Adjusting method suitable for once-through boiler dry and wet state conversion operation

Abstract

The invention discloses an adjusting method suitable for dry and wet state conversion operation of a once-through boiler. The adjusting method comprises the following steps that S1, the feed water flow W is kept stable during dry and wet state conversion; s2, the unit electrical load value after state conversion is preliminarily calculated, the final-state electrical load P after the wet state is converted into the dry state is equal to W / 3.2, and 3.2 is the water supply flow corresponding to each MW electrical load; the final-state electric load P after the dry state is converted into the wet state is a target load, and the target load is determined to be 80-90 MW according to operation experience; s3, the boiler coal feed quantity value after state conversion is preliminarily calculated, the final state coal feed quantity M after the wet state is converted into the dry state is equal to P * 5, and 5 is the empirical coal feed quantity needed for generating 1 MW electricity every time; the final-state coal feeding amount M after the dry state is converted into the wet state is a numerical value determined according to the target load and the operation experience, and the initial setting is 35 t / h; s4, calculating the change rate k = deltaM / deltaP of the coal feeding amount in unit load increase and decrease; and S5, lifting the load of the unit.

Description

Technical Field

[0001] The invention relates to the technical field of dry-wet state conversion operation method of a direct current boiler, and in particular to an adjustment method suitable for dry-wet state conversion operation of a direct current boiler. Background Art

[0002] In order to reduce the coal consumption of the units and achieve the energy-saving goals of coal-fired power units, large supercritical and ultra-supercritical units are the inevitable choice for the thermal power generation industry. During the start-up and shutdown process, the boilers supporting supercritical and above pressure level units will inevitably go through a process of changing from wet to dry or from dry to wet. With the advancement of the "dual carbon" work and the large-scale construction and commissioning of new energy stations, thermal power generating units will gradually transform into deep peak-shaving units in the power energy structure, mainly playing the role of bottom-line guarantee of the power energy system. During the deep peak-shaving period of about 25% of the rated load, direct-current boilers also frequently implement dry-wet state conversion operations.

[0003] In the process of dry-wet state conversion, the dry-wet state conversion goal of the direct-current boiler is achieved mainly by adjusting the three parameters of boiler feed water flow, unit load, and boiler coal supply, and by auxiliary adjustment of other parameters. During the adjustment process, due to the high-frequency mismatch problem of multi-parameter adjustment, the intermediate superheated steam temperature after the boiler ceiling superheater and the screen superheater drops rapidly in a short period of time. First, it is easy to cause a sharp drop in the temperature of the steam entering the turbine and cause a water hammer accident. Second, it is easy to cause water plugging and bursting of the superheater tube bank of the direct-current boiler. Second, it is easy to cause the oxide scale in the high-temperature section superheater tube bank of the direct-current boiler to fall off and block and burst the tube.

[0004] In view of the above situation, in order to prevent the risk of unit accidents caused by large fluctuations in the intermediate superheated steam temperature during the dry-wet state conversion of the direct-current boiler, it is necessary to consider further optimizing the manual operation control strategy of the dry-wet state conversion of the direct-current boiler, reduce the fluctuation amplitude of the intermediate superheated steam temperature as much as possible, and improve the stable operation capability of the unit. Summary of the invention

[0005] In view of the above technical problems, the present invention provides an adjustment method suitable for dry-wet state conversion operation of a direct current boiler.

[0006] In order to achieve the above object, the technical solution of the present invention is as follows: An adjustment method applicable to dry-wet state conversion operation of a once-through boiler comprises the following steps: S1, keep the water flow rate W stable during dry-wet state conversion; S2. Preliminary calculation of the unit electrical load value after the transition The final electrical load after the wet state is converted to the dry state is P=W / 3.2, where 3.2 is the water flow rate corresponding to each MW electrical load; The final electrical load P after the dry state is converted to the wet state is the target load, which is determined to be 80-90MW based on operating experience; S3. Preliminary calculation of the boiler coal supply value after the transition The final coal supply after the wet state is converted to dry state is M=P×5, where 5 is the empirical coal supply required for generating 1MW of electricity; The final coal feeding rate M after the dry state is converted to the wet state is a value determined according to the target load and operating experience, and is initially set at 35t / h; S4. Calculate the rate of change of coal feeding amount per unit load rise and fall k=ΔM / ΔP, where ΔM is the difference between the initial coal feeding amount and the final coal feeding amount, and ΔP is the difference between the initial electrical load and the final electrical load; S5. Raise or lower the load of the unit, and at the same time increase or decrease the coal supply according to the product of the load increase or decrease of 1MW and the coal supply change rate k per unit load increase or decrease. Fine-tune the control according to the changes in the steam temperature and steam pressure of each section of the superheater to achieve a smooth conversion between the dry and wet states of the direct current boiler.

[0007] The beneficial effects of the present invention are: 1. The present invention breaks the adjustment principle of the conventional direct-current boiler dry-wet state conversion adjustment control strategy, minimizes the adjustment control variables, and reduces the fluctuation amplitude of the intermediate superheated steam temperature as much as possible while ensuring that the direct-current boiler feed water, load, and coal ratio are reasonable and the parameters are relatively stable.

[0008] 2. The present invention optimizes the adjustment variables in the dry-wet state conversion process of the direct current boiler to maintain a relatively stable feed water flow rate, and reduces the main adjustment variables from 3 in the original adjustment method to 2, so as to reduce the adjustment and improve the matching degree of the operating parameters, thereby achieving relative stability of the intermediate superheated steam temperature and improving the stable operation level of the unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is an operation flow chart of the present invention. DETAILED DESCRIPTION

[0010] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with specific embodiments. It should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present invention. In addition, in the following description, the description of known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present invention.

[0011] Example 1 Adjustment control strategy of once-through boiler from wet state to dry state like Figure 1 As shown in the figure, during the unit startup process, the electrical load rises to 80MW, the water feed flow is 360t / h, the coal feed is 35t / h, and the wet-to-dry operation is ready to be implemented: 1) Maintain the water flow rate W at 360t / h without adjustment; 2) Calculate the electrical load after the dry state: P = 360 / 3.2 = 112.5MW; 3) Calculate the coal feeding rate after drying: M = 112.5 × 0.5 = 56 t / h; 4) According to the above calculation data, it is determined that in the process of wet state to dry state, the coal supply needs to be increased by ΔM=56-35=21t / h, which will increase the unit power generation load by ΔP=112.5-80=32.5MW, so k=ΔM / ΔP=21 / 32.5=0.65; 5) Increase the unit load and increase the coal feed at a rate of 0.65 t / h for every 1 MW increase in load. Fine-tune the control according to the changes in steam temperature and pressure in each section of the superheater to achieve a smooth transition from wet to dry state of the direct current boiler.

[0012] Example 2 Adjustment control strategy of once-through boiler from dry state to wet state like Figure 1 As shown in the figure, during the load reduction process, the power load will reach 120MW. At this time, the feed water flow is 380t / h and the coal flow is 57t / h. The dry-to-wet operation is ready to be implemented: 1) Maintain the water flow rate W at 380t / h without adjustment; 2) According to experience, the electrical load P after the wet state is 80MW; 3) According to experience, the coal feeding rate M after wet state is 35t / h; 4) According to the above data, it is determined that during the transition from dry state to wet state, the coal feed rate needs to be reduced by ΔM=57-35=22t / h, and the unit power generation load needs to be reduced by ΔP=40MW, so k=ΔM / ΔP=22 / 40=0.55; 5) Reduce the unit load and reduce the coal feed by 0.55t / h for every 1MW load reduction. Fine-tune the control according to the changes in steam temperature and steam pressure in each section of the superheater to achieve a smooth conversion from dry to wet state of the direct current boiler.

[0013] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An adjustment method for dry-wet state conversion operation of a once-through boiler, characterized in that: The following steps are involved: S1, keep the water flow rate W stable during dry-wet state conversion; S2. Preliminary calculation of the unit electrical load value after the transition The final electrical load after the wet state is converted to the dry state is P=W / 3.2, where 3.2 is the water flow rate corresponding to each MW electrical load; The final electrical load P after the dry state is converted to the wet state is the target load, which is determined to be 80-90MW based on operating experience; S3. Preliminary calculation of the boiler coal supply value after the transition The final coal supply after the wet state is converted to dry state is M=P×5, where 5 is the empirical coal supply required for generating 1MW of electricity; The final coal feeding rate M after the dry state is converted to the wet state is a value determined according to the target load and operating experience, and is initially set at 35t / h; S4. Calculate the rate of change of coal feeding amount per unit load rise and fall k=ΔM / ΔP, where ΔM is the difference between the initial coal feeding amount and the final coal feeding amount, and ΔP is the difference between the initial electrical load and the final electrical load; S5. Raise or lower the load of the unit, and at the same time increase or decrease the coal supply according to the product of the load increase or decrease of 1MW and the coal supply change rate k per unit load increase or decrease. Fine-tune the control according to the changes in the steam temperature and steam pressure of each section of the superheater to achieve a smooth conversion between the dry and wet states of the direct current boiler.

Images