RU2080146C1 - Method of adiabatic distillation of solutions - Google Patents

Abstract

FIELD: chemical engineering. SUBSTANCE: solution is heated to boiling temperature and sprayed with injector assistance into medium of its saturated vapor. Mixture of vapor with dispersed liquid is then introduced into separator, for example, cyclone, where liquid is separated and vapor phase is transferred into condenser where saturated vapor is condensed. EFFECT: simplified separation into pure phases. 1 dwg

Description

The invention relates to the distillation of solutions and can be used for separation into pure phases, solutions of all types:
liquids miscible in all respects, that is, the so-called "true"solutions;
partially miscible liquids;
this method is applicable for the separation into pure phases of positive azeotropes (having a minimum boiling point);
It is impossible to separate negative azeotropes (having a maximum boiling point) by adiabatic distillation into pure components, but if the solution forms a negative azeotrope, then it can be divided into an azeotrope and pure component A or B, which is in excess in the initial solution.

 The essence of the method consists in spraying a liquid (solution) into the volume of its saturating vapor, which determines the process in an adiabatically isolated system. The spontaneous process of transformation of solution droplets into pure liquid droplets occurs without heat influx from the outside and without changing the volume of the system, which shows the droplet transformations as a second-order phase transition. It is clearly seen that the known methods for the separation of solutions simple distillation and rectification, based on a phase transition of the first kind of evaporation, are not analogues of the adiabatic distillation method.

 In adiabatic distillation, molecular exchanges occur between the droplets of the dispersed liquid and the vapor saturating liquid. The volume of liquid vapor saturating in which droplets of solution are sprayed expresses an adiabatically isolated system that does not exchange heat with the environment (Q = const, P = const, T = const). This eliminates the possibility of one-sided processes of evaporation of the dispersed liquid, or condensation of the vapor phase. The volume of the system remains unchanged (V = const). Therefore, both the number of moles of the dispersed liquid and the number of moles of the vapor phase remain unchanged. As a result of molecular exchanges, only the compositions of the liquid and vapor phases turn out to be variable. In droplets of liquid, the lower boiling component is present as dissolved gas. The solubility of the gas at the boiling point of the liquid becomes zero, which determines the complete release of gas molecules from the droplet when its temperature rises to the temperature of its saturating vapor. At the initial moment of spraying, the temperature of the droplet is lower, and can even be significantly lower than the temperature of its saturating vapor. The droplet is heated as a result of condensation of its vapor molecules on the droplet surface. When the temperature of the droplet becomes equal to the temperature of its vapor, the droplet is completely self-cleaning (desorbed) from gas molecules. A drop becomes clean. Thus, the adiabatic distillation method determines the possibility of complete separation of the solution into pure phases.

 The method of adiabatic distillation of solutions is carried out in a distillation apparatus shown in the drawing.

Distillation apparatus operates as follows. Pump 1 sends the solution to heat exchanger 2, where it is heated by the heat of liquid A, then solution x enters the condenser 3, where it is additionally exposed to the heat of condensation of the vapor of liquid A. From the condenser, the hot solution x flows into the collector 4. From the collector, the solution enters the steam injector 5, where it is sprayed, and in the form of a vapor-liquid mixture it enters the separator, (for example), cyclone 6. In a cyclone, liquid droplets, in the medium of its saturating vapor, are completely purified (desorbed) from the low-boiling component gas as a result of molecular exchanges and B, are clean. In a cyclone, droplets of liquid are centrifugally thrown onto the walls and flow down. Pure liquid A from the cyclone flows into heat exchanger 2, where it gives off part of the heat to solution x, and leaves the heat exchanger as a finished product of distillation with pure liquid A (x 0). From the cyclone, the vapor-gas mixture enters the condenser 3, where the vapors of component A condense, and the gas of component B passes through the condenser with almost no delay. Since the condensate temperature is slightly lower than the boiling point of liquid A, a small portion of gas B will dissolve in condensate A and form a solution of low concentration x, which flows into collector 4 for re-distillation. Of course, there will also be a breakthrough of a small amount of liquid vapor A from the condenser 3 along with gas B. Therefore, an additional condenser 7 is installed to deeply drain the gas B from the liquid vapor A. The condenser operates in the hard mode of deep liquid supercooling. The resulting solution has a high concentration and can be used as an independent distillation product. The almost dried gas B exiting from the condenser 7 enters the condenser-cooler 8, where it condenses, cools and leaves the finished product of distillation with an almost pure liquid B (x 1 B (x = 1 - Δx).
Example 1. For distillation took a water-alcohol solution with a concentration of 8 wt. This concentration is usually found in alcohol mash. The specific gravity of alcohol is 0.8, which means 100 kg of mash, a concentration of 8 wt. affairs. contains one deciliter of alcohol.

Initial data: the amount of mash 100 kg; concentration of mash 8 wt. mash temperature 28 ^o C; heat capacity of brew 1.0 Kcal / kg; bard heat capacity 1.0 Kcal / kg; heat of evaporation of water 537 Kcal / kg; heat of evaporation of alcohol at 100 ^o C 199 Kcal / kg; vapor phase concentration y0.45 mol.d. or 67 wt. share.

The heat consumption during distillation of the solution consists of: heating the mash from the initial temperature of 28 ^o C to a final temperature of 100 ^o C, and the flow of saturated water vapor in the adiabatic process of cleaning liquid drops from alcohol molecules.

Example 2. Heated mash from an initial temperature of 28 ^o C to a temperature of 50 ^o C, produced by the heat of bards. The amount of bard obtained, taking into account the weight of the condensate, is at least 100 kg, the heat capacity of the mash and bard are assumed equal. This allows you to warm the mash in the simplest heat exchanger to an average temperature of 64 ^o C. We restrict ourselves to heating the stillage heat to a temperature of 50 ^o C.

Example 3. Further heating of the mash was carried out by the heat of condensation of water vapor in the condenser 3. The vaporous phase entering the condenser 3 has a concentration of 67 wt. So, in the amount of 8 kg of alcohol gas contains the mass of water vapor in the amount
(8 • 0.33) / 0.67 4.95 kg.

The condensation heat of 4.95 kg of water vapor is 4.95 • 537 4150 Kcal, which is sufficient to heat 100 kg of mash, taking into account heat loss, by 40 ^o C, i.e. from a temperature of 50 ^o C to a temperature of 90 ^o C.

Example 4. The final heating of 100 kg of mash from a temperature of 90 to 100 ^o C produced by steam in the injector adiabatic distiller. Heat is needed to heat the mash: 0 100.1 (100 90) 1000 Kcal, which determines the steam consumption equal
1000/537 1.85 kg
Example 5. The distillation of a droplet liquid occurs as a result of condensation of water vapor molecules on the surface of liquid droplets, which leads to the evaporation of alcohol molecules in an equal thermal ratio. The heat of evaporation (condensation) of water at 100 ^o C is equal to 537 Kcal / kg, the heat of evaporation of alcohol at 100 ^o C is 199 Kcal / kg. Consequently, condensation of 1 kg of water vapor leads to evaporation
537/199 2.7 kg
ethyl alcohol.

100 kg of brew contains 8 kg of alcohol, which determines the steam consumption equal
8 / 2.7 3 kg.

 The total steam consumption for distillation of 100 kg of mash and obtaining one decaliter of pure anhydrous ethyl alcohol is 4.85 kg / dal.

 Compare with the flow rate of steam upon receipt of one decaliter of "absolute" alcohol, for example by the method of rectification.

 Obtaining an "absolute", anhydrous alcohol by rectification is carried out on a combined rectification apparatus consisting of a three-column distillation apparatus supplemented with a dehydration apparatus. This installation is considered the most effective in terms of technical and economic indicators. The average steam consumption on this unit to obtain one decaliter of anhydrous alcohol is 59 kg / dal.

 By adiabatic distillation, the need for steam to produce one decaliter of anhydrous alcohol is only 5 kg / dal. those. an order of magnitude lower.

When adiabatic distillation is an order of magnitude lower, the flow rate of cooling water, which is used only for condensation of alcohol vapor and cooling alcohol to a final temperature of 20 ^o C, is carried out in a combined refrigerator condenser (drawing).

Initial data: amount of alcohol vapor 8 kg; the heat of vaporization (condensation) of alcohol 214.4 Kcal / kg; heat capacity of alcohol 0.58 Kcal / kg; the heat capacity of water is 1.0 Kcal / kg; cooling water temperature 15 ^o C; final water temperature 60 ^o C; the condensation temperature of alcohol is 78.3 ^o C.

 The amount of heat of condensation of alcohol vapor is 8 • 214.4 1730 Kcal.

 The amount of heat of cooling of alcohol is 8 • 0.58 • (78-20) 270 Kcal.

In total, it is required to remove heat 1730 + 270 2000 Kcal. Amount of cooling water
2000 / (60 15) 44 kg.

 During rectification, the cooling water consumption is 600 kg.

Claims (1)

 A method of adiabatic distillation of solutions, characterized in that the liquid (solution) is heated to a boiling point, then sprayed with an injector or other device into a medium that saturates the liquid vapor, after which the mixture of vapor with dispersed liquid enters the separator, where the liquid exiting the separator is separated the vapor phase enters the condenser, where the saturating vapor of the liquid condenses.