MIST ELIMINATION TECHNIQUES AIR WATER SOIL · PDF fileTIDEVANES MIST ELIMINATOR AIR WATER SOIL CORPORATION Varieties of Vane Pack Mist Eliminators Non-pocket Vane Packs: ... WESP :

AIR WATER SOIL CORPORATION

AIR WATER SOIL CORPORATIONMIST ELIMINATION TECHNIQUES


Definition of aerosol: fume, mist and spray

• Fume, Mist and spray are part of the main family of aerosols, which are suspended particulates, either solid or liquid, which are slow to settle by gravity.

• The particle sizes are from 0.01 mm up to 1000 mm

• Fumes are submicronic dispersions resulting from shock cooling with particle size lessthan 1 mm.

• Mists are fine suspended liquid dispersions usually resulting from condensation andranging upward in particle size less than 10 mm.

• Spray refers to entrained liquid droplets. The droplets may be entrained from atomizingprocess. Size will range from the finest 10 mm up 1000 mm.


mm0.01 0.1 1 10 1000100

MIST

SPRAY

Particle size

FUME

CIGARETTES SMOKE CLOUDS AND FOG RAIN


mm

0.01 0.1 1 10 1000100

DRYING

TOWER

(DT)

FINAL

ABSORPTION

TOWER

(FAT)

INTERPASS

ABSORPTION

TOWER

(IPAT)

SO2

CLEANING


Sources in sulphuric acid plants

Distribution in terms ofnumber of particles


FINAL

ABSORPTION

TOWER

(FAT)

Typical particle size distribution


Distribution in terms of % weight


INTERPASS

ABSORPTION

TOWER

(IPAT)

Typical particle size distribution



Mechanisms of mist removal


Inertial Impaction As the gas approaches the mist elimination target, the gas streamlines spread out and flow around the target. Droplets larger than a certain size will leave the gas streamline due to their inertia and impact on the target. In sulfuric acid plants, droplets larger than 5 to 10 microns diameter are removed from the gas stream by this mechanism. Efficiency of this mechanism increases as either the velocity increases.

Droplets size > 5 mm

Droplets

Fiber

Wire




Droplets size > 1 mm

Droplets

Fiber

Wire

Direct Interception Smaller droplets continue to follow the gas streamlines because of their lower inertia. If these droplets pass close enough to touch the target, they will be collected. In sulfuric acid plants, droplets 1 to 10 microns diameter can be collected by this means.




Brownian Diffusion Droplets well below 1 micron diameter, because of their low mass, exhibit random Brownian motion caused by collisions with gas molecules. This random motion increases the probability that these droplets will collide with the targets. More targets, smaller targets and more residence time (lower velocity) increase removal efficiency from Brownian diffusion.

Fiber

Droplets size < 1 mm

Droplets


Total effect of particle elimination


The elimination efficiency decreases with particle size for momentum (inertial impaction) and interception separation mechanisms, but increase for Brownian motion separation. In between, by a particle size of approximately 0.2 microns, there is as a result a minimum separation efficiency.


Equipments used in aerosol removal

FIBERWIND

IM TYPE

WESP

MESHPADS

FIBERWIND

BM TYPE


0.01 0.1 1 10 1000100

VENTURI

TIDEVANE

FOR LIQUID

AND SOLID AEROSOL

FOR LIQUID

AEROSOL

Specially in SMELTERS, sulphuric acid plant yield strongly depends on good performances of equipments like mist eliminators, WESP & Venturi

AIR WATER SOIL CORPORATIONAIR WATER SOIL CORPORATION

Equipments used for aerosol removal in sulphuric acid plants

mm

0.01 0.1 1 10 1000100

DRYING

TOWER

(DT)

FINAL

ABSORPTION

TOWER

(FAT)

INTERPASS

ABSORPTION

TOWER

(IPAT)

SO2

CLEANING

- FIBERWINDTM BM

- FIBERWINDTM IM3(Not suggested by AWS)

- FIBERWINDTM BM

- FIBERWINDTM IM2(Not suggested by AWS)

- VENTURI

- WESP

- FIBERWINDTM IM1

- MESHPADS

- TIDEVANETM


FIBERWIND BM TYPE


The Brownian Movement candles are manufactured in cylindrical from. The fibre bed consist of special glass fiber wound with uniform density and thickness, packed to an exact technical specification between two concentrical cages. The FIBERWIND™ mist eliminators are installed vertically on a tube sheet either in hanging or standing configuration. The mist laden gas flows radially through the fiber. Because of the vertical configuration of candles, liquid accumulating on the fibers is moved horizontally through the fiber bed by the drag force of the gas and drains by gravity along the downstream side to the bottom of the fiber bed where it is collected.

STANDING TYPE

GAS FLOW - INSIDE/OUTSIDE

HANGING TYPE

GAS FLOW - OUTSIDE/INSIDE


FIBERWIND BM TYPE: Efficiency – mist distribution

CRITICAL DIAMETER


TYPICAL FIBERBEDVELOCITY

LOWER CONTACT TIME LOWER EFFICIENCY

ON CRITICAL DIAMETER


Picture Gallery: Sulphuric acid plants



Picture Gallery: Sulphuric acid plants



Oldgeneration

Actualgeneration

Future generation

Lower Dp BULK FIBER

Higher Dp

WOUNDCANDLE

High reliability

2/3 actual Dp

INNOVATIVE STYLE

smaller elements


FIBERWIND BM TYPES


• 4H+ + 4F- + Si4+ + 4OH- SiF4 + 4H2O

• ION F- EXTREMELY REACTIVE AND WILL FORM SIF4

• SMELTERS SOME TIME 100/200 ppm FLUORIDES

• EVERY PPM OF FLUORIDES PASSING THROUGH THE FIBERBEDS WILL REACT WITH Si4+ IONS SIF4 SUBLIMATES STACK


FIBERWIND BM : a special application

FLUORIDES ATTACK OF THE GLASS

STANDARD FIBERGLASS CANDLES AWS CARBON FIBER CANDLES


• RISK OF FIBER PLUGGING AT THE INLET OF THE CANDLE

• PLANTS WITH PROBLEMS OF SOLIDS OR SALTS IN THE GAS STREAM



SOLIDS BARRIER

SOLUTION: SOLIDS BARRIER (FIBER WITH LESS DENSITY) AT THE INLET OF THE CANDLE

SOLIDS BARRIER


• RISK OF LIQUID DROPLETS RE-ENTRAINEMENT

• DUE TO HIGH FIBERBED VELOCITY AND HIGH LIQUID LOADS (THE DROPS TERMINAL VELOCITY DOES NOT EXCEED THE GAS VELOCITY)



LIQUID DRAINAGE

SOLUTION: DRAINAGE LAYERS AT THE OUTLET OF THE CANDLE FILTERS

DRAINAGE LAYERS


FIBERWIND IM TYPE


The IMPACTION Movement candles can be manufactured in cylindrical form standing type, or in panel form. The fibre bed consists of special glass fiber (rope or mattress) and mesh.

Different types are available according to application:

DRYING TOWERIM1 : bed velocity > 425 ft/min

IPAT IM2 : bed velocity 350÷400 ft/min

FATIM3 : bed velocity around 150 ft/min


FIBERWIND IM TYPE : several configurations MIST ELIMINATORS


FIBERWIND IM TYPE : re-entrainment problem


WIRE MESH MIST ELIMINATOR





Single Component Mesh Pads:

• Metal or plastic wires• 99.9% separation efficiency at 5-15 µm droplets

Single-zone:Traditional uniform mesh build-up

Multi-zone:Non-uniform mesh build-up, gradually increasing surface area towardsthe downstream side, allowing a higher capacity




Dual Component Mesh Pads:

• Metal or plastic wires• Increased surface area• Increased efficiency• 99.9% separation efficiency at 2-3 µm droplets

Type determining parameters:• Wire diameter• Mesh geometry• Mesh density• Surface area• Free volume



WIREMESH : SX/A20 + PTFE WIREMESH : SX/A20 WIREMESH : SS316

WIREMESH : SS316L TEFLON COATED WIREMESH : SS316L AND GLASS FIBRE

MIST ELIMINATORS

ONE SPECIAL PRODUCT: SS316 teflon coated wire mesh


PTFE COATING

MIST ELIMINATORS


TIDEVANES MIST ELIMINATOR


Benefits:

• Low pressure drop of non-pocket Vane Packs• Suitable for horizontal and vertical gas flow• Smooth surfaces + large open area minimises

fouling potential• Increased gas and liquid capacity• Higher corrosion / erosion resistance• Wide variety of construction materials

Limitations:

• Moderate separation efficiency• Single pocket Vane Packs have an

elevated pressure drop




Operating principle of Vane Pack Mist Eliminators

Horizontal gas flowVertical gas flow




Varieties of Vane Pack Mist Eliminators

Non-pocket Vane Packs:

• Mainly used in vertical flow applications• 99% separation efficiency at 20-50 µm droplets

Pocket Vane Packs:

• Mainly used in horizontal flow applications• 99% separation efficiency at 8-25 µm droplets

Type determining parameters:

• Blade spacing• Blade geometry• # of pockets• # of passes


INSTALLATION : PRE-DRYING TOWER


CASE HYSTORY: XXXXXX

BLANKED PLATE


VENTURI SCRUBBERS

Venturi scrubber is designed to use theenergy from the inlet gas stream toatomize the liquid being used to scrub thegas stream.The inlet gas stream enters the convergingsection and, as the area decreases, gasvelocity increases. Liquid is introducedeither at the throat or at the entrance tothe converging section.The inlet gas, forced to move at extremelyhigh velocities in the small throat section,shears the liquid from its walls, producingan enormous number of tiny droplets.Particle and gas removal occur in the throatsection as the inlet gas stream mixes withthe fog of tiny liquid droplets. The inletstream then exits through the divergingsection, where it is forced to slow down.


VENTURI SCRUBBERS

The relatively high liquid-to-gas ratio, liquidatomization, and open internal design provideeffective scrubbing of heavily contaminatedgases with minimal maintenance and virtuallyunlimited turndown capabilities. Its ability tohandle wide ranging conditions whileremoving both toxic gases and particulatematter makes the Venturi one of the mostflexible designs available. It is often used as afirst stage in a multi-stage pollution controlsystem.


VENTURI SCRUBBERS : DESIGN


VENTURI SCRUBBERS : DESIGN

The Venturi – scrubber is a good technology to remove solid aerosol bigger than 1 microns.


WESP : Wet Electrostatic Precipitator


WESP : working principle

The principle of operation of an electrostatic precipitator is that the particles are passed through an electrical field where they receive an electrical charge. Charged particles are deflected and collected across the electrical field on a grounded tube.

The WESP is the right technology to remove solid aerosol smaller than 1 microns.


WESP : From OLD to NEW design

OLD WESP made of lead replaced with new conductive plastic materials : from lead coated plates to PP or FRP conductive tubes

PP conductive

tubes

FRPconductive

tubesLead coatedplates

WESP & VENTURI



OLD WESP made of lead replaced with new hastelloy materials : from leadcoated ionizing rods to hastelloy ionizing rods

Hastelloyionizing rods

Lead coatedionizing rods

WESP & VENTURI



OLD WESP made of lead replaced with new plastic materials : from leadcoated housing to FRP casing

FRP housing …Shining

Lead coatedhousing … tearful !

WESP & VENTURI


AIR WATER SOIL CORPORATIONGRAZIE ..….

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MIST ELIMINATION TECHNIQUES AIR WATER SOIL · PDF fileTIDEVANES MIST ELIMINATOR AIR WATER SOIL CORPORATION Varieties of Vane Pack Mist Eliminators Non-pocket Vane Packs: ... WESP :