boiler manual 3x135mw

7/25/2019 Boiler Manual 3x135MW

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REV.

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INSTRUCTION FOR BOILER OPERATION

SG-420/13.9-M2305MODEL OF PRODUCT

420t/hNAME OF PRODUCT 420t/h Circulating Fluidized Bed Boiler

2305-1-8603SERIES No.


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Instruction For Boiler Operation 2305-1-8603 P 2/61

Table of Contents

INSTRUCTION ....................................................................................................................... 5

1 GENERAL CONDITIONS OF BOILER ............................................................................. 6

1.1BRIEF INTRODUCTION OF BOILER..................................................................................... 6

1.2MAIN TECHNICAL PARAMETERS OF BOILER..................................................................... 7

1.3MAIN PERFORMANCE INDEXES OF BOILERDESIGN COAL,TMCRWORKING CONDITION

.............................................................................................................................................. 8

1.4FUEL ................................................................................................................................ 8

1.5LIMESTONE (IN BRIEF)..................................................................................................... 9

2. COMMISSIONING TEST OF BOILER ............................................................................. 9

2.1IMPORTANCE OF BOILER COMMISSIONING........................................................................ 9

2.2PREPARATION BEFORE BOILER OVERALL STARTUP........................................................ 10

3. HYDROSTATIC TEST ..................................................................................................... 10

3.1TEST REQUIREMENTS ..................................................................................................... 10

3.2MAINTENANCE AFTER HYDROSTATIC TEST.................................................................... 11

4. WATER TREATMENT (IN BRIEF) ................................................................................ 11

5BOILER DRY-OFF ......................................................................................................... 11

5 1 PURPOSE OF BOILER DRY OFF 11


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8.6PURGING OF MAIN STEAM PIPELINE................................................................................ 25

8.7PURGING OF REHEATER INLET PIPELINE......................................................................... 25

9. NORMAL PRINCIPLES FOR BOILER OPERATION ................................................... 25

9.1GENERAL RULES ............................................................................................................ 25

9.2WATER FILLING AND VENTING...................................................................................... 26

9.3STARTUP ........................................................................................................................ 26

9.4BOILER SHUTDOWN ....................................................................................................... 27

9.5WATER LEVEL............................................................................................................... 28

9.6BOILER WARM-UP AND EXPANSION............................................................................... 29

9.7AIR PREHEATER............................................................................................................. 29

9.8SOOT BLOWING .............................................................................................................. 29

9.9REGULATION OF STEAM TEMPERATURE......................................................................... 30

9.10SUPERHEATER AND REHEATER.................................................................................... 30

9.11BLOW-OFF ................................................................................................................... 32

9.12TUBE DAMAGE ............................................................................................................. 32

9.13FURNACE EXPLOSION ................................................................................................... 33

9.14FLY ASH WEAR............................................................................................................ 34

9.15INSPECTION................................................................................................................. 34

9.16MAINTENANCE OF BOILER AND FREEZING PREVENTION............................................... 35

10 BOILER OPERATION PROCEDURE ............................................................................ 36

10.1STARTUP AND OPERATION OF BOILER.......................................................................... 36

10.2PREPARATION BEFORE BOILER STARTUP...................................................................... 37

10 3 COLD/WARM STATE STARTUP 38


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12.4FIGURE 4 HOT-STATE STARTUP CURVE...................................................................... 60

12.5FIGURE 5 SHUTDOWN CURVE.................................................................................... 61


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Instruction

Combining the experience in design, manufacture and operation of dozens of

ultra-supercritical circulating fluidized bed boiler, the 420t/h class circulating fluidized bed

boiler is completely designed by Shanghai Boiler Works Co., Ltd, which is developed by

Shanghai Boiler Works Co., Ltd using advanced technology of circulating fluidized bed.

This instruction for boiler operation, based on the design features of circulating

fluidized bed boiler, introduces the utilization requirements, operation procedures and

matters needing attention of the boiler body. The various contents of the instruction are basic

requirements proposed for the boiler utilization process to ensure the safe operation and

service life of the boiler. The boiler startup and shutdown procedures are closely related to

the other units of the boiler, e.g. turbine, various auxiliary equipment, control system, etc.

Therefore, the specific operation specifications for the complete set of generator unit to

match with the boiler shall be prepared by the user with reference to the applicable

specifications of the industry. This instruction is only for information when the user prepares

boiler startup and operation specifications.


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1General conditions of boiler

1.1 Brief introduction of boiler

SG-420/13.9-M2305 circulating fluidized bed boiler is an ultra-supercritical

intermediate reheat, natural circulation boiler with single drum, which is designed and

manufactured by Shanghai Boiler Works Co., Ltd using advanced technology of circulating

fluidized bed. Balanced draft, centralized downcomer and water-cooling cyclone separator

are adopted in the boiler, and 2 slag discharge tubes and 1 accident slag discharge tube are

arranged at the bottom of furnace combustion chamber. Membrane waterwall is adopted in

furnace and the lower part uses refractory furnace lining. The boiler has 4 coal feeding points

and 4 limestone feeders, which are all set at the front wall. For this boiler, on-bed startup

ignition mode is adopted. Totally 4 high-power ignition oil guns (2 for each of the left and

right side walls respectively) are arranged on the bed. Convection heating surface is arranged

in the boiler rear pass and two-stage water spray temperature adjustment is adopted in

superheater. Reheater mainly uses flue gas damper temperature adjustment, supplemented by

accident water spray device.

1.1.1 Steam-water system of boiler

The steam-water system of the boiler includes tail economizer, boiler drum, evaporation


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the primary air fan is heated in the steam air heater and primary air preheater. Then one route

enters the primary air chamber in the bottom of the furnace and the bed material is fluidized

through the wind cowl on the air distribution board, forming solid circulation going upwards

through the furnace. For the second route, an air pipe is led from the primary air duct to the

furnace coal falling tube as coal spreading air. For the third route, a stream of high-pressure

cold air is led from the cold air duct behind the outlet of the primary air fan as the sealing air

for the furnace coal falling tube and coal feeder. After the secondary air is heated by the air

heater and secondary air preheater, a certain number of branch tubes are led from the

secondary air chamber. The air enters the furnace combustion chamber from front and back

wall of the furnace and upper dense-phase zone as two layers. Meanwhile, the secondary air

is also used for ignition of the on-bed oil guns and oil gun cooling.

After the gas with solid particles left the furnace, it tangentially enters the cyclone

separator through two inlet duct respectively. Coarse particles are separated from the gas in

the separator, and gas enters rear pass through separator center cylinder. After cooled by

heating surface, the gas enters dust collector through tubular air preheater to remove fine

particles and finally discharges into the atmosphere through stack by induced draft fan.

One stream of the high-pressure fluidization air is used as fluidization air for the


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Superheater outlet steam temperature 543 543

Reheater steam flow t/h 351.108 351.108

Reheater inlet steam pressure MPa(g) 2.757 2.757

Reheater outlet steam pressure MPa(g) 2.632 2.632

Reheater inlet steam temperature 319.6 319.6

Reheater outlet steam temperature 543 543

Feedwater temperature 252.1 252.1

1.3 Main performance indexes of boilerDesign coal, TMCR working condition

Item Unit Value

Computational efficiency of boiler (as

per net calorific power)% 93.29

Guaranteed efficiency of boiler (as per

net calorific power)% 92.5

Solid incomplete combustion heat loss % 1

D t di h t ti t


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As-received gross calorific value

HHVQgr.ar Kcal/kg 4500

1.4.2 Ignition and combustion supporting oil

Light diesel oil is adopted in this project as ignition and combustion supporting oil. The

analysis data of the oil are as follows.


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exist in boiler and auxiliary equipment, in order to take effective measures in time. To train

the operating personnel concerned about equipment performance and primary adjustments of

operation, which lays a good foundation for pilot production and commercial operation.

2.2 Preparation before boiler overall startup

Besides separated commissioning of the main equipment of each system, hydrostatic

test, dry-off, cold aerodynamic characteristic test, boiler body cleaning, steam pipeline

purging, boiler ignition test, boiler safety valve setting, auxiliary equipment interlock

protection test and boiler main protection test should be done before the boiler overall

startup commissioning. A complete inspection of boiler proper and its steam-water system,

flue gas and air system, combustion system, relevant auxiliary equipment, thermal control,

chemical water treatment equipment and site environment should be carried out according to

the commissioning program, operating standard and boiler operation instruction before cold

start, to meet the requirements of boiler safe startup.

3. Hydrostatic test

Hydrostatic test should be carried out according to the requirements of relevant boiler

regulations.

3.1 Test requirements


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that results in cracking, deformation and damage of the refractory materials, or even

peeling-off of the wear-resistant materials in severe case. Therefore, before the boiler is put

into operation officially, it is necessary to dry off the boiler with controlled heating method.

Meanwhile, boiler dry-off can accelerate the physical/chemical variation process of the

boiler wall materials, making the performances stable so that it can work for long term under

high temperature.

5.2 Preparation required before boiler dry-off and conditions

1) The installation work for the boiler proper, material returning system and gas/air

system is completed. The construction of the wear-proof refractory materials is

completed. The air leakage and air pressure test is passed.

2) Open the door holes in the various positions and allow it to dry naturally for more than

72 hours.

3) Carry out internal inspection of the furnace, flue gas/air duct, cyclone separator,

material returning device, etc. Remove the foreign matters.

4) Temporary exhaust valve is installed on the top cover of the cyclone separator, and

temporary partition is installed in outlet duct of the separator.

5)

The fuel oil system is installed. All the jobs such as hydrostatic test and instrument test


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boiler with controlled heating method. The boiler dry-off curve of wear-resistant refractory

materials should be made by insulating material manufacturer, user and boiler manufacturer.

This instruction recommends the dry-off methods which uses extra burner to heat CFB

boiler. In this method, extra burners are arranged through the manhole doors and observation

eyes in the furnace and gas ducts at the positions laid with wear-resistant refractory materials

for heating and temperature control, the heat source generated is hot gas, which will not

flush the refractory insulation materials directly or generate local high temperature.

Moreover, with this method, it is easier to control the furnace and the gas duct at different

temperature.

Drying of the refractory materials is only a stage for accomplishing the engineering

plan. However, for CFB boiler, it is a very important link. This job is usually implemented

and accomplished by the refractory material installer by providing with temporary burners.

Once the refractory material drying procedure starts, it must proceed continuously as

per the temperature control curve without interruption until the boiler dry-off is completed.

This is critical for drying the refractory materials thoroughly and for ensuring the

performances of the refractory materials.

After a period of insulation, the furnace temperature cooled down is about 370. The


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10) The door holes in the furnace and separator shall be closed to prevent heat from

escaping out of the door hole.

11)

Feed water into the boiler drum to the normal operation level.

12) Adjust the main steam exhaust and drain valve before starting boiler dry-off.

13) Drum exhaust door Open/Pressure up to 175Pa Close

14)

Main steam exhaust/drain Open

15) Startup exhaust valve Open 25%

16) Reheater exhaust/drain Open

17)

Adjust the openness of the fan inlet movable vane to be consistent with that of the

baffle.

18) Primary air fan inlet movable vane 5%-10%

19) Secondary air fan inlet movable vane 5%-10%

20) Induced draft fan inlet movable vane 5%-10%

21) Secondary air fan upper/lower baffle Close

22) During the drying of refractory materials, maintain the steam drum at normal water

pressure.

23)

During the boiler dry-off, monitor the temperature of the gas entering the preheater


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5Recorder for recording the temperature of each thermocouple.

6Operating personnel 24 hour uninterrupted shift.

7Provide boiler dry-off report (including summary, copy and electronic edition of original

boiler dry-off record)

5.3.4 Duration

1) Preparation time is about four weeks from the delivery of boiler dry-off equipment.

2) About one week to install pipe to burner position.

3) About three day for equipment startup preparation.

5.3.5 Other requirements

1) Elevator/crane for lifting boiler dry-off machine (800kg).

2)

Compressed air used during boiler dry-off (3m3/h/burner0.25Mpa), atomized fuel oil.

3)

Electric power 18kw/220/380 volt power, 50

100kg/h fuel 14 boiler dry-off machine.4) Oil supply pipe connected to boiler dry-off machine, use hose for the tube at about 15

inches near the end the boiler.

5)

Set aside a plane space of 3 inches 3 inches for temporary boiler dry-off machine area.

5.3.6 Position of burner and thermocouple for boiler dry-off

B t


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Storage areatemporary storage area is arranged beside the boiler or between two

boilers.

Temporary storage tankthis is sign on and beside temporary storage tank (truck oil

tank)

Temporary pipelinefrom storage tank to boiler area and then to the connection of

temporary burner.

In addition, where there is oil return line, there is isolating valve.

5.3.8 Boiler dry-off heating/cooling rate (see Figure 1).

5.3.9Temperature rising requirements for the first startup

After the boiler dry-off with dry-off machines is completed, all the dry-off machines

and the related devices shall be removed. When the complete-group startup conditions are

met and the boiler is started for the first time, in order to protect refractory material, boiler

main oil gun should be used to heat up as per the curve below. To meet the requirements of

heating curve, the oil quantity for the oil guns and the number of oil guns put into use shall

be controlled strictly.

50/h rises to

670 , keep at 670

f 4 h

50/h rises to

500 , keep at

00 f 2 h

Tubes

must be

fill d


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critical fluidization air volume, and provide with references for the hot-state operation of the

boiler to ensure the combustion safety of the boiler, to prevent coking on the bed and to

protect the equipment from being damaged.

Caution

Cold aerodynamic characteristic test is the foundation and

reference basis for boiler startup commissioning, boiler

combustion adjustment and boiler safe and economical

operation. It should be done in accordance with the relevant

regulations. Relevant data collection should be done as well.

6.2 Main content of test

Furnace ventilation circuit test

1)

Performance examination of primary/secondary air fans and high-pressure fluidizationair fan;

2)

Test of coal feeder air quantity distribution features;

3) Calibration for measuring devices of primary/secondary air volume and fluidized air

volume of material-returning machine;

4)

D i i f h l i f f h i i d b ffl


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in-furnace dense-phase zone. The difference between the two is the resistance of the air

distribution board. Draw the relationship curve between the primary air volume and the air

distribution board resistance in cold state. Through temperature correction, the relationship

curve between the primary air volume and the air distribution board resistance in hot state

can be obtained. During the operation of the boiler, if failure occurs at the bed pressure

measurement point, the quantity of on-bed materials can also be judged on the basis of the

relationship curve between air chamber pressure & air volume and air distribution board

resistance, thereby reducing the operation blindness.

6.5 Test of critical fluidization air volume

The various cold-state measurement tests before this test are carried out with no bed

materials filled. The critical fluidization air volume refers to the minimum air volume

necessary for the bed materials to turn from fixed state to fluidized state. It is the minimum

primary air volume during the operation of the boiler. Method for determine the critical

fluidization air volume: Select 0~1mm or 0~1.5mm river sand or CFB boiler slag as bed

materials. Add bed materials to static height of 1100 mm (sand) or1200mm (ash). Increase

the primary air volume. On the initial stage, the bed pressure increases gradually along with

the increment of primary air volume. When the air volume exceeds a certain value, continue


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There are various kinds of chemical cleaning. Users can choose the appropriate method

according to relevant standards.

This chapter only introduces the cleaning method with low-temperature low-foam

cleanser by virtue of out-laid circulating pump for forced circulation. It is an effective, quick

and economical cleaning method.

The concentration recommended by merchant should be checked, since commercial

cleanser concentration is changed (for example, diluted with water). Normally, the

recommended cleanser concentration is 0.6 percent by volume at 21 ambient temperature

(i.e. to add 1L cleanser into 167L water). If the boiler is cleaned at above 65.6, the

recommended cleanser concentration is 0.3 percent by volume.

7.1Preparation for cleaning

1)

All the water/steam separation devices in the steam drum have been removed.

2) Provide with a temporary circulating pump with a capacity of 14 t/h to circulate the

solution in the furnace. This pump shall suck the solution from the bottoms of the

furnace lower header and of the evaporation screen header. The solution is discharged

from the economizer inlet header. The size of the pipes from the pump to such positions

on the boiler shall match. All the high-pressure pipes connecting to the boiler and all the


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7) Provide with a sampling connection complete with valve, and attach an appropriate tag.

8) Before cleaning, remove the residues in the boiler drum and header mechanically as

long as possible. Check all the bolt sealing components in the boiler drum.

9) All the pressured parts must be checked carefully for any blockage. If any, carry out

necessary hydrostatic test. Inspect the blow-off pipes and dosing pipes inside the boiler

drum and make sure the interiors are smooth and clean.

10) During the cleaning, the operators on duty shall be familiar with the normal combustion

and operational procedures, as well as preventive actions, and learn safety operation

procedures for cleaning. This is very important. Special care shall be employed when

taking any measures that may cause leakage. Take appropriate measures to protect the

personal safety in case of any accidental leakage event.

11) Desalted water is used to fill reversely the SH to ensure that the SH is fulfilled, for ease

of observing the increase of drum water level.

7.2 Flushing with cleanser under ambient temperature

Fill the boiler, evaporation screen and economizer with water until the bottom water

level of the level gauge is in visible range. Through the temporary chemical pipeline, inject

the cleaning liquor slowly. Again add water until the water level is higher than the boiler


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7.3 Matters needing attention

1) Discharge of the cleanser does not need to be done under the presence of nitrogen.

Nitrogen is a nontoxic gas, but is unfavorable for human respiration. If nitrogen-filling

is adopted for draining the boiler and a man needs to enter it after the drainage,

appropriate ventilation must be carried out before a man is allowed in.

2)

If the boiler will be left free fora couple of days after the cleaning, the boiler and the

superheater need to be maintained as described in the maintenance procedure.

3) Before the counter-flushing of the superheater is completed, perform chemical analysis

for the water used (conductivity, pH and chlorine) to confirm that no pollution exists.

4) After the cleaning and before the ignition of the boiler, the water in the superheater and

steam pipeline shall be sampled, analyzed and inspected for any contamination.

5) If cleanser overflows into the superheater due to carelessness during the chemical

cleaning, carry out thorough counter-flushing with sufficient flow before ignition is

allowed in order to ensure that the various contaminants are all removed.

6) In the chemical treatment process, take special care to prevent the cleanser from doing

harm to human being.

7)

Inspect the steam drum and remove any loose deposit from the inner surface of the


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of steam pipe purging, as well as the protection against over-pressure or over-temperature,

are all the responsibilities of the user.

Warning

Because the water level of the steam drum fluctuates greatly

during the purging, the operator shall do the preparation work

sufficiently in advance to avoid any steam drum overflow or

water shortage accidents. Pipe purging can cause certain

damage to the boiler. So the number of purging times shall be

minimized while meeting to the applicable examination

standards.

8.3 General rules

To achieve the best purging effect, when purging the steam pipelines, the steam flowconditions of system should equal to normal operation conditions at maximum load. Because

the purging conditions when discharging into the atmosphere is unlikely to be repeatedly in

accordance with operation conditions, equivalent operation conditions is expected to be

achieved, i.e. steam flow when purging under low pressure multiplies velocity is normal

i di i f ll l d h fl h b b i d b d i d


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If a cut-off valve is installed in the main steam pipeline of the boiler, if the design of

valve allows such operation mode, this valve can also be used as purging valve.

For any component with more than one route of steam pipeline, it is necessary to

consider installation of temporary pipeline so that every route of pipeline could be purged

independently. In this case, make sure to resolve the flow unbalance and expansion problems

at the connections of the pipeline system.

The cleanliness of the components being purged is shown by the target plate provided

at the outlet of the purging pipeline on the final stage of the purging.

The pitting level of the target plate after the purging is used to determine the purging

cycle of certain components.

8.4 Matters needing attention

1) The purging process may result in abnormal and severe conditions for the boiler and

steam pipeline. During every purging cycle, tremendous and quick temperature change

will occur. This change causes much severer damage as compared with normal

operation. In the thick-wall parts of the system such as boiler drum, header and pipeline,

excessive thermal stress may be generated. Therefore, during the purging, such

conditions shall be considered carefully. While meeting the system cleanliness


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8) To ensure that the hot gas will not leak out of the furnace, the furnace shall be operated

in vacuum state (-50Pa).

9)

To make the tubes in furnace and convection pass heating surface overheated or

dry-burned, the gas temperature of the furnace and cyclone separator shall be kept below

538.

8.5 Operation procedure

Due to the requirement for low ignition rate, the fluid bed may be not started during

steam purging. Fire the startup burner steadily, and assume that burner adjustment is good,

dust collector is not necessary.

To avoid excessively high thermal load that may cause thermal corrosion of the

refractory material, the mean rising rate of the steam drum water temperature shall not

exceed 50/h. Start up induced draft fan firstly, then start up primary fan and secondary fan,

thus the startup procedure begins. As long as the material-returning machine nozzle is cover

by ash or sand, the high-pressure fluid fan in not necessary.

Start the boiler as per cold-state startup procedure in normal way. Formal suggestion

and regulation about fuel burning equipment, air treatment equipment, drainage and exhaust

shall be followed. If the boiler start up in normal operation mode, for any newly-built boiler,


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generate the purging flow required, the purging process can start.

8.6 Purging of main steam pipeline

1)

Turn off or hold startup burners. Open the temporary discharge valve gradually. Purge

through the superheater and main steam pipelines and discharge through the temporary

discharge pipe (refer to Matters needing attention). The initial purging is normally

carried out under depressurization in order to inspect the supporting and fixing devices

of the temporary piping system.

2)

When the steam drum pressure drops to about 1.38MPa, close the temporary discharge

valve and re-ignite the unit to establish the purging conditions.

3) Repeat the above operation cycle until the inspection to the flushing target plate on the

final stage shows that the cleanliness is qualified.

8.7 Purging of reheater inlet pipeline

1)

Turn off or hold startup burners. Open the temporary discharge valve gradually. Purge

through the superheater and main steam pipelines and discharge and the pipes

temporarily connected to the reheater and exhaust through temporary discharge pipe

(refer to Matters needing attention). Important note: The initial purging is normally

carried out under depressurization in order to inspect the supporting and fixing devices


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fuel property and the equipment used for measurement. Representative fuel samples shall be

taken regularly to analyze the chemical component, calorific value, viscosity (liquid fuel)

particle size distribution and other physical features of the fuel. All these can cause effect on

the operation and efficiency.

As an index for measuring the economical efficiency of boiler operation, the discharged

gas analysis of the boiler is of important value. The combustion shall be completed before

the gas departs from the cyclone separator. Adoption of the optimal excess air factor depends

on the fuel properties, design of fuel combustion equipment and other factors. And, the

optimized excess air factors shall be established under different loads.

When the heat conduction surface is kept clean, at the given percentages of steam and

excess air, the gas temperature at the outlet of the preheater and the resistance of the gas

passing through the gas duct shall generally be kept constant. To record these operation data

starting from the startup is necessary. The operation data shall be recorded in the tables in

order to compare with the data obtained under the various similar operation conditions.

Standard value for judging the operation satisfaction shall be established when the

equipment is new. In this way, when the operation conditions deviate from the standard,

steps shall be taken to determine and correct the cause of the deviation.


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When the pressure rises, the drainage valve can be throttled, but shall not be shut

completely. Refer to the operation instructions of the valve (Refer to instruction for valve

operation).

During the startup, burning rate should be controlled to keep the highest gas temperaure

of rear pass under 538 (inspected by the temperature element in cyclone separator and

rear pass) until ranked with turbine. After turbine running, the rise of turbine throttle valve

steam temperature and pressure shall always comply with the regulations made by the

turbine manufacturers.

When a new boiler unit is started for the first time, the combustion rate must be

controlled. The increment of combustion rate shall be maintained at a relatively slow rate in

order to inspect the expansion displacement and clearance. The later startup rate can be

relatively quicker, but the temperature rise of the saturated steam shall not exceed 93

(refer to boiler startup procedures) or the limited gas temperature of cyclone separator outlet

mentioned above. The temperature rise of the saturated steam can be slow depending on the

heating rate of the insulation material, refer to the instructions of the insulation material

manufacturer. In this period, combustion regulation is normally carried out manually. Never

try to start up with the combustion control or feed water equipment in automatic status.


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water.

Whatever shutdown mode is chosen, cooling rate cannot make saturated-steam

temperature drop exceed 85 per hour.

9.5 Water level

Prior to the ignition, the operator shall check the steam drum water level with the water

meter column and level gauge blow-off method. Normally, slowly opening drain valve of

high pressure gauge is enough. Normally, an unblocked blow down can clean the foreign

matters probably exist on drain valve seat. When warm up the new unit, the gauges shall be

blown off for several times under low pressure and verify the consistency of remote and

local level gauges. During the operation of boiler, the water level gauges shall be inspected

once per shift (refer to the instructions for the water level gauges). If the water in water

gauge is stagnant when open or close the drain valve, investigate for the cause and correct

the conditions immediately. To protect the glass of the water level gauges, the blow-off

volume shall be kept to minimum during the normal operation.

During the normal operation, the water level of the water level gauge shall also be

observed regularly even if the boiler may be provided with reliable water level regulator or

remote water level indicator.


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out the visible range of the gauge, except the instant water level fluctuation caused by rapid

and sharp variation of load, proper action shall be taken immediately to flame out the boiler.

9.6 Boiler warm-up and expansion

When the pressure of the boiler is raised, it is necessary to take measures in the

beginning to open all the drain valves and bypasses (if any) to drain the cold steam pipes

sufficiently.

During the initial ignition, check the expansion conditions of the boiler regularly and

make records, and make sure that the guard plates, headers and pipes can expand freely

relative to the steel structure. The expansion indicator shall be installed at appropriate

position to facilitate inspection (refer to the arrangement diagram or expansion displacement

diagram of pressured components). During the service life of boiler, inspect its expansion

regularly to determine whether the expansion is normal and uniform. All the hanger rods and

the related pipes shall be inspected regularly for their appropriate displacement and function.

9.7 Air preheater

Abnormal increment of the ventilation resistance in the gas side or air side of the air

preheater indicates that the ash blockage is increasing and various measures shall be taken

immediately. Especially when the unit is started, observe closely the temperature of the gas


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important to the prevention of pressure parts erosion. In no case should plash be in the

pipeline. Normally, a hole at the drain valve can continuously discharge the water. Before

the soot blower put into operation, steam shall be used to purge freely, and enough long time

is needed to heat the pipelines.

9.9 Regulation of steam temperature

Steam side regulates through firing in the furnace and control furnace outlet gas

temperature to regulate and keep outlet steam temperature. The medium side normally keeps

final superheater and final reheater design temperature with desuperheating water. Only

when the outlet temperature of reheater cannot be kept within the specified range of outlet

temperature, spray desuperheating is used.

Whatever method is used to control the temperatuer of superheater and reheater, there

are some factors which may cause abnormal fluctuation of steam temperature:

Causes for abnormal low steam temperature:

1) Insufficient excess air;

2) Feed water temperature higher than design value;

3) Boiler fuel carries excessive moisture;

4)

Contamination on superheater/reheater outer surface or inner surface;


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and reheater shall be as even as possible, and the maximum temperature where gas flows

through the superheater tubes (gas temperature at outlet of cyclone separator) shall be

monitored and controlled.

The gas temperature at outlet of cyclone separator is usually measured with the

thermocouples installed in the outlet gas duct of the cyclone separator. The maximum

temperature at outlet of cyclone separator shall be limited at 538, until the turbine carries

loads and the reheater establish normal steam flow.

To ensure that the condensation water in superheater coil is removed, steam flow

through the superheater shall have appropriate flow when start up. Before the ignition and

firing of the boiler, the drainage valves and vent valves in the outlet headers and/or main

steam pipes shall be opened and shall be kept open until the boiler generates steam and is

loaded. When the boiler drum pressure increases, these startup drainage valves and/or vent

valves can be throttled gradually to make sure that sufficient steam flows through the

superheater throughout the startup. When the turbine is in line with load and appropriate

steam flow is ensured, the startup drainage valves and/or vent valves of the superheater can

be closed.

All drain valves of reheaters shall be open before ignitions. When boiler pressure rises,


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of steam carrying water is doubtable, take measures immediately and investigate to remove

the causes that result in steam carrying water. If the research show that steam carrying water

is not caused by poor water quality, internal device of steam-water separation, water level

control and indicating equipment where problem may probably occur shall first inspected.

From the heat conduction and corrosion point of view, deposition of solid substances on

the superheater and reheater is harmful. Under the presence of chemical substance like

caustic alkali and chlorine, stainless steel pipes of superheater and reheater are much more

likely to be eroded. Therefore, whether during carrying or filling water (hydrostatic test,

chemical cleaning), solid matter shall be prevented from getting inside.

9.11Blow-off

Continuous blow-off is the best method to control and keep the relative stable

concentration of the soluble solid substances in the boiler water. The blow-off data shall be

recorded. Total blow-off quantity is better to be determined according to the boiler water

chemical analysis. Because each power plant has a different water treatment system, person

in charge of water condition shall specify the water treatment system according to the

feedwater analysis and give necessary instruction of blow-off.

However, the blow-off quantity will affect the heat loss and water supplement volume


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load condition requires to keep operating, the boiler can keep operating until the chance of

shut-down for necessary overhaul. Under such circumstance, other tubes are often damaged

when the boiler operate for quite some time. When the tube damage is more than one and

affect the water gauge losing water level, the boiler shall be shut down in normal mode. The

purpose is to prevent all equipment from suffering sudden temperature change.

Low water level, various measures shall be taken to make water level approach the

normal level until the boiler is fully cooled down and allowed for drainage.

When leakage of superheater or reheater components happens, it shall be analyzed as

soon as possible. The boiler shall be shut down in normal mode.

The above information is only for suggestion, and cannot take the place of the correct

judgment of the stokers responsible for operating these equipment.

Bear in mind that prolonging the operation of the tubes with leakage may cause the

damage to adjacent tubes and increase maintenance works, exceeding the former short scope

of maintenance.

9.13 Furnace explosion

Furnace explosion is usually result of the following conditions:

1)

Unburned fuel accumulates in the furnace due to incomplete combustion.


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4) It is absolutely unallowable to ignite the oil burner when the ignition energy source

needed is lost. Ensure that the air in air atomization oil gun is dry, do not use heavy

oil/mechanical atomization oil gun for boiling out, ignition and boiler warm-up, while

light oil/ air atomization or heavy oil/steam atomization oil gun is preferred.

5) Prior to any startup and during the normal operation, inspect the functions of the furnace

safety supervision system regularly, including interlock, tripping, etc.

6) During the downtime of the furnace, regulate, inspect and maintain the furnace safety

control system thoroughly.

9.14 Fly ash wear

Fly ash wear refers to the wear of the residual ash particles carried over in the gas to the

metal surfaces. Wear normally occurs in local zones with high gas speed. The wear level is

related to the ash content of the fuel (quantity and component). Firing coal with high wear

characteristics and high ash content makes boiler wear a main problem.

Caution: Wear usually occurs in: the end and bend of economizer tube and

low-temperature superheater and around soot blowing area, gas duct and induced draft fan

(fan blade and shell).

The boiler design parameters are based on conservative mean gas velocity and normal


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section of superheater and reheater panel where water cannot be drained, and measures shall

be taken to prevent getting frozen.

Before entering the steam drum, make sure that all the valves in the steam drum

connection pipes are closed tightly (feed water, auxiliary steam, dosing pipe, blow-off,

drainage, sampling, level gauge drainage, etc.). Open the manhole cover to inspect the

tightness and cleanliness of the interiors of the steam drum. Inspect the steam drum for

corrosion and surface pit. Oxidized pit is a common form of corrosion, and normally occurs

in the steam drum above the normal water level, and sometimes in the tubes and lower

headers. Open sufficient number of hand hole covers in the various headers of the water wall

to remove the dirt.

Check the heating face of the preheater for cleanliness. If there is corrosion, it should

occur in the cold end part of the preheater, especially in the places where ash and filth tend

to accumulate.

Inspect the gas side thoroughly and clean it as necessary. Check if the soot blower is

deflective. Inspect the equipments such as coal spreading trough, igniter, oil gun, scanning

air fan, connection rod and air door for cleanliness and damage, and carry out operation and

flexibility inspection. For the FSSS system, inspect and test the control valve, relay,


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4) Cold boiler shall not be switched to dry type corrosion prevention. If it is necessary,

ignite and raise the pressure to 30% of the rated pressure and then reduce the pressure.

Adopt the afterheat drying method for the maintenance.

9.16.2 Maintenance method

Select the maintenance method according to the maintenance principle. The

maintenance and operation can be implemented depending on the specific conditions of the

power plant with reference to the applicable specifications of the power authorities.

9.16.3 Freezing prevent for boiler

The freezing prevention measures shall be checked before winter begins. No pipe is

allowed to be bare. Anti-freezing and heating devices for each part of pipeline proper shall

be put into operation. Heating tubes of fuel line are in operation whole year and cannot be

overhauled in winter. Water in gauge pipe shall be drawn off. Hole door and damper of spare

boiler shall be closed, and measures shall be taken to prevent cold air from entering into the

boiler in overhaul.

In winter, during the shutdown of boiler, adopt dry-type maintenance as can as possible,

and air heater shall be put into use when the wall temperature of superheater is below

20.


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10.2 Preparation before boiler startup

10.2.1 Inspection and cleaning before boiler startup

Before initial ignition and every cold startup or after service of the boiler, the interior

and exterior of furnace shall be inspected and cleaned. And all foreign maters shall be

removed completely from the pressure parts, all pipes and conduit tubes, which may limit

the normal expansion of the boiler, shall be removed. All person shall leave, and all doors

and openings shall be closed. Check whether the indication of the boiler drum water level

gauge is consist with the reading of local glass water level gauge, whether there is any block

at air distribution boards of the furnace and material-returning machine, and inspect and start

the atomization nozzle of the burner. And all these check shall be prepared by the

departments which is in charge of operation. Be familiar with the startup and operational

procedures for boiler and auxiliary machines.

10.2.2 Steam pipeline purging

For a new boiler or a boiler the main pressure parts of which has been repaired, the

purging of main steam pipeline and reheating steam pipeline shall be done before startup to

remove the rust and foreign matters in order to avoid the damage ti turbine. The purging of a

new boiler shall be done after pickling and before the setting of drum and reheater safety


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10.2.5 Filling bed materials into boiler

Before the CFB boiler is started, inert substances (appropriate sand particles or CFB

bed ash) are loaded into the furnace as bed materials. Used CFB bed ash is optimal due to its

excellent fluidization features. To ensure appropriate heat transfer and system insulation,

sufficient bed materials must be introduced. Each boiler needs about 200t bed materials

(including the furnace and material-returning machine). The particle size of the bed materials

loaded shall meet the particle size limits allows by the design. If no ash is unloaded from the

system or if the bed materials exist before the operation, no further loading is needed.

10.3 Cold/warm-state startup

When the turbine high pressure rotor probe temperature is lower than 100, or when

the boiler starts up in cold state with no pressure, it is called cold-state startup. When the bed

temperature (the average temperature shown in the middle-level thermocouple) is lower than

680, coal cannot be put into the furnace directly; instead, it is necessary to purge the

furnace according to the cold-state startup mode and then to put the startup burners into

service to increase the be bed temperature. The startup mode in such state is called

warm-state startup. In case of cold-state or warm-state startup, the furnace must be purged.

Only after the purging is completed can the startup burners be put into service. After the


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10.3.2.1 Starting of induced draft fan

Induced draft fan is the first air fan in circulating fluidization air and gas system during

boiler start-up. Before the induced draft fan is started, its inlet baffle is regulated to the

minimum position to avoid over-current of the motor of the induced draft fan during the

startup. After the induced draft fan is started, check the outlet baffle which shall be open,

note that the vibration indication value of the air fan bearing, the voltage and current values

and the temperature should be within the specified range. Open the vane control baffle at the

inlet of the induced draft fan slowly. Put the furnace vacuum (separator outlet) control to

automatic. Monitor the furnace pressure. Subsequently, the air volume of the induced draft

fan will regulate the control baffle automatically for operation, maintaining appropriate

furnace pressure at the outlet of the combustion chamber.

If tripping or downtime of induced draft fan for any reason occurs during boiler start-up,

primary air fan and secondary air fan shall be shutdown.

10.3.2.2 Starting of high-pressure fluidization air fan

During boiler start-up, after the induced draft fan is started, start the high-pressure

fluidization air fan and check the air volume of every chamber of the material returning

valve.


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out. The furnace purging air volume shall, as a minimum, be more than 30% of the total air

volume under the rated load. For the detailed purging steps when the boiler is started up or

shut down, refer to the boiler operational procedures provided by FSSS suppliers.

10.3.4 Boiler ignition startup and temperature/pressure raising

Before the ignition of startup burner, cold/warm-state boiler shall have periodic purging

according to the permissive ignition condition of start-up burner.

1) Electrify the electrostatic precipitator

2)

Start up the induced air fan.

3)

Put the furnace pressure control to automatic, and keep the furnace pressure at -125Pa.

4) Start up the high-pressure fluidization air fan, ensure that there is at least one

high-pressure fluidization air fan under operation.

5) Start up the secondary air fan.

6)

Start up the primary air fan, ensure that there is at least one primary air fan under

operation.

7) Put the boiler air flow to automatic. Adjust the set value of total air flow to be no less

than 30% of the air flow at full load. Inspect all equipment until they meet furnace

purging. Control the primary, secondary air volume at 50% of air volume at rated load.


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13) Along with the increasing furnace temperature, the temperature difference between

material-returning machine and upper furnace shall be kept with 38, in order to

prevent the damage of heat insulating material of cyclone separator and material

returning machine. When the temperature of material-returning machine is 38 or

much lower than upper furnace, primary air volume shall be added as needed to reduce

temperature difference.

14) When the steam drum pressure achieves 0.17MPa, close the steam discharge valve and

vent valve in the boiler drum connection pipe.

15)

Along with the increasing boiler drum pressure, regulate the drainage of the superheater

outlet header gradually or start other discharge valves or drainage valves. During the

startup, sufficient steam flow must be maintained to remove the condensate on the

superheater components.

16) Blow the boiler off as necessary during boiler warm-up. Maintain the water level within

the visible range during the blow-off.

17)

Maintain the water level of boiler drum at normal valve, and inspect the concentration

and composition of boiler water as needed, to maintain qualified boiler water condition.

18) Before the condenser forms vacuum, make sure that the exhaust valves and drain valves


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1. Temperature of main steam or reheat steam pipelines suddenly drops without rhyme or

reason.

2.

Steam line vibrates and causes water shock.

3. Abnormal vibration and expansion reading record shown in turbine monitoring

equipment.

Operating personnel shall take necessary measures to prevent water from entering and

damaging the turbine. Refer to the specification provided by turbine manufacturer.

21)

When bed temperature (average temperature of middle-level thermocouple) achieves

575, the first coal feeder can be started manually to load coal at the minimum rate.

After coal is loaded, observe the variation of bed temperature. When the bed

temperature rises gradually while the oxygen quantity decreases continuously, it can be

identified that the coal is in combustion. To spread the fuel evenly on the bed face,

firstly load coal through the middle coal feeding tube. Now attention shall be paid to the

air quantity in the coal feeding tube. If the bed pressure is low and the air quantity is

small, the dampers in the two sides can be turned down appropriately. However, in the

beginning when coal is loaded, increase or decrease gradually depending on the

combustion conditions in the furnace. For further heating and temperature rising, follow


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boiler when the bed temperature(average temperature measured by the lower thermocouple)

is more than 650. If the bed temperature is higher than the allowable coal feeding

temperature after the fan is started, it is not necessary to purge the furnace or to put the

startup burners into operation. After feeding coal directly and igniting with the coal feeder at

the minimum rotary speed, the boiler can be brought to the full load rapidly. It is also not

necessary to consider the limit in temperature rising rate for the wear-resistant refractory

materials in the furnace. This is because there is quite high accumulation of heat in the

furnace and cyclone separator in this time.

10.5 Regulation during normal operation of boiler

The boiler will be put to automatic control during operation, however opertaing

personnel shall pay attention to the operating condition of the unit to ensure the safety and

economics of boiler operation and to the control of emmssion in fuel gas. Steam flow,

temperature and pressure parameter of superheater and reheater shall be kept within the

allowable range of normal operation.

10.5.1Regulation of boiler load

The regulation of boiler load is mainly achieved by changing the coal feeding quantity

and the corresponding air volume. When the load increases, increase the air volume firstly


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maintained. However, because the bed temperature is restricted by multiple factors, the

variation amplitude is limited.

10.5.2 Regulation of bed temperature of boiler

The design value of the bed layer temperature of the boiler is 892 under the rated

load. Considering the load variation and the requirements in other aspects, the bed layer

temperature is controlled at 850~910. When the bed temperature exceeds this range, it

must be regulated in time.

Regulate the bed temperature by changing the ratio of primary air to secondary air.

When the primary air volume is increased or the secondary air volume is reduced, the bed

temperature will decrease. Conversely, the bed temperature will increase.

By increasing the quantity of bed materials to improve the circulation of the materials,

the bed temperature can be increased. By increasing the slag discharge quantity to reduce the

bed pressure and the quantity of bed materials, the bed temperature will rise.

If the mean size of the bed materials is excessively large, relatively speaking, the

useable materials that can participate in the internal and external circulations of the boiler

will decrease, causing the boiler to operate at relatively high bed temperature. By increasing

the slag discharge quantity, removing the bed materials with larger particle size and adding


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10.5.4 Regulation of steam temperature

Primary and secondary spray type desuperheater are set respectively between platen

superheater cold section, platen superheater hot section and high-temperature superheater in

superheater system, to regulate steam temperature, primary for coarse control and secondary

for fine tuning.

Reheater regulate steam temperature mainly by gas damper, supplemented by

emergency water spray device.

The steam temperature is regulated with water spray. The operators shall pay close

attention to the water spray quantity and the steam temperature before and after water spray

to ensure that the desuperheated steam temperature should be higher than the saturation

temperature under such pressure by 11.

10.5.5 Control of SOx emission quantity

If the control of SOx emission quantity is not needed, please skip this section.

The SOx emission quantity is normally controlled by controlling limestone feed rate

automatically and manually, i.e. to increase or decrease the mole ratio of calcium and sulfur.

However, many other factors like bed temperature, limestone granularity will affect the

desulfurization efficiency of a CFB boiler.


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the nitrogen oxides generated from the organic nitrogen compounds in the fuel which are

oxidized in the combustion process. For the fluidized bed boiler, the NOx emission quantity

is controlled through control of bed temperature and segmental combustion.

When the bed temperature is controlled in 790~900, the NOx emission quantity is the

lowest.

The primary/secondary air ratio affects the NOx emission. While the bed temperature

and the normal combustion in the furnace are guaranteed, regulating the primary/secondary

air ratio within a certain range can bring the NOx emission to a relatively low level.

10.5.7 Protection of reheater

Turbine bypass shall remain hot stand-by during boiler normal operation, in order to

protect the reheater heating surface when unexpected accidents such as turbine tripping

happen. CFB boiler is different from conventional PC boiler, when accidents such as turbine

tripping happen and cause MFT, huge heat storage still exists in the furnace and the

temperature is high in the furnace, even higher than the anti-oxidation temperature of tube

material. Therefore, bypass is needed to start up to make a certain amount of steam flowing

through superheater and reheater to cool the heating surface.

10.5.8 Re-fluidization of bed materials


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5) Recover the normal control.

10.5.9 Use and maintenance of bed temperature thermocouple

Bed temperature is the average temperature of each thermocouple at different place of

the bed. If the temperature of a thermocouple differs by more than 170from average

temperature, the temperature will not be included in the calculation.

Bed temperature thermocouple passes through wear-resisting material layer for about

150mm. If the length is exceeded, the wear will be increased and the service life will be

shortened.

10.5.10 Maintenance of bed temperature measuring equipment

Bed temperature measuring equipment is different from conventional pressure

measurement. Purging air shall be arranged, because pressure measuring point and pressure

measuring pipeline can be easily blocked by fluid bed material.

In order to remove the accumulated bed material at pressure measuring hole, purging

shall be continuous. It is realized by zero transferring at site.

Instruction: Pressure measuring holes shall be inspected on by one for blockage before

boiler is put into operation. Because of the error of construction, the distance between each

hole and air distributor may deviate from design location and causes large pressure


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furnace temperature drop curve.

Steam temperature drop speed shall be in line with the requirements of turbine

manufacturer.

Steam temperature control, combustion control and water feeding control can keep

using automatic way until manual way is better, change into manual way.

Caution: During and after shutdown, carefully prevent water from entering into main

steam pipeline, hot reheat pipeline and cold reheat pipeline, in order to prevent the damage

to turbine in future restart. Water may come from:

1Overflow into superheater from drum because of high water level.

2Enter into superheater from desuperheater because of desuperheating control

valve open or leakage.

2) Reduce the coal feeding quantity

When the middle-level thermocouples show that the temperature is near 680, put the

startup burners into service. Control the boiler reducing rate according to the shutdown curve.

When the middle-level thermocouples show that the temperature is below 680 without

startup burners running or when startup burners is in operation and the middle-level

thermocouples temperature is lower than 630, coal feeding must be stopped. Once coal


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8) If the boiler to be emptied, boiler water temperature shall be below 90 before

drainage.

9)

When an appropriate operating temperature is realized for boiler shutdown, continue to

purge the furnace, cyclone separator, material-returning leg and material-returning

machine for around 30mins to protect the refractory materials, then shut off the air fan.

10)

The stop subsequence of fans: primary air fan-- secondary air fan-- induced air

fan--high-pressure fluidized air fan.

10.6.2 Normal boiler shutdown to hot standby

Boiler shutdown time is short (below 8 hours) and certain pressure and temperature are

maintained. Furnace bed temperature shall be kept higher than the allowable temperature of

pulverized coal ignition during operation as far as possible. The pressure of superheater

pipeline shall be reduced to an expected value, and it shall be kept by using superheater

outlet exhaust valve or reheater protection system.

The procedure similar to that for normal shutdown to cold state shall be observed

except for the following conditions:

With the decrease of unit load, do not lower the drum pressure. The pressure decrease

rate shall be much smaller than the rate of normal boiler shutdown. Referring to the


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Under the condition that the coal powder ignition is allowed, maintain the bed

temperature as high as possible.

4)

Turn off the secondary air fan when the gas temperature of cyclone separator is lowered

to 538. Continue with the purging with high-pressure fluidization air fan for 10

minutes to remove the combustible gas in the material returner and the solid substances

in the cyclone separator, material returner and material-returning leg. Then turn off the

induced draft fan and close the baffles in all the air ducts to minimize the heat loss in the

furnace.

5)

The boiler can be re-started in hot-state or warm-state mode depending on the bed

temperature.

10.7 Slag-cooling system

There are slag notches at the bottom of the furnace. Bottom slag enters into slag cooler

through slag notches, and is discharged after being cooled. Discharge quantity is controlled

by variable frequency motor speed, and inlet quantity is controlled by the pressure

difference between the inlet air pressure of hot primary air chamber at the bottom and

furnace outlet air pressure. Slagging begins when bed pressure is beyond 13.5Kpa

(tentative, the specific value is determined after site commissioning).


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6) Limestone system doesnt run normally.

Countermeasures:

1)

Inspect the bed temperature thermocouples;

2) Check if the operation and control of the coal feeder are normal;

3) Distribute the air reasonably, and regulate the primary-secondary air ratio;

4)

Adjust the particle size of the coal fed into the furnace;

5) If necessary, increase the slag discharge quantity and add bed materials of appropriate

particle size.

11.2 Excessively high or low bed pressure

Phenomenon:

1) Excessively high or low display of CRT interface; Excessively high or low display of

bed pressure;

2)

Bed pressure high or low alarm;

3) Severe increment of slag discharge load of slag cooler, or slag discharge almost stopped;

4) Excessively high or low pressure at bottom of air box.

Cause:

1)

Bed pressure measurement failure;


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1) In case of slight cracking or weld leakage, hiss of steam can occur and the feed water

flow increases slightly;

2)

In case of severe conditions, obvious popping and steam spraying sound appears at the

tube cracking place, the negative pressure in the furnace turns positive, the feed water

flow becomes abnormally higher than the steam flow, and keeping of water level

becomes difficult in severe case.

3) Atomization phenomenon occurs in the non-tight boiler wall places;

4)

In severe case, the current of the induced draft fan increases and white steam is emitted

from the chimney;

5) The bed temperature and the temperature at the inlet/outlet of the cyclone separator

decrease.

Cause:

1)

The quality of boiler water and feed water exceeds the standard for long term, causing

scaling in the tubes, increment of local thermal resistance and over-temperature;

2) The water circulation is not good, resulting in local over-temperature;

3) Unqualified tube material, poor welding quality, or severe wear of external wall of

tubes;


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2) The furnace vacuum reduces or turns positive, and the pressure of the superheated steam

decreases.

Cause:

1) Scaling on the inner wall of the tube or blockage of the tube with foreign materials,

resulting in deteriorated heat conduction;

2)

Wear of outer wall of tubes, or high-temperature corrosion;

3) The steam temperature or wall temperature exceeds the limit for long term;

4)

Unqualified tube material, improper welding quality, or improper steam soot blowing.

Countermeasures:

1) If the tube blasting is not severe, it is allowed to operate for a certain period. However,

reduce the load appropriately and prepare for shutdown.

2) In case of severe tube blasting;

1.

With the induced draft fan running, control the bed temperature decreasing rate not

to exceed the specified value;

2.Maintain small quantity of feed water and keep normal water level;

3.Proceed with the other operations as per the normal boiler shutdown procedure.

11.5 Coking on bed surface


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3) If it the condition does not improve after the regulation, shut down the boiler

immediately.

11.6 Power interruption of system

Phenomenon:

1) The water level in the steam drum is relatively low or is invisible;

2)

Collapse of the bed materials in the furnace bed face or in the bed face of the material

returning valve;

3)

Power interruption causes all the auxiliary machines to stop.

Countermeasures:

1) Close the main steam valve and open the atmosphere vent valve of the superheater.

Avoid tripping of the safety valve as long as possible. Control the steam flow at

approximately 2kg/s;

2)

Open the connection between the drainage of the economizer and the concentrated

downcomer so that the water of the economizer could be supplemented into the water

wall;

3) Because of the high heat accumulation in the boiler, open the baffles of the various air

ducts to reduce the temperature level in the boiler at the maximum speed;


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Countermeasures:

1) Firstly, compare the indication conditions of all the level gauges to judge the

truthfulness of the water shortage accident and the water shortage extent;

2) If relatively severe water shortage is caused by severe failure of electrical equipment,

judge quickly and request for instructions for emergency shutdown;

3)

When water shortage is not serious, generally, there is no failure which may affect the

operation of boiler, such shortage is caused by improper operation probably. Water

supply shall be enhanced by manual operation to restore normal water level.

11.8 Water fullness accident

Phenomenon:

1) Water level is invisible at the sight glass of the level gauge, and the boiler water

becomes dark;

2)

The water level alarm gives high-level alarm signal;

3) The superheated steam temperature drops and the salt content of the steam increases;

4) The feed water flow becomes higher than the steam flow suddenly.

Cause:

1)

The operators omits in monitoring the water level;


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In case of water attack in the steam pipeline, start the drainage valve of the superheater

system. Drain sufficiently and vent the remaining air out of the pipeline. For the feed water

pipeline, stabilize the water pressure and eliminate the air.


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Instruction For Boiler Operation 2305-1-8603 P 57 / 61

,

THIS DRAWING OR DOCUMENT BELONGS TO SBWL AND MAY NOT BE REPRODUCED OR DISCLOSED TO ANY THIRD PARTY IN ANY FORM WITHOUT THE PRIOR WRITTEN PERMISSION

OF SBWL..

12 Appendix

12.1 Figure 1 Boiler dry-off heating/cooling rate


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,


OF SBWL..

12.2 Figure 2 Cold-state startup curve


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,


OF SBWL..

12.3 Figure 3 Warm-state startup curve


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,


OF SBWL..

12.4 Figure 4 Hot-state startup curve


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,


OFSBWL

12.5 Figure 5 Shutdown curve

boiler manual 3x135mw

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