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ABSTRACT This paper pertains to the characterization and chemistry of scale formation occurring in an industrial tungsten chemical process. In tungsten process, scales typically form in filter presses, pipes (carrying various solutions and waste waters) and evaporation crystallizers. This paper presents our results on the scale that forms in a filter press. Scale is formed on the plate supporting filter cloth and located in the exit side of wash solution. Major constituents of the scale were two tantalum compounds: Na14(Ta0.715Nb0.285)12O37?31H2O and Na3Ta0.715Nb0.285O4. It is suspected that the scale formation may be related to the filtration of tungsten values from sludge generated as a result of the high-temperature digestion of tantalum containing feeds in sodium hydroxide. It seems to be forming after the water-wash of the wet sludge. Because scale formation interferes in the normal operation of the filter press, chemistry of its formation and methods for its mitigation need to be investigated. INTRODUCTION Tungsten is used in the production of numerous end use items. It is one of the most important refractory metals used in the manufacturing of crucial components of light source. Tungsten is also used in the manufacturing of super alloy, hard metals (cemented carbide) and catalysts (hydrodesulphurization and hydrodenitrogenation). Other applications of tungsten are in the manufacturing of tungsten-copper and tungsten-silver composites. These composites are used in mechanical and electrical engineering; their typical applications include high-, medium-, and low-voltage circuit breakers, resistance welding electrodes, electrode materials for electrical discharge machining, and heat sink materials for microelectronic packaging. In military applications tungsten is employed in the manufacturing of high kinetic energy penetrators. Figure 1 presents a general flow diagram of tungsten process. Industrially, tungsten is produced mainly from tungsten ores: wolframite and scheelite and tungsten carbide scraps. Composition of these ores and scraps suggests that these feed materials also contain several impurity elements / compounds in addition to tungsten compounds. Therefore, processing of tungsten feed materials produces solutions, which has a potential to form impurity scales. Other factors which caused scale formation in tungsten process are the use of high temperature digestions in concentrated caustic solutions, as well as the use of chemicals employed in the purification steps. Evaporative crystallization of purified and impure tungsten solutions also causes scale formation. In this paper we report on the characterization and chemistry of the scale that forms in a filter press. Scale is formed on the plate supporting the filter cloth and located in the exit side of wash solution. Specifically, we report on the identification of the scale, its composition and chemistry of formation. EXPERIMENTAL Sample Scale sample was collected during the cleaning of filter press used in the filtration of sludge from soluble tungsten values after the ore/scrap digestion in NaOH (first step in the general flow diagram of tungsten process as depicted in Figure 1). The wet scale sample was dried at 110 °C, powdered and sieved through a 50-mesh sieve for the characterization work. Scale sample was white in color.
- Well Drilling > Drilling Fluids and Materials > Drilling fluid selection and formulation (chemistry, properties) (1.00)
- Reservoir Description and Dynamics (1.00)
- Production and Well Operations > Production Chemistry, Metallurgy and Biology > Inhibition and remediation of hydrates, scale, paraffin / wax and asphaltene (1.00)
In-Situ Monitoring The Inhibiting Effect Of Detpmp On Caco3 Scale Formation By Synchrotronx-Ray Diffraction
Chen, Tao (School of Mechanical Engineering, University of Leeds) | Neville, Anne (School of Mechanical Engineering, University of Leeds) | Sorbie, Ken (Institute of Petroleum Engineering, Heriot-Watt University) | Zhong, Zhong (Brookhaven National Laboratory)
ABSTRACT The formation of calcium carbonate mineral scale is a persistent and expensive problem in oil and gas production. The aim of this paper is to further the understanding of scale formation and inhibition by insitu probing of crystal growth by synchrotron radiation Wide Angle X-Ray Scattering (WAXS) in the absence and presence of DiEthyleneTriaminePenta (MethylenePhosphonic acid) (DETPMP) scale inhibitor at elevated temperature. It has been shown that the nucleation and growth of various calcareous polymorphs and their individual crystal planes can be followed in real time and from this the following conclusions are reached. Two stages of scale formation have been identified: e and e stages. DETPMP significantly increases the induction time obviously at 10 ppm. DETPMP suppresses calcite formation and favours vaterite formation. DETPMP causes the change of lattice parameters of calcite crystals.
- Materials > Chemicals (1.00)
- Energy > Oil & Gas > Upstream (1.00)
- Water & Waste Management > Water Management > Constituents > Salts/Sulphates/Scales (0.35)