Modeling of Reactor Furnace of Sulfur Recovery Units from Acidic Gases

Transcription

1 0 nd International Conerence on Chemical Engineering and Applications IPCBEE vol. (0 (0 IACSIT Press, Singapore Modeling o Reactor Furnace o Sulur Recovery Units rom Acidic Gases Maryam Otadi, Mahdi Goharrokhi, Reza Rezazade Feyz Abadi Department o Chemical Engineering Central Tehran Campus, Islamic Azad University, Tehran, Iran Department o Chemical Engineering South Tehran Campus, Islamic Azad University, Tehran, Iran Shadid Hashemi nejad Gas Processing Co., Sarakhs, Iran Abstract. Reaction urnace o Claus Sulur recovery unit is modeled using Claus reaction equilibrium relation and Sames &Paskall's experimental equations. Concentration o components in outlet stream, H S and S conversion and urnace temperature are calculated. Computer program is provided based on the model. Keywords: Modelling, Claus, Furnace, Acidic Gas, Experimental and equilibrium relations. Introduction The Claus process is the most current process or sulphur production rom acidic gases that contents H S and CO. Claus process was introduced to industry or producing sulphur rom H S and air beore 00 years ago (88. Modiied Claus method was started or improvement previous method by I.B.Farbenindustrie (9[].. Claus Process Claus reaction is based on oxidation o H S with air in presence catalyst (Bauxite in a one stage reactor. H S O S H O ΔH C Kj/Kgmole Controlling o exothermic reaction is very hard and the setting o sulur removing eiciency is in a range o %. Modiied Claus method contents two stages[]: Burning / o acidic gas with total necessary air or reaction. H S O SO H O ΔH C -00 Btu/lbmole Blending remaining acidic gas with production CS rom irst stage. H S SO S x H O ΔH C -00 Btu/lbmole x.. Straight Through At irst, in this method acidic gas eed stream enter to reaction urnace. Acidic gas blend with stoichiometry air or burning / o total existent H S i.e. it converts to SO and all o hydrocarbons convert to CO. Thereore remaining o H S will react with the ormed SO and product sulphur. [9].. Reaction Furnace: Reaction urnace is a main part o sulur recovery unit. Reaction urnace has two primal targets. First: Burning / o existent H S in eed and product SO or Claus equilibrium process, Catalytic process and preparation H S relation or doing Claus equilibrium process with predicting conversion. SO Corresponding author. Tel.: ; ax: 980 address: mm_otady@yahoo.com 9

2 Second: Destruction and burning any type o component that may be damaged downstream equipments operation. [, ]... Reaction Furnace Ovservations All o reaction is evented in urnace and reaction rates don't speciy. Thereore Sames&Paskall 's experimental equations and Claus equilibrium reaction or modeling is used. R(CO 0.00A 0.0 exp (. A R(H 0.0 ( ± 0.0 R(CS. A 0.9 exp( -0.9 A R(S.8A.099 exp (-0.A R(C0S 0.0tangent (00A or 0 A 0.8 or R(C0S 0. or A > 0.8 where R(CO is Fraction o initial carbon to ormat CO, R(H is Fraction o initial H S to ormat H, R( COS is raction o initial carbon to ormat COS, R(CS is raction o initial carbon to ormat CS,, R(S is raction o initial carbon to ormat S, A is mol raction o H S in acidic gas in dry state, respectively [,8,9]. Available method in relation urnace is Straight state, reaction urnace pressure: 0-0 KPa, pressure drop: 0 KPa, Steady state and heat transer rate is considered negligible. Table : Chemical Reaction H S O SO H O H S SO S H O CH O CO H O K P [ H O ] [ S ] π [ H S ] [ SO ] totalmoles CO CO O H S S H CH S CS H S CO S COS where Kp is pressure equilibrium Constant, π is pressure, [ ]is Mol rate o component and X is HS consumption mol rate in Claus equilibrium reaction, respectively. Ater writing sum o existent components mol rate in reaction[,]: Total i ( H S ( i ( CH ( i ( N R ( CO i ( H O Relation between K p and react urnace temperature is coming in a graph o GPSA[]. Interpolation dierent value o graph can help or getting a straight equation between temperature and equilibrium constant [-]. i ( CO X ( R ( CO K p 0.T-0.9 T ( C, K p (kpa ( A X ( B 0. X π ( K (( ( C X ( / 0. X ( D 0. T 0. i ( H S 0.9 / 0.0 A B C D i ( H O i ( CH i ( H S i ( H S ( ( i ( H S i ( CH i ( CH i ( H S i ( CH R ( CO ( i ( N ( i ( H O 9 0. R ( COS i ( CO ( ( i ( CH i ( CO R ( CO

3 .. Reactor Furnace Energy Balance: Energy Consumption- Production Energy Initial Energy Outlet Energy Initial Stream Energy : Outlet Stream Energy: H H in( in( i i bi ci d i bi ci d i (T ( ait T T T ( ait0 T0 T0 T0 H i (T0 bi ci d i bi ci d i (T ( ait T T T ( ait0 T0 T0 T0 H i (T0 E in H i(ch H i(co H i( H S H i( HO H i(o H i( N bj c d b c d j j j j j Hout ( j (T (a jt T T T ( a jt0 T0 T0 T0 H j(t0 E out H H O( SO O( CH H H 8 O( S O( CO H H 9 O( CO O( H S H H 0 O( CS O( H O H H O( O O( COS H H 8 O( H O( N E in is a unction o x and numerical orm and E out is unction o x &, T. Writing and simpliication equation can help to get below equation: X A B 0 0 AT BT A T B T C T C T DT D T T. 0. ( A X ( B 0. X π (( 0. ( C X ( / 0. X ( D 0. i ( H S 0.9 / 0.0 Using these equations and trial and error methods, temperature (T and conversion (x can be calculated. A 0 A A B 0 B B C C D D are constant parameters that speciied with initial stream conditions and computate numeral orm... Results and Discussion In this project, H S Concentration change in eed stream will change urnace temperature, H S & S conversion and H S, S, H,, COS, CS concentration in outlet stream. Increasing H S concentration in eed stream will increase urnace temperature, H S total & equilibrium conversion, S & H concentration in outlet stream but H S concentration decreases and SO concentration at irst will decrease and next increase (Fig.,,,,,. Increasing initial eed and air streams temperature occur to urnace temperature, H S & S concentration (Fig., 8, 9. Furnace pressure is aected in H S & S conversion. Pressure increase will increase urnace temperature but H S & S conversion decrease (Fig. 0,,. T ( k H S in (mole% Fig. : Predicting reaction urnace temperature against H S concentration Fig. : Predicting reaction urnace H S total conversion (blue and equilibrium conversion(red against H S concentration 9

4 Sulur Conversion % H S in (mole% Fig. : Predicting reaction urnace S conversion against H S concentration Sulur Conversion % S out (mole % H S in S in (mole% Fig. : Predicting reaction urnace S concentration against H S concentration HSout (mole% H S in (mole% Fig. : Predicting reaction urnace H S concentration in outlet stream against H S concentration TReactor Furnace ( C Hout (mole % H S in (mole% Fig. : Predicting reaction urnace H concentration in outlet stream against H S concentration H S Conversion % ( 0ºC, 9ºC.. ( 0ºC,.% T Acid Gas & Air ( C Fig. : Predicting reaction urnace temperature against air and eed initial streams temperature Sulur Conversion % T Acid Gas & Air ( C ( 0ºC,.% Fig. 9: Predicting reaction urnace S conversion against air and eed initial streams temperature T Acid Gas & Air ( C Fig. 8: Predicting reaction urnace H S conversion against air and eed initial streams temperature T Reactor Furnace ( C P Reactor Furnace ( Kpa A Fig. 0: Predicting reaction urnace temperature against pressure change 9

5 H S Conversion % P Reactor Furnace ( Kpa A Fig. : Predicting reaction urnace H S conversion against pressure change Sulur Conversion % P Reactor Furnace ( Kpa A Fig. : Predicting reaction urnace S conversion against pressure change. Reerences [] H. G. Paskall, " Reaction Furnace Chemistry and Operational Models," Sulphur Recovery, Western Research Calgary, Alberta, Canada, 990 (originally published in 98. [] J. A. Sames and H.G. Paskall,"Sulphur Recovery," Sulphur experts,western Research,Elevencth Edition, 008 [] J. A. Sames and H.G. Paskall, " Simulation o Reaction Furnace Kinetics or Split-Flow Sulphur Plants, " Sulphur, Recovery, Western Research,Calgary,Alberta,Canada, 99 (originally published as a paper or the Sulphur, 8 conerence, November, 98. [] J. A. Sames, P. R. Dale and B. Wong, "Evaluation o Reaction Furnace Variables in Modiied Claus Plants," Sulphur Recovery,Western Research, Calgary, Alberta, Canada, 990. (originally published or the Laurence Reid Gas Conditioning Conerence, March, 98. [] J. A. Sames, H. G. Paskall, D. M. Brown, M. S. K. Chen and D. Sulkowski, "Field Measurements o Hydrogen Production in an Oxygen Enriched Claus Furnace," Sulphur Recovery, Western Research, Calgary, Alberta, Canada, 990 (also in preprints o Sulphur 990 International Conerence, April,990. [] W. D. Monnery, W. Y. Svrcek and L. A. Behie, "Modelling the Modiied Claus Process Reaction Furnace and the Implications on Plant Design and Recovery," Department o Chemical and Petroleum Engineering,University o Calgary, Calgary, Alberta, Canada TNI, 00. [] H. S. F. Chin, " The Fate o Methane in the Reaction Furnace o a Modiied Claus Plant," Department o Chemical and Petroleum Engineering, University o Calgary, Calgary, Alberta, Canada, AUGUST, 000. [8] Sulur Experts Western Research, "Sulur plant evaluation at NIGC khangiran gas plant," 00. [9] M. Sassi and A. K. Gupta, " Sulur Recovery rom Acid Gas Using the Claus Process and High Temperature Air Combustion(HiTAC Technology," The Combustion Laboratory University o Maryland, College Park, International Workshop on Advances in Combustion Science IIT Kanpur December,00-Jan,