Linear refinery

Most refineries develop iadividual octane blending equations which do a good job of predicting that refinery s blending behavior. In order to use these equations ia refinery planning and operations, these may be linearized ia a piecewise fashion. 

Butene. Commercial production of 1-butene, as well as the manufacture of other linear a-olefins with even carbon atom numbers, is based on the ethylene oligomerization reaction. The reaction can be catalyzed by triethyl aluminum at 180—280°C and 15—30 MPa ( 150 300 atm) pressure (6) or by nickel-based catalysts at 80—120°C and 7—15 MPa pressure (7—9). Another commercially developed method includes ethylene dimerization with the Ziegler dimerization catalysts, (OR) —AIR, where R represents small alkyl groups (10). In addition, several processes are used to manufacture 1-butene from mixed butylene streams in refineries (11) (see BuTYLENEs). 

Butylenes are C Hg mono-olefin isomers 1-butene, <7j -2-butene, trans-2-huX.en.e and isobutylene (2-methylpropene). These isomers are usually coproduced as a mixture and are commonly referred to as the fraction. These fractions are usually obtained as by-products from petroleum refinery and petrochemical complexes that crack petroleum fractions and natural gas Hquids. Since the fractions almost always contain butanes, it is also known as the B—B stream. The linear isomers are referred to as butenes. 

Production Controls The nature of the produc tion control logic differs greatly between continuous and batch plants. A good example of produc tion control in a continuous process is refineiy optimization. From the assay of the incoming crude oil, the values of the various possible refined products, the contractual commitments to dehver certain products, the performance measures of the various units within a refinery, and the hke, it is possible to determine the mix of produc ts that optimizes the economic return from processing this crude. The solution of this problem involves many relationships and constraints and is solved with techniques such as linear programming. 

Until comparatively recently the bulk of general purpose phthaiate plasticisers have been based on the branched alcohols because of low cost of such raw material. Suitable linear alcohols at comparative prices have become available from petroleum refineries and good all-round plasticisers are produced with the additional advantage of conferring good low-temperature flexibility and high room temperature resistance to plasticised PVC compounds. A typical material (Pliabrac 810) is prepared from a blend of straight chain octyl and decyl alcohols. 

These non-linear equations can be embedded into the refinery s linear program (LP) to achieve compliance and optimize the gasoline blend. The key FCC gasoline components that influence RFG are ... 

Polarisation resistance This technique, sometimes referred to as linear polarisation resistance (LPR), has been applied widely in industrial monitoring because of its ability to react instantaneously to a corrosion situation or change in corrosion rate " " . The limitation of the technique arises from the necessity to have a defined electrolyte as the corrosive (the author has seen an LPR probe installed in a dry gas-line in an oil refinery). 

Production of chemicals became increasingly important. The recovery of oxygenates from the Fischer-Tropsch aqueous product was expanded to include niche chemicals, such as 1-propanol.45 Ethylene and propylene extraction was increased and even supplemented by the addition of a high-temperature catalytic cracker.46 Linear a-olefin extraction units for the recovery of 1-pentene, 1-hexene, and 1-octene were added to the refinery,45-47 and a new facility for the extraction of 1-heptene and its... 

Most commercial Fischer-Tropsch refinery designs (Figures 18.1 to 18.9) included the co-production of chemicals with transportation fuels. The chemicals potential of Fischer-Tropsch syncrude has been pointed out repeatedly.38,47,65 66 This is a natural consequence of the properties of Fischer-Tropsch syncrude, that is, richness in linear hydrocarbons, olefins (especially linear a-olefins), and oxygenates. Furthermore, it is sulfur-free and nitrogen-free, which enables access to synthetic routes sensitive to such compounds. 

ENSORB [ExxoN adSORBtion] A process for separating linear from branched hydrocarbons, using a zeolite molecular sieve. The adsorbed gases are desorbed using ammonia. It operates in a cyclic, not a continuous, mode. Developed by Exxon Research Engineering Company, and used by that company on a large scale at the Exxon refinery in Baytown, TX. Asher, W. J., Campbell, M. L., Epperly, W. R., and Robertson, J. LHydrocarbon Process., 1969, 48(1), 134. 

MLDW [Mobil lube dewaxing] A catalytic process for removing waxes (long-chain linear aliphatic hydrocarbons and alkyl aromatic hydrocarbons) from lubricating oil. Developed by Mobil Research Development Corporation and operated at Mobil Oil refineries since 1981. Eight units were operating in 1991. 

Octol A process for making mixed linear octenes by the catalytic dimerization of mixed butenes. A proprietaiy heterogeneous catalyst is used. Developed jointly by Hiils and UOP, and now offered for license by UOP. First operated in 1983 in the Hiils refinery in Marl, Germany. Another installation began production in 1986 at the General Sekiyu Refineries in Japan. 

TSF [Texaco Selective Finishing] A process for separating linear from branched-chain aliphatic hydrocarbons by PSA, using zeolite 5A as the adsorbent. The desorbent is a hydrocarbon having two to four carbon atoms less than the feed. Developed by Texaco in the late 1950s. Believed to be still in operation in its Trinidad refinery as of 1990. 

The alkylation unit in a petroleum refinery is situated downstream of the fluid catalytic cracking (FCC) units. The C4 cut from the FCC unit contains linear butenes, isobutylene, n-butane, and isobutane. In some refineries, isobutylene is converted with methanol into MTBE. A typical modern refinery flow scheme showing the position of the alkylation together with an acid regeneration unit is displayed in Fig. 1. 

In addition to their use as stand-alone systems, LPs are often included within larger systems intended for decision support. In this role, the LP solver is usually hidden from the user, who sees only a set of critical problem input parameters and a set of suitably formatted solution reports. Many such systems are available for supply chain management—for example, planning raw material acquisitions and deliveries, production and inventories, and product distribution. In fact, the process industries—oil, chemicals, pharmaceuticals—have been among the earliest users. Almost every refinery in the developed world plans production using linear programming. 

The problem is to allocate optimally the crudes between the two processes, subject to the supply and demand constraints, so that profits per week are maximized. The objective function and all constraints are linear, yielding a linear programming problem (LP). To set up the LP you must (1) formulate the objective function and (2) formulate the constraints for the refinery operation. You can see from Figure El6.1 that nine variables are involved, namely, the flow rates of each of the crude oils and the four products. 

On the basis of the indirect investigations and in eompliance with the prescriptions of the Italian Environment Ministry, environmental investigations were carried out at the refinery using eontinuous eore recovery drilling (water was used as the drilling fluid for a total of approximately 2,700 linear meters of drilling. A total of 50 Lugeon... 

The gasoline Molex process is the first of three processes since it separates the lowest molecular weight feed of the three Molex normal paraffin separahon processes. Gasoline Molex was developed to optimize a Refiner s octane pool by extracting low octane value normal paraffins (specifically C5, 5) from naphtha. In a typical refinery flow scheme, a gasoline Molex unit is integrated with a catalyhc isomeriza-hon unit (Penex unit) which converts the Molex unit s extracted normal paraffins into desired iso-paraffins. These iso-paraffins are desirable because they possess higher octane value than their linear counterpart. 

Symonds, G.H. (1955) Linear Programming-The Solution of Refinery Problems, Esso Standard Oil Company New York. 

This example illustrates the planning of petroleum refinery operations as an ordinary single objective linear programming (LP) problem of total daily profit maximization. 

In this chapter, we tackle the integration design and coordination of a multisite refinery network. The main feature of the chapter is the development of a simultaneous analysis strategy for process network integration through a mixed-integer linear program (MILP). The performance of the proposed model in this chapter is tested on several industrial-scale examples to illustrate the economic potential and trade-offs involved in the optimization of the network. 

---