JP2005061478A - Cryogenic liquid heating method and its device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cryogenic liquid heating method and its device capable of accurately heating cryogenic liquid with a wide range of a flow rate to 0 °C or higher in a simple device structure. <P>SOLUTION: In the cryogenic liquid heating method, numerous heat transfer tubes 14 are arranged within a vertical type exterior body 11, a heater 10 forming an inlet chamber 15 and an outlet chamber 16 is used on a top and a bottom of the heat transfer tube 14, cryogenic liquid such as ammonia liquid is flowed from the inlet chamber 15 to the heat transfer tube 14, and the cryogenic liquid is heated in the outlet chamber 16 at zero °C or more by supplying steam to an upper portion within the exterior body 11. A condensed water phase 41 and a gaseous phase 40 caused by steam are formed within the exterior body 11 of the heater 10. Condensed water in the condensed water phase 41 is drained to a pressurized drain tank 26, and inert gas is supplied to a gaseous phase 43 within the pressurized drain tank 26. A level L of the condensed water phase 41 in the heater 10 is adjusted in proportion to a flow rate of cryogenic liquid by adjusting its pressure of the drain tank 26. The condensed water in the drain tank 26 is discharged outside the drain tank 26 without any contact with the inert gas via a trap 28. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a low-temperature liquid heating method and apparatus for heating a low-temperature liquid such as ammonia liquid and LPG to 0 ° C. or higher with a heating source such as steam, and in particular, the flow rate of the low-temperature liquid is 100 to 25%. The present invention relates to a low-temperature liquid heating method and apparatus capable of accurately heating the same even if it fluctuates over a wide range.

  Usually, for example, when ammonia liquid (-33 ° C) is to be heated to 0 ° C or higher with steam using a shell and tube heat exchanger, it is heated with a hot water heating system and an intermediate heat medium heater. It has been known.

(1) Hot water heater and system When steam is used as a heat source, generally steam is blown into the circulating water and used as hot water, and this hot water is allowed to flow to the outer trunk side of a shell and tube heat exchanger. In the heat transfer tube to control the temperature of the cryogenic liquid at the outlet of the heat transfer tube.

(2) Intermediate heat medium type heater This is a system in which heat is transferred from a heating source (steam, etc.) to a cryogenic liquid via a heat medium. That is, the intermediate heat medium is evaporated with a heating source, and the low temperature liquid is condensed and heated with this vapor. For example, an ammonia solution is stored in a container to a certain level, a heat transfer tube is installed in the solution, ammonia is evaporated by steam, and the heat transfer tube of the low temperature liquid installed in the upper gas phase is condensed and heated. It is a heating method.

JP 11-210992 A

  However, the components of the system of (1) have a problem that the device configuration becomes complicated because a device for producing circulating water having a constant temperature by steam blowing, a hot water circulation pump, a heater, and the like are used as control instruments. In general, when a heater is manufactured in the form of a shell and tube, the flow rate fluctuation range in which the temperature of the heated fluid can be controlled with high accuracy is said to be about 70% to 100%, so a wide range of 25% to 100%. When the flow rate is changed, it is necessary to divide the flow into three units and select the number of bases used according to the change in the flow rate to control the temperature of the cryogenic liquid.

  Therefore, the system (1) has a problem that the number of installed devices is increased, the number of control points is increased, the installation area is increased, and the overall cost is increased.

  In the intermediate heat medium heater of (2), when the heating amount is large, the evaporator and the heater are separate heat exchangers. With this type of heater, the heating temperature can be accurately controlled in a wide range of flow rates, but since a heat medium is interposed in the middle, the temperature difference for heat transfer is doubled between the evaporation side and the heating side (condensation). Although there is no problem if it exists and operates at a constant flow rate, if there is a flow rate variation, it takes time to stabilize because the response is slow. In particular, the heat transfer coefficient of the heat medium used compared to steam is inferior to a fraction of both the heat transfer of evaporation and condensation, so the heat transfer area for both the evaporator and the heater is very large, and the container to store is also It becomes large. The shell needs to have a sufficient pressure resistance design when it reaches a normal temperature due to the properties of the heat medium used. For this reason, the cost is high. There is also a problem that the intermediate heat medium must be used by selecting a fluid that does not freeze with a low-temperature heat transfer tube.

  Accordingly, an object of the present invention is to solve the above-described problems and provide a low-temperature liquid heating method and apparatus capable of accurately heating a low-temperature liquid having a wide flow rate range to 0 ° C. or more with a simple apparatus configuration.

  In order to achieve the above object, a first aspect of the present invention provides a heater comprising a heat exchanger in which a large number of heat transfer tubes are provided in a vertical outer cylinder, and an inlet chamber and an outlet chamber are formed above and below the heat transfer tubes. In a low-temperature liquid heating method for flowing a low-temperature liquid such as ammonia liquid from an inlet chamber to a heat transfer tube, supplying steam to the upper part of the outer body and heating the low-temperature liquid to 0 ° C. or higher in the outlet chamber, A condensed water phase and a gas phase are formed in the outer shell by steam, and the condensed water in the condensed water phase is drained to the pressurized drainage tank, and the inert gas is supplied to the gas phase in the pressurized drainage tank and the pressure This is a low-temperature liquid heating method that adjusts the level of the condensed water phase in the heater quickly according to the flow rate of the low-temperature liquid, and in particular, to quickly adjust the liquid level when the flow rate decreases, Condensed water is drawn from the pressurized drainage tank. That.

  The invention according to claim 2 is the low-temperature liquid heating method according to claim 1, wherein the pressure in the pressurized drainage tank is controlled so that the gas phase in the pressurized drainage tank becomes a plus gauge pressure.

  The invention of claim 3 is a low-temperature liquid heating apparatus for heating a low-temperature liquid such as ammonia liquid to 0 ° C. or more with steam, and a plurality of heat transfer tubes are provided in a vertical outer body. A heater in which an inlet chamber and an outlet chamber are formed above and below, a supply line for supplying a cryogenic liquid such as ammonia liquid to the inlet chamber of the heater, an outlet line for the cryogenic liquid connected to the outlet chamber, and a heater A steam line for supplying steam to the upper part of the outer cylinder to form a condensed water phase and a gas phase in the outer cylinder, a drain discharge line for draining condensed water of the condensed water phase in the heater, and drain discharge A low-temperature liquid heating apparatus connected to a line and supplied with an inert gas and having a pressurized drainage tank for adjusting the level of condensed water in the heating chamber.

  According to a fourth aspect of the present invention, there is provided a cryogenic liquid heating apparatus according to the third aspect, wherein a cap-shaped trap is provided in the lower part of the pressurized drainage tank, and the discharge nozzle of the drain discharge line is provided in the trap. It is.

  In the invention of claim 5, the capacity of the pressurized drainage tank is set such that the liquid amount above the cap-shaped trap is larger than the volume corresponding to the change in the level of the condensed water phase in the heater. Item 5. The low-temperature liquid heating apparatus according to Item 3 or 4.

  In short, according to the present invention, the outlet temperature can be accurately heated within the set temperature range even if the flow rate of the low-temperature liquid changes in a wide range of 25% to 100%.

  Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

  In FIG. 1, reference numeral 10 denotes a heater, which is composed of a vertical shell and tube heat exchanger, and a plurality of heat transfer tubes 14 whose upper and lower sides are supported by tube plates 12 and 13 are provided in a vertical outer cylinder 11. The inlet chamber 15 is provided in the upper part, and the outlet chamber 16 is provided in the lower part.

  A supply line 17 for a low-temperature liquid such as ammonia liquid or LPG is connected to the inlet chamber 15, and a flow rate controller 18 and a flow rate control valve 19 whose opening degree is controlled by the flow rate controller 18 are provided in the supply line 17. It is done.

  A low-temperature liquid outlet line 20 is connected to the outlet chamber 16, and an outlet temperature controller 21 is connected to the outlet line 20.

  A steam line 22 as a heating source is connected to the upper portion of the outer cylinder 11, and a steam flow rate controller 23 and a steam flow rate control valve 24 whose opening degree is controlled by the steam flow rate controller 23 are connected to the steam line 22. The The detected temperature of the outlet temperature controller 21 of the outlet line 20 is input to the steam flow rate controller 23, and the steam flow rate controller 23 sets the flow rate and controls the steam flow rate control valve 24. .

  A drain discharge line 25 is connected to the lower portion of the outer trunk 11, and a pressurized drainage tank 26 is connected to the drain discharge line 25.

  As shown in FIGS. 1 and 2, the pressurized drainage tank 26 includes a sealed container 27, and a cap-shaped condensate trap 28 is provided therein. The drain discharge line 25 is provided so as to enter the sealed container 27 and reverse there to open the discharge nozzle 29 into the condensed water trap 28. Further, the condensed water trap 28 is provided such that a water collection port 31 of a drain drain line 30 provided so as to penetrate the bottom of the sealed container 27 is opened. A condensed water level control valve 32 is connected to the drain drain line 30. The condensed water level control valve 32 is controlled by a condensed water level controller 33 provided in the sealed container 27. The heater 10 is also provided with a liquid level controller 33a.

  An inert gas inlet line 34 of nitrogen or the like and an inert gas outlet line 35 are connected to the upper portion of the sealed container 27. The inert gas inlet line 34 is connected to a pressurized drainage tank pressure control valve 36, and this pressure control valve 36 is controlled by a pressurized drainage tank pressure regulator 37 provided at the upper part of the sealed container 27. . An excess pressure regulating valve 38 is connected to the inert gas outlet line 35.

  In the above, steam as a heating source is supplied from the steam line 22 into the outer body 11. This steam is adjusted to the steam flow rate installed in the steam line 22 via the flow rate controller 23 so that the outlet temperature becomes the set temperature based on the detected temperature of the outlet temperature controller 21 of the outlet line 20 for the cryogenic liquid. The valve 24 is controlled.

  The steam is separated into the gas phase 40 and the condensed water phase 41 in the outer cylinder 11, and most of the heating is performed in the gas phase portion 40, and heated to the final set temperature of the low-temperature liquid in the condensed water phase 41. The condensed water of the condensed water phase 41 is supplied from the drain discharge line 25 to the pressurized drainage tank 26.

  Condensation is achieved by adjusting the pressure and the gas phase capacity of the pressurized drainage tank 26 so that the pressure of the gas phase 40 of the outer shell 11 does not become a negative pressure even at the lowest flow rate and does not exceed the steam supply pressure even at the highest flow rate. The liquid level of the water phase 41 is adjusted, the volume of the gas phase 40 is adjusted, and the amount of heat exchange is adjusted at the same time. As shown in the figure, the flow rate of the low temperature fluid is, for example, the liquid level L100 at 100% load. The liquid level is adjusted in the range of the liquid level L50 at the time of 50% load, the liquid level L25 at the time of 25% load and the flow rate range of 100 to 25%.

  In this case, the liquid level of the pressurized drainage tank 26 is the lowest liquid level at the liquid level L25 at 25% load, and the highest liquid level at the liquid level L100 at 100% load. Accordingly, the capacity of the pressurized drainage tank 26 is such that the amount of liquid at the level above the trap 28 is greater than or equal to this variable volume. When the flow rate decreases, the liquid level of the condensed water phase 41 rises. However, since this amount of water is quickly replenished from the pressurized drainage tank 26, the temperature is accurately controlled because the time for setting the liquid level is short. The

  The level of the liquid phase 44 in the pressurized drainage tank 26 becomes the lowest when the level of the condensed water phase 41 in the outer shell 11 is L25. At this time, the gauge pressure of the gas phase 40 is made positive. Then, the control valve 36 is operated and adjusted by the inert gas pressure regulator 37 so that the pressure of the gas phase 43 of the pressurized drainage tank 26 is maintained. At the liquid level L100 at the time of 100% load, the volume of the gas phase 43 of the pressurized drainage tank 26 is minimized by the drainage from the outer cylinder 11 of the heater 10, so that the pressure of the compressed gas phase 43 is balanced. The pressurized drainage tank 26 determines the volume of the gas phase 43 at the lowest liquid level of the liquid phase 44 so that the pressure of the gas phase 40 does not exceed the supply pressure of steam.

  Low-temperature liquids such as ammonia liquid and LPG flow into the inlet chamber 15 from the supply line 17, flow into the outlet chamber 16 while flowing down through the heat transfer tubes 14, and are heated to 0 ° C. or higher from the outlet line 20. Supplied to the system.

  By condensing and heating the low-temperature liquid in the gas phase 40 with steam having a high heat transfer coefficient, the heat transfer area is reduced and the heating system is simplified to make the entire heater 10 compact.

  In order to prevent freezing of steam condensate on the surface of the heat transfer tube 14 due to the low temperature liquid, most of the low temperature liquid is heated with the heat of condensation of the high temperature steam. In this way, the outer surface of the heat transfer tube 14 is set to 0 ° C. or higher so that the condensed water is not frozen.

  The water condensed by heating the low temperature liquid in the gas phase 40 is accumulated in the condensed water phase 41, and the temperature of the low temperature liquid is controlled by heating the low temperature liquid with this condensed water.

  In the gas phase 40, heat transfer of about 85% of the heating amount is performed, and the remaining heat amount is transferred from the condensed water phase 41.

  Since the volume of the gas phase 40 for transferring most of the heating amount is relatively small, the pressure (condensation temperature) is likely to fluctuate due to fluctuations in the control valves 24, 19, 32 (steam, liquid level, ammonia flow rate, etc.) In addition, since the heat capacity of the gas phase 40 is small, the pressure (temperature) is likely to change, and heat transfer to the fluid is not stable.

  In order to relieve the temperature change of the gas phase 40, condensed water having a large heat capacity is accumulated in the lower part of the heater 10 to form a condensed water phase 41. The condensed water phase 41 has a heating temperature in the gas phase 40 set to a set value. When it drops further, it heats up, and when it gets higher, it cools down and relaxes the temperature change of the fluid.

  The condensed water in the condensed water phase 41 is discharged from the drain discharge line 25 to the bottom of the pressurized drainage tank 26.

  The pressure drainage tank 26 and the heater 10 adjust the liquid level by the liquid level control valve 32 via the controller 45 by the liquid level controllers 33 a and 33, and the pressure controller 37 and the liquid level controller 33. By controlling the pressure with the pressurized drainage tank pressure regulating valve 36 via the regulator 42, the heat transfer area of the heater 10 is changed to the required area corresponding to the heat transfer amount by entering and exiting the condensed water to and from the tank 26. The condensed water phase 41 is discharged out of the tank 26 through the drain drain line 30 while automatically adjusting so as to be.

  The inert gas is supplied to the gas phase 43 of the pressurized drainage tank 26 from the inert gas inlet line 34, and the pressure regulator 37 controls the pressure regulating valve 36, so that the pressure of the tank 26 becomes a positive gauge when the minimum liquid level is reached. Maintained at pressure.

  Since the condensed water from the heater 10 contains almost no inert gas such as air, a large amount of gas is absorbed when it comes into direct contact with the inert gas in the gas phase 43 at the liquid level of the pressurized drainage tank 26. If discharged as it is, the consumption of inert gas will increase. In order to reduce this consumption, the condensed water from the drain discharge line 25 is discharged into a trap 28 installed at the bottom of the tank 26 to prevent contact with the inert gas.

  That is, the condensed water from the heater 10 may be at a temperature higher than the condensed water (stored water) in the liquid phase 44 of the pressurized drainage tank 26 that is cooled by the outside air. In this case, the condensed water discharged into the trap 28 of the tank 26 tends to float on the liquid surface due to the difference in specific gravity due to temperature, but is prevented from floating because of the trap 28. As shown in FIG. 2, the difference in height h between the height of the discharge nozzle 29 into the trap 28 and the lowest position of the skirt of the trap 28 is determined by the condensed water from the nozzle 29 and the condensed water of the liquid phase 44 in the tank 26. If the difference is larger than the liquid column difference calculated from the specific gravity difference of (stored water), the condensate is blocked by the trap 28 and does not go out of the trap 28 and is discharged from the drain drain line 30 when a constant flow rate is applied. It will be. Accordingly, since the condensed water does not float on the liquid surface, there is almost no contact with the inert gas, and the amount of dissolution is reduced, so that the amount of consumption is very low.

  The liquid level of the pressurized drainage tank 26 is fixed at a certain level by selecting a preset value according to the flow range of the low temperature liquid. The temperature control of the low temperature liquid of the heater 10 in this flow rate range is performed by adjusting the pressure (temperature) of the gas phase 40 of the heater 10 with the temperature controller 21, the steam flow controller 23, and the steam flow control valve 24. Do it.

  When the supply pressure of the heated steam is 0.6 MPa, the flow range that can be adjusted by changing the condensation pressure (temperature) of the steam with a constant heat transfer area is 40 to 50%. If the flow rate range is 25% to 100%, the minimum number of steps is 2 to 3 in this case.

  In the set step, the liquid level of the condensate is kept constant and heated by a constant heat transfer surface of the gas phase 40. Therefore, the steam supply amount is adjusted for changes in the flow rate of the low temperature liquid. , Control the heating temperature by changing the condensation pressure (temperature) of steam. In this case, the heater 10 automatically creates an appropriate temperature difference to obtain the necessary heat transfer amount, and transfers the necessary heat amount to the cryogenic liquid. By detecting the heating temperature with the temperature controller 21 and adjusting the control value of the flow rate controller 23 to control the flow rate control valve 24, an amount of steam that matches the amount of heat transfer is fed into the heater 10.

  When the control value of the outlet temperature of the heater 10 is 25% compared to the flow rate of 100% due to the fluctuation of the flow rate control valve 24 due to the sensing delay of the temperature controller 21 or the vibration of the opening of the liquid level control valve 32 Usually varies greatly.

  When the low-temperature ammonia liquid (−33 ° C.) is heated, the heat transfer tube 14 in the condensed water provided to relieve the temperature change in which the gas phase 40 is finely moved, and the heat transfer area in the condensed water phase 41 and the gas phase 40. If the ratio of the heat transfer area inside is about 1: 1 to 1: 1.5 (at 100% flow rate), the outlet temperature can be accurately controlled even in the flow rate range of 25 to 100%.

  When the pressurized drainage tank 26 is made to have a positive gauge pressure with inert gas, the operation differential pressure of the liquid level control valve 32 can be increased, and the operation is stabilized. At the same time, the steam control valve 24 operates smoothly without vibration. Therefore, the entire apparatus can be operated stably.

  When the flow rate of the low-temperature liquid is changed beyond the liquid level set value of the heat transfer tube 14, it is necessary to quickly enter and exit the condensed water in the heater 10.

  The operating state in which the liquid level in the heater 10 is quickly adjusted is as follows.

  The drainage when the flow rate is increased can be dealt with by quickly changing the set values of the liquid level controllers 33 and 33a and operating the condensed water level control valve 32. Since the gas phase 43 of the pressurized drainage tank 26 is controlled by the pressure controller 37 and the pressure control valve 36 so as to maintain a certain pressure or higher, the gas phase 40 gauge pressure of the heater 10 becomes negative. There is no.

  When the flow rate decreases, water flows into the heater 10. For this purpose, a water amount equal to or greater than the fluctuation level of the liquid level is stored and placed in the pressurized drainage tank 26 so that the water flows backward. The backflow operation is performed in the following state. When the flow rate is decreased, the heat transfer area of the gas phase 40 of the heater 10 before the decrease is larger than the necessary heat transfer area after the decrease, so that the detected temperature of the temperature controller 21 at the outlet of the heater 10 is the flow rate. Since it rises with a decrease, the steam flow is reduced by the steam control valve 24 via the temperature controller 23.

  As a result, the pressure of the gas phase 40 of the heater 10 becomes lower than the pressure before the flow rate is reduced, so that the condensed water (stored water) 44 in the pressurized drainage tank 26 flows backward. Since the gas phase 43 of the pressurized drainage tank 26 is controlled by the pressure regulator 37 and the pressure regulator valve 36 so as to maintain a positive gauge pressure or higher even at the maximum volume, condensed water (stored water) is added to the heater 10. ) 44 does not cause negative pressure even if it flows backward. Therefore, the liquid level can be quickly adjusted regardless of the steam condensation rate.

  In order to keep the pressure of the gas phase 43 with an inert gas and the gauge pressure to a positive pressure, it does not suck in air and water that dissolves air during operation and stop, and there is no supply of oxygen Effective for preventing corrosion.

  Next, a more specific example of the present invention will be described.

The case where an ammonia liquid (-33 degreeC) is heated to 1 degreeC below is demonstrated.
(1) Outline of heater specifications An example of the steam pressure (temperature) with respect to the flow rate in the case of heating a low temperature ammonia liquid and the heat transfer area of the gas phase part and the liquid phase part are as follows.

Steam concentration pressure (partial pressure) and heater specifications:
Ammonia liquid flow rate kg / h 12,500
Inlet temperature ℃ -33
Outlet temperature ℃ 1
Ammonia liquid flow range% 25-100
Primary supply pressure of steam Saturated MPa 0.6
Gas phase pressure MPa 0.05-0.5
Inert gas in pressurized drainage tank Lower limit pressure MPa 0.05
Flow rate and heater level setting% Flow rate 100% 50% 25%
Liquid level setting% 60% 70% 81%
Steam pressure (temperature) and flow rate
Pressure MPa 0.4 0.25 0.15
Temperature 143.6 127.4 111.4
Gas phase heat transfer area m ² 3.37 2.53 1.60
Condensate heat transfer area m ² 5.05 5.89 6.82
Total heat transfer area m ² 8.42 8.42 8.42
Heat transfer tube dimensions
Heat transfer tube length m 5
Inner diameter m 0.038
Outer diameter m 0.045
Number of passes Vertical book 12
Steam supply control valve differential pressure MPa 0.2 0.35 0.45
(2) Description of Example Operation and function will be described in the case of heating a low-temperature ammonia liquid (−33 ° C.) based on the heater system flow of FIG. 1 and the trap details of the pressurized drainage tank of FIG.

1) Preparation for start-up Water is stored in the outer body 11 side of the heater 10 and the pressurized drainage tank 26.

  The condensate liquid level controller 33 is set so that the liquid level setting value of the heater 10 with respect to the flow rate is automatically switched.

  When the liquid level position of the pressurized drainage tank 26 is not at the same level as the liquid level of the heater 10, the liquid column height of the difference from the liquid level of the heater 10 is added to the liquid level position of the pressurized drainage tank 26. The liquid level position must be set in the liquid level controller 33 as a set value. When the condensed water level controller 33a is directly installed in the heater 10, no correction is necessary.

  The inert gas is automatically supplied to the set pressure (for example, 0.15 MPa) or more at the minimum liquid level by the pressurized drainage tank pressure controller 37 and the pressurized drainage tank pressure control valve 36 in the gas phase 43 of the pressurized drainage tank 26. Set to enter.

  The control value of the outlet temperature controller 21 is set to the heating control temperature (1 ° C.) of the ammonia liquid.

2) Operation The ammonia liquid is controlled in flow rate by the steam flow rate controller 23 and the steam flow rate control valve 24 and flows in from the upper part of the heat transfer tube 14 of the gas phase 40 of the heater 10.

  The flow rate of the ammonia liquid is gradually increased by the ammonia liquid flow rate controller 18 and the ammonia flow rate control valve 19 until a predetermined flow rate is reached.

  At this time, since the temperature of the outlet temperature controller 21 is usually higher than the heating control temperature (1 ° C.) due to the outside air temperature or the like, the steam flow rate adjusting valve 24 is closed. When the ammonia liquid begins to flow out of the heater 10, the temperature gradually decreases, and when the temperature falls below the control temperature, the steam flow rate adjustment valve 24 operates according to an instruction from the outlet temperature controller 21 to supply steam to the heater 10.

  By the inflow of steam, the condensed water in the heater 10 is pushed down to form a gas phase 40, which expands to the set position of the liquid level. The condensed water is controlled by a liquid level controller 33 and a liquid level control valve 32 attached to the pressurized drainage tank 26 and discharged outside the apparatus. During this operation, the temperature is always controlled to the set value (1 ° C.) by the outlet temperature controller 21, the low-temperature liquid flow controller 18, and the flow control valve 19.

  Usually, since the water temperature in the heater 10 is high, the ammonia liquid becomes a temperature higher than the set control temperature until the ammonia liquid is warmed with water and the water temperature reaches the balance temperature.

  At the time of start-up, the ammonia liquid flows out while cooling down the stored water in the heater 10 until it reaches the outlet temperature controller 21, so that it converges to the control temperature after the cool-down is completed.

  The ammonia liquid flowing into the heat transfer tube 14 of the gas phase 40 is heated with steam. The amount of heating with steam in the gas phase 40 is about 80% in the steady state after the cool-down. Condensed by heating (steam) falls to the water surface accumulated at the bottom and accumulates in layers in order on the liquid surface due to the difference in specific gravity.

  The ammonia liquid heated in the gas phase 40 flows into the heat transfer tube 14 installed in the stored water (condensed water) below the heater 10 and is heated by the condensed water. Since the condensed water is condensed at a temperature balanced with the pressure (partial pressure) of the steam in the gas phase 40, the water surface is in a high temperature state (about 110 to 140 ° C.). On the other hand, the ammonia liquid from the gas phase 40 is 0 ° C. or less, and the condensed water is in a temperature condition sufficient for heat transfer. Therefore, the heating of the ammonia liquid is performed based on the balance of the heat transfer amount in the gas phase 40 and the condensed water phase 41.

  Since the heat transfer tubes 14 in the condensed water phase 41 are arranged downward from the liquid level, the ammonia liquid in the heat transfer tubes 14 flows downward from the liquid level. On the other hand, the condensed water cooled by the heat transfer tube 14 becomes a downstream downstream due to a specific gravity difference, and heat exchange is performed in a co-current state. The temperature of the condensed water is lowered downward from the surface, and a laminar flow with a stable temperature gradient results in stable heat transfer.

  The heat transfer coefficient in the steam condensing region is large. When the steam conditions (pressure and temperature) change, the amount of heat transfer also changes greatly, so the heating temperature changes. Since the volume of the gas phase 40 of the heater 10 is usually very small, the pressure change cannot be alleviated even if the steam amount fluctuates slightly due to other changes in the control system. The small change in the temperature of the gas phase 40 is absorbed and relaxed by the condensed water phase 41 below the heater 10.

  Since the condensed water has a large heat capacity per unit volume, it can store a large amount of heat compared to steam. By utilizing this characteristic, a small change in the temperature of the ammonia liquid heated in the gas phase 40 can be absorbed by a small amount of the condensed water phase 41. Since the temperature of the condensate hardly changes when the temperature of the ammonia liquid changes for a short time, the temperature difference for heat transfer changes correspondingly to the change in the inlet temperature of the ammonia liquid, so the temperature difference for relaxation can be made quickly. Further, heating or cooling can be effectively performed. In this case, when the ratio of the heat transfer surface of the gas phase 40 to the transfer surface in the condensed water is about 1: 1 to 1: 1.5, the ammonia liquid can be heated to a stable temperature in a wide range of flow rates.

  The temperature of the outlet of the ammonia liquid at the heater 10 is detected by the temperature controller 21. When the temperature deviates from the control temperature, the flow rate control valve 24 is fed back to the flow controller 23 to control the steam amount to an appropriate flow rate. The temperature is controlled by controlling.

  The water condensed in the heater 10 is discharged to the pressurized drainage tank 26 through the drain drainage line 25 while maintaining a water surface level corresponding to the ammonia flow rate (step). The condensed water flowing into the pressurized drainage tank 26 is controlled by the liquid level controllers 33, 33 a and the liquid level control valve 32 so as to maintain an appropriate liquid level of the heater 10, and is discharged outside the tank 26. The

  If there is a level difference between the liquid level L of the heater 10 and the liquid level of the pressurized drainage tank 26, the level value for each flow range set in the liquid level controller 33 must be determined in consideration of this level difference. . When there is no difference between the two and when the liquid level controller 33 is installed in the heater 10, the level difference need not be considered.

  The condensed water sent to the pressurized drainage tank 26 is discharged into a trap 28 installed at the lower part of the tank 26. The trap 28 is blocked by the upper plate and the skirt of the trap 28 so that the high-temperature suspected water that has been sent does not diffuse directly into the stored water. The depth of the skat is set to be deeper than the weight of the stored water and the condensed water, and discharged from the drain drain line 30 inserted at the same level as the level of the discharge nozzle 29 without exiting the trap 28. . When the temperature of the condensed water is lower than that of the stored water, the condensed water accumulates at the bottom of the tank 26 due to the difference in specific gravity, and is discharged from the drain drain line 30 by the liquid level control valve 32 without contacting the inert gas.

  The set liquid level by the liquid level controller 33 or 33a has the following three stages in the example.

Ammonia flow rate 25% 50% 100%
Condensed water level (in the heater) 81% 70% 60%
The liquid level setting value (in the above table) of the liquid level controller 33 or 33a automatically changes according to the change in the flow rate range. With regard to the flow rate before and after the set value, the steam condensing pressure (temperature) is automatically adjusted to the pressure (temperature) required for the amount of heat transfer, and functions.

  By pressurizing the pressurized drainage tank 26 with an inert gas, the heat transfer portion of the heater 10 is pressurized to prevent air from entering (preventing corrosion) and stabilize the heat transfer. The differential pressure can be increased to make the operation smooth even for large fluctuations in the amount of condensed water.

  The inert gas in the gas phase 43 of the pressurized drainage tank 26 gradually dissolves and diffuses in the condensed water and is lost together with the drainage, so that the gas phase pressure is lowered. When the pressure is reduced to the lower limit (usually about 0.5 to 0.1 MPa), the inert gas is sent to the pressure corresponding to each set liquid level by the pressure control valve 36.

  A minute vent hole is formed in the upper plate of the trap 28 or in the vicinity of the skirt plate so that the gas in the trap 28 can escape.

It is a figure which shows one embodiment of this invention. It is a figure which shows the detail of the pressurized drainage tank in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Heater 11 Outer cylinder 14 Heat exchanger tube 15 Inlet chamber 16 Outlet chamber 26 Pressurized drainage tank 40 Gas phase 41 Condensed water phase 43 Gas phase

Claims (5)

  A low-temperature liquid such as ammonia liquid is provided from the inlet chamber to the heat transfer tube by using a heater consisting of a heat exchanger in which a large number of heat transfer tubes are provided in the vertical outer cylinder and an inlet chamber and an outlet chamber are formed above and below the heat transfer tubes. In the low-temperature liquid heating method for supplying the steam to the upper part in the outer cylinder and heating the low-temperature liquid to 0 ° C. or higher in the outlet chamber, the condensed water phase and the gas phase by the steam are put in the outer cylinder of the heater. The condensed water phase is drained into the pressurized drainage tank, and the inert gas is supplied to the gas phase in the pressurized drainage tank and the pressure is adjusted to adjust the level of the condensed water phase in the heater. A method for heating a low-temperature liquid, comprising adjusting the flow rate of the low-temperature liquid.   The low-temperature liquid heating method according to claim 1, wherein the pressure in the pressurized drainage tank is controlled so that the gas phase in the pressurized drainage tank becomes a plus gauge pressure.   In a low-temperature liquid heating apparatus for heating a low-temperature liquid such as ammonia liquid to 0 ° C. or higher with steam, a large number of heat transfer tubes are provided in a vertical outer cylinder, and an inlet chamber and an outlet chamber above and below the heat transfer tubes A heater, a supply line for supplying a cryogenic liquid such as ammonia liquid to the inlet chamber of the heater, an outlet line for the cryogenic liquid connected to the outlet chamber, and a steam in the upper part of the outer shell of the heater A steam line for forming a condensed water phase and a gas phase in the outer shell, a drain discharge line for draining condensed water of the condensed water phase in the heater, and an inert gas connected to the drain discharge line And a pressurized drainage tank for adjusting the level of condensed water in the heating chamber.   The low-temperature liquid heating apparatus according to claim 3, wherein a cap-shaped trap is provided at a lower portion in the pressurized drainage tank, and a discharge nozzle of the drain discharge line is provided so as to be positioned in the trap. 5. The low temperature according to claim 3, wherein the capacity of the pressurized drainage tank is set such that the amount of liquid above the cap-shaped trap is larger than the volume corresponding to the change in the level of the condensed water phase in the heater. Liquid heating device.

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