Thermally conductive partition

A partition of high thermal conductivity is provided to separate a furnace heating zone from a furnace reaction zone, the reaction zone being at least partially heated by radiant heat from the heating zone. In a preferred embodiment, the partition means comprises a plurality of individual panels which are arranged in horizontally extending rows across the furnace. A ceramic seal plate is secured over the longitudinal interface between the adjacent panels in the same horizontal row. The seal plates in one horizontal row which extend across the width of the furnace are slightly offset from the seal plates in adjacent rows to compensate for thermal expansion forces which may tend to move the panels and sealed expansion spaces are provided between adjacent panels in the width-wise and longitudinal direction.

BACKGROUND OF THE INVENTION 
This invention pertains to a partition for separating zones in furnaces of 
the type wherein one zone is at least partially heated by radiant heat 
emanating from another zone. In some furnaces it is desirable to provide a 
substantially gas impervious separation between zones so that the sweep 
gas, for example, may be kept separate from combustion gases from burners 
located in another zone. 
In fossil fuel burning furnaces, separation between heating and reaction 
zones is also desirable to eliminate product contamination by direct 
contact with combustion products. 
This invention is also applicable to electrically heated furnaces. For 
example, the provision of a means for providing substantially gas 
impervious separation may serve to prevent possible detrimental reaction 
between sweep gases or outgases with electric heating elements. 
Further, in many electric and fuel fired heating zones, it is necessary to 
provide a partition means of high thermal conductivity so that the 
requisite reaction temperatures can be obtained in the reaction zone. 
Additionally, it is highly desirable to provide a partitioning structure of 
high heat strength wherein the bending load exerted thereon is 
substantially equally distributed throughout the structure so that the 
high temperature existing in the heating zone will not cause cracking or 
degradation of the partition.

DETAILED DESCRIPTION OF THE INVENTION 
Specific terms will be used hereinafter in the detailed description for the 
purposes of describing the invention. However, the use of such specific 
terms should in no way limit the scope of the invention, which scope is 
defined in the appended claims. 
With reference to FIG. 1 of the drawings, there is shown in longitudinal 
view, a furnace in accordance with the invention. The furnace comprises 
feed port 2 into which the material to be heat treated is admitted to the 
furnace. The furnace is partitioned into heating chamber 26 and reaction 
chamber 28 by means of muffle 30. Transversely arranged beams 32 and 
longitudinally extending beams 31 secure the muffle 30 in the furnace. 
Beams 31 are keyed into furnace sidewalls 40, 42 and the transverse beams 
32 are mounted within notches in the beams 31 and span the furnace in the 
width-wise direction. The transverse beams 32 are anchored in grooves 104 
which are spaced apart from one another on the longitudinal sidewalls of 
the furnace. Ceramic seals 82, 84 are provided along the wall zone. 
As shown, heating zone 26 is heated by means of a plurality of fuel burners 
20, which burners may be adapted for either oil or gaseous fuel 
consumption. Flue 24 extending through roof 34 of the furnace provides 
escape for the waste gases emanating from the burners 20. Reaction zone 28 
is at least partially heated by radiation from the heating zone 26. In 
this respect, it is important that the muffle 30, which separates the 
heating and reaction zones, be composed of highly thermally conductive 
material and that it be very strong at high temperature. 
Shaft 8 of the screw conveyor having screw flights 6 is coupled to inner 
support shaft 12 by flange 10. Drive pulley 4 and its associated drive 
belt are provided to impart rotation to the shaft 12 and screw flight 
shaft 8. Although FIG. 1 shows only one such shaft 6, 8, a plurality may 
be used and a gear 5 is provided to drive an adjacent screw of the group. 
The screw conveyor and its relationship with the furnace are the subject 
of my co-pending application Ser. No. 951,384, filed Oct. 16, 1978. 
Adjacent to the respective ends of the inner shaft 12 are provided outboard 
bearings 14 which are urged, each by means of a spring 16, in a downward 
direction. These outboard bearings 16 cooperate with novel bearing plugs 
(shown and explained in the aforementioned co-pending application) and 
with the fixed inboard bearings 86, 88 to distribute the bending load on 
both the inner and outer shaft in such a manner that relatively low stress 
is exerted on the regions within the reaction chamber 28. This is highly 
advantageous in light of the fact that the furnace is to be ideally 
operated at temperatures in excess of 2,000.degree. F. wherein excessive 
stress on the shafts could lead to serious degradation thereof. 
Hearth 18 is mounted on screw jacks 36 or like means which are reciprocated 
by motor 38 and associated linkage members. In this manner, the hearth 18 
may be lowered for cleaning purposes and then raised for operation. 
Exit port 46 is provided along the hearth 18 for discharge of the heat 
treated material after it has been transported through the furnace by the 
screw flights 6. Exit gas port 44 is provided for discharge of the 
reaction gases. Port 90 is provided in one of the longitudinal sidewalls 
of the furnace and may be used for introduction of sweep air. Of course, 
the positioning of the ports 44, 90 may be reversed in practice. 
Usually, multiple pairs of screw assemblies (see FIG. 4) are provided in 
the furnace chamber 28. Preferably, the flight pitch of one screw in a 
pair is opposite from that of the other screw in the pair and the screw 
flights of each screw intermesh with those of the other screw in the pair 
so that the desired material to be heat treated is advanced through the 
furnace when the screws in the pair are rotated in opposite directions. 
At the left-hand side of FIG. 1, there is shown a cooling fluid entry means 
by which cooling fluid is pumped through the inner shaft 12. Preferably, 
cool air is pumped through the inner shaft 12. 
Turning now to FIG. 2, the partitioning muffle 30 of this invention 
comprises a plurality of individual panel members 30a. These panels 30a 
are composed of a high thermally conductive material, preferably silicon 
carbide, which has a thermal conductivity of, for example, at least 
approximately 150 BTU/in/hr ft.sup.2 when the furnace is operated at 
2,000.degree. F. The panel members 30a are disposed in adjacent width-wise 
extending rows 48 and are supported by horizontal beams 32 which are also 
preferably composed of the same silicon carbide material having high 
strength at high temperature. Expansion spaces 50a, b, c, d and e are 
provided between the adjacent width-wise rows 48 so as to allow for a 
certain degree of expansion of the members 30a caused by the high 
temperature condition in the combustion zone 26. 
Seal plates 52 cover the longitudinally extending interfaces between 
adjacent panel members 30a in the same row 48. Preferably, adjacent panels 
30a are spaced from each other by a fraction of an inch at this 
longitudinal interface. The seal plates in one width-wise row 48 are 
slightly offset from the cover plates in an adjacent width-wise row 48 so 
as to inhibit longitudinal shifting of the panels 30a which otherwise may 
occur due to the high temperatures existing in the heating zone 26. 
Ceramic bolts 54 secure the panels 30a to the seal plates 52. As shown, 
certain of the end-wise panels in the horizontal rows 48 are secured to a 
ledge or the like which is disposed along the width-wise walls of the 
furnace. 
Turning now to FIG. 3, transverse beams 32 are supported by longitudinal 
beams 31 which are keyed into the furnace walls 40, 42 as shown at 58, 60. 
A fibrous ceramic blanket 56 (see also FIG. 5) extends along the lengths 
of the transverse beams 32 to act as a seal underneath the expansion 
spaces 50a, b, c, d and e (see also FIG. 5). Ceramic seals 82, 84 are 
formed adjacent end walls 40, 42. Preferably, ceramic fiber packing 105 
(FIG. 5) is inserted in the grooves of the longitudinal beams 31 into 
which the transverse beams 32 are received (see FIG. 5). 
With reference now to FIG. 4, three pairs of intermeshing screws 8 are 
shown, for example. They extend longitudinally through the furnace 
reaction zone 28. Longitudinal ceramic gaskets 92, 94 are provided along 
longitudinally extending sidewalls 96, 98 to provide a seal between the 
heating zone 26 and the reaction zone 28. Underlying the seal plates 52 
are longitudinally extending ceramic fiber blankets 100 which seal the 
longitudinally extending interfaces between adjacent panels 30. 
In FIG. 5, which is an enlarged sectional view, fiber blanket 56, which 
extends along beam 32, is shown as sealing the partitioning structure 
along expansion space 50c, which is formed along two of the horizontally 
extending rows of panels 30a. Seal plates 52 are secured to panels 30a by 
the provision of ceramic bolts 54, ceramic sleeve 62a and ceramic nut 62. 
Ceramic blanket 100 is sandwiched between the seal plate 52 and panel 30a 
to insure sealing along the longitudinally extending interface between 
adjacent panels disposed along the same horizontal row. During 
installation, the ceramic bolts 54 are hand tightened only so that the 
bolts 54 will be able to expand and contract somewhat in the high 
temperature condition existing within the furnace without cracking either 
the seal plates 52 or panels 30a. 
With reference to FIG. 6, the seal plates 52 in adjacent rows are slightly 
offset from their neighboring seal plates 52. This decreases the tendency 
of certain panels to shift or rack into the next adjacent row. The 
longitudinal clearance 102 between adjacent panels 30a in the same row 48 
is preferably only a fraction of an inch. 
It will be appreciated that in order to radiate heat from the heating zone 
to the reaction zone, it is necessary that the panels 30a be constructed 
of a highly thermally conductive material. In this respect, it is 
desirable that the conductivity of the plates be on the order of about 150 
BTU/in/hr ft.sup.2 or more when the furnace is operated at 2,000.degree. 
F. At the same time, the thermal expansion and contraction of the 
structure should be relatively low so as not to build excessive stress on 
the structure which would otherwise tend to crack or degrade the 
partition. Thermal expansion on the order of about 2.7.times.10.sup.-6 
IN/IN .degree.F. at 2,000.degree. F. is desirable for all of the members 
30(a), 31 and 32. 
Further, by the provision of a partition which comprises a plurality of 
individual panel members, the stress factors are generally equalized from 
one portion of the panel to another panel portion as opposed to a 
partition comprising a single sheet material wherein different portions of 
the same sheet may bear different thermal stress loads and wherein "hot" 
and "cold" spots may exist at various locations along the sheet and cause 
cracking thereof. 
For these reasons, it is highly desirable that the panels, horizontal 
beams, and seal plates alike be composed of a silicon carbide material 
which is able to attain the desired high thermal conductivity and low 
thermal expansion properties, combined with high strength at high 
temperatures. 
Those skilled in the art will be able to fashion equivalent members and 
means as substitutions for the various structural members herein 
disclosed. For instance, those skilled in the art will be able to devise 
equivalent sealing structures to provide sealing between the heating and 
reaction zones. Further, other materials may be utilized in accordance 
with the invention as long as these materials contribute the required 
thermal conductivity and thermal expansion properties to the partition 
while at the same time providing particularly high strength at 
temperatures of about 2,000.degree. F. and above. All such equivalent 
means and members are intended to be covered by the appended claims.