FR2507617A1 - Triple distn. column plant installation for superfine alcohol prodn. - has heat exchanging condenser at head of each column for substantial energy savings - Google Patents

Abstract

Plant installation comprises at least three distn. columns. The columns, in succession, are employed respectively for purificn. rectification and demethanolisation. The head of each column is equipped with a heat exchanger serving to condense and extract "off-flavourings" in the first two columns and methanol in the final column. Heat is applied at the base of each column to evaporate incoming liq. and drive the vapour counter-current through liq. percolating down via distribution trays. Condensation in each heat exchanger takes place on the exterior of tube surfaces of a tube bundle. Heat extracted by condensation is transferred to liq. passing through the tubes and drawn from the tail of one or more of the columns. Pref. the installation includes a mechanical compressor which is used to compress low pressure head vapours from the second and third columns and returning the vapours to the bases of the first column and, optionally to the base of a fourth, purifying column. The column head heat exchangers achieve a great saving in the heat input required in the process. When a mechanical, recycling compressor is added, the heat input is only about 33% of earlier installations.

Description

 The invention relates to a plant for the production of rectified extra neutral rectified alcohol.

 An installation for manufacturing such an alcohol comprises at least three distillation columns, including a purification column, a rectification column and a demethanolization column.

 For this production, the installation receives raw alcohols, with a high degree of concentration, that is to say greater than ninety-two percent by volume, commonly called "phlegm", which successively run through the three columns, and this, in the above order.

 Prior to this course of the three columns, the phlegm undergoes a dilution in water which, in fact, is essential for obtaining the desired purification, because the more the dilution at the inlet of the purifier the stronger, the better the so-called purification, which is then generally called hydroselection.

 At the head of the hydroselection column, a portion of the vapors is reconcentrated at ninety-two percent to extract the alcohol known as "bad taste" used for purposes other than food and for example to form methylated spirits .

 From a certain dilution of phlegm, this concentration is no longer operated directly.

 Indeed, at the head of the purification column, the alcohol is then preferably withdrawn at a low degree of concentration so as to concentrate it only in a fourth distillation column, called column of the purification heads.

 Whether it is an installation with three or four columns, each of these columns must be provided at its base with a heating means capable of causing the boiling of the liquid present at this base which therefore forms a boiling pot .

 The vapors thus released must have sufficient pressure to rise towards the head of the column by crossing for this several times at least one liquid circulating against the current by pouring in cascade on a succession of plates provided for this purpose.

 Thus arriving at the head of the columns after having poured the liquid flowing on the plates, the vapors must then be condensed for, in addition to the extraction of the alcohol "bad taste" or methanol according to the column in question , create a return of alcohol, at the top of the column.

 It is indeed this return, called "demotion", which makes it possible to operate in each column the concentration and the work of classification of alcohols and impurities.

In the achievements known to date, while
on the one hand, to obtain this condensation of the vapor from each of the column heads, this vapor must be sent into a tubular bundle of an exchanger which, for its cooling, must itself be immersed in water constantly renewed,
- on the other hand, to heat the bases of the four columns they must receive, generally independently of each other, live steam which must itself be produced expressly in a boiler, for example fuel oil.

 Per hectolitre of phlegms treated, the consumption of live steam from the boilers of each column of a conventional installation can be evaluated at one hundred kilograms for the purification column and its column for the purification heads, at two hundred kilograms for the column rectification and sixty five kilograms for the demethanol column, for a total of three hundred and sixty kilograms of live steam.

 To produce all this live steam, the boiler must develop a quantity of heat which can be evaluated at two hundred and fifty therms per hectolitre of superfine alcohol produced.

 A boiler of such power obviously consumes a lot of primary energy.

 A result which the invention aims to obtain is a plant for the production of rectified superfine alcohol which consumes three times less primary energy.

 To this end, it relates to an installation of the type mentioned above, in particular characterized in that each of the exchangers to which the vapors which reach the head of the main columns have access, consists of an evaporator in which the said vapors condense outside tubes of a tube bundle in which, so that the vapors provide heating, is brought by a special circuit the liquid taken from the base of a column such as the superfine alcohol present at the base of the demethanolization column or the so-called phlegmasses, present at the base of the rectification column.

 The invention will be better understood with the aid of the description given below, by way of nonlimiting example, with reference to the attached drawing which schematically represents an installation according to the invention.

 Referring to the drawing, it can be seen that the installation comprises three main columns 1, 2, 3 including a purification column 1, a rectification column 2 and a demethanolization column 3.

 Line 8 at the outlet of the demethanolization column 3 delivers the superfine alcohol.

 To improve the purification, prior to this course the # phlegm undergoes a dilution using phlegmasses which a pipe 9 takes from the base of the rectification column 2 in order, by means of a pump 10, to bring them into head of the purification column which operates by hydroselection.

 The alcoholic vapors present at the head of columns 1, 2, 3 are taken off via pipes 11, 12, 13 which bring them separately to separate exchangers 14, 15, 16 for, at their outlet 17, 18, 19, from on the one hand, extract the "bad taste" alcohol 20, 21 or methanol 22, according to column 1, 2 or 3 in question, and, on the other hand, create a return 23 at the top of each column, 24, 25 able to carry out the concentration and work of classification of alcohols and impurities.

 In the example shown, the installation also comprises a column of purification heads 26 ensuring the concentration of the alcohol which can therefore be drawn off at a low degree of concentration at the head of the hydroselection column 1.

 The vapors at the head of this fourth column are also, via a line 27, brought to an exchanger 28, namely a condenser comprising a tubular bundle cooled by water, at the outlet 29 from which the alcohol "bad taste" is extracted 20 and creates a return 30 at the top of the fourth column 26.

 Each of the columns 1, 2, 3, 26 is provided at its base with a heating means capable of causing the boiling of the liquid present at this base and of giving the vapors sufficient pressure to allow them to rise towards the head in crossing several times the liquid 31 circulating against the current, pouring out in a cascade of a succession of plates 32, 33.

According to one characteristic of the invention, the exchangers 14, 15, 16 to which the pipes 11, 12, 13 arrive, which at the head of the columns 1, 2, 3 take the alcoholic vapors,
- do not each consist of a condenser comprising a tube bundle immersed in cooling water but,
- each consist of an evaporator in which the alcoholic vapors condense outside the tubes of a tubular bundle in which the liquid sampled at the base of a column circulates so that the alcoholic vapors, brought to this evaporator, ensure the heating of this liquid such as the superfine alcohol sampled by a pipe 34 at the base of the demethanolization column 3 or the waters, generally called "phlegmasses", sampled by a pipe 35 at the base of the rectification column 2.

 The alcoholic vapors taken from the top of the purification column 1 may have, thanks to the increase in dilution, a high temperature of the order of ninety eight degrees, they manage to heat sufficiently for example to around ninety three degrees, the surfin taken from the base of the demethanol column which surfin, when it is at atmospheric pressure, boils at seventy eight and a half degrees.

 These vapors are therefore sufficient to produce by themselves the heat necessary for the demethanolization column which can therefore be placed in series with the purification column.

 Circuit 34 therefore returns there directly.

 On the other hand, at the head of the rectification 2 and demethanolage 3 columns, in which the alcohol is not diluted, the vapors which have only a temperature of seventy-eight and a half degrees, only succeed in carrying the phlegmasses at a temperature of about seventy-three degrees, while at the base of the purification column 1, like the column of the purification heads 26 and the rectification column 2, in order to boil it, bring the liquid to about one hundred and six degrees.

 According to an essential characteristic of the invention, each of the pipes 36, 37 at the outlet of those 15, 16 of the evaporators which are connected at the head of the rectification columns 2 and of; demethanol 3, is connected to the inlet line 38, 39 at the base of the purification column 1 or the rectification column 2 or even to the inlet line 40 at the base of the head column purification 26, by means of a mechanical compressor 41.

 The compressor creates in the evaporators 15, 16 a relative vacuum sufficient for the phlegmasses to evaporate at low temperature; for example, a pressure of zero bar thirty five absolute will suffice to boil the water to seventy three degrees.

 By the compressor 41, the low pressure water vapors are then compressed to a pressure of the order of one bar thirty two absolute so as to raise their temperature to the one hundred and six degrees # necessary.

 To obtain such an exchange efficiency in evaporators, the skilled person will obviously know that he can play on the exchange surfaces of the evaporators.

 According to another essential characteristic of the invention, the installation comprises only a single compressor receiving, indifferently at its inlet 42, the low pressure vapors from the two evaporators 15, 16 and distributing, via its outlet 43, its high pressure steam in the three lines 38, 39, 40 between which the distribution is effected by valves 44, 45 mounted respectively on lines 38 and 40 in order to send approximately two thirds of the high pressure steam to the base of the rectification column by a valve 45 and the remaining third of the high pressure steam both at the base of the hydroselection column and that of the column of the purification heads.

 Thanks to this technique, all the main columns are heated directly (columns 1, 2, 26) or via column 1 (column 3) exclusively by the vapors recompressed in the compressor 41.

 Of course, the rectification, purification columns and purification heads will have been adapted to operate with a supply by a single compressor and therefore with the same vapor pressure at their base.

 To do this, the skilled person obviously knows that he can play on the number and characteristics of the plates of the different columns.

 The energy consumed by the installation is therefore limited to that consumed by the motors, for example electric, (not shown) driving the compressor 41 and the pumps 6, 10 which, in total, should consume approximately twenty seven kilowatts per hectolitre.

 The electrical energy thus consumed results in an excess of vapors sufficient to compensate for the heat losses through the insulation and to heat the column of the purification heads, the head vapors of which are however not captured.

 For safety, to prevent the installation from stopping due to a breakdown of the electrical power distribution network, which would cause downgrading of impurities on all the trays, the installation may include an emergency generator.

 The duration of commissioning of the group does not exceed half an hour, it is enough to ensure continuity, to provide a low-power boiler capable of temporarily maintaining in the columns a flow rate of vapors just sufficient to avoid downgrading of impurities .

Claims (4)

 1. Installation for the production of extra neutral rectified alcohol, superfine, from phlegms with a high degree of concentration passing successively through a purification column by hydroselection (1), a rectification column (2) and a demethanolization column (3 ) to which purification column, to promote its action, phlegm is brought in after dilution, which implies that the installation also operates reconcentration at the head of the purification column, whether directly at the head of said column or in a fourth column (26) called column - of the purification heads, in which installation whether it is three or four columns, each of these columns must be provided  - At the top of the column, an exchanger (14, 15, 16, 28) capable of causing the condensation of alcoholic vapors both to extract certain products from it, such as "bad taste" alcohol or methanol, and to create head of column a return of alcohol known as demotion,  - At the base of each column, a heating means capable of causing the boiling of the liquid present at this base and of giving the vapors thus released sufficient pressure to enable them to reach the head of the column after having this preferably passed through several times, the liquid 31 circulating against the current by pouring out in a cascade of a succession of plates 32, 33,  this installation being CHARACTERIZED in that each of the exchangers (14, 15, 16) to which the alcoholic vapors reaching the head of the main columns (1, 2, 3) access, consists of an evaporator in which the said vapors condense on outside of the tubes of a tube bundle in which, in order for the alcoholic vapors to heat it, is brought, by a circuit (34, 35), the liquid taken from the base of a column (2, 3) such  the superfine alcohol present at the base of the demethanoling column (3) or the so-called phlegmass waters present at the base of the rectification column (2).  2. Installation according to claim 1, characterized in that the circult (34), which collects the superfin at the base of the demethanolization column (3), brings it into the evaporator (14) where the alcoholic vapors sampled at the top of the purification column (1), then returns directly to the base of the said demethanolization column (3) which is therefore in series with the purification column (1)  3. Installation according to claim 1 or 2 characterized in that the circuit (35) which pre-lifts the phlegmasses at the base of the rectification column, brings them to each of the evaporators (15, 16) which access the alcoholic vapors withdrawn at the head of one of the rectification (2) and demethanolization (3) columns and in that, at the outlet of this evaporator (15, 16), the circuit (36 or 37) of these phlegmass vapors is connected to an inlet pipe (38 or 39) at the base of the rectification column (2) or of the purification column (1) or even of its possible column of the purification heads (26), via a mechanical compressor (41) of a type suitable not only for delivering the vapors of phlegmasses from the evaporator (15, 16) after having compressed them but also for creating at its inlet (42) and consequently in the said evaporator (15, 16) a relative vacuum to achieve a boiling of the phlegmasses at the low temperature communicated to them by the s alcoholic vapors.  4. Installation according to claim 3 characterized in that it comprises a single mechanical compressor (41) receiving indifferently at its inlet (42) the low pressure vapors of phlegmasses from the evaporators (15, 16) receiving meanwhile, the vapors heads of the rectification (2) and demethanolization (3) columns, and in that at the outlet (43) of this mechanical compressor (41) is provided at least one valve (44, 45) distributing the high pressure vapors of phlegmasses between the base of the rectification column, that of the purification column (1) and that of its possible column of purification heads (26).