Bypass Steam Research Articles

Improving power ramp rate of a coal-fired power plant by a bypass steam accumulator

The increasing penetration of high-volatility renewable energy sources in the power system presents higher demands for flexibility from coal-fired power plant (CFPP). To enhance the flexibility of CFPPs, researchers have conducted a significant amount of thermal-system-level research in recent years on increasing system peak shaving depth. However, the load ramp rate of CFPPs under deep peak shaving is rarely discussed, despite its significance to the overall flexibility performance of CFPPs. This paper proposes a steam accumulator storage system integrating to the turbine's bypass system. The steam accumulator charges directly with working fluid from the live steam or reheat systems and discharge to the turbine, responding quickly to power ramp commands. A steady state model and a dynamic model of the proposed system were built and validated, and the calculation shows that the proposed scheme provides a load change of +2.13 % Pe and −8.3%Pe during a round-trip with a power efficiency of 63.6 % at a unit load of 40 % THA. The unit's load increase rate under coordinated control was enhanced by 1.5 % Pe/min, reaching 3 % Pe/min, using the proposed steam accumulator without revising the original controls, and the load decrease rate reached at least 5 % Pe/min. The results indicate that the proposed system provides a straightforward, easy-to-implement, and efficient solution for enhancing the load ramp rate of CFPPs at low loads.

Ways to increase the maneuverability characteristics of the CCGT when operating in load control modes (for example, CCGT-450)

THE PURPOSE The article is devoted to the analysis of the problems that arise during the operation of heating CCGTs of the type CCGT-450 at reduced loads with their participation in the regulation of electrical and thermal loads. The description of the main limitations of the adjustment range of gas turbines, and the maneuverability characteristics of the CCGT, an analysis of some existing technical proposals for expanding the adjustment range is given. It is shown that the application of these proposals, expanding the boundaries of the adjustment range in small quantities, does not solve the problem as a whole. The description and research results of the proposed new technical solutions to expand the adjustment range and maneuverability characteristics of the CCGT - 450 are given.METHODS. When solving the tasks, the analysis, comparison and generalization of energy characteristics, modeling of modes were carried out.RESULTS. It is shown that: the use of methods for converting part of the central heating system and the central heating system as a whole of the T-125/150 steam turbine into a low-steam mode together with bypass steam distribution will expand the adjustment range to a level comparable to the adjustment range of condensing power units on gas-fuel oil;. when shutting down the CCGT-450 operating in condensation mode and when operating it in the GTU-CHP mode during periods of night failure of the electrical load, the conversion of the steam turbine to motor mode significantly improves the maneuverability and reliability characteristics of the steam turbine and the CCGT as a whole. conclusion. The use of methods for transferring part of the central heating system and central heating system as a whole and bypass steam distribution expand the adjustment range of the CCGT-450, respectively, by 7.8, 10.1 and 16.0% of the rated power; When the CCGT-450 is operating in condensation mode when the CCGT is stopped and when it is operating in the GTU-CHP mode during periods of night failure of the electric load, the steam turbine is transferred the MR significantly improves the maneuverability and reliability characteristics of the steam turbine by reducing the duration of start-up and loading of the steam turbine by 40 and 14.5 minutes, respectively, reducing starting fuel losses, eliminating temperature fluctuations of steam and metal of the steam intake organs of the central pump and the control stage during start-up;

Thermodynamic analysis on a novel bypass steam recovery system for parabolic trough concentrated solar power plants during start-up processes

Most concentrated solar power plants undergo daily start-up and shut-down processes, which consume much energy. If the start-up energy losses can be recovered, the power plant efficiency may be enhanced. The energy loss of bypass steam is one of the major start-up energy losses, but the method to recover bypass steam is absent. Therefore, we proposed a novel system to recover bypass steam by integrating a steam accumulator, and the recovered bypass steam was used to replace the extraction steam of regenerative heaters. The dynamic models of the bypass steam recovery system were developed, and the design parameters and discharging strategy of the steam accumulator were optimized. Results show that simultaneously increasing the initial pressure and volume of the steam accumulator can increase recovered exergy, and switching the regenerative heater received steam during the steam accumulator discharging process can improve electricity production. The optimal initial pressure and volume of the steam accumulator are 2.6 MPa and 246.4 m3, respectively, by balancing the tradeoff between the annual electricity production and the steam accumulator volume. Integrating the steam accumulator with optimal design parameters can improve the annual electricity production by 1.1 GWh (0.55%) for a 50 MW parabolic trough concentrated solar power.

Оценка эффективности использования паровых турбин с обводным парораспределением при участии в первичном регулировании частоты тока в энергосистеме

This paper evaluates efficiency of steam turbines with bypass steam distribution involved in a process of primary frequency control in power systems. We calculated power of a steam turbine and power unit in general, and absolute electrical efficiency for both bypass and throttle steam distribution. It was found that bypass steam distribution increases absolute electrical efficiency of steam-gas units while operation under lower capacity. Economic indicators calculated for combined cycle gas units confirm effectiveness of steam turbines with bypass steam distribution involved in primary frequency control.

Increasing the reliability and manoeuvrability of the CCGT when operating in the variable part of the power consumption schedules by switching the CCGT steam turbine to the motor mode

The report is devoted to the problem of increasing the reliability and manoeuvrability of the CCGT when it operates in power control modes of the power system. The generalized results of research on improving the reliability and expanding the adjustment range of the PGU-450 based on the use of bypass steam distribution, reducing the duration of start-up operations and increasing the loading speed of the steam turbine and CCGT in general in the modes of CCGT power reserve during the night load gap by transferring the CCGT steam turbine to the motor mode when the CCGT operates in the condensation mode or in the heating mode according to the GTU-CHP scheme are presented. Additional advantages of the motor mode are noted: improved reliability of the steam turbine due to the elimination of cyclic temperature fluctuations of its steam inlet valves and vibrations in the last stages of the low-pressure cylinder and the possibility of operating the steam turbine generator in the synchronous compensator mode.

Using the steam turbines with bypass steam distribution at CCGT for primary frequency control

The system of bypass regulation of the steam turbine for the more effective participation in primary frequency control is examined. Power and relative internal efficiency ratio of turbine with bypass steam distribution for various steam consumptions are calculated. It is shown that the steam turbine with bypass steam distribution in the combined-cycle plant in the hot standby mode with reduced power (to provide power reserve) provides a higher efficiency than when the steam is throttled in the control valve without bypass steam distribution. In addition, power change of the steam turbine with bypass steam distribution provides greater acceleration compared to the operation at the sliding steam pressure and the opportunity of overloading the turbine to the required power level.

Thermal Energy Storage Configurations for Small Modular Reactor Load Shedding

The increased penetration of intermittent renewable energy technologies such as wind and solar power can strain electric grids, forcing carbon-based and nuclear sources of energy to operate in a load-follow mode. For nuclear reactors, load-follow operation can be undesirable due to the associated thermal and mechanical stresses placed on the fuel and other reactor components. Various methods of thermal energy storage (TES) can be coupled to nuclear (or renewable) power sources to help absorb grid variability caused by daily load demand changes and renewable intermittency. Two TES techniques are investigated as candidate thermal reservoirs to be used in conjunction with a small modular reactor (SMR): a two-tank sensible heat storage system and a stratified chilled-water storage system. The goal when coupling the two systems to the SMR is to match turbine output and demand and bypass steam to the TES systems to maintain reactor power at approximately 100%. Simulations of integral pressurized water reactor dynamics are run in a high-fidelity FORTRAN model developed at North Carolina State University. Both TES systems are developed as callable FORTRAN subroutines to model the time-varying behavior associated with different configurations of these systems when connected to the SMR simulator. Simulation results reveal the sensible heat storage system is capable of meeting turbine demand and maintaining reactor power constant while providing enough steam to power four absorption chillers for chilled-water production and storage. The stored chilled water is used to supplement cooling loads of an adjacent facility.

Technical and economic feasibility of development innovative technological solutions for expansion the adjustment range of high-power CCP

The analysis of technical and parametric constraints on the adjustment range of highpower CCP and recommended technological solutions in the technical literature for their elimination. Established that in the conditions of toughening the requirements for economy, reliability and maneuverability on the part of the system operator with the participation of CCP in control the frequency and power in the power system, existing methods do not ensure the fulfillment of these requirements.The current situation in the energy sector — the lack of highly manoeuvrable power equipment leads to the need participate in control of power consumption diagrams for all types of power plants, including CCP, although initially they were intended primarily for basic loads. Large-scale research conducted at the department of Automated control systems of technological processes, showed the possibility of a significant expansion of the adjustment range of CCP when it operating in the condensing mode and in the heating mode. The report presents the main results of these research for example the CCP-450 and CCP-450T. Various technological solutions are considered: when CCP in the condensation mode — the use of bypass steam distribution schemes, the transfer of a part of the steam turbine into a low-steam mode; when CCP operation in the heating mode — bypass steam distribution and the transfer CCP to gas turbine unit — power heating plants mode with the transfer the steam turbine to the motor mode. Data on the evaluation of the technical and economic feasibility of the proposed innovative technological solutions are presented in comparison with the methods used to solve this problem, which are used in practice, such as passing through the failures of the electric load graphs by transferring the CCP to the mode of operation with incomplete equipment. When comparing, both the economics, and the maneuverability and reliability of the equipment are considered.