TITLE : Design of Filter Holder with Seal Assembly for
Mounting Hot Gas Filter Element
FIELD OF INVENTION
The invention relates generally to hot-gas cleanup systems used for filtering high
temperature coal fuel gases containing particulate materials. More particularly,
the invention relates to an improved filter holder device that acts as a barrier
seal between the body of the filter element and the filter holder when mounted
to a hot gas cleanup system.
BACKGROUND OF THE INVENTION
In advanced coal gasification combined cycle power generation, a hot gas filter
system which is used to filter the fine ash dust present in hot coal fuel gas,
before the fuel gas enters the gas turbine. The main equipments in the advanced
Coal gasification combined cycle power generation are high pressure gasifier, Hot
gas cleanup system, and finally a Turbine to generate electricity at higher
efficiency and lov^er emissions than the conventional power plants. The gas
turbine used for firing fuel gas from a high pressure gasifier, can accept particles
of concentration < 5 mg / Nm3 of average size 5 micron. This is achieved by
using a plurality of cyclones disposed in series for removing coarse particles and
a hot gas filter system working upto 500 deg C and having ceramic tubular filter
elements with a membrane coating, for removing fine particles to the
requirements of gas turbine. The conventional electrostatic precipitator, fabric
filter and paper filter are low pressure and low temperature filter systems and
are not suitable for this high pressure high temperature application. In contrast,
the hot gas filter system consists of a thermally insulated high pressure steel
vessel, in which hot gas ceramic tubular filter elements in groups are supported
on a steel tube sheet which separates the dusty gas stream from clean gas
stream as stated herein below.
The tubular hot gas filter elements are mounted In respective filter holders with a
seal assembly to prevent the dusty gas stream mixing with the clean gas stream.
The filtration of fine particles in industrial applications are usually done using
electrostatic precipitator, fabric filter and paper filter, but these are low pressure
and low temperature systems. The materials and the configuration used in this
art are not applicable to hot gas ceramic tubular filter which has to withstand the
required temperature and pressure in coal gasification applications. In the rear
area of hot gas filtration, the filters are fixed in a collar with a ceramic gasket
and the filter movement is restricted by tubular counter weights located above
the collar as disclosed in patent GB 2 262 053. The disadvantage in this art is
that, under reverse pulse jet there is a possibility of dislocation of seal and
subsequent leakage of dusty gas into the clean gas stream. Alternatively a
clamping arrangement with bolt and nut has been used to keep the seal intact as
in the configuration described in US patent 6,468,322. But this design is
elaborate, cumbersome and occupies more space.
Thus, an object of the present invention is to provide an improved filter holder
device which will securely mount filter elements within hot gas filtration system.
Another object of the invention is to provide an improved filter holder device
which eliminates the disadvantages of the prior art including use of the
complicated counterweight and clamping arrangement.
A further object of the invention is to provide an improved filter holder device
which ensure a leakage-proof-sealing of the filter assembly under operating
temperature and pressure of the system.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 - shows a hot-gas filtration system
Figure 2 - shows a filter element mounted on a filter-holder device according to
the present invention
Figure 3a - shows a filter-holder device according to the present invention
Figure 3b - shows a filter-holder and an inner seal gasket of the device
according to the present invention
Figure 3c - shows a top seal gasket of the device of the present invention
Figure 3d - shows a metallic ring of the device of the invention
Figure 3e - shows a lock-bush nut of the device according to the present
Invention
SUMMARY OF THE INVENTION
Accordingly there is provided an improved filter holder device (20) for securely
mounting a filter-element (08) within a hot gas filtration system, the device
comprising: a filter holder (01) configured from a both end-open metallic collar
so as to have an identical internal and outer contour profile with a reduced
bottom position, and being connected by welding to a tube sheet (13), the outer
contour profile matchingly accommodating a flanged end of the filter element
(08), an inner seal gasket (02) configured to have a profile matching to the inner
contour profile of the filter holder (01), and accommodated to cushion against
leakage, a top seal gasket (03) having an annular configuration and disposed on
a top flat surface of the flanged end of the filter element (08), a metallic ring
(04) having an inner and outer diameter respectively corresponding to the inner
diameter of the flanged end of the filter element (08) and the inner diameter of
the filter holder (01), a lock bush unit (05) having atleast two diametrically
PRESENT INVENTION
Figure 1 shows a filtering system (18) for separating particulate matter from a
gas stream. The system comprises a filter vessel (7) in which are disposed a
plurality of filter elements (8). The filter-vessel comprises a dome-shaped head
(9) for mounting auxiliary attachments. The body (10) of the vessel (7) has
atleast one dusty gas inlet (11) and one clean gas outlet (14). A tube sheet (13)
supporting a plurality of filter element housing which accommodate the filter
elements (8). The body (10) is joined by a frustoconical ash hopper (12) for
receiving particulate matter. Each filter element (8) is held by a filter holder
device (19).
The hot gas filter element (8) used for gas filtration applications is a one end
closed tubular ceramic filter with the other end integrally shaped with a higher
diameter to serve as a flange for mounting in the improved filter holder device
(19) as shown in Figure 2.
The present invention discloses an improved filter holder device (19) for
mounting the filter (08) as described below and as shown in Figure 2.
The improved filter holder device (19) comprises a filter holder (01), an inner
seal gasket (02), a top sea gasket (03), a metallic ring (04) and lock bush nut
(05) and the device in assembled condition is shown in Figure 3a. The filter
element mounted on the filter holder device as shown in Figure 2.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 - shows a hot-gas filtration system
Figure 2 - shows a filter element mounted on a filter-holder device according to
the present invention
Figure 3a - shows a filter-holder device according to the present invention
Figure 3b - shows a filter-holder and an inner seal gasket of the device
according to the present invention
Figure 3c - shows a top seal gasket of the device of the present invention
Figure 3d - shows a metallic ring of the device of the invention
Figure 3e - shows a lock-bush nut of the device according to the present
Invention
SUMMARY OF THE INVENTION
Accordingly there is provided an improved filter holder device (20) for securely
mounting a filter-element (08) within a hot gas filtration system, the device
comprising: a filter holder (01) configured from a both end-open metallic collar
so as to have an identical internal and outer contour profile with a reduced
bottom position, and being connected by welding to a tube sheet (13), the outer
contour profile matchingly accommodating a flanged end of the filter element
(08), an inner seal gasket (02) configured to have a profile matching to the inner
contour profile of the filter holder (01), and accommodated to cushion against
leakage, a top seal gasket (03) having an annular configuration and disposed on
a top flat surface of the flanged end of the filter element (08), a metallic ring
(04) having an inner and outer diameter respectively corresponding to the inner
diameter of the fianged end of the filter element (08) and the inner diameter of
the filter holder (01), a lock bush unit (05) having atleast two diametrically
opposite holes on top flanged surface for tightenningly hold the device
characterised in that the said holding device mounts by adequate welding to hold
filter workable under high temperature and pressure of one system ensuring a
leakage proof wherein the inner seal gasket (02) comprises a flexible and
compressible aluminosilicate ceramic fibre material of high density and the top
seal gasket comprises a flexible and compressible aluminosilicate ceramic fibre
material of high density and an inner diameter of the lock bush nut (05) is
selected in registration with the flanged end of the filter element (08), and
wherein the outer portion of the lock bush nut (05) having a step configured with
a threaded top portion for locking with the filter holder (01).
The performance improvement achieved by implementation of new invented
filter holder with assembly over the prior art patents is improvement in pressure
drop efficiency of filtration is 24%, assembly time savings of 32% and material
cost savings of 14%.
The filter holder (01) shown in Figure 3b Is a shaped, both ends open annular
metallic collar and is machined to the configuration shown in figure 3b. It is
made of metal, like alloy steel or stainless steel to withstand the required
temperature with minimum but sufficient wall thickness to make threads inside
the top portion. The outer contour profile of the filter holder (01) follows its inner
contour profile and is welded to the bottom side of the tube sheet (13). This
configuration gives a reduction in diameter of the filter holder (01) in the bottom
portion and since many filter holders (01) are distributed in the tube sheet (13),
this feature reduces the overall diameter of tube sheet (13) and that of the filter
vessel (07). Further, as the hole area corresponding to filter holder area in the
metallic tube sheet (13) decreases, the strength of the tube sheet (13) also
increases requiring lesser thickness of tube sheet (13). The inner contour profile
of the filter holder (01) follows the outer contour profile of the flanged end of the
tubular filter (08) and is dimensioned to accommodate the filter (08) with the
inner seal gasket (02).
The inner seal gasket (02) is made of flexible and compressible alumuniosilicate
ceramic fibre material of high density and being flexible and compressible, it can
be shaped to the inner contour profile of the filter holder (01) as shown in
Figure 3b. After assembling the hot gas filter element (08), the inner seal gasket
(02) prevents the dust leaking from dusty gas side to the clean gas side and can
withstand the required temperature and differential pressure across the dusty
gas stream and clean gas stream. The inner seal gasket (02) also acts as a radial
thermal expansion cushion for the ceramic hot gas filter element (08) at high
temperature. The filter holder (01) with inner seal gasket (02) is shown of
figure 3b.
After the tubular filter (08) is assembled inside the filter holder (01) having the
inner seal gasket (02), the top seal gasket (03), as shown on figure 3c, is placed
on the top flat surface of the flanged end of the tubular filter (08). The top seal
gasket (03) is of annular configuration with suitable thickness, made of flexible
and compressible aluminosilicate ceramic fibre material of high density to
withstand the temperature. The top seal gasket (03) further effectively prevents
the leaking of dusty gas to clean gas side and can withstand the required
temperature and differential pressure across the dusty gas stream and clean gas
stream. The top seal gasket (03) also acts as a thermal expansion cushion for
the ceramic filter (08) and lock bush nut (05 described below) at high
temperature.
The metallic ring (04), is of annular configuration as shown in Figure 3d, made of
alloy steel or stainless steel metal of suitable grade to withstand the temperature
and has an inner diameter corresponding to the inner diameter of the flanged
end of the filter (08) and an outer diameter corresponding to the inner diameter
of filter holder (01) above the top seal gasket (02) with suitable thickness. This
metallic ring (04) is located above the top seal gasket (02) in the filter holder
(01) after mounting the filter element (08), to prevent the movement of top seal
gasket (02) while tightening the lock bush nut (05) into the threads of the filter
holder (01).
The lock bush nut (05) is of annular configuration as shown in figure 3e, made of
alloy steel or stainless steel of suitable grade to withstand the temperature. The
inner diameter of the lock bush nut (05) is maintained same as that of the top
flanged end of the tubular filter (08), top seal gasket (03) and metallic ring (04).
The outer body of the lock bush nut (05) has a step which is male
threaded to drive through the female threaded top portion of the filter holder
(01) to lock the annular metallic ring (04) with top seal gasket (03) and keep the
filter (08) intact. The filter (08) is held securely in position during the reverse
pulse jet cleaning operation as otherwise it may move up as a reaction to the
forward momentum of the pulse jet via the valves (16). The outer diameter of
the top flanged portion of the lock bush nut (05) corresponds to the outer
diameter of the filter holder (01). The lock bush nut (05) has two holes
diametrically opposite on its top flanged surface as shown in the figure 3e to
tighten or loosen it with the help of a special spanner.
WE CLAIM
1. An improved filter holder device (20) for securely mounting a filter-
element (08) within a hot gas filtration system, the device comprising:
- a filter holder (01) configured from a both end-open metallic collar
so as to have an Identical internal and outer contour profile with a
reduced bottom position, and being connected by welding to a tube
sheet (13), the outer contour profile matchingly accommodating a
flanged end of the filter element (08);
- an inner seal gasket (02) configured to have a profile matching to
the inner contour profile of the filter holder (01), and
accommodated to cushion against leakage;
- a top seal gasket (03) having an annular configuration and
disposed on a top flat surface of the flanged end of the filter
element (08);
- a metallic ring (04) having an inner and outer diameter respectively
corresponding to the inner diameter of the flanged end of the filter
element (08) and the inner diameter of the filter holder (01);
- a lock bush unit (05) having atleast two diametrically opposite
holes on top flanged surface for tightenningly hold the device;
characterised in that the said holding device mounts by adequate welding
to hold filter workable under high temperature and pressure of one
system ensuring a leakage proof wherein the inner seal gasket (02)
comprises a flexible and compressible aluminosillcate ceramic fibre
material of high density and the top seal gasket comprises a flexible and
compressible aluminosillcate ceramic fibre material of high density and an
inner diameter of the lock bush nut (05) is selected in registration with the
flanged end of the filter element (08), and wherein the outer portion of
the lock bush nut (05) having a step configured with a threaded top
portion for locking with the filter holder (01).
2. The device as claimed in claim 1, wherein the filter holder (01) comprises a
metal capable to withstand high temperature and pressure, for example,
alloy steel, stainless steel, and wherein a top portion of the filter holder
(01) having a threaded configuration.
3. The device as claimed In claim 1, wherein the metallic ring (05) comprises
alloy steel or stainless steel, and has an annular configuration.
4. An improved filter holder device for securely mounting a filter element
within a hot-gas filtration system as substantially described herein with
reference to the accompanying drawings.

The invention relates to an improved filter holder device (20) for securely
mounting a filter-element (08) within a hot gas filtration system, the device
comprising a filter holder (01) configured from a both end-open metallic collar so
as to have an identical internal and outer contour profile with a reduced bottom
position, and being rigidly connected to a tube sheet (13), the outer contour
profile matchingly accommodating a falnged end of the filter element (08), an
inner seal gasket (02) configured to have a profile matching to the inner contour
profile of the filter holder (01), and accommodated to cushion against leakage a
top seal gasket (03) having an annular configuration and disposed on a top flat
surface of the flanged end of the filter element (08), metallic ring (04) having an
inner and outer diameter respectively corresponding to the inner diameter of the
flanged end of the filter element (08) and the inner diameter of the filter holder
(01), a lock bush unit (05) having atleast two diametrically opposite holes on top
flanged surface for tightenningly hold the device.