JPS62153621A - Soot blowing process in boiler - Google Patents

Abstract

PURPOSE:To enable an accurate control over a decreased temperature to be performed by a method wherein a steam pressure and a steam temperature which are the most appropriate for blowing of soot are stored, a pressure of steam before decreasing its pressure is sensed, a corresponding temperature is selected, they are compared to each other, water is supplied until the steam temperature after decreasing of temperature is coincided with the calculated and selected steam temperature in reference to an output of comparison and then a soot blowing steam is decreased in its temperature. CONSTITUTION:When soot is blown, both pressure and temperature of over-heated vapor fed from an over-heated steam pipe are sensed by a pressure sensor 12 and a temperature sensor 13, converted into an electrical signal and then sent to a computer. The computer calculates and selects a steam temperature corresponding to the inputted steam pressure from a safe and the most appropriate combination of the steam temperature and pressure in reference to a constant enthalpy. A comparison calculation for the calculated and compared steam temperature and the actual previously inputted steam temperature, a comparison output signal is sent to a temperature adjusting unit 6, a decreased temperature water control valve 1 is opened, and the decreased hot water is discharged to the temperature decreasing part through the temperature decreased water supplying pipe 11. The opening operation of the decreased temperature water control valve 1 is carried out until the actual steam temperature reaches the calculated and selected temperature. With this arrangement, it is possible to perform an accurate decreased temperature control.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a boiler soot blowing method.

More specifically, the soot blowing method for boilers where many impurities are relatively likely to adhere to heat transfer surfaces such as the heat transfer surfaces of black liquor recovery boilers, the heat transfer surfaces of park boilers, or the heat transfer surfaces of waste heat recovery boilers.
No: Regarding.

[Prior Art] As is well known, soot blowing methods have been used to remove soot from boiler heat transfer surfaces.

Important points in this soot blowing method are, as is well known, the pressure that can blow away the soot more efficiently depending on the type of boiler, the soot on the heat transfer surface (-t7I), etc.
This involves spraying superheated cleaning air of AA degree.

For this reason, a method of soot-blowing the incoming air (superheated) that meets the conditions has been investigated, but the temperature reduction of soot-blown N air is difficult because water droplets are in the air. If contaminated, there was a risk of generation of erosions on the boiler heat transfer surface, and there was a risk of cooled water flowing into the boiler, so the temperature was not reduced. Also, when the temperature is reduced, the volume JJ- becomes smaller compared to the high-temperature washing air before the temperature reduction, so it was thought that if the pressure was turned, the amount of steam used would increase as a result. Conventionally, one step for this purpose was to reduce the pressure of the superheated steam, that is, to reduce the pressure to an extent that was optimal for soot blowing.

[Problems to be solved by the invention] In this way, in the past, only the pressure was reduced, so the temperature of the steam,
Although the ripeness h: is very high as it is, the excessive thermal energy of this steam reduces the soot blowing efficiency to 7. However, there is still little influence on boiler type, boiler type, etc.
Soot blowing is not carried out under conditions that allow for the most efficient removal of soot depending on the conditions of soot adhesion on the heat transfer surface.

Therefore, the L1 point of the present invention is to make the excessive thermal energy do a corresponding amount of soot blowing work, and remove soot most efficiently depending on the type of boiler as a whole, the conditions of soot adhesion on the heat transfer surface, etc. It is to provide a method in which a suite blow is implemented under conditions that can be done.

[Means 9 actions for solving the problems] ①- [In order to achieve the first objective, the present invention has the following technical means. That is, the present invention is a soot blowing method in which a part of superheated steam to be sent from a boiler to a turbine is taken out, reduced to a predetermined pressure, and blown onto the heat transfer surface of the boiler to remove soot. Prepare various combinations of safe and optimal steam temperature and steam pressure for soot blowing based on constant caulking enthalpy, and when the soot blow steam pressure before depressurization is detected, the above-mentioned combinations corresponding to the detected pressure value are prepared. Calculate the steam temperature in the combination, compare the calculated steam temperature with the actual steam temperature after temperature reduction,
This boiler soot blowing method is characterized in that cooled water is poured out until the steam temperature after the cooled temperature reaches a calculated temperature.

In this way, the present invention stores in advance the optimum combinations of steam pressure and steam temperature that are safe and often suitable for soot blowing, based on constant enthalpy, and selects from among these combinations before depressurization. When the steam focus is detected, the temperature corresponding to the pressure is selected, and then the actual steam temperature and the selected steam temperature are compared and calculated, and the comparison output determines the steam temperature after temperature reduction. The soot-blown steam is cooled by injecting water until it matches the temperature of the selected steam, so the steam temperature can be changed to )^(
This allows for more accurate temperature reduction control than when the temperature reduction control is performed by closing the door. Therefore, as a result of this precise temperature reduction control, it is safe to soot blow by pre-caulking the air pressure and temperature according to the type of boiler, the condition of the heat transfer surface, etc. If you set it to the correct and optimal setting, you can get the expected results and completely avoid the two-lotion phenomenon and the risk of explosion due to moisture contamination. In particular, the pressure of superheated steam for soot blowing can be accurately controlled to an optimal level, neither too high nor too low, and the soot blowing effect can be maintained at a high level.

[Example] The present invention will now be described in detail with reference to the accompanying drawings.

Figure 1 shows a diagram for carrying out this soot blowing method.
When 1 is indicated, a part of the superheated steam sent to the turbine is taken out from the boiler (e.g. black liquor recovery boiler, bark boiler, waste heat recovery boiler), the pressure is reduced to a predetermined pressure by a pressure reducing valve, and the superheated steam is injected. lead to the tube. As is well known, this injection tube is located outside the boiler wall when not in use, and is configured to be moved in and out at regular intervals by an electric motor or the like so that it advances toward the heat transfer surface within the boiler wall when in use. ing.

A reduced-temperature water supply pipe equipped with a reduced-temperature water regulating valve 1 is connected to a position upstream of the pressure reducing valve in the overripe air passage. On the other hand, at an upstream position of the pressure reducing valve, a steam pressure detection means 2 for detecting the pressure of the steam before pressure reduction is arranged, and a steam temperature detection means 3 for detecting the temperature of the steam after temperature reduction is arranged.

During soot blowing, the pressure of superheated steam before depressurization is detected by the pressure detection means 2 and sent to the calculation means 4.

Information on various combinations of steam pressure and steam temperature that are safe and optimal for soot blowing after temperature reduction is sent to the calculation means 4 based on the constant enthalpy in the fertilizer means 5. , the n;l calculation means 4 calculates and selects the steam temperature corresponding to the L detected pressure. Since the actual temperature of the air is detected by the steam temperature detection means 2 and sent to the calculation means 4, the temperature calculated and selected by the calculation means 4 is different from the detected actual steam temperature. A comparison is made and the comparison output signal is sent to the temperature controller 6. In the temperature regulator 6, the reduced temperature water control valve 1 is operated so as to pour out the reduced temperature water until the steam temperature after the temperature reduction reaches a temperature selected based on constant enthalpy.

To explain more specifically, superheated steam introduced from a superheated steam pipe connecting a boiler and a turbine (not shown) is passed through a conduit 7,
Separator 8. Injection via pressure reducing valves 9a, 9bφ...
i? 10a, 1Ob-·ψ. -h The injection pipe moves in and out of the boiler wall as described above. The above-mentioned pressure reducing valves 9a, 9b... A reduced temperature water supply pipe 11 having a reduced temperature water regulating valve 1 in the middle is connected to a position on the upstream side and upstream side of the separator 8.
On the upstream side of..., there is a pressure detector 12 for detecting the A pressure of reduced pressure rm and a Jl for detecting the steam temperature after temperature reduction.
d A temperature-resistive body temperature detector 13 is provided.

The pressure value detected by the pressure detector 12 is converted to 1 and no signal by the electric signal converter 14 and sent to the microcomputer constituting the calculation means 4. Similarly, the temperature value detected by the temperature detector 13 marked F is transmitted to the electrical signal converter 1.
5 converts it into an electrical signal and sends it to the microcomputer.

The steam pressure detector 12 and the electric signal converter 14 constitute the steam pressure detection means 2, and the steam temperature detector 13 and the electric signal converter 15 constitute the steam temperature detection means 3.

The microcomputer is mainly composed of a central processing unit 16, a storage section 17 constituting the storage means 5, and an input/output signal processing circuit 18.

”The storage unit 17 stores the following information based on constant enthalpy.
Various combinations of steam temperature and steam pressure that are safe and optimal for soot blowing are stored. for example,
As shown in the graph of constant enthalpy, vapor pressure and temperature in Figure 4, and the table in the graph, the enthalpy is 698, 8 kc.
Various combinations of steam temperature and air pressure that are safe and optimal for soot blowing based on a constant al/kg are stored.

The enthalpy of any of these combinations is 698.8kca
It is constant at 1/kg. Therefore, when the pressure of the steam before depressurization is detected by the pressure detector 12 and the electrical signal is sent to the microcomputer via the electrical signal converter 14, the arithmetic section 16 of the microcomputer receives the pressure from the notation section 17. From the combinations 1- to 1-, a temperature value corresponding to the steam detection pressure L is selected by operation 'r1. Il, Book 7
The actual temperature value detected by the N air temperature detector 13 is compared with the selected temperature (tti) indicated by -L, and the result of the comparison is used to adjust the temperature via the human output signal processing circuit °18. In the temperature controller 6, the temperature-reduced water is supplied to the temperature-reduced water until the steam temperature after temperature-reduced reaches a selected temperature based on constant enthalpy, according to the comparison output shown in l-. Operate the reduced-temperature water control valve l to pour out the water.

Next, the operation will be explained.

Soot blowing is performed under a fixed time period. During soot blowing, the pressure and temperature of the superheated steam guided from the superheated steam pipe connected to the boiler and passing through the conduit are measured by a pressure detector 12.
, detected by the temperature detector 13, converted into an electrical signal, and sent to the computer (step P), for example, 36 k
A signal indicating a value of g/Cff172, 428°C is input. At each step P, the computer assumed constant enthalpy. It is safe for soot blowing [from among the optimal steam temperature and pressure combinations]
L calculates and selects the steam temperature corresponding to the input steam pressure. For example, as a combination of the above, as shown in FIG. If it is stored, the input steam pressure is 36 kg/cra72, so a temperature of 279.6°C corresponding to this pressure is calculated and selected. Next, in step P2, a comparison calculation is performed between the steam temperature 279.6°C selected by this calculation and the actual steam temperature 428°C previously input in step P2. Then, the comparison output signal is sent to the temperature regulator 6, which opens the reduced temperature water control valve l, and the reduced temperature water is poured into the reduced temperature section via the reduced temperature water supply pipe 11 (step P). This opening operation of the reduced temperature water control valve 1 is performed until the actual steam temperature reaches the calculated and selected temperature. Since the temperature and pressure of the superheated steam introduced into the conduit 7 constantly change, the above control is performed continuously. The superheated steam injected from the injection pipes 10a, 1Ob, etc. of the soot blowing device toward the heat transfer surface of the boiler at any time is safe and optimal for soot blowing based on the constant enthalpy described in . The temperature is reduced to the selected steam temperature above. In addition, the steam pressure at this time was controlled to have constant enthalpy, so although the pressure was reduced, it was not extremely reduced.
The steam pressure that was appropriately selected during the initial soot blowing is maintained. Conventionally, temperature reduction control in the temperature reduction section has been performed by controlling the steam temperature after temperature reduction. (As a quasi-substance, water injection-1 control was used, and the temperature and pressure of the incoming superheated steam fluctuate greatly, so even if the temperature could be maintained constant after cooling, the pressure would drop by 75 atm). This makes it unsuitable for soot blowing, and it is not possible to control the temperature reduction by standard methods, but this allows effective control.

[Effects of the Invention] The present invention stores in advance a combination of steam pressure and steam temperature that is safe and optimal for soot blowing based on constant enthalpy, and selects steam before depressurization from among the combinations. When the pressure of
Since the soot-blown steam is cooled by injecting water until the temperature of the steam after temperature reduction matches the temperature of the steam selected by calculation, compared to the case where temperature reduction control is performed based on the steam temperature, Accurate temperature reduction control is possible. Therefore, as a result of accurate temperature reduction control, the pressure and temperature of the superheated steam to be soot blown can be pre-caulked according to the type of boiler, the state of soot adhesion on the heat transfer surface, etc., and it is safe to soot blow. If the settings are set optimally, expected results can be obtained, and the risk of explosion and the double lotion phenomenon due to moisture contamination can be completely avoided. In particular, it is possible to precisely control the pressure of the superheated steam to be soot-blown to an optimum value that is neither too high nor too low, and the soot-blowing effect can be maintained at a high level. In particular, conventionally the superheated steam sent from the boiler to the turbine was approximately 20K, which is ideal for soot blowing.
Since it is virtually impossible to reduce the pressure to about 72 g/cm and control temperature reduction based on temperature standards, the actual situation is that the temperature and amount are blown out as they are naturally.

Compared to this case, it was confirmed through experiments that according to the present invention, the steam Ij% injected per unit time from the four injection tubes to the heat transfer surface increases. This Is means that the mass acceleration acting on the heat transfer surface increases, and the effect of removing soot from the heat transfer surface is greatly improved.

[Brief explanation of drawings]

The attached drawings show embodiments of the present invention, and FIG. 1 is an overall configuration diagram for carrying out the method of the present invention, FIG. 2 is an implementation system diagram, and FIG.
The figure is a flowchart for executing the control, and FIG. 4 is an example of a graph together with a table showing various combinations of steam pressure and inlet air temperature based on constant enthalpy. Patent applicant Mitsubishi Paper Mills Co., Ltd. Technoj! ,':'-',+L':,,f'.

Claims (1)

[Claims] In a soot blowing method, a part of the superheated steam sent from the boiler to the turbine is removed, reduced to a predetermined pressure, and blown onto the heat transfer surface of the boiler to remove soot: Prepare in advance various combinations of safe and optimal steam temperature and steam pressure for soot blowing based on constant enthalpy, and when the soot blow steam pressure before decompression is detected, correspond to the detected pressure value. Calculate the steam temperature in the above combination, compare the calculated steam temperature with the actual steam temperature after temperature reduction, and reduce the temperature until the steam temperature after temperature reduction reaches the calculated temperature. A boiler soot blowing method characterized by pouring out hot water.