What Is Continuous Distillation?

Distillation is a thermodynamic separation process. It utilizes different boiling points of components in a mixed liquid or liquid-solid system to evaporate low-boiling components and then condense to separate the entire component. It is an evaporation and condensation operation. Union of unit operations. Compared with other separation methods, such as extraction, filtration and crystallization, it has the advantage that it does not require the use of other solvents than system components, thereby ensuring that no new impurities are introduced.

Distillation is a thermodynamic separation process. It utilizes different boiling points of components in a mixed liquid or liquid-solid system to evaporate low-boiling components and then condense to separate the entire component. It is an evaporation and condensation operation Union of unit operations. Compared with other separation methods, such as extraction, filtration and crystallization, it has the advantage that it does not require the use of other solvents than system components, thereby ensuring that no new impurities are introduced.

Chinese name: Distillation
Foreign name: distillation
Subject / Subject: Thermodynamics

Method: Physical method
Purpose: Separation substance
Classification: Simple distillation, equilibrium distillation
Main instrument: Distillation flask

Distilled Word Explanation

1. [distill]: heating the liquid to vaporize, and then vaporizing the vapor, thereby removing the impurities therein.

2. [still]: Manufactured or extracted by distillation.

3. Distilled words have two meanings: evaporation or volatilization, which is not obvious at normal temperature, and can be clearly observed after heating to the boiling point; when cold, the vapor becomes liquid, commonly known as distillate.

4. Describe hot steam transpiration.

Ming and Song dynasty's "Gift to Liu Junmin's Ancestor" poem: "This year, we are going to Lingling, the heat is very distilling."

5. Heat the liquid to turn it into a vapor, and then cool the vapor to condense to remove the impurities.

Lu Xun's "New Stories · Water Management": " drink, how much they want, and you can't finish it for 10,000 generations. Unfortunately, it contains a little loess. You should distill it before drinking."

Distillation definition

Refers to the mass transfer process that separates components by utilizing the differences in the volatility of each component in the liquid mixture. A process of evaporating and condensing the vapor produced by boiling a liquid into a condensate tube to cool and condense it into a liquid. Distillation is an important operation technique for separating mixtures with large differences in boiling points, especially for the separation of liquid mixtures, which has important practical significance. That is, distillation conditions: 1. The liquid is a mixture. 2. Each component has a different boiling point.

Distillation characteristics

1. Through the distillation operation, the desired product can be directly obtained, and other components such as absorption and extraction are required.

2. Distillation separation is widely used and has a long history.

3 The energy consumption is large, and a large amount of gas phase or liquid phase is generated in the production process.

Distillation classification

1. Divided by mode: simple distillation, equilibrium distillation ^[1] , rectification, special rectification

2. Divided by operating pressure: normal pressure, pressurization, decompression

3 According to the components in the mixture: two-component distillation, multi-component distillation

4 Divided by operation mode: batch distillation, continuous distillation

Distillation main instrument

Distillation flask (with branch tube), thermometer, condenser tube, horn tube, alcohol lamp, asbestos net, iron stand, branched conical flask, rubber stopper.

Introduction to Distillation Classification

Distillation can be divided into column distillation and non-column distillation.

Judging from the development history of the world's distillation, 3000-5000 years ago, there was a requirement for separation and purification in the production of alcohol.

However, the long-term alcohol content is around 15-20 degrees. After numerous inventors have solved the problem, the prototype separation device has been launched. The 42-56 degree ethanol content is a peak of purification, which is the current range of liquor content.

More than 200 years ago, French inventors used a distillation tower to produce 95% ethanol, which has been recognized by the distillation industry. More than 30 years later, British inventors invented a rectification tower based on a distillation tower and produced With 99-99.9% ethanol, the term "alcohol" was first produced, which means the essence of wine. Methanol or ethanol production plants, standing 20-120 meters in height and 0.3--13.5 meters in diameter. [Distillation] towers with various structures, all originated from French and British inventor products. Distillation [rectification] tower is the largest The annual production can reach 50,000-300,000 tons, which is the main purification method of organic solvents.

Beginning in 2005, Anyang Haichuan Chemical Research Institute (formerly Anyang High-tech Zone Contemporary Chemical Research Institute) began its unique purification research. Many domestic users call it towerless distillation (rectification) and towerless refining. The tower-less refining equipment appeared in December 2010 and obtained a patent certificate. From March to August 2011, the tower-free distillation machine and tower-free distillation machine came out. One patent was authorized and one patent passed the preliminary examination. The industrial purification test of 20% ultra-low content waste methanol was used in a large pharmaceutical production company in Shangqiu City, Henan Province, and the initial distillate content was 86%. In August 2011, a large pharmaceutical company in Anyang City, Henan Province Industrial purification test of% waste ethanol, with column-free distillation [extended range] machine purification to 98%, methyl acetate content in ethanol 0.1%, which is significantly better than the 0.26% separation effect of the distillation column in this plant. After the 2010s, the towerless distillation equipment has been highly valued by users for the purification of numerous organic solvents. The institute not only devotes itself to the research and development of separation equipment, but also strives to bring the accumulated rich purification experience to a theoretical level.

Distillation history

In ancient Greek times, Aristotle once wrote: "By distillation, water is first made into steam and then liquid, which makes seawater drinkable." This shows that people discovered the principle of distillation at that time. The ancient Egyptians used distillation to make spices. In the early Middle Ages, the Arabs invented the distillation of wine. In the tenth century, a philosopher named Avicenna described the still in detail.

Distillation principle

Distillation overview

By using the difference in the volatility of each component in the liquid mixture, the liquid mixture is partially vaporized and the vapor is partially condensed, so as to achieve the separation of its contained components. It is a unit operation that belongs to mass transfer separation. Widely used in oil refining, chemical, light industry and other fields.

Ordinary distillation device The principle is based on the separation of a two-component mixture. The material liquid is heated to partially vaporize it, and the volatile components are concentrated in the vapor, and the non-volatile components are also concentrated in the remaining liquid, which achieves the separation of the two components to a certain extent. The greater the difference between the volatility of the two components, the greater the degree of enrichment described above. In industrial distillation equipment, a part of the vaporized liquid phase is brought into direct contact with a part of the condensed gas phase for vapor-liquid interstitial mass transfer. The volatile components are partially transferred to the gas phase, that is, partial vaporization of the liquid phase and partial condensation of the vapor phase are achieved at the same time.

Liquid molecules tend to overflow from the surface due to molecular motion. This tendency increases with increasing temperature. If the liquid is placed in a closed vacuum system, the liquid molecules continue to overflow and form vapor on the liquid surface. At the end, the speed at which the molecules escape from the liquid is equal to the speed at which the molecules return from the vapor to the liquid, and the vapor remains constant. pressure. At this time, the vapor on the liquid surface reaches saturation, called saturated vapor, and the pressure it exerts on the liquid surface is called saturated vapor pressure. Experiments show that the saturated vapor pressure of a liquid is only related to temperature, that is, the liquid has a certain vapor pressure at a certain temperature. This is the pressure at which a liquid is in equilibrium with its vapor, and is independent of the absolute amount of liquid and vapor in the system.

The operation of heating the liquid to boiling, turning the liquid into a vapor, and then cooling the vapor to condense the liquid into a liquid, is called distillation. Obviously, distillation can separate volatile and non-volatile materials, as well as liquid mixtures with different boiling points. However, the boiling points of the components of the liquid mixture must be very different (at least 30 ° C or higher) to obtain better separation results. When performing distillation at normal pressure, the atmospheric pressure is often not exactly 0.1 MPa, so strictly speaking, the correction value should be added to the observed boiling point, but the deviation is generally small, even if the atmospheric pressure differs by 2.7KPa, this correction value It is only about ± 1 ° C, so it can be ignored.

Distillation bumping

The flask containing the liquid was placed on an asbestos net, and the bottom was heated by a gas lamp. Vapor bubbles were formed on the bottom of the liquid and the heated contact surface of the glass. The air dissolved in the liquid or the air adsorbed on the bottle wall in the form of a film helps the formation of such bubbles, and the rough surface of the glass also promotes it. Such small bubbles (called gasification centers) can serve as the core of large vapor bubbles. At the boiling point, the liquid releases a large amount of vapor into small bubbles. When the total pressure of the bubble increases to more than atmospheric pressure and is sufficient to overcome the pressure generated by the liquid column, the vapor bubbles rise and overflow the liquid surface. Therefore, if there are many small air or other gasification centers in the liquid, the liquid can boil smoothly. If there is almost no air in the liquid, the bottle wall is very clean and smooth, and it is very difficult to form bubbles. When heated in this way, the temperature of the liquid may rise above the boiling point without boiling. This phenomenon is called "overheating". Once a bubble is formed, because the vapor pressure of the liquid at this temperature far exceeds the sum of atmospheric pressure and liquid column pressure, the rising bubble increases very quickly, and even the liquid overflows the bottle. This abnormally boiling This phenomenon is called "bumping." Therefore, a boiling aid should be added before heating in order to introduce the gasification center to ensure a smooth boiling. Boilers are generally porous, porous, and air-absorbed objects, such as broken porcelain and zeolites. It is also possible to introduce several capillaries with closed ends to introduce the gasification center (note that the capillaries are of sufficient length to allow the upper end to rest on the neck of the retort with the open end facing down). In any case, it is forbidden to add boiling aids to liquids that have been heated to near boiling, otherwise, a large amount of liquid is often ejected from the mouth of the distillation bottle due to the sudden release of a large amount of vapor, which is dangerous. If you forget to add the boiling aid before heating, you must remove the heat source before adding, and wait until the heated liquid is cooled below the boiling point before adding. If the boiling has stopped halfway through, add a new boiling aid before reheating. The boiling aid that was added initially expelled part of the air when heated, and absorbed the liquid when cooled, so it may have failed. In addition, if you use indirect heating of the bath, keep the bath temperature not exceeding 20 ° C of the boiling point of the distillate. This heating method can not only greatly reduce the temperature difference between the various parts of the distillate in the bottle, but also make the steam bubbles not only from the flask. Rising at the bottom can also rise along the edge of the liquid, thus greatly reducing the possibility of overheating.

Distillation process

Pure liquid organic compounds have a certain boiling point under a certain pressure, but liquids with a fixed boiling point are not necessarily all pure compounds, because some organic compounds often form binary or ternary azeotropic mixtures with other components. They also have a certain boiling point. The boiling point of an impure substance depends on the physical properties of the impurity and its interaction with the pure substance. If the impurities are non-volatile, the boiling point of the solution is slightly higher than the boiling point of the pure substance (but during the distillation, the boiling point of the impure solution is not actually measured, but the temperature at which the escaped vapor balances with its condensation, ie Is the boiling point of the distillate, not the boiling point of the distillate in the bottle). If the impurities are volatile, the boiling point of the liquid will gradually increase during the distillation or due to the azeotropic mixture of two or more substances, the temperature can remain unchanged during the distillation and stay within a certain range. Therefore, the constant boiling point does not mean that it is a pure compound.

When distilling a mixed liquid with a large difference in boiling point, the one with the lower boiling point is distilled off first, and the one with the higher boiling point is then distilled off, leaving the non-volatile in the still, so that the purpose of separation and purification can be achieved. Therefore, distillation is one of the commonly used methods for the separation and purification of liquid compounds. It is an important basic operation and must be mastered. However, when a mixture with a relatively close boiling point is distilled, the vapors of various substances will be distilled out at the same time, but the lower boiling point is more, so it is difficult to achieve the purpose of separation and purification, and only by means of fractional distillation. Pure liquid compounds have a small boiling range during distillation (0.5 to 1 ° C). Therefore, distillation can be used to determine the boiling point. The method of determining the boiling point by distillation is a constant method. This method requires a large amount of sample, which should be more than 10 mL. If there are not many samples, the micro method should be used.

Distillation fractionation

Definition: Fractionation is a method that uses a distillation column to complete multiple gasification-condensation processes in one operation. Therefore, fractional distillation is actually multiple distillation. It is more suitable for separating and purifying liquid organic mixtures with little difference in boiling points. ^[3]

Necessity of fractional distillation: (1) Incomplete separation by distillation. (2) Multiple distillation operations are cumbersome, time consuming, and extremely wasteful.

After the mixed liquid is boiled, the vapor enters the fractionation column and is partially condensed. The condensate is in contact with the steam that continues to rise during the decline. The two exchange heat. The high-boiling components in the steam are condensed. The low-boiling components in the liquid are heated and gasified, and the high-boiling components still fall into a liquid state. The result is an increase in low-boiling components in the rising steam and an increase in high-boiling components in the falling condensate. After multiple heat exchanges in this way, it is equivalent to continuous ordinary distillation. As a result, the vapors of the low-boiling components keep rising and are distilled out; the high-boiling components keep flowing back into the distillation flask to separate them.

Distilled solution distillation

Introduction to Distillation

Since the x solvent in the solution is <1, the vapor pressure of the solvent in the solution is always lower than that of the pure solvent. Distillation curve of sucrose aqueous solution. Curves 1 and 2 represent temperature-vapor pressure curves of water and aqueous sucrose solutions, respectively. The presence of sucrose molecules in the solution reduces the density of water molecules on the surface of the solution, thereby reducing the vapor pressure of the solution. So at the same temperature, the vapor pressure of the solution (point B) is lower than the vapor pressure of the water (point A). Water will boil (at 1 atmosphere) at 100 ° C, while the solution will not boil. Only at higher temperatures (point B ) will the solution boil. For this type of solution, distillation is used either to recover pure solvents or to obtain solid solutes.

Distilled mole fraction

When the solution containing non-volatile components is distilled, the solvent vapor is led out by the condenser tube, and the non-volatile components are left in the residual liquid in the bottle, and most of the solvent can be distilled off in one simple distillation, thereby achieving the purpose of separation. According to Raoul's law, under a certain pressure, the vapor pressure of a solvent in a dilute solution is equal to the vapor pressure of a pure solvent times the molar fraction of the solvent in the solution:

p solvent = po solvent x solvent

In the formula, p solvent and po solvent are the vapor pressure of the solvent in the solution and the vapor pressure of the pure solvent, respectively.

Summary of distillation methods

Flash distillation

After heating the liquid mixture, it undergoes a partial vaporization separation operation.

Simple distillation

A separation operation in which the mixed liquid is gradually vaporized and the vapor is condensed in time to be collected in stages.

Distillation

The use of reflux to achieve high purity and high recovery separation operations is the most widely used. For mixed liquids with equal or similar volatility of each component, in order to increase the relative volatility of each component, solvents or salts can be added during rectification separation. This type of separation operation is called special distillation, which includes azeotropic distillation. Distillation, extractive distillation and salt-added distillation; and those that undergo a chemical reaction between the components of the mixed liquid during rectification are called reactive distillation. ^[4]

Distillation experiment operation

For distillation applications

Distillation is a commonly used experimental technique in chemical experiments and is generally applied in the following areas:

Steam distillation

(1) Separation of liquid mixture can achieve more effective separation only when the boiling point of each component in the mixture is greatly different;

(2) Determine the boiling point of pure compounds;

(3) Purification, which improves the purity by distilling substances containing a small amount of impurities;

(4) Recover the solvent, or distill off part of the solvent to concentrate the solution. Steps

Adding: Carefully pour the liquid to be distilled through the glass funnel into the distillation bottle, taking care not to let the liquid flow out of the branch pipe. Add a few boiling aids, and install the thermometer. The thermometer should be installed at the side of the mouth leading to the condensation tube . Check again that the parts of the instrument are tightly and properly connected.

Heating : When using a water condensing tube, first slowly pass cold water from the lower opening of the condensing tube, flow from the upper opening to the water tank, and then start heating. When heating, you can see that the liquid in the distillation flask gradually boils and the vapor gradually rises. The thermometer reading also rose slightly. When the tip of the vapor reaches the mercury bulb of the thermometer, the thermometer reading rises sharply. At this time, the flame of the gas lamp should be appropriately reduced or the voltage of the heating furnace or heating jacket should be reduced to slow down the heating rate slightly. The top of the vapor stays in place, the upper part of the bottleneck and the thermometer will be heated, and the temperature of the droplets and vapor on the mercury ball will reach

Distillation flask balance. Then slightly increase the flame and perform distillation. Control the heating temperature and adjust the distillation speed, usually 1-2 drops per second is appropriate. Condensed droplets should always be present on the mercury ball of the thermometer throughout the distillation process. The temperature at this time is the temperature at which liquid and vapor are in equilibrium, and the reading of the thermometer is the boiling point of the liquid (distillate). The flame to be heated during distillation must not be too large, otherwise it will cause overheating in the neck of the distillation flask, which will cause part of the liquid vapor to directly receive the heat of the flame, so that the boiling point read by the thermometer will be higher; on the other hand, distillation also Do not proceed too slowly, otherwise the thermometer's mercury ball cannot be fully infiltrated by the distillate vapor, so the boiling point read on the thermometer is low or irregular.

Observe boiling point and collect distillate : Prepare at least two receiving bottles before performing distillation. Because the lower boiling liquid evaporates before the boiling point of the desired substance is reached. This part of the distillate is called the "front cut" or "distillation head". After the first distillate has been distilled and the temperature has stabilized, the purer substance is distilled off. At this time, a clean and dry receiving bottle should be replaced to accept it. Record the thermometer readings when this part of the liquid begins to distill and the last drop. Is the boiling range (boiling point range) of the fraction. Generally, the liquid contains more or less high-boiling impurities. After the required fractions are distilled off, if the heating temperature is further increased, the reading of the thermometer will increase significantly. If the original heating temperature is maintained, it will no longer be Distillate evaporates and the temperature suddenly drops. Distillation should stop at this time. Even if the content of impurities is very small, do not evaporate it to avoid the distillation bottle rupture and other accidents.

After the distillation is completed, the heating should be stopped first, then the water flow should be stopped, and the instrument should be removed. The order of disassembling the instrument is the reverse of the order of assembly. Remove the receiver first, and then remove the tail tube, condenser tube, distillation head, distillation bottle, etc.

Precautions for distillation

Pay attention when operating

(1) Put a small amount of broken porcelain pieces in the distillation flask to prevent the liquid from boiling.

(2) The position of the mercury ball of the thermometer should be on the same horizontal line as the lower end of the branch pipe mouth.

(3) The liquid contained in the distillation flask must not exceed 2/3 of its volume, nor less than 1/3.

(4) The cooling water in the condensate tube enters from the lower port and exits from the upper port.

(5) The heating temperature must not exceed the boiling point of the highest boiling substance in the mixture.

Cautions Cautions Cautions Cautions In the distillation operation, the following points should be noted:

(1) Control the heating temperature. If a heating bath is used, the temperature of the heating bath should be a few degrees higher than the boiling point of the distilled liquid, otherwise it is difficult to distill the distillate. The more the heating bath temperature is higher than the boiling point of the distilled liquid, the faster the distillation speed. However, the temperature of the heating bath must not be too high, otherwise the vapor pressure of the top of the distillation flask and condenser will exceed atmospheric pressure, which may cause accidents, especially when distilling low boiling point materials. Generally, the temperature of the heating bath must not be higher than the boiling point of the distilled material by 30 ° C. Add the bath liquid at any time during the whole distillation process to keep the liquid level of the bath liquid at least one centimeter above the liquid level in the bottle.

(2) When distilling high-boiling substances, it is easy to be condensed, and often the steam has been condensed before it reaches the side tube of the distillation flask and dripped back into the distillation flask. Therefore, short-necked distillation flasks or other insulation measures should be used to ensure the smooth progress of the distillation.

(3) Before distillation, the boiling point and saturated vapor pressure of the substance to be distilled and its impurities must be known to determine when (ie at what temperature) to collect the fractions.

(4) Round bottom flasks should be used for distillation flasks. Liquids with a boiling point of 40-150 ° C can be liquids with a temperature of 150 ° C or above, or simple distillations with an unstable temperature and pressure even if the boiling point is below 150 ° C. For liquids with a constant boiling point and easy thermal decomposition, vacuum distillation and steam distillation can be used.

Distillation Chemistry Tips

The screen heats the cold pipe, and the upper and lower edges are flat.

Need to add broken porcelain to prevent bumping, hot air and cold water reverse.

The liquid limit in the bottle is well grasped, and the wine lamp is removed before stopping ^[4] .

Related explanations

The cold pipe is heated by the screen: "cold pipe" refers to the condensation pipe. This means that the asbestos net should be used when heating the distillation flask (to prevent the distillation flask from being broken due to uneven heating), and the condenser tube should be tilted downwards.

The upper edge and the lower edge are two-phase: it means that the upper edge of the mercury ball of the thermometer should be exactly on the same horizontal line as the lower edge of the branch tube connection of the distillation flask.

Hot air cold water goes backwards: it means that the cooling water must flow continuously from bottom to top, which is opposite to the direction of the flow of hot steam.

The liquid limit in the bottle is well grasped: it means that the liquid limit in the distillation flask must be well grasped, at most it should not exceed 2/3 of the volume of the sphere of the distillation flask, and the minimum cannot be less than 1/3.

Withdraw the wine and water before stopping: It means that when the distillation is over, the fire should be stopped first and then the cooling water should be stopped.

Distillation- related artifacts

Distillation archeological finds

Archaeologists unearthed more than 440 Han tombs on the east side of Zhangjiabao Square in Xi'an. One of the higher-special Western Han dynasty tombs found a cup of strangely crafted copper still, which may be the earliest in history Distiller.

Copper still This cup of copper still has a height of 36 centimeters, and consists of a cylindrical shape, a copper spoon and a bean-shaped lid. Among them, the bottom of the cylinder has a Miguel-shaped cymbal, which is used as an interlayer in ancient cooking utensils. There is a small tubular flow at the bottom, copper-shaped three-hoof foot, the upper part of the bean-shaped device cover is disc-shaped, and the joint is a tenon-rivet structure, which can move freely within a certain range. Placed in an orderly manner when unearthed, the copper cymbals were placed in a cylinder, and the bean-shaped lid was placed on the copper cymbals. Such a combined still has never been discovered before, and although its working principle is not clear, from the structural point of view, it should be used as a distilling medicine and wine.

It is understood that previously, a bronze distiller from the Eastern Han Dynasty was unearthed in China, and the copper distiller found in the Han Tomb of Zhangjiapu in Xi'an was earlier. Cheng Linquan, deputy director of the Xi'an Institute of Cultural Relics and Archeology, said that the excavation provided valuable materials for the study of diet and medical technology in the Han Dynasty.

In addition, in the tomb number M115 where the distiller was unearthed, archeologists also unearthed more than 200 artifacts, including five large bronze tripods and four large glazed pottery tripods. According to Zhou Li, Emperor Tian was buried with Jiuding during the Western Zhou Dynasty. The tombowner of M115 admired the Zhou Dynasty etiquette and used Jiuding's funeral to show his special status. Jiuding and another funeral imitation copper-glazed pottery are real physical evidence of Wang Mangtuo's ancient reformation, which has extremely important academic value and historical significance.

Distillation artifacts location

More than 440 Han tombs excavated this time are located on the east side of the Chang'an City in Han Dynasty, only 2,500 meters away from Chang'an City. Nearly 3,000 various cultural relics such as pottery, copper, iron, lead, jade, bone, etc. Pieces. These tombs are mainly small Han tombs, of which three medium-sized tombs from the late Western Han to the New Mang period are the most important. , , stove, etc. In the tomb M110, fragments of jade clothes were also unearthed. Large exquisite glazed pottery unearthed from tomb M114 is also rare in the tombs of the Han Dynasty in Xi'an. Experts said that this excavation provided important materials for studying the social life of the Han Dynasty and the layout of the Chang'an City in the Han Dynasty, and helped further interpret the formation and development of the Han culture.

Application of distillation technology

Distilled spirits

Distilled spirits Distilled spirits are various alcoholic beverages with a higher ethanol concentration than the original fermentation product. Brandy, whiskey, rum and Chinese liquor are all distilled spirits, and most of them are high-strength spirits.

The raw materials of distilled spirits are generally rich in natural sugars or starches that are easily converted into sugars. Such as honey, sugar cane, sugar beet, fruits and corn, sorghum, rice, wheat potatoes and so on. Sugar and starch are fermented by yeast to produce alcohol. The boiling point of alcohol (78.5 degrees Celsius) and the boiling point of water (100 degrees Celsius) are different. When the original fermentation broth is heated to between the boiling points of the two, the alcohol content can be distilled out and collected. And fragrance substances.

The special liquor is used to heat the wine liquor, wine goblet or wine goblet. Due to the different volatility of various substances contained in them, the relative content of various substances in steam and wine liquor during heating and distillation will be The difference. Alcohol (ethanol) is more volatile, the concentration of alcohol contained in the steam generated after heating increases, and the concentration of alcohol in the liquor or wine liquor decreases. The wine is collected and cooled, and although the liquor is colorless, the smell is spicy and strong. Its alcoholic content is much higher than that of the original liquor. Generally, the alcoholic beverage has an alcoholic content of less than 20%. Distilled wine can be as high as 60%. Distilled spirits in China are mainly obtained by distilling after brewing from grain raw materials.

The distilled spirits that people are familiar with today are divided into "baijiu" (also called "shochu"), "brandy", and "whiskey". "Vodka", "rum" and so on. Liquor is unique to China, and is generally distilled after the grain is brewed. Brandy is distilled from wine, and whiskey is distilled from fermented grains such as barley. Rum is distilled from sugarcane.

Distilled distilled water

Pure water prepared by distillation. Can be divided into one and multiple distilled water. Water passing

Distilled water In one distillation, the non-volatile components (salts) remain in the container and are removed. The volatile components (ammonia, carbon dioxide, organic matter) enter the initial fraction of distilled water. Usually only the middle part of the fraction is collected, which accounts for about 60%. To get more pure water, you can add alkaline potassium permanganate solution in one distilled water to remove organic matter and carbon dioxide; add non-volatile acid (sulfuric acid or phosphoric acid) to make ammonia into a non-volatile ammonium salt. Because glass contains a small amount of water-soluble components, quartz distillation vessels must be used for two or more distillations to obtain very pure water. The obtained pure water should be stored in quartz or silver containers. The distilled water machine adopts the principle of falling film evaporation from the tube. The raw material water is evenly distributed on the tube wall through a special distributor, which greatly improves the evaporation efficiency. The special spiral separation device can reliably remove pyrogens and particles. The repeated use of secondary steam makes full use of thermal energy and has obvious energy saving effects. It is an ideal distilled water equipment for hospitals, pharmaceutical factories, electronics, scientific research and other industries.

Molecular distillation

Molecular distillation equipment Molecular distillation is a continuous distillation process that performs liquid-liquid separation operations under high vacuum. Under high vacuum conditions, the distance between the heating surface and the condensation surface of the molecular still is less than or equal to the average free path of the molecules of the material being separated. When molecules evaporate from the surface of the liquid film formed on the heating surface, the intermolecular Collisions occur with each other, and they move toward the condensation surface without blocking and condense on the condensation surface, so as to achieve the purpose of separation. ^[1]

Molecular distillation is volatile at a temperature far below the boiling point of atmospheric pressure, and the residence time of each component is short under heat, which is very suitable for the separation of natural products with high boiling point, high viscosity and heat sensitivity. Molecular distillation technology can therefore achieve operation away from the boiling point, and has the characteristics of low distillation pressure, short heating time, high degree of separation, etc., can greatly reduce the separation cost of high boiling point materials, excellent protection of the quality of heat-sensitive substances. In the 1930s, molecular distillation technology appeared in foreign countries, and industrialization began in the 1960s. Domestic research and development of molecular distillation technology began in the mid-1980s. In the late twentieth century, this technology has been widely used in petrochemicals, food spices and other fields, and is particularly suitable for the extraction and separation of natural substances. This article briefly describes the principle of molecular distillation, extractor and its application in the flavor and fragrance industry.