From the PCC, the air stream enters the first Cloud Generation Vessel (CGV #1)
mixing with the cloud of positively charged water droplets created by the Charging Head. B. CGV #1 performs several functions.
- Neutral particles, including ultra fine particles, are attracted to the droplets
and captured through monopole induced dipole charging effects.
- Particles in the exhaust that are already negatively charged
are electrostatically attracted to the positive droplets and captured.
- The second stage of gas scrubbing takes place.
Exiting CGV #1, the air stream enters CGV #2 and is mixed with a cloud
of negatively charged droplets. C. CGV #2 performs several functions.
- Residual neutral particles, including ultra fine particles and TAC are further removed.
- Particles in the exhaust that are already positively charged
are electrostatically attracted to the negative droplets.
- The third and final stage of gas scrubbing takes place.
The cleaned air passes through a mist eliminator and goes to the wet stack.
Cloud Chamber Technology:
A New Approach to Fine Particles and Ultra Fine Particles The Cloud Chamber Scrubber® (CCS®) was developed by Dr. Clyde Richards,
Atmospheric Physics, Inc. (Albuquerque, NM), and is licensed to Tri-Mer Corporation.
See History web page. With its broad treatment capabilities, the CCS is an effective air pollution control solution
for any exhaust application that produces coarse, fine or ultra fine particles, including difficult
applications such as diesel exhaust and glass furnace exhaust. CCS technology works by passing the dirty gas stream through a chamber that contains a
carefully generated “scrubbing cloud” of high-density, charged water droplets. Inside the
Cloud Chamber system, billions of charged droplets rapidly interact with the particle-bearing
process stream. When a particle and a droplet pass within 20 microns, electrical forces cause
mutual attraction and the particle (being less massive by orders of magnitude) is pulled into the
droplet. Each individual water droplet becomes a particle collector. The droplets collect particles as they interact with the process gas stream, then “rain” into a
sump at the bottom of the system. Captured particles agglomerate within the sump, settle
out, and are removed as a low volume slurry from the bottom. Relatively clean water from the
top of the sump is re-circulated by pump to the charging grid, where it is recharged, completing
the cycle. 
A low concentration of particulate does not affect the ability to charge the water, so relatively
clean water from the top of the sump is filtered for very coarse particles and re-circulated to
the charging nozzles. Since the charged droplets act as particle collectors, there is no need for fibrous filters,
collector plates, venturi throats, layered pads, bags, or cartridges. Several factors are involved with optimizing the effectiveness of a particular Cloud Chamber
application. These include droplet size, droplet charge, particle size, particle charge, particle
retention time, and electric field effect. For each application, a computer simulation can be
run to analyze these factors, along with expected inlet loading, gas type and concentration. Gases to be treated, if any, are taken into consideration. These simulations help determine
the ideal system configuration in terms of recirculation flow, gas-to-cloud contact time,
and vessel size. Any required fine-tuning of parameters occurs during operational start-up. Advantages of Cloud Chamber Scrubbers Introduction Particles are, by definition, both solid bits and tiny liquid droplets of condensed pollutants.
Size definition for both solid particles and liquid particles has been set by the U.S. EPA as follows:
- Coarse = particles 2.5 micron & larger
- Fine = 2.5 micron & smaller
- Ultra fine particles = 0.1 micron & smaller
Gases usually refers to acid gases and include toxic vapors that can
condense into liquid particles. Caustic fumes such as ammonia and its
compounds are sometimes called gases. Coarse particles are easily removed by the CCS. Fine particles between 0.1 and 2.5 microns
are removed at very high efficiencies, often 99% or better. Remarkably, even ultra fine particles
as small as 0.01 micron can be effectively treated after controlled agglomeration growth in the
system’s “pre-conditioning” section. The equipment can handle inlet mass loadings greater
than 3,000 mg/m3, reducing mass emissions to below 5 mg/m3. This is equivalent to
1.3 grains/ft3 reduced to 0.002 grains/ft3. Competitive Initial Costs CCS is a cost-effective, multi-pollutant technology. When gas scrubbing is required in
addition to particle removal, further savings are realized because the CCS eliminates the
need for a separate scrubber. Low Operating Costs (Electrical) The CCS offers significant operating cost savings. A proprietary, patented method is used to
charge the water droplets. The system’s charge generation modules require a maximum of 10
watts of power per 1000 cubic feet per minute (cfm). An ordinary 100 watt light bulb draws as
much power as a charging head for 10,000 cfm. Power consumption for charging is usually
1% or less of that required by ESP technology. The key is that only water droplets are charged,
and that the charge generating module works under controlled steady-state conditions,
putting charge on a highly receptive medium. The main power draw in a CCS system is the pumps that recirculate water to the heads.
The CCS recirculates (but does not consume) more water than wet ESP. The net result, however,
is that the CCS still uses substantially less total power to operate. Maintenance costs are also
much lower. The differences are dramatic. Low Operating Cost (Pressure Drop) The CCS chambers are completely open, with no packing or baffles. Pressure drop is very low,
less than 0.75-inch water (H2O) per stage. This results in low fan energy requirements.
Most of the 0.75-inch H2O pressure drop comes from a mist eliminator at the end of the system
and the connecting ductwork. The obstruction-free vessels themselves create nearly zero
pressure
drop. Low Operating Costs (Maintenance) The open chambers of the CCS reduce typical maintenance problems because there is no
fouled packing to clean or biological growth problems to treat. Most importantly, the system
has a minimum number of moving parts – only a reliable standard recirculation pump on
each vessel and an ID fan, in some cases. The charging heads themselves are very durable
and simple in design, having no moving parts. The power supplies are small, the size of a
shoebox. The nozzles are inexpensive standard issue and are protected from plugging by
redundant prevention approaches. Nozzle replacement has been a non-issue even for
units operating 24/7 for over five years. Application Flexibility A CCS can be used as a stand-alone scrubber or as a tail gas scrubber for existing systems.
With the addition of pH adjustment chemicals to the sump liquid, CCS can treat scrubbable
gases (such as “ammonia slip” and sulfur dioxide, S02) in addition to fine and ultra fine particles.
Because of the small pressure drop, using a CCS as a tail gas scrubber usually does not
require additional fan equipment. The CCS smoothly handles changes in flow volume and can be turned down over a wide range,
typically 10- to -1 or better. Charging scheme does not change. Moreover, CCS is relatively
unaffected by changes in particle loading and loading constituents (including TAC) due to the
physics of charged clouds. There is built-in redundancy in a standard 2 CGV configuration
because a single CGV already has a very high capture efficiency. |
