Hot gas filtering apparatus

A filtering apparatus for separating particulate matter from a gas stream. The filtering apparatus has a pressure vessel defining an interior chamber having a dirty gas inlet opening and a clean gas exit opening. A tubesheet is coupled within the pressure vessel thereby dividing said pressure vessel into a dirty gas side and a clean gas side. A support pipe for supporting a plenum chamber within the pressure vessel dirty gas side is securely coupled with the tubesheet. The plenum chamber for supporting a plurality of filter elements is coupled to the support pipe. The plenum chamber has a side wall having at least one dirty gas port and clean gas exit formed therein. The side wall further defines a clean gas chamber. A plurality of filter element guides are securely coupled within the clean gas chamber for supporting at least one filter element and preventing filter elements from moving laterally. A removable dirty gas port coupler for providing a particulate barrier seal between the dirty gas port and the plenum clean gas chamber is provided. A filter element support plate for supporting a filter element within the clean gas chamber is securely coupled adjacent the dirty gas port. The filter element support plate has at least one slot which is aligned coaxially with at least one of the plenum chamber dirty gas ports.

FIELD OF THE INVENTION 
The present invention relates generally to hot-gas cleanup systems and more 
particularly to a filtering apparatus for separating solid or liquid 
(aerosols) particulate matter from a carrier fluid such as a flue gas 
derived from combustion or gasification and other like processes. 
BACKGROUND OF THE INVENTION 
Hot gas cleanup systems that are implemented to clean particulate matter 
from a gas stream are well known in the art. These systems are currently 
used to clean coal fired gas, pressurized fluidized bed combustion gas, 
gasification, and waste incineration. Additionally, gas cleanup systems 
may be applied to catalyst and precious metal recovery, calcination, 
catalytic cracking, and material recovery during chemical processing. 
An example of a conventional hot gas cleanup system is disclosed in U.S. 
Pat. No. 5,143,530, to Haldipur et. al. and assigned to Westinghouse, and 
is hereby incorporated by reference. This hot gas cleanup system comprises 
a filter assembly which is mounted within a pressure vessel having a clean 
gas side and a dirty gas side. The filter assembly further comprises a 
plurality of filter element arrays supported within the dirty gas side of 
the pressure vessel, a plurality of tubesheets for supporting the filter 
element arrays, plenum pipes for channeling filtered clean gas to the 
clean side of the pressure vessel, and a back pulse system for cleaning 
particulates from the outer surface of the filter elements. These systems 
may employ various types of filter elements to filter particulate matter 
from a dirty gas steam. 
Typical filter elements employed to filter particulate matter include 
cross-flow filters, ceramic circular cylindrical filters (candle filters), 
bag or fabric filters, and porous metal candle filters. These filter 
elements are generally mounted within a pressure vessel so that a hot gas 
can first flow through the filter elements outside surface such that a 
substantial part of fine particulate matter within the dirty gas can be 
removed therefrom. 
Typically, as a gas stream flows through a filter element, dirty fine 
particulates collect on the outer surface of the filter elements while the 
clean gas flows through the filter media, into the plenum pipes, and out 
into the clean gas side of the pressure vessel. A substantial amount of 
the fine particulate matter that is collected on the outside of the filter 
is removed therefrom by a reverse gas pulse provided by the back pulse 
system which removes the particulate matter from the filter element outer 
surface. The removed particulate matter is then collected in a hopper and 
discharged. There are several problems, however, that may arise during the 
operation of a hot gas cleanup system. 
One problem is the formation of bridges of ash between the outer surfaces 
of adjacent filter elements. The bridging of ash can contribute to the 
failure or breakage of filter elements which would require that the entire 
system be shut down so that the filter elements can be replaced. It would 
therefore be desirable to provide a filtering apparatus that reduces the 
potential for bridging of ash. 
Another problem is that a broken filter element may drop from its array and 
potentially cause damage to other intact filters or damage to other 
components within the clean up system. It would therefore be desirable to 
provide a means for protecting intact filters and other components within 
the system from falling broken filter elements. 
Another problem with conventional cleanup systems is that replacement of an 
individual filter element requires that surrounding pressure vessel 
components be moved in order to gain access to individual filter elements. 
It would be desirable to provide a pressure vessel that provided easy 
access to individual filter elements. 
SUMMARY OF THE INVENTION 
The present invention provides a filtering apparatus for separating 
particulate matter from a gas stream. The filtering apparatus comprises a 
pressure vessel that defines an interior chamber having a dirty gas inlet 
opening and a clean gas exit opening. A tubesheet is securely coupled 
within the pressure vessel thereby dividing the pressure vessel into a 
dirty gas side and a clean gas side. A support tube for supporting a 
plenum chamber within the pressure vessel dirty gas side tube is securely 
coupled with the tubesheet. A plenum chamber for supporting a plurality of 
filter elements is coupled to the support tube within the dirty gas side 
of the pressure vessel. The plenum chamber comprises a side wall having at 
least one dirty gas port and clean gas exit formed therein. The side wall 
further defines a clean gas chamber. A plurality of filter element guides 
are securely coupled within the clean gas chamber. The filter element 
guides support at least one filter element within the plenum chamber and 
prevent the filter element from moving laterally. A removable dirty gas 
port coupler is employed for providing a particulate barrier seal between 
the dirty gas port and the plenum clean gas chamber. A clean gas flow pipe 
is employed for providing a flow path for filtered gas. The flow pipe is 
securely coupled with the clean gas exit. A filter element support plate 
for supporting a filter element within the clean gas chamber is securely 
coupled adjacent the dirty gas port. The filter element support plate has 
at least one slot which is aligned coaxially with at least one of the 
plenum chamber dirty gas ports.

DETAILED DESCRIPTION OF THE PRESENT INVENTION 
FIGS. 1 shows a filtering apparatus 20 for separating particulate matter 
from a dirty gas stream in accordance with the present invention. The 
filtering apparatus 20 comprises a conventional pressure vessel 21 having 
a domed-shaped head 22, a body 24, and required insulation (not shown). 
The domed-shaped head 22 defines an exit opening or nozzle 28 for the gas 
processed within the pressure vessel 20. The body 24 includes a dirty gas 
inlet 30, an upper part 38 having a generally circular cylindrical shape 
joined by a frusto conical lower part 39 for receiving the particulate 
matter terminating in a linear tip defining an opening or nozzle 42 
connected to a hopper (not shown) for collecting particulate matter. A 
plurality of ports 10 extend from the dome-shaped head 22 and provide a 
site for inserting instrumentation and for viewing the interior of the 
dome-shaped head 22 during shut-down periods. Tubes 12 for supplying a 
back pulse burst of gas for cleaning the filter elements 70 are sealed 
through each port 10. 
Also shown in FIG. 1 is a primary tubesheet 8 that divides the pressure 
vessel into a dirty gas side 9a and a clean gas side 9b . In accordance 
with the present invention, a plurality of plenum chambers 26 are 
generally shown. Each plenum chamber 26 is supported within the dirty gas 
side 9a of the pressure vessel. Each plenum chamber 26 houses a plurality 
of filter elements 70. The filter elements 70 are securely coupled within 
the plenum chamber 26. 
A first row of plenum chambers 26 are coupled to the primary tubesheet 8 
and a support pipe 11 (shown in FIG. 2) depending from the primary 
tubesheet 8. The remaining rows of plenum chambers 26 are supported by 
corresponding secondary tube sheets which are integrated into structural 
units by tubular members. Each tubular member is secured centrally 
(coaxially) within the pressure vessel 22. A shed or particle-deflector 
having a generally frusto-conical shape is attached above each plenum 
chamber 26. The plenum chambers 26 are supported within the pressure 
chamber by a method that is similar to the method used in conventional 
pressure vessels for supporting filter clusters as described in U.S. Pat. 
No. 5,143,530 and disclosed in the Background of the Invention above. The 
plenum chamber 26 is shown in more detail in FIGS. 2 through 4 and 
described more fully below. 
FIG. 2 shows a single plenum chamber 26 supported within the pressure 
vessel 21. The plenum chamber 26 is supported by a support pipe 11 that is 
coupled to the tubesheet 8. The plenum chamber 26 comprises a sidewall 40 
which defines a clean gas chamber 41. A plurality of dirty gas ports 44 
and at least one clean gas exit 46 are formed in the side wall 40. It is 
preferable that the clean gas exit 46 and dirty gas ports 44 be formed on 
opposite sides of the side wall 40. At least one clean gas flow pipe 83 is 
coupled to the clean gas exit 46. The back pulse pipe 54 is securely 
positioned above and adjacent to the clean gas flow pipe 83. The plenum 
chamber 26 is preferably made of a steel material. 
FIG. 2 also shows filter element guides or springs 52 securely coupled 
within the clean gas chamber 41. A filter element support plate 56 having 
a plurality of slots 56a that are aligned coaxially with corresponding 
dirty gas ports 44 is also provided. A plurality of filter elements 70 are 
shown supported within the clean gas chamber 41. Preferably, the filter 
elements 70 are hollow tubular candle filter elements. It is noted that 
other types of filter elements, such as cross-flow filters and filters 
having internal channels, may be incorporated in accordance with the 
present invention. 
Each candle filter element 70 comprises a porous sidewall 72 having a 
closed end 76 and an open end 74. The sidewall 72 has an outer surface 78 
and an inner surface 80. The porous side wall 72 defines a bore 82 which 
extends beginning at the open end 74 and terminates at the closed end 76. 
The bore 82 provides a path for the particulate laden gas to flow thorough 
so that the gas can be filtered. 
Each filter element closed end 76 is supported between a set of filter 
element guides 52 to prevent potential lateral movement along the filter 
element closed end 76, while the filter element open end 74 is coupled to 
the support plate 56 and adjacent to the dirty gas port 44 by a dirty gas 
port coupler 48. The filter elements 70 are positioned such that the 
filter element outer surfaces 78 are exposed to the clean gas within the 
clean gas chamber 41. 
Referring to FIGS. 3 and 4, at least one particulate barrier gasket 50 is 
placed between the dirty gas port coupler 48 and filter element open end 
74, and dirty gas port 44 and filter element 70 to provide a particulate 
barrier seal between the dirty gas side 9a and the clean gas chamber 41. 
The filter element open end 74, gaskets 50, and dirty gas port coupler are 
securely coupled with the support plate 56. 
FIG. 4 shows the plenum chamber dirty gas ports 44 and dirty gas port 
couplers 48 in more detail. The dirty gas port couplers 48 are shown 
securely coupled to corresponding dirty gas ports 44. When it is necessary 
to gain access to a particular filter element, a corresponding dirty gas 
port coupler 48 can be disconnected so that the filter element 70 can be 
remove from within the plenum chamber 26. 
The operation of the filter apparatus will now be discussed. Dirty gas 
enter into the pressure vessel 20 through the inlet nozzle 30. The dirty 
gas travel upwards through the multiple dirty gas inlet ports 44, support 
plate slot 56a and into the open end 74 of each filter element. The 
particulate laden gas flows through the bore 82 and the inner surface 80 
to be filtered while the clean gas passes through the outer surface 78 of 
the filter element into the clean gas chamber 41. Particulate matter is 
collected on the inner surface of the filter element 70. The clean gas 
within the clean gas chamber 41 then flows through the plenum flow pipe 54 
through the domed-shaped head 22 exit nozzle 28 to a desired location. 
The gas pressure drop across the filter system will increase as particulate 
matter accumulates within the inner surface 80 of the filter element 70. A 
pulse of clean gas from the back pulse system is injected to discharge any 
accumulated particulate matter from within the filter element 70. The 
discharged particulate matter will be captured at the pressure vessel 
bottom and discharged out through the nozzle 42. 
In accordance with the present invention, the plenum chamber arrangement 
prevents the potential for ash formation between filter elements. A 
further advantage of this arrangement is an that the filter elements may 
be packed more compactedly than in conventional filters without worrying 
about ash building up along the filter elements, thereby increasing the 
filtering surface area through which the hot gas flows and is filtered. 
The filter arrangement also provides easy maintainability, handling, and 
replacement of individual filter elements. A further advantage is that 
should a filter element break or fracture, it is likely to remain in place 
in the close packed bundle and partially seal small leaks by natural dust 
accumulation. 
It is to be understood that even though numerous characteristics and 
advantages of the present invention have been set forth in the foregoing 
description, together with details of the structure and function of the 
invention, the disclosure is illustrative only, and changes may be made in 
detail, especially in matters of shape, size and arrangement of parts 
within the principles of the invention to the full extent indicated by the 
broad general meaning of the terms in which the appended claims are 
expressed.