semi合集-English.pdf - 第3771页
SEMI F5-1101 © SEMI 1990 , 2001 15 can be subject to stricter regulatory requ ire ments. Ensure th at an y o xidation un i t does not create new an d more hazardou s co m pounds, s uch as dioxins . A1-3.2.7. 2 Sulfur a n…
SEMI F5-1101 © SEMI 1990, 2001 14
due to solids and/or biological growth is required. The
chevron style is typically used in conjunction with a
weir, as they are not very effective on the smaller
droplet associated with spray nozzles; however they are
very immune to plugging from solids and/or biological
growth. The entrainment separators are discussed in
Sections A1-1.3 and A1-1.5.
A1-2.15 Chlorine, fluorine and possibly other soluble
gases can be entrained in scrubber wastewater, and
released in facilities drains/vents. Materials such as
fluorine are incompatible with many plastics and can
damage drains/ vents resulting in leak, odors, and
facilities interruptions.
A1-3 VOC Abatement Equipment Design and
Selection
A1-3.1 Design Criteria for Adsorption Systems
A1-3.1.1 Adequate contact time must be achieved
between adsorption media and VOC-laden exhaust
stream. The adsorption matrix must be sized so that
adequate residence time within the media is maintained.
Also, the exhaust stream flow must be distributed
uniformly over the adsorption matrix.
A1-3.1.2 Pressure drop across the adsorption matrix
should be minimized to reduce energy consumption for
air handling equipment.
A1-3.1.3 Materials of construction must be resistant to
any corrosive action by the VOC' s or by-products
formed during adsorption or adsorbent matrix
regeneration.
A1-3.1.4 Hydrophobic zeolites and activated carbon in
fixed beds, fluid beds or rotating wheels are being used
for adsorption.
A1-3.1.5 Adsorption materials have a finite capacity
for VOC adsorption and must be regenerated when their
capacity is exhausted.
A1-3.1.6 Monitoring of the exhaust stream as it exits
the adsorption bed may be necessary to determine when
regeneration or replacement of the adsorption medium
is needed.
A1-3.1.7 Pretreatment of the VOC-laden exhaust
stream for removal of entrained particles or liquids may
be required to prevent plugging of the adsorption unit.
A1-3.1.8 Regeneration is accomplished by flushing the
adsorption bed with a carrier, typically steam, hot air or
hot nitrogen.
A1-3.1.8.1 Desorbed VOC' s must be recovered or
destroyed.
A1-3.1.8.2 Current practices for VOC recovery
requires condensation or distillation.
A1-3.1.8.3 Current practices for VOC destruction is
usually oxidation.
A1-3.2 Design Criteria for Oxidation Systems
A1-3.2.1 Adequate residence time, mixing with air and
temperature, must be provided for high efficiency
destruction of the VOC' s.
A1-3.2.2 Pretreatment of the VOC-laden exhaust
stream for removal of entrained particles or liquids may
be required to prevent plugging of the oxidation unit.
A1-3.2.3 Downstream abatement of the oxidation unit
exhaust will be required if corrosive combustion
products [such as hydrogen chloride (HCl) from
chlorinated vapors] or particles [such as silicon dioxide
(SiO
2
) from hexamethyldisilazane (HMDS)] are
present.
A1-3.2.4 Concentrations of the incoming VOC' s
should be limited, especially when using a concentrator.
Typical incoming VOC concentrations should not
exceed 25% of LEL.
A1-3.2.5 Energy costs for heating VOC-laden exhaust
streams must be considered. Straight thermal oxidizers
are costly to use with high-volume, low VOC
concentration exhaust streams. Therefore, a
concentration process followed by recuperative or
regenerative oxidation offers a more cost-effective
solution.
A1-3.2.5.1 Catalytic oxidation may also offer cost
savings; however, the composition of incoming
compounds must not poison the catalyst.
A1-3.2.5.2 A regenerative thermal oxidizer (without a
preceding concentrator) may offer cost savings in
certain applications.
A1-3.2.6 Hybrid systems (combinations of adsorption
and oxidation systems) may provide a cost-effective
approach for abating dilute concentrations of VOCs in
exhaust streams by combining adsorption beds with
recuperative/regenerative oxidation, to destroy the
VOCs.
A1-3.2.6.1 All design considerations for adsorption
systems and oxidation systems are relevent for any of
the multitude of possible hybrid systems.
A1-3.2.6.2 Levels of oxidation by-products must also
be considered such as oxides of nitrogen (NOx), carbon
monoxide (CO) and products of incomplete combustion
(PICs).
A1-3.2.7 Potential problem areas to be reviewed in any
equipment selection procedure:
A1-3.2.7.1 Halogenated Materials — Additional care
must be exercised with chlorinated compounds, which
SEMI F5-1101 © SEMI 1990, 200115
can be subject to stricter regulatory requirements.
Ensure that any oxidation unit does not create new and
more hazardous compounds, such as dioxins.
A1-3.2.7.2 Sulfur and Hexamethyldisilazane (HMDS)
— Both have the potential to poison many catalysts,
and hexamethyldisilazane (HMDS) will oxidize to form
silicon dioxide, which can result in particle build up in
heat exchangers and oxidizers.
A1-3.2.7.3 Moisture Levels — Moisture can
significantly affect adsorption capability.
SEMI F5-1101 © SEMI 1990, 2001 16
APPENDIX 2
POU ABATEMENT TECHNOLOGY TYPES
NOTE: The material in this appendix is an official part of SEMI F5 and was approved by full letter ballot
procedures on August 27, 2001.
A2-1 POU Abatement Technology Types:
1. Wet scrubbing systems
2. Oxidation systems
3. Cold bed systems (adsorbers/ chemisorbers)
4. Hot chemical bed systems
5. Reactor systems (e.g., plasma, microwave)
6. Traps/filters/cyclones/precipitators
A2-2 Wet Scrubbing Systems
A2-2.1 Water Scrubber
A2-2.1.1 Principle of Operation — Exhaust gas is
passed through an enclosed space into which water is
sprayed. The desired result is that gases will dissolve in
or react with the water. A large contact area between
gas and water is required to maximize the dissolution or
reaction. Numerous designs exist to achieve this. The
“packed-bed” scrubber is filled with open structure
objects (e.g., hollow balls) that are fully wetted by the
water spray. The gas passes over this large wet surface
area. If the water spray is in the opposite direction to
the gas path the design is “counter current”; if in the
same direction, it is “co-current”; and if at 90° it is
“cross flow”. Other designs to maximize gas/water
contact use meshes, atomized sprays, or multi chamber
systems that reverse the gas direction several times.
A2-2.1.2 Capacity — Total gas flow is determined by
the size of the unit.
A2-2.1.3 Efficiency — Efficiency is determined by the
solubility of the gas in water and retention time in the
unit as well as the given mass transfer from gas to
liquid phase. Acid gases are best removed; many other
process gases may not be removed. If gas does dissolve
in water then effectiveness of unit will be determined
by design input gas flow and inlet compound
concentrations.
A2-2.1.4 Limitations — Water scrubbers are only
suitable for water-soluble gases. Many process gases
(e.g., silicon compounds) will produce insoluble solids
(silica) on contact with water resulting in solids forming
that may block the water sprays, scrubber packing or
gas inlet port.
NOTE 1: Compatibility of scrubber drains with the
compounds being entrained in the liquid effluent should be
considered.
A2-2.2 Water Scrubber with Energy Input (e.g.,
Venturi)
A2-1.2.1 Principle of Operation — Same as water
scrubber but gas and water are forced to mix by the
input of energy. Most commonly this is done by a
venturi through which the gas and water pass. Other
designs have used rapidly rotating blades in the
enclosed scrubbing space. The “active” scrubbing area
is often combined with a passive spray chamber or
packed bed.
A2-2.2.2 Capacity — Energy enhanced water
scrubbers have the same capacity as water scrubbers.
A2-2.2.3 Efficiency — Added energy improves
efficiency over water scrubbers due to forced mixing,
which improves efficiency of particulate removal.
A2-2.2.4 Limitations — The limitations are the same
as for water scrubbers.
A2-2.3 Chemical Dosed Scrubber
A2-2.3.1 Principle of Operation — Chemical Dosed
Scrubbers operate the same as a water scrubber but a
chemical solution is added to the water. This increases
the range of gases that can be removed, from those that
dissolve in water to those that will react with the chosen
chemical solution. The chemical medium is selected to
react with the known input gases producing water-
soluble salts. The two reaction systems most
commonly employed are acid/base and
reduction/oxidation (redox). Addition of solutions of
sodium hydroxide (NaOH), potassium hydroxide
(KOH) or sulfuric acid are frequently used to enhance
effectiveness, and where chemical oxidation is needed
hypochlorites, periodates, or peroxides are introduced.
A2-2.3.2 Capacity — Same as water scrubber.
A2-2.3.3 Efficiency — Same as water scrubber but
increased efficiency by using chemical dosing. The
number of gases, which can be removed, will also
increase.
A2-2.3.4
Limitations — Even though a wider range of
gases can be removed with this chemical dosing, it is
applicable only to those emissions that can be water
scrubbed. The potential for fouling by silica solids