Liquid heating method, liquid heating apparatus, and heated liquid supplying apparatus

Abstract

A liquid heating method and apparatus including a heat device 7 having a flow passage member forming a tubular flow passage for passing a sulfuric acid solution, a heater arranged on an outside of at least one of opposing flow passage surfaces of the tubular flow passage, a liquid draining line 10, an atmosphere opening line 12, valves 11 and 13, a liquid draining mechanism for draining the sulfuric acid solution heated at least in a heat receiving area between the opposing liquid flow passage surfaces of the tubular flow passage, a flow meter 6 for measuring a flow rate of the sulfuric acid solution, and a control unit 14 responsive to the flow meter 6 for determining a defective liquid flow in the tubular flow passage and for draining the sulfuric acid solution using the liquid draining mechanism.

Claims

1. A liquid heating method for heating a liquid flowing in a heat receiving area of a heating liquid flow passage by means of a heater arranged outside the heating liquid flow passage while flowing the liquid in the heating liquid flow passage, wherein during the heating by the heater or when remaining heat in a portion other than the liquid, caused by the heating, and at least exceeding the boiling point of the liquid is left after the heater is stopped, the liquid heated by the heater or receiving the remaining heat at least in the heat receiving area is drained to the outside of the heating liquid flow passage before boiling in the heat receiving area in response to a defective liquid flow in the heating liquid flow passage.

2. The liquid heating method according to claim 1, wherein the defective liquid flow is a stop of the liquid flow, or a decrease in a flow rate to a value equal to or lower than a predetermined value during the liquid flow.

3. The liquid heating method according to claim 1, wherein a depth of the heating liquid flow passage with respect to the heater is equal to or less than 10 mm, and the liquid passes the heat receiving area in 0.5 to 10 seconds by the liquid flow.

4. The liquid heating method according to claim 1, wherein the liquid is a sulfuric acid solution having 65 to 96% by mass in sulfuric acid concentration, and the heater heats the sulfuric acid solution to 140 to 220.

5. The liquid heating method according to claim 1, the heating liquid flow passage is arranged vertically, and in case of the defective liquid flow in the heating liquid flow passage an upper side of the heating liquid flow passage is opened to the atmosphere pressure so that the liquid is drained from a lower side of the heating liquid flow passage to flow down by its own weight.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a schematic diagram showing a liquid heating apparatus according to an embodiment of the present invention.

(2) FIG. 2 is a schematic diagram showing a heating device in the liquid heating apparatus according to the embodiment of the present invention.

(3) FIG. 3 is a schematic diagram showing the liquid heating apparatus according to another embodiment of the present invention.

(4) FIG. 4 is a schematic diagram showing the liquid heating apparatus according to still another embodiment of the present invention.

(5) FIG. 5 is a schematic diagram showing the liquid heating apparatus according to yet another embodiment of the present invention.

(6) FIG. 6 is a schematic diagram showing a general household gas instantaneous water heater.

MODE FOR CARRYING OUT THE INVENTION

First Embodiment

(7) A description will now be given of a heated liquid supplying apparatus provided with a liquid heating apparatus according to an embodiment of the present invention referring to FIGS. 1 and 2.

(8) The heated liquid supplying apparatus 1 includes a preheating tank 2 for preheating a sulfuric acid solution containing persulfuric acid, and a heating device 7 for heating the sulfuric acid preheated by the preheating tank 2 as shown in FIG. 1. The heating device 7 corresponds to a heating unit of the present invention, and is arranged so that a heating liquid flow passage passes through in a vertical direction. Moreover, the preheating tank 2 has a function as a collection unit of the present invention.

(9) The preheating tank 2 retains the sulfuric acid solution including persulfuric acid. The sulfuric acid concentration of the sulfuric acid solution is 65 to 96% by mass. A sulfuric acid solution containing persulfuric acid generated by electrolysis of the sulfuric acid solution is supplied to the preheating tank 2. It should be noted that an SPM solution manufactured by mixing a sulfuric acid solution and a hydrogen peroxide solution may be used as the sulfuric acid solution containing persulfuric acid.

(10) A heater, which is not shown, is provided in the preheating tank 2, and the heater can preheat the sulfuric acid solution stored in the preheating tank 2. Moreover, an atmosphere opening line 3 is connected to the preheating tank 2 to open the inside of the preheating tank 2 to the atmospheric pressure.

(11) An upstream end of the upstream side supply line 4 for supplying the heating device 7 with the sulfuric acid solution in the preheating tank 2 is connected to the preheating tank 2. A downstream end of the upstream side supply line 4 is connected to a liquid inlet side of a bottom portion of the heating device 7. An air pump 5 for feeding the sulfuric acid solution from the preheating tank 2 side toward the heating device 7 side is interposed on the upstream side supply line 4. The air pump 5 corresponds to a pump of the present invention. It should be noted that various pumps may be used in place of the air pump 5.

(12) Moreover, a flow meter 6 for measuring a flow rate of the sulfuric acid flowing through the upstream side supply line 4 is provided on a downstream side of the air pump 5 on the upstream side supply line 4. The flow meter 6 constructs a monitoring unit of the present invention. An output signal of the flow meter 6 is transmitted to the control unit 14.

(13) The control unit 14 controls the entire heated liquid supplying apparatus 1, can be constructed mainly by a CPU and a program for operating the CPU, and additionally includes a RAM serving as a work area, a ROM for storing the program and the like, and a nonvolatile memory for storing predetermined values used for determining defective liquid flow. Namely, the control unit 14 functions as a liquid draining control unit of the present invention.

(14) An upstream end of the downstream side supply line 8 for supplying a cleaning machine, which is not shown, with the sulfuric acid solution heated by the heating device 7 is connected to a discharge side of a top portion of the heating device 7. A thermometer 9 for measuring a liquid temperature of the sulfuric acid solution flowing through the downstream side supply line 8 is provided on the downstream side supply line 8. An output signal of the thermometer 9 is transmitted to the control unit 14. The control unit 14 for receiving the output signal of the thermometer 9 adjusts an output (pump flow rate) of the air pump 5 and a heating temperature in the heating device 9 so that the sulfuric acid solution heated by the heating device 7 reaches a predetermined temperature.

(15) A description will now be given of a specific structure of the heating device 7 referring to FIGS. 2(a), 2(b), and 2(c).

(16) FIG. 2(a) is a cross sectional view along a horizontal plane of the heating device 7, FIG. 2(b) is a vertical cross sectional view of the heating device 7, and FIG. 2(c) is a horizontal cross sectional view enlarging a tubular flow passage 70.

(17) The heating device 7 includes a double tube constructed by an inner tube wall 71a and an outer tube wall 71b, and forming a tubular flow passage 70 through which the sulfuric acid flows, heaters 72 and 73 for heating the sulfuric acid in a heat receiving area inside the tubular flow passage 70, and a housing 74 having a heat insulating structure as shown. The inner tube wall 71a, the outer tube wall 71b, and the heaters 72 and 73 are stored in the housing 74. The tubular flow passage 70 corresponds to a heating liquid flow passage of the present invention. Moreover, the inner tube wall 71a and the outer tube wall 71b correspond to a flow passage member of the present invention.

(18) The tubular flow passage 70 is formed by the double tube structure having diameters close to each other, and the tubular flow passage 70 is secured between the inner tube wall 71a and the outer tube wall 71b. The inner tube wall 71a and the outer tube wall 71b are respectively made of quartz. The thickness of the tubular flow passage 70 (difference between an inner diameter of the outer tube wall 71b and an outer diameter of the inner tube wall 71a) is preferably equal to or less than 10 mm, and is more preferably 1 to 5 mm. The residence time of the sulfuric acid solution in the tubular flow passage 70 is preferably 0.5 to 10 seconds, and the flow rate of the sulfuric acid solution supplied to the tubular flow passage 70 is preferably 0.5 to 1.5 L/min. In this case, a quantity of the sulfuric acid solution (liquid holdup quantity) residing in the tubular flow passage 70 is 100 to 150 mL when the supply of the sulfuric acid solution to the tubular flow passage 70 is stopped.

(19) The tubular flow passage 70 is arranged so that an axial direction aligns with the vertical direction, the downstream end of the upstream side supply line 4 is connected to the bottom side, which is the liquid inlet side of the tubular flow passage 70, and the upstream end of the downstream side supply line 8 is connected to the top side, which is the liquid discharge side of the tubular flow passage 70 as described above.

(20) A plurality of heaters 72 in a rod shape in the axial direction of the tubular flow passage 70 are arranged at an equal angular interval in a circumferential direction concentric with the tubular flow passage 70 outside an outer periphery of the tubular flow passage 70. Moreover, one heater 73 in a rod shape is arranged at a center position of the tubular flow passage 70 along the axial direction of the tubular flow passage 70 inside an inner periphery of the tubular flow passage 70. Halogen lamp heaters, for example, are used as heaters 72 and 73.

(21) It should be noted that the configuration of the heating device 7 is not limited to the configuration shown in FIG. 2, and various configurations can be employed.

(22) One end of the liquid draining line 10 branches and is connected to the upstream side supply line 4 connected to the liquid inlet side of the tubular flow passage 70 on a downstream side of the flow meter 6 as shown in FIG. 1. The other end of the liquid draining line 10 is connected via a valve 11 to the preheating tank 2. Namely, the liquid draining line 10 connects via the upstream side supply line 4 with a bottom side of the tubular flow passage 70, which is the heating liquid flow passage.

(23) The valve 11 corresponds to a second valve of the present invention. The valve 11 is usually in a closed state, and an opening/closing operation is controlled by the control unit 14 described below.

(24) It should be noted that the preheating tank 2 is arranged below the heating device 7 so that the sulfuric acid solution in the tubular flow passage 70 of the heating device 7 flows down by its own weight, and the sulfuric acid solution is collected via a part of the upstream side supply line 4 and the liquid draining line 10 in the preheating tank 2 when the sulfuric acid solution is drained as described below.

(25) Then, the connection position to the upstream side supply line 4 is at the highest position, and the connection position to the preheating tank 2 is at the lowest position on the liquid draining line 10. The height on the liquid draining line 10 preferably decreases gradually from the connection position to the upstream side supply line 4 to the connection position to the preheating tank 2. It should be noted that the liquid draining line 10 may include a portion which remains at the same height.

(26) One end of the atmosphere opening line 12 branches and is connected to the downstream side supply line 8 connected to the liquid outlet side of the tubular flow passage 70 on the downstream side of the thermometer 9. The other end of the atmosphere opening line 12 is connected via a valve 13 to the preheating tank 2. Namely, the atmosphere opening line 12 connects with a top side of the tubular flow passage 70, which is the heating liquid flow passage, via the downstream side supply line 8. The valve 13 corresponds to a first valve of the present invention. The valve 13 is usually in a closed state, and an opening/closing operation is controlled by the control unit 14.

(27) The valves 11 and 13 are connected to the control unit 14 in a controllable manner. The control unit 14 receives a measurement result by the flow meter 6 to control the opening/closing of the valves 11 and 13 in response to the measurement result.

(28) Moreover, the air pump 5 is connected to the control unit 14 in a controllable manner. The control unit 14 can transmit a control signal for controlling the pump flow rate of the air pump 5 to the air pump 5, and the control unit 14 can also transmit a control signal for stopping the power supply to the air pump 5 to stop the air pump 5 to the air pump 5.

(29) Moreover, the heating device 7 is connected to the control unit 14 in a controllable manner. The control unit 14 can transmit a control signal for controlling the heating temperature of the heating device 7 to the heating device 7, and the control unit 14 can also transmit a control signal for stopping the power supply to the heating device 7 to stop the heating device 7 to the heating device 7.

(30) The control unit 14 can function as a power supply control unit of the present invention for controlling the power supply to the heating device 7 and the power supply to the air pump 5.

(31) Moreover, an apparatus stop instruction unit (not shown) for providing the heating device 7 and the air pump 5 with stop instructions can be connected to the control unit 14. The operator provides the control unit 14 with the stop instruction via the apparatus stop instruction unit to stop the heating device 7 and the air pump 5.

(32) The heating apparatus according to the present invention is constructed by the heating device 7, the liquid draining line 10, the atmosphere opening line 12, the valves 11 and 13, the flow meter 6, and the control unit 14 according to the first embodiment.

(33) A description will now be given of an operation of the liquid heating apparatus shown in FIGS. 1 and 2.

(34) The stored sulfuric acid solution is heated to and is maintained at 90 to 120° C., for example, by the heater, which is not shown, in the preheating tank 2.

(35) The sulfuric acid solution in the preheating tank 2 is introduced by the air pump 5 via the upstream side supply line 4 into the liquid inlet side (bottom side) of the tubular flow passage 70 of the heating device 7. The sulfuric acid solution introduced into the bottom side of the tubular flow passage 70 generates an upward stream, rises in the tubular flow passage 70, and is discharged from the top side which is a liquid outlet side of the tubular flow passage 70. The sulfuric acid solution is heated by radiation heat of the heaters 72 and 73 while the sulfuric acid solution rises in and passes through the tubular flow passage 70. The sulfuric acid solution passes through a heat receiving area of the tubular flow passage 70, namely an area receiving the radiant heat from the heaters 72 and 73, in 0.5 to 10 seconds, for example. It should be noted that the temperature of the sulfuric acid solution introduced into the tubular flow passage 70 is 90 to 120° C. as a result of the heating by the preheating tank 2. The sulfuric acid solution discharged from the tubular flow passage 70 has a liquid temperature of 140 to 220° C., for example, as a result of the heating by the heaters 72 and 73.

(36) It should be noted that the control unit 14 maintains the valves 11 and 13 in the closed state while the defective liquid flow is not generated, and the sulfuric acid solution is heated by the heating device 7 as described above.

(37) The sulfuric acid solution discharged from the top side of the tubular flow passage 70 is supplied via the downstream side supply line 8 to the cleaning machine. The temperature of the sulfuric acid solution flowing through the downstream side supply line 8 is measured continuously or intermittently by the thermometer 9 to control the pump 5 and the heaters 72 and 73 so as to attain a predetermined temperature.

(38) Namely, the control unit 14 transmits a control signal for controlling a pump flow rate of the air pump 5 to the air pump 5 in response to a request from the cleaning machine or the like to control the pump flow rate of the air pump 5. Moreover, the control unit 14 receives a measurement result by the thermometer 9, and transmits a control signal for controlling the heating temperature by the heating device 7 to the heating device 7 in response to the measurement result to control the heating temperature by the heating device 7.

(39) An electronic material substrate such as a semiconductor wafer is cleaned by the sulfuric acid solution supplied from the downstream side supply line 8 in the cleaning machine.

(40) While the sulfuric acid solution is heated in the heating device 7 as mentioned above, a flow rate of the sulfuric acid solution flowing through the upstream side supply line 4 is continuously or intermittently measured in the flow meter 6. A supply state of the sulfuric acid solution supplied to the tubular flow passage 70 of the heating device 7 is monitored by the flow meter 6 in this way. A measurement result by the flow meter 6 is transmitted from the flow meter 6 to the control unit 14.

(41) The control unit 14 receives a measurement result by the flow meter 6, and determines a liquid flow state in the tubular flow passage 70 of the heating device 7 based on the measurement result. Specifically, the control unit 14 determines that the defective liquid flow occurs in the tubular flow passage 70 if the flow rate of the sulfuric acid solution measured by the flow meter 6 is zero or equal to or less than a predetermined value. It should be noted that the predetermined value is set in advance, and is stored in the nonvolatile memory of the control unit 14.

(42) If the control unit 14 determines that the defective liquid flow occurs, the control unit 14 generates a control signal for bringing the valves 11 and 13 from the closed state to the open state, and transmits the control signal to the valves 11 and 13 thereby bringing the valves 11 and 13 from the closed state to the open state. Simultaneously, the control unit 14 generates control signals for stopping the air pump 5 and the heating device 7, transmits the control signals to the air pump 5 and the heating device 7, thereby stopping the air pump 5 and the heating device 7. It should be noted that the air pump 5 may continue the operation for a certain period, and may then stop after the heating device 7 is stopped.

(43) When the valves 11 and 13 are brought into the open state by the control unit 14, an inside of the atmosphere opening line 12 connected to the preheating tank 2 opened to the atmospheric pressure is opened to the atmosphere. As a result, the inside of the tubular flow passage 70 is opened to the atmospheric pressure via the atmosphere opening line 12. The sulfuric acid solution in the tubular flow passage 70 is then drained so as to flow down by its own weight, and is collected via a part of the upstream side supply line 4 and the liquid draining line 10 in the preheating tank 2. As a result, even if the heating is being carried out by the heaters 72 and 73 or the residual heat remains after the heaters 72 and 73 stop, the sulfuric acid solution is prevented from boiling, and the generation of the overheated vapor is avoided. Control without the liquid draining can be carried out if defective liquid flow occurs in a state where the liquid is not overheated such as a case where a time has elapsed after the heaters 72 and 73 stopped. A case where a predetermined time has elapsed after the heaters 72 and 73 stop, a case where the liquid in a predetermined amount of the liquid has flowed through the tubular flow passage 70 after the heaters 72 and 73 stop, and a case where the residual heat temperature of the heating unit is equal to or less than a predetermined temperature can be mentioned as the case where the liquid draining is not carried out.

(44) A control logic of automatically bringing the valves 11 and 13 into the closed state upon a recovery from the trouble causing the defective liquid flow such as a power interruption is built into the control unit 14. Moreover, a control logic of maintaining the stop state of the air pump 5 and the heating device 7 is preferably built into the control unit 14 even upon the recovery from the trouble if the air pump 5 and the heating device 7 are stopped due to the trouble. As a result, it is possible to prevent a case where the sulfuric acid solution is supplied to the heating device 7 immediately after the recovery from the trouble, and the sulfuric acid solution instantaneously boils.

(45) When the temperature in the heating device 7 decreases as a result of release of the heat from the heating device 7 after the recovery from the trouble, the supply of the sulfuric acid solution can safely be resumed. If the temperature at a liquid contact portion in the heating device 7 is equal to or less than the boiling point of the sulfuric acid solution, though the sulfuric acid solution will not boil, it is generally difficult to directly measure the temperature of the liquid contact portion. Thus, preferably, a temperature at an intermediate portion such as a heat insulating material in the heating device 7 is measured, a worker or the like confirms that the temperature at the intermediate portion is sufficiently low compared with the boiling point of the sulfuric acid solution, thereby estimating that the temperature at the liquid contact portion is lower than the boiling point, the operation of the air pump 5 is restarted, and the operation of the heating device 7 is restarted.

(46) Moreover, when the operation of the liquid heating apparatus in which the heating device 7 and the air pump 5 are in the operating state is usually stopped, the worker provides the control unit 14 with a stop instruction via the apparatus stop instruction unit, which is not shown.

(47) When the control unit 14 receives the stop instruction from the apparatus stop instruction unit, the control unit 14 carries out control of stopping the power supply to the heating device 7 to stop the heating device 7, continuing the operation of the air pump 5, and then stopping the power supply to the air pump 5 to stop the air pump 5. After the predetermined time has elapsed from the stop of the heating device 7, after the predetermined amount of the sulfuric acid solution has flowed through the heating flow passage 70, or after the temperature of the sulfuric acid solution discharged from the heating device 7 has reached a temperature equal to or less than the predetermined temperature, the control unit 14 carries out control of stopping the power supply to the air pump 5 to stop the air pump 5.

(48) The heating device 7 and the air pump 5 are stopped, and the operation of the liquid heating apparatus is generally stopped in this way.

Second Embodiment

(49) A description will now be given of the liquid heating apparatus according to another embodiment of the present invention referring to FIG. 3. It should be noted that like configuration are denoted by like numerals as of the first embodiment, and a description thereof is therefore omitted or simplified.

(50) Though a description is given of the case where the supply state of the sulfuric acid solution supplied to the tubular flow passage 70 of the heating device 7 is monitored by the flow meter 6 in the first embodiment, a supply state of the sulfuric acid may be monitored by a pressure gauge for measuring a pneumatic pressure of the air pump 5.

(51) The liquid heating apparatus according to this embodiment is a liquid heating apparatus constructed by providing the liquid heating apparatus shown in FIGS. 1 and 2 with a pressure gauge 20 for measuring the pneumatic pressure of the air pump 5 in place of the flow meter 6, and monitors the supply state of the sulfuric acid solution by the air pump 20.

(52) The liquid heating apparatus according to this embodiment includes the pressure gauge 20 for measuring the pneumatic pressure of the air pump 5, and the pressure gauge 20 is connected to the air pump 5 as shown in FIG. 3. The pressure gauge 20 partially constructs the monitoring unit of the present invention.

(53) The pressure gauge 20 is connected to an uninterruptible power supply, which is not shown, and can operate by a power supply from the uninterruptible power supply during the power interruption.

(54) The pressure gauge 20 is connected to the control unit 14, and an output signal serving as a measurement result by the pressure gauge 20 is transmitted to the control unit 14.

(55) The valves 11 and 13 are connected to the control unit 14. The control unit 14 receives a measurement result by the pressure gauge 20, and transmits control signals to bring the valves 11 and 13 from the closed state to the open state to the valves 11 and 13 in response to the measurement result.

(56) A description will now be given of an operation of the liquid heating apparatus shown in FIG. 3.

(57) The heating of the sulfuric acid solution by the heating device 7 is carried out, and the heated sulfuric acid solution is supplied via the downstream side supply line 8 to the cleaning machine in the liquid heating apparatus shown in FIG. 3 as in the liquid heating apparatus shown in FIGS. 1 and 2. An electronic material substrate such as a semiconductor wafer is cleaned by the sulfuric acid solution supplied from the downstream side supply line 8 in the cleaning machine.

(58) While the sulfuric acid is heated in the heating device 7, the pneumatic pressure of the air pump 5 for feeding the sulfuric acid solution to the tubular flow passage 70 of the heating device 7 is continuously or intermittently measured in the pressure gauge 20. Namely, a supply state of the sulfuric acid solution supplied to the tubular flow passage 70 of the heating device 7 is monitored by the pressure gauge 20.

(59) The control unit 14 receives a measurement result by the pressure gauge 20, and determines the defective liquid flow in the tubular flow passage 70 of the heating device 7 based on the measurement result. Specifically, the control unit 14 determines that the defective liquid flow occurs in the tubular flow passage 70 if the pneumatic pressure measured by the pressure gauge 20 is zero or equal to or less than a predetermined value. Such a defective liquid flow can be generated by a trouble such as a stop or a decrease in output of the air pump 5 due to a power interruption, a failure, an error in the control logic, and the like as in the first embodiment. It should be noted that the predetermined value is set in advance, and is stored in the nonvolatile memory of the control unit 14.

(60) If the control unit 14 determines that the defective liquid flow occurs, the control unit 14 generates a control signal for bringing the valves 11 and 13 from the closed state to the open state, and transmits the control signals to the valves 11 and 13 thereby bringing the valves 11 and 13 from the closed state to the open state. Simultaneously, the control unit 14 generates control signals for stopping the air pump 5 and the heating device 7, transmits the control signals to the air pump 5 and the heating device 7, thereby stopping the air pump 5 and the heating device 7.

(61) When the valves 11 and 13 are brought into the open state by the control unit 14, the sulfuric acid solution in the tubular flow passage 70 flows down by its own weight, and is drained via the part of the upstream side supply line 4 and the liquid draining line 10 from the tubular flow passage 70, and is collected in the preheating tank 2 as in the first embodiment.

(62) The operation of the liquid heating apparatus shown in FIG. 3 can be normally stopped as in the case of the first embodiment.

(63) Moreover, though a description is given of the case where the pressure gauge 20 is provided in place of the flow meter 6, the pressure gauge 20 is provided along with the flow meter 6 provided as in the first embodiment, and the supply state of the sulfuric acid solution may be monitored by both thereof.

Third Embodiment

(64) A description will now be given of the liquid heating apparatus according to still another embodiment of the present invention referring to FIG. 4. Like configurations are denoted by like numerals as of the first and second embodiments, and a description thereof is therefore omitted or simplified.

(65) Though the valves 11 and 13, the flow meter 6, and the pressure gauge 20 are connected to the control unit 14 for the detection and the control according to the first and second embodiments, their operations stop during the power interruption. To address this problem, such a configuration is employed that they are connected to an uninterruptible power supply so as to operate even during the power interruption. However, the valves 11 and 13 and the like and the uninterruptible power supply need to be connected with each other via wiring cables or the like, the apparatus configuration becomes complex, and the cost slightly increases. The increase in complexity of the apparatus configuration and the slight increase in cost can be avoided by using, in place of the valves 11 and 13, valves each having a valve actuator including a failsafe mechanism for handling the power interruption.

(66) The liquid heating apparatus according to this embodiment uses, in place of the valves 11 and 13, valves 31 and 33 each having a valve actuator including a failsafe mechanism handling the power interruption in the liquid heating apparatus illustrated in FIGS. 1 and 2 in order to avoid the increase in complexity of the apparatus configuration and the slight increase in cost.

(67) As illustrated in FIG. 4, the valve 31 including the valve actuator is interposed in place of the valve 11 on the liquid draining line 10. The valve actuator of the valve 31 has a failsafe mechanism for maintaining the valve 31 in the closed state in the power supply state, which is the normal state, and opening the valve 31 from the closed state to the open state when the power interruption occurs. Moreover, the valve 31 can be operated also by the control signal from the control unit 14 as the valve 11.

(68) Moreover, the valve 33 including the valve actuator is provided in place of the valve 13 on the atmosphere opening line 12. The valve actuator of the valve 33 has a failsafe mechanism for maintaining the valve 33 in the closed state in the power supply state, which is the normal state, and opening the valve 33 from the closed state to the open state when the power interruption occurs. Moreover, the valve 33 can be operated also by the control signal from the control unit 14 as the valve 13.

(69) The flow meter 6 and the control unit 14 operate similarly to the flow meter 6 and the control unit 14 in the liquid heating apparatus shown in FIGS. 1 and 2, but they are not connected to an uninterruptible power supply.

(70) A description will now be given of the operation of the liquid heating apparatus illustrated in FIG. 4.

(71) The sulfuric acid solution is heated by the heating device 7 and the heated sulfuric acid solution is supplied to the cleaning machine via the downstream side supply line 8 in the liquid heating apparatus illustrated in FIG. 4 similarly to the liquid heating apparatus illustrated in FIGS. 1 and 2. An electronic material substrate such as a semiconductor wafer is cleaned by the sulfuric acid solution supplied from the downstream side supply line 8 in the cleaning machine.

(72) If a power interruption which abruptly stops the power supply to the air pump 5 and the like occurs while the sulfuric acid solution is heated by the heating device 7 as described above, the valve actuator of the valve 31 carries out the operation to bring the valve 31 from the closed state to the open state as a result of the action of the failsafe mechanism. The valve actuator of the valve 33 simultaneously carries out the operation to open the valve 33 from the closed state to the open state as the result of the action of the failsafe mechanism. The valves 31 and 33 are closed in the power supply state, and open when the power supply is interrupted.

(73) When the valves 31 and 33 are brought into the open state by the respective valve actuators, the sulfuric acid solution in the tubular flow passage 70 flows down by its own weight, and is collected via the part of the upstream side supply line 4 and the liquid draining line 10 in the preheating tank 2 as in the first embodiment. The sulfuric acid solution in the tubular flow passage 70 is drained to the outside of the tubular flow passage 70 in this way during the power interruption where the defective liquid flow occurs in the tubular flow passage 70.

(74) Moreover, the operation of the liquid heating apparatus shown in FIG. 4 can be normally stopped as in the case of the first embodiment.

Fourth Embodiment

(75) A description will now be given of the liquid heating apparatus according to yet another embodiment of the present invention referring to FIG. 5. Like configurations are denoted by like numerals as of the first to third embodiments, and a description thereof is therefore omitted or simplified.

(76) A difference in level is secured between the heating device 7 and the preheating tank 2, and the sulfuric acid solution in the tubular flow passage 70 flows down by its own weight, and is collected via the part of the upstream side supply line 4 and the draining line 10 in the preheating tank 2 for draining the liquid according to the first to third embodiments.

(77) However, there can be a case where the difference in level cannot be secured between the heating device 7 and the preheating tank 2 for the sake of the arrangement of the devices and the like. A collection container may be installed independently of the preheating tank 2 and the drained sulfuric acid solution may be collected in the collection container in this case.

(78) The liquid heating apparatus according to this embodiment has such a configuration that a collection container 40 for collecting the drained sulfuric acid solution is installed independently of the preheating tank 2.

(79) The preheating tank 2 is similarly installed below the heating device 7 in the liquid heating apparatus according to this embodiment as shown in FIG. 5. However, a sufficient difference in level for the sulfuric acid solution in the tubular flow passage 70 of the heating device 7 to flow down by its own weight and to be collected in the preheating tank 2 is not secured between the heating device 7 and the preheating tank 2.

(80) One end of the liquid draining line 10 branches and is connected to the upstream side supply line 4 on the downstream side of the flow meter 6 in the arrangement of the heating device 7 and the preheating tank 2 which do not secure a sufficient difference in level.

(81) A portion of the upstream side supply line 4 from the liquid inlet side of the bottom portion of the heating device 7 to the branch connection portion to the liquid draining line 10, and the liquid draining line 10 are preferably arranged vertically so that the sulfuric acid solution in the tubular flow passage 70 of the heating device 7 can flow down by its own weight when the sulfuric acid solution is drained.

(82) The collection container 40 is installed on a downstream end of the liquid draining line 10. The collection container 40 corresponds to a collection unit of the present invention. The sulfuric acid solution drained to the outside of the tubular flow passage 70 is collected via the part of the upstream side supply line 4 and the liquid draining line 10 into the collection container 40.

(83) A description is given of such a configuration that the tubular flow passage 70 in the heating device 7 is arranged in the vertical direction, the upstream side supply line 4 is connected to the bottom side of the tubular flow passage 70, the downstream side supply line 8 is connected to the top side, and the upward flow of the sulfuric acid solution is formed in the tubular flow passage 70 as shown in FIG. 2 according to the first to fourth embodiments.

(84) However, it is possible to employ such a configuration that a downward flow of the sulfuric acid solution is formed in the tubular flow passage 70 in place of the configuration for forming the upward flow. The upstream side supply line 4 is connected to the top side of the tubular flow passage 70, and the downstream side supply line 8 is connected to the bottom side in this case. Moreover, the liquid draining line 10 branches and is connected to the downstream side supply line 8 connected to the bottom side of the tubular flow passage 70. Moreover, the atmosphere opening line 12 branches and is connected to the upstream side supply line 4 connected to the top side of the tubular flow passage 70. As a result, the sulfuric acid solution in the tubular flow passage 70 can be caused to flow down by its own weight, and is drained to the outside of the tubular flow passage 70 also in such a configuration that the downward stream of the sulfuric acid solution is formed in the tubular flow passage 70. It should be noted that bubbles can reside in case of the downward flow, and the configuration for forming the upward steam is thus preferably used for a safer embodiment.

(85) Though a description is given of the embodiments of the present invention, the present invention is not limited to contents of the embodiments, and can be properly modified as long as the modification does not depart from the scope of the present invention.

EXAMPLE

Example

(86) A sulfuric acid solution of 86% by mass in sulfuric acid concentration was flowed through the tubular flow passage 70 of the heating device 7 at a flow rate of 1.5 L/min to heat the sulfuric acid solution in the liquid heating apparatus shown in FIGS. 1 and 2. The inlet temperature of the heating device 7 was 50° C. and the outlet temperature was 180° C. An emergency stop button was depressed to stop the liquid heating apparatus when the sulfuric acid solution was being heated. The emergency stop button is not described in each of the embodiments, and is an instruction button to stop the apparatus in emergency. The emergency stop immediately stopped the heaters 72 and 73 and the air pump 5, and the valves 11 and 13 were brought from the closed state to the open state. The open operation of the valves 11 and 13 may be controlled by the control unit 14 depending on the determination as the defective liquid flow in the liquid heating apparatus in FIG. 1, or may be carried out upon the power interruption by the fail safe mechanisms to open the valves 11 and 13 in the liquid heating apparatus in FIG. 2.

(87) When the valves 11 and 13 were opened, the sulfuric acid solution in the tubular flow passage 70 of the heating device 7 was immediately drained, and was collected in the preheating tank 2.

(88) After the sulfuric acid solution in the tubular flow passage 70 had completely been drained, the outlet temperature of the heating device 7 rose to 200° C., though which was extremely in a short period. It is considered that this is caused by such a phenomenon that residual vapor and the air present in the heating device 7 were heated and expanded, and a part thereof rose to an installed position of the thermometer.

(89) Then, the heating device 7 was cooled by radiation, an outer surface temperature of the quartz flow passage member constructing the tubular flow passage 70 decreased to a temperature equal to or less than 150° C., the supply of the sulfuric acid solution was resumed, the sulfuric acid solution passed through the tubular flow passage 70 of the heating device 7 without boiling, and the heating operation for the sulfuric acid solution could be resumed.

Comparative Example

(90) The normal heating operation for a sulfuric acid solution of 90% by mass in sulfuric acid concentration was carried out in the liquid heating apparatus shown in FIG. 5.

(91) It was assumed that the valves 11 and 13 were not provided, and the heater 72 and the air pump 5 were stopped while the valves 11 and 13 were maintained in the closed state. A part of the residual liquid abruptly boiled approximately 10 seconds after the stop, overheated vapor was then generated, and the outlet temperature of the heating device 7 reached 300° C. The temperature further rose, and when the temperature exceeded 350° C., a neighborhood of a joint constructed by a PFA tube provided at the outlet of the heating device 7 was eroded, and a sulfuric acid vapor spouted.

DESCRIPTION OF THE REFERENCE NUMERAL

(92) 2 preheating tank 3 atmosphere opening line 4 upstream side supply line 5 air pump 6 flow meter 7 heating device 9 thermometer 10 liquid draining line 11 valve 12 atmosphere opening line 13 valve 14 control unit 20 pressure gauge 31 valve 33 valve 40 collection container 70 tubular flow passage 71a inner tube wall 71b outer tube wall 72 heater 73 heater