Steam distribution apparatus

A steam distribution apparatus includes a first header having an inlet for steam and a plurality of discrete outlets for steam arranged along the header. The outlets increase in size with distance from the inlet. A first chamber surrounds the first header to receive steam from the outlets in the first header. There are first, relatively large outlets in the first chamber. The relative positions of the first header and the first chamber ensure that steam leaving the plurality of outlets in the first header impinges on the interior of the chamber and must travel around the chamber to reach the first outlets in the first chamber. A second chamber communicates with the first outlets from the first chamber. There are outlets in the second chamber. A shrouding is positionable above a paper web and communicates with the elongate outlets in said second chamber. The apparatus permits uniform steam flow along the entire length of the distributor.

FIELD OF THE INVENTION 
This invention relates to a steam distribution apparatus particularly 
useful in paper making. 
DESCRIPTION OF THE PRIOR ART 
During the paper making process it is frequently necessary to provide steam 
along a relatively long distance, for example the application of steam in 
the press section of pulp and paper making machines. It is clearly 
desirable to provide a uniform source of steam across the relatively great 
width of the web but, previously, the provision of such a uniform source 
has been difficult. 
SUMMARY OF THE INVENTION 
The present invention seeks to provide a steam distribution apparatus in 
which uniform steam flow along the entire length of the apparatus and thus 
across the whole width of a paper web can be achieved. 
Accordingly, in a preferred aspect, the present invention is a steam 
distribution apparatus comprising a header having means defining an inlet 
for steam and means defining a first plurality of discrete outlets for 
steam arranged along the header, the outlets increasing in size with 
distance from the inlet; means defining a first chamber surrounding the 
header to receive steam from the outlets in said header; means defining 
first, relatively large outlets in said first chamber; the relative 
positions of the header and the first chamber ensuring that, in use, steam 
leaving said plurality of outlets in the header impinges on the interior 
of the chamber and must travel around the chamber to reach the first 
outlets in the first chamber, the exterior of the header being relatively 
close to that part of the first chamber containing the first outlets so as 
to form a restricted zone immediately before said outlets to assist in 
obtaining uniform steam pressure along the length of the steam 
distribution apparatus; means for defining a second chamber communicating 
with said first outlets from the first chamber; means defining outlets in 
said second chamber; a shrouding positionable above a paper web and 
communicating with said outlets in said second chamber whereby, in use, 
uniform steam flow along the entire length of the steam distribution 
apparatus can be achieved. 
Preferably there are second, relatively small outlets in said first chamber 
communicating with the shrouding. These permit steam to be directed 
downwardly at the leading edge of the distribution apparatus to contact a 
web moving beneath the apparatus and to prevent air being drawn into the 
shrouding by the moving web. The leading edge of the apparatus is the edge 
under which the web passes first as it enters the shrouding. 
The exterior of the first header is relatively close to that part of the 
first chamber containing the first outlets. A baffle can, in one 
embodiment, extend from the exterior of said header to adjacent the outlet 
to assist in forming the restricted zone immediately before the outlets. 
In a further aspect the second chamber is divided into a plurality of 
compartments. There are a plurality of pipes, generally one to each 
compartment. Each pipe has an inlet communicating with the first chamber 
and an outlet communicating with one of the above compartments. Each pipe 
extends outwardly from the first chamber and then returns through the 
first chamber to an outlet. There is a valve in each pipe to regulate 
steam flow through the pipe. Such an arrangement permits control of steam 
flow across a web, a procedure known in the art as profiling. 
It is desirable that there be an insulating jacket extending around the 
apparatus. 
The outlets in the second chamber may be in the form of one or more 
continuous slots or they may be slots arranged in two discrete rows with a 
plurality of discrete slots in each row. The outlets may also be holes 
arranged in rows. The outlets in each row should be staggered relative to 
the outlets in the other row.

DESCRIPTION OF PREFERRED EMBODIMENTS 
The drawings illustrate a steam distribution apparatus comprising a first 
header 2 having an inlet 4 for steam and a plurality of discrete outlets 6 
for steam. These outlets 6 generally increase in size with distance from 
the inlet 4. It is generally convenient that they proceed in a plurality 
of steps. That is the outlets may be arranged in groups, the group nearest 
the inlet 4 having one diameter, a second group having a larger diameter 
and so on through the outlets 6 most remote from the steam inlet 4, which 
have the greatest diameter. 
In the embodiment illustrated in FIGS. 1 to 3 there is a second plurality 
of discrete steam outlets 8 of uniform size along the first header 2, 
adjacent the first plurality of outlets 6. However, this second set of 
uniform, discrete outlets 8 is not essential to the invention. 
There is a first chamber 10 surrounding the first header 2 to receive steam 
from the outlets 6 in said first header 2. First, relatively large outlets 
12 (see FIG. 3) and second, relatively small outlets 14 are positioned in 
said first chamber 10. The outlets 14 are positioned in a small 
compartment 15 added to the exterior of the first chamber 10. Openings 17 
permit access between first chamber 10 and compartment 15. The compartment 
15 tends to create a uniform steam flow from outlets 14. 
Outlets 14 operate to provide a steam curtain to prevent air being drawn in 
by the belt or web moving below the distribution apparatus in the 
direction of the arrow A. The arrangement is described and claimed in my 
copending application that is a continuation of my application Ser. No. 
924,399, filed July 14, 1978, now abandoned; the disclosure of the 
continuation application is incorporated by reference. 
As most clearly shown in FIGS. 3 and 4, the relative positions of the first 
header 2 and the first chamber 10 are such as to ensure that in use steam 
leaving said plurality of outlets 6 in the first header 2 impinges on the 
interior of the first chamber 10 and must travel around the chamber 10 to 
reach the first outlets 12 in the first chamber 10. The direction of flow 
of steam is shown in FIGS. 3 and 4 by arrows. In both cases the flow 
starts at the first header 2. 
There is a second chamber 16 communicating with the first chamber 10 near 
the first outlets 12 in the first chamber 10. Thus steam leaves the first 
header 2 passes around the interior of the first chamber 10, out through 
the outlets 12 into the second chamber 16. There are outlets 18 in the 
second chamber 16. The outlets 18 may comprise a single slot extending the 
length of the second chamber 16 (FIG. 5C) or may be of the pattern shown 
in FIG. 5A, that is slots arranged in rows, the elongate outlets in each 
row being staggered relative to the elongate outlets in the other row, or 
may be circular holes arranged on isometric centres, for example, as shown 
in FIG. 5B. 
There is a shrouding 20 into which steam from the second chamber 16 passes 
from the outlets 18. Shrouding 20 forms a heating zone in which the steam 
is directed onto a paper web when the steam distribution apparatus is in 
use. Steam also passes directly from the first chamber 10 through the 
second, relatively small outlets 17 to the chamber 15 and through outlets 
14 to the shrouding 20. Thus there is a uniform steam distribution at the 
leading edge 22 and the trailing edge 24 of the steam distribution 
apparatus-see FIGS. 3 and 4. 
FIG. 3 illustrates an embodiment of the invention in which the first header 
2 is positioned relatively close to that part of the first chamber 10 
containing the first outlets 12. There is a baffle 26 extending from the 
exterior of the header 2 to adjacent and just below the outlets 12. The 
effect of both the positioning of the first header 2 relatively close to 
the wall of the first chamber 10 and the positioning of the baffle 26 
creates a restricted zone generally indicated at 28 immediately before the 
outlets 12 and this smooths out steam pressure differences in the 
cross-machine direction to produce uniform steam flow from the first 
chamber 10 to the second chamber 16. 
In the embodiment illustrated in FIG. 4 the second chamber 16 is divided 
into compartments by walls 30, one of which is shown in FIG. 4. There are 
a plurality of pipes 32 each having an inlet 34 communicating with said 
first chamber 10 and an outlet 36 communicating with one of said 
compartments of said second chamber 16. Each pipe 32 extends outwardly 
from the first chamber 10 and then returns to a compartment in the second 
chamber 16 through an outlet 36. There is a valve 38 in each pipe 32 
adjustable to regulate steam flow through the pipe. 
In both FIGS. 3 and 4 the apparatus is provided with an insulating jacket 
40 that extends around the apparatus to minimize heat losses. 
The apparatus of the present invention has end plates 42 having holes 
46--see particularly FIG. 3--to provide a means of lifting the unit. It is 
mounted by brackets (not shown). 
The steam distribution apparatus of the present invention provides a 
uniform source of steam across a relatively long length for, for example, 
application in the press sections of pulp and paper making machines. The 
invention ensures uniform pressure across the entire length of the steam 
distribution apparatus so that there is a uniform source of steam 
discharging from the unit across its entire length for all variations in 
steam flow rates. For example the unit is effective for a steam turn down 
ratio of at least 5 to 1. 
The unit of FIG. 4, which includes a plurality of pipes 32 permits 
incremental moisture profile control. This profiling is done by tapping 
steam from the top of the first chamber 10 and by controlling the flow of 
the tapped steam by the valve 38. The separation of the second chamber 16 
into separate compartments means that incremental flow can be established. 
Furthermore, by passing the profiling pipes 32 through the first chamber 
10 any condensate contained in the steam will tend to evaporate. 
A further advantage of the steam distribution apparatus is compact 
installation. 
Dimensions of the apparatus may be varied within limits easily 
ascertainable by calculation.