Abstract
The separation processes in industry are a common practice especially in the developed countries as well as in the developing world. As a result, it is a good step to improve the separation techniques to ensure a better process for the production of the finished commodities. The classification of the distillation columns and the packed bed columns together with an analysis of their ability to perform efficiently in the industry is vital. Therefore, the paper entails an analysis of each group of distillation columns, taking into account their ability to carry out their duties, as well as the reason as to why one type is preferred to another. The comparison enables one to choose between the columns ad go for one that is more efficient for a better production experience. The analysis of each of the distillation columns highlighted in the research, as well as each of the packed columns, explored their advantages and disadvantages in detail, to enable a wider view of the expected experiences when a choice is made to apply a particular type of distillation column or packed bed reactor.
Introduction
There exist various types of distillation columns, each designed to serve a particular purpose in industry. In general, the distillation columns appear in different forms depending on the functions they perform. A distillation column is an industrial equipment that separates various liquid components based on the differences in their volatility (Rawlings 89). Every distillation column operates on a series of temperature regimes that include the boiling points as well as the transition temperatures for some of the components to turn gaseous.
The internal environment of a distillation column is always very aggressive because there are high temperatures. The components of the distillation columns are subject to extreme temperature conditions, to effect the separation mechanisms that enable one to obtain the desired viscosity of the product.
The building of distillation columns takes place using high-temperature resistant materials like steel, to withstand the high temperatures. Additionally, the materials for making such columns should not react with the reactants, and that necessitates the application of lining materials like enamel (Rawlings 89).
Additionally, the materials for the manufacture of distillation columns tend to be resistant to corrosion by concentrated acids or bases. Therefore, the choice of material for the construction of a distillation column follows specific principles to ensure that the various requirements are met, for better performance.
Moreover, some distillation columns are automatic, while others are manual. The size of a distillation column depends on the function it serves, though the smaller sizes sometimes take priority because of the high quality it guarantees for the product (Rawlings 103). The applications of distillation columns are diverse because they range from the distillation of high energy commodities like crude oil to smaller functions like the pharmaceutical products.
Therefore, there exist various types of distillation columns. The classifications depend on various factors, for example, specific types of operations they perform. Each type of distillation column has a unique form of complexity that makes it different from the other types. Additionally, the distillation columns differ regarding the forms of operation, that is, batch or continuous columns (Rawlings 100). There exist multi-component columns, which contain more than one component, and the single component distillation columns comprising of one component.
Types of Distillation Columns
As already mentioned in the introduction section of the research paper, distillation columns exist in different types. In the current section, the various types of distillation columns, as well as their pros and cons, will take the greatest percentage of the explanations.
Batch Distillation Column. The batch distillations process is an unsteady state operation that takes place in batches. A batch is a column that equals to numerous equilibrium stages. The feed enters at the top of the column, an area, which also acts as the passage for the gaseous components of the system (Mallaiah, & Venkat 405). Condensation occurs at the top of the column, with a portion of the condensate getting back into the column for reflux and the distillate proceeds for various uses. The withdrawal or addition of components before the end of the run cannot occur.
Advantages of Batch Columns
Moreover, for a batch distillation column, switching from one mixture to another is easy and takes a shorter time (Mallaiah, & Venkat 405). The batch distillation column also allows better product integrity, alongside the achievement of high-quality products like the pharmaceutical products.
Disadvantages of Batch Distillation Columns
The batch distillations columns have one common drawback, which is the length of time it takes for a single mixture to acquire high temperature. As a result, the risk of thermal degradation of the products is high, as well as the associated high-energy requirement compared to the continuous distillations.
Continuous Distillation Columns. Continuous distillation column involves a single feed comprising a mixture of at least two components. The continuous distillation column aids the separation of the binary mixture into the two products known as the top product or the distillate, overhead product, and the bottom product is known as the bottoms (Mallaiah, & Venkat 404). The column has trays and packings, which enable it to facilitate the vapour-liquid movement within the column.
Advantages of Continuous Distillation
Firstly, for a continuous distillation column, there is no significant change in the control parameters; hence, the process is stable from the beginning to the end in a steady state operation regime. Secondly, the material condensation process takes place only in the system. Hence there is no cooling process required because the column is an all-condenser equipment. The reflux process remains fluid bubble point, an act that will guarantee the effectiveness of the process (Mallaiah, & Venkat 406).
Moreover, the large chase volume, the large specific surface, the efficient application of the filler, leads to an efficient distillation process. Therefore, the continuous distillation column has a reduced cost of operation, because of reduced energy consumption, as well as low material consumption, and equipment cost.
Disadvantages of a Continuous Column
Multi-component Distillation columns. As the name suggests, the multi-component distillation column has many components. The components include the light components, which are the most volatile components, and the less volatile ones that are famous as heavy components. Therefore, the components segregated in the tower are said to be the light key, which involves light components, and the heavy key, famous as the heavy key.
Advantages of Multi-Component Distillation Columns
Disadvantages of Multi-Component Distillation
It leads to a reduced relative volatility and makes separation process significantly significant. Therefore, it increases the reflux requirements for the process due to demand for a higher reboiler and condenser duties. It rises the bottom product temperature hence increasing the risk of chemical degradation, fouling, as well as the polymerization
Single Component Distillation Column. The single component distillation column is mainly applicable for the purification of substances, because there may be no significant separation processes taking place (Mallaiah, & Venkat 408). The column works by subjecting the single component to high-temperature regimes, to achieve a lighter distillate.
The advantage of a single component distillation column is that it does not require a lot of monitoring because the process is a continuous process. However, it is evident that a single distillation column restricts its operations to a single product.
Packed-Bed Columns. Equipment that is applicable in the industry to perform separation processes like stripping, absorption, and distillation. It is simply a pressure vessel, equipped with a packed section. The packed bed columns have a packing material allowing fluids to move from one end of the column to the other.
The column is a medium that enables an increased contact between a liquid and gas. The packing of the medium may be random, its structure restricts it through optimization to a particular reaction, and the packing incorporates the use of a catalyst to speed up the rate of the specific reaction (Mallaiah, & Venkat 409).
The performance of a packed bed depends on the flow of the material through it. The flow of the material depends on the packing of the column. The observation of the flow of liquids at different sections of the column is achievable through the application of the electrical tomography.
The capacitance or resistance topographies are the most suitable to serve the purpose, though the choice of either of the two depends on the nature of the material. It is also common for packed bed columns to make use of the ERT column sensors just like the chromatography and bubble columns.
Types of Packed-Bed Columns
The classification of packed columns depends on the types of packing, whereby packing places the columns into two common categories. Therefore, the two types of columns include randomly packed columns and structured packed-bed columns.
Random Packed-Bed Columns
The randomly packed columns exist in various categories like the rasching rings and metal ball rings. In a random packed column has an upper limit to the rate of flow of air, a process that is famous as flooding velocity (Mallaiah, & Venkat 410). They have a slight difference in the way they perform operations compared to structured packed columns though they serve the same purpose.
Advantages of Random Packed Columns
The random packed-columns are economical, and they increase the efficiency of the tower. The rasching rings products of carbon steel, graphite carbon black, exotic metallic alloys. Since the materials are corrosion resistant, they make the packed-bed columns very efficient for the purposes they serve (Mallaiah, & Venkat 405).
Disadvantages of Random Packed Columns
They are not suitable for low liquid flow rates. Therefore, they cannot be applicable for low flow rates of fluids, an act that restricts it to high flow rates of the liquids. Additionally, the randomly packed bed columns can only be applicable for the handling of foaming systems. They are very efficient in carrying out foaming processes and tend to have lower pressure drops.
Structured Packed Columns
Structured packing is another class of packed bed reactors that has the packing materials placed in an organized manner. The packing of the materials is uniform to guarantee efficiency (Mallaiah, & Venkat 406). Structured packed columns are efficient separation equipment because they offer high quality of products because of the packing materials. It has been in the application in the industry for a long time. However, the structured packed columns have both advantages and disadvantages associated with its industrial applications.
Advantages of Structured Packed Columns
There is an associated diminished foaming tendency for a structured packed column. Moreover, a structured packed column has a higher relative volatility for the separations that appear difficult to conduct due to the technical capability of the column (Mallaiah, & Venkat 405). Finally, the structured packed column has excellent fluid spreading features leading improved efficiency, and the offshore applications are subject to unchanged or unaltered tilt and motion.
Disadvantages of Structured Packed Columns
Firstly, a structured packed column requires a large number of the theoretical stages, which tends to complicate its operations because the person running the equipment might want to try to explore each of the stages. Additionally, the reduced vessel diameter sometimes leads to the reduction in the rate of production, hence the low efficiency of the packed column (Kiss, Anton & Costin 27). The scenario mentioned above happens on selected occasions because technology has continued to improve the efficiency of the packed columns through the modification of reaction mechanisms and geometry of the columns.
Therefore, based on the features mentioned above, it is evident that distillation columns have a significant difference from the packed-bed columns, with the differences ranging from the structural composition of the column to the particular types of functions they perform.
Therefore, the next section of the paper will involve a comparison of the processes of separation, between the distillation columns and the packed bed columns (Kiss, Anton & Costin 27). Such comparisons will give an opportunity for a wide scope of analysis of both types of columns, which include their functions as well as their benefits for the functions they perform in the various industrial settings.
Comparison between Separation with a Distillation Column and a Packed Bed
Column
It is evident that both classes of columns carry out the same processes, which are separation processes for the various components of the substances into different fractions. However, there exists a difference in how the columns perform the operations. The differences are the reasons as to why a given type of separation column is preferred to the other. Therefore, the next section of the paper will entail an overview of the differences between the columns, concerning their efficiency in separation processes and why a given column is commonly applicable in industry compared to the other type.
Additionally, the packed bed columns tend to be economical because the packings tend to reduce the volume of the reactor. Once the volume reduces, the amount of material processed also reduces to an amount that is manageable, and the quality of the product tends to rise due to the maximum attention the responsible parties give to the process. However, for a distillation column, it takes a long time for the components to reach the transition temperature, an act that delays that process, hence calling for a significant amount of the catalyst to speed up the rate of the reaction.
Moreover, the packing of the packed bed reactors tends to reduce the need for the reflux processes. Therefore, there will be a reduced need for extra energy to activate the reaction, as well as a reduced need for the employment of a catalyst in the process (Kiss, Anton & Costin 25). As a result, most people prefer the packed bed reactors to distillation columns, which require a supply of a large amount of energy for the distillation process to take place.
Therefore, it is evident that both types of columns are applicable in contacting separation processes, but the packed bed column is more preferable to the distillation columns, because of the associated high quality of the products, law maintenance and operation cost, low energy requirements due to the reduced need for reflux. Additionally, the packed-bed reactors have a low demand for the catalyst, making it more economical regarding the use of the catalyst and suitable for application in the manufacture of various products.
As a result, it is common practice that the packed bed columns are the most preferable in industry because they offer a cheap technique of doing things (Kiss, Anton & Costin 27). It guarantees the economic returns affiliated to a process because it is possible to achieve the required quality of the product at a constant volume. It also guarantees high yields at low cost and shorter time because the process takes place within a shorter span of time.
In conclusion, separation processes are common in the industry, because the separation processes are the ones that give a wide range of products that serve various purposes in the world. Most of the products of the separation processes are applicable tin the manufacture of other commodities, and that makes separation a very efficient and productive method appliance in industry for the generation of various finished commodities. For example, the distillation of crude oil is the process that leads to the production of motor fuel, as well as kerosene that is applicable for various purposes including lighting and cooking in developing countries. Additionally, most pharmaceutical processes make use of the distillation to generate the various commodities that shall apply in daily life situations as drugs for the treatment of the various disorders. Therefore, the distillation processes are very essential in life situations. The technological advancement tends to make the distillation processes more efficient by introducing the most efficient columns like the packed bed columns.
Works Cited
Kiss, Anton A., and Costin Sorin Bildea. "Revive your columns with cyclic distillation." Chem Eng Prog 111 (2015): 21-27.
Mallaiah, M., and G. Venkat Reddy. "Simulation of continuous packed bed reactive distillation column for the esterification process using activity based kinetic model." Theoretical Foundations of Chemical Engineering 50.4 (2016): 404-413.
Rawlings, James Blake, ed. Dynamics and Control of Chemical Reactors, Distillation Columns and Batch Processes (DYCORD'95). Elsevier, 2014.
