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China Geothermal Power Plant Contractor We are a Chinese leading geothermal power plant EPC contractor, main contractor or turnkey contractor from China. We have expertise in the design and manufacturing of the geothermal power plant, which is feathered with lower temperature and pressure of steam. NCG and silcan should be taken into consideration while design and manufacturing the critical equipments. Here are typical description of main equipments designed and provided by us for a 2x6MW geothermal power plant, which is under construction in Indonesia.
1 INTRODUCTION
1.1 GENERAL
1.1.2. The main technical parameters of the major equipment
1.1.2.1 Steam Turbine 2 sets
------Rated steam flow 56.7 t/h
1.1.2.2 Turbo-generator 2 sets
1.1.3 Main economic index of power plant -Capacity of power plant 2X6.8 MW -Rate for plant service power 10 ％ -Net output for power plant 2X6 MW -Annual operation hours >=7884 h -Heat rate 8590 kJ/kW.h -Operation lifetime 30 years
1.1.4 The Project will consist of major equipment: - Two turbine-generator and condenser - Condensate system - Water and wastewater treatment plant - Main control room - Control and instrumentation equipment - Fire protection and detection system - Ventilation and air conditioning system - All requires piping and valves - 20kV Substation and terminal substation - Main and Auxiliary Transformers - All civil, erection and installation works required for the above supplies - Other system as necessarily required
1.2 Power plant outline
The Power Plant shall be located Within the Owner’s Site.
The turbine and equipment will be located in turbine building. The buildings will consist of turbine generator, main control room, electronic room, and auxiliary equipment.
The scope of works of the power plant includes design, manufacture, supply, procurement, erection, test and commissioning of the geothermal power plant on EPC basis, and also basic design of civil workls.
2.1Civil Works
2.2 Mechanical works
B-1 Turbines
B-2 Steam piping & demisters
B-3 Jet Condensers
B-4 NC gas extraction system
B-5 Cooling water system
B-6 Re-injection water system Pumps, pipes and associated equipment
B-7 NaOH dosing system NaOH storage tank (10m3) and control valves
B-8 Service water supply
B-9 Fire fighting
B-10 Handling equipment
B-11 Laboratory and Personnel safety equipment Chemical analysis laboratory, H2S detection and protection system
B-12 Workshop equipment Special tools and devices for turbine and generator, common tools and appliances
B-13 Ventilation and air conditioning Ventilation and air conditioning
2.3 Electrical works
C-2 Transformers Main transformers and station transformer
C-3 Medium voltage system Switchgears
C-4 Low voltage system Switchgears
C-5 Control and monitoring system
C-6 Protection system Protection system for electric and mechanical equipment
C-7 Exigency serviced system Diesel generator, DC power system, UPS
C-8 Lighting and earthing Lighting and earthing system
2.4 Others
4 STEAM TURBINE AND TURBINE AUXILIARY
4.1 GENERAL
The steam turbine and turbine auxiliary will consist of:
4.2 STEAM TURBINE
The function of the steam turbine is to accomplish conversion of the thermal energy of steam produced by the geothermal energy required to drive the generator. The generator converts the mechanical energy to electrical energy, which is transmitted through, the generator breaker to the generator step-up transformer.
Two steam turbine generators are arranged in a turbine house. The two steam turbines will be single-cylinder, single-flow, down-exhaust, impulse-reaction condensing type, arranged longitudinally and installed indoors.
The condenser is of direct contact type and installed under the steam turbine. Two hot well pumps with 50% capacity and gas removal system are inside turbine house.
The control system of the plant and equipment were as such designed to require minimum operator intervention and supervision and maintain high reliability.
Main steam pipe will ensure a safe and reliable operation of the steam turbines. Take the emergency into account, one bypass that vent to sky passed steam silencer will be installed in the main steam piping .
4.2.2 Major features of steam turbine
The turbine shaft and generator couplings are amply strong to withstand shocks during operation, including generator short circuit conditions and synchronizing out of phase. The couplings will be designed so as to permit easy and rapid disconnection, re-assembly and alignment.
The steam turbine can operate under idling condition after trip-out not less than 15 minutes.
The rear part of the cylinder is equipped with the vent valve for low vacuum protection.
The shaft amplitude, shaft displacement and revolution rate at the main bearing are with 4-20mA standard output for connection to the DCS monitoring interface.
The turbine will be designed with sufficient drainports for moisture removal particularly during start up. The design will include passage ways and interstage drainage where appropriate to avoid erosion damage of low pressure blading in the wet region. The steam turbine will be equipped with one drain flash tank for maximum removal of water and the drain is let into the condenser through the drain flash tank.
The automatic main steam valve and foundation will be fixed by hangers. The steam turbine will be equipped with electric driven turning gears in power of 3kW. The turning gears can be automatically retreated and it will be equipped with manual operating device.
The steam turbine will be equipped with steam lock pressure automatic regulating device and steam lock air extraction device. The steam supply system for steam lock can automatically regulate its pressure under any working condition of the turbine. The steam lock system will be equipped with valves.
The steam turbine will be supplied with complete lubricating and control oil system. The oil system is for supply of oil to the regulation and security system, and for bearing lubrication and turning gears. The oil system will consist of reliable main oil supply equipment and auxiliary oil supply equipment. The oil tank in volume of 5 cubic meters will be equipped with exhaust fan and explosion-proof motor. The oil tank will be installed with emergency drain valve. Oil piping will be installed with exposed stem cast steel valves. Two oil coolers in volume of 2x100% will be supplied and the outlet piping of oil coolers will be installed with strainers.
Steam from the geothermal field will be sent to the steam turbine via the main steam piping. The main steam will pass through pneumatic stop valves before entering the steam turbine.
The steam turbine will be equipped with automatic main steam valve, which is kept in open position by the oil pressure of turbine. Once the pressure is lost, the valve is tripped and closed,
The condenser neck and the turbine low pressure cylinder will be connected by expansion joints, and be rigidly supported at the bottom. The expansion joints will compensate the downward expansion of the condenser and the rear cylinder.
The thrust force of steam piping beyond the allowed range by the manufacturers will not be applied onto the turbine casing.
All the equipment covered in this section are in conformity to ASME and IEC standards or equivalents.
Steam turbine monitoring: One set of monitoring instruments in 8000 series, to be supplied with steam turbine.
Steam turbine control: EHC electrical/hydraulic regulation system. The controller will be model 505 from WOODWORD USA. The turbine vendor will supply one WOODWORD 505 and one CPC, and perform configuration and one site commissioning.
Steam turbine security: An emergency security system for over speed prevention will be supplied. It will immediately close the main steam valve and control valves to cut off the steam source in case of failure. Additional over speed protection devices and standby assistant emergency stop devices will be supplied.
Automatic protection devices to close the main steam valve and governor valve under the following emergency conditions:
4.3 condenser
From the viewpoint of economy and performance, compact and high efficient heat exchange is requested for the condenser. For that purpose, direct contact type of condenser will be applied. The condenser is composed of main cooling part, where approximately 90% of steam is condensed, and cooling part. Spray jet type was applied to main cooling part and tray type was applied to main cooling part. The condenser neck and the low pressure cylinder of the steam turbine will be connected by expansion joint, and rigidly supported at the bottom.
The vertical spray water pipes are installed in the steam condensing part and swirl type spray nozzles are mounted on vertical spray water pipes in horizontal direction. The arrangement of the nozzles was so designed as to taking into consideration of no interference with water film of adjacent nozzles.
The condenser is designed for maximum continuous operation conditions of the steam turbine. The steam turbine exhaust pressure will be 0.06 ata, the circulation cooling water temperature will be 30° C at the operation condition of maximum exhaust.
The condenser will be designed to receive the following exhaust steam, drain and return water, and with good performance of deaerating.
4.4 condenser AIR extractION
The condenser air extraction system provides for the venting of the condenser steam space for removal of non-condensable gases during turbine generator operation. It also provides the capacity to rapidly reduce the condenser pressure from atmospheric before unit startup, allowing admission of steam to the condenser. The vacuum breaker valve allows air to be vented into the condenser to reduce the rolldown time of the turbine generator.
The condenser will be installed with two liquid-ring vacuum pumps of 100% volume.
The condenser air extraction system includes:
The vacuum breaker installed is to break condenser vacuum and reduce the turbine roll down time.
4.5 INJECTION SYSTEM
Geothermal steam contains harmful impurities such as silica or chloride and much non-condensable gas in comparison with thermal power plant. Impurities or non-condensable gas cause scaling or corrosion related problem. In addition, geothermal steam is usually saturated. And the measures shall be taken against scaling, corrosion and erosion problem for higher reliability and performance.
4.5.1 Reason
The following are possible mechanisms of precipitation for the silica that is carried over into the steam:
A. Precipitation due to over-saturation There is a relationship between the solubility curve of non-crystal silica and the silica concentration in the hot water after the cyclone separator process. These relationship shows that the hot water after having passed through the separator is over-saturated with respect to silica. This implies that the mist contained in the steam after separation is over-saturated, or nearly over-saturated, with silica. Therefore, if the temperature decreases, and flashing, boiling etc. occur in the mist, even slightly, over-saturated will lead to silica precipitation. Some of the silica scale is thought to originate in over-saturation, but it is difficult to qualitatively estimate how much silica scale is produced by this mechanism.
B. Precipitation due to flash Small pressure drops occur at the main stop valve, the sub-stop valve and the strainer, and this causes flashing of the hot water mist. This flash probably produces much of the silica scale adhering to these areas. Repeated precipitation of silica in the mist leads to progressive silica scale forming on the surfaces.
C. Precipitation due to boiling Numerical simulation and field experiments using real geothermal steam confirmed that the temperature of the first-stage turbine nozzle at the steam outlet side is higher than the steam temperature. This causes the mist covering the nozzle surface to boil; its water content vaporizes, and the dissolved components in the mist, such as silica, precipitate and solidify on the nozzle outlet.
4.5.2 Turbine Water injection system Over-saturation, flash and boiling of the mist are possible mechanisms for scale adherence. In these three cases, injecting water into the steam (preventing flash and boiling) and in lowering the concentration of the silica in the mist (preventing over-saturation). Washing off of the accumulated scale is also expected.
The turbine water injection equipment directly atomizes the circulating water (steam condensed water) through the injection nozzle into the main steam piping. The injection nozzle is positioned some distance before the main stop valve, and the distance allows the injected water and steam to thoroughly mix before they reach the steam turbine inlet. To prevent the steam turbine from corroding, wetness measuring equipment was installed before the turbine inlet.
The results of the turbine water injection tests indicated that water injection for two hours every two weeks was the most preferable, and the station will be operating stably with this routine.
Blade washing system utilizes water from the hot well pump outlet, pressurizes it by a pump and injects it into the main steam line. The injected water dissolves and removes scale deposited on the first stage nozzles.
4.5.3 Mist separator system It is difficult to efficiently separate minute mist particulates in the steam without changing their state. However, if the injected water is directly atomized into the steam line and the relatively large water droplets thus produced catch the mist particulates, it is easy to separate them downstream. This permits reducing the amount of mist in the steam and leads to a considerable decrease in the scale-adherence rate to the turbine nozzle, etc.
The equipment has ten nozzles, which directly atomize circulating water into the main steam piping, and two mist eliminators, which efficiently remove the injected water.
Water injection is accomplished with a venturi tube configuration. The mist separating equipment will be abbreviated as MSP (Mist Separator).
4.5.4 Conclusion To reduce scale formation at the Geothermal Power Station, turbine water injection equipment was installed. Water injection tests indicated that water injection of 1-2% of the steam weight is effective in preventing scale accumulation and in removing it. The steam turbine can be operated satisfactorily without causing shaft vibration, corrosion and so on.
By installing and operating the MSP upstream, the purity of the steam was improved, and significant improvements in the preventing of scale accumulation were achieved.
The noticeable effects of running the mist separating equipment and the water injection equipment are: reduced reconditioning costs for scale removal and avoiding output reductions
4.6 Turbine room crane
The turbine room crane will be provided for maintenance and overhaul of the steam turbine, generator and auxiliary equipment.
The crane will be an overhead, double girder bridge type with motor operated main and auxiliary hoists, trolley and bridge. Control of the crane will be performed from a crane supported operating cab.
Technical data of crane:
5 COOLING SYSTEM
5.1 General
The cooling system consists of the following systems:
Basic design information for circulating cooling water
Circulating cooling water volume:
5.2 COOLING WATER SYSTEM
5.2.1 Main design information
Water circulation system is used for cooling the condenser of steam turbine and air cooler & oil cooler of power station. After heat exchanging with the equipments, temperature of cooling water rises about 17℃. The hot water will be sent back to cooling tower by hot water pump. After exchanged with air in the tower, the hot water is cooled down to 30℃ and then flown to the cooling water basin then flows to the condenser by gravity. There is about 2-3% of the water will be lost during the operation and it will be maker up by cleaning geothermal water piping in the mill.
One side filtrater is set in this system, so a portion of the circulation water can be filtrated, in this case the water quality can be reached. A portion of cooled water will be re-flooding into the ground through a combination seal well and spreader channel.
The cooling water constant quality shall be maintained by means of chemical treatment defined by pH control and microbiological control. Chemical treatment of the cooling water shall be applied to achieve two specific objectives: --to maintain the pH of the cooling water to an optimum value of between 5 and 6.5 --to prevent biological fouling of the cooling tower
The cooling tower is of a mechanical forced draft counter-flow type. The material of tower structure is FRP (Fiber Reinforced Plastic) in stead of wood usually applied. In case of FRP structure, fire fighting system is not required and skilled carpenters are not required.
5.2.3 Location of Cooling Tower
The cooling water tower shall be located so that prevailing winds will not blow towards the power plant buildings as the mist and vapors may be corrosive and obnoxious, and humid air circulation, which would reduce tower performance, shall be avoided.
6 OTHER WATER SYSTEM
6.1 Water Fire Fighting Pump
The plant is protected against fire by any one or combination of the following systems.
The system is designed in accordance with the requirements of the U.S. National Fire Prevention Association codes and standards. Special fire protection provisions are made for the following areas, which are particularly susceptible to fires:
Service water is used for fire protection. Two electric fire fighting water pumps are provided and tank suction from the fresh water storage tank.
6.2 Sanitary
The sanitary wastes from the plant are managed in a sanitary sewage treatment plant. There will be some septic tanks. The discharge of the plant is monitored to ensure that it is within acceptable limits.
6.3 Waste water treatment system
Waste water from plant will be collected and treated in the waste water treatment system, for control of pH, suspended solids and heavy metals. This system will included a waste water pond to receive and store intermittent flows from drain and partition oil pond.
Oil contaminated waste water from power plant equipment wash and drain shall be routed through a oil-water separator prior to being routed to a partition oil pond. Oil-water separator is set in open ditch in the building, and oil-water separating pond is installed in the site.
7 VENTILATION AND AIR CONDITIONING SYSTEMS
7.1 Ventilation Systems
Ventilation systems are provided in the turbine generator building, baghouse, control building, and other areas such as diesel generator set room, air conditioning plant room, demineralizer building and various pump houses.
7.2 Air conditioning Systems
Air conditioning is required in various areas in the main control rooms that house control equipment. Air conditioning is provided by individual air conditioning units.
The air duct system should be equipped with necessary fire damps which should be interlocked with fire alarming system. When fire taking place, the fire damps should be operated to shut off the air flowing, and the air conditioning units should be shut down at the same time. After put out a fire completely, the fire damps should be come back to original state and the air conditioning system should be take into operation manually.
Office, classroom, test room and other necessary air conditioning room, should be conditioned by split air conditioner, The operation and installation should be depend upon the requirement of the manufactory.
The electrical rooms should be equipped with ventilation system to keep the rooms of positive pressure so that the H2S would not retain in the rooms and the content of H2S in these rooms should be kept at an acceptable level, and the ventilation system should also be used to discharge heat generated by the electrical devices.
Special protection has to be foreseen for electrical equipment with respect to H2S gas, which is usually found in the ambient air in geothermal power plant projects. The supply air to electrical switchgears, relay, computer and control rooms shall be treated (H2S filters)..The rooms requiring the supply of H2S free air shall be provided with special features, such as positive pressure with air tight doors etc. and monitored by H2S detectors accordingly.
8 INSTRUMENT & AUTOMATION
8.1 General description The Power plant will be monitored and controlled by DCS. The instrumentation and system for the project is a microprocessor-based distributed control system. The distributed control system is designed to provide: - High reliability - Failsafe operation - Capability of being upgraded - High productivity - Safety for equipment and personnel - Minimum number of discrete display and recording instruments The distributed control system includes the following functionally distributed subsystem: - Distributed digital control for closed loops - Programmable logic controller for open-loop controls - Operator console (unit control board) - Process data acquisition - Supervision subsystem (engineer console) - Programming subsystem - Historical data storage, retrieval, and calculation subsystem These subsystem are designed to ensure: - One to two-second response time - 100 ms data update rate - 1 ms data resolution for sequence of events points The distributed control system includes adequate redundancy at various levels. The system is designed for “fail-safe” operation and is in full conformity with the specifications and recommendations of codes and standards of recognized international technical bodies and institutes. In general, most of instruments composing the main control loops for plant operation will be electronic type. Regarding those control loops which are not critical or which do not require precise control, local pneumatic instruments will be used. The standard electronic signal level of 4-20 mA DC will be used for instruments. The power supply for instruments will be 220 V AC and 24 V DC.
Annunciator system, in accordance with specific requirements, will be provided so that abnormalities in critical systems can be observed.
The entire system will be so designed that systematic overall operation may be possible with a small complement of operators.
Each final control drive and/or control valve will be furnished with an electronic/pneumatic positioner where applicable to operate a pneumatic actuator capable of working on an air supply pressure.
Supervisory instruments (such as indicators, recorders, integrators), controllers, and annunciators will be mounted on control panels. Important control components such as remote control switches, indicating lamps, emergency stop buttons and annunciator test/acknowledge/reset buttons will be also mounted on control panel.
Main functional instruments such as controllers, various computing relays, alarm setters, signal converters, and power supply units will be mounted insides the control panel.
In the control room thermo-parameters and equipment will be supervised, controlled in normal operation and treated in emergency.
8.2 Scope of supply
8.3 Engineering standard of instrumentation
8.4 Process Measurements
The DCS system is standardized and of rigid design for location in industrial control room. The system includes necessary display for operation and dynamic process information, and also safety interlocking, alarms. “Trends” display can be used for easy process check-up; alarms and report can be printed via printers in control room. The DCS includes 3 operator stations (OS), one of OS will be also use as engineering station, and also include 2 printers. Main feature of DCS control system:
The operator and engineer station will be at least P4/2.0GHz, and 256M RAM, 19”CRT.
9 ELECTRIFICATION
9.1 General 9.1.1 All electrical equipment and materials shall be of high quality and reliable. In order to avoid corrosion of H2S, materials used for producing these equipments should be corrosive resistant. Aluminum is preferable than copper for usage, if copper is requisite in these equipment as material, then corrosive resistant coating materials are applied on the surface which would contact with H2S, the material or metal elements for coating can be zinc or other suitable materials.
9.1.2 All electrical equipment shall, if not otherwise specified, comply with the applicable following codes, standards and recommendations: ¾ IEC International Electrotechnic Commission
9.2 Scope of Supply
¾ Uninterruptible power supply system (UPS)
9.3 Power system
9.3.4 Grounding system High voltage 20kV Neutral isolated Medium voltage 6.3 kV Neutral isolated Low voltage 400/230V Neuter grounding solid Detail see electrical single line drawing
9.4 Design documentation and diagram of the electrical engineering
¾ Document schedules.
¾ MCC interconnection diagrams. ¾ Interlocking logic diagrams. ¾ Motor lists. ¾ Electrical bill of materials. ¾ Operation, maintenance and installation instruction manuals. ¾ The setting values and calculation for protection relays. ¾ Calculation for short circuit and voltage drop. ¾ Test report for all electrical equipment. Detailed specification for each and individual equipment. ¾ Grounding system engineering. ¾ Lightning protection design. ¾ Lighting design engineering. ¾ Battery and battery capacity design. ¾ Fire alarm system design ¾ Lighting layout design. ¾ Emergency lighting layout design. ¾ All drawings, data, calculations and manuals will be written in English.
9.5 Power consumption of plant motors The estimated installed power of the project will be 2MW, the estimated demand power will be 1.6MW. The estimate emergency power will be 50kW. 9.6 Protection relay and automatism equipment The protection relays and automatism set shall be the microcomputer type. The following Protection relay and automatism equipment will be installed:
9.6.1 Generator ¾ Differential ¾ Earthing fault (one site grounding for stator) ¾ Over voltage ¾ Over temperature ¾ Over current ¾ Excitation fault ¾ Under voltage ¾ Over load ¾ Automatic manual synchronizing system
9.6.2 20kV outgoing line ¾ Current and voltage fast protection 3ph ¾ time-delay current protection 3ph ¾ Over current protection 3ph ¾ Earthing fault ¾ Auto reclosing relay ¾ Automatic and manual synchronizing system
9.6.3 20/6.3kV step up transformer
¾ Buchholz protection ¾ Over temperature
9.6.4 6.3/0.4/0.23kV transformer ¾ current fast protection 3ph ¾ Over current protection 3ph ¾ Earthing fault ¾ Over temperature
9.6.5 Plant 0.38kV service motor
¾ current fast protection 3ph ¾ Over current protection 3ph ¾ Over load protection ¾ Long starting time protection ¾ Earthing fault ¾ Low voltage ¾ Others
9.8 DC System DC system will comprise of the following: ¾ Stationary batteries (220V DC) ¾ Battery charger connected to the LT switchboard ¾ 230V DC distribution switchboard ¾ Other accessories
The battery charger shall be monitor mode and automatic charging mode.
9.9 Lighting 9.9.1 Lighting voltage shall be 220V, single phase, 50Hz
9.9.2 Illumination levels ¾ 300 lux in control rooms and offices ¾ 200 lux in switchgear room and MCC room ¾ 200 lux in generator room and loading areas ¾ 50 lux on stairs and platforms ¾ 25 lux in the yard
9.9.3 Luminaire Fluorescent lamp for control room, offices and some indoor working areas.
Incandescent lamp for some emergency lighting, small room, etc.
Color-improved mercury or similar types with low energy lights for high building or structure, large working areas, flood lights. etc.
9.9.4 Emergency lighting The emergency lighting unit incorporated with battery-rectifier, normally will be used in process departments and other buildings.
The emergency lighting for control room and other important places within the power plant shall consists of incandescent lamps fed from the 220V DC battery unit.
9.10 Grounding The 20kV and 6.3kV system normally will be neutral isolated. The low voltage power distribution system normally will be neutral solid grounded (TN system). The overall resistance shall not exceed 1 ohm for any path to grounding. Conductors may be bare aluminum wire or galvanized steel.
9.10.1 Communication and Uninterruptible power supply system (UPS) Any required equipment and communication service will be provided.
One set of uninterruptible power supply system (UPS) (3kVA ) will be provided
9.10.2 Technical specification for electrical equipment All enclosure and equipment shall be tropicalized.
Detaisl see technical Schedules
A. 20kV switchgears and 6kV switchgears Switchgear shall be complete with protection and other necessary metering, testing, operating devices and special tools.
The space heater shall be installed.
B. 20kV Circuit breaker and 6kV circuit breaker The circuit breaker consist of spring charging of manual and motor driven. The control voltage of the circuit breaker is 220DC. C. 380V Switchboard The circuit breakers in the switchboard shall be of draw out or fixation type. The Cubicles shall be arranged in free standing vertical assemblies with ten small size starters at most in a single stack. The bottom enclosure of each stack should not contain a starter, it may be used for connections and fittings. The center itself be sized for future expansion. The starter and all controls for each motor shall be in single enclosure.
An automatic space heater shall be installed.
D. Transformers The step up transformers will be oil immersed type. The unit auxiliary transformers will be try type. Detail see technical Schedules.
E. Motor Low voltage AC Motor
Most of the motors will be squirrel cage induction type, and normally started directly on line.Soft-starter will be supplied as necessary. Motors from 0.37 to 200kW shall be 380V. ¾ Type ¾ Rated voltage 380V ¾ Frequency 50Hz ¾ Insulation class F ¾ Protection class IP54
All conductors that are exposed to air shall be aluminum or zinc coated copper.
Armored cable shall be used except where specific applications require conduits.
¾ Type Series YJLV ¾ Rated voltage 1kV ¾ Insulation XLPE
2. High voltage power cable ¾ Type Series YJLV ¾ Rated voltage 6kV ¾ Insulation XLPE
3.Control cable ¾ Type Series KVV ¾ Rated voltage 0.5kV ¾ Insulation PVC
G. Spare parts The Vender shall supply spare parts for two years operation.
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