Optimization of Motor Gasoline Production

Transcription

1 Optimization of Motor Gasoline Production Research Article 100 M.G.Diab 1, H.M. Mustafa 2, I.H. M.Elamin 3, G.A.Gasmelseed 4 (1-4) Department of Chemical Engineering, Faculty of Engineering, University of Science and Technology, P.O. Box 30, Omdurman, Sudan. (1) mrwdiab@yahoo.com (2) hamidmustafa5@gmail.com (3) Ibrahimelamin@yahoo.com (4) gurashigar@hotmail.com (Received: March 05, 2014; Accepted: June 09, 2014) Abstract This study focuses on the production and optimization of motor gasoline in KRC(Khartoum refinery co. Ltd).The gasoline produced by the refinery was analyzed using standard methods of analysis for the possibility of using ethanol as an additive ratio of 5%, 10% and 15%.Linear programming was used to determine the optimal production rate and optimal production cost of the blend,using this model, two cases were investigated namely final products of 92 and 94 RON. For 92 octane the percentage of ethanol varies inversely with production rate while the optimal production cost value varies linearly from 63.5 to 64.3$/bbl. For 94 octane 15% of ethanol is required for all production rates and that the optimal production cost value remains constant at 70.3 $/bbl. Index Terms Gasoline, Additives, Ethanol, KRC, Octane Number K I. INTRODUCTION RC (Khartoum refinery co. Ltd) is a joint venture between Ministry of Petroleum of Sudan (MOP) and China National Petroleum Corporation (CNPC). The Refinery was originally designed to process 2.5 million tons per year of crude oil.it started production on 16 th May The processing capacity of the refinery has been increased to 5 million tons per year of crude oil. The main processing units of the refinery are Atmospheric Crude Distillation Unit (CDU), Continuous Catalytic Reforming unit (CCR), Residue Fluid Catalytic Cracking unit (RFCC), Delayed Coking Unit (DCU), Diesel Hydro treating unit (DHT and GDHT) and Jet-A1 unit. Apart from the processing units, the refinery has self-dependant crude delivery system and utility system. Gasoline and diesel fuel produced can meet EURO II standard. Presently the main products of this refinery are: LPG, Motor Gasoline, Jet fuel, Diesel and coke [1].This work investigates the production of motor gasoline from RRCC and CCR units and possibility of using ethanol as an additive. Gasoline is a regulated fuel and its specifications keep on changing to meet environmental legislations and the change in engine and combustion technology. [2] Alcohols, ethers and the manganese additive MMT and the iron additive ferrocene are possible alternatives [3, 4]. In this Study ethanol will be the first choice as an additive in KRC Sudan. Ethanol is being produced in the Sudan-from molasses in many projects. Therefore the possibility of additives mainly ethanol will be also considered as another gasoline pool component. The RFCC and CCR gasolines plus ethanol - gasoline pool - are to be blended, in an optimal manner, to give the required type of gasoline in demanded amounts with good economic benefits. Ethanol in the blended fuel acts as an octane poster and an oxygenator. The application of ethanol as a supplementary CI engine fuel reduce environmental pollution, strengthen agricultural economy, create job opportunities, reduce diesel fuel requirements thus contribute to conserving a major commercial energy source [5]. The gasoline samples are to be characterized and analyzed and then KRC Refinery production rates and analysis data to be used as input data to the model equations of the optimization problem and then solved by linear programming (LP) techniques[7,8,9,10]. The LP software used for analysis in this study is MATLAB R2009a-Linprog. II. MATERIALS AND METHODS Materials The RFCC and CCR products as well as the final blend samples were obtained directly from Khartoum refinery while the ethanol additive brought from Kenana Sugar Company. Methods The gasoline and alcohol samples were mixed in order to obtain the flex-fuel samples, having concentrations of 0, 5, 10 and 15 vol. % of hydrated alcohol in gasoline types (final product, RFCC, CCR). The obtained alcohol - gasoline samples were analyzed for the 10, 50 and 90%v recovery temperatures, octane rating, and specific Gravity (S.G), Reid vapor pressure (RVP), and Copper strip corrosion.the samples were analyzed using ASTM D86 procedure. For the samples, the 10, 50 and 90%v vaporization temperatures and the end point were determined also the amount of final residue was founded [6]. In this study an IROX 2000 (Grabner Instruments Messtechnik Nfg. GmbH & Co KG) which is a Mid-FTIR spectrometer is used to obtain the RON and MON as well as the automatic measurement of the concentration of the most important components of gasoline: oxygenates, aromatics, alcohol, and olefins which were used to evaluate the sample. The Specific Gravity of the samples was determined using the ASTM D1298 method, while the Reid vapor pressure of the hydrated alcohol was measured according the ASTM D323

2 101 method [6]. The copper strip corrosion test of sample was done according to ASTM D130 method [6]. III. RESULTS AND DISCUSSION KRC Gasolines Analysis Results The analysis of results obtained for KRC gasolines are shown in Table (1), while results of the blended samples are shown in Table (2). Table (1).Properties of KRC Gasoline Test name KRC blend RFCC Gasoline CCR Gasoline Distillation 10%Recoverd ( C) %Recoverd ( C) %Recoverd ( C) FBP ( C) Residue Vol % (Ml) S.G@15 C (kg/l) Reid vapor pressure (RVP) kpa Octane number (RON) MON Olefins %V Aromatics %V Benzene %V Ethanol %V Oxygen %V Copper strip corrosion * 1a 1a 1a *1a: means no corrosion Table (2). Addition of ethanol to KRC blend Test name KRC blend KRC blend +5% KRC blend +10% KRC blend +15% Distillation 10%Recoverd ( C) %Recoverd ( C) %Recoverd ( C) FBP ( C) Residue Vol % ( Ml) S.G@15 C ( kg/l) Reid vapor pressure(rvp) kpa Octane number (RON) MON Olefins %V Aromatics %V Benzene %V Ethanol %V Oxygen %V Copper strip corrosion *1a *1b 1b 1b *1a and 1b: means no corrosion The results of analysis showed conformity according to the Sudanese specifications [11] and test methods as given in Table (3) below.

3 102 Test Name Distillation Table (3).Test methods and Sudanese specifications (SSMO) [11] Sudanese Test Method Units specifications Uncertainty C 10%Recoverd Max 70 C ± 2.3 ASTM D86 50%Recoverd 120 Max C ± %Recoverd Max 190 C ± 8.6 FBP Max 205 C ± 6.2 Residue Vol % Max 2.0 Ml Density meter In Density IROX Gasoline S.G@15 C analyzer Report Kg/L Reid vapor pressure (RVP) Octane number RON MON ASTM D323 ASTM D2699 ASTM D2699 1Nov-31Mar (45-80) 1Apr 31Oct (40 67) Min 90 - Olefins %V IR absorption Max 10 Vol. % Aromatics %V IR absorption Max 35 Vol. % Benzene %V ASTM D5845 Max 1 Vol. % Ethanol %V IR absorption - Vol. % Oxygen %V ASTM D Vol. % Copper strip corrosion ASTM D130 Max No.1 Mass% kpa Optimization of the Blending Process Model equations are formulated as shown below Objective Function Equation The objective function is to minimize the production cost of gasoline blend. The Processing costs of gasoline of different types and ethanol are: Table (4). production costs of gasoline pool components Types Production cost ($/barrel) RFCC gasoline 57.2 CCR gasoline 74.8 Ethanol 110 Hence the objective function is formulated as:. (1) Where: F1: barrels/day of RFCC gasoline F2: barrels/day of CCR gasoline F3: barrels/day of ethanol. Constraints Equations Ethanol constraints The amount of ethanol to be blended is set as 5%minimum and 15%maximum (2) From which: (3) And (4) Putting Eq. (3) in optimization form for the 5% minimum: (5) Putting Eq. (4) in optimization form for the 15% maximum:.. (6) Reid vapor pressure (RVP) constraints RVP constrains according to Sudanese specifications (SSMO) range (45-80) kpa From (RVP max) By rearrangement: From (RVP min) (7) By rearrangement: (8) Octane (RON) Specifications Requirements The Sudanese specifications - as in Table 1- sets gasoline RON requirement as 90 minimum. For this work we took the values RON = 92, and RON=94. For 92 octane: By rearrangement For 94 octane:. (9)

4 OPTIMUM COST $/bbl (10) Total production rate The production rates investigated were: [15000,17500,20000,22500,25000,25500,26000,27000,28250, bbl/day ]. (11) The above formulated optimization problem is solved using the software MATLAB R2009-Linprog.[7,9,10] Results Analysis Output results of the program are tabulated in Tables (5) and (6) and plotted in Figures (1and 2) respectively. Table (5). Targeting minimization of the production cost of RON 92 Production RFCC CCR Ethanol Optimum rate(bb/day) Rate % Rate % Rate % value($/bbl) Not terminated PRODUCTION RATE bbl/day x 10 4 Figure 1. Relationship between production rate and optimum cost for the 92 octane case

5 OPTIMUM COST $/bbl 104 Table (6).Targeting minimization of the production cost of RON 94 Production RFCC CCR Ethanol Optimum value rate(bb/day) Rate % Rate % Rate % ($/bbl) Not terminated PRODUCTION RATE bbl/day x 10 4 Figure 2.Relationship between production rate and optimum cost for the 94 octane case Firstly the free gasoline pool components were analyzed, from the analysis it has been found that the CCR octane number is equal to 94.8 compared to 89.8 for RFCC gasoline. This high octane value is due to the high aromatics content of CCR (30.02) compared to that of RFCC (13.2). The aromatics content falls within Sudanese specification value, however it is advisable that the aromatics content is to be reduced further. The maximum amount of gasoline produced by KRC without ethanol addition stands at bbl/day which satisfied the present market requirement. There is a trend of using the ethanol as an additive and from analysis it has been found that the ethanol acts as an octane booster for example when adding 10%ethanol the octane number increases from 91.4 to 94.8 an increase of 3.4 points. Ethanol also decreases the aromatics content from 24.6 to 17.4 which is a substantial change. Ethanol besides being a volume extender also acts as an oxygenator increasing the oxygen content to 3.8%v. Secondly the optimization of the blending process was done targeting minimization of the production cost, two cases 92 and 94 RON gasolines falling within Sudanese specification were investigated. For 92 octane the percentage of ethanol varies inversely with production rate while the optimal production cost value varies from 63.5 to 64.3$/bbl. Beyond production rate bbl/day all of the RFCC stream will be used, this necessitates increasing the RFCC gasoline production if higher production rates are required.

6 105 For 94 octane to produce gasoline of 94 octane 15% of ethanol is needed for all production rates.its noted that the optimal value remain constant at 70.3 $/bbl, also there will be an access of RFCC gasoline for example at a production rate bbl/day the final optimal production rate only 85%of RFCC gasoline will be used while almost all of CCR gasoline is used. IV. CONCLUSION It is concluded that ethanol is the best additive for KRC besides its many advantages as an octane booster, an oxygenator and as a volume extender, it is locally produced in the Sudan and many projects for its production from molasses are on the way. With use of the ethanol and its apparent advantage its necessary to investigate the environmental effects of using it. Linear programming has been used to determine the optimum production cost of gasoline/ethanol blends in KRC with maximum refinery benefits. Two type of motor gasoline blends namely 92 and 94 octane gasolines can be produced satisfying the local Sudanese specifications, 15%v addition of ethanol is needed for the production of 94 octane type, while 10-12%v ethanol addition is required for 92 octane type. It has been found that it is necessary to increase the production of RFCC gasoline, if maximum amount of gasoline produced by the refinery is targeted. The gasoline pool components were analyzed as shown in table (1) and from the analysis it is found that the CCR gasoline is of high octane value this is due to its high aromatic contents. V. ACKNOWLEDGEMENTS The authors wish to thank the College of graduate studies and scientific research, of Karrary University, for their support. This research is made in partial fulfillment of the requirements for degree of Ph.D. in Chemical Engineering at Karrary University. REFERENCES [1]The 2 nd Configuration Study of Expansion Project for Khartoum Refinery Co. Ltd.,( Ministry of Energy), 2011, local citation.. [ 2]Nelson, W. L., 1958 "Petroleum Refinery Engineering", 4th Edition, McGraw-Hill Book Co., New York. [3] Gary, J. H., and Handwerk, G. E., 1994 "Petroleum Refining Technology and Economics 3 rd edition, Marcel Dekker, Inc., New York. [4] _additives&oldid= " [5]Kim S, Dale BE., 2005, Environmental aspects of ethanol derived from no-tilled corngrain: nonrenewable energy consumption and greenhouse gas, Biomass and Bioenergy. [6] ASTM manuals [7] Allen, D. H., August 1971 "Linear Programming Models for Plant Operations Planning", British Chemical Engineering, vol. 16. [8] Williams, N., 1967, "Linear and Non-linear Programming in Industry", pitman, London. [9-]Al-Mutaz, I. S., and Al-Fariss, T. F., 1997, Optimum Gasoline Production in Oil Refineries By Linear Programming", Oil Gas-European Magazine. [10] Hamid M. Mustafa, and Tariq N. Al-Shaia, 2005, "Targeting high quality unleaded motor gasoline in a Saudi refinery", Engineering Journal of the University of Qatar, vol. [11] Sudanese Standards and Metrology Organization (SSMO).