DIFFERENT CONTROL LOOPS USED IN POWER PLANTS - ASKPOWERPLANT

DIFFERENT CONTROL LOOPS USED IN POWER PLANTS

DIFFERENT CONTROL LOOPS USED IN POWER PLANTS
BOILER OPERATION

DIFFERENT CONTROL LOOPS USED IN POWER PLANTS:-

In this article we discussed about the various control system which is used in safe operation of boiler , in this section we provides brief description of various control loops, boiler controls loop is very essential for safe operation of boiler in any power plant industries. In modern power plant industries boiler is provided with various controls to ensure safe, efficient and reliable operation of the plant.
Here are the some important control loops employed in the boiler plant operation:-

1. EXCESS AIR -O2 CONTROL LOOP
2. FURNACE INVENTORY CONTROL LOOP
3. FURNACE PRESSURE CONTROL LOOP
4. SUPER HEATER STEAM TEMPERATURE CONTROL LOOP
5. BED TEMPERATURE CONTROL LOOP
6. DRUM LEVEL CONTROL LOOP
7. AUTO COMBUSTION CONTROL LOOP
8. BED LEVEL CONTROL LOOP

1.EXCESS AIR -O2 CONTROL LOOP

Function of the excess air control loop is to maintain the excess air at the desired limit during the boiler operation. Signal from the O2 controller regulate the fan speed to supply the required air flow to maintain the excess air depends on the steam flow and fuel being fired. Control can be operated either in manual or automatic mode depends on the process requirement. O2% set point for auto control can be varied depends on the steam flow and quality of the fuel being fired. Excess air control loop is used to for batter fuel combustion .Control to be switched over to auto mode whenever the steam flow is increased above 60% MCR and boiler operation is stable. However close observation may be required as it may be difficult to maintain the O2 as per the predicted values during upset conditions like heavy bed, moist fuel and fluctuating steam demands.

2. FURNACE INVENTORY CONTROL LOOP

Furnace inventory control is an integrated part of bed temperature control. Function of this control loop is to maintain the DP across the furnace as per the steam flow, bed temperature andfuel being fired. As per the DP requirement the controller adjust the speed of MDC ash recycle RAVs.

3.FURNACE PRESSURE CONTROL LOOP

Furnace pressure control loop is used to maintain the furnace pressure at the desired limit, during the running boiler operation. In this loop signal from is used to the pressure controller modulate the ID Fan speed or Fan inlet damper opening to maintain the optimum furnace draft. Control can be operated either in manual or automatic mode depends on the process requirement. Furnace pressure set point for auto control can be varied depends on the process requirement. Control to be switched over to auto mode after the stabilization of firing. During bed activation, slumping and disturbed operating conditions,in AFBC boiler control may be switched over to manual mode as the air and gas flow may vary drastically & abruptly during such conditions.

4.SUPER HEATER STEAM TEMPERATURE CONTROL LOOP

Super heater steam temperature control loop is to maintain the final steam temperature at the desired limit during the Running boiler operation. There are two stages of at temptation provided between PSH I (primary super heater ) &II and between PSHII & SSH I/L(secondary superheater inlet ) for the fine control of main steam temperature. Signal from the individual temperature controllers modulate the respective attemperator spray control valve opening to maintain the steam temperature the at temptation line for spry is taken from the discharge of the feed line which are going for the economizer inlet for controlling the main steam temperature upto desired limits .attemptation Control can be operated either in manual or automatic mode depends on the process requirement. Steam temperature set point for auto control can be varied depends on the process requirement. Controllers to be switched over to auto mode after the steady steam flow is established. During disturbed operating conditions, controllers may be switched over to manual mode as the steam temperature may vary drastically & abruptly during such conditions

5.BED TEMPERATURE CONTROL LOOP

Function of the bed temperature control loop is to maintain the bed temperature as per the steam flow & fuel being fired. Bed temperature is controlled either by Bed Temperature only OR Bed Temperature/ Shaft differential pressure along with air flow depends on operating load and fuel being fired. Signal from the bed temperature control regulate the speed of MDC ash recycle RAV & air flow to furnace. The selection of the mode of control (based on Bed Temperature only OR Bed Temperature/ Shaft differential pressure) shall be selected by the operator from the control console.

6.DRUM LEVEL CONTROL LOOP

Dum level control loop is used to maintain the drum water level at the desired limit, during the running boiler operation. Signal from the level controller modulate the 30% or 100% feed water flow control valve opening (depends on the valve selection i.e. 30% or 100%) to maintain the drum level. For drum level control, two types of controls are provided in the boiler, i.e. single element and three element control. Single element control is employed during cold startups and steam flow less than 30% of MCR( maximum continuous rating ) flow conditions. In single element control loop only drum level is consider Three element control is a fine control, which work effectively on higher and steady load conditions. Three element control can be switched over to auto mode after steady and steam flow is ensured. In three elements controls system main steam flow , drum level and feed water flow is consider in this loop . Both 30% and 100% control valves can be operated either in manual or automatic mode depends on the process requirement

7.AUTO COMBUSTION CONTROL LOOP

Function of the auto combustion control loop is to maintain rated pressure of final steam during the boiler operation.Signal from the pressure controller regulates the air flow & fuel feed rate to maintain the desired steam pressure. Control can be operated either in manual or automatic mode depends on the process requirement. Pressure set point for auto control can be varied depends on the process requirement. Control to be switched over to auto mode, whenever the steam flow is increased above 60% MCR and
boiler operation is stable. These control loops are controlled through a monitoring system is called DCS (Distributed control system ) However close observation may be required as it may be difficult to maintain the final steam pressure as per the predicted values during upset conditions like heavy bed, continuous variation in fuel quality and fluctuating steam demands. If required controller can be switched over to manual mode as per the process requirement.

8. BED LEVEL CONTROL LOOP

Function of the bed level control loop is to maintain the required bed level and bed bulk density during the boiler operation. Signal from the bed level control initiate the ash cooler operation and stop the cycle as per the preset time. Ash cooler operation/sequence can be activated either in manual or automatic mode depends on the requirement. Bed level control loop is used for the purpose of maintaining the desired bed height during the ruining boiler for the maintaining the desired bed temperature and protect it from the clinker formation. Bed level set point for auto control may be varied depends on the steam flow and quality of the fuel being fired. Control can be operated in auto mode, however close observation of the furnace and drained bed material may be required to optimize the draining frequency.

 

IF YOU LIKE THIS POST DIFFERENT CONTROL LOOPS USED IN POWER PLANTS PLEASE LIKE , SHARE AND YOU COMMENTS IS VERY VALUABLE SO PLEASE GIVE YOUR SUGGESTIONS IN COMMENT BOX……..THANK’S

Facebook Comments
No Comments

Leave a Reply

Your email address will not be published. Required fields are marked *

working principal of benson boiler
BOILER OPERATION
Benson Boiler- Construction & Working Principal- Askpowerplant

Heii all my Askpowerplant readers after a long time of interval today I am coming back with a fresh topic which is related to boiler operation because now these days boiler operation becomes a trending job so everyone wants to know that how to do boiler operation in a safe …

what is combi boiler their advantages and disadvantages
BOILER OPERATION
WHAT IS COMBI BOILER? THEIR ADVANTAGES AND DISADVANTAGES

Heidi power plant engineers How are you? I think everybody is fine today we discuss a very important topic related to boiler family. We already discussed different types of the boiler like AFBC, CFBC, TRAVELING GRATE, PULSATING GRATE, DUMPING GRATE, GAS FIRED, HSD FIRED Boilers. They have their own advantage …

REASONS BEHIND CLINKER FORMATION IN BOILER FURNACE
BOILER OPERATION
1
TOP 10 REASONS BEHIND CLINKER FORMATION IN BOILER FURNACE

TOP 10REASONS BEHIND CLINKER FORMATION IN BOILER FURNACE Heii all power plant engineers I hope all is well today I wanna go to discuss a very important topic related to the thermopack heater as well this topic is very important to those who worked into boiler operation in the steam …

Translate »