|
|
Selective non-catalytic reduction process |
|
Selective catalytic reduction (SCR) or selective non-catalytic
reduction (SNCR) can be employed to reduce the levels of
nitrogen oxides (NOx) present in the flue gas. The SNCR
process, developed by Martin GmbH of Germany, reduces NOx
produced during combustion to nitrogen and water by injecting
aqueous ammonia (NH4OH), a reducing agent, into the furnace.
NOx values of up to 70 mg/Nm3 have been achieved using this
process.
The agent is injected in the temperature range of 850ºC to
1050ºC. A second mass flow is required to get a uniformly fine
distribution. Both softened fresh water and compressed air may
be used for this purpose in the system. The two mass flows are
combined in a mixing chamber directly up-stream of the nozzle
head. This arrangement ensures low dead times for control of
the aqueous ammonia mass flow, as well as optimized
consumption and low aqueous ammonia slip in the flue gas. The
control system ensures that injection always takes place in
the optimum temperature range as a function of the current
furnace temperature.
Contact: Martin GmbH für Umwelt und Energietechnik,
Leopoldstraße 248, D-80807 München, Germany. Tel: +49 (89)
35617-0; Fax: +49 (89) 35617-299
E-mail:
mail@martingmbh.de
Source:
www.martingmbh.de |
|
|
|
|
Multi-pollutant treatment technology |
|
EMx®, from EmeraChem, the United States, is a multi-pollutant
technology that significantly reduces such pollutants as
nitrogen oxides (NOx), sulphur oxides, carbon monoxide,
volatile organic compounds as well as particulate matter for
gas-fired turbines to ultra low levels (< 1 ppm for all
criteria pollutants). The United States Environmental
Protection Agency declared this technology as “the Lowest
Achievable Emission Rate” for NOx abatement, establishing the
standard against which all future emission reduction means
will be measured.
EMx is a continuous process that is designed to achieve the
required emission reduction at the maximum NOx flow rate. It
does not require a complex feedback control loop, and has
additional catalyst capacity, providing for future regulatory
certainty. EMx is also claimed to be the most effective
ammonia-free reduction technology available today for gas
turbine, reciprocating engines and industrial and utility
boilers. It avoids the fouling of downstream heat transfer
surfaces and guarantees net reduction of particulate matter.
Contact: EmeraChem, 1729 Louisville Dr., Knoxville, Tennessee
37909, United States of America. Tel: +1 (865) 246 3000; Fax:
+1 (865) 246 3001.
Source:
www.environmental-expert.com |
|
|
|
|
Microwave process for NOx abatement |
|
The CHA Corporation, the United States, has recently completed
a small business innovation research programme to investigate
the feasibility of using a novel microwave based filter device
to remove and destroy unwanted by-products of combustion in
exhaust gases. A Corning ceramic monolith soot filter that has
about 90 per cent soot removal efficiency was placed in a
housing that allowed for microwave regeneration. Two filters
were set up in parallel into the exhaust piping of a diesel
engine. After 4-hour periods of operation, the filters were
successfully regenerated employing microwave energy for more
than 50 cycles.
A prototype device for destroying ni-trogen oxides (NOx) in
the exhaust gas generated by a diesel engine (58 hp) was
constructed and tested. The NOx control device comprised two
separate fixed-bed reactors filled with catalyst beads. In the
first, a Pt/Pd catalyst was used to convert nitric oxide (NO)
into nitrogen dioxide (NO2) in the diesel exhaust. A reducing
agent and microwaves were supplied to the second reactor,
containing alumina-SiC pellets coated with a Pt/Rh/Pd
catalyst, to destroy NO2. As the NO oxidation efficiency
(45-55 per cent) is suppressed by the high concentration of
water in diesel engine exhaust, NOx destruction efficiencies
were only 30-40 per cent, 10-20 per cent lower than the NOx
destruction obtained from smaller reactors.
Test results obtained for this prototype microwave deNOx
device clearly identified techno-economic advantages, as well
as technical difficulties, of applying microwave-based filter
devices to control pollutants in diesel exhaust. Preliminary
experimental data indicate that the microwave reactor system
that was developed for NOx destruction can be also used for
destroying waste rocket fuels including hydrazine and
unsymmetric dimethylhydrazine in nitrogen or air streams.
Source:
www.stormingmedia.us |
|
|
|
|
Selective catalytic reduction package/catalyst |
|
irProtekt Ltd., the United Kingdom, supplies the total
selective catalytic reduction (SCR) package or the SCR
catalyst for control of nitrogen oxides (NOx) emission. The
catalyst technologies used are all tried and backed up by the
manufacturing and quality control standards from the largest
automobile catalyst manufacturer in the world.
The basic reactions that occur are as follows:
4 NH3 + 4NO + O2 ® 4 N2 + 6 H2O
8 NH3 + 6 NO2 ® 7 N2 + 12 H2O
These reactions break down NOx into harmless nitrogen and
water. Urea is used as the reducing agent since it is
generally unaffected by the oxygen present in the exhaust
gases and is readily available. In most exhaust gases,
virtually all of the NOx present is in the form of nitric
oxide (NO). The optimum temperature for the reduction of NOx
using a zeolite/base-metal catalyst is about 350º-550ºC.
The main advantages of the SCR process are that the catalyst
has a long life and provides a high NOX removal rate, and
extensive modifications to the engines are avoided. The
underlying principle of this type of catalytic process is the
use of ‘active’ catalytic sites on which the reactant species
are adsorbed. This allows combination of the reactant species
at much lower gas temperatures than needed for uncatalysed
reactions.
Contact: AirProtekt Ltd., Newton Hall, Newton, Cambridgeshire
CB2 5PE, United Kingdom. Tel: +44 (1223) 872 933; Fax: +44
(1223) 872 934
E-mail:
enquiries@airprotekt.co.uk
Source:
www.environmental-expert.com
|
|
|
|
|
A Multi-functional carbon filter process for
flue-gas clean-up |
|
Researchers from the University of Wyoming, the United States,
have developed and evaluated a multi-functional carbon filter
process, or MCFP, for separating carbon dioxide (CO2) and
other pollutants, such as NOx, SOx and mercury, of power plant
flue-gas.
The cost of the recovered CO2 using a carbon-rich adsorbent at
ambient pressure can be reduced by a factor of 2 or more,
relative to an amine-absorption benchmark. Such an adsorbent
is selective at near-ambient temperatures, easy to keep at
constant adsorption temperature, and easy to recover by direct
steam heat because its heat of adsorption is very low.
Besides, MCFP is relative-ly insensitive to flue-gas moisture,
which poses a serious problem for more hydrophilic sorbents
such as zeolites. Based on the data from their laboratory
experiments, the researchers concluded that MCFP technology
can be integrated with a coal power plant for producing an
enhanced oil recovery grade CO2.
Source:
www.aiche.confex.com
|
|
|
|
|
Regenerative thermal oxidation process |
|
The Biotox® process, from Biothermica Technologies Inc.,
Canada, is a patented regenerative thermal oxidation (RTO)
technology for treating emissions of volatile and condensable
organic compounds (VOCs & COCs) and corrosive emissions. In
more than 20 installations, it has successfully demonstrated
destruction efficiencies of more than 99 per cent and energy
efficiencies greater than 90 per cent for flows varying from
2,000 to more than 150,000 actual cubic feet per minute.
The Biotox RTO process consists of oxidizing in a combustion
chamber the VOCs and COCs contained in the industrial
emissions, and recovering usable heat from combustion gases by
means of ceramic beds. The recovered heat can then be used to
pre-heat entry gases, thanks to the efficient heat transfer
between entry and exit gases.
The typical combustion temperature is 800ºC while the
residence time is one second. The combustion gases, mainly
composed of water and carbon dioxide (CO2), are then released
into the atmosphere. A hot gas recirculating system is
installed to raise the COCs to a temperature sufficient for
avoiding condensation in the bottom of the beds.
Advantages of the patented Biotox process include:
- Energy recovery rates reaching 95 per cent, along with
substantial fuel savings and reductions in greenhouse gas;
- Low emissions of NOx and CO2;
- System adaptable to variations in VOC / COC
concentrations; and
- Choice of ceramics to suit specific applications.
Contact: Biothermica Technologies Inc., 426 Sherbrooke
East, Montreal, Quebec H2L 1J6, Canada. Fax: +1 (514) 488 3125
E-mail:
biothermica@biothermica.com
Source:
www.environmental-expert.com
|
|
|
|
|
Electron beam method for SOx and NOx reduction |
|
Chubu Electric Power Co. of Japan has devised an electron beam
process for the simultaneous removal of nitrogen oxides (NOx)
and sulphur oxides (SOx) from flue-gas. It is a dry process
without the need for any wastewater treatment or expensive
denitrification catalyst. The process yields, as a by-product,
a valuable fertilizer. A pilot plant of the system, with a
flue gas treatment capacity of 12,000 m3N/h, has demonstrated
a SOx / NOx removal efficiency of more than 94 per cent and 80
per cent, respectively.
After the floating ash in flue gas is roughly removed in the
dry type electrostatic precipitator, the gas flows through the
GGH extractor to be cooled to around 110ºC. In the spray
cooler, the gas is cooled further to 60º-70ºC, the desirable
level of temperature for desulphurization reaction. Then the
necessary quantity of ammonia for desulphurization and
denitrification is added. The gas then moves into the process
vessel, where an electron beam is applied to it. In the
process vessel, SOx and NOx are oxidized to become sulphuric
acid and nitric acid, respectively, which in turn react with
ammonia to produce fine particles of ammonium sulphate and
ammonium nitrate.
After the fine particles are collected and separated from the
flue gas in the dry type electrostatic precipitator and bag
filter, the purified gas is discharged to the atmosphere by
the booster fan through the stack. The test results from the
pilot plant have proved that the system fully satisfies the
requirements for flue gas treatment in coal-fired power
stations.
Source: www.gec.jp
|
|
|
|
|
Ceramic filters |
|
Ceramic filters from Caldo Environmental Engineering Limited,
United Kingdom, are high-temperature devices for the
continuous removal of particulates from air or other gases.
Caldo supplies a range of filter sizes and employs a modular
approach for larger gas flows. The addition of sorbent powder
enables the filters to function as dry scrubbers in waste gas
applications.
The ceramic filter element is vacuum-formed using alumino-silicate
ceramic fibres as a 1,000 mm long tube, flanged at one end and
closed at the other. It is stable even under extreme
conditions of temperature (up to 900ºC) and chemical corrosion
(except hydrofluoric acid). The elements hang vertically in
the filter vessel from the header plate. In use the hot gas is
sucked through the filter medium from outside to inside,
depositing the particles on the outer surface of the medium.
At controllable intervals a sharp pulse of air is blown back
down the inside of the filter element to detach the solids
accumulated on the outer surface of the filter elements. The
number of filter elements in the filter vessel determines the
capacity of the filter. Caldo has standard designs for 64,
120, 214 and 256 element filters.
Acid gases – a common gas-phase pollutant – can be very
effectively removed by the addition of lime or sodium
bicarbonate to the gas upstream of the ceramic filter. Both
chemicals react well with HCl, HF and H2SO4 and remove a
proportion of any NOx that is present.
Ceramic filters are useful on nearly all high-temperature
processes in which the exhaust gas may contain smoke, fume or
dust. Typical applications include:
- Incineration of wastes;
- Cleaning of fuel gases from pyrolysis or gasification
processes;
- Protection of catalysts in chemical processes;
- Cleaning of gases from metallurgical furnaces; and
- Collection of products manufactured through condensation
of hot gases.
Contact: Caldo Environmental Engineering Limited, No.1
Worcester Court, Saxon Business Park, Hanbury Road, Bromsgrove
Worcestershire B60 4AD, United Kingdom.
Source:
www.environmental-expert.com
|
|
|
|
|
Managing Healthcare Waste – A Practical Approach |
|
“Managing Healthcare Waste – A Practical Approach” is a
must-read for those interested in infection control and
management of medical wastes. The book offers a detailed
overview of technical elements in health care waste management
system, based on the life cycle approach.
Contact: KW Publishers Pvt. Limited, 5A/4A, Ansari Road,
Daryaganj, New Delhi 110002, India. Tel: +91 (11) 2326 3498;
Fax: +91 (11) 2326 3498
E-mail:
knowledgeworld@vsnl.net
|
|
|