Abstract:
An aromatics complex flow scheme has been developed in which C 7 -C 8  aliphatic hydrocarbons are recycled to an isomerization unit of a xylene recovery zone to increase the efficiency of the isomerization unit. This improvement results in an aromatics complex with savings on capital and utility costs and an improvement on the return on investment.

Description:
FIELD OF THE INVENTION 
     This invention relates to an aromatics complex flow scheme, which is a combination of process units that can be used to convert naphtha into basic petrochemical intermediates of benzene, toluene, and xylene. Based on a metal catalyzed transalkylation process that handles unextracted toluene and heavier aromatics and an olefin saturation process, the improved flow scheme removes items of equipment and processing steps, such as a deheptanizer column, resulting in significant economic benefits when producing para-xylene. Furthermore, the improved flow scheme improves the efficiency of the isomerization unit through the addition of a stream rich in C 7  and C 8  aliphatic hydrocarbons. 
     BACKGROUND OF THE INVENTION 
     Most new aromatics complexes are designed to maximize the yield of benzene and para-xylene. Benzene is a versatile petrochemical building block used in many different products based on its derivation including ethylbenzene, cumene, and cyclohexane. Para-xylene is also an important building block, which is used almost exclusively for the production of polyester fibers, resins, and films formed via terephthalic acid or dimethyl terephthalate intermediates. Accordingly, an aromatics complex may be configured in many different ways depending on the desired products, available feedstocks, and investment capital available. A wide range of options permits flexibility in varying the product slate balance of benzene and para-xylene to meet downstream processing requirements. 
     A prior art aromatics complex flow scheme has been disclosed by Meyers in the  Handbook of Petroleum Refining Processes,  2d. Edition in 1997 by McGraw-Hill. 
     U.S. Pat. No. 3,996,305 to Berger discloses a fractionation scheme primarily directed to transalkylation of toluene and C 9  alkylaromatics in order to produce benzene and xylene. The transalkylation process is also combined with an aromatics extraction process. The fractionation scheme includes a single column with two streams entering and with three streams exiting the column for integrated economic benefits. 
     U.S. Pat. No. 4,341,914 to Berger discloses a transalkylation process with recycle of C 10  alkylaromatics in order to increase yield of xylenes from the process. The transalkylation process is also preferably integrated with a para-xylene separation zone and a xylene isomerization zone operated as a continuous loop receiving mixed xylenes from the transalkylation zone feedstock and effluent fractionation zones. 
     U.S. Pat. No. 4,642,406 to Schmidt discloses a high severity process for xylene production that employs a transalkylation zone that simultaneously performs as an isomerization zone over a nonmetal catalyst. High quality benzene is produced along with a mixture of xylenes, which allows para-xylene to be separated by absorptive separation from the mixture with the isomer-depleted stream being passed back to the transalkylation zone. 
     U.S. Pat. No. 5,417,844 to Boitiaux et al. discloses a process for the selective dehydrogenation of olefins in steam cracking petrol in the presence of a nickel catalyst and is characterized in that prior to the use of the catalyst, a sulfur-containing organic compound is incorporated into the catalyst outside of the reactor prior to use. 
     U.S. Pat. No. 5,658,453 to Russ et al. discloses an integrated reforming and olefin saturation process. The olefin saturation reaction uses a mixed vapor phase with addition of hydrogen gas to a reformate liquid in contact with a refractory inorganic oxide containing preferably a platinum-group metal and optionally a metal modifier. 
     U.S. Pat. No. 5,763,720 to Buchanan et al. discloses a transalkylation process for producing benzene and xylenes by contacting a C 9   +  alkylaromatics with benzene and/or toluene over a catalyst comprising a zeolite such as ZSM-12 and a hydrogenation noble metal such as platinum. Sulfur or stream is used to treat the catalyst. 
     U.S. Pat. No. 5,847,256 to Ichioka et al. discloses a process for producing xylene from a feedstock containing C 9  alkylaromatics with the aid of a catalyst with a zeolite that is preferably mordenite and with a metal that is preferably rhenium. 
     U.S. Pat. No. 6,740,788 discloses an aromatics complex flow scheme which, as compared to a traditional complex, removes items of equipment and processing steps such as a reformate splitter column and a heavy aromatics column. 
     The present invention provides an aromatics complex flow scheme arranged and operated so that a traditional deheptanizer column in the xylenes recovery section may be eliminated. With this invention, capital costs are reduced, operating costs are reduced, and the yield of C 8  aromatics is improved. Furthermore, the efficiency of the isomerization unit is increased through the addition of a stream rich in C 7  and C 8  aliphatic hydrocarbons. 
     SUMMARY OF THE INVENTION 
     An aromatics complex flow scheme having a reformate splitter fractionation zone operated so that toluene and lighter materials are removed in an overhead which is substantially free of C 4  and lighter hydrocarbons and gasses, and which allows for the recycle of an entire isomerization unit effluent to the reformate splitter fractionation zone without passing the effluent though a deheptanizer column. Introducing a stream rich in C 7  and C 8  aliphatic hydrocarbons to the isomerization unit allows the unit to operate more efficiently and at a lower temperature. Some of the aliphatic hydrocarbons are converted to lighter aliphatic hydrocarbons and aromatics thereby increasing the overall yield of the process. C 8  aliphatic hydrocarbons do not build up in the xylenes recovery zone since they are removed in the reformate splitter fractionation zone. Another embodiment of the present invention comprises an apparatus that is based on the process steps, which efficiently converts naphtha into para-xylene. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       The FIGURE shows an aromatics complex flow scheme of the present invention, which includes operating the reformate splitter fractionation zone to generate an overhead stream containing toluene and lighter components and a bottoms stream containing xylenes and heavier components. A stream rich in C 7  and C 8  aliphatic hydrocarbons separated by extractive distillation from the reformate splitter fractionation zone overhead is recycled to the isomerization unit. The aromatics complex of the present invention does not include a deheptanizer column. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Feed to the complex may be naphtha, but can also be pygas, imported mixed xylene, or imported toluene. Naphtha fed to an aromatics complex is first hydrotreated to remove sulfur and nitrogen compounds to less than about 0.5 wt-ppm before passing the treated naphtha on to a reforming unit  13 . Naphtha hydrotreating occurs by contacting naphtha in a line  10  with a naphtha hydrotreating catalyst under naphtha hydrotreating conditions in a unit  11 . The naphtha hydrotreating catalyst is typically composed of a first component of cobalt oxide or nickel oxide, along with a second component of molybdenum oxide or tungsten oxide, and a third component inorganic oxide support, which is typically a high purity alumina. Generally good results are achieved when the cobalt oxide or nickel oxide component is in the range of about 1 to about 5 wt-% and the molybdenum oxide component is in the range of about 6 to about 25 wt-%. The alumina (or aluminum oxide) is set to balance the composition of the naphtha hydrotreating catalyst to sum all components up to 100 wt-%. One hydrotreating catalyst for use in the present invention is disclosed in U.S. Pat. No. 5,723,710, the teachings of which are incorporated herein by reference. Typical hydrotreating conditions include a liquid hourly space velocity (LHSV) from about 1.0 to about 5.0 hr −1 , a ratio of hydrogen to hydrocarbon (or naphtha feedstock) from about 50 to about 135 Nm 3 /m 3 , and a pressure from about 10 to about 35 kg/cm 2 . 
     In the reforming unit  13 , paraffins and naphthenes are converted to aromatics. This is the only unit in the complex that actually creates aromatic rings. The other units in the complex separate the various aromatic components into individual products and convert various aromatic species into higher-value products. The reforming unit  13  is usually designed to run at very high severity, equivalent to producing about 100 to about 106 Research Octane Number (RONC) gasoline reformate, in order to maximize the production of aromatics. This high severity operation yields very low non-aromatic impurities in the C 8   +  fraction of reformate, and eliminates the need for extraction of the C 8  and C 9  aromatics. 
     In the reforming unit  13 , hydrotreated naphtha from a line  12  is contacted with a reforming catalyst under reforming conditions. The reforming catalyst is typically composed of a first component platinum-group metal, a second component modifier metal, and a third component inorganic-oxide support, which is typically high purity alumina. Generally good results are achieved when the platinum-group metal is in the range of about 0.01 to about 2.0 wt-% and the modifier metal component is in the range of about 0.01 to about 5 wt-%. The alumina is set to balance the composition of the naphtha hydrotreating catalyst to sum all components up to 100 wt-%. The platinum-group metal is selected from platinum, palladium, rhodium, ruthenium, osmium, and iridium. The preferred platinum-group metal component is platinum. The metal modifiers may include rhenium, tin, germanium, lead, cobalt, nickel, indium, gallium, zinc, uranium, dysprosium, thallium, and mixtures thereof. One reforming catalyst for use in the present invention is disclosed in U.S. Pat. No. 5,665,223, the teachings of which are incorporated herein by reference. Typical reforming conditions include a liquid hourly space velocity from about 1.0 to about 5.0 hr −1 , a ratio of hydrogen to hydrocarbon from about 1 to about 10 moles of hydrogen per mole of hydrocarbon feed entering the reforming zone, and a pressure from about 2.5 to about 35 kg/cm 2 . Hydrogen produced in the reforming unit  13  exits in a line  14 . A debutanizer is part of the reforming unit and the debutanizer is operated to separate and remove gases and C 4  and lighter hydrocarbons. Therefore the reformate will be substantially free of gases and C 4  and lighter hydrocarbons. The term “substantially free” is meant herein to define the stream as containing no greater than 5 mass-% of gases and C 4  and lighter hydrocarbons and preferably no greater than 1 mass-% of gases and C 4  and lighter hydrocarbons. 
     An optional clay treater (not shown) may be used to treat residual olefin contaminants. In the clay treater, olefins will be polymerized, often to C 11 +, which is removed downstream in the aromatics complex. 
     The reformate comprising aromatics, non-aromatics, and which is substantially free of gases and C 4  and lighter hydrocarbons in a line  9  is combined with an ethylbenzene dealkylation and isomerization unit effluent in a line  18  and sent to a reformate splitter fractionation zone  54  via a line  19 . The reformate splitter fractionation zone  54  generally comprises at least one fractionation column. The reformate splitter fractionation zone  54  produces a toluene and lighter fraction which contains toluene and benzene, and lighter hydrocarbons including C 8 , C 7 , and lighter aliphatic hydrocarbons in a line  21  and a xylenes-plus-enriched fraction which contains xylenes, heavier aromatics and C 9  and heavier aliphatic hydrocarbons in a line  22 . The xylene-plus-enriched stream in line  22  from the bottom of the reformate splitter fractionation zone  54  is sent to a xylene recovery section  55  (described below) of the aromatics complex. 
     Line  21  containing toluene and lighter hydrocarbon is sent to a main distillation column  27  of an aromatic extraction zone which produces a benzene and toluene product stream in bottoms stream  29 ; rejects a by-product raffinate stream in a line  28 ; and produces a C 7 -C 8  aliphatic stream in line  61 . The raffinate stream comprising contaminates that are lighter than or co-boiling with benzene may be blended into gasoline, used as feedstock for an ethylene plant, or converted into additional benzene by recycling to the reforming unit  13 . The use of extractive distillation instead of liquid-liquid extraction or combined liquid-liquid extraction/extractive distillation processes may result in an economic improvement. However, liquid-liquid extraction is a suitable alternative. 
     Extractive distillation is a technique for separating mixtures of components having nearly equal volatility and having nearly the same boiling point. It is difficult to separate the components of such mixtures by conventional fractional distillation. In extractive distillation, a solvent is introduced into a main distillation column above the entry point of the hydrocarbon-containing fluid mixture that is to be separated. The solvent affects the volatility of the hydrocarbon-containing fluid component boiling at a higher temperature differently than the hydrocarbon-containing fluid component boiling at a lower temperature sufficiently to facilitate the separation of the various hydrocarbon-containing fluid components by distillation and such solvent exits with the bottoms fraction. Suitable solvents include tetrahydrothiophene 1,1-dioxide (or sulfolane), diethylene glycol, triethylene glycol, or tetraethylene glycol. The raffinate stream in line  28  comprising nonaromatic compounds exits overhead of the main distillation column, while the bottoms fraction containing solvent and benzene exits below. Often the raffinate will be sent to a wash column (not shown) in order to be contacted with a wash fluid such as water and thus remove any residual dissolved solvent. The side-cut C 7 -C 8  aliphatic hydrocarbon stream in line  61  may be passed through a trace solvent removal zone  62  in order to remove residual dissolved solvent. The substantially solvent free stream in line  63  is introduced to an isomerization unit  51 , discussed in detail below. The substantially solvent free stream contains no more than 10 ppm solvent and preferably no more than 1 ppm solvent. In one embodiment of the invention the trace solvent removal zone  62  is a wash column and in another embodiment of the invention the trace solvent removal zone  62  is a water wash column. 
     In an alternate embodiment, the extractive distillation zone may contain two or more columns with a main extractive distillation column as described above and one or more fractional distillation columns. In this embodiment, the overhead from the extractive distillation column would contain the non-aromatic hydrocarbons including the C 7 -C 8  aliphatic hydrocarbons that were removed in a side-cut stream in the embodiment described in the previous paragraph. A solvent removal unit (not shown) may be used to separate and recycle any solvent in the overhead stream. Then a fractional distillation column (not shown) would be used to separate at least some of the C 7 -C 8  aliphatic hydrocarbons from other non-aromatic hydrocarbons and the separated C 7 -C 8  aliphatic hydrocarbons would be conducted to an isomerization zone as discussed below. 
     The bottoms stream  29  from the main distillation column  27  is sent to a solvent recovery column  64 , where benzene and toluene is recovered in overhead line  65  and the solvent is recovered in bottoms  68  which is passed back to the main distillation column  27 . The recovery of high purity benzene and toluene in the overhead line  65  from extractive-distillation and solvent recovery typically exceeds 99 wt-%. Water may be removed from the high purity benzene in overhead line  65  using a benzene dryer column  56  to produce a dry benzene product stream  57 . Water is removed from benzene dryer column  56  in line  67 . Toluene is also separated from benzene in benzene dryer column  56 . The toluene is removed in line  66 . Toluene in line  66  is recycled to transalkylation unit  36  or is combined with line  6  for recycle to transalkylation unit  36  to form additional xylenes. 
     The toluene overhead from toluene column  8  is passed to transalkylation unit  36  via line  6 . Before being introduced into transalkylation unit  36 , the toluene in line  6  is usually combined with a stream rich in C 9  and C 10  alkylaromatics in a line  41  produced by a heavy aromatics column  3  and charged via a line  34  to the transalkylation unit  36  for production of additional xylenes and benzene. Also, as discussed earlier, the toluene in line  66  from benzene dryer column  56  may be combined with line  6 . Alternatively, each of lines  6 ,  66 , and line  41  can be independently introduced into transalkylation unit  36  without first being combined. 
     In transalkylation unit  36 , the feed is contacted with a transalkylation catalyst under transalkylation conditions. The preferred catalyst is a metal stabilized transalkylation catalyst. Such catalyst comprises a zeolite component, a metal component, and an inorganic oxide component. The zeolite component typically is either a pentasil zeolite, which include the structures of MFI, MEL, MTW, MTT and FER (IUPAC Commission on Zeolite Nomenclature), a beta zeolite, or a mordenite. Preferably it is mordenite zeolite. The metal component typically is a noble metal or base metal. The noble metal is a platinum-group metal is selected from platinum, palladium, rhodium, ruthenium, osmium, and iridium. The base metal is selected from the group consisting of rhenium, tin, germanium, lead, cobalt, nickel, indium, gallium, zinc, uranium, dysprosium, thallium, and mixtures thereof. The base metal may be combined with another base metal, or with a noble metal. Preferably the metal component comprises rhenium. Suitable metal amounts in the transalkylation catalyst range from about 0.01 to about 10 wt-%, with the range from about 0.1 to about 3 wt-% being preferred, and the range from about 0.1 to about 1 wt-% being highly preferred. Suitable zeolite amounts in the catalyst range from about 1 to about 99 wt-%, preferably between about 10 to about 90 wt-%, and more preferably between about 25 to about 75 wt-%. The balance of the catalyst is composed of inorganic oxide binder, preferably alumina. One transalkylation catalyst for use in the present invention is disclosed in U.S. Pat. No. 5,847,256, which is hereby incorporated by reference 
     Conditions employed in the transalkylation unit normally include a temperature of from about 200° to about 540° C. The transalkylation zone is operated at moderately elevated pressures broadly ranging from about 1 to about 60 kg/cm 2 . The transalkylation reaction can be effected over a wide range of space velocities, with higher space velocities effecting a higher ratio of para-xylene at the expense of conversion. Liquid hourly space velocity generally is in the range of from about 0.1 to about 20 hr −1 . The feedstock is preferably transalkylated in the vapor phase and in the presence of hydrogen supplied via a line  35 . If transalkylated in the liquid phase, then the presence of hydrogen is optional. If present, free hydrogen is associated with the feedstock and recycled hydrocarbons in an amount of about 0.1 moles per mole of alkylaromatics up to about 10 moles per mole of alkylaromatic. This ratio of hydrogen to alkylaromatic is also referred to as hydrogen to hydrocarbon ratio. 
     The effluent from the transalkylation unit  36  is sent to the transalkylation stripper fractionation zone  52  through line  17 . In transalkylation stripper fractionation zone  52  the LPG and gasses are removed via line  2  with the benzene, toluene, and heavier hydrocarbons being conducted from transalkylation stripper fractionation zone  52  in line  1 . Line  1  is combined with line  66  from benzene dryer column  56 , and the combination is introduced into toluene column  8 . Alternatively, the streams may be introduced to toluene column  8  independently. In general, in embodiments were streams are being combined prior to being introduced into units of the process it is also acceptable for the streams to be individually introduced into the units without being combined. 
     The xylene recovery section  55  of the aromatics complex comprises at least one xylene column  39 , and generally will further include a process unit for separation of at least one xylene isomer, which is typically the para-xylene product from the aromatics complex. Preferably such a para-xylene separation zone  43  is operated in conjunction with an isomerization unit  51  for isomerization of the remaining alkylaromatic compounds back to an equilibrium or near equilibrium mixture containing para-xylene, which can be recycled for further recovery in a loop-wise fashion. Accordingly, the xylene-plus-enriched stream in line  22  from the reformate splitter fractionation zone  54  is charged to xylene column  39 . The xylene column  39  is designed to conduct an overhead feed stream in line  40  to the para-xylene separation zone  43  the overhead feed stream having very low levels of C 9  alkylaromatics (A 9 ) concentration. A 9  compounds may build up in a desorbent circulation loop within the para-xylene separation zone  43 , so it is more efficient to remove this material upstream in xylene column  39 . The overhead feed stream in line  40  from the xylene column  39  is charged directly to the para-xylene separation zone  43 . 
     Material from the lower part of the xylene column  39  is withdrawn as a bottoms stream which is rich in both C 11 + materials and in C 9  and C 10  alkylaromatics via the line  38 . The mixture of C 11 + materials and C 9  and C 10  alkyl aromatics in line  38  is introduced into heavy aromatics column  3  where an overhead stream rich in C 9  and C 10  alkyl aromatics line  41  is separated from a bottoms stream rich in C 11 + materials  42 . The overhead stream rich in C 9  and C 10  alkyl aromatics sent to the transalkylation zone  36  for production of additional xylenes and benzene. 
     Alternatively, if ortho-xylene is to be produced in the complex, the xylene column is designed to make a split between meta- and ortho-xylene and drop a targeted amount of ortho-xylene to the bottoms. The xylene column bottoms are then sent to an ortho-xylene column (not shown) where high purity ortho-xylene product is recovered overhead. Material from the bottom of the ortho-xylene column is withdrawn as a stream rich in C 9  and C 10  alkylaromatics and C 11   +  material and is passed to heavy aromatics column  3  as discussed above. 
     The para-xylene separation zone  43  may be based on a fractional crystallization process or an adsorptive separation process, both of which are well known in the art, and preferably is based on the adsorptive separation process. Such adsorptive separation can recover highly pure para-xylene in a line  44  at high recovery per pass. Any residual toluene in the feed to the separation unit is extracted along with the para-xylene, fractionated out in a finishing column  58 , and then optionally recycled to the transalkylation unit  36  via line  59 . Having finishing column  58  allows for optimization and flexibility in operating the xylene column  39  since any toluene in the overhead from the xylene column would be removed from the para-xylene product in the finishing column  58  and recycled to the transalkylation unit  36 . Very high purity para-xylene product, as high as greater than 99 wt-% pure para-xylene, is removed from the process in line  60 . 
     The raffinate  45  from the para-xylene separation zone  43  is almost entirely depleted of para-xylene, to a level usually of less than 1 wt-%. Hydrogen and the raffinate  45  is sent to the alkylaromatic isomerization unit  51 , where additional para-xylene is produced by reestablishing an equilibrium or near-equilibrium distribution of xylene isomers. Any ethyl benzene in the para-xylene separation unit raffinate  45  is either converted to additional xylenes, transalkylated to a C 9  aromatic, or converted to benzene by dealkylation, depending upon the type of isomerization catalyst used. As discussed above, a stream of C 7 -C 8  aliphatic hydrocarbons is also introduced into isomerization unit  51 . Since C 7  and C 8  aliphatic hydrocarbons are intermediates in the conversion of ethyl benzene to xylenes, the presence of the C 7 -C 8  aliphatic hydrocarbons in the reaction mixture allows for the conversion of any ethyl benzene to xylene to happen more rapidly. The C 7 -C 8  aliphatic hydrocarbons further allow for the unit to be successfully operated at a lower temperature. 
     In the alkylaromatic isomerization unit  51 , the raffinate  45  is contacted with an isomerization catalyst under isomerization conditions. The isomerization catalyst is typically composed of a molecular sieve component, a metal component, and an inorganic oxide component. Selection of the molecular sieve component allows control over the catalyst performance between ethylbenzene isomerization and ethylbenzene dealkylation depending on overall demand for benzene. Consequently, the molecular sieve may be either a zeolitic aluminosilicate or a non-zeolitic molecular sieve. The zeolitic aluminosilicate (or zeolite) component typically is either a pentasil zeolite, which include the structures of MFI, MEL, MTW, MTT and FER (IUPAC Commission on Zeolite Nomenclature), a beta zeolite, or a mordenite. The non-zeolitic molecular sieve is typically one or more of the AEL framework types, especially SAPO-11, or one or more of the ATO framework types, especially MAPSO-31, according to the “Atlas of Zeolite Structure Types” (Butterworth-Heineman, Boston, Mass., 3rd ed. 1992). The metal component typically is a noble metal component, and may include an optional base metal modifier component in addition to the noble metal or in place of the noble metal. The noble metal is a platinum-group metal is selected from platinum, palladium, rhodium, ruthenium, osmium, and iridium. The base metal is selected from the group consisting of rhenium, tin, germanium, lead, cobalt, nickel, indium, gallium, zinc, uranium, dysprosium, thallium, and mixtures thereof. The base metal may be combined with another base metal, or with a noble metal. Suitable total metal amounts in the isomerization catalyst range from about 0.01 to about 10 wt-%, with the range from about 0.1 to about 3 wt-% preferred. Suitable zeolite amounts in the catalyst range from about 1 to about 99 wt-%, preferably between about 10 to about 90 wt-%, and more preferably between about 25 to about 75 wt-%. The balance of the catalyst is composed of inorganic oxide binder, typically alumina. One isomerization catalyst for use in the present invention is disclosed in U.S. Pat. No. 4,899,012, the teachings of which are incorporated herein by reference. 
     Typical isomerization conditions include a temperature in the range from about 0° to about 600° C. and a pressure from atmospheric to about 50 kg/cm 2 . The liquid hourly hydrocarbon space velocity of the feedstock relative to the volume of catalyst is from about 0.1 to about 30 hr −1 . The hydrocarbon contacts the catalyst in admixture with a gaseous hydrogen-containing stream in a line  46  at a hydrogen-to-hydrocarbon mole ratio of from about 0.5:1 to 15:1 or more, and preferably a ratio of from about 0.5 to 10. If liquid phase conditions are used for isomerization, then no hydrogen is added to the unit. 
     The effluent from the isomerization unit  51  containing at least a mixture of xylenes is sent via a line  18  to the reformate splitter fractionation zone  54 . There is no need for a traditional deheptanizer column between the isomerization unit and the reformate splitter fractionation zone, the entire effluent of the isomerization unit may be passed to the reformate splitter fractionation zone  54  thereby saving substantial capital costs and ongoing utilities costs. The C 7 -minus hydrocarbons that would have been removed from the xylenes in an overhead of a deheptanizer column are instead passed to the reformate splitter fractionation zone  54  and separated from the xylenes there. 
     Accordingly, the aromatics complex of the present invention displays excellent economic benefits. These improvements result in an aromatics complex with savings in capital costs and operating costs, and an improvement on the return on investment in such a complex.