PDF | On Feb 16, , Pande Vishal and others published Revised Edition of A Textbook on Pharmaceutical Engineering. PDF | Introduction Intricate modern pharmaceutical business activities Results and Discussion The model comprises engineering activities of. Major in Pharmaceutical. Engineering. Program Director: Pr Michel Baron, Asst Prof Olivier Lecoq. Objective. This program aims to produce engineers qualified.
|Language:||English, Spanish, Indonesian|
|Distribution:||Free* [*Register to download]|
Pharmaceutical Engineering: principles and practices deals with unit operations and processes utilized in the production of bulk drugs, dosage Format: PDF. PHARMACEUTICAL ENGINEERING. Mixing. Dr. Bhawna Mixing is one of the most common pharmaceutical operations. It is difficult to find a. Bachelor of Engineering with Honours in Pharmaceutical Engineering SIT's Pharmaceutical Engineering (PharmE) programme is the first in Singapore.
Mutagenic toxicity: carried out over 18—24 months under both in vitro and in vivo conditions. Pre-formulation studies Pre-formulation studies need to be carried out in order to determine the physicochemical characteristics of the molecule and thus the most appropriate dosage forms that can be used.
Solubility: in relation to liquid dosage forms and to identify the most appropriate salt to work with. Melting point: to determine crystalline solubility.
Assay development: using more sophisticated equipment and related to drug stability studies. Stability: in both liquid and solid dosage forms.
Microscopy: to identify particle size and crystal formation. Powder flow and compression properties: in relation to dry product dosage forms. Excipient compatibility: to ensure that the final dosage form will perform correctly. Once the pre-formulation studies have been completed, the most appropriate dosage form can be determined, based on such factors as the purpose for which the drug is intended and the physicochemical characteristics of the chemical entity.
Quality life cycle Biopharmaceutical studies As part of the process of finalizing the dosage form, it is necessary to carry out biopharmaceutical studies in order to ensure that the drug reaches the part of the body where it is required, and is maintained at the right concentration for the right period of time. This includes identification of the appropriate dosage levels and frequency.
Distribution: how the drug travels through the body. Metabolism: the way in which the drug is changed by the body. Elimination: how the drug leaves the body.
The amount of drug that reaches the bloodstream, and the speed at which it takes place is called its bioavailability. It is generally measured by means of pharmokinetic plasma studies of drug concentration against time. Stability studies Pre-clinical studies of the final dosage form will extend to include stability studies relating to the primary and secondary packaging materials that are planned to be used. These studies examine the physical, chemical or microbiological deterioration of the drug over time in order to determine the appropriate shelf life that can be guaranteed.
As an alternative to this, accelerated stability studies can be used, in which the packs are exposed to extremes of conditions such as heat, light and moisture. Results thus obtained can then be converted to equivalents for ambient conditions.
The extent of the trials will depend on the nature of the drug and its proposed application.
The trials are generally carried out in a number of stages. Phase I trials These are carried out over a period of three to six months and involve a group of around healthy volunteers. Each subject receives a small dose of the drug and is then monitored for physiological reactions.
Phase II trials These are carried out on patients, since the activity of the drug in healthy subjects may be different to that in subjects suffering from the disease for which the drug is intended. Comparison Of Chemical Reactors S. Reactor Working Application 1. In this process, all the reagents are added at the commencement and no addition or withdrawal is made while the reaction is progressing Fig.
Batch processes are suitable for small production and for processes where a range of different products or grades is to be produced in the same equipment for example, pigments, dye stuff and polymers. Figure 1: Batch Process Figure 2: For example, Haber Process for the manufacture of Ammonia.
Continuous production will normally give lower production costs as compared to batch production, but it faces the limitation of lacking the flexibility of batch production. Continuous reactors are usually preferred for large scale production. Semi Batch Process Process that do not fit in the definition of batch or a semibatch reactor is operated with both continuous and batch inputs and outputs and are often referred to as semi continuous or semi- batch.
In such semi-batch reactors, some of the reactants may be added or some of the products withdrawn as the reaction proceeds. A semi-continuous process can also be one which is interrupted periodically for some specific purpose, for example, for the regeneration of catalyst, or for removal of gas for example, a fermentor is loaded with a batch, which constantly produces carbon dioxide, which has to be removed continuously.
Another example is chlorination of a liquid. Catalytic Processes Most of the chemical reactions either proceed in the presence of catalysts or increases their yield in the presence of catalysts. A catalyst is a substance that, without itself undergoing any permanent chemical change, increases the rate of a reaction. The rate of a catalytic reaction is proportional to the amount of catalyst the contact with a fluid phase reagents. This is proportional to the exposed area, efficiency of diffusion of reagents in and products out, type of mixing turbulent, etc.
The assumption of perfect mixing cannot be assumed.
A catalytic reaction pathway is often multistep with intermediates that are chemically bound to the catalyst. Since the chemical binding is also a chemical reaction, it may affect the reaction kinetics. The behaviour of the catalyst is also a consideration.
Particularly in high temperature petrochemical processes, catalysts are deactivated by sintering, coking and similar processes. Homogeneous Reactions Homogeneous reactions are those in which the reactants, products and any catalyst used form one continuous phase; for example, gaseous or liquid. Homogeneous gas phase reactors will always be operated continuously.
Tubular Pipe line reactors are normally used for homogeneous gas phase reactions; for example, in the thermal cracking of petroleum, crude oil fractions to ethylene, and the thermal decomposition of dichloroethane to vinyl chloride. Homogeneous liquid phase reactors may be batch or continuous. Batch reactions of single or miscible liquids are almost invariably done in stirred or pump around tanks.
The agitation is needed to mix multiple feeds at the start and to enhance heat exchange with cooling or heating media during the process. Heterogeneous Reactions In a heterogeneous reaction two or more phases exist and the overriding problems in the reactor design is to promote mass transfer between the phases.
The possible combination of phases are: For example, reactions such as the nitration of toluene or benzene with mixed acids, emulsion polymerizations, saponification, etc.
Mechanically agitated tanks are favoured because the interfacial area can be made large as much as times that of spray towers. When agitation is sufficient to produce a homogeneous dispersion and the rate varies with further increase of agitation, mass-transfer rates are likely to be significant.
For example, platinum acts as a catalyst in the hydrogenation of oils. In the design of reactors for liquids in the presence of granular catalysts, account must be taken of heat transfer, pressure drop and contacting of the phases and sometimes provision for periodic or continuous regeneration of deteriorated catalyst. Several different kinds of vessel configurations for continuous processing are in commercial use.
Most solid catalytic processes employ fixed beds. Although fluidized beds have the merit of nearly uniform temperature and can be designed for continuous regeneration, they cost more and more, difficult to operate, require extensive provisions for dust recovery, and suffer from back mixing. For example, gasoline cracking using zeolite catalysts. It may be in a fixed bed or it may be suspended in fluid mixture.
In trickle bed reactors both phases usually flow down, the liquid as a film over the packing. In flooded reactors, the gas and liquid flow upward through a fixed bed, the slurry reactors keep the solids in suspension mechanically; the overflow may be a clear liquid or a slurry, and the gas disengages from the vessel.
In fluidized bed reactors a stable bed of solids is maintained in the vessel and only the fluid phases flow through, except for entrained very fine particles. For example, decomposition of azides, diazo compounds and nitramines. A product of reaction also is often a gas that must diffuse away from a remaining solid, sometimes through a solid product. Thus thermal and mass-transfer resistances are major factors in the performance of solid reactions.
For example, finely divided nickel is used in the preparation of nickel carbonyl b. Bio-chemical processes such as fermentation oxidation of studies sludges, production of proteins etc.
There could be at least three ways in which the reaction between a gas and a liquid may be made to react, that is, the gas may be either dispersed as bubbles in the liquid Fig. The choice between these models is critical and is dependent on factors. Such as magnitude and distribution of the residence times of the phases, the power requirements, the scale of the operation, etc.
Figure 3: Bubble Tower Figure 4: Spray Tower Figure 5: Falling Liquid Film Figure 6: However, it is convenient to classify reactor designs into the following broad categories. Stirred Tank Reactors: They are operated as batch reactors or continuous reactors. Several reactors may be used in series. Figure 9: CSTR with Air Heater The stirred tank reactor can be considered the basic chemical reactor; modeling on a large scale the conventional laboratory flask.
Tank sizes range from a few litres to several thousand litres. They are used for homogeneous and heterogeneous liquid-liquid and liquid-gas reactions and for reactions that involve freely suspended solids, which are held in suspension by the agitation. As the degree of agitation is under the designers control, stirred tank reactors are particularly suitable for reactions where good mass transfer or heat transfer is required. When operated as a continuous process the composition in the reactor is constant and the same as the product stream and except for very rapid reactions, this will limit the conversion that can be obtained in one stage.
The power requirements for agitation will depend on the degree of agitation required and will range from about 0. Tubular Reactors: Tubular reactors are generally used for gaseous reactions, but are also suitable for some liquid phase reactions. If high heat transfer rates are required small diameter tubes are used to increase the surface area to volume ratio.
Several tubes may be arranged in parallel, connected to a manifold or fitted into a tube sheet in a similar arrangement to a shell and tube heat exchangers. For high temperature reactions the tubes may be arranged in a furnace. Packed Bed Reactors: In chemical process industries, the emphasize is mainly on the designing of catalytic reactors. Industrial packed bed catalytic reactors range in size from small tubes, a few centimeters diameter to large diameter packed beds.
Packed-bed reactors are used for gas and gas-liquid reactions. Packed Bed Reactor Fig. Multibed Reactors with Interstage Heaters D. Fluidised Bed Reactors: It is very important to chemical engineering because of its excellent heat and mass transfer characteristics.
The essential features of a fluidised bed reactor is that the solids are held in suspension by the upward flow of the reacting fluid. This promotes high mass and heat transfer rates and good mixing. The solids may be a catalyst, a reactant in fluidized combustion processes or an inert powder, added to promote heat transfer.
Though the principal advantage of a fluidised bed over a fixed bed is the higher heat transfer rate, fluidised beds are also useful where it is necessary to transport large quantities of solids as part of the reaction processes, such as where catalysts are transferred to another vessel for regeneration. This is the limitation of the process. Figure Flow Distribution in a Fluidized bed Figure Aerosol Nanoparticle Reactor Fundamentals of Reactor Design The design of a chemical reactor deals with multiple aspects of chemical engineering.
Chemical Reactions: Brief representation of the chemical change in terms of symbols and formulae of the reactants and products is called a chemical equation. For example, when zinc reacts with hydrochloric acid, zinc chloride and hydrogen are produced.
Equations such as above, in which no attempt has been made to equalize the number of atoms of various elements on both the sides are called Skeleton equations. Therefore, in order to equitize the number of atoms of various elements, various species are multiplied with appropriate numbers.
This process is called balancing of a chemical equation. A chemical equation, therefore must fulfill the following conditions: For example, elementary gases like hydrogen, oxygen, etc. A chemical equation has both qualitative as well as quantitative significance. Qualitatively, a chemical equation tells us the names of the various reactants and products. Quantitatively, it expresses a The relative number of molecules of the reactants and products taking part in the reaction.
For example: Quantitatively, it conveys the following information. The chemical equation can be made more informative by incorporating the following changes: Enthalpy is the total energy associated with any system which includes its internal energy and also energy due to environmental factors such as pressure-volume conditions.
It is denoted by H. Chemical equations give the quantitative relationship between the reactants and the products. This quantitative information can be utilized to carry out variety of calculations which are required many a times, to assess the economic viability of the chemical process. Calculations based on the quantitative relationship between the reactants and the products are also referred to as Stoichiometry.
The word stoichiometry is derived from the Greek words Stoicheron meaning element and metron meaning measure. Stoichiometry is therefore, that area of chemistry and chemical technology on which determination of quantities of reactants and products of chemical reaction is based. Chemical Energetics: Chemical reactions are always associated with energy changes.
Quite often, the energy change accompanying a chemical reaction is more significant than the reaction itself. The branch of science which deals with the energy changes associated with chemical reactions is called chemical energetics. The energy changes occurring during the chemical reactions may not always appear as heat energy, but also as electrical energy, work energy and radiant energy as well. These energy changes take place because during chemical reactions certain bonds are cleaved and certain new bonds are formed.
Energy is consumed during cleavage of bonds while energy is released during the formation of bonds. Since the bond energy varies from one bond to another, the chemical reactions are always accompanied by absorption or release of energy. Most of the time the energy is in the form of heat. Therefore, it becomes imperative that some concepts of thermodynamics may be understood.
Thermodynamcis literally means conversion of heat into work and vice-versa because therm refers to heat and dynamics refers to movement. Thermodynamics may, therefore, be defined as the branch of science which deals with the quantitative relationship between heat and other forms of energies.
When thermodynamics of chemical processes is studied, it is often referred to as chemical thermodynamics. Thermodynamics is primarily based upon three fundamental generalisations, popular as Laws of Thermodynamics. They are: Therefore, the design of an industrial chemical reactor must satisfy the following requirements: The chemical factors: The kinetics of the reaction.
The design must provide sufficient residence time for the desired reaction to proceed to the required degree of conversion. The mass transfer factors: With hetereogeneous reactions, the reaction rate may be controlled by the rates of diffusion of the reacting species, rather than the chemical kinetics.
The heat transfer factors: The removal or addition of the heat of reaction. The safety factors: Economic factors: Minimum amount of money should be required to download and operate. Normal operating expenses include energy input, energy removal, raw material costs, labour, etc.
Energy changes can come in the form of heating or cooling, pumping, agitation, etc. The need to satisfy these are interrelated and often contradictory factors makes reactor design a complex and difficult task. However, in many instances one of the factors will predominate and will determine the choice of reactor type and the design method.
Design Procedure and Reactor Designing An industrial chemical reactor is a complex device in which heat transfer, mass transfer, diffusion and friction must be considered and it must be safe and controllable. A successful commercial unit is an economic balance of all these factors. A general procedure for reactor design is outlined below: The kinetic and thermodynamic data on the desired reaction is initially collected.
Values will be needed for the rate of reaction over a range of operating conditions, for example, pressure, temperature, flow rate and catalyst concentration. This data may be normally obtained from either laboratory or pilot plant studies. Data on physical properties is required for the design of the reactor. This may be either estimated, or collected from the literature or obtained by taking laboratory measurements.
The rate controlling mechanism which has a predominant role is then identified, for example, kinetic, mass or heat transfer. A suitable reactor type is then chosen, based on experience with similar studies or from the laboratory and pilot plant work. Selection of optimal reaction conditions is initially made in order to obtain the desired yield 6.
The size of the reactor is decided and its performance estimated. Since exact analytical solutions of the design relationship are rarely possible, semiemperical methods based on the analysis of idealized reactors are used. A preliminary mechanical design for the reactor including the vessel design, heat transfer surfaces etc. The design is optimized and validated An approximate cost of the proposed and validated design is then calculated.
In choosing the reactor conditions, and optimizing the design, the interaction of the reactor design with the other process operations must not be overlooked. The degree of conversion of raw materials in the reactor will determine the size and the cost of any equipment needed to separate and recycle unreacted materials. In these circumstances the reactor and associated equipment must be optimized as a unit. Reactor Designing — Mathematical Models Chemical reactors are vessels designed to contain chemical reactions.
The design of a chemical reactor deals with multiple aspects of chemical engineering including mathematical modeling.
A model of a reaction process is a set of data and equation that is believed to represent the performance of a specific vessel configuration mixed, plug flow, laminar, dispersed, etc. Chemical engineers, design reactors to maximize net present value for the given reaction. Designers ensure that the reaction proceeds with the highest efficiency towards the desired output product, producing the highest yield of product.
The equations used in mathematical modeling include the stoichiometric relations, rate equations, heat and material balances and auxiliary relations such as those of mass transfer, pressure variation, residence time distribution, etc. Correlations of heat and mass — transfer rates are fairly well developed and can be incorporated in models of a reaction process, but the chemical rate data must be determined individually.
Since equipments are now widely available to obtain such data, hence an initial exploratory work can be carried out. Once fundamental data is obtained, the goal is to develop a mathematical model of the process, which may be further utilized to explore possibilities such as product selectivity, start-up and shut down behaviour, vessel configuration, temperature, pressure and conversion profiles, etc.