Mechanical Operation: Practical Questions & Answers

a)      The power and power number for a helical ribbon and propeller in turbulent region.
Ans: the power number for a helical ribbon is lesser but the power consumption will be more due to high rotational speed required in turbulent region.

b)      Do the particles move along with the balls in the ball mill?
Ans: Particles move along with the ball depending on their size shape and friction with wall and
        crushed by attrition, rubbing and impact.

c)      Define mesh number and also explain the difference between BSS 5 and Tyler 5 mesh screens.
Ans: Mesh number is the number of square openings in 1 inch. the BSS5 and Tyler 5 mesh have
        different openings due to different wire diameters.

d)     Relation between slurry feed concentration and concentration per unit volume of filtrate.
Ans: The volume of filtrate (liquid) is less than that in slurry feed because some water is present in
        the cake. 

e)     Why the pressure drop doesn't change with velocity of fluid in fluidized bed?
Ans: after fluidization the bed start expanding and porosity increases which leads to constant pressure.

f) In scale up of a baffled vessel (D1:D2 = 1:3), in order to maintain an equal rate of mass transfer 
(equal power/volume), under turbulent condition, the ratio of agitator speed (N2:N1) should be:
Ans: equal power/volume= n^3D^2 is constant.

g)   How the settling velocity of a particle can be increased to achieve faster separation?
Ans: To increase the settling velocity, the density and viscosity can be decreased by increasing the
        temperature.

h) The significance of Froude number in power calculation of mixer/agitator.
Ans: Froude number signifies the effect of vortex formation. in a baffled tank or in the process 
       where Reynolds number is less than 300, Froude number is insignificant. 

i) Efficiency of crushing equipment is defined as: 
Theoretical power required to crush the material/actual power consumption

j) What kind of equipment would you suggest for reducing size of hard material: impact/cutting

k) In order to produce solid particles between 5 and 10 µm, the appropriate size reducing equipment 
     is fluid energy mill.

l) The clarifying filter could be used to filter a slurry containing 0.05 % CaCO3.

m) Sticky and pasty materials are transported by: screw (ribbon) conveyor

n) The porosity of a compressible cake is minimum the filter medium.

o) What are the methods available for determination of particle size?
Ans: Screening, SEM, TEM, particle size analyser. 

p)  Why are different sizes of ball used in Ball mill? What will happen if you use same sizes balls?
Ans: different size balls will have different critical speed, leads to different impact time.

q) Can the screening prior to classification be beneficial? Explain.
Ans: for a close size range, classification will give sharp separation according to their settling velocity.

r) To handle large gas flows what can be better: a large diameter cyclone separator or a no of 
small diameter cyclones separators and why.
Ans: large diameter cyclones will have less efficiency.

Fluid Flow: Type of Flow

The flow can be classified as uniform flow and non uniform flow or steady flow and unsteady flow. Uniform Flow: when the velocity is same throughout the system at any time, it is called uniform flow.  the velocity can be different wrt time.

Steady Flow: when the velocity is constant with respect to time at any point. the velocity can vary with position. 

In a water tank, water comes out of the tank under gravity, the velocity will change with time due to decrease in height of water in tank. i.e. unsteady flow but according to the continuity equation velocity will be same i.e uniform flow.

 In a venturimeter, the area changes, so does the velocity i.e. non-uniform flow. if the flow rate is constant, then the velocity will be constant at any point with time i.e. steady flow.  

Fluid Flow: Flow Measurement Devices

To measure fluid flow rate, there are different flow meters like venturimeter, orifice meter, wier, notches and rotameter.

Venturimeter, orifice meter and rotameter are used to measure flow in closed pipe/channel while wier, notches are used for open flow like river. 

These flow meters are classified as variable head meter and variable area meter. venturimeter, orifice meter are variable head meters where velocity head is converted into pressure head and in rotameter the area of flow in rotameter increases along the flow. when the fluid flows in rotameter, the float starts rising due to buoyancy and drag force. As the flow rate increases, the drag force ( at earlier point) increases that takes the float up in the meter, where the area is larger, leads to decrease in velocity to the earlier value and the the float attains equilibrium.  

Mechanical Operation: Particle Size

A particle can have any shape, which can be grouped into two regular shape like sphere, cubic, cylinder and irregular share like shape of stone or gravel. The size of any particle other than spherical is found based on some characteristic property like
Surface area: reaction in packed bed
Surface area per unit volume i.e. Sauter Diameter: Fluidization, Filteration
Volume: settling  of particle,
The effective diameter of a mixture of different size particles is calculated depending on different apllications. 

Mechanical Operation: Screen Efficiency Calculation

In a screening operation of feed size from mesh 4 to 45, the fraction of material retained on screen 8 and 14 as follows

Screen	Feed	Coarse fraction (Screen 8)	Middle fraction (Screen 14)	Fine fraction
4/6	18.5	64	4.2	0
6/8	27.5	24	35.8	0
8/14	39.5	12	49.1	46.7
14/20	9.1	0	10.1	20.2
20/28	3.4	0	0.8	19.6
28/35	2.0	0	0	13.5

To find the screen efficiency we have to calculate recovery and rejection
Recovery is the ratio of desired material in product to desired material in feed and rejection is undesired material in reject to undesired material in reject.
For an 8 mesh screen desired material is +8 fraction i.e. 4/6 and 6/8 (0.88) and undesired material is -8 fraction i.e. 8/14 (0.12).
for 14 mesh screen, desired material is +14 fraction i.e. 4/6, 6/8,8/14 (0.891) and undesired material is -14 fraction i.e. 14/20, 20/28 (0.109).

for basis of 100 gm of feed:
material bal of 4/6 and 6/8 fraction: coarse fraction=25
material bal of 14/20 and 20/28 fraction: middle fraction=60
material bal of 28/35 fraction: fine fraction=15

Efficiency of 1st screen:
Recovery of 1st screen: (0.88*25)/46=0.478
Rejection of 1st screen: [1-(0.12*25)/54]=0.944

Efficiency of 2nd screen:
Desired material in product (retained on 2nd screen): 4.2+35.8+49.1=0.891
Desired material in feed (2nd screen)= 18.5+27.5+39.5-25(retained on 1st screen)=60.5
Recovery of 2nd screen= (0.891*60)/60.5=0.88
Undesired material in product:0.101*60=6.54
Desired material in feed (2nd screen)=9.1+3.4+2=14.5
Rejection of 2nd screen= 6.54/14.5=0.451

Heat Exchanger: LMTD

In heat exchanger, we calculate log mean temperature difference (LMTD). LMTD gives the logarithmic mean of temperature difference between  hot streams and cold streams. there are other types of mean also like arithmetic mean, geometric mean, harmonic mean. In heat exchanger we use log mean because the temperature profile is logarithmic in a heat exchanger. in case of same temperature difference at the two ends of a heat exchanger which can be in counter current flow, arithmetic mean temperature difference is used.

Practical Aspects: can we increase the heat transfer rate by attaching fins to the tubes? 

Fluid Flow: Bernoulli theorem applicability

Bernoulli theorem is based on the principle of conservation of total energy with fluid. When the flow is divided into 2 or more streams, then how can we apply the Bernoulli theorem?

we can apply continuity equation, if density remains constant then Q1= Q2 + Q3. for same area velocity will be in relation v1=v2+v3. but will v2 be equal to v3? 

The relation between v2 and v3 will be found out by applying Bernoulli theorem. The total energy in will be equal to sum of the total energy out with two streams, but the energy per unit mass/weight will be same at any point in the fluid. So Bernoulli theorem can be applied between any two points.  

Mechanical Operation: Filtration and Fluidization Questions

1.      A constant pressure filtration test gave data that can fit an expression dt/dV = 9.3 V + 8.5; (t in seconds, V in liters). If the resistance of the filter medium is assumed unaffected with pressure drop and the compressibility coefficient of the cake is 0.3, what will be the time taken for the collection of 3.5 liters of filtrate at a filtration pressure twice that used in the test.     

2.      A pressure filter is operated in the constant rate mode to yield 10 m³ in the first ten minute, as the pressure increases from zero. In the next 20 minutes the filtration was continued at constant pressure, after which it was stopped. Assume filter medium resistance is negligible and the cake is incompressible.

a) Estimate the total volume of filtration obtained.

           b) Determine washing time if the volume of wash liquid equals the volume of filtrate obtained.

3.      Solid particles having a size of 0.12 mm, sphericity 0.88 and a density of 1000 kg/m³ are to be fluidized using air at 2 atm abs and 25°C. The voidage at minimum fluidizing conditions is 0.42. The cross section of the empty bed is 0.3 m² and the bed contains 300 kg of solid. Take viscosity of air 0.0185 cP.

a) Calculate the pressure drop across the bed.

b) Calculate the minimum fluidization velocity using Ergun’s equation for calculating pressure drop.                                  

   4.    A packed bed is composed of cylinders having a diameter of 0.02 m and height = 1.5 Diameter.           The density of the packed bed is 980 kg/m³ and the density of the solid cylinder is 1500 kg/m³.           Calculate the porosity of the bed, effective diameter and sphericity of the particle.

Chemical Reaction Engineering: CSTR vs PFR

To carry out reaction, there are two kinds of continuous reactors used: CSTR and PFR. In CSTR the concentration remains constant throughout the reactor which is equal to outlet concentration, while in PFR the concentration changes along the length of reactor. The rate of reaction depends on the concentration of the reactant for a non zero order reaction. Therefore,  the rate of reaction in CSTR remains constant corresponding to out concentration of the reactant, but the rate of reaction decreases along the length of reactor in PFR.

The shaded area corresponds to the volume of reactor required to carry out reaction. So, if the rate of reaction decreases as the concentration decreases, that means (1/-rA) increases, the rate of reaction in PFR is high intially and decreases along the length of reactor. So it can be seen that volume in case of PFR is less than that required for CSTR.
The volume required to achieve a specified conversion for a positive order reaction is less when we connect CSTRs in series than a single CSTR of volume equal to the sum of the volume of CSTRs connected in series. this is because of the increased rate of reaction in small CSTR. while in PFR the volume reamains same whether we use a single PFR or PFRs connected in series.

Mechanical Operation: Agitation and Mixing

Agitation is used to maintain homogeneity in the system while mixing is used to mix two of more phases in one phase. if we have calcium carbonate and water, initially we have 2 phases, as we start mixing it after some time it will form slurry and this slurry has to be agitated to make its concentration uniform. One more example of agitation is related to curd, when we agitate curd, ghee will come over and the rest yogurt (lassi) will remain below.

For agitation we can use Impellers which are categories in 3: Propeller, Turbine and High efficiency impellers.

Propellers produce axial flow like marine propeller, turbine produce generally radial but also axial like mixture grinder in home and improved of turbine is high efficiency impeller which reduces the power consumption. 

Heat Transfer and Thermodynamics

In chemical engineering we study heat transfer and chemical engineering thermodynamics both involve transfer of heat, yet there is difference between study of heat transfer and thermodynamics. In heat transfer, we study the system when heat transfer is taking place. like cooling of hot tea as time proceeds, while in thermodynamics we study the system before and after the heat transferred has taken place i.e. the state of hot tea and state of cold tea. The conclusion can be drawn that in heat transfer we can find the state of the system as a function of time while in thermodynamics we can determine the state of the system after the process has taken place.   

Mechanical Operation: Constant Pressure and Constant Rate Filteration

The total pressure drop is sum of the pressure drop across cake and filter medium. The cake filtration equation is obtained as follows:

The batch cake filtration can be carried out either at constant rate or constant pressure. If the pressure is held constant the rate of filtration will decrease with time and if the rate of filtration is to be held constant then pressure has to be increased due to rise in cake resistance with time. 

Mechanical Operation: Specific Cake Resistance

In filtration of high concentrated slurry, formation of cake takes place at the surface of filter medium. The pressure drop across the cake can be found by modifying the Kozeny-Carman equation which is used for finding pressure drop through bed of particles in laminar flow conditions.

As resistance is defined as driving force divided by flux. similarly here driving force is ΔPcA and flux is velocity v. and specific resistance will be resistance per unit mass of cake. Therefore, resistance is 

Here, the resistance also includes the resistance due to viscosity . Therefore the specific cake resistance (α)would be

 

and the expression of specific cake resistance also is

The expression represents the properties like porosity, density, surface to volume ratio or size and shape of particle which are the characteristics of the cake. For an incompressible cake, specific cake resistance would be constant.

Mechanical Operation: Particle size, shape, separation based Question

1.      What are the different types of diameter that can be calculated for an irregular shape particle with their applicability?

b)      Particles of average feed size 5 mm are crushed to an average product size of 1 mm at the rate of 10 tons per hour. At this rate the crusher consumes 25 kW of power of which 2 kW is required to run the mill empty. What would be the power consumption if 15 tons per hour of this product is further crushed to 0.2 mm size in the same mill? Assume that Rittinger’s Law is applicable.                                          

2.         a)  What does the sieve BSS 5 mean and find the width of aperture (sieve opening) of BSS 5 if the wire diameter is 1.727 mm? 

b)      Define the efficiency of a screen and derive the formula used to find it.                                  

3.      Apply the force balance on a particle settling against water flowing up the column. Explain the working of an elutriator which is used to separate a mixture into 3 or more fractions.

4.     A mixture of quartz and galena of a size range 0.15 mm to 0.65 mm is to be separated into two pure fractions using a classifier under laminar flow condition. What density of the fluid would you suggest that will give the separation? The density of galena is 7500 kg/m³ and the density of quartz is 2650 kg/m³         

5.  A finely ground mixture of galena and limestone in the proportion of 1 to 4 by mass is subjected to elutriation by an upward-flowing stream of water flowing at a velocity of 6 mm/s. Assuming that the size distribution for each material is the same, and is shown in the following table, estimate the percentage of galena in the material carried away and in the material left behind. The viscosity of water is 1cP and Stokes’ equation can be used. The densities of galena and limestone are 7500 and 2700 kg/m³, respectively.                  

  

    

Diameter (µm) 20 30 40 50 60 70 80 100 Undersize (% by mass) 15 28 48 54 64 72 78 100

                                                 

Process Calculation: Unit change in a formula

Fluid Flow: Bernoulli's theorem

Bernoulli's theorem is based on the principle of conservation of energy. In a flow of ideal fluid, we consider three types of energies on a macroscopic level, Potential Energy due to height from a reference point, Kinetic Energy due to velocity of fluid, Pressure Energy due to forces applied on the fluid. In Bernoulli's theorem three heads Potential head (z), kinetic head [(v^2)/2g] and pressure head (p/gρ). The total energy at every point in the flow is constant. the easy way to remember this equation is with the help of dimensions like [P/gρ =  (v^2)/2g = z ] have the same dimensions of length.

For a horizontal pipe flow, potential head is constant. the change in velocity head is converted into pressure head, which is the principle behind the flow meters.

As the area decreases pressure decreases according to Bernoulli's theorem but according to hydro-static law pressure is inversely proportional to area. In Bernoulli's theorem the pressure is hydrodynamic that means fluid is in motion. in this case, if area decreases velocity increases which results in decrease in pressure.

Mechanical Operation: Classification and Elutriation

The mixture of particles can be separated according to their settling velocity. the settling velocity for a system depends on diameter and density of particles. For two different types of materials having density difference can be separated into 3 fraction. one containing fine particles of lighter material, one containing coarse particles of heavier material and one having mixture of both as shown in figure.

In elutriation, a water stream is passed up to the column through bottom. the particles having settling velocity less than that of water velocity will be carried over and particles having larger settling velocity will be settled. to separate the mixture into more than 2 fraction, 2 or more elutriators can be connected in series with increasing area to reduce the water velocity.

The density of fluid can be taken in between the two fluids. for example in a mixture of quartz and galena with densities 2650 and 7500 kg/m3, if the fluid has density 2650 then quartz particle will have zero settling velocity and galena particles will settle down. But for a given size range we can calculate the minimum density of the fluid that can separate the particles. to find minimum fluid density we can equate the settling velocity for largest particle of lighter particle and settling velocity of smallest particle for heaviest particle. the density of fluid slightly greater than this will separate the particles. 

Mechanical Operation: Separation of Particles

The separation of particles is done on the bases of their properties, like size of the particle, density of particle. If the particles are of different sizes, then the separation can be done by either using screening or on the basis of difference between their settling velocities called sizing, and materials of same equivalent size are separated according to their densities called sorting.

because of size of particle and its density, particle will have different settling velocity, on the basis of which particles can be separated using a fluid whose density may be closer to one of the type of particles. the mixture of two types of materials A and B having same size range but different density, can be separated into 3 section consisting pure A, pure B and mixture of A and B.

   

Reverse Osmosis

Reverse osmosis is a phenomena used to get pure water. It is based on the reversal of the phenomena of osmosis. When a semi-permeable membrane (permeable for water) is placed between salt water and fresh water, water will start moving in direction of salt water, trying to equalize the concentration on both sides. This a natural phenomena, called osmosis resulting in dilution of concentrated solution. This process continues until the chemical potential becomes equal on both sides. The chemical potential of water in pure form is higher than that on the salt water side at same pressure. As water moves towards salted water, the pressure increases, which increases the chemical potential on that side. After some time the pressure reaches at a level at which the chemical potential on both sides becomes equal and the osmosis stops. Now the system is at equilibrium.

At osmotic equilibrium, at the same level, the pressure becomes P1 in the left and reaches P2 in the right. At this condition the chemical potential becomes equal. The difference in pressure is called osmotic pressure, and in order to get pure water (left side) a pressure greater than P2 has to be applied on the right (salt) side.  

Mechanical Operation: Size of an irregular particle

The size of of a sphere is taken in terms of diameter, but how can we determine the size of an irregular particle like gravels. The size of an irregular particle is taken as an equivalent diameter of a sphere. there are various basis on which the equivalent (nominal) diameter  is calculated. the basis of calculation depends on the application we use.
1. The largest dimension of the particle
2. The diameter of a sphere having
a) equal surface area of the particle like in adsorption, catalytic reaction
b) equal volume of particle like in fluid flow past immersed bodies, settling.
c) equal surface/volume of particle like gas liquid interface as in gas bubble
d) the same settling velocity as the particle
3. the size of the mesh screen like in crushing, grinding

Mechanical Operation

Mechanical Operation is a part of unit operation. It has wide applications from the point of view of chemical engineering. In mechanical operation, there are various operations, that are used in chemical engineering. In this, we study the operations involving solid particles with or without fluid. 

It involves studies regarding particle properties like size and shape of particles, particle size distribution, particle size reduction, separation of different size particles according to size using screens, separation of different particles using elutriation and classification, filtration, fluidisation, transportation of solids using conveyor. .  

Process Calculation: Absolute, Relative and Percentage Humidity

Humidity is a term to represent amount of water vapor in air. It is used in evaporative cooling, to tell weather conditions etc.
Absolute Humidity refers to amount of water vapor present in dry air. This value doesnt provide much information about the condition of air. Like absolute humidity of 0.5, air will have different conditions in summer and winter. We cant tell how close to saturation value.
 To get more information about air condition, we use relative humidity: ratio of amount of water vapor present to the amount of water vapor present if air is saturated with water at that temperature. RH = w(H2O)/w(H2O)sat For example relative humidity of 0.5 shows 50 % water vapor is present as compared to saturated air.
Percentage humidity: Ratio of absolute humidity to absolute humidity at saturation condition. It is slightly less than relative humidity.
PH: [w(H2O)/w(air)]/[w(H2O)/w(air)]sat

Chemical Engineer: An Enterpreneur

Now a days, there are large no of small industries that can be started related to chemical engg. For example one is oil extraction and cattle feed from cotton seed. In this there are conveyors to carry material, a machine to extract oil by squeezing it and refinery to purify oil.The single unit starts around 10 lacs. There are other small industries also like paper plates, plastic glass and various other industries.

Application based Education

In school, I was taught various subjects. After my 10th I opted science, then I thought why did I study social science, sanskrit. It seemed to be useless. But one thing that I understands every subject has its own significance like math improves calculation, ablity to strike the problem faster, social science and sanskrit improves memorization.
But one thing I coulnt undrrstand that likein maths tthere is matrix, differentiation and integration. I was not told their applications. Like matrix is used to solve simultaneous equations, usrd zo enter data in computation like in matlab, intergration is used to find the solution when we have to consider a differential elements. Like these applications can enhance the learning abilities of students.

Mass Transfer: Distillation Process

Distillation is a very important mass transfer operation which is used to separate components on the basis of difference in boiling points. It is mainly used in refineries to distil crude oil into useful petroleum products.
As in distillation, all the components are volatile, so all components will be there in liquid and vapour phase, but the more volatile component (lesser boiling point), has more tendency to be in vapour phase as compared to liquid phase at any temperature. 

Distillation column is divided into 2 sections depending on concentration of more volatile component. The two sections stripping section and rectifying section or extraction and enriching section. These sections are divided based on the location of feed plate.

Above the feed plate, where the more volatile component has higher concentration as compared to other component gets enriched or rectified is rectification/enriching section.

And below the feed plate, where the more volatile component generally has lower concentration as compared to other component gets extracted or stripped from the solution is stripping/extraction section.

In distillation of binary mixture let say benzene (x in liquid, y in vapor) and toluene ;
Let at any plate x = 0.3 and y = 0.6; then how can benzene be transferred from the liquid to vapour phase, that means low concentration (0.3) to high concentration (0.6)? The answer is equilibrium concentration of benzene in liquid and vapor phases.
The concentration can be expressed as pressure of benzene. The saturation pressure of benzene in the liquid phase (ideal) is calculated through Raoult’s law (p_A = x_APv) and vapor phase pressure is calculated by Dalton’s law (p_A = y_AP_T); if the saturation pressure in liquid phase is higher, then the component will go in vapor phase increases till the pressure in vapor phase becomes equal to liquid phase saturation pressure. The equilibrium composition changes with temperature, therefore the temperature increases as we go down the column.
When vapour and liquid streams at different temperatures (not in equilibrium) are brought in contact, more volatile in the liquid phase will vaporise and less volatile from the vapour phase will condense. So, vapour phase will be enriched with more volatile and liquid phase will be enriched with less volatile components.

Fluid Flow: Types of Fluids

Every fluid behaves differently according to particle size, shape, distribution, particle volume fraction, particle-particle interaction. There are some external parameters also that affect the behaviour like type, rate, and time of deformation. The fluids are categorized in time dependent (thixotropic and rheopectic) and time independent (Newtonian and non-Newtonian fluid).  

1. Thixotropic: Viscosity decreases with time of deformation, that does not get thicken with time like paint should be thixotropic

2. Rheopectic: Viscosity increases with time of deformation

3. Newtonian Fluid: Viscosity remains constant with time and rate of deformation

4. non-Newtonian Fluid:

a) Dilatant: Viscosity of fluid increases with rate of shear that doesn't get diluted i.e. shear thickening. These type of fluids can be used to make bullet proof jacket i.e. when force is applied it will behave like a solid. One more application can be in the knee joint, where we need a material that acts like a solid when we rest and act like a lubricant when we move.

b) Pseudoplastic: Viscosity of fluid decreases with rate of shear i.e. shear thinning. Like toothpaste, when we hold it in upside down, it will not come out, but when we apply a force, it starts coming. i.e. viscosity of the paste decreases.

Mini Projects

There are small projects but that can be helpful. like one
1. The timer for the turn indicator in motor bike. When we would like to take a turn, we give indicator. but sometime we forget to switch it off. there can be a timer set for 30 sec or 1 min to switch it off automatically.
2. The temperature of water cooler can be controlled to save electricity.
3. Security system for cycles, motor cycles.
4. The temperature of water in air cooler can be utilized to cool the temperature of water for other applications.
5. The water pump in air cooler can be controlled by the level of water in cooler.
6. The pump used to supply water at higher altitude can be controlled by flow of water inside the pipe.

Chemical Engineering Thermodynamics Questions and Solution

Chemical Reaction Engineering Practical questions

1. How the temperature is optimized for a particular reaction in views of thermodynamics?
2. How the value of Thiele Modulus helps in designing of a catalytic reactor?
3. What are the different parameters for increasing the selectivity?
4. How does a catalyst enhance the rate of reaction?
5. How can you fix the problem of dead zone formation in CSTR?
6. If there are multiple decaying peaks at regular intervals are coming in RTD for a pulse input, what       it tells about the behaviour of reactor?
7. The compartment model for Various RTD curves.
8. Difference between diffusivity and solubility.

Heat Transfer Problems

1. The LMTD profile for evaporator and condenser, what type of flow arrangement will be better co-current or counter-current
2. The length of two thermometers are same, yet they give different temperature scales
3. In an air cooler, if the temperature of air is 30°C, and temperature of water is 30°C, then will the temperature of air will decrease or not. and if the temperature decreases, why?
4. Biot number is defined as hd/k and Nusselt no is hd/k, then why there is a need of two different names?
5. The fin temperature depends on a parameter m = (hp/kA)^0.5, the higher or lower value should be taken for a high efficient fin
6. Difference between efficiency and effectiveness

Chemical Engineering: A need of Society

As the time is passing, there are a lot of issues related to life elements are coming up i.e. air and water. In India, drinking water is not enough for fulfilling the need, and similarly the quality of air is not up to the standards for a healthy life. The price of drinking water has gone double in last three years, the temperature on earth is increasing continuously. Every year we talk about "this year its hotter than the previous year". Being an human being its our duty to preserve the environment for future. Some are the common things that can contribute towards its control:

1. Carry the bag with you, if possible take an environment friendly bag and take it with you while going for shopping, if the market is closeby, try to walk to it.

2. Purchase large quantity products, that will be economic and environment friendly also

3. Instead of throwing water away, give it to the plants

4. Use both sides of paper and recycle the waste paper, do not burn it
5. Can it be possible to have refilling units for shampoos, toothpastes, handwash etc in order to reduce the new bottles.
6. The use of reusable items like instead of plastic glasses, use glasses made of steel or glass
7. The use of air cooler in more controlled way, a temperature sensor can stop the water pump if the temperature drops below a certain temperature
8. The water pump can be made to stop if the level of water goes below the certain level.

The duty of chemical engineer is more than this, he should take the responsibility to protect the environment. He should work on different process to reduce the waste, more economic and environment friendly techniques.
Some energy we are not utilising like the energy with rain water. if we have a tall building, can we design a system to utilise the kinetic energy of water to produce electricity. the energy with lightening, that has thousands of volts.