Cogeneration Steam Turbine Research Articles

MATHEMATICAL MODELS OF COGENERATION STEAM TURBINES BASED ON EXPERIMENTAL CHARACTERISTICS OF TURBINE STAGES AND COMPARTMENTS

The article covers approaches to building the mathematical models of cogeneration steam turbine units. The objective of this work is the development, justifi cation and practical implementation of methods of mathematical modeling of cogeneration steam turbines for solving research problems and improving the energy effi ciency of the CHP. The use of normative characteristics to solve these tasks, which require the calculation of variable modes, in most cases turns out to be unjustifi ed, due to a number of their signifi cant shortcomings. It is shown that the application of the developed mathematical models based on experimentally determined fl ow and power characteristics allows to solve various practical tasks arising during operation. We have given an example of constructing a computational mathematical model of a T-50-12.8 type turbine. The method of construction of this model is described, which consists of a large number of nonlinear equations (over 50), and an enlarged block diagram of calculations for this turbine (using the modernized Newton method with a step change of the iteration process in several variables) is provided. The method of calculating an arbitrary turbine compartment or a stage using some experimental fl ow and power characteristics is given as part of the general algorithm. A method for calculating the LPH-1 regenerative heater is also given as an example. It is shown how similar models of other equipment can be developed on the basis of the described mathematical model. The article provides examples of the use of mathematical models of turbines for solving problems of determining the most economical and safe operating modes and preventing ineffi cient solutions. The obtained results allow to determine the optimal operating modes of real CHP equipment and calculating their absolute and comparative energy efficiency.

All-regime combined-cycle plant: Engineering solutions

The development of distributed power generation systems as a supplement to the centralized unified power grid increases the operational stability and efficiency of the entire power generation industry and improves the power supply to consumers. An all-regime cogeneration combined-cycle plant with a power of 20–25 mW (PGU-20/25T) and an electrical efficiency above 50% has been developed at the All-Russia Thermal Engineering Institute (ATEI) as a distributed power generation object. The PGU-20/25T two-circuit cogeneration plant provides a wide electrical and thermal power adjustment range and the absence of the mutual effect of electrical and thermal power output regimes at controlled frequency and power in a unified or isolated grid. The PGU-20/25T combined-cycle plant incorporates a gas-turbine unit (GTU) with a power of 16 MW, a heat recovery boiler (HRB) with two burners (before the boiler and the last heating stage), and a cogeneration steam turbine with a power of 6/9 MW. The PGU-20/25T plant has a maximum electrical power of 22 MW and an efficiency of 50.8% in the heat recovery regime and a maximum thermal power output of 16.3 MW (14 Gcal/h) in the cogeneration regime. The use of burners can increase the electrical power to 25 MW in the steam condensation regime at an efficiency of 49% and the maximum thermal power output to 29.5 MW (25.4 Gcal/h). When the steam turbine is shut down, the thermal power output can grow to 32.6 MW (28 Gcal/h). The innovative equipment, which was specially developed for PGU-20/25T, improves the reliability of this plant and simplifies its operation. Among this equipment are microflame burners in the heat recovery boiler, a vacuum system based on liquid-ring pumps, and a vacuum deaerator. To enable the application of PGU-20/25T in water-stressed regions, an air condenser preventing the heat-transfer tubes from the risk of covering with ice during operation in frost air has been developed. The vacuum system eliminates the need for an extraneous source of steam for the startup of the PGU-20/25T plant. The vacuum deaerator provides prestartup deaeration and the filling of the entire condensate feed pipeline with deaerated water and also enables the maintenance of the water temperature before the boiler at a level of no lower than 60°C and the oxygen content at a level of no higher than 10 μg/L during operation under load. The microflame burners in the heat recovery boiler enable the independent adjustment of the electrical power and the thermal power output from the PGU-20/25T plant. All the innovative equipment has been tested on experimental prototypes.

Substantiation of the cogeneration turbine unit selection for reconstruction of power units with a T-250/300-23.5 turbine

The selection of a cogeneration steam turbine unit (STU) for the reconstruction of power units with a T-250/300-23.5 turbine is substantiated by the example of power unit no. 9 at the cogeneration power station no. 22 (TETs-22) of Mosenergo Company. Series T-250 steam turbines have been developed for combined heat and power generation. A total of 31 turbines were manufactured. By the end of 2015, the total operation time of prototype power units with the T-250/300-23.5 turbine exceeded 290000 hours. Considering the expiry of the service life, the decision was made that the reconstruction of the power unit at st. no. 9 of TETs-22 should be the first priority. The main issues that arose in developing this project—the customer’s requirements and the request for the reconstruction, the view on certain problems of Ural Turbine Works (UTZ) as the manufacturer of the main power unit equipment, and the opinions of other project parties—are examined. The decisions were made with account taken of the experience in operation of all Series T-250 turbines and the results of long-term discussions of pressing problems at scientific and technical councils, meetings, and negotiations. For the new power unit, the following parameters have been set: a live steam pressure of 23.5 MPa and live steam/reheat temperature of 565/565°C. Considering that the boiler equipment will be upgraded, the live steam flow is increased up to 1030 t/h. The reconstruction activities involving the replacement of the existing turbine with a new one will yield a service life of 250000 hours for turbine parts exposed to a temperature of 450°C or higher and 200000 hours for pipeline components. Hence, the decision has been made to reuse the arrangement of the existing turbine: a four-cylinder turbine unit comprising a high-pressure cylinder (HPC), two intermediate pressure cylinders (IPC-1 & 2), and a low-pressure cylinder (LPC). The flow path in the new turbine will have active blading in LPC and IPC-1. The information is also presented on the use of the existing foundations, the fact that the overall dimensions of the turbine unit compartment are not changed, the selection of the new turbine type, and the solutions adopted on the basis of this information as to LPC blading, steam admission type, issues associated with thermal displacements, etc.

Thermoeconomic modeling for CO2 allocation in steam and gas turbine cogeneration systems

Thermoeconomics is a discipline that connects Thermodynamics and Economics concepts, usually used for rational cost assessment partition to the final products of a thermal plant, by means of a model that describes the cost formation process of the overall system. Generally, exergy or monetary costs of the external resources are distributed to the final products. However, environmental consideration can be incorporated in the models to calculate the environmental costs, such as specific CO2 emission of each final product. This work aims at showing how the thermoeconomic models can be adapted to allocate the overall CO2 emission of four different gas and steam turbine cogeneration systems to the final products (net power and heat), in order to determine the specific CO2 emissions (in g/kWh) of each product. This subject is important in applications of Life Cycle Assessment encompassing processes with two or more products and also in quantifying the cogeneration environmental advantage. This paper also reveals that any thermoeconomic model can be easily adapted for allocation of the overall CO2 emissions or any other pollutant to the final products of a cogeneration or multi-product plant.

Energy Saving through Implementation and Optimization of Small and Medium Scale Cogeneration Technology

<p>Cogeneration or Combined Heat and Power (CHP) is defined as the sequential generation of two different forms of useful energy from a single primary energy source.This paper deals with a comparison study on the aspects of energy efficiency and energy economics in commercial building and industrial plant utility using conventional system and cogeneration system. This study presents the performance test result of micro turbine cogeneration application (60 kW) pilot project in comercial building and optimization of existing cogeneration system (40 MW) at utility plant of industry. The micro turbine cogeneration application for generating electricity and hot water while médium scale of gas turbine cogeneration is introduced in order to improve plant efficiency of existing steam turbine cogeneration. We found that cogeneration would be a financially viable option for building and for small and large size industrial plants. </p><p><strong>Key words</strong>: Cogeneration; energy efficiency; gas turbine; microturbine; steam turbine.</p>

Results of Mathematical Modeling to Study the Influence of Accounting the Process Moisture on Energy Indicators of Cogeneration Steam Turbines

The article proposes and being tested a methodology that allows using the mathematical model developed to clarify the possible impact of a precise process moisture measurement on the performance of energy efficiency of the cogeneration turbines.

Направления совершенствования конструкции цилиндра высокого давления теплофикационных паровых турбин семейства Т-100-130

Направления совершенствования конструкции цилиндра высокого давления теплофикационных паровых турбин семейства Т-100-130

Economic effectiveness of using super-high values of initial steam parameters in cogeneration power units

The present paper reports the results of numerical investigations into both thermodynamic and economic components of the effect of an increase in the initial steam parameters to super-high values for cogeneration power units. As an initial variant, the heat flow diagram of the turbine plant equipped with the T-250/300-23.5 TMZ steam turbine was adopted. In the course of investigations, the ranges of initial steam pressure p0 = 23.5–30.0 MPa, steam temperature t0 = 540–600°C, and steam pressure after single reheat prh = 3.6–4.5 MPa were considered. In the calculations of the thermodynamic efficiency, the extent of the effect of an increase in steam parameters on the out and the electric efficiency of a power unit when a cogeneration steam turbine operates in condensing and heat-extraction modes were estimated. In the economic part of the calculations, indicators of the commercial efficiency of investments into appropriate projects and the levels of total investment and production costs were determined. The results of the calculations made it possible to estimate the optimum level of super-high values of the initial steam parameters for a cogeneration power unit equipped with the T-280/335-26.1 steam turbine. The best indicators of the commercial efficiency were achieved for the variant with the following parameters of live steam and steam in the reheater: p0 = 26.1 MPa, prh = 4.035 MPa, t0/trh = 575/575°C. In this case, the following values were obtained: 42.56% gross efficiency, 40.94% net efficiency, 334 MW rated capacity in the condensing operation mode, and 279.1 MW in the heat-extraction mode at QT = 1381.6 GJ/h (330 Gcal/h). The use of higher steam parameters would result in a significant increase in the cost of projects. It has been shown that the restoration of initial design values of both live steam temperature and its temperature after reheat t0/trh = 565/560°C may be advisable at the upgrading of power units equipped with T-250/300-23.4 steam turbines.

Modern technologies for rendering information support to cogeneration steam turbine units in their design and operation stages

Application of modern information technologies in different stages of the lifecycle of cogenera� tion turbines is considered as one of possible ways for improving their competitiveness. Specific features relat� ing to rendering information support for steam turbine units during the periods of their design and operation, which are the main stages of their life cycle, are presented. Threedimension modeling, adaptive, and para� metric design technologies are applied in the equipment design stages. Information support technologies developed by the authors are applied during the operation stage. Information is integrated by using a product lifecycle management (PLM) system.

The T-100-12.8 family of cogeneration steam turbines: Yesterday, today, and tomorrow

The T-100-12.8 turbine and its versions, a type of cogeneration steam turbines that is among best known, unique, and most widely used ones in Russia and abroad, are considered. A list of turbine design versions and quantities in which they were produced, their technical and economic indicators, design features, schematic solutions used in different design versions, and a list of solutions available in a comprehensive portfolio offered for modernizing type T-100-12.8 turbines are presented. Information about amounts in which turbines of the last version are supplied currently and supposed to be supplied soon is given.

The longitudinal layout alternate version of cogeneration steam turbines with the generator placed on the side of the high-pressure cylinder

The schematic design of a cogeneration steam turbine with the generator placed on the side of the high-pressure cylinder is proposed. It is shown that the use of this solution is most promising for turbines with a longitudinal layout (like a T-175/210-12.8 turbine).

Diagrams of regimes of cogeneration steam turbines for combined-cycle power plants

General considerations regarding the form of the steam-consumption diagram for a three-loop cogeneration-type combined-cycle plant are formulated on the basis of well-known approaches. According to these considerations the diagram should consist of the main chart and numerous corrections that must be taken into account in using the diagram. The steam-consumption diagram of the T-113/145-12.4 steam turbine for the PGU-410 combined-cycle plant at the Krasnodar cogeneration station is presented.

Controlling the startup modes of cogeneration steam turbines operating as part of combined-cycle power plants

The results obtained from investigations of combined-cycle power plants produced by the Ural Turbine Works aimed at achieving high maneuverability, reliability and longevity of cogeneration steam turbines taking into consideration the possibilities of modern automated process control systems are presented. The dynamic models for simulating the heating of a steam turbine cylinder’s parts with the use of limited computation capacities are developed.

Retrofitting parts and assemblies of cogeneration steam turbines for improving their reliability

Typical flaws in cogeneration turbines produced by the Ural Turbine Works that revealed themselves under different conditions of their operation and due to which turbine failures occurred are determined. Generalized results obtained from investigations and approbation of a number of newly developed measures aimed at improving the reliability of the assemblies most susceptible to damages that were implemented in retrofitting or repairing cogeneration turbines are presented.

The cogeneration steam turbine of the T-40/50-8.8 type for the combined cycle power plant PGU-115

This paper describes the design of the steam turbine intended for a single-unit two-shaft combined-cycle plant and its main systems, the heat flow diagram, and turbine plant arrangement. The turbine should operate as part of the combined-cycle power plant that will be constructed on the basis of the modern PG6111FA gas turbine manufactured in the USA.

The cogeneration steam turbine of the T-63/76-8.8 type for a series of PGU-300 combined cycle power plants

This paper describes in detail the design of the T-63/76–8.8 steam turbine manufactured by Ural Turbine Works (refurbished significantly), its electrohydraulic control and protection system made according to the current requirements on control and protection, the heat flow diagram, and arrangement of the turbine. The T-63/76–8.8 steam turbine is intended to be used in double-shaft double-circuit combined-cycle monoblocks at a number of thermal power plants currently under construction. The turbine has a great future, since it may be employed in various combinations with gas turbine units having the output of 150–170 MW that are manufactured by virtually all firms.

Development of a system for monitoring technical state of the equipment of a cogeneration steam turbine unit

Generalized results from the work on developing elements of a comprehensive system for monitoring technical state of the equipment of cogeneration turbines are presented. The parameters of the electrohydraulic turbine control system are considered together with a number of problems concerned with assessing the state of condensers and delivery water heaters.

A new approach in CHP steam turbines thermodynamic cycles computations

This paper presents a new approach in mathematical modeling of thermodynamic cycles and electric power of utility district-heating and cogeneration steam turbines. The approach is based on the application of the dimensionless mass flows, which describe the thermodynamic cycle of a combined heat and power steam turbine. The mass flows are calculated relative to the mass flow to low pressure turbine. The procedure introduces the extraction mass flow load parameter ?h which clearly indicates the energy transformation process, as well as the cogeneration turbine design features, but also its fitness for the electrical energy system requirements. The presented approach allows fast computations, as well as direct calculation of the selected energy efficiency indicators. The approach is exemplified with the calculation results of the district heat power to electric power ratio, as well as the cycle efficiency, versus ?h. The influence of ?h on the conformity of a combined heat and power turbine to the grid requirements is also analyzed and discussed.

The T-120/130-12.8 and PT-100/130–12.8/1.0 cogeneration steam turbines produced by the ural turbine works for replacing turbines of the T-100 family

The basic design features and technical characteristics of the turbines installed on the foundation of the T-100 family turbines are presented.

Cogeneration in Sugar Industries: Technology Options and Performance Parameters—A Review

ABSTRACT This article presents a review of different technological options that are presently being practiced by sugar mills, and technological options that are identified as potentially promising future technologies. Different indices used to gauge the thermodynamic performance of cogeneration plants and facilitate the comparison of alternative systems are discussed. The most important performance parameters used to assess the steam turbine cogeneration plants in general and sugar mill cogeneration plants in particular are defined and developed. Criteria such as energy utilization factor, heat-to-power ratio, fuel energy savings ratio, exergetic efficiency and power generated per tonne of cane (tc) prove to be more important and relevant. Biomass-integrated gasifier/gas turbine cogeneration (BIG-GT) and biomass gasifier combined with steam injected gas turbine cogeneration (BIG-STIG) are considered as potentially promising future technologies. The existing modern, high pressure, high efficiency, steam turbine cogeneration plants generate 115–120 kWh/tc, while BIG-GT and BIG-STIG are potentially capable of generating up to 270–275 kWh/tc. Cogeneration plants using backpressure and condensing steam turbines perform with energy (First Law) and exergetic (Second Law) efficiency of approximately 60–70 % and 22–25%, respectively. The steam consumption in sugar mills at present varies from 480–550 kg/tc, while electricity consumption ranges between 16–22 kWh/tc (32–40 kWh/tc for electrified mills). These performance indices will help plant designers and engineers in improving their choice of system configuration and developing alternative schemes.