KR20030052912A - Oxygen concentration control method in case of firing multiple fuels - Google Patents

Abstract

PURPOSE: A method for controlling oxygen concentration in burning multifuel is provided to agree the desired control of oxygen concentration inside a flue to fuel conditions with corresponding to the composition of fuel and the instantaneous change of flow variation and combustion load and vary the oxygen concentration to an appropriate value and accordingly to increase the heat efficiency of combustion equipment by preventing the waste of fuel caused by incomplete combustion and by minimizing the loss of sensible heat generated by excess air combustion. CONSTITUTION: In an oxygen concentration controlling method controlling the air of a furnace by installing a system measuring the oxygen concentration of an oxygen concentration setter(10), a regulator(11), a limiter, a ratio controller, and an outlet of the furnace and feeding back to the oxygen concentration setter, a method for controlling oxygen concentration in burning multifuel is composed of an oxygen concentration set value calculator(30) embedding a fuel flow meter(31) measuring flow by fuels, a fuel composition measuring instrument(32) measuring fuel composition by fuels, and a numerical formula computing the desired control of oxygen concentration. The oxygen concentration set value calculator receives flow signals, fuel composition signals, and signals for needed air ratio by each fuel from the fuel flow meter and the fuel composition measuring instrument, computes desired oxygen concentration from fuel combustion conditions instantaneously varied, and accordingly adjusts the desired control value of the oxygen concentration setter by controlling the air of combustion equipment.

Description

Oxygen concentration control method in case of firing multiple fuels}

The present invention relates to precise oxygen concentration control in a combustion facility using several kinds of fuels. More specifically, the oxygen concentration setter calculates an appropriate control target oxygen concentration based on the instantaneous change of composition and amount of use for each fuel. The present invention relates to a method for controlling oxygen concentration in multi-fuel combustion that can reduce the fuel consumption of a combustion furnace by optimizing the set value of.

In general, the control of the air ratio (air fuel ratio) in the combustion equipment is very important in reducing fuel consumption and pollution prevention, and the air-fuel ratio control by setting the ratio of fuel amount and air amount is made.

In general, the measurement of the flow rate of air and fuel in an industrial combustion facility is not satisfactorily accurate, and the flow rate control itself is accompanied by an error, so it is very difficult to maintain a constant air-fuel ratio by manual operation.

Therefore, in recent years, the air-fuel ratio control in a combustion furnace such as a boiler is generally performed in parallel with the combustion gas analysis, and the excess air combustion is controlled by feeding back the analysis result of the oxygen concentration in the combustion gas to the air-fuel ratio control. Is oriented.

In such a normal air-fuel ratio control, factors that do not maintain a constant air-fuel ratio include those caused by instrumentation devices, fuels, pipes and burners, and those caused by disturbances.

In other words, fluctuations in fuel composition, unbalance of fuel and air supplied to the burners, load fluctuations, fluctuations in labor pressure, and responsiveness of air and fuel control valves are typical air fuel ratio fluctuation factors (oxygen concentration fluctuation factors in combustion gas). .

Therefore, in order to control the oxygen concentration aimed at low excess air ratio combustion, it is necessary to configure a control system and set operating standards that can respond to disturbances quickly and stably.

However, in the case of combustion equipment using multiple fuels, the amount of fuel used varies according to fuel supply and demand, and in particular, the composition of fuel changes frequently in facilities that use their own by-product gas. Will change from time to time.

In the normal air-fuel ratio control and oxygen concentration control, the combustion control is performed by setting the theoretical air fuel ratio and the target oxygen concentration based on the representative composition of each fuel. As a result, fuel shortages or excessive air combustion can cause waste.

The operation principle of such a general oxygen concentration control will be described in detail with reference to the accompanying drawings.

1 is a schematic diagram showing a conventional oxygen concentration control system, in which fuel and air are supplied to a combustion furnace 1 with a burner 2 through respective fuel and air flow controllers 3. At this time, the air flow rate is feedback-controlled using the oxygen concentration meter 4 and the oxygen concentration controller 5 installed in the flue 20.

Figure 2 shows a block diagram for achieving a conventional oxygen concentration control method, the oxygen concentration measuring instrument 4 is provided in the outlet flue 20 of the combustion furnace 1 to measure the oxygen concentration in the combustion gas, the measurement result Is fed back to the oxygen concentration setter 10.

The oxygen concentration setter 10 compares the oxygen concentration control target value with the oxygen concentration measured by the oxygen concentration measuring unit 4 and sends an accelerometer signal of the oxygen concentration to the controller 11.

The regulator 11 signals the ratio setter 13 through proportional integral control or the like so that the oxygen concentration measurement value follows the target value, and the ratio setter 13 transmits an airflow regulator (not shown). And the air flow rate supplied to the combustion furnace 1 is controlled.

Reference numeral 12 denotes a limiter that restricts the upper and lower limits of the air ratio in order to prevent malfunction of the control system.

In the conventional oxygen concentration control method having the above-described configuration, a fixed oxygen concentration control target value (eg, 2%) is input to the oxygen concentration setter 10, and oxygen concentration control (air volume control) is made to follow the single control target value. Will be made.

However, when using different types of fuel, the flow rate of each fuel varies depending on the supply and demand conditions of the fuel and the furnace load rate. When the flow rate of each fuel is changed, the required amount of air in the burner for complete combustion is changed, and thus the control target oxygen concentration in the year is changed.

However, according to the conventional method, since the fixed target value is input to the oxygen concentration setter 10, it cannot cope with the change of the appropriate oxygen concentration according to the change of the fuel condition, and as a result, it causes incomplete combustion or excessive air combustion, resulting in high efficiency. It is an obstacle to combustion operation.

In addition, in case of using by-product gas of the self-production process as a fuel, the fuel composition (heating amount) usually changes from time to time, and in this case, the required air amount and the control target oxygen concentration also change, but in the conventional method, Value is used in the oxygen concentration setter, it is impossible to cope with the change in fuel composition.

As described above, in the conventional air control method using oxygen concentration control, when the amount of fuel used or the composition of the fuel is changed, especially when various kinds of fuels are used, it is impossible to control the oxygen concentration in accordance with the fuel supply conditions. As such, there has been a demand for solving the above problems for high efficiency operation of combustion equipment.

The present invention is to improve the above-mentioned conventional problems, when multiple fuels are used in the same combustion equipment, instantaneously measure the composition and flow rate for each fuel, calculate the required air ratio for each combustion load, based on the fuel supply conditions By installing the oxygen concentration set value calculator with a formula that can calculate the oxygen concentration control target value for each year, calculate the proper control target set value in response to the instantaneous change of fuel supply conditions and add the result to the oxygen concentration setter. Accordingly, an object of the present invention is to provide a method for controlling oxygen concentration during multi-fuel combustion, in which the air flow can be appropriately controlled so that incomplete combustion and unnecessary over-combustion do not occur even during multi-fuel combustion.

1 is a schematic diagram showing a conventional oxygen concentration control system

Figure 2 is a block diagram for achieving a conventional oxygen concentration control method

Figure 3 is a schematic diagram showing a control system for achieving the oxygen concentration control method for burning multi-fuel fuel of the present invention

<Explanation of symbols for the main parts of the drawings>

1: combustion furnace 2: burner

3: fuel and air flow controller 4: oxygen concentration meter

5: oxygen concentration controller 10: oxygen concentration controller

11: controller 12: limiter

13: ratio setter 30: oxygen concentration set value calculator

31 fuel flow meter 32 fuel composition measuring system

As a means for achieving the above object, the oxygen concentration control method for the combustion of the multi-fuel fuel of the present invention, the flow rate signal measured in the fuel flow meter installed for each fuel and the fuel for continuously measuring the fuel in the fuel supply pipe to measure the composition change It is made by configuring the oxygen concentration setting calculator that controls the air volume of the combustion facility based on the calculation of the appropriate oxygen concentration in the year when the fuel composition signal of each fuel composition measuring instrument and the fuel demand for each fuel are used. In this oxygen concentration setting calculator, the theoretical air volume for each fuel is calculated by the combustion calculation, and the total air volume required for the combustion furnace is obtained by adding the theoretical air volume for each fuel by the flow rate for each fuel and the air ratio required for complete combustion for each fuel type and combustion load. By the combustion calculation Calculates the combustion gas volume, calculates the total combustion gas by multiplying the amount of combustion gas by the fuel, and divides the amount of oxygen by the total combustion gas, and calculates the oxygen concentration in the combustion gas. Calculate the relationship between air costs, calculate the weighted average theoretical air amount and the required air amount considering fuel consumption weight from fuel consumption and fuel consumption by fuel, calculate the weighted average air ratio by dividing the required air volume by the theoretical air volume, and calculate the weighted average air When the ratio is obtained, the control target oxygen concentration is calculated from this, and when the control target oxygen concentration is calculated, the appropriate oxygen concentration in the year when using multiple fuels is calculated according to the composition, flow rate, and required air volume by fuel ratio, and then burned based on this. To control the air volume of the equipment to adjust the control target of the oxygen concentration setter It characterized.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Figure 3 is a schematic diagram showing a control system for achieving the oxygen concentration control method for the combustion of multi-fuel fuel of the present invention, the basic configuration of the control system is the same as in Figure 2, but only as necessary means for achieving the present invention additionally described Is as follows.

First, an oxygen concentration set value calculator 30 is installed as an upper mechanism of the oxygen concentration setter 10. The oxygen concentration set value calculator 30 includes a flow rate signal measured by a fuel flow meter 31 installed for each fuel and a fuel supply pipe. The fuel composition signal of the fuel composition measuring device 32 for each fuel, which continuously samples the fuel and measures the composition change, is introduced.

In addition, the oxygen concentration set value calculator 30 includes an air ratio calculation formula necessary for complete combustion according to the fuel type and the combustion load for each burner, and accepts the necessary data, and calculates the oxygen concentration set value calculation result as an oxygen concentration setter 10. An input / output mechanism capable of transmitting to is included.

Moreover, the formula for setting the oxygen concentration target value by the method described below is incorporated.

When the composition of each fuel is measured by the fuel composition measuring device 32, the theoretical air amount of each fuel may be calculated by a combustion calculation (eg, C + O ₂ = CO _2, etc.).

The total air required for the furnace is the sum of the theoretical air volume per fuel multiplied by the flow rate for each fuel and the air ratio required for complete combustion for each fuel type and combustion load. That is, when the theoretical air amount per fuel is A _i , the flow rate for each fuel is Q _i , and the required air ratio for each combustion condition is M _i , the total required air amount A _t can be calculated as ∑ (A _i Q _i M _i ).

In addition, according to the combustion calculation, the amount of combustion gas can be calculated from the composition for each fuel and the required air ratio, and the total amount of combustion gas can be known by adding up the amount of the combustion gas for each fuel times the amount of fuel.

Oxygen concentration in the combustion gas is the amount of oxygen divided by the total amount of combustion gas, and the combustion equation can be used to derive the relationship between oxygen concentration and air ratio.

The weighted average theoretical air amount and the required air amount can be obtained from the consumption of fuel and the required air cost by fuel, and the weighted average air ratio can be obtained by dividing the required air by the theoretical air amount. Once the weighted average air ratio is obtained, the control target oxygen concentration can be estimated from this.

By deriving the control target oxygen concentration equation in the above manner, it is possible to calculate the optimal oxygen concentration in the year of simultaneous use of multiple fuels according to the composition, flow rate and load rate required by fuel, and based on the change in fuel and combustion conditions. Correspondingly, proper oxygen concentration control is possible.

That is, a fuel composition measuring system is prepared to respond to changes in fuel and combustion conditions when burning multiple fuels to measure fuel composition, measure fuel flow rate, and obtain necessary air ratio data considering burner performance according to combustion conditions. Likewise, the oxygen concentration set value calculator that can input / output data with a built-in formula to calculate the control target oxygen concentration is connected to the oxygen concentration setter to enable precise control of the oxygen concentration.

The above items are represented by specific formulas.

First, the formula used in the oxygen concentration set value calculator 30 will be described in detail as follows.

Hereinafter, a case in which four fuels such as blast furnace gas (BFG), converter gas (LDG), coke furnace gas (COG) and heavy oil are used will be described as an example.

Each combustion reaction formula for the standard composition of each fuel is as follows.

In the following formulas, m represents the air ratio.

(A) BFG

(0.207CO ₂ + 0.22CO + 0.032H ₂ + 0.541N ₂ ) + m (0.126O ₂ + 0.474N ₂ ) → 0.427CO ₂ + 0.032H ₂ O + (0.541 + 0.474m) N ₂ +0.126 (m-1 ) O ₂ (1)

(B) COG

(0.031CO ₂ + 0.003O ₂ + 0.029C ₂ H ₄ + 0.084CO + 0.266CH ₄ + 0.564H ₂ + 0.023N ₂ ) + m (0.94O ₂ + 3.536N ₂ ) → 0.439CO2 + 1.154H2O + (0.023+ 3.536m) N2 + 0.94 (m-1) O ₂ (2)

(C) LDG

(0.178CO ₂ + 0.001O ₂ + 0.642CO + 0.02H ₂ + 0.159N ₂ ) + m (0.33O ₂ + 1.241N ₂ ) → 0.82CO ₂ + 0.02H ₂ O + (0.159 + 1.241m) N ₂ +0.33 (m-1) O ₂ (3)

Oil + m (2.264O ₂ + 8.516N ₂ ) → 1.613CO ₂ + 1.228H ₂ O + 0.0098SO ₂ + (8.516m + 0.002) N ₂ +2.264 (m-1) O ₂ (4)

In Formula (4), the standard composition of heavy oil was based on 0.864C + 0.115H + 0.005O + 0.014S + 0.002N.

The flow rates of the BFG, COG, LDG and heavy oil supplied to the combustion equipment are called Q _BFG , Q _COG , Q _LDG and Q _Oil , respectively (where Q _BFG , Q _COG , Q _LDG is Nm ³ / hr, and Q _Oil is kg / hr), the sum of each fuel flow rate Q _f can be expressed as follows.

BFG: x _BFG = Q _BFG / Q _f

COG: x _COG = Q _COG / Q _f

LDG: x _LDG = Q _LDG / Q _f

Heavy oil: x _Oil = Q _Oil / Q _f

Therefore, when the four fuels are burned, the dry gas total amount G is summarized as follows.

G = 0.842x _BFG -0.478x _COG + 0.649x _LDG -0.639x _Oil + m (0.6x _BFG + 4.476x _COG + 1.571x _LDG + 10.78x _oil ) = A + Bm (5)

A and B in Equation (5) are coefficients for simplifying the equation, respectively.

In addition, the total oxygen amount GO ₂ is as follows.

GO ₂ = (m-1) (0.126x _BFG + 0.94x _COG + 0.33x _LDG + 2.264x _Oil ) = C (m-1) (6)

C in Formula (6) is a coefficient similar to A and B.

The oxygen concentration and the air ratio in the exhaust gas are calculated as follows.

(O ₂ ) = GO ₂ / G × 100

= 100C (m-1) / [A + Bm] (%) (7)

m = [100 C + A (O ₂ )] / [100 C-B (O ₂ )] (8)

If the air ratio required for complete combustion during combustion is 1.10 for heavy oil, COG, LDG, and 1.18 for BFG, the actual amount of air required (A _p ) is expressed as follows.

A _p = Q _a / Q _f

= 1.1 [4.476x _COG + 1.571x _LDG + 10.78x _Oil ] +1.18 [0.6x _BFG ]

= 0.708x _BFG + 4.924x _COG + 1.728x _LDG + 11.858x _Oil (9)

The theoretical air volume (A _o ) when the air ratio is 1.0

Ao = 0.6x _BFG + 4.476x _COG + 1.571x _LDG + 10.78x _Oil (10)

therefore. The actual weighted average total air ratio (m _p ) for the mixed combustion of four fuels at the time of combustion at the reference air ratio for each fuel is expressed as follows.

m _p = A _p / A _o (11)

The oxygen concentration in the combustion gas to maintain the air ratio in m _p is as follows.

(O _{2, p} ) = 100C (m _p -1) / [A + Bm _p ] (12)

By using Equation (12), the oxygen concentration control reference value in the case of mixing and burning four kinds of fuels as in the embodiment of the present invention can be calculated.

That is, Equation (12) is the final target equation used in the oxygen concentration set value calculator.

The above-described method can calculate the oxygen concentration setting value according to the fuel flow rate, composition change, and air ratio for each fuel required for complete combustion, and [Table 1] shows the results of calculating the oxygen concentration when burning two types of fuel, heavy oil and BFG. To show. That is, the control target oxygen concentration according to the change of fuel use ratio is calculated as the result of calculating the change trend of control target oxygen concentration according to the change of usage ratio by fuel for the case of using two fuels, heavy oil and BFG. It shows a change.

BFG (Nm ³ ) Oil (l) BFG calorie fraction Target Air Cost Target oxygen concentration (%) 100 0 One 1.18 1.463 100 One 0.89 1.168 1.498 100 2 0.80 1.16 1.53 100 3 0.73 1.153 1.558 100 4 0.668 1.148 1.583 100 5 0.617 1.143 1.605 0 One 0 1.1 2.018

On the other hand, when the composition of the fuel is changed, the combustion can be calculated in the same manner as described above from the measurement result by measuring the concentration of the flammable fuel in the fuel composition measuring system.

Hereinafter, the method of calculating the oxygen concentration set value according to the composition variation will be described in detail by taking the case of measuring the composition of BFG and LDG online (On-Line).

Here, COG and heavy oil are regarded as having no compositional change as shown in Equation (2) and Equation (4), and only BFG and LDG are considered to have compositional change. One embodiment.

The basic calculation flow is the same as described above, but the overall method is described in detail as follows.

The only combustibles in BFG and LDG are carbon monoxide (CO) and hydrogen (H ₂ ), so the concentration of the combustibles is measured and then the instantaneous theoretical air required for the combustion of BFG and LDG is calculated, and heavy oil and COG are fixed standards. Calculate the theoretical air volume using the composition.

The formula for calculating the required air amount is made using the theoretical air amount calculated from the fuel composition, the flow rate for each fuel, and the excess air amount (air ratio) required for complete combustion.

In addition, using the data and the above formula, the formula for setting the oxygen concentration in the flue gas within the flue as the control target for each combustion condition is prepared. And based on this, it is used to control the oxygen concentration.

The data that need to be secured for combustion control are as follows.

First, combustible composition of BFG and LDG (using analyzer measurement results).

Second, the flow rate for each fuel such as BFG, LDG, COG, and heavy oil, and the air cost for complete combustion.

Third, the combustion calculation formula is prepared using the data and calculation and control execution using a calculator.

The combustion control equations and the necessary programs are as follows.

(a) BFG composition

CO concentration = x ₁ , H ₂ concentration = x ₂ , where x ₁ and x ₂ are not% but fraction =% / 100

HBFG (BFG calorific value) = 3035x ₁ + 2570x ₂ (kcal / Nm ³ )

ABFG (BFG Theoretical Air Volume) = 2.38095 (x ₁ + x ₂ ) (Nm ³ -air / Nm ³ -BFG)

(b) LDG composition

CO concentration = y ₁ , H ₂ concentration = y ₂ , where y ₁ and y ₂ are not% but fraction =% / 100

HLDG (LDG calorific value) = 3035y ₁ + 2570y ₂ (kcal / Nm ³ )

ALDG (LDG theoretical air volume) = 2.38095 (y ₁ + y ₂ ) (Nm ³ -air / Nm ³ -LDG)

(c) Calculation of the amount of combustion air

Equation of combustion air volume considering the composition of BFG, LDG, flow rate and burner performance by fuel is as follows.

Where unit is gas / air Nm ³ / hr, oil kg / hr, subscript 1 = CO, 2 = H ₂ , and Q below is the flow rate of individual fuel.

1) theoretical air volume

A _o = 4.476Q _COG + 10.78Q _oil +2.38 (x ₁ + x ₂ ) Q _BFG +2.38 (y ₁ + y ₂ ) Q _LDG

2) Required air volume considering burner performance

A _p = 1.1 [4.476Q _COG + 10.78Q _oil +2.38 (y ₁ + y ₂ ) Q _LDG ] +1.18 [2.38 (x ₁ + x ₂ ) Q _BFG ]

The BFG calculates the required air ratio as 1.18, and the heavy oil, COG, and LDG as the required air amount as 1.1, and controls the amount of combustion air using this value.

3) Weighted average overall air cost

m _p = A _p / A _o

The overall air ratio is a set value of the theoretical excess air ratio, and becomes a reference air ratio for setting the oxygen concentration control target value.

(d) Calculation of control target oxygen concentration

When oxygen concentration is measured using a zirconia sensor, oxygen concentration = (the amount of oxygen in the combustion gas / total (wet) combustion gas) x 100 (%).

1) Wet Combustion Gas

G _t = 0.676Q _COG + 0.588Q _oil + [1-0.5 (x ₁ + x ₂ )] Q _BFG + [1-0.5 (y ₁ + y ₂ )] Q _LDG + m _p A _o = A + m _p A _o

Wherein A is 0.676Q _COG + 0.588Q _oil + [1-0.5 (x ₁ + x ₂ )] Q _BFG + [1-0.5 (y ₁ + y ₂ )] Q _LDG .

2) the amount of oxygen in the combustion gas

G _O2 = (m _p -1) [0.94Q _COG + 2.264Q _oil +0.5 (x ₁ + x ₂ ) Q _BFG +0.5 (y ₁ + y ₂ ) Q _LDG ] = C (m _p -1)

Wherein C is [0.94Q _COG + 2.264Q _oil +0.5 (x ₁ + x ₂ ) Q _BFG +0.5 (y ₁ + y ₂ ) Q _LDG ].

3) Control Target Oxygen Concentration (Relational Expression with Weighted Average Total Air Ratio)

(O ₂ ,%) = 100C (m _p -1) / (A + m _p A _o ): control target oxygen concentration (this is variable)

As described above, the instantaneous control target oxygen concentration is calculated in the oxygen concentration setting calculator, and by using the oxygen concentration setting, proper combustion control can be realized.

The flow of the combustion control equation combining the contents of the above embodiment is as follows.

First, Read x ₁ , x ₂ , y ₁ , y ₂ (read the measured values in the analyzer).

Calculate what is needed to read the measured values in the analyzer. That is, the calorific value and theoretical air amount of BFG and LDG are calculated.

Then, Read Q _BFG , Q _COG , Q _LDG , Q _Oil.

That is, the theoretical air volume calculation considering the fuel flow rate and composition (COG, heavy oil uses fixed theoretical air volume), the actual required air volume considering the excess air rate for each fuel, and the weighted average total air ratio (m _p = Calculate A _p / A _o ) and calculate the combustion air volume (adjust the actual input air volume using the required air quantity setpoint / calculated value).

Finally, the oxygen concentration setpoint is calculated using the combustion calculation equation and the oxygen concentration setpoint equation.

Next, Table 2 below compares the oxygen concentration setting values according to the method according to the present invention and the conventional method.

BFGCO (%) BFGH ₂ (%) BFG calorific value (kcal / Nm ³ ) LDGCO (%) LDGH ₂ (%) LDG calorific value (kcal / Nm ³ ) Oxygen concentration set value (%) according to the present invention Oxygen concentration set value (%) by the conventional method 22.36 3.47 768 78.59 0.72 2404 1.47 2.13 23.44 3.98 814 61.24 0.55 1873 1.49 2.21 21.55 3.75 750 53.44 0.76 1641 1.42 2.03 22.71 3.09 769 75.63 1.19 2326 1.47 1.97 20.97 3.46 725 52.73 1.12 1629 1.39 2.14 22.37 3.31 764 76.77 0.6 2345 1.46 2.24 20.91 3.17 716 48.63 0.89 1499 1.38 1.94 22.81 3.03 770 74.44 0.16 2263 1.47 2.09 22.59 3.35 772 73.76 0.84 2260 1.49 2.13 22.47 3.13 763 77.94 1.19 2396 1.46 2.10 21.45 3.39 738 46.86 2.17 1478 1.45 2.05

[Table 2] shows a comparison of the oxygen concentration set values according to the conventional method and the method according to the present invention, the present invention targets boiler equipment using four fuels, such as blast furnace gas, coke oven gas, converter gas, heavy oil. This is a result of comparing the oxygen concentration setting value with the oxygen concentration control method (system as shown in FIG. 3) during multi-fuel combustion.

According to the conventional air ratio calculation method, the oxygen concentration in the combustion gas is known to be about 2%. Therefore, in the conventional method, the target value of oxygen concentration control is maintained at about 2%.

As shown in Table 2 above, when the composition of the fuel changes at any time, the oxygen concentration setting value should also be changed, but it is maintained at a constant value in the conventional method.

The oxygen concentration in the flue was maintained at an average of 2.1% in the method of the present invention to 1.5% in the method of the present invention, thereby reducing the sensible heat loss of the combustion gas by about 10%.

As described above, according to the oxygen concentration control method in the combustion of the multi-fuel fuel of the present invention, the control target oxygen concentration in the year is adjusted to the appropriate value in response to the fuel composition, flow rate fluctuation, and instantaneous change of the combustion load. As a result, it is possible to prevent fuel waste due to incomplete combustion and to minimize the sensible heat loss due to excessive excess air combustion, thereby increasing the thermal efficiency of the combustion equipment.

Claims (2)

In a combustion furnace using two or more fuels simultaneously, the oxygen concentration setter 10, the regulator 11, the limiter 12, the ratio setter 13 and the combustion furnace outlet oxygen concentration are measured to measure the oxygen concentration setter ( 10. An oxygen concentration control method for controlling the amount of air in a combustion furnace having a system for feeding back a fuel, comprising: a fuel flow meter 31 for measuring a flow rate for each fuel, a fuel composition measuring device 32 for measuring a fuel composition for each fuel, and a control target An oxygen concentration set value calculator (30) having a built-in formula for calculating the oxygen concentration is configured, and the oxygen concentration set value calculator (30) is obtained from the fuel flow meter (31) and the fuel composition meter (32) for each fuel. Receive the flow signal for each fuel, fuel composition signal, and the required air ratio signal for each fuel, and calculate the control target oxygen concentration from the instantaneously changing fuel combustion conditions. An oxygen concentration control method for combustion of multiple fuels, characterized in that the control target value of the oxygen concentration setter (10) is adjusted by controlling. The equation for calculating the control target oxygen concentration incorporated in the oxygen concentration setting calculator (30) is based on the theoretical air amount for each fuel from the flow rate signal for each fuel, the fuel composition signal, and the required air ratio signal for each fuel. Calculating; Calculating the total air amount required for the combustion furnace from the theoretical air amount for each fuel, the flow rate for each fuel, the fuel type, and the air ratio required for complete combustion for each combustion load; Calculating an amount of combustion gas from the fuel composition and the required air ratio; Calculating a total combustion gas amount from the combustion gas amount and the fuel flow rate for each fuel; Calculating an oxygen concentration from the total combustion gas amount and the oxygen amount; Deriving a relationship between the oxygen concentration and the air ratio by using a combustion calculation formula; Calculating the weighted average theoretical air amount and the required air amount from the amount of fuel used and the amount of air required for each fuel; Calculating a weighted average air ratio from the required air amount and the theoretical air amount; Calculating a control target oxygen concentration from the weighted average air ratio; Then calculating an appropriate oxygen concentration in the year when the multi-fuel is used simultaneously according to the composition, flow rate and required air amount by load ratio; Oxygen concentration control method for the combustion of multi-fuel fuel characterized in that it comprises the step of controlling the amount of air in the combustion equipment on the basis of this.