SU1747808A1 - Method of automatic water temperature control upstream of hot-water boiler - Google Patents

Abstract

Usage: automatic control of the water temperature in front of the hot water boiler 1 with the upstream network water heater. SUMMARY OF THE INVENTION: Adjusting the temperature of the water in front of the boiler 1 when it is above a predetermined value and the recirculation is turned off is performed by changing the supply of return network water through the additional line of the network water bypass from the outlet of the network pump 2 to the input of the boiler 1 and maintain the specified value of pressure difference before and after the preheater preheater 3 changes the throttling of a portion of the return network water line, parallel to the bypass line with the preheater 3, 1 slug installed on it.

Description

The invention relates to heat and power engineering, Liphoenergy, in particular the automation of water boilers in circuits with pre-included net water heaters. A known method for automatically controlling the temperature of water in front of a hot-water boiler in a circuit with an preheating reverse supply water heater that heats the steam coming from the selection of the turbine, and the required pressure drop across the heater (flow rate through the flow through it) is provided by setting the throttle washer on the section of the main line of the return mains water parallel to the bypass line with the heater, by means of the action of a constant temperature regulator; Water storage in front of the boiler to change the flow of water to the boiler from the boiler recirculation line.

In this method of regulation, the use of the heat of the steam in the preheater is limited when the water temperature in front of the boiler is higher than the predetermined limit. values when the boiler recycle is closed. In this case, in order to maintain a constant temperature, it is necessary to reduce the heat load of the heater to a level that ensures the water temperature in front of the boiler is slave or below the preset limit value. Maintaining a constant water temperature in front of the boiler is necessary under the conditions for reliable and economical operation of the boiler. The differential pressure on the throttle washer, which provides the required differential pressure on the preheater, and consequently, the flow of water through it in the known method significantly deviates from the calculated one with changes in total

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consumption of network water, which reduces the reliability and cost-effectiveness of operation of the pre-included network water heater.

The purpose of the invention is to increase the efficiency of the boiler operation at the temperature of the water in front of the boiler above a predetermined limit value and closed recirculation of the boiler.

This goal is achieved by the fact that in the mode of increased heat consumption of the preheater, when the water temperature in front of the boiler exceeds a predetermined limit value, and the control valve on the recirculation line of the boiler is closed, the temperature of the water in front of the boiler is maintained by changing the return flow rate of the water (mixed with cold water boiler) through an additional bypass line with the issuance of a network pump to the input of the boiler. In order to change the position of the control valve on the additional bypass line when regulating the water temperature in front of the boiler did not lead to significant deviations of water flow through the heater, the proposed method uses a pressure regulator that maintains the specified water pressure after the heater with automatic correction of the water pressure deviations on the preheater, if they exceed the specified limit values. At the same time, the specified pressure drop of water on the preheater, and consequently, the required flow of water through it, is maintained both at a constant total flow of the supply water and at its changes.

At low heat loads of the preheater, when the water temperature to the boiler at the point of mixing flows is below a predetermined limit value, the constant water temperature in front of the boiler is maintained by means of a control valve in the boiler recirculation line. As the heat load of the preheater increases, the temperature of the water to the boiler rises, causing the control valve to be closed in the boiler recirculation line.

If the water temperature in front of the boiler exceeds a predetermined limit value, the control valve in the recirculation line of the boiler is closed and using an analog relay converter, the effect of the constant temperature controller in front of the boiler is disconnected from the control valve in the recirculation line and connected to the control valve in the line additional bypass.

With a constant total flow rate of supply water, a change in the position of the control valve in the additional bypass line under the action of the water temperature regulator in front of the boiler leads to pressure deviations at the mixing point

flows (behind the preheater), which are compensated by the pressure regulator in such a way that a predetermined pressure drop across the preheater and, consequently, the required water flow through

0 him.

When the total flow rate of the network water changes (the water pressure at the outlet of the network pump in accordance with its characteristics), the water pressure drop across

5, if at the same time its deviation from the required one exceeds a predetermined value, the analog-to-relay converter operates, controlling the integrator, the output signal of which

0 is the reference for the pressure regulator.

The change in the task to the pressure controller is made until the moment of compensation of the deviation of the pressure drop from the required one with the given accuracy and release

5 analog relay converter. After the pressure drop on the preheater has been restored, the pressure regulator maintains the new value of the water pressure in the main line to the boiler (behind the preheater).

0 The deviations of the water flow through the boiler and the water line bypass line are compensated for by the constant water flow regulator through the boiler acting on the control valve in the main line

5 network water behind the boiler, and a temperature regulator of the direct network water, which controls the control valve on the network water bypass line. . The drawing shows the implementation scheme

0 of the proposed method of automatically regulating the temperature of the water in front of the boiler.

In the drawing, the following notation is accepted: 1 - hot water boiler; 2 - network

5 pump; 3 - mains water heater; 4 - recirculation pump; 5 - control valve in the recirculation line; 6 - control valve on the section of the main line of the return network water parallel to the bypass line with a heater; 7 - water pressure sensor behind the heater; 8 — pressure regulator; 9 - integration unit (pressure regulator setter); 10 - analog-to-relay converter

5 water pressure drop across the heater; 11 - control valve on the additional bypass line; 12-water temperature sensor in front of the boiler; 13 - regulator of constant water temperature in front of the boiler; 14-analog relay converter on the water temperature in front of the boiler; 15 - measuring diaphragm for water flow through the boiler; 16 - control valve on the main water line behind the boiler; 17 - water flow sensor cut-in boiler; 18 —constant water flow regulator through the boiler; 19 - water temperature sensor behind the boiler; 20 - boiler heat load regulator; 21 - control valve for fuel supply to the boiler; 22 —electric network direct temperature sensor; 23 - temperature regulator of direct supply water; 24 - control valve on the line of the water network bypass; 25 - heating steam from the selection of the turbine; 26 - heating steam condensate drainage; 27 - element ZONA SENSITIVITY; 28 - sensor for differential pressure of network water on the heater; 29 - unit for controlling the heat load of the boiler; 30 is the setpoint of the regulator of the direct water temperature.

A water temperature sensor 12 in front of the boiler 1 is connected to an input of a regulator 13 of a constant water temperature in front of the boiler and to an input of an analog-relay converter 14, to another input of which a reference signal on water temperature in front of the boiler is connected. The output of the regulator 13 is connected via an analog-relay converter 14 with a regulating valve 5 in the boiler recirculation line or with a regulating valve 11 on an additional bypass line.

The water pressure sensor 7 behind the heater is connected to the first inverting input of the pressure regulator connected to the control valve 6 in the section of the main return network water line parallel to the bypass line with the heater. The second input of the pressure regulator 8 is connected to the output signal of the block and integration 9, to the input of which, in turn, the output logic signals of the analog-relay converter 10 are connected. The output signal of the element 27 of the ZONE of SENSITIVITY is connected to the input of the latter, which is connected to the water pressure differential sensor 28 on the mains water heater 3. To the other input of the converter 10 a pressure differential signal is connected to the heater. A constant water flow regulator 18 through the boiler is connected to the water flow sensor 17 by the pressure differential across the orifice plate 15 in the line behind the boiler and with the control valve 16 in the water line behind the boiler.

The boiler heat load controller 20 is connected to a sensor 19 for water temperature behind the boiler, a setting device 29 and a regulating

valve 21 in the fuel line in tel. The temperature sensor of the direct supply water 22 is connected to the input of the regulator 23 of the temperature of the direct supply water, which is connected with the regulating valve 24 in the supply line of the supply water, as well as with the setting device 30.

The method is carried out as follows.

10 In the steady state operation of the preheater, the boiler and the network, their thermal loads, as well as the temperature of the direct and reverse supply water behind the mixing point and in front of the boiler are constant. The pressure behind the preheater is constant and equal to the given one. The constant water temperature regulator 13 in front of the boiler, connected via analog-relay converter 14 to the control valve 5 in the recirculation line, is balanced by the balance water pressure regulator 8, the control valve 11 in the additional bypass line is closed.

After being disturbed by an increase in the temperature of the water behind the heater, caused by an increase in its heat load, the temperature of the water to the boiler beyond the mixing point rises. This causes the signal from sensor 12 to turn on the regulator 13 in the direction of compensation of the disturbance - closing valve 5. Reducing the flow of water from the recirculation circuit leads to a decrease in water pressure in front of the boiler, which causes the signal from sensor 7 to affect the valve 8 6 aside

5 disturbance compensation - open the valve.

The speed of the pressure regulator 8 is such that deviations of the water flow through the boiler, caused by a change in the water pressure in front of the boiler when the recirculation of the boiler changes, are insignificant and do not cause the constant flow regulator 18 to turn on.

At the same time, the temperature of 5 pa of water behind the boiler rises, which, by a signal from the temperature sensor 19, causes the heat load regulator of the boiler 20 to affect the fuel supply valve 21 in the closing direction. An increase in the temperature of the water behind the boiler after a period of time caused by the delay in the change indicated

 temperature when fuel is disturbed,

stops and the temperature rises

direct network water at a signal from the sensor

5 2 is compensated by temperature control 23, by acting on the valve 24 in the direction of opening. Deviations of the water pressure to the boiler and the flow of water through the boiler, caused by the opening of the valve 24, are compensated by the regulators 8 and 18 in the same way as described

earlier. The temperature of the water in front of the boiler due to a decrease in the proportion of more heated water to the boiler decreases, the temperature of the water behind the boiler also decreases to the desired one. In the steady state, the temperature of the water behind the boiler must be adjusted to less in accordance with the heat balance of the heater with the boiler and the network.

An increase in the heat load of the supply water heater 3 at steady state operation of boiler 1 leads to an increase in water temperature to the boiler beyond the mixing point and to cover valve 5 in the boiler recirculation line from regulator 13, and when it reaches the specified limit value, it triggers an analog relay. - converter 14, Disconnecting the output of the regulator 13 from the control valve 5 and connecting it to the control valve 11 in the additional bypass line.

In the steady state, the increased heat load of the network water heater corresponds to the value of the water flow in front of the boiler close to the specified limit value, the position of the control valve 5 in the boiler recirculation line is close to full closing, and the control valve 11 in the additional bypass line is intermediate.

After disturbance, for example, by increasing the temperature, the species behind the preheater raises the temperature of the water to the boiler beyond the point of mixing of the streams. This leads to a signal from the water temperature sender in front of the boiler 12 to turn on the regulator 13 in the direction of compensation of disturbance - opening valve 11 (increasing cold water supply to the mixing boiler). This changes the network characteristic, which leads to an increase in water pressure in front of the boiler and The signal from sensor 7 is activated by the pressure regulator 8 in the direction of closing valve b in the main line. At the same time, the flow of water through the boiler increases, which is compensated by the signal from the flow sensor 17 by the regulator 18 on the control valve 16 in the direction of closing, and the water flow through the bypass line increases, which leads to a decrease in the temperature of the direct supply water and causes the signal from the sensor temperature 22, turning on the regulator 23 in the direction of compensating the disturbance - closing the valve 24.

In the steady state after the end of the transient processes, the initial values of water flow through the boiler, network water heater are restored, the water temperature to the boiler stabilizes, behind the boiler into the network at a new level exceeding the task, which requires adjusting the task of the controller 20 to lower the temperature behind the boiler to level, providing a balance of heat loads of the heater with the boiler and the network

The regulation of the differential pressure on the preheater with significant changes in the flow rate of the supply water is carried out as follows.

0 In steady-state mode, with constant water pressure to the boiler and pressure drop on the preheater, after increasing the total flow rate of the supply water, the pressure on the output of the main pump decreases and

5, respectively, the differential pressure on the heater. This results in the occurrence of a differential deviation signal at the output of the sensor due to the differential pressure 28. If, moreover, the deviation of the specified signal is less than

0 exceeds the half of the dead zone of the element 27, then the analog-to-relay converter 10 is triggered and by decreasing the Integration downward along

5 the output logic signal of the converter 10 changes the output signal of the integrator 9, which is the task of the pressure regulator 8. The regulator acts on the control valve b towards

0 closes the water pressure to the boiler until the signal when the differential pressure deviation from sensor 28 through element 27 decreases to a value equal to half the dead zone of the transition. When this is released, the analog-to-relay converter 10 and the change in the setting of the controller 8 stops.

In statics, after the end of transient processes, a reduced

0, the pressure of water in the main line to the boiler, i.e., the predetermined differential on the preheater and the constant flow of water through it are preserved with the required accuracy. The flow of water through the boiler that changes towards the bottom is restored by the constant flow controller 18 of the boiler, and The reduction in water flow through the bypass line is compensated in the steady state by the controller 23 (by opening the valve 24

0 on the signal from the temperature sensor 22),

The temperature control of the water in front of the boiler in case of disturbances by changing the temperature of the return network water is performed as follows.

5 In the steady state operation of the equipment at a constant temperature of direct supply water, in front of and behind the boiler after being disturbed by an increase in the temperature of the return supply water, the temperature of the water to the boiler rises and

An increase in the temperature of the direct mains water. In this case, the signal from the temperature sensor 22 controls the temperature controller 23 to open the valve 24, and the controller 13 of the water temperature in front of the boiler sends a signal from the sensor 12 to the valve 11 to close. . The decrease in the water flow through the boiler, associated with the opening of the valve 24 in the supply water line bypass from a signal from the sensor 17, is compensated by the influence of the constant flow controller 18 on the valve 16 in the direction of opening.

Deviation of water pressure to the boiler; caused by the cover of the control valves 24 and 11 under the action of the temperature controllers, are directed in opposite directions and can be compensated. If the total deviations of the water pressure to the boiler exceed the dead zone of the pressure regulator 8, then according to a signal from the sensor 7, the regulator 8 acts on the control valve 6 in the direction of compensation of disturbance.

In statics, after the end of the transient processor, the initial values of the parameters are restored.

If the temperature of the water network increases before and behind the boiler when the temperature of the return supply water, associated with a decrease in the load on the heating network, increases, the controller of the heat load 20 reduces the supply of fuel to the boiler by means of the valve 21. At the same time, an increase in the temperature of the water behind the boiler after a period of time caused by a delay in the change of the specified temperature due to fuel disturbance slows down, stops, and as the temperature of the water in front of the boiler exceeds the set temperature, the temperature of the water behind the boiler is also higher than the specified value. An increase in the temperature of the direct supply water due to an increase in the temperature of the water behind the boiler leads to the activation of the regulator 23 and the movement of the valve 24 in the direction of opening. Deviations of the water flow through the boiler and the pressure of water to the boiler are compensated in the same way as previously described. The temperature of the water in front of the boiler as a result of a decrease in the proportion of more heated water begins to fall, the temperature of the water behind the boiler also decreases and at some point causes the control of the boiler heat load 20 to activate the fuel supply. In the established mode, the temperatures in front of the boiler, behind the boiler, are stabilized at the network at a new level, higher than the task, which requires adjusting the task to controller 20 for Less in accordance with the balance of the heater and the network.

The change of the task according to the temperature of the water behind the boiler is controlled by the controller 20 of the heat load of the boiler using the setting unit 29, and the setting according to the temperature of the direct supply water is set by the setting device 30

The decrease in return water temperature caused by an increase in the load on the heating network leads to a decrease in the water temperature in front of the boiler and is compensated by the influence of the regulator 13 on the valve 11 in the direction of closing or (when the water temperature in front of the boiler drops below the limit value) on the valve n 5 in the recirculation line boiler in the direction of open. The temperature of the water in front of the boiler is controlled while the temperature of the water behind the boiler is lowered in the same way as described, but with the opposite sign.

Compared with the prototype, the proposed automatic control method allows to increase the economic efficiency of the joint operation of the boiler and the network water heater, as well as to improve the accuracy of maintaining the network water flow through the heater.

Claims (1)

Invention Formula A method for automatically controlling the temperature of water in front of a hot-water boiler with a heated water recirculation line and an upstream return network preheater installed on the return network water bypass line, by measuring the water temperature at the boiler inlet and its deviation from the set value of the change in water supply through the recirculation line control valve installed on the latter, characterized in that, in order to increase the efficiency of the boiler operation, when the water temperature in front of the boiler is higher than the back the limit value and the closed control valve on the recirculation line, the temperature of the water in front of the boiler is controlled by supplying the return network water from the outlet of the supply pump to the boiler entrance, and the pressure of the return network water is additionally measured before and after the preheater, and when it reaches the specified limit value, it maintains the specified pressure value after the preheater, and from the moment the specified limit value is reached, phenomena support a predetermined pressure drop change throttling portion return water line, a bypass line parallel with the heater mounted thereon.