JP2013053823A - Supply water preheating boiler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent excessive temperature rise of supply water in an economizer in a supply water preheating boiler preheating the supply water by the economizer 4.SOLUTION: In the supply water preheating boiler supplying water to a boiler body 6 via the economizer 4 and having an operation controller 8 controlling water supply to the boiler based on the boiler state, there are provided a water level detector 12 detecting a water level of the boiler, a preheated water temperature detector 5 detecting a temperature of preheated water taken out of the economizer 4, and a saturation temperature detector 7 detecting a saturation temperature of the boiler. The operation controller 8 controls to start water supply when the water level in the boiler detected by the water level detector 12 is lowered down to a water supply start water level, or when the preheated water temperature detected by the preheated water temperature detector 5 is increased up to a set temperature determined based on the saturation temperature, and to stop water supply when the water level in the boiler detected by the water level detector 12 is increased up to a water supply stop water level.

Description

  The present invention relates to an economizer that preheats feed water and a feed water preheat boiler that has a boiler body that generates steam by further heating feed water preheated by the economizer.

  An economizer that preheats feed water is installed in the exhaust passage of the boiler, and the temperature of the feed water is widely raised by exchanging heat between the exhaust gas discharged from the boiler and the water supplied to the boiler. ing. The economizer installs a heat transfer pipe in the exhaust gas passage through which the exhaust gas passes, and feeds water to the boiler through the economizer so that the water supplied through the heat transfer pipe recovers the heat of the exhaust gas flowing around the heat transfer pipe. . The temperature of the exhaust gas is lowered by exchanging heat with the boiler body, but the temperature is still sufficiently higher than the feed water temperature. Therefore, it can utilize for the preheating of feed water etc., and the total recovery amount of heat can be increased by preheating the feed water with exhaust gas. Thus, if the amount of heat absorption in the economizer is increased, the efficiency of the boiler can be improved.

  Water supply to the boiler is often performed by checking the water level in the can with a water level detection device and supplying water intermittently. In this case, the water in the heat transfer tube is used when water is supplied inside the economizer. When the water supply is stopped and water supply is stopped, the water stays in the heat transfer tube alternately. When the time period during which water is not supplied becomes longer, the water supply inside the economizer continues to be heated, and when the preheated water temperature in the economizer continues to rise and approaches the saturation temperature, the water in the economizer changes from liquid to gas and bubbles are generated. Will occur and the possibility of boiling will occur. In this case, since the water supply is cooled at the portion where the economizer exits, there is a problem that the bubbles generated in the preheated water in the economizer are rapidly reduced, and a water hammer is generated.

  For this reason, in the invention described in Japanese Patent Application Laid-Open No. 2008-298308, a preheated water temperature detecting device is provided at the economizer outlet to detect the preheated water temperature, and when the preheated water temperature rises, the water is forcibly supplied to the inside of the economizer. The water supply temperature is not raised too much. When the water moves by supplying water, the water supply temperature does not increase excessively. However, since this water supply is performed regardless of the water level in the boiler, the water level in the boiler may increase more than necessary. If the water level in the boiler becomes too high, a carryover that takes out canned water along with the steam will occur, leading to a drop in steam quality, or the boiler water must be drained to reduce the water level in the boiler. There was also a problem of disappearing.

JP 2008-298308 A

  The problem to be solved by the present invention is to provide a boiler capable of preventing the feed water temperature from rising excessively in the economizer in a feed water preheating boiler that preheats the feed water with an economizer.

  It has an economizer that preheats the water supply and a boiler body that generates steam by further heating the water preheated by the economizer. Water is supplied to the boiler body through the economizer and the water supply to the boiler is controlled based on the state of the boiler. In a feed water preheating boiler having an operation control device, a water level detection device that detects the water level of the boiler, a preheating water temperature detection device that detects the temperature of the preheating water taken out from the economizer, and a saturation temperature detection device that detects the saturation temperature of the boiler In the operation control device, the preheat water temperature at which water supply is started is determined based on the boiler saturation temperature, and the boiler water level detected by the water level detection device has decreased to the feed water start water level, or preheat water When the preheated water temperature detected by the temperature detector rises to the preset temperature, water supply is started and the water level is detected. Performs control boiler water level is detected by the device stops the water supply when raised to the water supply stop level.

  By carrying out the present invention, the water supply temperature does not rise excessively in the economizer, and it is possible to prevent the occurrence of a water hammer and the occurrence of steam pressure fluctuations. In addition, because the water supply is stopped at the water supply stop water level, operation can be performed within the appropriate water level control range, and if the water is supplied more than necessary, the water level in the boiler becomes high, causing an abnormal carryover. Or waste of draining water for adjusting the water level can be eliminated.

Flow diagram of boiler implementing the present invention The water supply pump operating condition explanatory drawing in one Example of this invention

  An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a flow chart of a boiler embodying the present invention, and FIG. 2 is an explanatory diagram of the operation status of a feed water pump in one embodiment of the present invention. The boiler body 6 has a large number of heat transfer tubes installed in parallel, and the top and bottom are connected by a header. The economizer 4 is connected to form a continuous flow path with a large number of heat transfer tubes, and is installed in the middle of the exhaust gas passage 1 through which the exhaust gas discharged from the boiler body 6 passes. The preheated water outlet of the economizer 4 and the water supply inlet of the boiler body 6 are connected by a preheated water pipe 10. When the water supply pump 2 in the middle of the water supply pipe 3 connected to the other end of the economizer 4 is operated, Reaches the boiler body 6 through the economizer 4. A preheated water temperature detecting device 5 for detecting the temperature of the preheated water preheated by the economizer 4 is provided in the middle of the preheated water pipe 10. The preheating water temperature detection device 5 is connected to an operation control device 8 that controls the operation of the boiler, and the preheating water temperature detected by the preheating water temperature detection device 5 is output to the operation control device 8.

  The boiler body 6 supplies water from the lower part by connecting the preheated water pipe 10 to the return water pipe from the steam separator or the lower header. Boiler water is heated in a vertical heat transfer tube, and steam generated by heating the boiler water is collected in the upper header. Connected to the upper header of the boiler body 6 is a steam take-out pipe 11 for sending boiler water that has boiled up with steam to the steam separator 9, and steam is sent to the steam separator 9. The steam / water separator 9 separates steam and boiler water, the separated steam is supplied to the steam use section, and the boiler water passes through a return water pipe connecting the lower part of the steam / water separator 9 and the lower header of the boiler body. Reflux into the boiler body.

  A water level detection device 12 that detects the internal water level is installed in the boiler, and information on the water level detected by the water level detection device 12 is also output to the operation control device 8. The operation control device 8 is also connected to the water supply pump 2 and supplies water by operating the water supply pump 2. In the water level detection device 12, the electrode rod E1 and the electrode rod E2 which are electrode rods having different lengths are installed, and it is determined whether or not there is water up to the position of the electrode rod depending on whether or not the boiler water is energized. When the operation control device 8 detects that the water level has risen beyond the lower end position of the electrode rod E1 that detects the presence or absence of the water level at a high position, the water supply command is stopped, and the electrode rod E2 that detects the presence or absence of the water level at a low position. When it is detected that the water level has dropped to below the lower end position, a water supply command is output.

  Further, the operation control device 8 is set to start the operation of the water supply pump 2 even when the preheated water temperature detected by the preheated water temperature detecting device 5 becomes higher than the set temperature. The preset temperature when water supply is started based on the preheated water temperature is determined based on the saturation temperature (boiling point) in the boiler. The boiler is provided with a saturation temperature detection device 7, and the operation control device 8 takes in the saturation temperature information from the saturation temperature detection device 7. Since the saturation temperature of the boiler water in the boiler body 6 is uniquely determined from the pressure in the boiler body 6, the saturation temperature is detected by detecting the steam pressure in the boiler body 6 and converting the saturation temperature from the steam pressure value. You may do. In the operation control device 8, the saturation temperature detected by the saturation temperature detection device 7 or a value lower than the saturation temperature by a certain width is determined as the set temperature for supplying water based on the preheating water temperature, and the preheating water temperature detection device 5 When the detected temperature of the preheated water reaches the set temperature, the operation of the feed water pump 2 is started.

  Also in this case, the water supply is stopped by detecting that the water level in the boiler has risen to the water supply stop water level. That is, the operation of the feed water pump 2 is performed when the water level detection device 12 detects that the water level has dropped to the water supply start water level, or when the preheating water temperature detection device 5 detects that the preheated water has risen to the set temperature. When the water level detecting device 12 detects that the water level has risen to the water supply stop water level, the operation of the water supply pump 2 is stopped.

  The exhaust gas after the heat exchange with the boiler body 6 is discharged outside through the exhaust gas passage 1. Although the temperature of the exhaust gas passing through the exhaust gas passage 1 is lowered by applying heat to the boiler body 6, it can be used for preheating water supply having a lower temperature. The exhaust gas that has flowed through the exhaust gas passage 1 and reached the economizer 4 portion is further heat-exchanged by the economizer 4. The economizer 4 is a continuous water supply flow path by connecting a large number of heat transfer tubes, and the water supply flowing through the economizer 4 is water having a temperature lower than that of the exhaust gas, and the water supply in the economizer is caused by the heat of the exhaust gas. Heat. The temperature of the exhaust gas is further lowered by heating the heat transfer tube of the economizer 4, and thereafter the exhaust gas is discharged outdoors.

  Since the economizer 4 is a continuous flow path, when the water supply pump 2 is operated, the water supply flows through the economizer 4 and when the operation of the water supply pump 2 is stopped, the flow of the water supply is stopped. When the feed water pump 2 is operating, the water supply in the economizer 4 is switched, so that the preheat water temperature after preheating in the economizer 4 is increased only to a certain extent. However, when the feed water pump 2 is stopped, the feed water in the economizer 4 is not replaced, so the preheated water temperature continues to rise. Since the economizer 4 and the boiler body 6 are connected, the pressure in the economizer 4 is the same as the pressure of the boiler body 6 and the boiling point rises due to the pressure rise, but if the feed water temperature rises above that boiling point, the economizer In some cases, bubbles are generated in the heat transfer tube 4.

  The saturation temperature varies with the pressure of the boiler. When the saturation temperature is low, the preheated water temperature needs to be lowered. In other words, when the saturation temperature is high, no bubbles are generated even if the preheated water temperature is increased to some extent. Therefore, the saturation temperature is detected by the saturation temperature detection device 7 so that the preheated water temperature in the economizer portion is maintained at a temperature lower than the saturation temperature and lower than the necessary temperature difference. If the upper limit value of the preheated water temperature is changed in accordance with the saturation temperature, a constant relationship with the saturation temperature during operation can be maintained, and if the saturation temperature is high, the preheated water temperature is lowered more than necessary or saturated. It is no longer possible to reduce the temperature of the preheated water required when the temperature is low. As described above, since the generation of bubbles in the economizer can be prevented, even if the preheated water is cooled by heat radiation at the portion of the preheated water pipe 10 exiting the economizer, the generation of a water hammer or pressure fluctuation at that portion may be caused. Disappear.

  For example, if the saturation temperature at a certain point in time is 165 ° C. and the temperature setting value for starting water supply based on the preheated water temperature is 5 ° C. lower than the saturation temperature, the water supply start based on the preheated water temperature is started. The set value is 160 ° C. In this case, as shown in FIG. 2, the operation control device 8 detects when the water level in the boiler detected by the water level detection device 12 becomes the feed water start water level (E2) and by the preheated water temperature detection device 5. When the preheated water temperature rises to 160 ° C., the operation of the feed water pump 2 is started. When the feed water pump 2 is operated, feed water having a low temperature enters the economizer 4, so that the preheated water temperature in the economizer 4 decreases. The water supply is stopped based on the water level regardless of which water supply is started. The water level in the boiler rises by supplying water, and when the water level detected by the water level detection device 12 reaches the water supply stop water level (E1), the operation of the water supply pump 2 is stopped and the water supply is terminated.

  Stopping water supply stops at the water supply stop water level, so operation can be performed within the appropriate water level control range. Supplying water more than necessary will raise the water level in the boiler and cause a carryover abnormality. And waste of draining water for adjusting the water level can be eliminated.

The present invention is not limited to the embodiments described above, and many modifications can be made by those having ordinary knowledge in the art within the technical idea of the present invention.

DESCRIPTION OF SYMBOLS 1 Exhaust gas path 2 Water supply pump 3 Water supply pipe 4 Economizer 5 Preheating water temperature detection apparatus 6 Boiler main body 7 Saturation temperature detection apparatus 8 Operation control apparatus 9 Steam-water separator 10 Preheating water pipe 11 Steam extraction pipe 12 Water level detection apparatus

Claims (1)

It has an economizer that preheats the water supply and a boiler body that generates steam by further heating the water preheated by the economizer. In a feed water preheating boiler having an operation control device, a water level detection device that detects the water level of the boiler, a preheating water temperature detection device that detects the temperature of the preheating water taken out from the economizer, and a saturation temperature detection device that detects the saturation temperature of the boiler In the operation control device, the preheat water temperature at which water supply is started is determined based on the boiler saturation temperature, and the boiler water level detected by the water level detection device has decreased to the feed water start water level, or preheat water When the preheated water temperature detected by the temperature detector rises to the preset temperature, water supply is started and the water level is detected. Water preheating boiler, characterized in that boiler water level is detected by the apparatus performs control to stop the water supply when raised to the water supply stop level.

Images