FIELD OF INVENTION
The present invention relates generally to improved particulate filters for enhanced
collection and regeneration to clean high temperature gases. The applications extend
from hot gas cleanup for gasifier to exhaust gas after treatment typically from diesel
powered engines either stationary or mobile. More specifically the present invention
relates to new design for gas stream filtration typically for those applications with
high particulate load where frequent cleaning or regenerating the filter is required.
BACKGROUND OF THE INVENTION
Ceramic honeycomb based particulate filters are widely used for exhaust gas cleanup
particularly from diesel powered internal combustion engines. The major problem
encountered during operation of existing particulate filter is the difficulties in removal
of particulates from the filter because of high restriction of the narrow channels
thereby limiting the performance of these devices by the more intense complicated
procedures to be employed for removal of respective particulate matters by periodic or
continuous procedures.

Most common type of regeneration method used for cleaning particulate filters
particularly for diesel exhaust application involves expensive catalysts or electric
heating. The catalyst can get deactivated in presence of certain impurities in fuel and
electric heating need to be controlled and restricted to limit thermal stress on the
ceramic filter elements. Various attempts have been made to improve the particulate
filters particularly to address the issue of cleaning the trapped particulates as
summarized in the following.
US Patent No. 7,258,723 (August 21, 2007) titled "Particulate filter assembly and
associated method" of Crawley, et al. assigned to Arvin Technologies, Inc. includes an
electrode assembly in a particulate filter assembly, a particulate filter positioned in an
electrode gap defined between two electrodes of the electrode assembly, a power
supply electrically coupled to the electrode assembly, and a controller for controlling
operation of the power supply to apply a regenerate-filter signal to the electrode
assembly to oxidize particulates collected by the particulate filter. An associated
method of regenerating the particulate filter is disclosed. However this method
involves high power supply cost and safety concerns.
US Patent No. 7,524,360 (April 28, 2009) titled "Method and apparatus for filtering
exhaust particulates" of Cheng, assigned to GM Global Technology Operations, Inc.
addresses the issue of the increasing accumulation of ash particles within the filtration
body with time. Because catalytic or thermal arrangements within the exhaust
system, which serve to effect regeneration of the filtration element,

cannot remove ash particles. They provided a solution by new wall-flow filtration
element has pores defining a porosity sufficient to trap exhaust particulates and to
pass ash particles (post regeneration), having a pore size equal to or greater than 55
micrometers and equal to or less than 250 micrometers. Although a part of the ash
particles are avoided by this method, but the problem of regeneration of trapped
exhaust particulates remain and the current method of regenerating the same is
complicated and expensive.
US document 2009/0266040 Al (Oct 29, 2009) titled "Diesel particulate filter
assembly" discusses the shortcomings of existing current monolithic style filters and
need for alternatives to address the complicated particulate separation and
regeneration issues. They proposed to use envelop type filters based on pleated fiber
filter media supported by a separate ceramic frame. According to the disclosure the
exhaust emissions flow through the filter assembly, the particulates contained in the
emissions are collected within the pleated filter element. Therefore the entire load of
the particulate trapped need to be heated and incinerated within the pleated fiber
element for regeneration causing more power requirement and considerable thermal
stress for the fiber element. There are instances when large volume of diesel
particulate soot are incinerated in the filter, the temperature increases uncontrollably
due to exothermic nature of the reactions causing melting of ceramic materials which
constituted the filter, fiber or the ceramic frame. In addition there will be difficulties in
sealing the mating parts of the fiber filter and ceramic frame and also supporting the
ceramic frame in the metal canister. Further they suggested to manufacture the

ceramic frame by injection moulding or by casting, which will be expensive considering
the size and mechanical strength requirement of such ceramic frame.
US Patent No. 6,773,478 (August 10, 2004) titled "Gravity-induced ash removal system
for particulate filters" of Broering, et al. assigned to Fleetguard, Inc. improves the
existing practice by providing a catch basin for the collection of oxidation by-products
from the particulate filter. Important in the design is to orient the particulate filter in a
generally vertical orientation based upon the normal orientation of the diesel engine
when in use. By vibration of the engine due in part to engine operation and due in part
to vehicle vibrations, oxidation by-products expected to shake loose from the
particulate filter and fall through a connecting conduit. By positioning a catch basin
below the particulate filter and connecting it to the conduit, the oxidation by-products
are able to be collected in the catch basin for removal at a later time. With this method
a part of the oxidation by-products such as carbon-based soot and ash are expected to
be removed targeting reduce load for the regenerative procedures which could be
based on expensive and complicated catalyzed or electric heating or burner
regeneration. However it is found that the benefits are meager because only a little
quantity of particulate could have been collected before it enters to the particulate
filter. In actual practice since the majority of the particulates is soot, which comprises
of sticky un-burnt oily substance, thereby it is difficult to dislodge majority of them
from the porous filter walls. The difficulty of dislodging further increases because of
the narrow long channels of the state-of-the-art filters which have less than
2mm opening for each of the channels constituting the filter facilitate

bridging of the accumulated particulate soot. Another practical difficulty is to
accommodate the vertically oriented filter unit in the available underbody space of
common diesel vehicles.
Indian Patent No. 212 077 (November 4, 2007) titled "A novel exhust emission
control device for diesel particulate" of R.N. Das et al. granted to Bharat Heavy
Electricals Ltds further improves the existing diesel particulate filter system by
addressing the above stated two difficulties. Retaining its normal horizontal orientation
best suited for the underbody of diesel vehicles, this Indian Patent provides a novel
design and cleaning method. By incorporating appropriate design inside the filter
construction, the invented regeneration method allows for a short period of initial
electrical heating which dislodge the particulate accumulated insid" the ceramic
channels and sticking on to the inner walls of the monolithic filter trap, and using a
compressed air blowing provision in the apparatus removes bulk of the accumulated
soot. This invented apparatus when fitted with city buses found beneficial since for the
required cleaning it requires only less than 30 mins regeneration operation for a full
day running. Bulk of the accumulated soot is found coming out in the form of stick
having the internal impression of the filter channels formed by the agglomeration of
the particulate matter inside each filter channels.
However, some difficulties were faced since the regeneration operation essentially
needs facility of electrical power to be connected to the system off-line when the diesel
vehicle is stationary. Further it was found after long running beyond a year or longer,

some accumulation of refractory ash on the porous filter surfaces of the channel walls.
These accumulations triggered two major concerns; (1) although utilizing the
method of this patent, the ceramic filter unit is subjected to less heat and less severe
thermal cycling, but use of electrical heating on the filter wall and occasional
uncontrolled burning of the traces of un-burnt oil carried on the filter surface make the
micron and sub-micron sized ash particle melt or fuse and irreversibly stick blocking
the pores and (2) bridging happens in the narrow channels involving partially burnt
particles in strategic locations makes dislodging operation ineffective because the
sticky materials are less organic and cannot be destroyed by burning to dislodge.
There is a need to overcome the above stated difficulties and further improve the
performance of the filter and at the same time reduce the operation cost. It was
necessary to make the design and method of filtration further simplified in order to
achieve the goal of improved performance at lower cost.
SUMMARY OF THE INVENTION
The main object of the present invention is to provide a simplified method of filtration
for achieving improved performance at lower cost.
Another object of the invention is to achieve simplicity and ease of mass production of
the particulate filter by retaining the monolithic nature of the filter while adopting
simplified method of filtration.

Various configurations of the ceramic honeycomb based particulate filters are
fabricated using the established existing manufacturing methods and facilities. Finally a
unique configuration is invented by joining the channels which are meant for
particulate trapping by a simple manufacturing method, which can be automated and
invented filters can be mass produced.
An embodiment of the present invention includes a particulate filter for the filtration
system configured to eliminate narrow restricted channels, which cause difficulty in
dislodging the trapped particulates. Presently as per the known art these filter
channels are narrow having square or hexagonal or even circular cross-section. The
filter invented in this patent application is fabricated by joining and widening the
channels which are used to trap the particulates, whereas the narrow configuration of
other channels for filtered gas flow are not changed, thereby retaining the mechanical
integrity of the monolithic filter. Generally in a diesel particulate filter element only half
of the channels (or half of the total volume of the filter) is used to trap the particulates
and the other half are used only for the clean gas flow. The same volume ratio is
maintained here, but at the same time nature of the filter element is drastically
changed into a thin but wide ceramic-walled envelop type filter. This inventive step is
possible to realize because adjacent channels of the envelop meant for cleaned gas are
kept unaltered providing a strong support of plurality of inner walls, supporting two
filtering envelop on either sides.

Another embodiment of the present invention includes positioning of a collection
chamber or catch basin appropriately directly under the enlarged particulate trapping
channels for the natural collection of part or majority of the particulate load depending
on the nature of the particulate.
Another embodiment of the present invention includes the inlet and the outlet of the
filtration system configured to position in such way so as to direct the particulates
naturally travel towards the collection chamber with the help of gravity or design of
flow contours or both.
Yet another embodiment of the present invention includes providing plurality of
inclined baffles above the collection chamber to prevent collected particulate mass to
travel upward into the filtering section due to turbulence or other cause. These baffles
can normally be supported only on one end leaving the other end free, so that it
vibrates while engine running or any other movement, aiding fine particulates to travel
downward to the catch basin.
Another embodiment of the present invention is to use the same mass manufacturing
process of manufacturing the invented monolith filters, using only the minor additional
process at the green stage i.e. before firing the monolithic filter.
Yet another embodiment of the present invention is to manufacture major part of the
filter element by conventional extrusion of honeycomb by altering the die design

replicating the through and through channel construction, which may or may not be
mechanically supported by a finishing operation at the green stage before firing. An
advantage of this alternative manufacturing process for the invented filter element is
that the supported envelops can be constructed inclined so that it will be further
advantageous to easily dislodge the trapped particulates sticking on the envelop wall.
A further embodiment of the present invention includes presence of water or any
suitable liquid at the collection chamber in order to naturally trap some of the
particulate in the liquid for improved performance and easy disposal of the collected
particulate.
Yet another embodiment of the present invention includes suitably provide the inlet
gas pipe arrangement so as to pass the inlet gas first through the water or any
suitable liquid in order to trap part of the particulate and prevents it to fly to increase
load of the main filter section.
Further objects and advantages of this invention will be more apparent from the
ensuing description.
At the outset of the description that follows, it is to be understood that the ensuing
description only illustrates a particular form of this invention. However, such a
particular form is only intended as an exemplary embodiment and teching of the
invention and not intended to be taken restrictively.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
FIG. 1 illustrates views of an exemplary embodiment of (a) schematic view of a
monolithic filter element and (b) outside view of a filter assembly in accordance with
the present invention.
FIG. 2 (a) shows another isometric view of the Filter Element illustrating the
exemplary embodiment of the present invention.
FIG. 2 (b) shows two views of the Filter Element as manufactured illustrating the
exemplary embodiment of the present invention.
FIG. 3 is a schematic perspective cross-sectional view illustrating an exemplary
embodiment of the Filter Assembly incorporating the exemplary Filter Element of Figs.
1-2.
FIG. 4 illustrates another variation of the embodiment where open channels of the
filter element are further enlarged and opened at three faces.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The following description of the invention is provided as an enabling teaching of the
invention in its best currently known embodiments. To this end, those skilled in the

relevant art will recognize and appreciate that many changes can be made to the
various embodiments of the invention described herein, while still obtaining the
beneficial results of the present invention. It will also be apparent that some of the
desired benefits of the present invention can be obtained by selecting some of the
features of the present invention without utilizing other features. Accordingly, those
who work in the art will recognize that many modifications and adaptations to the
present invention are possible and can even be desirable in certain circumstances and
are a part of the present invention. Thus, the following description is provided as
illustrative of the principles of the present invention and not in limitation oof.
A schematic view of an embodiment of invented monolithic filter element 10 is shown
in Fig. 1(a), where face A and Face C are visible in the sketch. The monolithic filter
module is made from cordierite (2Mg0.2AI203.5Si02), alumina (AI203), mullite
(3AI203. 2Si02), silicon carbide (SiC), porcelains, aluminium titanate, alumina-silica
mixtures, glasses, glass-ceramics, inorganic refractory materials, metal oxides, and
sintering aids. Further during manufacturing processing materials such as binders,
plasticizers and other additives and pore formers are mixed with the composition as
required.
When the inlet gas with its suspended particulates enter the filter element, 10
through the multiple openings 11 of Face A, rejects part of the particulates through
openings in face B while filtering operation takes place inside 10 through the porous
ceramic-wall envelops, which are the projected part of the cavities, the openings of

which are seen as 12 on face C. Each opening on face A is connected with respective
opening on face B without any restriction, but these openings are separated by
filtering envelops, which constitutes an enclosed cavity opens only on face C, which
are marked as 12. On filtering through the thin-walled envelops the clean gas flows
out of openings 12 through face C. The porous ceramic thin-walled envelops are
mechanically held by a large number of walls 14, which are the par extruded
honeycomb cells.
The invented filter element 10 can have any desired predetermined size and shape.
For example, although the invented filter element 10 in Fig. 1 is exemplified as a
cubical shape with rectangular cross-section for easy of explaining the finer aspects of
the invention, it should be understood that the invented filter element 10 can be
shaped to provide cylindrical, elliptical or polygon cross-section. To that end,
exemplary and non-limiting monolith cross-sectional shapes include ellipses, circles,
rectangles, square, pentagonal, hexagonal, octagonal and the like. For consistency
and simplicity, cubical form of the invented filter element 10 has been used primarily
in the subsequent discussions.
The above ceramic element is housed in the filter assembly, a schematic view of
which is shown in Fig. 1 (b) as an example. In this example the filter element 10 is
assembled in the same orientation as shown in the figure so that the exhaust gas
with particulate enters the apparatus through the inlet 30, travels through the cone
35, enters the filtering chamber 60 where the filter element 10 is mounted, enters the
filter element 10 through the openings 11 on face A. A cross-sectional view of the

illustration can be seen at Fig. 3. On entering the filter element 10 the gas flows
unrestricted towards opening on face B, but eventually due to pressure gradient flows
through the ceramic envelops inside the filter element 10. While clean gas flows
through the envelop to the cavities which are opens at 12 on face C, the particulates
larger than the pores of the envelop wall remain in the channels connecting between
face A and face B. While clean gas flows out of the filtering element through 12 on
face C, it travels through the cone 45 to the outlet pipe 40 to go out of the apparatus.
The trapped particles either stick to the envelop wall or falls through the openings of
face B to the particulate collector 20 through the collection cone 25, but will be
restricted to go out through face A during its operation because of the predominant
flow of the inlet gas in opposite direction. The particulates collected in particulate
collector 20 may be cleaned or emptied periodically.
Fig. 2 further illustrates the filter element 10 where face A and face B both are visible
with the openings on them. Each pair of openings on both the faces equidistance
from any common perpendicular plane are internally connected forming a channel. In
one example of the present invention the diesel engine exhaust gas laden with
particulates is directed to flow through this channels and thin-walled envelops
defining the channel are responsible for filtering particulates from the earn.
Construction and working of the particulate filter assembly 90 as an exemplary
embodiment is further illustrated in Fig. 3. The ceramic filter element 10 as a
monolithic structure is mounted on the filtering chamber 60 with a compressive seal
65 to isolate the area of cleaned gas from the filtering area. The compressive seal

could be made of in tumescent or non-intumescent compressive mat well known to
the person skilled in engine emission control or any other similar type of compressive
seals. The compressive mat is also to take care of the mechanical integrity of the filter
element mounting as known in the art.
During operation of the filter assembly 90, the filter element 10 receives the exhaust
gas through its openings on face A, filters and provide clean gas through its openings
on face C and part of the particulates trapped will be falling through hits openings on
face B. Particulates falling through openings on face B travels through the collector
cone 25 attached to the particulate collector 20. Inside the collector cone a number of
inclined baffles 50 made out of thin metallic sheets are provided which are supported
only on one end leaving the other end free, so that it vibrates while engine running or
any other movement, aiding fine particulates to slide downward to the particulate
collector. These baffles also help to prevent the fine particulate to drift upward away
from the particulate collector 20.
In another aspect of the present invention, insulated electrical heating coil 70 may be
employed if required in order to dislodge or incinerate some of the particulate sticking
on the ceramic envelop.
According to another embodiment of the invention the filter element can be
manufactured in the conventional extrusion-based manufacturing process of ceramic
honeycomb as known in the art. After the extrusion and drying stages of the green
honeycombs, a simple fixture can be employed to cut the channels show rough

the face A and B of filter element 10. Plugging of the required cells on face B and face
C will be done as per the existing practice known in the art. All these operations are
done as a part of the finishing process before the monoliths are sent for firing.
In another variation of the embodiment each channel connecting face and face B
are enlarged to open up through two adjoining faces namely face A and B or through
three adjoining faces namely A, B and D faces as shown in Fig 4 in contrast to Fig 2.
Though these variations particularly the one presented in Fig 4 are mechanically
weaker than the variation presented in Fig 2, there are many advantages of these
designs leading to higher amount of particular collection in some cases.

Ceramic monolithic particulate filters for hot gas filtration and diesel particulate
filtration have issues of particulate accumulation and regeneration. The particulate
filter fabricated according to the present invention is capable of collecting trapped
particulates due to its inventive construction. A thin-walled filtering envelop
supported by a large number of honeycomb cell walls of the present invention will
help in tailoring the hot gas filter characteristics and widen its application.