Thermal cracking of heavy oils

Example 3 Thermal Cracking of Heavy Oils (Visbreaking)... 

M. G. Yang, I. Nakamura and K. Fujimoto. Hydro-thermal cracking of heavy oils and its model compound. Catalysis Today, 43, 273-280 (1998). 

Zaikina, R.F., Zaikin, Y.A., and Nadirov, N.K. 1997. Mechanisms and kinetics of radiation-induced thermal cracking of heavy oil fractions. Oil and Gas, Kazakhstan 2 83-100. 

Furthermore, the analysis of polyaromatic fractions following the reaction (M3 products) showed that these molecules had relatively lower MW, shorter chains and were more aromatic. The results of this woik confirm that side chain fragmentation and hydrogenation/dehydrogenation reactions are major routes in the thermal cracking of heavy oils and bitumen (see Tables 9-10). 

The thermal chemistry of heavy oils and bitumen is extremely complicated because of wide variations in chemical compositions. The most refractory components in petroleum feedstocks are asphaltenes, which contribute the most to coke formation dining thermal cracking. Next to asphaltenes, resins and large aromatics also contribute to coke. To investigate the effect of these three heavy oil components on the mesophase induction period, Athabasca bitumen fractions containing varying amounts of asphaltenes (obtained by supercritical fluid extraction) and Venezuelan heavy... 

Not only do oil and gas engineering systems handle very complex mixtures, but they also operate within exceptionally wide ranges of pressure and temperature conditions. Extremely low temperatures are required in liquefied natural gas (LNG) applications, while very high temperatures are needed for thermal cracking of heavy hydrocarbon molecules. Between these two extremes, hydrocarbon fluids are found underground at temperatures that can reach 90 °C or more, while surface conditions can hover around 20 °C. Pressure can vary from its atmospheric value (or lower in the case of vacuum distillation) to a number in the hundreds of MPa. Due to their complexity, multi-family nature and ample range of conditions, petroleum fluids undergo severe transformations and various phase transitions which include, but not limited to, liquid-vapour, liquid-liquid and liquid-liquid-vapour. 

We will use the results of laboratory investigations into the process of the light thermal cracking of fuel oil and recycle material (Table 30). In this process the recycle material was heavy reflux that boiled in the range 350-500°. The problem was to determine the furnace charge and the yields of the lightcracking products on cracking a mixture of fuel oil and recycle material in the steady state. 

Material balance of light thermal cracking of fuel oil with recycling of the heavy reflux... 

The basic technological diagram of the light thermal cracking of fuel oil with recycling of the heavy reflux in order to produce residue containing cracking petroleum-asphalt was described earlier (Fig. 35). 

Bergius cerlairdy recognised the relationship between his work and the catalytic hydrogenation of heavy cmde oil fractions, relative to the newly introduced thermal cracking. Thermal cracking of cmde oil fractions was first rrsed in refineries aroimd 1911-1912 to increase the yield of gasoline. By about 1924 the... 

In recent years great interest has been focussed on the prepciration and the characterization of different typ>es of pillared clays and also on possible applications for these materials primarily as catalysts or adsorbents. One of the most interesting potential applications for pillared clays is as active components in cracking catalyst formulations designed for cracking of heavy oil fractions. The commercial use of pillared clays for this application has, however, been limited by their lack of thermal and hydrothermal stability. 

Production of maleic anhydride by oxidation of / -butane represents one of butane s largest markets. Butane and LPG are also used as feedstocks for ethylene production by thermal cracking. A relatively new use for butane of growing importance is isomerization to isobutane, followed by dehydrogenation to isobutylene for use in MTBE synthesis. Smaller chemical uses include production of acetic acid and by-products. Methyl ethyl ketone (MEK) is the principal by-product, though small amounts of formic, propionic, and butyric acid are also produced. / -Butane is also used as a solvent in Hquid—Hquid extraction of heavy oils in a deasphalting process. 

FIG. 23-3 Temperature and composition profiles, a) Oxidation of SOp with intercooling and two cold shots, (h) Phosgene from GO and Gfi, activated carbon in 2-in tubes, water cooled, (c) Gumene from benzene and propylene, phosphoric acid on < uartz, with four quench zones, 260°G. (d) Mild thermal cracking of a heavy oil in a tubular furnace, hack pressure of 250 psig and sever heat fluxes, Btu/(fr-h), T in °F. (e) Vertical ammonia svi,ithesizer at 300 atm, with five cold shots and an internal exchanger. (/) Vertical methanol svi,ithesizer at 300 atm, Gr O -ZnO catalyst, with six cold shots totaling 10 to 20 percent of the fresh feed. To convert psi to kPa, multiply by 6.895 atm to kPa, multiply by 101.3. 

Carbon black includes several forms of artificially prepared carbon, such as furnace black, channel black, lamp black, and animal charcoal. It is a finely divided form of carbon consisting of particles of extremely fine size. It is obtained by partial combustion (in 50% required air) of vapors of heavy oil fraction of crude oil in a furnace or by thermal cracking of natural gas. Carbon black is used in many abrasion-resistant rubber products including tire treads and belt covers. It also is used in typewriter ribbons, printing inks, carbon paper, and paint pigments. It also can be an absorber for solar energy and UV radiation. 

Flame color depends on fuel composition. Gas often burns blue, but heavy fuel oil burns yellow. A yellow flame is caused by thermal cracking of the fuel. There is nothing wrong with a yellow flame it is the general shape of the flame which is important. If in doubt as to the right flame shape for a particular furnace, contact the burner manufacturer for details. 

Figure 17.35. Temperature and conversion profiles of mild thermal cracking of a heavy oil in a tubular furnace with a back pressure of 250 pag and at several heat fluxes [Btu/hr(sqft)].

Some authors assume that soot formation is only a result of thermal cracking of a portion of the hydrocarbon (Eq. 57), resulting at least partly from insufficient mixing of the reactants after the burner nozzle. Others relate it partially to the fact that Boudouard limit is reached during cooling down. Ash particles in the heavy oil fractions also seem to act as nuclei of condensation or catalysts (Ni) for soot formation [512], [513],... 

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