DE2530820B2 - Process for the removal and recovery of ugine sulfonates, sulfated alcohols and aromatic sulfonates from a precipitated, aqueous, protein-containing sludge - Google Patents

Description

The invention relates to a method for the removal and recovery of lignosulfonates, sulfated Alcohols and aromatic sulfonates from a precipitated, aqueous proteinaceous sludge which the sludge is thickened at the same time. The organic precipitation medium recovered in the process can be reused for the precipitation of other proteins.

It is known that a number of substances on an industrial scale as precipitants in the Recovery of proteins or protein materials from wastewater, such as process water, can be used can. The most important group of precipitants used for this purpose are the lignosulfonic acids and their derivatives. In several countries plants for the purification of industrial wastewater are under simultaneous recovery of considerable quantities

to proteins in which lignosulfonic acids are used as precipitants (see the U.S. Patent 33 90 999). Other organic substances that have already been used as precipitants, are organic sulfonates, for example aryl, alkaryl and aralkyl sulfonic acids (see Canadian Patent 8 82 398) and organic sulfonates, for example Sulfuric acid esters, monohydric and polyhydric alcohols such as lauryl sulfate, glycerol trisulfate and sulfatiene 6-valent alcohols and sulfated 6-valent carbohydrates (see Norwegian patent specification 1 17 339 and the Canadian Patent 8 87 899). A method is also known from US Pat. No. 23 20 766 in which albumins can be separated from solutions containing them using water-soluble sulfonated organic compounds from the group of the sulfonated naphthas, sulfonated Naphthenes and sullonaphthenic acids as precipitants. Most of these organic sulfonic acids and Although sulfonates have a very good cleaning effect, their use leads to relatively high costs for the chemicals used in water purification on an industrial scale. There the proteins made using the said Precipitants from sludges containing them are recovered, are mainly used as feed or feed additive, is one endeavors to keep the content of precipitant in the recovered protein as low as possible, in order to avoid the resulting health problems in the animals fed with it. By Separation and recovery of the precipitant would also allow the commercial value of the recovered protein material as animal feed increase and at the same time the relatively high Reduce the costs of the precipitant used through its recovery and reuse. From the German Offenlegungsschrift 21 46 388 is a method known in which calcium chloride as Precipitant is used for waste water containing proteins, the waste water being in the presence of the Precipitant and at a pH within the range 5.5 to 7.0 to a temperature of

■ 55 is heated to at least 60 ° C. According to the information in the US Patent 23 28 361 can improve the filterability of a conventionally precipitated and in the Heat coagulated sludge by adding a calcium salt, such as calcium chloride, to this sludge

f, o to be improved · This is the wastewater with a Protein precipitants such as aluminum sulfate, aluminum chloride, thorium nitrate, iron (III) sulfate or Iron (! Ll) chloride, treated to flocculate the materials suspended in it, after which the pH of the treated wastewater is adjusted to 4.0 to 5.0. After the partial dewatering of the sludge this is heated to a temperature above 65 ° C and a small amount of one is added before filtering

water-soluble calcium salt added to the mud

In the known method for precipitating proteins, in particular from industrial wastewater, is the precipitate obtained is then removed from the water phase using any conventional mechanical means Process, for example by flotation, separated, being a sludge with a dry matter content from 5 to 15% is retained. This sludge often has to be further thickened, for example by filtering or centrifugation after a suitable pretreatment, for example by heating and / or under Adding lime before subjecting it to the final treatment substantial part of the precipitant returned in the sludge and a disproportionately large proportion of the Proteins to be precipitated are removed with the water phase.

The invention had the object of providing a method for the removal and recovery of Lignosulfonates, sulfated alcohols and aromatic sulfonates from a precipitated, aqueous To develop protein-containing sludge, with the help of which it is possible to use the organic Protein precipitants effectively; to recover the sludge so that it can be used again Precipitation of proteins can be reused.

It has now been found that this object is achieved in a method of the type described above can be solved that the sludge at least one alkaline earth compound in one to form the proteins sufficient amount and, if the pH value is still below 6.5, an additional one Base from the group of alkaline earth and alkali hydroxides is added until the pH value is above 6.5, then the sludge is expediently supplied with steam and with stirring up to at least 60 ° C heated and the water phase which separates out, which contains precipitating agents and precipitates Proteins can be reused, separated.

The method of the invention is based on the finding that when an alkaline earth compound is added and, if necessary, an alkaline earth or alkali hydroxide until a pH of about 7 to about 9 to the proteinaceous sludge and then heating it to at least 60 ° C surprisingly a cleavage of the protein complex in question into precipitants and proteins takes place, the proteins coagulate as alkaline earth proteinate and the precipitating agent in the separated Water phase goes into solution By washing out the coagulated protein material, it is beyond that possible to recover the precipitant almost quantitatively. If you have an alkaline earth hydroxide, such as calcium hydroxide, used alone before the heat treatment of the proteinaceous Sludge is carried out, only a small part of the precipitant goes into solution, so that only one lower proportion of the precipitant can be recovered, which is presumably due to it is that the calcium salts of the precipitants in question are less soluble. An advantage of the However, the use of lime alone is that the coagulated material has a firmer consistency and is easier to separate, for example more easily filterable

By using an alkaline earth compound in one sufficient for the formation of alkaline earth proteinate Amount and of alkali hydroxide in an amount sufficient to neutralize the precipitating agent goes as Alkali salt in solution, which has a high solubility so that an almost quantitative recovery of the Precipitant is possible during coagulation the sludge separating water phase is expedient by displacing with water on a Filter or in a suitable centrifuge

ίο separated An alkaline earth metal salt, in particular calcium chloride, is preferably used as the alkaline earth compound, and calcium hydroxide or sodium hydroxide is preferably used as the base.
According to a further preferred embodiment of the invention, the protein-containing sludge is added to the protein-containing sludge before heating until its pH value is between 7.5 and S » coagulated sludge is displaced The heating or warming of the tube is expediently carried out with the supply of superheated steam for a period of at least about 2 minutes. The displacement of the precipitant-containing, separated water phase with water is expediently carried out by means of a centrifuge, preferably with cooling

It is particularly useful to use alkaline earth compounds with a high buffer capacity, for example alkaline earth salts to use fatty acids and / or the sludge in addition to another coagulation aid with a high buffer capacity, in particular proteins that can be coagulated by heat, and preferably blood and / or ground meat.

The protein-containing sludge is expediently first slowly slowly with vigorous stirring for so long heated until coagulation begins, whereupon it is quickly brought to a temperature above 60 ° C and preferably to a temperature of about 70 to about 100 ° C further heated. The heating can Secondly, take place with the supply of steam.

Particularly good results are achieved if both blood and lime are added to the mud. at this embodiment of the process of the invention does not necessarily result in a product having a particularly high dry matter content, but compliance with certain working conditions is essential not as critical with regard to temperature, pH and the like as, for example, when using Lime alone.

The invention is illustrated in more detail by the following examples

example 1

In order to carry out the experiments, one would go through Precipitation of prcteinen from a slaughterhouse wastewater separated lignoprotein sludge with a Dry matter content of 14.5% used.

to The sludge, which had a pH of 4.1, Lime was added until its pH was increased to 8.0. After that, the mud was on a Heated to a temperature of 95 ° C at which it coagulated. After a sufficient reaction time, the

hi centrifuged mud. The centrifugate was then used as Precipitant used to precipitate proteins from a protein solution, of which the optimal amount added known from a lignin sulfonic acid. Of the

Protein solution was the centrifugate in certain, different amounts of ligninsulfonic acid corresponding Quantities added. The protein material fell out of the solution, whereupon the content fell organic substances in the decantate obtained was determined by measuring the COD.

As a protein solution for the recovery test, slaughterhouse wastewater of the same quality as that used, from which the examined lignoprotein sludge had been precipitated.

The results obtained in these experiments are shown in Table I below.

Table I.

Addition to 500 ml protein solution COD COD curve

in the no.

Ligno- sulfur centri decant rings-

l'Ügdt

tion

mg / ltr. mg / ltr. ml mg O ₂ / % 1 L tr. O 0 0 4690 0 O 600 0 3886 17.14 O 700 5 1259 73.15 50 700 5 1178 74.89 100 700 5 1189 74.64 2 150 700 5 1239 73.59 200 700 5 1276 72.79 250 700 5 1300 72.29 0 600 0 3886 17.14 3 0 700 5 1259 73.15 0 700 10 1341 71.41 0 700 15th 1706 63.64 250 600 0 1036 77.91 300 600 0 1016 78.34 350 600 0 1022 78.20 400 600 0 1075 77.07

If more lignosulfonate is added, then there will be the precipitation of proteins from the protein solution as a result of the overdose less effective. This effect of an overdose can also be clearly seen from curve 3, which shows that the optimal dosage of lignosulfonate is 300 mg / liter. Since more than 70 mg lignosulfonate per Liters when used in combination with 5 ml centrifugate do not give a better COD reduction (see. Curve I), one can assume that the recovered precipitant in the centrifugate a Dosage of about 300-70 = 230 mg / liter or 115 mg / 500 ml. If you go from this reasonable assumption, the added centrifugate should contain 11 mg / ml or approx. 20 g / liter.

Example 2

The same sludge that was used in Example I was treated with one Amount of calcium chloride added, whereupon the pH value sodium hydroxide was adjusted to 8.0. Thereon the sludge was heated up to 95 ° C, whereupon coagulation occurred. After a sufficient period of and reaction time at this temperature, the sample was centrifuged. The centrifugate was analyzed and used as a source of lignosulfonate by adding a certain amount of it to a protein solution zuese.it, to which different amounts of lignosulfonic acid were added. It turned out that when using the centrifugate as a precipitating agent, a significantly better precipitation of the proteins is achieved so that the resulting liquid phase was clear and pure. The liquid phases of the samples were analyzed for their COD value to obtain a Obtain parameters for the recovery of the protein precipitant. The ones in these attempts The results obtained are shown in Table II below.

The test results listed in Table I and the curves clearly show that the centrifugate contains a large amount of recovered precipitant ml protein solution. The COD reduction in this case is 73.15 percent, while it is only 17.14 percent with the addition of sulfuric acid alone. Curve 2 shows that the optimal added amount of centrifugate for the precipitation of proteins from the protein solution is about 8 ml / 500 ml of protein solution would have to be, which would result in a COD value in the decantate of around 1190 mg O ₂ / liter, corresponding to a COD reduction of around 74.6 percent. If one compares this (extrapolated) result with the extrapolated part of curve 3, it can be assumed that the recovered amount of precipitant would correspond to a dosage or an addition of about 150 mg / liter or about 87 mg / 500 ml. This means that the concentration of precipitant in the centrifugate is about 87

= £ - mg / ml or should be around 10 g / liter.

Curve 1 shows that the optimal dosage of the addition of lignosulfonate when this is in Combination with 5 ml centrifugate / 500 ml protein solution is used, amounts to about 70 mg / liter

Table Il 500 ml protein solution) Centri COD COD curve Addition (to fugat in De Min sulfur ml cantat change Ligno acid sulfonate mg / ltr. 0 mgÜ2 / % mg / ltr. 0 Ltr. 0 5 4690 0 0 600 5 3886 17.14 0 700 5 1126 75.99 4 0 700 5 1084 76.88 50 700 5 1117 76.18 100 700 5 1148 75.52 150 700 5 1173 74.98 200 700 10 1210 74.20 250 700 15th 1126 75.99 5 0 700 1146 75.56 0 700 1312 72.02 0

The results obtained according to example 2 can be best matched with the results of example 1 Compare by comparing curve 4 (example 2) with curve 1 (example 1) and curve 5 (example 2) with compares curve 2 (example 1)

In comparison to curve 1, curve 4 shows that one

according to Example 2 a better COD reduction than according to Example I is obtained, and that the optimal dosage or added amount is slightly lower than in Example 1. This means that the centrifugate, by coagulation of the sludge is made with calcium chloride and sodium hydroxide, a larger amount of precipitant than the centrifugate obtained according to Example 1 contains.

The ¹ ; is also evident from a comparison of the results obtained in the protein filling experiments with centrifugate alone. Curve 5 (example 2) is well below curve 2 (example 1), which means that the specific COD reduction with the centrifugate from example 2 is better. Furthermore, when the amount of centrifugate is increased beyond the optimum dosage, curve 5 has a lower slope than curve 2, which means that the proportion of substances without

protein-precipitating properties in the centrifugate from example 2 may be lower than in the centrifugate from example 1 got to.

Example 3

Before coagulation at 95 ° C., 3 samples of the same sludge as in Examples 1 and 2 had been used, mixed with different amounts of lime, so that the pH value of the samples at 7.8 or 9 lay. The separation of the aqueous liquid phase excreted during coagulation was carried out carried out analogously to Example 1, whereupon the centrifuges in the manner indicated in Examples 1 and 2 were examined.

The results obtained in these experiments are shown in Table III below.

III

Addition (to 500 ml protein solution) Centrifugate COD in de- COD- Curve PH value Decantate Decrease. at the Ligno- sulfur ml Coagulate sulfone. acid 5 mg / ltr. mg / ltr. 5 mg 02 / ltr. 0 700 5 1372 70.74 6th 7th 0 700 5 1259 73.16 8th 0 700 5 1168 75.09 9 50 700 5 1265 73.02 7th 7th 50 700 5 1178 74.88 8th 50 700 5 1143 75.62 9 100 700 5 1225 73.88 8th 7th 100 700 1189 74.64 8th 100 700 1202 74.37 9

Comparing the above test results in the same manner as in Examples 1 and 2, so is from this the dependence on or the importance of the pH value (s) when coagulating the precipitated protein material or the protein sludge.

D'e curve 6 showing the results of the protein precipitation experiments illustrated with centrifugate alone, shows that the precipitation effect of the centrifugates Coagulation attempts, which were carried out at increasingly higher pH values, are significantly better. The curves 7 and 8, in which the results of precipitation tests are shown in which the Protein solution was added in addition to the centrifugate 50 or 100 mg lignosulfonate per liter show that when using lignosulfonate in an amount of 50 mg / liter additionally to an addition of 5 ml of centrifugate a higher COD reduction than when using Centrifugate achieved alone as a precipitant, but the increase in COD reduction compared to the Use of centrifugate alone, which was obtained by coagulation at pH 9, is very low on the other hand, if 100 mg of lignosulphonate per liter are added to the protein solution in addition to the centrifugate, one obtains a COD reduction that was worse than that achieved with centrifugate from coagulation at pH 9 COD reduction is. This is illustrated by the curve S, from which it can be clearly seen that the optimal dosage of lignosulphonate, if this is used in addition to 5 ml of centrifugate, approx 50 mg / liter. If one evaluates this result in the manner explained in Example 1, one arrives at concluded that the amount of precipitant recovered in that by coagulating the sludge Centrifugate obtained at pH 9 should correspond to an addition of 300-50 = 250 mg / liter, so that the Precipitant concentration in this centrifugate

-5-mg / ml or 25 g / liter, and thus around 25

Percent is higher than the precipitant concentration in the corresponding, when coagulating at pH 8 (Example 1) obtained centrifugate.

Example 4

4 samples of 100 g each of the same lignoprotein sludge used in the previous examples were used, were at 95 ° C after the addition of calcium chloride and NaOH (for 2 samples) or calcium hydroxide alone (also for 2 samples), whereby the pH value was adjusted to 9, coagulates

The samples were dehydrated in two different ways, namely in such a way that each of the with Calcium chloride and sodium hydroxide:> like the samples prepared with calcium hydroxide alone in the in the previous examples was centrifuged, while the remaining two Each sample through a glass fiber filter (Whatman

GF / C) filtered and the filter cakes were washed twice with 50 ml of water each time.

Then the centrifugate and filtrate quantities were measured and the precipitant concentration

because by proteic precipitation attempts in the above Examples described type determined.

The results of these tests can be seen in Table IV below.

Tabilla IV

Conditioning Dewatering method Liquid precipitant yield

phnsen-

quantity% yield

ml concentration

mg / ml

recovered
lot

mg

Centrifuge CaCl ₂ + NaOH

CaCi ₂ - ^ NaOH freeze

Ca (OH) ₂ centrifugation

Filter Ca (OH) ₂

58 35 2030 66.6 i2i 20th 2420 79.5 72 25th 1800 59.1 150 15th 2250 73.9

In addition, the filtration rate and volume yield were determined using cold (15 ° C) or warm (65 ° C) water for Wash out of the coagulated material determined. An experiment was also carried out with the addition of cold Water (15 ° C) is carried out after coagulation and stirring to cool the material before separation. These additional tests showed that the filtration rate and the volume yield were as expected greatest when using warm water to wash out the coagulated material are, but by adding cold water and stirring before separation an even greater one Filtration speed and an even higher volume yield for the liquid phase achieved became. A cooling of the material to about 50 ° C before separation is therefore apparently beneficial.

The volume yield during centrifugation or filtration shows that the separability is best at a sludge conditioned with calcium hydroxide alone, while the precipitant yield shows that conditioning with calcium chloride and sodium hydroxide prior to coagulation is the best resp. As far as possible recovery of precipitant leads from the protein sludge

The lignoprotein sludge used, with a dry matter content of 14.5 percent, contains as a result the consumption of lignosulphonate in the production of the sludge as well as due to the residual content Lignosulphonate in the treated wastewater 21 percent ligninsulphonate, based on the dry matter content, which corresponds to an amount of lignosulfonate of 14.5 χ 0.21 = 3.045 g of lignosulfonate in 100 g of sludge Table IV shows that by washing out with water after conditioning with Calcium chloride + sodium hydroxide or calcium hydroxide alone coagulated sludge an increase the yield of recovered precipitant was achieved from 66 to 79.5 and from 59.1 to 733 percent

Example 5

To investigate the possibility of other precipitants from precipitated protein sludge too remove or separate and recover, various types of protein sludge have been carried out by Precipitation of proteins from protein-containing wastewater produced with the help of the following precipitants:

Lauryl sulfate,
Glyceryl trisulfate,
Dodecylbenzenesulfonic acid and aluminum sulfate.

The same slaughterhouse wastewater with a COD value of 4590 mg 02 / liter as in the production of the in the previous examples used lignoprotein sludge. There were also parallel tests with wastewater from a slaughterhouse waste destruction plant (production of meat-bone-meal and technical fat) as well as experiments with diluted blood water from pig slaughter.

Calcium hydroxide was added to the separated sludge up to a pH value of 9, at 95 ° C coagulated and then centrifuged. The centrifugates obtained from the various types of sludge were subjected to the same protein precipitation experiment as in the previous examples, where 500 ml each of the same protein solution or the same slaughterhouse waste water as in the previous ones Examples as precipitants each 5, 10 or 15 ml of centrifugate were added. Apart from the Precipitation with the centrifugate from the protein sludge precipitated with aluminum sulfate, at which the pH value was set to 6, sulfuric acid was added in each case in all precipitation attempts in an amount which gave a pH of 3. The decantates obtained in the protein precipitation experiments were by determining the COD value, which is used to calculate the recovery of the feces was characterized

The results of these tests can be seen in Table V below.

11th Table V 25 30 820 12th Curve Precipitants 10 Laury! Sulfate Centrifugate
i addition to 500 m
(ml) COD in
I decantate
mg O ₂ / ltr. COD-
reduction
% 11th Glyceryl trisulfate 5
10
15th 1426
1172
1542 68.9
74.5
66.4 12th Dodecylbenzenesulfonic acid 5
10
15th 2380
1438
1567 48.1
68.7
65.8 13th Aluminum sulfate 5
10
15th 2135
1529
1813 53.5
66.7
60.5 5
10
15th 3220
3072
3030 29.8
33.0
34.0

If one compares the above test results sulphates comparably high, while Alutniniummit the result of Example 1, curve 2, so too sulfate is considerably lower. However, it is clear too recognize that also from using other precipitants _> -> recognize that the method of the invention is general

precipitated types of protein sludge remove the precipitant in the same way as with lignin sulfonate precipitated protein sludge is removed. Here is the degree of recovery for organic sulfonates and

for the removal of precipitants from precipitated protein sludge in reusable if necessary Form is applicable.

In addition 5 sheets of drawings

Claims (9)

Claims; 1. A process for the removal and recovery of lignosulfonates !!, sulfated alcohols and aromatic sulfonates, from a precipitated, aqueous, protein-containing sludge, in which the sludge is thickened at the same time, characterized in that the sludge has at least one alkaline earth compound in one to bind the proteins sufficient amount and, if the pH value is still below 6.5, a base from the group of alkaline earth and alkali metal hydroxides is added until the pH value is above 6.5, then the sludge, expediently with the addition of steam and can be heated with stirring up to at least 60 ⁰ C and contains thereby precipitating water phase, the precipitant and -wiederverwendet for precipitating proteins, is separated. 2. The method according to claim 1, characterized in that the water phase which separates out is separated by displacement with water on a filter or in a suitable centrifuge. 3. The method according to claim i or 2, characterized in that an alkaline earth compound is used Alkaline earth salt, preferably calcium chloride, and an alkali hydroxide, preferably sodium hydroxide, can be used as the base. 4. Verfahrt. · According to claim 1 or 2, characterized marked that a's ErdalMiver connection and as Base an alkaline earth hydroxide, preferably calcium hydroxide, is used. 5. The method according to any one of claims 1 to 4, characterized in that the base up to Achieving a pH between 7.5 and 9 is added. 6. The method according to any one of claims 1 to 5, characterized in that the separating, Water phase containing precipitant by washing the coagulated scarf with warm water is displaced. 7. The method according to any one of claims 1 to 6, characterized in that the sludge is heated for at least two minutes with superheated steam. 8. The method according to any one of claims 1 to 7, characterized in that the displacement of the precipitant-containing, precipitating water phase through water using a centrifuge, preferably with cooling. 9. The method according to claim 8, characterized in that the sludge as Koagulierungsmitiel Blood and calcium hydroxide as an alkaline earth compound.