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/(CTO/RTO)
Feng Tang Chang
:[email protected][email protected]
Mobile: 0933147075
/(CTO/RTO)
VOC THERMAL OXIDATION
VOC Destruction Mechanism
VOC + O2 CO2 + H2O + HCl + SO2 + N2
More precisely: (where X is any one of halogen atoms (chlorine, flurine, bromine, iodine)
CaHbNcOdSeXf+(a+e+o.25(b-f)-0.5d)O2 aCO2+0.5(b-f)H2O+fHX+eSO2+0.5cN2
Operating parameters for 99% Destruction
Temperature : 750 ~ 850
( 300 ~ 350 . with Catalyst)
Residence Time : 0.5 ~ 1 sec
Turbulence : Re > 10,000 (Re = V D / )
O2 Concentration : Over 12% at 800
(3 T)
VOC THERMAL OXIDATION
(Thermal Oxidizer ; TO)
(Catalyst Thermal Oxidizer; CTO)
(Recuptive Thermal Oxidizer)
(Regenerative Thermal Oxidizer; RTO)
KINDS OF THERMAL OXIDIZER & COMPARISON
Direct firing RTO RCO
Systemflow
OperatingTemp.
HeatExchange
Type
ThermalRecovery
Eff.
CTO
Exhaustgas
Exhaustgas
750 ~ 850 300 ~ 350 750 ~ 850 300 ~ 350
Recuperative Recuperative Regenerative Regenerative
40 ~ 70 % 40 ~ 70 % 95 % over 95 % over
catalyst catalyst
Low Fuel Consumption
Exhaustgas
Exhaustgas
VOC THERMAL OXIDATION
Direct thermal oxidizer
VOC THERMAL OXIDATION
Catalyst thermal oxidizer
VOC THERMAL OXIDATION
CTO (Catalyst Thermal Oxidizer)CTO (Catalyst Thermal Oxidizer)
VOC THERMAL OXIDATION
Con
vers
ion
(%)
Con
vers
ion
(%)
Temperature (Temperature () @ 40,000 1/hr VHSV) @ 40,000 1/hr VHSV
VOC THERMAL OXIDATION
(Catalyst Type)(Catalyst Type)
Lifetime: approroximate 24years
DEVELOPMENT OF RTO
2 Bed 3 Bed Rotary type
Systemflow
MotorPurge gas
PurgeAir
Untreated gas emit
when valve switch
Pressure fluctuation
Many Numbers of valve
Trouble factor
No fluctuation of
pressure
Single valve (Rotary)
Problem&
Develop-ment
Develop Prevention of untreated gas
Emission
Pressure fluctuation
when Valve switch
Develop
1st generation 2nd generation 3rd generation
MECHANISM OF 2T-RTO
Heat RecoverMedia
Heat RecoverMedia
1,400F 1,500F
From ProcessT=150F
250F
Flow Schematic
Valves switch every 90 180 secs.
MECHANISM OF 3T-RTO
Clean Process Air
Purge Air
Independent Burners
Heat Exchange Media
Solvent-Laden Process Air
MECHANISM OF RRTO
Temp.
A Bed B Bed
Heat MediaA
Outlet gas
Inlet gas
Heat MediaB
A B
Ceramic Media
A
Bed
Pyro bloc
B
Bed
Motor
Purge Air
Treated gasExhaust
gas
ROTARY TYPE RTO
Cylindrical type Rectangular type
LG Chem Kuck-Do Chem
STRUCTURE OF R-RTO
Combustion chamber
Burner
Ceramic media chamber
Rotary valve
Cylindrical type
Rectangular type
R-RTO PRINCIPLE OF OPERATING
Inlet ZONE
Outlet ZONE
: Influent
: Effluent
: Flushing
: NON-FLOW
F
NFlushing
Chamber
NON FLOW
Chamber
N
F
N
F
N
F
N
F
N
F
Straight-through
Air paths
Constant
Flow path
(No. Short
Circuit)
ADVANCED STRUCTURED BLOCK (HEAT MEDIA)
RTO--Honeycomb Monoliths
CONTROL & MONITORING PC SCREEN (Example)
VOC THERMAL OXIDATION
Acid Gas Dewpoints (Halogenated gases and SO2/SO3 become corrosive to metals when they reach their dewpoint (liquid condensation).
Hydrochloric acid (HCl)
1000/Tdp=3.7358-0.1591 ln(PH2O)-0.0326ln(PHCl)+0.00269ln(PH2O)ln(PHCl)
Hydrofluoric acid (HF)1000/Tdp=3.8503-0.1728 ln(PH2O)-0.02398ln(PHF)+0.001135ln(PH2O)ln(PHF)
Hydrobromic acid (HBr)1000/Tdp=3.5639-0.135 ln(PH2O)-0.0398ln(PHCl)+0.00235ln(PH2O)ln(PHCl)
Sulfuric acid (H2SO4)1000/Tdp=1.7842-0.0269 ln(PH2O)-0.1029ln(PSO3)+0.0329ln(PH2O)ln(PSO3)
Where: Tdp dewpoint temperature (K)
P partial preesure (atm) (Source: Kiang. Y.H., Predicting dewpoints of acid gas, chem. Eng.,1981 & Pierce, R.R., Chem., April 11, 1977.)
Issue#1
VOC THERMAL OXIDATION
Acid Gas Dewpoints --- example
Combustion of waste gas containing hydrogen sulfide produces com
bustion products at atmospheric with the following composition:CO2 6.03% ; H2O 11.41% ; N2 77.23% ; O2 5.31% ; SO2 0.0283% ; SO3
0.0003%,
Please caculate sulfur acid dewpoint.
============================================
Using the equation for sulfuric acid (H2SO4):
1000/Tdp=1.7842-0.0269 ln(PH2O)-0.1029ln(PSO3)+0.0329ln(PH2O)ln(PSO3)
PH2O = (11.41/100)=0.1141 atm
PSO3=(0.003/100)=0.000003 atm
Substituting into the equation:
Tdp = 400 K = 127 oC = 261 oF
Issue#1
VOC THERMAL OXIDATION
Issue #2 (Stoichiometric air)
(1)C + O2CO212g22.4L22.4L
21:79lkg
1kg8.9m3
VOC THERMAL OXIDATIONIssue #2 (Stoichiometric air)
VOC THERMAL OXIDATION
Issue #2 (Stoichiometric air)
VOC THERMAL OXIDATION
Issue #3 Energy balance
LHV = HHV (N x 18.02) / MWVOC x 120
Where: LHV lower heating value (kcal/kg)HHV higher heating value (kcal/kg)N number of moles of water vapor produced per mole of VOCMWVOC molecular weight of VOC120 heat (kcal/kg) required to evaporate water at 25 oC (77oF) & 1 atm.
Usually, a value of 90% of the HHV is a close approximation to the LHV.LHV 0.9 HHV
Assume: 1 NM3/hr 600,000ppm(60% vol.)(propane;C3H8)25oC700oC28.3 x 0.6=17 NM3/hr
a.) (propane;C3H8)(Q release) = 60% x 1 NM3/hr x 1.82kgs/NM3x 12,034 kcal/kg x 0.9 =11,827 kcal/hrb.) (Q require) 17 NM3/hr x 1.293kgs/NM3 x 0.26 kcal/hr.oC x (700-25)oC = 3,858 kcal/hrc.) 11,827 kcal/hr (1.293x0.26x(700-25))= 52 NM3/hr.
VOC THERMAL OXIDATION
Issue #3 Energy balance
Assume: 1 NM3/hr 20,000ppm(2% vol.)(propane;C3H8)25oC700oC28.3 x 0.02=0.57 NM3/hr
a.) (propane;C3H8)(Q release) = 2% x 1 NM3/hr x 1.82kgs/NM3 x 12,034 kcal/kg x 0.9=394 kcal/hrb.) 17 NM3/hr(Q require) 17 NM3/hr x 1.293kgs/NM3 x 0.26 kcal/hr.oC x (700-25)oC = 3,858 kcal/hr
(: 3,858 394 = 3,464 kcal (add 0.18 NM3 PG fuel))
(65%) Q require = 3,858 x (1-0.65) = 1,350 kcal/hr RTO (90%) Q require = 3,858 x (1-0.90) = 386 kcal/hr (Self sustain)
c.) 394 kcal/hr (1.293x0.26x(700-25))= 1.7 NM3/hr.
VOC THERMAL OXIDATIONIssue #3 Energy balance
VOC THERMAL OXIDATION
Issue #4 /
VOC THERMAL OXIDATION
Issue #4 /
VOC THERMAL OXIDATION
Issue #5 Safety & others
: Flame arrestor()fresh air purge: : 25oC/min
30 mins,+65% 60 mins, 30 mins, 120 180 mins.
VOC THERMAL OXIDATION
Issue #5 Safety & others
Flashback prevention techniques:Minimum velocity technique for flashback
prevention.Flashback flame arrestor.Flashback prevention by using air to dilute
waste stream to below LEL.Seal pot (sealing fluid) flash arrestor.
Flashback velocity (ft/s) = 0.2015 x G x DWhere G critical bounadry velocity gradient (1/s)
Dduct or pipe diameter (ft)(G value: Methane=400 ; Ethane=650 ; Propane=600 ; Propylene=700)Source from Nutcher,P.B. Maximum achievable control technology AWMA 87th Annu.,1994.
VOC THERMAL OXIDATION
Issue #5 Safety & others
Explosive limit in air
CmHxOy + zO2 mCO2 + x/2 H2O
LEL,(%) = 0.55 (100)/(4.7m + 1.19x + 1 2.38y)UEL,(%) = 3.50 (100)/(4.76m + 1.19x + 1 2.38y)
LELmixture, (%) = 1 / (yi/LELi)UELmixture, (%) = 1 / (yi/UELi)
yi mole fraction of component i on a combusitible basis.
Example: Propane(C3H8) LEL=2.1 vol.% ; UEL=9.5 vol.%Acetone(C3H6O) LEL=2.6 vol.% ; UEL=12.8 vol.%
VOC THERMAL OXIDATION
(Catalyst Price)(Catalyst Price)Catalyst Description: PRO-PEL 14518, SPH, 1/8"
Catalyst Type: Platinum and palladium catalyst on alumina spheres.Catalyst size: Nominal 1/8" diameter spheres
Catalyst Space Velocity: ~10,000 1/hrMinimum Catalyst Depth: 10"
Catalyst Price: $ 765 USD per cubic foot1,000 scfm 6 cubic foot $4,590USD (NT$151,470)
Catalyst Description: PRO-