JP2008038175A - Method for injecting powdery material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for injecting powdery material with which the powdery material is discharged from a feed-tank in high accurate discharging speed and can be inject into a furnace. <P>SOLUTION: This method for injecting powdery material, is performed as the followings, with which in the case of receiving no powdery material into the feed-tank, the proofreading of a powdery material flow-rate meter is performed by using the weight measured value with a load-cell set in the tank, and in the case of receiving the powdery material into the tank, too, the discharging speed of the powdery material is measured and controlled in high accuracy. Further, the powder discharging amount is controlled in the high accuracy, in the case of being the differential pressure between the pressure in the tank and the pressure in a powder transporting piping at lower than a prescribed value by using a differential pressure control, or in the case of being the differential pressure at the prescribed value or higher by using the opening degree control of a powdery material flow-rate adjusting valve. Depending on this control method, even in the case of which either one of the load cell or the powdery material flow-rate meter can not be used, the stable powder injection can be continued by combining the differential pressure control and the useable load cell or the opening degree control of the powdery material flow-rate adjusting valve using the powdery material flow-rate meter. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a powder blowing method used when a powder such as pulverized coal conveyed by gas through a pipe is blown into a furnace in a refining furnace such as a blast furnace or a combustion heating furnace of a power plant. About.

  In a powder blowing method such as pulverized coal injection in a smelting furnace such as a blast furnace or a combustion heating furnace of a power plant, a pressure vessel (hereinafter also referred to as a “feed tank”) is used to accurately inject powder. It is necessary to accurately control the cutting speed of the powder from the powder, that is, the discharging speed. When changing the operating conditions, of course, even when certain operating conditions are set, the properties of the powder such as pulverized coal are not always constant, or in the feed tank while continuously operating There are disturbance factors that vary the discharge speed from the feed tank, such as when powder is supplied.

  In order to control the discharge speed of the powder from the feed tank, a discharge speed detecting means and a discharge speed adjusting means are required. The following methods are known as methods for detecting and adjusting the discharge rate of powder.

(A) Detection method of discharge speed (a) The discharge speed of the powder from the feed tank is obtained by time differential operation of a signal obtained by a weight measuring device (load cell) attached to the feed tank.
(B) The discharge rate of the powder from the feed tank is determined using a signal obtained by a powder flow rate measuring device (powder flow meter) attached to the powder transport pipe.

(B) Method for adjusting discharge speed (c) The powder discharge speed is adjusted by adjusting the pressure in the feed tank.
(D) The powder discharge speed is adjusted by a powder flow rate control valve such as a rotary feeder installed at the bottom of the feed tank.

  In an actual powder discharge or powder blowing process, the powder discharge speed is controlled by appropriately combining the above techniques.

(1) Method of controlling discharge speed by adjusting the opening of the powder flow rate control valve The discharge speed of pulverized coal from the feed tank is obtained by time differentiation of the signal obtained by the load cell installed in the feed tank. In this method, the discharge rate of the powder is controlled by adjusting the opening of the control valve.

  FIG. 1 is a diagram showing a configuration example of a conventional pulverized coal blowing device for carrying out the above method. The pulverized coal 20 is temporarily stored in the pressure equalizing tank 1 and supplied to the feed tank 2 under pressure. A load cell 5 for measuring the mass of pulverized coal in the feed tank 2 is installed in the feed tank 2, and a powder flow rate adjusting valve 3 is installed at the lower discharge port of the feed tank 2. When the mass of the pulverized coal in the feed tank 2 is measured by the load cell 5 and the signal is transmitted to the powder flow rate indicating controller 6, the powder flow rate indicating controller 6 calculates the time derivative of this signal to calculate the fine powder. The discharge rate of charcoal is calculated, and the opening of the powder flow rate control valve 3 is adjusted so that this discharge rate becomes a predetermined rate. By such a method, the discharge speed amount of pulverized coal is controlled.

(2) Discharge rate control method by adjusting the pressure in the feed tank Discharge of pulverized coal from the feed tank by calculating the time derivative of the signal obtained by the powder weight measuring device (load cell) installed in the feed tank This is a method of controlling the discharge speed of pulverized coal by calculating the speed and adjusting the pressure in the feed tank.

  The feed tank 2 is provided with a load cell 5 for measuring the mass of pulverized coal in the feed tank 2, a powder flow rate indicating controller 6 connected to the load cell 5, the pressure in the feed tank 2, and the carrier gas book A differential pressure indicating controller 9 that detects a differential pressure with respect to the pressure in the pipe 16 and adjusts the pressure in the feed tank 2 is installed. When the mass of the pulverized coal in the feed tank 2 is measured by the load cell 5 and the signal is transmitted to the powder flow rate indicating controller 6, the powder flow rate indicating controller 6 calculates the time derivative of this signal to calculate the fine powder. The discharge speed of charcoal is calculated, and a signal is sent to the differential pressure indicating controller 9 so that the discharge speed becomes a predetermined speed.

  The differential pressure indicating controller 9 has an appropriate pressure difference between the pressure in the feed tank 2 and the pressure in the carrier gas main pipe 8 obtained from the relationship between the previously determined differential pressure and the pulverized coal discharge rate. The pressure in the feed tank is adjusted by introducing a pressurizing gas into the feed tank 2 or exhausting the gas in the feed tank 2 so as to achieve a differential pressure. By such a method, the discharge speed of pulverized coal is controlled.

(3) Control method of discharge speed by adjusting pressure in feed tank and powder flow rate control valve This method is a control method of discharge speed of pulverized coal applied to continuous blowing of pulverized coal by carrier gas. The method disclosed in Patent Document 1 is known.

  The apparatus for carrying out this method includes an internal pressure control valve 12 for introducing a pressurizing gas into the feed tank 2 and an exhaust for keeping the tank internal pressure constant when the pulverized coal 20 is received into the feed tank 2. Control valve 13 and powder flow meter 4 for detecting the flow rate of powder passing through powder transport pipe 8. Further, a differential pressure instruction for detecting a differential pressure between the pressure in the powder transport pipe 8 and the pressure in the feed tank 2 and adjusting the opening of the internal pressure control valve 12 so that the differential pressure becomes a predetermined value. It has a controller 9 and a powder flow rate adjusting valve 3 installed at the lower outlet of the feed tank 2.

  A mechanism for keeping the differential pressure in the feed tank 2 and the powder transport pipe 8 constant, and quantitatively cutting the pulverized coal by the differential pressure, and adjusting the opening of the powder flow rate control valve 3 and discharging the pulverized coal. The discharge speed is controlled by combining with a mechanism for adjusting the pressure.

  However, the powder discharge rate control method described in the above (1) to (3) has the following problems.

Japanese Patent No. 3083593 (Claims, paragraph [0013], etc.) Japanese Utility Model Publication No. 58-93815 (claims, pages 3-4, etc.) JP 2006-77267 A (claims, paragraphs [0005] to [0007])

  The following problems remain in the powder discharge rate control technique described above. That is, in the method of adjusting the powder flow rate control valve described in (1) above, the powder discharge speed is obtained by differentiating the signal obtained by the load cell, so that the powder is received in the feed tank. The powder discharge rate cannot be calculated during the operation. Further, the method of adjusting the pressure in the feed tank described in (2) has a problem that the response speed is slow.

  In order to solve the problems in the above (1) and (2), the discharge amount of the powder is reduced by adjusting the pressure in the method of the above (3), that is, the pressure in the feed tank and adjusting the opening of the powder flow rate control valve. A powder flow meter that detects the flow rate of powder passing through the powder transport pipe and a signal from the powder flow meter so that the powder flow rate becomes a predetermined value. A method for controlling the opening of the powder flow rate control valve has been disclosed. As a result, the control response becomes faster, and the discharge speed can be detected even while the powder is being received in the feed tank.

  However, for example, in recent blast furnace operations, the amount of pulverized coal injected into the furnace has increased, and as the amount of pulverized coal injected increases, the amount of fluctuation in the discharge rate of pulverized coal from the feed tank also increases. There is an increasing trend, and further improvement in the accuracy of the discharge speed control is required. In particular, a powder flow meter represented by a differential pressure type or a capacitance type has a characteristic that the calibration curve of the flow rate changes depending on the properties of the powder, the concentration of the powder, and the like. In order to further improve the control accuracy, it is necessary to provide a calibration function for the calibration curve.

  Patent Document 2 discloses a technique for correcting a measurement error caused by a change in dielectric constant in a method of measuring the flow rate of a solid component in a solid-gas two-phase flow using a capacitance flow meter. Yes. In other words, when detecting the difference between the flow rates flowing in a plurality of branched pipes, if the overall flow rate can be determined by another method such as gravimetric method, the influence of the dielectric constant will affect all pipelines. As it appears in the same way, a method of proportionally correcting the flow rate in the branch pipe with the total flow rate is shown.

  Patent Document 3 discloses a powder blowing equipment having a feed tank equipped with a weigher, a distributor tank, and a branch part of a powder transport pipe, and a capacitance type powder attached to the branch part. In addition to the flow meter, for the output signal of the capacitance type powder flow meter, the zero point adjustment unit that corrects the zero point of the powder flow rate, and the powder concentration that corrects the fluctuation of the output signal due to the type and concentration fluctuation of the powder A powder blowing facility provided with a correction unit is disclosed.

  However, in the method disclosed in Patent Document 2, when several types of powder are used, the powder is not completely mixed. Therefore, it is difficult to proportionally correct the flow rate in the branch pipe with the total flow rate. In addition, the method disclosed in this document is an effective method for facilities having a plurality of branched pipes. However, as in the method of the present invention, for example, the powder discharged from the feed tank is a single pipe. In this case, this method cannot be used because there is no branch pipe that can be compared.

  Furthermore, in the method disclosed in Patent Document 3 described above, when powder adheres to the inside of the flow meter, the output signal of the detector varies. On the other hand, in the case of using a plurality of types of powders or a powder in which a plurality of types of components are mixed, the detection signal varies when the type or component of the powder is changed. Therefore, when the powder type or composition is changed, if powder adheres to the inside of the flow meter at the same time, it is difficult to identify the fluctuation factor of the output signal of the detector. It is speculated that it cannot be done.

  The present invention has been made in view of the above-described problems that occur when powder is discharged from a feed tank at a highly accurate discharge speed, and the problems are as follows (a) to (c). It is to provide a powder blowing method provided. That is, (a) a powder weight measuring device (load cell) and a powder flow rate measuring device (powder flow meter) provided with a powder transport pipe can be used in combination as a powder discharge rate detecting means; ) As a means for adjusting the powder discharge speed, it is possible to selectively use the control based on the differential pressure of the gas and the opening degree control of the powder flow rate control valve, and (c) as the control method based on the differential pressure of the gas in (b) It is possible to perform differential pressure control between the pressure in the tank and the pressure in the powder transport pipe downstream from the joining part of the carrier gas supply pipe and the powder transport pipe.

  The gist of the present invention is the powder blowing method shown in the following (1) to (3).

  (1) In a powder blowing method in which powder received in a feed tank for containing powder is discharged from the feed tank and blown into a furnace with a carrier gas through a powder transport pipe connected to the feed tank. When the powder is discharged from the feed tank in a state where the powder is not received in the feed tank, the mass of the powder in the feed tank based on the measured value by the powder weight measuring device installed in the feed tank. The rate of decrease is obtained, the rate of mass decrease is used as the powder discharge rate from the feed tank, and the measured value of the powder flow rate by the powder flow rate measuring device provided in the powder transport pipe is discharged. When the powder is discharged from the feed tank while calibrating according to the speed and receiving the powder into the feed tank, it is provided in the powder transport pipe. Is a powder blowing method, characterized in that the powder discharge rate from the feed tank measurements of the powder flow rate by the powder flow rate measuring apparatus was calibrated to powder flow rate by the powder discharge rate.

  (2) In the powder blowing method, the powder in the feed tank for containing the powder is discharged from the feed tank, and blown into the furnace with a carrier gas through a powder transport pipe connected to the feed tank. The pressure difference obtained by subtracting the pressure measurement value in the powder transport pipe from the pressure measurement value in the feed tank is obtained, and when the fluctuation ratio of the differential pressure is less than 15% of the differential pressure in the reference period, the feed A period in which the differential pressure is adjusted by adjusting the opening degree of one or both of the pressure control valve and the exhaust pressure control valve of the tank to control the discharge amount of the powder, and the fluctuation ratio of the differential pressure is a reference period When the pressure difference is 15% or more, the powder discharge speed is controlled by adjusting the opening of the powder flow rate control valve.

  (3) In the powder blowing method according to (1), when either the powder weight measuring device or the powder flow measuring device installed in the feed tank cannot be used, the above (2) It is a powder blowing method characterized by switching to the described powder blowing method.

  In the present invention, “furnace” means a smelting furnace such as a blast furnace and a converter, or a combustion heating furnace used in power generation facilities.

  “Powder” refers to pulverized coal that is blown as a heat source or reducing agent into a smelting furnace such as a blast furnace or converter, flux powder such as lime-silica-magnesia that is blown as a slagging agent, and thermal power generation It means pulverized coal that is blown as fuel in a coal-fired boiler.

  “Differential pressure fluctuation ratio” is defined as {(ΔP2−ΔP1) / ΔP1} × 100 (%), where ΔP1 is a differential pressure value in a reference period and ΔP2 is a differential pressure value in a control target period. Means the value represented.

  According to the powder blowing method of the present invention, when the powder is not received in the feed tank, the powder mass flow rate of the powder flow meter is measured using the powder mass reduction rate measured by the load cell installed in the feed tank. By performing calibration as needed, it is possible to detect the powder discharge speed with high accuracy when powder is received in the feed tank. In addition, differential pressure control performed when the differential pressure between the pressure measurement value in the feed tank and the pressure measurement value in the powder transport pipe is less than a predetermined value, and the powder flow rate performed when the differential pressure is greater than the predetermined value By combining with the opening control of the control valve, it becomes possible to control the powder discharge amount with high accuracy. Furthermore, even when either the load cell or the powder flow meter becomes unusable, the differential pressure control and the opening control of the powder flow control valve using the usable load cell or powder flow meter are performed. By combining, powder blowing can be continued.

  Therefore, the powder blowing method of the present invention can greatly contribute to a high-precision, continuous and stable blowing operation of powder in a smelting furnace such as a blast furnace or a combustion heating furnace of a power plant.

  In the present invention, as described above, when powder is not received in the feed tank, the powder flow meter is calibrated at any time using the measured value by the load cell installed in the feed tank, so that the feed tank can be calibrated. This is a powder blowing method capable of detecting the powder discharge speed with high accuracy when receiving the powder. Also, differential pressure control performed when the differential pressure between the pressure in the feed tank and the pressure in the powder transport pipe is less than a predetermined value, and the opening of the powder flow rate control valve that is performed when the differential pressure is greater than the predetermined value This is a powder blowing method that can control the amount of discharged powder with high accuracy by combining it with control, and even if either the load cell or the powder flow meter becomes unusable, the above differential pressure control In addition, by combining the opening control of the powder flow rate control valve using a usable load cell or powder flow meter, powder blowing can be continued.

  Below, the preferable aspect of the powder blowing method of this invention and its reason are demonstrated in detail. In the following description, a case where pulverized coal is used as the powder and a blast furnace is used as the furnace will be described as an example.

(1) Basic Configuration of Powder Blowing Method FIG. 2 is a diagram showing a configuration example of a pulverized coal blowing device used for carrying out the present invention. The pulverized coal 120 is charged and temporarily stored in a pressure equalizing tank 101 for supplying the pulverized coal 120 to the feed tank 102 under pressure. After the pressure in the pressure equalizing tank 101 is increased, the feed tank 102 under pressure is added. To be supplied. The pulverized coal 120 supplied into the feed tank 102 is controlled to a predetermined pulverized coal discharge speed by adjusting the opening of a powder flow rate adjusting valve 103 installed at a lower discharge port of the feed tank 102 and is conveyed by a carrier gas. The flow rate is measured by the powder flow meter 104 while being blown into the furnace through the powder transport pipe 108. Here, the opening degree of the powder flow rate control valve 103 is controlled to an appropriate opening degree for obtaining a predetermined pulverized coal discharge rate by a powder flow rate indicating controller 106 that operates in response to a signal from the powder flow meter 104. Is done.

  When the pulverized coal 120 is discharged from the feed tank 102 without receiving the pulverized coal into the feed tank 102 in the above blowing, the measurement is performed by the powder weight measuring device (load cell) 105 installed in the feed tank 102. The pulverized coal mass reduction rate, that is, the pulverized coal discharge rate is calculated from the time change of the pulverized coal mass in the feed tank. Then, the discharge rate of the pulverized coal is compared with the measured value of the pulverized coal flow rate measured by the powder flow meter 104, and the measured value of the pulverized coal flow rate by the powder flow meter 104 is measured by the load cell 105. Calibration (correction) is performed based on the pulverized coal discharge rate calculated based on the above.

  When the powder is discharged from the feed tank 102 while accepting the powder to the feed tank 102, the measured value of the powder flow rate by the calibrated powder flow rate measuring device 104 provided in the powder transport pipe 108. Is the discharge rate of the powder from the feed tank 102.

Further, a differential pressure obtained by subtracting the pressure measurement value in the powder transport pipe 108 by the powder transport pipe pressure gauge 107 from the pressure measurement value in the feed tank 102 by the feed tank pressure gauge 110 is continuously obtained. When the fluctuation ratio of the differential pressure is less than 15% of the differential pressure in the reference period, the difference is obtained by adjusting the opening degree of one or both of the pressure control valve 113 and the exhaust pressure control valve 112 of the feed tank 102. The amount of discharged powder is controlled by controlling the pressure, and when the fluctuation ratio of the differential pressure is 15% or more of the differential pressure in the reference period, the opening of the powder flow rate control valve 103 is adjusted to adjust the powder flow rate. Controls body discharge speed.

  The powder flow rate control valve 103 can continuously change the cross-sectional area of the powder flow path by changing the opening degree of the valve, and is as linear as possible between the opening degree and the flow rate. Those having a proportional relationship are preferable. As the powder flow meter 104, a differential pressure flow meter, a capacitance flow meter, or the like can be used.

  The installation position of the powder transport pipe pressure gauge 107 for measuring the pressure in the powder transport pipe is the carrier gas installed upstream from the position where the carrier gas and the pulverized coal transported from the feed tank 102 merge. Although it is possible to set the position of the piping pressure gauge 114, the pressure and powder in the feed tank 102 are set at a position downstream of the position where the carrier gas and the pulverized coal conveyed from the feed tank 102 merge. Since the differential pressure with the body transport piping internal pressure becomes large, the detection accuracy of the differential pressure is improved, which is preferable. Furthermore, the installation position of the powder transport pipe pressure gauge 107 is preferably downstream of the powder flowmeter 104. In the case of powder blowing into the blast furnace, a distributor (not shown) is provided in the transport pipe to the blast furnace. ) Is preferably provided upstream of the distributor.

(2) Calibration of measured value of powder flowmeter based on rate of change in weight of powder in tank FIG. 3 is a diagram showing a change in weight measured by a weight measuring device of a feed tank and a change in pulverized coal blowing rate over time. (A) is a weight measurement value by a weight measuring device (load cell), (b) is a pulverized coal blowing speed calculated from time differentiation of the weight measurement value measured by the load cell, (c) is The measured values of the pulverized coal blowing rate by the powder flow rate measuring apparatus calibrated using the calibration curve are respectively shown.

  Since the feed tank 102 intermittently accepts the pulverized coal 120 from the pressure equalizing tank 101 while continuously discharging the pulverized coal 120, the weight measurement value by the load cell 105 varies periodically. Specifically, as shown in FIG. 5A, in a state where the pulverized coal 102 is not received from the pressure equalizing tank 101, that is, in a normal state, the weight measurement value decreases as the amount of pulverized coal discharged increases. However, in a state where the pulverized coal 120 is received from the pressure equalizing tank 101, the weight measurement value by the load cell 105 is increased even though the pulverized coal 120 is discharged. Therefore, as shown in FIG. 5B, when the pulverized coal 120 is received into the feed tank 101, the pulverized coal discharge rate calculation method using only the measurement value by the load cell 105 is used to calculate the accurate pulverized coal discharge rate. The calculation is difficult, and the fluctuation range of the pulverized coal injection speed becomes large.

  On the other hand, as shown in FIG. 5C, the measured value of the pulverized coal injection speed by the powder flow meter 104 calibrated using the calibration curve is the same even when the pulverized coal 120 is received in the feed tank 102. The fluctuation range of charcoal injection speed is small. As described above, when the so-called disturbance is relatively short, such as when the pulverized coal 120 is received in the feed tank 102, the detection value of the powder flow meter 104 has sufficient accuracy. When the charcoal type of the charcoal 120 is changed or during measurement over a long period of time, it is inevitable that the measurement accuracy decreases due to the pulverized coal 120 adhering to the piping or the detection part of the powder flow meter. .

  Therefore, when not accepting the pulverized coal 120 into the feed tank 102, the time change of the weight measurement value by the load cell 105 is taken as the measured value of the pulverized coal discharge rate, and when accepting the pulverized coal 120 into the feed tank 102, The measured value of the pulverized coal flow rate by the powder flow meter 104, which is periodically calibrated with the discharge rate obtained from the time change of the measured weight value of the pulverized coal by the load cell 105, is discharged from the pulverized coal. It is best to use speed. In the method disclosed in Patent Document 2, an error of each powder flow meter after the branching of the transportation pipe is a problem. In the method of the present invention, a plurality of powder flow meters are installed after the branching of the pipe. Since this is not a method, it is possible to calibrate the powder flow rate with high accuracy.

  FIG. 4 is a diagram showing a calibration curve obtained from a measurement value obtained by the weight measuring device of the feed tank and a measurement value obtained by the powder flow rate measuring device. FIG. 4A is a calibration curve in the period 1 shown in FIG. (B) shows a calibration curve in period 2 shown in FIG.

  After the reception of the pulverized coal 120 from the pressure equalizing tank 101 to the feed tank 102 is completed until the pulverized coal 120 is received from the pressure equalizing tank 101 to the feed tank 102 again, that is, the pulverized coal to the feed tank 102. During the period when the gas is not accepted, the pulverized coal discharge rate calculated from the time change of the weight measurement value measured by the load cell 105 installed in the feed tank 102 and the pulverized coal discharge rate measured by the powder flow meter A calibration curve representing the relationship between the two is created. The above calibration curve is created every period from acceptance of pulverized coal to acceptance of the next pulverized coal, as in the calibration curves in period 1 and period 2 of the figure, and updated to the most recent calibration curve each time. It is preferable to continue.

  When the operating conditions are changed when the load cell 105 is used, or when the fluctuation of the discharge speed becomes large due to some cause, there is a possibility that the discharge speed control is delayed. In preparation for such a case, not only controlling the pulverized coal discharge rate after actually detecting the weight change of the feed tank 102, but also as a method for measuring and grasping the pulverized coal discharge rate, It is preferable to employ a more rapid control method by using the flow rate measured by the powder flow meter 104 together.

(3) Effective use of differential pressure control by the pressurization / exhaust pressure control valve and opening control of the powder flow rate control valve As a control method of the pulverized coal discharge rate, the pressurization control valve 113 of the feed tank 102 and the exhaust pressure control As a result of comparing the differential pressure control between the pressure in the feed tank and the pressure in the transport pipe by the control of the valve 112 and the discharge amount control using the powder flow rate control valve, the control characteristics are different depending on the value of the fluctuation ratio of the differential pressure. Accordingly, it has been found that it is preferable to use a control method with high control accuracy in accordance with the magnitude of the differential pressure fluctuation ratio.

  The pulverized coal discharge rate calculated from the fluctuation of the pressure difference between the pressure in the feed tank 102 and the pressure in the powder transport pipe 108 (hereinafter also simply referred to as “differential pressure”) and the value detected by the load cell or powder flow meter. It is effective to prepare a calibration curve so that the values can be compared with each other and the values of both can be compared in advance. Further, when the pressure fluctuation occurs, the discharge rate is controlled based on the differential pressure adjustment by adjusting the pressurization control valve 113 and the exhaust pressure control valve 112, and the opening degree of the powder flow rate control valve 103 is adjusted. The control accuracy was compared with the case where the discharge speed was controlled by the control.

  In addition, as said differential pressure fluctuation | variation, the fluctuation | variation ratio of the differential pressure represented by the following (1) formula was employ | adopted, and it quantified by this.

Fluctuation ratio of differential pressure = {(ΔP2−ΔP1) / ΔP1} × 100 (%) (1)
Here, ΔP1 represents a differential pressure value (Pa) in a reference period, and ΔP2 represents a differential pressure value (Pa) in a control target period.

  FIG. 5 is a diagram showing the relationship between the differential pressure fluctuation ratio between the feed tank internal pressure and the powder transport pipe internal pressure, and the powder discharge speed fluctuation. In the figure, the value calculated by the following equation (2) was used for the fluctuation of the powder discharge speed.

Variation in powder discharge speed = | W2-W1 | (2)
Here, W1 represents the powder discharge speed (t / h) in the reference period, and W2 represents the powder discharge speed (t / h) in the control target period.

  When the differential pressure fluctuation rate is less than ± 15%, the discharge rate is controlled by adjusting the opening of the powder flow rate control valve, based on the differential pressure adjustment by adjusting the pressure control valve and the exhaust pressure control valve. The fluctuation of the discharge speed is smaller than that of controlling the speed. In this case, if the discharge speed is controlled by adjusting the opening of the powder flow rate control valve, the fluctuation of the discharge speed is increased. Therefore, when the differential pressure fluctuation ratio is less than ± 15%, it is possible to control the pulverized coal discharge speed with higher accuracy by controlling the discharge speed by adjusting the differential pressure.

  On the other hand, when the differential pressure fluctuation ratio is + 15% or more or -15% or less, the discharge speed fluctuation is smaller when the discharge speed is controlled by adjusting the opening of the powder flow rate control valve. If the discharge speed is controlled based on the differential pressure adjustment by the pressure control valve and the exhaust pressure control valve, the fluctuation of the discharge speed is promoted. Therefore, when the differential pressure fluctuation ratio is + 15% or more or -15% or less, controlling the discharge rate by adjusting the opening of the powder flow rate control valve can control the pulverized coal discharge rate with higher accuracy. it can.

  The reason why the above results were obtained is that when the discharge rate control is performed by adjusting the powder flow rate control valve when the differential pressure fluctuation rate is small, the control sensitivity is too high, This is because the discharge speed fluctuation is increased. That is, when the differential pressure fluctuation rate is small, the discharge speed control by adjusting the pressurization control valve and the exhaust pressure control valve can use the low control sensitivity characteristic, and the discharge speed control can be performed with high accuracy. It becomes possible. On the other hand, if the discharge amount control is performed by adjusting the pressurization control valve and the exhaust pressure control valve when the differential pressure fluctuation ratio is large, the control sensitivity is too low and the control becomes impossible. That is, when the differential pressure fluctuation ratio is large, it is possible to suppress a rapid fluctuation in the discharge speed by controlling the discharge speed using the powder flow rate control valve.

  In recent years, the amount of pulverized coal injection in iron and power plants has been increasing, and the technology for controlling the pulverized coal injection rate has become increasingly important. The control method of the pulverized coal discharge rate described above has a great influence when the injection cannot be performed due to a failure of the control device or the like. For example, in blast furnace operation, the furnace heat is lowered, and the reaction in the furnace , And adversely affect hot metal or slag fluidity.

  For example, when the powder flow meter becomes unusable, the pulverized coal is measured using the measured value by the load cell, as in the case of the pulverized coal discharge rate control using the measured value by the powder flow meter as the pulverized coal discharge rate. As shown in FIG. 5, the fluctuation of the discharge speed is obtained, and the fluctuation ratio of the differential pressure is compared with the fluctuation of the discharge speed of the pulverized coal calculated from the measurement value by the load cell. It is preferable to select a speed control method. In other words, by using the measured value by the load cell in combination, the differential pressure control by the pressurization / exhaust pressure control valve and the opening control of the powder flow control valve are used properly, so that high precision, continuous and stable pulverized coal injection operation is possible. Can be carried out.

  In order to confirm the effect of the powder blowing method of the present invention, the following test was conducted using a pulverized coal blowing facility into a blast furnace, and the result was evaluated.

As a result of performing the blowing test with the pulverized coal discharge rate set to 40 t / h and 70 t / h,
The measured values of the flow rate are (40 ± 0.3) t / h and (70 ± 0.5) t / h, respectively, and the deviation with respect to the set flow rate is small, both of which are ± 1% relative values. The following good control accuracy was obtained.

  Moreover, when the set value of the pulverized coal discharge rate was changed from 40 t / h to 70 t / h, the control of the discharge rate was quick and good controllability was exhibited.

  According to the powder blowing method of the present invention, when the powder is not received in the feed tank, the powder mass flow rate of the powder flow meter is measured using the powder mass reduction rate measured by the load cell installed in the feed tank. By performing calibration as needed, it is possible to detect the powder discharge speed with high accuracy when powder is received in the feed tank. In addition, differential pressure control when the pressure difference between the pressure measurement value in the feed tank and the pressure measurement value in the powder transport pipe is less than a predetermined value, and the powder flow rate control valve when the differential pressure is greater than the predetermined value In combination with the opening degree control, the powder discharge amount can be controlled with high accuracy. Furthermore, even when either the load cell or the powder flow meter becomes unusable, the differential pressure control and the opening control of the powder flow control valve using the usable load cell or powder flow meter are performed. By combining, powder blowing can be continued.

  Therefore, the powder blowing method of the present invention is widely used as a high-precision, continuous and stable blowing technique for powders in a powder blowing process into a smelting furnace such as a blast furnace or a powder blowing in a power plant. Applicable.

It is a figure which shows the structural example of the conventional pulverized coal blowing apparatus. It is a figure which shows the structural example of the pulverized coal blowing apparatus used in order to implement this invention. It is a figure which shows the time change of the weight change measured by the weight measuring apparatus of a feed tank, and pulverized coal blowing speed, The figure (a) shows the weight measurement value by a weight measuring apparatus (load cell), the figure (b). Shows the pulverized coal injection speed calculated from the time derivative of the weight measurement value measured by the load cell, and FIG. 6C shows the measured value of the pulverized coal injection speed by the powder flow rate measuring apparatus calibrated using the calibration curve. , Respectively. It is a figure which shows the calibration curve obtained from the measured value by the weight measuring apparatus of a feed tank, and the measured value by a powder flow rate measuring apparatus, The figure (a) shows the calibration curve in the period 1 shown in FIG. (B) represents a calibration curve in period 2 shown in FIG. It is a figure which shows the relationship between the differential-pressure fluctuation | variation ratio of a feed tank internal pressure and the powder transport piping internal pressure, and the fluctuation | variation of a powder discharge speed | rate.

Explanation of symbols

1: pressure equalization tank, 2: feed tank, 3: powder flow rate control valve, 4: powder flow meter,
5: load cell, 6: powder flow rate indicating controller, 8: powder transport piping, 9: differential pressure indicating controller, 10: pressure indicator in feed tank, 12: internal pressure adjusting valve, 13: exhaust adjusting valve, 14: pressure indicator, 15: powder weight indicator, 16: carrier gas main pipe, 20: pulverized coal, 101: pressure equalizing tank, 102: feed tank, 103 powder flow control valve,
104: Powder flow rate measuring device, 105: Powder weight measuring device, 106: Powder flow rate indicating controller, 107: Powder transport piping pressure gauge, 108: Powder transport piping, 109: Differential pressure indicating controller, 110 : Feed tank pressure gauge, 111: differential pressure indicator, 112: exhaust pressure control valve, 113: pressurization control valve, 114: carrier gas piping pressure gauge, 120: pulverized coal

Claims (3)

  In the powder blowing method, the powder received in the feed tank for containing the powder is discharged from the feed tank, and blown into the furnace by the carrier gas through the powder transport pipe connected to the feed tank. When the powder is discharged from the feed tank without accepting the powder to the feed tank, the mass reduction rate of the powder in the feed tank is determined based on the value measured by the powder weight measuring device installed in the feed tank. The mass reduction rate is determined as the powder discharge rate from the feed tank, and the measured value of the powder flow rate by the powder flow rate measuring device provided in the powder transport pipe is calibrated by the discharge rate of the powder. When discharging the powder from the feed tank while receiving the powder into the feed tank, Powder blowing method, characterized in that the measurement of the powder flow rate by the powder discharge rate with powder flow rate measuring apparatus was calibrated to powder flow rate and powder discharge rate from the feed tank.   In the powder blowing method, the powder in the feed tank for containing the powder is discharged from the feed tank and blown into the furnace by the carrier gas through the powder transport pipe connected to the feed tank. The pressure difference obtained by subtracting the pressure measurement value in the powder transport pipe from the pressure measurement value is obtained, and when the fluctuation rate of the differential pressure is less than 15% of the differential pressure in the reference period, the feed tank The differential pressure is adjusted by adjusting the opening degree of one or both of the pressure control valve and the exhaust pressure control valve to control the discharge amount of the powder, and the differential pressure during the period in which the fluctuation ratio of the differential pressure is a reference When the ratio is 15% or more, the powder discharge method is characterized by controlling the powder discharge speed by adjusting the opening of the powder flow rate control valve. The powder blowing method according to claim 1, wherein when either the powder weight measuring device or the powder flow rate measuring device installed in the feed tank becomes unusable, the powder blowing method according to claim 2. A powder blowing method characterized by switching to a pouring method.

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