JP6537830B2 - Boiler for detecting water pipe contamination - Google Patents

Description

  The present invention is a boiler having a combustion apparatus that increases or decreases the amount of combustion according to a required load, and performs heat exchange between combustion gas flowing outside the water pipe and boiler water in the water pipe to generate steam. The present invention relates to a boiler that detects contamination of a water pipe when a heat transfer coefficient lowering substance such as soot or scale adheres to the surface of the water pipe.

As described in Japanese Utility Model Application Publication Hei 2-140131, in a boiler that heats a water pipe with heat generated by combustion with a combustion device and heats boiler water in the water pipe to generate steam, When the soot adheres to the outer surface of the water pipe and deposits, the heat transmission rate from the combustion gas to the boiler water is hindered because the heat transmission rate of the soot is lower than that of the steel pipe constituting the water pipe. Also, inside the water pipe, the impurities contained in the water may be deposited by evaporation of the boiler water, and the scale may adhere to the inner surface of the water pipe, and the scale also has a low heat transfer coefficient. Transfer of heat to the boiler water is impeded.

When a heat transfer coefficient lowering substance such as soot or scale adheres to the water pipe of the boiler and the heat transfer amount from the combustion gas to the boiler water decreases, the steam generation amount decreases and the amount of heat discharged without being used is The boiler efficiency will decrease as it increases. Continuation of the boiler operation with reduced efficiency results in wasted fuel consumption, so the contamination of the water pipe should be monitored, and if the contamination occurs in the water pipe, the contamination should be removed. There is. When the heat transfer efficiency from the combustion gas to the boiler water decreases, the flue gas discharged from the boiler keeps a lot of heat and the temperature of the exhaust gas becomes high. Therefore, the water pipe is detected by detecting the rise in the exhaust gas temperature. You can judge the dirt of In the device disclosed in Japanese Utility Model Application Publication Hei 2-140131, the exhaust gas temperature is detected when combustion is continuously performed for a fixed time, and when the exhaust gas temperature exceeds a reference value, the occurrence of abnormality is judged. There is.

Here, the condition with the time of continuous combustion for a fixed time is attached because the temperature of the exhaust gas also changes depending on the conditions other than the contamination of the water pipe. If the combustion time is short or if the temperature in the boiler is low, the detected exhaust gas temperature will be low even if soot or the like adheres to the water pipe, so it is not possible to detect contamination of the water pipe. Further, the amount of combustion is changed as in high combustion / low combustion, and in the case of a boiler in which the amount of heat generated by the combustion device changes, the value of the exhaust gas temperature varies depending on the amount of combustion. Therefore, the contamination of the water pipe is detected based on the exhaust gas temperature when continuing for a fixed time with the maximum combustion amount.

However, depending on the installation environment of the boiler, it has been found that water pipe contamination can not be detected. For example, in an installation environment where the load is low and the combustion time in high combustion is extremely short, the amount of combustion is low even if the water pipe is contaminated and heat transfer efficiency from the combustion gas to the boiler water is reduced. Because of this, the exhaust gas temperature may be low. In this case, even if the exhaust gas temperature rises due to the contamination of the water pipe, the exhaust gas temperature does not rise to the reference value of the water pipe contamination judgment because the original temperature is low. It was supposed to be late to detect dirt.

Japanese Utility Model Application Publication Heisei 2-140131

  The problem to be solved by the present invention is to provide a boiler for detecting water pipe contamination which can accurately detect adhesion of a scale or a scale to a water pipe even in a boiler which changes the amount of combustion.

The invention according to claim 1 is a combustion apparatus capable of increasing or decreasing the amount of combustion, a heat pipe for heat transfer that generates steam and heats boiler water inside the water pipe by receiving heat generated by the combustion apparatus. Has an exhaust gas temperature detection device that detects the temperature of the combustion exhaust gas discharged from the steam generator, and a steam temperature detection device that detects the temperature of the steam generated in the boiler, and increases or decreases the combustion amount according to the required load amount In the boiler, the exhaust gas temperature abnormality judgment value is obtained by adding the correction value calculated from the steam temperature detection value detected by the steam temperature detection device to the setting value for each combustion amount set corresponding to the combustion amount. If the exhaust gas temperature detection value calculated and detected by the exhaust gas temperature detection device exceeds the calculated exhaust gas temperature abnormality judgment value continuously for more than the judgment setting time, it is judged that the water pipe is contaminated To do And butterflies.

  In the boiler according to the second aspect of the present invention, the correction value calculated based on the steam temperature detection value is predetermined with the steam temperature detection value detected by the steam temperature detection device. It is characterized in that the difference is calculated by multiplying the difference between the steam temperature setting value and the correction value that has been set according to the amount of combustion.

In the boiler according to the third aspect of the present invention, the set value for each amount of combustion is set to a large value when the amount of combustion of the boiler is large, and small when the amount of combustion is small. It is characterized in that it is set to a value.

By implementing the present invention, it is a boiler that changes the amount of combustion, and combustion time in high combustion is extremely short, and even in a boiler in which deviation occurs in the combustion state, adhesion of soot and scale to the water pipe Detection can be performed accurately.

Configuration of a boiler according to an embodiment of the present invention A-A sectional view of FIG. 1 Image of heat transfer from combustion gas to boiler water with no contamination on the surface of water pipe Image of heat transfer from combustion gas to boiler water when the water pipe surface is dirty

  One embodiment of the present invention will be described with reference to the drawings. 1 is a flow diagram of a boiler embodying the present invention, FIG. 2 is a sectional view taken along the line A-A of FIG. 1, and FIGS. 3 and 4 are image diagrams of heat transfer from combustion gas to boiler water. Shows a state in which the water pipe surface is not soiled, and FIG. 4 shows a state in which the water pipe surface is soiled.

The boiler has a can body in which ring-shaped tubers provided at upper and lower portions are connected by a number of vertical water pipes 2, and a central space surrounded by the water pipes 2 is a combustion chamber. A combustion device 1 for generating a flame downward is provided at the upper part of the combustion chamber, and fuel and combustion air are supplied to the combustion device 1 to perform combustion. The fuel supply to the combustion apparatus 1 is performed through the low combustion fuel valve 6 and the high combustion fuel valve 7, and the amount of fuel supplied when only the low combustion fuel valve 6 is opened is for combustion. The amount of fuel supplied is the amount of fuel supplied when both the low combustion fuel valve 6 and the high combustion fuel valve 7 are opened is the high combustion fuel amount. Therefore, at the time of high combustion, more fuel will be supplied than at the time of low combustion. The supply of combustion air to the combustion device 1 pressurizes the air with the blower 8 and supplies the air to the combustion device 1. The supply amount adjustment of the combustion air is performed by the increase and decrease of the rotational speed of the blower 8 and the increase and decrease of the flow passage area of the damper 10 provided in the middle of the air flow passage. In the case of combustion, the supply amount is low. The amount of combustion air supplied also supplies more combustion air at high combustion than at low combustion.

The water pipes 2 surrounding the combustion chamber are arranged in two rings, and in each water pipe row consisting of an inner water pipe row and an outer water pipe row, the adjacent water pipes are closed with fins. An annular space formed between the inner and outer water pipe rows is a combustion gas passage. In the inner water pipe row, a fin connecting the water pipes is opened at the lower part, and in an outer water pipe row, a fin connecting the water pipes is opened at the upper part. The combustion gas passage formed between the inner and outer water pipe rows is connected to the combustion chamber at the opening provided at the lower portion of the inner water pipe row, and connected to the exhaust gas passage 5 at the opening provided on the outer water pipe row. The combustion exhaust gas that has passed through the combustion gas passage is discharged outside through the exhaust gas passage 5.

When the combustion device 1 burns, the heat of the flame first heats the water pipe 2 facing the combustion chamber. Next, the high temperature combustion gas enters the combustion gas passage through the gap between the water pipes provided at the lower part of the combustion chamber. Since the gap between the water pipes at the lower part of the combustion chamber is provided on the entire periphery around the combustion chamber, the combustion gas flows radially from the combustion chamber, enters the combustion gas passage, and flows upward in the combustion gas passage. The combustion gas then heats the water pipe facing the combustion gas channel. Thereafter, the combustion gas flows from the upper portion of the combustion gas passage to the exhaust gas passage 5, and the combustion gas whose temperature is lowered by heat exchange in the boiler is discharged to the outside through the exhaust gas passage 5.

Water supply to the boiler is performed by means of a water supply device including a water level detection device not shown and a water supply pump. If the water level inside the boiler is detected in the boiler and the water level falls to the water supply start water level by evaporation, the water pump is activated to raise the water level in the boiler, and the water level rises to the water supply stop water level by supplying water. Keep the water level within a certain range by repeating the operation of the feed water pump. When the combustion gas is flowed to the outside of the water pipe 2 while the boiler water is supplied into the water pipe 2, the heat of the combustion gas is sent to the boiler water inside through the water pipe 2. The boiler water heated in the water pipe 2 generates steam and flows upward in the water pipe. The steam generated in each water pipe is collected at an upper header installed at the top of the water pipe and then sent to a steam separator, separated into steam and liquid in the steam separator, and then the steam is taken out from the boiler. The boiler is provided with a steam temperature detection device 4 for detecting the steam temperature, and the steam temperature detection device 4 detects the steam temperature. The steam temperature detection device 4 described here may be one that is converted from the steam pressure value or one that detects the temperature of the boiler water. Further, an exhaust gas temperature detecting device 3 for detecting the temperature of the combustion exhaust gas discharged from the boiler is provided in the exhaust gas passage 5.

The steam temperature detection device 4 and the exhaust gas temperature detection device 3 are connected to the operation control device 9 that controls the operation of the boiler, and the values of the detected steam temperature and exhaust gas temperature are output to the operation control device 9 . The operation control device 9 adjusts the amount of combustion so that the steam pressure value supplied from the boiler maintains a predetermined value. The operation control device 9 determines the amount of combustion based on the detected steam pressure value, and operates the low combustion fuel valve 6, the high combustion fuel valve 7, the blower 8, the damper 10 and the like. The operation control device 9 calculates the necessary combustion amount and controls the operation of the boiler so as to obtain the calculated combustion amount, and monitors the state of the boiler.

3 and 4 show the image of heat transfer in the water pipe 2 part, and an example of the heat transfer condition in the water pipe with no dirt on the surface of the water pipe, and the heat in the case where wrinkles and scales adhere to the surface of the water pipe Comparison of transmission status examples. The water pipe 2 is formed of a steel pipe, and the heat transferability in the steel pipe portion is very high. In the case where no substance that inhibits heat transfer such as soot or scale adheres to the surface of the water pipe, the heat transfer efficiency from the combustion gas to the boiler water is high. However, when soot generated during combustion adheres to and deposits on the outer surface of the water pipe, or hardness components such as calcium and magnesium contained in water concentrate in the water pipe and adhere as scales on the inner surface of the water pipe In such a case, it is difficult for heat to pass through the weir and scale, so if we try to transfer the same amount of heat to the boiler water in the water pipe, more heat is required. In the examples of FIG. 3 and FIG. 4, the temperature of the steam is 170 ° C., but the temperature of the exhaust gas differs depending on the presence or absence of a substance that inhibits heat transfer. In the case of the non-staining water pipe of FIG. 3, the water pipe outer surface temperature is 200 ° C., and the surface temperature of the water pipe inner surface is 190 ° C. In this case, the boiler water in the water pipe is in contact with the inner surface of the water pipe at 190 ° C., and the combustion gas outside the water pipe is in contact with the outer surface of the water pipe at 200 ° C. The combustion gas transfers heat to the outer surface of the water pipe at 200 ° C. When the temperature of the outer surface of the water pipe which is the side to be heated is low, the heat is transferred until the temperature of the combustion gas becomes lower. The exhaust gas temperature is 250 ° C.

On the other hand, in the case of the dirty water pipe of FIG. 4 in which scale adheres to the inner surface of the water pipe and wrinkles adhere to the outer surface, heat insulation occurs between the scale layer and the weir layer. There is a temperature difference between the surface and the inner and outer surfaces of the weir. In the example of FIG. 4, the temperature is 350 ° C. outside the weir attached to the outer surface of the water tube, and is 280 ° C. inside the weir and outside the weir, and 270 ° C. on the inner surface of the water tube It is 190 ° C. on the surface of the scale layer in contact. In this case, the boiler water temperature of 170 ° C. in the water pipe and the temperature 190 ° C. of the portion in contact with the boiler water are the same in FIGS. 3 and 4 and the heat quantity taken by the boiler water is the same in FIGS. 3 and 4 ing. However, in the case of FIG. 4, the surface of the crucible that absorbs heat from the combustion gas is 350.degree. This is because the heat transfer efficiency is poor in the weir and scale layers on the way, so the heat stops on the way. In this case, since the combustion gas directly heats the outer surface of the crucible which is at 350 ° C., it can not be heated unless it is a high temperature combustion gas. Therefore, the temperature of the exhaust gas in this case is 400.degree. The fact that the exhaust gas temperature is high means that the amount of heat transferred from the combustion gas to the boiler water is small, and a large amount of heat is discarded as the exhaust gas, so a substance that inhibits heat transfer adheres to the water pipe surface The efficiency of the boiler is reduced.

If the boiler is operated with the boiler efficiency reduced, the amount of fuel consumption will increase, so water pipe contamination is monitored, and if contamination is detected, weirs and scales will be removed. As described in FIG. 4, when the heat transfer inhibiting substance adheres to the surface of the water pipe, the exhaust gas temperature rises. Therefore, when the exhaust gas temperature becomes higher than the exhaust gas temperature abnormality judgment value, the water pipe is contaminated. And the judgment. However, the change of the exhaust gas temperature is caused not only by the contamination of the water pipe but also by the change of the amount of combustion in the combustion apparatus 1 and the temperature of the boiler water in the water pipe.

When the amount of combustion by the combustion device 1 is small, the amount of heat generated is small, so the temperature of the combustion gas for heating the water pipe is relatively low, and the temperature of the exhaust gas is accordingly low. Conversely, when the amount of combustion by the combustion device 1 is large, the amount of heat generated is large, so that the temperature of the combustion gas becomes relatively high, and the temperature of the exhaust gas also rises accordingly. When dirt adheres to the water pipe, the exhaust gas temperature rises. However, when the contamination of the water pipe is detected based on the exhaust gas temperature, it is necessary to equalize conditions such as the amount of combustion.

Since the exhaust gas temperature varies depending on the combustion state, generally, the setting value for abnormality determination of the exhaust gas temperature based on a state in which the exhaust gas becomes the highest due to continuous combustion with a maximum combustion amount for a fixed time. Is set, and when the detected value of the exhaust gas temperature becomes higher than the set value for abnormality determination, the abnormality is determined. However, in this case, if the installation environment is extremely short in high combustion time, it will not be possible to detect the contamination of the water pipe, and the operation will be performed with the efficiency reduced because of the contamination on the water pipe. Become.

Moreover, in the boiler supplying saturated steam, the steam pressure and the steam temperature have a one-to-one relationship, and the steam temperature changes as the steam pressure fluctuates, and the boiler water temperature in the water pipe also becomes the steam temperature It changes in conjunction. When the temperature in the water pipe is low, heat can also be taken from the combustion gas at a lower temperature, so the temperature of the combustion exhaust gas becomes lower. Conversely, when the boiler water temperature is high, the amount of heat transferred from the combustion gas to the boiler water decreases, so the temperature of the combustion exhaust gas also rises. Therefore, the exhaust gas temperature also changes due to the change of the steam temperature (boiler water temperature).

Due to the above properties, the rise is due to the change in the amount of combustion, or the temperature rise of the boiler water, just by comparing the detected value of the exhaust gas temperature and the magnitude of the judgment value. It will be impossible to distinguish between the case where no contamination that impedes transmission is attached and the case where contamination is attached to the water pipe.

Therefore, in the present invention, the exhaust gas temperature abnormality determination value for determining the contamination of the water pipe is corrected according to the operating condition of the boiler. Contamination determination of the water pipe is performed by the operation control device 9, and the operation control device 9 detects the steam temperature detected by the steam temperature detection device 4 in addition to the exhaust gas temperature detection value detected by the exhaust gas temperature detection device 3. The contamination of the water pipe is determined based on the detected value and the information on the amount of combustion of the boiler instructed by the operation control device 9.

The determination of water pipe contamination in the operation control device 9 is performed by detecting that the detected value of the exhaust gas temperature has become higher than the exhaust gas temperature abnormality determination value. The exhaust gas temperature abnormality determination value is calculated by adding a correction value determined by the vapor temperature detection value detected by the vapor temperature detection device to the setting value for each combustion amount set corresponding to the combustion amount. When the exhaust gas temperature detection value detected by the exhaust gas temperature detection device continuously exceeds the calculated exhaust gas temperature abnormality determination value for the determination set time or more, the abnormality determination is performed. The set value for each combustion amount set corresponding to the above combustion amount is set to a small value when the combustion amount is small, and is set to a large value when the combustion amount is large, for example, low combustion In the case of, 350 ° C, in the case of high combustion 400 ° C.

The correction value calculated based on the steam temperature detection value is a correction that is set according to the amount of combustion to the difference between the predetermined steam temperature setting value and the steam temperature detection value detected by the steam temperature detection device. Calculated by multiplying the coefficient. That is, exhaust gas temperature abnormality determination value = setting value for each combustion amount + correction value, and correction value = (vapor temperature detection value−vapor temperature setting value) × correction coefficient. For example, assuming that the predetermined steam temperature set value is 170 ° C., the detected steam temperature value is 175 ° C., and the correction coefficient is 1.2, the correction value = (175 ° C.-170 ° C.) × 1. 2 = + 6 ° C.

Assuming that the combustion state is low combustion, the set value per combustion amount at low combustion 350 ° C., steam temperature set value 170 ° C., steam temperature detected value 175 ° C., correction coefficient 1.2, judgment set time 5 seconds Since the exhaust gas temperature abnormality judgment value = 350 ° C. + (175 ° C.-170 ° C.) × 1.2 = 356 ° C., when the state where the exhaust gas temperature detection value is higher than 356 ° C. continuously for 5 seconds or more, the water pipe It is judged that dirt is attached to

Similarly, the combustion state is high combustion, and the set value for each combustion amount at high combustion is 400 ° C., the steam temperature set value is 170 ° C., the steam temperature detection value is 165 ° C., the correction coefficient is 1.0, and the judgment setting time is 3 seconds Assuming that the exhaust gas temperature abnormality judgment value = 400 ° C. + (165 ° C.-170 ° C.) × 1.0 = 395 ° C., the state where the exhaust gas temperature detection value is higher than 395 ° C. continuously continued for 3 seconds or more In the case, it is determined that the water pipe is contaminated.

In this way, when an appropriate judgment value is set according to the combustion state, most of the combustion time is low combustion, and the time when high combustion is short, and so on. Even in the case where a substance that inhibits heat transfer, such as wrinkles or scale, adheres to the surface of the water pipe, it is possible to detect the contamination of the water pipe. In addition, even when the correlation between the steam temperature and the exhaust gas temperature differs depending on the model or individual difference, the judgment value can be made an appropriate value by adjusting the correction coefficient, so the detection accuracy of the water pipe dirt can be made higher. .

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

1 Combustion device
2 water pipe
3 exhaust gas temperature detection device 4 steam temperature detection device 5 exhaust gas passage 6 fuel valve for low combustion 7 fuel valve for high combustion 8 blower 9 operation control device 10 damper

Claims (3)

The temperature of the combustion exhaust that is able to increase or decrease the amount of combustion, the heat generated by the combustion unit to heat the boiler water inside the water pipe, and the heat transfer water pipe that generates steam, and the exhaust gas discharged from the boiler In a boiler that has an exhaust gas temperature detection device that detects the temperature of the exhaust gas, and a steam temperature detection device that detects the temperature of the steam generated in the boiler, and changes the amount of combustion according to the required load, The exhaust gas temperature abnormality judgment value is calculated by adding the correction value calculated from the vapor temperature detection value detected by the vapor temperature detection device to the set value for each combustion amount, and the exhaust gas temperature detection device Water tube dirt characterized in that dirt is attached to the water tube when the detected exhaust gas temperature detection value continuously exceeds the calculated exhaust gas temperature abnormality determination value for the determination set time or more. Detection Boiler to do.   In a boiler for detecting water pipe contamination according to claim 1, a correction value calculated based on a steam temperature detection value is a steam temperature setting value predetermined with a steam temperature detection value detected by a steam temperature detection device. A boiler for detecting a water pipe contamination, which is calculated by multiplying the difference between the and the correction factor that has been set according to the amount of combustion. The boiler according to claim 1 or 2, wherein the set value for each amount of combustion is set to a large value when the amount of combustion of the boiler is large, and is set to a small value when the amount of combustion is small. A boiler for detecting water pipe dirt, characterized in that

Images