JP2005201506A - Combustion control method for boiler - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To positively maintain steam dryness without causing water level fluctuation in a combustion control method for a boiler having a water pipe. <P>SOLUTION: In the combustion control method for the boiler for adjusting the combustion quantity of a burner 6 for heating the water pipe 5, the combustion quantity is reduced when determining a lowering of steam dryness, and steam dryness is determined based on either one of steam pressure, electric conductivity of water in the water pipe 5 and the temperature of supply water to the water pipe 5. Further, steam dryness is determined based on a signal from a steam dryness sensor. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to a combustion control method for a boiler having a water pipe.
About.

  Some boilers having this type of water pipe generate steam by heating the water pipe with a burner. At that time, appropriate maintenance of dryness is required as the vapor quality. A method for maintaining this vapor dryness has been proposed (see Patent Document 1).

JP 11-287404 A

  In the conventional method, the dryness is maintained by driving a water supply pump. For this reason, there is a possibility that the water level in the water pipe may fluctuate and the steam dryness cannot be appropriately maintained.

  An object of the present invention is to maintain steam dryness without causing fluctuations in water level.

  The present invention has been made to solve the above-mentioned problems. The invention according to claim 1 is a boiler combustion control method for adjusting a combustion amount of a burner for heating a water pipe, according to a degree of steam dryness. It is characterized by maintaining steam dryness by adjusting the amount of combustion.

  According to a second aspect of the present invention, in a combustion control method for a boiler that adjusts the combustion amount of a burner that heats a water pipe, the steam dryness is maintained by adjusting the combustion quantity according to the water level in the water pipe. It is said.

  According to the present invention, since the steam dryness is maintained by adjusting the combustion amount, the steam dryness is more reliably maintained as compared with the conventional method using the feed water pump control.

(Embodiment 1)
Next, a first embodiment of the present invention will be described. Embodiment 1 of the present invention is applied to a combustion control method for a steam boiler having a group of water tubes (hereinafter simply referred to as a boiler). The boiler is not limited to a specific type and type as long as it includes a water pipe, a burner for heating the water pipe, and a flow rate adjusting valve for adjusting the combustion amount of the burner.

  The first embodiment is characterized in that the steam dryness is maintained by adjusting the combustion amount in accordance with the steam dryness in the combustion control method of the boiler for adjusting the combustion amount of the burner for heating the water pipe.

  In the first embodiment, when it is determined that the steam dryness is lowered, the amount of combustion of the burner is reduced, and the steam dryness is prevented from being lowered. The adjustment of the combustion amount is performed in addition to the adjustment of the combustion amount based on the steam load (steam pressure).

In the first embodiment, the burner is preferably a gas burner whose combustion amount can be easily adjusted. However, the type and form of the burner are not limited to specific ones as long as the amount of combustion is adjusted by changing the opening.

  It is known that the dryness of the steam boiler decreases when the steam pressure in the water pipe is low, when the electrical conductivity of the water in the water pipe is high, and when the feed water temperature to the water pipe is high. Therefore, the determination of the decrease in the steam dryness can be made on the basis of the steam pressure, the electrical conductivity of the water in the water pipe 4, and the water supply temperature to the water pipe 4.

  In the first embodiment, a plurality of water pipes are provided, and the water pipes can be connected between the upper header and the lower header to form a can body. In such a case, the steam pressure, the electrical conductivity of the water in the water pipe 4, and the water supply temperature to the water pipe 4 are the pressure in the can, the electrical conductivity of the water in the can (can water), and the can, respectively. It is equivalent to the temperature of water supply to the body.

  In addition, the determination may be performed based on a signal of a steam dryness sensor provided in the steam supply path. The steam supply path is connected to the can body and supplies generated steam to steam utilization equipment.

  In the first embodiment, the adjustment of the combustion amount is realized by adjusting the opening of the flow rate adjusting valve, and the mode of adjustment is performed by continuous adjustment or stepwise adjustment. When adjusting the opening, the amount of combustion air is also adjusted at the same time by means such as rotational speed control of a blower that supplies combustion air so that combustion is performed at an appropriate air ratio.

  The present invention is not limited to the first embodiment, but includes the following second embodiment.

(Embodiment 2)
Embodiment 2 is a combustion control method for a boiler that adjusts the combustion amount of a burner that heats a water pipe, and is characterized by maintaining the steam dryness by adjusting the combustion quantity according to the water level in the water pipe. .

  In the second embodiment, the steam dryness is maintained by increasing the combustion amount when the water level in the water pipe is low and decreasing the combustion amount when the water level is high.

  In the so-called multi-can installation system in which a plurality of boilers are installed in the second embodiment, when it is not desired to lower the quality of the steam, when the water level in the water pipe is close to the full water level, there is no problem even in low combustion. Includes a mode in which combustion is performed with a combustion amount smaller than low combustion. The combustion amount smaller than the low combustion is about 10 to 30% when the combustion amount at the low combustion is 50% at the high combustion.

  Hereinafter, a specific embodiment 1 of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic configuration diagram of the boiler according to the first embodiment, and FIG. 2 is a flowchart illustrating a control procedure according to the first embodiment.

  The first embodiment is applied to a small once-through boiler that generates steam. The boiler 1 includes a can 4 in which a large number of water pipes 5, 5,... Are connected between an upper header 2 and a lower header 3, and a gas burner (hereinafter simply referred to as a burner) 6 for heating the water pipes 5. The main components are a flow rate adjusting valve 7 for adjusting the combustion amount of the burner 6, a pump 8 for supplying water to the can body 4, and a controller 9 for controlling the flow rate adjusting valve 7, the pump 8 and the like. I have.

  Further, a water level detection cylinder 12 having a first water level detection 10 and a second water level detector 11 for detecting the water level in each water pipe 4 is connected to the can body 4. The first water level detector 10 is an electrode for controlling the water level in each water pipe 5 to the first water level A (water level at low combustion), and the second detector 11 is the water level detection cylinder 12. It is an electrode for controlling the inner water level to the second water level B (water level at the time of high combustion) lower than the first water level A.

  Further, the can body 4 includes a third water level detector 13 for detecting water pipe overheating and a pressure detector 14 for detecting the pressure in the can body 4.

  The flow rate adjusting valve 7 is adjustable in opening degree, the combustion amount of the burner 6 is 0, the combustion amount at the time of low combustion (combustion amount of about half of that when the high combustion time is 100%), and at the time of high combustion This is a proportional control valve that can be controlled to a combustion amount of 75% and a combustion amount at the time of high combustion, and is provided in the fuel supply passage 15. The fuel supply passage 15 is provided with a fuel cutoff valve (not shown). The pumps 7 are respectively provided in the water supply channels 16.

  The controller 9 inputs signals from the pressure detector 14, the first water level detector 10 to the third water level detector 13, etc., and controls the flow rate adjusting valve 7, the pump 8, the shutoff valve, and the like. Control is performed based on a predetermined processing procedure.

  The processing procedure of the controller 9 is such that the pressure in the can body 4 is set based on the signal from the pressure detector 14 so that the pressure in the can body 4 is set and the predetermined steam dryness is maintained. Based on the control procedure for combustion control for controlling the regulating valve 6 and the like and the signals from the first water level detector 10 and the second water level detector 11, the water level in the water level detection cylinder 12 is set to the first during low combustion. A control procedure for controlling the water level A to the second water level B during high combustion is included. The main part of the processing procedure of the combustion control is shown in FIG. The processing procedure of FIG. 2 shows only the procedure of controlling the flow rate adjusting valve 6 so as to maintain the predetermined steam dryness.

The processing procedure of the controller 9 is to detect the properties of the exhaust gas (O ₂ concentration, CO concentration, NOx concentration, etc.) of the boiler 1 and control the flow rate adjusting valve 6 for stabilizing the properties of the exhaust gas. Procedures are also included. Specifically, the amount of gas supplied to the burner 6 is decreased when the O ₂ concentration in the exhaust gas is reduced with respect to the set value, and the amount of supplied gas is increased when the concentration is increased. Further, if the CO concentration in the exhaust gas increases, the operation is performed at a high air ratio by reducing the supply gas amount, and if it still increases, the supply gas amount is increased and control is performed so that the CO concentration is within a certain range. Furthermore, if the NOx concentration in the exhaust gas increases, the amount of supplied gas is reduced and operation is performed at a high air ratio.

  Below, according to the process sequence of FIG. 2, the effect | action of Example 1 regarding the steam dryness maintenance of the said structure is demonstrated. In the following description, when the opening degree is adjusted by the flow rate adjusting valve 7, the combustion is performed by controlling the rotational speed of a blower (not shown) for supplying combustion air so that combustion is performed at an appropriate air ratio. The amount of working air is also adjusted at the same time.

  When the detection value of the pressure detector 13 becomes a set value (for example, 0.6 Mpa) or less, YES (determination of decrease in steam dryness) is determined in S1, and the flow proceeds to S2, and the flow rate adjusting valve 7 Is controlled to finely adjust the combustion amount, that is, as an example, it is reduced to 90% at the time of high combustion. Thereby, the boiling in each said water pipe 5 is suppressed, and the fall of a dryness is suppressed.

  If the detected value of the pressure detector 14 becomes a pressure higher than the set value by a differential amount, and NO is determined in S1, the flow rate adjusting valve 7 is controlled to increase the combustion amount and restore it.

In the first embodiment, the steam dryness is determined based on the detection signal of the pressure detector 13, but a sensor (not shown) for detecting the temperature of the water supply in the water supply channel 16 is provided. In addition, it is possible to make a determination based on the detection signal of this sensor, or to provide a sensor (not shown) for detecting the electrical conductivity of the can water in the can body 2 and to make the determination based on the detection signal of this sensor. it can. In addition, instead of indirectly detecting the steam dryness, a steam dryness detector (not shown) connected to the upper header 2 and supplying steam to a steam utilization facility (not shown) (not shown) (Not shown) may be provided and configured to make a determination based on the detection signal of the detector.

  Further, in a so-called multi-can installation system in which a plurality of boilers 1 are installed, when it is not desired to reduce the quality of the steam, when the water level in the can body 2 is almost full, that is, the first water level detector 10 is When detecting the presence of water or when the third water level detector 13 detects the presence of water, whether the low water level does not cause any problem even if the combustion is low, that is, whether the first water level detector 10 detects the absence of water Until the third water level detector 13 detects the absence of water, combustion can be performed with a smaller combustion amount (30% of high combustion) than low combustion (50% of high combustion).

It is explanatory drawing which shows schematic structure of Example 1 of this invention. It is a flowchart figure which shows the principal part of the process sequence of the Example 1. FIG.

Explanation of symbols

1 Boiler 5 Water Pipe 6 Burner 7 Flow Control Valve 9 Controller

Claims (2)

A boiler combustion control method for adjusting a combustion amount of a burner 6 for heating a water pipe 5, wherein the steam dryness is maintained by adjusting a combustion amount according to the steam dryness. In a boiler combustion control method for adjusting a combustion amount of a burner 6 for heating a water pipe 5, the boiler combustion is characterized in that the steam dryness is maintained by adjusting the combustion amount according to the water level in the water pipe 5. Control method.

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