Gas mixing system

Abstract

To provide a gas mixing system which can properly maintain an air fuel ratio and a calorific value when carrying out multifuel combustion of a main fuel gas and an auxiliary fuel gas with a simple configuration using a control valve.SOLUTION: A gas mixing system 1 includes: a main fuel gas control valve 2; a combustion air control valve 3 which controls a flow rate of combustion air A to be supplied to a device 10 using fuel according to a flow rate controlled by the main fuel gas control valve 2; and an auxiliary fuel gas control valve 4 which controls a flow rate of auxiliary fuel gas F2 mixed in the main fuel gas F1. The gas mixing system 1 further includes: an upper side branch pipe 631 which is connected to an upstream side position of the main fuel gas control valve 2 in a main fuel pipe 61 from a downstream side position of the auxiliary fuel gas control valve 4; a downstream side branch pipe 632 which is connected to a downstream side position of the main fuel gas control valve 2 in the main fuel pipe 61 from the downstream side position of the auxiliary fuel gas control valve 4; and a proportional control valve 5 which controls a flow rate of the auxiliary fuel gas F2 flowing in the downstream side branch pipe 632.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a gas mixing system.

Background Art

[0002] In fuel-using equipment that uses fuel gas such as city gas, there are cases where combustion is desired not only with city gas but also with fuel gases such as hydrogen and propane. In this case, a gas mixing system that supplies a mixed fuel gas generated by mixing two types of fuel gases to the fuel-using equipment is used.

[0003] As an apparatus for using a mixed fuel gas in an engine as a fuel-using device, for example, there is a fuel control device for a multi-fuel engine described in Patent Document 1. In this fuel control device, a first fuel injection valve for injecting a first fuel and a second fuel injection valve for injecting a second fuel are used, and the first fuel and the second fuel are supplied to the engine at a predetermined ratio.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] <opportune For example, in fuel-using equipment that burns only a main fuel gas such as city gas, when a sub-fuel gas having a composition different from that of the main fuel gas is mixed with the main fuel gas for co-combustion, a difference in calorific value between the main fuel gas and the sub-fuel gas may become a problem. Therefore, when co-combusting the main fuel gas and the sub-fuel gas in fuel-using equipment, in order to compensate for the difference in calorific value from the case of burning only the main fuel gas while appropriately maintaining the air-fuel ratio with a simple configuration, further improvements are required. <opportune <opportune

[0006] <opportune This invention has been made in view of the above problems, and aims to provide a gas mixing system that can appropriately maintain the air-fuel ratio and calorific value when mixing a main fuel gas and a secondary fuel gas with a simple configuration using a control valve. [Means for solving the problem]

[0007] One aspect of the present invention is, A gas mixing system that supplies a mixed fuel gas of a main fuel gas and a secondary fuel gas with a lower calorific value per unit volume than the main fuel gas to fuel-using equipment, A main fuel gas control valve is located in the main fuel piping to which the main fuel gas is supplied, A combustion air control valve is configured to control the flow rate of combustion air supplied to the fuel-using equipment in accordance with the flow rate controlled by the main fuel gas control valve, A secondary fuel gas control valve is placed in the secondary fuel piping to which the secondary fuel gas is supplied and configured to control the flow rate of the secondary fuel gas mixed with the main fuel gas. From the downstream position of the auxiliary fuel gas control valve, an upstream branch pipe is connected to the upstream position of the main fuel piping where the main fuel gas control valve is located, From the downstream position of the auxiliary fuel gas control valve, a downstream branch pipe is connected to the downstream position of the main fuel piping, where the main fuel gas control valve is located. The gas mixing system includes a proportional control valve configured to control the flow rate of the auxiliary fuel gas flowing through at least one of the upstream branch pipe and the downstream branch pipe. [Effects of the Invention]

[0008] In the gas mixing system according to the above embodiment, the piping connected to the main fuel piping by the auxiliary fuel gas control valve is divided into an upstream branch pipe connected to the upstream position of the main fuel gas control valve and a downstream branch pipe connected to the downstream position of the main fuel gas control valve. A proportional control valve controls the flow rate of the auxiliary fuel gas flowing through at least one of the upstream branch pipe and the downstream branch pipe. This configuration makes it possible to adjust the ratio of the flow rate of auxiliary fuel gas that flows to the fuel-using equipment via the main fuel gas control valve and the ratio of the flow rate of auxiliary fuel gas that flows to the fuel-using equipment bypassing (without passing through) the main fuel gas control valve.

[0009] More specifically, the flow rate of combustion air controlled by the combustion air control valve is adjusted according to the flow rate of the mixed fuel gas (main fuel gas and auxiliary fuel gas) flowing from the upstream branch pipe to the main fuel gas control valve. Then, by adjusting the opening degrees of the main fuel gas control valve, auxiliary fuel gas control valve, and proportional control valve, the mixed fuel gas that passes through the main fuel gas control valve is sufficient to maintain the opening degree of the combustion air control valve appropriately. This ensures that the air-fuel ratio of the mixed fuel gas supplied to the fuel-using equipment is appropriately adjusted. On the other hand, because the auxiliary fuel gas is mixed with the main fuel gas, the calorific value of the mixed fuel gas passing through the main fuel gas control valve is lower than the calorific value when only the main fuel gas passes through the main fuel gas control valve.

[0010] Therefore, the mixed fuel gas that has passed through the main fuel gas control valve is further mixed with the auxiliary fuel gas flowing from the downstream branch pipe. This compensates for any deficiency in the calorific value of the mixed fuel gas supplied to the fuel-using equipment, and the calorific value of the mixed fuel gas supplied to the fuel-using equipment is appropriately adjusted. For this reason, when co-firing the main fuel gas and auxiliary fuel gas, the air-fuel ratio and calorific value of the mixed fuel gas supplied to the fuel-using equipment are appropriately adjusted by using an upstream branch pipe, a downstream branch pipe, and a proportional control valve.

[0011] Therefore, according to the gas mixing system of the above embodiment, the air-fuel ratio and calorific value when mixing a main fuel gas and a secondary fuel gas can be appropriately maintained by a simple configuration using a control valve. [Brief explanation of the drawing]

[0012] [Figure 1] An explanatory diagram showing the configuration of a gas mixing system according to an embodiment. [Modes for carrying out the invention]

[0013] A preferred embodiment of the aforementioned gas mixing system will be described with reference to the drawings. <Embodiment> As shown in Figure 1, the gas mixing system 1 in this embodiment supplies a mixed fuel gas F3, which is a mixture of a main fuel gas F1 and a secondary fuel gas F2 having a lower calorific value per unit volume than the main fuel gas F1, to the fuel-using equipment 10. The gas mixing system 1 includes a main fuel gas control valve 2, a combustion air control valve 3, a secondary fuel gas control valve 4, an upstream branch pipe 631, a downstream branch pipe 632, and a proportional control valve 5.

[0014] The main fuel gas control valve 2 is located in the main fuel piping 61 to which the main fuel gas F1 is supplied. The combustion air control valve 3 is configured to control the flow rate of combustion air A supplied to the fuel-using equipment 10 according to the flow rate controlled by the main fuel gas control valve 2. The auxiliary fuel gas control valve 4 is located in the auxiliary fuel piping 63 to which the auxiliary fuel gas F2 is supplied, and is configured to control the flow rate of auxiliary fuel gas F2 mixed with the main fuel gas F1.

[0015] The upstream branch pipe 631 connects from the downstream position of the auxiliary fuel gas control valve 4 to the upstream position of the main fuel gas control valve 2 in the main fuel piping 61. The downstream branch pipe 632 connects from the downstream position of the auxiliary fuel gas control valve 4 to the downstream position of the main fuel gas control valve 2 in the main fuel piping 61. The proportional control valve 5 is located in the downstream branch pipe 632 and is configured to control the flow rate of the auxiliary fuel gas F2 flowing through the downstream branch pipe 632.

[0016] The gas mixing system 1 of this embodiment will be described in detail below. (Gas mixing system 1) As shown in FIG. 1, the gas mixing system 1 is used to supply a mixed fuel gas F3 of a main fuel gas F1 and a sub-fuel gas F2 to a fuel-using device 10 that uses fuel gas. The gas mixing system 1 is formed independently of the fuel-using device 10 and can be installed as a device that supplies the mixed fuel gas F3 to various fuel-using devices 10. The fuel-using device 10 includes a cogeneration device including a gas engine, a combustion device such as a burner, and the like.

[0017] (Main fuel gas F1 and sub-fuel gas F2) In this embodiment, city gas is used as the main fuel gas F1, and hydrogen gas is used as the sub-fuel gas F2. The calorific value per unit volume of the hydrogen gas as the sub-fuel gas F2 is lower than the calorific value per unit volume of the city gas as the main fuel gas F1. Therefore, when the mixed fuel gas F3 having the same flow rate as the flow rate in the case of exclusive combustion of the main fuel gas F1 is supplied to the fuel-using device 10, the higher the mixing ratio of the sub-fuel gas F2 to the main fuel gas F1, the lower the calorific value of the mixed fuel gas F3 supplied to the fuel-using device 10. Therefore, the calorific value of the mixed fuel gas F3 consumed in the fuel-using device 10 is ensured by supplying the sub-fuel gas F2 to the fuel-using device 10 by bypassing the main fuel gas control valve 2 through the downstream branch pipe 632 and the proportional control valve 5. Note that various fuel gases having different compositions may be used for the main fuel gas F1 and the sub-fuel gas F2.

[0018] (First control device 71 and second control device 72) As shown in FIG. 1, the gas mixing system 1 of the present embodiment is added to an existing fuel-using device 10 that burns a main fuel gas F1 and combustion air A, and can burn a mixed fuel gas F3 of the main fuel gas F1 and the sub-fuel gas F2 and the combustion air A at an appropriate air-fuel ratio and calorific value. The control device (referred to as the second control device 72) of the gas mixing system 1 of the present embodiment is provided separately from the control device (referred to as the first control device 71) of the fuel-using device 10. By operating the first control device 71 and the second control device 72 separately, the gas mixing system 1 can be applied to the existing fuel-using device 10 without changing the configuration of the existing fuel-using device 10.

[0019] The first control device 71 of the fuel-using device 10 of the present embodiment is configured to control the opening degree of the main fuel gas control valve 2 and the opening degree of the combustion air control valve 3 so that the combustion of the main fuel gas F1 and the combustion air A in the fuel-using device 10 is performed at a target air-fuel ratio. In other words, the first control device 71 is configured to perform exclusive combustion of the main fuel gas F1 at the target air-fuel ratio. The calorific value per unit time of the main fuel gas F1 supplied to the fuel-using device 10 is set to the target calorific value by the first control device 71.

[0020] The second control device 72 of the gas mixing system 1 determines the mixing ratio of the main fuel gas F1 and the sub-fuel gas F2 by controlling the opening degree of the main fuel gas control valve 2 and the opening degree of the sub-fuel gas control valve 4, and is configured to maintain the air-fuel ratio and calorific value in the fuel-using device 10 by controlling the opening degree of the proportional control valve 5. In other words, the second control device 72 is configured to adjust the opening degree of the proportional control valve 5 so as to maintain the air-fuel ratio in the fuel-using device 10 when performing exclusive combustion of the main fuel gas F1 and the calorific value per unit time in the fuel-using device 10 when performing exclusive combustion of the main fuel gas F1.

[0021] By using the first control device 71 and the second control device 72 in combination, it is easy to add the gas mixing system 1 to the existing fuel-using equipment 10. Alternatively, the functions of the second control device 72 may be integrated into the first control device 71 to form a single control device. In this case, the control configuration of the gas mixing system 1 can be constructed using the existing first control device 71.

[0022] (Main fuel gas control valve 2) As shown in Figure 1, the main fuel gas control valve 2 is located in the main fuel piping 61 to which the main fuel gas F1, such as city gas, is supplied, and is configured to control the flow rate of the main fuel gas F1 supplied to the fuel-using equipment 10. The main fuel gas control valve 2 has a function to measure mass flow rate and is composed of a mass flow controller capable of supplying the required mass flow rate of fluid. In order to supply a mixture of air and fuel with a target air-fuel ratio to the fuel-using equipment 10, the mass flow rate of combustion air A is determined by adjusting the opening degree of the combustion air control valve 3 based on the mass flow rate of the main fuel gas F1 adjusted by the main fuel gas control valve 2.

[0023] (Combustion air control valve 3) As shown in Figure 1, the combustion air control valve 3 is configured to control the flow rate of combustion air A supplied to the fuel-using equipment 10 according to the total flow rate of the main fuel gas F1 flowing through the main fuel gas control valve 2 and the auxiliary fuel gas F2 flowing through the main fuel gas control valve 2 via the upstream branch pipe 631. The combustion air control valve 3 is configured with a mass flow controller, similar to the main fuel gas control valve 2.

[0024] The combustion air control valve 3 is connected to or positioned downstream of the main fuel gas F1 flow in the main fuel piping 61, below the position of the main fuel gas control valve 2. More specifically, the main fuel piping 61 is joined and connected to the air piping 61, and a blower that takes in outside air as combustion air A is connected to the air piping 62. The combustion air control valve 3 is positioned in the air piping 62 and is configured to allow combustion air A to flow from the air piping 62 to the main fuel piping 61.

[0025] (Auxiliary fuel gas control valve 4) As shown in Figure 1, the auxiliary fuel gas control valve 4 is located in the auxiliary fuel piping 63 to which the auxiliary fuel gas F2, such as hydrogen gas, is supplied, and is configured to control the flow rate of the auxiliary fuel gas F2 supplied to the fuel-using equipment 10. The auxiliary fuel gas control valve 4 is configured with a mass flow controller, similar to the main fuel gas control valve 2.

[0026] The ratio of the opening degree of the main fuel gas control valve 2 to the opening degree of the auxiliary fuel gas control valve 4 sets the ratio of the mass flow rate of the main fuel gas F1 and the mass flow rate of the auxiliary fuel gas F2 used in the fuel-using equipment 10. In other words, the ratio of the opening degree of the main fuel gas control valve 2 to the opening degree of the auxiliary fuel gas control valve 4 sets the co-firing ratio of the auxiliary fuel gas F2 in the mixed fuel gas F3 used in the fuel-using equipment 10.

[0027] (Upstream branch pipe 631 and downstream branch pipe 632) As shown in Figure 1, the auxiliary fuel piping 63 branches into an upstream branch pipe 631 and a downstream branch pipe 632 downstream of the location of the auxiliary fuel gas control valve 4 in the flow of auxiliary fuel gas F2. The upstream branch pipe 631 is connected from the downstream side of the auxiliary fuel gas control valve 4 to the upstream side of the main fuel gas control valve 2. The downstream branch pipe 632 is connected from the downstream side of the auxiliary fuel gas control valve 4 to the downstream side of the main fuel gas control valve 2. A proportional control valve 5 is located in the downstream branch pipe 632, and the flow rate of auxiliary fuel gas F2 flowing through the downstream branch pipe 632 is restricted, so that the flow rate of auxiliary fuel gas F2 flowing from the downstream branch pipe 632 to the main fuel piping 61 is less than the flow rate of auxiliary fuel gas F2 flowing from the upstream branch pipe 631 to the main fuel piping 61.

[0028] (Proportional control valve 5) As shown in Figure 1, the proportional control valve 5 is located in the downstream branch pipe 632 connected to the downstream side of the auxiliary fuel gas control valve 4. The proportional control valve 5 is composed of a solenoid valve or the like, whose opening degree can be adjusted. By adjusting the opening degree of the proportional control valve 5, the flow rate of the auxiliary fuel gas F2 flowing to the downstream branch pipe 632 is adjusted, and consequently, the flow rate of the auxiliary fuel gas F2 flowing to the upstream branch pipe 631 is also adjusted. In this embodiment, by controlling the opening degree of the proportional control valve 5, the calorific value of the mixed fuel gas F3 of the main fuel gas F1 and auxiliary fuel gas F2 supplied to the fuel-using equipment 10 by the auxiliary fuel gas F2 flowing to the fuel-using equipment 10 via the downstream branch pipe 632 is configured to approach the calorific value of the main fuel gas F1 when only the main fuel gas F1 is supplied to the fuel-using equipment 10.

[0029] In other words, the opening degree of the proportional control valve 5 is set to adjust the flow rate of the auxiliary fuel gas F2 that flows to the fuel-using equipment 10 via the downstream branch pipe 632, so that the amount of heat generated per unit time of the main fuel gas F1 supplied to the fuel-using equipment 10 approaches the target amount of heat generated per unit time set by the first control device 71 of the fuel-using equipment 10. With this configuration, even when the gas mixing system 1 is applied to the existing fuel-using equipment 10, the amount of heat generated for the existing fuel-using equipment 10 can be appropriately secured.

[0030] The calorific value of the mixed fuel gas F3, consisting of main fuel gas F1 and auxiliary fuel gas F2, supplied to the fuel-using equipment 10 may be set to be equivalent to the calorific value of the main fuel gas F1 when only the main fuel gas F1 is supplied to the fuel-using equipment 10. In this case, the flow rate (volume flow rate) of the auxiliary fuel gas F2 flowing to the fuel-using equipment 10 via the upstream branch pipe 631 and the main fuel gas control valve 2 should be set to Q1 [m³] 3 ], the flow rate (volume flow rate) of the auxiliary fuel gas F2 that flows to the fuel-using equipment 10 via the downstream branch pipe 632 is Q2[m 3 ], the theoretical amount of air required to completely combust the main fuel gas F1 is A1[m 3 ], the theoretical amount of air required to completely combust the auxiliary fuel gas F2 is A2[m³ 3When this is the case, the opening degree of the proportional control valve 5 is adjusted so that the ratio of Q1 to Q2 is Q1:Q2=1:(A1 / A2)-1.

[0031] When considering the calorific value and co-firing ratio, the flow rates of the main fuel gas F1 and secondary fuel gas F2 can be treated as volumetric flow rates. On the other hand, when considering the air-fuel ratio, the flow rates of the main fuel gas F1 and secondary fuel gas F2 can be treated as mass flow rates.

[0032] In addition to the first control device 71, the main fuel gas control valve 2, combustion air control valve 3, main fuel piping 61, air piping 62, etc., may be those already installed in the existing fuel-using equipment 10. On the other hand, in addition to the second control device 72, the auxiliary fuel gas control valve 4, proportional control valve 5, auxiliary fuel piping 63, upstream branch pipe 631, and downstream branch pipe 632 may be added as a gas mixing system 1.

[0033] (Effects and Benefits) In this gas mixing system 1, the auxiliary fuel gas control valve 4 divides the piping connected to the main fuel piping 61 into an upstream branch pipe 631 connected to the upstream position of the main fuel gas control valve 2 and a downstream branch pipe 632 connected to the downstream position of the main fuel gas control valve 2. The proportional control valve 5 adjusts the ratio of the flow rate of auxiliary fuel gas F2 flowing through the downstream branch pipe 632 to the flow rate of auxiliary fuel gas F2 flowing through the upstream branch pipe 631. This configuration allows adjustment of the ratio of the flow rate of auxiliary fuel gas F2 flowing to the fuel-using equipment 10 via the main fuel gas control valve 2 and the ratio of the flow rate of auxiliary fuel gas F2 flowing to the fuel-using equipment 10 by bypassing (not passing through) the main fuel gas control valve 2.

[0034] More specifically, the flow rate of combustion air A by the combustion air control valve 3 is adjusted according to the flow rate of mixed fuel gas F3, which is a mixture of main fuel gas F1 and auxiliary fuel gas F2, flowing from the upstream branch pipe 631 to the main fuel gas control valve 2. Then, by adjusting the opening degrees of the main fuel gas control valve 2, the auxiliary fuel gas control valve 4, and the proportional control valve 5, the mixed fuel gas F3 that passes through the main fuel gas control valve 2 is adjusted to maintain the opening degree of the combustion air control valve 3 appropriately. This appropriately adjusts the air-fuel ratio of the mixed fuel gas F3 supplied to the fuel-using equipment 10. On the other hand, because auxiliary fuel gas F2 is mixed with the main fuel gas F1, the calorific value of the mixed fuel gas F3 passing through the main fuel gas control valve 2 is lower than the calorific value when only the main fuel gas F1 passes through the main fuel gas control valve 2.

[0035] Therefore, the mixed fuel gas F3 that has passed through the main fuel gas control valve 2 is further mixed with the auxiliary fuel gas F2 flowing from the downstream branch pipe 632. This compensates for any deficiency in the calorific value of the mixed fuel gas F3 supplied to the fuel-using equipment 10, and the calorific value of the mixed fuel gas F3 supplied to the fuel-using equipment 10 is appropriately adjusted. Thus, when co-firing the main fuel gas F1 and the auxiliary fuel gas F2, the air-fuel ratio and calorific value of the mixed fuel gas F3 supplied to the fuel-using equipment 10 are appropriately adjusted by the configuration using the upstream branch pipe 631, the downstream branch pipe 632, and the proportional control valve 5.

[0036] Therefore, according to the gas mixing system 1 of this embodiment, the air-fuel ratio and calorific value when co-firing the main fuel gas F1 and the auxiliary fuel gas F2 can be appropriately maintained with a simple configuration using a proportional control valve 5. Furthermore, the gas mixing system 1 can be added to existing fuel-using equipment 10 and can be realized by adding simple devices such as an auxiliary fuel gas control valve 4, an upstream branch pipe 631, a downstream branch pipe 632, and a proportional control valve 5.

[0037] The present invention is not limited to these embodiments, and further different embodiments can be constructed without departing from the spirit of the invention. Furthermore, the present invention includes various modifications, modifications within the equivalent range, and so on. [Explanation of Symbols]

[0038] 1. Gas mixing system 10 Fuel-using equipment 2. Main fuel gas control valve 3. Combustion air control valve 4. Auxiliary fuel gas control valve 5. Proportional control valve 61 Main fuel piping 62 Air Piping 63 Auxiliary fuel piping 631 Upstream branch pipe 632 Downstream branch pipe 71 First control device 72 Second Control Device F1 main fuel gas F2 auxiliary fuel gas F3 mixed fuel gas A Combustion air

Claims

1. A gas mixing system that supplies a mixed fuel gas of a main fuel gas and a secondary fuel gas with a lower calorific value per unit volume than the main fuel gas to fuel-using equipment, A main fuel gas control valve is located in the main fuel piping to which the main fuel gas is supplied, A combustion air control valve is configured to control the flow rate of combustion air supplied to the fuel-using equipment in accordance with the flow rate controlled by the main fuel gas control valve, A secondary fuel gas control valve is placed in the secondary fuel piping to which the secondary fuel gas is supplied and configured to control the flow rate of the secondary fuel gas mixed with the main fuel gas. From the downstream position of the auxiliary fuel gas control valve, an upstream branch pipe is connected to the upstream position of the main fuel piping where the main fuel gas control valve is located, From the downstream position of the auxiliary fuel gas control valve, a downstream branch pipe is connected to the downstream position of the main fuel piping, where the main fuel gas control valve is located. A gas mixing system comprising a proportional control valve configured to control the flow rate of the auxiliary fuel gas flowing through at least one of the upstream branch pipe and the downstream branch pipe.

2. The proportional control valve is located in the downstream branch pipe and is configured to control the flow rate of the auxiliary fuel gas flowing through the downstream branch pipe. The combustion air control valve is configured to control the flow rate of combustion air supplied to the fuel-using equipment according to the total flow rate of the main fuel gas flowing through the main fuel gas control valve and the auxiliary fuel gas flowing through the main fuel gas control valve via the upstream branch pipe. The gas mixing system according to claim 1, wherein the opening degree of the proportional control valve is controlled so that the calorific value of the mixed fuel gas of the main fuel gas and the auxiliary fuel gas supplied to the fuel-using equipment by the auxiliary fuel gas flowing to the fuel-using equipment via the downstream branch pipe is brought closer to the calorific value of the main fuel gas when only the main fuel gas is supplied to the fuel-using equipment.

3. The fuel-using equipment includes a first control device configured to control the opening degree of the main fuel gas control valve and the opening degree of the combustion air control valve so that the combustion of the main fuel gas and the combustion air is performed at a target air-fuel ratio, A gas mixing system according to claim 1 or 2, comprising: a second control device configured to determine the mixing ratio of the main fuel gas and the auxiliary fuel gas by controlling the opening degree of the main fuel gas control valve and the opening degree of the auxiliary fuel gas control valve, and to maintain the air-fuel ratio by controlling the opening degree of the proportional control valve.

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