Scale deposits, removal procedures

There is considerable potential, therefore, for mineral scale, such as barium sulfate (see the next section), to form during these procedures. The scale may be deposited in the formation, the wellbore, or in production tubing. Scale that forms in the formation near wells, known as formation damage, can dramatically lower permeability and throttle production. When it forms in the wellbore and production tubing, mineral scale is costly to remove and may lead to safety problems if it blocks release valves. 

Fig. 8. Schematic of the procedure used for fabrication of nanoscale molecular-switch devices by imprint lithography [62]. (a) Deposition of a molecular film on Ti/Pt nanowires and their micron-scale connections to contact pads, (b) Blanket evaporation of a 7.5 nm Ti protective layer, (c) Imprinting of 10 nm Pt layers with a mold that was oriented perpendicular to the bottom electrodes and aligned to ensure that the top and bottom nanowires crossed, (d) Reactive ion etching with CF4 and O2 (4 1) to remove the blanket Ti protective layer.

Internal Feedwater Treatment. Internal feedwater treatment is generally nothing more than the addition of the proper chemicals to prevent the deposition of scaling materials on the hot surfaces of the boiler. A sludge formed by the chemicals with calcium and/or magnesium carbonates drops to the bottom of the boiler or remains in suspension. In steam boilers, this sludge can be removed by proper blowdown procedures. The chemicals that are to be added to the boiler water, the blowdown procedure, and the analysis and maintenance of the feed-water conditioning should be handled by a water-treatment consultant. 

Industrial acid cleaning. This very important procedure is apphed chiefly to the removal of scale and other unwanted deposits from steam-generating equipment and from chemical and petrochemical reaction vessels, as well as cooling system. Hydrochloric acid is widely used, frequently with important assistance from hydrofluoric acid or fluorides. 

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