RU2230260C1 - Automatic control system for water heating plant employing waste heat of b oiler flue gases - Google Patents

Abstract

FIELD: automatic control systems of water heating plants; utilization of waste heat of flue gases; thermal power stations; self-contained boiler houses. SUBSTANCE: proposed system includes temperature regulator of direct heating-system water, temperature regulator of heating-system water preheater inlet and temperature regulator of heating-system water at preheater outlet. Control member of temperature regulator is made in form of valve to avoid cracking in area of welded seams on tube sheets of preheater. This valve is fitted in reverse water pipe line after branch shunting preheater. EFFECT: enhanced efficiency. 1 dwg

Description

The present invention relates to automatic control systems of heat power plants that produce waste waste heat from flue gases of boilers burning natural gas, and can be used in thermal power plants, autonomous boiler rooms.

Known (UDC 621.311.22.002.51.555.7-75 (075.8) Pletnev GP "Automatic regulation and protection of heat power plants of power plants." M .: "Energy", 1970, pp. 336-338) auto-regulation system network water heater, consisting of a direct network water temperature controller, a condensate level regulator in the network water heater, and a reverse network water pressure regulator. The source of heat for this type of network water heater is heating steam from regulated heat recovery units of steam turbines or redundant cooling units that reserve them.

The disadvantage of this system is the impossibility of its application in modern thermal power plants, where the boiler exhaust gas is used as a heat source.

Closest to the proposed invention, the well-known is a system for automatically controlling the temperature of the network water of a once-through boiler (UDC 621.182.26 Klyuev AS, Tovarnov OG "Setting up automatic control systems for boiler units." M .: "Energy", 1970 , p. 201-202). The system consists of the following controllers. The temperature regulator of the network water at the inlet to the boiler, receiving a pulse from the water temperature sensor at the inlet to the boiler and acting on the control valve for recirculation of part of the heated water from the boiler output to its entrance. Recirculation of part of the boiler water from the outlet to the entrance allows maintaining the temperature of the feed water not below the allowable limit determined by the "dew point". The direct water temperature controller receives a pulse from the temperature sensor of the network water supplied to the heating system and acts on the control valve on the jumper that mixes the cold return network water with the heated water. The boiler heat regulator receives an impulse from the temperature sensor at the outlet of the boiler and acts through the relay circuit on the actuators of the burners and on individual blowers.

The disadvantages of this auto-regulation system are, firstly, the impossibility of use in modern heat power plants (network water heaters), where the boiler exhaust gas is used as a heat source. Secondly, this system does not provide stabilization of the water temperature at the outlet of the boiler, as the operation mode of the boilers is conducted according to its temperature schedule, which differs from the heat supply schedule. If the water temperature at the outlet of the heat power plant (network water heater) often changes following a change in the mode of operation of the boiler, the metal of the heater, especially at its outlet, experiences alternating compressive or tensile stresses. This will inevitably lead to cracks in the area of the welds on the tube sheets of the heater. The heater will have to be repaired often.

The objective of the invention is to prevent the appearance of cracks in the area of welds on the pipe boards of the network water heater with changes in the mode of operation of the boiler and increase the reliability of its operation, increase the overhaul period.

The task in the automatic control system of the installation for heating the network water with the heat of the exhaust gas from the boiler, including the direct network water temperature controller, the network water temperature controller at the heater inlet, the network water temperature controller at the heater outlet, is achieved by the regulating body of the network water temperature controller at the outlet of the heater is made in the form of a valve located on the pipeline return network water after the pipe, shunting the heater, and before inserting a recirculation pipeline, part of the hot network water from the heater outlet. This regulator stabilizes the temperature of the supply water at the outlet of the heater when the boiler load changes. The temperature stability of the supply water at the inlet to the heater is ensured by an appropriate regulator. If the temperature of the supply water at the inlet to the outlet of the heater and out of it is stable, then the thermostability of the heater pipes is ensured, which prevents the appearance of cracks in the area of the welds on the heater tube sheets. Thus, the set of essential features set forth in the claims, allows to achieve the desired technical result.

The proposed automatic control system of the installation for heating the network water with the heat of the boiler flue gas is shown schematically in the drawing. A network pump 1 is installed on the return network water pipeline, pumping return water from the heating system through the network water heater 2, which is heated by the flue gases of the boiler. The recirculation pump 3 recirculates part of the heated network water from the heater’s outlet to its input 3. The network water temperature controller 4 receives an impulse from the sensor 5 for the temperature of the water entering the heater and acts on the control valve 6 on the recirculation pipeline 7 of the heated network water from the outlet of the heater to its entrance. The regulator 8 of the temperature of the direct network water receives an impulse from the sensor 9 according to the temperature of the water entering the heating system and acts on the control valve 10 on the pipe 11 shunting the heater of the network water. The regulator 12 of the temperature of the supply water at the outlet of the heater receives an impulse from the sensor 13 for the temperature of the heated water at the outlet of the heater and acts on the control valve 14 located on the return water pipe after the outlet 15 of the pipeline shunting the heater and before the insert 16 of the recirculation pipe heated network water from the heater output to its input. The signal from the flexible negative feedback on the position of its regulatory body from the position sensor 17 through the differentiator 18 is supplied to the network water temperature controller at the outlet of the heater.

The auto-regulation system works as follows. The regulator 4 of the temperature of the supply water at the inlet to the heater 2 maintains this temperature at 65 ° C (a limit that excludes dew formation on the heater metal with some reserve). This regulator controls the control valve 6 on the pipe 7 recirculation of part of the heated network water from the output of the heater 2 to its input, mixing hot water to cold return network water. The controller 12 for the temperature of the supply water at the outlet of the heater 2 maintains this temperature at 100 ° C. This controller controls the control valve 14 located on the return network water pipe after the outlet 15 of the pipe 11 shunting the heater, and before the insert 16 of the pipe 7 of the recirculation of part of the hot network water from the heater output. The regulator changes the amount of return network water entering the heater, depending on the amount and temperature of the flue gas of the boiler. Since the object of regulation of this regulator has the properties of an inertial unit with a large time constant, a flexible negative feedback is introduced into the circuit of the regulator 12 of the network water temperature at the outlet of the heater from the position of the regulator 14 from the position sensor 17 through the differentiator 18. The network water temperature controller 4 the inlet to the heater and the regulator 12 of the temperature of the supply water at the outlet of the heater ensure the temperature stability of the supply water at the entrance to the heater and at the outlet of it, and, as a consequence, the thermal stability of the entire heater when changing the boiler. This prevents cracks in the weld area on the tube sheets of the heater. The controller 8 of the temperature of the direct network water provides the currently required temperature of the water supplied to the heating system. This regulator performs the metered mixing of cold return network water to hot water from the heater by controlling the control valve 10 located on the pipe 11, shunting the heater 2.

Claims (1)

The automatic control system of the installation for heating the network water with the heat of the boiler flue gas, including the direct network water temperature controller, the network water temperature controller at the heater inlet, the network water temperature controller at the heater outlet, characterized in that the regulating body of the network outlet water temperature controller of the heater is made in the form of a valve located on the return network water pipe after the pipeline, shunting the heater, and before the pipe is inserted rovoda recirculating a portion of hot water at a heater output to its input.