Coal (석탄에너지 - KOCWelearning.kocw.net/KOCW/document/2015/inha/... · 2016. 9. 9. · Coal...
Transcript of Coal (석탄에너지 - KOCWelearning.kocw.net/KOCW/document/2015/inha/... · 2016. 9. 9. · Coal...
BET (Brunauer, Emmett & Teller) Equation
가스나 액체를 구체 표면에 등온흡착시켜 분말고체의
표면적을 측정하는 방법
P0 : 포화 증기압
c : 상수 (첫 단일층의 흡착에너지 상수)
v : 주어진 증기압에서 흡착된 증기의 부피
Vm : 단위 중량의 고체에서 단층으로 흡착된 증기의 부피
00
11)( P
Pcv
ccvPPv
Pmm
−+=
−
00
11)( P
Pcv
ccvPPv
Pmm
−+=
−
0 )(PvP- P
0PP
(C-1)/VmC
1/VmC
Y X
P/P0 = 0.05~0.35
일반적
)(10023.6)/(400,22),/()/( 123
3
32 − σ×××= mol
molcmSTPgcmVmgmS
Example Calculation of Surface Area from BET Equation
P/P0 Adsorbed N2 (cc/g)0.1090.1990.309
4.2144.8235.593
P/P0 (X) P/V(1-P/P0) (Y)0.1090.1990.309
0.029030.051510.07995
0.10 0.15 0.20 0.25 0.300.02
0.03
0.04
0.05
0.06
0.07
0.08
Y = 0.0011 + 0.2548 X 1/VmC = 0.0011
(C-1)/VmC = 0.2548
C = 231.64
Vm = 3.92 cc/g
S = (3.92 / 22400) x 6.02 x 1023 x 0.162 x 10-18
= 17.1 m2/g
Trace metals: Lead, Cadmium, Manganese, Arsenic, Antimony, Copper, Mercury, Barium, Nickel, Selenium, Berylium, Thalium, Chromium, Cobalt, and Zinc.
Other: Chlorine, Fluorine, PAHs, Sulfur, Dioxins.
Polycyclic aromatic hydrocarbons
Lead (Pb)
Mercury (Hg)
Coal CompositionCoal is not pure carbon, even Anthracite has impurities.
Coal Cleaning – Removal of sulfur from coal.Scrubbers are used to trap SO2 when coal is burned
Plentiful. Resource ~ 500 years (vs. gas/oil: ~100 years).
Inexpensive. 1-1.5 $/GJ HHV (vs. gas at 2.5+ $/GJ).
Ubiquitous. Wide geographic distribution (vs. middle east).
Clean?! Gasification, esp. with sequestration, produces little gaseous emissions and a chemically stable, vitreous ash.
Coal is of great interest because it is:
Expensive pollution controls
Acid rain
Global warming
Disadvantages
CO2 Emission
Coal Sources
Coal is the world’s most plentiful fossil fuel.Recoverable world coal reserves are estimated at about 1X1012 tons.
32%
29%
12%
8%
7%
7% 5%United States
Russia
China
Australia
Germany
South Africa
Poland
65-95%C2-7%H<25%O<10%S1-2%N
20-70%Char5-15%Ash2-20%H2O20-45%VMPr
oxim
ate
Ana
lysis
Elem
enta
l Co
mpo
sition
From CHNOS Analysis
Coal Composition
Coal Combustion
C + ½ O2 CO
CO + ½ O2 CO2
CO2 + C 2CO
C + O2 => CO2
Carbon Reaction
S + O2 SO2
H2 + ½ O2 H2O
H2O + C CO + H2
CO + H2O => CO2 + H2
Non-Carbon Reaction
1st step : Combustion of Volatile Matter
2nd Step : Combustion of Char
Main Processes in Coal Combustion
Coal Particle
Volatiles
char
homogeneouscombustion CO2, H2O,
…
Devolatilization
heterogeneouscombustion
CO2, H2O, …
tchar=1-2sectvolatiles=50-100mstdevolatile=1-5ms
t
Coal Combustion: Air Pollutants
CO2
CONOxSOxParticulate matterTrace metalsOrganic compounds
Six Pollutants : CO, Pb, NO2, O3, SO2, PM (Particulate Matter)
Coal combustion emissions in Israel:71% of total SO2 emissions.62% of total CO2 emissions.39% of total NOx emissions.38% of total SPM emissions.1% of total CO emissions.
Carbon Dioxide, CO2
C + O2 CO2
Almost 99% of C in coal is converted to CO2.CO2 sequestration is being tested.
Carbon monoxide, CO
C + ½O2 CO
air/fuel ratio residence time temperature turbulence
Hemoglobin (헤모글로빈)
적혈구 속에 존재하는 색소 단백질
철 함유 (4 Fe / Hemoglobin)
산소 운반 (1.36mL O2 / g Hemoglobin)
Coal-S (CS, S2, S, SH)
char
COS, CS2H2S
SO SO2 SO3
O2, M-SO4
SO2 molecule
radicals
SOx
Sources of sulfur in coal: Seawater sulfates, Limestone
Sulfur in Coal (<10%)
Organic sulfur (40%)Chemically bonded to the hydrocarbon matrix : thiophene, thiopyrone, sulfides and thiol.
Inorganic sulfur (60%)Imbedded in the coal, as loose pyrite - FeS2 or marcasite, and calcium/iron/barium sulfates.
H2S : H-S-H
Mercaptan : H-S-R
Nitrogen Oxides (NOx)
Thermal NOxN2 + O ↔ NO + NN + O2 ↔ NO + O
Strong temperature-dependence: >1300-1500°CNot a major source of NO in coal utility boilers.
ZeldovichZeldovich mechanismmechanism
Thermal NOx, Prompt NOx, Fuel NOx
Thermal NOx 생성 조건
(1) 연소온도가 높을때
(2) 연소영역에서 산소농도가 높을때
(3) 고온영역에서 연소가스의 체류시간이 길때
Prompt NO (Hydrocarbon + N2)N2 + CHx ↔ HCN + N + …
N + OH ↔ NO + H
Prevalent only in fuel-rich systems.
Not a major source of NO in coal utility boilers.
Fuel NO (Char-N, Volatile-N)1. Char-N
Char-N + ½O2 → NO
2. Volatile-NVolatile-N HCN/NH3HCN/NH3 + O2 NO
The major source of NO in coal utility boilers (>80%).
[Char-NO = ~25%] < [volatiles-NO = ~75%]
Name Structure ~ Relative amount Stability
Pyridine1
Pyrrole1
Aromatic amines
15-40% More stable
60% Less stable
6-10% Stable
N
NH
NH2
SCR (Selective Catalytic Reduction)SCR (Selective Catalytic Reduction)
* 선택적 촉매환원법(SCR)
NOx와 NH3를 촉매에 접촉시켜 NOx를 N2와 H2O로 생성하는 방법
주반응
4NO + 4NH3 + O2 ↔ 4N2 + 6H2O
2NO2 + 4NH3 + O2 ↔ 3N2 + 6H2O
경제성, NOx 제거 효율, 공정 특성 등 비교시 가장 우수한 공정
* SCR 촉매
금속산화물(Fe2O3, Pt, CuO, WO3)부터 zeolite에 이르기까지 다양
바나듐계(V2O5) 촉매가 우수한 것으로 알려짐
자세한 촉매의 특성은 알려지지 않음
전체 운전비의 약 70% 차지
NOx control options(from AP-42, EPA)
Control Technique NO Reduction Potential(%)
Overfire air (OFA) 20-30Low NOx Burners (LNB) 35-55
LNB + OFA 40-60Reburn 50-60SNCR 30-60SCR 75-85
LNB with SCR 50-80LNB with OFA and SCR 85-95
Particulate Matter
Bottom Ash, Fly Ash
Electrostatic precipitator (ESP)
99% (for 0.1>d(μm)>10)<99% (for 0.1<d (μm)<10)
Fabric filter (or baghouse) As high as 99.9%
Wet scrubber 95-99%
Cyclone 90-95% (d(μm)>10)
1) Bag House
2) Electrostatic Precipitator
효율이 좋다.
운영비, 설치비가 비싸다.
3) Cyclone
5 μm 이상의 입자제거
가장 일반적으로 쓰임
Organic CompoundsVolatile Organic Compound(VOC) Semivolatile Organic CompoundCondensable Organic Compounds
Polynuclear Aromatic Hydrocarbon (PAH)
Napthalene Benzopyrene
Coal Gasification
Reaction ΔH (kcal/mol)
Coal H2 CmHn, C 131.418.238.2
- 17.9- 9.8
- 49.0C + O2 CO2 - 97.0 Combustion
- 58.8
Coal Pyrolysis
C + H2O CO + H2 Steam Reforming
C + 2H2O CO2 + 2H2 Steam Reforming
C + CO2 2CO Boudouard Reaction
C + 2H2 CH4 Methanization
CO + H2O CO2 + H2 Water-Gas Shift Reaction
CO + 3H2 CH4 + H2O
2C + O2 2CO Combustion
Thermodynamic Equilibrium
•Step 1: Treat heated, crushed coal with superheated steam:
• C + H2O → CO + H2
Step 2: CO reacts with H2 to produce methane and water:
CO + 3H2 → CH4 + H2OOr reacts with water:
CO + H2O → CO2 + H2
•Step 3: Purification & Removal of CO2
Energy
< 3000 kcal/Nm3
5000 ~ 6000 kcal/Nm3
8500 ~ 10000 kcal/Nm3
Coal
Gasification
Oxygen or Steam
Gas Cleaning
CO Conversion
CO + H2
H2
Fuel cell Industrial fuel Household fuelCity gas For coal liquefaction
Transpotation fuel
AmmoniaAmmonia Synthesis
Chemical Synthesis
Power Generation
High Energy Density
Low Pollution
국내의 화력발전 환경규제치 강화 추세
Integrated Coal Gasification Cycle : IGCC
Year ‘91-‘94 ‘95-‘98 ‘99-SOx (ppm) 700 500 270 NOx (ppm) 350 350 350
Particulates(mg/m3) 250 100 50
2003년이후신규발전소NOx 80 ppm으로규제
“가스화”는 근본적으로 “연소”에 기초한 기존 화력발전과는 화학반응 자체가 틀림.
산소가 부족한 환원분위기 반응 : No SOx / NOx
석탄내 황성분 : H2S로 발생, 황산/유황으로 회수, 판매가능
석탄내 질소성분 : NH3 로 발생, 세정 편이
석탄내 회분 : 중금속 침출문제 없는 slag으로 발생, 도로포장재등으로 재활용
IGCCSOx : 25 ppm 이하
NOx : 60 ppm 이하
CO2 : 15 ~ 30% 감소
PM : 5 mg/m3 이하
30 40 50 60
0.1
0.2
0.3
Power generation efficiency(%)
CO 2
emis
sion
s (k
g/kW
h)
Coal
Crude oil
Natural gas
Pulverized coal combustionPFBC
IGCCMCFC
Combined Cycle
Combined CycleMCFC
0.0
,
IGCC (Integrated Coal Gasification Combined Cycle)
“Chemical conversion of coal to synthetic gas for combustion in a modified gas turbine”
30% increase in efficiency over brown coal steam power plantCorresponding 30% reduction in CO2 emissionsPower costs 30% less than conventional steam plantSuitable for high moisture fuels including biomass
Cf) ICFC (Integrated Coal Gasification Fuel CellCombined Cycle)
Comparative SO2 Emissions
1.85
0.160.00
New Coal Current IGCC New Natural gasEmis
sion
s in
Pou
nds
per M
WH
Comparative NOx Emissions
New Coal Current IGCC New Natural gas
Emis
sion
s in
Pou
nds
per M
WH
1.11
0.160.07
Carbon Capture and SequestrationCarbon Capture and Sequestration
Sequestration of Carbon in the OceansEnhancement of the Natural Terrestrial CyclesSequestration of Carbon in Underground Geologic RepositoriesManagement of Carbon by Sequencing Micro-organisms
Cost of Electricity in $/MWh
Conventional Coal
IGCC Conventional Coal
IGCC
Bituminous 46.6 45.8-48.3 75.4 61-67
Subbituminous 44 48-54 64-97 61
Without CCS With CCS
Clean Coal Technique
Coal Gasification
ICGC, ICFC
Coal Liquefaction
Coal To Liquid
석탄
가스화기가스 정제(CO+H2)
F-T합성
생성물분리/정제
디젤휘발유
수소공여 용매
산소수증기
액화반응기 upgrading refining
촉매
수소
석탄간접액화
석탄직접액화
Coal LiquefactionCoal LiquefactionDirect Method
Indirect Method1) Direct Method (Hydrogenation)