Sedimentation & filtration Present by : Ngoc Tran Shamia salih Hong Nguyen

Sedimentation Sedimentation is the natural process in which particles is carried to the bottom of a body of water and forms a solid layer

Sedimentation

Purpose To measure the diameter of the particles At fixed time intervals samples were taken from the suspension at different depth

Industrial use Water treatment Food industry In geology Blood test

Hydrometer Hydrometer is used to determine the specific gravity or relative density of liquids It is normally made of glass and it is usually weighted with mercury or lead shot to make it flow upright.

Hydrometer The operation of hydrometer is based on Archimedes’ principle The lower the density of the substances, the further the hydrometer will sink

Hydrometer There are different types of hydrometer used based on the density of the liquid variety of scales of hydrometer used depending on what you want to measure

A Type of Hydrometer

Procedure Measure a white solid powered (20g)

Procedure Fill a 1000ml cylinder with 900ml of water

Procedure Pour the white powder into the cylinder and shake it until the water and the powder are evenly distributed

Procedure Then place the hydrometer into the cylinder

Procedure Measure the temperature Then set the timer Measure the height of the hydrometer at 0 seconds And then start recording the height in time intervals until the height is constant

Motion of sphere particle

MOTION OF SPHERE PARTICLE If the particles are sphere of diameter Dp At low Reynolds numbers the drag coefficient varies inversely with Re of particle Re=G*D/µ)

calculation diameter of the particle To calculate values of effective depth from the equation: L = L1 + 0.5(L2 -VB /A) or table 2 L1 : distance along the stem of the hydrometer from the top of the bulb to the mark for a hydrometer reading. L2 : overall length of the hydrometer bulb (L2 = 14.0 cm) V B :volume of hydrometer bulb (V B = 67.0 cm3) A = cross-sectional area of sedimentation cylinder (A = 27.8 cm2) To find the value correction factor α from table 1 To find K value from table 3

SG=2.53  α=1.024

Reading L1=10  L=14.7

At 220C & SG=2.53  K=0.01307

CALCULATION & ANALYSIS T (min) Actual reading Effective L D (mm) % P 20 13.04   1 18 13.37 0.05 69.63 2 17 13.53 0.04 64.51 3 15 13.86 0.03 54.27 4 14 14.02 49.15 5 12 14.34 0.02 38.91 6 11 14.51 33.79 7 10 14.67 28.67 8 9 14.83 23.55 15.00 18.43 15.16 13.31 15.32 8.19 Temperature : 22 0C Volume (ml) 900ml Dry mass (gram) 20g Concentration: 22% SG : 2.53g/cm3 K (Table 3) 0.01307 a (Correction Factor Gs) 1.024 b (Correction Factor Temp) 4.4

THEORY OF FILTRATION Filtration is a very important step in the entire process of solid-liquid separation which can be sub-divided into four major stages (1) Pretreatment (2) Solids concentration (3) Solids separation (4) Post-treatment

Types of filtration Basically, there are two types of filtration (1) Depth filters - used for deep bed filtration where particle deposition takes place inside the medium and cake deposition on the surface is undesirable. (2) Surface filters – Used for cake filtration where the solids are deposited in the form of a cake on the up-stream side of a relatively thin filter medium.

Rotary Filtration Purpose: To separate water and solid

A pre-coat is a layer of fine particular material added on to the filter septum before filtration to form a coating cake

Rotary vacuum filter drum + consist of a drum rotating in a tub of liquid to be filtered. + pre –coat +vacuum sucks liquid and solids onto the drum pre- coat surface . + the solids adhere to the outside of the drum + knife cut the solid out of drum . The knife advances automatically as the surface is removed. https://www.youtube.com/watch?v=4MFI-JFhBAU&feature=youtu.be

The pump Vacuum filtration usually involves the use of a vacuum filter flask, a filter trap, a water pump the liquid is sucked down into the filter flask by the action of the water pump, and any excess liquid that overflows out of the filter flask is caught in the filter trap

Procedure Fill the tank with the mixture Turn on the valve for water go to the pump Turn off all the valves which are drain out the water from the tank, pump, and drum. Turn on the main switch and all the buttons.

Continue Vacuum pump Agitator drive Filter drive Pre-coat drive Filtrate pump

Valve for water come to the pump Valves drain out all water after finish Drain valve (blue)valve for water drain out the tank after finish (green )valve control the water go to the pump

The filter-cake resistance specific resistance the local porosity and permeability (or specific resistance), as well as the constitutive relations for the drag force between the phases and the solid matrix stress are required to obtain the numerical solution of the equations. The medium resistance is a function of the medium itself and the material being filtered. Resistance arises from the filter cloth, mesh, or bed, and to this is added the resistance of the filter cake as it accumulates. The filter-cake resistance is obtained by multiplying the specific resistance of the filter cake, that is its resistance per unit thickness, by the thickness of the cake. R = µr(Lc + L)

the properties of a filter cake The key properties of a filter cake are the cake porosity and permeability The cake porosity (ε ) is a measure of the fluid capacity of the formed cake or the fraction of a porous medium available for fluid flow. The cake permeability ( k ) is an indication of how easily the fluid can pass through its voids under an applied pressure gradient. The extent of permeability is determined by the porosity of the medium and also the sizes of pores in its internal structure.

Rotary filtration Batch filtration Dry cake Wet cake θ: Angle comprising the sector immersed in the suspension Batch filtration

mass balance for the solid in the cake Solids accumulate in cake = Solids removed from suspension. LAԐ the volume of water in the cake The volume of water contained in the LAԐ is much smaller than VF1 the volume of filtrate.

Pressure Drop During Cake Filtration

Rotary Vacuum Filtration Fraction Submergence of drum surface θ/2π : fk Time cycle 2π/ω : tc The time immersion period in each cycle : t= tc * fk Rotation velocity ω (rad/s) θ: Angle comprising the sector immersed in the suspension Filtration Flux If the Rm is very small Amount of solid

CONCLUSION The diameter of the particle The concentration of the particles The cake permeability ( k ) is an indication of how easily the fluid can pass through its voids under an applied pressure gradient The cake porosity (ε ) is a measure of the fluid capacity of the formed cake or the fraction of a porous medium available for fluid flow Pressure drop Total pressure drop: P drop cross filter & P drop due to filter medium Specific cake resident: the local porosity and permeability The speed of the drum rotation ω The filtrate flow rate The amount of solid

References Unit Operations textbook Dr. Lo Dr. Jang Mr. Minh Tran Friend: Cody http://www.engineering-resource.com http://www.filtration-andseparation.com http://www.engr.uky.edu

QUESTIONS