Laboratory distillation column. Guidelines for laboratory work "study of the rectification process" Laboratory workshop on the safe operation of distillation columns

We offer laboratory distillation columns made of glass or stainless steel (mixed designs are possible). Glass distillation columns are assembled on the basis of German borosilicate glass LENZ (the glass catalog can be downloaded from our website - see the CATALOGS section). We offer ready-made solutions, which can be modified taking into account the wishes of the customer.

In the distillation column, constant mass and heat exchange occurs between rising vapors and descending condensate. Due to such contact, it is possible to obtain a product of high purity, free from impurities. Laboratory distillation columns, as a rule, are assembled on the basis of borosilicate glass (up to 10 l). Semi-industrial distillation columns are made of stainless steel and special alloys.

Laboratory distillation columns have a spherical evaporation tank (cube) from 1 liter to 10 liters. The length of the column itself is limited by the height of the ceiling; it can consist of several sections and have product selection from several plates. The column has a mirror vacuum jacket, which provides thermal insulation of the contents. By default, bulk type columns are offered, laboratory columns disc type are rarely supplied due to more high cost and less efficiency.

For attachment we offer Raschig glass rings or spiral-prismatic steel attachment. Metal nozzle more effective due to the large contact surface, but if it is necessary to exclude contact of the product with metal, Raschig glass rings are used.

The reflux flow is controlled manually; in this case, the user adjusts the degree of opening of the reflux outlet valve so that it chokes and part of the reflux is returned to the column. When a column is equipped with a reflux modeler with a pneumatic or electric valve, the operation of the column can be set via a controller. In this case, the operator just needs to set the reflux ratio, and the controller will open/close the valve at the right time.

The distillation column can be installed on the chemical reactor in front of the condenser. In this case, it is possible to immediately synthesize and distill off the solvent (or product) with purification.

This step-by-step instruction- just one of the methods of distillation on a distillation (RK) or mash (BK) column, having mastered which you can obtain a highly purified product. However, for fruit, berry and grain distillates there are technological nuances, without knowledge of which instead aromatic drink it will be pure alcohol. Each type of nozzle has its own characteristics. Use the proposed method as a starting point for studying the operation of columns, practicing on sugar mash, or knowing that you will end up with rectified alcohol or a drink close to it.

Initial conditions. Raw alcohol is available - sugar mash distilled in a conventional distiller (moonshine still) and - RK or BK. In this case, the method of working on different types columns is almost identical, and the differences are described in the appropriate places in the instructions.

Technology of home rectification on RK and distillation on BK

1. Fill the cube with raw alcohol to no more than 3/4 of the height, making sure to leave at least 10-12 cm of vapor zone. However, it is also impossible to fill in too little, so that at the end of the distillation process, when there is almost no liquid left in the cube, the heating elements do not emerge (become bare).

The strength of the vat bulk should be about 40%. This value is related to the minimum reflux ratio required to achieve the selection of a given strength. As the strength of the vat bulk increases, the minimum reflux ratio decreases nonlinearly, reaching a minimum at a strength of about 45%. Therefore, if you start the process with a strength of 60%, you will have to reduce the reflux ratio down to 45% of the strength, and then increase it as the still alcohol content is further depleted. That is, first increase the selection from 60 to 45% of the pot strength, and then reduce it. As a result, rectification will not only be more difficult to manage, but will also take longer.

2 Turn on the heating element maximum power and bring the raw alcohol to a boil. The optimal power of the heating element for acceleration is 1 kW per 10 liters of bulk, then the time until boiling is 15 minutes for every 10 liters of bulk.

3. Shortly before the start of boiling, at a temperature of 75-80 °C in the cube, turn on the water supply. Once boiling begins, reduce heat to operating power. If the operating power is still unknown, reduce it to a level below the rated power by 200-300 W. Adjust the water supply so that the steam is completely condensed in the dephlegmator. The outlet water should be warm or hot. The column began to work for itself.

4. Monitor the values ​​on the thermometers in the column, wait for the readings to stabilize.

5. Determine the operating capacity of the column. To do this, after the temperatures have stabilized, check the pressure in the cube. You will need a pressure gauge up to 6000 Pa (0.06 kg/sq. cm, 400 mm water column), or a U-shaped differential pressure gauge; a pressure gauge from a tonometer will also work (if nothing else is available).

If the pressure is stable and does not increase, add heating power by 50-100 W. The pressure in the cube should rise and after 5-10 minutes stabilize at a new value. Repeat this operation until the pressure stops stabilizing and continues to increase, for example, after 20 minutes the increase continues. Remember the current readings - this is the power of the choke.

If there is a 50 mm column and a SPN 3.5 nozzle, then the last non-increasing pressure (in mm of water column) will be approximately equal to 20% of the column height in millimeters. If the pressure is 30-40% of the height of the column, this means that the phlegm is stuck, and then the process of choking continues. With a less dense nozzle with less holding capacity, the choking power will be higher.

If there is no pressure gauge, they are guided by the sounds of the column - when choking, the column may begin to sway, gurgling can be heard, increased noise, spontaneous emissions of alcohol through the communication tube with the atmosphere or into the refrigerator during steam sampling are also possible. For the first time, without experience, it is difficult to determine the flooding of the column, but it is possible.

After determining the power of the reflux, turn off the heating and wait a few minutes for the phlegm to flow into the cube. Turn on the heating at a power 10% less than the cold one. Wait until the temperature and pressure in the cube stabilize. If everything is in order, then this will be the operating power of the column.

If the operating power is much lower than the nominal one, this means that the nozzle or the supporting elements of the nozzle are not packed correctly into the column: the nozzle is too compacted, there may be a tangle, there are pockets of reflux concentration where steam stops it, flooding the column. In this case, you need to disassemble the column, pour in the nozzle, straighten out the confusion, then reassemble it and repeat the adjustment process.

The operating power of the column is determined once. In the future, the obtained value is used constantly, occasionally making adjustments.

With correctly selected operating power, the pressure in the cube will be the same every time. It does not depend on the diameter of the column and is usually 3.5 – 150-200 mm of water for the SPN packing. Art. for each meter of nozzle height, for SPN 4 - 250-300 mm of water. Art., for other attachments the value will be different.

When searching for operating power, you can also focus on the following practical data: for an etched heptagonal SPN 3.5, the operating power in Watt is approximately equal to 0.85-0.9 of the cross-sectional area of ​​the pipe in millimeters. If SPN 4 is used, the coefficient increases to 1.05-1.1. For less dense nozzles the coefficient will be higher.

6. After stabilizing at operating power, let the column work for itself for 40-60 minutes.

7. Set the selection of “heads” at a speed of 50 ml/hour for a 40 mm column, for 50 mm – 70 ml/hour, for 60 mm – 100 ml/hour, for 63 mm – 120 ml/hour. Provided that SPN is used.

The time for selecting “heads” is determined based on the volume of the bulk: 12 minutes (0.2 hours) for each liter of 40% raw alcohol. It must be remembered that this is not distillation on a conventional apparatus with a coil - in the columns there is a separation into fractions and their sequential output to the selection in a concentrated form.

Recommendations such as 3-5% of absolute alcohol are average values, but no one has canceled them, and precise control of the end of the selection of “heads” is done based on the smell of the output. It should be remembered that the time and speed of selecting “heads” are unrelated quantities. If you select the “heads” at twice the speed, they will simply end up in a less concentrated form.

General principle: when selecting any fraction, you cannot take more from the column than enters the selection zone. This will prevent disruption of the separation of fractions along the height of the column.

8. Changing the extraction rate is carried out only by adjusting the water supply to the reflux condenser for columns with steam extraction above the reflux condenser. If the column has liquid extraction, then simply a withdrawal valve.

The heating power should always remain constant; this ensures stability in the amount of steam supplied to the column and the operation of the column as a whole.

9. Select headrests - this is second-grade alcohol, slightly contaminated with head fractions. Its quantity is equal to 1-2 volumes of alcohol held by the nozzle in the column (150-500 ml). In essence, the nozzle is washed to remove any remaining “heads” and intermediate fractions accumulated in the column. To do this, the selection is set at 1/3 of the nominal level (about 500 ml/hour). Second grade alcohol is suitable for re-distillation.

10. Go to the “body” selection: set the initial selection speed equal to the nominal or slightly higher. The nominal speed (ml/hour) is numerically approximately equal to the operating heating power (in W). For example, if the operating power is 1800 W, then the initial rate of “body” selection is 1800 ml per hour. Towards the end of the selection, the power is reduced to 600 ml/hour,

11. Monitor the process using thermometer readings and pressure in the cube. There are several methods. The simplest one is to navigate by the temperature difference between the lower (20 cm from the bottom of the nozzle) and middle (at half or 2/3 of the column height) thermometers. After the start of the “body” selection, the difference between these readings should not change by more than 0.3 degrees. As soon as the difference increases by more than the accepted value, you need to reduce the sampling rate by 70-100 ml.

Special cases: if there is only one thermometer, act in exactly the same way, focusing on changes in its readings. For the lower one - a change of 0.3 degrees, for the upper one - 0.1 degrees. It's less exact method, since it is sensitive to changes in atmospheric pressure.

If there are no thermometers in the column at all, they focus on the change in temperature in the cube - reduce the selection by 6-10% after increasing the temperature in the cube by every degree. This is a good method that allows you to stay ahead of the temperature rises in the column.

12. After selecting half of the “body”, more and more often it is necessary to reduce the selection speed. When the temperature in the cube rises above 90 °C, fusel and other intermediate impurities leave the cube and accumulate in the nozzle. To cut them off more clearly, before reducing the selection, you can let the column work for itself for several minutes, then resume selection after the temperature difference returns to its previous level, naturally reducing the selection rate. This will make it possible to more clearly cut off the “tails” by creating an alcohol buffer in the selection zone.

13. When the selection decreases by 2-2.5 times relative to the initial one, the temperature regularly leaves the operating range, with the temperature in the cube being 92-93 °C. These are signals for the bookmaker that it’s time to move on to selecting “tails”. On the RK, due to the greater holding capacity, when loading less than 20 volumes of nozzle, selection can be continued up to 94-95 °C, but often the process is stopped, saving time and nerves.

Change the container, set the sampling speed to approximately half or 2/3 of the nominal one. Although these are “tails”, you need to try to take a minimum of impurities. Select up to 98 °C cubed. The "tails" are suitable for the second distillation.

14. Rinse the column. After selecting the “tails,” let the column work for itself for 20-30 minutes, during which time the remaining alcohol will collect at the top, then turn off the heating. The alcohol flowing down will wash the nozzle.

You also need to periodically steam the nozzle, removing any remaining fusel oils. This can be done by driving the raw alcohol “to dryness”, then continuing the selection at a decent speed until an odorless distillate comes out. The second method is to pour into a cube clean water and steam the column.

Rectification example 1

Initial mixture ethanol - water

Mixture consumption GF = 5000 t/h.
Concentration of the highly volatile component in the initial mixture, xF = 34% wt.
Concentration of the highly volatile component in the distillate, xD = 76% wt.
Concentration of the highly volatile component in the bottoms, xW = 3% wt.

(607.11 Kb) downloads202 times

Rectification example 2

Initial mixture ethanol - water
Mixture consumption GF = 8000 t/h.

Concentration of the highly volatile component in the distillate, xD = 80% wt.

Heating steam under pressure - 4 atm.

(610.42 Kb) downloads195 times

Introduction

2. Technological calculation

3. CONSTRUCTIVE CALCULATION

4. HYDRAULIC CALCULATION
5. Mechanical calculation
5.2 Calculation of shell thickness
5.2 Calculation of bottom thickness

5.4 Calculation of apparatus supports
Conclusion
Safety precautions

Conclusion

corrosion and erosion of the body,
mechanical damage.

Chloroform-benzene

Price for a course project on rectification from 2000 rubles

Rectification example 3

Mixture consumption GF = 6000 t/h.


Concentration of the highly volatile component in the bottom residue, xW = 4.5% wt.
Heating steam under pressure - 4 atm.

(935.21 Kb) downloads246 times

Rectification example 4

Initial chloroform-benzene mixture
Mixture consumption GF = 5000 t/h.

Concentration of the highly volatile component in the distillate, xD = 95% wt.
Concentration of the highly volatile component in the bottom residue, xW = 5.5% wt.
Heating steam under pressure - 4 atm.

(604.31 Kb) downloads178 times

Rectification example 5

Initial chloroform-benzene mixture
Mixture consumption GF = 12000 t/h.
Concentration of the highly volatile component in the initial mixture, xF = 45% wt.
Concentration of the highly volatile component in the distillate, xD = 88% wt.

Heating steam under pressure - 4 atm.

(992.92 Kb) downloads305 times

Introduction
1. Description of the technological scheme
2. Technological calculation
2.1 Calculation of the distillation column
3. CONSTRUCTIVE CALCULATION
3.1 Calculation of optimal pipeline diameters
4. HYDRAULIC CALCULATION
5. Mechanical calculation
5.2 Calculation of shell thickness
5.2 Calculation of bottom thickness
5.3 Calculation flange connections and lids
5.4 Calculation of apparatus supports
Conclusion
Safety precautions
LIST OF SOURCES USED

Conclusion

In this course project, as a result of engineering calculations, a distillation unit was selected for separating a binary mixture of ethanol - water, with a distillation column of diameter D, height H, in which sieve plates are used, the distance between which is h = 0.5 (m). The column is operating in normal mode.
One of the main conditions safe operation distillation columns– ensuring their tightness. The reasons for leakage may be:
increase in pressure in the apparatus beyond the permissible limit,
insufficient compensation for the increase in linear dimensions under temperature loads,
corrosion and erosion of the body,
mechanical damage.
The most dangerous cause of a sudden increase in pressure in the column can be the ingress of water into it. The instantaneous evaporation of water causes such rapid pore formation and an increase in pressure that the safety valves, due to their inertia, do not have time to operate, and the walls of the apparatus may rupture. To prevent water from entering the column, it is necessary to ensure that the raw materials and irrigation do not contain water, and periodically check the integrity of the tubes in the cube heater and in irrigation refrigerators. An increase in pressure in the column can also occur due to a violation temperature regime process of rectification and exceeding bandwidth columns for raw materials.
In the event of an unacceptable increase in pressure, the columns are equipped with safety valves that discharge part of the product into the flare line. If the number of trays is more than 40, then according to the PBVHP rule - 74, taking into account the possibility of sharp resistance, it is recommended to install safety valves in the bottom part of the column.
When entering the columns, the vapor-liquid stream of the product has high speeds, which can cause erosion of the walls of the apparatus. To protect the body of the apparatus, raw materials are introduced into the cavity of a special device - a volute, which is equipped with a breaker area that receives the impact of the jet and a protective sleeve that is replaced as it wears out.

Toluene-carbon tetrachloride

Rectification example 6

Initial mixture of toluene-carbon tetrachloride
Mixture consumption GF = 9000 t/h.
Concentration of the highly volatile component in the initial mixture, xF = 30% wt.
Concentration of the highly volatile component in the distillate, xD = 90% wt.
Concentration of the highly volatile component in the bottoms, xW = 3.5% wt.

(703.25 Kb) downloads261 times

Introduction
1. Description of the technological scheme
2. Technological calculation
2.1 Calculation of the distillation column
3. CONSTRUCTIVE CALCULATION
3.1 Calculation of optimal pipeline diameters
4. HYDRAULIC CALCULATION
5. Mechanical calculation
5.2 Calculation of shell thickness
5.2 Calculation of bottom thickness
5.3 Calculation of flange connections and cover
5.4 Calculation of apparatus supports
Conclusion
Safety precautions
LIST OF SOURCES USED

Conclusion

In this course project, as a result of engineering calculations, a distillation unit was selected for separating a binary mixture of ethanol - water, with a distillation column of diameter D, height H, in which sieve plates are used, the distance between which is h = 0.5 (m). The column is operating in normal mode.
One of the main conditions for the safe operation of distillation columns is to ensure their tightness. The reasons for leakage may be:
increase in pressure in the apparatus beyond the permissible limit,
insufficient compensation for the increase in linear dimensions under temperature loads,
corrosion and erosion of the body,
mechanical damage.
The most dangerous cause of a sudden increase in pressure in the column can be the ingress of water into it. The instantaneous evaporation of water causes such rapid pore formation and an increase in pressure that the safety valves, due to their inertia, do not have time to operate, and the walls of the apparatus may rupture. To prevent water from entering the column, it is necessary to ensure that the raw materials and irrigation do not contain water, and periodically check the integrity of the tubes in the cube heater and in irrigation refrigerators. An increase in pressure in the column can also occur due to a violation of the temperature regime of the rectification process and exceeding the throughput of the column for raw materials.
In the event of an unacceptable increase in pressure, the columns are equipped with safety valves that discharge part of the product into the flare line. If the number of trays is more than 40, then according to the PBVHP rule - 74, taking into account the possibility of sharp resistance, it is recommended to install safety valves in the bottom part of the column.
When entering the columns, the vapor-liquid stream of the product has high speeds, which can cause erosion of the walls of the apparatus. To protect the body of the apparatus, raw materials are introduced into the cavity of a special device - a volute, which is equipped with a breaker area that receives the impact of the jet and a protective sleeve that is replaced as it wears out.

Carbon disulfide-carbon tetrachloride

Price for a course project on rectification from 2000 rubles

Rectification example 7

Initial mixture of carbon disulfide-carbon tetrachloride
Mixture consumption GF = 7000 t/h.
Concentration of the highly volatile component in the initial mixture, xF = 20% wt.
Concentration of the highly volatile component in the distillate, xD = 85% wt.
Concentration of the highly volatile component in the bottom residue, xW = 1.4% wt.
Heating steam under pressure – 1 atm.

(994.3 Kb) downloads193 times

Methanol-water

Price for a course project on rectification from 2000 rubles

Rectification example 8

Initial methanol-water mixture caps
Mixture consumption GF = 3000 kg/h.
Concentration of the highly volatile component in the initial mixture, xF = 22% wt.
Concentration of the highly volatile component in the distillate, xD = 82% wt.
Concentration of the highly volatile component in the bottom residue, xW = 0.5% wt.
Heating steam under pressure - 4 atm.

(315.89 Kb) downloads285 times

Rectification example 9

Initial methanol-water mixture
Mixture consumption GF = 13000 t/h.
Concentration of the highly volatile component in the initial mixture, xF = 24% wt.
Concentration of the highly volatile component in the distillate, xD = 97% wt.
Concentration of the highly volatile component in the bottom residue, xW = 0.8% wt.
Heating steam under pressure - 4 atm.

(945.76 Kb) downloads329 times

Rectification example 10

Initial methanol-water mixture
Mixture consumption GF = 3700 kg/h.
Concentration of the highly volatile component in the initial mixture, xF = 25% wt.
Concentration of the highly volatile component in the distillate, xD = 96% wt.
Concentration of the highly volatile component in the bottoms, xW = 1% wt.
Heating steam under pressure - 4 atm.

(926.64 Kb) downloads215 times

Rectification example 11

Initial methanol-water mixture
Mixture consumption GF = 6500 kg/h.
Concentration of the highly volatile component in the initial mixture, xF = 27% wt.
Concentration of the highly volatile component in the distillate, xD = 98% wt.
Concentration of the highly volatile component in the bottoms, xW = 2% wt.
Heating steam under pressure - 4 atm.

(948.82 Kb) downloads241 times

Introduction
1. Description of the technological scheme
2. Technological calculation
2.1 Calculation of the distillation column
3. CONSTRUCTIVE CALCULATION
3.1 Calculation of optimal pipeline diameters
4. HYDRAULIC CALCULATION
5. Mechanical calculation
5.2 Calculation of shell thickness
5.2 Calculation of bottom thickness
5.3 Calculation of flange connections and cover
5.4 Calculation of apparatus supports
Conclusion
Safety precautions
LIST OF SOURCES USED

Conclusion

In this course project, as a result of engineering calculations, a distillation unit was selected for separating a binary mixture of ethanol - water, with a distillation column of diameter D, height H, in which sieve plates are used, the distance between which is h = 0.5 (m). The column is operating in normal mode.
One of the main conditions for the safe operation of distillation columns is to ensure their tightness. The reasons for leakage may be:
increase in pressure in the apparatus beyond the permissible limit,
insufficient compensation for the increase in linear dimensions under temperature loads,
corrosion and erosion of the body,
mechanical damage.
The most dangerous cause of a sudden increase in pressure in the column can be the ingress of water into it. The instantaneous evaporation of water causes such rapid pore formation and an increase in pressure that the safety valves, due to their inertia, do not have time to operate, and the walls of the apparatus may rupture. To prevent water from entering the column, it is necessary to ensure that the raw materials and irrigation do not contain water, and periodically check the integrity of the tubes in the cube heater and in irrigation refrigerators. An increase in pressure in the column can also occur due to a violation of the temperature regime of the rectification process and exceeding the throughput of the column for raw materials.
In the event of an unacceptable increase in pressure, the columns are equipped with safety valves that discharge part of the product into the flare line. If the number of trays is more than 40, then according to the PBVHP rule - 74, taking into account the possibility of sharp resistance, it is recommended to install safety valves in the bottom part of the column.
When entering the columns, the vapor-liquid stream of the product has high speeds, which can cause erosion of the walls of the apparatus. To protect the body of the apparatus, raw materials are introduced into the cavity of a special device - a volute, which is equipped with a breaker area that receives the impact of the jet and a protective sleeve that is replaced as it wears out.