FR2751984A1 - New decontamination method for distillery residues - Google Patents

Abstract

A decontamination method (I) for residues resulting from secondary distillations carried out during the preparation of spirits comprises: the clarification (II) of the residues, the concentration of the copper contained in the clarified residues and the recovery (III) of the copper.

Description

The subject of the invention is a method for depolluting residues of

  distillation. The production of certain alcohols, such as whiskey, cognac, armagnac, brandy or calvados, requires two successive distillations. This is called the double heating technique in discontinuous stills. Each of these distillations gives rise to residues whose

  distilleries are looking to get rid.

  The residues from the first distillation, very rich in organic matter, cannot generally be rejected as is. They are subject to specific treatments such as concentration for later recovery. The treatment of second distillation residues poses a particular problem. Indeed, these residues, called "Spent Lees" when it comes to the production of whiskey and "Seconds of good heating" when it comes to the production of cognac, are characterized by a low organic matter load, which can be easily reduced by treatment at a biological station. They are also characterized by copper contamination from the stills used for the manufacture of alcohol. As

  indicative, the Whiskey Spent Lees contain 15 and 70 mg / l of copper.

  After biological treatment, the copper concentration of second distillation effluents is greatly reduced, but can still pose problems when they are discharged into a river at low flow. But above all, the copper is then concentrated in biological sludges whose spreading results in long-term contamination

agricultural land used.

  So far, numerous studies have been carried out to remedy this pollution by copper present in distillery discharges,

  but to date no satisfactory solution has been found.

  The invention relates to a process for depolluting the residues of second distillation obtained during the preparation of the alcohol comprising - the clarification of said residues, - the concentration of the copper contained in the clarified residues,

- copper recovery.

  Clarification of second distillation residues has been found

  be an essential step in the subsequent copper extraction treatment.

  Indeed, these residues contain suspended solids (20 to 250 mg / l) which are particularly clogging due to their waxy appearance and which come

  disrupt the subsequent extraction step.

  According to an advantageous embodiment of the process according to the invention, the clarification of the residues is carried out by a tangential microfiltration which has the advantage of completely ridding the residues of the particles in suspension. In addition, this technique has proven to be very

  interesting from an economic point of view.

  In the context of the present invention, the membranes used to carry out tangential microfiltration are membranes

classic minerals.

  Mineral membranes have the advantage of being able to work at relatively high temperatures (50 to 60 C), which makes it possible to obtain significant permeate flows. In addition, cleaning operations

are simplified.

  The membranes used in the context of the invention are TECHSEP KERASEP TM membranes having a cutoff threshold of 0.10 1 with internal channels with a diameter of 3.5 mm. The permeate flows obtained are between 200 and 600 l / h / m2. But the invention is not limited to

  this type of membranes in particular.

  It is thus possible to clarify the residues of second distillation

  with a conversion factor greater than 90%.

  According to another embodiment of the process according to the invention, the extraction of copper from the clarified residues is carried out by reverse osmosis. Indeed, it has been found, unexpectedly, that this technique makes it possible very effectively, to retain copper by

  concentrating using reverse osmosis membranes.

  Since reverse osmosis gives rise to a retentate in which the copper is retained and to a permeate representing all that has not been retained, the retentate in fact undergoes a certain number of cycles of reverse osmosis, which has the effect to concentrate it a little more in each cycle by eliminating the water. This is how the retentate can be concentrated a hundred times by elimination

99% of the water.

  It should be noted that when tangential microfiltration is used to clarify the residues from second distillation, the subsequent reverse osmosis flows are considerably improved. Indeed, in this case, more than 98% of the copper contained in the residues of second distillation can be retained in the retentate by the reverse osmosis membranes, and the permeate, which represents all that has not been retained, contains

then less than 0.5 mg / 1 of copper.

  The reverse osmosis membranes which can be used in the context of the present invention are membranes having a sufficiently low porosity to be able to retain copper. This is particularly the case for reverse osmosis membranes conventionally used for desalination of water. By way of example, mention may be made of Filmtec membranes from the company DOW (reference BW 30-330), the copper retention rate of which remains greater than 98%, whatever the operating conditions, but

  the invention is not limited to this type of membranes.

  Copper is thus found in concentrated form in the osmosis retentate, at a concentration which depends on the raw material to be treated but which, for example in the case of Whiskey Spent Lees grading at the start 20 mg / l, will present at the end of reverse osmosis phase a content of the order

of 2 g / 1.

  Regarding the recovery of copper from the retentate, this can be carried out later since the retentates, due to the

  the small volume they represent can be transported before treatment.

  One way to recover copper from retentates is to use electrolysis cells with copper deposition

in metal form on the cathode.

  The invention is not limited to the present description and will be better

  understood in light of the figure and the following example.

EXAMPLE

  1050 1 of Whiskey Spent Lees were treated by microfiltration

  on Techsep Kerasep membrane with a cutoff threshold of 0.10 k.

  1000 l of clarified permeate with a concentration of 18 mg / l of copper were obtained. This product was then treated by reverse osmosis on a Filmtec BW 30-330 membrane to recover 14 l of a retentate containing 1.26 g / l of

  copper and 986 I of a permeate containing 0.3 mg / l of copper.

  The table indicates the copper content of the permeate in mg / l as a function of the volume concentration factor during the phase of

reverse osmosis treatment.

BOARD

  Cu2 + Volume Concentration Factor in the permeate (mg / l) (FCV *) (instantaneous)

1.4 0.2

1.8 0.2

2.4 0.3

4.6 0.3

0.4

0.45

1.35

  Average overall permeate 0.3 mg / l% Retention (in the retentate) 98.30% Volume of permeate + Volume of retentate

  * FCV --------------------------------------

  Retentate volume The figure represents the evolution of the quantities of copper recpectively contained in the retentate and the permeate during the phase of

  concentration of Spent Lees clarified in the context of the example.

Claims (4)

  1 / Process for depolluting the residues of second distillation obtained during the preparation of an alcohol by double distillation comprising: - the clarification of said residues, - the concentration of copper contained in the clarified residues, - copper recovery.   2 / depollution method according to claim 1, in which the   clarification of the residues is carried out by tangential microfiltration.   3 / depollution method according to claim 1 or 2, wherein   copper extraction is carried out by reverse osmosis.   4 / depollution method according to one of claims i to 3, in   which recovery of copper is carried out electrochemically.