NL8104012A - METHOD FOR CONCENTRATING AQUEOUS GLYCOL SOLUTIONS. - Google Patents

Description

813190 / vdV / mk * '»

Short designation: Method for concentrating aqueous glycol solutions.

The invention relates to a new method for concentrating aqueous solutions of glycols using multistage distillation in vertical thin layer exchangers in successive steps of one or more vertical columns.

Aqueous glycol solutions are currently concentrated using a series of series evaporators 10 and evaporators as indicated in the flow chart of Figure 1.

In this flow chart, the aqueous low-concentration glycol solution is fed through line 1 and exchanger 2 (which is heated by steam 3) to the first evaporator. At the bottom of the evaporator, the concentrate with a higher concentration is fed via line h, line 5 and exchanger 6 to the second evaporator, from which the solution goes to the third evaporator via line 7, exchanger 8 and line 9. From here, the even more concentrated solution goes via line 10, exchanger 11 and line 12 to the last evaporator V4, which is kept with jet pump 16 under a vacuum of about 150 mm mercury.

The solution is concentrated even further in an evaporator and passed via 13 and pump Ik to storage container 13 *

On top of the first three evaporators comes a mixture of steam and small amounts of glycol condensed in exchanger 6, 8 and 11 and collected in containers 17 and 18.

The vapor emerging from the top of the fourth evaporator is condensed in cooling device 19 and returned to the glycol plant along with the other glycol-containing condensates.

To prevent excessive losses of glycol in the vapors, wash water is fed through 20 at the top of the evaporators and fed.

It has now been found that it is easier to concentrate the glycols in a multi-stage column with significant savings in steam using the principle of multistage distillation using vertical thin layer exchangers.

The invention therefore provides a new method for concentrating aqueous glycol solutions, which is distinguished in that it uses a single vertical column divided into a number of cylindrical divisions, each of which is provided with: 8104012 ς'-.

* »-2- a) one or more thin layer evaporators with vertical tube bundles without Outer jacket, b) one or more small dishes connected from the bottom to the top of the tube bundle of one of the thin layer evaporators in the same section, wherein the small dishes in the last section without thin-layer evaporator are connected to a tube leading to a stock container for the concentrated solution of glycols, while they are at the top with the bottom tube plate of one of the thin layer evaporators "in the upper section and the small trays in the first section are directly connected to the tubes supplying the glycol solution to be concentrated; c) a system for airtight closing and control of the flow introduced in the bottom of all the small trays with which the flow of the solution of glycols from the small dish to the underlying thin layer exchanger is controlled; d) openings at the top in the side walls of the small dishes, with the exception of the dishes in the first section; e) one or more siphon tubes connecting two consecutive compartments and with which the condensate collected in the compartments is fed to the next compartment, the first compartment additionally comprising tubes for supplying the solution to be concentrated in the small dishes. (b) and the supply of saturated steam for heating said solution, the latter section being provided with tubes for discharging the condensates, draining the concentrated glycol solution and connecting to the vacuum system.

The new method for concentrating aqueous solutions of glycols is now explained in more detail with reference to the vertical column shown in Figure 2.

For example, the total number of stages is set at nine, with each stage provided with one small tray and one thin layer evaporator.

In the drawing, column 1 shows the first three compartments or stairs with 1a, 2a and 3a and the last three compartments with 7a, 8a and 9a, the three intermediate compartments not being shown due to lack of space.

The solution to be concentrated, which comes out of the ethylene oxide plant as a result of the exothermic reaction of ethylene oxide + ^ 0- ^ glycol, goes hot via line 2 to small tray k of the first stage.

From small dish k, the solution goes through the sealing ^ 0 system and the flow rate control system 6 to thin 810.4012 ♦ «Γ.

-3- low-evaporator 8, in which the solution is again heated with fresh steam from 5, and from there to the small dishes and the evaporators underneath them 8, whereby the solution becomes increasingly concentrated, until in the last stage 9a the maximum concentration is reached. and the solution is passed through line 10 to the storage container.

The vapors generated in the small trays after the first stage are allowed to expand through the discharge openings 7 and condense outside the tubes 8 of the thin-layer evaporators while simultaneously heating the solution flowing inside the tubes.

The condensates collected at the bottom of each stage go from one stage to the next through the siphon tubes or pipes 9 to the last, from which they are discharged via line 11. The vapors from the small tray of the last stage 9a are condensed in the jacketed cooling device 14.

The tubes and valves 12 serve to carry any inert gases present from one stage to the next up to the last stage, which is connected to the vacuum system via line 13.

To demonstrate the advantages of the new method of concentrating aqueous solutions of glycols compared to the known methods, an example of a test of concentrating a solution of glycols is carried out using two devices, one known and one a new single column, at the same temperature and pressure per hour, is fed with the same amount of aqueous solution of glycols.

25 The results are summarized in the table.

KNOWN DEVICE POWER SUPPLY THIS DEVICE

41370 kg / h (a 12.7 / 5 * 5 41370 kg / h solution of glycols)

150 ° C Temperature 150 ° C

30 13 kg / cm2 Pressure 13 kg / cm2 5952 kg / hour Amount obtained 5900 kg / hour concentrated solution 84.85 wt. # Concentration 88 wt.%

84 ° C Discharge temperature 73 ° C

33 0.2 kg / cm2 Discharge pressure 0.1 kg / cm2 9150 kg / hour Steam consumption 1690 kg / hour at 17 kg / cm2 at 3.7 kg / cm2

In the example above, the concentration of the supplied solution is 12.7% by weight and that of the discharged solution is 88% by weight.

40 If the concentration of supply or discharge changes, the 8104012 5 ^ will also change

J * L

supply and exhaust pressure and temperature of the column

For concentrating glycol from 0 to 100% 2, a pressure of 20 to 0.03 kg / cm and a temperature of 200 to 30 ° C is usually used. * The use of the new process of the invention provides the following benefits.

(a) Substantial savings in steam when heated. Concentrating 1370 kg of solution per hour according to the known method consumes 915 kg of steam, while treating the same amount of solution according to the new method requires about 1690 kg of steam, ie a steam saving of 9150 - 1690 100 = 81.5 $.

9150 (b) Lower costs for generating saturated steam for heating 2 because according to the new method a steam pressure of 3.7 kg / cm is sufficient and according to the known method steam with a pressure of 17 kg / cm is required . The saturated steam pressure for heating is from 2 to p kg / cm, depending on the initial and final concentration of the solution.

(c) Greater simplicity and reliability of the entire system. In the new method, a single column replaces the assembly of several 20 columns of the known system.

(d) Due to the lower operating costs, the start-up costs for the new facility can be amortized within approximately 2 years. The cost of a new installation that processes ^ 1370 kg of solution per hour is estimated at approximately Lit 1050 million. Assuming that the number of operating hours 25 per year is 8000, the saturated steam at 3.7 kg / cm costs 7 lire per kg and the cost of saturated steam at 17 kg / cm costs 10 lire per kg, resulting in annual savings (10 x 9150 - 7 x 1690) x 80OO = Lit 637 million a year. The invested capital of Lit 1050 million can therefore be amortized within two years.

30 35 8104012

Claims (3)

Method for concentrating aqueous solutions of glycols, characterized in that the said solutions are allowed to evaporate in the form of a thin liquid layer in a number of vertical thin-layer evaporators using the principle of multistage distillation. 2. Process according to claim 1, characterized in that the aqueous solutions of glycols 10 are concentrated in a single vertical column which is divided into a number of cylindrical compartments, each comprising: a) one or more thin layer evaporators with vertical tube bundles without external jacket; b) one or more small dishes connected via the bottom to the top tube plate of one of the thin layer evaporators located in the same compartment, said small dishes in the last compartment without a thin layer evaporator connected to a tube which leads to the stock container for the concentrated solution of glycols, while they are connected at the top to the bottom tube plate of one of the 20 thin layer evaporators in the top section and the small trays in the first section directly to the supply tubes for the concentrate solution of glycols in compound; c) a system for maintaining and controlling the flow rate in the bottom of the small dishes that controls the flow of the solution of glycols from the small dish to the underlying thin layer exchanger; (d) openings at the top of the side walls of the small dishes, excluding those in the first section; e) one or more siphon tubes connecting two consecutive compartments and with which the condensate collected in the compartments is fed to the next compartment, the first compartment additionally comprising tubes for supplying the solution to be concentrated to the small dishes. (b) and for the supply of saturated steam for heating said solution while the latter section is provided with tubes for discharging the condensed water, discharging the concentrated solution of glycols and connecting to the vacuum system. 3. Process according to claim 2, characterized in that the pressure of the saturated steam for further preheating the solution of glycols is from 2 to k kg / cm. 8104012 k. Process according to claim 2, characterized in that the concentration of the aqueous solutions of glycols for all glycol concentrations takes place at a pressure between 20 and 0.03 kg / cm and a temperature of 200 to 30 ° C . -5 8104012