CN1858043A - Method for producing furol by extruding plant stalk - Google Patents

Abstract

A method for producing furfural by extruding plant straws, which belongs to the field of furfural preparation, is characterized in that: 1) cutting plant straws into 2-4 cm particle segments, and then bundling and storing them; 2) cutting plant straw particle segments After acid mixing, the plant stalks are continuously extruded by a screw extrusion feeder and put into the hydrolysis kettle, and the extruded dilute acid is returned to the acid mixer for acid mixing; water vapor is introduced into the hydrolysis kettle; 3) The furfural stock solution obtained in the hydrolysis process is introduced into the subsequent process, and the furfural is extracted through the initial distillation tower, and then refined in the furfural continuous refining equipment to finally obtain commercial furfural. The invention has stable and reliable production, reduces furfural production cost, improves furfural yield, ensures furfural quality, expands the range of raw materials for furfural production, and provides a realistic approach for comprehensive utilization of industrialized production of furfural and plant straw.

Description

A method for producing furfural by extruding plant stalks

technical field

The invention relates to the field of furfural preparation, in particular to a method for preparing furfural by extruding plant stalks.

Background technique

Furfural is an organic chemical product that has not been synthesized from chemical raw materials but can only be extracted from plant materials such as agricultural waste. Furfural is an excellent selective solvent and a raw material for the production of various furan compounds. It is widely used in foundry binder, tetrahydrofuran, lubricating oil refining, organic synthesis, plastics, medicine, chemical anticorrosion, etc.

Furfural has long been industrialized and mass-produced in the world. There are many production methods, but most of them adopt direct method. The direct method is to put the raw material containing polypentose into a hydrolysis kettle, and under the action of catalyst-sulfuric acid and heat, the polypentose is hydrolyzed into pentose, and at the same time, the pentose is dehydrated to form furfural, and then through extraction of crude aldehyde, The continuous refining of furfural finally yields the finished product furfural.

There are many kinds of raw materials for extracting furfural. In theory, raw materials with high pentosan content, such as: corncobs, corn stalks, sunflower seed husks, cotton stalks, wheat straw, cottonseed husks, bagasse, rice husks, broadleaf Furfural can be extracted from leaves, etc. However, due to the special process difficulties in the hydrolysis stage, the raw materials used in the industrial production of furfural are mostly granular raw materials or easily crushed raw materials. In China, corn cobs are the main raw materials. For other plant straws containing pentosan, the fibers are long, difficult to crush, difficult to store and low in bulk density, and there is no stable and practical industrial production method for plant straw raw materials with a grassy structure. This objective situation, on the one hand, makes the shortage of raw materials an important factor restricting the development of furfural production. On the other hand, plant straw raw materials similar to grassy structure are wasted in large quantities, and even cause environmental pollution. Take corn stalks as an example. The harvesting of corn stalks in East China is very concentrated. In order to plant wheat in time, farmers usually remove corn stalks from the field within 2 to 3 days after harvesting corn. However, there are no field plants dedicated to storing straws. Straw utilization is relatively low. Ordinary households do not burn straw as fuel. Therefore, most farmers burn the straw on the spot in the field, and the fields and roads are filled with "smoke" in the busy season, which pollutes the environment and affects the traffic of vehicles and the take-off and landing of aircraft. The same is true for other plant straws such as grassy straws such as wheat straw.

The hydrolysis process stage of extracting furfural is mainly divided into four processes, namely raw material crushing, transportation, acid mixing, and hydrolysis. The main technological difficulties in the four hydrolysis stages of producing furfural from plant straws are as follows. The first is the cutting and crushing of plant straw. Due to the long fiber and soft texture of plant straw, it cannot be crushed or squeezed directly. The water should not be too large, otherwise it will affect the crushing effect and affect the subsequent process. The second is the storage of plant stalks. It takes about 16-22 tons of plant stalks to produce one ton of furfural. Such a large storage capacity requires a very large site and because of its good air permeability, it will not be as dry as corncobs after raining. The first layer is moldy, and the plant straws have good flammability. Such a large plant straw stockyard has brought great pressure to the fire prevention of the site. The third is that the bulk density of crushed plant straw is about 95-105kg/m ³ , and the amount of raw materials contained in the same volume of hydrolysis kettle is small and the utilization rate of equipment is low, which leads to high steam consumption and greatly increases the production cost of furfural. Fourth, because the plant straw density is small, it is easy to be brought into the pipeline and the next process with the steam in the hydrolysis kettle, so that the operation of blocking the pipeline and affecting the next process is difficult to produce in an industrialized device.

Contents of the invention

The purpose of the present invention is to provide a method for producing furfural by extrusion of plant straws, which solves the above four problems in the production of furfural by direct crushing of plant straws, and at the same time solves the air pollution caused by burning plant straws in some areas question.

The technical solution of the present invention is: the method for producing furfural by extruding and granulating plant stalks, including cutting plant stalks, extruding and packaging, transporting, mixing acid, extruding and potting, hydrolyzing, and distilling, and is characterized in that:

1) Cut the whole plant straw into 2-4cm particle segments with a grass cutter, then compress and bundle them with a baler and store them;

2) Mix the unbundled plant straw granules with an acid mixer and then use a screw extrusion feeder to continuously compress them according to a solid-liquid ratio of 1:0.3 to 0.8 and a compression ratio of 1:2 to 1:8 Plant straw is extruded and loaded into the hydrolysis kettle, and the extruded dilute acid is returned to the acid mixer for acid mixing; water vapor with a pressure of 0.45-0.75 MPa is introduced into the hydrolysis kettle to maintain the hydrolysis temperature at 145-180°C , the hydrolysis period is 1.5-4 hours, and the bulk density of plant straw after extrusion is about 260-350kg/m ³ ;

3) The furfural stock solution obtained in the hydrolysis process is introduced into the subsequent process, and the furfural is extracted through the initial distillation tower, and then refined in the furfural continuous refining equipment to finally obtain commercial furfural.

Technical effect of the present invention is:

Compared with the existing corn cob furfural production technology, the present invention has its characteristics, advantages and positive effects mainly reflected in the following aspects.

One is to make the production stable and reliable, capable of continuous operation, and suitable for industrial production.

The second is to improve the screw feeder used in the continuous steaming system of the pulp and paper industry, making it more suitable for extrusion feeding of plant straw, and can make the mixed acid of the material uniform, which is more conducive to the hydrolysis of raw materials, and improves the yield of furfural.

The third is to optimize the hydrolysis process conditions suitable for plant straw particles, expand the range of raw materials for furfural production, reduce the production cost of furfural, increase the yield of furfural, and ensure the quality of furfural.

Fourth, plant straw is cheap and can produce nearly 75% more furfural slag. Using plant straw slag to burn boilers for power generation can generate nearly three-quarters more steam and electricity and save more than simply using corncob slag to burn boilers for power generation About 30-35% coal. The ability to comprehensively utilize plant straw and clean production will make a huge contribution to the national economy.

Fifth, with the improvement of rural economic level, plant straw is no longer used as fuel for burning, but is burned on the spot in the field or piled up in the wild to rot, which not only causes a lot of pollution but also brings great pressure to fire prevention in dry weather. The realization of the invention can solve the problem of waste environmental protection, turn waste into wealth, provide a realistic approach, and enable comprehensive utilization of a large number of plant straws to obtain economic benefits and increase farmers' income.

Detailed ways

Several examples are given below to describe the present invention in detail.

The screw extruding feeder of the present invention adopts the screw feeder used in the continuous steaming system of the pulp and paper industry, and its structure and operating parameters are modified to make it more suitable for plant straw particles. The modified screw feeder is composed of feeding screw, conical shell and plug tube, etc. Its function is to feed materials continuously and evenly, and squeeze out excess dilute acid, so that the raw materials are gradually compressed into dense materials. Plug into the hydrolysis pot, thereby increasing the bulk density of raw materials. The length of the plug tube and the compression ratio are important parameters of the screw feeder, which are generally determined through experiments according to different raw materials. The length of the plug tube is generally 5-15 cm, and the screw with a longer compression section is more adaptable. . The selection of the compression ratio is mainly based on the natural bulk density and compressibility of the raw material (that is, the rate of change of the material density). For plant straw, the compression ratio is generally 1:2 to 1:8. All the other equipments are with prior art.

Example 1:

The raw material is corncobs air-dried in spring, and its water content is 23%. After the corncob is dedusted by a vibrating screen, it is crushed into 1-1.5cm corncob particles by a hammer mill, and then transported by the elevator to the acid mixing truck for acid mixing. The acid concentration is 5-10%, and the amount of acid used is kept at With a specific solid-to-liquid ratio, it is sent to the hydrolysis kettle through a belt conveyor. The volume of the hydrolysis kettle is 10 cubic meters, and the packing density of corncobs is 150-180kg/m ³ . Enter water vapor with a pressure of 0.45-0.75MPa, hydrolyze at a temperature of 145-180°C, and hydrolyze for 2 hours to 4 hours. The furfural stock solution obtained by hydrolysis is introduced into the subsequent process, and the gross aldehyde is extracted, and the furfural is continuously refined to obtain commercial furfural. See Table 1 for details of furfural quality detection indicators. The yield of furfural in this example is 9-10%, and the unit consumption is shown in Table 2 for details.

Example 2:

The raw material is cut, pulverized and granulated corn stalk granules, and the water content of the granules is 27%. It is transported by the hoist to the acid mixing truck for acid mixing. The acid concentration is 5-20%, and the amount of acid used is kept at a specific solid-liquid ratio. It is sent to the hydrolysis tank through the belt conveyor, and the volume of the hydrolysis tank is 10 cubic meters. Rice, using double kettles in series operation, the packing density of corn stalk particles is 300-420kg/m ³ , after filling the hydrolysis kettle, feed water vapor with a pressure of 0.45-0.75MPa, hydrolysis temperature is 145-180°C, hydrolysis for 2 hours to 4 hours. The furfural stock solution obtained by hydrolysis is introduced into the subsequent process, and the gross aldehyde is extracted, and the furfural is continuously refined to obtain commercial furfural. See Table 1 for details of the furfural quality detection indicators in this example. In this example, the yield of furfural is 5.5-6.5%, and the consumption is shown in Table 2 for details.

Example 3:

Cut corn stalks were used as raw materials, and the water content was 22%. After continuous acid mixing and extrusion equipment, the acid concentration is 5-10%, the amount of acid used is kept at a specific solid-to-liquid ratio, and it is continuously sent to the hydrolysis kettle. The volume of the hydrolysis kettle is 10 cubic meters, and a double kettle is used. Operation in series, the packing density of corn stalks after extrusion is 280-300kg/m ³ , after filling the hydrolysis tank, the water vapor with a pressure of 0.45-0.75MPa is introduced, the hydrolysis temperature is 145-180°C, and the hydrolysis takes 2 hours to 4 Hour. The furfural stock solution obtained by hydrolysis is introduced into the subsequent process, and the gross aldehyde is extracted, and the furfural is continuously refined to obtain commercial furfural. See Table 1 for details of the furfural quality detection indicators in this example. In this example, the yield of furfural is 5.5-6.0%, and the consumption is shown in Table 2 for details.

Table 1: Comparison list of the results of furfural quality inspection in the examples and the indicators specified in GB 1926.1-88

Table 2: Example furfural production cost comparison table cost item unit Raw material unit price Example 1 Example 2 Example 3 Unit consumption the amount Unit consumption the amount Unit consumption the amount direct material Corn cob t 360 11 3960 Corn stalks t 100 16.5 1650 16.1 1610 sulfuric acid kg 0.3 623 186.9 858.8 257.64 620.6 186.18 Alkali powder kg 4.000 3.943 4.05 power cost electricity kW·h 0.53 160.5 85.07 256.7 136.05 218.6 115.86 steam t 21.5 21.3 21.7

Claims (1)

1, a kind of method of utilizing the straw extruder grain to produce furfural comprises cut-out, extruding packing, conveying, nitration mixture, extruding dress pot, hydrolysis, the distillation of straw, it is characterized in that:

1), whole straw cut into the particle section of 2～4cm with chaffcutter, then with storing behind the packing machine compression bundling;

2), will tear straw particle section after the bundle open and use after with nitration mixture machine nitration mixture screw extrusion material feeder successive according to 1: 0.3～0.8 solid-to-liquid ratio, pack into after with the straw extruding in the hydrolysis kettle again by 1: 2～1: 8 compression ratio, the diluted acid that extruding is come out turns back to again and carries out nitration mixture in the nitration mixture machine; Feeding pressure in hydrolysis kettle is the water vapour of 0.45～0.75MPa, and keeping hydrolysis temperature is 145～180 ℃, and the hydrolysis cycle is 1.0～4 hours, the about 260～350kg/m of tap density of extruding back straw ³

3), the furfural stoste that obtains in the hydrolytic process is introduced subsequent handling, after primary tower extracts hair aldehyde in furfural continuous treating equipment refining final commodity furfural.