An antiscalant is a chemical or pre-treatment chemical that prevents the formation of scale, or crystallized mineral salts, commonly used in water purification systems, pipelines and cooling tower applications. Antiscalants are also known as scale inhibitor agents. Scale formation occurs when the concentration of dissolved salts in water exceeds their solubility limits, leading to the precipitation of these salts onto surfaces as hard deposits. Antiscalants dissolve the substances accumulated near the membrane surface and reduce the rate of fouling.[1] They play a crucial role in preventing scale formation, thus improving the efficiency and longevity of industrial equipment and processes.
Common ingredients
editAntiscalants could be broadly classified into 3 main categories: phosphorus based AS, synthetic polymeric AS and natural green AS.[2] Common active ingredients include phosphonates, polyphosphates, polymers, aminophosphonates[3] and organic acids. Antiscalants typically contain a combination of active ingredients that interfere with the crystallization process of scale-forming salts. Phosphorus-based antiscalants has the largest application use globally and they can be further classified into phosphorus-based and phosphonate-based AS. Green antiscalants usually contain natural polymers such as starch and are recently being more widely investigated due to discharge requirements. Polymer-based AS are synthetic polymers that have functional groups like carboxylic acid groups, acrylic acid, sulfonic acid, and phosphonic acid groups.[4][5] Common global suppliers of antiscalants include Kurita Water Industries, Avista, Nalco, and Veolia.
Chemistry and mechanism
editThese compounds work by various mechanisms such as suppression of crystallization, dispersion and crystal distortion.[6][2]
Suppression of crystallization
editAntiscalants contain molecules that can complex with metal ions present in the water, preventing them from participating in scale formation reactions. Phosphonates and polyphosphates are particularly effective in sequestering calcium, magnesium, and other metal ions.
Dispersion
editAntiscalants may also work by dispersing small-scale particles, preventing them from agglomerating and forming larger, more problematic deposits. Polymers are often used for their dispersing properties.
Crystal modification
editSome antiscalants alter the crystal structure of scale-forming salts, making them less likely to adhere to surfaces and form stubborn deposits. At a submicroscopic level, these soft non-adherent scales with antiscalant use would appear distorted, more oval in shape and less compact.[1]
Applications
editReverse osmosis and desalination
editIn reverse osmosis (RO) and desalination plants, antiscalants are vital for preventing scale formation on membrane surfaces. Scaling can severely impair the efficiency of these processes and lead to increased maintenance costs. Antiscalants help maintain optimal performance and prolong the lifespan of membranes. Scales form in the RO or desalination plants occurs when the ionic product of sparingly dissolved salts in the concentrated flow equals or exceeds its solubility product. The extent and degree of scaling phenomena are determined not only by the supersaturation conditions that occurred, but also by the precipitation kinetics.[7][8]
Water treatment
editScale deposition in boilers can reduce heat transfer efficiency and increase energy consumption. Antiscalants are added to boiler feedwater to prevent scale formation on heat transfer surfaces, piping, and other boiler components. Water treatment plants can use antiscalants to maintain filtration.[3]
Cooling water systems
editIndustrial cooling water systems are susceptible to scale formation due to high temperatures and concentrations of dissolved minerals.[9] Antiscalants help mitigate scale deposition in cooling towers, heat exchangers, and condensers, preserving their efficiency and reducing the need for maintenance.
Mining and oil and gas industry
editAntiscalants are used in mining operations and oil & gas production to prevent scale deposition in pipelines, drilling equipment, and processing facilities.[2] Scaling in these industries can lead to decreased flow rates, equipment damage, and production downtime. Preventing the formation of scale from blocking or hindering fluid flow through pipelines, valves, and pumps used in oil production and processing. Oilfield scaling is the precipitation and accumulation of insoluble crystals (salts) from a mixture of incompatible aqueous phases in oil processing systems.[10]
References
edit- ^ a b Yu, Wei; Song, Di; Chen, Wei; Yang, Hu (September 2020). "Antiscalants in RO membrane scaling control". Water Research. 183: 115985. Bibcode:2020WatRe.18315985Y. doi:10.1016/j.watres.2020.115985. PMID 32619802.
- ^ a b c Chuan Yee Lee, Brandon; Tan, Eileen; Lu, Yinghong; Komori, Hideyuki; Pietsch, Sara; Goodlett, Robb; James, Matt (2023-10-01). "Antiscalant and its deactivation in zero/minimized liquid discharge (ZLD/MLD) application in the mining sector – Opportunities, challenges and prospective". Minerals Engineering. 201: 108238. Bibcode:2023MiEng.20108238C. doi:10.1016/j.mineng.2023.108238. ISSN 0892-6875.
- ^ a b Armbruster, Dominic; Müller, Uwe; Happel, Oliver (2019). "Characterization of phosphonate-based antiscalants used in drinking water treatment plants by anion-exchange chromatography coupled to electrospray ionization time-of-flight mass spectrometry and inductively coupled plasma mass spectrometry". Journal of Chromatography A. 1601: 189–204. doi:10.1016/j.chroma.2019.05.014.
- ^ Karaburun, Emre; Sozen, Yigit; Çiftçi, Celal; Sahin, Hasan; Baba, Alper; Akbey, Ümit; Yeşilnacar, Mehmet İrfan; Erdim, Eray; Regenspurg, Simona; Demir, Mustafa M. (September 2022). "Experimental modeling of antimony sulfides-rich geothermal deposits and their solubility in the presence of polymeric antiscalants". Geothermics. 104: 102452. Bibcode:2022Geoth.10402452K. doi:10.1016/j.geothermics.2022.102452. ISSN 0375-6505.
- ^ Reiss, Amit G.; Gavrieli, Ittai; Ganor, Jiwchar (December 2020). "The effect of phosphonate-based antiscalant on gypsum precipitation kinetics and habit in hyper-saline solutions: An experimental and modeling approach to the planned Red Sea – Dead Sea Project". Desalination. 496: 114638. Bibcode:2020Desal.49614638R. doi:10.1016/j.desal.2020.114638. ISSN 0011-9164.
- ^ Yu, Wei; Song, Di; Chen, Wei; Yang, Hu (2020-09-15). "Antiscalants in RO membrane scaling control". Water Research. 183: 115985. Bibcode:2020WatRe.18315985Y. doi:10.1016/j.watres.2020.115985. ISSN 0043-1354. PMID 32619802.
- ^ Ahmed, Mahmoud A.; Amin, Sherif; Mohamed, Ashraf A. (2023-04-01). "Fouling in reverse osmosis membranes: monitoring, characterization, mitigation strategies and future directions". Heliyon. 9 (4): e14908. Bibcode:2023Heliy...914908A. doi:10.1016/j.heliyon.2023.e14908. ISSN 2405-8440. PMC 10102236. PMID 37064488.
- ^ "Contrasting Behaviors between Gypsum and Silica Scaling in the Presence of Antiscalants during Membrane Distillation". doi:10.1021/acs.est.0c07190.s001. Retrieved 2024-04-25.
{{cite journal}}: Cite journal requires|journal=(help) - ^ Wu, Zhigen; Yan, Zihan; Zhang, Qinghong; Zhu, Yuting; Luo, Maohui; Zhou, Dan (2023). "Review on descaling and anti-scaling technology of heat exchanger in high-salt wastewater thermal desalination". Water Science & Technology. 88 (8): 2081–2107. doi:10.2166/wst.2023.325. PMID 37906460.
- ^ Frenier, Wayne W.; Ziauddin, Murtaza (2008). Formation, removal, and inhibition of inorganic scale in the oilfield environment. Society of Petroleum Engineers. Richardson, Tex: Society of Petroleum Engineers. ISBN 978-1-55563-140-6.