Modular Concept of a Gas Turbine Power Plant

Transcription

1 THE AMERICAN SOCIETY OF MECHANICAL ENGINEERS 345 E. 47 St., New York, N.Y The Society shall not be responsible for statements or opinions advanced in papers or in discussion at meetings of the Society or of its Divisions or Sections, or printed in its publications. Discussion is printed only if the paper is published in an ASME Journal. Papers are available from ASME for fifteen months after the meeting. Printed in USA. Copyright 1985 by ASME Modular Concept of a Gas Turbine Power Plant by A. V. RAPPARD, Project Manager and A. WICKI, Dept. Manager, Gas Turbines BBC Brown, Boveri & Co. Ltd. CH-5401 Baden/Switzerland ABSTRACT A modular concept of a power plant has been developed on the basis of a modern 45 MW gas turbine. The most important aspects of this design concept described in this paper, such as layouts, cooling system and electrical equipment, take into consideration the requirements in different countries. In general, a customer demands short delivery and erection times, quick commissioning and good quality. Examples of plant layout planning, the mechanical equipment drawn upon and the sequence of assembly are outlined. INTRODUCTION The output range of gas turbine power plants extends from a few megawatts to more than 1000 MW. Large gas turbine plants have already been built with more than 20 units. Apart from the number of units involved, the layout and equipment for a power plant will depend considerably upon the different needs and the local ambient conditions. These items include fuel flexibility, different filter systems depending on the pollution of the ambient air, different systems for lube oil and generator cooling, fire fighting systems and noise abatement. These wants and needs gave rise to further development of the modular power plant concept for the Type 8 gas turbine [1-3]. The basic ideas of this concept are To realize these ideas, the power plant was split up into different modules. These modules can be tailored to specific requirements by pre-engineered variants. The tailoring is performed in the supplier's workshop. The final, inspected modules will then be brought as units to the site where they are connected by prepared interfaces in a short time. The different modules will be presented in the next chapter. The possibilities and combinations as well as an assembly procedure will be outlined. CONCEPTS OF LAYOUT The first step to meet the different requirements with a prepared standard is to define the modules which remain unchanged and to fix their allocation in a standard layout. Fig. 1 shows the layout of a power plant with two units, with all the plant components assigned to a turboset. The only additional equipment required for each unit is a fuel supply line for each of the fuels in question and the connection to the network. - short delivery time - high flexibility for = different number of units = different types of plant layout = different configuration of systems = different accessories - good access for maintenance Presented at the 1985 Beijing International Gas Turbine Symposium and Exposition Beijing, People's Republic of China September 1-7, 1985

2 ball II I OWN' DIP ad El 1, wiii ootoo IM MiA =, pomtld rig Fig. 1 Layout of the power plant components for outdoor installation BBC = Generator module 2 = Gear module 3 = Gas turbine module 4 = Exhaust gas stack 5 = Exhaust gas silencer 6 = Intake silencer 7 = Air filter 8 = Recooler 9 = Fuel pump unit 10 = Gas control module 11 = Control system module (A) 12 = Starting module (C) 13 = Medium voltage module (B) 14 = Block transformer In addition to the machine modules (1-3), the power plant comprises the exhaust gas and air intake systems (4-7), the cooling system with the recoolers 8, the fuel pump unit 9 and/or the gas control module 10 and the control and switchgear unit with the modules A (11), B (12) and C (13) and the connection to the unit transformer 14. All modules can be prepared. Special open or closed loop control options can be added easily. The definite allocation of each component, especially of the recoolers or the control unit, is a basic requirement for the prompt delivery and assembly of all prepared standardized connections linking the modules. Four different types of standard plant layouts were worked out for which a significant portion of the hardware can be prepared in advance (see Fig. 2a,b,c,d). Fig. 2 Installation layouts a) Standard outdoor layout A mobile crane is used to erect this type of power plant. A crane is permanently installed for maintenance work on the combustion chamber. b) Outdoor layout with overhead crane The overhead crane simplifies setup and overhaul work considerably. c) Indoor layout with bridge crane. All erection and overhaul work can he carried out quickly under all weather conditions. d) Indoor layout in a hall. The machine and control units of the power plant are installed in a large hall. This is by far the most favorable arrangement in respect of working conditions. In the indoor layout, the individual turbine units can be surrounded by acoustic enclosures. PRINCIPAL REQUIREMENTS ACOUSTIC REQUIREMENTS The necessity of soundproofing various components to meet acoustic requirements is widely accepted. Guidelines for noise emission were therefore established and the emission itself graded. According various standards (e.g. ISO/R 1966, VD and S1A 181). Silencers in the intake and exhaust systems, the enclosures for the turbine module, the control unit and the fuel pump unit. Were optimized to ensure that the total emitted noise does not exceed the stipulated values. 2

3 The graduation and the decrease of sound levels with the distance of the noise source is plotted in Fig Sound level 90 di, 70 LpA MIC t... kb, ' D% - RNIS rn.. i.- ;` MI,'IliM.s WI. Ai. I.. I iii 11. A lb...1ii."ii... MIMİ..,q,,,iii I. 1lb CHmtance Fig. 3 Decrease in sound pressure level with distance and grades A - F. FIREFIGHTING EQUIPEMENT Firefighting equipment is a standard feature of power plants and is integrated in the design concept. The fire alarm unit is pre-installed in the control unit. Table I lists the standard equipment of the individual modules for the various layouts. The fire-extinguishing agent used is chlorinefree halon 1301 (halogenated hydrocarbon). This complies with the classes A to C in both the European standard DIN-EN 2 and the American National Fire Protection Association (NFPA) standard. Halon, in contrast to CO 2, is less injurious to human life, more effective as a fire extinguisher and needs less space for equipment and tanks. A = Outdoor layout (combustion chamber surrounded by enclosure) B = Indoor layout without soundproofing enclosure C = Indoor layout with soundproofing enclosure (soundproofing enclosure does not surround the combustion chamber) Any requested additions can be integrated in the firefighting concept. MECHANICAL EQUIPMENT The kind and quality of the fuels in question, pollution of the ambient air and different cooling media have an important influence on the design of the respective systems. Fuel supply system The complete system includes the fuel supply from the unloading station to the combustion chamber. The individual subsystems were optimized and provide for electrical preheating, additive dosage and various stages of the instrumentation and reserves. Air filter system The basic design provides for various systems with coarse and fine filters, and for selfcleaning filters. In [4] the different systems are dealt with in detail and guidelines are given for the evaluation. Cooling One of the three cooling systems shown in Fig. 4 will be used, depending upon whether there is cooling water available, and if there is, upon its quality. The elements making up these systems are the same in each case. Table I: Summary of standard firefighting equipment Fire-extinguishing system: - Gas turbines - enclosures - overall protection - Combustion chamber - equipment protection - Control unit with three modules - overall protection - Fuel pump unit (if present) - overall protection - Fire detection system A B C x - x BEIC2.371 Fig. 4 Cooling circuits 1 = Generator cooler, air/water 2 = Orifice 9 = Recooler, water/water 3 = Lube oil cooler, oil/water 4 = Recooler, water/air 5 = Recooler, water/water 3

4 Schematic diagram A shows the air-cooled system. In a two-section closed circuit, the generator losses are dissipated by cooling air in cooler 1 and the gearing and bearing friction losses by the lube oil in cooler 3. These losses are then passed to the ambient air in the recooling units 5. The recooling units consist of four identical elements, so that further elements can be added at any time as a back-up. The orifice 2 ensures optimum flew distribution in the closed circuit. In schematic diagram B, the air-cooled recooling unit (item 5 in schematic diagram A) is replaced by a water-cooler, enabling lowquality cooling water to be used to dissipate the heat. Schematic diagram C shows the open circuit. This, however, may only be used when suitable water is available. CONTROL AND ELECTRICAL EQUIPMENT The overall control and electrical systems, which are installed in the three control modules A, B and C (Fig. 5) are assigned to each unit. The control system in module A employs programmable processors and therefore supplementary equipment can be easily added to the basic system at any time. The medium voltage equipment placed in module B allows connections for the following features: - Feeding of a black-start diesel set or a gas compressor - Feeding of a general power plant auxiliaries busbar from the auxiliary transformer In power plants with several units, changeover equipment permits selection of one of two different starting converters located in module C. Consequently, starting availability will be enhanced even if there are fewer converters than gas turbine units. The starting converters can also be used for functions such as turning the rotor when cleaning the compressor or purging the exhaust system in combined-cycle plants. The electrical connections between the modules A, B and C and the pre-wired machine modules are of the plug-in type and factorytested. ASSEMBLY SEQUENCE AT SITE The layouts of the individual modules were established with an easy assembly process in mind. The sub-assembly of the materials was optimized with the activities in the field. Thus, it is possible to save time on the the manufacturing as well as on the assembly process. The pictures below (of the previously described model) are to illustrate this sequence and concludes the sequence of assembly activities for one machine set Fig. 5 Control unit configuration for a gas turbine set 1 Gas turbine module 2 Gear module 3 Generator module Control unit A: I = Turbine control system 2 = Generator protection 3 = Voltage regulation 4 = AC supply 5 = DC supply B: 6 = Generator circuit breaker 7 = Station auxiliaries E = Auxiliary transformer C: 9 = Starting converter 10 = Starting transformer Fig. 6 Preparing the concrete foundations. Foundation anchors with molds, grounding material, tools and accessory materials are shipped beforehand. The two foundations for the main machine set and the steel frame are prepared. Module B allows connections for the following features: 4

5 Fig. 7 Assembly of the machine set. The individual machine modules - generator, gear and gas turbine - are placed on the machine foundation, aligned and joined to the intermediate shafts. Any alignment work on the bearings can be performed at this stage. Fig. 9 Assembly of the exhaust stack and the control unit. While the exhaust stack is being erected, all electrical connections for the machine set and the other modules most of them of the plug-in type - are connected. All cables laid in the PVC pipes in the concrete are connected as well. Thus, the entire lube oil system is functional and can be inspected , Atakiri Fig. 8 Assembly of the mechanical systems. Intake duct and exhaust gas diffuser are mounted. Auxiliaries and cooling module are set up and connected to the machine set. Finally, the rotor cooling system is installed with the proper heat exchanger that cools the rotor cooling air. Fig. 10 Construction of the steel frame. The enclosure is added and the combustion chamber mounted. 5

6 Available space The distance between the axes of adjacent units was optimized with respect to the actual need and may be cut down to a minimum of 13.5 m (45 ft.). The steel structure can be extended to fit several, additional units. Interfaces of the mechanical systems There is only one interface between individual units, namely a common fuel supply system that was separately. All other optimized, mechanical systems operate independently for each unit. Fig. 11 Air intake and cooling system. Silencers, filters and the previously mentioned recoolers are installed. Interfaces of the controls and monitoring systems There is a remote control connection board in the control module A allowing for a central data acquisition unit, an operator's console in the control room or a remote control system. Power plant auxiliaries, which depend on local conditions can be fed from one unit. The changeover equipment of the static starting device connects different units in a power plant. It is installed in the control module C and will be controlled like the static starting system. All other systems for control and monitoring as well as voltage supply are separately assigned to each unit. Waste heat processing A waste heat boiler can easily be connected to the axial exhaust gas outlet (Fig. 13). With a bypass stack, both kinds of operation - either gas turbine alone or cogeneration - are possible. Adding a steam turbine unit to convert the gas turbine power plant into a combined cycle plant does not necessitate much additional equipment on the gas turbine side. Fig. 12 Fuel pump unit. Located outside of the turbine enclosure, it is connected to the combustion chamber. The crane for the combustion chamber - if needed - can also be mounted at this time. COMPLETION OF A POWER PLANT WITH SEVERAL GAS TURBINES AND WASTE HEAT PROCESSING The described, modular power plant is selfcontained. It still needs the appropriate fuel supply system, a main current line from the generator-breaker and the feed for the auxiliaries used for start-up. Thus, the possible number of interfaces is predestined to be small in a power plant with several units. The most important local conditions and interfaces are summarized in the sections below. Fig. 13 Model of a standard power plant with a boiler for cogeneration of power and steam. (Outdoor layout) 6

7 CONCLUSION This paper shows the modular structure of power plants employing one or more gas turbines. Four different layouts were presented as examples consisting of two outdoor and two indoor versions. A boiler connection is also included in the layout permitting waste heat processing. The individual gas turbine units with their separate mechanical and electronic equipment as well as their instrumentation and controls systems, are divided into modules. For these modules, different variants were developed to meet individual requirements. The time for manufacturing, testing, field assembly and commissioning as well as the weight/volume ratio important for the transport were taken into consideration as optimization parameters. Consequently, the following characteristics are typical for the layouts introduced in this paper: - few modules with established interfaces - individual sub-systems which may consist of several modules are sub-assembled, inspected and tested at the factory - the mechanical connections of all modules are standarized - the length of the electrical connections for the modules is pre-established and whenever possible, the connections are of the plug-in type - the possibility for extension is given Therefore, the modular concept promises short delivery times with increased reliability and availabilty. REFERENCES [1] Endres, W., The medium size gas turbine type 8 from Brown Boveri, development and testing". ASME Paper 83, Tokyo, IGTC 112. [2] Wicki, A. and Farkas, F., "Design and testing of a 45 MW gas turbine." ASME Amsterdam 84-GT-16. [3] v.rappard, A, Haessig, C. and Zimmermann, M., "Modular component system for power plants with type 8 gas turbines". Brown Boveri Review 1985, vol.72, no. 1, pp. [4] Zaba, T. and Lombardi, P., "Experience in the operation of air filters gas turbine installations". ASME Amsterdam 84-GT-39. 7