1. Luding Hydropower Station
Luding Hydropower Station is the 12th cascade station in the “three reservoirs and 22 cascades” Dadu River hydropower program of Luding Hydropower Station, connecting Huangjinping Cascade Power Station. The engineering dam site is located on the reaches, about 2.5km at the upper reaches of Luding County, Ganzi Tibetan Autonomous Prefecture, Sichuan.
The elevation of the power station dam crest is 184.00m, the dam crest is 12m wide, and the bottom elevation is 1300.00m. The normal water level is 1387.00m, the corresponding normal water storage capacity 219.5 million m3, water level of check flood is 1381.15m, the corresponding capacity 240 million m3, and dead water level 1375.00m. The critical discharge mode shall be employed for the water level in the flood season, with the dam backwater of 78m high and maximum dam height of 84m.
The operation mode of the water level before the dam based on the cascade discharge regulation shall be adopted for Luding Reservoir in flood season, and the proposed operation mode is:
Before the impoundment of Changheba Reservoir, the 1370m water level shall be adopted for the sediment releasing in the flood season (May ~ October) before the dam. If the water level before the dam in the non-flood season is between the 1375m dead water level and 1378m normal impounding level, the daily regulation shall be adopted.
After the impoundment of Changheba Reservoir, in the flood season (May ~ October), when the storage volume is less than the 2100m3/s cascade discharge, the water level before the dam shall be reduced to 1373m. When the inflow discharge is greater than 21000m3/s but smaller than 2700m3/s, the water level before the dam shall be lowered to 1373m. When the inflow is greater than 2700m3/s, the water level before the dam shall be reduced to the 1370m water level for the sediment releasing in the flood season. The water level before the dam in the non-flood season shall be equal to 1375m; if the water level before the dam in the non-flood season is between the 1375m dead water level and 1378m normal impounding level, the daily regulation shall be adopted..
2. Huangjinping Hydropower Station
The dam site of Huangjinping Hydropower Stationin is located about 3km at the upstream of Huangjinping, Guzan Town, Kangding County, Ganzi Tibetan Autonomous Prefecture in Sichuan Province, about 30km down to Luding County.
The normal water level of the reservoir is 1476.00m, the corresponding normal water storage capacity 128 million m3, water level of check flood is 1478.93m, the total corresponding capacity 140 million m3, and dead water level 1473.00m. The operating water level in flood season is 1472.00m, with the dam backwater of 73m high and maximum dam height of 95.5m The reservoir has the capacity of daily regulation.
In the flood season, critical discharge mode shall be adopted: in the flood season (June ~ September), when the discharge flowing into the reservoir is 2500m3/s, the water level before the dam shall be equal to the level used for the sediment releasing in the flood season, and the water in October to next May shall be from the normal water level to the dead water level for daily regulation. .
Changheba Hydropower Station
The site of Changheba Hydropower Station is situated on the reaches, about 4.7km from the estuary of Jintang River at the downstream in Kangding County, Ganzi Tibetan Autonomous Prefecture, Sichuan Province, about 30km down to Luding County.
正常蓄水位库容约10.1亿m3 ，死水位1680m时库容8.9亿m3 。水库
When the normal water level is 16910m, the maximum water depth before the dam is 213m, the corresponding normal water storage capacity is about 1.01 billion m3. When the dead water level is 1680m, reservoir capacity is 890 million m3. The reservoir has the capacity of quarterly regulation, and can effectively control sediment.
Operation mode of reservoir: the reservoir is usually regulated on a daily and weekly basis, and the water level of the reservoir varies between the 1690m normal impounding level and the 1680m normally used dead water level. In the event of extremely low water year or in order to meet the power need of the grid, the water level of the reservoir can be reduced to the 1650m dead water level, which can be operating quarterly and weekly to give full play to role of regulation of Changheba Reservoir.
The proposed Huangjinping and Changheba Reservoirs at the upstream of the Yuanyangba shall be subject to the operation and regulation on a daily basis. In the flood season, they will not intercept the flood. After the completion, they will not have huge impact on the natural flood process of the reaches of flood control works in the silicon factory. Natural water supply is still used for the flood in Yuanyang reaches.
(II) Analysis of sediment scouring and silting of Luding Reservoir
To predict the sediment scouring and silting evolution of the reservoir as well as the impact of the deposition on the land for the production and construction of Ganzi Xinyuan Silicon Industry Co., Ltd. of the Yuanyangba at the rear of reservoir, the scouring and silting calculation of the reservoir is calculated.
Conditions for calculating sediment scouring and silting
Vertical and horizontal sections in reservoir area
For the sections used to calculate the sediment scouring and silting in Luding, there are 24 cross sections in the19.5km section of the reservoir area. Of that, Yuanyangba reaches where the project is located shall have the cross sections calculated, increased and amended in accordance with the flood control wall lines proposed in the design of engineering planning.
See Table 5 for the points coordinates of the flood control wall on the five representative cross sections.
Table 5 Statistics of the points coordinates of the flood control wall on the five representative cross sections of the reaches of silicon factory
(2) Sediment conditions in the reservoir
According to the suspended load sediment series of Luding Hydrological Station, the years of 1989 (the year of high water and high sediment), 1988 (the year of medium water and medium sediment) and 1959 (the year of dry water and low sediment) were selected as the representative years to calculate calculating sediment scouring and silting. In these representative years, the average sediment runoff is 9.71 million tons, and sediment concentration is 348g/m3, which are similar to the perennial average value of the long series.
In view that the construction period of Changheba Hydropower Station is longer than that of Luding Hydropower Station, Changheba Hydropower Station impounds water in the first three years. Therefore, the sediment transport process is employed in the first three years for Luding Hydropower Station, and from the 4th year, it will impound water for Changheba Hydropower Station. Then, the results of the suspended load sediment gradation of grain which is obtained from the weighted integration of sediment runoff of the sediment out of the reservoir of Changheba Hydropower Station and interval natural sediment shall be adopted.
Results of scouring and silting calculation
Luding Reservoir operates one to three years, and most of the sediment deposits in the reservoir. Three years later, due to the impoundment and sediment detention of the reservoir of Changheba Hydropower Station at the upstream, most of the suspended load and all suspended load sediment at the upstream is retained, the grains out of the reservoir is fine, so it will be unlikely to deposit in the reservoir of Luding Hydropower Station. The sediment in the reservoir of Luding Hydropower Station is mainly the suspended load and bed load of the section, so the deposit of sediment becomes slower.
Luding Reservoir operates for three years, the head of the deposit island of the suspended load is thrust to 11.3km from the dam, the total siltation of the reservoir volume is 15.62 million m3, and the average siltation elevation before the dam is 1312.0m, the out-of-reservoir rate of suspended load 28.8%, reservoir capacity loss below the normal water level is 7.24%, and the average sediment concentration out of the reservoir is 101g/ m3. The start point of the sediment siltation is at the downstream of Lengzhuguan powerhouse, and the sediment is deposited at the reaches of Yuanyangba.
Luding Reservoir operates for 20 years, the head of the deposit island of the suspended load is thrust to 9.434km from the dam, the total siltation of the reservoir volume is 24.27 million m3, and the average siltation elevation before the dam is 1312.0m, the out-of-reservoir rate of suspended load 82.6%, reservoir capacity loss below the normal water level is 11.3%, and the average sediment concentration out of the reservoir is 82.9g/ m3. The start point of the sediment siltation is still at the downstream of Lengzhuguan powerhouse, and there is no sediment deposit at the reaches of Yuanyangba.
Luding Reservoir operates for 100 years, the head of the deposit island of the suspended load is thrust to 4.0km from the dam, the total siltation of the reservoir volume is 64.89 million m3, and the average siltation elevation before the dam is 1314.7m, the out-of-reservoir rate of suspended load 83.1%, reservoir capacity loss below the normal water level is 29.6%, and the average sediment concentration out of the reservoir is 85.0g/ m3. The start point of the sediment siltation is still at the downstream of Lengzhuguan powerhouse, and there is no sediment deposit at the reaches of Yuanyangba.
Fig. 3 shows the longitudinal section of sediment deposit of Luding Reservoir.
(IV) Calculation of flood surface line
In order to impacts of the rising backwater at Yuanyangba reaches on the project as well as the upper reaches, the backwater calculation has been done for the reservoir of Luding Hydropower Station. The bed surface that has 20 years of sediment deposition is adopted for the backwater calculation to calculate the backwater surface profile in case of floods in different frequencies.
In the above Equations (1), (2) and (3), the parameters represent: Q for discharge, B for channel width, H is water depth, U is the water level, X for the calculation of river reaches length, K for discharge modulus, subscripts i and i +1 for the number of the upper and lower river sections, F for overflow area, △x for length of reaches, and n for roughness of reaches.
In view that the impacts of the backwater of the project mainly occur in the flood season, the influences of non-flood season are small. Therefore, only the flood water surface profile in the flood season has been calculated. During the calculation of backwater, the flood with the 100 recurring interval is taken as the upper limit in the flood season and the flood with the 50 recurring interval as the lower limit. The flood discharge is 6530m3/s and 6080m3/s. When Luding Hydropower Station is put into production, the operating water level for sediment release of Luding Hydropower Station in flood season is 1370m.
The roughness of the natural river way is calculated. For the reaches below Lengzhuguan Hydropower Station, according to the measured water edge in September 10, 2004 (corresponding discharge of 2150 m3/s), the water level ~ discharge relationship at the tail water of Lengzhuguan Hydropower Station powerhouse after the recheck in 2005; and for the reaches above Lengzhuguan Hydropower Station, according to the flood marks from Yuanyangba to Guzan which were investigated in 1992 as well as the water level discharge relationship of the Yueliangwan water gauge section, the natural roughness is generally around 0.06, and even up to 0.09 in some cases.
For the roughness of reservoir area after the sediment deposits, the roughness of the suspended load sediment silting reaches shall be 0.04, and the integrated roughness of natural waterway shall be adopted for the reservoir tail and natural water way.
Calculation of results
See Table 6 and Table 7 for the backwater calculation results of Luding Reservoir in the flood season before and after the construction of flood control walls in the silicon factory.
Table 6 Backwater calculation results (flood wall) of Luding Reservoir in flood season before and after the construction of embankment (flood control walls)
The results show that: As the back water of the Luding dam site is high, when the reaches of Dadu River in the reservoir area are attacked by the flood of the same frequency, the water level rises largely compared with natural level. The farther the reaches are from the dam site, the smaller the increases in the water level will be. Because dam’s backwater has a large overflow area, the flow slows down much more than the natural situation. The nearer the reaches are from the dam site, the more the velocity will reduce. As the water level at the reaches of the reservoir tail rises by a small value, the velocity will be close to that in the natural situation.
After the flood control wall is built in the silicon factory, in the event of a 50-year flood in the flood season (Q=6080m3/s), the water level at the representative section at Yuanyangba reaches (14#+1) is 1383.96m, 0.04m higher than natural water level; in case of 100-year flood (Q=6530 m3/s), the representative sections of Yuanyangba reaches has a 1384.71m water level, 0.25m higher than the natural situation.
See Figs 3 and 4 for the water surface profiles of natural water and siltation.
Fig. 3 Siltation backwater diagram of Luding Reservoir (50-year flood)
Fig. 4 Siltation backwater diagram of Luding Reservoir (100-year flood)
Overflow area of sections and analysis of river width changes
To understand the changes in the waterway cross sections before the construction of flood control wall, five typical sections were selected according to the engineering arrangement. The section points GM1, GM2, GM3, GM4 and GM5 of the corresponding flood control wall lines are used for analysis. See Fig. 2 for the location of the typical sections. As Luding Hydropower Station has been commenced, only the cross sections of all typical sections are drawn in this report. See Table 8 for the calculated overflow area of all typical sections and changes in water surface width under two magnitudes after the impoundment of Luding Hydropower Station.
Table 8 Calculation results of typical section changes after the commencement of flood control walls in the silicon factory
1. Each boiler shall be installed with one set in light of this system, and the independent materials list (excluding drainage system) shall also be reckoned as one set.
2. The pipe installation shall be made according to the actual conditions of the site. Except that steam-water door of coal grinding mill is installed in 0m floor, the others shall be installed in a place easy to operate in 7.0m operating stratum.
3. The supports and hangers of pipes shall be considered on site, and the interval of supports and hangers shall also be 2m.
4. The hydraulic pressure test with test pressure of 13kg/cm shall be conducted after installation of pipes is complete.
5. The closed template shall be installed at the inlet of equipment, and the thickness of asbestos plate shall also be determined through site test (operating pressure of steam can break through).
6. The steam for fire-extinguishing can be led out from deaerating & heating steam mains.
4.1 Circulating Water System
4.1.1 Systematic Configuration
The circulating water system shall be single pipe-main scheme recirculating sea water supply system. Two sets of condensate turbosets shall be equipped with two mechanical draft cooling towers with 12×12m2 , three circulating water pumps, one piece of Dn800 circulating water inlet pipe and one piece of Dn800 circulating water outlet pipe. The circulating water pump shall be installed and arranged in circulating water pump house near cooling tower.
4.1.2 Main Design Parameters of the System
a）Water requirement of cooling water
Cooling ratio m＝65 times
Cooling water volume of the condenser of each turbine 1482m3/h
Cooling water volume of two turbines 2964m3/h
Namely, the designed water volume of circulating water system shall be 2964m3/h.
b）Circulating water pump
Model of mating motor: Y280S-4、N=75KW
When three sets of circulating water pumps make parallel operation, the flow rate of single pump shall be 988m3/h and the lift shall also be 17.87m. When two turbines and one pump operate, the flow rate of single pump shall be 1112m3/h and the lift shall also be 16.74m.
Two sets of condensate turbosets shall be equipped with two mechanical draft cooling towers with 12×12m2.
Fan of cooling tower: L6 type; diameter of fan: Φ6000mm.
Wind volume: 106×104m3/h
Power of mating motor: 75KW
Zhejiang Shangyu Dongjie Cooling Tower Co., Ltd shall be responsible for the design and supply of cooling tower. Under the designed conditions of meteorology, the cooling water volume of each cooling tower shall be 1600m3/h and the inlet water temperature of the tower shall be 40.8℃; and the outlet water temperature of the tower shall also be no more than 32℃.
4.1.3 System Control
The main equipments of circulating water system shall be centrally controlled in circulating water pump house.
4.2 Auxiliary Cooling and Industrial Water Systems
The auxiliary cooling and industrial water system shall be single pipe-main scheme recirculating fresh water system. The auxiliary machinery of three steam turbosets and industrial water of the power station shall be equipped with two glass reinforced plastic mechanical draft cooling towers, three industrial water pumps, one piece of Dn400 industrial water inlet pipe and one piece of Dn400 industrial water outlet pipe. The industrial water pump shall be arranged in auxiliary cooling water pump house set near auxiliary cooling tower.
4.2.1 Main Design Parameters of the System
a）Water requirement of cooling water
The volume of auxiliary cooling water of three steam turbosets shall be 360m3/h.
The volume of industrial water for power station shall be 240m3/h.
The designed water volume of auxiliary cooling water and industrial water systems shall be 600m3/h.
b）Industrial water pump
The power station shall be equipped with three industrial water pumps including two sets under operation and one set for standby.
Power of mating motor: 55KW
The auxiliary cooling water and industrial water systems shall be provided with totally two glass reinforced plastic mechanical draft cooling towers. The cooling water volume of single tower shall be 300m3/h.
Fan of cooling tower: TF-34 type, fan diameter of Φ3400mm
Wind volume: 16×104m3/h
Power of mating motor: N=11KW
The designed meteorologic condition of cooling tower shall be the same as circulating water system.
Inlet water temperature of cooling tower: 40.8℃; outlet water temperature: ＜32℃
4.2.2 System Control
The main equipment of auxiliary cooling and industrial water systems shall be controlled in auxiliary cooling water pump house.
4.3 Water Replenishing System
4.3.1 Water Replenishing System of Circulating Water
The max. replenishing volume of sea water for circulating water system of electric power station shall be 61.7m3/h. The makeup water of the system comes from cooling tank in sugar manufacture part, and the main body design unit of sugar manufacture shall be responsible for the design of water supply and drainage. This design is merely involved with water delivery pipes connected from sea water replenishing pump house to water tank of circulating water cooling tower of electric power station.
4.3.2 Auxiliary Cooling and Industrial Water Systems
The fresh water shall be adopted for auxiliary cooling water and industrial water systems of electric power station. The max. water replenishing volume of circulating and cooling parts shall be 12.5m3/h (excluding partial water volume of unrecovered loss of industrial water). The makeup water shall be desalted with sea water and supplied by the owners. This design is merely involved with water delivery pipes connected from fresh water orifices to auxiliary cooling water tank.
4.4 Outdoor Water Supply & Drainage System
4.4.1 Outdoor Water Supply System
Outdoor water supply system shall consist of industrial water supply pipe, industrial water return pipe, raw water pipe, domestic water supply pipe, service water pipe, firefighting water supply pipe and circulating water replenishing pipe, etc.
The main trunk pipes of industrial water supply and return pipes shall be Dn400 PE compound pipes reinforced with mesh steel strip, which are used for water supply of auxiliary cooling water and industrial water of main workshop and industrial water of the entire plant. The water in this part shall also be recovered into auxiliary cooling tower for cooling and then used for recycling use.
The main trunk pipes of raw water pipe shall be Dn200 diameter and belongs to PE compound pipes reinforced with mesh steel strip which are used for water supply of chemical water treatment chamber.
The main trunk pipes of service water pipe shall be Dn100 diameter and belongs to PE compound pipes reinforced with mesh steel strip which are used for water flushing of coal handling system of electric power station and coal bunker bay of main workshop and washing water as well as greenery water of the roads in plant area.
The main trunk pipes of firefighting water supply pipe shall be Dn200 diameter and belongs to PE compound pipes reinforced with mesh steel strip which are used for supply of indoor & outdoor firefighting water in electric power station.
The main trunk pipes of domestic water supply pipe shall be Dn100 diameter and belongs to PE compound pipes reinforced with mesh steel strip which are used for domestic water supply in electric power station.
The main body design unit of sugar manufacture part shall be responsible for the design of firefighting water and domestic water in electric power station. This design is merely involved with indoor & outdoor firefighting and domestic water in buildings and structures in the power station.
This design scope shall be involved with installation of pipeline systems such as industrial water supply and return pipes, service water pipes and raw water pipes in electric power station and booster pumps.
4.4.2 Outdoor Water Drainage System
The outdoor water drainage system shall consist of rainwater drainage system, industrial waste water and domestic sewage as well as coal-water drainage systems, etc.
Rainwater drainage system shall be connected through open ditch into drain ditch crossing the entire plant area along the two sides of the roads in plant area and then finally discharged out of the plant area.
Industrial waste water and domestic sewage of electric power station shall be centrally discharged out of the plant area through combined pipe network. The main body design unit of mineral manufacture shall be responsible for treatment or discharge.
The washing water of coal handling system involved with electric power station, floor washing water around dry coal shed and rainwater in initial stage shall be discharged into flood drainage ditch through deposition of coal sedimentation tank.
The water displacement of circulating water system of electric power station shall be 21.6m3/h, which is discharged into rainwater system.
The water displacement of Industrial waste water and domestic sewage of electric power station shall be 63.2m3/h, which is discharged into the disposal system.
The diameter of drain pipe shall be d300, and the gradient of drain pipe shall be i＝0.003; when the flow rate is designed, the fullness degree shall be 0.41 and flow rate shall also be 0.64m/s.
4.5 Firefighting System
4.5.1 Water Firefighting System
The water firefighting system of electric power station adopts independent firefighting pipeline system with firefighting water volume of 173m3/h and firefighting water pressure of 70m. The firefighting water sources come from sugar manufacture part. The main body design unit of sugar manufacture part shall be responsible for the design of system control.
The outdoor fire hydrants shall be set along the roads outside power station chambers, and indoor fire hydrants shall also be set in main buildings chambers.
The coal handling trestle and coal bunker bay shall be equipped with automatic fire-extinguishing sprinkler system.
For design contents of fire detection and alarm parts of electric power station, please see the Design Drawings of Heat Control Discipline for details.
5.1 Construction Precautions
The project construction shall be made according to the design drawings, and general technical modification shall be executed upon the consent of design representative of work site. The change of important principles shall also be examined and approved according to the formal procedures.
The design specifications and relevant character marking shall be generally specified in shop drawings of all volumes, but it shall also pay attention to the following items during construction. So that it ensures construction quality and meets the requirements of project quality.
（1）The metal pipes used for water supply part shall be processed, welded, installed, tested and accepted according to the regulations of “Technical Specification for Construction and Acceptance of Electric Power Construction (Piping Chapter)”（DL5031-94）. The plastic pipes shall be carried out according to the regulations of “Technical Specification for Buried Unplasticized Polyvinyl Chloride (PVC-U) Pipeline of Water Supply Pipe Engineering” (CECS17:2000). The indoor water supply shall be carried out according to the “Code for Construction and Acceptance of Indoor Sanitation Engineering”, and the outdoor water supply & drainage pipes shall also be carried out according to the “Code for Construction and Acceptance of Water Supply & Drainage Pipes Engineering”（GB50268-97）.
（2）The construction of water supply pipes shall be uniformly arranged with underground facilities of electric power station. The sequence of construction shall generally vary from deep to shallow, vary from free-flow conduit to pressure pipe, or vary from small pipe to large pipe or pressure pipe to free-flow conduit at crossing of the pipes.
（3）All equipment, foundations and reserved holes shall be placed with concrete after checking the dimensions of received equipment and design drawings. Besides, the construction of civil works such as reserved hole and embedded parts of buildings, etc shall be only made after the installers coordinate and check it without leakage.
（4）Before test run, the hydraulic structures such as pipe, ditch and water tank involved with water supply part shall be cleaned and not leaved with such sundries as sand, stone, cement, brick, wood and asphalt, etc.
（5）The structures and mounting equipment & pipes jointly constructed by two construction units shall be closely matched at demarcation line. It’s also required to carefully inspect and check the dimensions, positions and elevations of reserved holes in order to prevent the misplacement and disconnection.
（6）Before design and construction of all process systems involved with water supply part, carefully acquaint with design documents and drawings, understand and master design contents for purpose of being convenient for construction.
（7）The main equipment of water supply shall be installed under onsite direction and cooperation of the personnel from the manufacturer who are responsible for checking on all procedures and creating good conditions for its operation.
（8）The design specifications shall be specified in important fascicules of water supply part. The construction and operation shall also be conducted strictly according to the design specifications.
（9）The installation quality of cooling tower has great influence in cooling effect, so the manufacturer is required to appoint the relevant personnel to make onsite direction.
（10）Firefighting water system is an independent system, so any other branch pipes are not allowed to be freely led and connected from firefighting water pipes.