Desalting, petroleum

The presence of these acids in crude oils and petroleum cuts causes problems for the refiner because they form stable emulsions with caustic solutions during desalting or in lubricating oil production very corrosive at high temperatures (350-400°C), they attack ordinary carbon steel, which necessitates the use of alloy piping materials. 

Desalting is a water-washing operation performed at the production field and at the refinery site for additional cmde oil cleanup. If the petroleum from the separators contains water and dirt, water washing can remove much of the water-soluble minerals and entrained soflds. If these cmde oil contaminants are not removed, they can cause operating problems duting refinery processiag, such as equipment plugging and corrosion as well as catalyst deactivation. 

Refining crude oil into useful petroleum products can be separated into two phases and a number of supporting operations. The first phase is desalting of crude oil and the subsequent distillation into its various components or "fractions." The second phase is made up of three different types of "downstream" processes combining, breaking, and reshaping. 

As already noted (Chapter 3), petroleum oil often contains water, inorganic salts, snspended solids, and water-soluble trace metals. As a first step in the refining process, to reduce corrosion, plugging, and fouling of equipment and to prevent poisoning the catalysts in processing units, these contaminants must be removed by desalting (dehydration). 

Since desalting is a closed process, there is little potential for exposure to the feedstock unless a leak or release occurs. However, whenever elevated temperatures are used when desalting sour (sulfur-containing) petroleum, hydrogen sulfide will be present. Depending on the crude feedstock and the treatment chemicals used, the wastewater will contain varying amounts of chlorides, sulfides, bicarbonates, ammonia, hydrocarbons, phenol, and suspended solids. If diatoma-ceous earth is used in filtration, exposures should be minimized or controlled. 

A modem petroleum refinery in the United States processes between 100,000 and 500,000 barrels/day of crude oil. The incoming cmde is first desalted and then passed through an atmospheric pressure distillation column that separates it into fractions, as shown in Figure 2-12. 

Donald R. Burris "Field Desalting a Growing Producer Problem Worldwide" Petroleum Engineer International (June 197<0. 

Mannich bases are present as auxiliaries and additives throughout the whole working process of the petroleum industry, from crude oil extraction up to the final products. Indeed, they are used as oleophilizers in drilling fluids- or in the treatment of cmde oil, such as desalting and prevention of paraffin deposits. Mannich bases and derivatives are, moreover, employed as antifoulants - in heat exchangers as well... 

Descriptions are provided for (1) desalting and dewatering (2) separation processes, of which distillation is the prime example (3) conversion processes, of which coking and catalytic cracking are prime examples and (4) finishing processes, of which hydrotreating to remove sulfur is a prime example. Descriptions of the various petroleum products (from fuel gas to asphalt and coke) sire also given. 

Boc-Cys(Npys)-OH DCHA was desalted in EtOAc by washing with aq 5% citric acid. Boc-Cy-s(Npys)-OH was obtained by precipitation with petroleum ether yield quant mp 153-155 °C (dec) [a]o -88.7 (c 1, MeOH). 

Crystallization Sedimentation Major problem in evaporators and crystallizers very frequent in food processing Major problem in petroleum-refinery crude unit desalters and oii storage tanks also present in cooling-tower basins... 

IMULSIONS OF OIL AND WATER are one of many problems directly associated with the petroleum industry, in both oil-field production and refinery environments. Whether these emulsions are created inadvertently or are unavoidable, as in the oil-field production area, or are deliberately induced, as in refinery desalting operations, the economic necessity to eliminate emulsions or maximize oil-water separation is present. Furthermore, the economics of oil-water separation dictate the labor, resources, and monies dedicated to this issue. Before we describe the methods and economics of emulsion breaking at commercial facilities, we will restate several key concepts concerning emulsions and the petroleum industry. 

Oil-Water Interface Control. In any petroleum processing unit in which emulsions are resolved, an interface between oil and water must occur. The quality of this interface is directly related to the efficiency of demulsification in either a refinery desalter or an oil-field free-water knockout or treater. The sharper the transition between clean water and clean oil (or the tightness of the interface), the better the ability to control oil and water retention times and quality and operate the vessel. 

Aqueous desalter effluent contains sediments, oil, dissolved salts, and sulfides. It is treated initially by using an American Petroleum Institute (API) separator for residual oil removal and recovery (Fig. 18.9). Any oil droplets larger than about 150 p.m (0.15 mm) in diameter are collected as an oil phase, which is routed to the refinery slop oil stream to join any other off-specification liquid oil streams for reprocessing. Inclined plastic plates inserted into an oil-water separator of this type substantially increase the speed and... 

These requirements and other reasons make the preparation of petroleum before processing very necessary. Petroleum preparation includes drying (removal of water or dewatering) and desalting of petroleum, and complete or partial removal of dissolved gas. 

The processes of drying and desalting are very similar. In desalting, however, the water is removed from the petroleum together with the dissolved mineral salts. If it is desired, more complete desalting is achieved by introducing additional fresh water to the petroleum to dissolve the mineral salts and subsequent drying. 

Electrical desalting and drying of petroleum is especially widely applied in the industry, but less often in the oil wells. The opportunity created by the application of the electrical method in combination with many other methods can be attributed to one main advantage of this method. 

In the modern petroleum industry, complex petroleum preparation is carried out in areas close to the oil wells. Therefore, complex installations for petroleum preparation at the petroleum wells also integrate the processes of drying, desalting and stabilization. 

Wastewater and contaminants are discharged from the bottom of the settling tank to the wastewater treatment facility. The desalted crude is continuously drawn from the top of the settling tanks and sent to the petroleum rectification unit. All the apparatus for petroleum desalting and drying can be classified in two big groups ... 

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