U.S. patent application number 11/576285 was filed with the patent office on 2008-10-30 for catalyst delivery system.
This patent application is currently assigned to LGR LLC. Invention is credited to Bernard M. Gibbs, Trevor R. Griffiths, Richard C. Lundin, Shyamal K. Roy.
Application Number | 20080264047 11/576285 |
Document ID | / |
Family ID | 33427902 |
Filed Date | 2008-10-30 |
United States Patent
Application |
20080264047 |
Kind Code |
A1 |
Griffiths; Trevor R. ; et
al. |
October 30, 2008 |
Catalyst Delivery System
Abstract
The present invention provides a catalytic aerosol delivery
system for generating an aerosol containing chemical catalyst
pre-cursors for delivery either directly into the flame zone of a
combustion reaction system, or directly into the inlet air or inlet
fuel or the fuel/air mixture, or directly into the hot exhaust
gases of a combustion reaction, or any combination of these three.
The system and the composition of the invention enables a reduction
in pollution emitted from the combustion chambers and ensures more
efficient and clean combustion. In most applications, the
combustion system and composition of the invention results in
improved fuel economy.
Inventors: |
Griffiths; Trevor R.;
(Mankato, MN) ; Gibbs; Bernard M.; (Mankato,
MN) ; Roy; Shyamal K.; (Mankato, MN) ; Lundin;
Richard C.; (Mankato, MN) |
Correspondence
Address: |
FOLEY HOAG, LLP;PATENT GROUP, WORLD TRADE CENTER WEST
155 SEAPORT BLVD
BOSTON
MA
02110
US
|
Assignee: |
LGR LLC
Mankato
MN
|
Family ID: |
33427902 |
Appl. No.: |
11/576285 |
Filed: |
September 27, 2005 |
PCT Filed: |
September 27, 2005 |
PCT NO: |
PCT/GB2005/003717 |
371 Date: |
March 18, 2008 |
Current U.S.
Class: |
60/299 ;
60/303 |
Current CPC
Class: |
C10L 10/02 20130101;
B05B 7/0892 20130101; F23K 2400/10 20200501; F23J 2215/60 20130101;
F23L 2900/00001 20130101; B05B 7/10 20130101; F01N 2610/1453
20130101; F23J 7/00 20130101; F23K 2300/103 20200501; F23D 14/68
20130101; F23K 2201/505 20130101; F23J 15/003 20130101; B05B 7/0416
20130101 |
Class at
Publication: |
60/299 ;
60/303 |
International
Class: |
F01N 3/10 20060101
F01N003/10 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 1, 2004 |
GB |
0421837.6 |
Claims
1. An aerosol delivery system for use in conjunction with a
combustion apparatus, the system comprising: a chamber, comprising
a first inlet for supplying a source of gas to the chamber, a
second inlet for supplying a catalyst solution to the chamber,
wherein the catalyst solution contains one or more inorganic metal
salts in a solvent, and an atomising nozzle for releasing fluid
from the chamber in the form of an aerosol; wherein the first inlet
and the second inlet and atomising nozzle are arranged so that the
gas and fluid in the chamber mix and combine to form an aerosol
when released through the nozzle; and the nozzle is in fluid
communication with one or more of: a pre-combustion zone, a
combustion zone and a post-combustion zone.
2. The aerosol delivery system of claim 1, wherein the nozzle is
present in the combustion zone.
3. The aerosol delivery system of claim 1, wherein the nozzle is
present in a pre-combustion region where air and fuel are mixed
prior to combustion.
4. The aerosol delivery system of claim 1, wherein the nozzle is in
a pre-combustion region where there is only fuel or the nozzle is
in a pre-combustion region where there is only air.
5. The aerosol delivery system of claim 1, wherein the nozzle is in
a post-combustion region.
6. The aerosol delivery system of claim 1, wherein the nozzle is a
conical shape.
7. The aerosol delivery system of claim 1, comprising more than one
nozzle.
8. The aerosol delivery system of claim 1, wherein the supply of
gas and catalytic solution to the chamber is continuous so aerosol
is sprayed continuously from the nozzle.
9. The aerosol delivery system of claim 1, wherein the catalytic
solution comprises a metal selected from: platinum, palladium,
rhodium, rhenium, ruthenium, osmium, cerium, iridium, indium,
magnesium, aluminium, titanium, copper, zinc, lithium, potassium,
sodium, iron, molybdenum, manganese, gold and silver.
10. The aerosol delivery system of claim 9, wherein the metal is
present in solution in a concentration of from 0.1 to 2.0
mg/ml.
11. A method for catalysing the combustion of a fuel, the method
comprising the steps of: a) providing a supply of a solution of
catalyst and a supply of a pressurised gas to a chamber, wherein
the chamber includes a nozzle in fluid communication with one or
more of: a pre-combustion zone, a combustion zone and a
post-combustion zone, b) mixing the solution and the gas in the
chamber, and c) forcing the mixture of solution and gas through the
nozzle to form an aerosol in the pre-combustion zone, combustion
zone or post-combustion zone.
12. The method of claim 11, wherein the aerosol and the fuel are
introduced into the combustion zone of a fuel injection diesel or
petrol engine simultaneously or separately.
13. The method of claim 11, wherein the aerosol is introduced into
the hot exhaust gas streams of a combustion system.
14. The method of claim 11, wherein the pressurized gas is selected
from: air, steam, nitrogen, argon, helium, carbon monoxide, carbon
dioxide and combinations thereof.
15. The method of claim 14, wherein the gas is subjected to a
pressure in the range of from 30 to 90 psi.
16. The method of claim 11, wherein the solution is subjected to a
pressure in the range of from 20 to 70 psi.
17. A method of pre-treating fuel, the method comprising the steps
of: a) providing a supply of a solution of catalyst and a supply of
a pressurised gas to a chamber, wherein the chamber includes a
nozzle in fluid communication with one or more of: a pre-combustion
zone, a combustion zone and a post-combustion zone, b) mixing the
solution and the gas in the chamber, and c) forcing the mixture of
solution and gas through the nozzle to form an aerosol, wherein the
aerosol is applied to solid fuel so as to pre-treat the fuel prior
to combustion.
18. The method of claim 17, wherein the fuel is a solid fuel.
Description
[0001] The present invention provides a catalytic aerosol delivery
system for generating an aerosol containing chemical catalyst
pre-cursors for delivery either directly into the flame zone of a
combustion reaction system, or directly into the inlet air or inlet
fuel or the fuel/air mixture, or directly into the hot exhaust
gases of a combustion reaction, or any combination of these three.
The system and the composition of the invention enables a reduction
in pollution emitted from the combustion chambers and ensures more
efficient and clean combustion. In most applications, the
combustion system and composition of the invention results in
improved fuel economy.
[0002] Delivery systems for generating sparging gases containing
catalyst particles and delivering them into a flame zone of
combustion systems are known in the art.
[0003] Searles and Bertelsen (In Business Briefing: "Global Truck
and Commercial Vehicle Technology"; London' World Marketing
Research Centre; 2000; p. 97-102; EU Directive 1999/99 EC) have
reviewed the existing technologies that are able to meet the EU and
US exhaust emission regulations for diesel-powered trucks and other
commercial vehicles, or heavy-duty vehicles. These technologies
include diesel oxidation catalysts, DeNOx catalysts and nitrogen
oxide (NOx) adsorbers, selective catalytic reduction (SCR) and
diesel particulate filters (DPFs), as well as filter technology for
particulate matter crankcase emission control.
[0004] The catalytic converter was first introduced in the US in
1974 in passenger cars and currently more than 275 million of the
world's 500 million cars and nearly 90% of all new cars produced
worldwide are equipped with catalytic converters. However, exhaust
emission control technology for diesel powered heavy-duty engines
has not yet experienced a similar, widespread application.
[0005] Another area of concern is the sulphur content of diesel
fuel. Sulphur has a major negative impact on the catalyst
performance due to the strong adsorption of sulphur on to the
catalyst surface. Therefore the surface area of the catalyst is
reduced and as a result the amount of nitrogen dioxide formed on
the oxidizing catalyst is reduced. This presents a problem for some
DPFs and NOx adsorbers as they rely on nitrogen dioxide for their
regeneration. Further, sulphur reacts with chemical NOx traps more
strongly than NOx, thereby decreasing NOx storage capacity and
requiring more vigorous and frequent regeneration, and hence
increasing fuel consumption.
[0006] It should be noted that a diesel oxidation catalyst converts
carbon monoxide and hydrocarbons to carbon dioxide and water.
Therefore these systems decrease the mass of particulate matter
emissions but it has been found that these systems have little
effect on NOx emissions.
[0007] Diesel oxidation catalysts may also be used in conjunction
with NOx adsorbers, DeNOx catalysts, DPFs or SCR to decrease
nitrogen dioxide levels or to clean up any bypass of injected
hydrocarbons, urea or ammonia.
[0008] The conventional automotive catalytic converter consists
essentially of a ceramic honeycomb, through which the exhaust gases
pass. The insides of the catalytic converter are coated with a fine
layer of platinum or palladium, rhodium and cerium catalyst. The
platinum component of the catalyst oxidizes CO to CO.sub.2 and
UHC's to CO.sub.2 and steam, and the rhodium reduces the levels of
NOx formed.
[0009] It is known that catalytic converters degrade with time and
use. Since 1984 catalytic converters have been fitted to all
vehicles in Germany. As a result of this, trace amounts of platinum
and rhodium have been detected alongside autobahns.
[0010] WO 02/083281 discloses a sparging gas catalyst delivery
system wherein a catalyst mixture receptacle comprises an air inlet
to an inlet tube, a secondary splash chamber and a gas outlet. Gas
is sparged through the liquid in the receptacle via a tube having
an outlet near the bottom of the liquid and the resulting
combination of gas, vapour from the liquid, liquid splashes and
catalyst is directed towards the combustion zone. However,
according to this document it is important that the liquid vapour
and liquid catalyst splashes are not transported to the combustion
zone and WO 02/083281 thus discloses that a secondary splash
chamber is necessary. This chamber serves to reduce the effects of
liquid catalyst splashing into or condensing within the connecting
duct between the receptacle and the combustion zone as this reduces
the performance of the system. It is also stated in WO 02/083281
that such splashing is undesirable as it results in an
uncontrollable rate of consumption of the catalyst mixture. This
can lead to unpredictable combustion and/or too high a rate of
catalyst consumption.
[0011] U.S. Pat. No. 6,776,606 also discloses a catalytic delivery
system comprising a sparging tube connected to a gas inlet through
which a gas, usually air, is bubbled through the catalytic mixture
via a tube having an outlet near the bottom of the liquid. In this
way, it is stated, catalyst particles may be non-evaporatively
fluidised and carried into the oxidation flame zone by a gas stream
through the popping of the bubbles at the liquid-gas interface. The
catalyst particles are then carried via a transport line into a
flame zone by the gas stream
[0012] One problem which is associated with the use of sparging gas
to introduce catalysts or catalyst precursors into combustion
systems is that some of the catalysts or catalyst precursors can
adhere to surfaces with which the gas stream comes into contact.
Therefore, some of the catalyst precursors used in the prior art
will adhere to the surfaces of any feed lines into which the
sparging gas leaving the catalyst solution receptacle flows before
reaching the combustion chamber. This reduces the efficiency of the
system and represents a waste of expensive catalyst material.
[0013] An aerosol is defined as a fine dispersion of solid or
liquid particles in a gas. The aerosol delivery system used in the
present invention works in a similar manner to that used in the
spraying of a dilute solution into a flame as employed in atomic
absorption spectroscopy. The process of generating aerosols as fine
sprays may be referred to as nebulization or atomization. Aerosols
are generated by sucking up or pumping a liquid and mixing it under
turbulent flow with a gas, usually air, and ejecting it through one
or more small orifices. The loading of the air depends on a variety
of parameters, including gas flow and liquid flow rates. Aerosols
can also be generated by ejecting a liquid alone under high
pressure through one or more small orifices. Ultrasound devices can
also be used to generate finely dispersed aerosols. In the context
of the present invention the terms atomization and nebulization can
be used interchangeably as indicating the provision of an aerosol:
this aerosol consists of a fine spray of catalytic material that is
delivered into a pre-combustion zone and/or a combustion zone
and/or to a post-combustion zone. Aerosol delivery systems are
known in the art. However, to date systems of this type have not
been employed in the delivery of catalytic materials to combustion
zones.
[0014] The production of an aerosol in accordance with the
invention is to be distinguished from the principle of sparging
which involves the process of bubbling a chemically inert gas
through a liquid. In the case of the present invention, an aerosol
is formed by turbulent mixing of liquid containing catalyst in
solution with the gas, under pressure, immediately prior to
ejecting it through a fine nozzle. Mixing and nebulizing in this
way provides a steady and continuous supply of aerosol which
contains catalyst at trace levels.
[0015] It is an aim of the present invention to overcome various
disadvantages of or improve on the properties of the prior art
systems. Thus it is an aim of the invention to provide an aerosol
delivery system that can be introduced directly into one or more of
the inlet air or the combustion zone or into the hot exhaust gases
of a combustion system.
[0016] It is a further aim of the invention to provide an aerosol
delivery system that provides a significant improvement in the
reduction of CO, Nox, UHC's and sulphur oxide emissions from
combustion systems relative to the prior art systems.
[0017] It is a further aim of the present invention to provide an
aerosol delivery system that reduces the corrosion that occurs
within combustion systems employing low-NOx burners and thereby
increases the lifetime of such combustion systems relative to the
systems of the prior art.
[0018] It is a further aim of the present invention to provide an
aerosol delivery system that increases the combustion efficiency of
a combustion system relative to the systems of the prior art. It is
therefore an aim of the present invention to maintain the flame
temperature of the combustion system and reduce the excess air
levels so as to improve the thermal efficiency of the combustion
system.
[0019] It is also desirable that the aerosol delivery system of the
present invention reduces the amount of carbon and char that is
deposited on the interior of the combustion system.
[0020] Furthermore it would be desirable that the aerosol delivery
system of the present invention reduces the noise and vibration
associated with combustion systems relative to prior art
systems.
[0021] It is a further aim of the present invention to provide an
aerosol delivery system that can be used to revive inefficient
converters, such as those which have been in service for a period
of time.
[0022] It is a further aim of the present invention to provide an
aerosol delivery system wherein the catalyst is retained within the
combustion system.
[0023] It is a further aim of the present invention to provide an
aerosol delivery system that interacts with the mercury found in
coal, and other combustible materials and high temperature gas
streams, and prevents or reduces the amount emitted in the exhaust
gas.
[0024] The applicant has surprisingly found that these and other
problems can be addressed by delivering the catalysts or catalyst
precursors directly into and around the combustion site by use of
an aerosol delivery system. Thus, the present invention satisfies
some or all of the above aims.
[0025] According to one aspect of the present invention there is
provided an aerosol delivery system for use in conjunction with a
combustion apparatus, the system comprising:
a chamber including a first inlet for supplying a source of gas to
the chamber, a second inlet for supplying a catalyst solution
containing one or more inorganic metal salts in a solvent to the
chamber, and an atomising nozzle for releasing fluid from the
chamber in the form of an aerosol; wherein the first inlet and the
second inlet and atomising nozzle are arranged so that the gas and
fluid in the chamber mix and combine to form an aerosol when
released through the nozzle; and wherein the nozzle is in fluid
communication with one or more of: a pre-combustion zone, a
combustion zone and a post-combustion zone.
[0026] In an embodiment, the nozzle is present in the combustion
zone. In another embodiment, the nozzle is present in a
pre-combustion region where air and fuel are mixed prior to
combustion. In another embodiment, the nozzle can be in a
pre-combustion region where there is only fuel and/or the nozzle
can be in a pre-combustion region where there is only air i.e.
before they two components are mixed. In another embodiment, the
nozzle can be in a post-combustion region. The nozzle thus provides
aerosol to the combustion products in an exhaust region. The nozzle
includes one or more discharge orifices to allow the fluid mixture
to exit in the form of an aerosol. The shape of the aerosol
discharge exiting the nozzle depends on the size, number and
arrangement of the discharge orifices in the nozzle. The aerosol
shape can thus be produced as required. A substantially conical
shape for the nozzle is preferred as this leads to a conical
aerosol.
[0027] In another embodiment, more than one nozzle can be present.
Thus, nozzles can independently supply aerosol to one or more of
the above regions. The catalytic solution may be the same or
different in each case. The nozzle shape and arrangement of
discharge orifices can be the same or different in each case where
more than one nozzle is present.
[0028] In an embodiment of the present invention, the supply of gas
and catalytic solution to the chamber is continuous so that the
aerosol may be sprayed continuously from the nozzle. Alternatively,
the supply of the gas or the solution to the chamber may be
interrupted so that the aerosol is sprayed intermittently from the
nozzle.
[0029] Aerosols can also be generated without the use of air. If
the catalyst precursor solution is subjected to high pressure and
allowed to exit through a very fine nozzle it exits as an aerosol.
Thus in an alternative embodiment of the above applications, where
an aerosol is described as being generated using a gas, for example
air, in combination with a solution of catalyst then such a
generation system can be replaced by a high pressure gasless
system; there is no need for a supply of pressurised gas. It is
sufficient simply to supply a solution of the catalyst under
pressure to the nozzle. This embodiment has applications in all of
the cases for which the aerosol is produced by mixing gas and
solution, such as industrial burners, boilers and SI and diesel
engines (i.e., both open and closed flame systems).
[0030] The combustion may take place in open flame or closed flame
applications. Open flame applications include coal, gas and oil
fired boilers and furnaces. Closed flame applications include
petrol and diesel internal combustion engines. In an embodiment of
the present invention, the aerosol is used in vehicles that have
been fitted with a catalytic converter.
[0031] As used herein, a combustion zone means and includes an area
where oxidation of a fuel occurs and the area immediately
surrounding that area, for example, a combustion chamber.
[0032] The one or more metal salt in the catalyst solution is a
catalyst for the combustion of the fuel being consumed or for the
oxidation or reduction of the combustion products (exhaust) to
harmless or cleaner products. The catalyst may be a simple or
binary compound, a complex metal salt, or an organometallic
compound.
[0033] Preferably the catalytic solution of the present invention
comprises one or more inorganic salts or organometallic compounds
of platinum, palladium, rhodium, rhenium, ruthenium, osmium,
cerium, iridium, indium, magnesium, aluminium, titanium, copper,
zinc, lithium, potassium, sodium, iron, molybdenum, manganese, gold
or silver. Preferably the solution of the present invention
comprises one or more compounds of a Group VIII element (i.e. Fe,
Ru, Os, Co, Rh, Ir, Ni, Pd, Pt), magnesium or aluminium. More
preferably the compound is a compound of platinum, rhodium,
rhenium, magnesium or aluminium. If only one compound is used the
solution must contain either a platinum or a rhodium salt.
[0034] In an embodiment, the compound is present in solution in a
concentration of from 0.1 to 2.0 mg/ml. More preferably the
concentration is from 0.2 to 1.0 mg/ml. The molecular weight of the
compounds may be from 200 to 2000, and more preferably is in the
range 200 to 750.
[0035] It is especially preferred that the inorganic metal salts
are present as H.sub.2PtCl.sub.6, RhCl.sub.3, HReO.sub.4,
MgCl.sub.2 and AlCl.sub.3. The complex ions that are formed in
water from such inorganic metal salts include [PtCl.sub.6].sup.2-,
[Rh(H.sub.2O).sub.6].sup.3+ and [ReO.sub.4].sup.-.
[0036] In a preferred embodiment of the invention the catalyst
precursor solution concentrate comprises one or more metal salts
wherein the metal is selected from platinum, rhodium, rhenium or
aluminium. The concentration of platinum as
H.sub.2PtCl.sub.6.6H.sub.2(O) in the catalyst precursor solution
concentrate is in the range of 0.2 to 1.0 mg/ml; more preferably in
the range of 0.5 to 0.7 mg/ml; especially preferably at a
concentration of 0.6 mg/ml. The concentration of rhodium in the
catalyst precursor solution concentrate as RhCl.sub.3 is preferably
in the range of 0.04 to 1.2 mg/ml; more preferably in the range of
0.06 to 0.09; especially preferably at 0.07 mg/ml. The
concentration of rhenium in the catalyst precursor solution
concentrate as HReO.sub.4 is preferably in the range of 0.05 to 1.5
mg/ml; more preferably in the range of 0.08 to 1.2 mg/ml;
especially preferably in the range of 1.0 mg/ml. The concentration
of aluminium as AlCl.sub.3 in the catalyst precursor solution
concentrate is preferably in the range of 0.05 to 1.0 mg/ml; more
preferably at a concentration of 0.07 mg/ml.
[0037] In a further preferred embodiment of the invention aluminium
in the solution of the present invention is substituted by
magnesium such as MgCl.sub.2 at a concentration in the range of
from 0.05 to 1.0 mg/ml; more preferably at a concentration of 0.07
mg/ml.
[0038] In a still further preferred embodiment of the invention
only a proportion of the aluminium is replaced by magnesium so that
the catalyst precursor solution comprises both aluminium and
magnesium.
[0039] In a still further preferred embodiment of the invention,
where both platinum and rhodium are present in the catalytic
solution, the ratio of platinum to rhodium is about 8.6:1; the
ratio of platinum to aluminium is about 8.6:1; the ratio of
platinum to rhenium is about 6:1 and where aluminium is substituted
by magnesium the ratio of platinum to magnesium is about 8.6:1.
[0040] However, the ratios of components of the invention may vary
above and below these limits. Therefore, the ratio of platinum to
rhenium is preferably in the range of from 30:1 to 1:1; more
preferably in the range of 15:1 to 2:1. The ratio of platinum to
aluminium or magnesium is preferably in the range of 30:1 to 1:1;
more preferably in the range of 15:1 to 2:1. The ratio of platinum
to rhodium is preferably in the range of from 30:1 to 4:1; more
preferably from 15:1 to 4:1.
[0041] In a further embodiment of the invention the catalyst
precursor solution comprises only platinum and one other inorganic
metal salt of rhodium, rhenium, magnesium or aluminium.
[0042] The solvent may be any solvent which is capable of
dissolving the one or more metal salt (catalyst) and which is
capable of forming a stable aerosol. Ideally, the solvent has a
significant vapour pressure at normal temperature and pressure
though the solvent must not be too volatile otherwise the catalyst
could be deposited prematurely in the feed line and/or consumed too
quickly. The most effective solvents have boiling points in the
range 80.degree. C. to 140.degree. C. at normal temperatures and
pressure. The solvent is preferably water. Alcohol (such as
methanol or ethanol) or a hydrocarbon solvent may also be used as a
solvent. The solvent may also be a mixture of suitable solvents.
Water is the preferred solvent due to its ability to dissolve a
number of inorganic metal salts and its ability to form a stable
aerosol.
[0043] The solvent may additionally include an antifreeze such as,
for example, ethylene glycol. Other additives can also be included
as necessary.
[0044] In a further aspect, the present invention provides a method
for catalysing the combustion of a fuel, the method comprising the
steps of: [0045] a) providing a supply of a solution of catalyst
and a supply of a pressurised gas to a chamber, wherein the chamber
includes a nozzle in fluid communication with one or more of: a
pre-combustion zone, a combustion zone and a post-combustion zone,
[0046] b) mixing the solution and the gas in the chamber, [0047] c)
forcing the mixture of solution and gas through the nozzle to form
an aerosol in the pre-combustion zone, combustion zone or
post-combustion zone of fuel combustion apparatus.
[0048] The aerosol of the present invention and the fuel may be
introduced into the combustion zone of a fuel injection diesel or
petrol engine either simultaneously or separately.
[0049] In an embodiment of the present invention the, aerosol may
be introduced into the combustion zone of an engine with the air
from the carburettor. In order to minimize the distance between the
point at which the inorganic metal salts are introduced to the
combustion system and the required point of use (i.e. the
combustion zone) the aerosol is introduced into the air stream of
spark ignition engines just before it enters the carburettor so
that it is mixed with the vaporized fuel and the mixture then
enters the engine. For diesel engines, the aerosol is introduced
into the air stream after it has passed through the air filter.
[0050] Combustion requires the presence of radicals in and around
the flame, and the catalytic material, such as platinum and/or
rhodium, that the system of the present invention introduces into
the combustion process improves the process significantly. This is
achieved by enabling a greater amount of radicals to be generated,
and thus reducing the amount of excess oxygen normally required,
and hence saving fuel. This also improves emissions.
[0051] In an embodiment, the present invention provides a method
for reducing the harmful emissions of a combustion system,
particularly NOx, by introducing an aerosol containing one or more
inorganic metal salts into the final hot exhaust gas streams of
combustion systems exiting a combustion system. These systems may
or may not employ emission reduction systems or technologies in,
before or just after the combustion zone. Preferably the aerosol of
the present invention is introduced into the hot exhaust gas
streams of an internal combustion engine (using diesel, petrol,
bio-diesel and alternative fuels etc) or power or process station
boilers, burners and dryers.
[0052] Coal is one fuel that benefits from the combustion
technology of the present invention. One major application of the
invention is thus to the various NOx reduction techniques used in
coal combustion. In particular the process can be applied to coal
combustion in furnaces and boilers employing various NOx reduction
devices and procedures for reducing carbon in ash, etc.
[0053] The two major mechanisms of NOx formation in combustion
processes are thermal-NOx and fuel-NOx. The former is dominant when
the fuel contains no inherent nitrogen (e.g., natural gas) and the
latter dominant when the fuel is coal or heavy fuel oil or similar.
Combustion modification techniques aim to limit NOx formation in
the early stages of the combustion process. Our process is
compatible with and applicable to these methods.
[0054] Preferably the aerosol of the present invention is
introduced into the hot exhaust gas streams of combustion systems
in combination, directly or indirectly, with ammonia or urea and,
as required, in conjunction with added hydrocarbons and air to
attain the required reaction temperature. The aerosol of the
present invention may be introduced simultaneously or separately
into the hot exhaust gas stream, or other appropriate site, of the
combustion system employing the ammonia/urea/hydrocarbon/air system
for NOx, CO and carbon reduction, particularly in coal-fired and
similar oil or solid fuel-fired plant employing SNCR (Selective
Non-Catalytic Reduction) strategies to reduce emissions.
[0055] In the air staging method to reduce NOx, the combustion air
is staged so that the primary combustion zone operates with an
overall fuel-rich stoichiometry and the remaining air is injected
downstream. Applying our process to this method involves injecting
the catalyst at suitable point(s) in both stages. Low-NOx burners
are designed to achieve the staging effect through partitioning the
air and fuel flow inside the burner in such a manner so as to delay
combustion, reduce the availability of oxygen and reduce peak flame
temperature. All of these factors help reduce NOx. Applying our
process to this method involves the aerosol catalyst being
introduced at all points so that it can additionally enhance the
radical reactions that reduce the NOx that is still formed, thereby
improving their efficiency and the overall efficiency of NOx
reduction as well as that of the combustion process as a whole.
[0056] NOx levels can also be reduced by the technique of flue gas
recirculation, which introduces a diluent into the combustion
chamber. Applying our process to this method involves introducing
the aerosol catalyst and intimately mixing it with the diluent.
Another way of lowering NOx is by lowering excess air levels. This
reduces NOx but can cause unwanted problems such as unstable
combustion, reduced burnout, slagging, fouling and corrosion.
However, using the aerosol catalyst of the present invention
minimises these problems since it enables the combustion process to
proceed normally. This is due to the extra radicals it generates in
the flame.
[0057] There are also a number of post-combustion NOx control
techniques. These are generally termed flue gas treatments, and can
be subdivided into: (a) Selective Catalytic Reduction (SCR), (b)
Selective Non-catalytic Reduction (SNCR), and (c) Non-selective
Catalytic Reduction (NSCR).
[0058] Method (b) employs the injection of ammonia gas or aqueous
ammonia or aqueous urea into the flue gas. The radical reaction
that takes place essentially converts the NOx into oxygen and
nitrogen, but the reaction only takes place within limited reaction
conditions. The introduction of aerosol catalyst in accordance with
another aspect of the present invention into flue gases (in the
same manner as the aerosol catalyst is introduced into the
combustion region or the pre-combustion region) will enhance these
reactions, and extend the operation temperature window. In
accordance with the process of the present invention, the catalyst
is injected into or with the ammonia gas or aqueous ammonia or urea
and ammonium and/or other salts are added as necessary into the
flue gas.
[0059] The catalyst supplied to the flue gas in accordance with the
method of the present invention can also be used to maintain the
efficiency and extend the lifetime of SCR catalysts, be they
platinum-based or comprising other recognised catalytic agents. The
platinum and rhodium homogeneous catalyst in the gas stream
entering the catalyst grid system will aid the catalysis taking
place on the catalyst, and the platinum and rhodium that attach and
remain on the catalyst, platinum-based or otherwise, will help
prevent carbon and char build-up on the SCR catalyst by
participating catalytically in their oxidation to carbon dioxide
gas.
[0060] One example concerns combustors employing SCR, SNCR or NSCR
techniques to reduce NOx. It is possible, and common, that some NOx
still remains and exits the plant through the final stack into the
atmosphere. A technique used to reduce final stack NOx is to employ
final stack injection of ammonia or urea. If the temperature is not
high enough then a pilot flame, burning a suitable hydrocarbon gas,
is also employed to bring the exiting gases within the temperature
window and thus enable the ammonia or urea to react with the NOx.
The nebulized catalyst can be injected into the pilot flame prior
to entering the radical reaction region. This will create the
platinum and rhodium catalyst species and also lower the
temperature window so that the radical reaction will be more
efficient and the quantity of gas required for the pilot flame will
be reduced, leading to a fuel saving.
[0061] The process of the present invention has a number of
applications. The aerosol or nebulizing spray that is generated is
injected into an air stream that mixes with fuel and enters a
combustion zone. This concept can be extended to all high
temperature reactions that involve chemical and radical mechanisms.
Thus the present invention also includes the concept of the
introduction of an aerosol catalyst into all situations where it is
known or supposed that vapour phase radical reactions are taking
place (since the catalyst generated at the elevated temperature
involved will increase the number of radicals present): the
applications of the process are thus not limited to those involving
combustion but can include high temperature chemical reactions
involving radicals, particularly those also involving homogeneous
and heterogeneous catalysts in the oil refining industry. The
oil-refining industry and certain related industries use platinum
catalysts at high temperatures. These deteriorate with time and
usage and have to be cleaned or replaced. The present invention has
the potential to extend the life and efficiency of such
catalysts.
[0062] The technology of the present invention as described herein
will also have applications in the oil refining industry because
the catalytic combustion process of the invention provides
increased performance and output, and also reduced maintenance. One
particular problem in this area is unwanted soot deposition in the
furnaces that supply thermal energy to, for example, oil
distillation plant, and the soot has to be removed periodically.
The present invention provides a solution to this problem.
[0063] The process of the present invention can also be used for CO
clean-up as well as soot and char burn-off. All of these processes
can be enhanced by the injection of the catalyst aerosol, since
radical reactions are involved in each of these processes.
Applications include catalytic crackers, reformers and other
refining processes, and fluidised bed combustion processes.
[0064] In a further embodiment of the invention, spray injection of
an aerosol is used to achieve sulfur capture using one or more
additives based on compounds of elements in Group II of the
Periodic Table. There are various chemicals and procedures employed
to remove oxides of sulfur from exhaust and flue gases. It is
believed that the co-injection of noble metal catalyst with these
chemicals, or upstream if the gas temperatures are too low to
generate the elemental metals, will improve their sulfur removal
efficiency and extend the lower temperature limit of the reactions
involved.
[0065] This process also enables trace amounts of mercury be
captured in a similar way. Currently the technology for removing
mercury from coal during combustion is desired but unproven or not
fully proven. Mercury readily forms amalgams with most metals (but
not iron) but including the noble metals and it is believed that it
will attach to the platinum and rhodium coated surfaces formed
within coal-fired boilers and under the conditions pertaining
therein. Of the mercury removal technology currently under test
none of the techniques employs the property of mercury to form
amalgams.
[0066] In one embodiment the metal (catalyst) derived from the
solution used in the present invention is either retained in the
combustion chamber or adheres to the surface through which exhaust
gases pass or it is trapped within the honeycomb structure of the
catalytic converter. This is advantageous as the adhered metal
(catalyst) then participates in heterogeneous catalyst reactions
and therefore provides a continuously renewed catalytic surface
upon which continuous reactions occur.
[0067] In another aspect of the present invention there is provided
a method of pre-treating fuel, the method comprising the steps of:
[0068] a) providing a supply of a solution of catalyst and a supply
of a pressurised gas to a chamber, wherein the chamber includes a
nozzle in fluid communication with one or more of: a pre-combustion
zone, a combustion zone and a post-combustion zone, [0069] b)
mixing the solution and the gas in the chamber, forcing the mixture
of solution and gas through the nozzle to form an aerosol, [0070]
wherein the aerosol is applied to solid fuel so as to pre-treat the
fuel prior to combustion.
[0071] The fuel is preferably solid fuel.
[0072] Embodiments of the invention may include the use of an
aerosol catalyst composition and delivery system in either open or
closed flame applications such as boilers, power or process station
boilers, burners and dryers, furnaces, turbine engines,
reciprocating engines, incinerator engines, open flames, spark
ignition engines, natural gas engines, gasoline engines, rotary
engines, internal combustion engines using diesel, petrol,
bio-diesel and diesel or petrol engines and other alternative fuel,
etc., or systems wherein fuel is oxidised. Usually oxidation of the
fuel involves combustion in air or an oxygen rich medium. Oxidation
may be affected by supplying other sources of oxygen that liberate
oxygen under combustion conditions.
[0073] The aerosol delivery system of the present invention
comprises a rigid container that is impervious to the solution that
it contains. The container may be made from any material that is
suitable for the desired use of the aerosol. In a preferred
embodiment of the invention the container of the aerosol is made
from ceramics, metals or plastic or combinations thereof.
[0074] The pressurized gas of the aerosol delivery system may be
any gas that is suitable for the desired use of the aerosol such as
a positively or negatively ionized or neutral gas, for example
selected from air, steam, nitrogen, argon, helium, carbon monoxide,
carbon dioxide and combinations thereof. Preferably the pressurized
gas is air. Under certain circumstances the pressurized gas
comprises air and an additional oxygen component or ammonia
gas.
[0075] The gas of the aerosol delivery system is preferably
subjected to a pressure in the range of from 30 to 90 psi. More
preferably a pressure in the range of from 50 to 70 psi is
required.
[0076] The solution of the aerosol delivery system is subjected to
pressure. Preferably the solution is subjected to a pressure in the
range of from 20 to 70 psi. More preferably the solution is
subjected to a pressure in the range of from 30 to 50 psi.
[0077] There is a wide range of ways for generating aerosols. Any
system that generates an aerosol can in principle be used to
generate the catalyst aerosol, and the choice will depend upon the
intended application of the catalyst aerosol.
[0078] The pH of the catalyst pre-cursor solution used in the
aerosol delivery system of the present invention should be such as
to prevent deterioration or decomposition with subsequent formation
of a colloid or fine precipitate and is preferably less than 5.
More preferably the pH of the catalyst precursor solution is in the
range of from 4 to 1; even more preferably in the range of 3.0 to
1.4; especially preferably in the range of from 1.6 to 2.2.
[0079] In a preferred embodiment the present invention generates
several catalysts in the flame, or in the exhaust gases, having
introduced their precursors directly or by means of the inlet air,
into the flame or the exhaust gases. This leads to increased oxygen
atom concentration and free radical generation to improve
combustion rates and thus efficiency during residence time.
[0080] It is believed that certain of the inorganic metal salts and
organometallic compounds decompose into elemental form within the
hot flame or within the hot exhaust gases creating the traditional
combustion elements which catalyse reactions with oxygen and the
molecules and radicals formed as intermediates in the combustion
process. In the present invention the elemental form of at least
one of platinum, palladium, rhodium, rhenium, ruthenium, osmium,
cerium, iridium, indium, magnesium, aluminium, titanium, copper,
zinc, lithium, potassium, sodium, iron, molybdenum, manganese, gold
or silver are present in the flame or within the hot exhaust gases
at a level in the region of ppm to ppb. Preferably platinum and
rhodium are present in the flame or within the hot exhaust gases at
a level in the region of ppm to ppb. The concentration of the
inorganic metal salts or organometallic compounds in the aerosol
introduced into the combustion system or hot exhaust gases is
dependent upon the size and characteristics of each combustion
system.
[0081] The aerosol delivery systems of the present invention
contain inorganic metal salts or organometallic compounds in an
amount in the ppm to ppb level that is dependent upon the thermal
output and size of the combustion system. Preferably one or more
inorganic metal salts are present in the solution at a
concentration in the range of from 1 to 1000 ppb. More preferably
the one or more inorganic metal salts are present in the solution
at a concentration in the range of from 50 to 100 ppb. It has been
advantageously found that only low levels of the inorganic metal
salts are required to act as catalysts. This enables ppb to ppm
levels of these catalyst precursors to be carried into the
combustion chambers such as the combustion chambers of coal or
gas-fired industrial boilers or spark ignition and diesel engines.
Therefore, the aerosol of the present invention effectively places
the inorganic metal salts or organometallic compounds in the region
where combustion takes place.
[0082] The dose rate of the diluted catalyst pre-cursor solution in
the form of an aerosol of the present invention is dependent upon
the desired use. However, the dose rate is preferably in the range
of from 0.1 to 1 US gallons per hour. More preferably the dose rate
is 0.5 US gallons per hour. The extent of dilution is dependent
upon the rate at which the fuel is consumed or the thermal energy
supplied by the boiler.
[0083] In a further embodiment of the invention the aerosol is used
in connection with combustion chambers using fuel such as diesel
fuel, gasoline, number 2 fuel oil, bunker oil, fuel oils refined
from crude oil, compressed natural gas, liquefied natural gas,
gasohol, hydrocarbons, corn oil, vegetable oil, mineral oil, coal,
coal gas, asphalt vapours, oxidisable vapours, wood, paper, straw,
biofuels, combustible waste and combinations thereof.
[0084] The operating temperature of the combustion system suitable
for use in connection with the aerosol of the present invention is
preferably in the regions of 500 to 2000.degree. C.; preferably 900
to 1600.degree. C.; more preferably 1000 to 1500.degree. C.
[0085] Viewed from a still further aspect the present invention
provides a miniature aerosol delivery system for use with diesel or
petrol engines. The dimensions of the aerosol delivery system
depend on the intended use of the aerosol. Since the system can be
arranged not to experience the high temperatures pertaining to, for
example, coal-fired plant, a miniature system employing an
ultrasonic generator (see above) to produce the fine aerosol can be
employed.
[0086] Preferably the width of the miniature aerosol delivery
system of the present invention can be from between 10 cm to 2 m
depending on the intended use.
[0087] It is a further advantage of the invention that vibrations
of the engine to which the aerosol delivery device and method of
the present invention is applied ensures thorough mixing of the
catalyst precursor solution.
[0088] A further benefit of the invention is that the elemental
form of the catalyst salts or organometallic compounds, e.g.,
platinum and rhodium, adheres to the interior of the furnace and to
other compounds adhering to the furnace interior that are derived
from the components of the catalyst aerosol and therefore catalytic
activity continues beyond the period over which the catalytic
mixture is sprayed into the system.
[0089] The aerosol delivery system may advantageously reduce the
noise and vibration associated with combustion engines. For
example, the presence of platinum is thought to cause the flame to
burn in diesel engines at a lower temperature and thus it does not
go out before the piston has reached the end of its travel. A
feature of diesel engines is their "rattle," better termed
harmonics. This arises when the energy of the expanding gases has
decreased beyond a certain point, partly due to the drop in
temperature arising from adiabatic expansion and when the flame
goes out. When this occurs the piston still has approximately one
quarter of its travel still to go. The piston movement at this
point changes from a push to a pull action, creating rattle. When
the aerosol delivery system of the present invention is installed,
the harmonics are much reduced and the engine is much quieter and
smoother. Under normal circumstances, when combustion is initiated
the resulting expansion pushes the cylinder down. It is believed
that the platinum containing aerosol system of the present
invention is involved in producing oxygen atoms and thus keeps the
flame and expansion going longer. Furthermore, it is believed that
the platinum makes for a faster burn, thereby sustaining the flame
and contributing to the increased power levels experienced.
[0090] The optimum conditions for operating a spark ignition engine
for minimum CO and NOx emissions are somewhat opposed. The higher
the temperature in the combustion chamber the lower the amount of
CO formed and therefore by operating the engine at as high a
temperature as possible will minimize CO emissions. However, the
reverse is true for the formation of NOx, and for minimum emissions
the temperature in the combustion chamber should be as low as
possible. Currently, engines are tuned to be close to the crossover
in the plots of CO and NOx formation as a function of temperature
and in conjunction with the efficiency of the catalytic
converter.
[0091] The unique advantage of the aerosol delivery system of the
present invention is that combustion temperatures no longer have to
be designed to range around the above crossover temperature for
minimizing CO, NOx and unburned hydrocarbon levels in the exhaust
gases from the combustion chamber. The lower temperature regime
consequently means that the amount of NOx formed is less, and this
quantity is further reduced by the presence of rhodium in the
combustion chamber. Another consequence and advantage is that the
workload on the catalytic converter is now much reduced and so its
efficiency and lifetime is extended.
[0092] The inclusion of rhenium in the catalyst concentrate of the
present invention is believed to contribute to smoother and quieter
engine running and hence its role is considered to be that of
making for a smoother flame burn and a smooth front to the
flame.
[0093] The applicants have surprisingly found that the aerosol
delivery system of the present invention improves the burn
characteristics of a fuel and therefore less carbon deposited in
the combustion system. Furthermore, the amount of catalyst may be
later or subsequently reduced. In some circumstances the aerosol
delivery system of the present invention results in the production
of bright blue flames, which are indicative of particularly
efficient fuel combustion. The advantage of this technique is that
the combustion system has a cleaner interior, cleaner fly ash, and
a small but steady injection of catalyst so that catalyst erosion
or poisoning does not take place. Therefore, the present invention
provides an increase in the lifetime of the combustion system.
[0094] The present invention will now be illustrated by the
following figures in which:
[0095] FIG. 1 is a schematic diagram showing an open flame
application according to one aspect of the present invention,
[0096] FIG. 2 is a side view of an aerosol delivery system
according to the present invention,
[0097] FIG. 3 is a top view of the aerosol delivery system of FIG.
2, and
[0098] FIG. 4 is a side view of another aerosol delivery system
according to another embodiment of the present invention.
[0099] In FIG. 1, a supply of air 1 is fed to blower 2 and into
mixer 3 where it is combined with fuel from fuel source 4. Oxygen
could be used to supplement or instead of the air. The mixture 5 of
air and fuel are fed into combustion chamber 6 where combustion
takes place. The combustion products 7 i.e. the exhaust gases then
exit the combustion chamber and pass through an exhaust region 8
which includes a heat exchanger 9.
[0100] The reference letters a to i indicate suitable injection
sites for placement of the aerosol delivery system of the present
invention. Thus, aerosol spray containing the catalytic solution
may be delivered at any of the sites indicated by the letters a to
i. More than one such site may be present in the apparatus. Where
more than one site is present the catalytic solution delivered may
be the same or different as another aerosol delivery site in the
same application. The preferred sites are at one or more of a, c
and d since this improves combustion and reduces fuel consumption.
For reducing NOx levels, aerosol delivery sites in the
post-combustion zones are preferred. Thus, delivery at g, h or i
are preferred. Injection can also take place with or without the
addition of ammonia or urea (not shown) to these regions.
[0101] FIG. 2 shows a simple injector in which a tangential entry
duct 10 supplies catalyst solution to swirl chamber 11 in aerosol
delivery head 12. Pressurised gas is delivered by duct 13 to swirl
chamber 11. An atomising nozzle 14 includes orifices 15 which are
sized and arranged to provide a fine aerosol mist 16. In the
example shown, the atomising nozzle 14 is generally conical in
shape leading to a conical shape aerosol mist 16. Intimate mixing
of the gas and catalysis solution takes place in the swirl chamber
11 prior to ejection through orifices 15 in nozzle 14 due to the
positioning of gas duct 13 and duct 10 in swirl chamber 11.
[0102] FIG. 3 shows a simplified top view of the aerosol delivery
device of FIG. 2. Discharge orifices 15 can be seen disposed in a
regular pattern around atomising nozzle 14. The pattern of the
orifices is governed by the shape of atomised spray that is
desired. FIG. 3 shows a conical atomising nozzle 14 since this
leads to a conical spray of aerosol 15 which gives rise to the most
advantageous effects in terms of reducing fuel consumption and
improving NOx levels.
[0103] FIG. 4 shows a water-cooled atomiser 17 which passes through
furnace wall 18 and the inner insulating ceramic brick lining 19 of
the furnace. The atomiser 17 is made of metal and includes a water
jacket 20 which is formed by providing a source of cooling water 21
through channel 22 within the body of the atomiser 17. Catalyst
solution 23 is fed via channel 24 to swirl chamber 25. Pressurised
gas 26, in this case air, is fed to the swirl chamber 25 by channel
27. The catalyst solution and air mix in swirl chamber 25 and pass
through atomising nozzle 28 and form a spray cone of aerosol
29.
[0104] The following examples demonstrate the effectiveness of the
invention.
EXAMPLE 1
[0105] A boiler (Johnston 800 hp rated at 33 million BTU's per
hour)) was becoming less efficient at producing steam and to offset
this the amount of gas supplied was increased. The boiler was
examined and found to have a defective air supply resulting in
incomplete combustion and carbon deposits within the furnace. The
air supply system of the boiler was repaired and theaerosol
delivery system of the present invention was installed. Subsequent
measurements showed that after installation of the aerosol of the
present invention the noise level had decreased from 107 to 97
decibels. The boiler was run for a month at close to maximum load
in operation with the aerosol delivery system of the present
invention. After a month it was found that the interior of the
furnace was much cleaner and that the fuel savings were around 4%.
Further measurements showed that the NOx levels were reduced by
26.8% after 6.5 weeks, from 149 ppm to 109 ppm. After 13 weeks of
operation with the aerosol delivery system it was found that the
NOx levels had been reduced by 33% overall to 100 ppm and the
overall fuel saving was around 4%.
EXAMPLE 2
[0106] Another boiler (Johnston 800 hp rated at 33 million BTU's
per hour)) was run at around 25% load. After determining the
baseline NOx level and the percentage excess of oxygen the aerosol
delivery system of the present invention was installed and in
operation for three weeks. The results showed that the boiler could
be maintained at 25% load with excess oxygen reduced by 45% and
hence a fuel reduction of about 4%. The NOx level of this boiler
was reduced by 36% from 136 ppm to 87 ppm. The flame was described
by the company boiler engineer as the bluest flame he had seen
closest to a pure hydrogen flame.
* * * * *