JP7776358B2 - Liquefied flammable gas utilization device, liquefied flammable gas utilization method, and cement manufacturing equipment - Google Patents

Description

The present invention relates to an apparatus for utilizing liquefied flammable gas, and in particular to an apparatus for utilizing liquefied flammable gas that can be attached to cement manufacturing equipment. The present invention also relates to a method for utilizing liquefied flammable gas, and in particular to a method for utilizing liquefied flammable gas that can be used in the cement manufacturing process. The present invention also relates to cement manufacturing equipment that can utilize liquefied flammable gas.

It is known that a large amount of _CO2 is emitted during the production of cement. There are two reasons for this. The first reason is that the cement manufacturing process requires burning the cement raw materials at high temperatures in a furnace, which requires the use of large amounts of fossil fuels to generate the combustion energy. The second reason is that limestone, the main raw material for cement, causes a decarbonation reaction ( _CaCO3 → CaO + _CO2 ).

_CO2 is a greenhouse gas that has a significant impact on global warming. Therefore, cement manufacturing plants are being asked to reduce _CO2 emissions.

Against this background, the use of combustible gas fuels, which have a lower CO ₂ emission intensity than coal, the main fuel used in the past, has recently been considered for cement production.

For example, Patent Document 1 below proposes using ammonia as a supplementary fuel in addition to fossil fuels, which are the conventional main fuel, when producing cement.

Japanese Patent Application Laid-Open No. 2019-172484

In order to use flammable gases such as ammonia as fuel in cement production, the flammable gas must be introduced into the cement manufacturing plant. There are two possible methods for this. The first method involves installing a gas pipeline connecting the flammable gas supplier's facilities with the cement manufacturing plant, and supplying the flammable gas in gaseous form to the cement manufacturing plant through this pipeline. The second method involves liquefying the flammable gas at the supplier's site, then transporting tanks filled with the liquefied flammable gas by land or sea to the cement manufacturing plant, where it is vaporized for use. However, because the first method has many problems in terms of both initial and running costs, it is considered that the second method should be adopted.

When the second method is adopted, as mentioned above, the liquefied flammable gas must be vaporized at the cement manufacturing plant. A commonly known method of vaporizing liquefied ammonia is to use a vaporizer to vaporize it with hot water or steam heated by a heater. However, when using this method, it is necessary to add to the liquefied ammonia as thermal energy the sensible heat required to raise the water temperature from ambient temperature to hot water temperature (generally around 40°C) and the latent heat of vaporization of the liquefied ammonia. Considering that liquefied ammonia will be used as part of the fuel used in cement production, the initial costs of installing the equipment to supply the above-mentioned thermal energy, as well as the running costs during actual operation, are expected to be enormous.

Such cost issues hinder the use of liquefied flammable gas as an alternative fuel in cement production, and are unlikely to lead to a reduction in _CO2 emissions during cement production. Patent Document 1 does not mention at all the above-mentioned problems that may arise when liquefied flammable gas is actually used in a cement manufacturing plant, or measures to address these problems.

In view of these problems, the present invention aims to provide a liquefied flammable gas utilization device and a liquefied flammable gas utilization method that enable liquefied flammable gas to be vaporized in a simple and inexpensive manner in a cement manufacturing plant. The present invention also aims to provide cement manufacturing equipment that can vaporize and utilize liquefied flammable gas in a simple and inexpensive manner.

The present invention provides a device for utilizing liquefied flammable gas that can be attached to a cement manufacturing facility that includes a calciner for calcining cement raw materials, a cement kiln for burning the cement raw materials calcined in the calciner to produce clinker, and a clinker cooler connected to the front end of the cement kiln,
a flammable gas piping that connects a tank in which a liquefied flammable gas is stored to one or more injection points that belong to a group consisting of the clinker cooler and a calciner extraction piping through which the extracted gas extracted from the clinker cooler flows toward the calciner,
The flammable gas pipe is characterized in that it supplies the liquefied flammable gas or a flammable gas obtained by vaporizing the liquefied flammable gas while it is flowing to the injection point.

The inventor's extensive research has confirmed that methane is more susceptible to combustion retardation than coal, which is the primary fuel used in cement production. The reason for this is that combustible gases such as methane do not contain fuel particles, unlike coal, so oxygen and fuel do not mix as easily as with coal, which is thought to result in concerns about combustion retardation. Given this, it is expected that even greater combustion retardation will occur if combustible gases such as ethane, propane, butane, and ammonia, which have slower combustion rates than methane, are used as fuel.

If combustion delays occur before the kiln during the cement manufacturing process, the clinker will not achieve the appropriate temperature history, which could have a negative impact on quality, such as an increase in free lime. Furthermore, this can lead to reduced cement production due to temperature limits in downstream equipment.

In the liquefied flammable gas utilization device of the present invention, flammable gas is injected in liquid or vaporized form into one or more injection points that belong to a group consisting of a clinker cooler and a calciner extraction pipe through which extracted gas extracted from the clinker cooler flows toward the calciner.

The clinker cooler installed in cement manufacturing facilities receives and cools cement clinker (hereinafter referred to as "clinker" where appropriate) burned in a cement kiln. The clinker cooler typically cools the clinker by blowing in ambient air at room temperature, which exchanges heat with the clinker at temperatures above 1000°C (typically around 1350°C). Therefore, the clinker cooler contains air (atmospheric gas) whose temperature has been raised by heat exchange with the high-temperature clinker.

For this reason, when liquefied flammable gas is injected into the clinker cooler, the clinker cooler acts as a vaporizer, vaporizing it into flammable gas within the clinker cooler. Furthermore, when the flammable gas mixes with high-temperature air within the clinker cooler, it reaches its ignition point and begins to burn. Once burning, the flammable gas flows from the clinker cooler into the front of the cement kiln and is used as part of the fuel for burning the cement raw materials. This reduces the risk of delayed combustion within the cement kiln.

The liquefied flammable gas may be vaporized while flowing through the flammable gas piping, in which case the resulting vaporized flammable gas is injected into the clinker cooler. Even with this configuration, concerns about combustion delays within the cement kiln are reduced for the same reasons as above.

A portion of the high-temperature atmospheric gas (air) inside the clinker cooler is extracted through the extraction pipe. Depending on its temperature, the extracted gas (hereinafter referred to as "extracted gas") is sent to the calciner and used as combustion air for the calciner, or sent to the raw material processing process and used to dry the raw materials. In addition, a portion of the low-temperature atmosphere is released as exhaust gas.

The ambient temperature within the clinker cooler decreases as it approaches the outlet from which the clinker is discharged. Specifically, the space within the clinker cooler is divided into a first zone where the ambient temperature is in the range of 150°C to 300°C, a second zone where the ambient temperature is in the range of 250°C to 650°C, and a third zone where the ambient temperature is in the range of 600°C to 900°C. Typically, a portion of the atmosphere within the third zone is extracted through a calciner extraction pipe and sent to the calciner. A portion of the atmosphere within the second zone is extracted through a raw material drying extraction pipe and sent to the raw material process. A portion of the atmosphere within the first zone is extracted through an exhaust gas extraction pipe and discharged to the atmosphere (outside the system) via a chimney or the like.

In other words, the extracted gas extracted from the clinker cooler by the calciner bleed air piping and flowing toward the calciner is relatively hot. Therefore, even if liquefied flammable gas is injected into the calciner bleed air piping rather than the clinker cooler, the calciner bleed air piping functions as a vaporizer, vaporizing the gas into flammable gas within the calciner bleed air piping. Furthermore, when the flammable gas mixes with high-temperature air (bleed gas heading toward the calciner) within the calciner bleed air piping, the concentration of the flammable gas in the mixed gas reaches a flammable range and a temperature above its ignition point, causing the flammable gas to begin combustion. In particular, the calciner bleed air piping is relatively long, sometimes reaching over 100 meters. Therefore, the bleed gas (high-temperature air) and flammable gas are sufficiently mixed before reaching the calciner, making it easier for combustion to begin.

Once combustion has begun, the combustible gas flows into the calciner and is used as part of the fuel when calcining the cement raw materials inside the calciner. As a result, concerns about combustion delays in the calciner and in the cement kiln located downstream are reduced.

The flammable gas obtained by vaporizing the liquefied flammable gas while it is flowing through the flammable gas piping may be injected into the calciner extraction piping. Even with this configuration, concerns about combustion delays in the calciner and cement kiln are reduced for the same reasons as above.

According to the above configuration, the flammable gas piping is arranged so as to reach the clinker cooler or the calciner bleed piping, and the liquefied flammable gas is passed through the flammable gas piping and injected into the clinker cooler or the calciner bleed piping, thereby making it possible to vaporize and use the liquefied flammable gas at the cement manufacturing plant. This makes it possible to easily use the flammable gas as an alternative fuel in the cement manufacturing process, which is expected to contribute to reducing _CO2 emissions.

A liquid transfer pump may be used to transfer liquefied flammable gas from the tank to the flammable gas piping. On the other hand, the flammable gas piping does not need to be equipped with a blower to promote the flow of gaseous flammable gas. The expansion pressure generated by the vaporization of liquefied flammable gas during flow can act as a driving force for the gaseous flammable gas to flow through the flammable gas piping.

The liquefied flammable gas may contain 70% by volume or more of one or more gases belonging to the group consisting of ammonia, methane, ethane, propane, and butane. Preferably, the liquefied flammable gas contains 70% by volume or more of ammonia.

The flammable gas piping is arranged so that it passes through either or both of the clinker cooler and the exhaust gas extraction piping through which the extracted gas extracted from the clinker cooler flows toward the discharge port. The flammable gas obtained by vaporizing the liquefied flammable gas in a liquid state while flowing through the flammable gas piping may be supplied to the injection point.

In the above configuration, the piping through which the liquefied flammable gas flows (flammable gas piping) is arranged so that it passes through either or both of the clinker cooler and the exhaust gas extraction piping through which the extracted gas extracted from the clinker cooler flows. In other words, the flammable gas piping is arranged so that it passes through an area where a high-temperature atmosphere exists (hereinafter referred to as the "high-temperature area"). As a result, as the liquefied flammable gas flows through the flammable gas piping, it passes through the area where a high-temperature atmosphere exists, whereby it is vaporized through heat exchange through the piping. The above-mentioned high-temperature area can be, for example, an area within the range of 150°C to 1000°C.

As a result, the combustible gas vaporized while flowing through the combustible gas piping is supplied to the clinker cooler or the calciner extraction piping, where it is mixed with high-temperature air and combusted. The combustible gas in the burning state is then used as an alternative fuel for burning raw materials or calcining raw materials in the cement kiln or calciner.

Flammous gases with high purity will not ignite regardless of temperature. In the case of ammonia, the flammable range is 15.5% to 27% by volume, and if the purity exceeds 80% by volume, for example, it will not spontaneously ignite. Even for hydrogen, the flammable gas most susceptible to spontaneous combustion, the maximum flammable range is 75% by volume. For this reason, it is unlikely that flammable gas will spontaneously ignite while flowing through flammable gas piping, regardless of the temperature range within the clinker cooler or extraction piping that the flammable gas passes through.

The liquefied flammable gas utilization device comprises:
a burner attached to an end of the flammable gas pipe on the injection point side, for injecting the liquefied flammable gas in a gaseous state into the injection point;
a primary air pipe that passes through one or both of the clinker cooler and the exhaust gas extraction pipe and is connected to the combustible gas pipe at a position upstream of the burner,
The flammable gas pipe may be configured to introduce a mixed gas of the flammable gas and the primary air to the burner at a position downstream of the connection point with the primary air pipe.

With the above configuration, the flammable gas is vaporized while flowing through the flammable gas piping, and the gaseous flammable gas is injected from the injection point after merging with the primary air flowing through the primary air piping. At this time, the primary air piping is configured to pass through either or both the clinker cooler and the extraction piping, so that the primary air flowing through the primary air piping is heated and merges with the flammable gas. This allows the flammable gas to be injected from the injection point in a more preheated state, further improving combustibility at the injection point.

In this case, the concentration of flammable gas in the flammable gas piping decreases after the point where the primary air piping and flammable gas piping join. As a result, depending on the flow rate of the primary air, the concentration of flammable gas may fall within the flammable range. If this were to occur, the mixture of flammable gas and primary air flowing through the flammable gas piping could combust, potentially damaging the piping.

For this reason, it is preferable to adjust the temperature of the mixed gas at the confluence of the primary air piping and the flammable gas piping so that the gaseous flammable gas is below its ignition temperature. Adjusting the temperature of the mixed gas can be achieved, for example, by designing the primary air piping so that it passes only through the first zone. Another method of adjusting the temperature is to design the primary air piping so that it can pass through multiple zones (two or more of the first, second, and third zones) and adjust the flow rate of the flammable gas flowing through each zone using a valve, etc.

The flow rate of primary air and the flow rate of (liquefied) flammable gas may be adjusted so that the concentration of flammable gas contained in the mixed gas in the flammable gas piping does not fall within the flammable range. In this case, it is acceptable for the flammable gas to exceed its ignition temperature at the confluence of the primary air piping and the flammable gas piping. The concentration of flammable gas contained in the mixed gas can be adjusted by adjusting the flow rate of primary air flowing through the primary air piping with a valve, or by adjusting the flow rate of liquefied flammable gas sent to the flammable gas piping with a liquid feed pump.

The liquefied flammable gas utilization device comprises:
a burner having a plurality of ports, attached to an end of the flammable gas pipe on the injection location side, for injecting the flammable gas into the injection location through one or more of the ports;
The burner may also be provided with a primary air pipe that is connected to one of the multiple ports provided in the burner, other than the port to which the flammable gas pipe is connected, via one or both of the clinker cooler and the exhaust gas extraction pipe.

In the above configuration, the primary air flowing through the primary air piping is sent to the burner in a heated state. Combustible gas in a gaseous state is blown in from the burner along with the heated primary air through the blow-in point, further improving combustibility at the blow-in point.

In this configuration, the heated primary air and the flammable gas do not mix within the piping. Therefore, even without adjusting the temperature or flow rate of the flammable gas, the possibility of the flammable gas burning while flowing through the piping is extremely low.

The primary air flowing through the primary air piping can be atmospheric air, atmospheric gas inside the clinker cooler, or bleed gas from the exhaust gas bleed piping.

When the atmospheric gas inside the clinker cooler or the bleed gas from the exhaust gas bleed pipe is used as primary air, these gases contain fugitive dust, primarily from the clinker. Because combustible gas contains almost no ash, it has lower radiant heat transfer during combustion than coal, the main fuel. However, as described above, by injecting primary air containing fugitive dust into the injection point along with the combustible gas, the fugitive dust functions as a radiant heat transfer medium during combustion of the combustible gas, contributing to stabilizing the combustion of the combustible gas.

On the other hand, when using the atmospheric gas in the clinker cooler or the bleed gas in the exhaust gas bleed pipe as primary air, it is possible that the primary air piping may be thinned by scattered dust in some locations, or that scattered dust may adhere to the walls of the primary air piping, causing the primary air flow rate to change over time. From this perspective, a dust collector for collecting scattered dust may be provided in the primary air piping. In other words, the primary air piping may be equipped with a primary air blower that promotes the flow of one or both of the atmospheric gas in the clinker cooler and the bleed gas in the bleed pipe through the primary air piping, and a dust collector that collects scattered dust contained in the gas flowing through the primary air piping.

The scattered dust collected by the dust collector can be mixed with the clinker discharged from the clinker cooler, or with cement during the finishing process of cement production where gypsum and other additives are added. This is expected to reduce the cost of crushing clinker.

The present invention relates to a method for utilizing liquefied flammable gas in a cement manufacturing process in which cement raw materials are burned to produce a cement kiln, the method comprising:
injecting liquefied flammable gas into a flammable gas pipe connected to one or more injection points that belong to a group consisting of the clinker cooler and a calciner extraction pipe through which the extracted gas extracted from the clinker cooler flows toward the calciner;
and supplying the liquefied flammable gas or a flammable gas obtained by vaporizing the liquefied flammable gas while it is flowing to the blowing point.

Further, the cement manufacturing equipment according to the present invention includes:
a calciner for calcining cement raw materials;
a cement kiln that produces clinker by firing the cement raw materials calcined in the calciner;
a clinker cooler connected to the front of the cement kiln;
a tank in which the liquefied flammable gas is stored in a liquefied state, and a flammable gas piping that connects the tank to one or more injection points that belong to a group consisting of the clinker cooler and a calciner extraction piping through which the extracted gas extracted from the clinker cooler flows toward the calciner,
The flammable gas pipe is characterized in that it supplies the liquefied flammable gas or a flammable gas obtained by vaporizing the liquefied flammable gas while it is flowing to the injection point.

This invention makes it possible to vaporize and utilize liquefied flammable gas in a simple and inexpensive manner at cement manufacturing plants.

1 is a conceptual diagram schematically illustrating a configuration example of a cement production facility according to a first embodiment. FIG. 2 is a diagram schematically illustrating a portion of the cement manufacturing facility of FIG. 1 . 2 is a diagram schematically illustrating a portion of the cement production facility of FIG. 1, and corresponds to a conceptual diagram schematically illustrating an example of the configuration of a liquefied flammable gas utilization device of the first embodiment. FIG. 10 is a diagram schematically illustrating a configuration example of a liquefied flammable gas utilization device according to a second embodiment. 10 is a diagram schematically illustrating another configuration example of the liquefied flammable gas utilization device of the second embodiment. 10 is a diagram schematically illustrating another configuration example of the liquefied flammable gas utilization device of the second embodiment. 10 is a diagram schematically illustrating another configuration example of the liquefied flammable gas utilization device of the second embodiment. 10 is a diagram schematically illustrating another configuration example of the liquefied flammable gas utilization device of the second embodiment. 10 is a diagram schematically illustrating another configuration example of the liquefied flammable gas utilization device of the third embodiment. 10 is a diagram schematically illustrating another configuration example of the liquefied flammable gas utilization device of the third embodiment. 10 is a diagram schematically illustrating a configuration example of a liquefied flammable gas utilization device according to a fourth embodiment.

The liquefied flammable gas utilization device of the present invention is an apparatus that can be attached to a cement manufacturing facility that produces cement clinker (hereinafter abbreviated as "clinker") from cement raw materials. Below, each embodiment of the liquefied flammable gas utilization device, liquefied flammable gas utilization method, and cement manufacturing facility of the present invention will be described with reference to the drawings. Note that the following drawings are schematic illustrations, and the dimensional ratios in the drawings do not match the actual dimensional ratios. Furthermore, the dimensional ratios do not necessarily match between the drawings.

In each of the following diagrams, the flow of fluid (gas or liquid) is represented schematically by dashed double-dashed lines.

[First embodiment]
Fig. 1 is a conceptual diagram showing a schematic structure of a cement production facility according to a first embodiment. The cement production facility 1 includes a preheater 11 that preheats cement raw materials M1, a calciner 13 that calcines the cement raw materials M1, a cement kiln 20 that produces clinker 3 by burning the cement raw materials M1 calcined in the calciner 13, and a clinker cooler 30 that is connected to a kiln front section 20b of the cement kiln 20 and cools the produced clinker 3. As shown in Fig. 1, the calciner 13 is connected to the kiln end section 20a of the cement kiln 20.

In this embodiment, the cement manufacturing equipment 1 is equipped with a flammable gas burner 55, which is connected to a tank 51 in which liquefied flammable gas 50a is stored in liquid form via a flammable gas pipe 53. In the configuration example shown in Figure 1, the flammable gas burner 55 injects liquefied flammable gas 50a into the clinker cooler 30. In other words, in this embodiment, the clinker cooler 30 corresponds to the injection point of the liquefied flammable gas 50a.

A liquid feed pump 52 is provided in the flammable gas piping 53, and the liquefied flammable gas 50a stored in the tank 51 is sent to the flammable gas piping 53 by the pressure of the liquid feed pump 52. However, as long as the liquefied flammable gas 50a stored in the tank 51 can be sent to the flammable gas piping 53, the liquid feed pump 52 is not an essential element in the present invention.

The liquefied flammable gas 50a may be a gas containing 70% by volume or more of one or more gases belonging to the group consisting of ammonia, methane, ethane, propane, and butane. Typically, the liquefied flammable gas 50a is liquefied ammonia, liquefied methane (liquefied natural gas), liquefied propane (liquefied petroleum gas), or liquefied butane, and most typically, it is liquefied ammonia.

The powder of raw material M1 supplied to the top of the preheater 11 flows downward. As raw material M1 moves through the preheater 11, it is preheated by high-temperature exhaust gas and sent to the calciner 13. The calciner 13 is equipped with a calciner burner 14 that uses pulverized coal or the like as its main fuel. In the calciner 13, raw material M1 is further preheated (calcined) by high-temperature gas from the calciner burner 14 and the cement kiln ₂₀ , and CaCO3, the main component of limestone contained in raw material M1, is thermally decomposed (decarbonated) into CaO and _CO2 . The temperature of the powder of raw material M1 reaches approximately 750°C to 800°C.

The raw material M1 calcined in the calciner 13 enters the cement kiln 20 from the kiln end 20a and moves while rolling toward the exit at the kiln front 20b. The main burner 21 mentioned above is installed on the kiln front 20b side. The main burner 21 supplies the main fuel, such as pulverized coal, and primary air 25 for firing to the cement kiln 20.

In the cement kiln 20, raw material M1 is heated to approximately 1450°C to 1500°C, producing clinker 3. After the temperature of this clinker 3 drops to approximately 1300°C to 1350°C, it is discharged into the clinker cooler 30.

The clinker cooler 30 cools the clinker 3 using ambient air CA at room temperature (approximately 20°C to 30°C) sent in by a cooling fan (not shown). Typically, multiple plates are laid on the bottom of the clinker cooler 30 so that they can move back and forth. The back and forth movement of the plates guides the clinker 3 downstream (to the outlet side of the clinker cooler 30). The temperature of the clinker 3 decreases as it approaches the outlet of the clinker cooler 30, and it is then discharged from the outlet and stored in a clinker silo (not shown).

In the clinker cooler 30, the cooling air CA exchanges heat with the high-temperature clinker 3. As a result, high-temperature air is generated in the clinker cooler 30. Some of this air is sent from the kiln front section 20b into the cement kiln 20 and used as secondary air for combustion.

As described above, in the cement manufacturing equipment 1 of this embodiment, liquefied combustible gas 50a is injected into the clinker cooler 30. Because the space within the clinker cooler 30 is a high-temperature environment, when liquefied combustible gas 50a is injected into the clinker cooler 30, the liquefied combustible gas 50a vaporizes within the clinker cooler 30 and changes into gaseous combustible gas 50b (see Figure 3). Furthermore, when the combustible gas 50b mixes with the high-temperature air present within the clinker cooler 30, it reaches or exceeds its ignition point and begins to burn. Once combustion has begun, the combustible gas 50b is sent into the cement kiln 20 from the kiln front section 20b side along with the high-temperature air (secondary air) within the clinker cooler 30.

That is, according to the cement production equipment 1 of this embodiment, the combustible gas 50b supplied together with secondary air from the clinker cooler 30, as well as the main fuel such as pulverized coal supplied from the main burner 21, can be used as fuel for burning the raw material M1 in the cement kiln 20. In other words, according to this cement production equipment 1, the amount of main fuel can be reduced, while the combustible gas 50b, which has a lower _CO2 emission intensity than coal, can be used as auxiliary fuel, and therefore, an effect of reducing _CO2 emissions during cement production can be expected.

Furthermore, since this combustible gas 50b is supplied into the cement kiln 20 in a state where combustion has already begun, delays in combustion of the main fuel are unlikely to occur even while the combustible gas 50b is used as auxiliary fuel within the cement kiln 20.

Figure 2 is a schematic diagram of a portion of the cement production equipment 1 shown in Figure 1. However, for ease of explanation, the flammable gas piping 53 is omitted from Figure 2.

As described above, the temperature of the clinker 3 decreases toward the downstream side within the clinker cooler 30. Therefore, the temperature of the atmospheric gas within the clinker cooler 30 also decreases toward the downstream side. Typically, the internal space of the clinker cooler 30 has a first region 31 where the ambient temperature is in the range of 150°C to 300°C, a second region 32 where the ambient temperature is in the range of 250°C to 650°C, and a third region 33 where the ambient temperature is in the range of 600°C to 900°C. Of the first region 31, second region 32, and third region 33, the first region 31 is closest to the outlet end of the clinker cooler 30, and the third region 33 is closest to the cement kiln 20.

Because the ambient gas in the clinker cooler 30 has a temperature distribution, it is sent to different locations for use depending on its temperature, taking thermal efficiency into consideration. In the example of Figure 2, a portion of the ambient gas present in the third zone 33 of the clinker cooler 30 is extracted through the calciner extraction pipe 43 and sent to the calciner 13, where it is used as part of the combustion air (see also Figure 1). A portion of the ambient gas present in the second zone 32 of the clinker cooler 30 is extracted through the raw material drying extraction pipe 42 and sent to the raw material process, where it is used to dry the raw material M1 (see also Figure 1). On the other hand, the ambient gas present in the first zone 31 of the clinker cooler 30 has a temperature in the 150°C to 300°C range, and therefore has little value in terms of thermal efficiency, etc. Therefore, it is extracted through the exhaust gas extraction pipe 41 and then discharged to the atmosphere (outside the system) through a chimney or the like (see also Figure 1).

Figure 3 is a schematic diagram of a portion of the cement manufacturing equipment 1 in Figure 1, and is displayed similarly to Figure 2. However, for convenience of illustration, the various extraction pipes (41, 42, 43) shown in Figure 2 have been omitted, while the flammable gas pipe 53 and flammable gas burner 55 are shown.

As described above, in the cement manufacturing equipment 1 of this embodiment, the flammable gas burner 55 injects liquefied flammable gas 50a in a liquid state into the clinker cooler 30. The injected liquefied flammable gas 50a vaporizes and converts into flammable gas 50b in the clinker cooler 30, and is supplied into the cement kiln 20 from the kiln front section 20b in a combustion-started state. In other words, it is preferable that the liquefied flammable gas 50a is injected by the flammable gas burner 55 into an area within the clinker cooler 30 where the ambient temperature is equal to or higher than the ignition point of the flammable gas 50b.

For example, if the liquefied flammable gas 50a is ammonia, the ignition point of ammonia is approximately 650°C. Therefore, it is preferable for the flammable gas burner 55 to inject the liquefied flammable gas 50a into the third region 33 or second region 32 of the clinker cooler 30, and more preferably into the third region 33. Since the ignition point of methane is roughly the same as that of ammonia, the same applies when the liquefied flammable gas 50a is methane. Since the ignition points of ethane, propane, or butane are 100°C or more lower than that of ammonia, even when the liquefied flammable gas 50a is one of these gases, combustion will similarly begin within the clinker cooler 30 when the liquefied flammable gas 50a is injected into the third region 33 or second region 32 of the clinker cooler 30.

With the configuration shown in FIG. 3, the liquefied flammable gas 50a stored in the tank 51 is simply guided through the flammable gas piping 53 to the flammable gas piping 53, and the liquefied flammable gas 50a is then blown into the clinker cooler 30 in its liquid form from the flammable gas piping 53, allowing the liquefied flammable gas 50a to be vaporized and used in the cement manufacturing facility 1. Therefore, the liquefied flammable gas 50a can be vaporized in the cement manufacturing facility 1 in a simple and inexpensive manner.

In this embodiment, the liquid feed pump 52 that feeds the liquefied flammable gas 50a, the flammable gas piping 53 through which the liquefied flammable gas 50a flows, and the flammable gas burner 55 that injects the liquefied flammable gas 50a that has flowed through the flammable gas piping 53 into the clinker cooler 30 correspond to the liquefied flammable gas utilization device.

[Second embodiment]
A second embodiment of the liquefied flammable gas utilization device, the liquefied flammable gas utilization method, and the cement production facility according to the present invention will be described below. Note that, with regard to the parts common to the first embodiment, the description will be simplified or omitted as appropriate.

Figure 4 is a diagram that schematically illustrates the structure of the liquefied flammable gas utilization device of this embodiment, modeled after Figure 2. This embodiment differs from the first embodiment in that the liquefied flammable gas 50a is vaporized while flowing through the flammable gas piping 53, and the gaseous flammable gas 50b is blown into the clinker cooler 30 from the flammable gas burner 55. Hereinafter, the liquefied flammable gas 50a in its liquid state before being vaporized will be simply referred to as "liquefied flammable gas 50a," and the gaseous liquefied flammable gas 50a after being vaporized will be referred to as "flammable gas 50b."

In this embodiment, the flammable gas piping 53 is arranged so that a portion thereof passes through an area where a high-temperature atmosphere exists (high-temperature area). Therefore, while flowing through the flammable gas piping 53, the liquid liquefied flammable gas 50a is vaporized by heat exchange through the pipe wall of the flammable gas piping 53, becoming gaseous flammable gas 50b. In the example shown in Figure 4, the flammable gas piping 53 is arranged so that a portion thereof passes through the clinker cooler 30. In other words, the area within the clinker cooler 30 is the above-mentioned high-temperature area.

As described above, inside the clinker cooler 30, the cooling air CA exchanges heat with the high-temperature clinker 3 (see Figure 2), causing the ambient temperature inside the clinker cooler 30 to become high. Because the flammable gas piping 53 is arranged to pass through an area with a high-temperature atmosphere, the liquefied flammable gas 50a is vaporized while flowing through the flammable gas piping 53.

In the example shown in FIG. 4, the flammable gas piping 53 is arranged to pass through the first region 31, where the ambient temperature is in the range of 150°C to 300°C. As described above with reference to FIG. 2, the atmosphere in the first region 31 is extracted through the exhaust gas extraction piping 41 and then discharged to the atmosphere (outside the system) through a chimney or the like. Therefore, with the configuration shown in FIG. 4, the discharged thermal energy can be effectively utilized to vaporize the liquefied flammable gas 50a in liquid state. Note that in the first embodiment, the liquefied flammable gas 50a in liquid state is blown into the clinker cooler 30, and therefore the latent heat of vaporization is consumed when the liquefied flammable gas 50a vaporizes within the clinker cooler 30. When the liquefied flammable gas 50a is vaporized, the flammable gas piping 53 is cooled by the latent heat. However, since the high-temperature region is constantly supplied with high-temperature hot air that has cooled the clinker 3, the heat source is not lost.

On the other hand, by routing the combustible gas piping 53 through the clinker cooler 30, as in this embodiment, it is possible that the scattered dust contained in the atmosphere of the clinker cooler 30 will adhere to the walls of the combustible gas piping 53, causing a decrease in heat exchange efficiency over time. From the perspective of using the combustible gas 50b as combustion fuel in the cement kiln 20 while minimizing changes in combustion conditions over time, it can be said that a configuration in which the liquefied combustible gas 50a is injected into the clinker cooler 30 while remaining in liquid form is preferable.

When installing the flammable gas piping 53 inside the clinker cooler 30, it is preferable to install it at a high vertical height, for example, near the interior wall near the ceiling, so as not to obstruct the airflow inside the clinker cooler 30. However, the present invention does not limit the location inside the clinker cooler 30 where the flammable gas piping 53 can be installed.

As mentioned above, the area of the flammable gas piping 53 that passes through the clinker cooler 30 is intended to exchange heat with the atmospheric gas (high-temperature air) inside the clinker cooler 30. From this perspective, the shape of the flammable gas piping 53 installed in this area may be appropriately processed to increase its surface area. The shape may be any shape, and examples include a spiral shape, an uneven shape, etc.

(Variations)
The liquefied flammable gas utilization device of this embodiment has various variations. Each variation will be described below. Note that each variation can be combined with each other.

<1> In FIG. 4 , the flammable gas pipe 53 is arranged so that it passes through the first region 31 of the clinker cooler 30 and then connects to the flammable gas burner 55 via the outside of the clinker cooler 30. However, it is optional which region of the clinker cooler 30 the flammable gas pipe 53 passes through. For example, the flammable gas pipe 53 may be arranged so that it passes through the second region 32 in addition to the first region 31. As another example, the flammable gas pipe 53 may be arranged so that it passes through the second region 32 of the clinker cooler 30 and then connects to the flammable gas burner 55 via the outside of the clinker cooler 30. As yet another example, the flammable gas pipe 53 may be arranged so that it passes through the third region 33 of the clinker cooler 30 and then connects to the flammable gas burner 55 via the outside of the clinker cooler 30.

If the flammable gas 50b has a high purity, the likelihood of it igniting is extremely low, regardless of temperature. For example, the flammable range of ammonia is 15.5% to 27% by volume, and it will not spontaneously ignite if its purity exceeds 80% by volume. Even for hydrogen, the flammable gas most susceptible to spontaneous combustion, the maximum flammable range is approximately 75% by volume. For this reason, it is unlikely that the flammable gas piping 53 will spontaneously ignite while the liquefied flammable gas (50a, 50b) in liquid or gaseous state is flowing through it, regardless of the temperature range within the clinker cooler 30.

However, from a safety standpoint, if the flammable gas piping 53 is routed through the clinker cooler 30, it is more preferable to route it through an area showing a temperature below the ignition point of the flammable gas 50b. For example, if the liquefied flammable gas 50a is ammonia, the ignition point of ammonia is approximately 650°C, so it is preferable to arrange the flammable gas piping 53 so that it passes through one or both of the first area 31 and the second area 32 of the clinker cooler 30.

〈2〉 As shown in Figure 5, the gaseous flammable gas 50b may be mixed with primary air 73 flowing through primary air piping 72 and then blown in from the blowing point (flammable gas burner 55).

The liquefied flammable gas utilization device shown in Figure 5 comprises a primary air blower 71, a primary air pipe 72 through which primary air 73 flows, and a valve 74 installed on the primary air pipe 72. The flammable gas pipe 53 passes through a region (high-temperature region 53a) within the clinker cooler 30 and is connected to the primary air pipe 72 at a position before reaching the injection point. The primary air pipe 72 is arranged so that a portion of it passes through a region within the clinker cooler 30. In other words, the primary air pipe 72 is arranged so that it passes through the high-temperature region 72a. The primary air pipe 72 passes through a region (high-temperature region 72a) within the clinker cooler 30 and is connected to the flammable gas pipe 53 at a position before reaching the injection point.

With the above configuration, the primary air 73 flowing through the primary air piping 72 is heated as it passes through the high-temperature region 72a, and then mixed with the flammable gas 50b flowing through the flammable gas piping 53. As a result, the flammable gas 50b is injected in a preheated state, improving the combustion efficiency of the flammable gas 50b.

In the configuration shown in FIG. 5, the flammable gas 50b is mixed with the primary air 73 while flowing through the flammable gas piping 53. For this reason, the concentration of the flammable gas 50b contained in the mixed gas may fall within the flammable range, and in such a case, there is a concern that the flammable gas 50b may ignite while flowing through the flammable gas piping 53. In light of this, it is preferable to set the piping routes of the flammable gas piping 53 and the primary air piping 72 in advance so that the gas temperature at the confluence of the flammable gas piping 53 and the primary air piping 72 is below the ignition point of the flammable gas 50b.

Alternatively, the valve 74 may be adjusted so that the concentration of the flammable gas 50b contained in the mixed gas does not fall within the flammable range.

As shown in Figure 6, the combustible gas 50b and heated primary air 73 may be supplied to a common injection point (combustible gas burner 55) without being mixed. Specifically, the combustible gas burner 55 may have multiple ports, and the primary air pipe 72 may be connected to a port other than the port to which the combustible gas pipe 53 is connected. In this case, unlike the configuration shown in Figure 5, there is little risk of the combustible gas 50b igniting while flowing through the combustible gas pipe 53.

<3> In the configurations shown in Figures 5 and 6, atmospheric air is used as primary air 73, and the primary air piping 72 through which this primary air 73 flows is arranged to pass through the clinker cooler 30. In contrast, as shown in Figure 7, atmospheric gas within the clinker cooler 30 may also be used as primary air 73. In this case, too, the primary air piping 72 passes through the high-temperature region of the clinker cooler 30 before being directed to the injection point (combustible gas burner 55).

The atmospheric gas within the clinker cooler 30 primarily contains fugitive dust derived from the clinker 3. Because the combustible gas 50b contains almost no ash, its radiant heat transfer during combustion is lower than that of coal, the primary fuel. According to the configuration shown in Figure 7, primary air 73 containing fugitive dust is injected into the injection point along with the combustible gas 50b. This allows the fugitive dust to function as a radiant heat transfer medium during combustion of the combustible gas 50b, contributing to stabilizing the combustion of the combustible gas 50b.

In the example of Figure 7, similar to Figure 6, the flammable gas pipe 53 and the primary air pipe 72 are not connected, and flammable gas 50b and primary air 73 are blown in from the same flammable gas burner 55. In contrast, as in Figure 5, the two pipes (53, 72) may be connected, and a mixed gas formed by the merging of flammable gas 50b and primary air 73 may be blown in from the flammable gas burner 55. The same applies to Figure 8 below.

〈4〉 When the atmospheric gas inside the clinker cooler 30 is used as primary air 73, a dust collector 75 for collecting scattered dust contained in the extracted atmospheric gas may be provided on the path of the primary air piping 72 (see Figure 8). The scattered dust collected by the dust collector 75 can be used, for example, to mix with the clinker 3 discharged from the clinker cooler 30, or to mix with cement in the finishing process of cement production where gypsum or the like is added.

<5> The combustible gas 50b flowing through the combustible gas piping 53 and the high-temperature primary air 73 flowing through the primary air piping 72 may be mixed using an ejector. The mixed gas is blown in through the combustible gas burner 55. The ejector can be powered by the vaporized, high-pressure combustible gas 50b. If the ambient gas in the clinker cooler 30 is used as the primary air 73, a dust collector 75 may be provided, as shown in Figure 8, to prevent the ejector from being thinned by flying dust contained in the extracted ambient gas.

<6> In this embodiment, the flammable gas 50b is sent through the flammable gas piping 53 to the flammable gas burner 55 by the liquid delivery pressure of the liquid delivery pump 52 and the vaporization expansion pressure generated when the liquefied flammable gas 50a is vaporized. However, the present invention does not exclude a configuration in which a blower such as a Roots blower is installed in the flammable gas piping 53 to ensure the pressure required to blow the vaporized flammable gas 50b from the flammable gas burner 55.

〈7〉 In Figures 5 and 6, the primary air piping 72 passes through an area (high-temperature area 53a) within the clinker cooler 30, but it may also pass through the air extraction piping (41, 42, 43: see Figure 2) for extracting atmospheric gas from the clinker cooler 30. This point is also related to the content of the third embodiment, and will be explained in the section about the third embodiment.

[Third embodiment]
A third embodiment of the liquefied flammable gas utilization device, the liquefied flammable gas utilization method, and the cement production facility according to the present invention will be described below. Note that, with regard to the parts that are common to the parts already described in the above embodiments, the description will be simplified or omitted as appropriate.

Figure 9 is a diagram that schematically illustrates the structure of the liquefied flammable gas utilization device of this embodiment, following the example of Figure 2. This embodiment differs from the second embodiment in that the area through which the flammable gas piping 53 passes is not inside the clinker cooler 30, but inside the bleed piping (here, the exhaust gas bleed piping 41) for bleed-out atmospheric gas from the clinker cooler 30.

As described above, the exhaust gas bleed pipe 41 is a pipe for extracting the atmospheric gas present in the first region 31 of the clinker cooler 30 and directing it outside the system. In other words, the interior of the exhaust gas bleed pipe 41 contains air at a temperature similar to that of the atmosphere present in the first region 31 of the clinker cooler 30. Therefore, the internal space of the exhaust gas bleed pipe 41 corresponds to the high-temperature region 53a.

In other words, in this embodiment, as in the second embodiment, the delivered liquefied flammable gas 50a is vaporized as it passes through the high-temperature region 53a while flowing through the flammable gas piping 53, becoming flammable gas 50b. This flammable gas 50b flows through the flammable gas piping 53, is supplied to the flammable gas burner 55, and is then blown into the clinker cooler 30.

In the example of Figure 9, the flammable gas piping 53 passes through the inside of the exhaust gas extraction piping 41, but it may also pass through the inside of other extraction piping (raw material drying extraction piping 42, calciner extraction piping 43). Figure 10 shows a configuration example in which the flammable gas piping 53 passes through the inside of the raw material drying extraction piping 42, following the example of Figure 9.

As described above with reference to FIG. 2 , the bleed gas extracted from the clinker cooler 30 through the calciner bleed piping 43 is sent to the calciner 13 and used as part of the combustion air. The bleed gas extracted from the clinker cooler 30 through the raw material drying bleed piping 42 is sent to the raw material process and used as part of the drying air for the raw material M1. If the flammable gas piping 53 is routed through these bleed piping (42, 43), the temperature of the bleed gas flowing through each bleed piping (42, 43) may decrease slightly due to heat exchange between the piping wall of the flammable gas piping 53, through which the liquefied flammable gas 50a flows, and the atmosphere within the clinker cooler 30. On the other hand, the bleed gas flowing through the exhaust gas bleed piping 41 is not used for combustion or drying purposes and is discharged outside the system. For this reason, if the combustible gas piping 53 passes through the extraction piping that extracts the atmospheric gas from the clinker cooler 30, it is particularly preferable for it to pass through the calciner extraction piping 43.

The configuration of this embodiment can be appropriately combined with the configurations described above in the second embodiment.

In the second embodiment described above with reference to Figures 5 and 6, the ambient air serving as primary air 73 taken into the primary air piping 72 from the primary air blower 71 is heated while passing through the region (high-temperature region 53a) within the clinker cooler 30. However, similar to the flammable gas piping 53 of this embodiment, the primary air 73 in the primary air piping 72 may also be heated by passing through the extraction piping (41, 42, 43).

[Fourth embodiment]
A fourth embodiment of the liquefied flammable gas utilization device, the liquefied flammable gas utilization method, and the cement production facility according to the present invention will be described below. Note that, with regard to the parts that are common to the parts already described in the above embodiments, the description will be simplified or omitted as appropriate.

Figure 11 is a diagram that schematically illustrates the structure of the liquefied flammable gas utilization device of this embodiment, following the example of Figures 2 and 3. This embodiment differs from the first embodiment in that the flammable gas burner 55 is connected to the calciner bleed air piping 43 rather than the clinker cooler 30. In other words, in the configuration shown in Figure 11, the flammable gas burner 55 injects liquefied flammable gas 50a in a liquid state into the calciner bleed air piping 43.

As described above with reference to Figure 2, the calciner bleed pipe 43 bleeds the relatively high-temperature atmospheric gas (secondary air) from the third zone 33 of the clinker cooler 30 and leads it to the calciner 13. In the calciner 13, this high-temperature secondary air is used as part of the air for combustion of the main fuel.

As such, because extremely high-temperature bleed gas flows through the calciner bleed gas piping 43, when liquefied flammable gas 50a is blown into the calciner bleed gas piping 43, the calciner bleed gas piping 43 functions as a vaporizer, and the liquefied flammable gas 50a is vaporized within the calciner bleed gas piping 43 to become flammable gas 50b. Furthermore, within the calciner bleed gas piping 43, the flammable gas 50b mixes with the high-temperature air heading toward the calciner 13, causing the concentration of the flammable gas 50b contained in the mixed gas to fall within the flammable range and reach a temperature above its ignition point, causing the flammable gas 50b to begin combustion. Once combustion has begun, the flammable gas 50b flows into the calciner 13 and is used as part of the fuel used to calcinate the raw material M1 in the calciner 13.

Therefore, with the configuration of this embodiment, the combustible gas 50b can be used as part of the fuel in the calciner 13 while reducing concerns about combustion delay.

In the example shown in Figure 11, liquid liquefied flammable gas 50a is injected into the calciner bleed gas piping 43. However, by appropriately adopting the configurations of the second to third embodiments, it is also possible to inject gaseous flammable gas 50b obtained by vaporizing liquefied flammable gas 50a while it flows through the flammable gas piping 53 into the calciner bleed gas piping 43.

1: Cement manufacturing equipment 3: Clinker 11: Preheater 13: Calciner 14: Calciner burner 20: Cement kiln 20a: Kiln bottom section 20b: Kiln front section 21: Main burner 25: Primary air 30: Clinker cooler 31: First zone 32: Second zone 33: Third zone 41: Exhaust gas extraction pipe 42: Raw material drying extraction pipe 43: Calciner extraction pipe 50a: Liquefied flammable gas 50b: Gas vaporized from liquefied flammable gas (flammable gas)
51: Tank 52: Liquid pump 53: Combustible gas piping 53a: High temperature region 55: Combustible gas burner 71: Primary air blower 72: Primary air piping 72a: High temperature region 73: Primary air 74: Valve 75: Dust collector CA: Atmosphere M1: Cement raw material

Claims (12)

A liquefied flammable gas utilization device that can be attached to a cement manufacturing facility that has a calciner that calcines cement raw materials, a cement kiln that produces clinker by burning the cement raw materials calcined in the calciner, and a clinker cooler that is connected to a kiln front of the cement kiln,
a flammable gas piping that connects a tank storing a liquefied flammable gas with an injection point set in a specific region within the clinker cooler;
the specific region is a region in the clinker cooler where the atmospheric temperature is in the range of 600°C to 900°C, and, when a raw material drying extraction air pipe for extracting a part of the atmospheric gas in the clinker cooler for drying the cement raw materials is connected to the clinker cooler, the specific region is a region closer to the cement kiln than a connection point between the raw material drying extraction air pipe and the clinker cooler,
A device for utilizing liquefied flammable gas, characterized in that the flammable gas piping supplies the liquefied flammable gas or a flammable gas obtained by vaporizing the liquefied flammable gas during flow to the injection point. The device for utilizing liquefied flammable gas described in claim 1, characterized in that the flammable gas piping is not equipped with a blower that promotes the flow of the flammable gas. The liquefied flammable gas utilization device described in claim 1, characterized in that the flammable gas piping supplies the liquefied flammable gas to the injection point. The liquefied flammable gas utilization device described in claim 1 or 2, characterized in that the flammable gas piping is arranged to pass through either or both of the clinker cooler and the exhaust gas extraction piping through which the extracted gas extracted from the clinker cooler flows toward the discharge port, and the flammable gas obtained by vaporizing the liquefied flammable gas in a liquid state while flowing through the flammable gas piping is supplied to the injection point. The liquefied flammable gas utilization device described in claim 4, characterized in that the flammable gas piping passes through an area within the clinker cooler where the ambient temperature is within the range of 150°C to 1000°C. a burner attached to an end of the flammable gas pipe on the injection point side, for injecting the liquefied flammable gas in a gaseous state into the injection point;
a primary air pipe that passes through one or both of the clinker cooler and the exhaust gas extraction pipe and is connected to the combustible gas pipe at a position upstream of the burner,
6. A liquefied flammable gas utilization device as described in claim 4 or 5, characterized in that the flammable gas piping is configured to guide a mixed gas of the flammable gas and the primary air to the burner at a position downstream of the connection point with the primary air piping. a burner having a plurality of ports, attached to an end of the flammable gas pipe on the injection location side, for injecting the flammable gas into the injection location through one or more of the ports;
6. The device for utilizing liquefied flammable gas as described in claim 4 or 5, characterized in that it comprises a primary air pipe that is connected to one of the plurality of ports provided in the burner, other than the port to which the flammable gas pipe is connected, via one or both of the clinker cooler and the exhaust gas extraction pipe. The liquefied flammable gas utilization device described in claim 6 or 7, characterized in that the primary air piping is configured so that one or both of the atmospheric gas in the clinker cooler and the bleed gas in the exhaust gas bleed piping flow toward the burner side. 9. The device for utilizing liquefied flammable gas according to claim 8, characterized in that the primary air piping is provided with a primary air blower that promotes the flow of one or both of the atmospheric gas in the clinker cooler and the bleed gas in the exhaust gas bleed piping through the primary air piping, and a dust collector that recovers scattered dust contained in the gas flowing through the primary air piping. A method for utilizing a liquefied flammable gas in a cement production process for producing clinker using cement production equipment including a calciner for calcining cement raw materials, a cement kiln for burning the cement raw materials calcined in the calciner, and a clinker cooler connected to a kiln front of the cement kiln , the method comprising:
Injecting liquefied flammable gas into a flammable gas pipe connected to an injection point set in a specific region within the clinker cooler;
supplying the liquefied flammable gas or a flammable gas obtained by vaporizing the liquefied flammable gas during flow of the liquefied flammable gas to the blowing point ;
the specific region is a region within the clinker cooler where the ambient temperature is in the range of 600°C to 900°C, and, when a raw material drying extraction piping for extracting a portion of the ambient gas within the clinker cooler for drying the cement raw materials is connected to the clinker cooler, the specific region is a region closer to the cement kiln than a connection point between the raw material drying extraction piping and the clinker cooler . The method for utilizing liquefied flammable gas described in claim 10, characterized in that the liquefied flammable gas contains 70% by volume or more of one or more gases belonging to the group consisting of ammonia, methane, ethane, propane, and butane. a calciner for calcining cement raw materials;
a cement kiln that produces clinker by firing the cement raw materials calcined in the calciner;
a clinker cooler connected to the front of the cement kiln;
A tank in which liquefied flammable gas is stored in a liquefied state is provided, and a flammable gas piping is provided to connect the tank to an injection point set in a specific region within the clinker cooler,
the specific region is a region in the clinker cooler where the atmospheric temperature is in the range of 600°C to 900°C, and, when a raw material drying extraction air pipe for extracting a part of the atmospheric gas in the clinker cooler for drying the cement raw materials is connected to the clinker cooler, the specific region is a region closer to the cement kiln than a connection point between the raw material drying extraction air pipe and the clinker cooler,
A cement manufacturing facility characterized in that the flammable gas piping supplies the liquefied flammable gas or a flammable gas obtained by vaporizing the liquefied flammable gas during flow to the injection point.