DE1567988C - Process for the production of sodium carbonate and sodium sulfite - Google Patents

Description

leads and is removed from the system and a return of the remaining mother liquor that Contains sodium hydroxide and small amounts of sodium carbonate or sodium sulfite. The procedure is characterized in that the mother liquor is fed back into the amalgam decomposition plant and the sodium hydroxide concentration of the returning mother liquor between 28 and 45 percent by weight and the sodium carbonate or sodium sulfite concentration of the entire decomposition plant supplied aqueous liquid holds at 0.1 to 1.0 or 0.01 to 0.7 percent by weight.

In the method according to the invention, it is not necessary to evaporate the water supplied to the formation reaction of sodium carbonate together with the sodium hydroxide, but it is possible to reuse this water as water for the decomposition plant. Therefore, even if about 50 _^0/0 sodium hydroxide is used, which is formed in the usual mercury electrolysis, sodium carbonate, anhydrous sodium carbonate or anhydrous sodium sulphite are produced is required without additional thermal energy.

The formation reaction for sodium carbonate from sodium hydroxide is formally a dehydration according to the following equation:

2NaOH + CO ₂ ■ + - Na ₂ CO ₃ + H ₂ O (1)

As a result, the water content is increased by this reaction. The amalgam decomposition is however formally hydration after the following implementation:

2Na + 2H ₂ O - * - 2NaOH + H ₂ (2)

Therefore, if these two reactions are combined in the reverse flow process, as in the case of the invention Procedure is the case, then the overall reaction is hydration according to the following Equation that requires the addition of water:

2Na + CO ₂ + H ₂ O - + ■ Na ₂ CO ₃ + H ₂ (3)

It is evident that the addition of water is easier than is the evaporation of water. When adding additional water, this can also be used a lot of water are supplied that prevents crystal precipitation in the decomposition system and thus the Control of the process is facilitated. The production of sodium sulfite occurs essentially in the same way, using sulfur dioxide in place of carbon dioxide. The reaction proceeds in this case according to the following formula:

2 NaOH + SO ₂ - * - Na ₂ SO ₃ + H ₂ O (1 a)

Therefore, if this reaction is combined with the amalgam decomposition according to equation (2), then the resulting reaction can be represented by the following formulas:

2Na + SO ₂ + H ₂ O - »- Na ₂ SO ₃ + H ₂ (3 a)

The reaction according to equation (3a) is in contrast to the dehydration according to equation (la) one Reaction that consumes water and is therefore preferable. In this case the water is in the form of a Sodium hydroxide solution containing a small amount of sodium sulfite returned to the decomposition plant.

The invention is described in more detail for further explanation with reference to the drawings.

F i g. 1 shows the flow diagram for a process for the production of sodium carbonate according to the invention;

F i g. 2 shows a flow diagram for a process for the production of sodium sulfite according to the invention. According to FIG. 1, water A containing sodium hydroxide and 1% or less sodium carbonate is sent to a decomposition plant I, to which the sodium amalgam B to be decomposed flows from an electrolytic cell II, so that a sodium hydroxide solution having a high concentration is formed. The mercury C returns to the electrolysis cell II in the return current.

The liquid flowing out of the decomposition plant is led to a first crystallization vessel III and mixed with sodium carbonate monohydrate, which is in a pulpy state and flows in from a second crystallization vessel V. The sodium hydroxide concentration in the resulting mixture is adjusted to 28% or more, whereby the sodium carbonate is turned into an anhydride. The slurry is fed to a separator IV in which the anhydrous sodium carbonate D is separated off. The water adhering to the crystals formed is dried away in a suitable manner, whereupon the desired product results.

The mother liquor, from which the crystals have been separated in separator IV, is diverted into two return flow channels initiated. One part of the mother liquor is transferred to the second crystallization vessel V and in this mixed with a sodium carbonate solution, which is fed from an absorption tower VI, with it the sodium carbonate monohydrate crystals precipitate and a pulp is formed.

In the second crystallization vessel V, which is a sedimentation vessel in the manner of a thickener, the slurry is concentrated and then passed to the first crystallization vessel III, while the supernatant liquid is passed to the absorption tower VI. In a modified embodiment, a crystallization vessel and a separator can be provided separately from one another, the slurry or crystals and the clear mother liquor being separated from one another in the separator and fed to the first crystallization vessel III or the absorption tower VI. The concentrated liquid fed to the absorption tower VI is brought into contact with dilute carbon dioxide gas E , the sodium hydroxide in the solution being converted into sodium carbonate. At the same time, the liquid is concentrated by the heat generated during the reaction, and water vapor is carried away through an outlet line F together with exhaust gases.

The other part of the mother liquor from the separator IV is used again as treatment water and fed to the decomposition plant together with the additional water G.
If, in the process described above, the concentration of sodium carbonate in the treatment water A, which is fed to the decomposition plant I, is significantly greater than the saturation concentration of the sodium hydroxide solutions flowing in or out, then sodium carbonate will precipitate in the decomposition plant. As a result, the decomposition efficiency decreases undesirably and the decomposition plant becomes clogged. Care must therefore be taken to ensure that the concentration of the

5 6

Sodium carbonate flowing in in the solution does not make both crystallizers into one unit

is above 1%. possible. For example, if the crystallization

The concentrations of sodium hydroxide or if a sediment sodium carbonate is used for thickening in which the decomposition plant I is tion device and in the excess water carbon back-flowing treatment water A is automatically introduced 5 dioxide gas. B. by the concentration of sodium alone as an adsorption device and crystallization device hydroxides in the first crystallization vessel III, through which act. If, on the other hand, a trickle tower is used in a different execution concentration of the sodium hydroxide at the outlet of the formation form, the decomposition plant I and the upper end of the decomposition plant determine the amount of water evaporated by the decomposition plant. If you are larger than 10, then sodium hydroxide is sprayed, while 10 or 0.1 percent by weight, if 55% or less of the lower part of the tower is conducted with carbon dioxide and concentrated sodium hydroxide is used, then anhydrous sodium carbonate can be added to the Mercury electrolysis of NaCl is also available in a single process step. can be obtained.

The absorption tower VI and the two crystalline 15 If a monohydrate is desired, then

Sation vessels III and V are in the F i g. 1 in general the within the crystallization

shown embodiment is separated from the following vessel formed crystals, and it is,

Reasons for the crystallization of anhydrous sodium if the concentration in the separated mother liquor

umcarbonate used. tion of sodium hydroxide is low and the sodium car-

The carbonate content flowing back to the absorption tower VI is high, this a sodium hydroxide solution-sodium hydroxide solution expediently has a solution of even higher concentration added, a concentration of about 10 to 20 percent by weight, so that the sodium hydroxide concentration is 28% cent. Above this concentration range is or more, preferably 33% or more, is pending the possibility of precipitation in the tower increases. Sodium carbonate is used here in the form of standing sodium carbonate and to clog the anhydrous crystals or in the form of MonoTurm. Therefore, the concentration of sodium hydrate crystals should be precipitated and separated while hydroxide solution in the second crystallization vessel V with the resulting mother liquor in a suitable manner preferably 20 percent by weight or less, dilute water and return to decomposition plant I. At this concentration the sodium is crystallized.

umcarbonate as a monohydrate. Therefore an additional 30 If one, however, the concentration of the sodium

the first crystallization vessel III is provided, in which the hydroxides in the crystallization vessel V are increased and equal-

the sodium hydroxide concentration to 28 times the temperature of this solution below the

percent or more, preferably to 33 weight percent temperature of the transition from monohydrate to

cent or more, is maintained to keep the monohydrate anhydrous sodium carbonate at that concentration

is converted into an anhydride. 35 of the sodium hydroxide holds in the crystallizer,

Since the concentration of sodium hydroxide in then can be in the concentrated sodium hydroxide

first crystallization vessel III in this case high monohydrate crystals in a single step

is, the amount of sodium dissolved in the mother liquor is to be obtained. If still in some cases

carbonate low, and also the decomposition plant I once the conversion of the sodium carbonate into

backflowing amount of sodium carbonate is in an anhydride in crystallization vessel III,

desirably low. then the anhydride can be dissolved in dilute caustic soda

The conversion of sodium carbonate monohydrate or a saturated solution of sodium carbonate

in an anhydride is to be reproduced by the concentration of the Na-

trium hydroxide and the temperature is determined. Even with the aid of FIG. 2 is now the erfindungsgewenn the sodium hydroxide concentration is 28% based on the manufacture of anhydrous sodium sulfite or lower, occurs at high temperature (i.e. wrote:

at about 75 ⁰ C or more) a conversion to anhydrous water, which is sodium hydroxide and 0.7 hydride. If the sodium hydroxide concentration weight percent or contains less sodium sulfite, decreases, the solubility of the sodium is for decomposing sodium amalgam B, which carbonate to, and in a solution / o ° is supplied to less than 50 of an electrolytic cell II 28 °, contains sodium hydroxide, the solubility of the decomposition system I initiated increases, whereby a concentrated sodium carbonate is formed in the liquid to 5% by weight sodium hydroxide solution. The mercury percent or more. silver C returns to the electrolytic cell II. The con-

Even if this solution is diluted with water and concentrated caustic soda becomes a first crystalline, is the sodium carbonate concentration in the 55 sationgefäß VII, where it is with one of a

to the decomposition plant I conducted water A into the separator IX inflowing saturated sodium sulphate

in most cases above 1% and thus above fit solution is mixed so that a sodium sulfite

the solubility at which the crystal slurry is normally formed at the exit.

Decomposition plant I present concentration During this process it is desirable to use the (35 weight percent or more). As a result, 60 concentrations of sodium hydroxide in the solution result in

those mentioned above and in the decomposition plant located in the first crystallization vessel VII

Occurring precipitations lead to undesirable results. To keep 20 or more percent by weight and

The sodium hydroxide concentration of the solution, at which point the concentration of the dissolved sodium sulfite

Sodium carbonate anhydride crystals precipitate and must be kept at a low level. The first crystalline

Her at 28 percent by weight or more, preferably 65 sationsgefäß VII thus serves as a thickener, and the

between 33 and 45 percent by weight. Sodium sulfite crystals that are formed in it are

A combination of two or more fronts together with the solution to a second crisis

directions, namely the absorption tower and the installation vessel VIII, where they are

7 8

nem adsorption tower X inflowing mixture of sodium carbonate or sodium sulfite in the crystalline

Sodium bisulfite and sodium sulfite are mixed and lowered to the sationsgefäß.

Reaction to be brought. Sodium sulphate is formed in the two exemplary embodiments.

fit crystals and a saturated sodium sulfite solution. all additional treatment water either directly

In this process section, the first 5 (Fig. 1) or indirectly (Fig. 2) of the decomposition

Crystals formed in second layer I are supplied to crystallization vessel VII. However, it is not absolutely necessary

th crystallization vessel VIII continues to increase until dig, the entire proportion of this treatment water

forms a pulp. This slurry is fed through the SeparatorIX as additional water in this way,

out, whereby the sodium sulfite crystals D separate but you can also split it into several parts

separate and after drying the desired product and the individual parts at such points of the overall

form duct. systems, where a crystallization for the

The mother liquor from the separator IX is undesirable in two operations, and thereby the crystalline

Parts shared. The first part flows to the first to prevent crystallization at these points by dilution,

sationsgefäß VII and the other part for absorption For a better understanding of the invention are now

tower X, where it implemented with sulfur dioxide gas E 15 described some embodiments in more detail,

will. This creates sodium bisulfite. Simultaneously . · 1 1

evaporates due to the heat development that in the B e 1 s ρ 1 e 1 1

Solution located water, so that the solution After the on hand of the F i g. 1 described

concentrated. The evaporated water is combined with anhydrous sodium carbonate.

carried away with other exhaust gases through a channel F. 20 places. To do this, an aqueous solution that weighs 848 kg

The supernatant liquid in the first crystallization contains NaOH and 8 kg of Na ₂ CO ₃ , with a flow

tion vessel VII is fed by water G speed of 2680 kg / hour. continuously in the

thins and re-introduced as treatment water A for the decomposition plant I from above to get through

Decomposition plant I used. Contact within the decomposer 0.2 ° / ₀ sodium

If in the production of sodium sulfite the 25 (percent by weight) sodium amalgam, which is supplied from the concentration of the sodium hydroxide solution at the outlet of the electrolysis cell II and 434 kg / hour. Decomposition plant I contains less than or equal to 55% sodium. This results in an is, then the sodium hydroxide concentration of the temperature of 80 ⁰ C with a rate of treatment water A at 20 percent by weight or 3082 kg / hour. an aqueous, 52% sodium hydroxide more and the sodium sulfite concentration at 0.01Ge-30 solution, which are 1603 kg (52%) NaOH and 8 kg (0.26%) weight percent or more. Contains Na ₂ CO _3. As a result of hydrogen formation

If, however, the proportion of sodium sulphite in the system is greater than the concentration of a speed of 13 kg / hour in this process with tap water A. Water and sodium hydroxide solution at the outlet of the decomposition plant (when steaming.

Equilibrium), then in the decomposition plant I 35 the sodium sulfite given off by the decomposition plant I precipitates, and the efficiency of the decomposed trium hydroxide solution is immediately reduced in the first crystallization. Therefore, during normal operation, the notification vessel III is initiated and agile with a suspension that the sodium sulfite concentration is mixed at a rate of 2225 kg / maximum value of 0.7 percent by weight. Hours from the second crystallization vessel V and the temperature of the sodium hydroxide at the exit contains 40 and 981 kg of Na ₂ CO ₃ and 185 kg of NaOH (input of the decomposition plant I at least 50 ^° C. or a larger part, namely 848 kg of the Na ₂ CO ₃ , is suspended in the form of monohydrate crystals ), the _t also in the production of sulfite, it is temperature by injection of air within the Ge- (X \ not absolutely necessary, the adsorption tower X fäßes III is maintained at 70 ° C. In this vessel, III ^ and the two crystallization vessels VII and VIII 45 evaporates water at a rate of separating from each other, but you can also use two 34 kg / h, and everything from the second crystallization or _{Na 2} CO ₃ supplied to a single device vessel for several of these devices is combined in the anhydrous criterion. For example, if the transformation form is converted.

Settlement of concentrated sodium hydroxide solution The one produced in the first crystallization vessel III

and SO _{2 is carried out} in an absorption tower, then 50 anhydrous sodium carbonate (973 kg / h) is added in

a sodium hydro separator IV is separated in a single process step. Because 5% of the mother liquor from

oxide solution can be obtained, the anhydrous sodium in this crystallization vessel still attached to the crystals

Contains sulfite crystals. adhere and contain about 21 kg NaOH, these will

To reduce the amount of dissolved sodium crystals dried in a stream of hot air, the

carbonate or sodium sulfite in the first crystallization 55 contains carbon dioxide gas, 1000 kg of anhydrous

vessel it is desirable to create the concentration of sodium sodium carbonate.

hydroxide to 28 or more percent by weight, preferred as mother liquor, from which the crystals in the separa-

wise to 35 to 45 percent by weight. Cut off at gate IV, it is

Place of or together with the use of speed of 4254 kg / hour. get a solution that

High sodium hydroxide concentrations can produce 60 1767 kg (41.7%) NaOH and 16 kg (0.38%) Na ₂ CO ₃

to lower the concentration of sodium. This solution is divided into two parts, by

carbonates or sodium sulfite (at equilibrium) which one part (of 848 kg of NaOH and 8 kg of Na ₂ CO ₃

also small amounts of sodium salt, e.g. B. NaCl or contains) with a flow rate of

Sodium sulfate, as a foreign salt within the total 2040 kg / hour. as treatment water A for decomposition

systems and at the same time the temperature generation system I flows back. At the same time, the

low. Although these foreign salts nowhere do decomposition plant I with a flow velocity

of the system crystallize out by itself, causes its speed of 640 kg / hour. Water supplied. The remaining

Presence that the equilibrium solubility of the bende portion of the above solution, the 919 kg of NaOH

and 8.3 kg of Na ₂ CO ₃ , namely 2214 kg / hour, is fed to the second crystallization vessel V.

As the second crystallization vessel V, a continuously operating sedimentation device is used in the manner of a thickener, in which a saturated sodium carbonate solution flowing in from the absorption tower VI and an approximately 40% sodium hydroxide solution flowing in from the first crystallization vessel III can be mixed and in which the sodium carbonate partially dissolves In the form of monohydrate crystals, with the settled crystals collecting and concentrating in the central part of the vessel while the surrounding fluid is clarified. Through inlet openings in the middle part of the second crystallization vessel V from the absorption tower VI at a rate of 5011 kg / hour. a sodium carbonate solution containing 1501 kg Na ₂ CO ₃ , and introduced the mother liquor from the separator IV and mixed in the crystallization vessel V. The sodium carbonate partially settles in the form of monohydrate crystals, and the concentration of the mother liquor within the vessel is adjusted so that it contains 15 percent by weight NaOH and 10.8 percent by weight Na ₂ CO ₃ . The deposited crystals are collected at a central exit opening and led to the first crystallization vessel III. By admitting air the interior of the crystallization vessel V is maintained at a temperature of 7O ⁰ C, so that 110 kg of water to evaporate.

From the outer, the clarifying part of the second crystallization vessel V is at a rate of 3893 kg / h. withdrawn a solution containing 734 kg of NaOH and 530 kg of Na ₂ CO ₃ , and passed to absorption tower VI, where it _{reacts with combustion gases containing about 10 volume percent CO 2} , and at a rate of 404 kg / h. CO ₂ absorbed. At the same time, at a speed of 285 kg / hour. Water evaporates. The resulting solution, which is 1502 kg / hour. Contains Na ₂ CO ₃ , is returned to the second crystallization vessel V.

During the entire process, only that contained in the combustion exhaust gases is used from the outside Heat energy supplied, which is used to dry the anhydrous sodium carbonate. The in Absorption tower IV. Combustion gases are used to remove soot beforehand with water washed and cooled to room temperature.

Example 2

In almost the same manner as in Example 1, anhydrous sodium carbonate is prepared. The difference is that there is no absorption tower VI and that the _{combustion exhaust gases containing about 10 percent by volume of CO 2} are blown into the clarification part of the second crystallization _{vessel V, so that 404 kg of CO 2 are} absorbed there and 412 kg of water are evaporated.

In this case, the liquid in which the CO _{3 is} absorbed is returned from the outer part of the crystallization vessel V to the middle part of this vessel, where it is mixed with 2265 kg of a solution containing 40.9% NaOH and 0.4% Na ₂ CO ₃ contains and flows in from the first crystallization vessel III. This separates monohydrate crystals. Otherwise, the process is carried out exactly as in Example 1, and 1000 kg of Na ₂ CO _{3 are produced} .

Example 3

A single reaction vessel is used, which simultaneously functions as the absorption tower and the two crystallization vessels. In this reaction vessel is at a solution temperature of 95 ° C and a rate of 417.2 kg / hour. a sodium hydroxide solution continuously passed the 2.86 kg (50%) NaOH and 1.1 kg (0.26%) Na ₂ CO ₃

ίο contains. At the same time, combustion exhaust gases are fed into the reaction vessel so that at a rate of 40.4 kg / hour. CO _{2 is} absorbed. In order to avoid that on the parts where CO ₂ gas is blown in, due to the formation of Na ₂ CO ₃ impurities, a soft rubber hose is placed on the tip of the blower lance that blows in the CO _{2 gas.} so that the crystals separated at the tip fall off due to the vibrations caused by the blowing in.

The anhydrous sodium carbonate crystals formed immediately in the reaction vessel are shown in Example 1 treated, and there are 100 kg / hour. anhydrous sodium crystals.

As the mother liquor, from which the crystals have been separated, is at a rate of 306.7 kg / hour. obtain a solution, the 133,1kg (43.4 ° / ₀₎ NaOH and 1.1 kg (0.36%) of Na ₂ CO _3. This solution is with 70.3 kg / hour. Diluted water and fed to the decomposition plant I. The resulting sodium hydroxide solution has a composition suitable for charging the reaction vessel. In this way, the process takes place with continuous backflow. During the process, the water in the reaction vessel or in the decomposition plant is displaced at a rate of 940.1 and 1.3 kg / hour, respectively. evaporates.

Example4

From the part of the crystallization vessel V used for clarification, 4895 kg / hour are obtained. a 734 kg NaOH and 532 kg Na ₂ CO ₃ containing solution drawn off and fed to the absorption tower IV, in which the liquid is brought into contact with a combustion exhaust gas which contains 10 percent by volume of CO ₂ , which at a rate of 415 kg / h. is absorbed and leads to a solution containing 1532 kg of Na ₂ CO ₃ . .

This solution is divided into two parts with approximately equal flow rates, one part being sent immediately to the crystallization vessel V, while the other part is used for washing anhydride crystals, after which the washing liquid is returned to the crystallization vessel V. In the crystallization vessel V, the solution mentioned is at 2139 kg / hour. a solution flowing in from the separator IV, which contains 875 kg of NaOH and 7 kg of Na ₂ CO ₃ , so that 878 kg of Na ₂ CO _{3 are} deposited in the form of monohydrate.

From the crystallization vessel V are 1301 kg / hour. a pulp containing 973 kg of Na ₂ CO ₃ and 141 kg of NaOH, passed to the crystallization vessel III and there at 2934 kg / hour. a sodium hydroxide solution flowing in from the decomposition plant I and containing 1466 kg (50.0%) NaOH and 8 kg (0.27%) Na ₂ CO ₃ , all of the Na ₂ CO ₃ contained in the slurry precipitating in the form of anhydride crystals.

The precipitated crystals are in the separator IV

separated, and the remaining mother liquor, which contains 711 kg of NaOH and 8 kg of Na ₂ CO ₃ , with 795 kg / hour. Diluted water and returned to decomposition plant I. The separated anhydride crystals are washed with one half of the sodium carbonate solution formed in absorption tower VI. When washing, the anhydrous sodium carbonate is hydrated and converted into monohydrate crystals.

The monohydrate is dried at a temperature below 10O ⁰ C, and sodium carbonate monohydrate is obtained 1000 kg.

During the process described, 305 or 73 or 13 kg of water in the absorption tower VI or evaporated in the crystallization vessel V or in the decomposition plant I. It also weighs 233 kg Water as the formation water of the sodium carbonate monohydrate crystals or as adhering to it Water evaporates.

Example 5

After the on the basis of FIG. 2, anhydrous sodium sulfite is produced. For this purpose, a solution containing 828 kg of NaOH and 1 kg of Na ₂ SO ₃ is added at a rate of 2582 kg / hour. continuously introduced from above into the decomposition plant, where it is mixed with sodium amalgam, which is supplied from the electrolysis cell II, and is charged at 365 kg / hour. Contains sodium, is brought into contact and at a temperature of 8O ⁰ C at a rate of 2924 kg / hour. about a 50 ° / _o NaOH solution is formed. At the same time, as a result of the hydrogen evolution taking place in the decomposition plant I, about 10 kg / hour. Water evaporates.

The sodium hydroxide solution formed in the decomposition plant I is immediately introduced into the first crystallization vessel VII and mixed in this with a mother liquor, which at a rate of 724 kg / hour. flows in from a filter system (separator) IX and contains _{158 kg of Na 2} SO _{3 as a saturated solution.} During this process, the interior of the first crystallization vessel VII is cooled and kept at a temperature of 50 ^° C. by adding water at a rate of 60 kg / hour. is evaporated.

Almost all of the Na ₂ SO ₃ contained in the filtrate is crystallized out and together with 1487 kg / hour.

a solution containing 685 kg of NaOH and 0.8 kg of Na ₂ SO ₃ , discharged in the form of a slurry from the lower part of the first crystallization vessel VII. The slurry is passed into the second crystallization vessel VIII and mixed in this with a mixture of sodium bisulfite ίο and sodium sulfite, which flows in from the absorption tower X, so that sodium sulfite crystals precipitate.

Here, 158 kg of sodium sulfite crystals are transferred together with the NaOH solution from the first crystallization vessel VII into the second crystallization vessel VIII and form granulated sodium sulfite crystals. The mother liquor is then about 22 ° / ₀ aqueous sodium sulfite solution.

The resulting sodium sulfite crystals are separated by filtration, and about 40 kg of them Adhering water is dried off, "so that 1000 kg of anhydrous sodium sulfite is formed.

The filtrate is divided into two parts, one of which goes to the first crystallization vessel VII and the one others with a flow rate of 5200 kg / hour. is directed to absorption tower X, where he with 508 kg / hour. of about 7% (by volume) Sulfur dioxide is reacted. At the same time, water is evaporated and sodium sulfite converted into sodium bisulfite, which flows into the second crystallization vessel VIII.

The supernatant liquid is at a flow rate from 1940 kg / h stripped off, being careful to avoid crystals of sodium sulfite are contained in it. The liquid drawn off is at 643 kg / hour. Water diluted and as Treatment water introduced into the decomposition plant I.

During the process 450 kg / hour are used. Water evaporates, the heat of reaction being the heat energy and the heat of solution of sodium hydroxide can be used. From the outside, during the entire process only the heat of the combustion gases supplied to dry the anhydrous Sodium sulfite is used.

1 sheet of drawings

Claims (1)

1 2 ■ finally a process known in which Na ₂ S ₂ O ₅ . Claim: and Na ₂ SO ₃ of high purity in three stages Addition of caustic soda of increasing at each level Process for the production of sodium car concentration are produced. In the first stage, carbonate or sodium sulfite from the Natriumamal- 5 separates Na ₂ S ₂ O _5, while wircL particular obtained in the second and yarn obtained in the electrolysis of salts after the third stage Na ₂ SO ₃ in mercury method, wherein a solution of the third Verfahrensstufe.wird 6ine 65 to 75 ° / _o strength sodium hydroxide and a small amount of sodium hydroxide solution added, and triumcarbonat the mother liquor or contains sodium sulfite and becomes recycled to the first stage whereby the decomposition of the Sodium amalgams can be fed to a decomposition plant or another energy source can be obtained without an evaporation device.
is, with the formation of sodium carbonate or Well, sodium carbonate, sodium sulfite and sodium sulfite are from some of the resulting similar compounds very cheap substances, so that the sodium hydroxide solution with carbon dioxide or when large amounts of heat to remove the water-sulfur dioxide reacted, so trained 15 sers are required, this process step contributes considerably-sodium carbonate or sodium sulfite largely in borrowed to the production costs, so that it is desirable for crystals of anhydrous sodium carbonate, for example in the production of sodium carbonate trium carbonate monohydrate or anhydrous sodium, if only so much Water transferred to the trium sulfite and removed from the system is involved in the reaction, as is generated by the self-generated and a return of the remaining 20 heat, e.g. B. Heat of formation of the sodium carbonate mother liquor, the sodium hydroxide and low or the heat of solution of the sodium hydroxide, ver-quantities of sodium carbonate or sodium sulfite can be evaporated or removed,
holds, is carried out, characterized in fact based on this principle and the Verdaß the mother liquor in the return current of the drive according to the USA. Patent 3,103,413, feeds at amalgam decomposer and the sodium ig ^it and higher-owned sodium hydroxide triumhydroxidkonzentration 25 to 63%, the backflowing, which occurs during the mercury electrolysis, is used to manufacture mother liquor between 28 and 45 percent by weight of anhydrous sodium carbonate and the sodium carbonate or sodium sulfite is used. concentration of the whole, the decomposition plant The production of such high-percentage Na- fed aqueous liquid at 0.1 to 1.0 30 trium hydroxide with the help of mercury electrolysis or 0.01 to 0.7 percent by weight. however, it leads to a reduction in efficiency the connected decomposition plant and is also disadvantageous because only specially designed decomposition systems can be used. 35 In addition, the temperature at which the The invention relates to a process for the preparation of a solution of sodium hydroxide which is still solid, at 30 ° C of sodium carbonate and sodium sulfite from sodium or less if its concentration is above hydroxide, which is obtained from mercury electrolysis. of 55 ° / ". It is therefore necessary to use the sodium Not least to eliminate the inequality between hydroxide also during storage or the see the need for chlorine and sodium hy- 4 ° transport to keep at a higher temperature, droxid, which due to the stormy development as a result, is in some cases more heat energy originated in the chlorine processing industry is necessary than in the production of the sodium carbonate as a good use for the sodium nate is released. hydroxide a suitable process for the production of the object of the invention is therefore a process which desires sodium carbonate and sodium sulfite. 45 both without additional energy sources for the on-off of the German patent specification 1141 627 is a steaming as well as without the use of hochkonzen Verfahreri for the production of soda from caustic soda trated caustic soda. From the outside, only in a continuous cycle process, that heat is to be supplied, which is _{necessary for drying by the soda by converting NaOH and CO 8 of} the crystals of anhydrous sodium carbonate, Na on a carbonization stage and sodium carbonate trium carbonate monohydrate or anhydrous sodium monohydrate in an evaporation stage e are generated sulfite serves. The apparatus required to carry out the process and part of the mother liquor in the evaporation-agile apparatus should also be cheap and easy to produce, and another one in the carbonization stage. to be led. However, it is not possible to achieve this without the subject matter of the invention is a method for damper or other energy sources. 55 Manufacture of sodium carbonate or sodium sulphite From British patent specification 23 733 is a Ver from the sodium amalgam, which in the electrolysis of drive known, in which gaseous carbon dioxide is obtained in salts by the mercury process, with a diaphragm-type electrolytic cell introduced a solution containing sodium hydroxide and a low level and heating the cell solution to contain the amount of sodium carbonate or sodium sulfite on the anode generated chlorine to prevent itself in the electrolyte 60 and to decompose the sodium amalgam as Aufzu dissolve, and in which sodium hydroxide solution continues to be fed to a decomposition plant with preparation water Gaseous carbon dioxide is converted into soda and that is, with the formation of sodium carbonate or mother sodium sulfite obtained after separating the soda crystals from a part of the resulting Lye is returned to the electrolytic cell, using sodium hydroxide solution with carbon dioxide or Schweder recycled solution from time to time reacted sodium 65 field dioxide, the so formed sodium carbochloride is added, which in the electrolysis cell cerium or sodium sulphite largely turns into crystals should be set. anhydrous sodium carbonate, sodium carbonate - From the German Auslegeschrift 1186 450 is monohydrate or anhydrous sodium sulfite over-