WO2006016354A2

WO2006016354A2 - Process for the prevention and elimination of foam

Info

Publication number: WO2006016354A2
Application number: PCT/IL2005/000850
Authority: WO
Inventors: Mira Bergstein-Freiberg; Haim Straze
Original assignee: Bromine Compounds Ltd.
Priority date: 2004-08-09
Filing date: 2005-08-08
Publication date: 2006-02-16
Also published as: IL163419A; WO2006016354A3

Abstract

A process for the prevention and/or elimination of foam in the production of bromine comprises the step of mixing with the feed brine an amount of up to 20 ppm of an anti-foam silicon-free compound containing hydroxyl groups, wherein said ppm amount refers to the weight of the anti-foam in the total feed brine.

Description

PROCESS FOR THE PREVENTION ANB ELIMINATION OF FOAM

Field of the Invention

The present invention relates to the prevention and elimination of the foam which forms

during the bromine production process. The invention has been developed with particular

reference to brines used and formed during the production of bromine from the Dead Sea, but

is generally applicable to brines having a similar composition and to processes in which foam

is formed in such or similar brines.

Background of the Invention

The invention will be described with reference to the bromine production process carried out

by Dead Sea Bromine (hereinafter DSB) , which produces bromine from the Dead Sea brines,

as will be defined hereinafter. This fact however is not a limitation of the invention, which

could be implemented advantageously in other bromine production processes from natural

sources other than the Dead Sea (including bromine recovery processes) and processes

containing brines at various concentrations and at high temperatures.

DSB produces bromine by means of the steaming-out process, which consists of simultaneous

chlorination and steam blowing, and which is well known to persons skilled in the art. The

feed brine is preheated before its introduction into the column and heated inside the column to

near boiling. Chlorine and steam are also fed into the column. As the bromine in the feed

brine is set free by the chlorine, the bromine is steam-distilled (more information may be

found in the well-known book Bromine and its Compounds, edited by Z.E. Jolles). - -

The brines in which foam forms and in which it must be prevented and eliminated are

essentially constituted by calcium and magnesium chlorides, and to a lesser extent sodium and

potassium chlorides and bromides. They may contain such impurities as sulfates and

carbonates. Said brines are called and will be called hereinafter "feed brines" (FB).

Below is a typical composition of the feed brine:

The formation of foam during the production process is highly undesirable and has negative

effects in the production process of bromine from Dead Sea brines. The foam raises the

pressure in the bromine production column, which lowers the production throughput and may

even overflow from the production columns and contaminate other equipment and the

surroundings. Attempts have been made to eliminate or "collapse" the foam by means of additives, the most common in the prior art is soy oil. No known additive, however, possesses

all the properties that are needed from the technical and from the economical viewpoint. Said

properties may be summarized as follows:

1. Such effectiveness as totally to prevent and/or eliminate the foam at

concentrations lower than 2 ppm.

2. Stability under the conditions of use, particularly no degradation when

mixed with the feed brine at temperatures up to 120⁰C.

3. Resistance to oxidation in the presence of bromine and chlorine and

species formed during the production process.

4. Low cost.

Soy oil does not have those properties. It is not fully effective and does not prevent or totally

eliminate the foam, particularly at low concentrations. It affects the purity of the products, it is

relatively costly, and is not stable enough, tending to decompose under the severe conditions

of its use. Other compounds, e.g. diesel fuel and siliconic antifoams, have been tried as foam

preventors and eliminators, but have been found to be inefficient and sometimes even

counterproductive in that they do not prevent the formation of the foam and even swell the

foam

It is therefore an object of the present invention to provide a process for the prevention and/or

elimination of foam in the production of bromine, which is based on the use of an anti-foam

additive that is fully effective even at low concentrations, preferably at concentrations below 2

ppm. It is another object to provide such a process that is adapted to the production process of bromine from the Dead Sea.

It is a further object to provide such a process for the elimination of foam from the feed brines

existing in the production process of bromine from the Dead Sea.

It is a still further object to provide such a process wherein the anti-foam additive is stable in

contact with the brine containing bromine and other compounds at temperatures up to 120⁰C.

It is a still further object to provide such a process wherein the anti-foam additive does not

react/undergo oxidation in contact with bromine or chlorine or compounds formed during the

production of bromine.

It is a still further object of the present invention to provide such a process that is economical

and does not require costly materials.

Other objects and advantages of the invention will become apparent as the description

proceeds.

Summary of the Invention

The invention provides a process for the prevention and/or elimination of foam which

comprises the step of mixing with the feed brine to the production column, an amount up to

20 ppm, preferably up to 5 ppm, and most preferably from 0.8 to 2 ppm (the ppm being

always referred to the weight of the feed brine), preferably at temperatures from ambient to - -

the boiling temperature of the brine during the production process, of an anti-foam silicon-

free compound containing hydroxyl groups (such as Dehydran®-D, a product of Henkel).

The anti-foam can be preferably added into the feed brine by means of a continuous dosing

system, before said feed brine enters the production column. The anti-foam can also be

introduced directly into the production column.

By this process, foam in the production column is prevented and/or totally collapsed even at

concentrations of anti-foam agent lower than 2 ppm. The Dehydran®-D anti-foam agent is

stable to oxidation in the presence of chlorine and bromine and compounds formed during the

production of bromine, is chemically stable when mixed with the feed brine at the boiling

point of the brine during the production process, and it has long shelf life since its activity is

not reduced by exposure to elevated temperatures for long periods of time.

Brief Description of the Drawings

In the drawings:

Fig. 1 schematically illustrates an experimental setup for testing the activity

and efficiency of an anti-foam agent;

Fig. 2 illustrates the time dependence of the foam height at several

concentrations of Dehydran®-D antifoam agent;

Fig 3 illustrates the time dependence of the foam height on the exposure of

Dehydran®-D antifoam agent to elevated temperatures before use; and - -

Fig 4 illustrates the time dependence of the foam height for various feed brine densities.

Detailed Description of the Invention

The following examples of embodiments of the invention are illustrative and not limitative.

Example 1

In a production facility, 0.8 ppm of Dehydran®-D was added to the feed brine. In one

instance, it was added before the inlet of the feed pump and in a second instance it was added

after the outlet from the feed pump. No increase in pressure was detected in the production

columns during this operation. At a lower concentration of Dehydran®-D, an increase in

pressure was detected in the production columns.

Example 2

The effectiveness of the process of the invention can be evidenced by means of an

experimental setup schematically illustrated in Fig. 1 , which simulates the process carried out

in the bromine production plant. It comprises a laboratory glass column 10 (which in the

present specific tests was 75 cm long and 3 cm in diameter). Numerals 11 and 12 indicate

openings for the air (for artificial enhancement of the foam) and chlorine inlets, respectively.

Numeral 13 indicates a septum through which the anti-foam agent is injected. 14 is an outlet.

15 is an oven. 16 is a thermometer. 18 is an outlet for a gas mixture which contains air,

chlorine and bromine, and proceeds to a NaOH trap for ecological reasons, which is not

shown. 20 is a millimetric scale. - -

In each test, 350 cm³ of Dead Sea feed brine (FB) were put in the column through the top of

the column and heated to boiling temperature (approximately 120⁰C) by means of oven 15.

Concurrently, clean dry air was continuously introduced ( in order to enhance foam) at a low

flow rate and its flow was monitored with a flow meter. As the temperature stabilized at the

boiling point, the air flow was increased to 320±30 cm³. From 2 to 20 ppm of anti-foam agent

(Dehydran®-D) was then injected through septum 13. After 10 seconds following the

injection, chlorine (99.0% purity) was introduced for one minute at a flow rate of 0.02

mol/min. It was calculated that at this rate all the bromine from the feed brine is oxidized

within one minute. The test continued for another 4 min, while only air flowed through the

column. During the test, the foam height was measured by means of millimβtric scale 20. The

measurement accuracy of the foam height was ±2 cm. The brine temperature was measured at

intervals of 30 seconds.

Fig. 2 shows the variation of the foam height with time. It is seen that, after the introduction

of chlorine, the foam height first rises and drops sharply, then stabilizes at a certain level,

drops after 120 seconds, and remains practically constant well below 5 cm. The final foam

height varies only slightly with the concentration of the anti-foam agent.

Fig. 3 illustrates the time dependence of the foam level at 2 ppm in Example 2 when the

Dehydran®-D was: a) maintained at 80⁰C for 8 days prior to the injection, b) maintained at

40⁰C for 8 days prior to the injection, and c) maintained at room temperature prior to the

injection. It is seen that the efficiency of the process does not vary significantly. - o -

Fig. 4 illustrates how the foam level in Example 2 depends on the density of the feed brine.

Here too, it is seen that the efficiency of the process does not vary significantly.

Comparative tests carried out by attempting to use other compounds as anti-foam agents have

shown that they are not efficient and certainly not comparable to Dehydran®-D. Diesel fuel,

for instance, does not reduce the formation of foam. Other compounds decompose after 10

seconds or are halogenated and lose any effectiveness. Other compounds require high

concentrations, e.g. 20 ppm, to produce any effect.

While examples have been given for purposes of illustration, it will be understood that they

do not limit the invention, which can be carried into practice by skilled persons with many

modifications, variations and adaptations, without departing from its spirit or exceeding the

scope of the claims.

Claims

1. Process for the prevention and/or elimination of foam in the production of bromine,

which comprises the step of mixing with the feed brine an amount of up to 20 ppm of an anti-

foam silicon-free compound containing hydroxyl groups, wherein said ppm amount refers to

the weight of the anti-foam in the total feed brine.

2. Process according to claim 1, wherein the amount of the anti-foam silicon-free

compound containing hydroxyl groups is up to 5 ppm.

3. Process according to claim 2, wherein the amount of the anti-foam silicon-free

compound containing hydroxyl groups is from 0.8 to 2 ppm.

4. Process according to claim 1, wherein the anti-foam silicon-free compound containing

hydroxyl groups is Dehydran®-D.

5. Process according to claim I₅ wherein the anti-foam silicon-free compound containing

hydroxyl groups is mixed with the feed brine at temperatures from ambient to the boiling

temperature of the brine during the production process.

6. Process according to claim 4, wherein the Dehydran®-D is mixed with the feed brine

in an amount up to 20 ppm, at temperatures from ambient to the boiling temperature of the

brine during the production process.

7. Use of Dehydran®-D as agent for the prevention/elimination of foam from feed brines in

the production of bromine.