HSRG (Bathurst)

A Heat Recovery Steam Generator, HRSG consists of a gas turbine and gas boiler.

  • Gas turbine produces electricity for plant consumption. Excess electricity will be injected back to the grid for fiancial gain.
  • Hot waste gas heat from the turbine exhaust is fed to a downstream gas boiler. This exhaust heat will assist boiler steam generation and hence save energy bill.
 

HRSG System Overview Panelview Screen

Drum Pressure PID Loop


  • Process Variable, PV = Drum Pressure
  • Control Variable, CV = Gas Burner Firing Rate
  • Setpoint, SP = Operator Input ( production requirement)
  • Feed Forward = Boiler Outlet Steam Flow Rate x Factor

Boiler pressure pre-emptive control as per steam consumption.

Fluctuation of steam flow will directly change the burer firing rate and hence provide instant change to the boiler pressure.

Drum Level Master / Slave PID Loop



Both PID loops work together to control the drum level as per operator setpoint.

The slow master loop is to provide a slow adjustment to the drum level. The fast slave loop is to match the steam flow rate with the drum water flow rate. A feed-forward is added to the setpoint of the slave loop. This is to provide a pre-emptive level control as per changes in the steam consumption. Fluctuation of steam flow will instantly change the slave PID loop setpoint (=drum water flow rate). Consequently, this will have a direct effect to the drum level.


Master PID Loop

  • Process Variable, PV = Drum Level
  • Control Variable, CV = Slave PID Loop Setpoint ( water flow rate )
  • Drum Level Setpoint, SP = Operator Input ( as per Boiler Spec.)
  • Feed Forward = Boiler Outlet Steam Flow Rate x Factor

Slave PID Loop

  • Process Variable, PV = Drum Inlet Water Flow Rate
  • Control Variable, CV = Drum Water Valve Opening
  • Drum Water Flow Rate Setpoint, SP = Master Loop CV
  • Feed Forward = Boiler Outlet Steam Flow Rate x Factor

Feed Water Return PID Loop


This PID loop is to control the water flow rate ( as per setpoint by pump supplier ) through the feed water pumps. The PID loop constantly modulates the return water valve to maintain the total water flow rate as the demand for drum water changes (flow rate). A failure to do so may damage the feed water pumps.

  • Process Variable, PV = return feed water flow rate
  • Control Variable, CV = return water valve
  • Setpoint, SP = Pump minimum flow rate - drum feed water flow rate

Heater Start-Up Sequence


Heat Recovery Steam Generator, HRSG Start-Up sequence is listed and aminated on the HMI ( panelview ). The animation will inform operator about the start-up status and alarm operator where it is faulted.

Operator can see the alarm message on the Alarm Summary screen.

Drum Feed Water Pumps Duty Cycle


  • Operator can configure the duty cycle timer for the two water pumps so that they can be run evenly.
  • Operator can also swap the running pump instantly as per production requirement.

Boiler Consumption Totaliser


This screen is display the consumption of steam and fuel gas. It also totalise the pump running hours for maintenance reasons.

 

Boiler Water Flow Rate Trend Screen (Start-Up Trends)


  • Startup to Normal Production Transition
  • Boiler water flow rate parameters (drum level, drum inlet water, supply return water, total water supply [drum inlet and return]), returning to stable ( transition) running condition after a bolier warm start-up.
  • PID Loops programmed in Rockwell Controllogix PLC
  • Drum Pressure , Drum Water ( feed forward ) and Return Water.

Boiler Water Flow Rate Trend Screen (Normal Running Trends)


  • Boiler water flow rate parameters (drum level, drum inlet water, supply return water, total water supply [drum inlet and return]), during production.
  • PID Loops programmed in Rockwell compactLogix PLC
  • Drum Pressure , Drum Water ( feed forward ) and Return Water.

Key Parameter Trend Screen


Boiler key parameters ( drum pressure, drum level ) are controlled nicely during normal production. As a result, a stable steam flow for plant consumption is achieved. Thanks for Rockwell's CompactLogix PLC and Panelview 600+.