Criteria for integration of combined cycle cogeneration systems in the process industries

Cogeneration systems often provide a very effective means of integrating power generation with the provision of thermal energy to an industrial process. Various types of power generating machines can be used, but combined cycle cogeneration systems can offer significant advantages over other technologies in many medium and large scale applications. The systems that are used consist of fired prime movers (usually gas turbines), discharging their exhaust heat into heat recovery steam generators. The steam raised in this way is passed through back-pressure steam turbines to extract additional power before finally delivering its residual heat content to process heating duties.This paper presents an overview of the economic trade-offs in the design of single cycle and combined cycle systems. Generalizations are derived from this investigation, leading to the identification of three distinct classes of problem for which different types of cogeneration systems (combined cycle or single cycle) are appropriate. Case study results are presented to illustrate the principles employed.     

Effect of control modes and turbine cooling on the part load performance in the gas turbine cogeneration system

This work aims to analyse the part load performance in a cogeneration system which consists of a single shaft gas turbine and a heat recovery steam generator. Two distinct part load control modes are considered: the constant air flow and the variable air flow. Meanwhile, the effect of variation in the coolant fraction is evaluated, whose purpose is to maintain the blade temperature as high as possible and thus minimise the coolant consumption. The design point parameters of the heat recovery steam generator are determined by the limiting factors on the part load operation, which are represented by the pinch point temperature difference and the approach temperature difference. It turns out that for both air flow control modes, the variable control of coolant fraction leads to improvement of the gas turbine efficiency, while it reduces the heat recovery potential. On the whole, the variable control of coolant fraction has a favourable effect on the overall fuel economy in the cogeneration system.     

Developments in geothermal energy in Mexico—part thirty-four. Numerical steady-state simulation of the steam supply system of the cerro prieto geothermal plant

The philosophy used in the mathematical modelling of the steam supply network of Cerro Prieto geothermal power stations is described. In order to form the simulation model of this system, mathematical models were developed for: the surface equipment such as separators, pressure control stations, steam turbines, low and high pressure interconnections, purges and wells. With the above mentioned models a computer programme was produced which operating conditions in the steam supply system.     

Cogeneration plant with exhauster gas turbine and external combustion

The paper presents the method and results for technical and economical study of a cogeneration plant with exhauster gas turbines fueled by solid fuel. The search of fundamental regularities of the processes allowed us to recommend optimal parameters for different variants of power plant operation and formulate recommendations for optimal configuration of a cogeneration plant with EGT.     

The effect of the operating parameters of heat recovery steam generators on combined cycle/sea-water desalination plant performance

Combined gas/steam turbine cycle plants have been proposed for cogeneration of electricity and process steam. Examples are combined-cycle power plants coupled with sea-water desalination, district heating plants, chemical industries, etc. In combined heat and power plants, the gas turbine exhaust heat is utilized through the use of heat recovery steam generators (HRSG's). As a result, these waste heat generators (boilers), whether fired or unfired, control the performance of the combined plant lower side (bottoming cycle). Moreover, any changes made in the HRSG operating parameters (i.e. the pinch point, approach temperature, first and second stage pressures, and mass ratios) can greatly affect the HRSG performance and will eventually affect the overall combined plant performance. This paper presents a method to predict the performance of the heat recovery steam generators (HRSG)/steam bottoming cycle combined with sea-water desalination plant at various steam and exhaust gas conditions.     

A case study of cogeneration for Jeddah and Yanbu petromin refineries in Saudi Arabia

The Petromin refineries in Jeddah and Yanbu, Saudi Arabia produce power and process steam separately. The Jeddah refinery gas turbines that have an installed capacity of 88 MW, run at less than 50% utilization factor. The refinery demand of steam is 70–120 tons h⁻¹.The electric power demand of Yanbu refinery is supplied by The Royal Commission of Yanbu at a rate of 16–25 MW. The steam consumption is 68 tons h⁻¹. Data were collected for the performance and requirement for both plants. An integrated system for cogeneration is proposed which consists of a gas turbine, heat recovery steam generator equipped with a supplementary duct burner and economizer. The thermal and economical analyses have proved the feasibility of the proposed system with payback periods of 23 and 36 months for Jeddah and Yanbu refineries, respectively. However, the payback period for Jeddah refinery can be reduced to 15 months if the utilization factor is improved, and the excess power generated by the gas turbines is connected to the public utility grid. In fact, it is worth mentioning that the present study is considered the first to be carried out in Saudi Arabia; more studies and investigations could lead to tremendous saving in the fuel consumption in this country.     

An effective approach to optimizing the parameters of complex thermal power plants

A new approach has been developed to solve the optimization problems of continuous parameters of thermal power plants. It is based on such organization of optimization, in which the solution of the system of equations describing thermal power plant, is achieved only at the endpoint of the optimization process. By the example of optimizing the parameters of a coal power unit for ultra-supercritical steam parameters, the efficiency of the proposed approach is demonstrated and compared with the previously used one, in which the system of equations was solved at each iteration of the optimization process.     

Modeling and analysis of simultaneous laser transmission welding of polycarbonates using an FEM and RSM combined approach

In this paper, simultaneous laser transmission welding process is systematically investigated via process modeling, using an FEM and RSM combined approach. The objective of the present research is to study the effects of process parameters on the temperature field and weld bead dimensions. The thermal field is simulated by solving a three dimensional transient heat diffusion equation with temperature dependent material properties using the ANSYS^® multi-physics. Response surface methodology is then applied for developing mathematical models based on simulation results. The second order equations developed by RSM can predict the values of the responses with significant accuracy. The effect of parameters and their interactions on the responses are studied using the developed response surface models. The mathematical models are further used in search of the optimal process window for obtaining an acceptable weld. The graphical optimization results into a couple of overlay contours plots, which allow quick visual inspection of the area of feasible response values in the factor space to choose the favorable welding parameter combination.     

燃气轮机机理建模与性能监测

燃气轮机电厂是电网调峰和分布式能源系统中的重要组成部分,其安全稳定运行和快速响应对燃气轮机性能要求较高,因此对燃气轮机进行性能监测有着重要意义。本文采用了模块化机理建模的方法,基于MATLAB平台,建立了简单循环单轴燃气轮机数学模型,并以某典型9E燃气轮机的实际运行数据进行了模型验证,结果表明本文所建模型可以较准确地反映燃气轮机性能。此外,本文所建数学模型具有一定的普适性,通过输入不同的设计参数,可以用于不同等级、不同型号燃气轮机的性能研究。     

Optimization of steam-turbine power unit of a coal mini-HPP with variable schedule of heat and electric energy loads

The technique for optimization of parameters of a power unit of a gas-turbine small-size heat and power plant was developed with regard for seasonable nature of heat and electric energy loads; the approach uses linear versions of dependency of outlet parameters on the inlet parameters. A mathematical model of the energy unit of a mini-HPP was developed. Optimization calculations for a coal gas-turbine mini-HPP were carried out for several optimization criteria: minimal revenue from the produced heat and electric energy (at different levels of fuel price), minimum of fuel consumption during year, and minimal investment at a given internal return rate.     

Waste heat recovery of dura (Iraq) oil refinery and alternative cogeneration energy plant

The first part of this paper presents a waste heat recovery scheme for the Dura (Baghdad, Iraq) oil refinery energy plant. Both the wasted heat of the process return condensate and the flue gases are utilized for low temperature feedwater and fuel heating. The steam saved, both from the main steam line and turbine extraction system, was found to increase the steam and plant overall efficiency by 18%.An alternative cogeneration energy plant is presented in the second part of this study. The proposed plant utilizes the gas turbine exhaust, in conjunction with a heat recovery boiler, to produce the process steam requirement. With this alternative plant, the overall efficiency increases by 31.6%, while the steam efficiency increases by 19%. The outstanding features and advantages of the proposed plants are highlighted.     

蒸汽侧循环给水加热系统的综合优化

1前言联合循环中蒸汽侧循环给水加热系统的综合优化是总系统整体优化必不可少的重要环节。虽然也有一些相关的研究，但至今仍很不充分，对给水加热系统的设计多凭经验进行，依赖于设计者的直觉而缺乏科学的依据。另外，对不同的蒸汽循环系统，其给水加热系统差异很大；而增压流化床燃煤联合循环PFBC—CC［‘］中给水加热系统比较复杂，为多加热源，不仅要合理抽汽加热，还要充分利用燃机的排气余热。再者，PFBC—CC是以蒸汽侧循环为主的联合循环，蒸汽侧循环给水加热系统的优化对整个系统性能的改善有更大的意义。本文以复杂的PFBC—…     

Computer program for determining optimal running conditions of a steam turbine cogeneration system

Cogeneration is an efficient way of using energy and at a national level permits an important saving in primary energy. Different systems include those with a back-pressure steam turbine and those with a pass-out condensing steam turbine.This paper deals with the basis and structure of a software pack that enables the user to determine the optimal running conditions in either case. The program is interactive, written in FORTRAN 77 and composed of six program blocks. Each block is responsible for one basic aspect of the analysis process.Because the objective function is non-linear and only point values are available, instead of algebraic expressions, the complex optimization algorithm is used. The object of the function is to minimize the hourly fuel and electricity costs during operation.Finally, the program has been applied to a cogeneration installation with a 970 kW back-pressure turbine. The results indicate that the system sometimes produces more steam per hour than required, the excess being due to the fact that the profit from the sale of electricity is greater than the cost of steam production.     

Predicting the Performance Deterioration of a Three-Shaft Industrial Gas Turbine

The gas turbine was one of the most important technological developments of the early 20th century, and it has had a significant impact on our lives. Although some researchers have worked on predicting the performance of three-shaft gas turbines, the effects of the deteriorated components on other primary components and of the physical faults on the component measurement parameters when considering the variable inlet guide valve scheduling and secondary air system for three-shaft gas turbine engines have remained unexplored. In this paper, design point and off-design performance models for a three-shaft gas turbine were developed and validated using the GasTurb 13 commercial software. Since the input data were limited, some engineering judgment and optimization processes were applied. Later, the developed models were validated using the engine manufacturer’s data. Right after the validation, using the component health parameters, the physical faults were implanted into the non-linear steady-state model to investigate the performance of the gas turbine during deterioration conditions. The effects of common faults, namely fouling and erosion in primary components of the case study engine, were simulated during full-load operation. The fault simulation results demonstrated that as the severity of the fault increases, the component performance parameters and measurement parameters deviated linearly from the clean state. Furthermore, the sensitivity of the measurement parameters to the fault location and type were discussed, and as a result they can be used to determine the location and kind of fault during the development of a diagnosis model.     

环境温度对燃气轮机功热并供装置及联合循环变工况性能的影响

采用动力机械变工况性能解析分析方法,研究了大气温度变化对燃气轮机功热并供和联合循环装置性能影响．指出燃气轮机在带有余热利用的条件下,大气温度的影响明显减弱,并对不同燃气轮机设计参数和蒸汽设计参数影响做了分析比较。     

国产优化300／600MW汽轮机通流部分气动设计──第一部分：设计体系与通流设计特点

本文介绍了用于大功率汽轮机通流部分气动设计的准三维／全三维设计体系。使用该设计体系把复合倾斜叶片、可控涡流型等先进的汽轮机气动设计思想，成功地应用到了３００／６００ＭＷ汽轮机的改型设计中，以期较大程度地改进机组的热力性能。     

Two case studies of cogeneration systems design and economic feasibility

Cogeneration is an ideal method of power production for applications which require both heat and power simultaneously, hence the name combined heat power (CHP). In this paper, design studies of cogeneration systems for two specific applications are presented. The results indicate the economic feasibility of such installations and how much energy can be saved, especially if the system is analysed on a long-term basis. It is shown that an essential requirement for cogeneration is the proper matching of power and heat demands.The first design study is of a combined power and heating system for a small suburban hospital which requires both steam and power for its various needs. The cogeneration system which was designed for this application consisted of a conventional turbo-charged spark ignition engine with heat exchange from its exhaust and engine cooling systems, coupled with an existing boiler. When the cogeneration system is inadequate to meet the electricity demands, the excess power would be bought from the grid supply. For an initial outlay of approximately $250,000 (1990 prices), an annual saving of $140,000 was conservatively predicted, with an internal rate of return of some 40% over 15 yr.The second design study is for the energy system of a large sugar confectionery factory with power and heat requirements, mainly for lighting, air conditioning and several manufacturing processes. The hardware which was chosenfor the cogeneration system for this case comprises a diesel engine converted for use with natural gas connected to a vertical shell and tube exhaust gas boiler. For an initial investment of approximately $700,000, an annual saving of about $130,000 (1991 prices) is predicted for a 10–15 yr project. The savings and the payback period depend on the electricity buy-back tariffs and the company's plans for future expansion.     

Optimum running conditions for a gas turbine cogeneration system

There are currently compact and reliable gas turbines that prove very suitable for cogeneration. The present paper deals with the basic structure of a program package that makes it possible to simulate, using manufacturers' data, four of the ways in which such installations can be configured.Furthermore, this package makes it possible to determine optimum running conditions for the system analysed. The complex algorithm is used to yield the minimum operation cost, which is the function sought. We conclude with an example of software application.     

Non-linear models of geophysical hydrodynamics and the problem of forecasting stream patterns I

The dynamic stochastic approach to the study of mathematical models of thermohydrodynamic large-scale fields is developed in which the mathematical image of stochasticity is the strange attractor of the real atmosphere. This approach is based on methods of analysing non-linear equations of atmosphere. The approximation of these equations is mostly effected using Galerkin's procedures. This reduction is based on the theorem of invariant manifold, especially on the theorem of central manifold for semi-flow of the Navier-Stokes equation. According to the theorem of the central manifold, all significant phenomena related to dynamic systems of thermohydrodynamic equations of atmosphere occur in a particular finite-dimensional formulation. General circulation could be modelled with the aid of relatively single dynamic systems. We shall continue deal with the finite-dimensional approximations of the dissipative, non-divergent, barotropic flow and the bifurcation analysis of the spectral models with a small number of spectral modes and an external force acting only on fundamental modes.     

IDENTIFICATION OF MODAL PARAMETERS FROM MEASURED OUTPUT DATA USING VECTOR BACKWARD AUTOREGRESSIVE MODEL

In this paper, a modal identification system that is based on the vector backward autoregressive (VBAR) model has been developed for the identification of natural frequencies, damping ratios and mode shapes of structures from measured output data. The modal identification using forward autoregressive approach has some problems in discriminating the structure modes from spurious modes. On the contrary, the VBAR approach provides a determinate boundary for the separation of system modes from spurious modes, and an eigenvalue filter for the selection of physical modes is existent in the proposed method. For convenience of application, the backward state equation established from VBAR model is transformed into a forward state equation, which is termed as transformed VFAR model in this paper. In addition, the extraction of equivalent system matrix of state equation of motion for structures from the transformed VFAR model has been developed, and then the normal modes can be calculated from the identified equivalent system matrix. Two examples of modal identification are carried out to demonstrate the availability and effectiveness of the proposed backward approach: (1) Numerical modal identification for a three-degree-of-freedom dynamic system with noise level in 20% of r.m.s of measured output data; (2) experimental modal identification of a cantilever beam. Finally, to show the advantage of the proposed VBAR approach on the selection of physical modes, the modal identification by stochastic subspace method was performed. The results from both methods are compared.