Upload
danilo-jose-saavedra-mayer
View
154
Download
15
Tags:
Embed Size (px)
Citation preview
PIERALISI Centrifuge Training
Centrifuges for Solid-Liquid, Liquid-Liquid and 3 Phase Separation3-Phase Separation
Decanter:A continuous settling centrifugeA continuous settling centrifuge
Presented by:Prof. Dipl.-Ing. M. H. Kopf
July 2010 1PIERALISI Decanter Technology
Decanter: a continuous settling centrifugeWhat we are talking about:What we are talking about:
2PIERALISI Decanter TechnologyJuly 2010
Decanter: a continuous settling centrifugeOverview and basic principle:
A DECANTER is also named solid-bowl conveyor centrifuge. The latter name already describes very well the main parts of the machine and their functions.
Overview and basic principle:
y p
BowlCentrate Discharge Ch b
ConveyorScraper Scraper
DriveChamber
y
Gear Box
Solids Discharge Feed PipeSetting
Differential speed
3
chamberDifferential speed
July 2010 PIERALISI Decanter Technology
Decanter: a continuous settling centrifugeProcess technologies with a decanter:
Clarifying of liquids with simultaneous +
Process technologies with a decanter:
settling of feed-solids
Sludge thickening +
Dewatering of crystalline solids,sludges and pasty solids
+
Wet classifying for particulate solids
S ti f lid
+
Sorting of solids(using a special, density-adapted fluid)
3 Ph ti
+
+3-Phase-separation, (liquid / liquid / solid dispersions)
+
++
4
Extraction +
July 2010 PIERALISI Decanter Technology
Decanter: a continuous settling centrifugeOverview and basic principle:
You could think of a decanter as the result of a geometry-change with which the settling area of a flat settling tank has be transformed to a concentrical cylinder wrapped around
Overview and basic principle:
g y ppa center-line.
Feed Solids discharge
Liquid discharge
5July 2010 PIERALISI Decanter Technology
Decanter: a continuous settling centrifugeOverview and basic principle
You could think of a decanter as the result of a geometry-change with which the settling area of a flat settling tank has be transformed to a concentrical cylinder wrapped around
Overview and basic principle
g y ppa center-line.
Doing that, the solids-scraper shown below is transformed to a conveyor.
Conveyor FeedFeed
Solids discharge
Liquid discharge
6July 2010 PIERALISI Decanter Technology
Decanter: a continuous settling centrifugeOverview and basic principle:
You could think of a decanter as the result of a geometry-change with which the settling area of a flat settling tank has be transformed to a concentrical cylinder with wrapped
Overview and basic principle:
g y pparound a center-line.
The “tank-bottom” forms the bowl.
Bowl
7PIERALISI Decanter TechnologyJuly 2010
Decanter: a continuous settling centrifugeMain parts schematic cross section:Main parts, schematic cross section:
8PIERALISI Decanter TechnologyJuly 2010
Decanter: a continuous settling centrifugeThe main parts 3 D cut:The main parts, 3- D cut:
BowlBowlEffluent weirs
Solids outlet
Gear-box
Feed inlet
Main drivemotor
Feed tube
motor
Secondary motor(differential speed)
9PIERALISI Decanter TechnologyJuly 2010
Decanter: a continuous settling centrifugeApplying G force:
As the bowl is rotating a centrifugal acceleration is developed, the effect of which is similar to the gravitational acceleration in the earth field – only the magnitude is very
Applying G-force:
g y g ymuch different.
G-force: > 2.500 x g
10PIERALISI Decanter TechnologyJuly 2010
Decanter: a continuous settling centrifugeBasic calculations:Basic calculations:
( )ieNiv rrh −=Pond dept
( )Mean radius ( ) 2/rrr iem +=
G-force: C-Valueg
rC2
m rω⋅
=
11
g
PIERALSI Decanter TechnologyJuly 2010
Decanter: a continuous settling centrifugeSizing and scale up: Theory of equivalent settling area ΣSizing and scale-up: Theory of equivalent settling area Σ
The eq i alent settling area Σ is the prod ct of m ltipl ing the settling areaThe equivalent settling area Σ is the product of multiplying the settling areawith the C-value.
Remember: the settling area is the area onto wich particles are settling and on g p gwhich the vector of the driving force stands rectangular.
)r(cylm clr2 ⋅⋅⋅π=Σ
12
)r(cylm m
PIERALISI Decanter TechnologyJuly 2010
Decanter: a continuous settling centrifugeSizing and scale up: The pond volumeSizing and scale-up: The pond volume
Th d l (bl l d) i l l t d i f ti l i ith thThe pond volume (blue colured) is calculated as a circumferrential ring with the:- the inner bowl diameter as outer diameter and- the inner liquid diamter as inner diameter- the length is the cylindr. length as minimum. g y g
( ) cyl2
i2
epond lrrV ⋅−⋅π=
13PIERALISI Decanter TechnologyJuly 2010
Decanter: a continuous settling centrifugeSizing and scale up: Important remarkSizing and scale-up: Important remark
Si th di t d th l th t b t k i t t f l l ti bSince the diameters and the length to be taken into account for calculation can be varied, i.e. depend on the piont of view and the basic assumptions made, there aredifferent equations calculating for the same parameter.In example we have 7 different calculations to get Σ and at least 3 for the pond-volume.p g p
14PIERALISI Decanter TechnologyJuly 2010
Decanter: a continuous settling centrifugeDewatering on the conical extension: Crystalline productsDewatering on the conical extension: Crystalline products
C Product:- crystalline particles- rel. low fitration resistance
Conveyor flight
Dewatering:by drainage
Decanter bowl:shallow pond
- by drainage - liquid flows back into the pondthrough the cake porosity
- shallow pond
15PIERALISI Decanter TechnologyJuly 2010
Decanter: a continuous settling centrifugeDewatering on the conical extension: Sludges and pasty productsDewatering on the conical extension: Sludges and pasty products
Product:C - pasty products - high filtration resistance
Conveyor flight
Dewatering:- by sediment compression - liquid flows to cake surfaceand (if possible) meanders
Decanter bowl:- deep pond
back ito pond.
16PIERALISI Decanter TechnologyJuly 2010
Decanter: a continuous settling centrifugeInfluences on the separation: Machine based parameter
Bowl diameter:
Influences on the separation: Machine based parameter
pond volume / residence time, max. speed / G-force
Slenderness ration (l/d): ( )length of clarification zone (cyl. Length) /residence time
Geometry of conical extension: yslippage force, torque-level, dewatering-kinetics
Conveyor geometry: y g ypitch, flight-angle, number of flights
Material and surface quality of the bowl and the conveyor flights:q y y gfriction forces / slipping
17PIERALISI Decanter TechnologyJuly 2010
Decanter: a continuous settling centrifugeInfluences on the solids transport and dewatering: Number of flights
The geometry, e.g. the number of flights is important with respect to the solids conveying Especially for crystalline products the dewatering will be influenced by the
Influences on the solids transport and dewatering: Number of flights
conveying. Especially for crystalline products, the dewatering will be influenced by the cake formation/ geometry in front of the flight.
Rule of thumb: a double flight conveyor decreases the “cake height” by half.
Double flightSingle flight
18PIERALISI Decanter TechnologyJuly 2010
Decanter: a continuous settling centrifugeInfluences on the separation: Hydraulic lift disc
Discharging pasty products like cell-biomass or sludges often requires a „helping hand“ by employing hydraulic pressure
Influences on the separation: Hydraulic-lift-disc
by employing hydraulic pressure.
This led to the development of the so-called „hydraulic-lift-disc“ (orig. baffle-disc).
The result of using a baffle-disc is both better sludge conveying and higher dry-solids via a press-dewatering.
Radius < neutral
Neutral line
Compressing gap
19
Co p ess g gap
PIERALISI Decanter TechnologyJuly 2010
Decanter: a continuous settling centrifugeConveyor design: Baffle Disc and flightsConveyor design: Baffle Disc and flights
20PIERALISI Decanter TechnologyJuly 2010
Decanter: a continuous settling centrifugeInfluences on the separation: Effluent discharge; 2 and 3 phase
The discharge of effluent via paring device enables for foam-free and gas-free discharge d d f i dj t t f th d d t ll
Influences on the separation: Effluent discharge; 2 and 3-phase
under pressure and for an in-process adjustment of the pond-dept as well.
Heavy phase
Light phase
2-phase, 3-phase, 3-phase,
Light phase
p ,paring disc
p ,conventional
p ,paring device
21PIERALISI Decanter TechnologyJuly 2010
Decanter: a continuous settling centrifugeInfluences on the separation: Hard surfacingTo comply with the abrasion properties of many solids, a special surface protection is needed.
Influences on the separation: Hard surfacing
Below, the maximum surface protection is shown: Tungsten Carbide Tiles.
22PIERALISI Decanter TechnologyJuly 2010
Decanter: a continuous settling centrifugeProcess demands: Sealing systems
To comply with the process demands regarding containment, e.g. ATEX regulation, different sealing systems are on the market
Process demands: Sealing systems
g y
Lip-seal
Espey-Seal:
23
Multi-chamber seal
PIERALISI Decanter TechnologyJuly 2010
Decanter: a continuous settling centrifugeInfluences on the separation: Operational parameter
Throughput:
Influences on the separation: Operational parameter
g pResidence time of liquid- and solid-phase in the centrifugal field, i.e. the clarification zone and the dewatering zone.
Bowl speed:pG-force, shear-force, vortices
Differential speed (Δn):Solids capacity / residence time, dry-solids, dewatering p y , y , g
Weir or paring-device setting: Pond dept, dry beach,
24PIERALISI Decanter TechnologyJuly 2010
Decanter: a continuous settling centrifugeInfluences on the separation: Differential speed Δn
Differential speed
I i th diff ti l d lt i
Influences on the separation: Differential speed Δn
Increasing the differential speed results in:
Decreasing of solids residence time in the dewatering zone, increasing of solids capacity (if possible in terms of dewatering kinetics).
Increasing of residual moisture
Increased turbulence in the clarification section, possibly resulting in decreased separation efficiency subsequently demanding a reduced capacity.p y q y g p y
GetriebeGear-boxGetriebe
Planetary gear-box
Gear-box
Differential speed control
Planetary gear-box, 2- or 3-stage
25
1. and 2. Stage
PIERALISI Decanter TechnologyJuly 2010
Decanter: a continuous settling centrifugeInfluences on the separation: Differential speed ΔnInfluences on the separation: Differential speed Δn
Gear Box
Getriebe
Pinion
Differential speed Δn: n – nBowl Conveyorinnn PinionBowl −
=Δ
26PIERALISI Decanter TechnologyJuly 2010
Decanter: a continuous settling centrifugeInfluences on the separation: Differential speed ΔnHow to set differential speed:
Influences on the separation: Differential speed Δn
Variable Δn via a special d i h
Variable Δn via a hydraulic drive (Rotodiff) setting the pinionsecondary motor setting the
pinion speed.(Rotodiff) setting the pinion speed.
27PIERALISI Decanter TechnologyJuly 2010
Decanter: a continuous settling centrifugeInfluences on the separation: Product based parameter
Density difference of the phases to be separated
Influences on the separation: Product based parameter
y p pSettling velocity, capacity
Particle- or / and droplet-size and shape; PSD,Settling velocity, sediment compressibility, cut-sizeg y, p y,
Physical-chemical properties of the phases involvedMaterials to be used, product sensitivities
Flow behavior and viscosity of the carrying fluidFlow-behavior and viscosity of the carrying fluid
Solids concentration in feedConveyor geometry, capacity
Sediment behaviorflow-behavior, filtering-resistance, torque requirement
28PIERALISI Decanter TechnologyJuly 2010
Decanter: a continuous settling centrifuge
…need a break…
29PIERALISI Decanter TechnologyJuly 2010