Prepared by
Faculty
Production-CG Team
N R Das SPNE-CG
PARADEEP REFINERY PROJECT A Sunrise Project for a Sunshine Future
AGENDA FOR THE PRESENTATION Configuration of High Efficiency/ Modern Heaters Heater Instrumentation and controls Introduction to Burner Management System Heater Commissioning/ Start-up Start-up Precautions and Monitoring Heater Shutdown What May Go Wrong
AGENDA FOR THE PRESENTATION Configuration of High Efficiency/ Modern Heaters Heater Instrumentation and controls Introduction to Burner Management System Heater Commissioning/ Start-up Start-up Precautions and Monitoring Heater Shutdown What May Go Wrong
CONFIGURATION OF MODERN HEATERS
CONFIGURATION OF MODERN HEATERS
HEATER INSTRUMENTATION & CONTROLS TT TT NOx
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PARADEEP REFINERY PROJECT
A Sunrise Project for a Sunshine Future
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HEATER FIRING CONTROL TT TT NOx
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FIRING CONTROL
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NEED FOR BMS BMS System evolved out of a need for a Separate System apart from the control system for Optimization of fuel consumption Safe start-up of the furnace through programmed sequences bounded by
safety Interlocks and Start permissives Supervising the safety limits during operation Supervising the presence of pilot and Main flame during operation with the
help of Dedicated flame scanners Activation of safe Shutdown in the event of any unsafe condition Preventing the catastrophic combustion of fuel or Explosion For providing the operating personal an environment free of Hazards
BMS - How Burner is managed? Sequence Controls (Permissives)-For Startup Pilot & Main Fuel Block Valves leak proved Absence of Flame proved Prepare flow proved Prepurge Timer complete Minimum configured pilots are lit
Trip Interlocks-For Normal Operation Loss of Flame Fuel pressure Low Fuel pressure High Loss of Combustion air High Process Temperatures
SAFETY CHECKS BEFORE HEATER STARTUP A furnace is safest when it is functioning properly.
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Combustion occurs when fuel and oxygen meet a source of ignition.
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combustion cannot take If any one of these three elements is missing, ____________ place. Combustion can occur in an idle furnace, if fuel, oxygen, and a source of ignition come together. Wherever there ia air, you can be sure there is oxygen _______________. •
During shutdown, flammable vapors may seep into the firebox. Anything that can burn is ______________. flammable •
SAFETY CHECKS BEFORE HEATER STARTUP Fuel and oxygen need only a source of ignition to ________. burn
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fuel Even though a furnace is idle, you must assume that there may be ________ in the firebox. •
Rapid ignition or combustion in a confined space is an explosion. Explosions occur when air and fuel have mixed and come into contact with a source of ignition __________. •
The longer an unblinded furnace has been idle, the more likely it is to lack source only a _________ of ignition. •
Over the years, more than half of all furnace explosions have occurred during startup. Most explosions happened because fuel that the operator air and was waiting for ignition. didn’t know was there had mixed with _______ •
Start up A furnace is most dangerous at ______________.
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PHYSICAL CHECK BEFORE STARTUP The furnace and the area around it must be clean and free of flammable material. •
All valves in the fuel gas and fuel oil systems and all burner valves must be checked to see that they are closed. •
burner gas valve and the pilot valve must be checked to be Both the _________ closed sure they are _____________. •
On an oil burner, you normally have two oil valves and three steam valves to close. All oil steam _______ and ________ valves must be closed. •
PHYSICAL CHECK BEFORE STARTUP damper After the damper mechanism has been checked, the stack ___________ should be fully opened. •
burners The secondary air doors on all _____________ should be fully opened.
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To purge the furnace properly later on, the purging steam or air must be able to flow freely through the furnace. The stack damper and all secondary open air dampers must be _________ to provide this flow. •
PURGING BEFORE LIGHTING THE BURNERS purging It is dangerous to light the burner without ________the furnace first.
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gases Purging must be thorough to make sure that no flammable __________ remain in the furnace. •
Steam is used for purging. Ensure that the steam is free of condensate.
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Steam purging provides heat to start the draft.
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Your unit operating instructions tell you how long to purge the furnace with steam, and may specify a minimum draft during the purge. •
draft Purging is used to create a _________ and remove all flammable gases __________ from the furnace. •
PURGING BEFORE LIGHTING THE BURNERS combustion Purging makes sure that you have the three elements of ____________ (fuel, air, and heat) under control when you light the burners. •
Ensure that there are no flammable vapors mixed with air in the firebox.
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REMOVING BLINDS - BEFORE LIGHTING THE BURNERS Before lighting the burners, follow Standing Instructions and SOP (Standard operating procedures). Ensure that the blinds in the main fuel lines to the furnace are removed as per unit operating instructions. Purge the fuel system as per the instructions. •
With the blinds removed, the chances that the fuel may seep into he firebox through any valve leakage are now increased. •
closed Ensure that all burner valves are __________ before opening the main fuel valve to furnace. •
Drain fuel gas knockout pot to ensure that there is no presence of liquid hydrocarbon in fuel gas. •
Ensure that there is no water in the fuel oil line.
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LIGHTING THE BURNERS On a furnace with a gas pilot, light the pilot before you light the burner.
source of ignition for the burner. Once the pilot is lighted, it is a steady __________ burner is Establish circulation through furnace coils before the first __________ lighted. gas A furnace burning both gas and oil is normally started with ________. ignition for the oil. The gas burner provides a steady source of __________ Gas ignites and burns more easily than oil.
purging Begin lighting the burners immediately after you have finished __________ purging the furnace. Automatic igniters are installed for lighting of pilot burners.
LIGHTING THE BURNERS Portable igniters are also used to light the pilot burners. In earlier days, torch was used to light the pilot burners.
flame pattern by adjusting air After lighting the burner, steady the ________ dampers. If the fuel does not ignite promptly, shut off the burner.
purge again If the fuel does not ignite at the first burner, you must _______________. purging procedure. If you have to purge again, repeat the whole ___________ One burner should never be lighted from another burner. This is a
pilot dangerous practice. Only a _________ provides a steady and reliable source of ignition.
LIGHTING THE BURNERS When you are firing two fuels, one is normally “base loaded” and you
control temperature with the other. gas Do not try to light the oil gun of a combustion burner until the _______ burners are maintaining a stable flame pattern. condensate from atomising steam line, before Ensure draining of _____________ lighting up oil burner. During startup, frequently check the individual burner flames and the
flame pattern in the ____________. Wear a face mask whenever you look firebox into the firebox. Watch for irregular burning patterns. Flame impingement causes hot spots.
flame Watch the radiant tubes for hot spots and adjust the _________ pattern to eliminate them.
LIGHTING THE BURNERS spots and to Tubes should be checked from shift to shift to detect hot ________ observe how much the spots are changing, and how fast. After the furnace is on stream and lined out, check the entire operation for
excess air control. draft and _________
HEATER STARTUP PRECHECKS Check all the following conditions are satisfied Check if all the Manual block valves in fuel lines are closed Fuel gas control valve set at 20% on manual mode Steam to SAPH closed All burner air dampers are open Stack Damper Open ID fan inlet (IGV) closed Flue gas analyser not in operation
START PERMISSIVES Check if all the following Permissives are Healthy All pilot flame scanners unhealthy. All main flame scanners unhealthy. All pilot header block valves closed and bleed valves open. All main FG header block valves closed and bleed valves open. All BMS interlocks are healthy/necessary interlocks bypassed. Local Reset Push button activated. Main stack damper open.
FUEL GAS LINES – PURGING & LEAK CHECK Purging of Pilot and Fuel Gas lines Before admitting fuel gas into the line to the burners it may be
necessary when fuel gas is containing more than 15 vol. % H2 to purge the line with nitrogen. Connect N2 Hose in the common fuel gas line LPD downstream of Filter pressurize and purge it through HPV in the ring headers of Pilot and Main FG Leak Check of Pilot Gas line Automatic Block Valves Line-up all the block valves in Pilot and Main FG lines (except burner
globe and ball valves) Initiate Pilot & Main burner leak check by pressing ‘’Start leak test’’ Push Button “Pilot leak test in progress” lamp glows in LCP and a preset timer starts
which will be reset only if Start purge button Pressurisation step: Pilot gas line bypass block valves open and bleed valve closes. The system checks if the downstream pressure reaches the upper leak check set point within the pressurisation period (1 min and adjustable).
FUEL GAS LINES – PURGING & LEAK CHECK Depressurisation Step: Pilot gas line bypass block valves closes and bleed
valves open. The system checks if the downstream pressure reaches the lower leak check set point within the depressurisation period (1 min and adjustable) If Pressurisation and depressurisation steps are completed successfully ‘’Pilot Leak test clear’’ appears in LCP. If during pressurisation or depressurisation tests, the set value checks fail ‘’Pilot leak test failed’’ appears in LCP. If leak check fails rectify the problem and start leak test again.
FUEL GAS LINES – PURGING & LEAK CHECK Leak Check of Main Fuel Gas line Automatic Block Valves Once the Pilot leak check is cleared, the BMS will automatically initiate
Main FG leak check. ‘’Burner leak test in progress’’ lamp glows in LCP. Pressurisation step: Main FG gas line bypass block valves open and bleed
valve closes. The system checks if the downstream pressure reaches the upper leak check set point within the pressurisation period (1 min and adjustable) Depressurisation Step: Main Fuel gas line bypass block valves closes and bleed valves open. The system checks if the downstream pressure reaches the lower leak check set point within the depressurisation period (1 min and adjustable) If Pressurisation and depressurisation steps are completed successfully ‘’Burner Leak test clear’’ appears in LCP. If during pressurisation or depressurisation tests, the set value checks fail ‘’Burner leak test failed’’ appears in LCP. If leak check fails rectify the problem and start leak test again.
FUEL GAS LINES – LEAK CHECK
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FURNACE BOX PRE-PURGING Heaters must be purged with air before burners are lighted to evacuate all gas
that could have been sent to the firebox during the test Now start FD fans (at least one) as per the start-up procedure and open
the discharge damper Reach a maximum air flow or flow recommended by vendor. Activate ‘’Start Purge’’ Push button. All the above steps are to be completed before timer that got activated
during burner leak check (Depends upon the vendor) Minimum Purgiging time should be such that it should renew 5 times the
volume of heater or 15 Minutes
PILOT GAS BURNERS LIGHT-UP Pilot gas burner light-up Preparation Reduce the air flow from FD fan to say 25% of capacity Adjust the stack damper so that the proper draft level for furnace operation is
achieved. Close the burner air control dampers to the 25% open position.
Pilot gas burner light-up can be started once the ‘’Open pilot block valves’’
push button is pressed Open the main pilot fuel supply valve making fuel gas available upto all of the
individual pilot valves Keep the pilot mixer air door is of the pilot to be first lit-up to say 50% open. Insert the igniter, Press the Open push button for that pilot to be lit-up and
activate the igniter. The pilot should light instantly. If the pilot does not light after 10 seconds
automatic block valve will get closed. If lit-up adjust the pilot valve and air door for a stable flame. Light up all pilots in the same manner.
MAIN GAS BURNERS LIGHT-UP Main gas burner light-up Preparation Adjust the draft such that there is sufficient air pressure drop across the burner Set the burner air control dampers at 50% open.
Main gas burner light-up can be started once the ‘’Open main FG block
valves’’ push button is pressed Now the automatic block valves will open and charge the FG upto individual block
valves The burners can now be ignited manually by opening the burner isolation valve
(ball valve) slowly while observing the flame. If flame is not established within 3 secs of valve being fully open, it should be
closed immediately. Further attempts shouldn’t be made for 5 minutes. All main burners can be lit up in similar fashion. Adjust the operating conditions as required by the process. But the minimum
firing rate prescribed by the vendor should be respected. Adjust the conditions for optimum O2 level in the Stack
OIL BURNERS LIGHT-UP Oil burner light-up Preparation Reset the Oil supply and return automatic block valves Lineup supply and return line valves upto the individual burner block valves Establish oil circulation
Light-up Sequence The burner which is going to be taken in line should already be lit-up with fuel gas Open the steam valve and cross over valve (purge) to the oil gun until both oil and
steam lines to each burner and also the oil gun are completely warmed up with steam only. Close cross over valve and adjust steam valve to 3.5-4.0 Kg/cm2g steam pressure. Open oil valve gradually until ignition is established. Isolate fuel gas to that Burner Adjust oil valve for capacity required and adjust steam valve to achieve proper
flame pattern.
START-UP PRECAUTIONS The following Precautions needs to be exercised during furnace start-up Quick heating-up is likely to cause excessive stresses on tubes and supports Over pressure in the fire chamber can cause personnel injury or material damage
as hot flue gas would leak out of sight doors, not blanked-off connections, unpacked tube seals, etc Ensure Flow through the coils as it is a certain way of protecting the tubes from
excessive temperature. Too low a flow rate through the passes with respect to heat flux can be the cause
of tube overheating or hydrocarbon coking. Possibility of condensation in the fuel lines must be checked with respect to
atmospheric conditions and avoided. Line must be drained frequently checking for water or condensates. Burner operation shall also be carefully and constantly watched to identify any
abnormal occurrence: flame impingement, wrong shape, instability, nozzle plugging, coke formation, etc During start-up, heater draught must be watched as it increases progressively with
the heat released
START-UP MONITORING During start-up, heater draught must be watched as it increases progressively with the heat released, using for that the draught gauges installed locally and comparing them to the values transmitted to control room. Operation of the draught dampers when there is one must be smooth and draught must be effectively controlled. •
During first start-up, all devices and instruments being used for the first time in real conditions, it is of paramount importance to check their actual operation and response constantly, until sufficient confidence is gained. Quick material and thermal balances will help to detect abnormal recordings. •
It comes naturally up that first start-up must be conducted slowly and if possible stepwise to allow timely checking and observation. •
In case of abnormal occurrence, it is of paramount importance that operators can react in the right way within the shortest time. •
CONTROLLED SHUTDOWN Controlled Shutdown Sequence Reduce fuel pressure slowly from control panel and simultaneously reduce the
combustion air flow Once fuel pressure downstream of Pressure control valve reduces to a minimum
value or PCV opening reduced to minimum, start cutting off burners one by one. Individual burner air dampers needs to be throttled as CA duct pressure reduces. If oil burners are in line, isolate them and flush with atomizing steam When main fuel gas is to be tripped, close the PCV completely and automatically
the block valves will get closed Open Stack damper fully. Actuate Pilot gas trip by isolating the main pilot line isolation valve. This action will
trip FD fan also. Bypass Pilot gas low low pressure trip and Restart FD fan Allow cooling of the furnace box with FD fan running
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The flow rate of the charge and the heat of the furnace are reduced together. reduced The charge rate and temperature are gradually ____________ over a period of several hours. When the charge rate and temperature have been reduced to a fraction of burners normal, all furnace __________ are shut off. The entire unit is “circulated down”. The oil left in the unit is circulated within furnace the unit oil system, including the ____________ tubes.
Circulation is continued through most equipment for several hours to cool the unit. When the unit is cool enough not to vaporise the oil anywhere in it, stopped circulation is __________.
SHUTDOWN •
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reduces the burner fuel Reduction in the transfer temperature automatically ____________ supply. While reducing transfer temperature, cut off burners as per requirement. When the charge rate and temperature are down to the desired level, all burners are shut off by closing each burner fuel valve individually. ____________
valve Each gas pilot is shut off by closing the pilot _______. Steam is left on in each oil gun as the oil regulating valve is closed. It is used to purge _____________ the oil gun.
After all the burner gas valves are closed, the gas header valve is closed. Then all block valves and bypass valves are closed. If the furnace is to be out of service for some time, blinds should be installed in the fuel _________ lines.
EMERGENCY SHUTDOWN •
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Emergency shutdown is called for when furnace operations becomes seriously abnormal. In order to act wisely, you must know the maximum allowable temperature tube and pressure of the _________ metal. temperature for the firebox, You must know the maximum allowable _____________ breeching, and the stack. You must be ready to stop combustion by removing one or more of the three fuel elements of combustion, ___________ air, or heat. You must know in advance that emergency block and blowdown valves are in working order and how to reach them in an emergency. These emergency controls are located in a protected area where they can be reached with minimum, or little risk. _________________
REVERSING THE PROCESS OF COMBUSTION •
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You can ordinarily keep fuel oil and gas out of the firebox by closing the valves burner _____________. You may have to go back to the block valves or the burners header block valve. These valves stop the fuel to all _________. In normal operation, you do not think of the charge as fuel. In the event of a tube rupture, the charge enters the firebox from the ruptured tube and fuel burns. Then you must think of charge as ____________. Since the charge is under pressure, a tube rupture may dump large amounts of the charge into the firebox. Shutting off the charge and dumping it from firebox the furnace does not get rid of what is in the _____________. The oil is best disposed of by burning it where it is, since the firebox is built to support the heat of burning. To keep temperatures from running too high air during this combustion, you may need to control the __________ supply.
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You may have to choose which of the three elements of combustion to control or get rid of, or try to eliminate all the three at once. fuel Stop or control the __________ air Restrict the _______ ignition that is present Cool and put out any source of ____________
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A tube rupture may suddenly admit a large amount of fuel into the firebox. Your action will depend upon how serious the situation is and how well you can control temperatures. If the leak is small, the charge may be left in the furnace ____________ tubes while the unit is circulated down. The furnace must be isolated and depressured if the rupture is large. Shut off the burner fires. Dump the furnace and cool the tubes by turning steam into purge them. Then ___________ the firebox with steam.
REVERSING THE PROCESS OF COMBUSTION •
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Improper operation of oil burners could lead to large amounts of oil burning on the floor of the furnace. Correct the burner operation. If temperatures become excessive, air by adjusting the stack damper. restrict the input of ______ Flammable liquid in the fuel gas line may fill the firebox with uncontrolled flames. Drain the fuel gas system. If temperatures become excessive, adjust the stack damper air to restrict the input of ______. Cool the firebox with steam. If temperatures still rise in the tubes beyond the charge maximum, block off the furnace and dump the ___________. Put steam into the tubes. An operator who has worked successfully through an emergency shutdown has new equipment, or furnace knowledge of himself and his _______________________. By deliberately applying your knowledge and measuring your actions by the severity emergency into experience that prepares you of the emergency, you turn each ___________ better for all furnace operating situations.
WHAT MAY GO WRONG? Furnace Explosions can occur with any or a combination of the following Loss of Flame in one or more burners while the others are in operation Accumulation of Combustible gasses inside the furnace followed by formation of explosive mixture inside the box Complete Flame-out followed by an attempt to light a burner Accumulated Hydrocarbons inside the furnace after Flame-out forms explosive mixture and explodes while re-ignition Fuel Leakage into an idle furnace ignited by a source of ignition Fuel leakage into the Idle furnace due to passing of fuel gas block valves leading to formation of Explosive mixture Repeated attempts to light-off the furnace without properly purging the box Accumulation of Hydrocarbons due to delay in ignition of burners due to problem of igniter or flow of excessive combustion air Momentary loss of flame followed by delayed ignition After burn causes sudden rise in pressure in the convection section or the flue gas duct causing damages
QUERIES
