Fermentation technology of beer fermentation technology

Modern fermentation technology mainly includes large-capacity fermentation tank fermentation method (which is mainly cylindrical open-air conical fermentation tank fermentation method), high-concentration saccharification and then dilution fermentation method, continuous fermentation method and so on.

(a) conical fermenter fermentation method

Traditional beer is in the square or rectangular fermentation tank (or pool), the volume of equipment is only 5 ~ 30m, beer production scale is small, the production cycle is long. 1950s, due to the rapid development of the world economy, the scale of beer production has increased dramatically, the traditional fermentation equipment in order to meet the production needs, large-capacity fermentation equipment has attracted attention. Large-capacity fermentation equipment has been emphasized. The so-called large-capacity fermenter refers to the volume of the fermenter compared with the traditional fermentation equipment. Large-capacity fermenters include cylindrical conical fermenters, sunrise tanks, universal tanks and spherical tanks. Cylindrical conical fermenter is currently the world's common fermenter, the tank body is cylindrical, the top of the tank for the arc, the bottom of the conical, with a considerable height (height greater than the diameter), the tank is equipped with a cooling and insulation device, for the fully enclosed fermenter. Cylindrical conical fermenter is suitable for both below the fermentation, but also for the top fermentation, processing is very convenient. German brewer invented the vertical cylindrical conical fermenter because of its many advantages, after continuous improvement and development, and gradually in the world to be popularized and used. China since the mid-1970s, began to use outdoor cylindrical conical bottom fermenter fermentation method (referred to as the conical tank fermentation method), the current domestic beer production almost all use this fermentation method.

1. The characteristics of the conical tank fermentation method

(1) the bottom of the conical to facilitate the production process at any time to discharge the yeast, the requirements of the cohesive yeast.

(2) The tank itself has a cooling device, easy to control the fermentation temperature. The production is easy to control, the fermentation cycle is shortened, there is less chance of bacterial contamination, and the quality of beer is stable.

(3) The tank is equipped with a heat preservation device, and the tank can be placed outdoors, which reduces construction investment, saves floor space and facilitates expansion.

(4) Adopting airtight tank, it is convenient for CO2 washing and CO2 recovery, and fermentation can be carried out under certain pressure. It can be used as a fermentation tank, also can be used as a wine storage tank, also can be fermentation and wine storage into one, called a tank fermentation method.

(5) The fermentation liquid in the tank produces a CO2 gradient (i.e., forms a density gradient) due to the height of the liquid. Through cooling control, the fermentation liquid can be subjected to natural convection, and the higher the tank, the stronger the convection. Due to the presence of strong convection, the yeast fermentation capacity is increased, the fermentation rate is accelerated and the fermentation cycle is shortened.

(6) The fermentation tank can be controlled by meter or microcomputer, which is convenient for operation and management.

(7) The conical tank is suitable for both below and above fermentation.

(8) CIP automatic cleaning device can be used, easy to clean.

(9) The conical tank is easy to process (can be processed on-site) and is practical.

(10) The capacity of the equipment can be flexibly adjusted according to the production needs, and the capacity can be varied from 20 to 600m, up to 1500m.

2. The working principle of the conical tank and the tank structure

(1) The working principle of the conical fermenter

The reason for the conical tank fermentation method of the short fermentation cycle and the fast fermentation speed is due to the hydrodynamic characteristics of the fermentation liquid in the conical tank and the modern beer fermentation method. hydrodynamic properties and the results of modern beer fermentation technology used.

After inoculation of yeast, due to the cohesive effect of yeast, which makes the cell density of yeast at the bottom of the tank increase, resulting in faster fermentation, the amount of carbon dioxide produced during the fermentation process increases, and at the same time, due to the hydrostatic pressure generated by the height of the column of fermentation liquid, but also make the carbon dioxide content with the change of the liquid layer is a gradient change (see Table 4-3-1), and therefore the density of the fermentation liquid in the tank also shows a gradient change,. In addition, the temperature at each stage of fermentation can be artificially controlled due to a cooling device outside the conical tank. Under the action of these driving forces of static pressure difference, fermentation liquid density difference, carbon dioxide release effect and temperature difference generated by the cooling of the upper part of the tank (1 ~ 2 ℃), the fermentation liquid in the tank produces a strong natural convection, which enhances the contact between the yeast and the fermentation liquid and promotes the metabolism of the yeast, so that the speed of beer fermentation is accelerated greatly, and the beer fermentation cycle is shortened significantly. In addition, the increased inoculation temperature, beer main fermentation temperature, diacetyl reduction temperature and yeast inoculation volume also favored the acceleration of yeast fermentation, thus enabling the fermentation to proceed rapidly.

(2) Basic structure of conical fermenter

①Top part

The top of the tank is a domed structure, the central hole is used to place a removable large-diameter flange for installing CO2 and CIP pipelines and their connectors, and the top of the tank is also installed with anti-vacuum valves, over-pressure valves, pressure sensors and so on, and the inner side of the tank is fitted with a washing device, and there are platforms and passages installed for the top of the tank. The inner side of the tank is equipped with a scrubbing device, as well as a platform and access for operation on the top of the tank.

②Tank part

The tank is a cylinder, which is the main part of the tank. The height of the fermenter depends on the diameter and height of the cylinder. Due to the large diameter of the tank low pressure, the general diameter of the conical tank does not exceed 6 m. The processing of the tank is easier than the top of the tank, the tank is used for the installation of the external cooling device and insulation, and to leave a certain position to install the temperature and pressure measurement components. Tank part of the cooling layer has a variety of forms, such as coils, Miller wrench, jacketed, and is divided into 2 to 3 sections, with the pipeline leading to the cooling medium into the pipe connected to the cooling layer covered with polyurethane foam plastic and other thermal insulation materials, thermal insulation and then wrapped in a layer of aluminum alloy or stainless steel plate, there is also the use of colored steel plate for the protective layer.

3 conical bottom part

The angle of the conical bottom is generally 60º~80º, there are 90º~110º, but this is mostly used for large-capacity fermentation tanks. Cone bottom height of the fermenter with the angle, the smaller the angle of the cone bottom part of the higher. General tank height of the bottom of the cone accounted for about 1/4 of the total height, do not exceed 1/3. cone bottom of the outer wall should be set up to cool the cooling layer, in order to cool the bottom of the cone precipitation of yeast. The bottom of the cone should also be installed in and out of the pipeline, valves, mirrors, temperature and pressure sensing elements.

In addition, the tank diameter and height ratio is usually 1:2 ~ 1:4, the total height of the best not to exceed 16m, so as not to cause strong convection, affecting the yeast and coagulation settlement. Tank material can be stainless steel or carbon steel, if you use carbon steel, the inner wall of the tank must be coated with non-toxic coatings that do not affect the taste of beer. The working pressure of the fermentation tank can be determined according to the nature of the work of the tank, the general working pressure of the fermentation tank is controlled at 0.2 ~ 0.3MPa. The inner wall of the tank must be smooth and flat, stainless steel tank inner wall should be polished, carbon steel tank inner wall coating should be uniform, no concave and convex surfaces, and no granular protrusions.

(3) conical fermentation tank to determine the main dimensions

①Ratio of diameter and height conical tank was cylindrical cone bottom shape, the ratio of the diameter of the cylinder body and the height of 1:1 ~ 4. Generally the larger the diameter and height of the ratio of the fermentation of natural convection is more intense, the yeast fermentation speed, but the yeast is not easy to settle, the beer clarification difficulties. General diameter and wort level total height ratio should be 1:2, diameter and columnar part of the wort height ratio should be 1:1 ~ 1.5.

② tank capacity The larger the capacity of the tank, the longer the wort full tank time, the fermentation of proliferation of more, longer, will cause the formation of bis-acetyl precursor substances increased, bis-acetyl production, reduction of time is long. In addition, it will also cause the non-production time such as wine discharge, cleaning, re-feeding wort, etc. to be extended, and the peak value of the peak cooling period is high, resulting in a tight cooling supply. Due to the release of carbon dioxide and foam production, the effective volume of the tank is generally about 80% of the total tank.

3 cone angle is generally between 60 ° ~ 90 °, commonly used 60 ° ~ 75 ° (stainless steel tanks commonly used cone angle of 60 °, inside the coating of steel tanks cone angle of 75 °), in order to facilitate the settlement and separation of yeast.

4 cooling jacket and cooling area of the conical fermenter cooling is often used indirect cooling. Domestic general use of semi-circular pipe, channel steel, curved pipe jacket, or Miller plate's jacket at low temperature and low pressure (-3 ℃, 0.03MPa) with liquid secondary refrigerant cooling, foreign countries use more heat exchanger sheet type (explosion molding) disposable refrigerant direct evaporative cooling. Disposable cold enzyme (such as liquid ammonia evaporation temperature of -3 ~ -4 ℃) evaporated pressure of 1.0MPa ~ 1.2MPa, the jacket pressure resistance requirements are high. As the freezing point temperature of beer is generally -2.0 ~ -2.7 ℃, in order to prevent the beer in the tank local icing, refrigerant temperature should be -3 ℃ or so. Domestic often used 20% ~ 30% of the alcohol water solution, or 20% propylene glycol water solution as refrigerant.

Depending on the capacity of the tank, the cooling can be two-stage or three-stage type. Cooling area according to the material of the tank, stainless steel material is generally 0.35 ~ 0.4m/m fermentation liquid, carbon steel tank for 0.5 ~ 0.62m/m fermentation liquid. Cone bottom cooling area should not be too large, to prevent icing of beer during the storage period.

⑤Heat insulation and protective layer The material of heat insulation layer requires small thermal conductivity, low volume mass, less water absorption, non-flammable and other characteristics. Commonly used insulation materials are polyamide resin, self-extinguishing polystyrene plastic, polyurethane, expanded perlite powder and slag cotton. The thickness of the insulation layer is generally 150 ~ 200mm. 0.7 ~ 1.5mm thick aluminum alloy plate, tin plate or 0.5 ~ 0.7mm stainless steel plate, corrugated board is more popular recently.

6 pressure resistance of the tank Fermentation produces a certain amount of carbon dioxide to form the tank top pressure (tank pressure), there should be a carbon dioxide regulating valve, the tank top with a safety valve. When carbon dioxide is discharged, the speed of the next wine is too fast, and carbon dioxide is dissolved when the fermenter is washed, it will cause negative pressure in the tank, so a vacuum valve must be installed. Back pressure with carbon dioxide or compressed air should be used before laying down the wine to avoid the generation of negative pressure in the tank, causing the fermenter to deflate.

3. Conical tank fermentation process

(1) the combination of conical tank fermentation

Conical tank fermentation production process combination of the following forms:

①Fermentation - wine storage This way, the two tanks are not the same requirements, the pressure resistance is also different, for the modern brewing, the way is not very meaningful.

②Fermentation - post-processing type, that is, one tank for fermentation, the other tank for the maturing process. For the fermentation tank, the fermentable components are completed at once, basically no fermentable components are retained, all the CO2 produced by the fermentation is recovered and stored for backup, and then transferred to the post-processing tank for maturation. The process is to separate the fermentation liquid at the end of fermentation by centrifugation, remove the yeast and cold solidification, then cooled to the storage temperature by a thin-plate heat exchanger, and start filtration after 1 to 2 days of low-temperature storage.

3) Fermentation-post-adjustment type That is, the previous fermentation tank is similar to the one-tank method for fermentation and wine storage, completing the fermentation of fermentable components, recovery of CO2, recovery of yeast, CO2 washing, and then after appropriate low-temperature storage, the color, stability, CO2 content and other indicators in the post-adjustment tank can be adjusted, and then can be properly stabilized to start filtration operations.

(2) Determination of the main process parameters of fermentation

①Fermentation cycle

Determined by the type of product, quality requirements, yeast performance, inoculum, fermentation temperature, season, etc., generally 12 to 24 days. Usually, the fermentation cycle of ordinary beer is shorter in summer, the fermentation cycle of high-quality beer is longer, and the fermentation cycle of off-season is extended appropriately.

②Yeast inoculation

Generally based on the performance of the yeast, the number of generations, aging, product type and so on. The size of the inoculum is determined by the number of yeast after adding yeast. At the beginning of fermentation: 10～20×10/ml; at the time of vigorous fermentation: 6～7×10/ml; after the discharge of yeast: 6～8×10/ml; at about 0℃ when storing the wine: 1.5～3.5×10/ml.

3) Maximum temperature of fermentation and the temperature of bis-acetyl reduction

The temperature of the beer at the time of vigorous fermentation is known as the maximum temperature of fermentation, and the beer fermentation can be divided into three types: low-temperature fermentation and diacetyl reduction temperature

The temperature at the time of vigorous fermentation of beer is known as the maximum temperature of fermentation. General beer fermentation can be divided into three types: low-temperature fermentation, medium-temperature fermentation and high-temperature fermentation. Low-temperature fermentation: vigorous fermentation temperature of about 8 ℃; medium-temperature fermentation: vigorous fermentation temperature of 10 to 12 ℃; high-temperature fermentation: vigorous fermentation temperature of 15 to 18 ℃. The general fermentation temperature in China is 9～12℃. Diacetyl reduction temperature refers to the temperature at the end of vigorous fermentation when the beer is matured (mainly eliminating diacetyl), generally the diacetyl reduction temperature is equal to or higher than the fermentation temperature, which can ensure the quality of the beer and help to shorten the fermentation cycle. If the fermentation temperature is increased, the fermentation period will be shortened, but the amount of metabolic by-products will be increased, which will affect the flavor of the beer and is easy to be contaminated with bacteria; if the diacetyl reduction temperature is increased, the maturing time of the beer will be shortened, but it will be easy to be contaminated with bacteria and is not conducive to the sedimentation of the yeast and clarification of the beer. Low temperature, the fermentation cycle is prolonged.

④Tank pressure

Determined according to the type of product, wort concentration, fermentation temperature and yeast strains. Generally the maximum tank pressure during fermentation is controlled at 0.07 to 0.08 MPa. The maximum tank pressure is generally the highest fermentation temperature value divided by 100 (in MPa). The use of pressurized fermentation can inhibit the proliferation of yeast, reduce the phenomenon of excessive metabolic by-products due to warming, prevent the production of excessive high-level alcohols and esters, and at the same time is conducive to the reduction of diacetyl, as well as to ensure the CO2 content in the wine. The relationship between CO2 content in beer and tank pressure and temperature is:

CO2 (%, m/m) = 0.298+0.04p-0.008t

Where p - tank pressure (gauge reading) (MPa)

t - beer temperature (℃)

⑤Full time

From the first batch of wort into the tank to the last batch of wort to the last batch of wort to the last batch of beer. The time from the first batch of wort into the tank to the last batch of wort into the tank is called full tank time. Full tank time is long, the yeast proliferation, the production of metabolic by-products α-acetyl lactic acid, high peak diacetyl, generally in 12 ~ 24h, preferably in 20h or less.

6 Fermentation

Can be divided into low fermentation, medium fermentation, high fermentation and ultra-high fermentation. For light-colored beer fermentation degree is divided into: low fermentation degree beer, its true fermentation degree 48% to 56%; medium fermentation degree beer, its true fermentation degree 59% to 63%; high fermentation degree beer, its true fermentation degree 65% or more, ultra-high-fermentation degree beer (dry beer), its true fermentation degree is 75% or more. At present, the more popular domestic fermentation degree of light refreshing beer.

(4) conical fermenter process requirements

①Should be effective in controlling the quality of raw materials and the effect of saccharification, the composition of each batch of wort should be uniform, if the composition of each batch of wort is too large a difference, will affect the propagation of yeast and fermentation. Such as 10ºP wort composition requirements are: concentration % (m/m) 10 ± 0.2, color (EBC units) 5.0 ~ 8.0, pH 5.4 ± 0.2, α-amino nitrogen (mg / L) 140 ~ 180.

② The capacity of the large tank should be compatible with the amount of cold wort per saccharification and the number of times per day, the requirement of the saccharification of the 16h full A can, not more than 24h at most, into the can of cold wort on the thermal coagulation should be removed as far as possible, such as cold coagulation can be separated as far as possible is better.

3 cold wort temperature control should be considered each time the wort into the tank interval and the number of full tanks, if the interval is long and many times, you can consider raising the temperature of the wort batch by batch, you can also consider the first one or two batches of yeast is not added, and then a few batches of the full amount of yeast will be added to a certain proportion, add the proportion of small to large, but should pay attention to avoid the wort staining bacteria. There is also the use of the first few batches of wort to add yeast, the last batch of wort without yeast.

④Cold wort dissolved oxygen control can be based on the amount of yeast added and yeast reproduction, generally require each batch of cold wort should be oxygenated according to the requirements of the cold wort, mixed cold wort dissolved oxygen is not less than 8mg / L.

⑤Control of the fermentation temperature should be kept relatively stable, to avoid the sudden high and low. Temperature control to use automatic control is good.

6. CO2 recovery should be carried out as much as possible, so as to facilitate CO2 washing, replenish CO2 in the wine and back-pressurize with CO2.

⑦The fermenter should be made of stainless steel to facilitate cleaning and sterilization. When carbon steel is used to make the fermenter, the coating layer should be kept even and firm, and there should be no unevenness on the surface, and the coating should not be peeled off in the process of using. The fermenter should be equipped with a high-pressure spray washing device, spray washing pressure should be controlled at 0.39 ~ 0.49MPa or higher.

(5) Operation steps (one-tank method of fermentation)

①Inoculation Select the 0-generation yeast that has been cultivated or the fermenter yeast that has normal fermentation sugar reduction, fast diacetyl reduction and qualified microbiological indexes in the production as the seed, and the latter can be used in the way of jar-jar for the string of seeds. The amount of inoculation is based on the number of yeast in (1.2~1.5)×10/ml after full tank.

②Time of full tank Under normal circumstances, the time required for full tank is not more than 24h, and the expansion can be based on the inspiration. After the full tank every 1 day discharge of cold condensate, *** discharge 3 times.

3 main fermentation temperature 10 ℃, ordinary wine 10 ± 0.5 ℃, quality wine 9 ± 0.5 ℃, peak season can be elevated 0.5 ℃. When the appearance of the sugar level down to 3.8% ~ 4.2% can be closed tank pressure. The pressure of the fermenter is controlled at 0.10～0.15MPa.

④Diacetyl Reduction After the main fermentation is finished, turn off the refrigerant and raise the temperature to 12℃ for diacetyl reduction. When the diacetyl content drops to below 0.10mg/L, the temperature reduction starts.

⑤ Cooling down After the end of diacetyl reduction, cool down the temperature from 12℃ to 5℃ within 24h, and stay for 1 day for yeast recovery. Yeast can also be recovered at 12℃ during fermentation to ensure more highly active yeast. Yeast can be recovered directly after the end of the main fermentation in peak season or when there is not enough yeast.

6. Wine storage After the yeast is recovered, the conical tank will continue to be cooled down, and the temperature will be reduced to -1℃～-1.5℃ within 24h, and the wine will be stored at this temperature. Storage time: more than 7 days in low season and more than 3 days in high season.

4. Recovery of yeast

The recovery of yeast in the conical tank fermentation method is different from that of traditional fermentation, with the following main differences: the recovery time is not fixed, and the yeast can be discharged at any time after the beer is cooled down to 6-7℃, while the traditional fermentation can only be carried out at the end of the fermentation; the temperature of the recovery is not fixed, and the recovery can be carried out at 6-7℃, or 3-4℃ or 0-1℃; the number of recoveries is not fixed, and the recovery can be done only at 6-7℃, or 3-4℃ or 0-1℃; and the number of times of recovery is not fixed, and the recovery is not fixed. The number of times of recovery is not fixed, the conical tank recovery of yeast can be divided into several times, mainly according to the actual need for multiple recovery; recovery of different ways, generally using yeast recovery pumps and metering devices, pressurization and oxygenation devices, while equipped with a yeast tank and a larger volume to accommodate several tanks of recovery of the yeast (the same or similar generation); storage methods are different, the conical tank is not generally yeast washing, storage temperature Can be adjusted, storage conditions are better.

Generally, the yeast should be recovered in time when the temperature drops below 6-7℃ at the end of fermentation. If the yeast is not recovered in time, the yeast at the bottom of the cone will quickly appear autolysis. Before recovering the yeast, the cone bottom valve should be sterilized with cotton balls of 75% (v/v) alcohol solution, and the pipeline for recovering or adding yeast should be washed regularly with NaOH (commonly known as kerosene) solution at 85℃ for 20 minutes; the pipeline should be passed through hot water at 85℃ for 30 minutes and 0.25% disinfectant solution (H2O2, etc.) for 10 minutes before each use; and the pipeline should be rinsed with water for 5 minutes after use, and then hot water at 85℃ should be used to Sterilize for 20 minutes.

The more generations of yeast are used, the more anaerobic contamination generally increases, and it is best not to use more than 4 generations of yeast. The yeast contaminated with anaerobic bacteria should not be recovered, it is best to do sterilization before discharge.

Recovery of yeast, pay attention to: to slow recovery, to prevent the yeast in the pressure suddenly lowered caused by yeast cell rupture, the best appropriate preparation pressure; to remove the upper and lower yeast, recovery of the middle layer of strong yeast; yeast recovery storage temperature of 2 ~ 4 ℃, the storage time should not be more than 3 days.

After the yeast sludge recovery, it should be timely to add 2 to 3 times 0.5 ~ 2.0 ℃ sterile water dilution, filtered by 80 ~ 100 purposes of the yeast sieve to remove impurities, and washed 2 ~ 2.5 times a day.

If the recycled yeast sludge contaminated with stray bacteria can be acid washed: edible grade phosphoric acid, diluted with sterile water to 5% (m/m), add the recycled yeast sludge, modulation of pH 2.2 ~ 2.5, stirring evenly after standing for more than 3h, pour off the upper layer of acid water can be put into use. After acid washing, it can kill more than 99% of bacteria.

Yeast using generations: some research found that under the same conditions, 2 generations of yeast fermentation cycle is longer, but the ability to lower sugar, reduce diacetyl is better; 3 generations of yeast in the fermentation cycle, lower sugar, reduce diacetyl ability is the best, the yeast activity is the strongest; 4 generations of yeast, after the gradual extension of fermentation cycle, yeast ability to lower sugar and the ability to reduce diacetyl is also gradually declining, product quality will deteriorate. The quality of the product will deteriorate.

If the wort is rich in nutrients (α-amino nitrogen content is high, more than 180mg/L), the activity of the recovered yeast is high, while the wort lacks nutrients, the activity of the recovered yeast is very poor, and it has a significant impact on the next round of fermentation and the quality of beer.

Recovered yeast sludge with 0.01% beauty blue staining to determine the yeast mortality rate, if the mortality rate of more than 10% can not be reused, the general mortality rate of recovered yeast should be less than 5%.

5. CO2 recovery

CO2 is an important by-product of beer production, according to theoretical calculations, every 1kg maltose fermentation can produce 0.514kg of CO2, every 1kg glucose can produce 0.489kg of CO2, the actual fermentation of the first 1 to 2 days of CO2 impurity, can not be recovered, the actual recovery of CO2 is only 45% to 70% of the theoretical value. The actual CO2 recovery rate is only 45% to 70% of the theoretical value. The actual CO2 recovery rate is only 45% to 70% of the theoretical value. The empirical data is that the actual CO2 recovery rate is about 2 to 2.2kg per 100 liters of wort in the process of beer production.

The process of CO2 recovery and use is as follows:

CO2 collection→washing→compression→drying→purification→liquefaction and storage→gasification→use

①Collection of CO2: after 1 day of fermentation, the purity of the CO2 is checked to be 99% to more than 99.5%, and the CO2 recovery is more than 99%, and the CO2 is more than 99%. 99.5% or more, the pressure of CO2 is 100~150kPa, after foam trap and water washing tower to remove the foam and trace alcohol and fermentation by-products, and continuously send into the rubber airbag, so that the CO2 recovery equipment operates continuously and equably.

②Washing CO2 into the water washing tower countercurrent, the water is sprayed down from the top. Some are also equipped with potassium permanganate scrubber, which can remove organic impurities in the gas.

③Compression After washing, the CO2 gas is compressed by 2 stages of oil-free lubricated CO2 compressor. The first stage is compressed to 0.3MPa (gauge pressure) and condensed to 45℃; the second stage is compressed to 1.5~1.8MPa (gauge pressure) and condensed to 45℃.

④Drying After 2-stage compression of CO2 gas (about 1.8MPa), it enters a dryer, which is equipped with silica gel or molecular sieve to remove water vapor from CO2 and prevent icing. Drying is also placed after the purification operation.

⑤Purification The dried CO2 is purified by an activated carbon filter. The filter is equipped with activated carbon to remove fine impurities and odor from the CO2 gas. Requirements for two parallel, one of the regeneration standby, there is an electric heating device, some with steam regeneration, the requirements should be regenerated once in 37h.

6 liquefaction and storage CO2 gas is dried and purified, through the column tube CO2 purifier. When the CO2 gas flowing in the column tube condenses to below -15℃, it turns into liquid CO2 of -27℃ and 1.5MPa, and enters into the storage tank, and the refrigerant R22 flowing outside the column tube is evaporated and inhaled into the cooling machine.

⑦Gasification Liquid CO2 storage tank pressure of 1.45MPa (between 1.4 and 1.5), through the steam heating evaporation device, the liquid CO2 into gas CO2, delivered to the various gas electricity.

Recovered CO2 purity should be greater than 99.8% (v/v), of which the highest content of water is 0.05%, the highest content of oil is 5mg / L, the highest content of sulfur is 0.5mg / L, the highest content of the residual gas is 0.2%, will be dissolved in the CO2 can not be unpleasant taste and smell.

6. conical tank cleaning and sterilization

In beer production, health management is crucial. Production links in the cleaning and disinfection sterilization is not strict in the direct consequences are: mild contamination of the beer taste poor, short freshness, poor quality; serious contamination can make the beer rancid and scrapped.

(1) microbial control of fermentation tanks Beer fermentation is pure beer yeast fermentation, the fermentation process of harmful microbial contamination is through the wort cooling operation, delivery piping, valves, inoculation of yeast, fermentation tanks and other ways of spreading the fermentation tanks are the largest source of pollution. Therefore, beer fermentation tanks must be washed and disinfected and sterilized.

(2) the choice of disinfectant equipment, methods, disinfectants play a decisive role in the quality of washing large tanks, while the choice of economic, efficient and safe disinfection and sterilization is the key. Most of our breweries use sterilizers such as CIO2, hydrogen peroxide, peroxyacetic acid, formaldehyde, etc., and the best one is CIO2.

(3) Selection of washing method

①Water - alkaline water - water, this is a primitive method of washing, which is currently used in small and medium-sized breweries, and it can't kill all the microorganisms, and it will affect the taste of the beer, even though it is low cost. Although the washing cost is low, it can not fully kill all the microorganisms, and it will have an impact on the taste of beer. There is also the use of regular washing with formaldehyde sterilization, but it is not safe.

② water - alkaline water - water - fungicide (CIO2, peroxyacetic acid, hydrogen peroxide) It is generally believed that the final decomposition products of the above three disinfectants have no toxic side effects, do not have to rinse after washing. More manufacturers use this method, and the quality of their beer, especially the taste and freshness will be improved by one grade compared with the first method.

3 clear water - alkaline water - clear water - disinfectant - aseptic water Some manufacturers believe that this method of microbial control is safer, but also to avoid side effects in case of disinfectant residues, but if the aseptic water bacterial control is unqualified can also be brought to the large tanks of repeated contamination.

4 water - dilute acid - water - alkaline water - water - sterilizer - sterile water This method is considered to be the more ideal washing method. By examining the inner wall of a large tank that has been used for a long period of time, it can be found that there are adhering brewers' rocks consisting of calcium oxalate, calcium phosphate and organic matter. Removing the brewers' rocks with dilute acid (phosphoric acid, nitric acid, sulfuric acid) before washing and sterilizing and disinfecting them will be beneficial to the quality of the beer.

(4) the impact of other factors on the washing of large tanks

①CIP system design: especially the angle of the pipeline, the capacity and distribution of washing tanks, washing water recovery methods, etc., will have an impact on the washing sterilization. Some use pressure recovery of washing water, too high a pressure will make the washing water jet resistance and affect the washing effect.

②Scrubber: the current production of many types of scrubber, should choose the spray angle is complete, not easy to block the universal scrubber. Regularly open the top cover of the tank to check the scrubber, so as to avoid clogging the scrubber due to foreign objects.

3 washing pump and pressure: if the pump pressure is too small, the washing liquid jetting powerless, but also in the tank wall will leave a dead corner, washing pressure should generally be controlled in the 0.25 ~ 0.4MPa.

4 tank wall: some of the tank wall using epoxy resin or T541 paint anticorrosive, after a period of time after the use of blisters or peeling, if not timely inspection and maintenance, it will be in the These dead ends harbor bacteria and contaminate the beer.

5 washing time: as long as the method is correct, the equipment is normal, the general water rinse each time 15 ~ 20 minutes, alkaline washing time 20 minutes, sterilization time 20 ~ 30 minutes, the total time control in 90 ~ 100 minutes is ideal.

6 micro-check sampling method: after washing the large tank put clean water, close the bottom valve for a few minutes, and then open, with a sterile test tube or sterile triangular vials, take samples on the flame for aseptic petri dish culture for 24 hours or anaerobic bacteria culture for 7 days, sampling method is incorrect or the culture is not rigorous will make the microbial determination is not accurate.