1. ZERO WATER INDUSTRY AND INDUSTRIAL WATER EFFICIENCY-CASE STUDY (CS6) WATER CONSUMPTION OF THERMAL POWER PLANTS OF DAMODAR VALLEY CORPORATION By SHYAMA PRASAD PATRA, SE (M) SATYABRATA BANERJEE, DCE (C) HIRANMOY CHATTERJEE, CHIEF ENGINEER-I(M) 1

2. MISSION AND VISION OF DVC Damodar Valley Corporation (DVC), the 1 st multi-purpose River Valley Project of independent India, was formed in the year 1948 by an act of Parliament, similar to the Tennessee Valley Authority (TVA) of the United States, with the following responsibilities:  For taming the wild and erratic Damodar river from its ravaging floods  Irrigation, water supply and soil conservation in the command area  Generation, transmission and distribution of electricity  Socio-economic development of the Damodar Valley

3. MISSION AND VISION OF DVC  However, over the past few decades, power generation has gained momentum.  Other objectives of DVC remain part of its primary responsibility.  Accordingly, thermal power plants were set up by DVC in a phased manner by utilizing the available water resource in the command area so as to be a leading integrated power major while discharging the mandated responsibilities towards flood control, irrigation, water supply and soil conservation, with a firm commitment to the socio- economic development of the command area.  To provide quality power and best in class services at competitive rates to our customer.  Inculcate a culture of value, ethics and integrity in the organisation.

4. CONSUMPTIVE WATER REQUIREMENT Consumptive water requirement in Thermal Power Plants is governed mainly by the following factors:  Quality of raw water (river water/sea water)  Type of condenser cooling system(Closed cycle/open cycle cooling)  Quality of coal  Type of ash disposal system (Dry fly ash, High concentrated slurry disposal, Wet ash)  waste water management system etc.

5. TYPICAL WATER REQUIREMENT FOR 2X500 MW PLANT  Cooling tower make up(80% of total water requirement) : 3,450 m3 /h (1020 m3/h for Evaporation of each Cooling Tower)  Ash disposal : 1,300* m3 /h (330 m3/h for Blow Down to maintain COC of each CW System)  DM water make up : 120 m3 /h  Potable & service water : 250 m3 /h  Clarifier sludge etc. : 110 m3 /h  Coal dust suppression : 70 m3 /h Total : 4000 m3 /h *Tapping has been taken from CW system as blow down water and as such not considered as consumptive water.”

6. AREAS FOR OPTIMAZATION  Cooling water system-Maintaining higher Cycle Of Concentration (COC)  Ash handling system- Adoption of dry fly system or HCSD  Recovery of waste water- Effluent Treatment Plant (ETP) -Ash Water Recovery System (AWRS)  Power cycle make up- Use of Condensate Polishing Unit (CPU)

7. AREAS FOR OPTIMAZATION  Cooling water system-Maintaining higher Cycle Of Concentration (COC) COC is a very important parameter in Cooling Tower operation. This is determined by calculating the ratio of concentration of dissolved solids in the circulating water compared to the make-up water. So, higher COC indicates higher concentration of dissolved solids that may cause scaling in Condenser tubes. Typical COC is of the order of 4-5. However, COC can be further increased by improving the chemical regime of circulating water, thereby decreasing the amount of Blow Down effectively.

8. AREAS FOR OPTIMAZATION  Cooling water system-Maintaining higher Cycle Of Concentration (COC)  Ash handling system- Adoption of dry fly system or HCSD Ash generated due to combustion of coal in a thermal power plant is of two types namely fly ash (80%) and bottom ash (20%). Fly ash is disposed off in wet or dry mode. In wet mode, concentration of slurry is around 30% in case of lean mixture and is around 60-70% for HCSD. However, bottom ash is disposed off in wet mode only as proven technology is not available. Huge amount of water is saved for disposal of ash in dry mode as no water is required and very less water is required for HCSD.

9. AREAS FOR OPTIMAZATION  Cooling water system-Maintaining higher Cycle Of Concentration (COC)  Ash handling system- Adoption of dry fly system or HCSD  Recovery of waste water- Effluent Treatment Plant (ETP) -Ash Water Recovery System (AWRS) Waste water generated in a thermal power plant typically includes clarifier sludge, filter back wash, CT blow down, regeneration waste of DM plant & CPU, Boiler blow down, oil & dust laden effluent etc. Oil laden effluent is passed through oil skimmer (Corrugated plate interceptor) to separate oil. Dust laden effluent is passed through clarifier for dust separation. Chemical effluent is neutralized by suitable chemical dosing before sending to CMB.

10. AREAS FOR OPTIMAZATION The waste water after initial treatment in ETPs is collected in Central Monitoring Basin (CMB). It has high TDS on account of regeneration waste and CT blow down water. Here, Alum/lime dosing is done for PH balance as well as to reduce TDS. The treated water from CMB is utilized in ash water make up/ gardening. Fly ash and bottom ash collected in wet mode is disposed off in ash pond. Around 70% of water used in wet ash disposal is recovered through Ash Water Recovery System (AWRS). The recovered water is again utilized in the form of ash water make up.

11. AREAS FOR OPTIMAZATION  Cooling water system-Maintaining higher Cycle Of Concentration (COC)  Ash handling system- Adoption of dry fly system or HCSD  Recovery of waste water- Effluent Treatment Plant (ETP) -Ash Water Recovery System (AWRS)  Power cycle make up- Use of Condensate Polishing Unit (CPU) The use of CPU can reduce the power cycle make up to below 1%.

12. LATEST GUIDELINES FOR WATER AVAILABILITY As per latest MoEF notification dated 7.12.2015:  Specific water consumption shall be 3.5 Cub. M/MW per hour within two years.  New plants installed after 1 st January, 2017 shall meet specific water consumption of 2.5 Cub. M/MW per hour and shall achieve zero waste water discharge.

13. CHALLENGES TO THE POWER INDUSTRY-ZERO DISCHARGE As per latest MoEF guidelines, the water available for a typical 2x 500 MW power plant to be installed after 1 st January, 2017 is 2,500 m3/h out of which a round 2,000 m3/h is required against evaporation loss in Cooling Tower. The balance 500 m3/h shall meet other requirement of CT blow down, power cycle make up, potable & service water requirement, ash disposal system, coal dust suppression etc. The possible way out:  Adoption of Plant (ultra super critical) with higher cycle efficiency to reduce cooling water requirement (less evaporation loss in Cooling Tower)  Fly ash disposal only in dry mode  Bottom ash disposal in wet mode with AWRS  Higher COC in Cooling Tower to reduce blow down  Effective utilization of CPU to reduce power cycle make up  RO plant in CMB to utilize the recovered water (recovery of waste water).

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