Heat soak technique

It has been clearly demonstrated that extensive and irreversible damage to the catalyst can occur during such procedures and they have been largely replaced by the heat soak technique. In this procedure the inlet temperature to the catalyst bed is held at some 15 - 20 C above normal for several hours and it is generally effective in removing intrapore retained sulfur. 

A variety of techniques have been used to accomplish this. Branching comonomers such as divinylbenzene can be used.The amount needed to branch the polymer adequately is generally so low that the reagent can hardly be detected in the final product. Additives which cause metalation of the polymer chains can be included in the polymerization mixture or added after polymerization to create new growth sites along the polymer chain.12 Or, polymer can be heat soaked by increasing the residence time. 

PFA tubes and pipe liners can be butt-welded in a similar procedure to that used for PTFE (Sec. 7.4.2). PFA does not require adhesive to form a bond. PFA is easily welded by a heated platen technique in which the liner ends contact the heated plate until a bead is formed. A heater plate temperature of 399°C, a contact time of 15-30 secs, and a soak time of 90-105 secs are required for liners with a diameter of 2.5-... 

Steam is injected into a reservoir to reduce oil viscosity and make it flow more easily. This technique is used in reservoirs containing high viscosity crudes where conventional methods only yield very low recoveries. Steam can be injected in a cyclic process in which the same well is used for injection and production, and the steam is allowed to soak prior to back production (sometimes known as Huff and Puff). Alternatively steam is injected to create a steam flood, sweeping oil from injectors to producers much as in a conventional waterflood. In such cases it is still found beneficial to increase the residence (or relaxation) time of the steam to heat treat a greater volume of reservoir. 

Sample preparation for the modified Fischer assay technique, a standard method to determine the Hquid yields from pyrolysis of oil shale, is necessary to achieve reproducible results. A 100-g sample of >230 fim (65 mesh) of oil shale is heated in a Fischer assay retort through a prescribed temperature range, eg, ca 25.5—500°C, for 50 min and then soaked for 20 min. The organic Hquid which is collected is the Fischer assay yield (7). The Fischer assay is not an absolute method, but a quaHtative assessment of the oil that may be produced from a given sample of oil shale (8). Retorting yields of greater than 100% of Fischer assay are possible. 

Secondary recovery, infill drilling, various pumping techniques, and workover actions may still leave oil, sometimes the majority of the oil, in the reservoir. There are further applications of technology to extract the oil that can be utilized if the economics justifies them. These more elaborate procedures are called enhanced oil recovery. They fall into three general categories thermal recoveiy, chemical processes, and miscible methods. All involve injections of some substance into the reservoir. Thermal recovery methods inject steam or hot water m order to improve the mobility of the oil. They work best for heavy nils. In one version the production crew maintains steam or hot water injection continuously in order to displace the oil toward the production wells. In another version, called steam soak or huff and puff, the crew injects steam for a time into a production well and then lets it soak while the heat from the steam transfers to the resei voir. After a period of a week or more, the crew reopens the well and produces the heated oil. This sequence can be repeated as long as it is effective. 

This may be achieved by complete immersion of full-thickness skin in trypsin solution or by placing the heat-separated epidermis for 24 h at 37°C on a filter paper soaked with the enzyme preparation [64, 83]. Other techniques, such as vacuum or chemically induced blistering, stretching, application of staphylococcal exfoliatin, or proteolytic digestion of viable cells, are seldom reported [74, 87-89],... 

Use a small amount of heated sulfuric acid in a fume hood. Roll the item around so the acid comes in contact will all areas of the piece. Unless the item needs to soak (for example, 30 minutes of soaking time is recommended for the removal of silicone grease), immediately empty the glassware and rinse. Although more dangerous to use than a base bath, this technique can be used to remove silicone grease from volumetric ware without concerns about altering the volume of volumetric ware. 

A mixture of boric acid (1 g) and urea (11.8 g) was taken in 40 ml distilled water and heated at 70 °C until the solution became viscous the a-CNTs were soaked in it for nearly 2 h. They were later separated physically and dried in air at 40 C overnight. The dried sample was thermally treated at 970 °C for 3 h for 40 nm nanotubes in a N2 atmosphere, and for 12 h in the case of the larger diameter (170 nm) nanotubes, and then cooled down to room temperature. The product was subsequently heated in an NHt atmosphere at 1050 °C in case of 170 nm nanotubes and 900 C in case of 40 nm nanotubes for three hours to give black-coloured boron-carbon-nitride nanotube brushes. The products were investigated by transmission electron microscopy and other physical techniques. 

Those monoliths can be produced from a piece of structured foam polymer with macropores. The piece of polymer is soaked in a sol that will form a ceramic of the desired material after heat treatment. The sol-soaked structure is dried, and it is burned at a suitable temperature to remove the polymer. The remaining structure will be a ceramic one with macropores, permitting the wall-flow of gases. This technique is also used to produce heat plates and pipes with macroporous walls for gas separation purposes. The polymers used are often derived from polyurethanes [45-46]. 

Advantages High oil yields follow the steam soak treatment heat losses along the well column are lower than with the other two techniques during the steam injection, the casing string is not heated as much as with the other two techniques. 

To overcome these shortcomings, steaming by block-cyclic technique has been developed at the Zybza field through both experimental work and field testing. In this variant of steam soak, separate closed and relatively stable high temperature fields are created by the thermodynamic process. Each one of these fields encloses a descrete block of the petroleum reservoir. Each field is confined within pre-selected boundaries beyond which the heat front does not extend. This method insures both maximum distance of penetration by the heat carrier into the individual reservoir sections of microporosity type and high oil recovery factors for this type of reservoir. 

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