(a) molasses dilution process requirements
Molasses is generally hammered 80-90Bx, containing more than 50% sugar, must be diluted with water before fermentation, in the process known as dilution, dilution of molasses concentration varies with the production process and operation, usually molasses dilution of the process conditions:
(1) a single-concentration process of diluted sugar solution concentration of 22% ~ 25%
(2) double concentration process mother of wine diluted sugar solution 12% to 14%
basic diluted sugar solution 33% to 35%
(2) molasses dilution method
Molasses dilution method can be divided into intermittent and continuous method of two kinds:
⒈ ⒈ Intermittent Dilution Method
Molasses diluted intermittently in a dilution tank; dilution tank with a stirrer. If the factory original saccharification pot equipment, generally use the saccharification pot for dilution equipment.
Molasses intermittent dilution method is the first molasses from the pump into the high tank, after weighing the scale into the dilution tank, while adding a certain amount of water, turn on the agitator to fully mix, that is, the required concentration of dilute sugar solution, after filtration can be used for the mother of wine culture and fermentation.
Peak continuous dilution method
Chinese molasses alcohol factory mostly use continuous dilution method, molasses continuous dilution is carried out through the continuous diluter, commonly used continuous diluter has the following two types:
1) continuous diluter without agitator, the diluter is a cylindrical tube, along the length of the tube is equipped with a number of holes plate partition and a sieve, in order to make the molasses and water better mixing, the plate on the water, the molasses and the water, the molasses and the water, the water, the water, the sugar and the water. In order to make better mixing of molasses and water, the holes on each plate are staggered, i.e., one hole is in the upper part and one hole is in the lower part, so that the liquid in the flow process is turbulent movement, and the diameters of the holes on the partition plates are calculated based on ensuring turbulent flow of the liquid in the apparatus. The partition is fixed on a pair of horizontal shafts and can be dismantled together with the shafts for cleaning. Diluter is usually installed with the outlet end tilted downward, this diluter has a better mixing effect and also saves power.
(2) vertical continuous diluter the diluter is also a cylindrical tube, it is the use of cross-sectional area is constantly changing, to ensure that the liquid in the turbulent flow to achieve the purpose of the molasses and water evenly mixed. When the molasses is continuously diluted, the molasses is first sent to the high level tank by a pump, and then flows to the diluter by means of the potential pressure to mix with the hot water from another high level tank. Ensure a certain concentration of dilute sugar solution is the key to continuous diluter operation, adjusting the concentration of dilute sugar is relying on the corresponding valve with manual control, in large factories using a linkage pump that can adjust the flow of water and molasses to control.
(C) dilution of molasses water calculation
Molasses dilution, control of the concentration of dilute sugar is a key link, in order to prepare a certain concentration of dilute sugar and accurate calculation of the amount of water and molasses required, can usually be calculated using the following formula:
Pc=V-d-c1
The formula p --amount of molasses (kg)
c --concentration of molasses (Bx)
V --volume of diluted sugar solution (kg)
d - specific gravity of the diluted sugar solution
c1 - concentration of the diluted sugar solution (Bx)
The amount of molasses required:
P=V-d-C1/C
The amount of water required to be added to the dilution law is w, < /p>
Then W=Yd-p
And V-d=pC/C1
W=PC/C1-P
∴W=P(C-C1)/C1 Considering that there are many impurities such as ash and colloidal substances in molasses, contamination by harmful microorganisms , the lack of nutrient salts and the adjustment of suitable acidity. Therefore, at the same time as molasses dilution, acidification, sterilization, clarification and addition of nutrient salts must be carried out. Intermittent dilution operation law is carried out one by one. China's molasses alcohol plant more than continuous dilution of hot acid clarification of molasses, acidification, sterilization, adding nutrient salts and clarification at the same time together.
Climate ⒈ molasses acidification
Molasses acid acidification is to prevent the propagation of stray bacteria, accelerate the molasses ash and colloidal material precipitation, while adjusting the acidity of the dilute sugar solution, so that it is suitable for the growth of yeast. Because sugar cane molasses is slightly acidic, sugar beet molasses is slightly alkaline, and yeast fermentation optimal pH 4.0-4.5, so the process requires molasses dilution to add acid. For beet molasses, adding acid can make the Ca++ generate calcium sulfate precipitation, thus accelerating the molasses in the colloidal material and ash together with precipitation and removal.
The method of adding acid varies slightly from place to place. Usually intermittent fermentation, the more common is to use the method of adding acid to the dilute sugar solution. There is also acid added directly to the molasses, but this method is rarely used in China. Molasses alcohol factories in China mostly use molasses diluted to 40-60%, then add acid, then heat to clarify, take the clear liquid and then dilute. This can not only improve the sterilization effect of acid, but also accelerate the precipitation, and can reduce the volume of acidification equipment, improve equipment utilization. Its advantages are: molasses must only be diluted once, simplifying the production process, is conducive to the implementation of automation; add acid can be carried out outdoors to reduce the height of the plant; no need to set up a separate acid pipeline. But the disadvantage is: due to the viscosity of molasses, in order to ensure that the molasses and acid evenly mixed, there must be a special mixer; acidified storage. Tank walls must be coated with leaching varnish or paved PVC boards and other acid-resistant materials. Molasses acidification, usually with sulfuric acid to acidification, can also be used hydrochloric acid, but with hydrochloric acid, in the future production process does not generate precipitation, and sulfate is one of the main reasons for the accumulation of scale production equipment. Acidification with hydrochloric acid after the recovery of yeast color is better, because the Cl- ions can play a certain role in bleaching, but hydrochloric acid is more corrosive, in the absence of acid-resistant materials, the use of hydrochloric acid with some difficulty.
Add acid amount and method generally vary with the type of molasses, sugar cane molasses dilution can be added directly to the amount of dilute sugar 0.2-0.3% of the concentrated sulfuric acid, mixing can be, the amount of acid (specific gravity of 1.86, 66Be industrial sulfuric acid) 2-3.5 liters/1 ton of molasses; or 0.7-l liters/1m3 of molasses; or 0.7-l liters/1m3 of molasses; or 0.7-l liters/1m3 of molasses. -l liter/1m3 fermentation mash. Sugar beet molasses is mostly alkaline, so the amount of acid used is more than sugar cane molasses, for a single concentration process, the basic dilute sugar solution generally do not add acid, while the mother of the dilute sugar solution acidity should be 6-7 °.
Beet molasses in the organic alkali (-NH2), in the addition of acid and acid can release a highly toxic yellow-brown gas NO2, in order to avoid poisoning, acidification tanks must have exhaust holes, acidification section should have good ventilation equipment.
Peak molasses sterilization
Molasses is often contaminated with a large number of microorganisms, including wild yeast, Candida albicans, and lactobacilli a class of acid-producing bacteria. In order to prevent the sugar solution contaminated bacteria, to ensure the normal fermentation, in addition to adding acid to improve the acidity of the sugar solution, it is best to also be sterilized, there are two methods of sterilization:
1) heating sterilization through the steam heated to 80-90 ° C, maintained for 1 hour, you can achieve the purpose of sterilization. Dilute sugar solution heating in addition to sterilization, but also conducive to the clarification effect, but the heating process requires a large amount of steam consumption, and the need for additional cooling, clarification equipment, the general factory should not be used.
(2) drug preservation Chinese molasses alcohol factory commonly used preservatives are: bleaching powder, dosage of 200-500 grams per ton of molasses; formaldehyde, dosage of 40% formaldehyde 600 ml per ton of molasses; sodium fluoride, dosage of mash 0.01%; sodium pentachlorophenol, dosage of 0.004%. The structural formula of sodium pentachlorophenol is shown on the right. When used, it should be noted that it decomposes into pentachlorophenol and sodium salt in an acidic environment, so it should be added to the unacidified molasses dilution.
The alcohol workshop of Jilin New China Sugar Factory in China had used many kinds of drugs to sterilize the molasses with serious bacterial contamination test, respectively, by adding the content of 92% of the sodium pentachlorophenol 0.0004, the content of 40% of the formaldehyde 0.084%, and the bleaching powder 0.006%. The test results indicate that sodium pentachlorophenol is the most effective, bleach is the second most effective, and formaldehyde is even less effective.
In recent years, antimicrobial substances have also been used to prevent contamination of stray bacteria during fermentation. Some Soviet alcohol factories use a kind of antimicrobial substances called anti-lactobacillus, which is isolated from the mycelium of purple actinomycetes 135/1, when added to the fermentation broth l-20 micrograms / ml (dissolved in 50% alcohol solution), it can inhibit lactic acid bacteria activities, without affecting the growth of molds and yeasts. Molasses fermentation with the addition of a dose of 0.005% of anti-lactobacillus, does not affect the yield and quality of alcohol, while the inhibition of lactic acid bacteria is very effective.
Molasses clarification
Molasses contains a lot of colloidal material, ash and other suspended substances, its presence on the growth of yeast and alcohol fermentation are harmful, so it should be removed as far as possible, the clarification of molasses methods:
(1) add acid ventilation precipitation method, which is also known as the cold acid ventilation treatment method. Molasses diluted with water to about 50Bx, add 0.2% ~ 0.3% sulfuric acid, through the compressed air for 1 hour, static clarification of 8 hours, remove the supernatant as the preparation of sugar with ventilation on the one hand, can be driven away from harmful gases such as SO2 or NO2, as well as volatile acids and other volatile substances; on the other hand, can increase the oxygen content of the sugar solution to increase the oxygen coefficient of the solution in order to facilitate the proliferation of yeast.
(2) hot acid treatment method at higher temperatures and acidity, the sterilization of harmful microorganisms in the molasses and colloidal substances, ash impurities in the clarification of the settling effect are stronger. The use of hot acid treatment method, usually acid sterilization and clarification at the same time, process in the original molasses dilution, the use of stage dilution method. In the first stage, the molasses is first diluted to 55~58Bx with 60℃ warm water, and at the same time, concentrated sulfuric acid is added to adjust the acidity, PH3.0-3.8, for acidification, and then left to stand for 5-6 hours. In the second stage, the sugar solution that has been acidified is then diluted to the concentration of 12-14% required for the yeast culture solution, while the molasses for the fermentation mash is diluted to the required concentration by adding water at one time through a continuous diluter. It then flows into the main fermenter.
In addition, an alcohol plant in China using hot acid ventilation precipitation process is as follows: molasses diluted with water to a concentration of 40%, and then add a certain amount of sulfuric acid, the pH will be adjusted to 4.0-4.5, and put the clarification tank is heated to 80-90 ° C, ventilated for 30 minutes, ventilated and then held at 70-80 ° C static clarification of 8-12 hours, and then take out the upper layer of clear liquid cooling, and later processing According to the general process flow. The resulting precipitated material can be added 4-5 times the water to mix thoroughly, and then static clarification of 4-5 hours, the resulting clarified solution can be used as the next dilution of molasses water, the residue is discarded. From the purification effect, this method is better than the cold acid ventilation treatment. But the disadvantages of this method are: longer clarification time, need more clarification barrels, covers a large area, spend more labor. From the reduction of equipment corrosion, no cooling equipment, shorten the production cycle, large-scale production using cold acid ventilation precipitation method is more appropriate. Some domestic factories test to add polyacrylamide (PAM) flocculant for the mother of wine dilute sugar liquid clarification treatment, can greatly reduce the clarification time. Polyacrylamide is composed of about 40,000 propionamide monomer CH2=CH-CONH2.
Add flocculant to accelerate the clarification of the settlement process is as follows: first molasses diluted with water 40-50Bx, add a certain amount of sulfuric acid pH 3.0-3.8, heating 100 ℃, add 8 ppm PAM, stirring, flocculation clarification of the static for 1 hour, take the supernatant can be prepared for the dilute sugar solution.
Most of the domestic molasses alcohol plant is only considered to be used as the mother of the dilute sugar solution for clarification, while the basic sugar solution is not clarified, which can greatly simplify the production and improve efficiency.
(3) mechanical separation method using filter press or centrifuge separation method.
Sung Nutrient Salt Addition
Yeast needs a certain amount of nitrogen, phosphorus, growth factors, magnesium salts, etc. for growth and reproduction. Fresh sugarcane juice or beet juice contains enough nitrogen compounds, phosphates and growth factors for yeast, but most of them have disappeared due to sugar production and molasses treatment. Molasses due to the different methods of sugar production, the composition is different, often lack of yeast nutrients in the dilute sugar solution, not only directly affect the growth of yeast, but also affect the yield of alcohol. Therefore, molasses must be analyzed to check whether the lack of nutrients, to understand the extent of the lack, and then add the necessary nutrients appropriately.
1) Nutrients and growth factors to be added to sugarcane molassesSugarcane molasses for yeast requires the addition of nitrogen sources, phosphorus sources, magnesium salts and growth factors.
①Nitrogen sourceThe amount of nitrogen needed can be calculated based on the number of yeast cells and the amount of nitrogen in the molasses. For example, each milliliter of mature mother mash contains 150 million yeast cells, i.e., one liter contains 150 billion, and each 100 million yeast weighs 0.07 grams, so the weight of yeast cells in each kilogram of mother mash is 1500 × 0.07 = 10.5 grams.
It is known that the nitrogen content of fresh yeast is 2.1%, so the nitrogen content of each kilogram of mother liquor mash is 10×0.021=0.21 grams, and 150 grams of molasses is used to prepare one kilogram of mother liquor mash.
Sugarcane molasses contains about 0.5% nitrogen, which can be utilized by the yeast amino nitrogen and other nitrogen is only 20% to 25%, that is, 150 grams of molasses contains 0.15 grams of nitrogen that can be utilized, the nitrogen in the sugarcane molasses can not satisfy the needs of the growth and reproduction of the yeast, so the sugarcane molasses needs to be added to the source of nitrogen.
China's sugarcane molasses alcohol factories generally use ammonium sulfate (NH4) 2SO4 as a source of nitrogen, because ammonium is easy to be digested by the yeast, the amount of nitrogen per ton of molasses to add 21% of ammonium sulfate 1.0-1.2 kilograms, i.e., 0.1% to 0.12%, more than 1 gram of ammonium sulfate per liter of molasses added to the area of Neijiang, Sichuan. Some factories add urea, urea nitrogen content of 46%, and thus can be appropriately reduced dosage, usually half the amount of ammonium sulfate.
Some factories add yeast autolysate as a nitrogen supplement to the dilute sugar solution. Take the separation of alcohol yeast mud, placed in 35% ~ 40 ℃ temperature, so that the yeast cells autolysis, through the body of the protease yeast cell decomposition into amino acids as a nitrogen source of supplementation, so that can reduce the amount of ammonium sulfate 3/4.
Some factories add bran as a supplement to the nitrogen source. Bran is rich in protein, but can not be used directly for the yeast, such as the proteolytic capacity of Aspergillus glutinosa made of bran, and then heated to 50 ℃, insulation for 6 hours, you can make the protein decomposition into soluble nitrogen, at the same time Aspergillus can also synthesize the growth of the yeast needs, so add bran in addition to supplementing the nitrogen source of the dilute sugar solution, but also supplement the growth of the growth of the elements, which can be a great saving of ammonium sulfate and urea.
② phosphorus source of Chinese sugar cane molasses alcohol plant added phosphate, most of the use of sodium, potassium, ammonium, calcium salts, because the solution is acidic, suitable for yeast growth and reproduction and alcoholic fermentation, the common use of calcium superphosphate, the dosage of molasses 0.25-0.3%
③ magnesium salt magnesium salt presence not only promotes the growth and reproduction of yeast. Expand the effectiveness of yeast growth factor, but also to promote alcoholic fermentation, because the catalytic reaction of the kinase prerequisite is inseparable from the Mg + +, at the same time, the yeast growth factor needs to have magnesium salts *** with the presence of the performance. Therefore, the addition of magnesium salt in the production of alcoholic fermentation is of practical significance to improve the fermentation rate. China's molasses alcohol plant usually add magnesium sulfate, the amount of molasses 0.04-0.05%.
Magnesium chloride or magnesium nitrate alone added to dilute sugar solution has no effect, such as with ammonium sulfate at the same time, there is to promote the effectiveness.
4 growth factors yeast necessary growth factors are vitamin B1, vitamin B2, with nicotinic acid, inositol, biotin and pantothenic acid, etc., a variety of molasses in the growth factors due to high temperature evaporation in the sugar process or molasses processing when heated and destroyed, it is appropriate to add the appropriate yeast growth factors, generally is to add an appropriate amount of corn paddles, rice bran or parabranched autolysates as a supplement to the yeast growth factors. However, from the production practice of selection and breeding of isolated domesticated yeast strains, the requirement for growth factor is not prominent, so the large-scale production of the use of added growth factor is less. However, for the alcoholic fermentation of low-purity molasses and poor-quality molasses, the requirement for growth factors deserves attention.
(3) Nutrient Salts Required to be Added to Beet Molasses In beet molasses there is often a sufficient source of nitrogen and only a lack of phosphate, and based on a nitrogen content of 0.21 grams per liter of the mother mash, and 150 grams of molasses used in the preparation of each liter of the mother mash, the beet molasses contains about 1.5 to 3 grams of nitrogen. It is known that 50% of the nitrogen in beet molasses can be utilized by the yeast during aeration, i.e. 150 grams of molasses contains 0.75-1.5 grams of nitrogen that can be utilized, which is 6 times the amount needed, so generally beet molasses is not deficient in nitrogen under aeration. However, in the non-aerated culture of wine mother, and sometimes molasses containing low amount of injustice, can be added to the ammonium sulfate or yeast from the solution to supplement the nitrogen source, the general ammonium sulfate (nitrogen content of 21%) dosage of molasses of 0.36-0.40%.
Generally beet molasses alcohol plants are used as a phosphorus source of calcium superphosphate, its dosage for the amount of beet molasses 1%, leachate concentration of 5-6%, and directly with phosphoric acid as a phosphorus source of phosphoric acid, industrial phosphoric acid content of 70% (specific gravity of 1.5), the dosage of 0.03% (on the count of sugar beet molasses). In addition, also available diammonium hydrogen phosphate (NH4) 2HPO4 as a source of phosphorus, which in addition to phosphorus, but also contains 20% of nitrogen, so you can properly reduce the amount of ammonium sulfate.