Scaling inhibitors

Scale cleaning Scale inhibitors Scale removal Scales... 

Plant investment and maintenance costs are relatively high for a new iodine plant in the United States or in Japan because of the deep weUs required for brine production and disposal as weU as the corrosive nature of the plant streams. The principal materials cost is for chlorine and for sulfur dioxide, although in the United States the additives used for the brines, such as scale inhibitors and bactericides, also have a considerable influence on costs. 

Organophosphoms compounds, primarily phosphonic acids, are used as sequestrants, scale inhibitors, deflocculants, or ion-control agents in oil wells, cooling-tower waters, and boiler-feed waters. Organophosphates are also used as plasticizers and flame retardants in plastics and elastomers, which accounted for 22% of PCl consumed. Phosphites, in conjunction with Hquid mixed metals, such as calcium—zinc and barium—cadmium heat stabilizers, function as antioxidants and stabilizer adjutants. In 1992, such phosphoms-based chemicals amounted to slightly more than 6% of all such plastic additives and represented 8500 t of phosphoms. Because PVC production is expected to increase, the use of phosphoms additive should increase 3% aimually through 1999. 

The most commonly used scale inhibitors are low molecular weight acrylate polymers and organophosphoms compounds (phosphonates). Both classes of materials function as threshold inhibitors however, the polymeric materials are more effective dispersants. Selection of a scale control agent depends on the precipitating species and its degree of supersaturation. The most effective scale control programs use both a precipitation inhibitor and a dispersant. In some cases this can be achieved with a single component (eg, polymers used to inhibit calcium phosphate at near neutral pH). 

McumerdOOO Scale Inhibitor, Rohm and Haas Co., Philadelphia, Pa., 1992. 

Environment Internal Cooling water treated with scale inhibitor External Refractory... 

Scale Inhibitors. When scaling conditions exist, scale inhibitors can be used to control the scaling tendencies, and keep metal surfaces free of scale deposits. Scale inhibitors are chemicals that interrupt and deform the normal crystalline growth pattern of carbonate scales. The three most commonly used classes of scale-inhibiting chemicals used in drilling fluid are [191,197] ... 

Scale Inhibitor. About 3 to 5 gal (20 to 30% active) of scale inhibitor per day should be sufficient for scale inhibition. The treatment can be reduced to 1 to 3 gal per day once the scale formation is under control. The chemical can be introduced to the system by injecting it into the pump suction line. 

Aminotri(methylenephosphonic acid) [ATMP or AMP] is the least expensive phosphonate. It is a good, general-purpose, cost-effective scale inhibitor an effective chelant and the most thermally stable of all the common phosphonates. It is satisfactory up to at least 700 psia. However, if fed as a concentrate AIMP may easily form insoluble calcium phosphonate and it may also affect copper. ATMP has a sequestration value of 870 mg CaC03/g product at a pH level of 11 and for iron, a sequestration value of 150 mg Fe/g product at a pH level of 10. The pentasodium salt has a MW of 409. Examples include Dequest 2000/2006, Mayoquest 1230, Phos -2, Briquest 301-50A, Unihib 305, and Codex 8503. 

Maleate chemistry has proved to be an enduring mainstay of many water treatment formulations, primarily as non-phosphate-containing calcium carbonate scale inhibitors. For most water treatment applications, polymaleic acid and its derivatives offer a good alternative to phosphonate chemistries, when required. 

Amine salts of ether carboxylates inhibit internal corrosion of oil storage tanks and pipelines [230]. Furthermore it is possible to use ether carboxylates as corrosion and scale inhibitors for industrial recirculating cooling water systems, metalworking fluids, and hydraulic fluids [28,231-233]. 

Lignin amines with high nitrogen content are water soluble at both alkaline and acidic pH values. The lignin amines have various useful properties. For example, they are active as flocculants, filtration aids, scale inhibitors, fluid loss additives, oil well cement additives, and corrosion inhibitors among other potential uses. The nitrogen is introduced into the lignins with the Mannich reaction [1570]. 

Conventional scale inhibitors are hydrophilic, that is, they dissolve in water. In the case of down-hole squeezing, it is desirable that the scale inhibitor is adsorbed on the rock to avoid washing out the chemical before it can act as desired. However, adsorption on the rock may change the surface tension and the wettability of the system. To overcome these disadvantages, oil-soluble scale inhibitors have been developed. Coated inhibitors are also available. Often, scale inhibitors are not applied as such, but rather in combination with corrosion inhibitors. 

A method to estimate the optimal dose of a scale inhibitor has been described [1223]. The method starts with noting the chemical composition and temperature of the water. From these parameters a stability index is calculated, allowing for the prediction of the optimal dose of a scale inhibitor. 

Acids, when used as scale inhibitors, are extremely corrosive. Their effectiveness has been laboratory tested. Parameters include acid type, metallurgy, temperature, inhibitor type and concentration, duration of acid-metal contact, and the effect of other chemical additives [279]. Lead and zinc sulphide scale deposits can be removed by an acid treatment [922]. 

Encapsulated scale inhibitors have been developed. This type of scale inhibitor allows chemical release over an extended period [865,1452], Microencapsulated formulations may contain a gelatin coating with a multipurpose cocktail, such as [1006,1007] ... 

Conventional polymer and phosphonate scale inhibitors may not be appropriate for application in high-pressure and high-temperature reservoirs. Only a limited range of commercially available oil field scale inhibitor chemicals are sufficiently thermally stable at temperatures above 150° C. These chemicals are homopolymers of vinyl sulfonate and copolymers of acrylic acid... 

Field desorption mass spectrometry [1606], C nuclear magnetic resonance, and fourier-transform infrared spectroscopy [1337] have been used to characterize oil field chemicals, among them, scale inhibitors. Ion... 

Phase diagrams of a polyacrylate-phosphonate system with temperature and calcium ion concentration can be established with turbidimetric measurements [1830]. Conductometric titrations also are suitable to characterize the phase behavior of scale inhibitors [514] (Table 7-2). 

Organic phosphates and organic phosphonates are known as scale inhibitors. At the same time, substances in this class can be nutrients for certain bacteria. Therefore a phosphorous nutrient injection system can both prevent scales and act as a nutrient in favorite cases [903,904],... 

The formation of calcium carbonate (CaCOs), calcium sulfate, and barium sulfate scales in brine may create problems with permeability. Therefore it is advantageous that newly made fractures have a scale inhibitor in place in the fracture to help prevent the formation of scale. Formulations of hydraulic fracturing fluids containing a scale inhibitor have been described in the literature [1828]. 

A solid, encapsulated scale inhibitor (calcium-magnesium polyphosphate) has been developed and extensively tested for use in fracturing treatments [1451-1453]. The inhibitor is compatible with borate- and zirconium-crosslinked fracturing fluids and foamed fluids because of coating. The coating... 

R. T. Barthorpe. The impairment of scale inhibitor function by commonly used organic anions. In Proceedings Volume, pages 69-76. SPE Oilfield Chem Int Symp (New Orleans, LA, 3/2-3/5), 1993. 

L. S. Boak, G. M. Graham, and K. S. Sorbie. The influence of divalent cations on the performance of BaS04 scale inhibitor species. In Proceedings Volume, pages 643-648. SPE Oilfield Chem Int Symp (Houston, TX, 2/16-2/19), 1999. 

N. P. Chilcott, D. A. Phillips, M. G. Sanders, I. R. Collins, and A. Gyani. The development and application of an accurate assay technique for sulphonated polyacrylate co-polymer oilfield scale inhibitors. 2nd Annu SPE Oilfield Scale Int Symp (Aberdeen, Scotland, 1/26-1/27), 2000. 

I. Drela, P. Falewicz, and S. Kuczkowska. New rapid test for evaluation of scale inhibitors. Water Research, 32(10) 3188-3191, October 1998. 

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