JP4481373B2

JP4481373B2 - Feeding control method for multi-tube once-through boiler

Info

Publication number: JP4481373B2
Application number: JP10576398A
Authority: JP
Inventors: 敬重松
Original assignee: Miura Co Ltd
Current assignee: Miura Co Ltd
Priority date: 1998-03-31
Filing date: 1998-03-31
Publication date: 2010-06-16
Anticipated expiration: 2018-03-31
Also published as: JPH11287404A

Description

【０００１】
【発明の属する技術分野】
この発明は、貫流型等のボイラにおける給水制御方法に関するものである。
【０００２】
【従来の技術】
従来、貫流型等のボイラにおける一般的給水制御方法は、次の通りである。
ボイラの缶体への給水量の調節は、缶体内の水位を検出し、所定水位以下になるとＯＮ−ＯＦＦ制御式の給水ポンプをＯＮし、所定水位以上となると給水ポンプをＯＦＦする。即ち、缶体への単位時間当たりの給水量は給水ポンプの給水ポンプの選定により固定され、缶体内の水位検出手段により規定される。そして、通常給水ポンプにより固定される給水量は、ボイラの単位時間当たりの蒸発量よりも多く設定される。
【０００３】
【発明が解決しようとする課題】
こうした従来の給水制御方法によれば、缶体内水位が不安定となり蒸気の乾き度が安定しないという課題があった。本発明は、こうした課題を解決することを目的とするものである。
【０００４】
【課題を解決するための手段】
本発明は、上下ヘッダ間に多数の水管を設けた缶体と、前記缶体内の水位を検出する第一検出端およびこの第一検出端よりも所定値だけ低い水位を検出する第二検出端を設けた水位検出手段と、前記缶体へ給水する給水ポンプと、前記水位検出手段からの信号に基づき前記缶体内水位が第一検出端および第二検出端の間の水位となるように前記給水ポンプをＯＮ−ＯＦＦ制御する制御器とを備える多管式貫流ボイラの給水制御方法であって、前記給水ポンプを回転数が調節可能なポンプとするか、または前記給水ポンプと別に調節弁を設け、前記ポンプの回転数を調節するか、前記調節弁の開度を調節することにより、単位時間当たりの給水量を増減可能な給水手段を構成し、前記缶体内の検出圧力を所定圧力値毎に複数の圧力帯に分割し、各圧力帯毎の前記給水手段による単位時間当たりの給水量を前記検出圧力の上昇に応じて増大させるように設定し、前記水位検出手段による検出水位に基づいて前記給水ポンプをＯＮ−ＯＦＦ制御するとともに、前記缶体内の圧力を圧力検出手段により検出し、検出圧力と前記設定とに基づいて前記給水手段による単位時間当たりの給水量を増減する多管式貫流ボイラの給水制御方法を特徴とするものである。
【０００５】
【発明の実施の形態】
本発明の実施の形態を以下に説明する。この実施の形態においては、ボイラの缶体内の圧力を検出し、前記缶体へ給水する給水手段による単位時間当たりの給水量を前記検出圧力の上昇に応じて増大させる。前記給水手段は、例えば缶体に給水する給水ポンプとこの給水ポンプに直列に接続される調節弁とから構成される。この調節弁は、その開度が連続的或いは段階的に調節可能な弁とし、例えば比例制御弁が用いられる。
【０００６】
そして、前記缶体内の圧力を検出する圧力検出手段を設け、この圧力検出手段の検出圧力が上昇すると、給水手段の単位時間当たり給水量を増大させ、前記検出圧力が下降すると、前記給水量を減少させる。こうした給水量の制御により、缶体内の水位変動が緩和され、水位が安定し、供給蒸気の乾き度が安定する。
【０００７】
前記給水手段として、ＯＮ（起動）−ＯＦＦ( 停止）制御式の給水ポンプと調節弁を用いた場合には、調節弁の開度を調節することで、単位時間当たりの給水量を増減する。その調節方法としては、前記検出圧力を所定圧力値毎に複数の圧力帯に分割し、各圧力帯毎に調節弁の開度を設定する。こうして設定した開度の切り替えのタイミングは、例えば缶体の水位を検出する水位検出手段により設定水位以下に缶体内水位が下降し、前記給水ポンプをＯＮする時とする。前記の調節弁の開度を設定した後、缶体内の水位の変化の状態応じて更に調節弁の開度を微調整することも可能である。
【０００８】
前記給水手段の形態としては、回転数を調節可能な給水ポンプ、例えばインバータ周波数制御の給水ポンプとすることができる。又、他の形態としては給水ポンプとこの出口側に設けた三方調節弁とすることもできる。この三方調節弁はその第一出口を前記缶体に、第二出口を給水ポンプの入口側に接続し、第一出口と第二出口との流出量を調節することで前記缶体への単位時間当たりの給水量を増減する。
【０００９】
【実施例】
以下、本発明の具体的な実施例を図面に基づいて詳細に説明する。図１は、本発明を実施した多管式貫流ボイラの一実施例の概略を示す説明図である。図２は、調節弁の開度制御に用いる、缶体内の検出圧力と調節弁の開度との関係を示す制御テーブルである。
【００１０】
図１において、ボイラ本体１には、上，下ヘッダー２，３間に多数の水管４を環状に設けた周知の缶体５を設けている。缶体５には缶体５内水位を検出および制御する手段として水位制御筒６が付設されている。前記缶体５と水位制御筒６とは、缶体５の蒸気部に接続される第一連絡管７及び缶体５の水部に接続される第二連絡管８によって連通している。この水位制御筒６には、ボイラ本体１の缶内水位に連動する水位制御筒６内の比較的高い水位を検出する第一検出端Ｈとこの第一検出端Ｌよりも所定値だけ低い水位を検出する第二検出端Ｌとを設けている。これらの両検出端Ｈ，Ｌは、２本の電極棒をもって構成する。缶体５には缶体内の蒸気圧力を検出する圧力検出器（圧力検出手段）Ｐを備える。
【００１１】
更に、前記缶体５には給水ライン９と排水ライン１０と蒸気供給ライン１１とを接続している。給水ライン９には、弁開度が連続的に調節可能な調節弁１２とＯＮ−ＯＦＦ制御式の給水ポンプ１３とを設け、排水ライン１０には開閉弁１４を設けている。給水ライン９を通して供給された水は、前記缶体５において燃焼装置１５により加熱され、蒸気となって蒸気供給ライン１１を通して蒸気使用設備（図示省略）へ供給される。
【００１２】
マイクロコンピュータからなる制御器１６は、前記第一検出端Ｈ、第二検出端Ｌ及び圧力検出器Ｐからの信号を入力して、前記調節弁１２、給水ポンプ１３、燃焼装置１５を制御する。制御器１６は、給水ポンプ１３のＯＮ−ＯＦＦ制御を行うと共に調節弁１２の弁開度を図２の制御テーブルに従い制御する。この制御テーブルは、検出圧力（例えば０〜１０ｋｇ／ｃｍ^２）を所定圧力値（例えば２ｋｇ／ｃｍ^２）毎に複数（例えば５つ）の圧力帯に分割し、各圧力帯毎に調節弁１２の開度をそれぞれ例えば１０％、２０％、５０％、７５％、９０％に設定する。
【００１３】
前記制御器１６による前記給水ポンプ１３の制御はＯＮ−ＯＦＦ制御であり、次のようにして行う。前記制御器１６は、前記第一検出端Ｈを超えて水位が上昇するとポンプ１３をＯＦＦし、前記第二検出端Ｌを超えて水位が下降すると前記給水ポンプ１３をＯＮする。前記調節弁１２の弁開度の制御は次のようにして行う。前記制御器１６は、前記第二検出端Ｌを超えて水位が下降し、前記給水ポンプ１３をＯＮするタイミングに同期して前記圧力検出器Ｐによる検出圧力が前記制御テーブルのどの圧力帯に位置するかを判定し、これに基づき、弁開度値を設定し、調節弁７の開度を制御する。
【００１４】
更に、前記の弁開度の制御に加えて、調節弁１２の開度を給水ポンプ１３のＯＮと同時に調節した後、缶体内水位が第一所定時間内に第一検出端Ｈに到達するようであれば、開度を第一所定値だけ増大させ、逆に第二所定時間内に第二検出端Ｌに到達するようであれば、開度を第二所定値だけ減少させる制御を行うこともできる。
【００１５】
こうした給水ポンプ１３と調節弁１２とによる給水量調節が缶体５内圧力に基づき行われることにより、缶体の水位の変動が少なくなり、その結果として蒸気供給ライン１１から供給される蒸気の乾き度を安定したものとすることができる。又、給水ポンプ１３のＯＮ−ＯＦＦ回数が減少し、給水ポンプ１３の長寿命化、即ち長期にわたる使用を実現できる。
【００１６】
次に、本発明の他の実施例を図３に従い説明する。図３は図１の給水ポンプ１３と調節弁１２とからなる給水手段を給水ポンプ１３と三方調節弁１７に変えたもので、その他の構成は図１の実施例と同様である。この三方調節弁１７は、その第一出口１８を前記缶体５に、第二出口１９を給水ポンプ１３の入口側に接続する。前記第一出口１８と第二出口１９とは互いの開度が逆に増減するよう構成され、両出口の開口割合を調節することで缶体５への単位時間当たりの給水量を増減する。この実施例においては、給水ポンプ１３は停止することなく連続運転が可能となる。
【００１７】
【発明の効果】
以上のように、この発明によれば、上下ヘッダ間に多数の水管を設けた缶体と、前記缶体内の水位を検出する第一検出端およびこの第一検出端よりも所定値だけ低い水位を検出する第二検出端を設けた水位検出手段と、前記缶体へ給水する給水ポンプと、前記水位検出手段からの信号に基づき前記缶体内水位が第一検出端および第二検出端の間の水位となるように前記給水ポンプをＯＮ−ＯＦＦ制御する制御器とを備える多管式貫流ボイラの給水制御方法において、前記給水ポンプを回転数が調節可能なポンプとするか、または前記給水ポンプと別に調節弁を設け、前記ポンプの回転数を調節するか、前記調節弁の開度を調節することにより、単位時間当たりの給水量を増減可能な給水手段を構成し、缶体内の圧力を検出し、検出圧力を所定圧力値毎に複数の圧力帯に分割し、前記缶体内の検出圧力を所定圧力値毎に複数の圧力帯に分割し、各圧力帯毎の前記給水手段による単位時間当たりの給水量を前記検出圧力の上昇に応じて増大させるように設定し、前記水位検出手段による検出水位に基づいて前記給水ポンプをＯＮ−ＯＦＦ制御するとともに、前記缶体内の圧力を圧力検出手段により検出し、検出圧力と前記設定とに基づいて前記給水手段による単位時間当たりの給水量を増減するので、缶体内の水位が従来に比較して安定し、その結果蒸気の乾き度が安定する。
【図面の簡単な説明】
【図１】この発明を実施した多管式貫流ボイラの一実施例の概略を示す説明図である。
【図２】同実施例における給水制御の制御テーブルを示す図である。
【図３】この発明を実施した多管式貫流ボイラの他の実施例の要部を示す説明図である。
【符号の説明】
５缶体
１２調節弁
１３給水ポンプ
１６制御器
Ｈ上位検出端
Ｌ下位検出端
Ｐ圧力検出器[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a water supply control method in a once-through boiler or the like.
[0002]
[Prior art]
Conventionally, a general water supply control method in a once-through boiler is as follows.
The adjustment of the amount of water supplied to the boiler body is performed by detecting the water level in the can body, turning ON the ON-OFF control type water pump when the water level is lower than a predetermined level, and turning OFF the water pump when the water level is higher than the predetermined level. That is, the amount of water supplied to the can body per unit time is fixed by the selection of the water supply pump of the water supply pump, and is defined by the water level detecting means in the can body. And the amount of water supply fixed with a normal water supply pump is set more than the evaporation amount per unit time of a boiler.
[0003]
[Problems to be solved by the invention]
According to such a conventional water supply control method, there is a problem that the water level in the can becomes unstable and the dryness of the steam is not stable. The present invention aims to solve these problems.
[0004]
[Means for Solving the Problems]
The present invention includes a can body provided with a number of water pipes between upper and lower headers , a first detection end for detecting a water level in the can body, and a second detection end for detecting a water level lower than the first detection end by a predetermined value. A water level detecting means provided with a water supply pump for supplying water to the can body, and based on a signal from the water level detecting means, the water level in the can is a water level between the first detection end and the second detection end. A feed water control method for a multi-pipe once-through boiler comprising a controller for ON-OFF control of a feed water pump , wherein the feed water pump is a pump whose rotation speed is adjustable, or a control valve is provided separately from the feed water pump Providing a water supply means capable of increasing or decreasing the amount of water supply per unit time by adjusting the rotation speed of the pump or adjusting the opening of the control valve, and the detected pressure in the can body is set to a predetermined pressure value Divided into multiple pressure zones Together set to increase in response to water supply amount per unit time by the water supply means for each pressure zone to the increase in the detected pressure, to ON-OFF control the water supply pump based on the detected water level by said level detecting means the pressure of the can body is detected by the pressure detecting means, wherein water supply control method of the multi-tubular boiler to increase or decrease the amount of water supply per unit time by the water supply means on the basis of said set and detected pressure Is.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below. In this embodiment, the pressure in the boiler body is detected, and the amount of water supplied per unit time by the water supply means for supplying water to the can is increased in accordance with the increase in the detected pressure. The water supply means includes, for example, a water supply pump for supplying water to the can body and a control valve connected in series to the water supply pump. This control valve is a valve whose opening degree can be adjusted continuously or stepwise, for example, a proportional control valve is used.
[0006]
Then, pressure detecting means for detecting the pressure in the can body is provided, and when the detected pressure of the pressure detecting means increases, the amount of water supplied per unit time of the water supplying means is increased, and when the detected pressure decreases, the amount of water supplied is reduced. Decrease. By controlling the amount of water supply, fluctuations in the water level in the can are mitigated, the water level is stabilized, and the dryness of the supplied steam is stabilized.
[0007]
When an ON (start-up) -OFF (stop) control type water pump and a control valve are used as the water supply means, the amount of water supplied per unit time is increased or decreased by adjusting the opening of the control valve. As the adjustment method, the detected pressure is divided into a plurality of pressure bands for each predetermined pressure value, and the opening degree of the adjustment valve is set for each pressure band. The switching timing of the opening thus set is, for example, when the water level in the can drops below the set water level by the water level detecting means for detecting the water level of the can and the water supply pump is turned on. After setting the opening of the control valve, it is possible to further finely adjust the opening of the control valve according to the state of change in the water level in the can.
[0008]
As a form of the water supply means, a water supply pump capable of adjusting the rotation speed, for example, a water supply pump with inverter frequency control can be used. As another form, a water supply pump and a three-way control valve provided on the outlet side can be used. This three-way control valve has its first outlet connected to the can body, the second outlet connected to the inlet side of the water supply pump, and the unit to the can body is adjusted by adjusting the outflow amount of the first outlet and the second outlet. Increase or decrease the amount of water supply per hour.
[0009]
【Example】
Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings. Figure 1 is an explanatory diagram showing an outline of an embodiment of a multi-tube once-through boiler embodying the present invention. FIG. 2 is a control table showing the relationship between the detected pressure in the can and the opening degree of the regulating valve, which is used for controlling the opening degree of the regulating valve.
[0010]
In FIG. 1, a boiler body 1 is provided with a known can body 5 in which a large number of water pipes 4 are annularly provided between upper and lower headers 2 and 3. The can body 5 is provided with a water level control cylinder 6 as means for detecting and controlling the water level in the can body 5. The can body 5 and the water level control cylinder 6 are communicated with each other by a first connecting pipe 7 connected to the vapor section of the can body 5 and a second connecting pipe 8 connected to the water section of the can body 5. The water level control cylinder 6 includes a first detection end H for detecting a relatively high water level in the water level control cylinder 6 interlocked with the water level in the boiler body 1 and a water level lower than the first detection end L by a predetermined value. And a second detection end L for detecting. Both of these detection ends H and L are constituted by two electrode rods. The can body 5 includes a pressure detector (pressure detecting means) P for detecting the vapor pressure in the can body.
[0011]
Furthermore, a water supply line 9, a drain line 10 and a steam supply line 11 are connected to the can body 5. The water supply line 9 is provided with a control valve 12 whose valve opening degree can be continuously adjusted and an ON-OFF control type water supply pump 13, and the drainage line 10 is provided with an opening / closing valve 14. The water supplied through the water supply line 9 is heated by the combustion device 15 in the can 5 and becomes steam and is supplied to the steam use facility (not shown) through the steam supply line 11.
[0012]
A controller 16 comprising a microcomputer inputs signals from the first detection end H, the second detection end L and the pressure detector P, and controls the control valve 12, the feed water pump 13 and the combustion device 15. Controller 16, the valve opening degree of the regulating valve 12 is controlled according to the control table of FIG. 2 performs ON-OF F control of the water supply pump 13. The control table, the detected pressure (e.g. 0~10kg / cm ²⁾ a predetermined pressure value (e.g., 2 kg / cm ²⁾ is divided into a pressure zone of a plurality (e.g., five) for each, control valve in each pressure zone 12 Are set to 10%, 20%, 50%, 75%, and 90%, for example.
[0013]
The control of the water supply pump 13 by the controller 16 is ON-OFF control, and is performed as follows. The controller 16 turns off the pump 13 when the water level rises beyond the first detection end H, and turns on the water supply pump 13 when the water level falls below the second detection end L. The valve opening degree of the control valve 12 is controlled as follows. In the controller 16, the water level drops beyond the second detection end L, and the pressure detected by the pressure detector P is located in any pressure zone of the control table in synchronization with the timing of turning on the water supply pump 13. Based on this, the valve opening value is set, and the opening degree of the control valve 7 is controlled.
[0014]
Further, in addition to the control of the valve opening described above, the water level in the can reaches the first detection end H within the first predetermined time after the opening of the control valve 12 is adjusted simultaneously with the ON of the water supply pump 13. If so, the opening is increased by the first predetermined value, and conversely, if the second detection end L is reached within the second predetermined time, the opening is decreased by the second predetermined value. You can also.
[0015]
By adjusting the amount of water supplied by the water supply pump 13 and the control valve 12 based on the pressure in the can 5, the fluctuation of the water level of the can is reduced, and as a result, the steam supplied from the steam supply line 11 is dried. The degree can be stabilized. In addition, the number of ON / OFF operations of the water supply pump 13 is reduced, and the life of the water supply pump 13 can be extended, that is, it can be used for a long time.
[0016]
Next, another embodiment of the present invention will be described with reference to FIG. FIG. 3 shows a structure in which the water supply means including the water supply pump 13 and the control valve 12 in FIG. 1 is replaced with a water supply pump 13 and a three-way control valve 17, and the other configurations are the same as in the embodiment of FIG. The three-way control valve 17 has a first outlet 18 connected to the can 5 and a second outlet 19 connected to the inlet side of the water supply pump 13. The first outlet 18 and the second outlet 19 are configured such that the opening degrees of the first outlet 18 and the second outlet 19 increase or decrease, and the amount of water supplied to the can 5 is increased or decreased by adjusting the opening ratio of both outlets. In this embodiment, the water supply pump 13 can be continuously operated without stopping.
[0017]
【The invention's effect】
As described above, according to the present invention, the can body provided with a large number of water pipes between the upper and lower headers , the first detection end for detecting the water level in the can body, and the water level lower than the first detection end by a predetermined value A water level detection means provided with a second detection end for detecting water, a water supply pump for supplying water to the can body, and the water level in the can between the first detection end and the second detection end based on a signal from the water level detection means In a feed control method for a multi-tube type once-through boiler comprising a controller for ON / OFF control of the feed water pump so that the water level is equal to the water level, the feed water pump is a pump whose rotation speed is adjustable, or the feed water pump Separately, a control valve is provided, and by adjusting the number of rotations of the pump or adjusting the opening of the control valve, a water supply means capable of increasing or decreasing the amount of water supply per unit time is constructed, and the pressure in the can is adjusted. Detect and detect pressure Dividing into a plurality of pressure zones for each force value, dividing the detected pressure in the can into a plurality of pressure zones for each predetermined pressure value, and detecting the amount of water supply per unit time by the water supply means for each pressure zone It is set to increase in response to an increase in pressure, and the water supply pump is controlled on and off based on the water level detected by the water level detection means, and the pressure in the can is detected by the pressure detection means, since increasing or decreasing the amount of water supply per unit time by the water supply means based on said setting, the water level of the can body is stabilized as compared with the prior art, resulting dryness of the vapor is stabilized.
[Brief description of the drawings]
FIG. 1 is an explanatory view showing an outline of an embodiment of a multitubular once-through boiler embodying the present invention.
FIG. 2 is a diagram showing a control table of water supply control in the same embodiment.
FIG. 3 is an explanatory view showing a main part of another embodiment of a multi-tube once-through boiler embodying the present invention.
[Explanation of symbols]
5 Can 12 Control valve 13 Water supply pump 16 Controller H Upper detection end L Lower detection end P Pressure detector

Claims

Water level provided with a can body provided with a large number of water pipes between upper and lower headers, a first detection end for detecting the water level in the can body and a second detection end for detecting a water level lower than the first detection end by a predetermined value Based on a detection means, a water supply pump for supplying water to the can body, and a signal from the water level detection means, the water supply pump is turned on so that the water level in the can becomes a water level between the first detection end and the second detection end. A feed control method for a multi-tube once-through boiler comprising a controller for performing OFF control ,
The feed water pump is a pump whose rotation speed can be adjusted, or a control valve is provided separately from the feed water pump, and the rotation speed of the pump is adjusted, or the opening of the control valve is adjusted, so that the unit time Construct water supply means that can increase or decrease the amount of water supply per unit,
The detected pressure in the can is divided into a plurality of pressure zones for each predetermined pressure value, and the amount of water supplied per unit time by the water supply means for each pressure zone is set to increase in accordance with an increase in the detected pressure. ,
The water supply pump is ON / OFF controlled based on the detected water level by the water level detecting means, the pressure in the can is detected by the pressure detecting means, and the unit of time per unit time by the water supplying means is determined based on the detected pressure and the setting. A water supply control method for a multi-tube once-through boiler, characterized by increasing or decreasing the amount of water supply .