Waxy deposits

Recent investigations have shown that increasing the diameter of a fixedcatalyst temperatures [22. Kinetic measurements on laboratory-scale recycle reactors have been used to predict product distributions for pilot plant reactors and were in good agreement with experimental results 1231. 

To remove the waxy deposits online, block in and bypass the tube side of the fouled exchanger, while continuing sheUside flow, which heats the tubes. After a while, waxy deposits are melted off and harder deposits are spalled off due to thermal shock. After 20 min, restore normal flow. According to Lieberman (1997), this method works well in several cases. 

Continue shell-side flow. This heats the tubes. Waxy deposits are melted off. Harder deposits are spalled off due to thermal shock. 

A sudden rise in vacuum tower top temperature, which occurs simultaneously with the onset of cold weather, can be due to freeze-ups of the seal legs. Plugging with waxy deposits is also possible. 

Fig. 5.24. Scanning electron micrographs of the surface of Mammilaria (upper) and Ferocactus (lower) showing stomata and waxy deposition on surface...

Characterization factor. If the characterization factor is above 12 (paraffinic), the crude oil is expected to form waxy deposits. 

In waxy crudes, the wax has a tendency to become deposited during storage of the crude oil in tanks or while flowing through pipelines. The deposition in the pipeline severely affects the pipeline throughput. The deposits have to be removed periodically from the storage tanks and the pipelines by pigging operations. 

Additive-induced combustion chamber deposits form near the intake valve. The deposit forms directly onto the surface and has a waxy appearance. These deposits do not undergo alterations as do fuel-derived deposits. Also, additive-induced deposits do not readily flake off of the combustion chamber surface. The effect of engine design on combustion chamber deposit formation is being investigated. 

This non-ASTM method is utilized to help predict the tendency of waxy fuel to plug small lines leading from outdoor fuel storage tanks. Fuel which flows from storage through smaller transfer lines may deposit wax on the internal surface of these lines or onto filter screens. Accumulation of wax can restrict or halt the flow of fuel from the system. This problem usually occurs slightly below the cloud point of the fuel. 

The compressor is disassembled. I get the opportunity to accompany the rotor to Dallas, in the back of a van that needed a new suspension. Once there, I watched the manufacturer s machinist crew clean and rebalance the wheels. I noticed that the salt deposits were thickest on the middle wheel. The last wheel was only slightly encrusted while the first wheel was clean, except for some waxy grease. 

Other factors indicated m the data of Tables 1 and 2 include Pour Point—defined as the lowest temperature at which the material will pour and a function of the composition of the oil in terms of waxiness and bitumen content Salt Content—which is not confined to sodium chloride, but usually is interpreted in terms of NaCl Salt is undesirable because of the tendency to obstruct fluid flow, to accumulate as an undesirable constituent of residual oils and asphalts, and a tendency of certain salt compounds to decompose when heated, causing corrosion of refining equipment Metals Content—heavy metals, such as vanadium, nickel, and iron, tend to accumulate in the heavier gas oil and residuum fractions where the metals may interfere with refining operations, particularly by poisoning catalysts. The heavy metals also contribute to the formation of deposits on heated surfaces in furnaces and boiler fireboxes, leading to permanent failure of equrpment, interference with heat-transfer efficiency, and increased maintenance. 

Organics are often present in large process cooling systems as a result of process contamination. The deposit may have a greasy, waxy, charred, or tarlike texture, but it is more usually found as a black, highly carbonized, friable material. Organic materials are usually reported in the deposit analysis as a loss on ignition. 

Oil Shale (Shale Oil) Sedimentary rock that contains kerogen, a solid, waxy mixture of hydrocarbon compounds. Heating the rock to very high temperatures will convert the kerogen to a vapor, which can then be condensed to form a slow flowing heavy oil that can later be refined or used for commercial purposes. The United States contains vast amounts of oil shale deposits, but so far it has been considered not economically feasible to produce from them on a large scale. 

Opal is a common mineral in chemical sediments, as deposits around hot springs, replacing fossils such as wood, or as secondary vein-filling. Most opal is common opal, without the internal play of colors that makes some opal precious. Common opal is usually light colored, and has a distinctive waxy luster. 

Parallel flow paths of this type are even less wise in a situation where a relatively small downward temperature excursion causes waxes to form and creates danger that deposits of waxy catalyst will block some tubes entirely. Until the mid-1970s, Sasol s operations were plagued by involuntary shutdowns (Mclver, personal communication, 1972) for clearing blocked tubes with jets of high pressure water or more severe mechanical means (Shingles and McDonald, 1988). 

A hydrophobically modified polybetaine proved to be an efficient pour point depressant (PPD), to inhibit the deposition of wax, and to improve the viscosity of waxy crude oil from the Kumkol-Akshabulak oil field (western Kazakhstan) [282]. The inhibition of wax deposits in the presence of the hydrophobic polybetaine was interpreted in terms of its interference with the wax crystalhzation process, due to the formation of inverse micellar structures. While the zwitterionic parts on the polymer backbone stabilize the... 

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