Crudes, Thermal Refining

Thermal cracking was the first crude oil refining process to contribute more useful products from a barrel of oil than straight distillation [80]. Houdry s development of catalytic cracking shortly before World War II spurred then Standard Oil of New... 

Other physical properties such as the smoke, flash, and fire points of oils and fats are measures of their thermal stability when heated. The smoke point is important for the oils and fats used for deep-frying. The flash point and fire points are a measure of residual solvent in crude and refined oils and are also a safety requirement. 

Movement of fats and oils may be as the crude, partially refined, or finished oils and may be by rail tank cars, tank trucks, barges, and tanker ships. Rail tank cars are usually of the standard 60,566-L (16,000-gal 120,000-lb) or the jumbo 232,170-L (61,333-gal 460,000-lb) size. Standard cars are designed with a thermal expansion area of about 2% of the total capacity as a dome in the car. However, the rated capacity of the jumbo cars does not include any expansion space. Rather, these cars are equipped with a permanently installed bar marker located in the passageway, above which the quantity of oil should not be loaded. Heating coils can be installed for handling higher melting fats. 

The quality of tar sand bitumen is low compared to that of conventional crude oil and heavy oil. The high carbon residue of bitumen dictates that considerable amounts of coke will be produced during thermal refining (Table 3). 

Thermal refining of the crudes consists of two basic operations i.e. atmospheric and subsequent vacuum distillation. The boiling range of the atmospheric distillates extends to approximately 370 °C and yields the fractions ... 

In crude oil refining, the visbreaker process, the delayed coking process (see Chapter 13.1.2) and thermal cracking are used in the middle-temperature range to convert heavy petroleum residues into lighter gasoline fractions and middle distillates. The aromaticity of the fractions recovered, however, is relatively low. 

The production of lead metal can be divided into two broad areas - the basic smelting operation to produce a crude lead bullion, and the refining operation. Since the sinter plant-blast furnace method of smelting coupled with thermal refining has been the workhorse of the industry they are examined in greater detail herein as a benchmark for other processes. 

There are little or no olefins in crude oil or straight run (direct from crude distillation) products but they are found in refining products, particularly in the fractions coming from conversion of heavy fractions whether or not these processes are thermal or catalytic. The first few compounds of this family are very important raw materials for the petrochemical Industry e.g., ethylene, propylene, and butenes. 

H2S is found with the reservoir gas and dissolved in the crude (< 50 ppm by weight), but it is formed during refining operations such as catalytic cracking, hydrodesulfurization, and thermal cracking or by thermal decomposition of sulfur[Pg.322]

Figure 2 shows a simplified flow plan for a typical conversion type refinery. The atmospheric P/S residuum can be fed to a vacuum pipestill. The vacuum tower enables the refiner to cut deeper into the crude, at the same time avoiding high temperatures (above about 750 °F) which cause thermal cracking with resultant deposition of coke and tarry residues in the equipment. 

Caustic that is added downstream of the crude oil desalter. Caustic is injected downstream of the desalter to control overhead corrosion. Natural chloride salts in crude decompose to HCl at typical unit temperatures. Caustic reacts with these salts to form sodium chloride. Sodium chloride is thermally stable at the temperature found in the crude and vacuum unit heaters. This results in sodium chloride being present in either atmospheric or vacuum resids. Most refiners discontinue caustic injection when they process residue to the FCC unit. It can still be present in purchased feedstocks, however. 

Physical Form. JP-4 is a colorless to straw-colored liquid with the odor of gasoline and/or kerosene. JP-7 is a liquid, usually colorless and with the odor of kerosene. JP-4 can be made by refining either crude petroleum oil or shale oil. It is called a wide cut fuel because it is produced from a broad distillation temperature range and contains a wide array of carbon chain lengths, from 4- to 16. It consists of approximately 13% (v/v) aromatic hydrocarbons, 1.0% olefins, and 86% saturated hydrocarbons. JP-7 is made by refining kerosene, a product of refined crude petroleum. It was developed for use in advanced supersonic jets because of its thermal stability and high flash point. ... 

Also, the tellurium metal can be prepared by thermal reduction of dioxide. However, prior to reduction crude dioxide is refined by successive caustic leaching and neutralization steps mentioned above. 

Crude oil typically contains little to no olefinic compounds. Through refining and processing, however, olefins are produced and become a part of various crude oil fractions. Olefins can be found in thermally cracked and catalytically cracked gasoline fractions as well as in FCC cycle oils and coker gas oils. For this reason, it is not unusual for finished gasoline and distillate blends to contain a high-olefin-content stream. 

Most of these units adopt physical or chemical processes to separate the components and then thermal treatment for smelting and refining. The components are polypropylene (from the cases), lead and lead compounds (from the grids, terminals and paste slurry), acid (from the electrolyte) and other residues (separators, fibres, etc.). Smelting is typically conducted in furnaces designed to produce crude lead. Further refining is used to synthesize a range of alloys to meet specific mechanical, electrical and chemical characteristics. Electrochemical processes are occasionally used. 

Understanding refining chemistry not only allows an explanation of the means by which these products can be formed from crude oil but also offers the luxury of predictability. This is very necessary when the different types of crude oil accepted by refineries are considered. And the major processes by which these products are produced from crude oil constituents involves thermal decomposition. There have been many simplified efforts to represent refining chemistry (Figure 4-4) that, under certain circumstances, are adequate to the task. However, refining is much more complicated than such representations would indicate (Speight, 1999). 

Refining engineers and chemists are most interested in the ease of desulfurizing petroleum using thermal and thermocatalytic treatments. The sulfur is removed primarily as hydrogen sulfide. Thermal and thermocatalytic studies have established that non-thiophenic sulfur (aliphatic as in thiols, acyclic and cyclic sulfides) evolve H2S much more readily than thiophenic sulfur (aromatic heterocyclic compounds). Thus, the relative abundances of nonthiophenic (aliphatic) and thiophenic (aromatic) sulfur is a critical characteristic for all fuels with respect to ease of desulfurization. Analytical methods were developed in the 1960s for classifying the total sulfur in crude... 

Once the synthetic crude oils from coal and oil shale have been upgraded and the heavy ends converted to lighter distillates, further refining by existing processes need not be covered in detail except to note the essential character of the products. The paraffinic syncrude from oil shale yields middle distillates which are excellent jet and diesel fuel stocks. The principal requirements are removal of nitrogen to the extent necessary for good thermal stability of the fuels and adjustment of cut points to meet required pour or freeze points, limited by the presence of waxy straight-chain paraffins. The heavy naphtha from shale oil can be further hydrotreated and catalytically reformed to acceptable octane number, but with considerable loss of volume because of the only moderate content of cyclic hydrocarbons, typically 45-50%. On the other... 

Deodorizer distillate flow is much lower in the case of chemical refining (0.2-0.5% of the oil flow to the deodorizer). Consequently, contaminant concentration in the distillate can theoretically become 200-500 times higher than in the crude oil. For pesticides, the observed concentration factor is significantly lower, mainly because of thermal decomposition of some pesticides and incomplete condensation of volatile pesticides in the vapor scmbber. The limited amount of data available in the literature, combined with our own research figures, indicate that pesticide concentration in soybean, sunflower seed, and rapeseed deodorizer distillate is usually... 

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