TY - THES

T1 - Decrease of oxygen content in the solid residue from recycled drill bits

AU - Sobotka, Evelyn

N1 - embargoed until 09-05-2024

PY - 2019

Y1 - 2019

N2 - In the field of metallurgy, the conservation of natural resources has been a major concern for many years, leading to an increased importance of recycling optimization for processed metals. Hard metal drill bits contain a hard phase made of tungsten, tungsten carbide (WC), and cast tungsten carbide (CTC) which is cemented by a ductile binder consisting of Cu, Mn, Ni, and Zn. These materials are used for the oil and gas industry and need to be recycled at the end of their product life cycle by a wet chemical approach. The leaching with nitric acid leads to the disintegration of the drill bit. The binder alloy rapidly dissolves while the surface of the tungsten containing compounds is transformed into tungsten oxide which serves as a protection against digestion but also poses a challenge to the reuse in new drill bits. Thus, the oxygen content needs to be lowered. The aimed at content lies at less than 500 ppm. Possible methods for lowering the amount of oxygen in such a solid residue comprise the abrasion of the brittle oxide layer, the separation of the oxides via ammonia as well as the reduction with hydrogen.

AB - In the field of metallurgy, the conservation of natural resources has been a major concern for many years, leading to an increased importance of recycling optimization for processed metals. Hard metal drill bits contain a hard phase made of tungsten, tungsten carbide (WC), and cast tungsten carbide (CTC) which is cemented by a ductile binder consisting of Cu, Mn, Ni, and Zn. These materials are used for the oil and gas industry and need to be recycled at the end of their product life cycle by a wet chemical approach. The leaching with nitric acid leads to the disintegration of the drill bit. The binder alloy rapidly dissolves while the surface of the tungsten containing compounds is transformed into tungsten oxide which serves as a protection against digestion but also poses a challenge to the reuse in new drill bits. Thus, the oxygen content needs to be lowered. The aimed at content lies at less than 500 ppm. Possible methods for lowering the amount of oxygen in such a solid residue comprise the abrasion of the brittle oxide layer, the separation of the oxides via ammonia as well as the reduction with hydrogen.

KW - hard metal

KW - tungsten carbide

KW - drill bit recycling

KW - Hartmetall

KW - Wolframkarbid

KW - Bohrkopfrecycling

M3 - Master's Thesis

ER -