Refinery practices

All lation. The combination of olefins with paraffins to form higher isoparaffins is termed alkylation (qv). Alkylate is a desirable blendstock because it has a relatively high octane number and serves to dilute the total aromatics content. Reduction of the olefins ia gasoline blendstocks by alkylation also reduces tail pipe emissions. In refinery practice, butylenes are routinely alkylated by reaction with isobutane to produce isobutane—octane (26). In some plants, propylene and/or pentylenes (amylenes) are also alkylated (27). 

Sodium and potassium are restricted because they react with sulfur at elevated temperatures to corrode metals by hot corrosion or sulfurization. The hot-corrision mechanism is not fully understood however, it can be discussed in general terms. It is believed that the deposition of alkali sulfates (Na2S04) on the blade reduces the protective oxide layer. Corrosion results from the continual forming and removing of the oxide layer. Also, oxidation of the blades occurs when liquid vanadium is deposited on the blade. Fortunately, lead is not encountered very often. Its presence is primarily from contamination by leaded fuel or as a result of some refinery practice. Presently, there is no fuel treatment to counteract the presence of lead. 

As you continue to read, scan over the sidebar discussions. These provide a summary of the toxicity and fate data for the principal hazardous chemicals released by petroleum refinery operations. The sidebar discussions also provide descriptions of the most common routes by which these pollutants enter the environment as a result of common refinery practices and operations. 

Washing light hydrocarbons with water is a common refinery practice. It finds application on the feed to catalytic polymerization plants. It is used to remove any entrained caustic from the mercaptan removal facilities as well as any other impurities such as amines which tend to poison the polymerization catalyst. Another use for water wash is in alkylation plants to remove salts from streams, where heating would tend to deposit them out and plug up heat exchanger surfaces. Water washing can be carried out in a mixer- settler, or in a tower if more intimate contacting is necessary. 

The cost of obtaining incremental performance numbers by refining processes is difficult to determine because of variations in refinery practices and equipment, in product demand from refinery to refinery, and in crude sources. The cost of obtaining a similar incremental increase in performance number by use of tetraethyllead can be accurately obtained. 

Long-standing refinery practice is to size drain water treating equipment to remove oil droplets 150 microns in diameter or larger. If no other data are available, it is recommended that this be used in sizing sumps and disposal piles... 

Specific heats are extremely important engineering quantities in refinery practice because they are used in all calculations on heating and cooling petroleum products. Many measurements have been made on various hydrocarbon... 

A previous chapter (Chapter 7) has dealt with the processes used in refineries that were developed for conventional feedstocks (Figure 9-1). The current chapter will deal with those processes that are relatively late comers to refinery scenarios. These processes have evolved during the last three decades, and were developed (and installed) to address the refining of the heavy feedstocks. Thus, refining heavy feedstocks has become a major issue in modem refinery practice and several process configurations have evolved to accommodate the heavy feedstocks (RAROP, 1991 Shih and Oballa, 1991 Hydrocarbon Processing, 1998). 

One of the most important variables in the TPD of CO from a supported Pt catalyst is the sample pretreatment. Calcination at 500°C for one hour followed by reduction is the conventional method to obtain the maximum exposed Pt and this follows closely to refinery practice for start-up and regeneration of commercial catalysts. The final step in our case was a 600°C He sweep for 30 minutes to ensure a fully dehydrated catalyst up to this temperature so that no water evolved during the subsequent TPD. We had previously observed that a high temperature He sweep could reduce the Pt catalyst without a prior H reduction presumably by the decomposition of the Pt oxide. 

It is well known in refinery practice that sulfiding a Pf — AI2O3 catalyst results in a more stable although somewhat less active catalyst. If it is assumed that the sulfiding simply deactivates single platinum atoms on the surface, the multiplet theory can easily account for the behavior. 

The mercaptans may be regenerated by acidification of the caustic solutions, or these solutions may be deliberately oxidized to yield disulfides (57). It should be pointed out that, just as in the case of the gas purifying processes, hydrogen sulfide reacts with all the other alkalis in the aforementioned processes. Because the amount of hydrogen sulfide is usually large and because of its activity toward ordinary caustic solutions, a common refinery practice is to remove a major part of the hydrogen sulfide with inexpensive caustic so as not to overload the subsequent sweetening processes. 

A refinery aqueous stream flows at 600 gal/min and contains 15 Ib/hr benzene. The benzene is to be removed at a stripping efficiency of 99.95%. A tray column is to be used. Consider two operating pressures, 2.0 psia and 14.7 psia. With no attempt at optimization, evaluate the parameters that should be considered for design. In keeping with refinery practice, use conventional English units. 

One option for managing coal quality for power generation is to blend one particular coal with others until a satisfactory feedstock is achieved (Jones, 1992). This is similar to current petroleum refinery practice where one refinery actually accepts a blend of various crude oils and operates on the basis of average feedstock composition the days of one crude oil are no longer with us. 

If, in actual refinery practice, a trip is creating a hazard that the designer did not anticipate, the process engineer may have to recommend discontinuing the use of the trip to management. The alternate course of improving the reliability of the trip to a satisfactory level may not always be feasible. 

If a leaking water cooler cannot be isolated without shutting down an entire process unit, it is a common refinery practice to let it leak. However, if one can see a hydrocarbon haze rising from the cooling cell decks or if the gas test meter shows a localized concentration in the explosive range, the leaking exchanger should be removed from service without delay. 

Asphaltenes from Athabasca bitumen were first separated using n-pentane by Pasternak and Clark in 1951. In most refinery practices, the solvent of choice is n-heptane and asphaltenes are defined as materials soluble in toluene or a solvent having a solubility parameter in the 17.5-21.6 Mpa range. As the carbon number of the extracting solvent increases, the amount of asphaltenes that precipitate decreases. Fundamentally, it is important to note that during asphaltene precipitation by any solvent, smaller asphaltene molecules, as well as some maltene materials, co-precipitate because of... 

NACE International, Refinery Practice RP0472-87,1987, Standard Recommended Practice, Methods and Controls to Prevent In-Service Cracking of Carbon Steel (P-1) Welds in Corrosive Petroleum Refining Environments, NACE, Houston, TX. 

Steam reduction involves heating to 550 to 660°F in the presence of large amounts of steam. In early refinery practice cylinder stock was exposed to steam in shellstills for many hours. Modem practice simply involves the use of steam in large amounts in a continuous distillation system. The effect of steam in reducing the boiling point is discussed in connection with Eq. (15-8) and Example 15-2. 

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