Pretreatment method of corn bran raw material

Abstract

The invention relates to the technical field of ethanol production, in particular to a pretreatment method of a corn bran raw material. The method comprises the following steps: step 1, hot water infiltration, step 2, crushing and grinding, step 3, vacuum filtration, and step 4, basic salt pretreatment. According to the pretreatment method, the corn bran raw material is pretreated, the solid recovery rate is high after the corn bran raw material is processed through the pretreatment method, and most lignin can be removed under the condition that more cellulose and hemicellulose are reserved.

Description

Technical field:

[0001] The invention relates to the technical field of ethanol production, and in particular to a pretreatment method for corn husk raw materials. Background technology:

[0002] Corn husk, i.e. the seed coat of corn kernels, mainly contains hemicellulose, cellulose, lignin, bound starch and protein, accounting for 6% to 10% of the mass of the kernels. Corn fiber fuel ethanol technology is to pre-treat the seed coat of corn kernels to destroy the dense structure of components such as cellulose, hemicellulose and lignin, and then use cellulase system for enzymolysis, and finally use pentose / hexose yeast for fermentation to produce ethanol. Most domestic fuel ethanol plants use the first generation of fuel ethanol technology, which uses corn as raw material and undergoes processes such as liquefaction, saccharification and fermentation to convert the starch in corn into ethanol, while the corn fiber is not converted into ethanol. Unused corn fiber enters the alcohol distillation residue in the late fermentation stage and becomes part of the dry distiller's grains and its solubles (corn dry whole distiller's grains DDGS). It is sold as feed, and the maximum value of corn fiber is not reflected. The starch bound to the corn husk (accounting for 2.6% to 2.8% of the corn kernels) is wrapped in a fiber and protein matrix. This process cannot use this part of starch and cannot convert it into ethanol.

[0003] Corn fiber has a complex structure, high hemicellulose content, and a large number of branches and connecting bonds, and requires pretreatment before conversion.

[0004] Corn husk pretreatment technologies mainly include grinding, acid hydrolysis, high-pressure hot water cooking, steam explosion, ammonia explosion, etc. Corn fiber pretreatment technologies that have been industrially applied abroad mainly include grinding, acid hydrolysis and steam explosion.

[0005] Steam explosion, also known as steam explosion, is the cooking of raw materials under high temperature and high pressure. During this process, the hemicellulose is partially degraded, the cellulose structure swells, the degree of polymerization decreases, and the crystal structure is destroyed. At the end of the reaction, the pressure is released instantly, the material is ejected, the cellulose crystal area is further destroyed, the structure becomes loose, and the cellulose crystal core is exposed, which is conducive to the catalytic degradation of cellulase. Adding chemicals during the steam explosion process can improve the pretreatment effect. Summary of the invention:

[0006] The technical problem to be solved by the present invention is to provide a pretreatment method for corn husk raw materials. The method realizes the pretreatment of corn husk raw materials. After the corn husk raw materials are processed by the pretreatment method of the present invention, the solid recovery rate is high. The present invention can remove most of the lignin while retaining more cellulose and hemicellulose.

[0007] The technical solution adopted by the present invention is: a method for pretreating corn husk raw materials, the method steps are as follows:

[0008] Step 1, hot water soaking: soak the corn husk raw material with 80°C to 100°C hot water for 1h to 2h;

[0009] Step 2, crushing and grinding: using a disc mill or a high-speed mill, grinding or crushing the corn husk raw material into a crushed material with a particle size of 0.5 mm to 1 mm at a speed of 50 r / min to 2000 r / min;

[0010] Step 3: Vacuum filtration: The crushed material is filtered by vacuum using filter paper or filter cloth as the filter medium to obtain filter cake and filtrate;

[0011] Step 4, alkaline salt pretreatment: add filter cake to alkaline salt solution according to 5% to 15% of the mass of alkaline salt solution, soak at 30°C to 50°C for 1h to 4h, transfer to a high temperature and high pressure reactor after soaking, and keep warm at 100°C to 160°C for 0.3h to 2h. After the reaction is completed, separate the solid and liquid, and wash the solid residue with deionized water to neutrality; the filter cake after alkaline salt pretreatment is enzymatically fermented with the filtrate to produce ethanol.

[0012] Furthermore, the corn husk raw material is corn husk coarse material obtained from the starch industry.

[0013] Furthermore, the corn husk raw material is wet distiller's grains obtained by corn fermentation, and the wet distiller's grains obtained by corn fermentation contain corn husks.

[0014] Furthermore, the corn husk raw material is corn dried whole distiller's grains feed, and the corn dried whole distiller's grains feed contains corn husks.

[0015] Furthermore, the alkaline salt is a weak alkaline salt, and the weak alkaline salt is sodium phosphate, sodium acetate, sodium carbonate, sodium sulfide, sodium hypochlorite or sodium silicate.

[0016] Furthermore, the concentration of the weak alkaline alkaline salt solution is 2% to 20% by mass.

[0017] Furthermore, the concentration of the weak alkaline salt solution is 2% to 15% by mass.

[0018] The beneficial effects of the present invention are:

[0019] 1. Pre-treating the corn husk raw material. After the corn husk raw material is processed by the pre-treatment method of the present invention, the solid recovery rate is high;

[0020] 2. The present invention can remove most of the lignin while retaining more cellulose and hemicellulose. Specific implementation method:

[0021] Example 1: Pretreatment method using corn husk obtained from starch industry as raw material

[0022] Corn husks obtained from the starch industry were tested for components: protein content was 10.17%, crude cellulose content was 15.48%, moisture content was 6.7%, and ash content was 1.15%. 100g of corn husk raw material was placed in a beaker and soaked with 700ml of 80℃ hot water for 1h; the soaked material was ground with a disc mill at a speed of 1000r / min, and then sieved with a 0.5mm-1mm screen; filter paper or filter cloth was used as the filter medium, and vacuum filtration was used to obtain filter cake and filtrate; 88.63g of filter cake was added to 1000g of 2% (mass fraction) Na3PO4 solution, sealed with plastic wrap, and soaked at 30℃ for 4h, and the soaked corn husk was poured into a 2L high temperature and high pressure reactor, the temperature was raised to 140℃, and the temperature was kept for 0.3h. After the reaction was completed, the temperature was cooled in an ice water bath for 10min, solid-liquid separation was performed, and the solid residue was washed with deionized water until neutral. The solid recovery rate of the pretreated sample was 71.92%. The crude fiber content of the pretreated sample was 35.56%.

[0023] Example 2: Pretreatment method using corn husk obtained from starch industry as raw material

[0024] Corn husks obtained from the starch industry were tested for components: protein content was 10.17%, crude cellulose content was 15.48%, moisture content was 6.7%, and ash content was 1.15%. 100g of corn husk raw material was placed in a beaker and soaked with 700 ml of 100℃ hot water for 2 hours; the soaked material was ground with a disc mill at a speed of 1000r / min, and then sieved with a 0.5mm-1mm screen; filter paper or filter cloth was used as the filter medium, and vacuum filtration was used to obtain filter cake and filtrate; 88.15g of filter cake was added to 1000g of 7% (mass fraction) Na3PO4 solution, sealed with plastic wrap, and soaked at 30℃ for 4 hours, and the soaked corn husk was poured into a 2L high temperature and high pressure reactor, the temperature was raised to 140℃, and the temperature was kept for 1 hour. After the reaction, the reaction was cooled in an ice water bath for 10 minutes, solid-liquid separation was performed, and the solid residue was washed with deionized water until neutral. The solid recovery rate of the pretreated sample was 56.67%. The crude fiber content of the pretreated sample was 50.13%.

[0025] Example 3: Pretreatment method using corn husk obtained from starch industry as raw material

[0026] Corn husks obtained from the starch industry were tested for components: protein content was 10.17%, crude cellulose content was 15.48%, moisture content was 6.7%, and ash content was 1.15%. 100g of corn husk raw material was placed in a beaker and soaked with 700ml of 90℃ hot water for 2h; the soaked material was ground with a disc mill at a speed of 1000r / min, and then sieved with a 0.5mm-1mm screen; filter paper or filter cloth was used as the filter medium, and vacuum filtration was used to obtain filter cake and filtrate; 87.49g of filter cake was added to 1000g of 15% (mass fraction) Na3PO4 solution, sealed with plastic wrap, and soaked at 30℃ for 4h, and the soaked corn husk was poured into a 2L high temperature and high pressure reactor, the temperature was raised to 140℃, and the temperature was kept for 1h. After the reaction was completed, the temperature was cooled in an ice water bath for 10min, solid-liquid separation was performed, and the solid residue was washed with deionized water until neutral. The solid recovery rate of the pretreated sample was 45.91%. The crude fiber content of the pretreated sample was 59.66%.

[0027] Example 4: Pretreatment method using corn husk obtained from starch industry as raw material

[0028] Corn husks obtained from the starch industry were tested for components: protein content was 10.17%, crude cellulose content was 15.48%, moisture content was 6.7%, and ash content was 1.15%. 100g of corn husk raw material was placed in a beaker and soaked with 700ml of 95℃ hot water for 1h; the soaked material was ground with a disc mill at a speed of 1000r / min, and then sieved with a 0.5mm-1mm screen; filter paper or filter cloth was used as the filter medium, and vacuum filtration was used to obtain filter cake and filtrate; 87.26g of filter cake was added to 1000g of 20% (mass fraction) Na3PO4 solution, sealed with plastic wrap, and soaked at 30℃ for 4h, and the soaked corn husk was poured into a 2L high temperature and high pressure reactor, the temperature was raised to 140℃, and the temperature was kept for 0.8h. After the reaction was completed, the temperature was cooled in an ice water bath for 10min, solid-liquid separation was performed, and the solid residue was washed with deionized water until neutral. The solid recovery rate of the pretreated sample was 40.95%. The crude fiber content of the pretreated sample was 63.27%.

[0029] Example 5: Pretreatment method using wet distiller's grains obtained from corn fermentation as raw material

[0030] The components of the wet distiller's grains obtained by corn fermentation were determined as follows: protein content was 18.52%, crude cellulose content was 6.5%, moisture content was 30.2%, and ash content was 6.7%. 100g of the wet distiller's grains raw material was placed in a beaker and soaked with 600ml of 85℃ hot water for 2h; the soaked material was ground into a particle size of 0.5mm-1mm using a pulverizer with a rotation speed of 2000r / min; a filter cake and filtrate were obtained by vacuum filtration using filter paper or filter cloth as the filtration medium; 66.549g of the filter cake was added to 592g of 9% (mass fraction) Na3PO4 solution, sealed with plastic wrap, placed in a 40℃ environment and soaked for 2h, the soaked corn husks were poured into a 1L high temperature and high pressure reactor, the temperature was raised to 140℃, and the temperature was kept for 1h. After the reaction, the reaction was cooled in an ice water bath for 10min, solid-liquid separation was performed, and the solid residue was washed with deionized water until neutral. The solid recovery rate of the sample after pretreatment was 59.2%. The crude fiber content of the sample after pretreatment was 41.51%.

[0031] Example 6: Pretreatment method using DDGS as raw material

[0032] DDGS determination components: protein content is 20.52%, crude cellulose content is 7.2%, moisture content is 12.3%, ash content is 7.8%. Take 100g of DDGS raw material in a beaker, soak it with 800ml of 90℃ hot water for 2h; grind the soaked material into a particle size of 0.5mm~1mm with a pulverizer with a rotation speed of 2000r / min; use vacuum filtration, use filter paper or filter cloth as the filter medium to obtain filter cake and filtrate; add 74.898g of filter cake to 500g of 5% (mass fraction) Na3PO4 solution, seal it with plastic wrap, place it in a 30℃ environment and soak it for 4h, pour the soaked corn husk into a 500mL high temperature and high pressure reactor, raise the temperature to 120℃, keep it warm for 0.75h, cool it in an ice water bath for 10min after the reaction, separate the solid and liquid, wash the solid residue with deionized water to neutrality, and the solid recovery rate of the pretreated sample is 48.6%. The crude fiber content of the sample after pretreatment was 25.01%.

[0033] Example 7: Pretreatment method using wet distiller's grains as raw material and enzymatic fermentation to produce ethanol

[0034] The wet distiller's grains obtained from the corn fuel ethanol device were used as raw materials, and the pretreated material was prepared according to the method of Example 2. There was no obvious change in the color of the wet distiller's grains raw materials before and after the pretreatment. The distiller's grains recovery rate was 59.2%.

[0035] The solid residue and the filtrate obtained by vacuum filtration were enzymatically fermented to produce ethanol. After 60 minutes of hydrolysis, the glucose concentration in the hydrolyzate was 37.26 g / L and the xylose concentration was 58.48 g / L. Yeast was inoculated for ethanol fermentation test. After 48 hours of fermentation, the ethanol concentration reached 23.92 g / L and the residual glucose dropped to 0.41 g / L.

[0036] Comparative Example: Dilute acid pretreatment method using wet vinasse as raw material and enzymatic fermentation method for producing ethanol

[0037] Wet distiller's grains obtained from corn fuel ethanol plant were used as raw materials. 100 g was taken into a beaker, and 567 g of 0.7% (mass fraction) dilute sulfuric acid solution was added. The reaction was carried out at 140°C for 20 minutes, and the distiller's grains recovery rate was 40.8%. The color of the distiller's grains raw materials after pretreatment was deepened.

[0038] The pretreated lees were enzymatically fermented to produce ethanol. After 60 minutes of hydrolysis, the glucose concentration in the hydrolyzate was 24.84 g / L and the xylose concentration was 39.59 g / L. Yeast was inoculated for ethanol fermentation. After 48 hours of fermentation, the ethanol concentration reached 14.35 g / L and the residual glucose dropped to 0.62 g / L.

[0039] It can be understood that the above specific description of the present invention is only used to illustrate the present invention and is not limited to the technical solutions described in the embodiments of the present invention. Those skilled in the art should understand that the present invention can still be modified or replaced by equivalents to achieve the same technical effects; as long as the use requirements are met, they are within the protection scope of the present invention.

Claims

1. A method for pretreating corn husk raw material, characterized in that: The steps of this method are as follows: Step 1, hot water soaking: soak the corn husk raw material with 80°C to 100°C hot water for 1h to 2h; Step 2, crushing and grinding: using a disc mill or a high-speed mill, grinding or crushing the corn husk raw material into a crushed material with a particle size of 0.5 mm to 1 mm at a speed of 50 r / min to 2000 r / min; Step 3: Vacuum filtration: The crushed material is filtered by vacuum using filter paper or filter cloth as the filter medium to obtain filter cake and filtrate; Step 4, alkaline salt pretreatment: add filter cake to alkaline salt solution according to 5% to 15% of the mass of alkaline salt solution, soak at 30°C to 50°C for 1h to 4h, transfer to a high temperature and high pressure reactor after soaking, and keep warm at 100°C to 160°C for 0.3h to 2h. After the reaction is completed, separate the solid and liquid, and wash the solid residue with deionized water to neutrality; the filter cake after alkaline salt pretreatment is enzymatically fermented with the filtrate to produce ethanol.

2. The method for pretreating corn husk raw material according to claim 1, characterized in that: The corn husk raw material is corn husk coarse material obtained from the starch industry.

3. The method for pretreating corn husk raw material according to claim 1, characterized in that: The corn husk raw material is wet distiller's grains obtained by corn fermentation, and the wet distiller's grains obtained by corn fermentation contain corn husks.

4. The method for pretreating corn husk raw material according to claim 1, characterized in that: The corn husk raw material is corn dried whole distiller's grains feed, and the corn dried whole distiller's grains feed contains corn husk.

5. The method for pretreating corn husk raw material according to claim 1, characterized in that: The alkaline salt is a weak alkaline salt, and the weak alkaline salt is sodium phosphate, sodium acetate, sodium carbonate, sodium sulfide, sodium hypochlorite or sodium silicate.

6. The method for pretreating corn husk raw material according to claim 5, characterized in that: The concentration of the weak alkaline salt solution is 2% to 20% by mass.

7. The method for pretreating corn husk raw material according to claim 6, characterized in that: The concentration of the weak alkaline salt solution is 2% to 15% by mass.