Numerical simulation of fuel staged swirl combustion in the invert furnace of boiler on advanced ultra-supercritical steam parameters

The paper considers the schemes of Kuznetsky lean coal combustion for the M-shaped boiler. With such a boiler profile, it is possible to significantly reduce the length of main steamlines, which is especially important for the advanced ultra-supercritical parameters of the superheated steam. The furnace in this boiler unit is performed downward (invert). In this work, the aerodynamics of 6 combustion schemes was simulated by means of computational fluid dynamics. All considered schemes were designed on the basis of direct-flow burners and nozzles. For the most aerodynamically reasonable scheme the thermal processes in the boiler furnace firing Kuznetsky lean coal have been simulated by means of computational hydrodynamics. The simulation results showed a high efficiency of fuel burnout: loss due to unburned combustible equaled 0.1%, carbon-in-ash loss equaled 0.8%. Carbon monoxide concentration at the furnace outlet in conversion to excess air equal α = 1.4 amounted 226 mg/m3, the nitrogen oxides concentration in the flue gases (in conversion to normal conditions) equaled 424 mg/m3. It is appropriate to use the results obtained in this research in the development of new solid fuels combustion schemes.

FACTOR ANALYSIS OF THE THERMAL SCHEME OF CHP WITH SUPER CRITICAL STEAM CYCLE ON THE BASIS OF EXERGY METHOD

The most promising direction of CHP modernization is the introduction of power units on supercritical steam parameters. Increasing steam parameters is one of the most effective ways to increase the efficiency of a CHP plant. Thus, the development of the concept of thermal schemes turbines for supercritical steam parameters, taking into account the characteristics of their operation at the existing CHP Ukraine is an actual scientific problem. The solution to this problem will make it possible to replace or modernize the power generating equipment that has exhausted its resource with modern power units that meet world economic and environmental standards. The method of exergy analysis is adapted to the study of thermal schemes of CHP plants with supercritical steam cycle. As an example of application of a method the exergy analysis of the power plant working on the one-stage thermal scheme is carried out. Within the framework of the proposed method, a thermodynamic and topology-exergetic model of the power plant is created. Based on the topology-exergetic model the indicators of thermodynamic efficiency of the power plant operating on supercritical parameters of steam are determined. It is proposed to apply the theory of experiment planning in exergy analysis of the thermal circuit of a CHP. With the involvement of this theory, a multifactor numerical experiment was conducted to determine the impact on the exergetic efficiency of the thermal scheme of CHP of the main determining variable factors, such as adiabatic and thermal efficiency of the plant, as well as the operating parameters. The generalized equation of functional interrelation of exergetic efficiency of system and exergetic efficiency of elements of thermal scheme of CHP is received. The proposed equation can be used as a tool for further training of neural networks and their application both in the design and in the diagnosis of energy efficiency of CHP. According to the results of the factor analysis, a rather high conservatism of the considered one-stage scheme of CHP to the change of the varied parameters was revealed. This indicates the presence of more rigid structural links between the elements, which is generally a positive aspect of the reconstruction.

DEVELOPMENT OF CONCEPTUAL TECHNICAL SOLUTIONS AND METHODS OF THEIR IMPLEMENTATION DURING THE DESIGN OF A DUST COAL STEAM GENERATOR OF SUPER-SUPER CRITICAL PARAMETERS OF STEAM 28 MPa / 600 °С / 600 °C FOR 300 MW ENERGY UNIT. PART 2

In the second part of the work, using the mathematical model described in first unit, a direct-flow pulverized coal boiler with supercritical steam parameters of 28 MPa /600 °C /600 °C was calculated for a 300 MW power unit at loads of 50–70 %. It is shown that: a) the temperature of contaminated screens 1234 °С in the active combustion zone, where 92 % of the initial fuel burns out, is lower than the temperature of slagging beginning (1268 °С) of ДГ-100 coal, which indicates the slag-free operation of the screens of the lower radiation part (LRP) b) over the entire range of the boiler load change of 50–100 %, the temperature at the exit from the active combustion zone will be higher than the minimum permissible temperature of 1250 °C, below which the flame is attenuated; c) upon transition to 50 % load, the temperature of gases at the outlet from the active combustion zone decreases from 1506 °C to 1342 °C, as a result of which the specific thermal stress of the LRP screens decreases by 1.469 times, while the feed water consumption at the inlet of the boiler falls by 2 times, which leads to an increase in the temperature of the LRP steam, the middle and upper radiation parts, screens of the ceiling and rotating chamber; d) to reduce the thermal stratification of the inlet stage of the secondary steam superheater (ППП1), and as a consequence, the pipe wall temperature, it is necessary to divide the ППП1 surface into two packets, installing an intermediate mixing manifold between them with full steam mixing. Bibl. 5, Fig. 13, Tab. 3.

DEVELOPMENT OF CONCEPTUAL TECHNICAL SOLUTIONS AND METHODS OF THEIR IMPLEMENTATION DURING THE DESIGN OF A DUST COAL STEAM GENERATOR OF SUPER-SUPER CRITICAL PARAMETERS OF STEAM 28 MPA/600 °С/600 °С FOR 300 MW ENERGY UNIT. PART 1.

Increasing efficiency of power plant unit, reducing fuel costs, and CO2, NOx and SOx emissions can be achieved by increasing the pressure and temperature of the steam. Analysis carried out for boilers designed for supercritical steam parameters, showed that the increase in pressure and temperature is directly related to the stresses arising in the metal of the superheater, and, consequently, with the need of using high-temperature alloys. Thus, steam generators can be conventionally divided into three groups: supercritical (SC), super supercritical (SSC) and ultra supercritical (USC). The efficiency of the power units of the USC is 3–4 % higher than the efficiency of the SC units, and the efficiency of the power units of the USC is 6–8 % higher than the efficiency of the SC units. For the manufacture of USC boilers, steels based on nickel alloys are required, which are mainly at the stage of development and testing, while for the production of SSC steam generator, steels are manufactured on an industrial scale, therefore, currently, the best option is the construction of SSC power unites. The first part of the work describes the calculation method, the algorithm and the program with the help of which the design and verification thermal calculations of the SSC 28 MPa/600 °С/600 °С were carried out for a 300 MW power unit at rated loads. Two designs of vortex burners (coiled-blade and blade-blade) with a thermal power of 34.471 MJ/s and productivity (for coal) of 5902 kg/h have been developed. Original technical solutions have been developed to improve the reliability of the live steam output stage and to reduce the surface of the first stage of the reheater. Bibl. 5, Fig. 4, Tab. 1.

Efficiency of operation of 300 MW condensing thermal power blocks with supercritical steam parameters in sliding pressure mode

The previous research of the application of sliding pressure has shown certain advantages in the operation of high-power condensing blocks with supercritical steam parameters in sliding pressure mode in comparison to the one with constant pressure. The maintenance of stable temperature regime and thermal expansion of turbine elements, prolongation of service life of materials of steam pipes and heating surfaces of the boiler due to the decrease in pressure of the working medium are only some of those advantages. On the other hand, the operation mode of a condensing block with sliding pressure is characterized by the change in cost-effectiveness. The result of this change is mainly due to the de-crease of steam throttling in the turbine's balancing valves and the increase of its internal action in a high pressure turbine, then also due to reduced steam consumption of the feed turbo pump just like a drop in the feed water pressure at the steam boiler inlet. A model has been developed within the framework of this study that follows such changes and their graphical interpretation is provided. The analysis results show that switching 300 MW blocks from the constant to the sliding pressure regime in the 30-60% load range increases the block efficiency respectively by 6.70-1.05%.

STEAM TURBINE DEVELOPMENT FOR SUPERCRITICAL STEAM PARAMETERS

The paper reports the expediency and substantiation of the necessity for the gradual transition to power units on supercritical stream parameters in world power engineering. Basic stages in the development of steam turbine manufacturing with supercritical steam parameters are considered. The parameter increase at the input makes a profound impact upon the design of a flowing part of turbines. To operate a great difference in enthalpies in a cylinder without changing stages number one has to modernize them and sometimes to change the design completely. In the paper there is considered the expediency of the application of axial highloaded stages developed by the Polytechnics of Leningrad (LPI). There are also described the stages of designing steam turbine plants with critical and supercritical steam parameters at the input in a turbine. As an example there is analyzed SKR-100-300 steam turbine with the initial steam parameters of 29.4MPa and 650S. The results of solution computations directed to the efficiency increase of a regulatory stage of K-300-240 steam turbine with supercritical parameters of 580C and 29.0 MPa are presented. The application as a profile of an impeller the blade design of LPI allows increasing turbine plant efficiency in a wide range of mode parameters and also reducing a general number of turbine stages.