SATHYABAMA UNIVERSITY (Established Under Section 3 of the UGC Act 1956) Accredited with B++ Grade by NAAC JEPPIAAR NAGAR, CHENNAI – 600 119.
DEPARTMENT OF CHEMICAL ENGINEERING MECHANICAL OPERATION LABORATORY MANUAL
STUDENT NAME ROLL NO COURSE SEMESTER
: : : :
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MECHANICAL OPERATION LAB MANUAL LIST OF EXPERIMENTS CYCLE 1
SL. NO.
NAME OF THE EXPERIMENT
1
BALL MILL
2
JAW CRUSHER
3
DROP WEIGHT CRUSHER
4
SCREEN EFFECTIVENESS BY MECHANICAL METHOD
5
SCREEN EFFECTIVENESS EFFECTIVEN ESS BY MANUAL METHOD
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1. BALL MILL AIM: To determine the energy required for crushing the given feed and thus obtain the work index for the same. Also determine the reduction ration and critical speed of the mill. THEORY: The ball mill is classified as an intermediate and fine grinder where the action of the grinding is based on impact and attrition. The ball mill consists of a cylindrical shell slowly turning about a horizontal axis and filled to about half its volume with a solid grinding medium. The shell is usually steel lined with silica rock and rubber. When the mill is rotated the balls are picked by the mill wall and carried nearly to the top where they break contact with the wall and fall to the bottom to be picked up again. Centrifugal force keeps the ball in contact with the wall and with each other during the upward movement. At low speeds of rotation the balls simply roll over one another and little crushing action is obtained. At slightly higher speeds, they are projected short distances across the mill, and at still higher speeds balls are thrown greater distance and considerable wear of the lining of the mill takes place. At very high speeds the balls are carried right round in contact with the sides of the mill and little grinding takes place, the mill is then said to be centrifuging. The speed of the mill at which centrifuging occurs is called Critical speed. For efficient operation of the mill, it should always be run at a speed less than the critical speed and hence determination of critical mill speed becomes important. APPARATUS REQUIRED: Ball mill experimental setup, sample and sieves. PROCEDURE: 1. The grinding elements are placed in the mill and the mill is allowed to run under no load condition. 2. Time takes for 1 revolution of the disc in the energy meter is noted for the operation of ball mill under no load condition. 3. Mill is stopped and about 250 grams of the sample is charge In to the ball mill along with the balls. Before feeding the sample into the mill feed size (D f ) is measured either by volume displacement method or Feret’s method. 4. The ball mill is started and allowed to run for 15 minutes. 5. Time taken for 1 revolution of the disc in the energy meter is noted for the operation of ball mill under on load condition. 6. The sample after crushing is transferred to the sieves and mechanically agitated for 10 minutes. 7. The quantity of sample retained on each sieve is weighed and tabulated as shown in the table. The screen analysis data is used to determine the mass mean diameter of the product (D p). 3
OBSERVATION: Quantity of feed sample Feed size, Df Time taken for 1 complete revolution ( no load) Time taken for 1 complete revolution ( on load) Total time the mill is put to operation Energy meter constants for ball mill (To be observed from the Experimental Setup)
= =
= = =
Tones mm hr hr hr
=
TABULATION: SL. NO
Mesh No.
Size of Aperture Da (mm)
Average Particle size in each fraction Dpi (mm)
Mass in each fraction (gms)
Mass fraction xi
Dp= xi Dpi
FORMULAE REQUIRED: 1) 2)
3) 4)
Energy required for crushing E=[n1-n] ÷ [m x EMC] kW hr/Tones Work Index Wi=[E]÷[1/ ∫Dp-1∫Df] Reduction ration = Feed size % Product size Critical speed of ball mill nc=1/2π[∫g÷R-r]
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Where n1 is the no. of revolutions of the energy meter disc during the mill operation under on load condition. n is the no. of revolution of the energy meter disc during the mill operation under no load condition. m is mass of sample in tones. EMC is Energy meter constant. Dp is mass mean diameter of the product sample in mm Df is the diameter of the feed sample in mm 2 g is acceleration due to gravity in m/sec -2m R is radius of the Ball mill in m (25 x 10 ) -2 r is the radius of the ball in m (4.125 x 10 m) RESULT: Using the Ball mill experimental setup the following were determined 1) Energy required for crushing =_________________ k W hr/Ton 2) Work index=_____________________kW hr ∫mm/Ton 3) Reduction ratio =_______________ 4) Critical speed of the ball mill=______________rps
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JAW CRUSHER AIM: To determine the crushing law constants using Blake jaw crusher Experimental setup. THEORY: Crushers are slow speed machines for coarse reductions and can break large lumps of various hard materials as in the primary and secondary reduction of rocks and ores. In a jaw crusher, the feed is admitted between the two jaws, said to form v-open at the top. 0 0 One jaw is fixed and the other is movable. It makes an angle of 20 - 30 with the fixed jaw. The movable jaw is driven by eccentric motor so that it applies great compressive force, large lumps caught in between the upper part of the jaw are broken then drop into the narrow space below and are crushed again at the bottom of the jaw. After sufficient reduction, they drop out from the bottom of the machine. A crusher cannot be expected to perform satisfactorily unless. a) The product is removed as soon as they are of desirable size. b) Unbreakable material is kept out of the machine. c) In the reduction of low melting and high sensitive products, heat Generated in the mill is removed. APPARATUS REQUIRED: Jaw crusher setup, screens, sample. PROCEDURE: 1) Jaw crusher is started. 2) Before the feed is fed into it, the time taken for one revolution of the energy meter disc is noted for no load condition. 3) The feed (1000 g ms) is fed now at constant and steady rate so as to avoid jamming and choke feeding. 4) When the jaw crusher is running under on load condition, time taken for one revolution of the energy meter disc is noted. 5) Also the time taken for feeding the entire material is noted. 6) The crushed material is transferred to a sieve stack and mechanically agitated for 10 minutes. 7) The quantity of sample retained on each sieve is weighed and tabulated as shown in the table. The screen analysis data is used to determine the volume surface mean diameter of the products (D p) OBSERVATION: Quantity of feed sample = Tones Feed size, Df mm = Time taken for 1 complete revolution ( no load) = hr Time taken for 1 complete revolution ( on load) = hr Total time the mill is put to operation = hr Energy meter constants for ball mill (To be observed from the Experimental Setup) = 6
TABULATION: SI.NO Mesh No.
Size of Aperture Da (mm)
Average Particle size in each fraction Dpi (mm)
Mass in each fraction (gms)
Mass fraction
X /D i pi
FORMULAE REQUIRED: 1) Energy required for crushing E=[n1-n] ÷ [m x EMC] kW hr/Tones 2) Volume surface mean diameter of the product Dp=1 ÷ {x /D i pi 3) Work Index Wi=[E] ÷ [1/ ∫Dp-1/ ∫Df ] 4) Rittinger’s constant KR f c=[E] ÷ [1/Dp-1/Dr] 5) Kick’s Constant KKf c=[E]÷1n(D /D f p] Where n1 is the no. of revolutions of the energy meter disc during the mill operation under on load condition. n is the no. of revolution of the energy meter disc during the mill operation under no load condition. m is mass of sample in tones. EMC is Energy meter constant. Dp is mass mean diameter of the product sample in mm Df is the diameter of the feed sample in mm RESULT: The crushing law constants are determined I. Wi =_____________________ II. KRf c =_________________________________ III. Kkf c=__________________________________
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3. DROP WEIGHT CRUSHER AIM: To determine the crushing law of constants using drop weight crusher. APPARATUS REQUIRED: Drop weight crusher set up, sieves, samples etc. PROCEDURE: 1. About 25 grams of the sample size 4+5 is taken in the crusing chamber. 2. The weight of the metallic block (weight to be dropped) and the height through which it falls is determined. 3. The block is kept in position and the plunger is placed on the top to the feed. 4. The weight Is allowed to drop on the plunger. The sample in the chamber is reshuffled after every 5 drops, so that the lower layers are also exposed to the impact. 5. The product is analyzed after 100 drops using he standard set of screens. 6. The crushed material is transferred to a sieve stack and mechanically agitated for 10 minutes. 7. The quantity of samples retained on each sieve is weighed and tabulation as shown in the table. The screen analysis data is used to determine the volume mean diameter of the product (Dp) OBSERVATION Quantity of feed sample = Tones Feed size, Df mm = Height through which weight falls, h = m Weight of the drop, w = Tones No.of Drops, n = TABULATION: SL. NO
Mesh No.
Size of Aperture Da (mm)
Average Particle size in each fraction Dpi (mm)
Dpi
Mass in each fraction (gms)
Mass Fraction (Xi)
xi/Dpi
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FORMULAE REQUIRED: 1) Energy required for crushing E=[nwgh] ÷ [m] kW hr/Ton 2) Volume surface mean diameter of the product 3]1/3 Dp=[1÷ ∑x /D i pi 3) Work Index[Bond’s law constant) Wi=[E] ÷[1/ ∫Dp-1/ ∫Df ] 4) Rittinger’s constant KR f c=[E] ÷[1/Dp-1/Df] 5) Kick’s Constant KKf c=[E]÷1n(D /D f p)
RESULT: The crushing law constants are determined Wi =_____________________ KRf c =_________________________________ Kk f c=__________________________________
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4. SCREEN EFFECTIVENESS BY MECHCANICAL METHOD AIM: To determine the percentage effectiveness of the given screen by mechanical Agitation of the Screen stack. THORY: Screen is a method of separating particles according to size alone. In practice, the solids are dropped or thrown into a screening surface. The undersize or fines pass through the screen opening. Materials passed through a series of screens of different sizes are separated into two fractions. In most screen, the particles drop through the opening by gravity, coarse particle drop easily through the large opening in a stationary surface whereas with fine particles the screen surface must be agitated in same way. PROCEDURE: 1) Arrange a set of standard screens serially in a stack with the smallest mesh at the bottom and the largest at the top. 2) Place the pan at the bottom 3) After placing (500gms) the sample, shake mechanically to obtain the oversize and undersize separately. 4) After shaking, weigh the particle from each mesh individually. Keep the pockets separately. 5) Place oversize particles, shake mechanically to obtain the oversize separately. 6) Place undersize particles, shake mechanically to obtain the undersize separately. Convert the weight into the mass fraction. CALCULATIONS: Total feed taken
=
Feed fraction acc. Given mesh screen X f
=
Fraction of over size X D
=
Fraction of under size flow x B
=
(XF-XB) x (XD-XF) x XD(1-XB) E=______________________ 2 (XD-XB) x XF(1-XF)
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TABULATION: Mesh No. Aper. Size
wt . of sample Feed
O.S
Diff. analysis U.S
Feed
O.S
U.S
Cumm. Mass fraction Feed O.S
U.S
A graph has to be drawn between cum. Mass fraction & Mesh No. RESULT: The percentage effectiveness of the given screen is=
%
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MECHANICAL OPERATION LAB MANUAL LIST OF EXPERIMENTS CYCLE 2
SL NO.
NAME OF THE EXPERIMENT
1
BATCH SEDIMENTATION
2
COMPARISON – SCREEN EFFECTIVENESS
3 4
PLATE AND FRAME PRESS VACCUM LEAF FILTER
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1.BATCH SEDIMENTATION AIM: To determine the minimum area of a continuous thickener required to concentrate a feed of 4% calcium carbonate slurry at a rate of 150 tons/day solids to give an underflow concentration of 50% by carrying out the batch sedimentation. THEORY: Sedimentation is a separation process by which dilute slurry is divided into a clear liquid and a slurry of high solid concentration by settling. When the particles are at sufficient distance from the boundaries of the container and from other particles, so that it falls without being affected, then it is called “free settling”. For low Reynolds’s number the drag force on the particle obeys Stock’s law. The law is valid at low velocities when the particles move through the fluid. In the gravitation settling ‘g’ is constant and drag increase with velocity called the terminal velocity. The mechanism shows newly prepared slurry having uniform concentration throughout the cylinder. As the process begins, the particles start setting. Different zones of varying concentration are formed. Zone ‘d’ consists of heavier faster setting particles, Zone ‘C’ is called the transition layer consisting of variable size distribution and non uniform concentration. The layers present are channels through which fluid rises upward and particles settle down. At this stage. The solid present in these layers split out into the clear zone. APPARATUS REQUIRED: One liter glass measuring jar, Calcium carbonate, Stirrer, scale etc. PROCEDURE: 1. Prepare a 4% calcium carbonate slurry by taking 40 grams of dry sample into a beaker. 2. Add a minimum amount of water and transfer the contents to a graduated cylinder. 3. Make up the level by adding water up to the mark. 4. Stir the slurry vigorously and constantly in a vertical manner until the concentration is uniform throughout the cylinder. 5. Takeout the stirrer and start the stop clock. 6. Note down the time for each centimeter traveled by the particles. 7. Measure the height by using a scale fixed to the side of cylinder. 8. For about half the length, note the time for every one centimeter. 9. After that not down the time for every 0.5 cm drop in the height of the bed. 10. Stop the experiment.
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OBSERVATION: Initial height of the interface Initial solid concentration S.No
= =
Volume of clear liquid (ml)
cm 3 kg/m Time taken for setting (sec)
Height (cm)
FORMULAE REQUIRED: 1. Slurry concentration at time ‘t’, C=[OA/OT]C 0 2. Settling velocity is obtain by drawing slopes to the curve obtained as . shown in the graph below 3.
Amin= Q u____ (I/C – I/Cu)max
Where 3 c- Concentration of slurry at any time ‘t’ (kg/m ) 3
C0 – Initial slurry concentration (kg/m ) 3
Cu –Underflow concentration (kg/m ) u- Settling velocity of particles Q- Feed rate (kg/sec)
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MODEL GRAPH:
A U = dz / dt
Z CM
T sec TABULATION: S.No
Time sec
Height of Interface (z) cm
Slurry Concentration 3 kg/m
(I/C)-(I/C u) 3 m /kg
Settling U Velocity 1/C – 1/Cu (u)
RESULT: The minimum area of the thickener is __________ m
2.
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COMPARISON OF SCREEN EFFECTIVENESS BY MANUAL & MECHANICAL METHOD 2.
AIM: To compare the percentage effectiveness of the give screen stack by Mechanical and Manual Agitation. THEORY: Screening is a method of separating particles according to size alone. In practice, the solids are dropped or thrown into a screening surface. The undersize or fines pass through the screen opening. A material passed through a series of screens of different sizes is separated into two fractions. In most screen, the particles drop through the opening by gravity, coarse particle drop easily through the large openings in a stationary surface whereas fine particles the screen surface must be agitated in same way. PROCEDURE: 1. Arrange a set of standard screens serially in a stack with the smallest mesh at the bottom and the largest at the top. 2. Place the pan at the bottom. 3. After placing (500gms) the sample, shake mechanically to obtain the oversize and undersize separately. 4. After shaking, weigh the particle from each mesh individually. Keep the pockets separately. 5. Place oversize particles, shake mechanically to obtain the oversize separately 6. Place undersize particles; shake mechanically to obtain the undersize separately. Convert the weight into the mass fraction. 7. Repeat the screen Analysis by Manual method. 8. Determine and compare the effectiveness of the screen. CALCULATIONS: Total feed takes Feed fraction acc. Given mesh screen X f Fraction of oversize X B Fraction of under size flow X D
= = = =
(XF-XB) x (XD-XF)x XD(1-XB) E=______________________ 2 (Xn-XR) x XF(1-XF)
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TABUALTION: Mechanical Agitation Mesh No. Aper. Size
wt . of sample Feed
O.S
Diff. analysis U.S
Feed
O.S
U.S
Cumm. Mass fraction Feed O.S (Xf ) (Xd )
U.S
Cumm. Mass fraction Feed O.S (Xf ) (Xd )
U.S (XB)
Manual agitation: Mesh No. Aper. Size
wt . of sample Feed
O.S
Diff. analysis U.S
Feed
O.S
Plot Comparative charts for Feed, Oversize and Undersize drawn between cum. Fraction & Mesh No.
U.S (XB)
Mass
RESULT : The percentage effectiveness of the give screen by Mechanical Agitation is = % The percentage effectiveness of the give screen by Manual Agitation is = %
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3.
PLATE AND FRAME FILTER PRESS
AIM: To determine the characteristic of plate and frame filter press at a constant pressure and to calculate the filter cake resistance ‘a’ and the filter cake resistance ‘R m’ THEORY: Filter is the process where by a solid is separate from a liquid or gas by means of porous medium which retain the solid but allows the fluid to pass. A filter cake gradually builds upon the medium and the resistance to flow problem can be regarded as two parts: 1. Through filter medium. 2. Through bed formed by the particles on the medium 3. The plates and frames arranged alternatively are supported on a pair of rails. Plate has a ribbed surface and press is closed by means of a screw. A chamber is therefore formed between each pair of successive frames. APPARTUS REQUIRED: Plate and frame filter press, Calcium Carbonate slurry, stop clock. PROCEDURE: The plate and frame filter press is arranged by keeping wet filter medium between the frames. Few liters of water is pour in to the tank by closing the discharge value. The water is kept agitated by air and the pressure is adjusted to 5 psi using the value in the vessel. The outlet valve is opened. The pure filtered water is collected in the collection tank. This is just done to checkout for leakage of the press. If any leakage is there it has to be arrested by taking care in the tightening of the screws. After ensuring there is no leakages the following procedure is followed. 5 liters of 3% calcium carbonate slurry is prepared. This slurry is poured into the tank by closing the discharge valve. The slurry is kept agitated by air and the pressure is adjusted to 5psi using the valve in the vessel. The outlet valve is opened. The pure filter water is collected in the collection tank. After seeing the level in the level glass a stop clock is started. Time is noted for every 1 cm. rise in the level glass. After the completion of filtration, valves are closed and compressor is switched off. The filter press is carefully opened. A small quantity of wet cake is taken off the medium And is weighed using a previously weighed watch glass and dried in a oven. After some time the dry cake weight is also noted.
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OBSERVATION: Diameter of the filter press, D No. of plate No. of frames No. of chambers formed,n Area offered by one chamber, A Total filter area, Af Pressure drop p (observed from pressure gauge) Diameter of the collection tank, D c Area of the collection tank, A c Weight of the empty watch class, Weight of the watch glass + Wet cake, m w Weight of the watch glass + Dry cake, m d Slurry concentration, C s
TABULATION: Height . h (cm)
Total time, t (sec)
= = = = = = = = = = = = =
m
2
2
π D /4 m 2 n x Am 2 k/gm m 2 π Dc /4m2
Volume of filtrate 3 collected V=Ac x h(m )
t/V (sec/m )
CALCULATIONS: 1) Concentration of the feed slurry, C C5 C=______________________ 1-[(mw /md)-1]C5 / ρ
2) To Calculate the cake and medium resistances the experimental data is used and a graph is plotted as shown below
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T/v
Slope
Intercept V
The slope of the curve and the intercept are determined Slope = Kc /2 Intercept = 1/q 0 Specific cake resistance, 2 A=(Kc)(^p)(Af )(g) ÷ (C x µ) m/kg Specific medium resistance -1 Rm=(1/q0)( ^p)Af g ÷ µ m RESULT: The specific cake resistance, ᾀ= The filter medium resistance, R m =
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4. VACUUM LEAF FILTER AIM: To determine the specific cake resistance and the filter medium resistance for the filtration of the calcium carbonate slurry using the vacuum leaf filter. THEORY: The separation of solid from a suspension in a liquid by means of a porous medium which retains the solids allows the liquid to pass is termed as filtration. In filtration the resistance to flow increase with time as the filter medium becomes clogged. Filtration can be carried at constant pressure or at constant rate. Vacuum filter is a type of cake filter since large amounts of solids are separated out in the form of cake. The overall pressure drop at any times is the pressure drop over the medium and cake. OBSERVATION: Diameter of the leaf, D Area offered by one face of the leaf, A Total filter area, A f Pressure drop ^p= ρHg g hHg Diameter of the collection tank, D c Where pHg is density of mercury Hg is level of mercury inside the manometer Area of the collection tank, A c Slurry concentration, c s
= = = =
= = = =
m 2 2 IID /4 m 2 2xAm 2 kg/m m 3 13600 kg/m 2
2
II Dc /4 m
=
PROCEDURE: 1. 5 Lits of 3 % Calcium carbonate is prepared in bucket. 2. The agitation is kept at suitable speed such that uniformity if maintained in excessive agitation. 3. The vacuum pump is started and 5 cm Hg vacuum is maintained by adjusting the vacuum release valve. 4. On applying vacuum filtration begins and clear filtrate gets collected in the collection tank. 5. When a notable level is reached in the level gauge a stop watch is started. The level gauge readings along with time are recorded. 6. The vacuum pump is switched off after opening the vacuum release valve when the slurry level in the feed tank drops below the leaf. 7. The remaining slurry is drained, the Leaf is taken off. 8. A small quantity of wet cake is taken in a pre-weighed watch glass and weight is determined. 9. The watch glass is then placed in an oven and the dry weight of the cake is also noted.
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TABULATION: Height . h( cm)
Total time, t (sec)
CALCULATION: Weight of the empty watch class, Weight of the watch glass + Wet cake, m w Weight of the watch glass + Dry cake, m d 1) Concentration of the feed slurry, C CS C=______________________ 1-[(mw /md)-1]CS /p
Volume of filtrate 3) collected V=Ac x h(m
t/V (sec/m )
= = =
2) To Calculate the cake and medium resistances the experimental data is used and a graph is plotted as shown below T/v
Slope
Intercept V
The slope of the curve and the intercept are determined Slope = K c /2 Intercept = 1/q0 Specific cake resistance, 2 a=(Kc)(p)(Af )(g) % (C x u) m/kg Specific medium resistance -1 Rm=(1/q0)(p)Af g % u m RESULT: The specific cake resistance, a= The filter medium resistance, R m =
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