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HYDRAULIC PIPE SIMULATION NETWORK MODELING – A CASE STUDY

ACW PUMPS HYDRUALIC MODEL

Gist

  • Auxiliary Cooling Water (ACW) Pumps caters cooling water for DG, Lube Oil Coolers, STG Coolers, Control Room AC Units, BFPs, Air Compressors etc.
  • There are 4 fours of centrifugal pumps are installed to cater cooling water for all these auxiliary users.
  • ACW 1 & 2 are connected in a common header is designed to deliver flow rate of 750 m3/h against the head of 45 mWC.
  • ACW 3 & 4 are connected in a common header is designed to deliver flow rate of 500 m3/h against the head of 45 mWC.
  • These two pumping circuits are connected in common header from a 4’’ line near to STG lube oil cooler.
  • Normally ACW 1 & 3 are operated in parallel to cater water flow rate for all these 11 no’s of auxiliary users.

Performance Study on ACW Pumps

Design Details / Pump Identification Units  ACW 1 ACW 3 Combined
Measured Flow rate m3/h 675 80 755
Suction pressure kg/cm2 0.25 0.25 0.25
Discharge pressure kg/cm2 46.5 46.5 46.5
Measured total Head m 44 44 44
Measured power kW 104 38.9 142.9
Pump Operating efficiency % 77.8 24.6 63.3

Situational Analysis

  • It is obvious pressure mismatch due to operating different duty pumps in parallel, which results in throttling effect of ACW 1 on ACW 3.
  • ACW 3 is performing very inefficiently due to this operating scenario. Hence parallel operations of ACW 1 and ACW 3 should be avoided.

ACW3 be closed and with proposed network modification, ACW1 alone would cater the requirement – more than Rs 20 Lakhs savings.

ACW 1 & 3 - BASE CASE MODEL – Flow Profile

ACW 1 & 3 - BASE CASE MODEL – Velocity Profile

ACW 1 & 3 - BASE CASE MODEL – Pressure Profile

Major Observations

  • 10’’ Main Header has a pressure drop of 3.2 mWC
  • Also 2’’ Lines has a pressure drop of minimum  4 mWC

ACW 1 - CFB & AFBC 4’’ Line Modification + DG Valve Closed + ACW 3 Off – Flow Profile

Pump in Operation – ACW 1

Total Flow – 668 m3/h

Total Head – 46.8 mWC

Users like STG Lube Oil Cooler, Control Room AC and CFBC/AFBC auxiliaries has to be throttled to maintain flow balance

ACW 1 - CFB & AFBC 4’’ Line Modification + DG Valve Closed + ACW 3 Off – Pressure Profile

Pressure drop has been reduced to  1 mWC after throttling as per requirement

ACW 1 – 16’’ Main Header + CFB & AFBC 4’’ Line Modification + DG Valve Closed + ACW 3 Off – Flow Profile

Pump in Operation – ACW 1

Total Flow – 711 m3/h

Total Head – 44.7 mWC

Users like STG Lube Oil Cooler, Control Room AC and CFBC/AFBC auxiliaries has to be throttled to maintain flow balance

ACW 1 – 16’’ Main Header + CFB & AFBC 4’’ Line Modification + DG Valve Closed + ACW 3 Off – Pressure Profile

Pressure drop has been reduced to 0.38 mWC and velocity reduced to 1.5 m/s after throttling as per user requirement

ACW 1 – 16’’ Main Header Line Modification + DG Valve Closed + ACW 3 Off – Flow Profile

Pump in Operation – ACW 1

Total Flow – 714 m3/h

Total Head – 44.5 mWC

Users like STG Lube Oil Cooler, and Control Room AC has to be throttled to maintain flow balance

ACW 1 – 16’’ Main Header Line Modification + DG Valve Closed + ACW 3 Off – Pressure Profile

Pressure drop has been reduced to 0.38 mWC and velocity reduced to 1.5 m/s after throttling as per user requirement

Summary – ACW Hydraulic Network Analysis

Condition Pumps Operated Flow Rate Delivered 

m3/h

Total Head Delivered

mWC

Observations & Comments
Base Condition ACW 1 & 3 755 46.5
  1. Pressure drop of 3 to 4mWC in 10’’ Main Header and 2 ‘’ CFBC Line – Flow
  2. Starvation in CFBC 2’’ users
  3. Inefficient operation of ACW 3
DG Closed + ACW 3 Off + 4’’ Line Replacement ACW 1 668 46.5
  1. Pressure drop reduced to 1 mWC in CFBC Users
  2. Overall flow got reduced
  3. Pressure drop of 4 mWC in 10’’ Main Header
DG Closed + ACW 3 Off + 4’’ Line & 16’’ Line Replacement ACW 1 711 44.3
  1. Pressure drop reduced to 1 mWC main header
  2. DG Closed
  3. Flow shall be balanced by minimal throttling
DG Closed + ACW 3 Off +  16’’ Header Line Replacement ACW 1 714 44.5
  1. Pressure drop reduced to 1 mWC main header
  2. DG Closed
  3. Flow shall be balanced by minimal throttling
  4. Flow starvation in CFBC 2’’ Line

Recommended Case – Saves 39 kW Power of ACW 3 with higher flow rate

HEAT & MASS BALANCE ANALYSIS OF COMBINED HEAT & POWER PLANT

A Holistic Approach on Energy Utilization Enhancement

Energy Profile – Paper Mill

Approach & Methodology for HMBD Analysis

Coal Fired Boiler (CFB)

Indirect Efficiency Pie Chart

Direct Efficiency of SRB

Direct Efficiency of SRB

HMBD - 30MW CHP Plant – Base case

HMBD - 30MW CHP Plant – Proposed Case

Elimination of HP heater in 30MW CHP

  • vSteam from LP wander bleed is  passed through the HP heater to rise the feed water enthalpy up to 30 kCal / kg
  • v This  enthalpy rise of 30 kCal/kg across the HP heater is taken care also by HP wander bleed by reducing through PRDS,
  • vOn the other hand MP steam is also generated by reducing 65 ksc HP steam to MP steam via PRDS to match 50 TPH requirement.
  • vSo it is highly advisable to eliminate the existing HP heater to avoid energy loss to generate MP steam by PRDS.

HMBD - 25 MW CHP Plant – Base case

HMBD - 25 MW CHP Plant – Case II – Utilization of Back Pressure Turbine

HMBD - 25 MW CHP Plant – Case II – Utilization of Back Pressure Turbine

  • vPRV in place for pressure reduction from 61.1 ksc to 11.6 ksc
  • vDe-superheated to further reduce temperature down to 210 deg C
  • vMicro turbine installation in place of PRV would recover useful energy for additional power generation
  • vRecommended as an energy efficient alternative for wasteful drop in pressure across the PRV through an isenthalpic process
  • vPower generation potential of 1.27 MW is anticipated
  • vThis initiative will payback in less than one year

HMBD - 25 MW CHP Plant – Case III – Turbine Replacement

Turbine Replacement (SRB)

  • PRV in place for pressure reduction from 61.1 ksc to 11.6 ksc
  • De-superheated to further reduce temperature down to 210 deg C
  • Turbine replacement to extract steam at 11.6 ksc and 213 deg C is suggested as an energy efficient alternative
  • Recommended in place of wasteful drop in pressure across the PRV through an isenthalpic process
  • Power generation potential of 1.56 MW is anticipated
  • This initiative will payback in less than 2 year

Sum Up

Turbine Replacement with MP extraction is highly recommended Energy Efficient Case considering its Techno, Economical &  Environmental Credits