EP0227349A1

EP0227349A1 - Heating apparatus

Info

Publication number: EP0227349A1
Application number: EP86309424A
Authority: EP
Inventors: Daniel D. Bradford
Original assignee: Daniel's Engineering & Manufacturing Co
Current assignee: Daniel's Engineering & Manufacturing Co
Priority date: 1985-12-04
Filing date: 1986-12-03
Publication date: 1987-07-01
Also published as: KR870006624A; JPS62169964A

Abstract

A processing unit for heating corrosive liquids, primarily ultra-pure, deionized water and other corrosive reagents common to semiconductor processors. The apparatus uses perfluoroalkoxy (PFA) fluorocarbon resin materials throughout the plumbing system which includes a nested pair of coils (52, 54) which are heated within a heating box (30). The apparatus provides a fluid circuit (76, 32, 78) for heating reagent and sampling it for resistivity changes. An alternative flow path (124, 146, 150) bypasses the heating core (32) and directs ambient temperature fluid to a different outlet (100). An alternative function selection provides for periodic flushing of the entire system.

Description

Field of the Invention

The present invention is directed to a heater for corrosive liquids, e.g., ultra-pure, de-ionized water and other aqueous reagents used in processes for manufacturing semiconductors. Because the fluids are corrosive, a perfluoroalkoxy (PFA) fluorocarbon resin is used for all components in the flow path. The PFA material cannot be bent and, consequently, must be molded or machined and then welded. The heating core of the present invention comprises tubes and other molded members welded together to form substantially rectangular nested coils. Thus, more particularly, the present invention is directed to heating apparatus for aqueous semiconductor reagents wherein the apparatus includes a heating core comprising PFA resin coils.

Background of the Invention

Traces of undesired materials in semiconductor devices are a serious processing deficiency and elimination of contaminants is widely sought. With this purpose in mind, semiconductor manufacturers have focused on cleaning the air in the work space and on isolating production personnel in noncontaminating garments. Semiconductor wafer processors are now also focusing their efforts on the environment to which the wafer is exposed during processing. Attention is therefore drawn to the purity needs for the chemical reagents used in wet processing, and to the containers and piping used in the storage and transport of the reagents.
An important reagent used by semiconductor processors is ultra-pure, de-ionized water. Ultra-pure, de-ionized water and many other semiconductor processing reagents are highly corrosive. Because the reagents are corrosive, and because it is necessary to eliminate leaching and other contaminating influences from the components of the flow, path, only particular materials are appropriate for processing equipment. Since metallic materials deteriorate and are, therefore, inappropriate, it has been very difficult to design a heater for aqueous semiconductor reagents. Layton, in U. S. Patent 4,461,347, disclosed a heat exchanger assembly comprising coaxially-arranged inner and outer pipes, the annular space between the pipes defining a flow passage. The inner pipe is made of a metal with good thermal conductivity and is used to enclose a heat source, such as steam. The inner pipe is sheathed in a heat-shrinkable tube of nonreactive material, such as PTFE or polypropylene. The inner wall of the outer pipe is also formed of a similar nonreactive material. Terminations at the ends of the inner and outer pipes to couple the passageway to additional piping are also made of nonreactive materials. The mechanism of Layton minimizes contamination and provides for heating, but the mechanism is complicated and has limitations in that the coaxial pipes must be either very long, since they are straight, or the flow rate of the reagent must be very slow unless only a small temperature increase is needed.
The present invention, on the other hand, is not limited to a low flow rate or to a low temperature increase, and is rather compact and much less complicated than the heater shown in the art.

Summary of the Invention

The present invention is directed to apparatus for heating a corrosive semiconductor reagent wherein the apparatus comprises a housing, an inlet for receiving the reagent, an outlet for discharging the reagent, and mechanism for directing the reagent between the inlet and the outlet. The apparatus further includes a pump for moving the reagent through the directing mechanism and mechanism for controlling the pump. The directing mechanism is attached to the housing and includes inner and outer multiple looped, substantially rectangular coils wherein the inner and outer coils are in fluid communication with one another. Heating mechanism and mechanism for controlling the heating mechanism heat the coils. In this way, the reagent may remain for a much longer time in the coils and is heated more than would be possible with the straight coaxial tube device, for example, of the prior art.
In another embodiment, the present invention is an apparatus for heating corrosive reagents comprising an inlet for receiving the reagent, a plurality of outlets for discharging the reagent, and mechanism for directing the reagent between the inlet and one of the plurality of outlets. The directing mechanism includes a plurality of nested substantially rectangular coils and mechanism for passing the reagent through said coils and directing the reagent to a first of the outlets. The directing mechanism also includes mechanism for bypassing said passing mechanism and directing the reagent at its ambient temperature to a second of the outlets. The directing mechanism further includes mechanism for flushing portions of each of the passing mechanism and bypassing mechanism and directing the reagent to a third of the outlets. This apparatus includes mechanism for heating the coils and mechanism for controlling the heating means. In addition, the apparatus includes a pump for moving the reagent and mechanism for selecting at least one of the passing mechanism, the bypassing mechanism, and the flushing mechanism for a reagent flow path. In all embodiments, the inlet, the outlet and the directing mechanism of the apparatus are made preferably from a perfluoroalkoxy (PFA) fluorocarbon resin.
The present invention is particularly advantageous as a result of the nested inner and outer PFA resin coils. In a preferred embodiment, the coils are supported within a heating box which is insulated and supported within a compartment of the housing. The coils have a centreline which is substantially vertical. A plurality of linear heating elements are attached to the heating box both inside and outside the turns of the coils and extend approximately parallel to the centreline of the coils. In this way, the air in the heating box is heated which in turn heats the coils and the reagent therein. The coils include many loops so that reagent stays within the coils in the hot heating box for a sufficient period to be heated to a desired temperature.
A further important advantage of the present invention is that the heating means may be bypassed so that reagent may pass through the apparatus at its ambient temperature. Also of advantage is the provision for flushing both the heating branch and the ambient passing branch of the plumbing of the apparatus. The flushing reagent is discharged from a different outlet than heated or ambient temperature reagent and passes to drain.
The present invention is still further advantageous in that a sample of the heated reagent may be continuously tested for resistivity with the sampled reagent passing to drain. In addition, pressure switches may maintain a desired pressure for discharged heated and ambient reagent. Also, heat sensors may be used to maintain the desired temperature for the reagent, while protecting the coils from overheating and failing structurally.
These advantages and other objects obtained by the present invention are explained more fully and may be better understood by reference to the detailed descriptive matter which follows and which refers to the drawings described briefly hereinafter.

Brief Description of the Drawings

FIGURE 1 is a perspective view of the front and left side, with the upper front cover exploded from the housing, of apparatus in accordance with the present invention;
FIGURE 2 is an elevational view of the rear side of the apparatus of FIGURE 1;
FIGURE 3 is a cross-sectional view as taken along line 3-3 of FIGURE 1;
FIGURE 4 is a cross-sectional view as taken along line 4-4 of FIGURE 3;
FIGURES 5A AND 5B are a schematic illustration of the electrical system of the apparatus of the present invention;
FIGURE 6 is a schematic illustration of the plumbing for the reagent in accordance with apparatus of the present invention; and
FIGURE 7 is a schematic illustration of the pneumatic plumbing in accordance with the present invention.

Detailed Description of the Preferred Embodiment

Referring now to the drawings wherein like reference numerals designate identical or corresponding parts throughout the several views, and more particularly to FIGURE 1, an apparatus for processing a corrosive, semiconductor reagent in accordance with the present invention is designated generally by the numeral 10. The reagent of particular interest for the preferred embodiment is ultra-pure, de-ionized water. In the preferred embodiment, apparatus 10 includes a housing 12 having an upper compartment 14 and a lower compartment 16. Housing 12 is generally a rectangular frame 18 made from a plurality of angle members 20 and panels 22 attached thereto to create a generally rectangular box having the upper and lower compartments 14 and 16. Panels 22 may be split so that a different panel 22 covers upper compartment 14 than the one which covers lower compartment 16 on a particular side of housing 12.
Upper compartment 14 contains most components of the electrical, pneumatic and hydraulic systems of apparatus 10. A panel 24 serves as the front panel and includes controls 26. A rear panel 28 (see FIGURE 2) opposite front panel 24 provides through which various plumbing components and electrical wires may pass.
Lower compartment 14 houses a heating box 30 which holds a heating core 32 and a plurality of linear heating elements 34 as discussed in more detail hereinafter. Access to lower compartment 16 is provided through a door 35 at the rear of housing 12.
Housing 12 is preferably mounted on a plurality of castors 38 to allow apparatus 10 to be moved between various locations.
As shown more particularly in FIGURES 3 and 4, heating box 30 is located in lower compartment 16 of housing 12. Heating box 30 has a bottom 36, a top 38 and side walls 40. In like fashion, lower compartment 16 has a bottom 42, a top 44 and a plurality of side panels 22 serving as walls. The bottom 36 of heating box 30 is supported near side walls 40 by the upper ridges of an open ended box-like support member 46. In this way, heating 30 is spaced-apart from bottom 42 and includes open space between bottom 36 and support member 46 for the wiring of elements 34. Support member 46 may be fastened with a screw or other mechanism (not shown) to bottom 42. Heating box 30 is retained on support member 46 by downwardly extending flanges 48. Also, box 30 may be fastened with a screw or other mechanism (not shown) to support member 46 for more permanent placement.
Heating box 30 contains heating core 32. Heating core 32 comprises inner and outer, multiple turn, substantially rectangular coils 52 and 54. Inner coil 52 is preferably not touching, but is closely adjacent to outer coil 54. Both coils preferably have the same substantially vertical centerline 56. Since apparatus 10 is intended for heating in particular ultra-pure, de-ionized water, coils 52 and 54 as well as the rest of the hydraulic system of apparatus 10 must be made from a material which will not deteriorate or contaminate the ultra-pure water passing therethrough. Metallic materials are not acceptable. Of the nonmetallic materials, the best and, therefore, the preferable material is perfluoroalkoxy (PFA) fluorocarbon resin. Such material is manufactured by only a few entities and only custom shapes are available. Consequently, a coil of such a material is not available. Furthermore, arcuate tubes are not available. The manufacturing entities make only straight tubes and elbows and other fitting members. The prior art makes use of straight plastic members and various fittings. The present invention utilizes straight tubing and various fittings, but does so in a fashion not heretofore thought possible. That is, inner and outer coils 52 and 54 are formed as substantially rectangular spirals of a plurality of loops. Inner coil 52, for example, builds from its lowermost loop so that its uppermost loop 58 is shown in FIGURE 3. The uppermost loop includes a plurality of elbows 60 and straight tubes 62 welded together by a known process. One of the straight tubes 64 extends beyond the profile of inner coil 52 to mate with an elbow 66 to begin forming the uppermost loop 68 of outer coil 54. Loop 68 is similarly made from a plurality of straight tubes 62ʹ and elbows 60ʹ with the fourth tube 70 inclining to meet the next loop downwardly from uppermost loop 68. Subsequent loops continue to spiral downwardly so that core 32 comprises a plurality of inner loops spiraling upwardly to form inner coil 52 and a plurality of outer loops spiraling downwardly to form outer coil 54. In this fashion, inner coil 52 and outer coil 54 are in fluid communication with one another. Preferably, each of the lower loops of inner and outer coils 52 and 54 have an open end 72, 74, respectively. The ends 72, 74 connect to input and output connecting tubing 76 and 78 for further connection to the rest of the hydraulic circuit as explained more fully with respect to FIGURE 6.
Each of the upper loops 58 and 68 of inner and outer coils 52 and 54 includes a vent tube 80 extending at least slightly upwardly for upper loop 58 and upper loop 68. Each vent tube 80 includes a closure member 82. Vent tubes 80 provide a mechanism for venting air in coils 52 and 54 to prevent airlocks from developing and inhibiting liquid flow.
Heating core 32 is supported in heating box 30 by a plurality of heat insulating fire bricks 84. Each fire brick is placed on edge. Four fire bricks are located at the corners of the core 32 and extend diagonally so as to support a portion of each of inner and outer coils 52, and 54. Two additional fire bricks provide transverse support for each of coils 52 and 54 along the longer sides of the coils. Each fire brick is held in place by a spaced apart pair of angle members having one leg fastened to bottom 36 of heating box 30 and the other leg extending upwardly to retain a side of the fire brick 84.
In addition, a pair of spaced apart angle members 88 are fastened centrally to each of side walls 40 of fire box 30. A ceramic or other heat insulating tile 90 is fastened between each pair of angle members 88. Each tile 90 extends approximately from the lowermost loop of outer coil 54 to approximately the uppermost loop. Each tile 90 is closely adjacent to if not touching coil 54. In this way, heating core 52 is supported by heat insulating materials above bottom 36 and away from side walls 40 of heating box 30.
Preferably, insulation 92 is fastened or otherwise installed along top 38 and all side walls 40 to hold heat within heating box 30. Additional insulation could be installed around the outside of heating box 30 or as an alternative to insulation 92.
A plurality of heating elements 34 extend substantially vertically from bottom 36 to top 38 in heating box 30. In this orientation, elements 34 are substantially parallel to centerline 56. Heating elements 34 are attached to bottom 36. Wiring from elements 34 accumulates in the space between support 46 and bottom 36 and passes out through an opening in support 46 and upwardly along the space between a sidewall 40 of heating box 30 and a side panel 22 of housing 12. The upper portions of heating elements 34 pass through openings in top 38. All wiring passes through an opening in top 44 of second compartment 16 for further connection with elements in first compartment 14 according to the schematic as discussed more fully with respect to FIGURES 5a and 5b. Heating elements 34 are regularly spaced on both the outside of heating core 32, and the inside of heating core 32. Thus, heating elements 34 heat the air in box 30 which then heats core 32 and the liquid within coils 52 and 54.
The hydraulic system for apparatus 10 is illustrated schematically in FIGURE 6. The hydraulic system includes an inlet 98 and a plurality of outlets 100, 102, 104. Inlet 98 and outlets 100, 102, 104 are also shown in FIGURE 2. Inlet tube 98 leads to pump 106 which is driven by a motor 108. Pump 106 has an outlet line 110 leading to flow meter 112. The outlet line 114 from flow meter 112 leads to filter 116 and then either to a first pneumatically actuated valve 120 via tube 118 or to a second pneumatically actuated valve 122 via tube 124. When ultra pure, de-ionized water is to be heated, first valve 120 is open and second valve 122 is closed. With first valve 120 open, the liquid passes through tube 76 to the inlet end 72 of heating core 32. The liquid fluid flows through core 32 and out outlet end 74 and tubing 78 to first differential pressure switch 126. First switch 126 is connected via tube 128 to third pneumatically actuated valve 130 which is connected to the hot liquid outlet 104.
As discussed hereinbefore, heating elements 34 provide the heating mechanism for heating core 32. Elements 34 are wired through relay 220 for regulation by known controller 131. The surface temperature of coils 52 and 54 in heating core 32 is monitored by a thermoswitch 135 as schematically connected via line 133 to control relay 220. Similarly, the liquid temperature is sensed at sensor 137 which provides the necessary thermostatic information to controller 131 via line 139. These elements are more fully discussed hereinafter with respect to the electrical schematic shown in FIGURES 5a and 5b.
When ultra-pure, de-ionized water is processed through apparatus 10, it is appropriate to monitor the resistivity of the water to insure that the water is being maintained at the appropriate de-ionized level. For this reason, the hydraulic system includes a branch which samples water from the main heating flow path and discharges the sampled water to drain outlet 102. In particular, the sampling branch is in fluid communication with tube 78 and leads through tube 132, check valve 134, and tube 136 to resistivity monitor 138. From monitor 138, water is directed through tube 140, check valve 142, and tube 144 to outlet drain 102.
If first valve 120 is closed, while second valve 122 is open, then liquid fluid flows from second valve 122 through line 146 to second differential pressure switch 148. Second switch 148 is also connected via line 150 to fourth pneumatically actuated valve 152 and then to cold liquid outlet 100. When liquid flows through this branch, it bypasses heating core 32 and is discharged at its ambient temperature.
When apparatus 10 is not in continuous use, especially when its primary use is with ultra pure, de-ionized water, bacteria and other contaminants tend to become a fac tor. It is appropriate, therefore, to provide a mechanism for flushing the hydraulic system. Although the flushing cycle is discussed in more detail hereinafter, it is pointed out that branches off both the heating branch and the ambient passage branch of the hydraulic system are connected to drain outlet 102 which allows for both branches to be flushed and thereby cleansed. In particular, a tube 154 leads from tube 150 to fifth pneumatically actuated valve 156 and then outlet drain 102. In a similar fashion, tube 158 leads from tube 128 to sixth pneumatically actuated valve 160 and then via line 162 to drain outlet 102.
The pneumatic system illustrated in FIGURE 7 is the mechanism preferable for actuating valves 120, 122, 130, 152, 156 and 160 of the hydraulic system. Pressurized air from a source (not shown) is input at line 164 to pressure regulator 166. The regulated air is made available to first solenoid actuated, four-way valve 168 via line 170, second solenoid actuated, three-way valve 172 via line 174, third solenoid acutuated, four-way valve 176 via line 178 and fourth solenoid actuated, three-way valve 179 via line 181. One port 169, 173, 177 and 183 in each of valves 168, 172, 176 and 179, respectively, may be opened to vent. A second port of valve 168 is connected via line 180 to a first inlet of first dualinlet, check valve 182. A second port of valve 168 is also connected via lines 180 and 184 to the actuation mechanism of third hydraulic valve 130. The outlet of check valve 182 is connected via line 186 to the actuation mechanism of first hydraulic valve 120. A third port of valve 168 is connected via line 188 to the first inlet of second dual-inlet, check valve 161. The outlet of check valve 161 leads via line 163 to the actuation mechanism of fourth hydraulic valve 152.
Valve 172 is connected via line 190 to a tee which leads to lines 192 and 194. Line 192 is connected to the first inlet of third dual-inlet, check valve 185. The outlet of check valve 185 leads via line 187 to the second inlet of first check valve 182. Line 194 is connected to the first inlet of fourth dual-inlet, check valve 196. The outlet of check valve 196 is connected via line 198 to the actuation mechanism of second hydraulic valve 122.
A second port of valve 176 is connected via line 200 to the actuation mechanism of fifth hydraulic valve 156. Line 200 is teed to lead via line 202 to the second inlet of check valve 196. A third port of valve 176 is connected via line 204 to the actuation mechanism of sixth hydraulic valve 160.
Valve 179 is connected via line 189 to the second inlet of check valve 185. Line 189 is teed and via line 191 also leads to the second inlet of check valve 161.
As shown in FIGURES 5A and 5B, the electrical system is designed for 480 volt alternating current service. The service connection is indicated at box 206 of FIGURE 5A. The three wire 480 volt service is connected via lines 208, 209, 210, to circuit breaker 212 and via lines 214, 215, 216 to circuit breaker 218. Circuit breaker 212 is wired to the contacts of relay 220 via lines 222, 223, and 224. Heating elements 34 are wired to various 240 volts pairs of lines 226, 227, 228 which are connected to the other side of the contacts of relay 220.
Circuit breaker 218 is connected via lines 230, 231, 232 to pump motor 108, which is also wired to ground via line 236.
The 240 volts primary of step down transformer 238 is wired via lines 240 and 242 to wires 208 and 209 coming from the service connection. A fuse 244 is wired inot line 240. The 120 volt secondary side of transformer 238 is wired in series via lines 246 and 248 to safety switch 250 which is located to open with the opening of door 36, start and stop switch mechanism 252, and the solenoid 254 of the control circuitry relay 260.
Lines 256 and 258 lead to the control circuitry and are in parallel with the switching circuit just described. Lines 256 and 258 lead to one side of the contacts of relay 260. The other side of the contacts of relay 260 are wired via lines 262 and 264 to a number of parallel control element branches. Four such branches actually include a four position, rotary switch 266 having a plurality of in terminals and a plurality of out terminals. Switch 266 may be moved between a "hot" liquid position, a "cold" liquid position, a "hot and cold" liquids position, and a flush position. In the "hot" position, line 268 leads from line 262 to switch 266 and then via line 270 to solenoid 272 which controls first pneumatic valve 168. Solenoid 272 is then wired to line 264 via lead 274. In the "hot" position, line 262 is also connected to switch 266 through line 276. Switch 266 is then wired to differential pressure switch 126 and the solenoid 278 of a pump motor relay (internal to motor 108 and not shown) via lines 280 and 282. Solenoid 278 is also wired to line 264 via line 284.
In the "cold" position, line 262 is connected to switch 266 via line 286. Switch 266 is then connected to solenoid 288 of third pneumatic valve 176 via line 290. Solenoid 288 is also wired to line 264 via line 292. Also in the "cold" position, line 262 is wired to switch 266 via line 294. Switch 266 is then electrically connected via line 296 to differential pressure switch 148 and the solenoid 278 of pump motor relay (not shown) via lines 296 and 298. Although the liquid source is usually pressurized, it is often desirable to deliver a different pressure to the outlets of apparatus 10. Differential pressure switches 126 and 148 control solenoid 278 of the pump motor relay (not shown) to control pump 106 and thereby the pressure of the liquid flowing through the system.
In the "hot and cold" position, line 262 is connected to switch 266 at lines 300, 302 and 304. Each of these connections are internally connected in switch 266 to lines 270 leading to solenoid 272 which controls the "hot" liquid branch of the hydraulic circuit, line 290 leading to solenoid 288 which controls the "cold" branch of the hydraulic circuit, and line 296 which is connected through differential pressure switch 148 to pump motor solenoid 278.
In the flush position, line 262 is connected to switch 266 via line 306. Switch 266 is then connected in to timer 308 via line 310. Solenoid 312 is wired via line 314 to timer 308 on one side and line 264 via line 316 on the other side. Solenoid 312 controls second pneumatic valve 172.
Liquid temperature sensor 137 is connected to line 262 by line 320 and via line 322 to line 264. Ordinarily, sensor 137 provides thermostatic information to controller 131 via line 139 (see FIGURE 6) which then controls the current to heating elements 34. However, when liquid temperature reaches a predetermined high level, sensor 137 internally switches to energize solenoid 342 via lines 340 and 342. Solenoid 342 controls fourth solenoid valve 179. At the predetermined temperature controller 131 turns heaters 34 off.
Similarly, the resistivity sensor 138 is energized by being connected to lines 262 and 264 via lines 234 and 326. Finally, line 262 is connected via line 328 to the power switch 330 of controller 131 which is connected in series via line 332 to surface skin temperature switch 135 of coils 52 and 54. Switch 135 is connected via line 334 to the solenoid 336 of relay 220. The other side of solenoid 336 is connected via line 338 to line 264.
In use, door 36 of lower compartment 16 is closed so that switch 250 is closed (see FIGURES 5A AND 5B). The four position rotary switch 226 is turned to a desired position. Assume firstly that a "hot" reagent is desired so that switch 266 is turned to the appropriate position. When starting switch 252 is functioned to close the circuit, solenoid 254 closes the contacts on relay 260 and solenoid 272 is energized. Also, assuming the pressure level of the reagent is outside the differential pressure which does not require additional pumping, switch 126 is closed and pump motor solenoid 278 functions to start pump motor 108.
A desired temperature for the reagent is input into controller 131. With power switch 330 closed, solenoid 336 is energized which in turn closes the contacts of relay 220 and energizes heating elements 34. The reagent temperature is sensed at sensor 137 and the current to heating elements 34 controlled appropriately. As elements 34 get hot, they heat the air in heating box 30 thereby heating heating core 32 comprising inner and outer coils 52 and 54. Sensors 135 monitor the surface temperature of coils 52 and 54. If the temperature exceeds a predetermined high value, sensor 135 includes a switching element which opens to deenergize solenoid 336 thereby opening the contacts of relay 220 and deenergizing elements 34. Reagent pressure is measured at switch 126 and, if it exceeds a predetermined value, switch 126 opens which turns off pump motor starter solenoid 278 and pump motor 236.
When solenoid 272 is energized, as shown in FIGURE 7, valve 168 is functioned to pass air from pressure regulator 166 through check valve 182 to actuate and open first hydraulic valve 120. In addition, air from valve 168 flows to actuate and open third hydraulic valve 130. As seen in FIGURE 6, this allows the reagent to flow through pump 106, flow meter 112 and filter 116 to first hydraulic valve 120. Since valve 120 is open, the water flows into heating core 32 and circulates through inner and outer coils 52 and 54. The temperature of the exiting water is measured by sensor 137. The heated reagent flows through pressure switch 126 which, as mentioned, controls pump motor solenoid 278 and pump motor 108 to maintain output pressure in a given range. The reagent continues to flow through third hydraulic valve 130 to the third outlet 104.
Whenever water is flowing through the heating core, water near the outlet is monitored for ionization by resistivity meter 138. Sampled water flows from meter 138 to the second outlet 102 which discharges to drain.
If the heated water rises beyond a predetermined temperature, such temperature is sensed by sensor 137 which causes solenoid 342 to be energized. This in turn causes first and fourth hydraulic valves 120 and 152 to be opened. Sensor 137 in combination with controller 131 thermostatically reduces the current to heaters 34. At the same time heating core 32 is flushed with ambient reagent which is passed to second drain 102, rather than third outlet 104. In this way, heating coil 32 is rapidly cooled to avoid an overheating failure. After the liquid reagent cools sufficiently, solenoid 342 is deenergized, and the usual operation for the "hot" selection of the four position rotary switch 266 resumes.
If the surface temperature of coils 52 and 54 as it is monitored by sensor 135 reaches a predetermined temperature, switch 135 opens thereby deenergizing solenoid 336 and switching off the power to heating elements 34 at relay 220. The heating elements are not reenergized until the surface temperature as sensed by sensor 135 falls below the predetermined temperature.
If four position rotary switch 266 is positioned for the passage of "cold" or ambient temperature liquid through the system, solenoid 288 is energized and if liquid pressure is lower than a predetermined level, pump motor starter sole noid 278 is energized to start pump motor 108. As shown in FIGURE 7, energization of solenoid 288 functions third pneumatic valve 176 to pass air from pressure regulator 166 to dual imput valve 196 to actuate and open second hydraulic valve 122. Also, air is passed to actuate and open fifth hydraulic valve 156. As shown in FIGURE 6, reagent liquid then flows from inlet 98 through pump 106, flow meter 112, and filter 116 to second hydraulic valve 122. The water flows from valve 122 to differential pressure switch 148 which maintains the pressure in a predetermined range. The liquid then flows through fifth hydraulic valve 156 to the first outlet 100. In this way, liquid reagent completely bypasses heating core 32 and provides the capability for the heater apparatus to either heat the reagent or bypass the heating core 32 and provide ambient temperature reagent depending on particular process needs.
If the four position rotary switch 266 is placed in the "hot and cold" position, the operation of apparatus 10 includes a combination of the functions of both the "hot" position and the "cold" position as described hereinbefore. The result is that hot ultra-pure water is discharged at third outlet 104 and cold ultra-pure water is discharged at first outlet 100. Thus, a single source of ultra-pure water may be plumbed through apparatus 10 and directed to both a process needing hot water and a process needing cold water.
If the four position rotary switch 266 is placed in the "flush" position, then timer 308 begins timing and periodically energizes solenoid 312 and auxiliary solenoids 315 and 317. When solenoid 312 is energized, pneumatic valve 172 allows the air to pass from pressure regulator 166 to each of dual inlet check valves 185 and 196. From valve 182, air flows through dual inlet check valve 182 and to actuate and open first hydraulic valve 120. From valve 196, air actuates and opens second hydraulic valve 122. Auxiliary solenoid 315 energizes to actuate valve 168 and to pass air from its third port to actuate and open fourth hydraulic valve 152. Auxiliary solenoid 317 energizes to actuate valve 176 to pass air and to actuate and open sixth hydraulic valve 160. As shown in FIGURE 6, flushing fluid then passes throughout the entire system, being stopped only at fourth hydraulic valve 152 thereby being prevented from passing flushing fluids to first outlet 100 and being stopped at third hydraulic valve 130 thereby being prevented from passing flushing fluid to the third outlet 104. Rather, all the flushing fluid is directed to second outlet 102 which discharges to drain. A periodic flushing cycle is particularly important for processes using heated ultra-pure, de-ionized water in order to prevent any bacteria buildup and thereby to keep the system free from contamination.
The present apparatus is, thus, a versatile and efficient processing unit which provides for heating ultrapure, de-ionized water or other corrosive reagents and provides for bypassing the heating branch in order to pass ambient temperature water or reagent. The apparatus continously monitors the hot water for resistivity changes. The system provides for a periodic flushing when such function is selected by the operator. In addition, not only are these various functions available, but the heating core of the present apparatus is particularly advantageous. Heretofore, it has not been possible to easily heat significantly or provide rapid flow rates of heated water or reagent since the materials necessary for containing the corrosive reagents in a noncontaminated environment have not allowed for devices having other then straight passageways with fittings at the ends. The present invention uniquely provides for nested coils supported in a heating box and surrounded by heating elements. The result is that the corrosive liquids which are processed by the apparatus may be significantly heated and, furthermore, passed through the system at relatively fast flow rates.
Thus, the various advantages and the details of structure and function of the present invention have been described in detail. It is understood, nevertheless, that the present preferred embodiment is representative of the concept of the invention. Consequently, in summary, it is understood that changes made to the full extent extended by the general meaning of the terms in which the appended claims are expressed, are within the principle of the present invention.

Claims

1. Apparatus for heating an ambient temperature, corrosive, liquid reagent, comprising:
a housing;
an inlet for receiving said reagent;
a first outlet for discharging said reagent;
means for directing said reagent between said inlet and said outlet, said directing means being attached to said housing, said directing means including nonmetallic inner and outer multiple turn, substantially rectangular coils, said inner and said outer coils being in fluid communication with one another;
means for heating said coils;
means for controlling said heating means;
a pump for moving said reagent through said directing means; and
means for controlling said pump.

2. Apparatus in accordance with claim wherein said coils have substantially the same centerline, said centerline being approximately vertical, said heating means including a plurality of linear heating elements extending approximately parallel to said centerline, some of said elements being outside said coils and others of said elements being inside said coils.

3. Apparatus in accordance with claim 1 or claim 2 wherein said coils have an outer surface and wherein said heating means includes a heating box for containing said coils, said heating means further including a plurality of heating elements in said heating box and means for controlling said heating elements, said controlling means including means for sensing the temperature of the outer surface of said coils so as to reduce heat from said heating elements when said temperature sensed reaches a predetermined level thereby protecting said coils from being damaged.

4. Apparatus in accordance with claim 1 whereby said heating means includes a heating box for containing said coils, said box having a first top, a first bottom and first sides, said housing including a first compartment for receiving said box, said first compartment having walls including a second top, a second bottom and second sides, said apparatus further including means for supporting said box with respect to said second bottom, said box being spaced from said second top, said second bottom and said second sides.

5. Apparatus in accordance with claim 4 wherein said coils have substantially the same centerline, said centerline being approximately vertical, said heating means including a plurality of linear heating elements extending approximately parallel to said centerline, some of said elements being outside said coils and others of said elements being inside said coils, said elements being attached to the first bottom of said heating box.

6. Apparatus in accordance with claim 5 including a plurality of heat insulating firebricks for supporting said coils with respect to the first bottom of said heating box, said apparatus further including a plurality of heat insulating means for laterally supporting said coils to keep said coils approximately centered with respect to said heating box.

7. Apparatus in accordance with claim or claim 6 wherein said directing means includes input and output connecting tubing in fluid communication with said coils and wherein said inner and outer coils include upper and lower loops, one of said lower loops in said coils including a first end for connecting to said input connecting tubing and the other of said lower loops of said coils including a second end for connecting to said output connecting tubing, each of said upper loops including a closable vent for venting gaseous fluid from said coils.

8. Apparatus in accordance with any one of claims 1 to 7, including a second outlet and first means for bypassing said coils, said first bypassing means being in fluid communication with said directing means and said second outlet.

9. Apparatus in accordance with claim 8 including a drain outlet and second means for bypassing said first and second outlets, said second bypassing means being in fluid communication with said directing means, said first bypassing means and said drain outlet.

10. Apparatus in accordance with any one of claims 1 to 9, including a drain outlet for discharging said reagent, said apparatus further including means for sensing said reagent temperature and means for quickly cooling said coils with ambient temperature reagent, said cooling mean draining said reagent to said drain outlet.

11. Apparatus for heating a corrosive liquid reagent, comprising:
an inlet for receiving said reagent;
a plurality of outlets for discharging said reagent;
a plurality of nested, substantially rectangular coils;
means for directing said reagent between said inlet and one of said plurality of outlets, said directing means including means for passing said reagent through said coils to a first of said outlets, said directing means also including means for bypassing said coils and passing said reagent at its ambient temperature to a second of said outlets, said directing means further including means for flushing portions of each of said passing means and said bypassing means and directing said reagent to a third of said outlets;
a pump for moving said reagent;
means for heating reagent in said coils; and
means for selecting at least one of said passing means, said bypassing means and said flushing means for a reagent flow path, said selecting means including means for controlling said pump.

12. Apparatus in accordance with claim 11 wherein said passing means includes means for sensing reagent pressure, said sensing means including means for switching said pump on and off depending on pressure level sensed.

13. Apparatus in accordance with claim 11 wherein said bypassing means includes means for sensing reagent pressure, said sensing means including means for switching said pump on and off depending on pressure level sensed.

14. Apparatus in accordance with claim 11 wherein said flushing means includes timing means for switching said pump on and off periodically.

15. Apparatus in accordance with claim 11 wherein said passing means includes means for measuring resistivity of said reagent.

16. Apparatus for heating a corrosive fluid, comprising:
a housing having first and second compartments, said first compartment including a first top, a first bottom, and first sidewalls;
an inlet for receiving said reagent;
first, second and third outlets for discharging said reagent;
inner and outer multiple turn, substantially rectangular coils in fluid communication with one another and with said inlet and said third outlet, said coils having substantially the same centerline, said centerline being approximately vertical;
a heating box for containing said coils, said box having a second top, a second bottom and second sidewalls;
means for supporting said heating box including means for spacing said box from said first top, said first bottom, and said first sidewalls of said first compartment;
means for heating said reagent in said coils, said heating means including a plurality of linear heating elements extending approximately parallel to the centerline of said coils, some of said elements being outside said coils and others of said elements being inside said coils, said elements being attached to the second bottom of said heating box and extending between said second bottom and said second top of said heating box;
means for directing said reagent between said inlet and one of said plurality of outlets; said directing means being attached to said housing, said directing means including means for passing said reagent through said coils to the first of said outlets, said directing means also including means for bypassing said coils to the second of said outlets, said directing further including means for flushing portions of each of said passing means and said bypassing means and directing said reagent to a third of said outlets, said flushing means including timing means for switching on and off at periodic predetermined times;
a pump for moving said reagent through said directing means; and
means for selecting at least one of said passing means, said bypassing means and said flushing means for a reagent flow path, said selecting means including means for controlling said pump.

17. Apparatus for heating a liquid reagent, comprising:
a housing;
an inlet for receiving said reagent;
a first outlet for discharging said reagent;
means for directing said reagent between said inlet and said outlet, said directing means being mounted in said housing and comprising nonmetallic inner and outer multiple turn coils, and turns of said coils being formed substantially of straight tubing and elbows, said inner and said outer coils being in fluid communication with one another;
means for heating said coils;
means for controlling said heating means;
a pump for moving said reagent through said directing means; and
means for controlling said pump.

18. Apparatus in accordance with any one of claims 1 to 17, wherein said inlet, said outlet, and said directing means including said coils are comprised of a perfluoroalkoxy (PFA) fluorocarbon resin.