NO138817B - LIGHT-SENSITIVE REPRODUCTION MATERIAL. - Google Patents

Description

Procedure for treating the sludge-shaped residue from

an alkaline oxidation of lignosulfonic acid compounds.

The present invention relates to the production of useful materials, including vanillin, acetovanillon, lignin substance, calcium oxalate and sodium compounds.

looks from the sludge which forms the solid phase in processes for the production of oxidation products from lignosulfonic acid compounds, such as e.g. such as are described in Norwegian patent no. 80 639 of 25 August 1952. Such solid phases or sludge have a somewhat varying composition, but the essential components are remaining lignin, calcium carbonate, calcium sulphate and calciumoxa

together with remaining free slaked lime and such vanillin products and by-products as are adsorbed or included in the sludge.

In the Norwegian patent no. 80 639, it is clearly described (page 4, section 3 in column 1 et seq.) a characteristic feature of the production of vanillin and other compounds from sulphate waste sludge by regulated alkaline oxidation in the presence of lime as active alkali, namely that in the liquid discharged from the reactor, both liquid and solid phases are present, and the latter constitutes a sludge, and there is a distribution of vanillin and various by-products between the liquid phase and the sludge, and the materials united with the sludge are much harder to recover than those present in the liquid phase, and to ensure that a maximum amount of the vanillin substance remains in the liquid phase, it is a preferred way of working according to the Norwegian patent 80 639 that the liquid phase and the sludge from the reactor outlet are separated before fermentation to release free vanillin from them. It was even stated that in the practical embodiment according to the invention according to the aforementioned Norwegian patent, it may be economically advantageous to dispose of the sludge as waste and only recover the part of the vanillin substance that was present in the liquid phase.

However, we have discovered that this sludge, which indeed contains certain useful products, can be treated in such a way that it becomes possible to extract these useful products in an economically advantageous way.

As stated by Fisher and Marshall in the Norwegian patent 80 639 (page 4, column 2, paragraph), this sludge contains the majority of reaction products of a different nature than vanillin, acetone vanillin and certain related derivatives. Thus, it contains inorganic materials (mainly calcium sulphate, calcium oxalate, calcium carbonate) and lignin residues essentially in the form of their calcium salts or derivatives. We have now discovered a method by which these materials can be extracted from the sludge. The present invention thus represents an improvement of the methods described in the aforementioned patents

ter, and provides further means for obtaining useful materials from processes, where ligninsulfonic acid compounds are used as starting materials, as described here.

Accordingly, the present invention consists in treating the aforementioned sludge so that one or more of the following useful products are obtained from it, namely calcium carbonate, vanillin, acetovanillon, lignin substance and calcium oxalate and so on; sodium compounds are recovered from the reacting substances used.

In accordance with the foregoing, the method according to the invention involves treating the sludge-shaped residue from an alkaline oxidation of lignosulfonic acid compounds, where the oxidation is carried out in the presence of lime as active alkali, and the characteristic feature of the method is that the sludge is treated with an aqueous solution of sodium carbonate and that the sludge is then separated into a solid and a liquid phase, where the solid phase essentially consists of calcium carbonate and the liquid phase contains sodium derivatives of vanillin, acetovanillon, lignin substance and oxalic acid, and isolation in a known manner of a or several of the products in the liquid phase.

Preferably, said sodium carbonate is added in excess of the amount required for the formation of said calcium carbonate.

Other features of the method will appear from the following description.

The attached drawings show the practical implementation of the invention. Fig. 1 is a diagram which generally indicates the various steps of the method. Fig. 2 is a diagram showing further steps in addition to those shown in fig. 1, and this drawing represents a preferred embodiment of the invention. Fig. 3 schematically shows an apparatus which can be used in carrying out the invention.

We have discovered that when the above-mentioned sludge is leached with an aqueous solution of sodium carbonate, preferably at a temperature of the order of 70 °C or higher, essentially all of the sludge's constituents are dissolved with the exception of calcium carbonate. In general, the solution contains the components in the form of the corresponding sodium derivatives or salts, and an equivalent formation of additional calcium carbonate takes place. The amount of sodium carbonate required to effect such leaching can be reduced if an aqueous suspension of the sludge gas is treated with carbon dioxide either before or during the treatment with sodium carbonate. The carbon dioxide reacts with the free lime present in the sludge, and converts it into calcium carbonate. Useful and valuable products can then be obtained by means of the method which is generally indicated in the schematic drawing fig. 1. Thus, the calcium carbonate can be separated by filtration, taken to a lime kiln 3g converted to quicklime, which can be returned for use as active alkali in the treatment of lignosulphonic acid compounds according to the method according to the aforementioned Norwegian patent 80 639 or used for other purposes. The filtrate can be acidified, e.g. with sulfuric acid in a sufficient amount to liberate free vanillin in solution from its sodium derivative form, after which the vanillin can be extracted using solvents such as benzene, toluene, etc., as are known per se, or alternatively the acidification step can be bypassed and the vanillin extracted in the form of the sodium compound according to such methods as are described in US patent 2,104,701, Sandborn; US patent 2,399,607, Service; US Patent 2,489,200, Sankey and Marshall and US Patent 2,721,221, Bryan. After extraction of the vanillin substance, the raffinate can be further acidified to a pH of approximately 4, thereby precipitating lignin substance. This lignin substance results from the oxidation and desulfonation that is effected in the presence of lime as active alkali according to Norwegian patent 80 639. This lignin substance can be removed by filtration and converted into a soluble form, e.g. in the form of the sodium salt, which can be used as a dispersant. After the removal of the lignin substance, the filtrate can be treated with regulated amounts of lime to precipitate calcium oxalate, which in turn can be removed by filtration. The calcium oxalate can then be converted to oxalic acid. Finally, significant amounts of sodium compounds are present in the filtrate residue from the excretion of calcium oxalate, and these can be recovered, e.g. by evaporation and crystallization in the form of sodium sulfate. Alternatively, the residual liquid can be evaporated and removed to recover the sodium compounds in the form of sodium carbonate. As an example of a working technique that can be used for this purpose, reference should be made to "Chemical Recovery from Neutral Sulphite Semi-Chemical Spent Liquors by the Atomized Suspension Technique", Lee & Gauvin, TAPPI, Volume 41, pages 110-116, March 1958 and Canadian patent 552 789 issued 4 February 1958 to Gauvin. Alternatively, other known methods for converting sodium sulphate to sodium carbonate can be used. Such methods are e.g. described by Haywood, "Possible Processes for Recovering Soda and Sulfur from Semi-Chemical and Acid Sulphite Wash Liquors", TAPPI, Vol. 37, No. 2, pages 134A-136A and in US Patent 2,788,273 issued April 9, 1957 to Shick.

If sodium compounds are recovered in the form of sodium carbonate, this can be used to leach additional sludge according to the method according to the invention.

In the following example, the application of the invention shall be made clear.

Example 1.

Lignosulfonic acid materials were treated according to the method of Canadian patent 483 829. The reactants were filtered and a quantity of the filter cake or sludge containing 400 g of dry solids was collected in the water to give a 20% suspension, i.e. 400 g solids in a total volume of 2 litres. This suspension was carbonized with CO2 gas to a pH slightly above 10 to neutralize excess lime, after which a 20% aqueous solution of sodium carbonate was added (0.38 g of sodium carbonate per g of solids in the sludge), and the mixture was stirred for 1 hour at approx. 80°C. The resulting sludge was then filtered to remove 332 g of a light brown colored material consisting essentially of calcium carbonate. After separation, the latter was calcined to form quicklime, which was found to contain 86 per cent available lime when tested. This lime was of a satisfactory quality for use according to the methods according to patent no. 80 639. After the removal of the carbonate, the filtrate was diluted with water corresponding to 35 per cent of its volume, acidified to pH 6 with sulfuric acid and extracted with toluene . 2.1 g of vanillin was then recovered from the toluene extract. During the extraction of vanillin, there was some difficulty with emulsion formation. This was eliminated by adding a small amount of a surfactant as a de-emulsifier ("Oronite" wetting agent "S" manufactured by Oronite Chemical Company). After the extraction of the vanillin, the toluene residue in the liquid was removed by evaporation and approx. 5 percent of the liquid was evaporated. The remaining liquid was acidified with sulfuric acid to pH 4. A precipitate of lignin substance was formed and this precipitate was removed by filtration and dried to 94 g equivalent dry weight. The filtrate residue after the lignin separation was treated with sufficient slaked lime to precipitate the oxalate content in the form of calcium oxalate. This precipitate was also filtered and reduced to 36 g of equivalent dry substance. The residual liquid after the removal of the calcium oxalate was evaporated to dryness and gave a residue containing approx. 180 g of a mixture of sodium sulphate and sodium bisulphate.

In a number of other experiments which have been carried out, the advantages of certain working steps became apparent and these represent preferred embodiments of the invention. The preferred amount of sodium carbonate used in the leaching step is that which is equivalent to the calcium content of the calcium compounds, except for the calcium carbonate present in the sludge. In the example given above, reference was made to the conversion of free lime into calcium carbonate and the purpose of this conversion is to reduce the requirements for sodium carbonate. If an excess of sodium carbonate is used, this will require additional acid, but can ultimately be recovered in the form of sodium compounds. If too little sodium carbonate is used, the result is an incomplete leaching of the soluble part of the sludge. Contamination of the calcium carbonate residue in the solids in the leachate with calcium sulphate and other calcium compounds will be caused, and this will cause filtration difficulties and also reduce the yields of other valuable materials, e.g. lignin, oxalate and sodium sulphate correspondingly. Under these conditions, we have found that there is an increased tendency for the vanillin to be adsorbed on the lignin substance, which means that the separation and removal of the vanillin becomes more difficult.

In Example 1, "Oronite" wetting agent "S" was used as a suitable surfactant during the vanillin extraction step. We have also found that the following surfactants can be used with satisfactory results: "Tet-raprene AS", Canadian Aniline & Extract Co. Ltd.; "Parmol 85", Jacques Wolf &Co.;

"Nacconol NR", National Aniline Div.: Allied Chemical & Dye Corp.; "Monosulph," Nopco Chemical Co,; "Kreelon 4G", Wyan-dotte Chemical Corporation; "Kaywet no.

40", Kraft Chemical Co. Inc.; "Solvadine G". Ciba Co. Inc.

It is generally known that the effectiveness of a specific surface-active agent with regard to reducing, limiting or preventing the formation of emulsions depends on the physicochemical properties of the materials present and on the working conditions such as e.g. the temperature. The choice of such an agent for a specific purpose must therefore be established by trial. We have determined that the above-mentioned surfactants are suitable for use in the present invention. It should be noted that the agents listed all belong to the general class of alkyl-aryl sulfonates which therefore appear to be generally, but not necessarily absolutely suitable for the purpose. The selection of other suitable agents can readily be determined experimentally by those skilled in the art.

When in this description and the claims reference is made to a de-emulsifying agent or to a surface-active agent as a de-emulsifying agent, this means a material selected from the class that includes the above-mentioned surface-active agents and other surface-active materials that exert the same effect under ar - the curing conditions in the method according to the invention.

We have also found that the lignin substance is more easily separated by filtration when it is precipitated at a temperature in the range 40-70° C. Coagulation takes place more easily the higher the temperature is in this range, but if the lignin is heated at too high a temperature, or in for too long, it will tend to melt and thereby form a material that is difficult to remove. The exact maximum temperature at which this takes place varies somewhat and it is generally preferred to precipitate the lignin at a temperature of approx. 60°C. We have occasionally had an unwanted melting of the lignin substance between 60 and 70°C, depending on variations in the composition of the starting material.

If it is desired to recover valuable sodium compounds in order to recover the sodium in the form of sodium sulfate instead of as a mixture of sodium sulfate and sodium bisulfate, the liquid must be neutralized to a higher alkalinity than pH 4 before evaporation. Regulation to pH 7 before evaporation is preferable. A further reason for such a regulation of the acidity before evaporation is that if the material is evaporated at pH 4, as in example 1, the sulfate tends to be contaminated with lignin substance that remains in the liquid, i.e. which is not precipitated in the previous step. At the higher pH, the sodium salt of lignin is very soluble, and such residual lignin as is present tends to remain in the mother-nite, from which the sodium sulfate is separated.

When the solid phase prepared according to the method according to Norwegian patent no. 80 639 is treated with sodium carbonate, the remaining solids (essentially calcium carbonate) which are not leached out of the sodium carbonate solution are extremely difficult to filter. We have discovered that the filtration rate of this remaining solid can be greatly improved by subjecting the sludge to superatmospheric pressure and passing through it a gas containing free oxygen in fine-dispersed form. The temperature at which this process is carried out must be in the range between 120 and 200°C, and it is preferred to carry it out at a temperature of over 140°C. Under such oxidation conditions, part of the remaining lignin substance that is present in the sludge, be converted to vanillin and other by-products including acetovanillin. It will be understood that this vanillin and by-products are in addition to the vanillin and by-product content that is adsorbed or included in the sludge obtained by the method according to Norwegian patent no. 80 639. To effect this oxidation of the lignin substance that is present in the sludge, additional alkali is required. Accordingly, lime is added to the mixture before such an oxidation step, or alternatively, when performing the alkaline oxidation of lignosulfonic acid materials in accordance with the method according to Norwegian patent no. 80 639, additional lime is provided in excess of the amount required, and this excess of lime will be entrained during said method by the sludge, and consequently it will be present when required according to the method according to the present invention. Additional sodium carbonate is also required. In view of the necessity of maintaining an appropriate alkalinity for this preferred working step, treating an aqueous slurry of the sludge with carbon dioxide gas prior to the treatment with sodium carbonate solution would naturally be undesirable according to this modification of the present invention and should be omitted.

It is not desired that calcium compounds of a different nature than calcium carbonate are present in the solid phase residue from the oxidation step in the present method. It is preferable that the amount of lime added before such an oxidation step should be limited so that no such calcium compounds are present. The presence of calcium compounds of a different kind than calcium carbonate in the reacting substances after the oxidation step is easy to detect, because when such compounds are present, the solid phase that is discharged from the reaction zone has a typical light brown color instead of a white or gray color. The difficult filtering property of such a solid phase is also an almost certain sign of the presence of such compounds. If an excessive amount of lime has been added resulting in the above undesirable condition, this can be corrected by treating the materials exiting the reaction zone with carbon dioxide gas at a pH of 12 or higher or alternatively by adding additional sodium carbonate to the materials after they have been taken out of the reaction zone.

The amount of lime to be used is in a certain relationship to the amount of sodium carbonate present. Sodium carbonate is first required, as noted above, in an amount corresponding to the calcium content in the sludge minus the amount of calcium that is present in the form of calcium carbonate in said sludge. Additional alkali must then be present in a sufficient amount to maintain a suitable alkalinity during the oxidation step, and this suitable alkalinity may be that corresponding to a pH = 12 or higher, as determined by a sample removed from the reaction zone and cooled to room temperature . Such further alkali is provided according to the invention by means of sodium carbonate and lime. The amount of lime used must therefore not exceed the amount that corresponds to the amount of sodium carbonate present beyond that required to exclude the sludge as described above. In practice, some excess of lime beyond the above-mentioned amount can be suitably used, because during the oxidation step some of the materials in the reaction zone are oxidized to carbon dioxide, which in turn reacts with the free lime present to form calcium carbonate. The use of an amount of lime in accordance with the conditions stated above allows a satisfactory implementation of the method according to the invention. If the amount of lime is limited to that which corresponds to the amount of sodium carbonate added in excess beyond the amount required for the leaching process as described above, no difficulties will be encountered as a result of the presence in the solid phase of calcium compounds of another kind than calcium carbonate.

As a general guide with regard to the amount of lime to be used, reference should also be made here to the various examples given. Under the conditions of the described experiments, the presence of calcium compounds of a different kind than calcium carbonate in the solid residual phase from the oxidation step was avoided in any case.

After the oxidizing step has been completed, the various useful products can be isolated generally according to the method shown purely schematically in fig. 2. The separation of calcium carbonate

can be effected much more easily and is of a high

degree of purity. Significantly increased amounts of vanillin substance and by-products are extractable. The same circuit processes which include reuse of the isolated products according to the invention are applicable, except that the lime which is formed can also be used in the oxidizing treatment of the aqueous slurry of the sludge as described above.

It is common knowledge that when lignin substance is exposed to alkaline oxidation under such conditions that vanillin is formed, the formed vanillin will itself be exposed to oxidation in the reaction zone and that the net vanillin yield is thereby reduced in accordance with this. A reaction time must therefore be selected which takes into account the strength of the oxidation conditions, so that unnecessary splitting of the formed vanillin does not take place, i.e. so that a high net vanillin yield is achieved. In the practical implementation of the invention, we have generally found that the preferred reaction time is less than two hours and that a shorter time is preferable in the event that particularly strong oxidation conditions prevail, such as e.g. at higher temperatures, higher partial oxygen pressure and/or a stronger air flow. We have also found that the net vanillin yield has a tendency to be reduced as a result of oxidation of formed vanillin under reaction conditions, where particularly high partial oxygen pressures prevail. It is therefore preferred to work at a partial oxygen pressure (at the beginning of the reaction zone) lower than 1.4 kg/cm2 and when reaction temperatures of the order of 175°C and higher are used, it is preferred to use a partial oxygen pressure of less than 0.7 kg/cm2. The present invention reveals that satisfactory yields of vanillin can be obtained in the general working range indicated here and the choice of the preferred working conditions with regard to the strength and time of the oxidation within this range can be easily determined by those skilled in the art.

During the reaction, a suitable stirring of the reacting substances in the reaction zone is highly desirable. This stirring serves to disperse the gas containing oxygen into small bubbles and in this way the gaseous oxygen content in said gas bubbles will become more easily accessible to the materials to be oxidized. The stirring also maintains the solid phase in suspension in the reactor.

The above-mentioned modification of the method for obtaining useful products is indicated in the schematic drawing in fig. 2, and the execution of this modification will be apparent from the description given above.

In the practical implementation of this and other modifications of the invention which include an oxidizing step, an apparatus which is shown in fig. 3, which schematically shows an apparatus which has been used in part of the experiments carried out, and which comprises a reaction vessel 1, into which the reacting substances are introduced from the tank 2 by means of the pump 3 and the line 4, a lid 5 which exhibits a opening 6 which leads to a regulating pressure safety valve 7, which limits the maximum pressure in the reaction system to a predetermined value and maintains the pressure at this value. The reactor contents are stirred by a stirrer 8, as shown in fig. 3 is shown as a turbo-mixer type stirrer. The turbo-mixer is driven by the engine 9. Compressed air is introduced from the compressor 10 through the tank 11 and the line 12 into the reactor, where it is distributed by the impact of the turbo-mixer 8 and the pressure and air flow rate are regulated by the valve 13, 14.

The reaction vessel is heated by direct steaming through the line 15 and the steam is supplied from the boiler 16 and regulated with regard to pressure and flow rate by the valves 17, 18. Other suitable heating means can of course be used. The reaction vessel is also equipped with a pressure - manometer 19 and a thermometer container 20, which contains a thermometer 21. React-

tion vessel can be emptied through the opening 22 which is regulated by the valve 23 which provides

for a general depletion of fluid. This emptying is carried out through the cooler 24. A sampling line 25 is also used, which is regulated by means of the valve 26 and which is led through the cooler 27 and with the help of which small samples can be taken from time to time. A general safety valve 28 is also provided for a general pressure reduction when this is required.

In the following, an example is given which will serve to clarify this embodiment of the invention.

Example 2.

Lignosulfonic acid materials were treated according to the method of Canadian Patent 483,829. The reactants were filtered and a quantity of the filter cake or sludge, containing 400 g dry solids equivalent, was suspended with 240 g sodium carbonate and 13.2 g slaked lime to an aqueous sludge which was filled up to a total volume of two litres. This mixture was introduced into a reactor as shown in fig. 3.

The batch was heated to a temperature of 170°C and this temperature was maintained throughout the rest of the treatment. Air was introduced into the reactor at a rate of 425 liters per second. hour for 40 minutes. A back pressure valve (7) was regulated to 10.9 kg/cm2 excess pressure so that the total pressure during the entire reaction was automatically kept at this pressure level. From the measurement of the vapor pressure and the total working pressure, the partial oxygen pressure was calculated to be 0.8 kg/cm2. After the treatment as indicated above, the air flow was interrupted, the reactor was allowed to cool and the total reaction products were removed. By filtration, 303 g of solid material was removed, which essentially consisted of calcium carbonate. After separation, the calcium carbonate was calcined to form quicklime which, on examination, was found to contain 93 per cent available lime. The filtrate after removal of the carbonate was diluted by the addition of water in an amount corresponding to 60 percent of its volume and was acidified to pH 6 and extracted with toluene, using a small amount of the "Oronite" wetting agent "S" as de-emulsifier. 6.1 g of vanillin and 0.3 g of acetovanillon were finally recovered from the toluene extract. After the extraction of the vanillin, the remaining toluene in the liquid was removed by stripping as in example 1. The remaining liquid was acidified with sulfuric acid to pH 4 and thereby lignin substance was precipitated. This was removed by filtration and the amount reduced to 38 g based on dry weight. The filtrate remaining after the removal of the lignin was treated with a sufficient amount of slaked lime to precipitate the oxalate content as calcium oxalate. 42 g of calcium oxalate were obtained in this way. The remaining liquid after the removal of the calcium oxalate was evaporated to dryness and gave a residue containing approx. 280 g of a mixture of sodium sulfate and sodium sulfate.

Example 3.

A number of experiments were carried out in a similar manner to example 2, where the temperature at the reaction stage, the excitation time and other variables were regulated as indicated below:

In the practical implementation of the invention, the specified degree of acidity, at which the lignin begins to precipitate, depends on the concentration of the lignin substance and also partly on the concentration of other substances, as large amounts of inorganic compounds tend to salt out the lignin. In addition, there will be some variations between different loads of the sludge. The extraction of vanillin from a liquid in which precipitated lignin substance is suspended often entails serious emulsion difficulties, which make the process essentially unfeasible. It is therefore an important feature of the implementation of the invention that the vanillin is extracted from a liquid which is free of suspended lignin substance. If under such acidity conditions that are desirable for vanillin extraction, a precipitation of lignin substance takes place, it is therefore preferable to regulate the acidity to a level of e.g. pH 5.5 or 5.0, after which the lignin substance is removed by filtration and then the vanillin extraction is carried out without further acidification from the filtrate obtained after the removal of lignin substance. It will be obvious that if valuable sodium compounds are to be recovered by evaporation, excessively strong dilution should be avoided in order to reduce the amount of water to be evaporated during the recovery of said valuable sodium compounds. The preferred mode of operation with regard to recovering sodium compounds necessitates the maintenance of a relatively high concentration of solids during the treatment steps, including the vanillin recovery step and the equation recovery step. Such a high concentration is favorable for lignin elimination at a higher pH. It is therefore a preferred embodiment of the invention that such a high concentration of solids is maintained and in this case it would be preferable —• and is in reality of decisive importance — to precipitate and remove the lignin substance before the extraction of the vanillin. Nevertheless, the precipitation of the lignin substance before the extraction of the vanillin can be avoided by diluting the mixture so that the concentration of lignin substance is reduced to a level so that it does not precipitate. Although we try to avoid working under such conditions, such working methods are within the scope of the invention.

When the lignin substance is precipitated before the vanillin extraction, an adsorption or inclusion of vanillin takes place on the lignin. Recovery of such adsorbed or included vanillin is highly desirable and can be achieved by washing the lignin substance. However, we have discovered that when the lignin substance is washed with water, it tends to disintegrate and form a slimy mass, which has very poor filtration properties. Effective washing is therefore very difficult to carry out. We have discovered that an appropriate recovery of vanillin can be achieved without it

any significant change in the lignin substance filtration properties if any

washing is carried out with the raffinate residue after the extraction of vanillin after that

then the following steps in the process. It is likely that the use of a liquid containing the same dissolved inorganic materials that were present in the liquid where the lignin substance was originally precipitated results in no significant change of the lignin structure taking place, and we have found that this raffinate is an effect -tive detergent to remove adsorbed or included vanillin. The recovery of vanillin from lignin substance by washing with said raffinate therefore represents an important preferred embodiment of the invention, which enables a significantly improved recovery of both vanillin and lignin substance. A further important advantage of using raffinate to wash the lignin is that the dilution of the liquid at one stage or another before the recovery of the sodium compounds is avoided.

Example 4.

Lignosulphonic acid materials were treated according to the procedure of N.P. No. 80 639. The reactants were filtered and a quantity of the filter cake or sludge, containing 400 g based on dry solids, was suspended with 240 g of sodium carbonate and 13.2 g of slaked lime in an aqueous sludge, which was filled up to a total volume of two litres. The aforementioned mixture was fed into a reactor of the type shown in fig. 3.

The charge was heated to a temperature of 170°C and the temperature was maintained at approximately this point throughout the rest of the treatment. Air was introduced into the reactor at a rate of 425 liters per second. hour for 40 minutes. A back pressure valve (7) was regulated at 10.9 kg/cm2 so that the total pressure during the entire reaction was automatically maintained at this pressure. From the measurement of the vapor pressure and the total working pressure, the partial oxygen pressure could be determined to be 0.8 kg/cm2. After the treatment as indicated above, the air flow was interrupted, the reactor was allowed to cool and the total reaction products were discharged. By filtration, 303 g of solid materials were removed, which essentially consisted of calcium carbonate. The filtrate after the removal of carbonate was acidified to pH 5 with sulfuric acid. Lignin substance corresponding to 42 g dry weight was precipitated. This was removed by filtration and the filtrate then extracted with toluene using a small amount of the Oronite wetting agent "S" as a de-emulsifier. 5.3 g of vanillin was recovered from the toluene extract. The lignin was washed three times in each case with a volume corresponding to 10 percent of the liquid from which it had been precipitated, with the raffinate from the toluene extraction. These washing liquids were then extracted with toluene and a further 0.6 g of vanillin was recovered. The combined raffinates from the toluene extraction were later worked up to extract valuable calcium oxalate and valuable sodium compounds in a similar way as in the preceding examples.

The invention can also be carried out in practice by slurrying the solid phase as prepared according to Norwegian patent no.

80,639 in an aqueous medium containing

dissolved lignosulfonic acid compounds. Instead of treating the solid phase with an aqueous solution of sodium carbonate, the solid phase can thus be treated with an aqueous solution of sodium carbonate from sulphite leachate or in the same liquid which has been previously treated to utilize the liquid's content of fermentable sugar. The liquid remaining after the sulphite waste liquor has been subjected to fermentation to produce ethyl alcohol (which

residual liquid in the following shall be denoted by the term "distillery waste liquid" — S. F. A.) is a particularly suitable material for the application of the invention in this respect.

According to this modification of the invention, useful materials are obtained both from the sludge and from the lignosulfonic acid compounds present in the distillery waste liquid. Such lignosulphonic acid compounds are subjected to a regulated alkaline oxidation, whereby additional vanillin is formed. Such solid phase, which is formed as a result of the simultaneous presence of lime as active alkali, becomes in situ additional raw material for the method according to the invention, and from such solid substances additional vanillin and other useful products can be extracted. The amount of alkali (sodium carbonate and lime) required to carry out the reaction must of course be increased corresponding to the needs for the lignosulfonic acid materials present.

In view of the final recovery of sodium compounds, the advantage of avoiding any unnecessary or too strong dilution of the reacting substances is emphasized above. If an attempt is made to leach lime directly into the distillery waste liquid, part of the lime particles will be coated with calcium derivatives of lignosulfonic acid materials and the leaching process will thereby be difficult to carry out and strong foaming will occur. We have found that this can be avoided if the required amount of sodium carbonate is dissolved in the distillery waste liquid prior to the leaching process. The lime is then dissolved in such a solution. Such a method is therefore a preferred embodiment of this particular application of the invention and is strongly recommended. When sodium carbonate is dissolved in the distillery waste liquid, precipitation of lignin substance can still take place if either the concentration of sodium carbonate is too high or if the temperature is too high at a certain concentration. Such precipitation is undesirable. The exact concentration of sodium carbonate at which precipitation takes place depends on the temperature and the concentration of lignin substance in the distillery waste liquid. In general, we have found that precipitation does not take place under the liquor conditions if the concentration of sodium carbonate in the distillery waste liquid is not greater than 0.35 kg/litre. A concentration of 0.35 kg/litre or less is therefore recommended. In this embodiment, precipitation and filtration of the lignin substance before the extraction is also preferable for the same reasons as previously stated, and furthermore it is preferable in such a case to wash the lignin precipitation in order to recover vanillin substances with a raffinate obtained by extraction, of vanillin with a suitable solvent, e.g. toluene.

The following examples shall serve to clarify the implementation of this modification of the invention.

Example 5.

The solid residual phase from the treatment of distillery waste liquid in accordance with the method according to Norwegian patent 80 639 was separated by filtration and a sludge was produced from the filter cake containing 18.3 kg of dry substances in

92.7 litres. 14.6 kg of sodium carbonate was dissolved in 61.8 liters of alcohol waste liquid (which contained 0.088 kg of solids per liter) and this solution was used to slake an amount of quicklime which is sufficient to give 6.40 kg of slaked lime . All of the above-mentioned materials were fed into a reactor which was essentially constructed according to fig. 3. The reactor was heated to 162°C and air was then introduced into the reactor at a rate of 16,990 liters per hour. The total pressure in the reactor was maintained at 10.57 kg/cm 2 (corresponding to a partial oxygen pressure of 0.35 kg/cm 2 ). The reaction is exothermic and the temperature rose to 180°C and remained constant at this value. After a total reaction time of 45 minutes, the air was disconnected and the reactor was emptied during rapid cooling of the charge. The reacting substances were then treated according to the method specified in example 4 and the following results were obtained:

Example 6.

A series of experiments were carried out in a similar manner to that set out in Example 5, where the variable quantities of the reaction were as follows:

Example 7.

An experiment was carried out in a similar way as in example 5, where the reaction temperature was 140°C, the total pressure 4.4 kg/cm2, the air flow passing through the reactor 9910 liters per hour and the corresponding partial oxygen pressure 0.35 kg/cm2, the reaction time 125 minutes and the produced vanillin 0.32 kg and the produced lignin 3.63 kg.

It will be understood that circuit processes where lime produced from calcium carbonate that is recovered in accordance with the invention is used, and that circuit processes for the use of sodium carbonate when the sodium compounds are recovered in this form, can be used in the above application

led to modification of the invention in a completely similar way as in the previous examples.

In the examples given to clarify the method according to the invention, the separation or recovery of a number of useful products has been described. It will be understood that one or more of such useful products will be secreted or extracted from economic considerations,

and that it is not a technical necessity that the complete procedure in

according to the invention as described here

know, is followed in any case. If e.g. sodium compounds are to be extracted by evaporation and combustion in the form of sodium carbonate, the oxalate extraction step is not necessary. The extraction of lignin is similarly only necessary if vanillin substances are to be extracted and if

re conditions are such that a lignin precipitation takes place at the pH chosen for the vanillin extraction. Means to avoid

such a precipitation is indicated.

When the term "pressure" is used in the description, it must be understood that reference is made here to relative pressures and not absolute pressures.

When the allegations refer to use

ken of a pH of 12 or greater, then reference is made to a determination of pH in a liquid sample which is discharged from the reactor and then cooled to room temperature and determined according to the methods described here.

When the expression "lignosulphonic acid compounds" is used in the description and claims, this means materials that originate from lignin when lignin has been treated so that sulphonic acids are formed from it, e.g.

when lignin-containing substances are exposed

is used for the sulphite boiling process and the expression also includes salts of said sulphonic acids. The term sulphite waste disposal shall include a

such lye as such and also sulphite waste lye that has been previously treated to transform

reduce the perishable sugar content of alcohol

hol, but the expression does not include materia-

clays that arise from lignosulfonic acid compounds, which have been treated in such a way that substantial or complete de-sulfonation takes place. Thus, the lignin proportion in the solid phase residue is excluded in particular

from alkaline oxidation of lignosulphonic acid compounds, e.g. when the alkaline oxidation has been carried out in the presence of lime as the active alkali.

When the description and claims use the expression "refinery residue from the extraction of vanillin" this means the aqueous liquid that is discharged from an extraction device, e.g. the one which is led through the line 6 in fig. 1 and wire 9

on fig. 2, from which vanillin has been removed from the solution by means of a solvent which is relatively immiscible

mustache with water.

Claims (6)

1. Procedure for treatment of the sludge-shaped residue from an alkaline oxidation of lignosulfonic acid compounds, where the oxidation is carried out in the presence of lime as active alkali, characterized in that the sludge is treated with an aqueous solution of sodium carbonate, and that the sludge is then separated into a solid and a liquid phase, where the solid phase essentially consists of calcium carbonate and the liquid phase contains sodium derivatives of vanillin, acetovanillon, lignin substance and oxalic acid, and isolation in a known manner of one or more of the products in the liquid phase. 2. Method as stated in claim 1, characterized in that prior to the division of said sludge into a solid and a liquid phase, the sludge is kept, as is known per se, in a reaction zone at superatmospheric pressure and at a temperature in the range of from 120 to 200°C, while a gas containing free gaseous oxygen is passed through said reaction zone, and the rate of addition and removal of said gas to and from said reaction zone is such that a partial pressure of oxygen is maintained in said reaction zone of less than 1.4 kg/cm2, and the sludge is maintained during the passage of said gas through the reaction zone at a pH of at least 12 (determined on a sample taken out of the reaction zone and cooled to the ambient temperature), the pH value being set at addition of sodium carbonate in excess of the amount required for the formation of calcium carbonate, and lime. 3. Method as stated in claim 1, characterized in that the sludge either before or during the mixing of said sludge with said aqueous solution of sodium carbonate, is exposed to the influence of carbon dioxide gas in an amount sufficient to react with all the content of slaked lime in said sludge, so that calcium carbonate is formed. 4. Method as stated in claims 1 to 3, characterized in that acid is added to the liquid phase in a known manner to precipitate the lignin substance that is separated, after which the liquid phase is extracted in a known manner to extract vanillin and acetovanillon, and the raffinate residue from this is used as washing liquid for the separated lignin substance in order to recover additional amounts of vanillin and acetovanillon which are adsorbed or included in the lignin substance. 5. Method as stated in claim 4, characterized in that after removal of the lignin substance, the acidified liquid is treated with lime to precipitate calcium oxalate. 6. Method as stated in claim 5, characterized in that after the precipitation of calcium oxalate, the liquid phase is evaporated and pyrolysed to recover valuable sodium compounds.