waste water treatment design

1. The Supervision of Water-steam Quality
in Boiler
Wells Zhu

2. 1 Introduction
2 The Analysis and Pre-control of Hazard Points
3 The Significance of Water Steam Items Supervision
4 The Most Vulnerable Parts Affected by Water-steam Quality
5 The Treatment of Water-steam Quality Deterioration
6 Operation Procedures
7 Conclusion
Content

3. Introduction
Water and steam cycle in boiler
T V

4. Introduction
Why should the water-steam quality in boiler be supervised ?
In order to prevent the corrosion, scale formation, and salt
accumulation of the boiler and thermal system, the supervision
of water-steam quality must be strictly in accordance with the
regulations to determine all of the items in the scope of the
standards to ensure the thermal equipments to operate safely.

5. GB/T
12145-2016
• Quality Criterion of Water and Steam for Power Plant and
Steam-generating Equipment
DL/T
561-2013
• Guide for Chemical Supervision of Water and Steam in Thermal
Power Plant
Theoretical Basis
Introduction

6. The analysis and pre-control of hazard points
Safety
PPE
Insepction
Analysis

7. The analysis and pre-control of hazard points
1 Head protection
3 Eyes protection
2 Breathing protection
4 Ears protection
5 Hands protection
6 Feet protection
7 Body protection
 PPE Part

8. The analysis and pre-control of hazard points
 Inspection Part
Prepare
inspection
tools
1
Check
flashlight is
good
2 3 Prepare
suitable
protective
equipments
4
Hands over
work to
inspector
5
Take or use
tools wrongly
Personal injury
Equipment trouble
Communication
equipments
are good
Illumination
is lack
Power or signal
is not good
Use inappropriate
PPEs
Explain
incompletely
to inspector
Personal injury
Personal injury
Equipment trouble
Scald
Other harms
Can not get the
rescue after
injury

9. The analysis and pre-control of hazard points
 Analysis Part
Prepare
chemicals
Take the
chemicals
mistakenly
Personal injury
Pollute Lab
environment
1 Prepare
equipments
and
glasswares
Wear PPEs
improperly
Break up
glasswares
Personal
injury
2
Prepare
chemical
solution
Prepare solution
improperly
Splash
chemicals out
Personal injury
Pollute Lab
environment
3 Put chemicals
back into
chemicals
cabinet
Cover chemical
bottles
untightly
Personal injury
Pollute Lab
environment
4

10. The significance of water steam items supervision
Water-steam items in boiler
Steam
(Na, CC, SiO2, Fe, Cu)
Boiler water
(Cl-, SiO2, CC, PO4,
pH)
Feed water
(CC, Na, SiO2, DO,
Fe, Cu, N2H4, pH)

11. The significance of water steam items supervision
The sodium content can represent salinity in steam.
The item represents the contribution of anions to conductivity.
The silicic acid in the steam can form SiO2 sediment in the turbine.
Prevent the deposition of metal oxides in the turbine.
Na
CC
Si
Fe
Steam

12. The significance of water steam items supervision
Limiting the silicon in the boiler water is to ensure the quality of steam.
Damage the protective film of water wall.
Prevent acidic corrosion or alkaline corrosion of water wall.
Control the hydrolysis of the silicate in boiler water.
Si
Cl
PO4
pH
Boiler water

13. The significance of water steam items supervision
The impurities in boiler water are mainly from feed water.
Na
Prevent calcium and magnesium scale in thermal system.
YD
Prevent oxygen corrosion in feed water systems and boiler.
DO
The pH controlles iron and copper corrosion at least.
pH
N2H4
Feed
water
Eliminate the dissolved oxygen.

14. The most vulnerable parts affected by water-steam quality
The most vulnerable parts affected by water-steam quality
Economizer
Water wall tube
Drum
Superheater tube
Reheater tube

15. The most vulnerable parts affected by water-steam quality
The dissolved
oxygen in feed
water causes
the corrosion
of inner wall
of economizer.
Economizer
The unqualified
boiler water
will cause
corrosion and
scaling in water
wall tube.
Water wall
The steam
washing device
and steam-
water separator
in drum can
ensure water-
steam quality.
Drum
Overtemperature
affected by
unqualified
steam will cause
superheater tube
damage or even
tube explosion.
Superheater tube
Reducing
the moisture
in turbine is
beneficial to
the safe
operation
of turbine.
Reheater tube

16. The treatment of water-steam quality deterioration
 The cause and treatment of steam quality deterioration
Unqualified boiler water Boiler operation
Steam desuperheater Boiler dosing concentration
Steam-water separator Washing steam device
The cause and
approach of
unqualified Na or Si
content in steam
Cause 1: The content of sodium or silicon in
the boiler water exceeds the limit.
Approach:
1. Find out unqualified water sources and take
measures to ensure water quality of the water
source qualified or reduce the usage amount of
unqualified water source;
2. Adjust the operation of continuous blowdown
flash tanks for boiler.
Cause 2: The boiler load is too large, the
water level is too high, and steam
pressure changes too fast.
Approach: Control the operation of the
boiler strictly.
Cause 3: The water quality of steam
desuperheater is poor or the desuperheater is
leakage.
Approach: When the desuperheater is
leakage, the desuperheater is stopped or
shutdown maintenance.
Cause 4: Boiler dosing concentration is too
large or dosing speed is too fast.
Approach: Reduce the concentration or
speed of boiler dosing.
Cause 5: Low efficiency of the steam-water
separator or the joints of separation
components are not tight.
Approach: Eliminate the defects of the
steam-water separator.
Cause 6: Washing steam device is not
horizontal or short circuit phenomenon.
Approach: Remove the defects of washing
steam device.

17. The treatment of water-steam quality deterioration
 The cause and approach of boiler water quality deterioration
The cause and approach of turbidity deterioration in boiler water
Turbid feed water Lack boiler blowdown Starts up after overhaul
 Find out turbid water
sources and treat or reduce
the use of the water source;
 Eliminate the possibility
of feed water which is
polluted by raw water.
 Carry out boiler
blowdown regulation
strictly.
 Increase the boiler
discharge until the water
quality is qualified.

18. The treatment of water-steam quality deterioration
The cause and
approach of
unqualified phosphate
in boiler water.
Phosphate dosage
is too much or
insufficient.
Dosing equipments
have defects or
pipes are blocked.
Adjust the dosage
of phosphate.
 The cause and approach of boiler water quality deterioration
Maintain
dosing
equipments or
clean the
blocked pipes.

19. The treatment of water-steam quality deterioration
The cause and approach of pH in boiler water which is lower than the standard
 The cause and approach of boiler water quality deterioration
Acidic
substances enter
into the boiler.
Increase phosphate dosage, if
necessary, increase NaOH
solution.
The phosphate
dosage is too low
or misuse
chemicals.
Adjust the phosphate
dosage, or check whether
the chemical is wrong.
Boiler
blowdown is
too much.
Adjust the boiler discharge.
1
2
3

20. The treatment of water-steam quality deterioration
 The cause and appoach of feed water quality deterioration
The cause and approach of unqualified CC and Si in feed water
Cause 1: The feed water sources
are not good.
Approach: Find out unqualified
water sources and take measures to
treat or reduce the usage of
unqualified water source.
Cause 2: The steam discharged
by continuous blowdown flash
tanks for boiler carries water.
Approach: Adjust the operation
of continuous blowdown flash
tanks for boiler.

21. The treatment of water-steam quality deterioration
The cause and
approach of
unqualified
dissolved oxygen in
feed water
 The cause and appoach of feed water quality deterioration
Adjust the
operation of
deaerator.
Deaerator runs
abnormally.
The internal structure
in deaerator exists
defects.
Check deaerator.

22. Operation procedures
 Pre-check up
01 03 05
02 04 06
Check the
equipments
in a good
standby.
Open sampling
devices and
dosing devices
primary valves.
Check
deminerali
zed water
is enough.
Check generator
inner cooling
water is
qualified.
Check turbine
oil and EH oil
is qualified.
Check sampling
points, dosing
room, and lab in
good lighting
condition.

23. Operation procedures
 Start up
1. The shift manager informs the condensate pump is started,
the chemical operator starts up the NH3 pump and N2H4 pump.
2. The shift manager informs the boiler ignition time,
the chemical operator starts up PO4 pump.
3. The shift manager informs the boiler pressure is 0.5-1.0 Mpa,
the chemical operator analyzes Fe in boiler. If qualified, the chemical
operator rinses the water-steam sampling pipes.
4. The chemical operator analyzes the boiler water, saturated steam, and
superheated steam.
If the quality can meet turbine turn standard, inform the shift manager.

24. Operation procedures
 Start up
5. After turbine turn, the chemical operator analyzes the condensate.
If qualified, inform the shift manager.
6. The chemical operator analyze Fe in LP and HP condensate.
If qualified, inform the shift manager.
7. Before combining to the grid, the shift manager informs the chemical operator
to analyze the generator internal cooling water.
If qualified, inform the shift manager.
8. After combining to the grid,
the pH, DD and O2 meters are started up 8 h later.
the SiO2, Na, and PO4 meters are started up 8 h later.

25. Operation procedures
 Inspection
# 01 steam
Na≤5μg/kg, CC≤0.15 μs/cm,
SiO2≤20 μg/kg,
Fe≤20 μg/kg, Cu≤3 μg/kg
# 02 boiler water
SiO2≤0.20 mg/L, Cl-≤0.5 mg/L, DD ≤20
μs/cm, CC ≤1.5 μs/cm, pH=9.0~9.7,
PO4 ≤1 mg/L
# 03 feed water
CC≤0.15 μs/cm, SiO2≤20 μg/L, Fe≤15 μg/L,
Cu≤3 μg/L, N2H4≤3 μg/L
Check and analyze the steam, boiler water, and feed water
quality meets the following standard.

26. Operation procedures
 Normal shutdown
1 2 3 4 5 6
Stop all
the water-
steam
instrumen
ts online.
Empty all
sampling
and
dosing
pipes.
Stop
dosing
pump.
Close
sampling,
dosing, and
continuous
blowdown
primary
valve.
Close the
sampling
cooler,
cooling
water inlet
and
outlet valve.
Protect
turbine
and
boiler.

27. Conclusion
The supervision work of water steam quality in thermal power has an
important impact on production capacity, environmental protection and
energy consumption indicators.