Technical Lignosulfonates Effect on Weld Corrosion in a Coal-Water Slurry

Hydrotransport of coal, iron ore, bauxite and other solid materials is known to be carried out through trunk pipelines. Hydrotransport of coal in the form of highly concentrated coal-water slurries (HCCWS) makes it possible to solve a whole range of problems from environmental ones to those when HCCWS are used as a fuel for energy boilers. The HCCWS combustion efficiency is determined by the concentration of the solid pulp phase and the particle size. The highest HCCWS combustion efficiency is observed when the mass concentration of the solid phase is 60--65 % and the particle size is up to 0.02 sm. In order to achieve stability of these slurries with the solid phase concentration, various additives are used to improve the rheological properties of coal-water slurries. In particular, such plasticizing agents as sodium tripolyphosphate, technical lignosulfonates, carbon-alkaline reagents and others are used. Plasticizing agents are known to change the rheological properties of coal-water slurries but the problems of corrosion activity of plasticizing agents are not well understood, especially with respect to welded joints of pipelines. Welded joints of slurry pipelines can be represented as macro-galvanic couples, in which the weld and base metal are electrodes of a galvanic element. The current magnitude of the macro-galvanic couple can be used to calculate the local corrosion value due to the work of the galvanic element of the base metal and the weld. The paper studies the effect of technical lignosulfonates (TLS) and TLS-based compositions in a coal-water slurry on the local currents of the base metal --- weld macro-galvanic couple made of 09G2S steel. Findings of research show that in the water-coal slurry the maximum inhibitory effect is observed when 0.75 % TLS + 0.25 % K₂CrO₄ (Na₂CO₃) is added to the slurry

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