Application of extraction steam graded heat storage in peak shaving of condensing units

Abstract

In order to alleviate the peak shaving pressure of power grid and further improve the deep peak shaving capacity of coal-fired units, this paper applies staged heat storage to condensing units. Under the condition of constant boiler load, the heat of regenerative steam extraction is stored to reduce the electrical load output of the unit. Taking a 660MW ultra-supercritical unit as an example,30%THA,40%THA and 50%THA were taken as the initial conditions of heat storage respectively to discuss the peak shaving range and power regeneration efficiency of different extraction steam positions for heat storage. The results show that the “storage 1# HP heater extraction steam” scheme with “two-stage three tank” heat storage and release structure has the largest peak shaving range of 37.3%~56.9% under 50% initial conditions. When the “two-stage three tank” heat storage and release structure selects the “storage 1# HP heater extraction steam ”scheme under 40% initial working condition, the “power regeneration efficiency” reaches the highest——78.3%. And the “power regeneration efficiency” of “two stage three tank” storage structure are always higher than the “single-stage” storage structure.

Analysis of heating transformation of different types of thermal power units

“…The working condition diagram is the relationship curve between the active power of steam turbine generation, main steam flow and regulated steam extraction under different combinations. By digitizing and dimensional conversion of the working condition diagram, the trend diagram of peak regulation upper and lower limits under different steam extraction of the unit can be obtained, and then the calculation model of peak regulation upper and lower limits formula and the calculation model of steam extraction upper limit formula of condensing unit can be obtained.The upper and lower limits of the unit's output under the current steam extraction and the upper limit of the unit's steam extraction under the current output can be obtained by selecting an appropriate section according to the formula [8] . According to the average steam extraction capacity and output of the unit in different heating periods, the electric load adjustment interval under the average steam extraction capacity of different capacity condensing heating units in the initial, middle and final heating periods and the upper limit of steam extraction capacity under 50%, 75% and 100% rated capacity can be obtained by substituting into the calculation model.…”

Research on operation of low-pressure cylinder zero output heat supply retrofit unit

“…2) Compared with optical shaft heating [7], high back pressure heating [8] and other heating technologies, low pressure cylinder zero output heating technology can realize the flexible switching between the condensing operation mode and the high back pressure operation mode of the heating unit, making the unit have the characteristics of high back pressure unit with large heating capacity and flexible operation mode of the condensing heating unit, The problem of replacing the low pressure cylinder rotor twice during the heating period and the problem of storing and maintaining the spare rotor in the high back pressure heat supply transformation (double rotors) and smooth axis transformation scheme are avoided, and the maintenance cost during unit operation is greatly reduced. 3) Supporting transformation of monitoring and measuring points for turbine proper operation; 4) Check the operation safety of the low pressure secondary and final stage blades and spray the anti water corrosion metal wear-resistant coating; 5) Improvement of exhaust cylinder spray desuperheating system; 6) Supporting transformation of heating system, air extraction system, condensate system, etc; 7) Reconstruction of supporting automatic control system.…”