PETROCHEMICAL CRACKER

Details are given of a visit by RECOUP to BP Chemical s feedstock recycling demonstration unit in Sunbury. The feedstock recycling technology has been developed by a consortium of companies, and will enable polyolefin rich plastic waste from domestic and commercial sources to be vapourised and then condensed to form a hydrocarbon wax. This can then be used to feed existing petrochemical crackers to produce polymers indistinguishable from virgin material, it is claimed. 

They are classified apart in this text because their use differs from that of petroleum solvents they are used as raw materials for petrochemicals, particularly as feeds to steam crackers. Naphthas are thus industrial intermediates and not consumer products. Consequently, naphthas are not subject to governmental specifications, but only to commercial specifications that are re-negotiated for each contract. Nevertheless, naphthas are in a relatively homogeneous class and represent a large enough tonnage so that the best known properties to be highlighted here. 

Propylene has many commercial and potential uses. The actual utilisation of a particular propylene supply depends not only on the relative economics of the petrochemicals and the value of propylene in various uses, but also on the location of the supply and the form in which the propylene is available. Eor example, economics dictate that recovery of high purity propylene for polymerisation from a smaH-volume, dilute off-gas stream is not feasible, whereas polymer-grade propylene is routinely recovered from large refineries and olefins steam crackers. A synthetic fuels project located in the western United States might use propylene as fuel rather than recover it for petrochemical use a plant on the Gulf Coast would recover it (see Euels, synthetic). 

The major aromatics (organics having at least one ring structure with six carbon atoms) manufactured include benzene, toluene, xylene, and naphthalene. Other aromatics manufactured include phenol, chlorobenzene, styrene, phthalic and maleic anhydride, nitrobenzene, and aniline. Benzene is generally recovered from cracker streams at petrochemical plants and is used for the manufacture of phenol, styrene, aniline, nitrobenzene, sulfonated detergents, pesticides such as hexachlorobenzene, cyclohexane (an important intermediate in synthetic fiber manufacture), and caprolactam, used in the manufacture of nylon. Benzene is also used as a general purpose solvent. 

Compounds considered carcinogenic that may be present in air emissions include benzene, butadiene, 1,2-dichloroethane, and vinyl chloride. A typical naphtha cracker at a petrochemical complex may release annually about 2,500 metric tons of alkenes, such as propylenes and ethylene, in producing 500,000 metric tons of ethylene. Boilers, process heaters, flares, and other process equipment (which in some cases may include catalyst regenerators) are responsible for the emission of PM (particulate matter), carbon monoxide, nitrogen oxides (200 tpy), based on 500,000 tpy of ethylene capacity, and sulfur oxides (600 tpy). 

The success of Linde s process and engineering contracting business is discussed. Its proprietary technology includes petrochemical projects, largely ethylene crackers, which account for roughly half of its sales, and over 300 processes protected by 1500 patents. 

The petrochemical products from olefins plants are ethylene, propylene, C4 s (butanes, butylenes, and butadiene) and a stream containing the BTXs, Refinery cat.crackers produce propylene and C4S. They produce some ethylene, but often it is not recovered. 

In 2000 two major petrochemical companies installed process NMR systems on the feed streams to steam crackers in their production complexes where they provided feed forward stream characterization to the Spyro reactor models used to optimize the production processes. The analysis was comprised of PLS prediction of n-paraffins, /xo-paraffins, naphthenes, and aromatics calibrated to GC analysis (PINA) with speciation of C4-C10 for each of the hydrocarbon groups. Figure 10.22 shows typical NMR spectral variability for naphtha streams. Table 10.2 shows the PLS calibration performance obtained with cross validation for... 

Steam crackers provide the traditional cost-effective approach for olefins production from lighter feed stocks such ethane, propane, naphtha, and AGO. However, these options typically provide higher E/P ratio. To meet the increasing demands of ethylene and particularly propylene, refiners and petrochemical producers are planning integrated facilities. The objectives are ... 

A major current refinery-petrochemical project is under construction for Saudi Aramco-Sumitomo Chemical at their Rabigh, KSA site. In conjunction with our JGC partner we have linked the upstream refinery expansion to a combined mega-DCC unit and mega-ethane steam cracker. Corresponding production rates are 1500 kta ethylene/950 kta propylene. The corresponding integrated layout is shown below in Figure 8.2. 

Trends in Cracker Technology, European Petrochemical Association, 2nd Meeting, Knokke, Belgium, Oct. 1968. 

Together with China Petroleum Chemical Corp. (Sinopec) in a 50-50 partnership, BASF planned to build its first Verbund project in East Asia - an integrated petrochemical site (IPS) on 220 hectares of land. The core of the project was an ethylene cracker with a capacity of 600,000 tons per year. Nine new plants downstream would be supplied by the cracker, producing 1.7 million metric tons of chemical products for local consumption, including ethylene, aromatics, poly-ethylenes, ethylene oxide and ethylene glycols, acrylic acid, acrylates, oxo alcohols, formic acid, propionic acid, methylamine, and dimethylformamide. 

Priority action was required in petrochemicals, in the large thermoplastics, in fertilizers, and in synthetic fibers where the most serious investment mistakes had been made. The hardest cases were those of petrochemicals and thermoplastics. For one thing, a steam cracker cannot technically operate under 60 percent of its capacity. For another, the products that emerge are linked to one another in almost invariable proportions. Finally, a polymerization unit cannot have its pace slowed down without this affecting the upstream monomer unit to the same extent. 

The 1983 agreement between ENI and Montedison put some order in Italy s chemical industry, as ENI took over the PVC and polyethylene operations of Montedison. Previously in France, Rhone-Poulenc had sold its petrochemicals division and its thermoplastics to the Elf Aquitaine group. At the same time, steam crackers were being shut down in Feyzin and Lavera, and a vinyl chloride unit in Jarrie. The association between BP Chimie and Atochem in polypropylene and the exchange of Atochem s Chocques unit for ICI s Rozenburg polyethylene unit were other instances of rationalization. 

Another UOP zeolitic process that produces petrochemical feedstocks is the MaxEne process (27). The MaxEne process, another member of the Sorbex family of processes, separates C5 to Cn full-range naphtha into an extract stream containing more than 90 wt-% normal paraffins and a raffinate stream containing over 99 wt-% non-normals, namely isoparaffins plus naphthenic and aromatic hydrocarbons. The high normal-paraffin content of the extract makes it a preferred feedstock for a naphtha steam cracker, and the absence of normal paraffins in the raffinate makes it a preferred feedstock for catalytic reforming. 

The appeal of an acetic acid process, based on ethane oxidation, lies mostly in the absence of the need for the energy demanding step for syngas production. On the other hand, it has to compete not only with the well established methanol carbonylation (Section 4.2), but also with the current utilization of ethane in steam crackers for ethylene manufacture. In fact, ethane feedstock becomes attractive for acetic acid production if it is locally abundant and can be supplied at minimal cost, e.g., in a petrochemical complex close to a large gas field. The construction of a semi-commercial plant of 30 kt/a in the Persian Gulf region has been announced. 

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