Environmentally safe sorbent from ash-and-slag waste of heat power engineering

Abstract

Objectives. To determine the physical and chemical properties (bulk density, ash content, total pore volume, abrasion, humidity, sorption capacity) of sorbent based on ash-and-slag waste from heat power engineering, calcined and modified with a Tiprom K organosilicon water repellent.Methods. The physicochemical properties of the modified sorbent were determined using an experimental method according to the methods of regulatory documents on equipment verified and certified in the prescribed manner.Results. Ash and slag taken from the ash dump of the Novocherkasskaya GRES power station were dried, then calcined at a temperature of 600 °C for 30 min and modified with a Silor hydrophobizing silicon-containing liquid (HSL). The modifier/ash ratios (by weight) were 1:20, 1:10, 1:5, 1:3, and 1:2. The optimal ratio was 1:5 at a sorption capacity with respect to hexane of 0.86 g/g. The modification temperature was optimized in the temperature range of 110–200 °C. The optimal approach it to dry samples at 160 °C to constant weight. At a temperature of 200 °C, sintering of the material was observed. The analysis of HSL modifiers was carried out in terms of the price/sorption properties ratio. The following were considered as HSL: Silor, HSL-11BSP, HSL 136-157M, PROFILUX, Tiprom K, Tiprom U. The optimal modifier Tiprom K was selected. The physicochemical properties of the modified sorbent obtained at a ratio of 1:5 (by weight) and dried at 160 °C were experimentally determined. The sorption properties were studied on the water surface with respect to various oil products: fuel oil, kerosene, AI-92 gasoline, nefras, oil sludge, and n-hexane. The smallest sorption capacity was obtained with respect to n-hexane, amounting to 0.86 g/g. During the experiment, it was found that half of the sorption capacity was filled with oil in the first minutes of contact. Complete sorption time was 30–40 min for relatively light hydrocarbons (n-hexane, AI-92 gasoline, kerosene, nefras), 40–60 min for oil sludge, and more than 60 min for fuel oil. Experiments established that the sorption process does not depend on the matrix (salinity) of water. A visual assessment of the color intensity of the residual spot of oil sludge allowed a conclusion to be made about a significant content of oil products in the case of sorption of oil sludge by quartz sand based on the residual yellow layer of oil sludge. In the case of sorption of oil sludge by calcined and modified sorbents, the residual oil products were insignificant. A comparative analysis of data on the effectiveness of the developed sorbent and currently available analogues based on sludge and slag is presented.Conclusions. The next physicochemical properties of the sorbent modified with HSL Tiprom K were determined: bulk density was 0.621 g/mL, ash content was 97.1%, total pore volume by water was less than 0.05 mL/g, attrition was 8.8%, humidity was less than 0.5%; sorption capacity, in g/g: for n-hexane, 0.86; for AI-92 gasoline, 0.89; for nefras, 0.93; for kerosene, 0.99; for oil sludge, 1.18; for fuel oil, 1.46. The efficiency of cleaning a solid surface from oil sludge with a calcined sorbent was 97%, and with a modified sorbent 95%. The modified sorbent has high buoyancy when saturated with oil products and the ability to retain them for a long time.