Carbon-based coatings for suppression of silica adhesion in geothermal power generation. (January 2023)

• Record Type: Journal Article
• Authors: Nakashima, Y.; Umehara, N.; Kousaka, H.; Tokoroyama, T.; Murashima, M.; Mori, D.
• Is Part Of: Tribology international. Volume 177(2023)
• Publication Date: 2023-01
• Subjects: Diamond like carbon -- Surface structure -- Silica adhesion -- Geothermal power generation; Tribology -- Periodicals; 621.89
• DOI: 10.1016/j.triboint.2022.107956
• Languages: English
• ISSNs: 0301-679X

Abstract

Abstract: Geothermal steam, the power source in geothermal power generation, contains a large amount of silica. Silica adhesion on geothermal power generator equipment hinders stable power generation. This work aimed to suppress silica adhesion by using diamond-like carbon (DLC). DLC with various surface structures was investigated by X-ray fine structure and elastic recoil detection analysis. The adhered silica amount was drastically reduced by using DLC rather than turbine steel. Further, the optimum DLC structure to reduce silica adhesion was revealed. Reducing the sp² bond fraction and increasing the hydrogen content of the outermost surface of DLC reduce the adhered silica amount, although there was no correlation with the surface energy. Therefore, silica adhesion has a different mechanism from conventional adhesion. Graphical Abstract: ga1 Highlights: Diamond-like carbon coating with a particular structure shows silica adhesion of at most 2% from conventional steel. The hydrogen content and sp 2 bond fraction on the surface of the DLC coating were critical against silica adhesion. Surface energy had no correlation against silica adhesion, which is different from the conventional adhesion mechanism. Imitated geothermal brine was adopted to enable repeated study because conventional studies evaluated in actual plants.