Temperature measuring apparatus

This invention relates to an apparatus and process for measuring the temperature of a fluid environment within a vessel. The apparatus features a chamber which opens into the vessel and thus contains a portion of the fluid environment. Structure is provided for preventing substantial convective movement between the portion of the fluid environment within the chamber and the remainder of the fluid environment. A temperature sensing device is also provided which is movable from a position within the chamber to a position into the remainder of the fluid environment for obtaining a temperature measurement. The chamber is maintained at a temperature cooler than that of the fluid environment. This invention also relates to a process for the periodic measuring of the temperature of a fluid environment in a vessel. The process features locating at least a portion of a temperature sensing device in a chamber which opens into the fluid environment and which chamber is kept at a lower temperature than the fluid environment by maintaining that portion of the fluid environment within the chamber and the remainder of the fluid environment in the vessel whereby they are substantially free of convective movement with respect to one another.

BACKGROUND OF THE INVENTION 
This invention relates to an apparatus and process for measuring the 
temperature of a fluid environment contained in a vessel. 
Radiation pyrometer-target tube combinations and tube protected 
thermocouples are oftentimes utilized as temperature sensing devices to 
obtain temperature measurement in reaction vessels. The thermocouple, its 
protecting tube and the target tube have to be comprised of materials 
which give them an acceptable life under the reaction conditions to which 
they are exposed. If the reaction temperatures are very high, such as the 
3000.degree. F. (1649.degree. C.) temperatures found in the partial 
oxidation of carbonaceous slurries, the aforementioned parts of the 
temperature sensing devices, despite their materials of construction, can 
expect to have a limited life, say 200 to 300 hours under reaction 
conditions. It is, however, possible to extend the service life of such 
parts, i.e., the number of process hours over which such parts are still 
usable, by taking the temperature measurements periodically and completely 
removing the parts from the vessel and its fluid environment when 
temperature measurements are not being taken. Such removal is time 
consuming and since temperature measurements may be required often, e.g., 
every half hour, it can be appreciated that removal of the parts sought to 
be protected is manpower intensive and thus, not very cost effective. 
It is therefore an object of this invention to provide an apparatus and a 
process for the taking of periodic temperature measurements of a vessel's 
fluid environment, which apparatus and process have decreased manpowe 
requirements for operation. It is another object of this invention to 
provide an apparatus and process which provides for the replacement of a 
temperature measuring device, which device is used for monitoring the 
temperature of a process occurring in a vessel, without necessitating 
process shutdown. 
The Invention 
The apparatus of this invention, to achieve the foregoing objects, features 
a chamber which opens into the interior of the vessel and which thus 
contains a portion of the vessel's fluid environment. (For the sake of 
convenience, the portion of the fluid environment within the chamber will 
be referred to as the chamber fluid environment while the remainder of the 
fluid environment in the vessel will be referred to as the vessel fluid 
environment.) The chamber can be of any suitable configuration and is 
sized to accommodate a movable temperature sensing device, hereinafter 
described, so that the chamber does not contact the temperature sensing 
device as it moves with respect to the chamber. Initially, the chamber 
fluid environment will need to be cooled to a temperature which does not 
adversely affect the service life of the temperature sensing device. This 
cooling is achieved by the use of a cooling mechanism associated with the 
chamber. Due to the fact that the chamber fluid environment will be at a 
temperature cooler than that of the vessel fluid environment, orientation 
of the chamber must be made so that there is no natural convection between 
the two environments as a result of a difference in their densities. Thus, 
the chamber should be oriented so that the chamber fluid environment does 
not pour out of the chamber by force of gravity. It has been found 
convenient and preferential that the chamber have a cylindrical shape for 
at least that portion most proximate the vessel fluid environment. 
The chamber has associated therewith structure for preventing substantial 
convective movement between the cooled chamber fluid environment and the 
vessel fluid environment. By minimizing and in some cases, totally 
preventing such convective movement, there will be little heat transfer 
between these two fluid environments. However, there can be some heat 
transfer from the vessel interior to the chamber fluid environment due to 
radiation and/or conduction. Should this heat transfer be of concern, the 
cooling mechanism can be continuously used to maintain the temperature of 
the chamber fluid environment at the desired level. A preferred cooling 
mechanism is a jacket about at least a portion of the chamber which jacket 
carriers a circulating heat transfer medium such as brine, water or steam. 
The temperature sensing device of the apparatus of this invention is 
movable between a first position and a second position. The first position 
locates at least a portion of the temperature sensing device within the 
chamber and keeps the entirety of the temperature sensing device out of 
contact with the vessel fluid environment. The first position is used 
between temperature measurements and provides, as before discussed, a cool 
location for the temperature sensing device. The second position locates 
at least a portion of the temperature sensing device exteriorly of the 
chamber and in contact with th vessel fluid environment and is used to 
obtain the temperature measurement of such environment. 
The temperature sensing device is preferably a protector tube-thermocouple 
combination or a radiation pyrometer-target tube combination. The tube 
protected thermocouple can be of conventional design, which design 
includes an elongated tube having at and within its probe end one of the 
thermocouple junctions. This junction and its associated electrical leads 
are conventionally held within the tube interior by powdered ceramic 
material. Th other thermocouple junction is located at the other end of 
the elongated tube and is connected to the first described thermocouple 
junction by electrical leads. The location is usually exterior of the 
tube. 
The radiation pyrometer-target tube combination includes a hollow elongated 
target tube and a radiation pyrometer which views, through the interior of 
the tube, the probe end of the tube. The radiation pyrometer does not 
contact either fluid environment at any time. 
In both of the above cases, the probe ends of the elongated tubes will be 
that portion of the temperature sensing devices which will make contact 
with the vessel fluid environment when the temperature sensing devices are 
in the second position. 
Movement of the temperature sensing device between the first and second 
positions is preferably powered. Double-acting pneumatic cylinders have 
been found especially suitable because the piston rod of the cylinder can 
be easily attached to the distal end of the elongated tube portion of the 
preferred temperature sensing devices, just described, whereby the 
elongated tube follows the axial to and fro movement of the piston rod. 
Even more preferred is a double-acting pneumatic cylinder which has a 
hollow piston rod, as the elongated tube can be partially located within 
the interior of the hollow rod. Such attachment between the hollow piston 
rod and the elongated tube will be at their respective distal ends. By 
having the tube carried in such a manner, easy replacement of the 
elongated tube can be made in the manner hereinafter described. 
This invention also relates to a process for the periodic measuring of the 
temperature of a fluid environment in a vessel. The process includes 
locating at least a portion of a temperature sensing device in a chamber 
which opens into the fluid environment. The chamber, by being open to the 
fluid environment, will contain a portion thereof. That portion of the 
fluid environment within the chamber and the remainder of the fluid 
environment are maintained substantially free of convective movement with 
respect to one another. This freedom from substantial convective movement 
is an especially important feature of the process of this invention a heat 
transfer between the portion of and the remainder of the fluid environment 
is minimized, if not prevented. The fluid environment within the chamber 
is initially brought to and maintained at a desired temperature which is 
cooler than the temperature of the remainder of the fluid environment. For 
example, the apparatus of this invention can be used to maintain a chamber 
temperature within the range of from about 70.degree. F. (21.degree. C.) 
to about 200.degree. F. (93.degree. C.) when used in vessels containing 
fluid environments having temperatures up to 3000.degree. F. (1649.degree. 
C.). Should radiation and conductive heat transfer to the chamber from the 
vessel interior raise the chamber temperature to unacceptable levels, then 
the chamber can be cooled by the use of a water jacket, etc., about the 
chamber. The temperature measurements are taken by moving a portion of the 
temperature sensing device from the cool chamber to a point within the 
remainder of the fluid environment. After the temperature measurement is 
taken, the portion of the temperature sensing device moved from the cool 
chamber is returned thereto until the next temperature measurement is 
needed.

Referring now to FIGS. 1-4, there can be seen an apparatus of this 
invention, generally designated by the numeral 10, mounted to a vessel 
wall, generally designated by the numeral 12. Vessel wall 12 comprises an 
outer metallic shell 14 and an inner refractory lining 16. This type of 
vessel wall is used for vessels in which high temperature/high pressure 
reactions are to occur, e.g., the partial oxidation of carbonaceous 
slurries to produce synthesis gas and the like. It is to be understood 
that apparatus 10 is useful with other types of vessels. Mounting of 
apparatus 10 to vessel wall 12 is achieved in a fluid-tight manner by way 
of flange fitting 18. 
Apparatus 10 has, at its proximate end, hollow cylinder 20. As can be seen 
in FIGS. 1 and 2, cylinder 20 extends through vessel wall 12 into the 
interior of the vessel. The extension of cylinder 20 into the interior of 
the vessel is not a requirement of this invention but is preferred since 
such an extension reduces the amount of radiant heat reaching into the 
space defined by cylinder 20 and since such extension provides protection 
for temperature sensing device 47 against damaging contact with solid 
particles or spray which may be moving about the interior of the vessel. 
To provide cooling of the interior space provided by cylinder 20, there is 
provided water jacket 22 which fits about the outer surface of cylinder 
20. Water jacket 22 is provided with an inlet 26 and an outlet 24 so that 
a cooling medium ca be circulated throughout the jacket. Water jacket 22 
is provided for initially cooling the fluid environment within cylinder 20 
and for offsetting the heat transfer to the interior of cylinder 20 which 
is a result of radiation or conduction from the interior of the vessel. 
Cylinder 20 and water jacket 22, at their distal ends, are flange-mounted 
to gate valve 28. The flanged fitting is fluid-tight. Gate valve 28 is of 
conventional construction. 
In flanged attachment to the distal side of gate valve 28 is a 
double-acting pneumatic cylinder, generally designated by the numeral 32. 
This latter flange fit is a fluid-tight fit. At the proximate end of 
double-acting pneumatic cylinder 32 is relief valve 30 which is seated 
within a portion of the cylinder flange 31. Double-acting pneumatic 
cylinder 32 has a proximate end plate 38 and a distal end plate 36 which, 
along with cylinder 34, defines a hollow cylindrical space into which is 
slidably carried piston 44. Piston 44 is attached to a hollow piston rod 
46 which has sufficient length so that irrespective of the position of 
cylinder 44, piston rod 46 is in sealing contact with annular proximate 
rod seal 40 and annular distal rod seal 42. The seal provided by these two 
seals is a fluid-tight seal. The space between proximate end plate 38 and 
distal end plate 36 is in gaseous communication with ports 52 and 50. 
These ports are in turn connected to a conventional, commercially 
available four-way valve 54 (valve 54 is shown in schematic form). Tube 56 
provides a conduit to valve 54 from a source for a pressurized gas such as 
nitrogen. Tube 58 provides a vent for valve 54 and hence pneumatic 
cylinder 32. 
Mounted within hollow piston rod 46 is tube 47. This mounting is 
accomplished at the distal ends of both tube 47 and hollow piston rod 46 
by way of a removable fluid-tight fitting 60. Such fittings are 
commercially available, for example, Conax Corporation of Buffalo, New 
York, produces several fitting assemblies which may be utilized for the 
purposes of this invention. 
Tube 47 provides protection for a thermocouple, not shown, which is located 
at and within the probe end 49 of tube 47. Maintaining the thermocouple 
and electrical conducting wires 70 and 72 in their respective positions 
within tube 47 is achieved by the utilization of ceramic materials 73 
which are shown in FIG. 4. The utilization of protective tubes, such as 
tube 47, for carrying within their interior a thermocouple is conventional 
and well known in the art. The materials of construction for tube 47 and 
the selection of the thermocouple materials is dependent upon the 
conditions which are encountered within the vessel. It is a feature of 
this invention that the entirety of tube 47 need not be made of expensive 
alloys as only probe end 49 of tube 47 will be subjected to the full 
vessel conditions. Therefore, tube 47, up to union 48, can be comprised of 
relatively inexpensive materials, such as stainless steel. Union 48 
couples probe end 49 to the remainder of tube 47. Probe end 49, since it 
will be exposed to the vessel conditions, will have to be of a suitable 
alloy to withstand such conditions. Probe end 49 can be a metal tube or a 
ceramic tube as conditions require. Exemplary of tube materials which can 
withstand temperatures of around 2000.degree. F. (1093.degree. C.) are 
nichrome and nickel. Ceramic tubes can withstand temperatures of about 
3000.degree. F. (1649.degree. C.) and can be made of silica or silicon 
carbide. The materials of construction for the thermocouple are dependent 
upon the temperatures which are to be encountered. For example: 90% 
Platinum-10% Rhenium vs. Platinum; and Chromel-P vs. Alumel are useful at 
temperatures of 3100.degree. F. (1704.degree. C.) and 2200.degree. F. 
(1204.degree. C.), respectively. When apparatus 10 is utilized for 
measuring temperature in a partial oxidation of carbonaceous slurry 
process, it has been found that probe end 49 is preferably made of 53% 
molybdenum-47% rhenium alloy and that the thermocouple housed therewithin 
is a 95% Tungsten-5% Rhenium vs 74% Tungsten-26% Rhenium thermocouple. 
The attachment of apparatus 10 to vessel wall 12 results in a portio of the 
vessel fluid environment to enter apparatus 10. In operation, apparatus 10 
will normally have tube 47 in the first position as shown in FIG. 1. The 
fluid environment within apparatus 10 is contained within a chamber 
defined by cylinder 20, gate valve 28 and the annular space defined by the 
inside wall of hollow piston rod 46 and the outside wall of tube 47. (This 
so contained fluid environment is referred to as the chamber fluid 
environment to differentiate it from the vessel fluid environment.) 
Convective movement between the chamber fluid environment and the vessel 
fluid environment is thwarted as the chamber is sealed (note the seals 
provided by the flange fittings, proximate seal 40 and by fitting 60) and 
thus no convective heat transfer between the chamber fluid environment and 
the vessel fluid environment will occur. In the first position, therefore, 
tube 47, its probe end 49 and the contained thermocouple are not subject 
to the temperature conditions inside of the vessel. When a temperature 
measurement is desired, valve 54 is actuated to cause pressurized gas to 
enter tube 50 and to cause tube 52 to be communicated with vent tube 58. 
Piston 44 moves in response to the resulting change in pressure in 
cylinder 34 thereby locating probe end 49 outside of the just defined 
chamber and into the interior of the vessel as is shown in FIG. 2. No 
substantial convective movement is experienced by the chamber fluid 
environment as the chamber is still sealed. After the thermocouple has 
provided the necessary output to obtain the desired temperature 
measurement, valve 54 is actuated to provide gas in tube 52 and to connect 
tube 50 to vent tube 58. Piston 44 returns to the position shown in FIG. 1 
and probe end 49 is returned to the chamber and within the cool zone 
provided by cylinder 20. 
Maintenance of the chamber seals can be easily monitored by the 
thermocouple as it resides in the cooled chamber. A chamber seal leak will 
allow convective movement of a portion of the fluid vessel environment 
into the chamber and a consequent rise in chamber temperature will occur. 
The thermocouple will sense this temperature rise and provide a 
temperature measurement for alerting operating personnel to re-establish 
chamber seal integrity. 
Even though the apparatus of this invention prolongs the service life of 
the temperature sensing device, the periodic temperature measurements will 
eventually consume the expected life of the temperature sensing device. 
Once the temperature sensing device is no longer operable, it has to be 
replaced. For the embodiment shown in the Figures, replacement of the 
temperature sensing device can be performed easily and while the reaction 
in the vessel continues. 
Referring to FIG. 3, first, valve 54 is actuated to feed pressurized gas to 
tube 52. The actuation of valve 54 will place tube 50 in communication 
with vent tube 58. Piston 44 is allowed to move back into the full 
retracted position. Fitting 60 is loosened to allow, with maintenance of 
the fluid seal provided by fitting 60 still intact, axial rearward 
movement of tube 47. This rearward movement will locate probe end 49 
rearwardly and clear of gate 27. Gate 27 is then lowered to the closed 
position. Pressure within the vessel is now sealed from that portion of 
apparatus 10 which is distal of gate 27. Vent 30 is opened to relieve any 
pressure found distally of gate 27. Fitting 60 is then completely loosened 
and the mount between tube 47 and hollow piston rod 46 is broken so that 
tube 47 can be withdrawn and disposed of. A new tube is reinserted in its 
place and fitting 60 is tightened to provide a fluid seal. Gate 27 is then 
raised, and tube 47 is then urged forwardly to the desired position within 
the cylinder 20 and fitting 60 is tightened further to fixedly mount tube 
46 to piston rod 45. The apparatus is now in the position of FIG. 2 and 
ready for continued operation. It should be noted that fitting 60 is 
designed for static and dynamic sealing, and loosening of its gland nut 
for positioning of tube 47 is permitted.