Interview Question

1-How can a chemical production engineer improve the process with respect to yield & quality? (answer)

2-what is the difference between unit operation and unit process ? (answer) In unit process there is no any physical changes but chemical changes occur. but in unit operation no any chemical changes, only physical chages occur

3-What is are the main terms in Unit Operations? and what is its charecteristics? (answer)

4-what is unit operation ? (answer) Unit operation involves all types of operations carried out in chemical and process industries which do not involve any chemical reaction. Hence the chemical properties of the substance do not change however the physical properties may change. Examples are Size reduction operation Different type of separation operations and heat transfer operations

In chemical engineering and related fields a unit operation is a basic step in a process. For example in milk processing homogenization pasteurization chilling and packaging are each unit

operations which are connected to create the overall process. A process may have many unit operations to obtain the desired product. Historically the different chemical industries were regarded as different industrial processes and with different principles. In 1923 William H. Walker Warren K. Lewis and William H. McAdams wrote the book The Principles of Chemical Engineering and explained the variety of chemical industries have processes which follow the same physical laws. They summed-up these similar processes into unit operations. Each unit operation follows the same physical laws and may be used in all chemical industries. The unit operations form the fundamental principles of chemical engineering. Chemical engineering unit operations consist of five classes:

1. Fluid flow processes including fluids transportation filtration solids fluidization 2. Heat transfer processes including evaporation condensation 3. Mass transfer processes including gas absorption distillation extraction adsorption drying 4. Thermodynamic processes including gas liquefaction refrigeration 5. Mechanical processes including solids transportation crushing and pulverization screening and sieving Chemical engineering unit operations also fall in the following categories:

• • •

Combination (mixing) Separation (distillation)

Reaction (chemical reaction)

Chemical engineering unit operations and chemical engineering unit processing form the main principles of all kinds of chemical industries and are the foundation of designs of chemical plants factories and equipment used

5-what kinds of questions may employers of chemcial engineering companies ask me? (answer) Mr. 1.Tell me about your self ? (They will test your way of talking and english) 2.In which are you intrested? (mass tr. or heat tr. and etc..) 3.For freshers most of the qns will come from Mass tr. and heat tr. 4.In which are you intrested to work? (procee production and etc. ) 5.And some general qns like.....If you are the manager or MD of this company this company then how you will control the employer and how you will feel and etc... Surri

6-why the efficiency of multiple effect evaporate is less then single effect evaporater? (answer) What is meaning of Eficiency? If meaning is water evaporation per unit heat transfer area provided in Evaporator Then the answer is 1. Single effect LMTD ( Log Mean Temperature Difference) is High 2. In mutiple effect evaporator Each Effect LMTD is lower.

7-how to seperate water from benzene? (answer) Water and Benzene are immicible. On standing it will separate in two layer. Bottom will be benzene layer and top will be water layer. However Benzene has some solubility say 0.2W/W% water. This water can be remove from benzene by adsoption on Molecular sieve.

8-What is physical significance of chemical potential & fugacity? (answer) --- Like there is gravitational potential or electrostatic potential there is chemical potential.

It is basically change in the internal energy of the system by addition of a new particle at constant volume and entropy. In terms of free energy, its the change in Gibbs free energy of a system by addition of a particle at constant temperature and pressure. So basically it tells you about the reactivity of a component in a phase. Transfer of molecule will always occur from high potential to low potential. Fugacity is escapability that is tendency of a particle to prefer one phase over other. The particle will be present in the phase having low fugacity (where the escapability is least). In terms of chemical potential it is the measure of how much the chemical potential of a component in a phase differs from the chemical potential in standard state, due to change in Pressure or mol fr of component. Fugacity is analogous to partial pressure when applying thermodynamics to any non ideal system for any component. For pure ideal gases fugacity --> partial pressure.

--- Chemical potential is the main driving force for any mass transfer operation to be occured and is very closely related with concentration of that corresponding species therefore we generally take concentration term instead of chemical potential while for very high pressures we generally calculate fugacities instead of pressures.

9- How to design distillation column? What is the role of chemical engg. in technology transfer in pharma company? (answer)

10- What is proplan, prodyne?

(answer)

11- What are the basis for selecting Deaerator operating pressure and temperature? (answer) Generally deaerator is designed slight high pressure than atm. around 1.2ksc Temp is maintained at about 120-130 degree centigrade because dm water should supply at this temp process heat is recovered by circulating this dm water down stream of deaerator bfw pump is there which increases pressure up to desired value. Designing of high pre and temp shell also too much costlier.

12- Why we use Flairing in the crude oil refining industry? (answer) Crude oil has many chemical components in it i.e. Natural Gas LPG Gasoline Diesel if you can see there the fraction of those components is different sometime gasoline is higher and

sometime diesel. the flaring is used to burn Natural Gas which is very small fraction in crude oil and not economical to store as it must use compressor. Furthermore the flaring of NG can burn poisonous gas contained in crude oil.

13- Difference between Distillation and Fractionation?

(answer) Distillation and fractionation and fractional distillation are all same. which all means seperation of key components based on the relative volatility and/or boiling points. there is no difference at all between them....!!

14- Discuss the important properties of solvent used in LEACHING? Leachng is unit operation in which a solid mixture is contacted with a liquid solvent for removal of one or more soluble constituents of solid mixture and it is also called a solid liquid extraction. The solvet used in it should be a selective solvent and should have low viscosity for it to circulate freely.

15- How does actual Capillary Action takes place?

The capillary action is due to surface tension. The surface tension force is the relative action between the adhesive force to the cohesive force

16- What is 3rd Law of Thermodynamics??

The entropy of a substance is zero at absolute zero temperature(0k)

You have two layer of material to provide insulation. They have heat transfer co-efficient (k1>k2). How will you obtain better insulation? (answer) --- The material which has lower thermal condutivity should be insulated first or the 17-

insulation should increase order of k to get effective insulation.

--- By applying higher insulation layer at lower surface & lower at upper surface Q/A K1*(dT/dX) Q/A K2*(dT/dX) K1(DT)1+K2DT2 Q/A*X

FOR(q/A) MAX. d(Q/A)/dX 0

18- What is the solid angle? The solid angle Ω is the angle in three-dimensional space that an object subtends at a point. It is a measure of how big that object appears to an observer looking from that point. For instance a small object nearby could subtend the same solid angle as a large object far away.

19- Why Iron Carbide diagram can be established upto 6.67% only? What are structure beyond

6.67% carbon?

20- When salt is added to water, what happens to its freezing point? Freezing point decreases