Table of Contents
Design Objective. 2
Executive Summary. 2
Table of Contents. 3
Chapter 1: Introduction. 5
Spirits distinction. 8
Liquor production methods. 8
Liquor production steps. 9
Chapter 3: Plant Mass and Energy Balances. 11
Chapter Introduction. 11
Base case for spirit manufacture from cider 11
The design model 12
Mass transfer or conversion processes during fermentation. 13
Glucose to ethanol conversion equation; 13
Glucose conversion to acetic acid equation; 13
Glucose conversion to succinic acid equation. 14
McCabe Thiele Graphical Analysis. 14
Optimum Reflux Ratio. 15
Chapter 4: Detailed Design. 17
Chapter introduction. 17
Batch distillation overview.. 17
Batch distillation advantages (Preference) 17
Batch Distillation Column Design. 18
Batch Rectifier 19
Appendices: Individual detailed design reports and others as appropriate. 20
Appendix A: Figures. 20
Chapter 1: Introduction
Fermentation industries are involved with a series of liquor production ranging from beer to spirits using a variety of methods depending on the alcohol content desired and the financial ability of the industry (Rumpunen et al., 2015). The liquor produced by such companies includes, but not limited to; distilled spirits, wines, brandy spirits, as well as the secondary products. The type of liquor produced depends on the raw material used while its quality depends on the effectiveness of the production method. In most fermentation industries, the commonly produced beverage distilled spirits includes; gins, rums, whiskies, vodka and brandies. Gins are processed from the fermentation of grains and its flavor is achieved through the addition of botanical extracts. Brandies on the other hand, are processed from the fermented fruits juices while the distilled spirit products are mainly processed from the fermentation of sugarcane and its by products such as molasses sourced from sugar cane processing industries (Hu et
al., 2015). The byproducts of fermentation and liquor processing are majorly used in production and processing of livestock feeds and additives necessary for various animal requirements. Table 1 shows the base ingredients for different distilled spirits.
Table 1: Distilled spirits and their corresponding raw materials (Adapted from Liang et al., 2009)
|Raw material (Base ingredients)
||Type fermentable product required
||Distilled spirits and liquor produced
Pinga, Basi, Cachao
||Apples, plums, pears, dates, raspberry and strawberry
||Calvados, alcohol blanca, poire, slivovitz, Mirabelle, Arrack, Framboise and Fraise
According to Caldeira et al., (2017), a spirit refers to an alcoholic drink with very high alcohol content and is the product of the distillation process of fermentable products. Spirits are distilled within their purification point, but they still contain the elements of the base material. This implies that if sufficient base material or the sufficient mother or raw material can get its way into the distilled spirit then the purity and standard assessment of the final product should be reviewed not only based on the fermentation and distillation process but also the raw material itself. Distilled spirits have been associated to a series of challenges, especially with the health ministries of various nation owing to the sudden rise in the demand that has made many suppliers to engage in dubious means of production. In most distilled spirit production industries, concern and interest has always been on the attached to the financial gain without taking care of the required health standards through following the recommended procedures. As a result, many users worldwide have lost their lives just by consuming wrongly prepared and the otherwise dangerous distilled spirits. As a consequence, there is a great interest that fermentation industries follow the right liquor production procedures and well laid standards in order to eliminate the possible loss of lives of the users.
The spirits liquor is manufactured using distillation which refers to a process of miscible liquid separation based on their physical properties. A liquid mixture, say the fermented sugarcane products in the form of a liquid, contain a series of liquids with individual physical properties variation. The variation of the physical properties, especially the varying boiling points enables the separation of the mixture into pure liquids. The word distillation was coined from a Latin word ‘destillare’ which mean to drip or to extract (Ballesteros et al., 2004). In production of liquor, distillation refers to the process by which liquor is extracted from the fermented materials using heat to vaporize them and exposing the desired vapor to condensation to retrieve the desired spirit (Nicol, 2015). Other than flavor addition after the distillation process to get the required flavor, concentration variation can also be achieved through dilution as well as mixing of different spirits in a given ration to achieve the required brand. Distillation can as well be considered as a method of increasing the alcohol content in the sense that before the distillation processes the alcohol content by volume is relatively low than the alcohol content by volume after the distillation process (Christoph et al., 2007). For instance, it is possible to achieve a 20% alcohol by volume distillate from 8% alcohol content by volume fermentable drink by boiling it off in a pot still. As a method of separation, distillation uses the fact that alcohol boils at a temperature (78 0C) relatively lower than the corresponding temperature at which water boils (100 0C). Thus, when an alcohol and water mixture are heated, when the temperature of the mixture reaches 78 0C, alcohol vaporizes and is condensed as a separate distillate (Liu et al., 2006). During vaporization of alcohol, temperature stays constant despite the fact that heating continues till all alcohol contents are vaporized. This implies that when the temperature just starts to rise, there is no need for further heating as the vapor that will be collected will be of a water.
The distinction of distilled spirits with regard to color (brown, white and or specialties), fermentation base or raw material (see table 1), method of distillation, alcoholic contents as well as the region or country of origin. The brown spirits mainly consist of whiskies while the white spirits involve the rum, vodka, gin and tequila. On the other hand, specialties include the spirituous beverages, cordials as well as the brandies. With respect to region of origin, spirits are also codified based on their origin. Example includes; Greece brandy from Greek, Swedish vodka from Sweden, Tequila which commonly associated to Mexico, Cognac and armagnac from France amongst other spirits attached to particular nations. In addition, the production methods majorly distinct the spirits depending on the purification method used rather than the natural fermentation process.
Liquor production methods
Generally, liquor is produced from a combination of two major processes, namely; fermentation and distillation. The former method converts the sugar content stored within the base material such as fruits, roots or even vegetables to alcohol while the later process purifies the alcohol manufactured and also strengthens it to the required alcohol content per volume of the distillate through boiling. Through fermentation, the sugar components available naturally in organic substance is converted to ethyl alcohol during a naturally occurring chemical reaction catalyzed by yeast cells. In this process, sugar is broken down into carbon (iv) oxide and ethanol or ethyl alcohol. As the gas is allowed to escape or tapped for other uses, the fermented products left behind mainly in the form of beer or wine is normally of low alcoholic content per unit volume and in addition, it contains a great proportion of the underlying characteristics and flavor from the base material. The fermented liquid is then subjected to a distillation process which basically involves heating the fermented product to not only purify the alcohol manufactured but also to strengthen it (Vandamme and Derycke, 1983). The strength of alcohol after distillation id directly dependent on the number of the distillation process, the distillate is exposed to. According to May et al., (2017), the first distillation after fermentation normally gives about 20% alcohol content by volume while the second one gives about 60% alcohol by volume. With subsequent distillation process, it is possible to achieve about 96% alcohol by volume. In terms of the alcohol content or alcohol strengths, spirits are categorized as the alcoholic drinks with alcohol contents in the range of 60% to 80% alcohol by volume. Other than achieving the required alcoholic strength, subsequent distillation also greatly minimizes the effect of the underlying characteristics and flavor from the base material (Bamforth, 2016).
Liquor production steps
While the major steps in the process of liquor production mainly consist of fermentation and distillation as described above and that is exactly what most literature provides. Nonetheless, depending on the specific spirit to be produced, there are a number of steps that occur before fermentation and even after distillation (Gaden, 1959). The steps before fermentation includes milling and mashing while the post-distillation steps includes Milling is a pre-fermentation process whereby the base materials are grounded into course meal so as to free the starch from the protective base material hull. Mashing involves the conversion of starch to sugar followed by a process where pure water is added into the product and further cooked to produce a mash which is then fermented (Gou et al., 2015).
For some spirits such as brandy, rum and whisky, additional maturity level is required in wooden casks to enable them develop a gradual distinctive aroma, color and or taste. This process is called ageing and is applicable to only some spirits after distillation. In addition, blending is also a post distillation process applicable to some spirits whereby two or more spirits of similar category are combined to give a distinctive blended spirits but within the category of the blending spirits (Saerens et al., 2016).
Chapter 3: Plant Mass and Energy Balances
In this chapter, optimization parameters of the plant mass with regard to energy balances through the integration of heat is discussed. The aim of this section in the overall liquor production plant was to reduce the plant operation cost by limiting energy use and correlated cost, yield efficiency increment and minimizing the loss of liquor through the waste from the plant. By maximizing the yield efficiency and reducing the energy use, the cost of production and operation will undoubtedly be comparatively lower hence making the production process as economical and as profitable as desired. In addition, by making the production process to be effective, efficient and produce a sufficient fuel liquor production plant do not just become economical and profitable but also produces a safe and standard liquor as per the desires of the clients as well as per the required standards of production.
Base case for spirit manufacture from cider
In this liquor production process, spirit is produced from the fermented product following the brewing of cider as the base material. At the end of fermentation process, beer is separated from the solid spirit and water mixture using stripping at the beer column just before subjecting the mixture to distillation. At the beer column, spirit is concentration is about 60% to 70% ABV and is further subjected to the batch rectifier to give an azeotropic water and spirit mixture (Jana and Maiti, 2013). The azeotropic mixture is further subjected to a centrifuge where additional separation of solid particles is which are then collected together with the first components then evaporated to dryness. The resulting solid matter is rich in animal nutritional requirements and are thus sold off as animal feed. This makes the production cost be lower as compared to situation where they are disposed-off as waste.
The design model
The design of the spirit production from cider was modelled through the use of equations that correlates the parameters especially the volumes of the liquor from the total volume from the original cider fermented. This design was based on the effective mass flow, mass flows of the respective components, fractions of the components and the corresponding temperature within the batch distillation network. Such are the parameters necessary for liquor production optimization. The following are the variable description as per the designed project;
- F (Reboiler, Condenser) represents the total mass flow rate from the reboiler to the condenser in kg/s
- Fc (j, Reboiler, Condenser) represents the j component mass flow from the reboiler to the condenser in kg/s
- X (j, Reboiler, Condenser) represents the mass fraction of the j component between the reboiler and the condenser
- T (Reboiler, Condenser) represents the temperature difference in 0C between the reboiler and condenser.
Note that j represents the components of the liquor produced and in this case, the components includes but not limited to starch, glucose, ethanol, water, lactic acid, acetic acid, proteins, glycerol, cell mass cellulose amongst other components. These components are sourced from either the base material or the fermentation or processing stages but are not removable within the waste elimination stages such as sieving and stripping (Harwardt and Marquardt, 2012). For instance, starch, glucose, proteins, cellulose are the products of the base material while cell mass comes from the yeast cells used to initiate the fermentation process (Johri et al., 2011). On the other hand, glycerol, acetic acid, fatty acid and ethanol are the major by-products of the brewing or fermentation process for cider. All these components are assumed to be water soluble with exception of starch, cellulose, oil, cell mass and ash. Gaseous components are not mentioned herein since they are allowed to escape or are rather trapped in different containers and thus are missing within the fermented cider in the form of liquid.
For every component j, component mass flow rate is correlated to the total mass flow rate by;
Fc (j, Reboiler, Condenser) = X (j, Reboiler, Condenser) * F (j, Reboiler, Condenser)
This implies that the total mass flow rate is the effective sum of the individual component mass flow rates. Thus;
F (Reboiler, Condenser) =
Mass transfer or conversion processes during fermentation
Fermentation process can be explained using equations showing how the individual components changes from time to time and from one component to another till ethanol and water mixture are obtained (Kumar et al., 2013). The following are the major equations relating to the conversions;
Glucose to ethanol conversion equation;
By balancing the masses, it implies that for every one kg of glucose, about 0.5114 kg of ethanol and 0.4885 kg of carbon (iv) oxide gas will be produced. Part of the gas produced will be used in further reaction while the remaining part will be eliminated.
Glucose conversion to acetic acid equation;
While the mole ratio for glucose to acetic acid is 1:3, the mass of the three molecules of acetic acid produced will be equivalent to the mass of the glucose used in making them.
Glucose conversion to succinic acid equation
From the mole ratio, every 1 kg of glucose combine with 0.4885 kg of carbon (iv) oxide gas to produce 1.3191 kg of succinic acid while liberating about 0.1776 kg of Oxygen. There are several equation relating to a series of conversions that occur within the process of fermentation most of which are ignored herein.
McCabe Thiele Graphical Analysis
This analysis technique is necessary for the understanding and comprehending the compositional based changes that occur at the distillation column as separation continues (Mayer et al., 2015). McCabe Thiele method provides a faster and equally easier solution to the binary distillation problem. The method is anchored on the on the material compositional change with regard to the equilibrium line (Wang et al., 2016). The equilibrium line is used to show the composition of the materials variation beneath and over the plates. The McCabe Thiele operating line was plotted on the same graph as the equilibrium line to enable the determination of the equilibrium stages number by the graphical construction. For the spirit (ethanol) water mixture within the distillation column, figure 4 shows the McCabe Thiele graph used to determine the equilibrium stages. The operating line equation was developed from;
Where xD is the distillate composition while R represents the reflux
R is defined as the ratio of flow returned as reflux to the flow of the top product taken off. The rectification column operates at the line which depends on variation of R, hence the required number of equilibrium stages is equally dependent on R. For poorly insulated distillation column, the effective reflux ratio may be greater than the R value (Jana, 2017). This was the basis of lagging the column to enhance the efficiency of liquor production. Irrespective of the design, reflux always falls within the two extreme ends, namely total reflux and minimum reflux. Total reflux occurs when there is no uptake of the products as well as no addition of feeds coupled with all condensate being returned to the column. A relatively fewer stages are required in in the separation process when dealing with total reflux design (Jana, 2017). Fenske equation can be used to calculate the minimum number of stages required for the total reflux where all vapor is assumed to be condensed and then returned as liquid. Fenske equation is given by;
On the other hand, minimum reflux occurs when at least two operating lines have their intersection within the equilibrium curve as shown in figure 5. When the feed is a liquid at the point of boiling, the minimum reflux can be calculated as follows;
Optimum Reflux Ratio
For optimum operation, it is necessary to first understand the effect of varying R value on the required number of plates and the corresponding production cost. Increasing R for instance, makes the diameter of the column bigger and thus equally reduces the capital cost. As a consequence, the number of plates gets smaller with comparatively higher heat exchange to increase the boiling and condensation. On the other hand, decreasing R calls for more stages and corresponding higher capital cost though with relatively less condensation and boiling. Figure 6 shows the variation of reflux ratio as a factor affecting the total cost, operating cost and fixed cost (Penniston et al., 2018).
Chapter 4: Detailed Design
In this chapter, a detailed description of the distillation process used in the liquor production is clearly described with respect to the theory behind it, reasons why it was chosen as the distillation process and design approach. Distillation process can be categorized either as a batch distillation or continuous distillation. Batch distillation is used mainly in chemical (both biochemical and pharmaceutical) industries while continuous distillation is preferred majorly in separation of bulk chemicals such as petrochemical. Figure 1 shows the schematic representation of the two distillation process.
Batch distillation overview
Distillation is generally considered as a way of separating miscible liquids based on their varied physical properties and purifying the distillates based on waste or unwanted component removal (Rawlings, 2014). According to Simasatitkul et al., (2017), batch distillation consists of a process in which feed is loaded within the boiler while the distillates are recovered from the column top as shown in figure 2.
Batch distillation advantages (Preference)
Just as mentioned earlier, distillation can be categorized as either batch or continuous distillation process. The preferences of either of the types is anchored on the unique advantages in one over the other depending on the desired outcomes as well as the chemicals to be separated. Batch distillation is preferred for separating small quantities of mixture with capacity which are smaller than required to justify the requirement of the otherwise expensive continuous distillation process. Secondly, batch distillation is flexible to handle a series of different feedstock resulting in a varied product range. Thirdly, batch distillation method is also attached to the possibility to obtain more than one product from a distillation process which effectively separates the products based on the characteristics. Batch distillation also makes it possible to attain different levels of purity from the same product with maximum elimination of fouling. In addition, batch distillation allows the separation of many products using only one column at a more convenient operation mode as compared to the continuous distillation (Kufer and Hasse, 2017). Nonetheless, batch distillation
Batch Distillation Column Design
The fermented product to be separated and purified into alcohol of varying ABV is fed at the reboiler when the operation starts for the constant reflux. The heat content within the boiler is absorbed by the feeds making them to evaporate while generating vapor which then moves within the column till it reaches the condenser. At the condenser, the vapor is converted into liquid through the absorption of heat of vaporization from the vapor. The condensed liquid is collected at the reflux tank from where part of the distillate is redirected to the column in the form of a liquid reflux. The liquid reflux then falls through the column in a counter current manner to the rising vapor. The interaction of vapor and reflux liquid results in the mass transfer hence making the light components within the reflux liquid to rise with the vapor while the heavy counterparts fall together with the liquid.
Mass transfer consequently subjects within the column a profile of varying temperature, concentration and pressures zones. At the upper section of the column, temperature and pressure are relatively lower since the lighter components have a lower boiling points coupled with the fact that the vapor losses pressure as it rises the plate packing within the column. As a consequence, the less volatile compounds tend to concentrate at the column bottom while the more volatile counter parts settles at the column top (Ding et al., 2015).
A batch rectifier consists of a reboiler within which heating element is located to provide the vaporization temperature necessary for fractional distillation. As the vapor condenses on the upper part of the column, part of the distillate is directed back to the column as a reflux. The remaining distillate sequentially feeds the receiver tanks. Figure 3 shows the schematic representation of batch rectifier. The batch rectification assumes that within the column, there was only ethanol (spirit) and water components at one atmospheric pressure operation. At this operation description, a maximum of 95% ABV can be achieved hence there was no need for further purification. Only dilution was therefore, a requirement to meet the desired ABV concentration.
Appendices: Individual detailed design reports and others as appropriate
Appendix A: Figures
Figure 1: Schematic representation of distillation process types; Batch distillation a) and continuous distillation b) (retrieved from Bortz et al., 2017)
Figure 2: Batch distillation feed and distillate flow
Figure 3: Batch rectifier schematic diagram
Figure 4: McCabe Thiele graph
Figure 5: McCabe Thiele graph with two operating lines intersecting at the equilibrium curve
Figure 6: Reflux ratio optimization
ABV Alcohol by volume
B Overall bottom flow rate
D Overall distillate flow
F Total feed
N Number of equilibrium stages
Nmin Minimum number of flow rate
R Reflux ratio
Rmin Minimum Reflux ratio
XB Mol fraction of the component at the column bottom
XD Mol fraction of the component within the distillate
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