The raw materials are treated through physical steps to make it suitable for chemical reaction. The subject Unit Operations is based on fundamental laws, physicochemical principles. Unit Operations gives idea about science related to specific physical operation; different equipments-its design, material of construction and operation; and calculation of various physical parameters mass flow, heat flow, mass balance, power and force etc. Examples of Unit Operations are listed in Table 1.

Author:Douzuru Zulusida
Language:English (Spanish)
Published (Last):27 January 2010
PDF File Size:3.7 Mb
ePub File Size:16.79 Mb
Price:Free* [*Free Regsitration Required]

The raw materials are treated through physical steps to make it suitable for chemical reaction. The subject Unit Operations is based on fundamental laws, physicochemical principles. Unit Operations gives idea about science related to specific physical operation; different equipments-its design, material of construction and operation; and calculation of various physical parameters mass flow, heat flow, mass balance, power and force etc. Examples of Unit Operations are listed in Table 1.

To perform chemical conversion basic knowledge of stoichiometry, reaction kinetics, thermodynamics, chemical equilibrium, energy balance and mass balance is necessary.

Many alternatives may be proposed to design a reactor for a chemical process. One design may have low reactor cost, but the final materials leaving the unit need higher treatment cost while separating and purifying the desired product. Therefore, the economics of the overall process also play a vital role to select a suitable alternative design. Each chemical process consists of series of assembly that are organized systematically to achieve the goal.

The physical and chemical steps in a process are set with the help of combined knowledge and experience of engineers, technologists and cost experts to produce a product. The individual operations have some common phenomena and are based on the same scientific principles e.

Heat transfer is the common phenomenon in evaporation, drying and crystallization. Table 2 A process designer designs a chemical process considering 1 efficiency of process and equipments 2 Safety with respect to the process, raw chemicals, finished products and long term effect on environment 3 financial viability of the products as demanded by the purchaser.

Fluid flow from one storage to reaction vessel. Filtration 6. Separation Movement of Solid 1. Fluid bed drying 3. Settling 4. Blending of powder 5. Powder flow 6. Conveying Mass Transfer Drying, Evaporation, distillation, chemical reaction, diffusion, extraction, humidification, adsorption, chemical kinetics. On the other hand conversion of starch to dextrose with the help of acid catalyst is a typical chemical reaction which involves transportation of raw materials, physical steps of mixing the reactants, heat transfer, reaction kinetics, fluid flow, separation of products, product purification, drying, screening, conveying and packaging.

General flow chart exhibiting product formation has been shown in Fig. The figure shows the sequence of basic components generally used in a typical chemical process in which each block represents a stage in the overall process for producing a product from the raw materials. The design of the process involves selection, arrangement of the stages and the selection of specification and design of the equipment required to perform the stages. Both theory and practice should be considered to yield designs for equipments that can be fabricated, assembled, operated and maintained.

A physical quantity is expressed with its magnitude and unit. Magnitude or numerical value tells us how many units are needed to make that up to required quantity. Because of growing importance of the SI system in science and engineering, it becomes necessary to put effort on its universal adoption as the exclusive system for all engineering and science. The SI system covers the entire field of science and engineering including electromagnetic and illumination.

The units are derivable from some basic equations with the help of arbitrarily chosen standards for mass, length, time, temperature, mole and arbitrarily chosen numerical values for the proportionality constants of the following basic equations. Unit of K is derived from the units used for measuring the variables in the equation. So, unit force lb force, gm force can be defined using unit mass. Length, mass, time, heat and temperature are primary or fundamental units. Secondary units are expressed in terms of primary ones.

The units of force, acceleration are secondary type. This age old mass balance concept is useful for assessing a process and sometimes improving management practices including waste reduction, on site tracking of toxic chemicals and transportation into and out of a facility. Moreover, material balance over a process helps to check performance against design, instrument calibration and to identify the source of material loss.

It also helps to extend often the limited data available from the plant instrumentation. Therefore, a good understanding of material balance is necessary. Einstein showed that mass and energy are equivalent. Energy can be converted into mass and mass into energy. The loss of mass associated with the production of energy is significant in nuclear reactions. In processes of nuclear fission and condensation the law of conservation of mass becomes invalid, but in ordinary industrial processes mass balance is highly practiced and it is accepted that energy and matter are to be separately conserved.

Material balance is carried over a certain element of volume. In steady state process i. A mass balance can be written for individual elements, compounds and for total materials. Direct measurements of quantity of components of both entering and leaving streams in a process during a given time interval needs no calculation. Calculation of material balance is indispensable when direct measurement of one or more components is not possible. The measurements require knowledge of conservation of mass and of the standard units for expressing mass data, composition, concentration, flow rate of flowing streams in a process.

If there is any change of physical or chemical properties of flowing streams, that must be accountable. Appropriate judgement must be exercised in selecting the methods for sampling, analysis and in choosing the frequency and duration of data acquisition of mass flows within a process. Gross deviation from mass balance indicates that errors have been made in sampling and quantifying one or more mass balance components or else it needs some relevant information.

So, precise evaluation is needed. In a mass balance operation, all chemical inputs to a manufacturing process and outputs from it and accumulations within are first identified and the masses are measured. The mass of inputs should be equal or closely approximate the mass of outputs plus accumulations.

Draw a block diagram of the process to show significant steps by flow sheet diagram. List all the available data. Indicate known quantities of the parameters on the block diagram. List all the information. Decide the system boundaries. Write out all the chemical reactions involved for the main products and byproducts. Note any other constraints if any, like azeotropes, phase equilibria, tie substances.

Check the number of conservation equations that can be written and compared with the number of unknowns. Decide the basis of calculation. The order of steps may vary according to need of the problem. With simple problems, having only one or two recycle loops; the calculation can often be simplified by careful selection of the basis of calculation and the system boundaries. Following is an example of block diagram showing the main steps in the balanced process for the production of vinyl chloride VC from ethylene C2H4.

Each block represents a reactor and several other processing units Fig. In this problem flow of C2H4 and DCE are unknown that can be calculated on the basis of the production rate of vinyl chloride with the help of algebraic method. Basis of Calculation: The initial step in tackling a mathematical problems starts with selection of a basis of calculation. This makes the solution of problem easier and simple. If the compositions of substances involved in a chemical reaction are given in weight percent, pound or gm of one of the substances entering or leaving system of a continuous process may be chosen as the basis of calculations and finally, the calculated values may be converted to other basis as per the desired statement of problem.

A choice of basis is made before calculation depending upon desired information on parameters like time, mass, mole, volume for gas , and batch for batch process. Calculate the airflow rate. Normal content of CO2 in air is 0. Solution: Inlet air contains 0. Excess Reagent In most chemical reactions carried out in industry, the components are seldom fed to the reactor in exact stoichiometric proportions. A reagent may be supplied in excess of the amounts theoretically required for combination with the others in order to maximize the use of an expensive reagent or to ensure complete reaction of a reagent.

As a result, the products contain some of the unreacted reactants. The amount of desired compound is determined by the amount of limiting reactant. The percentage excess of any reactant is defined as the percentage ratio of the excess to the amount theoretically required by the stoichiometric equation for combination with the limiting reactant.

It happens due to insufficient time or opportunity for completion to the theoretically possible equilibrium. The degree of completion of a reaction is ordinarily expressed as the percentage of the limiting reacting material, which is converted or decomposed into other products.

Calculate the moles of air required per mole of fuel. Conversion is a measure of the fraction of the reagent that converts due to reaction. If the conversion of a valuable reagent in a reaction process is appreciably less than percent, the unreacted material is recycled.

Yield is a measure of the performance of a reactor or plant. Calculate percentage of conversion of ethylene and the yield of ethanol and ether based on ethylene.

Solution: Basis: moles of feed Easier calculation on the basis feed components Inert remains unchanged. Yield of product ethanol and byproduct are calculated on the basis of ethylene, not on water as water is relatively cheaper than ethylene.

Water is fed in excess. Ethylene is the reagent. Problems on Material Balance 1. The composition of gas derived by the gasification of coal is, volume percentage: carbon dioxide 4, carbon monoxide 16, hydrogen 50, methane 15, ethane 3, and benzene 2, balance nitrogen. If the gas is burnt in a furnace with 20 per cent excess air, calculate: a The amount of air required per kmol of gas b The amount of flue gas produced per kmol of gas, c The composition of the flue gases, on a dry basis Assume complete combustion.

Ammonia is removed from a stream of air by absorption in water in a packed column. The air entering the column is at mmHg pressure and 20oC. The air contains 5.


Pharmaceutical Engineering By CVS Subramanyam

Arak Clear 2 learn preferred units Simply valuable. Shop with an easy mind and be rest assured that your online shopping experience with SapnaOnline will be the best at all times. It happens, just reset it in a minute. International Shipping at best shipping prices! See all free Kindle reading apps.


Ballmill diagram from cvs subrahmanyam pharmaceuticalengineering textbook



Download: Pharmaceutical Engineering Cvs Subrahmanyam.pdf



Download: Cvs Subrahmanyam Pharmaceutical Engineering.pdf


Related Articles