EP0188582A1 - Separation process with recovery of proteins and fats from substances of animal origin, organic substances or refluent from working organic substances and a plant to carry out the process - Google Patents

Abstract

The process of separation or recovery of proteins and fats from substances of animal origin, organic substances or resulting from the work of organic substances comprises the following steps: treatment of the substance with alkaline bisulfite which reduces the value of its pH and partially saponifies fats; addition to the substance thus treated of a concentrated hydroxy acid which disintegrates the lipid and protein fractions, carbonizes the impurities present, irreversibly precipitates the proteins in suspension and causes the decomposition of the basic soap, thus reforming the fatty acid and causing partially acid saponification with strong emulsifying properties; recovery with known physical techniques of proteins having the most precipitate and non-emulsified fats, demonstration of an aqueous fraction comprising proteins in suspension and, if necessary, depending on the starting substance, an emulsified lipid fraction which is then separated from the aqueous fraction by known physical techniques; inversion of the pH of the aqueous fraction, thereby coagulating the proteins in suspension, and mechanical recovery of the coagulated proteins and precipitation of the sulfuric ions from the aqueous fraction obtained.

Description

TECHNICAL FIELD

The present invention relates to a separation process with

recovery of proteins and fats from substances of animal origin, organic

substances or refluent from working organic substances and a plant to carry

out the process.

BACKGROUND OF THE INVENTION

In many activity fields the need occurs of discharging organic

substances of animal origin comprising proteins and fats. This requirement

cannot be satisfied except at the cost of considerable difficulties, as

proteins and fats are polluting substances which don't allow their

immediate discharging, but on the contrary involve their preventive removal

according to the rules in force.

The present invention relates to the separation of the proteins

and fats from organic substances of animal origin which comprise them.

Furthermore as such proteins and fats are residual products having the

opportunity of being reused, the present invention also relates to their

recovery.

The fields of application of the invention are various and

concern, for example, the food manufacturing, the treatment of butchery

waste, the treatment of sewer waters; indeed a field of particular interest

is that of the leather tanning industry either for the kind of treated

substances or huge quantities involved.

As it is known the skin consists, from the chemical point of

- 2 - view, of water, fats, proteins, mineral substances, and so on. During the

tanning the skins are firstly subjected to a depilation treatment for

affecting the epidermis and the root of hairs, thus allowing their

separation from the derma, and then to a calcination treatment in which the

fats provided in the skin are saponified, the keratin forming the hairs and

the epidermis are attacked and changed into keratasis which is easily

soluble in alkaline environment, and the collagen undergoes hydrolysis

which allows it to react more easily with the tanning substances.

From the calcination treatment, which takes place in pits, the

lime pit water is obtained as a residual product which is strongly basic

and also comprising fats and proteins in non much quantity.

The depilated skins are then fleshed, that is deprived of the

adipose tissue and the calcareous residues provided in it, and then reduced

to uniform thickness. All that is obtained from this working, together with

the pieces of skin which have been discarded before the fleshing,

constitutes the "shred of flesh", a substance rich in fats and proteins.

Both the lime pit water and the shred of flesh are refuses of

the tanning industry, but they cannot be immediately discharged, as already

said, due to the high polluting substances that proteins and fats are.

For what relates to the shred of flesh, it has already proposed

to take out from this the lipidic and proteic fractions with a process

including the steps of mechanically triturating the shred of flesh, heating

it up to 50-60 °C, centrifugating it to separate a little quantity of fats and toasting the proteic residue in a direct-heat rotary dryer.

A drawback of this known process consists in that it allows only

a partial recovery of fats, which amongs other things are of a poor

quality. Furhermore the recovered proteic fractions are denaturated as they

comprise sulfates, sulfides, chlorides and all the other chemical compounds

used in the calcination process.

Another known treatment of the shred of flesh foresees that this

is hydrolyzed by proteolysis enzymes to make easier the separation of the

fats and to allow in such a way to obtain a good lipidic fraction.

A drawback of this treatment consists in that the proteins,

which are present in the shred of flesh in a small quantity (about 10%),

are solubilized in.a large quantity of water and can be recovered only by a

quite expensive evaporation process. ^'

It is also known to hydrolyzed the shred of ^• flesh at high

temperature, but in this case a denaturation of the lipidic fraction occurs

and moreover a use of a large quantity of water.

At last it is also known to take out from the shred of flesh the

lipidic fraction by organic solvents which are later evaporated. This

process is very expensive due to the high cost of the solvent to be used

and the need of recovering the evaporated solvent which obviously cannot be

discharged into the atmosphere for polluting reasons.

For what concerns the lime pit water, a well known purification

process is based on the use of activated sludges. This process presents

- -

many difficulties of operating as the effluents coming from tanning

treatments comprise large quantity of sodium chloride and other chemical

compounds as cyanide, chlorine, cadmium and copper which reduce and at

times prevent the growth of the bacteric flora which is essential for the

purification process.

Moreover this well known purification process of the lime pit

water presents other drawbacks and i particular:

- the need of periodically stopping the plant for the evacuation of the

sludges with the consequent considerable loss of time and consumption of

energy for the subsequent restarting of the purification activity;

- the considerable energetic cost of the purification treatment;

- the need of having at disposal other purification units (usually

purifiers of an association) to treat the waters coming out from the

separate purifiers.

DISCLOSURE OF THE INVENTION

An aim of the invention is to eliminate all the above mentioned

drawbacks and to separate and recover the basic organic substances of

animal origin, proteins, fats with a process that:

- is applicable to the substances to be treated apart from their nature

and origin,

- allows to obtain with a very good efficiency a very high recovery of

proteic and fat substances,

- does not alter the recovered proteic and lipidic fractions,

- 5 -

- involves very low energetic consumptions, and

- requires a limited utilization of labour.

Another aim of the invention is to provide a plant to carry out

the process.

According to the invention these and other aims are attained

with a separation process with recovery of proteins and fats fro

substances of animal origin, organic substances or refluent from workin

organic substances including the step of:

- treating the substance with alkaline bisulfite, which reduces its p

value and partially saponifies the fats;

- adding to the so treated substance a concentrated hydroxy acid whic

disaggregates the lipidic and proteic fractions, carbonizes the presen

impurities, precipitates in an irreversible way the suspended protein

and causes the breaking of the basic soap, thus re-forming fatty aci

and partially causing an acid saponification having strong emulsifyin

properties,

- recovering with known physic techniques the most precipitated protein

and not-emulsified fats, evidentiating a watery fraction comprisin

further suspended proteins and if necessary, according to the startin

substance, an emulsified lipidic fraction which is then separated wit

known physic -techniques from the watery fraction,

- causing a pH inversion of the watery fraction thus coagulating th

suspended proteins, and

- recovering mechanically the coagulated proteins and precipitating from

the obtained watery fraction the sulfuric ions provided in it.

According to the invention to carry out the process a plant is

provided characterized in that it comprises in series:

- a first mixer for treating the first matter with alkaline bisulfite,

- a second mixer for treating the first matter, coming out from the first

mixer, with concentrated hydroxy acid,

- a separator for separating the precipitated proteins and the

not-emulsified fats from a watery fraction comprising further suspended

proteins and if necessary, according to the starting substance, an

emulsified lipidic fraction,

- a possible separator of the emulsified lipidic fraction from the watery

fraction,

- a third mixer of said watery fraction with a base to cause the pH

inversion and the consequent coagulation of the suspended proteins,

- a mechanical separator of the coagulated proteins, and

- a fourth mixer of the watery fraction, coming out from said mechanical

separator, with calcium hydroxide to cause the precipitation of the

sulfuric ions provided in it.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is further clarified in two preferred

embodiments with reference to the enclosed drawings.

Figure 1 shows schematically a plant to carry out the process according to

- - the invention,

Figure 2 shows a block diagram illustrating the various step of the

process, and

Figure 3 shows schematically a plant to carry out the process in a second

5 embodiment.

BEST MODE OF CARRYING OUT THE INVENTION

As it can be seen from the drawings the plant ^' to carry out the

process according to the invention comprises a screw mixer 1 to which a

displacement pump 2 is connected introducing sodium bisulfite. The outlet

10 of the mixer 1 is connected to a mixer 3, to which a displacement pump 4 is

connected introducing concentrated sulfuric acid. At the outlet of the

mixer 3 an agitator 5 is provided to which two vessels 6 and 7 are

connected comprising respectively sulfuric acid and caustic soda.

The outlet of the agitator 5 is connected to a continuous press

15 8, in its turn connected to a static decanter 9. At the outlet of the

decanter 9 a three-way valve 10 is provided having one outlet connected to

a mixer 11 and the other outlet connected to a filter 12 in its turn

connected to a plate centrifugal separator 13. The oulet of the centrifugal

separator 13 is connected, as well as the first outlet of the valve 10, to

20 the mixer 11 to which also a vessel 14 of caustic soda is connected.

The outlet of the mixer 11 is connected by choice, through a

three-way valve 19 to a filter press 17 or to a continuous press 18, having

their outlets of the watery fraction connected to a mixer 15, to which the

- 8 - outlet of a vessel 16 of calcium hydroxide 16 is connected.

The outlet of the mixer 15 is connected by choice, through a

three-way valve 20, to the outside of the plant for the disposal or to the

mixer 1 for the recycling.

The operating of the described plant carrying out the process

according to the invention is the following:

the treated first matter, which in the case of the tanning industry can be

shred of the flesh or the lime pit water, is introduced into the screw

mixer 1. In the case of the shred of flesh, it is subjected to a

trituration pre-treatment.

While the first matter is introduced into the mixer 1, it is

sprayed with sodium bisulfite causing the partial saponification of fats

and the pH reduction. The so treated first matter is transferred into the

mixer 3 where to it concentrated sulfuric acid is added making easier the

breaking of the membranes keeping the fats and causing the irreversible

precipitation of the proteins which are in solution or hydrolyzed.

More particularly the concentrated sulfuric acid acts on the

glycerides of the not-saturated acids, adding itself to their double bonds

and forming an unstable saturated glyceride, the tristearinsulfonic, which

is converted into glycerin and sulfostearic acid having high emulsifying

properties; the glyceride allows the scission of the fats in presence of

water.

Therefore in the mixer 3, other than the precipitation of the

- - fibrous proteins, the complete saponification of the fats, which have no

been saponified in the mixer 1, the breaking of the basic soap and th

re-formation of the fatty acid occur.

As the first matter introduced into the mixer 1 can hav

different characteristics also changeable with the passing of the time, i

is foreseen that at the outlet of the screw mixer 3 a pH control occurs

and if necessary a correction in the agitator .5 by introducing a correc

quantity of caustic soda or sulfuric acid to cause the optimum condition

of acidity of the first matter.

The first matter is then introduced into the continuous press

in which the separation of thefibrous proteins occurs from the watery

fraction comprising fats and suspended proteins and which is introduce

into the decanter 9.

There the separation of the not-emulsified fats occurs (whic

come up to the surface and can be forwarded to a collection place of th

fats) from a proteic sand (sedimenting on the bottom and wich can b

forwarded together with the fibrous proteins coming out from the continuou

press 8 to a collection place of the proteins) and from a watery fraction.

The composition of this watery fraction will be differen

according to the kind of the first matter.

If the first matter is lime pit water, the watery fraction onl

comprises suspended proteins whereas if the first matter is shred of flesh

the watery fraction also comprises emulsified fats other than proteins. I

- 10 - the first case it comes out from the valve 10 and directly reaches the

mixer 11, whereas in the second case it comes out from the valve 10,

reaches the filter 12, where the separation of the small mineral and

organic impurities and in case of emulsified fats occurs, and then the

centrifugal separator 13, where the separation of the fats from te watery

fraction comprising the suspended proteins occurs. Then the fats are

forwarded, together with those coming out from the decanter 9 to the

suitable collection place while the watery fraction is introduced into the

mixer 11. Here to the watery fraction, both coming out directly from the

decanter 9 and from the centrifugal separator 13, caustic soda is added

causing a sudden pH inversion and a consequent coagulation of the suspended

proteins. According to the sizes of the proteic particles, the watery

fraction passes from here, through the three-way valve 19, to the filter

press 17 or continuous press 18. Here the separation of the proteins occurs

which are collected together with those previously separated from the

watery fraction which is introduced into the mixer 15 and to which calcium

hydroxide is added to let the precipitation of the present sulfuric ions

take place.

The water coming out from the mixer 15, being in practice

lacking in polluting substances, can be directly discharged upon a possible

neutralization and desalination, this latter in order to allow the recovery

of the salts, or can be reused for further treatments also in the same

tannery, or, if the further extraction of the proteins is required,

- - reintroduced into the mixer 1 for the repetition of the cycle.

The process according to the invention and the plant to carry

out it allow to recover from the polluting first matter a lipidic fraction

which advantageously can be used for the alimentation in zootechnical

5 field, for the manufacturing of oils and soaps in cosmetic field and in

general in the stearic industry; a proteic fraction which in the same way

can advantageously be used in zootechnical and fishing field as fertilizer

and corrective; and a watery fraction which can be discharged without any

polluting hazard or can be reused, as already said, in the same tannery

10 both for repeating the calcination or washing phase on other skins, and for

diluting refluent waters which in themselves have polluting substances

higher than those the rules allow and therefore could not be directly

_ discharged.

Always in the tanning industry the process according to the

15 invention is very advantageous boh with respect to the traditional process

of treatment of the shred of flesh and to the traditional treatments of

lime pit water.

For what relates to the treatment of the shred of flesh, the

process according to the invention can be carried out cold and therefore

20 requiring a low consumtion of energy, not damaging the proteic substances

and the recovered fats, is extremely quick and requires low fixed assets.

For what relates to the treatment of lime pit water, the process

according to the invention

- 12 -

- requires energetic consumption so low as it cannot compared with thos

of the purifiers used at present,

- is of complete reliability not depending upon the growth of bacteri

flora which feels the affects of several factors such as the pH of th

first matter, the composition of the nutritional substratum, th

temperature and the seasonal conditions,

- allows to eliminate a possible source of poisonous gases formed by th

conversion of the sulfide into sulfydric acid, and

- allows to obtain commercial products having a value higher than th

treatment cost.

The following example serves to further clarify the invention:

in the mixer 1 to 1178 Kg of triturated shred of flesh subjected to a

expression pretreatment for eliminating some water 8.8 Kg of sodiu

bisulfite have been added and the whole has been transferred into the mixe

3, where 89 Kg of concentrated sulfuric acid at 98% have been introduced.

The product at the outlet of the mixer 3 had pH 2. Then it has bee

transferred into the continuous press 8 without the need of any p

correction and here the separation of 551 Kg of fibrous proteins having

humidity of 42.83%, a specific weight of 1.129 Kg/dm³ and a content of fa

matter of 6.77% occurred.

The watery fraction coming out from the continuous press 8 ha

been forwarded to the filter 12 and subsequently to the centrifuga

separator 13, where 15 Kg of emulsion, fat at 96.67%, having a humidity o

- - 3% and 0.09% of free glycerin. The composition of the separated fats in the

centrifugal separator 13, of which 7.6% consisted of glyceryn, resulted the

following:

capric acid 0.1%

lauric acid 0.15%

myristic acid 4.1%

C- ₁₄ 1.95%

n-pentadecanoic acid 0.4%

palmitic acid 30%

palmitoleic acid 7.7%

n-heptadecanoic acid 1%

C- ₁₇ 1%

stearic acid 9%

oleic acid 41.5%

linoleic acid 1.74%

eicosanoic acid 0.21%

linolenic acid 0.6%

The watery fraction separated in the centrifugal separator 13

consisted of 628 Kg of refluent water comprising 2.6% of soluble sodium

sulfate and 2.9% of proteins. This watery fraction has been introduced into

the agitator 11 and here to it an aqueous solution comprising 300 g of

NaOH has been added, causing the coagulation of 18 Kg of humid proteins to

be forwarded to the filter press 17 or the continuous press 18. - 14 - The water treated with caustic soda has been introduced into th

agitator 15 where to it an aqueous solution comprising 300 g of calciu

hydroxide has been added which caused the precipitation of about 8 Kg o

insoluble calcium sulfate.

In the embodiment schematically shown in Figure 3, the outlet o

the filter 12 is connected to a set of receivers, indicated with th

reference number 21, having the function of natural decanters, and the

have the upper outlet connected to the centrifugal separator 13, the middl

outlet connected to the mixer 11 and the bottom outlet connected to th

collection place of proteins. The outlet of the centrifugal separator 13 i

connected to the set of receivers 21.

The operating of the plant according to this second embodimen

is the following:

the watery fraction coming out from the filter 12 is introduced into th

receivers 21 where a natural decantation slowly occurs separating a fa

fraction (on the upper part) which is forwarded to the centrifuga

separator 13, a watery fraction (on the middle part) comprising suspende

proteins which is forwarded to the mixer 11 and a proteic sludge (on th

lower part) forwarded to the collection place of proteins.

The watery fraction coming out from the centrifugal separator 1

is reintroduced into the receivers 21 to allow a further separation of th

fats, which inevitably are present in it.

This second embodiment offers, with respect to the previous one - 15 - the possibility of separating from the watery fraction coming out from the

filter 12 a fraction richer in fats and a proteic sludge which can be

directly forwarded to the collection place of the fats and to the

collection place of proteins, increasing in such a way the efficiency of

the centrifugal separator 13 and allowing at the same time a direct

recovery of the proteic sludges which theyselves are a product that can be

directly used, particularly in the fodder field.

Claims

- 16 - C L A I M S

1. A separation process with recovery of proteins and fats from

substances of animal origin, organic substances or refluent from workin

organic substances including the step of:

- treating the substance with alkaline bisulfite, which reduces its pH

value and partially saponifies the fats;

- adding to the so treated substance a concentrated hydroxy acid which

disaggregates the lipidic and proteic fractions, carbonizes the present

impurities, precipitates in an irreversible way the suspended proteins

and causes the breaking of the basic soa , thus re-forming fatty acid

and partially causing an acid saponification having strong emulsifying

properties,

- recovering with known physic techniques the most precipitated proteins

and not-emulsified fats, evidentiating a watery fraction comprising

further suspended proteins and if necessary, according to the starting

substance, an emulsified lipidic fraction which is then separated with

known physic techniques from the watery fraction,

- causing a pH inversion of the watery fraction thus coagulating the

suspended proteins, and

- recovering mechanically the coagulated proteins and precipitating from

the obtained watery fraction the sulfuric ions provided in it.

2. A process according to claim 1 characterized in that said

- - substance is treated with sodium bisulfite.

3. A process according to claim 1 characterized in that said

substance is treated with concentrated sulfuric acid.

4. A process according to claim 1 characterized in that, after

5 having treated the substance with concentrated hydroxy acid, the pH value

is controlled and if necessary is corrected by adding an acid or a base.

5. A process according to claim 1 characterized in that the fibrous

proteins are recovered from the substances treated with concentrated

hydroxy acid by mechanical separation and then the precipitated proteins

10 and the not-emulsified fats are recovered by decantation.

6. A process according to claim 5 characterized in that the fibrous

proteins are recovered from the substance treated with concentrated hydroxy

acid"by mechanical separation with a continuous press.

7. A process according to claim 1, in the case the first matter

15 comprises fats, characterized in that the emulsified lipidic fraction is

separated from the watery fraction obtained from the first matter treated

with concentrated hydroxy acid by filtration and subsequent centrifugal

separation.

8. A process according to claim 7 characterized in that the

20 filtrated watery fraction is subjected to natural decantation to obtain a

lipidic fraction to be subjected to centrifugal separation, a watery

fraction comprising suspended proteins to be forwarded to coagulation

separation, and a proteic fraction to be directly recoverd.

- 18 -

9. . A process according to claim 8 characterized in that the watery

fraction, obtained by centrifugal separation is subjected to a further

natural decantation for the repeating of the cycle.

10. A process according to claim 1 characterized in that the watery

5 fraction is treated with caustic soda to cause its pH inversion.

11. A process according to claim 1 characterized in that the

coagulated proteins are recovered with a continuous press.

12. A process according to claim 1 characterized in that the

coagulated proteins are recovered with a filter press.

10 13. A process according to claim 1 characterized in that the watery

fraction, obtained from the mechanical recovery of the coagulated proteins,

is treated with calcium hydroxide causing theprecipitation of the free

sulfuric ions.

14.' A process according to claim 1 characterized in that the watery

15 fraction treated with calcium hydroxide is subjected to a further treatment

cycle.

15. A plant to carry out the process according to claim 1

characterized in that it comprises in series:

- a first mixer (1) for treating the first matter with alkaline bisulfite,

20 - a second mixer (3) for treating the first matter, coming out from the

first mixer (1), with concentrated hydroxy acid,

- a separator (8,9) for separating the precipitated proteins and the

not-emulsified fats from a watery fraction comprising further suspended - - proteins and if necessary, according to the starting substance, an

emulsified lipidic fraction,

- a possible separator (12,13,21) of the emulsified lipidic fraction from

the watery fraction,

- a third mixer (11) of said watery fraction with a base to cause the pH

inversion and the consequent coagulation of the suspended proteins,

- a mechanical separator (17,18) of the coagulated proteins, and

- a fourth mixer (15) of the watery fraction, coming out from sai

mechanical separator (17,18), with calcium hydroxide to cause th

precipitation of the sulfuric ions provided in it.

16. A plant according to claim 15 characterized in that i

comprises, downstream the second mixer (3) a pH meter and an agitator (5)

where the mixing of the first matter, coming out from the second mixer (3),

with a pH corrector occurs.

17. A plant according to claim 15 characterized in that sai

separator (8,9) consists of a continuous press (8) for the recovery of th

fibrous proteins and a decanter (9) for the recovery of the precipitate

proteins and not-emulsified fats.

18. A plant according to claim 15 characterized in that it comprise

at the outlet of the separator (8,9) a three-way valve (10) for directl

connecting said separator (8,9) to the third mixer (11) or to the separato

(12,13) in its turn connected to said mixer (11).

19. A plant according to claim 15 characterized in that th

- 20 - separator (12,13,21) put between the separator (8,9) and the third mixer

(11) comprises a filter (12) for separating mineral and organic particles

and possible emulsified fats, and a centrifugal separator (13) for the

recovery of the emulsified fats.

20. A plant according to claim 19 characterized in that downstream

the filter (12) a receiver (21) is provided for the natural decantation of

the watery fraction coming out from said filter (12), said receiver having

its upper outlet connected to said centrifugal separator (13), the middle

outlet connected to said mixer (11) and the bottom outlet connected to the

outside for the recovery of the proteic sludges, the outlet of the watery

fraction of said centrifugal separator (13) being connected to the inlet of

said receiver (21).

21 A plant according to claim 15 characterized in that the mixer

(11) is cnnected to the outlet of a vessel (14) of caustic soda.

22. A plant according to claim 15 characterized in that the

mechanical separator of the coagulated proteins consists of a filter press

(16).

23. A plant according to claim 15 characterized in that the

mechanical separator of the coagulated proteins consists of a' continuous

press (17).

24. A plant according to claim 15 characterized in that the fourth

mixer (15) is connected to the outlet of a vessel (16) of calcium

hydroxide.