IN THE CANADIAN PATENT OFFICE
DECISION OF THE COMMISSIONER OF PATENTS
Patent application 497,554 having been rejected under Rule 47(2)
of the Patent Regulations, the Applicant asked that the Final
Action of the Examiner be reviewed. The rejection has
consequently been considered by the Patent Appeal Board and by
the Commissioner of Patents. The findings of the Board and the
ruling of the Commissioner are as follows:
Agent for Applicant
Smart & Biggar
P.O. Box 2999
Station D
Ottawa, Ontario
K1P 5Y6
This decision deals with the Applicant's request that the
Commissioner of Patents review the Examiner's Final Action on
application 497,554 (Class 44-4), filed December 13, 1985
entitled "Three-stage Process for Burning Fuel Containing Sulfur
to Reduce Emission of Particulates and Sulfur-containing Gases".
The inventors, Melvin H. Brown and David H. DeYoung, have
assigned the application to the Aluminum Company of America. The
Examiner in charge issued a Final Action on February 26, 1990
refusing to allow the application. No request for an oral
hearing was made.
The application relates to a combustion process that reduces the
emission of particulates and sulfur compounds in combustion gases
by burning the fuel in a three-stage combustion process. In
particular, the invention relates to a process wherein the
removal of both sulfur and particulates is optimized to therefore
reduce the emission of both materials.
Figure 1 of the invention, reproduced below, is a flow diagram
that illustrates the process of the invention.
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Claim 1 of the application reads:
1. A three-stage combustion process for burning a fuel
containing sulfur characterized by low sulfur emission and
good ash removal comprising:
(a) mixing the sulfur containing fuel with an additive
capable of reacting with sulfur:
(b) burning the mixture in a first combustion stage
with less than 75% theoretical air and at a
temperature below the melting point of the ash but
sufficiently high to cause reaction between said
additive and any sulfur in said fuel to facilitate
removal of the sulfur compounds formed:
(c) passing combustible fuel gases from said first
stage to a second combustion stage:
(d) burning said gases in said second stage with less
than 100% theoretical air, based on theoretical
air for products from the first stage, at a
temperature above the melting point of the ash to
form a liquid slag which is removable from said
second stage: and
(e) burning combustible gases from said second stage
in a third stage with an excess of air to ensure
complete combustion of said fuel.
Steps b), d) and e) define the actual three stages of the
process, with the other steps being preparatory or transitory.
In the Final Action, the following art was cited by the examiner:
Australian Patent:
548,115 September 28, 1982 Moriarty
United States Patent:
4,232,615 November 1l, 1980 Brown
Claims 1 and 5 of the Moriarty patent read as follows:
1. A method for the entrained-flow combustion of a carbon-
nitrogen- and sulfur-containing fuel for substantially
reducing emission of gaseous sulfur compounds and
nitrogenous compounds formed during the combustion of fuel
with a substoichiometric amount of oxygen comprising:
introducing said fuel, an inorganic alkaline absorbent and
an oxygen-containing gas into a first combustion sulfur
capture zone of an entrained-flow combustor to form a
fluent mixture therein of fuel and absorbent entrained
in said gas,
the oxygen being present in said zone in an amount to
provide from about 25%-40% of the total stoichiometric
amount required for the complete combustion of the
fuel,
the inorganic alkaline absorbent being present in an
amount to provide a molar ratio of alkaline absorbent
to sulfur compounds of from about 1.0:1 to 3.0:1, said
ratio including any alkaline absorbents contained in
the fuel:
reacting said fuel and absorbent entrained in said oxygen-
containing gas by maintaining them in said zone at a
temperature from about 1000ø-1800øK. for a time
sufficient
(a) to gasify at least about 75% of the carbon content
of the fuel and substantially all of the sulfur in
a fuel,
(b) to combust the gasified fuel and oxygen to produce
a fuel-rich stoichiometry in the gas-phase, and
(c) to react in excess of about 70% of the fuel sulfur
with the inorganic alkaline absorbent to form a
solid alkaline sulfide compound,
introducing the resultant combustion mixture into a second
combustion zone:
maintaining said mixture at a temperature in the range of
1800øK.-2500øK. in said second combustion zone while
introducing additional air in an amount to provide
about 45%-75% of the total stoichiometric amount of air
required for complete combustion of the fuel:
maintaining said mixture including said alkaline sulfide
compound, at said temperature for a time sufficient to
reduce said nitrogenous compound content to a desired
level: and
discharging said mixture having a substantially reduced
gaseous sulfur compound and nitrogenous compound
content.
5. The method of claim 1 further including introducing the
combustion products from said second combustion zone into at
least a third combustion zone and maintaining said products
at a temperature of from about 1600ø to 2000· K. while
completing the combustion by the introduction of additional
air in an amount to provide from about 100% to about 120% of
the total stoichiometric requirements for complete
combustion of the fuel.
Claim 1 of the Brown patent reads as follows:
A method for burning a pulverized carbonaceous material
containing sulfur and ash, comprising forming a slurry
containing the carbonaceous material, water and a reagent
adapted to react with the sulfur, burning the slurry in a
first stage with less than 100% theoretical air, removing
the combustible gases from the first stage to a second
stage, and burning the gases in the second stage with
additional air.
In refusing the claims the Examiner, in her Final Action, said,
in part:
Moriarty describes as does the applicant a three stage
combustion process wherein in each subsequent stage, the
air/fuel stoichiometry is increased. The first stage in the
instant invention and references cited is directed to form
readily removable solid sulfur compounds using an additive.
Both references show in said first stage to use a
temperature sufficiently high to cause reaction between the
additive and the sulfur and lower or around the melting
point of ash, and less than 75% theoretical air. Brown
utilizes less than 100% theoretical air preferably 50%
theoretical air and Moriarty specifically 25-40% theoretical
air. Brown teaches the conditions set out in the second
stage of the instant invention with regard to form a liquid
slag which is removable, said conditions consist to maintain
a temperature above the melting point of ash with less than
100% theoretical air. Moriarty shows the third stage of the
instant invention to burn the combustible gases coming from
the second stage with an excess of air.
Brown also teaches the options described in the instant
invention of preparing a water-slurry with the fuel and the
additive, maintaining in the first stage a temperature below
1100·C (1373·K) and removing the sulfur compounds in the
first stage.
The applicant has argued that neither the Moriarty or the
Brown reference are applicable for the following reasons:
in the first reference,
- it is unconcerned with the problem of removing ash,
- the solid sulfur compounds formed in the first stage
are not stable enough to be passed to second stage
and be removed with the slag, and
- the temperature in the first stage of the process
can be above the melting point of ash.
In the second reference,
- it does not expressly describe the temperature in
the first stage to be below the melting point of
ash.
The applicant's argument is mistaken with respect to both
references. It is true that Moriarty is unconcerned with
the problem of removing ash because it is directed to fuels
having a low ash content. Consequently, the temperature in
second stage of the Moriarty's method was not set to take
into account ash removal. Moriarty is concerned with method
of reducing the amount of gaseous sulfur compounds and
nitrogen compounds. It forms in fact in the first stage a
very stable solid sulfur compound using as mentioned
previously specific conditions. Said sulfur compound can be
retained in a solid form in the second combustion stage
under a temperature of 1800øK-2500øK with 45%-75%
theoretical air.
Brown is directly concerned with the removal of ash. Brown
teaches that the melting point of ash varies depending upon
the particulate binding absorbent used. It shows the
alternative of removing the ash in a solid or liquid form
with less than 100% theoretical air. The temperature of
1100øC (1373øK) is preferred as explained by Brown because
of the thermal instability of sulfides above said
temperature.
Given the foregoing, it is expected skill to modify the
three stage combustion process of Moriarity in the manner
proposed by the applicant. Claims 1 to 19 are obvious in
view of Moriarity when considered in conjunction with the
general knowledge that is shown by Brown.
The Applicant's arguments in the submission responding to the
Final Action are as follows, in part:
It is believed that the Examiner has not correctly assessed
the disclosure of the references, and has not given
sufficient consideration to the comments previously made by
applicant in regard to the cited art. For these reasons, it
is believed that at the least, the Examiner was incorrect in
making the action final.
On page 3 of the Action, paragraph 4, the Examiner indicates
in the first sentence that applicant's argument is mistaken,
although in the next sentence the Examiner admits one aspect
of the argument, that Moriarty (Australian Patent 548,115)
is not concerned with the problem of removing ASH.
Besides this, applicant had argued that Moriarty does not
require temperature in the first stage to be below the
melting point of the ash while this is a requirement in the
present application. The Examiner casually dismissed this
point by saying that since Moriarty was only concerned with
fuels having a low ash content, consequently the temperature
in second stage of Moriarty's method was not set to take
into account ash removal. This appears to be circular
reasoning --- since Moriarty has got nothing to do with the
problem addressed by applicant, Moriarty is unconcerned with
applicant's essential steps. These, according to the
Examiner can simply be supplied by combining the disclosure
of Brown.
However, nothing is said by the Examiner as to any possible
reason for such combining, and applicant's view is that only
hindsight from reading applicant's specification leads to
the combination.
The Examiner states that Moriarty forms a stable sulfur
compound in the first stage. However, applicant pointed out
previously that the temperature range specified in the first
stage by Moriarty is (1000· to 1800· K).
Since the temperature range of Moriarty includes
temperatures above the ash melting point, Moriarty discloses
removal of sulfur under conditions when the ash removal is
made difficult. This goes to the very essence of
applicant's invention. Applicant previously argued:
In the discussion of the prior art in the present
specification, it is pointed out that it was known
in the art to remove sulfur as solids, and also to
remove ash. However, the known methods improved ease
of removal of sulfur but at the expense of making ash
removal harder, or when the method was directed to
easier removal of ash, problems with removal of sulfur
were created. By the particular essential requirements
of the present invention as specified in claim 1 parts
(b) and (d), the highly advantageous result was
achieved whereby optimum ease of removal of both sulfur
and ash was obtained.
Clearly, there is no reason for combining Moriarty with
Brown. The present claims therefore are believed to be
allowable.
The issue before the Board is whether or not the claims are
patentable in view of the cited prior art. More specifically, it
must determine if, as the examiner states in the Final Action, it
is but expected skill to modify the three stage combustion
process of Moriarity in the manner proposed by the applicant, and
whether the claims are obvious in view of Moriarity, when
considered in conjunction with the general knowledge shown by
Brown.
Upon analyzing the references, the Board finds that major
differences occur between the cited patents and the invention
described and claimed in the application in three main areas as
follows:
- The first difference is in the temperature used in the first
combustion stage. The upper half of the temperature range
specified by Moriarty, if used in the invention, would
render inoperable the process claimed in the instant
application, because the ash would be melted in the first
stage and the sulfur compounds would not be passed on to the
second stage, and some of the less stable sulfur compounds
would be broken down prior to their removal.
- The second difference occurs with respect to the second
stage of the instant process. The first stage of the Brown
reference teaches a temperature of less than 1100øC, whereas
the second stage temperature in the instant application is
greater than 1100·C. The use of the lower temperature in
the second stage of the application would favour the removal
of the ash in solid form in this stage or its transmission
to a further stage, both being contrary to the invention.
Furthermore, if as taught in Brown, the second stage of the
instant process were operated below 1100·C, and additives
were introduced in order to lower the melting point of the
ash, it would likely be melted in the first stage, which
event the applicant seeks to avoid. Use of the higher
temperature by the applicant, melts the ash and permits
smaller ash particles to be impinged on the thus resulting
molten, slag-coated walls.
- The third difference occurs in the last combustion stage.
The Moriarty reference teaches that a preferred embodiment
resulting from use of the process is that:
the solid sulfur compounds generated in the first
sulfur-capture combustion zone, are retained in the
combustion gases and, therefore, must pass through this
third combustion zone (24) (see column 9, line 68).
In Moriarity, the solid sulfur compounds are intended to be
removed from the combustion mixture by conventional
filtration techniques (column 4, lines 3 to 6). The process
of the instant application specifies the removal of all
sulfur products either in the first or second stage and is
designed not to pass any of the sulfur compounds on to the
third stage.
In order to determine whether or not the invention is obvious in
view of the prior art, the Board is guided by the following Court
decisions:
In Leithiser v Penao Hydra Pull, 17 C.P.R. (2d), 110 at 115,
Jackett C.J. said:
there is a further requirement that the thing claimed
as an invention must be the result of inventive
ingenuity and not mere "workshop" improvement or
development. See commissioner of Patents v Farbwerke
Hoescht Aktiengesellschaft vormals Meister Lucius &
Bruning...[1964] S.C.R. 49...per Judson, J. (delivering
the judgment of the Supreme Court of Canada) at pp. 56-
7.
Furthermore, the following guideline is set down in Niagara Wire
Weaving v Johnson Wire Works Ltd (1939) Ex. C.R. 259 at page
273,
Small variations from, or slight modifications of, the
current standards of construction, in an old art,
rarely are indicative of invention; they are usually
obvious improvements resulting from experience, and the
changing requirements of users.
and at page 276,
No step is disclosed there which could be described as
invention. There is not, in my opinion, that
distinction between what was known before, and that
disclosed... that called for that degree of ingenuity
requested to support a patent.
The consideration before the Board is, therefore, whether the
invention is directed towards a mere "workshop" improvement or
development, or whether it is the result of a small variation
from, or a slight modification of the current standards...in an
old art.
The Board is of the view that the invention described and claimed
in the application is more than an obvious improvement resulting
from experience and the changing requirements of users. The
distinctions between the invention claimed in the application and
the prior art references are more than slight and, in our
opinion, it would not be obvious for a person skilled in the art
to modify the three-stage combustion process of Moriarity to
arrive at the instant invention and to further incorporate the
ash melting step disclosed in the Brown reference into the
process.
The Board recommends, therefore, that the rejection of Claims 1
to 19, on the grounds of obviousness in view of the prior art, be
withdrawn.
F.H. Adams V. Duy A. J. Legris
Chairman Member Member
Patent Appeal Board Patent Appeal Board Patent Appeal Board
I concur with the findings and recommendations of the Patent
Appeal Board. Accordingly, I remand this application to the
examiner for prosecution consistent with the recommendation.
M. Leesti
Commissioner of Patents
dated at Hull, Quebec
this 19th day of November 1992
Smart & Biggar
P.O. Box 2999
Station D
Ottawa, Ontario
K1P 5Y6