Crude oil steam cracking

Kureha crude oil steam cracking technology was devdoped jointly with Union Carbide for the manufacture of ethylene (see Section 2.13.4). By operating at very temperature and with very short xomact dmes (0LOO3 to 0.010 s), approximately equal amounts of acetylene and ethylene can be produced from a number of crude oils. This is illustrated by Table 52 for Indonesian and Arabian crudes, cracked in the presence of steam at 2000 in a steam to feed weight rado of about 5, and with residence time of O.OOS s. In these conditions, the temperature at the reactor exit before quench reaches 1150-C. /... 

PkoDI-CTTO.V OF ACETYLENE AS a BY-WtODUCT OF THE MANT-TACTVTJRE OF ETHYLENE - BY THE K Li REHA CRUDE OIL STEAM CRACKING PROCESS ECONOMIC DATA -... 

To illustrate the economics of the approach being considered, we have considered a case in which 1 billion lbs/year of ethylene is produced from whole Kuwait crude using an H-Oil/steam cracking combination. Figure 4 presents the over-all process flow for this operation. Crude oil... 

Typically, thermal crackers are fed with residues from the two distillation processes of the crude oil. Steam crackers are primarily fed with light naphtha and other light hydrocarbons. After their preheating, often feedstocks are sent through a rising tube into the cracker s furnace area. Furnace temperature and feedstock retention time is carefully set, depending on the desired outcome of the cracking process. Retention time varies from fractions of a second to some minutes. 

Properly speaking, steam cracking is not a refining process. A key petrochemical process, it has the purpose of producing ethylene, propylene, butadiene, butenes and aromatics (BTX) mainly from light fractions of crude oil (LPG, naphthas), but also from heavy fractions hydrotreated or not (paraffinic vacuum distillates, residue from hydrocracking HOC). 

Selecting the naphtha type can be an important processing procedure. For example, a paraffinic-base naphtha is a better feedstock for steam cracking units because paraffins are cracked at relatively lower temperatures than cycloparaffins. Alternately, a naphtha rich in cycloparaffins would be a better feedstock to catalytic reforming units because cyclo-paraffins are easily dehydrogenated to aromatic compounds. Table 2-5 is a typical analysis of naphtha from two crude oil types. 

Liquid feedstocks for olefin production are light naphtha, full range naphtha, reformer raffinate, atmospheric gas oil, vacuum gas oil, residues, and crude oils. The ratio of olefins produced from steam cracking of these feeds depends mainly on the feed type and, to a lesser extent, on the operation variables. For example, steam cracking light naphtha produces about twice the amount of ethylene obtained from steam cracking vacuum gas oil under nearly similar conditions. Liquid feeds are usually... 

Crude oil processing is mainly aimed towards the production of fuels, so only a small fraction of the products is used for the synthesis of olefins and aromatics. In Chapter 3, the different crude oil processes are reviewed with special emphasis on those conversion techniques employed for the dual purpose of obtaining fuels as well as olefmic and aromatic base stocks. Included also in this chapter, are the steam cracking processes geared specially for producing olefins and diolefms. 

Kureha/Union Carbide A process for cracking crude oil to olefins and aromatic hydrocarbons, using steam superheated to 2,000°C. Reaction time is only 15 to 20 milliseconds. 

Crude oil fractionators are an example of a more elaborate system. They make several products as side streams and usually have some pumparound reflux in addition to top reflux which serve to optimize the diameter of the tower. Figure 3.13 is of such a tower operating under vacuum in order to keep the temperature below cracking conditions. The side streams, particularly those drawn off atmospheric towers, often are steam stripped in external towers hooked up to the main tower in order to remove lighter components. These strippers each have four or five trays, operate... 

Vanadium is present in crudes mainly in the +4 state (58). In fact, up to 50% of the total vanadium in crude oil can be found as V02+ in organometallic compounds such as porphyrins and naphthenates (59-63). During the cracking reaction in a FCCU, these compounds deposit V (probably in the form of VO+2 cations) on the catalyst surface. Then, after steam-stripping and catalyst regeneration, formation of V+5 surface phases occur. The effects of vanadium on FCC properties are more severe than any of the other metals present in petroleum feedstocks. In fact, vanadium causes an irreversible loss of cracking activity which is the result of a decrease in crystallinity, pore volume and surface area of the catalyst, Figure 5. 

The gaseous mixture recovered contains a large nuinber of compound which must be isolated and purified. This is because, whereas the basic steam cracking product is ethylene, the upgrading of the other hydrocarbons formed, particulariy in the treatment of liquid petroleum fractions, is indispensable for sound installation management. This trend received a strong impetus from the increase in crude oil prices. 

Water and often fine sand and silt are held in various crude oils in permanent emulsions. Particularly crudes obtained by secondary methods and those from tar sands where water or steam are used contain water and mineral matter emulsified therein by the surface forces on small particles and drops. Azeotropic distillation removes the relatively small amount of water, using the solvent as an entrainer which dilutes the crude. This allows the mineral matter to be separated easily without using centrifuges with their substantial cost and wear, free of organic material, so it may be discarded with-out hazards of fire or odors the bitumen to be recovered for such use or cracked to give volatile fractions and coked to an ash-free coke the water to be obtained as distilled water for reuse. 

The plant locations and capacity are listed in Table 1.7. Most of the Chinese plants are old, with capacities below 200,000 t/y. Many of these plants were designed to use gas-oil and naphtha as feedstock. This takes advantage of some of China s indigenous crude oil, which have high levels of paraffin wax in the gas-oil fractions. In steam cracking, such gas-oils give high yields of ethylene and propylene. Newer plants... 

The high temperature process is the only commercially proven process for the production of olefins and liquids from coal. Current developments favour a low temperature process which is commercially proven to produce liquids and wax from coal or gas. The low temperature process produces a waxy synthetic crude oil which is cracked to produce diesel of high cetane and naphtha. The naphtha, which has high level of Unear paraffins, is sold on the petrochemical naphtha market rather than conversion into gasoline. The conversion of this naphtha into olefins by steam cracking has been addressed in previous chapters. 

Table 31 provides some details of zeolite catalyst usage. The best kuowu is that of zeohte Y as a fluidized bed catalyst (FCC) to crack crude oil for gasoliue production. The zeohte is used as a promoter aud comprises up to 50% of a small composite with a clay or silica binder. As such it can remain stable throughout many cycles in the catalyst riser (at 480-520 °C), where it meets the downstream of crude oil followed by a steam blast to release the cracking products, and then a stream of air in a regenerator (590-730 °C). This regeneration process cleans the catalyst of coke and the residual oil products. 

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