Steam generator

Abstract

To provide a steam generator which can prevent a temperature of a heat transfer surface of an evaporator from increasing excessively during start of circulation of a liquid material.SOLUTION: A steam generator includes: a gas-liquid separator 10 having a first storage part 11a forming a space for storing a liquid material La, a liquid material supply part 12 configured to supply the liquid material La to the first storage part 11a, and a gas discharge part 13 serving as a discharge path of a gas in the first storage part 11a; an evaporator 20 having a second storage part 21a forming a space for storing the liquid material La, and heating means 23 configured to heat the liquid material La in the second storage part 21a; a lower pipe 30 serving as a passage that allows a lower part of the first storage part 11a and a lower part of the second storage part 21a to communicate with each other; an upper pipe 40 serving as a passage which allows an upper part of the second storage part 21a and an upper part of the first storage part 11a to communicate with each other; and a noncondensable gas supply part 50 which supplies a noncondensable gas Gb to the second storage part 21a or the lower pipe 30.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a steam generator that obtains steam made of a desired material by utilizing the thermosiphon phenomenon.

Background Art

[0002] For example, in an industrial plant or the like, when obtaining steam made of a desired material by heating and vaporizing a liquid material, a thermosiphon type steam generator as shown in Patent Document 1 may be used.

[0003] Fig. 3 shows an overview of a thermosiphon type steam generator. The steam generator 100 has a gas-liquid separator 101 and an evaporator 102. The lower parts and the upper parts of the gas-liquid separator 101 and the evaporator 102 are connected by a lower pipe 103 and an upper pipe 104 respectively, and a flow path is formed that loops through the gas-liquid separator 101, the lower pipe 103, the evaporator 102, and the upper pipe 104. A liquid material supply part 105 for supplying a liquid material La to the gas-liquid separator 101 and a gas discharge part 106 for discharging the gas in the gas-liquid separator 101 are provided. The liquid material La supplied from the liquid material supply part 105 is stored in the gas-liquid separator 101 and the evaporator 102.

[0004] In this state, when the evaporator 102 is heated and the temperature of the liquid material La in the evaporator 102 reaches near the boiling point, bubbles Ba made of the vaporized liquid material La are generated from within the liquid material La and steam V is released. This steam V flows into the gas-liquid separator 101 through the upper pipe 104 and is discharged from the gas discharge part 106 of the gas-liquid separator 101. By recovering this steam V, desired steam made of the vaporized liquid material La can be obtained.

[0005] Furthermore, at this time, the apparent density of the liquid material La in the evaporator 102 decreases due to the generation of bubbles Ba, creating a density difference between it and the liquid material La in the gas-liquid separator 101. As a result, liquid material La flows in from the gas-liquid separator 101 side, pushing the liquid material La in the evaporator 102 upwards and flowing into the gas-liquid separator 101 through the upper piping 104. In other words, a configuration is established in which the liquid material La circulates through the gas-liquid separator 101, the lower piping 103, the evaporator 102, and the upper piping 104. Therefore, in such a thermosiphon-type steam generator 100, by continuously heating the evaporator 102, the desired steam consisting of vaporized liquid material La can be obtained without using a pump, while the liquid material La self-circulates. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2010-169364 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] However, with the above-described steam generator 100, there was a risk that the evaporator 102 would malfunction due to excessive temperature, or that the liquid material La would deteriorate, making it impossible to obtain the desired steam. Specifically, in the initial heating stage, even when the evaporator 102 was heated, there was no flow of the liquid material La inside the evaporator 102, resulting in a poor heat transfer coefficient. As a result, the surface temperature of the heat transfer surface of the evaporator 102 rose too high. Consequently, the temperature of the evaporator 102 and the temperature of the liquid material La near the heat transfer surface became excessive, leading to problems such as the evaporator 102 malfunctioning or the liquid material La deteriorating.

[0008] In view of the above-mentioned problems, the present invention aims to provide a steam generator that can prevent the heat transfer surface temperature of the evaporator from becoming excessive when the circulation of liquid material is started. [Means for solving the problem]

[0009] To solve the above problems, the steam generator of the present invention includes a gas-liquid separator having a first storage section which is a space for storing liquid material, a liquid material supply section which supplies the liquid material to the first storage section, and a gas discharge section which is a gas discharge path for the gas in the first storage section; an evaporator having a second storage section which is a space for storing the liquid material, and a heating means for heating the liquid material in the second storage section; and a lower piping which is a flow path connecting the lower part of the first storage section and the lower part of the second storage section. The device further comprises an upper pipe which is a flow path connecting the upper part of the storage section and the upper part of the first storage section, wherein a circulation path for the liquid material is formed by the first storage section, the lower pipe, the second storage section, and the upper pipe, and a non-condensable gas supply section is provided to supply non-condensable gas to the second storage section or the lower pipe by discharging vapor generated from the liquid material in the second storage section heated by the heating means through the upper pipe and the gas discharge section.

[0010] In the steam generator of the present invention, by having a non-condensable gas supply unit, the supplied non-condensable gas helps to reduce the apparent density of the liquid material in the second storage unit, thereby forcibly initiating the circulation of the liquid material and preventing the heat transfer surface temperature of the evaporator from becoming excessive.

[0011] Furthermore, the non-condensable gas is preferably an inert gas.

[0012] By doing so, chemical reactions between the non-condensable gas and the liquid material are prevented, and the desired vapor can be obtained.

[0013] Furthermore, the gas discharge unit may further include a non-condensable gas separation unit that separates the non-condensable gas mixed in with the steam from the steam.

[0014] By doing so, non-condensable gases can be separated from the gas discharged from the gas outlet, and only the desired vapor can be obtained.

[0015] Furthermore, the non-condensable gas supply unit is preferably configured to stop supplying the non-condensable gas in synchronization with the start of circulation of the liquid material.

[0016] This reduces the amount of non-condensable gas mixed in with the gas discharged from the gas outlet. [Effects of the Invention]

[0017] The steam generator of the present invention makes it possible to prevent the heat transfer surface temperature of the evaporator from becoming excessive when the circulation of liquid material is started. [Brief explanation of the drawing]

[0018] [Figure 1] This diagram illustrates a steam generator in one embodiment of the present invention. [Figure 2] This is a cross-sectional view illustrating the inside of the steam generator of this embodiment. [Figure 3] This is a diagram illustrating a conventional steam generator. [Modes for carrying out the invention]

[0019] A steam generator in one embodiment of the present invention will be described with reference to Figure 1.

[0020] The steam generator 1 comprises a gas-liquid separator 10, an evaporator 20, a lower pipe 30, and an upper pipe 40, forming a flow path through which the liquid material La circulates. When the evaporator 20 is heated, the liquid material La inside the evaporator 20 is heated to near its boiling point, causing a thermosiphon effect. That is, as the liquid material La circulates in the flow path, the gas containing the vaporized liquid material La from the evaporator 20 flows through the upper pipe 40 into the gas-liquid separator 10. The gas that flows into the gas-liquid separator 10 is discharged from a gas discharge section 13, which is a gas discharge path located at the top of the gas-liquid separator 10, and by recovering this steam, steam V containing the vaporized liquid material La can be obtained.

[0021] Further, a non-condensable gas supply unit 50 is connected to the lower piping 30, and non-condensable gas Gb is supplied from the non-condensable gas supply unit 50 toward the evaporator 20.

[0022] The gas-liquid separator 10 is a container to which a liquid material La is supplied and from which vapor containing the vaporized liquid material La is discharged from the vapor generator 1, and includes a container portion 11, a liquid material supply portion 12, and a gas discharge portion 13.

[0023] The container portion 11 is a container that stores a relatively low-temperature liquid material La, and a first storage portion 11a that is a space for storing the liquid material La is formed inside. In the present embodiment, a residue discharge portion 15 is connected to the substantially lower end portion of the first storage portion, and when an opening / closing valve 16 provided in the middle of the residue discharge portion 15 is opened, the residue (such as concentrated liquid material La) remaining in the first storage portion 11a after the vapor generator 1 has been used for a long time is discharged to the outside of the first storage portion 11a. Usually, the opening / closing valve 16 is in a closed state.

[0024] The liquid material supply portion 12 is a mechanism that communicates with the first storage portion 11a and supplies the liquid material La to the first storage portion 11a. In operating the vapor generator 1, in order to store an amount of the liquid material La necessary for causing a thermosyphon phenomenon in the vapor generator 1 in the first storage portion 11a and a second storage portion 21a described later, the liquid material La is supplied to the first storage portion 11a, and the liquid material La is also supplied to the second storage portion 21a via the first storage portion 11a and the lower piping 30 described later.

[0025] Further, while the thermosyphon phenomenon is occurring, since a part of the liquid material La is discharged as vapor, the supply amount by the liquid material supply portion 12 is controlled so that the liquid material La equivalent to the discharge amount is replenished to the first storage portion 11a, whereby the amount of the liquid material La in the vapor generator 1 is maintained constant.

[0026] The gas discharge section 13 is a piping path that communicates with the approximate upper end of the first storage section 11a, and the gas filling the first storage section 11a is discharged to the outside of the steam generator 1 via this gas discharge section 13. In this embodiment, a non-condensable gas separation section 14 is also located in the middle of the gas discharge section 13 to separate the non-condensable gas Gb supplied from the non-condensable gas supply section 50 (described later) from the gas passing through the gas discharge section 13.

[0027] The evaporator 20 is a separate container from the gas-liquid separator 10 that heats the liquid material La to near its boiling point and partially evaporates it, and has a container section 21 and a heating means 23. As mentioned above, the evaporator 20 and the gas-liquid separator 10 are connected by lower piping 30 and upper piping 40. The liquid material La is supplied to the evaporator 20 from the liquid material supply section 12 via the first storage section 11a of the gas-liquid separator 10 and the lower piping 30, and the steam generated in the evaporator 20 is sent to the first storage section 11a via the upper piping 40.

[0028] The container section 21 is a container for storing liquid material La, and a second storage section 21a, which is a space for storing liquid material La, is formed inside. In this second storage section 21a, the liquid material La is heated to near its boiling point. At that time, the container section 21 expands due to thermal expansion, so to prevent the lower piping 30, upper piping 40, etc. from being subjected to load due to dimensional changes caused by thermal expansion, an expansion joint 22 is provided in the container section 21 to absorb the dimensional changes.

[0029] In this embodiment, the heating means 23 has a heat medium inlet 23a and a heat medium outlet 23b. The heat medium inlet 23a and heat medium outlet 23b are the inlet and outlet of a heat medium H having a temperature higher than the boiling point of the liquid material La. Although not shown in the figures, the flow path of the heat medium H between the heat medium inlet 23a and the heat medium outlet 23b is routed adjacent to the second storage section 21a. As a result, the heat medium H enters from the heat medium inlet 23a, heats the liquid material La in the second storage section 21a by heat exchange, and exits from the heat medium outlet 23b.

[0030] Furthermore, the flow path for the heat transfer medium H and the second storage section 21a are completely separated and not in communication with each other, so the heat transfer medium H does not mix with the liquid material La. Also, the heat transfer medium H is continuously supplied, at least while the steam generator 1 is operating. If thermal energy discharged from other processes (such as combustion exhaust gas) is used as the heat transfer medium H, the steam generator 1 can be operated with virtually zero energy.

[0031] Here, the heating rate of the liquid material La can be adjusted by adjusting the flow rate of the heat transfer medium H. Therefore, even under conditions where the amount of liquid material La supplied from the liquid material supply unit 12 cannot be adjusted, the amount of liquid material La in the steam generator 1 can be kept constant by adjusting the flow rate of the heat transfer medium H.

[0032] The lower piping 30 is a pipe that forms a flow path connecting the lower part of the first storage section 11a and the lower part of the second storage section 21a, enabling the liquid material La to move back and forth between the first storage section 11a and the second storage section 21a. In this embodiment, after the thermosiphon phenomenon occurs, it becomes a flow path for the liquid material La from the first storage section 11a to the second storage section 21a.

[0033] The upper piping 40 is a pipe that forms a flow path connecting the upper part of the first storage section 11a and the upper part of the second storage section 21a, and enables the movement of liquid material La between the first storage section 11a and the second storage section 21a. In this embodiment, after the thermosiphon phenomenon occurs, it becomes a flow path exclusively for liquid material La and evaporated liquid material La from the second storage section 21a to the first storage section 11a.

[0034] As described above, a looping flow path is formed by the first storage section 11a, the lower pipe 30, the second storage section 21a, and the upper pipe 40.

[0035] In this embodiment, the non-condensable gas supply unit 50 is a piping path connected to the lower piping 30, and supplies non-condensable gas Gb to the liquid material La in the lower piping 30. The non-condensable gas Gb supplied to the liquid material La in the lower piping 30 is made of a different material from the liquid material La, and is a gas that does not condense (liquefy) at least in the operating environment of the vapor generator 1, and rises in the liquid material La by forming bubbles. In this embodiment, the non-condensable gas Gb is an inert gas such as nitrogen or argon. Therefore, it is possible to prevent chemical reactions from occurring between the liquid material La and the non-condensable gas Gb.

[0036] Furthermore, in this embodiment, the tip of the non-condensable gas supply unit 50 is formed to face upward toward the second storage unit 21a, as shown in Figure 2. This prevents the non-condensable gas Gb from being released to the first storage unit 11a through the lower piping 30, and ensures that almost all of the non-condensable gas Gb is directed toward the second storage unit 21a.

[0037] Furthermore, in this embodiment, the non-condensable gas supply unit 50 constantly supplies non-condensable gas Gb while the steam generator 1 is in operation.

[0038] Next, the operation of the steam generator 1 in the present invention will be explained using Figure 2, a cross-sectional view of the steam generator 1.

[0039] In order to generate the thermosiphon phenomenon in the steam generator 1, first, as shown by the dashed lines in Figure 1, liquid material La is supplied from the liquid material supply unit 12 so that the liquid material La reaches a predetermined level in the first storage unit 11a and the second storage unit 21a.

[0040] Next, the supply of the heat transfer medium H to the heating means 23 of the evaporator 20 is started, thereby initiating the heating of the liquid material La in the second storage section 21a.

[0041] As the heating of the liquid material La in the second storage section 21a progresses and the temperature of the liquid material La reaches near its boiling point, bubbles Ba are generated from the vaporized liquid material La and rise within the liquid material La. When the bubbles Ba reach the liquid surface of the liquid material La, vapor consisting of the vaporized liquid material La is released.

[0042] When bubbles Ba are generated, the apparent density of the liquid material La in the second storage section 21a decreases due to the presence of bubbles Ba, creating a density difference between the liquid material La in the second storage section 21a and the liquid material La in the first storage section 11a. As a result, liquid material La flows in from the first storage section 11a, causing a flow from bottom to top of the liquid material La in the second storage section 21a. This flow increases the heat transfer coefficient, promoting heat supply from the heat transfer surface of the evaporator 20, and increasing the amount of bubbles Ba generated. As the amount of bubbles Ba increases, the apparent density decreases further, and the flow from bottom to top becomes more intense. This process repeats, resulting in a constant natural circulation flow rate.

[0043] The liquid material La and bubbles Ba that flow from the upper piping 40 into the first storage section 11a are separated into gas and liquid within the first storage section 11a. Specifically, the high-temperature liquid material La is mixed with the liquid material La stored in the first storage section 11a, and the vaporized liquid material La that formed bubbles Ba is released as steam within the first storage section 11a and discharged to the outside of the steam generator 1 via the gas discharge section 13.

[0044] In this embodiment, a baffle plate 17 is provided near the connection point between the upper pipe 40 and the first storage section 11a in order to prevent droplets of the liquid material La from being carried into the steam. As a result, the liquid material La containing bubbles Ba that flows in from the upper pipe 40 first hits the baffle plate 17, and the upward momentum of the liquid material La is canceled out.

[0045] Furthermore, as the vapor of the liquid material La is discharged from the gas discharge section 13, the amount of liquid material La in the vapor generator 1 decreases, so liquid material La is supplied from the liquid material supply section 12 to replenish it.

[0046] As described above, when a difference in the apparent density of the liquid material La occurs between the first storage section 11a and the second storage section 21a, the low-temperature liquid material La flows from the first storage section 11a to the second storage section 21a through the lower pipe 30, and the high-temperature liquid material La containing bubbles Ba flows from the second storage section 21a to the first storage section 11a through the upper pipe 40, thereby forming a self-circulating system of the liquid material La in the order of first storage section 11a, lower pipe 30, second storage section 21a, upper pipe 40, and first storage section 11a.

[0047] At this point, when the difference between the apparent density of the liquid material La in the second storage section 21a of the evaporator 20 and the apparent density of the liquid material La in the first storage section 11a, and the pressure loss due to natural circulation flow are balanced, a stable system is formed in which the liquid material La circulates and vapor is discharged by the thermosiphon effect.

[0048] On the other hand, in order for the liquid material La to circulate as described above, it is necessary for the liquid material La in the second storage section 21a to reach its boiling point, for bubbles Ba to be generated, and for the generated bubbles Ba to carry the liquid material La to the gas-liquid separator 10 side through the upper piping 40.

[0049] In this invention, as described above, non-condensable gas Gb is supplied from the non-condensable gas supply unit 50 to the lower piping 30. Since this non-condensable gas Gb is a gas that does not condense (liquefy) in the operating environment of the steam generator 1, the non-condensable gas Gb supplied to the lower part of the second storage unit 21a through the lower piping 30 exists as bubbles in the liquid material La, as shown by the hatched bubbles Bb in Figure 2, and rises within the liquid material La in the second storage unit 21a. At that time, the flow of liquid material La increases the heat transfer coefficient of the heat transfer surface of the evaporator 20, thereby improving heat transfer from the evaporator 20 to the liquid material La, and the early generation of bubbles Ba can be expected. Furthermore, the presence of bubbles Bb, like the presence of bubbles Ba, contributes to a decrease in the apparent density of the liquid material La.

[0050] Therefore, by supplying non-condensable gas Gb as in the present invention and causing bubbles Bb to rise in the second storage section 21a, it is possible to start the circulation of the liquid material La in a shorter time from the start of heating compared to the case without a non-condensable gas supply section 50. That is, the heat transfer surface temperature of the evaporator 20 is relatively low when circulation in the second storage section 21a starts, and thus it is possible to prevent overheating of the liquid material La.

[0051] Furthermore, in this embodiment, a perforated plate 24 is provided below the container section 21 so that bubbles Bb can be uniformly supplied horizontally (in the XY direction in Figure 2) to the liquid material La in the second storage section 21a. The evaporator 20 is generally composed of a large number of heat transfer tubes, and the aim is to uniformly distribute the non-condensable gas to each heat transfer tube.

[0052] As described above, by making the circulation start temperature of the liquid material La relatively low, it is possible to prevent malfunctions caused by the evaporator 20 itself becoming too hot.

[0053] Furthermore, if the vapor is obtained for a liquid material La whose quality is affected by temperature history, such as undergoing deterioration at high temperatures, then, as described above, suppressing the overheating of the liquid material La at the start of circulation can contribute to stabilizing the quality.

[0054] Furthermore, since it is possible to generate bubbles of Ba relatively quickly after heating, the time from the start of heating to reaching the circulation start temperature can be shortened, and the thermosiphon system stabilizes more quickly.

[0055] On the other hand, in this embodiment, since non-condensable gas Gb is always supplied from the non-condensable gas supply unit 50 while the steam generator 1 is operating, the steam V' that has just been discharged from the first storage unit 11a to the gas discharge unit 13 contains non-condensable gas Gb in addition to the vaporized liquid material La. For this reason, in this embodiment, a non-condensable gas separation unit 14 is provided in the middle of the gas discharge unit 13 to separate the non-condensable gas Gb from the steam V'. In this embodiment, the non-condensable gas separation unit 14 is a filter that absorbs non-condensable gas Gb, and the steam V that has passed through this non-condensable gas separation unit 14 does not contain non-condensable gas Gb, so a steam derived from the liquid material La with high purity can be obtained.

[0056] The steam generator described above makes it possible to prevent the heat transfer surface temperature of the evaporator from becoming excessive when the circulation of liquid material begins.

[0057] Herein, the steam generator of the present invention is not limited to the form described above, but may be of other form within the scope of the present invention. For example, in the above description, the non-condensable gas supply unit 50 is connected to the lower piping 30, but it is not limited to this, and for example, the non-condensable gas supply unit 50 may be provided in the evaporator 20 and the non-condensable gas Gb may be supplied directly to the second storage unit 21a. In this case, it is preferable that it be provided as far below the evaporator 20 as possible in order to properly circulate the high-temperature liquid material La in the second storage unit 21a.

[0058] Furthermore, in the above explanation, non-condensable gas Gb is continuously supplied from the non-condensable gas supply unit 50 even while the thermosiphon phenomenon is occurring. However, the supply of non-condensable gas Gb may be stopped in synchronization with the start of circulation of the liquid material La. By doing so, even if the non-condensable gas separation unit 14 is not provided in the gas discharge unit 13, the amount of non-condensable gas Gb mixed in with the gas discharged from the gas discharge unit 13 can be reduced. Note that synchronization includes meanings other than simultaneous, for example, the supply of non-condensable gas Gb may be stopped one minute after circulation starts. [Explanation of symbols]

[0059] 1. Steam generator 10 Gas-liquid separator 11 Container section 11a First storage section 12 Liquid material supply section 13 Gas discharge section 14 Non-condensable gas separation section 15 Residue discharge section 16. On / off valve 17 Obstacle board 20 Evaporator 21 Container section 21a Second storage section 22 Expansion 23 Heating means 23a Heat medium inlet 23b Heat medium outlet 24 perforated plates 30 Lower piping 40 Upper piping 50 Non-condensable gas supply unit 100 Steam generator 101 Gas-liquid separator 102 Evaporator 103 Lower piping 104 Upper piping 105 Liquid material supply section 106 Gas discharge section Ba bubbles Bb bubbles Gb non-condensable gas H heating medium La liquid material V Steam

Claims

1. A gas-liquid separator having a first storage section which is a space for storing liquid material, a liquid material supply section which supplies the liquid material to the first storage section, and a gas discharge section which is a gas discharge path within the first storage section, An evaporator having a second storage section which is a space for storing the liquid material, and a heating means for heating the liquid material in the second storage section, A lower pipe which is a flow path connecting the lower part of the first storage section and the lower part of the second storage section, An upper pipe which is a flow path connecting the upper part of the second storage section and the upper part of the first storage section, The first storage section, the lower piping, the second storage section, and the upper piping form a circulation path for the liquid material, and the vapor generated from the liquid material in the second storage section, which is heated by the heating means, is discharged from the gas discharge section via the upper piping. A steam generator further comprising a non-condensable gas supply unit that supplies non-condensable gas into the second storage unit or the lower piping, wherein the non-condensable gas supply unit supplies the non-condensable gas before the liquid material in the second storage unit reaches its boiling point.

2. The steam generator according to claim 1, characterized in that the non-condensable gas is an inert gas.

3. The steam generator according to claim 1, characterized in that the gas discharge unit further comprises a non-condensable gas separation unit for separating the non-condensable gas mixed in with the steam from the steam.

4. The steam generator according to claim 1, characterized in that the tip of the non-condensable gas supply section is formed to face upward toward the second storage section, and a perforated plate is provided below the second storage section.

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