Investigation of CaSO4 Scale Inhibition by Carboxymethyl Cellulose and Polyacrylamide
Kistanova, Natalya; Leontyev, Pavel; Elokhov, Aleksandr; Kudryashova, Olga
Perm State University, Russian Federation
The sealing of porous rock and soil formations to protect the mines from the inflow of brines can be achieved using typical grouts such as concrete, bentonite and others clays, bitumen, water glass, acrylamide. A novel technology of sealing suggests using directed crystallization process of slightly soluble minerals similar to those occurring in nature. Supersaturated solutions are used as grout. To defend of spontaneous crystallization the precipitation inhibitors are used. The formation of calcium carbonates and sulfates has provided in most cases to closure of flow paths.
Supersaturated solutions were prepared by mixing of CaCl2 and Na2SO4 solutions. The inhibitors under study was added to one of the components. Carboxymethyl cellulose (CMC) and polyacrylamide (PAM), with average molecular weight of 14 millions, were used as inhibitors. The influence of concentration inhibitors, calcium/sulfate ration on the precipitation of calcium sulfate was studied. Inhibition efficiency of two inhibitors was estimated from measurements of the calcium ion activity and specific solution conductivity in the supersaturated solutions during of the precipitation process.
Carboxymethyl cellulose (CMC) containing carboxylic groups were found to be particularly effective in preventing the crystallization of gypsum. Polymer concentrations as low as 0.4g/l increased induction time, preceding the formation of the sulfate calcium to 3 hours. Mixing 0.14M solutions results in final concentration 19g CaSO4/l. Gypsum has solubility approximately 2.0-2.5g/l at 25°C.
Obtained supersaturated solutions can be used in the technology of sealing soil or rock formations by directed crystallization process in the treated flow paths. All components of solutions are environmental friendly and are not source new pollutions.