JPS60256818A - Temperature control system for stored liquid - Google Patents

Abstract

PURPOSE:To attain the concentrated control for the temperature of the stored liquid in a monitor control room by transmitting the signals showing the working state of a control valve and the temperature and level of the stored liquid to an arithmetic and control unit together with an address designating signal. CONSTITUTION:A transmitter 6 compares the address setting signal and the address designating signal given from an arithmetic and control unit 7 with the generated address signal. When the coincidence of addresses is obtained, the working signal sent from the arithmetic and control unit 7 is sent to a control valve 4 as a drive signal. At the same time, the signals showing the temperature and the liquid level supplied from a thermometer 2 and a liquid level gauge 3 and the signal showing the working state and serving as the drive signal transmitted to the valve 4 are sent to the arithmetic and control unit 7 together with the generated address signal. The signals are transferred between the controller 7 and the transmitter 6 via a receiver 8 having a function that selects an address designating signal at an upper place. This reduces the load of the arithmetic and control unit 7 and therefore controls speedily the temperatures of more types of liquid stored in a tank 1.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control system for controlling the temperature of a stored liquid in a storage tank by controlling the flow rate of a heating medium such as steam, and particularly relates to a control system for controlling the temperature of a stored liquid in a plurality of storage tanks. This invention relates to a system for centrally controlling and managing the temperature of a remote location.

Petroleum refining 1 Petrochemical factories have numerous storage tanks for storing raw materials, intermediate products, products, etc.

Most of these stored liquids are heated and maintained at a desired temperature for convenience of transportation, shipping, etc.

Conventionally, as a method for controlling the temperature of these stored liquids, a temperature controller is provided for each storage tank, and heating using steam or the like is used to maintain the temperature of the stored liquid in the storage tank at the set value of the controller. The flow rate of the medium was controlled by a control valve.

In this method, whenever the holding temperature of the stored liquid is changed due to a change in the stored liquid or for other reasons, it is necessary to go to the storage tank and change the setting value of the temperature controller. Combined with the large yard, it is extremely inefficient and requires complicated work.Also, the heat capacity of the stored liquid is extremely large, and PID control using the aforementioned regulator is not sufficient. Temperature control is desired, but if the retention temperature of the stored liquid is on the safe side, detailed management is not possible.
This method has problems such as keeping the stored liquid at a high temperature unnecessarily and causing an extremely large loss of heating medium.

The present invention has solved such problems. 2. The purpose of the present invention is to be able to centrally and finely control the temperature of the stored liquid in each storage tank in a monitoring and control room remote from the storage tank.
It is an object of the present invention to provide a temperature control system for a stored liquid that can reduce the amount of loss of heating medium, save energy, and also enable optimal operation of heating medium generators throughout the factory.

That is, the present invention provides a storage liquid temperature control system that controls the temperature of a storage liquid in a storage tank by controlling the flow rate of a heating medium, in which an addressing signal and an operation signal of a control valve that controls the flow rate are controlled. The address designation signal from the arithmetic and control device is compared with the arithmetic and control device into which signals indicating the operating state of the control valve and the temperature and liquid level of the stored liquid are input, and the corresponding operating signal is transmitted to the control valve. A temperature control system for a stored liquid, which is provided with a transmitter that sends a signal indicating the operating state of the control valve and the temperature and liquid level of the stored liquid to the arithmetic and control unit together with an addressing signal. . Therefore, the present invention particularly has the following features:
The operating signal output from the arithmetic and control device sets either the pour point control temperature calculated from the pour point of the stored liquid or the viscosity control temperature calculated from the viscosity of the stored liquid as the set temperature,
The set temperature is changed in advance based on the temperature of the stored liquid itself or the expected temperature calculated based on the heat balance of the stored liquid.

This includes a signal for opening and closing a control valve for maintaining the temperature of the stored liquid at the set temperature. Furthermore, in the present invention, the set temperature has a range between an upper limit value and a lower limit value, and when discharging the stored liquid, the viscosity control temperature is set, and during receiving and normal storage, the set temperature is set to the pour point control temperature. , when the amount of heating medium generated is large, the temperature of the stored liquid is
This includes a mode in which control is performed using the lower limit of the set temperature when the amount of heating medium generated is small at the upper limit of the set temperature.

Below, nine aspects of the present invention will be described in detail based on drawings illustrating one embodiment.

In the figure, 1 indicates each storage tank, and each storage tank 1 has a thermometer 2 and a liquid level gauge 3 that measure the temperature and liquid level of the stored liquid, and a control valve 4 that controls the flow rate of steam as a heating medium. A heating pipe 5 is installed. The outputs of the thermometer 2 and the liquid level gauge 3 are input to a transmitter 6, and the transmitter 9 is wired so as to output a signal for driving the control valve 4.

The oscillator 6 is at least a circuit capable of setting an address, generating an address signal, and comparing and inspecting an address designation signal from an arithmetic and control unit 7, which will be described later, with the generated address signal.If the addresses match, the arithmetic and control unit 7 A circuit that transmits an operating signal from the controller as a drive signal to the control valve 4, a signal indicating the temperature and liquid level input from the thermometer 2 and the liquid level gauge 3, and a drive signal transmitted to the control valve 4. It is composed of a circuit that transmits a signal indicating the operating state to the arithmetic and control unit 7 together with the generated address signal.

The load on the arithmetic and control device 7 can be reduced by passing signals between the arithmetic and control device 7 and the transmitter 6 via a receiver 8 that has a function of selecting addressing signals at a higher level. The temperature of the liquid stored in a large number of storage tanks 1 can be controlled quickly.

The arithmetic and control device 7 is preferably a digital computer, and this device 7 receives signals from two transmitters 6 indicating the temperature and liquid level of the stored liquid in each storage tank 1 and the operating state of the control valve 4. K can input the properties of the stored liquid (viscosity, pour point, etc.) and receiving and dispensing plans (receiving time and liquid volume, dispensing time and liquid volume, temperature and properties of the receiving liquid, etc.) online or from the terminal device 9 as necessary. data is input. Based on these data, the operating signal for each control valve 4 of each storage tank 1 is determined and output together with the addressing signal.

This operation signal is determined within the arithmetic and control unit 7 by comparing the temperature of the stored liquid from the transmitter 6 (hereinafter referred to as "measured temperature") with a set temperature. In other words, if the measured temperature is higher than the set temperature, a close operation signal is sent, and vice versa if it is lower.

Outputs an open operation signal.

In addition, in the above, if a function is added to change the set temperature in advance based on the predicted temperature.

For example, after 1 minute, I received 1 high rmo* and 7" dirt.
If it is predicted that the IL storage liquid will exceed the set temperature, the storage liquid will not be heated by lowering the set temperature in advance. As a result, the receiver can effectively use the amount of heat brought in by the poured liquid to heat the stored liquid, and the stored liquid is not heated to an unnecessarily high temperature.

The amount of steam for heating can be significantly reduced. The predicted temperature is 1! ! When accepting high-temperature liquids such as products obtained from manufacturing equipment, the heat balance calculation is performed based on the amount of heat brought in by the liquid, the amount of heat retained by the stored liquid, the amount of heat released, etc. at the time of reception and after the reception of the liquid. The temperature is preferably calculated by a calculation function built into the calculation control device 7.

On the other hand, the set temperature may be input from the terminal device 9 together with the address of the storage tank 1 to the arithmetic and control device 7 for each storage tank.
It may also be generated by arithmetic operations within the arithmetic control device 7. In this case, the set temperature is preferably determined so that the stored liquid does not solidify in the storage tank 1 and maintains the lowest viscosity that allows the stored liquid to be transferred or shipped by a pump. Therefore.

It is preferable that the pour point of the stored liquid plus 5° C. as the point at which the stored liquid does not solidify is set as the pour point control temperature, and the value calculated by the following formula is set as the viscosity control temperature, and these are set temperatures.

Viscosity control temperature (°C) = 101e-273 where V' is
The kinematic viscosity (cst) of the stored liquid at temperature T''K, v is the target kinematic viscosity (cst) of the stored liquid determined by each storage tank (bo/bu capacity).
cSt), m is a constant determined by the stored liquid.

When setting either the pour point control temperature or the viscosity control temperature calculated in this way as the set temperature, the pour point control temperature is generally set as the set temperature when the viscosity control temperature is slightly lower than the pour point control temperature.

In other cases, a selection function for setting the viscosity control temperature as the set temperature may be provided.

However, if the receiving and distributing plan for the stored liquid has been decided and the receiving and distributing frequency is a little low, the pour point control temperature should be set as the temperature during receiving and normal storage.

If you adopt the method of determining the time required for heating by heating and heat radiation calculation to reach the viscosity control temperature at the time of dispensing, then determining the heating start time, and changing the set temperature to the viscosity control temperature from the said start time. , wasteful heating can be reduced, and energy can be saved.

Further, by providing a control period of about ±0.5 to 1.0° C. to the above-mentioned set temperature, the temperature of the stored liquid can be controlled more smoothly depending on the purpose. In other words, the lower limit of the set temperature is set to a temperature 0.5 to 1.0°C lower than the set temperature,
In addition, the upper limit is set at a temperature 0.5 to 1.0 degrees Celsius higher, and when the measured temperature or the aforementioned predicted temperature reaches the lower limit of the set temperature, the operation signal to open the control valve 4 is set to the set temperature. outputs an operation signal to close the control valve 4 when the upper limit of is reached;
The operation signal is not changed between the upper limit value and the lower limit value.

By the way, most factories generate their own electricity using steam to heat the stored liquid.

In many cases, the waste steam after the private power generation is used. In this case, the amount of heating steam increases or decreases depending on the amount of power generated by the private power generation.

It is preferable to perform control according to the amount of steam generated in order to effectively utilize steam. Therefore, in the control based on the upper limit value and lower limit value described above, when the amount of steam generation is large and the measured temperature or predicted temperature is between the upper limit value and the lower limit value of the set temperature.

It outputs an operation signal to open the control valve 4 to maintain the temperature of the stored liquid at the upper limit of the set temperature, and conversely, when the amount of steam generation is small, the measured temperature or predicted temperature is equal to the upper limit of the set temperature. If the temperature is between the lower limit value and the lower limit value, provide a control function that outputs an operation signal to close the control valve 4 to maintain the temperature of the stored liquid at the lower limit value. Temperature can be controlled.

The above-mentioned selection of the set temperature or control method in the arithmetic and control device 7 is performed using a command signal from the terminal device 9 or data set in advance in the arithmetic and control device 7 for each storage tank. Next.

Arithmetic *1 + control 1 7 for each storage tank 1iC7F''v, i designation signal No. 1.1 and operation signal are generated, first address designation signal 9 and then operation signal are output as a series of pulse signals. This pulse signal enters the receiver 8, where the addressing signal is compared and sent by the corresponding transmission line to the series-coupled transmitter 6. In the transmitter 6, the addressing signal is The signal is compared with the address signal generated in the transmitter 6, and if they match, it is determined whether the operating signal is open or closed.

A corresponding drive signal is added to the control valve 4.

By using an electric motor as the control valve 4 and providing a relay circuit in the transmitter 6, the control valve 4 can be easily opened and closed. In addition, if the stored liquid is a flammable fluid, the control valve 4
From the viewpoint of safety, it is preferable to use air as a driving source, to use a solenoid valve as the air supply valve, and to operate the solenoid valve by the reciprocating circuit.

On the other hand, if the addressing signal does not match the address signal generated within the transmitter 6, the operating signal is ignored.

The pulse signal outputted from this arithmetic and control device 7 is sequentially transmitted to each transmitter 6 provided for each storage tank.

Next, signals indicating the temperature and liquid level of the stored liquid in the storage tank 1 inputted to the transmitter 6 and a signal indicating the operating state, which is a drive signal added to the control valve 4, are an address signal generated by the transmitter 6. It is also transmitted as a pulse signal to the arithmetic and control unit 7 via the receiver 8, and is used for the aforementioned control and checking.

Further, the temperature and liquid level of the stored liquid in each storage tank, the open/closed state of the control valve 4, etc. are displayed on the terminal device 9 upon request or at predetermined time intervals.

As described above, the system of the present invention allows the temperature of the stored liquid in each storage tank to be centrally and finely managed in a monitoring control room that is separate from the storage tanks.

Tomo's sister is able to efficiently manage the temperature of the stored liquid.

It is possible to reduce the amount of loss of the heating medium, to save energy, and to achieve special effects such as making it possible to optimally operate the heating medium generating device for the entire factory.

[Brief explanation of the drawing]

The figure is a schematic diagram showing one embodiment of the system of the present invention. In the figure, 1 is a storage tank, 4 is a control valve, 5 is a heating tube, 6 is a transmitter, and 7 is an arithmetic and control unit. Patent applicant: Nippon Mining Co., Ltd. Representative Patent Attorney (7569) Keishi Jyujo

Claims (5)

[Claims] (1) In a storage liquid temperature control system that controls the temperature of a storage liquid in a storage tank by controlling the flow rate of a heating medium, an addressing signal and an operation signal are output for a control valve that controls the flow rate. Then, it compares and inspects the address designation signal from the arithmetic and control device into which signals indicating the operating state of the control valve and the temperature and liquid level of the stored liquid are input, and drives the corresponding operation signal to the control valve. A transmitter for transmitting a signal indicating the operating state of the control valve and the temperature and liquid level of the stored liquid to the arithmetic and control unit together with an addressing signal. Temperature control system. (2) The operation signal output from the arithmetic and control unit. The set temperature is either the pour point control temperature calculated from the pour point of the stored liquid or the viscosity control temperature calculated from the viscosity of the stored liquid, and a signal to open and close the control valve to maintain the stored liquid at the set temperature. A temperature control system for a stored liquid according to claim 1, characterized in that: (3) The operation signal output from the arithmetic and control unit. The signal is characterized in that it is a signal that opens and closes a control valve for changing the set temperature in advance and maintaining the temperature of the stored liquid at the set temperature based on the predicted temperature calculated from the heat balance of the stored liquid. A temperature control system for a stored liquid according to claim 1 or 2. (4) A temperature control system for a stored liquid according to claim 2 or 3, wherein the set temperature has a range between an upper limit value and a lower limit value. (5) Claims 2, 3, or 4, characterized in that the set temperature is the viscosity control temperature when discharging the stored liquid, and the pour point control temperature during receiving and normal storage. storage liquid temperature control system. 5. The temperature control system for stored liquid according to claim 4, wherein when the amount is small, the temperature is controlled at the lower limit of the set temperature.