-
Chapter 2 Boiler
第二章
锅炉
Air heater
空预器
Anchor
支座，固定
Anhydrous ammonia
无水氨
Anthracite
无烟煤
Atomized
雾化
Austenitic
奥氏体钢
Auxialiary
辅助机械
Axis
轴
Bagasse
甘蔗渣
Bare tube
光管
Bark
树皮
Beam
梁，横梁
Bituminous
coal
烟煤
Blade
叶片
Blast
鼓风
Blowdown
排污
Boiler
锅炉
Bulk
大块的
Burner zone
燃烧器区域
Butane
丁烷
Calcination
煅烧
Capacity
出力
Carbon steel
碳钢
Cerium
铈
Chromium
铬
床锅炉
Coal char
煤焦
Cogenerator
热点联产机组
Combustion
燃烧
Dwell time
保留时间
Economizer
省煤器
Embrittlement
脆性，脆化
29-1
Commissioning
试运行
Compressor
压缩机、压气机
Condenser
凝汽器
Containment
反应堆安全壳
Convection
对流
Coolant
制冷剂
Coordinated
坐标，定位
Corten
低合金耐腐蚀钢
Counterflow
逆流（换热器）
Creep
strength
蠕变强度
Criterion
标准
Critical pressure
临界压力
Culm
煤屑
Cyclone
furnace
旋风炉
Debris
残骸、有机残留物
Decane
癸烷
Decay
分解
Deposited
沉积，沉淀的
Deterioration
恶化
Diesel oil
柴油
Differential
差动，微分
Distillate
馏出物
Distortion
变形
Division wall
分隔墙，双面水冷壁
Drainage
疏水
Circulating fluidized bed CFB
循环流化
Drum
汽包
Equalization
均衡，平衡
Erosive
侵蚀的，腐蚀的
Ethane
乙烷
Evaluate
评估，评价
Evaporate
蒸发
Excess air
过量空气
Extended surface
扩展受热面
Fatigue
疲劳
Feedwater
给谁
Ferrite
铁素体
Fin
鳍片，肋片
Flange
法兰
Flue gas
烟气
Fouling
沾污
Furnace
炉膛
Generator
发电机
Geological
地质的
Girth
环形
Govern
控制、调节
Gravity
重力
Header
联箱，集箱
Helical
螺旋状的
Helium
氦
Heterogeneous
不均匀的
Hopper
斗，料斗
Husk
壳，外壳
Hydraulic
水力的，液压的
Ignite
点火
Impurity
杂质
Inert
惰性
Inferior
低级的，劣质的
Ingredients
成分
Ingress
进口，入口
In-line
顺列
Inorganic
无机的
Ion
离子
Jurisdiction
权限
Lignite
褐煤
Lime
石灰
Limestone
石灰石
Low alloy
低合金钢
Low-volatile
低挥发分的
Margin
裕量，安全系数
Matrix
矩阵
Membrane
膜
Methane
甲烷
Mill
磨煤机
Molecule
分子
Molten
熔化
Nitric oxide
氮氧化物
Nonpressure
非承压的
Nontoxic
无毒的
Organisms
有机体
Oxidation
氧化
Peat
泥煤
Pendants
superheat platen
悬吊式屏式过热器
Pentane
戊烷
Petrochemical
石油化工制品
Petroleum
石油制品
Plasma spray
coating
等离子喷涂
Platen
屏
Polymer
聚合物
Pores
气孔，小孔
Porosity
多空的
29-2
Potassium
钾
Prandtl numbers
普朗特数
Prefabricated
预制的
Premium fuel
优质燃料
Pressure loss
压力损失
Primary air
一次风
Propane
丙烷
Proximate
analysis
工业分析
Pulp
纸浆
Pyrites
黄铁矿
Radius
半径，范围
Rare earth element
稀土元素
Recuperator
间壁式换热器
Regenerator
回热器，蓄热器
Regulate
控制，调节
Repercussions
反应
Reservoirs
储气罐
Residuale fuel oil
渣油
Resonant
共振
Retract
缩回
Reynolds number
雷诺数
Rigid
刚性的，紧密地
Rollers
辊子
Scale
水垢，
Seal
密封
Sedimentary
沉积
Serpentine
tube
蛇形管
Shale
页岩
Silica
二氧化硅
Silt
淤泥
Single-phase
单相
Skin casing
外护板
Slag
结渣
Slurry
水煤浆
Sodium
钠
Solvents
溶剂
Sootblower
吹灰器
Sour gas
含硫气体
Specification
规格
Stable ignition
稳定着火
Stanton
number
斯坦顿数
Saturated
饱和的
Straw
稻草
Steam line blowing
蒸汽管路吹灰
Steams
茎，杆
Stress
corrosion
应力腐蚀
Structural formula
结构式
Stud
双头螺栓
Subbituminous
贫煤，次烟煤
Suction
真空，负压
Sulphur
硫
Superheater
过热器
Swamp
沼泽
Sweet gas
无硫气
Switchgear
配电装置，开关装置
Temperature-entropy
温熵图
Tenacious
黏的
Thermodynamics
热力学
Tube bundles
管束
Tubular
管状的
Turbine
汽轮机
Velocity
速度
Vertical
spidle mill
中速磨，立轴磨
Vessel
容器
Viscosity
黏度
V
olumetric expansion
体膨胀
29-3
Vulnerable
易损的，薄弱的
Wear
磨损
Welded
焊接
Wingwall
屏式凝渣管
Yttrim
釔
Abbreviations
AFBC
常压流化床燃烧
AFCO
燃料自动切断
AFWC
给水自动切断
ASME
美国机械工程师协会
ATM
标准大气压
BFP
锅炉给水泵
BUT
按钮
BWC
锅炉水浓度
BYP
旁路
CFBB
循环流化床锅炉
MCR
最大连续蒸发量
DAS
数据采集系统
2.1 Introduction
DEH
数字电液系统
DNB
偏离核态沸腾
FDF
送风机
FGD
烟气脱硫
FSSS
炉膛安全检测保护系统
HRB
回热锅炉
IDF
引风机
IGCC
整体煤气化联合循环
LMTD
对数平均温差
MFT
主燃料切断
MUF
锅炉补给水
NWL
正常水位
OFA
火上风，燃尽风
PFBC
增压流化床燃烧
SSC
刮板除渣机
TGA
热重分析仪
UBC
未燃烧
WFGD
湿法烟气脱硫
Boilers use heat to convert
water into steam for a variety of applications.
Primary
among these are electric power
generation and industrial process heating. Steam
has
become a key resource because of
its wide availability,
advantageous
properties and
non
toxic
nature.
The
steam
flow
rates
and
operating
conditions
can
vary
dramatically; from 1000lb/h (0.1kg/s)
in one process use to more than 10 million lb/h
(1260kg/s)
in
large
electric
power
plant;
from
about
14.7
psi
(1
bar)
and
212
?
F
in
some
heating
applications
to
more
than
4500
psi
(310bar)
and
1100
?
F
(593
℃
)
in
advanced cycle power
plant.
2.1
简介
SSC
锅炉利用热量使水转变成
蒸汽以进行各种利用。
其中主要是发电和工业供热。
由于蒸汽<
/p>
具有有利的参数和无毒特性，因此蒸汽作为一种关键的工质（资源）被广泛地应用。蒸汽流
量和运行参数的变化很大：从某一过程里
1000
磅
/
小时（
0.126kg
/s
）到大型电厂超过
10×
10
6
29-4
磅
/
小时（
1260kg/s
）
，压力从一些加热应用的
14.7
磅
/ in
2
（
1.0135
bar
）
212F
（
< br>100
℃）到先进
循环电厂的
4
500
磅
/ in
2
< br>（
310bar
）
1100F<
/p>
（
593
℃）
。
Modern
boilers
can
be
classified
by
various
criteria.
These
include
end
use,
firing
method,
operating pressure,
fuel and circulation method.
现代锅炉可根据不同的
标准分类。这些包括最终用途、燃烧方式、
运行压力、
燃料和循
环方式。
Utility
boilers
are
used
primarily
to
generate
electricity
in
large
central
power
stations.
They
are
designed
to
optimize
overall
thermodynamic
efficiency
at
the
highest
possible
availability.
A
key
characteristic
of
newer
units
is
the
use
of
a
reheater
section to increase overall cycle efficiency.
大型中心电站的电站锅炉主要用来发电。
它们经过优化设计，
可达到最高的热效率。
新
机组的关键特性是利用再
热器提高整个循环效率。
A
variety
of
additional
systems
also
produce
steam
for
power
and
process
applications.
These
systems
usually
take
advantage
of
low
cost
or
free
fuels,
a
combination
of
power
cycles
and
process,
and
recovery
of
waste
heat
in
order
to
reduce overall costs,
examples of these include:
各种附加的系统也产生蒸汽
用于发电及其他过程应用。
这些系统常常利用廉价或免费燃
料，
联合动力循环和过程，以及余热回收，以减少总费用。这些例子包括：
Gas turbine combined cycle
(CC)
use advanced gas turbines with
heat recovery
steam
generator
as
part
of
a
base
cycle
to
use
waste
heat
recovery
and
increase
thermal efficiency.
燃气轮机联合循环（
CC
）
：先进的燃气轮机，将余热锅炉作为基本循环的一部分，以利
用余热并提高
热效率。
Integrated
Gasification Combined Cycle (IGCC)
adds
a coal gasifier to the CC
to reduce
fuel cost and minimize airborne emissions.
整体煤气化联合循环（
IGCC
）
：在
CC
基础上增加煤气化炉，以降低燃料费用并将污染<
/p>
排放降到最低。
Pressurized
Fluidized-bed
Combustion
(PFBC)
includes
higher
pressure
combustion
with
gas
cleaning
and
expansion
of
the
combustion
products
through
a
gas turbine.
增压
循环流化床燃烧（
PFBC
）
：在更高
压力下燃烧，包括燃气净化，以及燃烧产物膨胀
并通过燃气轮机做功。
< br>
29-5
Blast furnace hood
heat recovery
generates steam using the
waste heat from a
blast furnace.
高炉排烟热量回收：利用高炉余热产生蒸汽。
Solar
steam
generator
uses
concentrators
to
collect
and
concentrate
solar
radiation and generate steam.
太阳能蒸汽发生器：利用集热器收集太阳辐射热产生蒸汽。
2.2 Development of Utility Boiler
The
modern
660MW
coal-fired
boiler
has
some
6000
tons
of
pressure
parts
which include 500 km
of tubing, 3.5 km of integral piping and 30,000
tube butt welds.
It is the culmination
教材
25
页
of some fifty years development and
while the basic concept of pulverized fuel
firing
into
a
furnace
lined
with
evaporator
tubes,
with
the
combustion
gases
then
passing
over
convection
superheater
and
heat
recovery
surface,
has
remained
unchanged,
the
advancement
of
steam
conditions,
increases
in
unit
size
and
the
properties
of
the
fuel
fired
have
required
major
changes
in
materials
employed,
fabrication techniques and operating
procedures.
2.2
电站锅炉的发展
现代
660MW
燃煤锅炉有大约
6000
< br>吨的压力部件，其中包括
500
千米的受热面管材，
3.5
千米连接管，
和
30000
个管接头焊口。
这是经过大约
< br>50
年发展的成果，
并形成了至今未
变的基本概念，
即煤粉在布置有蒸发管束的炉膛内燃烧，
然
后烟气通过对流过热器和热回收
表面。
蒸汽参数的提高，
机组容量的增大及燃料燃烧特性改进都要求在材料、
制造技术和运
行程序上相应发展。
In the years
immediately following the second World War, is was
customary to
install in a power
station, a greater number of boilers than
turbines, the boilers feeding
a range
to which the turbines were connected. This
arrangement reflected the inferior
availability of boilers compared with
turbines but increase in boiler availability in
the
late
1940s
led
to
the
acceptance
of
unitized
boilers
and
turbines.
The
change
to
unitized
boiler
and
turbine
allowed
reheat
to
become
practical
and,
with
the
availability
of
high
temperature
steels,
there
followed
a
continuous
advance
in
steaming
conditions
to
the
current
standard
cycle
of
2400
lbf/in
2
(165.5bar),
568
℃
with reheat to
568
℃
. To take full advantage
of the more advanced steam conditions
and
to
obtain
the
economies
of
size,
the
next
fifteen
years
also
saw
a
twenty-fold
increase in unit
size.
二战后的一些年里，
在电
厂安装锅炉的数量多于汽轮机是很常见的，
锅炉提供蒸汽到母
管
然后到汽机。
这种布置反应了锅炉的可用性低于汽轮机。
四十年
代后期，
随着锅炉可用性
的提高，
锅炉
和汽机开始可以相互配套使用。
这一变化使再热变得可行，
而且
随着高温钢材
29-6
可用性的提高，蒸汽参数不断变化，达
到了当前的
2400lbf/in
2
（
165.5bar
）
，
568
℃和
568
℃再
热的标准循环。为充分利用更高的蒸汽参数和获得更大的经济性，在接下来的
< br>15
年，机组
容量又增加了
20
倍。
A
utility
normally
procures
plant
from
specialist
manufactures
who
have
responsibility
for
design,
manufacture,
erection
and
commissioning.
While
the
manufactures
carry
out
development
of
manufacturing
process
and
continuously
update their
design methods, and change in operation conditions
and size necessarily
results in a new
plant being of a prototype nature. While some new
features can be
tested
in
advance
of
construction
the
only
real
test
of
a
new
boiler
design
is
in
operation and with its
associated turbine and generator. The commercial
success of a
new
design
is
proved
over
the
whole
projected
life
of
power
station
and
utility,
therefore, has to
balance the immediate economic advantages of a new
design in terms
of improved efficiency,
reduced capital costs, etc. against the risk of
poor availability,
need
for
major
modifications,
etc.,
which
might
result
from
a
new
development.
A
utility
normally
purchases
plant
against
generating
needs
and
the
repercussions
of
poor initial availability are not only
being unable to meet load demand but also having
to
use costly plant to
make up the shortfall.
This
period of major advance in
steam
cycle and unit size therefore required
quite exceptional interaction with manufacturers
in
design
and
fabrication
area
and
development
of
operation
and
maintenance
techniques to
ensure that the economic gains did not prove
illusory.
电站设备一般向负责设计、
制造、
建设和调试的专业厂商购得。
同时生产厂商实施生产
< br>过程的发展，
不断修正设计方法，
改变必要的运行参数和
容量
,
从而形成新电厂的原型。
虽<
/p>
然一些新的特性可以在安装前进行测试，
但一个新设计锅炉的真正
测试是和汽轮发电机组配
套运行后进行的。一个新的设计获得商业成功需要通过电站在整
个设计寿命中的使用来证
明。因此，
需要平衡考虑由效率提高、
投资成本减少等带来的直接经济效益，与新设计机组
可能产生的可靠性低和需要大的改进
等风险。
公用事业公司一般依靠发电需求购买设备，
并
且最初可用性较低的影响不仅不能满足负荷需求，还需要使用昂贵设备以弥补不足。因此，
在对蒸汽循环及机组容量进行较大改进的时期，必须和厂商在设计、制造领域，以及运行、
维护技术领域密切合作，以保证经济利益的可靠。
2.3 Fuel and combustion
The
fuels used in most boilers are coal, natural gas
and oil. However, during the
past few
decades, nuclear energy has also begun to play a
major role in at least the
electric
power generation area. Also, an increasing variety
of biomass materials and
process
byproducts
have
become
heat
sources
for
steam
generation.
These
include
peat,
wood
and
wood
wasters,
straw,
coffee
ground,
corn
husks,
coal
mine
wastes
(culm)[
煤屑
], waste
heat from steelmaking
教材
26
页
29-7
furnaces and even solar
energy.
2.3
燃料及燃烧
大部分锅炉以煤、天然气和石油作为燃料。然而，
在过去的几十
年里，
至少在发电领域
核能开始扮演一个主要角色。
同样，
不断增加的各种生物质和工业副产品也成为生产蒸汽的
热源。这些包括泥煤、木材及木材废弃物、麦秆、咖啡渣、玉米秆、煤矿废弃物（煤屑）
、
炼钢炉废热甚至太阳能。
The
dominant
fuel
in
modern
U.S.
central
stations
is
coal,
either
bituminous,
sub-bituminous or lignite. While
natural gas or fuel oil may be the fuel of choice
for
selected future fossil fuel power
plants, coal expected to continue its dominant
role in
supplying energy to new, base
power utility power station boilers.
现代
美国中心电站以煤作为主要燃料，
使用烟煤、
次烟煤或褐煤。<
/p>
虽然天然气和燃油也许
是未来化石燃料电厂的燃料选择，但对于带
基本负荷的新电站，煤仍将是主要的锅炉燃料。
2.3.1 Coal classification
A coal
classification system is needed because coal is a
heterogeneous substance
with
a wide range of composition
and properties. The properties
of a typical
China
coal are showed in table 2-1. Coals are
typically calssified by rank. This indicates the
progressive
alteration
in
the
coalification
process
from
lignite
to
subitiminous,
bituminous
and
anthracite
coals.
The
rank
indicates
a
coal
’
s
geological
history
and
characteristics.
表
2-1
（
27
页）
2.3.1
煤的分类
由于煤是一种不均匀的物质
，
且其组成和特性变动很大，
所以建立煤的分类系统是很必
要的。
中国煤的性质如表
2-1
所示。
以煤阶进行煤的分类是典型的做法。
这表现
为煤化程度
的大小：从褐煤到贫煤、烟煤以及无烟煤。煤阶表明了煤的地质历史和主要特
性。
The system
used in the U.S. for classifying coal by rank was
established by the
American Society for
Testing and Materials (ASTM). ASTM classification
is a system
which
uses
the
volatile
matter
and
fixed
carbon
(FC)
results
from
the
proximate
analysis
and
the
heating
value
of
the
coal
as
ranking
criteria.
This
system
aids
in
identifying
commercial
uses
of
coals
and
provides
basic
information
regarding
combustion
characteristics.
现在美国应用的煤分类标准是由美国材料试验学会
（
ASTM
）
建立的。
其分类是通过煤的
工业分析所确定的挥发分和固定碳的
含量以及煤的发热量作为分类标准。
这套系统目的在于
确定煤的
商业使用价值，并提供关于煤燃烧特性的基本信息。
2.3.2 Combustion systems
29-8
The combustion of
fossil fuels within a boiler for steam raising
purposes has been
practised
for
many
years.
However,
within
the
past
two
decades
combustion
techniques have been considerably
refined in order to reduce atmospheric emissions
and pollution to practicable minimum.
2.3.2
燃烧系统
锅炉内化石燃料燃烧以产生蒸汽的技术已成熟多年。
然而，
< br>在过去的二十多年中，
为了
将大气排放和污染降到可行的
最低程度，燃烧技术得到了很大程度的提高。
Oil combustion systems
Oil
is burned in all utility boiler, in coal boiler to
ignite the coal burners, to warm
up the
boiler and raise pressure before coal is admitted,
and in oil fired boilers as the
main
load
教材
27
页
fuel. In general, the oil is residual
Fuel Oil of 3500 sec. to 6500 sec. viscosity. In
order
to
burn
effectively
this
oil
must
be
heated
to
120-130
℃
and
divided
or
atomized into very small droplets.
油燃烧系统
所有的电站锅炉都燃用油
，
在燃煤锅炉中点燃煤粉，
在煤进入炉膛之前加热炉膛并升压，
而在燃油锅炉中则作为主要负荷燃料。一般地，燃油都是粘度在
3500 sec
到
6500sec
的
残
渣燃料油。为了有效的燃烧，
这些油必须被加热到
120
~
130
℃并被良
好地分散或雾化成很小
的微滴。
The
use
of
this
oil,
cheaper
than
normal
distillate
(diesel/gas
oil
etc.)
causes
problems, amongst them, acid smuts and
dust emissions. The smut problem is caused
by the sulfur content of the oil, which
may be up to 3%. In the early 1960s the utility
undertook an intensive development
program on oil burner design, which was aimed
at removing the problems of oil fired
emissions. This resulted in an oil burner,
“
the
Standard
Burner
”
which reduced
emissions
of
carbon
at
very low
excess air levels.
Considerable work was also done in
order to ensure that burner in a boiler received
the same amount of air, and the current
operating level for excess air in an oil fired
unit is 2%.
燃用渣油
，要比一般的馏分油（柴油，汽油等）便宜，但又带来一些问题：
酸性污染物和粉尘的排
放。
酸性污染问题是由石油中的硫产生的，
硫分的含量有
时可高达
3%
。在
2
0
世纪
60
年代早期，人们对油燃烧器
设计进行了深入研究和
开发，
目的在于解决燃油的排放问题。<
/p>
由此诞生了一种油燃烧器——
“标准燃烧
器”
，它可以在非常低的过量空气系数下减少碳排放。为保证锅炉中每个燃烧器
获得同样多的空气也做了大量的工作。
目前油燃烧过量空气系数运行水平
为
2%
。
29-9
Coal
combustion systems
Coal
burners
have
been
developed
in
a
similar
fashion
to
the
oil
burners,
and
considerable
emphasis
is
placed
upon
feeding
each
burner
with
carefully
regulated
amounts
of
coal
and
oil.
All
coal
fired
boilers
in
the
utility
fire
pulverized
coal
(produced
by
milling)
which
is
very
finely
divided
coal
carried
to
the
burner
on
a
stream
of
air
(primary
air).
The
design
effort
directed
at
flow
equalization
has
produced boilers which can be operated
at lower excess air levels than previously, and
thus
have increased overall
efficiency
without
increasing
unburned
carbon
levels
in
the ash.
煤燃烧系统
煤燃烧器的发展模式同油燃烧器类似，
而且重点放在准确控制每只燃
烧器煤和油的供给
量。实际中所有的燃煤锅炉都是燃烧煤粉（由磨煤机生产）
，这些煤粉经过很好的粉碎，然
后由空气流
（一次
风）送入燃烧器。
同以前相比，
在流动平衡上的设计成果现在已
能使锅炉
在较低的过量空气水平下运行，并在不增加飞灰含碳量水平的情况下提高了总的
效率。
This,
when
combined
with
the
development
of
low
NO
x
burners
will
result
in
reduced
gaseous emission in line with EEC directives and
is the main objective of two
boiler
conversions (both complete) to establish the level
to which NO
x
maybe reduced
in the exhaust from 500MW coal fired
boilers. A NO
x
reduction
development trial is
proposed on a
third boiler design,
这样，结合低
N
Ox
燃烧器的开发，就使气体排放达到欧共体的标准，这也
是两
代锅炉转换（已完成）的主要目的，即设定
500MW
燃煤锅炉
可能达到的
NOx
排放水平。在第三代锅炉的设计中进行了进一
步降低
NOx
的开拓性试验。
The arrangement of coal-
fired system components must be determined
according
to economic factors as well
as the attributes of the coal. The performance in
terms of
product fineness, mill outlet
temperature, and air-coal ratio must all be
determined as
part of overall
combustion system design.
煤燃烧系统部件的布置必须根
据经济因素和煤的性质来确定。
作为整个燃烧系统设计的
性能参
数，煤粉细度、磨煤机出口温度、空煤比等都必须达到要求。
Low NO
x
combustion systems
The
factors
affecting
NO
x
are
the
proportion
of
nitrogen
chemically
combined
with
the
fuel,
peak
flame
temperature,
the
available
oxygen
in
the
flame
and
the
residence
time
of
the
gases
within
the
system.
Some
of
the
coal
bound
nitrogen
is
released as volatiles as the chemical
structure of the coal breaks down on entering the
furnace. Nitric oxide produced from
atmospheric nitrogen as
“
thermal
NO
x
”
can be
29-10
limited by
minimizing residence times at high temperature,
which limiting the amount
of oxygen
available to the fuel during the combustion stage
results in the production
of harmless
nitrogen rather than NO
x
.
低
NO
X
燃烧系统
影响
NOx
生成的因素包括燃料含氮量、
火焰峰值温度、
火焰中的可用氧量
以及气流在锅
炉系统中的停留时间。
当煤进入炉膛其化学结构被
破坏时，
一些煤中的化合氮就作为挥发分
被释放出来。由大气中
的氮生成的一氧化氮即“热力型
NOx
”可以通过减少烟气在高
温区域
的停留时间而得到控制，这样就会控制燃烧阶段中可用氧量，最后生成的是无害氮
而不是
NOx
。
Since coal firing requires
some excess oxygen in the combustion zone to
achieve
total
carbon burnout
and nitrogen free coal
is
unavailable,
NO
x
reduction has
to
be
performed by boiler
and burner design.
因为煤在燃烧区的燃烧需要一定的过量氧气以
便使所有的碳燃尽，
且不含氮的煤是难以
获得的，因此
NOx
的减少必须依靠锅炉和燃烧器的设计来完成。
教材
28
页
Gas combustion systems
Natural
gas has been fired
at power stations for main load purposes.
However,
gas has not been
available to the utility for some years now and it
is not
envisaged
that, as a
premium fuel, it will ever be available again in
any quantity.
Propane is widely used in
igniters for the oil burners in both main oil and
coal
fired boilers.
天然气燃烧系统
天然气曾经作为电厂
主要燃料。
然而一些年来，
没有太多的天然气可供电厂使用，<
/p>
并且
人们没有正视这样的事实，即天然气作为一种优质燃料将会重
新得到大量应用。
丙烷常常作为一种点火剂，广泛地应用于燃
油锅炉和燃煤锅炉中的油燃烧器。
2.3.3 Fluidized-bed combustion
A
variation
on
PC
combustion
is
fluidized
bed
combustion
in
which
coal
is
burned with air in a fluid bed,
typically a circulating fluidized bed (CFB). CFBs
are
best
suited
to
low-cost
waste
fuels
and
low-
quality
or
low
heating
value
coals.
Crushed
coal
and
lime
stone
are
fed
into
the
bed,
where
the
lime
stone
undergoes
calcination to produce lime (CaO). The
fluidized bed consist only of lime, with a few
percent
coal
and
recirculated
coal
char.
The
bed
operates
at
significantly
lower
temperatures,
about
< br>427
℃
(800
?
F),
which
thermodynamically
favors
low
NO
x
formation and SO
2
capture by reaction with CaO to form
CaSO
4
. The steam cycle can
be
subcritical
and
potentially
supercritical,
as
with
PC
combustion,
and
generating
efficiencies are
similar. The primary advantage of CFB technology
is its capacity to
29-11
capture SO
2
in
the bed, and its flexibility to a wide range of
coal properties, including
coals with
low heating value, high ash coals and low
volatile coals, and changes in
coal type during operation. Several
lignite-burning CFB units have been constructed
recently, and CFBs are well suited to
co-firing biomass.
2.3.3
流化床燃烧
流化床燃烧是煤粉燃烧方式的一种，
采用这种燃烧方式时煤在空气中的燃烧发生
在流化
床中，典型的是循环流化床。循环流化床最适合于燃烧低成本废弃燃料、
低品质或低热量
煤。
将煤粒和石灰石投入到床中，
石灰石在床内煅烧成石灰。
流化床
中主要是石灰和少量的
煤，煤焦在其中循环。运行中的床温很低，只有
< br>427
℃
(800
℉
)
，在这个温度下的热力学环
境有利于减少
NOx
的形成和捕集
SO
< br>2
，使之与
CaO
反应生成<
/p>
CaSO
4
。对于煤燃烧，蒸汽循环
可以是亚临界，
也可能是超临界，
它们具有
相近的发电效率。
循环流化床技术的最大的优点
是它在床中捕捉
SO
2
的能力和它对煤质的广泛适应性
，其中包括低热量煤、高灰分煤和低挥
发分煤，
并且在运行中可
以改变煤种。
循环流化床锅炉适合与生物质共燃，
最近就新建了
几
台燃烧褐煤的循环流化床机组。
The most commonly used circulating
fluidized bed combustor is shown in Fig.
2-1. Coal and coal char are burned
while the coal, coal char, coal ash and sorbent
are
carried up through the furnace by
combustion air.
The solid
materials
are
separated
from the flue gas in
图
2-1
循环流化床锅炉设计布置实例
教材
29
页
the
cyclone
and
pass
through
a
convective
section
where
heat
is
transferred
to
boiler
tubes
generating
high-pressure
steam.
Additional
steam
is
generated
by
removing heat from the hot solids in
the fluidized bed heat exchange section before
they
are
returned
to
the
furnace.
There
are
no
boiler
tubes
in
the
lower
furnace
because
the
rapid
moving
solids
cause
excessive
erosion.
NO
x
is
managed
through
low
temperature
and
staged
injection
of
the
combustion
air.
SO
x
emission
is
controlled via the lime sorbent in the
bed. This saves significant capital for flue gas
cleanup, but low
SO
x
emission require low-
sulfur coal, and NO
x
emissions are limited
by combustion
chemistry. Extremely low emissions levels would
require the addition
of
flue
gas
clean-up
units
with
the
attendant
cost
increase.
The
largest
CFB
unit
is
330MW
e
in China,
and 600MW units have been designed, but no unit of
this size has
been built.
如图
2-1
所示，目前最常用的流化床技术是循环流化床燃烧技术。
煤和煤焦
燃烧的同时，空气携带煤、煤焦、煤灰和脱硫剂通过炉膛。固体材料通过旋风分
离器从烟气中分离出来，
然后通过对流烟道部分，
烟气把热量传给炉管以产生高
压蒸汽。另一部分蒸汽是由流化床中的高温固体
在返回炉膛前放出热量产生的。
炉膛内固体快速运动会引起过量的磨损，
因此炉膛底部不安装炉管。
通过低燃烧
29-12 <
/p>
温度和空气分级燃烧来控制
NOx
的生成
。
SOx
排放通过床中石灰脱硫剂控制。
这些为烟气净化节省了大笔的投资，但是低的
SOx
排放需要
燃烧低硫分煤，并
且
NOx
的排放受燃
烧反应的限制。极低的排放需要额外的烟气净化设备，同时
会增加相应的维护成本。
在中国最大的流化床锅炉是
330MWe
，
设计最大的锅炉
是
600
MWe
，但是还没有投建。
2.4
Pulverizing System
The
development
and
growth
of
coal
pulverization
closely
parallels
the
development
of
pulverized
coal-firing
technology.
In
order
to
achieve
efficient
combustion in the
boiler furnace the coal leaving the burner must be
sized so that it
can burn rapidly and
this means that it must be in the form of small
particles that can
quickly be heated up
to ignition temperature and get ready access to
the combustion
air. The job of the
pulverizers is to grind the feed coal down to a
suitable size for the
above
purposes.
Early
systems
used
ball-and-tube
pulverizers
to
grind
coal
and
holding bins
to temporarily store the coal before
firing. Evolution of the technology
to
eliminate
the
bins
and
direct
fire
the
coal
pneumatically
transported
from
the
pulverizers
required
more
responsive
and
reliable
grinding
equipment.
Vertical
air-swept
pulverizers met this need.
2.4
制粉系统
煤粉制备与煤粉燃烧技术的
发展是同步的。
为了使煤在炉膛中有效燃烧，
煤在离开燃烧
器时必须被粉碎到一定的大小，
这样才能迅速燃烧，
这就意味着煤必须被加工成小颗粒，
才
能被迅速加热到
着火温度并和空气良好混合。
磨煤机的工作就是把煤磨碎到符合上述要求的
合适的大小。
较早的系统使用筒式球磨机磨煤粉，
并
且在燃烧前利用储仓暂时储存煤粉。
如
果对该技术进行改进，<
/p>
去掉中间储仓而将从磨煤机出来的煤粉直接送去燃烧，
就会对磨煤
机
的可靠性有很高的要求。
On
pressurized
pulverizing
systems
the
primary
air
fan
which
provides
the
pulverized
fuel
transport
medium
is
situated
before
the
pulverizer
and
there
handle
clean
air
and
is
not
subject
to
erosive
wear
as
is
an
exhaust
fan.
This
is
the
chief
advantage
of
the
pulverizing
system,
however
the
pulverizer
does
need
sealing
air
which
is
usually
provided
by
a
separate
fan
at
a
pressure
higher
than
that
of
the
pulverizer interior.
正压制粉系统中，
提供煤粉输送介质的一次风机位于磨煤机前，
因而它运送的是清洁空
气，不会像排粉风机一样受到侵蚀磨损。
这是正压磨煤系统的主要优点。然而，磨煤机需要
由单独风机提供高于
磨煤机内部压力的密封空气。
A
disadvantage of the pressure type pulverizer is
that it must
be absolutely
air
tight
in
order
to
avoid
pulverised
fuel
leakage
to
the
atmosphere.
Conversely
the
standard
of
sealing
on
a
suction
pulverizer
need
not
be
so
high,
but
it
must
not
be
29-13
allowed
to
deteriorate
too
far
as
the
inwards
leakage,
being
cold
air,
will
make
it
difficult
to
dry
the
wetter
coals.
This
leakage
air
is
also
unmeasured
as
regards
its
quantity,
and
if
excessive
under
certain
conditions
produces
a
high
air/coal
ratio
which may be explosive should there be
an ignition source.
正压磨煤机的一个
缺点是它必须完全由空气密封以避免煤粉泄露到大气中。相对来说，
负压磨煤机的密封标
准并不需要这样高，
但也不允许漏入过多空气，
因为冷空气难以
干燥湿
煤。
这种方式泄露的空气量也无法测量，
如果达到高的空
/
煤比，
遇到
明火则可能发生爆炸。
2.4.1
Vertical air-swept pulverizers
The
roller
passes
over
a
layer
of
granular
material,
compressing
it
against
a
moving table. The movement of the
roller causes motion between particles, while the
roller pressure
教材
30
页
creates
compressive
loads
between
particles.
Motion
under
applied
pressure
within
the
particle
layer
cause
attrition
(particle
breakup
by
friction)
which
is
the
dominant
size reduction mechanism. The compressed granular
layer has a cushioning
influence which
reduces grinding effectiveness but also reduces
the rate of roller wear
dramatically.
When working surfaces in a grinding zone are close
together, near the
dimensions of single
product particles, wear is increased by three body
contact (roller,
particle
and table). Wear rates can be three
body contact
has
also
been observed in
operating
mills when significant amounts of quarts bearing
rock are present in sizes
equal to or
greater than the grinding layer thickness.
2.4.1
中速磨
磨辊在一层耐磨层上滚动，
通
过移动的磨盘把煤压碎。
磨辊的运动引起煤粒间的相互运
动同时
磨辊的压力在煤粒间形成压力负荷。
一定压力下在煤粒层上的运动引起摩擦
（煤粒依
靠摩擦力破碎）
，这就是磨煤机的工作原理
。耐磨层具有缓冲作用，虽然降低了磨的效率，
但也大大降低了磨辊的磨损。
当磨煤区的工作面间距离很近时，
比如到了一个颗粒大小，
三
个部件（磨辊，颗粒，磨盘）间的磨损就会大大增加，磨损速率会是正常磨煤
机的
100
倍。
当带有石英的石头尺寸
等于或大于磨层厚度时，也会在运行中发生三部件接触的磨损。
As
grinding
proceeds,
fine
particles
are
removed
from
the
process
to
prevent
excessive grinding,
power consumption and wear. Fig.2-2 presents a
simplified MPS
vertical
pulverizer,
showing
the
essential
elements
of
a
vertical
air-swept
design.
A
table
is turned from below and rollers, called tires,
rotate against the table. Raw coal is
fed
into
the
mill
from
above
and
passes
between
the
rollers
and
the
rotating
table.
Each passage of the particles under the
rollers reduces the size of coal. The combined
effects
of
centrifugal
force
and
displacement
of
the
coal
layer
by
the
rollers
spills
partly ground coal off the outside edge
of the table. An upward flow of air fluidizes
29-14