JPS6361565B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method of mixing a plurality of gaseous fuels with different combustion characteristics and varying amounts of which can be supplied, and supplying the mixture as a mixed gaseous fuel with constant combustion characteristics. Careful combustion management in combustion equipment is an important point to keep in mind when promoting energy conservation. However, the level of rational fuel supply technology in large-scale business establishments that mix multiple gaseous fuels with different combustion characteristics and fluctuating supply quantities and use them in various types of combustion equipment is becoming increasingly important. However, the current situation is that it lags behind other energy-saving technologies. For example, in an integrated steelworks, gaseous fuels such as blast furnace gas (hereinafter abbreviated as BFG) have different combustion characteristics and can be supplied in varying amounts. Three to four types of coke oven gas (hereinafter abbreviated as COG), refined coke oven gas (hereinafter abbreviated as RG), and converter gas (hereinafter abbreviated as LDG) are used at a rate per ^1Nm3 of the mixed gas fuel. They are mixed to maintain a constant calorific value and used in multiple heating furnaces, soaking furnaces, and other combustion equipment. For example, for heating furnace systems, COG, BFG,
For a soaking furnace system where LDG and RG are mixed,
COG, BFG, and LDG are mixed. The above-mentioned RG uses the surplus, and the surplus generation amount (supplyable amount) fluctuates widely. The above-mentioned LDG is generated intermittently, and its generation amount (supplyable amount) also fluctuates. In other words, the amount that can be supplied fluctuates widely. Although the amount of BFG and COG generated fluctuates depending on factors such as the operating rate of the furnace, the range of fluctuation is smaller than that of LDG. Therefore, conventionally, in order to keep the calorific value (calorie) of the mixed gas fuel constant by mixing just the right amount of LDG, RG, or LDG, COG, BFG, and LDG are mixed according to the amount of LDG, RG, or LDG that can be supplied. ,RG or COG,
The mixing ratio of BFG and LDG is adjusted sequentially (for example, every hour). This allows LDG, RG or
Although it is possible to control the calorific value of the mixed gaseous fuel at a constant level by mixing just enough LDG, the mixing ratio of each gaseous fuel to be mixed changes and the properties of each gaseous fuel to be mixed are different. Amount (less than or equal to
Ao) and density (hereinafter abbreviated as ρ)
changes, and Ao/√, which is Ao corrected by √, changes. Tables 1 and 2 illustrate that even if the calorific value is constant, Ao/√ changes depending on the mixing ratio. For details, see Mixed gas fuel with a calorific value of 1700 Kcal/Nm ³ by mixing BFG, COG, and LDG (Case 1)
The following shows the properties of the mixed gas fuel (Case 2) when a large amount of LDG was used, as the amount of LDG that could be supplied (generated amount) increased.

【table】

[Table] As shown in Fig. 2, when Ao/√ of the mixed gas fuel changes, it is possible to Combustion efficiency decreases. This shortcoming will be discussed in detail. In the general combustion furnace shown in FIG. 2, the furnace 10a
When the furnace temperature changes due to disturbance, the thermometer 11a
The amount of change in furnace temperature detected by the signal cable 16
a, the temperature controller 15a converts it into a flow rate control amount, and the signal cable 17a converts it into a valve closing degree control amount by the flow rate controller 12a, which controls the mixed gas fuel flow rate control valve 5a to properly control the furnace. Keeps you warm. Note that even if Ao/√ of the mixed gas fuel changes, the furnace temperature is maintained at an appropriate level. However, the mixed gas fuel
Combustion efficiency decreases as Ao/√ changes. That is, in general, the flow rate of mixed gas fuel is expressed by equation (1), However, Q ^f is the flow rate of the mixed gas fuel [Nm ³ /H] Δp is the differential pressure detected at the orifice of the mixed gas fuel [Kg/cm ² ] ρ is the density of the mixed gas fuel [Kg/Nm ³ ] k is the orifice Constant determined at the time of design [(Nm ³ ) 1/2 cm/H] The amount of air required for proper combustion is expressed by equation (2), so Q _A = m・Ao・Q ^f (2) where Q _A is the combustion Amount of air used [Nm ³ /H] m is the margin necessary for proper combustion
(Hereinafter referred to as air ratio) Ao is the theoretical amount of air required to burn 1 m ³ of mixed gaseous fuel [Nm ³ /Nm ³ ] From equations (1) and (2), the following equation (3) is established. . Here, regarding the amount of combustion air Q _A , in the combustion control system of the furnace temperature control system shown in FIG. It is multiplied by m and controlled by the flow rate controller 13a. In other words, in equation (3), k is a constant and m is fixed at a set value, so when Ao/√ changes, even though the air amount needs to be changed, the air amount changes from the mixed gas fuel It changes only by the differential pressure Δp of
Since it is not controlled by changes in Ao/√, there will be excess or insufficient air, leading to a decrease in combustion efficiency. In order to avoid this, it may be possible to install a special control mechanism, so-called exhaust gas O ₂ control mechanism, that detects the excess or deficiency of air based on the oxygen concentration of the combustion gas and adjusts the amount of air. This exhaust gas O ₂ control mechanism is required for each burner, which requires a huge amount of equipment investment. When mixing n types (n≧3) of gaseous fuels with different combustion characteristics and fluctuating supplyable amounts, the present invention provides (n-2) types of gaseous fuels with widely varying supplyable amounts. In large-scale business establishments where gaseous fuel is mixed in just the right amount and used in various combustion equipment, a mixed gaseous fuel with a constant Ao/√, that is, a constant air-fuel ratio, is supplied to the combustion equipment to perform combustion. The aim is to improve the combustion efficiency of equipment. The gist of the invention is as follows. The combustion characteristics are different and the amount that can be supplied varies.
species (n≧3) of gaseous fuels are mixed, and the supplyable amount of the gaseous fuels varies widely (n−
2) When mixing the types of gaseous fuels in just the right amount, for the type of gaseous fuel (n-2) whose supplyable amount fluctuates widely, the target supply amount is set sequentially according to the supplyable amount. , the flow rate is controlled to match the supply amount of gaseous fuel with the set supply amount, and for the other two types of gaseous fuels, the value of the ratio between the theoretical air amount and the square root of the density of the gaseous fuel after mixing is adjusted in advance. The air-fuel ratio is kept constant by determining a target supply amount of each gaseous fuel so as to be equal to a set target value, and controlling the flow rate so that the supply amount of each gaseous fuel matches the target supply amount. Method of supplying mixed gas fuel. Next, the method of the present invention will be explained based on the example of the apparatus shown in FIG. 1 where n=3, that is, three types of gaseous fuels, BFG, LDG, and COG, are mixed and supplied to the combustion equipment. In Figure 1, 1, 2 and 3 have different combustion characteristics,
LDG, BFG and COG whose supply capacity fluctuates
(hereinafter referred to as gaseous fuels A, B, and C) generation equipment. In particular, gaseous fuel A has a short generation period and its generation amount (supplyable amount) fluctuates. On the other hand, gaseous fuels B and C are generated almost stably over a long period of time, although the amount generated fluctuates due to wind shutdown of the furnace, partial repair of the furnace, etc. In this way, the gaseous fuel A is a gaseous fuel whose supplyable amount fluctuates widely, and in order to mix it in just the right amount, the target supply amount is successively set in the computer 21 according to the supplyable amount. It's fuel. Each of the gaseous fuels A, B, and C passes through each transport pipe 4, 5, and 6, and is transported to each storage facility 7, 8, and 9, and then each flow rate control valve 10, 11, and 12.
After adjusting the flow rate, the flow rate is measured by each flow meter 13, 14, and 15 having a throttle mechanism, and mixed by a mixing device 16 to become a mixed gas fuel,
Via transport pipe 17, combustion equipment 18, 19, 20
It is burned at The computer 21 calculates the amount of mixed gas fuel for gaseous fuels B and C every time the target supply amount of gaseous fuel A is changed according to the supplyable amount of gaseous fuel A.
A target supply amount that makes Ao/√ equal to the set target value is calculated, and these target supply amounts are provided to the calculator 22. Specifically, when the target supply amount of gaseous fuel A is changed, the flow rates of gaseous fuels A, B, and C input via the signal transmission cables 24, 25, and 26 and the input target of gaseous fuel A are changed. The target supply amount of gas A is set using the supply amount, the Ao value and ρ value of each gaseous fuel A, B, and C that have been input in advance, and the Ao/√ target value of the mixed gas fuel. Target supply amount of unknown B and C gaseous fuels excluding fuel
Find f _B and f _C by solving the following simultaneous equations (4) and (5). f′ _n =f′ _A +f′ _B +f′ _C (5) where Ao _A = theoretical air amount (Ao) value of gaseous fuel A
(Known) Ao _B = B's ( ) Ao _C = C's ( ) Ao _n /√ _n = Ao /√ target value of mixed gas fuel
( 〃 ) ρ _A = Density (ρ) value of gaseous fuel A ( 〃 ) ρ _B = 〃 B 〃 ( 〃 ) ρ _C = 〃 C 〃 ( 〃 ) f _A = Set supply amount of gaseous fuel A (known) f _B = Target supply amount of B (unknown) f _C = C (unknown) f′ _n = Current flow rate of mixed gaseous fuel (known) f′ _A = Current flow rate of gaseous fuel A ( ) f′ _B = 〃 B 〃 ( 〃 ) f′ _C = 〃 C 〃 ( 〃 ) Then, the calculator 21 calculates the target supply amount f _A and the gaseous fuel of B and C obtained by the set A and the simultaneous equations. Input f _B and f _C to the calculator 22. The computer 22 measures flow meters 13, 14 and 15, and uses signal transmission cables 24, 25 and 26.
The flow rate control valves 10, 11, and 12 are controlled via the signal cables 29, 30, and 31 so that the flow rate of each gaseous fuel inputted via the target supply amount matches the target supply amount, and the flow rate of each gaseous fuel is adjusted to match the target supply amount. The target supply amounts f _A , f _B , and f _C are controlled. In addition, when starting up the device, the flow rate of the mixed gas fuel is
Solving the simultaneous equations of equations (6) and (7) below with f _n as f _B ,
Find f _C. f _n = f _A + f _B + f _C (7) Furthermore, Ao _A , Ao _B , Ao _C in equations (4) and (5) above
For ρ _A , ρ _B , and ρ _C , a gas composition analyzer is installed on the upstream side of the mixing device, and the actual measured values are calculated using a computer 2.
1 and calculate f _B and f _C. In a device configured as shown in Figure 1, the LDG flow rate is sequentially changed every 1.2 hours on average in response to fluctuations in the amount of LDG that can be supplied.
Table 3 shows the energy consumption unit of a heating furnace using an MG in which the flow rate of the mixed gas fuel (hereinafter abbreviated as MG) is controlled to be constant by calculating and controlling the Ao/√ of the mixed gas fuel (hereinafter abbreviated as MG).

[Table] Table 3 also shows the results when the calorie was controlled at a constant level by changing the mixing ratio of the three types of LDG, BFG, and COG in response to fluctuations in the amount of LDG that could be supplied. From Table 3, it is clear that the method of the present invention can economically improve combustion efficiency and achieve energy saving effects compared to the conventional method. The above is an example of mixing BFG, COG, and LDG, but when mixing BFG, COG, LDG, and RG, the amount that can be supplied varies widely.
For LDG and RG, the target supply amount is set sequentially according to the available supply amount to control the flow rate, and BFG,
For COG, by determining the target supply amount where MG's Ao/√ is the target value and controlling the flow rate.
A constant MG of Ao/√ can be obtained by mixing LDG and RG in just the right amount. As detailed above, according to the method of the present invention, n
When mixing the types (n≧3) of gaseous fuels, among the above gaseous fuels, (n-2) types of gaseous fuels whose supply amount varies widely are mixed in just the right amount,
A mixed gas fuel having a constant Ao/√ value, that is, a constant air-fuel ratio, can be supplied, and the economic effect is very large.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the method of the present invention, and FIG. 2 is an explanatory diagram showing the configuration of a general combustion furnace. 1... Gaseous fuel A generation equipment, 2... Gaseous fuel B generation equipment, 3... Gaseous fuel C generation equipment, 4... Gaseous fuel A transport pipe, 5... Gaseous fuel B transport pipe,
6... Gaseous fuel C transport pipe, 7... Gaseous fuel A storage facility, 8... Gaseous fuel B storage facility, 9... Gaseous fuel C storage facility, 10... Gaseous fuel A flow rate control valve, 11... Gas Fuel B flow rate control valve, 12... Gaseous fuel C flow rate control valve, 13... Gaseous fuel A flow meter, 14... Gaseous fuel B flow meter, 15... Gaseous fuel C flow meter, 16... Mixing device, 17 ...transport pipeline,
18, 19, 20... Combustion equipment, 21... Computer, 2
2... Calculator, 23, 24, 25, 26, 27, 2
8, 29, 30, 31...signal transmission cable, 1
a...Mixed gas fuel blower, 2a...Air blower, 3a...Mixed gas fuel transport pipe line, 4a...Air transport pipe line, 5a...Mixed gas fuel control valve, 6
a...Air control valve, 7a...Mixed gas fuel orifice flow meter, 9a...Combustion burner, 10a...Combustion furnace, 11a...Thermometer, 12a...Mixed gas fuel flow rate control device, 13a...Air flow rate control device ,1
4a...Air ratio setting device, 15a...Temperature control device, 1
6a, 17a, 18a, 19a, 20a, 21
a, 22a, 23a...signal cable.

Claims (1)

[Scope of Claims] 1 A mixture of n types (n≧3) of gaseous fuels with different combustion characteristics and varying supplyable amounts, and among the gaseous fuels, the supplyable quantities vary widely (n −
2) When mixing the types of gaseous fuels in just the right amount, for the type of gaseous fuel (n-2) whose supplyable amount fluctuates widely, the target supply amount is set sequentially according to the supplyable amount. , the flow rate is controlled to match the supply amount of gaseous fuel with the set supply amount, and for the other two types of gaseous fuels, the value of the ratio between the theoretical air amount and the square root of the density of the gaseous fuel after mixing is adjusted in advance. The air-fuel ratio is kept constant by determining a target supply amount of each gaseous fuel so as to be equal to a set target value, and controlling the flow rate so that the supply amount of each gaseous fuel matches the target supply amount. Method of supplying mixed gas fuel.