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111455-O&M-Manual(Sec 3)

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OPERATION AND MAINTENANCE MANUAL SECTION 3 OPERATION AND MAINTENANCE 3.1 GENERAL a. The operator should be thoroughly familiar with the function and controls of the steam generator components and auxiliary equipment before operating the unit. The information given in this section is not intended to be a detailed procedure for operation of the steam generator, but is meant to serve as a guide together with the instructions of the auxiliary equipment manufacturers and with knowledge derived from initial unit operation. b. Circulating fluidized bed boilers are chemical process reactors, without a defined fireball, which behave differently than conventional boilers. They involve considerable inertia of solids inventory and thermal energy. c. The operator should be aware of the limitations imposed on the various parts of the boiler and its auxiliaries and be alert to the actual operating conditions during start-up and while operating per system demands. d. Inert bed material such as sand can be used for initial start-up of the unit. It is recommended to use saved, spent bed material for subsequent start-ups. The startup bed material should be blown into the lower furnace area with the PA, SA and ID fans running. Bed material should be added until the static pressure of the bed is 4.5-5.5 KPa (18”– 22” w.g.) e. The saved bed material should be sampled during any outage to check for any hardened material or for sticky conditions due to absorbed moisture. Hydrated bed material can break apart during start-up and increase fine bed material carryover. The bed static pressure should be monitored during each restart of the unit to see that the bed level is being maintained. If bed static pressure 3 - 1 (111455 Sec. 3)
Transcript

OPERATION AND MAINTENANCE MANUAL

SECTION 3 OPERATION AND MAINTENANCE 3.1 GENERAL a. The operator should be thoroughly familiar with the function and controls of the steam generator components and auxiliary equipment before operating the unit. The information given in this section is not intended to be a detailed procedure for operation of the steam generator, but is meant to serve as a guide together with the instructions of the auxiliary equipment manufacturers and with knowledge derived from initial unit operation. Circulating fluidized bed boilers are chemical process reactors, without a defined fireball, which behave differently than conventional boilers. They involve considerable inertia of solids inventory and thermal energy. The operator should be aware of the limitations imposed on the various parts of the boiler and its auxiliaries and be alert to the actual operating conditions during start-up and while operating per system demands. Inert bed material such as sand can be used for initial start-up of the unit. It is recommended to use saved, spent bed material for subsequent start-ups. The startup bed material should be blown into the lower furnace area with the PA, SA and ID fans running. Bed material should be added until the static pressure of the bed is 4.5-5.5 KPa (18 22 w.g.) The saved bed material should be sampled during any outage to check for any hardened material or for sticky conditions due to absorbed moisture. Hydrated bed material can break apart during start-up and increase fine bed material carryover. The bed static pressure should be monitored during each restart of the unit to see that the bed level is being maintained. If bed static pressure decreases below the minimum value of 4.5 KPa (18w.g.), additional start-up material should be added.

b.

c.

d.

e.

3-1(111455 Sec. 3)

OPERATION AND MAINTENANCE MANUALSECTION 3 3.2 PRECAUTIONS a. Exposure to excessive negative or positive pressures can result in serious damage to the unit and auxiliary equipment. Furnace draft is monitored constantly and automatically controlled. Alarm and MFT set points must be implemented. When a particular induced draft (ID), primary air (PA) and/or secondary air (SA) fans(s) is to be started, the corresponding inlet control vanes and outlet isolating (shut-off) dampers (if supplied) should be closed. However, if there are multiple fans, the dampers (and vanes) on the companion idle fans should be open to assure a clear air flow path (between ID, SA or PA fan inlet and stack) exists when starting the fans. All safety valves are set by the manufacturer but should be rechecked under actual operating conditions as the unit is being brought up to pressure during initial operation. If a safety valve does not lift at the pressure stamped on its nameplate or reseat properly, the valve should be readjusted. In some localities, it is required that only certain authorized personnel may change or adjust safety valve settings or that changes in safety valve settings be witnessed by authorized personnel. Consult governmental and insurance requirements before changing the setting of any safety valve. On installations where the safety valve relieving pressure exceeds 8.274 MPa(g) (1200 psig), it is recommended that checking and adjusting of safety valve settings prior to initial operation be performed by the valve manufacturer service engineer. A hydraulic or pneumatic device is recommended, if approved by the inspecting authority, to assist in testing valves on 8.274 MPa(g) (1200 psig) or higher installations. This device eliminates the need for raising boiler pressure above normal and minimizes the possibility of valve seat damage during testing.

b.

c.

Care should be exercised to insure that proper fuel-air ratio for combustion is maintained. The Summary Performance Sheet in Section 1 indicates the minimum excess air requirements. Operation with less than the minimum expected excess air can be detrimental from the standpoint of combustion, emission performance and safe operation of the unit. For purposes of monitoring start-up conditions during the life of the boiler, permanent thermocouples are installed to measure metal temperature of various tubes. These thermocouples are located in the unheated portion of the tubes before they enter the outlet headers. The locations and quantities are as follows: primary superheater (10), intermediate superheater (16), finishing superheater (7), Reheater I (10) and Reheater II (10). There are two (2) thermocouples on each cyclone outlet. There are six (6) thermocouples on the steam drum. All these thermocouples are to be used as aids in determining acceptable firing rates during start-up. The unit can be operated up to the temperature limits indicated in the table below. To protect the equipment, the operator should correct any condition which has caused an alarm to sound.

d.

e.

3-2(111455 Sec 3)

OPERATION AND MAINTENANCE MANUALSECTION 3 Location of Maximum Maximum Temperatur Short Long Term e Term Temperature Measureme Temperatu nt re* Primary Superheater Tubes to Outlet 487C (909F) 498C (928F) Header Intermediate Tubes to Outlet 596C (1105F) 604C (1119F) Superheater Header Finishing Superheater Tubes to Outlet 600C (1112) 611C (1132F) Header Reheater I Tubes to Outlet 613C (1135F) 627C (1161F) Header Reheater II Tubes to Outlet 610C (1130F) 621C (1150F) Header * Short term means a period not exceeding 4 hours per day. f. To prevent plugging, rusting, oxidation and faulty operation of equipment, service air used on the steam generator for operational purposes, whether for sealing, aspirating, or atomizing, should be free of dirt, oil and water. All high and low furnace pressure safety interlocks should be checked for proper values and correct switching action and should be in service before starting the induced draft fans. The automatic furnace draft control equipment should be checked and ready for service before starting the induced draft fans. Carbon monoxide (CO) should be monitored continuously during operation of the steam generator. Foster Wheeler recommends that CO monitoring equipment be permanently installed for this purpose. It is strongly recommended that the reliability of all drum level indicators be checked at least once a shift. This would include all gage glasses and remote level indicators. A water level indicator connection that is being used to control water level should not be blown down until the control is switched to another water level controller or feedwater control is put on manual. On commonly operated valves, such as superheater drains and vents, care should be taken maintain the integrity of the root valves. These valves should never be in a throttled position, and it may be beneficial to leave them open and only close the end valves. The root valve would then only be closed for end valve maintenance or downstream line maintenance. Both valves on waterwall wall drains can be left closed. In all cases, end valves should be closed before closing root valves and opened only after opening the root valve in order to minimize potential root valve seat damage. Section

g.

h.

i.

j.

3-3(111455 Sec 3)

OPERATION AND MAINTENANCE MANUALSECTION 3 k. Any of the following operating conditions require mandatory MFT. The flow rates and ratios are initial values and may be modified during commissioning. Condition/Situation Drum Level Low-Low Drum Level High-High Furnace Pressure High Furnace Pressure High-High Furnace Pressure Low Furnace Pressure Low-Low Loop seal Header Pressure LowLow Superheater/Waterwall Protection Cyclone Temperature > Maximum Primary Air Flow < Minimum Instrument Air Pressure Low-Low Total Air Flow < Minimum Air Fuel Ratio Low-Low No SA Fan in Service No PA Fan in Service No ID Fan in Service Furnace Bed Temperature HighHigh Furnace Bed Temperature Low Loss of all Fuel BMS/DCS Communication Failure Emergency MFT Pushbuttons Initiated Status -203 mm +203 mm +2.49 KPa +3.48 KPa -2.49 KPa -3.48 KPa 25 KPa Cyclone Temp.>1000F and Steam Flow


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