DE2166028A1 - Ferric chloride soln - for hydrogen chloride prodn by oxidising residual liquor from steel pickling - Google Patents

Abstract

Ferric chloride is prepd. in the form of an aqs. soln. by intimately mixing an aqs. soln. of ferrous chloride with free oxygen, either (a) at 80 degrees C and a superatmospheric pressure, or (b) at an elevated temp. in the presence of a promoter contg. ammonium, Cr, Co, Cu, Mn, Ni and/or Zn ions. The process is used to convert FeCl2 in the residual liquor from steel pickling with HCl soln. into FeCl3. The FeCl3 soln. can be thermally decomposed to give gaseous HCl which is recovered in the form of hydrochloric acid.

Description

Process for the production of iron (III) chloride from iron chloride The invention relates to the oxidation of a liquid aqueous ferrous chloride solution to a liquid aqueous iron (III) chloride solution, with an accelerator cation or combinations thereof can be used as oxidation inhibitors. The invention relates in particular to the recovery of the chlorine content of pickling liquids from steelworks (HO1) in the form of hydrochloric acid.

Hydrochloric acid is used to pickle steel to coat the oxide from the base metal. To freshen up the pickling liquids it is common an acid with a concentration of 20 to 30% is used, with acids with higher Starch are preferred. During the pickling operation, a Waste material formed, which is referred to as hydrochloric acid waste pickling liquid. This waste pickling liquid contains, in addition to water, about 18 to 25% by weight iron (II) chloride (FeCl2), less as 1% by weight of iron (III) chloride (FeC13) as well as variable, but small narrow of Free HCl as well as small amounts of organic inhibitors, soft the attack reduce the acidity to the base metal.

The waste pickling liquid is an acidic material, so its disposal poses a serious problem in terms of environmental pollution. Usually the waste pickling liquid is neutralized with lime, the resulting sludge is dewatered and the remaining residue is used as land fill. It can be seen that this procedure is very expensive, even if there is a waste area is readily available.

Hydrochloric acid is relatively expensive and the extraction of the chlorine content of the Waste pickling liquid as hydrochloric acid has been in expensive use since the beginning hydrochloric acid as pickling acid aimed at by the pickling agents. The currently offered in the trade Processes all include the thermal decomposition of the waste pickling liquid and the recovery of the HCl gas content of the gaseous decomposition products by washing with water. I am an illustrative example of a recently developed process that is just dishonest is offered is as follows: The waste pickling liquid is separated by a separating area sprayed onto a bed of refractory material where it turns into HCl gas and iron oxide decomposed. The iron oxide particles are picked up by probing and vibrating the bed periodically removed. The gases are washed to give an acid of 20 ° Bé will. The system is designed to ensure minimal pollution arranged in a closed loop (see Chemical & Engineering @ews, page 32, March 18, 1970).

Needless to say, the roasting methods - the only ones currently on offer - are very expensive, both in terms of the investment costs as well as the direct operating costs.

The focus on roasting processes for the treatment of waste pickling liquid turns out to be the result of unsuccessful iron (II) chloride in aqueous Oxidize solution to ferric chloride. In U.S. Patent 2,677,598 demonstrated that liquid aqueous ferrous chloride solutions when exposed to free oxygen are brought into contact, the ferric chloride only to a small extent the presence of the hydrochloric acid slowing down the reaction. In this Patent a method is proposed which the addition of hydrochloric acid to the aqueous iron (II) chloride solution up to a range of 3 to 5 n, then the oxidation of the HCl-FeC12 solution in the presence of a large amount of the chloride salt an anion exchange resin - a preformed salt - includes.

In US Pat. No. 2,677,598 it is postulated that in the aqueous Solution there is an equilibrium, which is essentially only the iron (II) ion favored. In this connection it was found that iron (III) chloride from the aqueous solution through the solid salt of an anion exchange resin and the HC1 is chemically absorbed, which shifts the equilibrium sufficiently is to the essential conversion of the iron (II) -ion in the iron (III) -ion to allow. The chemically absorbed ferric chloride and the. Hydrogen chloride are desorbed with water or preferably with dilute hydrochloric acid, whereby a solution of iron (III) chloride is obtained, which contains large amounts of dissolved HC1 contains.

US Pat. No. 2,428,221 describes the treatment of a waste pickling liquid, which has been strengthened with added hydrochloric acid, described with air to reduce the To convert iron (II) ion into iron (III) ion. Enough HG1l is added to allow a stoichiometric reaction between the Sisen (II) chloride and the HCl obtained, whereby the free oxygen with the liberated hydrogen to water implements. This patent describes the economic advantages of this approach pointed out.

The invention is directed to a process for the production of ferric chloride from iron (II) chloride by oxidation in liquid aqueous solution and on a further embodiment in which the aqueous solution obtained in this way, which contains sisen (III) chloride, is thermally decomposed to produce hydrogen chloride gas to deliver, which is obtained as hydrochloric acid.

The oxidation process involves the oxidation of a liquid aqueous Iron (II) chloride solution in the presence of an oxidation accelerator cation as defined herein or preferably in the presence of an accelerator ammonium ion and a defined one Metal ions.

1. The accelerated oxidation process: This is the process of crimping a liquid aqueous solution of sisen (II) chloride, preferably hydrochloric acid waste pickling liquid, or a solution derived from a saline acid waste pickling liquid with free oxygen, which can be oxygen gas or air, intimately mixed. Included If the iron (II) chloride solution contains at least one concentration that promotes oxidation of dissolved cations belonging to the class ammonium, chromium, cobalt, copper, magan, Nickel, zinc and their mixtures are selected. The response is increased at Temperatures, appropriately from 4d, 9 to 2600C, and about one carried out such a period that a liquid aqueous solution is obtained, which contains dissolved iron (III) chloride and dissolved accelerator cations. The oxidation is preferably carried out at overpressure and a temperature of about 93.3 to 17700. The preferred accelerator cations when only one accelerator is used are ammonium, etupfer (II) ions and ghrom (III) ions. It is particularly preferred a double accelerator system composed of an ammonium ion and one of the metal ions, in particular of copper, specifically the copper (II) ion. 0.1 to 6 parts by weight of the accelerator ion yielding compound per 100 parts by weight of added Sisen (II) chloride solution represents the preferred area for the application of the accelerator represent.

In a particularly preferred embodiment, three parts by weight Ammonium chloride and one part by weight of cupric chloride per 100 parts by weight of Iron (II) chloride solution used.

2. Combination process for the production of hydrochloric acid from hydrochloric acid Waste pickling liquid: In this combined process, a liquid aqueous iron (III) chloride solution by oxidation of the waste pickling liquid or a solution resulting therefrom, which is obtained by the accelerator method happens.

The liquid aqueous iron (III) chloride solution is brought to a temperature heated from about 121.1 to 204.400, with a stream of IICl gas and water vapor overhead is removed and in the decomposition zone an aqueous slurry of iron oxide is obtained. Hydrochloric acid is removed from the overhead stream following conventional measures obtained, It is preferred to carry out the ferric chloride decomposition under reduced pressure, either in a vacuum or under the conditions who received when the hot gas is injected into the liquid solution, which is preferably is done using an immersion torch. The defined "negative pressure" decomposition allows operation at the lower temperatures of those given above. Be like that e.g., excellent rates of decomposition are obtained by using hot submerged combustion gases and maintains the temperature of the decomposition zone in the region of 121.1 ° C.

The manner in which the decomposition is carried out and how it is handled of the HCl steam stream taken off overhead determines the concentration of the obtained hydrochloric acid. Acids with concentrations of 17 to 33 were obtained, even higher concentrations can also be obtained, if desired.

3. Decomposition process of iron (III) chloride: hydrochloric acid turns out a liquid aqueous solution of iron (TIT) chloride formed by adding the solution is heated to a temperature of about 121.1 to 204.4 ° C at negative pressure, what preferably done using hot submerged gases. To this The way is an overhead stream of HCl gas and steam and an aqueous suspension obtained from iron oxide in the bottom of the decomposition zone.

The invention is directed to (I) the oxidation using of free oxygen from ferrous chloride in liquid aqueous solution to obtain a liquid aqueous solution containing iron (III) chloride and (II) on the Decomposition of Sisen (III) chloride while it is in liquid aqueous solution located to ferric oxide and HCl gas, the HCl gas in the form of hydrochloric acid is won. it is possible to easily obtain the azeotropic composition, wherein in a particular embodiment of the invention, concentrations of 30 up to 37% can be obtained.

The oxidation process Introduction into the oxidation zone: The iron (II) ion is oxidized to the disene (III) ion by reaction with free oxygen, whereby Air is the preferred source of oxygen. This creates a large excess of oxygen preferred.

The iron (II) chloride is present in liquid aqueous solution. The concentrations of the solution can range from very dilute to saturated. It is preferred to use more concentrated solutions. Other materials can be used be present that do not interfere with the iron (II) ion to iron (III) ion conversion.

Iron (II) sulphate is currently used in large quantities in the pickling of steel formed with sulfuric acid. An aqueous solution of iron (II) chloride can be used in a simple manner Way by reacting iron (II) sulfate with an aqueous sodium chloride solution produced, whereby sodium sulfate is obtained, which has a higher market value owns. The aqueous iron (II) chloride formed after this reaction ceases a suitable starting product for the oxidation process according to the invention.

Furthermore, a hydrochloric acid waste pickling liquid is preferred aqueous iron (II) chloride source for the process according to the invention.

Other suitable solutions can be from saline acid waste pickling liquids originate. Solutions which are enriched in iron (II) chloride are particularly preferred are what either by adding ferrous chloride to the waste pickling liquid speed or by evaporation of part of the water content of the waste pickling liquid can happen. For example, a solution with 40% iron (II) chloride will give good results received, we] che by evaporation of a waste pickling liquid with about 20% ferrous chloride is obtained.

It is desirable to have this to some extent in the waste pickling liquid to preserve the free hydrogen chloride that is always present, which will happen can that you remove the hydrogen chloride from the solution either during the evaporation for the production of a concentrated hydrochloric acid waste pickling liquid or during the oxidation fails.

The HCl gas goes with the water vapor and nitrogen, if Air is used, and excess oxygen is gone. This loss is at an embodiment of the invention in such a way that you avoid the waste pickling liquid treated with finely divided iron oxide particles to reduce the IICl content in ferric chloride (mainly iron (III) chloride) to convert.

The iron oxide treatment is on the waste pickling liquid batch useful in itself and a must if a hydrochloric acid concentrated by evaporation Waste pickling liquid forms the charge of the oxidation reaction.

It has been found that finely divided iron oxide particles, as a dispersion are present in the liquid aqueous iron (II) chloride solution, a very significant one Have an effect on the initial rate of the oxidation reaction.

This applies in particular to the waste pickling liquid or a solution derived therefrom, with these solutions having an induction period have, during which the iron (II) ion is oxidized very slowly. This induction period is probably due to the inhibitors present in the hydrochloric acid pickling acid. The property even contained a small amount of finely divided iron oxide particles, which are dispersed in the solution results in intimate mixing with free oxygen to an almost immediate start of the oxidation reaction.

When operating with solutions containing HCl, such as a waste 3''rust liquid, it is necessary to add iron oxide in an amount sufficient to Convert HCl to iron chloricl, and preferably a small amount of finely divided To give iron oxide particles in the treated liquid in dispersed form. In the case of the waste concentrated pickling liquid, it is preferred to do so before starting of evaporation, enough iron oxide particles to make up the fresh waste pickling liquid to give to the amount for the reaction with HCl and a smaller one, the initial rate increasing amount to result. The smaller, accelerating amount of the particles can but can also be added to the concentrated waste pickling liquid before this Solution is brought into the oxidation zone.

Mixing and Oxidation: The rate of oxidation is through the intensity of mixing (or agitation) of the ferrous chloride solution and the gaseous oxidizing agent (free oxygen or air). iJin intimate mixing, as z.i3. by violent mechanical agitation the constituents of the oxidation zone is effected is reasonable for the achievement of Oxidation speed chains important. am mere penetration of the air into the solution results in essentially no oxidation reaction even at excess pressures.

It is preferred to use a large excess of the free oxygen beyond the theoretical need to introduce. However, it has been observed that at higher Temperatures and higher pressures determine the rate of oxidation when oxygen is consumed is excellent by only 150% of theory.

Oxidation process with added accelerator cations: Cation oxidation accelerator: It has been found that certain cations that are present in the liquid aqueous Lisen (II) chloride -Solution are dissolved, which are brought into the oxidation, to an increase in Oxidation rate of iron (II) ions lead to iron (III) ions.

The dissolved cations present in the Sisen (II) chloride solution can be made available through any connection whose other ions do not interfere with the oxidation reaction.

As an oxidation accelerator in the acceleration-oxidation process Dissolved cations used in the invention are available through compounds placed, which in aqueous solution ammonium ions or cations of the metals chromium, Cobalt, copper, mangari, nickel or zinc.

If a single accelerator ion is used, then it is preferred either an ammonium ion or a copper (II) ion or a chromium (III) ion to be used. Although the copper (II) ion alone and the chromium (III) ion alone are somewhat more effective as an accelerator is when the same amount by weight of the compound supplying the ion is used, the ammonium ion and specifically the compound ammonium chloride as a particularly preferred accelerator ion deems.

Mixtures of two or more of these cations can be used It is preferred to have a mixture of ammonium ions and at least one of the to use defined metal ions. In such a mixture the Hetaliioii referred to herein as the "co-accelerator" ion. A mixture of ammonium ions and copper (II) ions are particularly preferred as double accelerators.

It should be noted that dissolved ammonium chloride alone and dissolved copper (II) chloride alone the conversion of a major part or even melir as a major part of the dissolved iron (II) ion to iron (III) ions allow what by the amount of the dissolved iron (III) -ion in relation to the dissolved iron (II) -ion, that remains in the solution has been determined (forms part of the ferric ions insoluble iron (III) oxide). Surprisingly, the common use results of ammonium and copper (II) ions under comparable operating conditions an im substantial complete conversion of iron (II) ions into iron (III) ions, whereby aqueous solutions with 98% or more dissolved iron ions in the form of iron (III) ions are formed.

Preferred compounds for the delivery of the ammonium ions for the purpose of the oxidation process according to the invention are ammonium chloride, ammonium sulfate and ammonium phosphate. These substances are in the liquid aqueous iron (II) chloride solution dissolved to deliver the dissolved oxidation-accelerating ammonium ions. Quaternary ammonium compounds are sources for the purposes of this invention for immonium ions.

If the batch is waste pickling liquid or some other free, HCl containing solution is then at least some of the required ammonium ions can be obtained by reacting free ammonia (NH3) with the HCl of the solution. This procedure provides a simple method for replacement in large-scale operations represents where the dissolved ammonium ions are obtained and returned to the oxidation reaction and refreshment is required to cover the inevitable material losses balance.

The dissolved copper ions are preferably replaced by copper (II) chloride, Copper (II) fluoride or copper (II) sulfate made available.

The dissolved chromium (III) ions are preferably replaced by chromium (III) chloride or chromium (III) sulfate is made available.

The liquid aqueous solution of iron (II) chloride that is involved in the oxidation reaction is introduced, contains at least an oxidation-accelerating amount of dissolved cations. Given a certain set of conditions, the increase results the amount of dissolved accelerator ions up to the saturation amount is beneficial Effect on the rate of oxidation of the iron (II) ions in the solution.

The minimum amount that accelerates oxidation depends on these Factors such as the temperature of the oxidation zone, the concentration of ferrous chloride in the Cllargenlösung and the desired degree of conversion of the iron (II) ions the iron (III) ions and the accelerator ion itself.

In general, the compound providing the dissolved cation is in of the solution in an amount of no more than about 20 parts by weight per 100 parts by weight the liquid aqueous iron (II) chloride solutions introduced into the oxidation reaction available.

Herein below the limit range for the amount of compounds, which supply the ammonium ions, copper ions or chromium ions which are defined in the Iron (II) chloride solutions are available, for ammonium chloride, copper (II) chloride or chromium (III) sulfate is specified as an accelerator compound. It is easy to do this Limit quantities in the corresponding narrow for actually as an accelerator used to convert ammonium, copper or chromium compounds.

In general, when ammonium chloride is used, cupric chloride is used or chromium (III) sulfate, about 0.1 to about 6 parts by weight per amount used 100 parts by weight the solution used. Using the iglulonium chloride, copper (II) chloride or chromium (III) sulfate takes place in one tyi) Quietly scissors in amounts of about 1 to 4 parts by weight per 100 parts by weight the solution used as a batch. This latter area is of particular interest for ammonium chloride when used in combination with a metal cation.

Ammonium ion accelerator plus metal ion co-accelerator: Es it was found that the rate of oxidation was reduced by the use of a double accelerator system can be increased that of a mixture of ammonium ions and a metal cation consists. These co-accelerator metals are the same as the ones above as an accelerator per so specified. The fourth of the metal cation appears not to be significant.

Preferred salts that provide the co-accelerator cations, Üintl Copper (II) chloride, copper (II) fluoride and copper (II) sulfate.

In the iron (II) chloride solution converted into the oxidation reaction is in dissolved form at least a co-accelerating amount of the defined co-accelerator metal ion present in addition to the oxidation-accelerating amount of the ammonium ions.

@ Below is the limit range for the amount of Met all-Ko-accelerator compound, which is dissolved in the starting solution, for copper (II) chloride as a co-accelerator compound specified. These limit range quantities can be easily converted into the corresponding Amounts of actually used metal co-accelerator compounds are converted will.

Generally the dissolved cupric chloride is co-accelerator in an amount of no more than about 20 parts by weight per 100 parts by weight the starting solution is present.

The amount of GuCl2 co-accelerator used reads t preferably between about 0.1 and about 6 parts by weight per 100 parts by weight of the starting solution. More typically, the cupric chloride and the other metal ions become co-accelerators used in amounts less than the amounts of ammonium ion present. For example, 3% by weight of ammonium chloride and 1% by weight of cupric chloride give both based on 100 parts by weight of the starting solution, gives excellent results the waste pickling liquid.

Temperature and pressure conditions in the oxidation process: The following the term "dissolved accelerator ions" shall mean any of the above defined accelerator either individually or in the double accelerator combinations, those above with the dissolved ammonium ions and the metal co-accelerator ions were formed.

In the oxidation process according to the invention, the defined liquid aqueous iron (II) chloride solution that causes oxidation containing accelerating amount of dissolved accelerator ions, with free oxygen mixed at elevated temperatures for a sufficient period of time that a liquid aqueous solution, is obtained, soft dissolved iron (III) chloride and dissolved Contains accelerator ions.

It should be noted that the oxidation process according to the invention begins with a liquid aqueous solution of iron (II) chloride, which is a defined Amount of defined dissolved accelerator ions that it contains as a reaction in the liquid medium (solution) progresses during the oxidation reaction time and that he is with a liquid aqueous solution ends that resolved Contains iron (III) chloride and dissolved accelerator ions, the iron (II) chloride in the product solution from a small amount to a substantial amount each may be present according to the conditions of the oxidation reaction system. It is therefore necessary to keep the pressure in the oxidation reaction zone high enough that it is ensured that therein a liquid aqueous solution phase during the all the time that the oxidation is carried out. Because ferric oxide As a secondary product of the oxidation of iron (II) ions is formed, the concentrated Solutions are more or less in a muddy condition what is due to the insoluble iron oxide particles present in the oxidation zone available.

bs was found to be between the temperature at which the reaction is carried out, the pressure under which the oxidation zone is maintained, and the rate of oxidation of the dissolved iron (II) ions to the dissolved iron (III) ions there is a defined relationship. At any temperature leads to an increase in pressure in the reaction zone to an increase in the rate of oxidation of the iron (II) ions. On the other hand, every pressure is associated with a particular temperature, which gives a maximum rate of oxidation of iron (II) ions.

The oxidation reaction is exothermic. With more concentrated starting solutions and in the selection of the temperature at which the starting solution enters the reaction zone is introduced, it is possible to maintain the desired oxidation temperature and / or to be achieved without additional heating devices in the oxidation scene must be used, in a preferred mode of operation of the oxidation zone in keeping the temperature in the oxidation zone essentially constant, by taking off a stream of water vapor overhead. This approach is with a another advantage connected, namely that dc liquid aqueous Iron (III) chloride product solution is of a higher concentration than that introduced liquid aqueous iron (II) chloride solution. It is important, however, that in the oxidation reaction zone enough liquid water remains that all of the ferric chloride formed is resolved.

The temperature has a favorable influence on the rate of oxidation. Therefore, the oxidation reaction will take place at elevated temperatures, i.e. well above the normal room temperatures and expediently carried out above about 48.9 ° C. Since the hot iron (III) chloride solution is extremely corrosive, the upper temperature is limited more by the material of the construction than by the process limitations.

In general, the accelerated oxidation reaction is increased at Temperatures, usually between about 48.9 ° C and about 260 ° C. A more practical one The temperature range is between about 79.4 ° C and about 20400 (in the range of 204 to 2600C can be used as oxidation reactors with Teflon-lined steel vessels as well as some types of graphitic materials). A preferred one The range of oxidation temperatures is between about 93.3 and about 17700 (177 ° C is about the practical upper limit for steel vessels lined with glass).

At some temperatures and concentrations of the starting solutions negative pressures can be used. In these conditions, however, is the accelerated Oxidation rate too low. A sensible combination of temperature and the rate of oxidation is obtained at atmospheric pressure. Because of The high rate of oxidation will allow operation at higher overpressures preferred.

It has been found that - starting from a 40% iron (II) chloride solution using a moderate amount of an accelerator and draining about 20 vol .-% of the water as steam - at a temperature of about 149 ° C and one Oxidation occurs very quickly at a pressure of about 7.03 atm.

The oxidation can be carried out at a substantially constant temperature or the temperature can preferably be increased within the oxidation time will. In general, the total rate of oxidation will be at constant pressure by the combination of the decrease in the volume of the liquid solution in the oxidation reactor by removing at least part of the water vapor formed and gradually Increase in the temperature of the contents of the oxidation reactor.

When operating at normal pressure, for example when oxidizing Waste pickling liquid, it is preferred to use a waste pickling liquid from to start around 65.6 ° C and increase the temperature as the volume of the liquid decreases in the reactor. When the reactor components are about half of the If the original volume has decreased, then the temperature will rise to 82.2 to 87.8 ° C increased.

This temperature range gives the maximum speed at atmospheric pressure in the oxidation reactor. It was observed that the increase in temperature increased 93, @ ° C a significant decrease in the rate of oxidation of iron (II) ions gives.

The oxidation reaction results in a liquid aqueous solution, which is dissolved Contains iron (III) chloride and dissolved accelerator ions. A smaller amount of dissolved iron (II) chlorides is usually present in the product solution. at some embodiments is a big one in product solution lot of iron (II) chloride present. In addition to the liquid solution, there is iron oxide present as a by-product of the oxidation reaction.

Influence of temperature on the quality of the by-product Iron oxide: It has been found that at an oxidation temperature below about 149 ° C the iron oxide by-product of the iron (III) chloride-oxygen reaction is a brick-red, very finely divided material, even after a lengthy period Repeated weaning makes the weaned hate a bulky one for her weight Takes up space. The red iron oxide settles at a very slow rate. Even after a few days of allowing it to sit down, it retains the red that has set off more than dcm Iron oxide supernatant liquid has a reddish sludge-shaped opaque appearance.

If the oxidation is carried out at about 149 ° C or more, then There is a remarkable conversion in the appearance of the iron oxide by-product. The iron oxide now has a purple black color, with the particles is much coarser than that of the red sisenoxide.

The black iron oxide settles very quickly and - what a big deal Importance is - the supernatant liquid is almost traiispareiit clear. Farther The deposited mass of black iron oxide only accounts for about 25 to 30% of the volume one that occupies the same weight as red iron oxide.

The quality of the supernatant and the rate of settling is so great that decanting is the preferred method of separating the black Iron oxide, while filtration is the preferred method of separation which is red iron oxide.

Improving the purity of the iron (III) chloride solution: In product solutions, which contain larger amounts of dissolved ferrous chloride, the solution purity can in terms of ferrous chloride can be improved by adding the hot solution from the oxidation reactor is cooled to a temperature at which the iron (II) chloride preferably precipitates out of solution. That - at this lower temperature - Insoluble iron (II) chloride is filtered off and can be used in the oxidation reaction to be led back. Usually this ferrous chloride is used to to strengthen the batch solution for the oxidation reactor.

Preferred embodiments of the oxidation process: The preferred one The starting solution for the oxidation process according to the invention is the waste pickling liquid. Thus, preferred embodiments of the oxidation process are based on this special initial solution. A waste pickling liquid containing e.g. about 22% ferrous chloride and contains some free HCl, becomes with finely divided iron oxide particles in one treated in sufficient amount to convert the HCl content to ferric chloride and to a lesser amount of finely divided iron oxide particles in the treated waste pickling liquid to give in dispersion. The water is then made from the treated waste pickling liquid evaporated to give a concentrated liquid containing about 40,) ferrous chloride and has a temperature of about 104.4 ° C. Too hot concentrated The respective accelerator is added to the liquid and the accelerator solution in the liquid is transferred to an oxidation reactor, which with facilities for the supply of air and mechanical stirring devices is equipped to an intimate mixing of the solution with the Ensure air now. The pressure of the oxidation reactor is kept at about 7.03 atmospheres and a stream of water vapor is withdrawn at such a rate that the temperature in the reactor rises to around 1490C. Thereupon the temperature is set over the remainder of the oxidation reaction kept on this point. The iron (II) chloride is calculated according to the following equation in Iron (III) chloride and iron (III) oxide converted: 12FeCl2 + 3O2 = 8FeCl3 + 2Fe2O3 The ferric chloride product is available as a liquid aqueous ferric chloride solution present, which also contains the accelerator. The product solution also contains something dissolved, unconverted iron (II) chloride, which in some cases is in a larger amount may be present, as well as insoluble iron oxide dispersed therein. The iron oxide is filtered off or decanted from the hydrated solution.

The clarified product solution containing a large amount of ferrous chloride Contains, can be cooled to room temperature to prevent the precipitation of the solid To effect iron (II) chloride, whereupon this is separated to a purer product solution from iron (III) chloride.

Embodiment A: When using ammonium chloride as accelerator in an amount of about 3 parts by weight per 100 parts by weight of the hot concentrated Liquid one hour of oxidation gives a product solution that is a greater one Part of the iron ions in the form of fisen (-III) ions, i.e. as iron (III) chloride, contains.

Embodiment 11: When using a dual accelerator system out of about 3 want ammonium chloride and about 1 part cupric chloride each per 100 parts of the concentrated liquid unct with an oxidation time of one Hour a solution is obtained that contains around 98% of the dissolved iron ions contains as iron (III) ions.

Embodiment C: When using copper (II) chloride as accelerator in an amount of about 3 parts by weight per 100 parts by weight of the concentrated An oxidation time of one hour produces a product solution that is liquid Much more than a major part of the iron ions III form of iron (III) ions, i.e. as iron (III) chloride, namely about 85% iron (III) ions.

Decomposition method for the ferric chloride: An aqueous solution of iron (III) chloride with a temperature above about 121.1 ° C decomposes with formation of iron (III) oxide and HCl gas. The HCl gas and the water vapor are taken from the decomposer and condensed to obtain hydrochloric acid. in the decomposer Sufficient water must be present to contain essentially all of the ferric chloride to convert. It is possible to control the acid concentration by controls the amount of water present. It can easily be a hydrochloric acid can be obtained with 30 to 33% HCl and even more.

In general, the upper limit is the temperature in the decomposition reaction about 204 ° C. When producing an acid product with high concentration and operating the decomposer at about atmospheric pressure is the preferred decomposition temperature about 182 to 188 ° C.

It was found that the temperature required for rapid decomposition the aqueous iron (III) chloride solution is required, is considerably reduced, if the decomposition is carried out under reduced pressure, i.e. in a vacuum. The lower the pressure, the lower the temperature required. E.g. at a vacuum of 686 to 711 mm Hg at temperatures of 121.1 to 126.7 ° C rapid and complete decomposition. These results are similar to operation at atmospheric pressure and comparable at about 37.8 ° C higher.

It was further found that the advantages of direct vacuum operation by the denuding effect of the introduction of hot combustion gases, i.e. one hot inert gas, can be obtained into the aqueous solution in the decomposer. It will it is preferable to introduce the inert gas into the decomposition solution to obtain the necessary To provide the heat that is required for the decomposition reaction to be maintained, eliminating the need for indirect heating hours and the associated corrosion problems are eliminated. Hot submerged Combustion gases provided by a submersible burner are the preferred source of hot inert gas.

Under these conditions, decomposition occurs rapidly and substantially at a temperature in the region of 121-1 ° C completely.

When the hot submerged combustion gas is used for heating then the formed hydrogen chloride occurs not only with the accompanying water vapor, but also with the non-condensable gases that are formed during combustion be off. It is necessary to wash out the HCl from this dilute stream with water, whereby a lower concentration of the hydrochloric acid product is obtained than by decomposition processes that indirectly heat the ferric chloride solution include. The approximately 20% azeotropic acid is easily produced. It higher concentrations can by controlling the decomposition operation and especially by controlling of the water washing operation can be obtained when it is used. These concentrations are high enough to be able to use them for pickling steel or the ones there freshen up used products.

It has been observed that better control of the replacement operation is possible if a fairly clean watery one Iron (III) chloride solution is introduced. The solution expediently has only a small amount of iron oxide solids and only a low content of dissolved iron (II) chloride.

Although the decomposer up to the dry solids condition can be operated, it is preferred to control the decomposition operation so that that the bottom products te of the decomposer is an aqueous slurry of iron oxide (and the dissolved accelerator or even the solid accelerator).

If hydrochloric acid from the waste pickling liquid batch to the oxidation is recovered, then it is preferred using hot submerged Combustion gases decompose at a temperature of the order of 121.1 ° C.

A preferred embodiment of the recovery of hydrochloric acid from the hydrochloric acid waste pickling liquid: waste pickling liquid, which is about 22% dissolved It contains iron (II) chloride and some free HCl, with finely divided iron oxide particles mixed in an amount sufficient to react with the free Hel. if an ammonium chloride accelerator is required, then ammonia gas (@ H3) mixed with the waste pickling liquid before the iron oxide is added. In some cases all of the HCl is reacted with the ammonia. The treated Waste pickling liquid is concentrated in an evaporator, leaving enough water removed to produce a concentrated waste treated pickling liquid, which contains about 40% dissolved iron (II) chloride. The evaporation results in a hot liquid at about 104.4 ° C.

@ie hot ferrous chloride liquid is used to make the aqueous sludge bottoms from the decomposer for the aqueous Extract ferric chloride solution.

The extraction takes the accelerator that is in the soil products of the decomposer is dissolved and suspended, the ferrous chloride and the rest any iron (III) chloride present. A slight tightness of the finely divided sisenoxide, that is formed in the decomposer is also taken up, whereby the finely divided Iron oxide particles are provided, which is convenient at the beginning the oxidation are present in the oxidation real tor. If so desired, this can total bottom product of the decomposer with the hot concentrated ferrous chloride liquid mixed as the iron oxide does not interfere with the oxidation reaction.

The hot concentrated liquid at 104.40G and the beden product of the decomposer, which is also approximately at this temperature, become in a Oxidation vessel transferred, which is preferably a glass-lined vessel represents which is provided with an air inlet and a mechanical stirring device is to achieve an intimate or violent agitation in the oxidizer. The hot concentrated liquid contains approximately 3 parts by weight of ammonium chloride accelerator and about 1 part by weight of Supfer (II) chloride co-accelerator, each per 100 parts by weight the hot concentrated liquid. A pressure valve maintains a pressure of the components the oxidizer of about 7.03 atm. The components of the oxidizer are allowed to heat to a temperature of about 1490C and this temperature is maintained by taking a stream of water vapor, in about an hour the oxidizer contains iron oxide from the conversion of iron (II) ions into the sisen (III) ions and a liquid aqueous solution of iron (III) chloride and dissolved ammonium and copper (II) ions. Under these conditions, iron (II) ions converted into iron (III) ions in the order of 98%.

All of the material present in the oxidizer will transferred to a filter where the iron oxide particles are removed. The withheld Iron oxide is washed with water to produce an oltludierte iron (III) chloride solution to win. Part of this iron oxide is used to reduce the free IIGl content to neutralize the waste pickling liquid starting solution, the aqueous ferric chloride solution including the dissolved, unconverted sisen (II) chloride and the accelerator as well as the washing water are put into the decomposition vessel for the ferric chloride convicted. The filtration conditions are adjusted so that the batch for the decomposer approximately the desired decomposition temperature in the region of 121.1 ° C. The decomposer is kept at the desired temperature and the exposure conditions are made by a submersible burner running on natural gas and air is heated.

It is convenient to continuously stream a slurry from the To remove decomposer and this through a decanting vessel with a conical bottom to direct. This decanter gives a bottom product of the decomposer as an aqueous slurry of iron oxide and dissolved ammonium and cupric ions. This aqueous slurry is mixed with the hot concentrated liquid that is formed by the evaporator, mixed. The separated solution is in the Oxidizer returned.

From the decomposer, a stream of standardized, the KiCl gas, water vapor, nitrogen, carbon dioxide, oxygen and other combustion gases contains. The stream of water vapor that is formed in the oxidizer is combined with the decomposer overhead stream and then into an adiabatic one Absorber transferred. In this absorber absorbs a liquid Water flow the Höl gas. Nitrogen and other gases as well as water vapor are released out the absorber. A bottoms product made from hydrochloric acid is produced by the absorber taken. In this case the azeotropic acid is formed with about 20'a 'HC1.

From the above explanations it can be seen that in the method of the invention with the exception of minor losses that are inevitable in technical operation all of the chlorine content of the waste pickling liquid used is hydrochloric acid which is suitable for pickling can be obtained. The obtained iron oxide is essentially pure and it is suitable for making steel. That Accelerator system to be returned £ The only major environmental pollutant formed by the process of the invention is carbon dioxide from the decomposer. However, this contaminant can be tolerated.

The invention is illustrated in the examples.

Example: Oxidation of a liquid aqueous sisen (II) chloride solution at atmospheric pressure: with and without accelerator.

A number of standard solutions were prepared, each Standard solution of 270 g of iron (II) chloride tetrahydrate, analytically pure, and 441 g distilled water.

A 1 liter beaker with a Thermometer, mechanical propeller and air injection tube.

In this example, each run was run at a temperature of 79.4 ° C carried out. The Lisen (II) chloride solution was at this temperature brought before the accelerator, if used, was added. The air was injected and the stirrer was switched on to give a vigorous agitation of the components of the beaker. The oxidation of iron (II) ions The solution was monitored every hour, including a small sample of the contents of the flask was removed and the solids content was filtered off. The filtrate was with distilled water and then diluted according to the known procedures for the Determination of iron (II) ions and iron (III) ions titrated separately.

The results for each sample were expressed as dissolved ferric ions as a percentage of both the dissolved iron (II) ions and the dissolved iron (III) ions obtained (The solid by-product was essentially ferric oxide).

Experiment A: Only the standard solution was put into the oxidizer brought.

Experiment B: The standard solution plus 1.7 g ammonium chloride in dissolved form (0.24 wt .-, J, based on the standard solution) brought.

Experiment C: The standard solution plus 1.7 g ammonium chloride (0.24% by weight, based on the standard solution) plus 1.7 g copper (II) chloride dihydrate (0.19% by weight CuCl2, based on the standard solution), dissolved therein, brought.

Experiment D: The standard solution plus 78 g ammonium chloride (11% by weight, based on the standard solution) plus 10 g Nupfer (II) chloride dihydrate (1.1% by weight CuCl2, based on the standard solution).

The individual defined liquid batches were each five hours oxidized. The fifth hourly analysis of the liquid Product showed the following results. "% Iron (III) ions" mean the percentage Amount of iron (III) ions in the solution, based on the total in the analysis found, dissolved iron (III) and iron (II) ions.

Experiment% iron (III) ions A (without accelerator) B (with NH4Cl) 29 C (with NH4Cl and CuCl2) 42 D (with NH4Cl and CuCl2) 76 Experiment E: The oxidation of the components of Experiment D was carried out for a total of nine hours. the Analysis of the oxidizing solution showed that the iron (III) ions δ (; "j made up.

It was found that in each of these attempts of this example after an oxidation time of five hours approximately the fourth part of the volume the liquid present at the beginning of the experiment had evaporated.

Comments: Experiment B shows that the iron (II) chloride solution dissolved ammonium ions without any other accelerator effective oxidation accelerator present in this fluid system, even if they are only present in small amounts are.

Experiment C shows the benefits obtained when using a double accelerator, dissolved in the ferrous chloride solution, which is used in a lesser quantity is available.

Experiment D shows the advantage of using a double accelerator and greatly increasing the amount of both the ammonium chloride accelerator and of copper (II) chloride co- Accelerators on the rate of oxidation. It should be noted that in Experiment C approximately equal amounts of the two Accelerators were present, while in experiment D the weight ratio NH4Cl to CuCl2 was 10: 1.

Experiment E shows the advantages of increasing the reaction time the amount of dissolved iron ions in the product which are in the desired trivalent Shape are. These are present as dissolved iron (iII) chloride.

Example 2 Oxidation of the hydrochloric acid waste pickling liquid at atmospheric pressure: Nit and no accelerator.

The hydrochloric acid used pickling liquid of a steelworks, the 24.2 Containing% by weight iron (II) chloride was used in the experiments of this example as Standard solution used. The experimental set-up and the experiment was carried out as in example 1.

Experiment IIA: In this experiment, only the waste pickling liquid was used - without the addition of an accelerator - placed in the oxidation device.

Experiment EIB: The waste pickling liquid was placed in the oxidation device plus 1% by weight ammonium chloride, based on the waste pickling liquid.

Experiment IIC: The standard waste pickling liquid was placed in the oxidizer plus 1% by weight ammonium chloride dissolved therein plus 1% by weight cupric chloride dihydrate (0.8 wt .-% CuCl2), dissolved therein, brought. The amounts of the accelerators are based on the waste pickling liquid.

Experiment IID: Experiment IID differed from Experiment A to C in such a way that it was necessary to add distilled water to the waste pickling liquid give u to dissolve the large amounts of ammonium chloride that were desired. The experiment was carried out using 711 g of waste pickling liquid, to which enough distilled water had been added to just dissolve of the added solid ammonium chloride.

Approximately 75 g of water was added, In the starting solution for the oxidation was about 55% by weight ammonium chloride and about 5.5% by weight cupric chloride dihydrate (about 4.4 wt% CuCl2) present.

Experiments A to C were carried out for five hours. The attempt D was carried out for a total of acllt hours, with the results for the percentage Amounts of iron (III) ions for 5, 6 and 8 hours were determined. The received The results are compiled in the following table.

Experiment accelerator% iron (III) ions A (5 hours) none 15 B (5 hours) NH4Cl 1 @ C (5 hours) NH4Cl + CuCl2 25 D (5 hours ditto 78 D (6 hours) ditto 86 D (8 hours) ditto 94 Comments: The above experiments show that the Accelerator and the double accelerator system for the oxidation of iron (II) ions in the waste pickling liquid as well as in a pure iron (II) chloride solution are effective.

From the appearance of the contents of the oxidizer it was observed that a significant period of time (induction period ) after Air injection and mixing primed before a significant rate of oxidation was reached. When using the pure starting solution of Example 1 was only a slight delay was noted.

Example 3 Oxidation of the waste pickling liquid with a double accelerator at atmospheric pressure.

This example was carried out as in Example 1, with the waste pickling liquid of Example 2 was used to create double i3escilleuniger systems other than the To investigate the NH4Cl-CuCl2 system of Examples 1 and 2.

The oxidizer charge passed on every attempt this example from the standard waste pickling liquid plus 1% by weight ammonium chloride, dissolved therein, plus 1 wt. b1 of a soluble co-accelerator. Every attempt was made performed five hours. The results obtained are in the table below compiled.

Test co-accelerator% iron (lII) ions lIlA cobalt chloride (CoCl2) 20 IIIB nickel chloride (NiCl2) 20 IIIC manganese sulfate (MnSO4) 22 IIID chromium sulfate (Cr2 (SO4) 3 + 9H2O) 23 IIIE Zinc Chloride (ZnCl2) 22 In addition to the above effective co-accelerators further experiments were carried out which show that copper (II) chloride, copper sulfate, Manganese chloride (MnCl2) and chromium chloride (CrCl3) effective water-soluble inorganic Represent salts.

Example 4 Oxidation of concentrated waste pickling liquid at Overpressure with certain accelerators.

This example was made using the facilities of the procedure of Example 1, with the exception that the device is in a pressure vessel was included and that to the oxidizer at 1.5 hours and again at 2.5 Hours 200 ml of water were given. A 22% waste pickling liquid was used as the feed solution used, which evaporated to a concentration of about 40 ferrous chloride had been. For each experiment, 1400 ml of the 40% solution was added to the oxidizer brought in. In some experiments there was only one accelerator compound in the solution to be oxidized available. In some experiments there was a double solution in the solution to be oxidized Accelerator system available. The copper (II) chloride was used as the dihydrate.

The chromium sulfate was a mixed hydrate with about 9 water molecules used. All tests were carried out at 1490C and 7.03 atm. The used Accelerator compound tightness was expressed in percent by weight based on weight of the 40% waste pickling liquid used. The results of this Experiments are compiled below.

Experiment time, hours Accelerator% Iron (III) ions A 1 3% NH4Cl 68 B 1 3% CuCl2 85 C 1 1.5% NH4Cl + 1.5% CuCl2 92 D 1 3% Cr2 (SO4) 3 82 E 2 ditto 99 F 1 1.5% CuCl +1, 5% Cr2 (SO4) 32 86 Remarks: These attempts show that under these conditions copper (II) ions alone or chromium (III) ions alone represent better accelerators than ammonium ions alone.

Trial F shows no significant benefit for use a mixture of both metal ions. However, Experiment C shows a great one Advantage obtained by using the combination of ammonium ions and metal ions, z ß. Copper (II) ions used versus the use of the respective ions alone.

It was found that a double accelerator system of 3% NH4Cl plus 1% CuCl2 with the above conditions a percentage content of iron (III) ions of 99.0, i.e. a practically complete conversion of the iron (II) ions results. Because of the cost and the use of the NH3 for freshening up, the ammonium compound is the preferred larger component of the dual accelerator system.

Example 5 Oxidation of the waste pickling liquid with a double Accelerator at atmospheric pressure.

This example was made using the setup of the example 1 carried out. 700 ml of a waste pickling liquid containing 22% iron (II) chloride, were used as the starting product. The double accelerator system consisted of 3% by weight NH4Cl + 1% by weight CuCl2, based on the waste pickling liquid. The oxidation temperature was 82.2 ° C.

It was worked at atmospheric pressure. The results are in the The following table has been compiled.

Hours% iron (III) ions 1 11 3 25 5 44 hours % Iron (III) ions 7 62 9 70 15 82 21 86 25 89 35 90 37 90 Remarks: This example and Example 6 below show that a positive pressure operation for the oxidation with accelerators is beneficial.

Example 6 Oxidation of the waste pickling liquid at overpressure under Use of a double accelerator.

This example was made using the facilities and the procedure of Example 1, with the exception that the device is in a pressure vessel was included. 700 g of waste pickling liquid was used as a batch with 24.2 wt .-% iron (II) chloride and trace amounts of iron (III) chloride used. In each experiment there was 3% by weight of ammonium chloride in the waste pickling liquid and 1% by weight of copper (II) chloride hydrate (0.8% by weight of O CuC12), in each case based on the waste pickling liquid, dissolved. The percentage of iron (III) ions in the product solution was at different times, overpressures and temperatures certainly. The results obtained are summarized in the table below.

Test hours ° C atm% iron (III) ions A 3 82.2 3.16 86 B 1 82.2 7.03 66 2 82.2 7.03 96 2.3 82.2 7.05 97 G (footnote 1) 0.75 149 7.03 75 1.0 149 7, ° 3 98+ Footnote 1: Trial C differed from Trials A and B in the way that to ler batch of the reactor at the beginning of the experiment C 10 g of finely divided iron (III) oxide were given.

Comments: Experiments A and B show the advantage of the increase the pressure at constant temperature on the rate of oxidation. The trials 11 and C show the benefit of increasing temperature at constant overpressure (The number 98+ shows that within the analytical error at this ion content practically all iron (II) ions in the waste pickling liquid to iron (III) ions in the form were oxidized by dissolved iron (III) chloride and insoluble iron (III) -oi'd).

Example 7 Oxidation of the concentrated waste pickling liquid at Overpressure using a double accelerator: A flow of temperature.

In each of these experiments 1400 ml of the 40% concentration was concentrated Waste pickling liquid brought into oxidation.

us double accelerator system consisted of 3 wt .-% NH4Cl and 3 % By weight CuCl2, based on the 40% waste pickling liquid. every attempt was carried out at a pressure of 10.5 atmospheres.

Experiment A: temperature 1490C, time: 30 minutes, percent iron (III) ion content: 99% test B: temperature 177 ° C, time: 15 minutes, percentage iron (III) ion content: 93% Comments: The above results show that there is a marked benefit through the use of the accelerator during the oxidation even with these sharp Conditions is obtained.

Example 8 Influence of the addition of iron oxide particles on the speed the accelerated oxidation of the waste pickling liquid.

These experiments were carried out according to the procedure of the example 2 carried out, with a double accelerator system of 1 wt .-% NH4Cl + 0.8 Weight Só 0u0l2, based on the added waste pickling liquid, was used. The temperature was 79.4 ° C. It was worked at atmospheric pressure. In which Experiment A, the oxidation was carried out as in Example 2 without modification. At the Trial B became one of the waste pickling liquid before the start of air injection given a small amount of finely divided iron oxide particles. The following were Get results.

Time, hours Test A (no particles) Test B (% ferric ions added Particles) B-A% iron (III) ions 1 5 11- 6 2 7 17 10 3 11 22 11 4 19 27 9 5 27 53 6 It was observed that, although Experiment A without iron oxide only only the expected agitated appearance of the Oxidation constituents During the early part of the experiment, Experiment B showed the iron oxide particles the air was drawn in and enveloped in an air foam. The number of such brilliant ones Bubble was so large that the components of the oxidizer became almost opaque. Almost immediately afterwards, the formation of iron oxide by-product was due to discoloration evident. In the tests without adding iron oxide, there is always a certain amount Delay before oxidation starts. The difference B-A shows that after three hours the percentage of lisen (III) ions in both Trying to approach begins.

Example 9 Oxidation of waste pickling liquid at excess pressure with a return of the double accelerator.

This example was made with the setup and operation of the example 1, with the exception that the device was enclosed in a pressure vessel was. The oxidation feed solution for each run consisted of 700 grams of the 24.2% waste pickling liquid.

The return from the double accelerator was as follows obtained: Waste pickling liquid was oxidized as in Example 6, including 3% by weight dissolved NH4Cl and 1 wt .-% CuCl2 with an oxidation time of one hour, one Temperature of 14900 and a pressure of 7.03 atü were added, whereby in the Product solution a content of iron (III) ions of 98% was obtained. This solution was stripped of the iron oxide by-product and made into HOI and an aqueous slurry decomposed by ferric oxide. The liquid part of the slurry contained ammonium chloride, Copper (II) chloride and zisen (III) chloride.

The waste pickling fluid for this example was made with the slurry brought into contact with the decomposer to produce the ammonium chloride, copper (1i) chloride extract containing liquid.

The waste pickling liquid that doubles the extracted accelerator was treated under the conditions given above. The product solution this first oxidation, now referred to as Trial A, has a percentage Iron ion content of 98%.

Experiment B: The product solution from Experiment A was then decomposed, to form aqueous slurry bottoms. These soil products were then extracted with fresh AbÎall pickling liquid and the extract solution of the waste pickling liquid was then, as in experiment A, oxidized.

The product solution of experiment B contained 98% iron (III) ions.

Experiments G1 D and E: The procedure of experiment B was carried out three times repeated to complete four cycles of oxidation, decomposition and extraction of the double accelerator for reuse in the oxidation state.

In each of these further cycles, the percentage iron (III) ion content was 98%.

Remarks: This example shows that the dissolved accelerator ions through the oxidation and decomposition without any change or significant Loss ran. The percentage of ferric ions in the oxidation product solution was the same for all cycles. This example also shows that the resolved Accelerator ions are easily recovered for reuse in the oxidation state can be. This possibility of a return results in a economic Waste pickling liquid recovery method in terms of quantity the fresh accelerator required for technical operation.

Example 10 Decomposition of the aqueous iron (III) chloride solution Atmospheric pressure.

A flask with a mechanical oil stirrer, a water-cooled condenser and a receiving vessel was provided. the Test solution consisted of 32% ferric chloride, expressed on a weight basis, 4% iron (II) chloride and the remainder from water.

500 ml of the test solution at room temperature were put into the decomposer brought. The temperature of the constituents of the decomposer increased. The top product the decomposer was condensed and collected. The condensate became periodic examined for the HCl content.

As the constituents of the decomposer (a), a temperature of 130OC reached, a further amount of 100 ml of the test solution was added, and when (h) the ingredients reached a temperature of 1600C, another 100 ml of the test solution were added.

The condensate obtained showed a low HCl content until the Decomposition temperature reached about 171 ° C. Then there was a rapid leap Increase in the IICl content in the londensat.

At a temperature of 82 to 18,800, the condensate contained 33% hydrochloric acid.

The condenser was kept at 182-188 ° C. and 250 ml of test solution were given for this purpose. The condensate held a concentration of hydrochloric acid of 33% upright.

The experiment was stopped when the mechanical stirrer had difficulties got to move the slurry accumulated at the bottom of the decomposer flask.

Example 11 Decomposition of the aqueous sisen (III) chloride solution Vacuum conditions.

The apparatus of Example 10 was made by connecting a vacuum pump modified, A small flask was connected to the decomposer by means of a pipe. This small flask served as a trap for the ferric oxide slurry. The test solution filled the trap and the connecting pipe when the solution in the decomposer was brought, the connecting line remained throughout Try open.

The test solution in this example 11 was the product solution of Example 6A. About 85% of the dissolved iron ions in it were trivalent Shape and about 15; ' in the bivalent form.

The vacuum pump was started and the experiment was like carried out in Example 10 with the exception of the temperature conditions. As the ingredients the decomposer were concentrated and the temperature rose and As the vacuum increased, more test solution was added to reduce the liquid level in the decomposer.

When the temperature in the decomposer had risen to 126.70G, the vacuum was 686 to 711 mm Hg. The condensate had a concentration of 30Có hydrochloric acid obtained.

The iron oxide and solids in the decomposer will settle the way over the pipeline in the trap.

The experiment could be continued indefinitely by using the Trap, when filled with the precipitated solids, replace and separate add further test solution to the decomposer to determine the liquid level therein to maintain, the condensate has a hydrochloric acid concentration of 30%.

Example 12 Decomposition of the aqueous iron (III) chloride solution under Use of the heating gases from a submersible burner.

In this example, the decomposer was a 4 liter beaker that came with a Immersion burner and a cover was provided. The beaker came with a Tube from the cover connected to the bottom of a packed absorption column.

The column was provided with a water inlet at the top, in order to flow water downwards in countercurrent to the gases flowing up in the column allow.

The liquid in the decomposer was pumped through a Circulating decanting vessel in which the solids content is allowed to settle was brought and held. The clarified solution was returned to the decomposer.

In this example, the test solution consisted of an aqueous iron (III) chloride solution with a concentration of 18 wt .-, o. The immersion burner was lit and the test solution was in the decomposer with a sufficient Speed initiated to maintain a constant volume in the decomposer, The temperature in the decomposer gradually rose to 124.4 ° C and stabilized then at this value. The aqueous solution used as the bottom product of the absorption column emerged, corresponded to a 17% strength hydrochloric acid. Solid ferric oxide gradually filled in the decanting trap.

During the experiment the apparent pressure of the decomposer was about Atmospheric pressure. However, the temperature and the rate of decomposition were approximate the same as in the vacuum in Example 6.

This attempt could also be continued indefinitely as above will.

Claims (15)

Claims 1. Process for the production of iron (III) chloride from iron (II) chloride by contacting a liquid aqueous solution of iron (II) chloride with free oxygen, noting that the solution and the free oxygen at elevated temperature and in the presence of an accelerator, consisting of ammonium, chromium, Kolbalt, copper, manganese, nickel or zinc cations or mixtures thereof, intimately mixed with one another, creating a liquid aqueous Solution of iron (III) chloride is obtained. 2. The method according to claim 1, characterized in that g e k e n n -z e i c h n e t that the temperature is 48.9 to 26,000. 3. The method according to claim 1 or 2, characterized in that g e -k e n n z e i c h n e t that the accelerator consists essentially of ammonium cations, where the ammonium ions are preferably obtained from ammonium chloride, which in an amount full not more than about 20 parts by weight per 100 parts by weight of the liquid aqueous ferrous chloride solution is present. 4. The method according to claim 1 or 2, characterized in that g e -k e n n z e i c It does not mean that the accelerator consists of ammonium cations and that as a co-accelerator one or more cations of the metals chromium, cobalt, copper, manganese, nickel or Zinc are provided. 5. The method according to claim 4, characterized in that g e k e n n -z e i c h ii e t that the cations of the co-accelerator are obtained from a water-soluble salt which in an amount of no more than about 20 parts by weight, preferably 0.1 up to G parts by weight, per 100 parts by weight of the iron (II) chloride solution present and that the cations of the co-accelerator preferably consist of copper (II) chloride, Copper (II) fluoride or copper (II) sulfate can be obtained. 6. The method according to any one of the preceding claims, characterized g e k It is noted that in the oxidation zone a smaller amount of finely divided Slisen oxide particles dispersed in the sisen (II) chloride solution is present, if the mixing of the oxidizing solution is started. 7. The method according to any one of the preceding claims, characterized g e k One thing is that the iron (II) chloride solution is a waste pickling liquid is or originates from. 8. The method according to claim 7, characterized in that g e k e n n -z e i c h n e t that the waste pickling liquid with finely divided iron oxide particles in a sufficient amount has been treated that their HCl content is converted into ferric chloride and a minor amount of finely divided iron oxide particles is dispersed has been obtained in the treated liquid and that, if desired, the treated liquid by evaporating a considerable amount of water before the Mixing is concentrated, 9. The method according to any one of the preceding claims, in that the further stages of the heating of the obtained iron (III) chloride solution to a temperature of about 121.1 to 20400, the overhead removal of a stream of water vapor and HCl gas and the Obtaining an aqueous slurry of iron oxide are provided. 10. The method according to claim 9, characterized in that g e k e n n -z e i c h n e t that the dissolved ammonium ions by extraction of the aqueous slurry of Iron oxide with the liquid iron (II) chloride solution that is to be oxidized, can be obtained to recover at least a portion of the accelerator cations. 11. The method according to claim 9 or 10, characterized in that g e -k e n ii z e i c h n e t that the iron (III) chloride solution is heated under reduced pressure, that the heating is preferably using hot submerged combustion gases takes place and that the temperature is preferably about 121.1 ° C. 12. The method according to any one of claims 9 to 11, characterized g e k e n It should be noted that the aqueous ferric chloride solution is heated before it is cooled to precipitate a solid phase that removes the solids from the cooled liquid aqueous iron (111) chloride solution are separated, and that thereupon the cooled, separated liquid aqueous iron (III) chloride solution is subjected to heating. 13. Process for the preparation of hydrochloric acid from a liquid aqueous Solution of ferric chloride, such as a solution obtained according to claim 1, thereby g e k e n n n, z e i c h n e t that the Sisen (III) chloride solution is added a temperature of about 121.1 to 204 ° C, preferably about 121.1 ° C, and heated that one removes a stream of steam and HCl gas overhead, whereby one that Heating under negative pressure makes. 11F. Method according to Claim 13, characterized in that it is n -z e i c h n e t that heating can be achieved by using hot submerged combustion gases undertakes. 15. The method according to claim 13 or 14, characterized in that g e -k e n n z e i c h n t t that an aqueous slurry of iron oxide is obtained.