CEBU INSTITUTE OF TECHNOLOGYN. Bacalso Avenue, Cebu City

Chemical Engineeing Department

FINAL REPORTChE Lab 1

Title of Experiment

Juphil A. LamanilaoBSChE-5

Engr. Lyda P. Abellanosa

Instructor

Abstract:

Sedimentation is simply the process of letting suspended material settle by gravity. It is accomplished by decreasing the velocity of the water being treated to a point below which the particles will no longer remain in suspension. When the velocity no longer supports the transport of the particles, gravity will remove them from the flow. In a glass cylinder, when solids diffuse through the interface, the process starts then to settle from a slurry during a batch settling test and assumed to approach terminal velocities under hindered settling conditions. Thus, several zones of concentration will be established. The particle is not actually sent all the way to the bottom of the cell, resulting in a sediment. Rather, a low centrifugal field is used to create a concentration gradient- where more particles near the bottom of the cell than near the top. When the temperature decreases, the rate of settling becomes slower. Theresult is that as the water cools, the detention time in the sedimentation cylinder must increase. As sedimentation continues, heights of each zone vary and the point at which a single distinct interface forms between liquid and sediments will be reach.

Objectives:

1.) Effect of Initial Concentration on Sedimentation Characteristicsa. To plot the initial mass settling rate against concentration.b. To plot the ratio of sedimentation at final consolidation on semi-log paper.c. To plot the settling velocity against the limiting concentration.

2.) Effect of Initial Height on Sedimentation Characteristicsa. To plot the initial mass settling rate against concentration.b. To plot the ratio of sedimentation at final consolidation on semi-log paper.c. To plot the settling velocity against the limiting concentration.d. To deduce that the graph of settling of settling velocity against limiting

concentration are similar for all cases.

Materials & Equipment:

Sedimentation Apparatus, stopwatch, powder of CaCO3, electronic balance, beaker, spatula, watch glass, stirring rod

Sketch of the Set-up:

Procedure:

A. Two (2) liters of 2%, 4%, 6%, 8% & 10% by weight CaCO3 suspension in water were prepared. Each slurry was placed in sedimentation tubes at the same height. The readings of the interface were taken at the convenient time interval. The rise of sludge interface was also recorded at the base of the cylinder and then allowed for a period of 24 hrs. to elapse for final compaction readings.

B. The procedure above was repeated except that the slurry was of the same concentration, 4% but with different initial heights.

Tabulated Data & Result:

A.TimeInterval (mins)

Height of Interface Rise of Sludge2% 4% 6% 8% 10% 2% 4% 6% 8% 10%

0 0 0 0 0 0 0 0 0 0 02 10 15 23.6 27.5 28 10 15 23.6 27.5 284 11 17.5 25 33.4 35 11 17.5 25 33.4 356 13 19 27.9 37.5 42 13 19 27.9 37.5 428 13 20 31 40 47.5 13 20 31 40 47.510 13 20 31 40 50 13 20 31 40 5012 13.5 20 31 40 47 13.5 20 31 40 4714 13.5 20 31 40 47 13.5 20 31 40 4716 13.6 20 31 40 47 13.6 20 31 40 4718 13.5 20 31 40 47 13.5 20 31 40 4720 13.5 20 31 40 46.8 13.5 20 31 40 46.824

hrs.12.3 19.6 30.7 36.94

042 12.3 19.6 30.7 36.94

042

B.TimeInterval (mins)

Height of Interface Rise of Sludge1 2 3 4 5 1 2 3 4 5

0 0 0 0 0 0 0 0 0 0 02 3.8 5.6 8.9 9.8 12.2 3.8 5.6 8.9 9.8 12.24 3.9 6.5 9.3 10.5 12.8 3.9 6.5 9.3 10.5 12.86 40 6.9 9.9 10.9 13.5 40 6.9 9.9 10.9 13.58 3.9 6.9 10 11.4 14.1 3.9 6.9 10 11.4 14.110 3.9 7.0 10 11.4 14.8 3.9 7.0 10 11.4 14.812 3.9 7.0 10 11.5 15.0 3.9 7.0 10 11.5 15.014 3.8 7.0 10 11.9 15.2 3.8 7.0 10 11.9 15.216 3.8 7.0 10 20 15.2 3.8 7.0 10 20 15.218 3.8 7.0 10 20 15.2 3.8 7.0 10 20 15.220 3.8 7.0 10 20 15.2 3.8 7.0 10 20 15.224 3.8 7.0 10 11.2 14.8 3.8 7.0 10 11.2 14.8

hrs.

Computations:

Table A.

for 2% by wt. CaCO3; 0.02 = x/(x+y)x = 0.02(x+y)x = (0.02y)/0.98x = [0.02(1000)]/0.98x = 20.408 g CaCO3

for 4% by wt. CaCO3; 0.04 = x/(x+y)x = 0.04(x+y)x = (0.04y)/0.96x = [0.04(1000)]/0.96x = 41.67 g CaCO3

for 6% by wt. CaCO3; 0.06 = x/(x+y)x = 0.06(x+y)x = (0.06y)/0.94x = [0.06(1000)]/0.94x = 63.83 g CaCO3

for 10% by wt. CaCO3; 0.10 = x/(x+y)x = 0.10(x+y)x = (0.10y)/0.90x = [0.10(1000)]/0.90x = 111.11 g CaCO3

Table B.

for 200 ml(H2O);0.04 = x/(x+y)x = 0.04(x+y)x = (0.04y)/0.96x = [0.04(200)]/0.96x = 8.33 g CaCO3

for 400 ml(H2O);0.04 = x/(x+y)x = 0.04(x+y)x = (0.04y)/0.96x = [0.04(400)]/0.96x = 16.67 g CaCO3

for 600 ml(H2O);0.04 = x/(x+y)x = 0.04(x+y)x = (0.04y)/0.96x = [0.04(600)]/0.96x = 25 g CaCO3

for 800 ml(H2O);0.04 = x/(x+y)x = 0.04(x+y)x = (0.04y)/0.96x = [0.04(800)]/0.96x = 33.33 g CaCO3

for 1000 ml(H2O);0.04 = x/(x+y)x = 0.04(x+y)x = (0.04y)/0.96x = [0.04(200)]/0.96x = 46.67 g CaCO3

let x = mass CaCO3 y = mass H2O = 1000 g % wt. = x/(x+y)

const. 4% by wt. CaCO3varying volumes

Data Analysis :

At a short period of two minutes time interval, particles are well distributed in a water phase at its flocculated suspension initial state based on the nature of the CaCO3 particles suspended in water. In the medium time period of about 8 mins, clear supernatant above the surface is seen while remains cloudy in the middle interface and there is a cake formation at the bottom. One factor affecting sedimentation is the particle size diameter. The formed flocs will cause an increase in sedimentation rate due to increase in size of sedimenting particles. It does not only depend on size but also on porosity, preserve in the sediment which contains an amount of entrapped liquid. Thus, the final volume of sediment is relatively large. At the end of 24 hrs., there is a little change in sediment volume as seen from the experimental result above.

Recommendation:

Sedimentation practices are designed to be effective at retaining suspended solids that typically adsorb to solids. In every after the experiment, the retained solids must need to be removed. Since the apparatus is not that effective at retaining dissolved pollutants, there must be a way for this. Such apparatus must therefore be regularly inspected to determine its condition. The rear panel should be translucent enough in order for the students to have an improve observation of settling sediments in the column. It’s not so easy to measure settlement depth due to the graduated scale with no back lighting which means there are discrepancies in our data.

Application to ChE:

Sedimentation is one of the great classical methods where it is applied for polymer characterization. It can determine the concentration of a polymeric solute as a function of position from the center of a rapidly rotating cell. Also, the chemical industry has large scope manufacturers of pharmaceuticals where suspension is usually applicable for drug which is insoluble or poorly soluble. This is to prevent degradation of drug or to improve stability of drug and to mask the taste of bitter of unpleasant drug. Vaccines as an immunizing agent are often formulated as suspension and so does for X-ray contrast agents.