Steam Parameters Research Articles

New synthetic route for the production of mayenite support to enhance Ni resistance to coke deposition in the reforming of tar model compounds

Four nickel/mayenite catalysts were synthesized. Mayenite was prepared from different precursors, namely boehmite (AlO(OH)) + Ca(NO3)2·4H2O and gibbsite + Ca(OH)2, for each couple a specific procedure was followed. The effect of the Ni addition method was also evaluated, comparing wet impregnation and direct inclusion of nickel precursor during mayenite preparation. The obtained catalysts were characterized by XRD, BET, SEM/EDS and TPR. The Ni/mayenite catalysts were tested in steam reforming of toluene and pyrocatechol, chosen as tar model compounds. The experiments were conducted in a fixed-bed lab-scale atmospheric reactor, evaluating carbon conversion, hydrogen selectivity and stability. Characterization of the spent catalysts after toluene steam reforming experiments by XRD and DTG-TPO were performed to assess structural changes and carbon deposition. Kinetic parameters of toluene steam reforming were determined for the different catalysts.

Оптимизационные исследования угольного энергоблока на повышенные параметры пара мощностью 660 мвт

This paper carries out optimization studies of the 660 MW coal-fired power unit for elevated steam parameters by the criterion of maximum net efficiency and minimum specific investment. The dependence between the power unit efficiency and the lowest specific investment is built. Taking into account the need for accounting a large number of coal-fired power unit parameters the optimization studies were carried out using gradient methods of nonlinear mathematical programming. Due to the large number of calculations the computerized programming system (CPS) computational environment is used. The maximum efficiency obtained as a result of optimization calculation is 47.74%. The corresponding specific investment equals 3545.7 $/kW and the initial steam parameters are 35.4 MPa, 657/613 о С. The minimum specific investment is 1884.6 $/kW. The corresponding efficiency equals 42.08%. The initial steam parameters are 15.5 MPa, 613/540 о С. The 660 MW coal-fired power unit was optimized for elevated steam parameters by the criterion of maximum net efficiency and minimum specific investment. The dependence of the minimum specific investment on power unit net efficiency was obtained. It is shown that the minimum specific investment was obtained at low pressure and relatively high temperature of the main steam.

Influence of parameters of superheated steam on combustion of liquid hydrocarbons

The main characteristics of liquid hydrocarbon combustion in a jet of superheated steam were studied. The influence of main physical parameters of steam flow on combustion parameters (temperature distribution in flame, generated heat power, combustion products composition) were measured for the original burner apparatus.

Prospects of Application of Dual-Fuel Combined Cycle Gas Turbine Units

Dual-fuel combined cycle gas turbine units, including power units on the parallel scheme with predominant coal combustion are considered in the paper. The basic equations for determining the energy efficiency of dual-fuel combined-cycle power units are described. The interdependence of the efficiency of the gas turbine and steam turbine parts of the combined-cycle plant for the efficiency of the combined-cycle plant with a variable binary coefficient is presented. It is shown that 55-56% efficiency is achievable for parallel type combined cycle gas turbine units T with predominant solid fuel combustion on the basis of this interdependence between efficiency and binary coefficient. Comparison of competitiveness in the ratio of fuel prices for gas / coal with traditional coal technology and theoretical rejected combined cycle gas turbine units with an efficiency of 60% for dual-fuel combined cycle gas turbine units with the implementation of the Rankine cycle for subcritical (13 MPa) and supercritical (24 MPa) steam parameters is carried out. It is shown that the dual-fuel combined cycle gas turbine units are preferable to traditional coal steam turbine power units in the case when the ratio of the price of fuel does not exceed 5, binary rejected combined cycle gas turbine units, when the ratio of the prices by more 0,5.

Air staging application effects on overall steam boiler operation

This paper presents the results of calculation system of main processes in power steam boiler, before and after application of air staging. Modified air injection scheme was implemented during 2015 on the power steam boiler within unit 1 of TPP Kostolac B. Measurements performed on site showed that applied reconstruction led to a permanent loss of the steam boiler power. This study was performed in order to define the cause of such an occurrence and to consider the possibility for regaining the designed steam parameters along with keeping NO concentration in prescribed limits. This paper x discusses the influence of repositioning the air injection location on processes within the furnace. Furthermore, the influence of the redistribution of injected air-flow along the furnace height on important boiler operation parameters has been analyzed. Analysis showed that, with appropriate dosing of air along the height of the existing furnace, it is possible to achieve the optimum of the boiler's operation parameters. Results of research showed that air staging throughout the furnace height in best test case additionally reduces NO concentration (195-225 mg/Nm3) and increases the power of x considered boiler (828.8-751.1 MW) with an insignificant decrease of the boiler's efficiency (86.27-86.77%). Furthermore, the designed temperatures of superheated (540-498?C) and reheated (540-518?C) steam have been reached again, whereby the safety of the boiler's operation has been significantly increased. Results of this study improve the present explanation of the processes occurred in the furnace with applied primary measures. They also give directions on defining the most influential parameters on considered processes with the final purpose to increase the efficiency and availability of the entire plant.

Method of calculating the critical share of combined power generation at CHPP

AnnotationThe paper presents analysis of the value of absolute fuel saving due to combined heat and power generation as illustrated by the regional power supply system based on the steam turbine combined heat and power plants (CHPP) of the Volga region. It is established that the most part of the plants operate with negative fuel saving from cogeneration (heat extraction) due to high physical deterioration of the equipment, low initial steam parameters at certain CHPPs, low load of the turbine heat extractions, and large condensation power generation. Positive fuel saving can be obtained if the actual share of heat-extraction power generation (cogeneration) exceeds its critical value. The authors offer a method of determining the critical value of combined generation share depending on the total amount of electric power generated by CHPP. The paper contains calculations for determining the critical share of combined power generation for turbines T-55-130, T-110-130 and T-250-240. The method offered can be used when planning the load of CHPP turbines for ensuring the positive value of fuel saving due to combined heat and power generation at CHPPs.

Experimental Studies of Honeycomb Seals with Wavy Ridges on the Rotor

During steam turbine operation in transient modes, contact in labyrinth seals is possible. To avoid such contact in the regular stepped labyrinth seals, specialists of the Ural Turbine Works upgraded the end seals during major repairs in several T-250/300-23.5 type turbines of PAO Mosenergo: the regular seals on the rotor were replaced by straight-flow honeycomb seals with wavy ridges. After this upgrading, there were a reduction of air suctions through the end seals of low-pressure cylinder, the normalization of the ejector operation, and oil watering reducing. However, by these indirect indices, it is impossible to evaluate the actual change of leakages through upgraded seals. Therefore, the comparative experimental studies of flow and dynamic characteristics of the straight-flow seals with classic straight and wavy ridges were implemented. According to the investigation results, the flow characteristics of all studied models of straight-flow seals during transition from classical straight ridges to wavy ones deteriorated. The measurements of nonconservative components of the force in the seal models also revealed a deterioration of dynamic characteristics of the models of straight-flow seals during transition from straight ridges to wavy ones. In the end seals, increasing the nonconservative forces capable to cause a self-excited vibration of the shafting of the steam-turbine plant (STP) does not pose a threat owing to their low magnitude. However, in diaphragm seals, especially in the high-pressure section of STP to the supercritical steam parameters, using new honeycomb straight-flow seals with wavy ridges requires special caution, since these forces reach the highest values in the region of high pressures and are capable, in combination with the overbandage forces and forces arising in the oil layer of bearings, to cause low-frequency self-excited vibrations of shaftings. Taking into account that the level of nonconservative forces in the regular stepped seals is by 20% less than in the straight-flow seals, the transition to the straight-flow honeycomb seals with wavy ridges on the rotor in the diaphragm seals appears inappropriate.

On effect of rhenium on mechanical properties of a high-Cr creep-resistant steel

9–12%Cr martensitic steels are perspective materials for critical components of new high-efficiency power plants working at ultra-supercritical parameters of steam. Addition of 0.2% rhenium in the experimental steel improved the short-term creep strength at 650 °C. Comparison of kinetics of tungsten depletion from the matrix in different high-Cr martensitic steels showed that rhenium in the experimental 10Cr-3Co-3W-0.2Re steel did not lead to retaining an increased amount of solute W in the ferritic matrix during both aging and creep at 650 °C. At the same time, the precipitation of the high fraction of the fine Laves phase particles provided the effective particle strengthening.

COMPARATIVE ENERGY AND EXERGY ANALYSIS OF A POWER PLANT WITH SUPER-CRITICAL AND SUB-CRITICAL

The aim of this study that how to effect live steam parameters reheat and feed water preheater numbers on efficiencies of energy and exergy at coal-fired power plants. Moreover, two desuperheaters and a regenerative turbine are added USCPP (Case 3) to approach best results. Soma Power Plant (Case 1) consists of one reheat stage, two HPRHs and four LPRHs with one DEA. It is operated sub-critic and coal is used for a fuel. Live steam conditions of Soma Power Plant set at 13,92 MPa and 540 °C, and the reheat steam is reheated to 540 °C. Supercritical Power Plant (Case 2) consists of the same main components of Case 1. However, steam parameters of Case 2 are increased to 262.5 Bar and 600 °C to determine impact of the steam parameters on power plant efficiencies. USCPP which consists of two reheat stages, four HPRHs, six LPRHs with one DEA is designed to generate live steam under nominal conditions of 30 Bar and 600 °C. Besides, reheat steam are heated to 620 °C. Simulations have been carried out Ebsilon Professional software and pressure drops at preheaters and reheats are also considered. Some assumptions are made in the analysis. The thermal and exergy efficiencies of USCPP increase by 9.241 and 8.06 percentage points compared with Soma power plant, respectively. The results of this study that live steam parameters which are increased from sub-critical values to super-critical values have enormous influence on energy and exergy efficiencies. Secondly, adding second reheat stage has positive impact to improve power plant efficiencies. Finally, augmenting feed water preheater number, adding two desuperheater and one regenerative turbine increase power plant efficiencies. However, optimum numbers of feed water preheaters are determined considering economic parameters.

Heat transfer trait simulation of H finned tube in ventilation methane oxidation steam generator for hydrogen production

With the steam obtained by the energy released from ventilation air methane oxidation, the hydrogen production through gasification method is considered more commercial. In order to constrain the steam parameter fluctuation, the shunt honeycomb ceramics are adopted to fill between the heat exchange tubes. However, transient heat transfer characteristics of this kind of heat exchanger have not been fully studied. This paper carried out a numerical simulation study on the transient heat transfer characteristics of H finned tube under periodic reverse-flow conditions. Results show that the existence of shunt honeycomb ceramics enhances the effect of radiation. Gas flow direction reversing destructs the original boundary layer, achieving a sudden rise of the convective heat flux in the new upstream. It takes about 12s to form a new relative stable boundary layer. The apparent heat transfer coefficient achieves a maximum of 108.77 W m−2 K−1 and an average of 99.1 W m−2 K−1.

Environmental evaluation of Waste to Energy plant coupled with concentrated solar energy

Life Cycle Assessment (LCA) was applied to evaluate the environmental impact of a hybrid energy system based on the integration of a Waste to Energy plant with concentrated solar energy plant. In the Waste to Energy (WtE) section only saturated steam is produced, while the superheating takes place in an external superheater fed by the concentrated solar energy or, when this is not enough, by a natural gas backup boiler. Different couples of pressure and temperature, for the superheated steam (51 bar, 440 °C; 60 bar, 480 °C; 70 bar, 520 °C), different values for the solar multiple (1.5, 2.0 and 2.5) and different values for the thermal storage capacity (6 h, 10 h and 14 h) were considered, leading to 27 possible cases. Construction, operation and end-of-life phases were included in the LCA system boundary. Calculated global warming indicator, in kg of equivalent CO2 per MJ of produced electricity, slightly decreases for increasing steam parameter cases and for increasing storage hour cases, while a more relevant reduction was observed for increasing solar multiple values. The main contribution to global warming derives from the operation phase of the WtE part (67-86% of the operation), while the remaining part (14-33%) is given by the solar section, for which, in turn, the main contribution is the impact deriving from the natural gas combustion in the backup boiler.

CHALLENGES AND OPPORTUNITIES OF UTILIZATION OF ASH AND SLAG WASTE OF TPP (THERMAL POWER PLANT). PART 2

For existing and already constructed coal TPP plants, known methods of utilization of fly ash and slag wastes (FASW) may be in de­mand when all emerging environmental and economic risks are taken into account. But for the new power generating source when choosing coal combustion technology, it is necessary to increase the significance of the environmental component of the project more essentially. It is known that the most promising technologies for coal combustion, which increase environmental safety exactly by burning, are technolo­gies based on a circulating fluidized bed. These technologies can sig­nificantly reduce sulfur and nitrogen oxide emissions behind the boiler, but the solution to the problem of flay ash and slag waste remains at the same level. It is proposed to solve the problem of FASW utilization during the implementation of new energy projects or when replacing the decommissioning capacities of coal generation by replacing the method of coal combustion in a stream or fluidized bed with meth­ods of burning solid fuel in a bubbling slag melt. The descriptions and schemes of these methods are given. The comparison of the main qual­itative technical and ecological parameters of pulverized coal combus­tion and technologies of coal combustion in slag melt is presented. The development of coal generation is expected in two main areas: coal combustion with increasing steam parameters and gas generation with a combined cycle of electricity generation: steam and gas, based on the gasification of solid fuels. These directions will allow achieving electric efficiency of steam-power plants from 30 – 36 %, up to 44 – 45 % on supercritical steam parameters, and using a combined steam-gas cycle up to 50 – 55 %. A technological scheme of gasification of coal in a slag melt is proposed, which increases the electrical efficiency of the installation. The ecological and economic efficiency of the gasifica­tion method for solid fuel and the simplicity of the production of slag products by casting are shown. The quality of cast slagstone products is much higher than similar cement-sand products with the addition of fly ash, and the ease of transition from one casting mold to another allows quickly responding to market demands.

Increasing operational flexibility of supercritical coal-fired power plants by regulating thermal system configuration during transient processes

The operational flexibility of traditional coal-fired power generators has played crucial parts in many countries given the continuous integration of intermittent and fluctuant renewable power resources in their power system. This study is aimed at improving the short-term operational flexibility of thermal power units. The transient simulation models of a 660 MW supercritical coal-fired power system are developed by using the GSE software, and the six measures of regulating thermal system configuration, which can rapidly activate thermal storages in thermal systems, are introduced and compared. The greatest potential mode in each measure of regulating thermal system configuration is obtained on the basis of the utilization degree of the internal thermal storages. The dynamic characteristics of the thermal parameters of the selected measures are compared, and the results reveal that the measures of regulating extraction steam from low-pressure heaters has less negative effects on the live and reheat steam parameters but greater negative effects on the deaerator and condenser parameters than the measures of regulating extraction steam from high-pressure heaters. Moreover, the performance indexes of operational flexibility are also evaluated for all the measures of regulating thermal system configuration. Among five measures applied in the power-up process, the values of power ramp rate are from 1.26% to 6.31% of rated power per minute, the values of power capacity are from 12.87 to 48.35 MW, and the values of energy capacity during the regulating time of 120 s are 1009.73 to 5048.93 MJ. However, the measure of condensate water increasing of low-pressure heaters is an only way suitable for the power-down regulation process, and the value of power ramp rate is 0.61% of rated power per minute, the power capacity is −5.65 MW, and the energy capacity is −483.84 MJ. The best regulating measures are obtained on the basis of the different perspectives of operational flexibility. The findings of this study can help determine the best operational control strategies in different situations.

Unitized Power and Heat Generating Steam–Gas Plant

This paper considers the prospects of creating steam–gas thermoelectric plants for power supply to microdistricts and towns remote from centralized power plants. We propose a new type of thermoelectric plants with a waste heat boiler of medium steam parameters and an afterburner section located between its evaporation stages. It has been shown that fuel afterburning increases electric and thermal power and the specific electric power production at heat consumption.

Processing Ash and Slag Wastes from Thermal Power Stations. Part 2

For existing coal-fired power plants, current methods of utilizing ash and slag waste may be considered in addressing new environmental and economic risks. However, for new power sources, environmental considerations are much more important in selecting the coal-combustion technology. Technology based on a circulating fluidized bed is sometimes cited as the most promising approach to environmentally sound coal combustion. It permits significant decrease in emissions of sulfur and nitrogen oxides beyond the boiler, but is of no help in processing ash and slag waste. For waste disposal, a different approach is recommended for new plants or the upgrading of coal-fired plants: instead of coal combustion in a gas flux or a fluidized bed, combustion in bubbling slag melt. Such methods are described. The basic characteristics of pulverized-coal combustion and combustion in slag melt are compared. Two basic approaches to the development of coal-based power generation are proposed: coal combustion with supercritical steam parameters; and gas generation with a hybrid (steam + gas) power-generating cycle based on gasification of solid fuels. The electrical efficiency of steam-based plants may be increased from 30–36 to 44–45% with supercritical steam parameters; and to 50–55% when using a hybrid steam–gas cycle. The proposed industrial system for coal gasification in slag melt increases the overall electrical efficiency. The environmental and economic efficiency of carbon gasification is demonstrated. It is simple to produce components from slag by casting. The cast slag–coal components are of considerably higher quality than analogous cement–sand components with added fly ash. The ease of switching from one type of casting to another permits rapid response to market demand.

Methodology and mathematical model with the continuous time for the selection of the optimal power of the gas turbine set for the dual fuel gas-steam combined cycle in a parallel system

Technological rationality with regard to the use of existing coal resources in power sector is based on the use of so-called clean coal technologies. One of them is the dual fuel gas-steam combined cycle technology, which couples the Joule gas turbine cycle with the Clausius-Rankine cycle of the steam turbine. Systems coupled in parallel of such units, apart from the construction of new power plants, has a large modernization potential for already existing combined heat and power plants and coal-fired power plants. Dual fuel systems may in fact be the result of a gas turbine repowering of the existing thermal coal structures. This paper presents technical and economic calculation results for various investment outlays, when the steam part works with supercritical and subcritical parameters of fresh steam, assuming different efficiency of the Clausius-Rankine cycle. Figures were obtained using innovative methodology and mathematical models of total NPV profit, discounted for the current moment achieved from the operation of the dual-fuel gas-steam power unit with a continuous time. Results are presented for a wide range of changes in prices of energy carriers and environmental charges, such as the CO2 emission allowances, including current prices level and fees.

Economic analysis of heat production in existing medium size combined heat and power plant, with respect to the CO2 allowances purchasing cost

This paper presents mathematical modeling and economic analysis of a medium size combined heat and power (CHP) operation, installed in Poland. The plant is equipped with steam boilers, extraction condensing turbine, and the grade type water boilers. The paper determines the most efficient mode of CHP operations. The economic efficiency analysis is performed for transient seasons, characterized by low demands for heating, which obliged production units to operate out of its nominal conditions at a lower efficiency. The developed method is also suitable for analyzing complex power plants, with a few energy equipments.The developed mathematical model for simulating CHP performance gives the possibility to select the boiler type, and assess the probability and efficiency of each configuration. The dedicated tool calculates the selected operation mode, heating power demand, and enables models comparison. The algorithm includes real equipment operational parameters, technical limitations, actual energy prices and costs regarding energy law acts. The performed analysis is up-to-date, due to a few aspects: permanently increased fossil fuels costs, low electric energy prices, growing costs of CO2 emission allowances, and high electricity production cost on turbine’s condensing section at steam parameters of T = 435 °C and p = 34 bar. A detailed cost analysis is performed on each product separately: thermal energy, electric energy from cogeneration and electric energy from condensation, during every hour, frequently. The calculation is carried every an hour for a period of 24 h, the energy balance is ensured during the calculation. The most important result of this study is a comparison of CHP to water boiler operation profitability, also including the net profit comparison. Furthermore, the cost of the CO2 emission is studied, for the production profitability in two scenarios, as the price increases from 7 EUR/tone to 15 EUR/tone and 30 EUR/tone.

Numerical investigation on the effects of steam and water parameters on steam jet condensation through a double-hole nozzle

Steam jet condensation through multi-hole nozzles in a pressure relief pool is important for the design and safe operation of a nuclear reactor system. In this study, stable steam jet condensation through a double-hole nozzle was investigated at different water temperatures and steam pressures by CFD method. Simulation results indicated that the shape of steam cavity changed from conical to ellipsoidal with an increase in water temperature and steam pressure, and steam jet length gradually increased. Meanwhile, the interaction between two steam cavities was enhanced and they even merged under certain conditions. Expansion and compression waves were found by analyzing the thermal hydraulic parameters along the hole centerline. Water temperature and steam pressure exerted different effects on the intensity of expansion/compression waves and the positions of maximum expansion/compression. Finally, thermal hydraulic parameters along the nozzle centerline were analyzed. Steam volume fraction, temperature, and velocity initially increased and then decreased as axial distance increased, which appeared as evident peaks under the present conditions. When water temperature and steam pressure increased, the peak values of steam volume fraction, temperature, and velocity gradually increased and their positions moved downstream.

Development and Deployment of Welding Technologies for the Indian Sodium-Cooled Fast Reactor and Advanced Ultra Super Critical Thermal Power Programmes

Robust manufacturing technology for Sodium-cooled Fast Reactor (SFR) components necessitates development of various research-backed innovative welding technologies. Prior to the start of construction of the 500 MWe Prototype Fast Breeder Reactor, extensive technology development was planned and implemented for development of welding consumables, procedures and technologies for fabrication of components with stringent specifications. With close interaction amongst design, materials and non-destructive evaluation engineers, materials and welding consumable manufactures, and the fabrication industries, it has been possible to overcome the challenges and establish robust manufacturing technologies for fabrication of all the structural components. Extensive welding is involved in the fabrication of reactor vessels, steam generators, fuel sub-assemblies etc. Further, Activated Tungsten Inert Gas (A-TIG) welding process, along with activated flux developed in-house, has been successfully implemented on various SFR-related components. Also, a computational-intelligence based welding system for online monitoring and control during welding has been developed for obtaining near defect-free welded components. Plasma Transferred Arc Welding process has been deployed for deposition of the chosen nickel-base alloy for hardfacing of SFR components, which require improvement in resistance to high temperature wear, especially galling, of mating surfaces in liquid sodium. To reduce carbon footprint substantially, India has initiated a national mission programme of design, development and establishment of 800 MWe Advanced Ultra Supercritical (AUSC) power plant having steam parameters of 710°C / 720°C / 310 bar. Materials and fabrication technologies play decisive roles in the success of such mission project. For this purpose, two important India-specific high-temperature tube materials, 304HCu austenitic stainless steel (304HCu SS) and modified Alloy 617M, as also large cylindrical forgings of Alloy 617M of up to 800 mm diameter for turbine rotors have been indigenously developed. Development of welding consumables and welding procedure has also been established for TIG welding of the tubes, including the 304HCu SS/Alloy 617M dissimilar joint. Based on the tensile and creep tests properties, welding consumables for the tubes and their dissimilar joint have been finalized. Technology for dissimilar metal welding between Alloy 617M and 10Cr-steel forgings for turbine rotors has also been developed. Using narrow-gap TIG welding process, the dissimilar metal weld between 200 mm Alloy 617M and 10Cr-steel have been produced by directly welding the two forgings using Alloy 617 filler wire. The weld exhibited no lack-of-penetration defects and passed dye-penetrant, radiographic and ultrasonic examinations. Similarly procedure for NG welding of superheater headers has also been demonstrated. The details of the Indian efforts towards development and deployment of welding technologies for application to the fabrication to components for the Indian programmes for SFR-based nuclear power and AUSC thermal power plant are presented and discussed.

Exergo-Ecological Assessment of Waste to Energy Plants Supported by Solar Energy

Hybridization of Waste to Energy (WtE) plants with solar facilities can take competing energy technologies and make them complementary. However, realizing the benefits of the solar integration requires careful consideration of its efficiency. To analyse such systems from the point of view of resource efficiency, the pure energy analysis is not sufficient since the quality of particular energy carriers is not evaluated. This work applies the exergo-ecological analysis using the concepts of thermoecological cost (TEC) and exergy cost for the performance evaluation of an integrated Solar-Waste to Energy plant scheme, where solar energy is used for steam superheating. Different plant layouts, considering several design steam parameters as well as different solar system configurations, in terms of area of heliostats and size of the thermal storage tank, were studied. The results for the solar integrated plant scheme were compared with the scenarios where superheating is performed fully by a non-renewable energy source. The presented results of exergy cost analysis indicate that the most favorable system is the one supported by non-renewable energy. Such an analysis does not consider the advantage of the use of renewable energy sources. By extending the system boundary to the level of natural resource and applying the thermoecological cost analysis, an opposite result was obtained.