JP6582364B2 - Boiler system - Google Patents

Description

  The present invention relates to a boiler system that burns a boiler using a mixed fuel mainly composed of hydrogen gas.

2. Description of the Related Art Conventionally, a boiler system is known that includes a once-through boiler that generates steam by burning fuel and a fuel supply device that supplies gaseous fuel to the once-through boiler. In such a boiler system, gaseous fuel (for example, LNG or LPG) supplied from a fuel supplier is used as the fuel.
By the way, in a plant or the like in which a boiler system is installed, hydrogen gas may be generated as a by-product with the operation of the plant. Therefore, a boiler system that uses hydrogen gas generated in a plant as a part of fuel has been proposed (see, for example, Patent Document 1).

JP 2009-243711 A

From the viewpoint of fuel cost reduction and carbon dioxide emission reduction, it is preferable to operate the boiler system mainly using hydrogen gas generated as a by-product. However, since hydrogen gas has a higher combustion speed than LNG and LPG, when hydrogen gas is supplied as a gaseous fuel to a conventional once-through boiler, a backfire occurs in which a flame is ejected upstream of the burner. It becomes easy. Moreover, since hydrogen gas has a larger calorific value per unit mass than LNG and LPG, it is necessary to improve the heat resistance of the burner.
As described above, when hydrogen gas is used as a gaseous fuel in a conventional once-through boiler, there are various problems. Conventionally, as proposed in Patent Document 1, it is necessary to use a burner corresponding to the characteristics of hydrogen gas. was there.

  Accordingly, an object of the present invention is to provide a boiler system that can be stably combusted even when gaseous fuel mainly composed of hydrogen gas is supplied to an existing once-through boiler.

  The present invention provides a gaseous mixture of a once-through boiler that has a burner that burns gaseous fuel, generates steam, and hydrogen gas and a secondary fuel gas that has a combustion speed slower than that of the hydrogen gas and does not contain oxygen. A fuel supply device that supplies the once-through boiler as a fuel system, the fuel supply device comprising: a hydrogen gas line through which the hydrogen gas flows; a sub fuel gas line through which the sub fuel gas flows; A mixing device connected to the downstream side of the hydrogen gas line and the downstream side of the auxiliary fuel gas line to mix the hydrogen gas and the auxiliary fuel gas; and connecting the mixing device and the once-through boiler; and the mixing device A mixed gas line for supplying the gaseous fuel mixed in the burner to the burner, and a control for controlling the supply amount of the auxiliary fuel gas to 20% or more of the gaseous fuel supplied to the burner. Apparatus and relates to a boiler system comprising a.

  The auxiliary fuel gas is preferably a hydrocarbon gas having a combustion rate of 20 cm / s to 60 cm / s.

  The burner is preferably a premixed burner that mixes the gaseous fuel and combustion air in the burner.

  Further, the boiler system includes a bypass line that connects the auxiliary fuel gas line and the mixed gas line, a bypass opening / closing valve that is disposed in the bypass line and opens and closes the bypass line, and the bypass line in the mixed gas line An orifice arranged downstream of the connecting portion, a mixed gas branch line connecting the upstream and downstream sides of the orifice in the mixed gas line, and the mixed gas branch arranged in the mixed gas branch line It is preferable to further include a branch line opening / closing valve that opens and closes the line.

  According to the boiler system of the present invention, even if gaseous fuel mainly composed of hydrogen gas is supplied to an existing once-through boiler, it can be stably burned.

It is a figure showing composition of a boiler system concerning a 1st embodiment of the present invention. It is a figure which shows the structure of the boiler system which concerns on 2nd Embodiment of this invention.

Hereinafter, preferred embodiments of the boiler system 1 of the present invention will be described with reference to the drawings.
First, with reference to FIG. 1, the whole structure of the boiler system 1 of 1st Embodiment is demonstrated. In the following description, “line” is a general term for a flow path, a path, a pipeline, and the like.

  The boiler system 1 of the first embodiment is a boiler system capable of mixing and burning a plurality of types of fuel gas, and in particular, a boiler capable of using hydrogen gas generated as a by-product in plant equipment or the like as a main fuel. System. The boiler system 1 includes a fuel supply device 2, a once-through boiler 3, and a control device 4.

  The once-through boiler 3 mixes the gaseous fuel supplied from the fuel supply device 2 with combustion air supplied from a blower (not shown), burns it with a burner, and heats the water in the can to produce steam. Is generated. The once-through boiler 3 is connected to a load device (not shown) and supplies the generated steam to the load device. In the first embodiment, the once-through boiler 3 includes a premixed burner that mixes and burns gas combustion and combustion air in the burner without mixing them in advance.

The fuel supply device 2 includes a hydrogen gas line 21, a sub fuel gas line 22, a mixing device 23, a mixed gas line 24, a bypass line 25, and a mixed gas branch line 26.
The hydrogen gas line 21 supplies hydrogen gas as main fuel to the once-through boiler 3. The upstream side of the hydrogen gas line 21 is connected to the hydrogen gas supply device 100. Examples of the hydrogen gas supply device 100 include a storage facility that stores hydrogen gas generated in a plant in which the boiler system 1 is installed.

In the hydrogen gas line 21, shut-off valves 211 and 212, a hydrogen gas flow rate adjustment valve 213, and a pressure sensor 214 are arranged. The shut-off valves 211 and 212 are constituted by electromagnetic valves, and open or close the hydrogen gas line 21. By opening the shut-off valves 211 and 212, hydrogen gas is supplied from the hydrogen gas supply device 100 to the once-through boiler 3, and when closed, the supply of hydrogen gas from the hydrogen gas supply device 100 to the once-through boiler 3 is stopped. The shut-off valves 211 and 212 also have a function of preventing the backflow of hydrogen gas to the hydrogen gas supply device 100.
The hydrogen gas flow rate adjustment valve 213 adjusts the flow rate of the hydrogen gas in the hydrogen gas line 21 by adjusting the pressure of the hydrogen gas flowing through the hydrogen gas line 21. The pressure sensor 214 detects the pressure of hydrogen gas on the downstream side of the hydrogen gas flow rate adjustment valve 213 in the hydrogen gas line 21.

  The auxiliary fuel gas line 22 supplies auxiliary fuel gas to the once-through boiler 3. As the auxiliary fuel gas, a gas having a combustion speed slower than that of hydrogen gas and not containing oxygen is used. As the auxiliary fuel gas, it is preferable to use a hydrocarbon gas having a combustion speed of 20 cm / s to 60 cm / s from the viewpoint of suitably maintaining the combustion speed as a mixed gas with hydrogen gas. Specifically, city gas (LNG) or propane gas (LPG) can be used as the auxiliary fuel gas.

In the auxiliary fuel gas line 22, shut-off valves 221 and 222, an auxiliary fuel gas flow rate adjustment valve 223, and a pressure sensor 224 are arranged. The shut-off valves 221 and 222 are constituted by electromagnetic valves, and open or close the auxiliary fuel gas line 22. By opening the shut-off valves 221, 222, the auxiliary fuel gas is supplied to the once-through boiler 3, and when it is closed, the supply of the auxiliary fuel gas to the once-through boiler 3 is stopped. The shut-off valves 221 and 222 also have a function of preventing the back flow of the auxiliary fuel gas.
The auxiliary fuel gas flow rate adjustment valve 223 adjusts the flow rate of the auxiliary fuel gas in the auxiliary fuel gas line 22 by adjusting the pressure of the auxiliary fuel gas flowing through the auxiliary fuel gas line 22. The pressure sensor 224 detects the pressure of the auxiliary fuel gas on the downstream side of the auxiliary fuel gas flow rate adjustment valve 223 in the auxiliary fuel gas line 22.

  The mixing device 23 is connected to the downstream side of the hydrogen gas line 21 and the downstream side of the auxiliary fuel gas line 22 and mixes the hydrogen gas and the auxiliary fuel gas. The mixing device 23 can be constituted by an ejector, for example. Thereby, the other gas is sucked using the negative pressure generated when one gas passes, and the hydrogen gas and the auxiliary fuel gas can be mixed. In particular, when city gas is used as the auxiliary fuel gas, hydrogen gas can be sucked using the supply pressure of the city gas.

  The mixed gas line 24 connects the mixing device 23 and the once-through boiler 3, and supplies a mixed gas of hydrogen gas and auxiliary fuel gas mixed by the mixing device 23 to the burner as gaseous fuel. An orifice 241, a discharge valve 242, and a pressure sensor 243 are disposed in the mixed gas line 24.

The orifice 241 depressurizes the mixed gas flowing through the mixed gas line 24 and restricts (adjusts) the flow rate of the mixed gas flowing through the mixed gas line 24.
The discharge valve 242 is configured by a motor valve. By opening the discharge valve 242, the mixed gas flowing through the mixed gas line 24 is discharged to the external space.
The pressure sensor 243 is disposed on the upstream side of the orifice 241 in the mixed gas line 24. The pressure sensor 243 detects the pressure of the mixed gas upstream of the orifice 241 in the mixed gas line 24.

  The bypass line 25 connects the auxiliary fuel gas line 22 and the mixed gas line 24. The bypass line 25 bypasses the auxiliary fuel gas flowing through the auxiliary fuel gas line 22 to the mixed gas line 24 without using the mixing device 23. A bypass opening / closing valve 251 is disposed in the bypass line 25. The bypass opening / closing valve 251 is configured by an electromagnetic valve and opens / closes the bypass line 25.

  The mixed gas branch line 26 connects the upstream side and the downstream side of the orifice 241 in the mixed gas line 24. A branch line opening / closing valve 261 is disposed in the mixed gas branch line 26. The branch line opening / closing valve 261 is configured by an electromagnetic valve, and opens / closes the mixed gas branch line 26.

The control device 4 is electrically connected to the once-through boiler 3, the pressure sensors 214, 224, and 243 and various valves, and controls the combustion state of the once-through boiler 3 and the opening / closing or opening of the various valves.
Specifically, the control device 4 controls the combustion state of the once-through boiler 3 based on the pressure inside a steam header (not shown) that stores the steam generated from the once-through boiler 3. That is, the combustion state of the once-through boiler 3 is controlled so that more steam is generated when the pressure inside the steam header is lower than a predetermined value, and less steam is generated when the pressure inside the steam header is higher than a predetermined value. To control the combustion state of the once-through boiler 3.

  In the boiler system 1 of the first embodiment, hydrogen gas is used as a main fuel, and a mixed gas obtained by mixing LNG as a sub fuel gas with the hydrogen gas is burned in a burner as a gaseous fuel. Here, in this embodiment, gaseous fuel mainly composed of hydrogen gas is supplied to the once-through boiler 3 including a burner designed to use a general hydrocarbon gas such as LNG or LPG as the fuel gas. Therefore, the control device 4 performs control so that the supply amount (volume flow rate) of LNG as the auxiliary fuel gas is 20% or more of the gaseous fuel supplied to the burner. That is, since hydrogen gas has a higher combustion speed than LNG, if the proportion of hydrogen gas contained in the gaseous fuel increases too much, a backfire in which a flame is ejected upstream of the burner tends to occur. End up. In addition, hydrogen gas has a large calorific value per unit mass as compared to LNG, so that the durability of the burner is lowered.

  Therefore, by controlling the supply amount of LNG to be 20% or more of the gaseous fuel supplied to the burner by the control device 4, the combustion speed of the entire gaseous fuel mainly composed of hydrogen gas becomes too fast. In addition, it is possible to prevent the calorific value from becoming too large. That is, according to the boiler system 1 of the first embodiment, the flow rate of hydrogen gas contained in the gaseous fuel can be increased to 80% and the once-through boiler 3 can be burned, so that the hydrogen gas generated in the plant equipment can be used more effectively. Available to:

Specifically, the control device 4 determines the opening degree of the hydrogen gas flow rate adjustment valve 213 and the sub fuel gas flow rate according to the combustion instruction amount (combustion rate) of the once-through boiler 3 calculated based on the pressure inside the steam header. The opening degree of the regulating valve 223 is adjusted to control the flow rate of hydrogen gas and the flow rate of LNG, and control is performed so that the flow rate of LNG does not fall below 20% of the flow rate of the mixed gas.
In the first embodiment, the control device 4 controls the opening degree of the hydrogen gas flow rate adjustment valve 213 and the opening degree of the auxiliary fuel gas flow rate adjustment valve 223 based on the detected pressures of the pressure sensor 214 and the pressure sensor 224. Further, the control device 4 controls the opening degree of the hydrogen gas flow rate adjustment valve 213 and the opening degree of the auxiliary fuel gas flow rate adjustment valve 223 so that the detected pressure of the pressure sensor 243 becomes a predetermined value corresponding to the combustion state. .

  Further, the control device 4 closes the shut-off valves 211 and 212 and the shut-off valves 221 and 222 so that the mixed gas is not supplied to the once-through boiler 3 while the combustion of the once-through boiler 3 is stopped. By opening the discharge valve 242, the mixed gas staying in the mixed gas line 24 is discharged to the outside.

  Moreover, the boiler system 1 of 1st Embodiment is the bypass line 25, the bypass on-off valve 251, as a structure for burning the once-through boiler 3 by using only LNG as gaseous fuel, when hydrogen gas is not produced | generated in plant equipment. A mixed gas branch line 26 and a branch line opening / closing valve 261 are provided.

Next, operation | movement of the boiler system 1 of 1st Embodiment is demonstrated.
In the boiler system 1 of the first embodiment, when the once-through boiler 3 is combusted using a mixed gas of hydrogen gas and LNG as a gaseous fuel, the control device 4 first closes the bypass opening / closing valve 251 and the branch line opening / closing valve 261. To release.

  Next, the control device 4 opens the cutoff valves 211 and 212 and the cutoff valves 221 and 222. Further, the control device 4 causes the hydrogen gas pressure detected by the pressure sensor 214 and the LNG pressure detected by the pressure sensor 224 to be set pressures set in accordance with the combustion state of the once-through boiler 3. In addition, the opening degree of the hydrogen gas flow rate adjustment valve 213 and the opening degree of the auxiliary fuel gas flow rate adjustment valve 223 are adjusted.

  Thereby, the hydrogen gas supplied from the hydrogen gas line 21 and the LNG supplied from the auxiliary fuel gas line 22 are mixed in the mixing device 23, and the mixed gas is mixed into the mixed gas line 24 and the mixed gas branch line 26. It is distributed and supplied to the once-through boiler 3. In the once-through boiler 3, the mixed gas and the combustion air are mixed in the premix burner and then burned.

  On the other hand, when the once-through boiler 3 is combusted using only LNG as the gaseous fuel, the control device 4 first opens the bypass opening / closing valve 251 and closes the branch line opening / closing valve 261.

  Next, the control device 4 opens the shut-off valves 221 and 222 with the shut-off valves 211 and 212 closed. Further, the control device 4 adjusts the opening degree of the auxiliary fuel gas flow rate adjustment valve 223 so that the pressure of the LNG detected by the pressure sensor 224 becomes a set pressure set according to the combustion state of the once-through boiler 3. To do.

  Thereby, the LNG supplied from the auxiliary fuel gas line 22 flows through the bypass line 25 and the mixed gas line 24 and is supplied to the once-through boiler 3. In this case, hydrogen is not supplied from the hydrogen gas line 21. In the once-through boiler 3, LNG and combustion air are mixed in the premix burner and then burned.

  When the combustion of the once-through boiler 3 is stopped, the control device 4 opens the discharge valve 242 and discharges the mixed gas from the mixed gas line 24 and the mixed gas branch line 26. As a result, the pressure of the mixed gas does not increase inside the mixed gas line 24 and the mixed gas branch line 26, and as a result, the mixed gas can be prevented from flowing backward. Therefore, even when hydrogen gas is mixed, the boiler system 1 can be operated safely.

  According to the boiler system 1 of 1st Embodiment demonstrated above, there exist the following effects.

  (1) When the once-through boiler 3 is fueled by using a mixed gas containing hydrogen gas as a gaseous fuel, particularly when considering using hydrogen gas as the main fuel gas, various problems due to the unique properties of hydrogen gas arise. . Therefore, the boiler system 1 is configured to include a fuel supply device 2 that supplies a mixed gas of hydrogen gas and auxiliary fuel gas to the once-through boiler 3, and the fuel supply device 2 is supplied with gaseous fuel as the amount of auxiliary fuel gas supplied. It comprised including the control apparatus 4 which controls so that it might become 20% or more. Thereby, it is possible to prevent the combustion speed of the entire gaseous fuel mainly composed of hydrogen gas from becoming too fast, and to prevent the amount of generated heat from becoming too large. Therefore, even when gaseous fuel mainly composed of hydrogen gas is supplied to the existing once-through boiler 3 that uses LNG, LPG, or the like as fuel, the once-through boiler 3 can be stably burned. Moreover, since the rate of the hydrogen gas contained in gaseous fuel can be increased to 80% and the once-through boiler 3 can be burned, the hydrogen gas generated in plant equipment can be used more effectively and safely.

  (2) The burner was constituted by a premixed burner. As a result, the hydrogen gas can be prevented from being mixed with the combustion air on the upstream side of the burner, so that the occurrence of flashback can be suppressed.

  (3) When the combustion of the once-through boiler 3 was stopped, the discharge valve 242 was opened in the control device 4 and the mixed gas was discharged from the mixed gas line 24 and the mixed gas branch line 26. As a result, the pressure of the mixed gas does not increase inside the mixed gas line 24 and the mixed gas branch line 26, and as a result, the mixed gas can be prevented from flowing backward. Therefore, even when hydrogen gas is mixed, the boiler system 1 can be operated safely.

  (4) A suitable flow rate and specific gravity are different in a predetermined combustion state between the case where the mixed gas is used as the gaseous fuel and the case where LNG is used alone as the gaseous fuel. Therefore, the boiler system 1 is configured to include a bypass line 25, a bypass opening / closing valve 251, a mixed gas branch line 26, and a branch line opening / closing valve 261. As a result, when the mixed gas is used as gaseous fuel, the bypass line 25 is closed and the mixed gas branch line 26 is opened. When LNG is used as gaseous fuel, the bypass line 25 is opened and mixed. By closing the gas branch line 26, the flow rate of the gaseous fuel supplied to the once-through boiler 3 can be adjusted according to the type of gaseous fuel.

Next, a boiler system 1A according to a second embodiment of the present invention will be described with reference to FIG. In the description of the second embodiment, the same components are denoted by the same reference numerals, and the description thereof is omitted or simplified.
In the boiler system 1A of the second embodiment, the fuel supply device 2A includes a second auxiliary fuel gas line 27 that supplies the auxiliary fuel gas to the once-through boiler 3 independently of the auxiliary fuel gas line 22, and the like. Different from one embodiment.

  The second auxiliary fuel gas line 27 is provided independently of the auxiliary fuel gas line 22 and is connected to the mixed gas line 24. In the second auxiliary fuel gas line 27, shut-off valves 271, 272, a governor 273 as a flow rate adjusting member, an orifice 274, and a three-way valve 275 are arranged.

The shut-off valves 271 and 272 are constituted by electromagnetic valves, and open or close the second auxiliary fuel gas line 27. By opening the shut-off valves 271, 272, the auxiliary fuel gas is supplied to the once-through boiler 3, and by closing, the supply of the auxiliary fuel gas to the once-through boiler 3 is stopped. The shut-off valves 271 and 272 also have a function of preventing the back flow of the auxiliary fuel gas.
The governor 273 adjusts the pressure of the auxiliary fuel gas flowing through the second auxiliary fuel gas line 27 to be a predetermined pressure. The orifice 274 depressurizes LNG flowing through the second auxiliary fuel gas line 27 and restricts (adjusts) the flow rate of LNG flowing through the second auxiliary fuel gas line 27.

  The three-way valve 275 is disposed at a connection portion between the mixed gas line 24 and the second auxiliary fuel gas line 27. The three-way valve 275 causes the LNG to flow from the second auxiliary fuel gas line 27 to the downstream side of the three-way valve 275 in the mixed gas line 24, and the mixed gas from the upstream side to the downstream side of the three-way valve 275 in the mixed gas line 24. Switch to the state of distribution.

  The boiler system 1 </ b> A includes a branch line 28 that connects the upstream side and the downstream side of the orifice 274 in the second auxiliary fuel gas line 27, and an on-off valve 281 that is disposed on the branch line 28.

  In the boiler system 1A of the second embodiment, when the once-through boiler 3 is combusted using a mixed gas of hydrogen gas and LNG as gaseous fuel, the control device 4 closes the shut-off valves 271, 272, the shut-off valves 211, 212, and The shut-off valves 221 and 222 are opened. Further, the control device 4 causes the hydrogen gas pressure detected by the pressure sensor 214 and the LNG pressure detected by the pressure sensor 224 to be set pressures set in accordance with the combustion state of the once-through boiler 3. In addition, the opening degree of the hydrogen gas flow rate adjustment valve 213 and the opening degree of the auxiliary fuel gas flow rate adjustment valve 223 are adjusted.

  Thereby, the hydrogen gas supplied from the hydrogen gas line 21 and the LNG supplied from the auxiliary fuel gas line 22 are mixed in the mixing device 23, and the mixed gas is mixed into the mixed gas line 24 and the mixed gas branch line 26. It is distributed and supplied to the once-through boiler 3. In the once-through boiler 3, the mixed gas and the combustion air are mixed in the premix burner and then burned.

  On the other hand, when the once-through boiler 3 is burned using only LNG as the gaseous fuel, the control device 4 opens the shutoff valves 271 and 272 and closes the shutoff valves 211 and 212 and the shutoff valves 221 and 222.

  Thereby, the LNG supplied from the second auxiliary fuel gas line 27 flows through the mixed gas line 24 and is supplied to the once-through boiler 3. In this case, hydrogen is not supplied from the hydrogen gas line 21, and LNG is not supplied from the auxiliary fuel gas line 22. In the once-through boiler 3, LNG and combustion air are mixed in the premix burner and then burned.

  According to the boiler system 1A of the second embodiment, the above-described effects (1) to (3) are achieved.

  As mentioned above, although each preferred embodiment of the boiler system of the present invention was described, the present invention is not limited to the above-mentioned embodiment, and can be changed suitably.

  For example, in 1st Embodiment and 2nd Embodiment, although the mixing apparatus 23 was comprised by the ejector, it is not restricted to this. That is, the mixing device may be constituted by a plurality of flow rate adjusting valves.

DESCRIPTION OF SYMBOLS 1 Boiler system 2 Fuel supply apparatus 3 Cross-flow boiler 4 Control apparatus 21 Hydrogen gas line 22 Sub fuel gas line 23 Mixing apparatus 24 Mixed gas line 25 Bypass line 26 Mixed gas branch line 27 Second sub fuel line 241 Orifice 251 Bypass on-off valve 261 Branch line open / close valve

Claims (4)

A once-through boiler having a burner for burning gaseous fuel and generating steam;
Hydrogen gas generated as a by-product in a plant in which a boiler system is installed is a mixed gas in which a by-product gas having a combustion speed slower than the hydrogen gas and not containing oxygen is mixed as the by-product. The boiler system comprising: a fuel supply device that supplies the mixed gas that can increase the ratio of the hydrogen gas to a maximum of 80% according to the generated amount of the hydrogen gas as the gaseous fuel to the once- through boiler. Because
The fuel supply device includes:
And a hydrogen gas storage facility for storing the hydrogen gas,
An upstream side is connected to the hydrogen gas storage facility, and a hydrogen gas line through which the hydrogen gas flows,
A secondary fuel gas line through which the secondary fuel gas flows;
A mixing device connected to the downstream side of the hydrogen gas line and the downstream side of the auxiliary fuel gas line to mix the hydrogen gas and the auxiliary fuel gas;
A gas line for connecting the mixing device and the once-through boiler, and supplying the gaseous fuel mixed by the mixing device to the burner;
A control device for controlling the pressure of the hydrogen gas flowing through the mixing device and the pressure of the auxiliary fuel gas flowing through the mixing device to be set pressures set in accordance with the combustion state of the once-through boiler; Boiler system equipped with.   The boiler system according to claim 1, wherein the auxiliary fuel gas is a hydrocarbon gas having a combustion rate of 20 cm / s to 60 cm / s.   The boiler system according to claim 1 or 2, wherein the burner is a premixed burner that mixes the gaseous fuel and combustion air in the burner. A bypass line connecting the auxiliary fuel gas line and the mixed gas line;
A bypass on-off valve disposed in the bypass line for opening and closing the bypass line;
An orifice disposed downstream of a connection portion with the bypass line in the mixed gas line;
A mixed gas branch line connecting the upstream side and the downstream side of the orifice in the mixed gas line;
The boiler system according to any one of claims 1 to 3, further comprising: a branch line opening / closing valve that is disposed in the mixed gas branch line and opens and closes the mixed gas branch line.

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