Particulate control techniques

• Gravity settling chamber

• Mechanical collectors

• Particulate wet scrubbers

• Electrostatic precipitators

• Fabric filters

Gravitational Settling chambers

• Settling chamber:– Useful for large particulates (> 50 m)– Often in conjunction with a filter or precipitator

to reduce overall system and operation costs (pre-collector)

– May also contain baffles to serve as impingement devices

– Low overall pressure drop and efficiency

GSC

• Very low terminal air velocity• The velocity of a falling particle when the

gravitational force downward is balanced by the air resistance (or drag) force upward

• Efficiency < 50 %

Cyclone separators

• use the inertia of the particles for collection

• The particulate-laden gas stream is forced to spin in a cyclonic manner.

• More efficient than gravity settling chambers under heavier loads in Particle range: 15 - 50 mm• Efficiency requires cut diameter, dc, at which 50% of the particles with diameter dc can be removed.

Efficiency improvement

• if you want to increase the efficiency of a cyclone you can:

reduce the cyclone diameter,reduce the outlet diameter,reduce the cone angle,or increase the body length.

Efficiency improvement

• However, if you want to increase the capacity of a cyclone, you can:

increase the cyclone diameter,increase the inlet diameter,increase the outlet diameter,or increase the body length.

Efficiency improvement

• Increasing the pressure drop will also result in:

an increase in separation efficiencyhigher capacitydecrease the underflow to throughput ratiomore concentrated underflowcleaner overflow.

Wet Scrubbers

Fabric Filters

• Filters can be made of a variety of natural and synthetic materials, such as cloth, glass fiber and paper.

• Particles in the gas stream are removed by interception and interaction with fibers in the filter media; once particle attaches to the fiber it effectively increases the fiber size and collection ability

• Common to monitor pressure drop across filter and change filter media at pre-determined value

ESP