JP5168923B2 - Operation method of membrane filtration system - Google Patents

Operation method of membrane filtration system Download PDF

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JP5168923B2
JP5168923B2 JP2007026325A JP2007026325A JP5168923B2 JP 5168923 B2 JP5168923 B2 JP 5168923B2 JP 2007026325 A JP2007026325 A JP 2007026325A JP 2007026325 A JP2007026325 A JP 2007026325A JP 5168923 B2 JP5168923 B2 JP 5168923B2
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water
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JP2008188541A (en
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敦行 真鍋
康一 野口
幸男 野口
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Miura Co Ltd
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Description

この発明は、機器への給水ラインに設けられた濾過膜部と、この濾過膜部の上流側の前記給水ラインに設けられて前記濾過膜部へ給水を供給する給水ポンプとを備えた膜濾過システムの運転方法に関する。   The present invention relates to a membrane filtration provided with a filtration membrane part provided in a water supply line to an apparatus, and a water supply pump provided in the water supply line on the upstream side of the filtration membrane part to supply water to the filtration membrane part The present invention relates to a system operation method.

従来、蒸気ボイラ，温水ボイラ，クーリングタワー，給湯器等の熱機器や、洗浄装置等の水使用機器などの機器への給水ラインに、濾過膜部を設けた膜濾過システムが知られている。   2. Description of the Related Art Conventionally, there is known a membrane filtration system in which a filtration membrane section is provided in a water supply line to devices such as steam boilers, hot water boilers, cooling towers, water heaters, and other water-using devices such as cleaning devices.

前記濾過膜部の濾過膜にあっては、水温により水の粘性や膜特性が変化するため、前記濾過膜部からの処理水流量が、季節によって違ったものとなってしまう。ここで、処理水流量は、水温が低くなるほど低下する。したがって、前記濾過膜部の下流側の前記給水ラインに定流量弁を設けておき、前記濾過膜部の上流側の前記給水ラインに設けられた給水ポンプを、低温時でも所要の処理水流量が確保できるように予め高く設定された運転圧力で運転するといったことが行われている。このような膜濾過システムの運転方法によれば、処理水流量を一定にすることができるものの、水温が高い時には過剰な運転圧力になるため、年間を通じると、ほとんどがエネルギーロスになっていた。   In the filtration membrane of the filtration membrane part, the viscosity of the water and the membrane characteristics change depending on the water temperature, so that the treated water flow rate from the filtration membrane part varies depending on the season. Here, the treated water flow rate decreases as the water temperature decreases. Therefore, a constant flow valve is provided in the water supply line on the downstream side of the filtration membrane section, and the water supply pump provided in the water supply line on the upstream side of the filtration membrane section has a required treated water flow rate even at low temperatures. For example, the operation pressure is set at a high operating pressure so as to be secured. According to the operation method of such a membrane filtration system, although the flow rate of treated water can be made constant, excessive operation pressure occurs when the water temperature is high, so most of the energy is lost throughout the year. .

そこで、特許文献１では、前記給水ポンプの消費電力を抑えつつ処理水流量を所要の目標流量で一定にするための膜濾過システムの運転方法として、処理水流量が目標流量になるように、処理水流量の検出値に基づいて、インバータのＰＩＤ制御機能によって前記給水ポンプの回転数を制御する方法が提案されている。また、特許文献２では、前記濾過膜部の下流側に膜式脱気部を備えた膜濾過システムの運転方法として、水温が低下したときに処理水流量の減量運転を行うため、前記給水ポンプの回転数を制御する方法が提案されている。
特開２００５−２９６９４５号公報 特開２００５−２７９４５９号公報 Therefore, in Patent Document 1, as an operation method of the membrane filtration system for keeping the flow rate of the treated water constant at a required target flow rate while suppressing the power consumption of the water supply pump, the treatment water flow rate is set to the target flow rate. There has been proposed a method of controlling the rotation speed of the water supply pump by a PID control function of an inverter based on a detected value of the water flow rate. Moreover, in patent document 2, in order to perform the reduction | decrease operation of a treated water flow rate when water temperature falls as an operating method of the membrane filtration system provided with the membrane type deaeration part in the downstream of the said filtration membrane part, the said water supply pump There has been proposed a method for controlling the number of rotations.
JP 2005-296945 A JP-A-2005-279459

ところで、前記特許文献１に記載された方法で膜濾過システムの運転を行う場合、Ｐ制御（比例制御）の制御パラメータを大きくすれば、前記給水ポンプの運転開始時に、処理水流量が目標流量になるまでの時間を短くすることができる。しかし、Ｐ制御（比例制御）の制御パラメータを大きくすると、目標流量に対する処理水流量のオーバーシュート量が大きくなる。一方で、Ｐ制御（比例制御）の制御パラメータを小さくすれば、オーバーシュート量を抑制することができるものの、処理水流量が目標流量になるまでに時間がかかってしまう。   By the way, when the membrane filtration system is operated by the method described in Patent Document 1, if the control parameter of P control (proportional control) is increased, the treated water flow rate becomes the target flow rate at the start of operation of the feed water pump. The time to become can be shortened. However, when the control parameter of P control (proportional control) is increased, the amount of overshoot of the treated water flow rate with respect to the target flow rate increases. On the other hand, if the control parameter of P control (proportional control) is reduced, the amount of overshoot can be suppressed, but it takes time until the treated water flow rate reaches the target flow rate.

また、前記特許文献２に記載された処理水流量の減量運転において、前記給水ポンプの回転数制御を、前記特許文献１と同様にして処理水流量の検出値に基づくインバータのＰＩＤ制御機能によって行う場合、Ｐ制御（比例制御）の制御パラメータを大きくすれば、減量運転時に、処理水流量が目標流量になるまでの時間を短くすることができる。しかし、Ｐ制御（比例制御）の制御パラメータを大きくすると、目標流量に対する処理水流量のアンダーシュート量が大きくなる。一方で、Ｐ制御（比例制御）の制御パラメータを小さくすれば、アンダーシュート量を抑制できるものの、処理水流量が目標流量になるまでに時間がかかってしまう。   Further, in the reduction operation of the treated water flow rate described in Patent Document 2, the rotation speed control of the feed water pump is performed by the PID control function of the inverter based on the detected value of the treated water flow rate as in Patent Document 1. In this case, if the control parameter for P control (proportional control) is increased, the time until the treated water flow rate reaches the target flow rate during the reduction operation can be shortened. However, when the control parameter of P control (proportional control) is increased, the amount of undershoot of the treated water flow rate with respect to the target flow rate increases. On the other hand, if the control parameter of P control (proportional control) is reduced, the amount of undershoot can be suppressed, but it takes time until the treated water flow rate reaches the target flow rate.

この発明が解決しようとする課題は、機器への給水ラインに設けられた濾過膜部と、この濾過膜部の上流側の前記給水ラインに設けられた給水ポンプとを備え、前記濾過膜部からの処理水流量が目標流量になるように前記給水ポンプを運転する膜濾過システムの運転方法において、前記給水ポンプの運転開始時や処理水流量の減量運転時に、処理水流量をできるだけ短時間で目標流量にするとともに、オーバーシュート量やアンダーシュート量を抑制することである。   The problem to be solved by the present invention includes a filtration membrane part provided in a water supply line to an apparatus, and a water supply pump provided in the water supply line on the upstream side of the filtration membrane part, from the filtration membrane part In the operation method of the membrane filtration system for operating the feed water pump so that the treated water flow rate becomes the target flow rate, the treated water flow rate is targeted in the shortest possible time when the feed water pump is started or when the treated water flow rate is reduced. It is to reduce the overshoot amount and undershoot amount as well as the flow rate.

この発明は、前記課題を解決するためになされたもので、請求項１に記載の発明は、機器への給水ラインに設けられた濾過膜部と、この濾過膜部の上流側の前記給水ラインに設けられ、前記濾過膜部からの処理水流量が目標流量で一定になるようにインバータの出力周波数に応じて回転数が制御される給水ポンプとを備えた膜濾過システムの運転方法であって、前記給水ポンプの運転開始時および／または処理水流量の減量運転時に、処理水流量が目標流量になるように比例制御によって制御された前記インバータの出力周波数に応じて前記給水ポンプの回転数が制御される初期運転を行った後、処理水流量が目標流量に到達する前に、処理水流量が目標流量になるように比例制御および積分制御および／または微分制御によって制御された前記インバータの出力周波数に応じて前記給水ポンプの回転数が制御される通常運転に切り替えることを特徴とする。   This invention was made in order to solve the said subject, The invention of Claim 1 is a filtration membrane part provided in the water supply line to an apparatus, The said water supply line of the upstream of this filtration membrane part An operation method of a membrane filtration system provided with a feed water pump that is controlled in accordance with an output frequency of an inverter so that a treated water flow rate from the filtration membrane portion is constant at a target flow rate. At the start of operation of the feed water pump and / or at the time of reduced operation of the treated water flow rate, the rotation speed of the feed water pump is set according to the output frequency of the inverter controlled by proportional control so that the treated water flow rate becomes the target flow rate. After performing the controlled initial operation, before the treated water flow rate reaches the target flow rate, it is controlled by proportional control, integral control and / or differential control so that the treated water flow rate becomes the target flow rate. Rotational speed of the water supply pump and switches to normal operation, which is controlled according to the output frequency of the serial inverter.

請求項１に記載の発明では、前記給水ポンプの運転開始時および／または処理水流量の減量運転時に、比例制御によって制御された前記インバータの出力周波数に応じて前記給水ポンプの回転数が制御される初期運転を行うことにより、前記濾過膜部からの処理水流量が、より短時間で目標流量に近づく。また、初期運転を行った後、処理水流量が目標流量に到達する前に、比例制御および積分制御および／または微分制御によって制御された前記インバータの出力周波数に応じて前記給水ポンプの回転数が制御される通常運転に切り替えることにより、オーバーシュート量やアンダーシュート量が抑制される。   In the first aspect of the present invention, when the operation of the feed water pump is started and / or when the treated water flow rate is reduced, the rotation speed of the feed water pump is controlled according to the output frequency of the inverter controlled by proportional control. By performing the initial operation, the treated water flow rate from the filtration membrane unit approaches the target flow rate in a shorter time. In addition, after the initial operation, before the treated water flow rate reaches the target flow rate, the rotation speed of the feed water pump is set according to the output frequency of the inverter controlled by proportional control, integral control and / or differential control. By switching to the controlled normal operation, the overshoot amount and the undershoot amount are suppressed.

この発明によれば、前記給水ポンプの運転開始時および／または処理水流量の減量運転時に、初期運転を行った後、処理水流量が目標流量に到達する前に、通常運転に切り替えることにより、前記給水ポンプの運転開始時および／または処理水流量の減量運転時に、処理水流量をできるだけ短時間で目標流量にすることができるとともに、オーバーシュート量やアンダーシュート量を抑制することができる。   According to this invention, at the start of operation of the feed water pump and / or at the time of reduced operation of the treated water flow rate, after performing the initial operation, before the treated water flow rate reaches the target flow rate, by switching to normal operation, When the operation of the feed water pump is started and / or during the operation of reducing the treated water flow rate, the treated water flow rate can be set to the target flow rate in the shortest possible time, and the overshoot amount and the undershoot amount can be suppressed.

つぎに、この発明の実施の形態について図面に基づいて詳細に説明する。図１は、この発明を実施する膜濾過システムの一例を示す概略的な説明図、図２は、この発明に係る膜濾過システムの運転方法を実施したときの処理水流量の変化を示す図である。   Next, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic explanatory view showing an example of a membrane filtration system embodying the present invention, and FIG. 2 is a diagram showing a change in the treated water flow rate when the operation method of the membrane filtration system according to the present invention is implemented. is there.

図１において、膜濾過システム１は、水道水，工業用水，地下水などの水源から供給される原水を水処理して得られた給水を、後段に設置されたボイラなどの機器（図示省略）へ供給するものである。前記膜濾過システム１は、前記機器への給水ライン２を備えており、この給水ライン２には、濾過膜部３が設けられている。前記濾過膜部３の上流側の前記給水ライン２には、給水ポンプ４が設けられており、また前記濾過膜部３の下流側の前記給水ライン２には、流量センサ５が設けられている。   In FIG. 1, a membrane filtration system 1 is configured to supply water obtained by treating raw water supplied from a water source such as tap water, industrial water, and groundwater to equipment (not shown) such as a boiler installed in a subsequent stage. To supply. The membrane filtration system 1 includes a water supply line 2 to the device, and the water supply line 2 is provided with a filtration membrane unit 3. The water supply line 2 upstream of the filtration membrane unit 3 is provided with a water supply pump 4, and the water supply line 2 downstream of the filtration membrane unit 3 is provided with a flow rate sensor 5. .

前記濾過膜部３は、濾過膜モジュール（図示省略）により給水を濾過処理するように構成されている。この濾過膜モジュールは、濾過膜（図示省略）として、具体的には逆浸透膜（ＲＯ膜）やナノ濾過膜（ＮＦ膜）などを使用して形成されている。前記逆浸透膜および前記ナノ濾過膜は、ポリアミド系，ポリエーテル系などの合成高分子膜である。そして、前記逆浸透膜は、分子量が数十程度の物質の透過を阻止できる液体分離膜である。また、前記ナノ濾過膜は、２ｎｍ程度より小さい粒子や高分子（分子量が最大数百程度の物質）の透過を阻止できる液体分離膜である。前記ナノ濾過膜は、濾過機能の点において、前記逆浸透膜と、分子量が１，０００〜３００，０００程度の物質を濾別可能な限外濾過膜（ＵＦ膜）との中間に位置する機能を有する。前記濾過膜は、前記機器への給水が、所望の水質になるように選択される。   The said filtration membrane part 3 is comprised so that feed water may be filtered with a filtration membrane module (illustration omitted). This filtration membrane module is specifically formed using a reverse osmosis membrane (RO membrane), a nanofiltration membrane (NF membrane), or the like as a filtration membrane (not shown). The reverse osmosis membrane and the nanofiltration membrane are synthetic polymer membranes such as polyamide and polyether. The reverse osmosis membrane is a liquid separation membrane capable of preventing permeation of a substance having a molecular weight of about several tens. The nanofiltration membrane is a liquid separation membrane capable of preventing permeation of particles and polymers (substances having a maximum molecular weight of about several hundreds) smaller than about 2 nm. The nanofiltration membrane is located in the middle of the reverse osmosis membrane and an ultrafiltration membrane (UF membrane) capable of separating a substance having a molecular weight of about 1,000 to 300,000 in terms of filtration function. Have The filtration membrane is selected so that water supplied to the device has a desired water quality.

前記濾過膜部３では、一側から流入した給水が、前記濾過膜で濾過され、他側から透過水と濃縮水とが分離されて流出するようになっている。透過水は、前記給水ライン２へ流出するようになっている。これにより、前記機器へ所望の水質になった給水が供給されるようになっている。一方、濃縮水は、前記濾過膜部３と接続された濃縮水ライン６へ流出するようになっている。この濃縮水ライン６は、排水ライン７と、還流ライン８とに分岐しており、この還流ライン８は、前記給水ポンプ４の上流側の前記給水ライン２と接続されている。そして、前記濃縮水ライン６へ流出した濃縮水は、一部が前記排水ライン７を介して系外へ排水されるとともに、残部が前記還流ライン８を介して前記濾過膜部３の上流側の前記給水ライン２へ還流するようになっている。   In the filtration membrane part 3, the feed water flowing from one side is filtered by the filtration membrane, and the permeated water and the concentrated water are separated and flowed out from the other side. The permeated water flows out to the water supply line 2. Thereby, the water supply which became the desired water quality to the said apparatus is supplied. On the other hand, the concentrated water flows out to the concentrated water line 6 connected to the filtration membrane unit 3. The concentrated water line 6 branches into a drainage line 7 and a reflux line 8, and the reflux line 8 is connected to the water supply line 2 on the upstream side of the water supply pump 4. A part of the concentrated water flowing out to the concentrated water line 6 is drained out of the system through the drain line 7, and the remaining part is upstream of the filtration membrane unit 3 through the reflux line 8. It returns to the water supply line 2.

前記流量センサ５における流量検出信号は、ＣＰＵを備える制御部９へ入力されるようになっている。前記制御部９は、前記流量センサ５からの流量検出信号を受けると、これを周波数指示信号（たとえば、４〜２０ｍＡの電流値，もしくは１〜５Ｖの電圧値）としてインバータ１０へ出力するようになっている。そして、周波数指示信号を受けた前記インバータ１０の出力周波数に応じ、前記濾過膜部３からの処理水流量が目標流量になるように、前記給水ポンプ４の回転数が制御されるようになっている（定流量制御）。   The flow rate detection signal in the flow rate sensor 5 is input to a control unit 9 having a CPU. Upon receipt of the flow rate detection signal from the flow rate sensor 5, the control unit 9 outputs this to the inverter 10 as a frequency instruction signal (for example, a current value of 4 to 20 mA or a voltage value of 1 to 5 V). It has become. Then, according to the output frequency of the inverter 10 that has received the frequency instruction signal, the rotational speed of the feed water pump 4 is controlled so that the treated water flow rate from the filtration membrane unit 3 becomes the target flow rate. Yes (constant flow control).

さて、前記膜濾過システム１の運転方法について説明する。前記給水ポンプ４にあっては、処理水流量が目標流量になるように、前記インバータ１０の出力周波数に応じて回転数が制御される。具体的には、前記制御部９は、前記流量センサ５からの流量検出信号を受けると、これを周波数指示信号として前記インバータ１０へ出力する。そして、前記インバータ１０は、この周波数指示信号に応じて前記給水ポンプ４への出力周波数を制御する。前記制御部９は、後述する初期運転のときには比例制御，すなわちＰ制御により、また後述する通常運転のときには、比例制御（Ｐ制御）および積分制御（Ｉ制御）および／または微分制御（Ｄ制御），すなわちＰＩ制御，ＰＤ制御およびＰＩＤ制御により、処理水流量が目標流量になるように、その前記インバータ１０への周波数指示信号を制御する。ここで、前記制御部９のＰ制御機能，ＰＩ制御機能，ＰＤ制御機能およびＰＩＤ制御機能は、前記流量センサ５からの流量検出信号をフィードバック値として目標値と比較を行い、偏差をゼロにするように動作する機能である。これにより、処理水流量が目標流量になるように、前記インバータ１０の出力周波数に応じ、前記給水ポンプ４の回転数が制御される。   Now, an operation method of the membrane filtration system 1 will be described. In the feed water pump 4, the rotation speed is controlled according to the output frequency of the inverter 10 so that the treated water flow rate becomes the target flow rate. Specifically, when receiving the flow rate detection signal from the flow rate sensor 5, the control unit 9 outputs it to the inverter 10 as a frequency instruction signal. And the said inverter 10 controls the output frequency to the said feed pump 4 according to this frequency instruction | indication signal. The controller 9 performs proportional control, that is, P control during initial operation described later, and proportional control (P control), integral control (I control), and / or differential control (D control) during normal operation described later. That is, the frequency instruction signal to the inverter 10 is controlled by PI control, PD control and PID control so that the treated water flow rate becomes the target flow rate. Here, the P control function, the PI control function, the PD control function, and the PID control function of the control unit 9 compare the target value with the flow rate detection signal from the flow rate sensor 5 as a feedback value, and set the deviation to zero. It is a function that operates as follows. Thereby, the rotation speed of the feed water pump 4 is controlled according to the output frequency of the inverter 10 so that the treated water flow rate becomes the target flow rate.

この発明に係る前記膜濾過システム１の運転方法では、図２に示すように、前記給水ポンプ４の運転開始時に、初期運転を行った後、処理水流量が目標流量Ｘ１に到達する前に通常運転に切り替える。具体的には、処理水流量が第一運転切替流量ｘ１に達したとき、初期運転から通常運転に切り替える。第一運転切替流量ｘ１は、たとえば目標流量Ｘ１の８０〜９０％の流量に設定される。   In the operation method of the membrane filtration system 1 according to the present invention, as shown in FIG. 2, after the initial operation is performed at the start of the operation of the feed water pump 4, it is usually performed before the treated water flow rate reaches the target flow rate X1. Switch to driving. Specifically, when the treated water flow rate reaches the first operation switching flow rate x1, the initial operation is switched to the normal operation. The first operation switching flow rate x1 is set to a flow rate of 80 to 90% of the target flow rate X1, for example.

具体的に説明すると、前記膜濾過システム１では、前記給水ポンプ４の運転を開始すると、まず初期運転を行う。この初期運転は、処理水流量が目標流量Ｘ１になるように前記制御部９のＰ制御によって制御された前記インバータ１０の出力周波数に応じて前記給水ポンプ４の回転数が制御される起動運転である。   More specifically, in the membrane filtration system 1, when the operation of the water supply pump 4 is started, an initial operation is first performed. This initial operation is a start-up operation in which the rotation speed of the feed water pump 4 is controlled according to the output frequency of the inverter 10 controlled by the P control of the control unit 9 so that the treated water flow rate becomes the target flow rate X1. is there.

そして、前記濾過膜部３からの処理水流量が、第一運転切替流量ｘ１になると、前記制御部９は初期運転から通常運転に切り替える。この通常運転は、処理水流量が目標流量Ｘ１になるように、ＰＩ制御，ＰＤ制御およびＰＩＤ制御のいずれかによって制御された前記インバータ１０の出力周波数に応じて前記給水ポンプ４の回転数が制御される運転である。ちなみに、通常運転において、ＰＩ制御，ＰＤ制御およびＰＩＤ制御を行うときの制御パラメータは、目標流量に対する処理水流量のオーバーシュート量を抑制することができる値に設定する。   When the treated water flow rate from the filtration membrane unit 3 reaches the first operation switching flow rate x1, the control unit 9 switches from the initial operation to the normal operation. In this normal operation, the rotation speed of the feed water pump 4 is controlled according to the output frequency of the inverter 10 controlled by any one of PI control, PD control and PID control so that the treated water flow rate becomes the target flow rate X1. Driving. Incidentally, the control parameters when performing PI control, PD control, and PID control in normal operation are set to values that can suppress the overshoot amount of the treated water flow rate relative to the target flow rate.

以上説明した前記膜濾過システム１の運転方法によれば、前記給水ポンプ４の運転開始時に、前記インバータ１０の出力周波数がＰ制御によって制御される初期運転（すなわち、起動運転）を行うことにより、処理水流量がより短時間で目標流量Ｘ１に近づく。また、処理水流量が第一運転切替流量ｘ１に到達したとき、前記インバータ１０の周波数がＰＩ制御，ＰＤ制御およびＰＩＤ制御のいずれかによって制御される通常運転に切り替えることにより、目標流量Ｘ１に対する処理水流量のオーバーシュート量が抑制される。   According to the operation method of the membrane filtration system 1 described above, by performing the initial operation (that is, the start-up operation) in which the output frequency of the inverter 10 is controlled by P control at the start of operation of the feed water pump 4, The treated water flow rate approaches the target flow rate X1 in a shorter time. Further, when the treated water flow rate reaches the first operation switching flow rate x1, the processing for the target flow rate X1 is performed by switching to the normal operation in which the frequency of the inverter 10 is controlled by any one of PI control, PD control, and PID control. The overshoot amount of the water flow rate is suppressed.

つぎに、この発明に係る前記膜濾過システム１の運転方法では、図２に示すように処理水流量の減量運転時に、初期運転を行った後、処理水流量が目標流量Ｘ２に到達する前に通常運転に切り替える。具体的には、処理水流量が第二運転切替流量ｘ２に達したとき、初期運転から通常運転に切り替える。第二運転切替流量ｘ２は、たとえば目標流量Ｘ２の１１０〜１２０％の流量に設定される。   Next, in the operation method of the membrane filtration system 1 according to the present invention, as shown in FIG. 2, after the initial operation is performed at the time of the reduction operation of the treated water flow rate, before the treated water flow rate reaches the target flow rate X2. Switch to normal operation. Specifically, when the treated water flow rate reaches the second operation switching flow rate x2, the initial operation is switched to the normal operation. The second operation switching flow rate x2 is set to a flow rate of 110 to 120% of the target flow rate X2, for example.

具体的に説明すると、前記膜濾過システム１では、水温の低下の検知により、処理水流量の減量運転を開始すると、まず初期運転を行う。この初期運転は、処理水流量が目標流量Ｘ２（Ｘ２＜Ｘ１）になるようにＰ制御によって制御された前記インバータ１０の出力周波数に応じて前記給水ポンプ４の回転数が制御される移行運転である。   More specifically, in the membrane filtration system 1, when a reduction operation of the treated water flow rate is started by detecting a decrease in water temperature, an initial operation is first performed. This initial operation is a transition operation in which the rotation speed of the feed water pump 4 is controlled according to the output frequency of the inverter 10 controlled by the P control so that the treated water flow rate becomes the target flow rate X2 (X2 <X1). is there.

そして、前記濾過膜部３からの処理水流量が、第二運転切替流量ｘ２になると、前記制御部９は、初期運転から通常運転に切り替える。この通常運転は、処理水流量が目標流量Ｘ２になるように、ＰＩ制御，ＰＤ制御およびＰＩＤ制御のいずれかによって制御された前記インバータ１０の出力周波数に応じて前記給水ポンプ４の回転数が制御される運転である。ちなみに、通常運転において、ＰＩ制御，ＰＤ制御およびＰＩＤ制御を行うときの制御パラメータは、目標流量Ｘ２に対する処理水流量のアンダーシュート量を抑制することができる値に設定する。   When the treated water flow rate from the filtration membrane unit 3 reaches the second operation switching flow rate x2, the control unit 9 switches from the initial operation to the normal operation. In this normal operation, the rotation speed of the feed water pump 4 is controlled according to the output frequency of the inverter 10 controlled by any one of PI control, PD control and PID control so that the treated water flow rate becomes the target flow rate X2. Driving. Incidentally, the control parameters when performing PI control, PD control, and PID control in normal operation are set to values that can suppress the undershoot amount of the treated water flow rate with respect to the target flow rate X2.

以上説明した前記膜濾過システム１の運転方法によれば、処理水流量の減量運転時に、前記インバータ１０の出力周波数がＰ制御によって制御される初期運転（すなわち、移行運転）を行うことにより、処理水流量が短時間で目標流量Ｘ２に近づく。また、処理水流量が第二運転切替流量ｘ２に到達したとき、前記インバータ１０の周波数がＰＩ制御，ＰＤ制御およびＰＩＤ制御のいずれかによって制御される通常運転に切り替えることにより、目標流量Ｘ２に対する処理水流量のアンダーシュート量が抑制される。   According to the operation method of the membrane filtration system 1 described above, the process is performed by performing the initial operation (that is, the transition operation) in which the output frequency of the inverter 10 is controlled by the P control during the reduction operation of the treated water flow rate. The water flow rate approaches the target flow rate X2 in a short time. Further, when the treated water flow rate reaches the second operation switching flow rate x2, the processing for the target flow rate X2 is performed by switching to the normal operation in which the frequency of the inverter 10 is controlled by any one of PI control, PD control, and PID control. The amount of undershoot of the water flow rate is suppressed.

以上、この発明を実施形態により説明したが、この発明は、その主旨を変更しない範囲で種々変更実施可能なことは勿論である。   As mentioned above, although this invention was demonstrated by embodiment, it cannot be overemphasized that this invention can be variously implemented in the range which does not change the main point.

この発明を実施する膜濾過システムの一例を示す概略的な説明図である。It is a schematic explanatory view showing an example of a membrane filtration system for carrying out the present invention. この発明に係る膜濾過システムの運転方法を実施したときの処理水流量の変化を示す図である。It is a figure which shows the change of the treated water flow rate when the operating method of the membrane filtration system which concerns on this invention is implemented.

符号の説明Explanation of symbols

１ 膜濾過システム
２ 給水ライン
３ 濾過膜部
４ 給水ポンプ
１０ インバータ DESCRIPTION OF SYMBOLS 1 Membrane filtration system 2 Water supply line 3 Filtration membrane part 4 Water supply pump 10 Inverter

Claims (1)

機器への給水ラインに設けられた濾過膜部と、この濾過膜部の上流側の前記給水ラインに設けられ、前記濾過膜部からの処理水流量が目標流量で一定になるようにインバータの出力周波数に応じて回転数が制御される給水ポンプとを備えた膜濾過システムの運転方法であって、
前記給水ポンプの運転開始時および／または処理水流量の減量運転時に、処理水流量が目標流量になるように比例制御によって制御された前記インバータの出力周波数に応じて前記給水ポンプの回転数が制御される初期運転を行った後、処理水流量が目標流量に到達する前に、処理水流量が目標流量になるように比例制御および積分制御および／または微分制御によって制御された前記インバータの出力周波数に応じて前記給水ポンプの回転数が制御される通常運転に切り替えることを特徴とする膜濾過システムの運転方法。 Output of the inverter so that the flow rate of treated water from the filtration membrane unit provided in the water supply line to the equipment and the water supply line upstream of the filtration membrane unit is constant at the target flow rate An operation method of a membrane filtration system including a feed water pump whose rotation speed is controlled according to a frequency,
The rotation speed of the feed water pump is controlled in accordance with the output frequency of the inverter controlled by proportional control so that the treated water flow rate becomes the target flow rate at the start of operation of the feed water pump and / or during the reduction operation of the treated water flow rate. The output frequency of the inverter controlled by proportional control and integral control and / or differential control so that the treated water flow rate reaches the target flow rate after the initial operation is performed and before the treated water flow rate reaches the target flow rate The operation method of the membrane filtration system is characterized by switching to a normal operation in which the rotation speed of the water supply pump is controlled according to the operation.
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