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A very unique mimeographed manuscript crossed my desk that was penned by a Seagram employee, likely in the late 1930’s or early 1940’s, but before the famous 1943 Seagram text called “Fundamentals of Distillery Practice” written by Herman F. Willkie and Joseph A. Prochaska. I’m not aware of any informally published manuscript like this having been found by the distilling field. It came to me from an individual who wanted to contribute to the education of the new generation of distillers.
The manuscript is a bit scattershot and not exactly in any kind of order and contains a ton of information from the era not seen in the 1943 text. This was likely intended as an internal training document. These were the kinds of jobs where once you were in, you were in for life so they took education seriously.
This chapter is a great primer for anyone attracted to work in the industry or anyone that already has their feet wet. It is peppered with an optimistic industrial philosophy that has been horribly corrupted at this point in the 20th century.
If anything about the teaching style strikes you or similarities and differences between present day operation are noticed, feel free to comment.
In this chapter we will consider the various factors of control, both operational and laboratory, together with the related subject of quality. Indeed, no subject is of more consequence from a fundamental point of view, or more far reaching in a consideration of the process industries.
Essential to the efficient and successful operations of the distillery is the unceasing vigil maintained over each step in the process and over all materials entering into it. Under no circumstances may any factor concerning quality of raw materials, finished products, or materials in process, be taken for granted. In addition to this all supplies and equipment received by the distillery should be subjected to thorough and intelligent examination to detect flaws in workmanship, suitability for the purpose intended, and for damage which may have occurred in shipment. It is true that part of the plant organization devotes its entire time to the determination of quality and control over processes; however, this does not free others from the obligation of being quality and control conscious. Production, in a true sense, is a matter of teamwork wherein all must cooperate to achieve the manufacturing objective. It is possible for even the most accurate laboratory and operational control procedures to result in errors and such mistakes can only be discovered and remedied by conscientious watchfulness on the part of everyone concerned. The plant operational and controls staffs justify themselves only in proportion to their success in bringing about more efficient operation and higher quality finished products.
Mistakes in determining quality and failures in operational and laboratory control result in lessened efficiency and a degradation in finished product quality. Moreover, it is not sufficient to remain static with regard to quality and control. New methods must replace old wherever improvement is obtained as the result.
With the distilling industry there can never be lack of interest due to monotony of operation. Few industries may lay claim to as great a variety of individual problems. The chemical engineer unit operations and processes of grinding, size separation, fractional distillation, evaporation, drying, filtration, flow or fluids, and extraction are all to be met with in this industry. Such complexity of problems offers the opportunity for sound training and requires alertness and intelligent observation together with sound application of principles.
The object of this chapter is not to deal in detail with whiskey production but merely to consider the aspects of quality and operational and laboratory control with emphasis on operational control rather than chemical control. This objective can be achieved by a consideration of these matters in relation to the operations as they occur. The principle steps in whiskey and alcohol production are:
1. Grinding of the grain to meal
2. Conversion of the grain starches to fermentable sugars
3. Fermentation of the fermentable sugars to produce alcohol
4. Distillation of fermented mash
5. Recovery of the non-volatile, starch free materials in the still discharge
6. Maturing of the distillate
7. Rectifying and bottling
Alcohol may be produced by fermentation from any material containing starch or fermentable sugars or from any material which may be broken down into fermentable sugars. By subjecting cellulosic materials such as cotton or wood to hydrolysis fermentable sugars may be obtained. Fruit juices, of course, contain these sugars and need only to be fermented. Whiskey, by definition, must be produced from cereal grains only.
Since the quality of the finished products is influenced by the grain used, considerable space will be devoted to this subject. To insure high quality of grain received, all car lots are subjected to rigid grain grading and laboratory inspection. This phase of quality, grain grading, merits more superficial treatment. We are processing grain and for this reason we should have a sound knowledge of what constitutes a satisfactory grain for our purpose.
Introduction – The purpose of grain grading is to establish the class, quality, and condition of individual lots of grain. Grading standards have been established for all of the principal grains and are based on the official grain standards of the Department of Agriculture.
Quality is dependent on the general conditions of the grain, together with such factors as soundness, plumpness, cleanliness, dryness, and purity of type. The general conditions of the grain refer to whether it is musty, sour, heating; or whether it contains smut balls, garlic bulbs, stones, cinders, insects or foreign odors. Grain grading takes all these quality factors into account and specifies minimum requirements or maximum tolerances for each grading factor.
Sampling – It is obvious that grading analyses lose all significance if not made on a truly representative sample. For this reason the sampling procedure is of the utmost importance.
The sampler on opening the car carefully notes whether the grain is heating or hot, or whether objectionable odors are present. The presence of weevils or other insects is also noted. After these preliminaries they are ready to proceed with the sampling. In order to make certain that a representative sample will be secured, a definite sampling procedure is followed. The procedure for carload lots of grain is to make five or more well distributed probings throughout the car by means of a 60″ double shell slotted brass trier. The inner shell of the trier should be separated by partitions between each slot so that each slot will be the entrance to a separate compartment. This arrangement permits the separate examination of the grain in each compartment. The probe is inserted at an angle of 10 to 20 degrees from the vertical and the trier emptied on a canvas strip. Each probing should be examined for uneven loading, odor, whether heating or cool, and for the presence of weevils or other insects.
The combined probings secured in this manner are thoroughly mixed and all portions for future analysis are prepared by means of the Boerner divider. This device is used to secure representative portions of the sample by mechanical quartering.
The general factors which determine the numerical grade of a grain are as follows:
1. Minimum weight per bushel
2. Maximum limits of moisture
3. Dockage (maximum limits of cracked grain and foreign material)
4. Maximum limits of damage kernels
(A) Total damaged
(B) Heat damaged
The best for bushel weight is determined by means of the official bushel weight apparatus or by means which give an equivalent result.
There are three methods for determining moisture content. The most rapid of these is the Tag-Heppenstall moisture meter which measures the electrical resistance of the grain as it passes between two revolving, corrugated rolls acting as electrodes. However, this instrument must be check and calibrated at intervals either against an oven dried sample or by means of the Brown-Duvel moisture tester. The latter instrument consists of a distillation flask and an attached condenser. A sample, consisting of whole grain, is placed in the distillation flask which contains oil. Heat is applied and the water driven off the grain. The water is condensed and measured in a graduated cylinder.
Dockage in wheat or rye is all foreign matter that can readily be removed by the use of proper sieves or cleaning devices, or any shriveled or cracked grain that must be hand picked from the screened grain. The Emerson Dockage Tester may be used for this purpose. The foreign material in corn is usually very slight.
Damaged kernels result from a large number of causes both in the field and in storage. Frost damage, fungus damage, sprout damage, stack stain, ground damage, and weather damage all occur in the field. Storage damaged grain includes heat damaged, weevil damaged, and moldy grain. Most damage in grain is preventable if proper precautions are taken.
The determination for damaged kernels is made on a dockage free weighed sample by hand picking, the damaged kernels being weighed and the percentage of damaged grain computed.
(1) White corn, all grades, shall be at least 98% white.
(2) Yellow corn, all grades, shall be at least 95% yellow.
(3) Mixed corn, all grades, shall include corn of various colors not coming within the limits for color as provided for under white or yellow corn.
(4) All corn which fails to meet the requirements of any of the five numerical grades is classed as sample grade. This includes corn having an excessive percentage of moisture, damaged kernels, foreign matter, or “cracked” corn, or corn that is hot, heat damaged, infested with live weevils, or otherwise distinctly low grade.
Besides the three classes there are two varieties of corn; namely, Dent and Flint corn. Dent corn is characterized by a depression in the top of the kernel while the Flint variety has a rounded top. Mixtures of these two varieties are designated as “Flint and Dent”.
There is but one class for rye and four numerical grades and a sample grade. Special grade designations are applied to rye which is tough, smutty, garlicky, weevily, or ergoty. The designation tough is applied when the maximum moisture limitation for the numerical grades is exceeded. The presence of smut balls, garlic bulbs, weevils, ergot, or other insects causes the numerical grade to be qualified.
The presence of foreign odors is detected by the sampler when they open up the care preparatory to taking a sample. Any such odors should be noted at this time. The sampler also notes whether the grain is heating or hot; or whether it is infested with live weevils or other insects. The great danger with musty grain is that it may impart this odor and taste to the distillate. When this occurs even protracted maturation will not eliminate the objectionable, musty odor. Such whiskey must be redistilled involving much labor and expense. The grain grader should always be aware of the responsibilities involved in grain grading so that such occurrences will be eliminated.
Bacterial count – A bacterial count is made on a representative sample from all car lots of grain received. A high bacterial count indicates the possibility of dust and inferior grain, especially in the case of malted barley. High bacteria may also be detrimental to the fermentation.
Lintner – A further test made on malted barley is the determination of diastatic power of the malted barley which is a measure of its ability to bring about the conversion of grain starches to fermentable sugars.
Grain is never unloaded from the grain cars until final approval for quality is given. Having met the specifications in every respect, the grain is weighed and deposited in the mill house grain storage bins ready for grinding.
The grinding of grain which is to be processed into whiskey or alcohol requires accurate control over the size of meal particles. The degree of fineness of the meal determines to a considerable extent the ease with which various succeeding steps will be carried out. It goes without saying that the dried grain recovered from the stillage will be considerably influenced by this factor. However, since this subject will be treated with much greater completeness in a later chapter, we need not go into it here.
It is important, however, to note the part played by the hull surrounding the grain kernels. This protective hull prevents the inner part of the kernel from bacterial action so long as it remains intact. Once this protective coating is broken the meal becomes highly susceptible to such action. For this reason grain is ground only as needed. In general, two types of mills are suitable for our purpose—roller mills, and hammer mills. After grinding, the meal is deposited in the meal storage bins located above the mashing equipment in the distillery.
Meal bins – The meal bins are fabricated in such a manner that meal cannot become lodged in crevices and deteriorate with resulting contamination to the rest of the grain. Good practice requires periodic cleaning of the bins so that this condition may not arise.
Mashing is the process of converting the grain starches into fermentable sugars, and takes place in two steps. The reaction involved is an enzymatic hydrolysis brought about by the action of the enzyme diastase on the starch particles. This enzyme is furnished by a malted grain, usually barley malt.
Due to the fact that the starch granules are separated from each other by a protective cullulose wall the first step in mashing is designed to break down this interfering coating so that the starch will be exposed to the hydrolytic action of the diastase. This is done by subjecting meal to a high temperature under pressure. This step is called cooking and takes place in a cylindrical pressure vessel.
Briefly, the cooking process consists of adding corn or rye to water contained in the pressure cooker. The mixture of meal and water is heated under pressure until the cellulose wall surrounding the starch particles disintegrates, and the starch itself gelatinizes. This gelatinization of the starch exposes a large surface area to the enzymatic action of the diastase. After the complete gelatinization of the starch, the cooker is blown off. In other words, the temperature of the mash is lowered by reducing the pressure to that of the atmosphere. This cools the cook to its normal boiling temperature. Vacuum is applied to the cooker to still further lower the temperature. When the proper temperature for conversion is reached the vacuum is released.
To the cooled mash is now added the malted grain and the contents of the cooker transferred to a converting tub where the conversion of the starch to fermentable sugars takes place.
Cookers – The pressure cookers are cylindrical in shape and are fitted with rotating agitators. Heat is supplied with open steam. A pH meter attached to the water line is used to measure the acidity of the mash water as it enters the cookers.
Recording and indicating – The recording and indicating instruments used on the cookers are as follows:
Vacuum and Pressure—Gauges
Temperature—Thermometers (Mercury), recorders
Converters – The converting tubs are equipped with paddle agitators. A recording thermometer indicates the temperature during each conversion.
Variable factors – The variable factors which influence the mashing of grain are:
1. Acidity of mash water
2. Cooking temperature
3. Cooking time
4. Converting temperature
5. Converting time
6. Sugar concentration of converted mash
7. pH of converted mash
8. Meal size
9. Starch remaining after conversion
With so many variables it is not surprising that mashing is such a complicated subject. For this reason it will be considered in greater detail in a later chapter.
General considerations – Successful conversion of the starches to fermentable sugars depends to a large extent on the operational and chemical control exercised over the entire mashing procedure. On the operator rests the responsibility for accurate control over cooking and converting time and temperatures. In this regard it should be pointed out that subsequent examination of recorder charts may indicate the cause of a mashing failure but it will not correct the damage. Furthermore, too great faith should not be place in recording instruments. The recording thermometer on the cookers should frequently be check against the mercury thermometer. This is especially true of the maximum cooking temperature and the converting temperature, both of which should be absolutely accurate. The diastase is drastically reduced in potency when the converting temperature is either too high or too low.
Fermentation is the result of the action of yeast cells on fermentable sugars. Here again the reaction is brought about by the presence of enzymes. The two principle enzymes involved are maltase and zymase. Zymase is sometimes called alcoholase. The product resulting from the reaction are carbon dioxide and alcohol in the ratio of about 1 to 1.04 respectively.
The mash from the converters is transferred to the fermenting tubs after passing through coolers the purpose of which is to cool the mash to the proper setting temperature. Yeast is added to the fermenting tub at some time during the filling period. Water or thin stillage is added to the fermenter to bring the concentration of sugar to the proper concentration for fermentation and to adjust the pH and furnish protein matter for yeast activity.
Fermenters – The fermentation tubs have domed tops and conical bottoms. Automatically controlled cooling coils regulate the maximum fermentation temperature. These cooling coils may also be used to control the temperature of the tub if it is decided that the fermentation is taking place too rapidly. Compressed carbon dioxide is used for agitation. The carbon dioxide formed during fermentation is drawn off the tubs through connecting ducts by means of a central suction fan. Alcohol carried over by the carbon dioxide is removed by means of a scrubber and the scrubber water returned to the beer well.
Fermentation variables – The principal factors influencing fermentation are:
1. Initial concentration of fermentable sugars
2. Initial pH of fermenter
3. Setting temperature of fermenter
4. Fermentation time
5. Concentration of yeast food
6. Temperature during fermentation
7. Concentration of fermentable sugars at the end of fermentation
8. Alcohol concentration at end of fermentation
9. Activity of enzymes
10. Amount and viability of yeast used to stock fermenters
Yeast – Yeasting begins in the laboratory with the preparation of the pure yeast culture. Slants are prepared by allowing a mixture of agar and malt syrup solution to jell in a test tube supported at an angle. Yeast cells which have been found to be suitable, by microscopic examination, are placed on the jell surface and allowed to multiply under carefully controlled conditions. After a suitable period of time the yeast cells contained in the slant are transferred by successive stages to larger and larger quantities of yeast nutrient until several quarts of yeast-containing liquid is obtained. At this stage the yeast is ready to be removed from the yeast laboratory to the yeast room.
The yeast from the laboratory is transferred to a dona tub containing a sterile mash made from malted barley wherein yeast growth is continued. At the end of a suitable period the yeast in the dona tub is transferred to a yeast tub containing yeast mash. This yeast mash is made of rye and malted barley and has been previously inoculated with lactic acid-producing bacteria. The formation of lactic acid lowers the pH of the mash with the result that certain undesirable bacteria are inhibited. Prior to the addition of the dona yeast the sour yeast mash is pasteurized in order to destroy the lactic acid bacteria. The yeast mash from the yeast tub, after sufficient multiplication of yeast cells, is transferred to the fermenter.
The factors which influenced yeast growth are listed below:
1. Initial sugar concentration
2. Time of yeast growth
3. Time of souring of yeast mash
4. Temperature at which growth occurs
5. pH of media
6. Viability of yeast cells
7. Alcohol tolerance of yeast cells
8. Concentration of essential inorganic salt
9. Concentration of available nitrogenous material
10. Agitation and aeration
All equipment is sterilized before use and all yeast nutrient is pasteurized prior to adding the yeast.
A new method of growing yeast which at present is in an experimental stage will greatly change our present procedure. In this method the pure yeast cultured is added to a sterile wort prepared from corn, malted barely, and malt sprouts. The passage of air through the yeast containing wort results in increased cell multiplication rather than alcohol formation. This aeration method produces ten times as many yeast cells as the present method from the same quantity of yeast nutrient. The yeast cells are separated from the liquid and stored read for use at a low temperature. The advantages of this method are: absolutely sterile yeast, ease of preparation, smaller space requirements, and economy of yeast food. Centralization of all yeast production will permit greater uniformity and more accurate control.
[Fundamentals of Distillery Practice, page 74 describes malt sprout levels as high as 30% in a yeast mash and then states:
Although malt is adequate for yeast growth under anaerobic conditions, malt sprouts are required to increase the content in amino-nitrogen and growth factors of the medium for aerobic production of yeast.
This regards aerobic yeast grown in bioreactors, but may have parallels to 19th century use of okra as a replacement for skimmings in spontaneous rum fermentation.]
Sterilization and disinfectants
In this section the importance of cleanliness and sterilization of equipment will be considered. The gravest danger in the distillery is that through negligence bacterial action or wild yeasts may develop in the various stages of the process. The precautionary measures taken to prevent this and the consequences of failure will be discussed.
Both physical and chemical agents are widely used in destroying bacteria. Physical agents are heat, sunlight, diffused light and air. Some of the chemical agents are; lime, chlorinated lime, mercuric chloride, formaldehyde, phenol, potassium permanganate, chlorine, sulfur dioxide, carbon monoxide and carbon dioxide.
Distillery processing equipment is made sterile, most commonly, with moist heat. In other words, the equipment is heated for a period of time with steam. However, at times a chemical agent such as chlorinate lime is used.
Mashing equipment – After use, cookers, converters, and all lines should be flushed out with water and steamed. The procedure followed is to partially fill the cookers and apply steam, under pressure. The cooker is now blown-off and the water dropped to the converter below. The hot water is ten pumped through the mash lines to the sewer. Steam is put on the lines until ready for use. Once a week the cookers are treated internally with hot caustic to remove any caramelized material.
The outside of all mashing equipment must be kept clean and the floors, etc. scrubbed at regular intervals.
Fermentation equipment – The procedure followed with a fermenter which has just been emptied is of extreme importance. The tub should be carefully washed with hot or cold water until all adhering particles of grain have been removed. Direct steam is then applied until the metal is completely heated to the boiling temperature of the water. The tub is allowed to cool and is washed again with hot water after which it is read to be used.
Yeasting equipment – Dona and yeast tubs are sterilized in much the same way as the fermentation tubs. All lines carrying yeast or mash must be washed with hot water and then subjected to steaming when not in use.
General considerations – Cleanliness not only of all mashing, fermenting, and yeasting equipment, as well as lines, must be practiced, but also all meal bins and meal handling equipment must be kept clean. General cleanliness throughout the plant is essential.
The presence of butyric or acetic acid bacteria in the fermenting mash may result in a distillate so high in butyric or acetic acid that it becomes almost valueless. Furthermore, other forms of bacteria, if present, act on the fermentable sugars to form even less desirable products. “Pepper whiskey” is the direct result of failure to sterilize completely.
Wild yeasts lower the yield of alcohol produced and result in objectionable constituents being formed. In fact, no consideration in the whole process is of more importance than the prevention of bacterial and wild yeast growth.
There are several general types of stills used in the production of whiskey and alcohol from fermented mash. These principle types of distillation units are five in number.
1. Charge still for whiskey production
2. Continuous beer still
3. Batch still for alcohol production and reclamation
4. Coffey still for whiskey and alcohol production
5. Multiple column vacuum still for alcohol production
Charge still – This still consists of a series of pot stills placed one above the other in a single shell. This type of intermittent still is used for the production of heavier bodied whiskies.
Alcohol kettle and column – The batch process for alcohol production is carried out with a kettle and rectifying column. The kettle is charged with high wine from a continuous beer still and heat is supplied indirectly with steam in a steam coil situated within the kettle.
Coffey still – The coffey still is used in the production of high proof whiskey and neutral spirits. It consists of two column, a stripping column and a rectifying column. It derives its name from the inventor who brought the design forth in 1830. The rectifying column acts as the beer-heater.
Beer still – The production of whiskey and the first process in the production of alcohol from the fermented mash consists in the removal of all the non-volatile material and a good portion of water. This operation is carried out in the continuous beer still. The essential parts of such a unit are, in general:
1. A column
2. A feed heater
3. A condenser
4. Source of heat
Heat – The heat is supplied with open steam direct into the liquid at the base of the still. This method of heating is used because of its efficiency and because the residue leaving the still is aqueous and is, therefore, not harmed by the addition of water.
Feed heater – The fermented mash passes through a beer heater before entering the still. The function of the beer heater is to raise the temperature of the continuously entering feed to as near the boiling point as possible. However, with a beer still the feed does not reach this temperature. The heat is supplied for this purpose by the vapors from the column with are partially condensed in heating the entering feed in the beer heater.
Condenser – the enriched vapor from the beer heater passes to a condenser and is completely condensed. Water is used for this cooling, and the condenser used is of tube and shell construction.
Column – The column may be divided into two portions which are called, respectively, the exhausting portion and rectifying portion. the plate on which the feed enters is the dividing line. The plates below the feed plate are for exhausting, while rectification takes place on the plates above.
Operating factors – The requirements for successful continuous distillation with this type of still are two in number:
1. The fermented mash must not vary in concentration, temperature and rate.
2. The quantity of steam must be held constant.
Feed – The quantity of feed to the still must be accurately controlled. For this purpose an automatic feed controller is used. It is essential that the feed control be very sensitive so that regulations may be made with exactitude. To achieve these conditions the feed pump must deliver at almost a constant rate. A feed pump which fails to meet this requirement is unsatisfactory.
Steam – A steam regulator is used to maintain constant steam pressure automatically on the column. This controller must be sufficiently accurate so that a variation in pressure in the column to a fraction of an inch of water will be noted and automatically counteracted.
Indicators and recorders – Instruments for indicating and recording temperatures, pressures, steam flow, flow of distillate, and testers for observing proof of distillate and discharge are used as operational aids. These instruments are listed below:
1. Thermometers (mercury)
2. Manometers (mercury)
Measure of distillate
Proof of distillate and discharge
1. Hydrometer testers
The tester is a device for measuring the proof of the distillate or stillage by having the liquid rise continuously in a hydrometer well as it flows through the tester. The proof of the stillage is determined by continuously condensing a small quantity of vapor from one of the bottom plates of the still and passing this condensate through a tester. Since the condensed vapor is withdrawn from above the bottom plate, the condensate in the testing device is approximately ten times as concentrated in alcohol as the stillage. It is probable that the last traces of alcohol showing in a properly-stripped stillage represent residues of higher boiling alcohols.
Multiple column spirits unit – The distillation of fermented mash carried out on a multiple column still results in the highest purity of grain neutral spirits. The use of the continuous unit avoids rehandling of fractions at a considerable saving in time, labor, and expense.
At Lawrenceburg we have a four column continuous spirits unit and at Relay, a five column still. The beer still and aldehyde column of the Lawrenceburg still operate under vacuum while the rectifying and oil columns operate under atmospheric pressure. The beer still, aldehyde column, and rectifying column of the Relay unit are operated at reduced pressure and a fifth column, the pasteurizing column, as well as the oil column, operates at atmospheric pressure.
Vacuum distillation has two principle advantages over atmospheric distillation: the decrease in pressure, which increases the boiling point differentials of the various components, allows a cleaner separation; low temperature at which distillation occurs prevents the decomposition of certain undesirable products contained in the non-volatile material of the fermented mash. These decomposition productions, under atmospheric distillation, are carried over with the vapors from the beer still. Low temperature distillation also minimizes reactions between the various volatile components.
The comparable spirits unit planned for the Louisville plant will have only the beer still under vacuum. The other columns will operate at atmospheric pressure. The beer still for this unit will be so designed that the discharge from the still will leave at a temperature of less than 100°F. Obviously, this beer still will be revolutionary in design to meet this requirement for stillage temperature. The usual beer column consisting of perforated plates is automatically eliminated since with this type of column the still discharge leaves the still at a much higher temperature. The basis for this alteration in still design is founded on the results of work which indicate that a superior quality of spirit is produced when the fermented mash is never subjected to high temperatures during distillation. The decomposition products which form at higher temperatures are not present in sufficient quantities to permit analysis; however, their elimination should result in the finest quality of spirit that it is possible to produce.
For the sake of brevity, only the Relay vacuum spirits unit will be discussed.
Vacuum spirits unit – The multiple column, continuous spirits unit we will discuss is made up of five columns. The unit consists of the following columns.
1. A beer still
2. Aldehyde column
3. Rectifying column
4. Pasteurization column
5. Fusel oil column
Other principle equipment operated in conjunction with the five columns are:
1. A beer heater
4. An oil decanter
5. An ejector condenser
Beer still – The purpose of this still is to remove all of the non-volatile matter and most of the water from the fermented mash. This material, stillage, is discharged from the bottom of the still. The vapors pass to the aldehyde column.
Aldehyde column – The heads, consisting of low boiling aldehydes and esters, are withdrawn from this column. The impure alcohol issuing from the bottom of the aldehyde column is fed into the rectifying column.
Rectifying column – The almost pure product is withdrawn from this column and fed into the pasteurization column for final purification. A mixture of alcohol and fusel oil is also withdrawn from this column and fed into the oil column.
Oil column – Fusel oil is removed from the alcohol-oil mixture fed to the column. The oil goes to a decanter for separation and from there to the oil storage tanks.
Pasteurization column – The almost pure alcohol from the rectifying column is further purified in the pasteurization column.
Operational requirements – The following requirements are necessary for successful operation:
1. The feed to each column must be constant in quality, temperature and rate.
2. Steam flow and pressure to each column must be constant.
3. Cooling water to dephlegmators and condensers must be constant.
4. Vacuum must be held constant.
5. Reflux to each column must be regulated.
6. Product withdrawals must be regulated.
Feed – The quantity of feed to the beer still must be held constant. A regulator or governor insures a constant rate of feed.
Heat – Steam controls on all five columns automatically adjust the flow of steam with variations in the pressure within the stills.
Water – Dephlegmator and condenser cooling water must be held constant. These adjustments are made by the operator when needed. Changes in cooling results in reflux variation.
Vacuum – The beer still, aldehyde column and rectifying column are all under vacuum. A vacuum regulator maintains a constant vacuum on the system.
Indicating and recording instruments – Successful operations depend on the operator being aware at all times as to conditions within the various units of the still. For this purpose the following indicating and recording instruments are required:
Temperature—Thermometers (Hg), recorders
Pressure— Gauges, manometers
Flow of liquid—Rotameters, orifice flow-meters, weirs
Specific gravity—Hydrometer (testers)
Because of the extreme sensitivity of such a unit to external conditions a high degree of operational skill is required. The quality of the distillate and the efficiency of alcohol recovery depends to a large extent upon the skillful manipulation of the still unit by the operator.
The procedure followed in determining the best operating conditions for the Lawrenceburg vacuum unit is of interest because it illustrates a very important feature of operational control. The proper settings for the various operational factors were determined by experiment and the quality of spirits produced in each case compared. The changes were made one at a time so that differences in spirit quality could be definitely attributed to a single cause. The experiments are listed below in the order made:
1. The beer input was varied from 4000-5000 G.P.H. to determine the most satisfactory rate.
2. The proof from the top of the beer still was run at 70, 80, and 90° proof.
3. The heads draw-off was varied from 6-18%.
4. The vacuum was varied from atmospheric to 25 inches of mercury.
5. Varied entrance point of dilution water to aldehyde column.
6. Varied ester draw-off
7. Varied rectifying column reflux ratio.
8. Varied aldehyde column reflux ratio.
9. Varied spirits draw-off
A second problem which was solved by Research Development and Operational Control deals with the heads withdrawn from the aldehyde column. Approximately 10% of the alcohol is removed as heads. This lower boiling portion consists principally of aldehydes, esters, and ethyl alcohol. Previously, the heads were treated with alkaline permanganate and redistilled in a batch rectifying still. This procedure involves rehandling of the various fractions, and was quite costly. A more serious objection, however, was the low quality of spirits produced from the heads using this procedure.
A new method of treatment was developed, by the Research Department, which obviates most of these objectionable features. The heads are treated with alkali and then distilled in a batch rectifying column. the distillate from the batch still is fed back to the continuous spirits unit with the result that 99% of the alcohol from the fermented mash is now recovered as high grade spirits as compared with 90% using the old method.
[For some reason a short passage on gin was here in the manuscript. The manuscript had two different sections on gin.]
Food and feeds recovery plant
The non-startch part of the grain, which is not fermentable, remains in the still discharge. This non-volatile material consists principally of protein, fiber, oil and dead yeast cells. This material is recovered from the stillage in the foods and feeds recovery plant and is the principle by-product of the distilling industry. At present, this recovery product is sold in sacks or in bulk as a cattle feed. However, research now in progress would indicate the feasibility of utilizing part of this material as a food for human consumption and the advisability of isolating the grain oil as a separate product.
The principle equipment used in this recovery consists of screens, presses, rotary dryers, and multiple effect evaporators. The whole stillage is screened resulting in thick stillage, the material on the screen, and thin stillage which is the material passing through the screen. The thick stillage as it leaves the screen is passed through presses in order to remove excess liquid. The thin stillage and press-water is evaporated to a thick, syrup like concentrate in the multiple effect evaporators. The evaporator syrup and the press-cake are combined and the mixture dried, in rotary dryers, to the proper moisture content. The whole process is continuous so far as is possible.
Screens – The three principle types of screens used are stationary, vibrating and rotary screens. In all cases punched metal plates are used as the screening medium. The advantages of stationary screens are low initial and repair costs, and the ease with which replacements may be made. However, such screens are not very efficient and the capacity is not very great. Vibrating screens, on the other hand, are highly efficient but cost of up-keep makes their use prohibitive. Rotary screens are fairly efficient and repair costs are not too high with this type. A further advantage of this screen is the small space required.
The principle consideration in screening is to separate a high percentage of insoluble solids from the stillage. It is not particularly advantageous to obtain the least liquid thick stillage possible since this material is to be pressed at any rate.
Presses – Excess water is removed from the thick stillage by the application of mechanical pressure to the cake as it is carried through the press. It is essential that this press-cake be as dry as possible for reasons which will be explained later.
Multiple effect evaporators – The quadruple effect evaporators operate under vacuum produced by an ejector condenser. The first effect operate under a slight positive pressure; each succeeding effect being under increasing vacuum. The effects are always considered in the order of steam pressures. Thus, the first effect always means the highest pressure effect, no matter what the order of feeding is. There are four separate methods of feeding but only two will be considered here; forward feed and backward feed. In forward feed, the feeding is from the highest effect to the lowest, while backward feed is the reverse, the feed going initially to the last effect and then to the next lowest pressure effect, etc. We use forward feed although there may be some question as to the advisability of this.
Operating conditions – The operating factors are four in number:
1. Feed to various effects
2. Heat to first effect
4. Product from last effect
Continuous operation is absolutely essential and all valves regulating the evaporators should be set so that they do not have to be changed except at infrequent intervals. Such operation results in an even load on the boilers, water pumps, etc.; and the evaporator syrup produced is uniform in density with the final advantage of economic operation.
Feed – The feed to each effect should be maintained constant. This is done by setting the feed valves at the proper opening.
Heat – Steam should be introduced to the first effect at a constant rate.
Vacuum – The vacuum should also be held constant.
Economy and capacity – Considering identical conditions it is apparent that a multiple effect evaporator must have as much heating surface in each effect as a single effect would have to produce the same evaporation. In other words, the capacity of a single effect evaporator per square foot of heating surface is much greater than for a multiple effect evaporator. Therefore, the justification of multiple effect evaporators is not based on increased capacity over single effects, but resides in the increased steam economy of the multiple over the single effect evaporator. In general we may say that one pound of steam will evaporate one pound of water in a single effect, two pounds in a double, three in a triple and four in a quadruple. A good example of this would be to operate two single effects as a double effect evaporator and compare the amount of evaporation with that produced by the two effects operating singly. It will be found that the double effect will produce the same evaporation as that from just one of the effects operated alone. Hence, the advantage of multiple effect evaporation is based on steam economy rather than capacity.
Indicating instruments – Operation of the evaporators is facilitated by means of the following instruments:
Dryers – The rotary dryers consist of a revolving cylinder slightly inclined from the horizontal. The feed is fed in continuously at the upper end and discharged at the lower end. Heat is supplied through a bank of steam tubes within the drier running parallel to the long axis. A fan draws air through the discharge and into and through the drier.
Operating factors – The factors controlling operation of the driers are three in number:
3. Air supply
Feed – The feed should be held constant both in quality and in amount. The moisture content, when the heat is held constant, will increase with increase in feed and decrease with decrease in feed.
Heat – The steam should also be held constant but due to variations in feed quality and amount this is not usually practicable.
Air – Stack dampers provide a means of air supply control.
Indicating instruments – Instruments to indicate operating conditions are as follows:
Other considerations – Economy of operation is greatly influenced by the degree of dryness of both press-cake and syrup before being fed to the dryers. This is obvious when we realize that the amount of steam required to evaporate one pound of water in the dryers is over found times as great as the steam required to evaporate an equivalent amount of water in the quadruple effect evaporators. Hence, economical operation requires that as much evaporation as possible should be carried out in the evaporators. This means that both press-cake and evaporator syrup have as high a solid content as possible. Unfortunately, whee really high syrup concentrations are attempted, the evaporator tube have a tendency to become clogged. There is also a limit at which no further moisture may be removed by mechanical pressing.
Dried meal is a finished product and must meet high standards of quality and uniformity covering minimum requirements and maximum allowances. Excess moisture makes spoilage a possibility in either bulk or bag shipments. Another factor influencing quality is the presence of syrup balls in the finished meal. While such globules of dried syrup may not lessen its food value, they do give the grain a poor appearance and should be avoided for this reason.
In this chapter the importance of control and the need for accurate and logical thinking in all matters pertaining to production has been stressed. No effort has been made to give a detailed description of operations or equipment. the objective has been rather, to inculcate the logical appraisal of such matters as cost, control, and quality. With this as a background the more intensive study of individual operations, which is to follow, should be more readily appreciated.
It must never be forgotten that the manufacture of alcoholic beverages is dedicated to the direct consumer. This entails a heavy social responsibility that does not bear on industries which produce intermediate products. Their mistakes, costly or not, detected or eluded, are adjusted within the confines of the related industries. Out mistakes are judged directly and mercilessly by the public itself. Therefore, control is our only safeguard against this immense vulnerability.
It is particularly necessary that the distiller employee appreciate the sensitivity of the nose and taste organs in detecting differences. A definite psychological shock is experienced by the consumer who discovers a variation in product quality and the reaction evoked is generally antagonistic. As analysts in the physical sciences, we consider out methods sensitive when our variations are of the order of five milligram per liter; as analysts in psychophysics, we deal successfully with dilutions approaching molecules per cubic yard.
More personal to use as technical modern manufacturers is the actual ability to apply control on plant-scale operations. The degree to which we carry this is exactly the measure of our professional status in the technical world. The producers of control equipment all have their eyes upon us. Those who succeed in selling and installing such equipment in our plants are doubly watchful and they, too, are the ones who report the effectiveness of our methods with their equipment to other industrial leaders. It is a point of professional pride with us to maintain a clear record, and the reward for this is simply departmental praise—which is the basis of scientific integrity.