysis technology, which mixes corn cobs, sugarcane bagasse and other hemicellulose-rich raw materials with catalysts and puts them into a hydrolysis kettle. After a period of hydrolysis, steam is introduced to use the steam to bring out the furfural vapor (hereinafter referred to as aldehyde vapor) in the kettle. The collected aldehyde vapor enters the circulating water cooler and condenses into a raw liquid, which is then distilled and refined through a series of processes to finally produce furfural. The steam consumption for producing a ton of furfural is 15-20 tons, of which most of the steam is consumed in the process of bringing out the aldehyde vapor and then being cooled by circulating water. At present, the industry generally has no good use for this part of the heat. The furfural raw liquid is basically obtained by condensing it with circulating water. There are also very few methods that use ORC units to generate electricity or for heating. However, due to the production characteristics of furfural, the application effects are not very good, and the heat utilization rate of this part is very low. The hydrolysis kettle of furfural production equipment has the following disadvantages: the material in the hydrolysis kettle is dense in the middle and loose around, the steam utilization rate is low, and the steam distribution is uneven, which is also the reason for the large steam consumption. Therefore, the existing production system and process cannot meet the needs of actual use, so there is an urgent need for improved technology on the market to solve the above problems. Summary of the invention

[0004] The technical problem to be solved by the present invention is to overcome the existing defects and provide a furfural production system and process, which can fully recover the energy in the aldehyde vapor and recycle it for furfural production, greatly improve the energy utilization rate of furfural production, and significantly reduce the steam consumption per ton of furfural production from more than 15 tons to less than 5 tons. At the same time, by adding a material distributor to the hydrolysis kettle, uniform distribution of materials is achieved, and the steam usage is effectively reduced; by optimizing the steam distributor at the bottom of the hydrolysis kettle and adding a guide plate to the wall of the hydrolysis kettle, the steam is prevented from going along the wall of the hydrolysis kettle and rising, thereby improving the steam utilization rate, and the problems in the background technology can be effectively solved.

[0005] To achieve the above-mentioned purpose, the present invention provides the following technical scheme: a furfural production system and process, comprising an acid mixer, a hydrolysis kettle, a first separator, a distillation tower, and a heat energy recovery system, wherein the acid mixer is connected to the hydrolysis kettle and the first separator in sequence, and the feed port of the acid mixer is respectively connected to a silo and a dilute acid tank, the heat energy recovery system comprises a heat exchanger, a second separator, a buffer, and a compressor, the heat exchanger is connected in series with the second separator, the buffer, and the compressor in sequence, the discharge port of the first separator is connected to the feed port of the distillation tower through the heat exchanger, the waste outlet of the distillation tower is connected to a wastewater pool, a second water pump, a preheater, and an evaporator in sequence, the evaporator outlet is connected to the hydrolysis kettle inlet, the compressor is connected to the heat exchanger through the evaporator and the preheater, and the discharge port of the distillation tower is connected to a second cooler, a stratification tank, and a product tank in sequence.

[0006] Furthermore, the raw liquid outlet of the distillation tower is connected to a first cooler and a raw liquid tank, the raw liquid in the raw liquid tank is sent to the distillation tower through a first water pump, the distillation tower is connected to a second cooler, and the first cooler and the second cooler are respectively connected to circulating water.

[0007] Furthermore, a reflux bypass is provided at the compressor outlet, cooling water is provided on the compressor, and pressure-regulating steam is provided on the buffer, and the pressure-regulating steam is connected to the steam pipe network.

[0008] Furthermore, a steam guide device and a steam distribution device are arranged inside the hydrolysis kettle, a charging port is arranged on the top of the hydrolysis kettle, a material distributor is arranged on the upper part of the hydrolysis kettle, and the material distributor is connected to the top wall of the hydrolysis kettle through a flexible suspension rod.

[0009] Furthermore, the steam guide device includes a first layer of guide plates, a second layer of guide plates and a third layer of guide plates, and the first layer of guide plates, the second layer of guide plates and the third layer of guide plates are arranged on the inner wall of the hydrolysis kettle from bottom to top in sequence, and the first layer of guide plates, the second layer of guide plates and the third layer of guide plates are staggered.

[0010] Furthermore, the steam distribution device includes a hydrolysis steam pipeline, a steam distributor, and a steam nozzle. The steam distributor is arranged in a concentric ring shape and a partition is provided in the middle. The steam nozzle is installed on the steam distributor and the nozzle is directed downward to avoid nozzle clogging. The hydrolysis steam pipeline is provided with two routes, and the hydrolysis steam pipeline is connected to the steam distributor.

[0011] Compared with the prior art, the present invention has the following beneficial effects:

[0012] 1. Through the calculation of heat in each stage of furfural production system, heat balance calculation is realized, and efficient and rational utilization of heat energy is achieved, which reduces the steam consumption of furfural production by more than 10t, and can also greatly reduce the emission of carbon dioxide in the production process.

[0013] 2. The present invention can realize the energy recovery, energy enhancement and energy reuse system, so as to achieve the purpose of energy saving; through heat recovery, the amount of circulating water can be greatly reduced, and the production water consumption and cost have obvious advantages over the current process.

[0014] 3. The amount of steam used can be greatly reduced, so the furfural device no longer needs to be co-produced with the thermal power system, and the project investment amount can be greatly reduced. The present invention can fully recover the energy in the aldehyde steam and recycle it for furfural production, greatly improving the energy utilization rate of furfural production, and greatly reducing the steam consumption per ton of furfural production from more than 15 tons to less than 5 tons. At the same time, by adding a material distributor to the hydrolysis kettle, uniform distribution of materials is achieved, and the amount of steam used is effectively reduced; by optimizing the steam distributor at the bottom of the hydrolysis kettle and adding a guide plate to the wall of the hydrolysis kettle, it is prevented that the steam goes along the wall of the hydrolysis kettle and rises, thereby improving the steam utilization rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the structure of the present invention;

[0016] Figure 2 It is a schematic diagram of the structure of the hydrolysis kettle of the present invention;

[0017] Figure 3 This is a schematic diagram of the comparative structure of the guide plate of the present invention;

[0018] Figure 4 It is a schematic diagram of the structure of the steam distribution device of the present invention.

[0019] In the figure: 1 silo, 2 dilute acid tank, 3 acid mixer, 4 hydrolysis kettle, 5 first separator, 6 heat exchanger, 7 distillation tower, 8 temperature-adjusting steam, 9 first cooler, 10 circulating water, 11 raw liquid tank, 12 first water pump, 13 second cooler, 14 stratification tank, 15 product tank, 21 wastewater tank, 22 second water pump, 23 preheater, 24 evaporator, 31 second separator, 32 buffer, 33 pressure-adjusting steam, 34 compressor, 35 reflux bypass, 36 cooling water, 41 hydrolysis steam pipeline, 42 steam distributor, 421 partition, 43 steam nozzle, 44 first layer guide plate, 45 second layer guide plate, 46 third layer guide plate, 47 charging port, 48 material distributor, 49 flexible suspension rod. DETAILED DESCRIPTION

[0020] 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.

[0021] See also Figure 1-4 The present invention provides a technical solution: a furfural production system and process, including an acid mixer 3, a hydrolysis kettle 4, a first separator 5, a distillation tower 7, and a heat energy recovery system. The acid mixer 3 is connected to the hydrolysis kettle 4 and the first separator 5 in sequence. The feed port of the acid mixer 3 is connected to the silo 1 and the diluted acid tank 2 respectively. The heat energy recovery system includes a heat exchanger 6, a second separator 31, a buffer 32, and a compressor 34. The heat exchanger 6 is connected in series with the second separator 31, the buffer 32, and the compressor 34 in sequence. The discharge port of the first separator 5 is connected to the feed port of the distillation tower 7 through the heat exchanger 6. The heat energy recovery system forms a set of efficient heat energy extraction, heat energy quality improvement, and heat energy recovery systems to achieve full recovery and utilization of aldehyde vapor heat energy. The outlet of the compressor 34 is provided with a reflux bypass 35. The reflux bypass 35 can ensure the normal production of the compressor 34 by reflux at low load. The compressor 34 is provided with cooling water 36. Water 36 is used to lower the temperature of the compressed steam and reduce the compression power consumption. The buffer 32 is provided with a pressure-regulating steam 33, which is connected to the steam network. When the furfural production is unstable, the steam pressure of the buffer 32 is adjusted by the pressure-regulating steam 33 to ensure that the compressor 34 can operate normally. The waste outlet of the distillation tower 7 is connected to the wastewater pool 21, the second water pump 22, the preheater 23, and the evaporator 24 in sequence. The outlet of the evaporator 24 is connected to the inlet of the hydrolysis kettle 4. The compressor 34 is connected to the heat exchanger 6 through the evaporator 24 and the preheater 23. The discharge port of the distillation tower 7 is connected to the second cooler 13, the stratification tank 14 and the product tank 15 in sequence. The raw liquid outlet of the distillation tower 7 is connected to the first cooler 9 and the raw liquid tank 11. The raw liquid in the raw liquid tank 11 is sent to the distillation tower 7 through the first water pump 12. The distillation tower 7 is connected to the second cooler 13, and the first cooler 9 and the second cooler 13 are respectively connected to the circulating water 10.

[0022] The hydrolysis kettle 4 is provided with a steam guide device and a steam distribution device inside. The steam guide device includes a first-layer guide plate 44, a second-layer guide plate 45 and a third-layer guide plate 46. The first-layer guide plate 44, the second-layer guide plate 45 and the third-layer guide plate 46 are arranged on the inner wall of the hydrolysis kettle 4 from bottom to top in sequence, and the first-layer guide plate 44, the second-layer guide plate 45 and the third-layer guide plate 46 are arranged in a staggered manner. The steam rising along the inner wall of the hydrolysis kettle 4 is guided back to the material by the steam guide device for full utilization, so as to avoid the steam taking a shortcut. The steam distribution device comprises a hydrolysis steam pipeline 41, a steam distributor 42, and a steam nozzle 43. The steam distributor 42 is arranged in a concentric ring shape, and a partition 421 is arranged in the middle. The steam nozzle 43 is installed in the steam distributor 42, and the nozzle is directed downward to avoid nozzle blockage. The hydrolysis steam pipeline 41 is provided with two paths, and the hydrolysis steam pipeline 41 is connected to the steam distributor 42. The purpose of uniform distribution of steam in the hydrolysis kettle 4 can be achieved through the steam distribution device. The top of the hydrolysis kettle 4 is provided with a charging port 47. The hydrolysis kettle 4 is provided with a material distributor 48 at the upper part of the interior. The material distributor is a conical structure. The material distributor 48 is connected to the top wall of the hydrolysis kettle 4 through a flexible suspension rod 49. When entering the hydrolysis kettle 4, the material hits the material distributor 48 for secondary distribution, which can avoid the situation that the material in the hydrolysis kettle 4 is dense in the middle and loose around. The uniform distribution of materials is conducive to improving the utilization rate of steam and reducing consumption. The flexible suspension rod 49 has a certain buffering effect. The connection between it and the upper head of the hydrolysis kettle and the material distributor 48 is non-movable. Fatigue cracking under repeated impact of materials can be avoided. The present invention can fully recover the energy in the aldehyde steam for recycling in furfural production, greatly improving the energy utilization rate of furfural production, and greatly reducing the steam consumption per ton of furfural production from more than 15 tons to less than 5 tons. At the same time, by adding a material distributor to the hydrolysis kettle 4, uniform distribution of materials is achieved, and the steam usage is effectively reduced. In addition, by optimizing the steam distributor at the bottom of the hydrolysis kettle 4 and adding a guide plate to the wall of the hydrolysis kettle, it is avoided that the steam rises along the wall of the hydrolysis kettle 4, thereby improving the steam utilization rate.

[0023] A furfural production system and process, comprising the following steps:

[0024] Step 1: The production raw materials are fed from the silo 1 into the acid mixer 3, and are mixed evenly with the dilute sulfuric acid from the dilute acid tank 2 and then fed into the hydrolysis kettle 4. Steam is injected from the bottom of the hydrolysis kettle 4 to provide conditions for the reaction, and the materials react in the hydrolysis kettle 4 to generate furfural;

[0025] Step 2: The steam injected at the bottom of the hydrolysis kettle 4 takes out the furfural, and the mixture of furfural and steam, referred to as aldehyde steam, enters the first separator 5 to remove impurities therein, and the clean aldehyde steam enters the heat exchanger 6 as a heat source for heat exchange, releases heat and condenses into a 150°C stock solution; the 150°C stock solution enters the distillation tower 7 as a heat source for heating, and is further cooled to 110°C. The 110°C stock solution enters the first cooler 9 for heat exchange with circulating water 10 and is cooled to 80°C before entering the stock liquid tank 11; the stock solution in the stock liquid tank 11 is pressurized by the first water pump 12 and sent to the distillation tower 7 for distillation, and the operating temperature of the distillation tower 7 is controlled by the temperature-adjusting steam 8. The top discharge enters the second cooler 13 for heat exchange with the circulating water 10, and enters the stratification tank 14 after being cooled to 40°C. After standing and stratifying, the crude furfural in the lower layer enters the product tank 15;

[0026] Step 3: The material discharged from the bottom of the distillation tower 7 enters the wastewater pool 21, and then enters the preheater 23 after being pressurized by the second water pump 22, and enters the evaporator 24 after being preheated to 170°C to evaporate and generate secondary steam, and the secondary steam enters the bottom of the hydrolysis kettle 4, and repeats the process of step 2 to take out furfural;

[0027] Step 4: The heat source steam in the evaporator 24 that exchanges heat with the wastewater is condensed into steam condensate at 195°C. The high-temperature condensate enters the preheater 23 and exchanges heat with the wastewater and is cooled to 100°C. It then enters the heat exchanger 6, is heated by aldehyde vapor and evaporates into low-pressure steam, enters the second separator 31 for steam-water separation, enters the buffer 32 for pressure stabilization, and then enters the compressor 34 for compression into 1.3MPa steam, replacing the primary steam to enter the evaporator 24 for wastewater evaporation production.

[0028] Benefit estimation: The present invention can reduce the steam consumption per ton of furfural from 15-20t to 5t. Conservatively estimated, based on the steam saving of 10t and the steam price of 150 yuan / t, the steam saving benefit is 1500 yuan / t. However, due to the addition of a compressor, the power consumption per ton of steam compression is 100kWh. Based on the electricity price of 0.6 yuan, the power consumption cost per ton of furfural production increases by 600 yuan. Comprehensively calculated, the production cost per ton of furfural can be reduced by 1500-600=900 yuan.

[0029] At the same time, if this process and equipment are used, there is no need to simultaneously build thermal power equipment such as boilers, water treatment, and flue gas treatment. The project investment amount will be greatly reduced, and the financial cost will also be reduced.

[0030] This process achieves efficient recovery and reuse of furfural heat energy, and has great benefits in energy saving and carbon reduction. Saving 10t of steam reduces carbon emissions by 2,366kg and saves 0.91t of standard coal. Increasing electricity consumption by 1,000kW increases carbon emissions by 785kg. Comprehensive calculation shows that producing one ton of furfural can reduce carbon emissions by 1,581kg.

[0031] This process can reduce the use of circulating water by 600t / h. Based on the circulating water cost of 0.2 yuan / t, the production cost of one ton of furfural can be reduced by 120 yuan compared with the existing system.

[0032] In summary, without taking into account the reduced financial costs, this process can reduce the production cost of furfural per ton by RMB 1,020 compared with the existing process, and can also reduce carbon dioxide emissions by 1,581 kg.

[0033] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A furfural production system, comprising an acid mixer (3), a hydrolysis kettle (4), a first separator (5), a distillation tower (7), and a heat energy recovery system, characterized in that: The acid mixer (3) is connected to the hydrolysis kettle (4) and the first separator (5) in sequence. The feed port of the acid mixer (3) is connected to the silo (1) and the diluted acid tank (2) respectively. The heat energy recovery system comprises a heat exchanger (6), a second separator (31), a buffer (32), and a compressor (34). The heat exchanger (6) is connected in series with the second separator (31), the buffer (32), and the compressor (34) in sequence. The discharge port of the first separator (5) is connected to the feed port of the first separator (5) through the heat exchanger (6). The feed inlet of the distillation tower (7) is connected, the waste outlet of the distillation tower (7) is connected in sequence to a wastewater pool (21), a second water pump (22), a preheater (23), and an evaporator (24), the outlet of the evaporator (24) is connected to an inlet of a hydrolysis kettle (4), the compressor (34) is connected to a heat exchanger (6) via the evaporator (24) and the preheater (23), and the discharge port of the distillation tower (7) is connected in sequence to a second cooler (13), a stratification tank (14), and a product tank (15).

2. A furfural production system according to claim 1, characterized in that: The raw liquid outlet of the distillation tower (7) is connected to a first cooler (9) and a raw liquid tank (11); the raw liquid in the raw liquid tank (11) is sent to the distillation tower (7) via a first water pump (12); the distillation tower (7) is connected to a second cooler (13); and the first cooler (9) and the second cooler (13) are respectively connected to circulating water (10).

3. A furfural production system according to claim 1, characterized in that: The compressor (34) is provided with a reflux bypass (35) at its outlet, the compressor (34) is provided with cooling water (36), the buffer (32) is provided with pressure-regulated steam (33), and the pressure-regulated steam (33) is connected to a steam pipe network.

4. A furfural production system according to claim 1, characterized in that: The hydrolysis kettle (4) is provided with a steam guide device and a steam distribution device inside, a charging port (47) is provided at the top of the hydrolysis kettle (4), a material distributor (48) is provided at the upper part of the hydrolysis kettle (4), and the material distributor (48) is connected to the top wall of the hydrolysis kettle (4) via a flexible suspension rod (49).

5. A furfural production system according to claim 4, characterized in that: The steam guide device comprises a first-layer guide plate (44), a second-layer guide plate (45) and a third-layer guide plate (46), wherein the first-layer guide plate (44), the second-layer guide plate (45) and the third-layer guide plate (46) are arranged on the inner wall of the hydrolysis kettle (4) in sequence from bottom to top, and the first-layer guide plate (44), the second-layer guide plate (45) and the third-layer guide plate (46) are arranged in a staggered manner.

6. A furfural production system according to claim 4, characterized in that: The steam distribution device comprises a hydrolysis steam pipeline (41), a steam distributor (42), and a steam nozzle (43); the steam distributor (42) is arranged in a concentric ring shape and a partition (421) is provided in the middle; the steam nozzle (43) is installed on the steam distributor (42) and the nozzle is directed downward; the hydrolysis steam pipeline (41) is provided with two paths, and the hydrolysis steam pipeline (41) is connected to the steam distributor (42).

7. A production process using a furfural production system according to any one of claims 1 to 6, characterized in that: The following steps are involved: Step 1: The production raw materials are introduced from the silo (1) into the acid mixer (3), mixed evenly with the dilute sulfuric acid from the dilute acid tank (2), and then introduced into the hydrolysis kettle (4). Steam is injected from the bottom of the hydrolysis kettle (4) to provide reaction conditions. The materials react in the hydrolysis kettle (4) to generate furfural; Step 2: The steam injected into the bottom of the hydrolysis kettle (4) takes out the furfural, and the mixture of furfural and steam, referred to as furfural steam, enters the first separator (5) to remove impurities therein, and the clean furfural steam enters the heat exchanger (6) as a heat source for heat exchange, releases heat and condenses into a raw liquid at 150° C.; the raw liquid at 150° C. enters the distillation tower (7) as a heat source for heating, and is further cooled to 110° C. The raw liquid at 110° C. enters the first cooler (9) for heat exchange with circulating water (10) and is cooled to 80° C. before entering the raw liquid tank (11); the raw liquid in the raw liquid tank (11) is pressurized by the first water pump (12) and sent to the distillation tower (7) for distillation, and the operating temperature of the distillation tower (7) is controlled by the temperature-adjusting steam (8). The material discharged from the top of the tower enters the second cooler (13) for heat exchange with the circulating water (10), and is cooled to 40° C. before entering the stratification tank (14). After standing and stratifying, the crude furfural in the lower layer enters the product tank (15); Step 3: The material discharged from the bottom of the distillation tower (7) enters the wastewater pool (21), and then enters the preheater (23) after being pressurized by the second water pump (22). After being preheated to 170° C., it enters the evaporator (24) for evaporation to generate secondary steam. The secondary steam enters the bottom of the hydrolysis kettle (4), and the process of taking out furfural is repeated in step 2; Step 4: The heat source steam in the evaporator (24) that exchanges heat with the wastewater is condensed into steam condensate at 195°C. The high-temperature condensate enters the preheater (23) to exchange heat with the wastewater and is cooled to 100°C. It then enters the heat exchanger (6) and is heated by aldehyde vapor to evaporate into low-pressure steam. It then enters the second separator (31) for steam-water separation. It then enters the buffer (32) for pressure stabilization and then enters the compressor (34) to be compressed into 1.3 MPa steam. It replaces the primary steam and enters the evaporator (24) for wastewater evaporation production.

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