Inorganic scale deposition

Clean-in-place (CIP) units for periodic membrane washing and removal of organic deposits, inorganic scales, and biofouling... 

In certain compounds, especially inorganic salts, solubility may not be affected or may actually decrease at higher temperatures. A good example is calcium carbonate water (hardwater), which has lower solubility at higher temperatures. This reverse solubihty behavior causes troublesome scale deposits issue in hot water boilers because water is maintained at a higher temperature in the water boiler. Therefore, calcium carbonate becomes supersaturated and precipitates in the boiler. In the authors experience, however, reverse solubihty is very rare in fine organics or pharmaceuticals. 

Girault and co-workers reported the application of plane interdigitated microband electrodes to an inorganic electrosynthesis of industrial interest die hypochlorite generation from sea water electrolysis. The system was studied in a laboratory cell [17] and also in a pilot plant [19]. A major problem in this synthesis is related to the deposition of scale (calcium and magnesium hydroxide) on the cathode due to the local production of OH anions. The coupling of the electrode processes permits the pH excursions on the cathode to be restricted, leading to a decrease in scale deposition. 

Deposition of inorganic scale may occur during well production. Depending on well conditions and produced water characteristics, different scale types may form. Often, scale formation is associated with a breakthrough of water production. Common scales include calcium carbonate, iron carbonate, calcium sulfate, barium sulfate, strontium sulfate, andiron sulfide. Combinations may also form. Figures 3-2 and 3-3 show well samples of calcium carbonate and iron scale, respectively. 

The purpose of the preflush is to remove organic or inorganic scale from the wellbore tubulars prior to injection of the acid stage. An aromatic solvent, such as xylene, can be used to remove hydrocarbon deposits. For asphaltene deposits, specifically, terpene-based solvent solutions can be quite effective. Circulation of 5%-7.5% HCl downhole is adequate to remove rust and other inorganic scale for rust removal in particular, non-add (nearneutral) removal solutions exist and may be preferable at temperatures of MOT (60°C) and higher. 

Hard crystalline scale and deposition also may result from the interaction of silica, residual hardness, and inorganic coagulants carried over into the treated water. Also, pre-boiler system damage by erosion may occur. 

These processes are very rapid and allow the preparation of inorganic supports in one step. This technique allows large-scale manufacturing of supports such as titania, fumed silica, and aluminas. Sometimes the properties of the material differ from the conventional preparation routes and make this approach unique. Multicomponent systems can be also prepared, either by multimetallic solutions or by using a two-nozzle system fed with monometallic solutions [22]. The as-prepared powder can be directly deposited onto substrates, and the process is termed combustion chemical vapor deposition [23]. 

The crust is the largest carbon reservoir in the crustal-ocean-atmosphere factory (8 x 10 Pg C including the sediments). Most of this carbon is in the form of inorganic minerals, predominantly limestone, with the rest being organic matter, predominantly contained in shale and secondarily in fossil fuel deposits (coal, oil, and natural gas). The oceanic reservoir (4 X lO" Pg C) and the terrestrial reservoir (2 to 3 x 10 Pg C) are both far smaller than the crustal reservoir. The smallest reservoir is found in the atmospheric, primarily as CO2 (preindustrial 6 x 10 Pg C, now 8 x 10 Pg C and rising). The flux estimates in Figure 25.1 have been constrained by an assumption that the preindustrial atmospheric and oceanic reservoirs were in steady state over intermediate time scales (millennia). 

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