CN106681284A - Coal-fired boiler heat-absorbing surface slagging contamination degree on-line real-time monitoring method - Google Patents

Abstract

The invention provides an online real-time monitoring method for the degree of slagging and contamination on the heating surface of a coal-fired boiler. Simultaneously start with the parameters of the flue gas side and the steam-water side to calculate the steam-water heat absorption, flue gas heat release, and heat loss items of each heating surface of the boiler; calculate the steam-water heat absorption ratio and flue gas heat release ratio of each heating surface; Monitoring of the heat absorption ratio of steam and water on the heating surface and the change of the heat release ratio of flue gas. If there is a decrease in the heat absorption ratio of steam and water on a heating surface or a decrease in the heat release ratio of flue gas, it is considered that the heating surface has slagging and contamination. The method provided by the invention can start monitoring after the coal-fired unit is repaired and started, and the operator can take corresponding measures in advance according to the change of the monitoring parameters to reduce the probability of boiler slagging and reduce the degree of contamination of the heating surface. Improve the safety and economy of boiler operation.

Description

An online real-time monitoring method for the degree of slagging and contamination on the heating surface of a coal-fired boiler

technical field

The invention relates to a coal-fired boiler equipped in a thermal power plant, in particular to a method for judging the combustion state of the boiler, the slagging of the heating surface in the furnace, and the degree of contamination, and belongs to the technical field of boiler combustion in the thermal power plant.

Background technique

At present, thermal power accounts for about 70% of all power generation in my country. According to the new forecast for the medium and long-term development of the power industry, by 2020, my country's total installed capacity will reach 1.34 billion kilowatts, of which the total installed capacity of coal power will be 910 million kilowatts. Based on the installed capacity of coal-fired power of 380 million kilowatts in 2005, by 2020 the new installed capacity of coal-fired power will be 530 million kilowatts. It is estimated that by 2050, my country's thermal power generation will still account for 55% to 60% of all power generation.

However, at present, due to the influence of mine conditions, coal market and online prices, it is difficult for most thermal power plants to continue to use the designed coal types, to use relatively cheap coal types, and even to blend and blend different types of coal. The actual coal situation of the power plant. This will easily make the combustion control of the power plant boiler more difficult, the boiler is prone to slagging, and the degree of contamination of the internal heating surface will increase, which will seriously affect the safe operation of the boiler and even cause the unit to shut down.

Taking Zhundong coal in Xinjiang as an example, the predicted reserves of coal resources in Zhundong account for one-third of Xinjiang's total, and the planned mining scale is 582 million tons per year. It is the most important energy base for transportation and Xinjiang coal transportation. According to the plan, the capacity of power plants in Xinjiang will increase from the current 18 million kilowatts to 100 million kilowatts by the end of the "Twelfth Five-Year Plan", and the demand for coal will be huge. However, due to the characteristics of serious contamination, slagging, and high moisture, the coal in the Zhundong area can only be used as coal blending for traditional power plant boilers for a long time. The advantages of safety, low cost and large output in Zhundong open-pit coal mining cannot be fully utilized It has severely restricted the development of the coal industry in Zhundong region, and also restricted the development of electric power in Xinjiang to a certain extent.

At present, in my country's coal-fired units, there are many special methods for early warning of coal-fired boiler slagging and heating surface contamination, but many methods lack real-time performance, and can only be used when boiler slagging and heating surface contamination After a certain level, specific problems are discovered even when the safe operation of the boiler is affected. Due to the lack of advanced real-time monitoring methods, the operational safety of coal-fired unit boilers in my country has been seriously affected.

Contents of the invention

The technical problem to be solved by the invention is how to carry out online real-time monitoring of the degree of slagging and contamination on the heating surface of the coal-fired boiler.

In order to solve the above technical problems, the technical solution of the present invention is to provide an online real-time monitoring method for the degree of slagging and contamination on the heating surface of a coal-fired boiler, which is characterized in that the method consists of the following steps:

Step 1: Collect the operation data of the boiler side and the steam turbine side of the coal-fired unit in real time, and organize these data into a standard database;

Step 2: Simultaneously start with the parameters of the flue gas side and the steam-water side in the furnace, and calculate the steam-water heat absorption, flue gas heat release, and heat loss items of each heating surface of the boiler;

Step 3: Calculate the heat absorption ratio of steam and water and the heat release ratio of flue gas on each heating surface;

Step 4: Real-time monitoring of the heat absorption ratio of steam and water on each heating surface and the change of heat release ratio of flue gas. If there is a decrease in the heat absorption ratio of steam and water on a certain heating surface or the decrease in the heat release ratio of flue gas, it is considered that the heating surface is contaminated by slagging phenomenon occurs.

Preferably, in the step 1, the coal-fired unit DCS system data or SIS system data is used to collect the coal-fired unit boiler side and steam turbine side operating data in real time.

Preferably, in step 3, the steam-water heat absorption ratio of each heating surface is obtained by dividing the steam-water heat absorption of a single heating surface by the total steam-water heat absorption of all heating surfaces.

Preferably, in the step 3, the sum of all the heat releases and heat loss items of each heating surface is used as the denominator, and the heat release of each heating surface is divided by this denominator to obtain each heating surface The proportion of flue gas heat release.

Preferably, in step 4, the results obtained in step 3 are returned to the SIS system in real time, and connected with the DCS system in real time, so as to realize online real-time monitoring of the degree of slagging and contamination of the heating surface.

The method provided by the invention utilizes the data of the DCS or SIS system of the coal-fired unit to perform real-time calculation and statistics on the heat absorption of the heating surfaces at all levels in the boiler furnace, the heat release of the flue gas side and the loss items, and put them back into the SIS system or DCS screen , to achieve the purpose of monitoring. It can be implemented after the coal-fired unit is repaired and started, and the change of the heat absorption ratio of the heating surface can be monitored in real time. According to the change of the heat absorption ratio of the heating surface, the operator can take corresponding measures in advance to reduce the probability of boiler slagging or reduce the degree of contamination of the heating surface, so that the safety and economy of the boiler operation can be improved.

Description of drawings

Fig. 1 is the overall frame diagram of the online real-time monitoring method of the degree of slagging and contamination on the heating surface of a coal-fired boiler provided in this embodiment;

Fig. 2 is a flow chart of the heat absorption ratio of the steam-water heating surface on the main steam side, taking the once-through furnace as an example;

Fig. 3 is a flow chart of the heat absorption ratio of the steam-water heating surface on the reheating steam side, taking the once-through furnace as an example;

Figure 4 is a flow chart of the heat release ratio of the heating surfaces at all levels on the flue gas side, taking the once-through furnace as an example.

detailed description

Below in conjunction with specific embodiment, further illustrate the present invention. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the teachings of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of the present application.

With reference to Fig. 1, the present invention relates to the calculation and statistics of the heat absorption distribution ratio of each heating surface of the coal-fired unit boiler. Starting from the water circulation circuit, the heating surface of the boiler is divided into: economizer, water-cooled wall, wall-wrapped (four-sided covering) superheater, low-temperature superheater, partition screen superheater, rear screen superheater, final stage superheater; and high pressure Cylinder exhaust steam to low temperature reheater, wall (medium temperature) reheater, final stage reheater. Using the DCS data or SIS data of the coal-fired unit to start from the steam-water parameters, the pressure and temperature are known, and the enthalpy value of the steam-water parameters at this state point can be known, so that the heat absorption of each heating surface above can be calculated, and finally the individual heating The heat absorption of the surface is divided by the total heat absorption of all the above-mentioned heating surfaces, and the heat absorption ratio of each of the above-mentioned heating surfaces is obtained.

From the start-up of the coal-fired unit after major repairs (the cleanliness of the heating surface is the highest), real-time (calculation and statistics every 1 minute or several minutes) monitoring of the change of the heat absorption ratio of the heating surface is carried out. After running for a long period of time, if there is a decrease in the heat absorption ratio of a certain level of heating surface, such as a significant decrease in the heat absorption of the partition screen, it can be considered that there is slagging on the partition screen. A large number of daily statistical work realizes the monitoring of the combustion situation in the furnace, and the operating personnel can take corresponding other operating measures in advance according to the change of the heat absorption ratio of the heating surface, instead of waiting until the situation deteriorates to realize it, and reduce the heating surface. Slagging probability or degree of contamination.

In addition, real-time calculation and statistics are carried out on the heat release and loss of the flue gas side on the heating surface at all levels, combined with the heat absorption on the soda side, and finally the heat absorption ratio of each heating surface in the furnace is formed. , Flue gas heat release ratio value.

Taking the DC furnace as an example, the calculation of the steam-water side is explained as follows with reference to Figure 2 and Figure 3:

Starting from the boiler feed water, the pressure and temperature of the inlet and outlet of the economizer (these parameters can be collected in the SIS system, the following are the same, and will not be described again) to get the enthalpy difference between the inlet and outlet, and multiply it by the feedwater flow to get the heat absorption of the economizer The next step is the inlet and outlet pressure and temperature of the water wall (the pressure and temperature of the inlet of the water wall is the outlet pressure and temperature of the economizer) to get the enthalpy difference between the inlet and outlet, and multiply it by the feed water flow to get the heat absorption of the water wall; next is the wrapping wall The pressure and temperature at the inlet and outlet of the superheater are obtained by the enthalpy difference between the inlet and outlet, and multiplied by the feedwater flow rate to obtain the heat absorption of the wall-wrapped superheater; followed by the inlet and outlet pressure and temperature of the low-temperature superheater to obtain the enthalpy difference between the inlet and outlet, multiplied by the feedwater flow rate to obtain Get the heat absorption of the low-temperature superheater; the next step is the partition superheater. Here, we should pay attention to the flow calculation of the first-stage desuperheating water, the heat balance calculation of the outlet of the low-temperature superheater, and the first-stage desuperheating water after spraying and cooling, and obtain the first-stage desuperheating water. The desuperheating water flow rate, the inlet and outlet pressure and temperature of the partition superheater are obtained by the inlet and outlet enthalpy difference, multiplied by the feed water flow plus the first-stage desuperheating water flow, and the heat absorption of the partition superheater is obtained; the next step is the rear panel superheater, In the same way as the previous calculation of the first-stage desuperheating water flow rate, the second-stage desuperheating water flow rate is calculated, and the inlet and outlet enthalpy difference is obtained from the inlet and outlet pressure and temperature of the rear panel superheater, and multiplied by the feed water flow rate plus the first-stage and second-stage desuperheating water flow rates. Obtain the heat absorption of the rear screen superheater; finally the final stage superheater, get the inlet and outlet enthalpy difference from the pressure and temperature of the inlet and outlet of the final stage superheater, multiply it by the feed water flow rate plus the flow rate of the first and second stage desuperheating water to get the final stage superheat Heat absorption of the device.

The other part starts from the exhaust steam of the high-pressure cylinder, the enthalpy value is obtained from the pressure and temperature of the exhaust steam, the enthalpy value is obtained from the pressure and temperature of the reheater accident desuperheating water, the enthalpy value is obtained from the pressure and temperature of the steam after desuperheating, and the reheating value is calculated from the heat balance. Heater accident desuperheating water flow. The inlet and outlet pressure and temperature of the low-temperature reheater are obtained by the enthalpy difference between the inlet and outlet, and multiplied by the exhaust steam flow of the high-pressure cylinder (cold reheat steam flow) plus the accidental desuperheating water flow of the reheater to obtain the heat absorption of the low-temperature reheater ; Next is the wall-type (medium temperature) reheater, the enthalpy value is obtained from the outlet pressure and temperature of the low-temperature reheater, and the enthalpy value is obtained by reducing the pressure and temperature of the reheater by spraying a small amount of water, and the wall-type (medium temperature) after desuperheating The inlet pressure and temperature of the reheater are used to obtain the enthalpy value, and the flow rate of the micro-sprayed desuperheating water of the reheater is calculated from the heat balance. The inlet and outlet pressure and temperature of the wall-type (medium temperature) reheater are obtained by the enthalpy difference, multiplied by the exhaust steam flow rate of the high pressure cylinder (cold reheat steam flow rate), plus the accidental desuperheating water flow rate of the reheater and the micro spray desuperheating water of the reheater Flow rate, the heat absorption of the wall (medium temperature) reheater is obtained; next is the final reheater, the enthalpy difference is obtained from the pressure and temperature of the inlet and outlet of the final reheater, and multiplied by the exhaust steam flow of the high pressure cylinder ( Cold reheat steam flow) plus the flow rate of reheater accident desuperheating water and the flow rate of reheater micro spray water desuperheating water, is the heat absorption of the final reheater.

After the calculation of the heat absorption of all the heating surfaces above is completed, add them all together to get the total heat absorption of the heating surface on the steam-water side, and divide the heat absorption of a certain heating surface by the total heat absorption of the heating surface, which is the heat absorption heat ratio.

The soda side does not consider the heat loss, so the heat release ratio of the flue gas side must be added to the calculation, and then the heat transfer and dust pollution characteristics of the heating surfaces at all levels and the heat loss ratio of the flue gas can be obtained. The ratio of heat release on the flue gas side is explained as follows with reference to Figure 4:

Firstly, the elemental analysis values of the furnace coal are obtained according to the relevant literature and equations, and then according to the content of the boiler thermal calculation chapter in the conventional literature, according to the flue gas enthalpy temperature table, the results of the furnace and each heating surface, and material parameters, calculate the heating surface at all levels (at different flue gas temperatures) flue gas enthalpy. This involves the content of boiler thermal calculation, especially the calculation of radiation heat transfer in the furnace. These calculations are relatively mature content in conventional literature, and they can be sorted out to form a fixed module. For the heating surfaces at all levels, take the rear panel superheater as an example: through thermal calculation, combined with the relevant parameters of the front steam-water side, the smoke enthalpy of the flue gas entering and exiting the heating surface, the dust coefficient in the heat transfer characteristics and the The flue gas releases heat on the heating surface of the stage. The first-level heating surface is calculated all the way to the air preheater. After the blowdown temperature is collected, the boiler exhaust gas heat can be calculated, that is, the heat loss item. Add up the heat release of flue gas and the heat loss of flue gas at all levels of heating surfaces as the denominator, and then divide the heat release of flue gas at all levels of heating surfaces by this denominator to obtain the heat release ratio of the flue gas side of each heating surface.

After sorting out the above parameters and calculation results, and then returning them to the SIS system or DCS screen in real time, the purpose of real-time monitoring of the degree of slagging and contamination on the heating surface can be achieved.

Claims (5)

1. the on-line real time monitoring method of degree is stain in a kind of heating surface of coal-fired boiler slagging scorification, it is characterised in that the method is by such as Lower step composition：

Step 1：Real-time Collection coal unit boiler side, steamer pusher side service data, by these data compilations into standard database；

Step 2：Inner flue gas of the stove side and soda pop side parameter are set about simultaneously, calculate each heating surface of boiler soda pop caloric receptivity, Flue gas thermal discharge, heat loss item；

Step 3：Calculate soda pop heat absorption ratio, the flue gas heat release ratio of each heating surface；

Step 4：Each heating surface soda pop heat absorption ratio, monitoring of flue gas heat release ratio change is carried out in real time, if occur certain being heated Face soda pop heat absorption ratio declines or flue gas heat release ratio declines, then it is assumed that the heating surface has slagging scorification to stain phenomenon generation.

2. the on-line real time monitoring method of degree is stain in a kind of heating surface of coal-fired boiler slagging scorification as claimed in claim 1, and it is special Levy and be：In the step 1, using coal unit DCS system data or SIS system datas, Real-time Collection coal unit pot Furnace side, steamer pusher side service data.

3. the on-line real time monitoring method of degree is stain in a kind of heating surface of coal-fired boiler slagging scorification as claimed in claim 1, and it is special Levy and be：In the step 3, the soda pop caloric receptivity of single heating surface is recepted the caloric divided by total soda pop of all heating surfaces, drawn The soda pop heat absorption ratio of each heating surface.

4. the on-line real time monitoring method of degree is stain in a kind of heating surface of coal-fired boiler slagging scorification as claimed in claim 1, and it is special Levy and be：It is that the flue gas thermal discharge of each heating surface, heat loss item are all added up and as denominator in the step 3, will The flue gas thermal discharge of each heating surface is respectively divided by this denominator, just obtains the flue gas heat release ratio of each heating surface.

5. the on-line real time monitoring method of degree is stain in a kind of heating surface of coal-fired boiler slagging scorification as claimed in claim 2, and it is special Levy and be：In the step 4, step 3 acquired results are returned in real time SIS systems, docked in real time with DCS system, realized to receiving The on-line real time monitoring of degree is stain in hot face slagging scorification.