Novel calcium carbonate filler for cellulose industry

Precipitated calcium carbonate (PCC) filler is used in many industrial products like constructions, plastics, pharmaceutics, etc. In this study producing cationic precipitated calcium carbonate filler for paper industry was investigated. Hence, a cationic polyacrylamide and cationic corn starch have been incorporated into the PCC particles to produce a modified filler with cationic structure and improved hydrogen bonding ability with cellulose fibers. According to the FESEM and XRD results, cubic-like fillers with prominently calcite polymorph and a slight amount of aragonite were successfully produced from the industrial burnt lime using carbonation process. The presence of organic substances in the structure of the modified samples was confirmed by FT-IR analysis. Besides, based on the FESEM results, filler morphology and particle size could be affected by the polymer content. In conclusion, introducing cationic groups to mineral fillers could be considered as a possible strategy to overcome some detrimental effects of using mineral fillers in paper products.

Transformation Kinetics of Burnt Lime in Freshwater and Sea Water

Calcium oxide (CaO), also known as burnt lime, is being considered as a possible treatment to reduce the negative impact of sea urchins on tare forests in northern coastal waters and blue-green algal blooms in the surrounding of fish-farms. In this respect, the reaction kinetics of burnt lime in contact with sea water has been elucidated and compared to its behaviour in fresh water. In the first minutes of contact between burnt lime and water, it “slaked” as CaO reacted with water to yield calcium hydroxide (Ca(OH)2). Subsequently, calcium hydroxide reacted with magnesium, sulphate and carbonate from the sea water to yield magnesium hydroxide (Mg(OH)2), calcium sulphate dihydrate (gypsum, CaSO4·2H2O) and calcium carbonate (CaCO3), respectively. In a closed system of 1% CaO in natural sea water (where the supply of sulphate, magnesium and carbonate is limited), more than 90% reacted within the first 5 h. It is foreseen that in an open system, like a marine fjord, it will react even faster. The pH 8 of sea water close to the CaO particle surface will immediately increase to a theoretical value of about 12.5 but will, in an open system with large excess of sea water, rapidly fall back to pH 10.5 being equilibrium pH of magnesium hydroxide. This is further reduced to <9 due to the common ion effect of dissolved magnesium in sea water and then be diluted to the sea water background pH, about 8. Field test dosing CaO particles to sea water showed that the pH of water between the particles stayed around 8.

Transformation Kinetics of Burnt Lime in Freshwater and Sea Water

The reaction kinetics of burnt lime (CaO) in contact with sea water has been elucidated and compared to its behaviour in fresh water. In the first minutes of contact between burnt lime and water, it "slaked" as CaO reacted with water to yield calcium hydroxide (Ca(OH)2). Subsequently, calcium hydroxide reacted with magnesium, sulphate and carbonate from the sea water to yield magnesium hydroxide (Mg(OH)2), calcium sulphate dihydrate (gypsum, CaSO4&middot;2H2O) and calcium carbonate (CaCO3), respectively. In a closed system of 1% CaO in natural sea water (where the supply of sulphate, magnesium and carbonate is limited), more than 90% reacted within the first 5 hours. It is foreseen that in an open system, like a marine fjord, it will react even faster. The pH 8 of sea water close to the CaO particle surface will immediately increase to a theoretical value of about 12.5 but will, in an open system with large excess of sea water, rapidly fall back to pH 10.5 being equilibrium pH of magnesium hydroxide. This is further reduced to &lt; 9 due to the common ion effect of dissolved magnesium in sea water and then be diluted to the sea water background pH, about 8. Field test dosing CaO particles to sea water showed that the pH of water between the particles stayed around 8.

Design, optimization and modelling of a chemical recovery system for wet spinning of cellulose in sodium carbonate solutions

The aim of this study is to present the design, optimization and modelling of a chemical recovery system for a novel CS2-free viscose-type process that entails dissolution of pre-treated dissolving pulp in a continuous-flow reactor in cold alkali and wet spinning of cellulose in sodium carbonate solutions. Technologies already known to other industries for the recovery and reuse of chemicals, such as causticizing, recalcination, recarbonization and freeze-separation, were used. Chemical equilibria simulations were performed with OLI Studio 9.5, with the purpose to select experimental conditions which avoid undesired precipitations in each unit operation. Synthetic solutions mimicking the spent coagulation liquor were used in the laboratorial experiments. The proposed chemical recovery system was shown to be technically feasible and reduce chemical make-ups to a minimum of 45 kg/ton of NaOH and 4 kg/ton of H2SO4. Small amounts of Zn are expected to precipitate during recarbonization of the coagulation liquor at 30 °C and causticizing at 98 °C. Thus, a filter for ZnO particles should be included in the design of the recarbonization unit and a continuous purge of lime mud and input of fresh lime make-up should be needed to keep burnt lime availability at an acceptable level. Overall, the results presented in this study portray a solution to reduce operating costs and the environmental impact of novel viscose-type processes with alkaline spin dopes and wet spinning of cellulose in sodium carbonate solutions.

Elaboration of design and calculation of energy and power parameters of a facility for lime unloading from a shaft furnace

Operation of shaft furnaces for lime burning in the required technological mode to a great extent is effected by reliability and technical abilities of their finished product unloading systems. A system proposed for unloading a shaft furnace for lime burning, enabling to deliver in a stable mode crashed material providing it has large sintered pieces. The system includes a stationary round table, located symmetrically relating the vertical axis of the furnace body under the conical collector exit opening. The table has four semi-round scraper knives connected by hinges with four pushing rods, acting by drive hydraulic cylinders. Alternately one pair of cylinders is working for pushing, the other – for pulling the rods. It results in the scraper knives making turn motions relatively the table, rolling along its edge and pushing off it bulk material by their back round part. To design a pilot sample of the proposed unloading system for shaft burning furnace, a methodology was elaborated to calculate its power parameters. The methodology takes into account the technological loads, arising at the realization of the process of measured delivery of the burnt lime from the furnace. The proposed methodology enables to determine the required values of pressure and consumption of oil station working liquid. The oil station provide operation of the cinematically interconnected four hydraulic cylinders, which make the two pair of scraper knives moving along a set trajectory on the table surface of the furnace to deliver from it the bulk material. The rightness of the technical solutions applied to the design of the elaborated shaft furnace unloading system as well as the correctness of the proposed theoretical dependences used for calculation of its energy and power parameters, were confirmed by the experiments. The experiments were carried out at an operating physical model, manufactured in the scale 1:10 to the natural facility.

Analysis of technical and economic indicators of the pyrometallurgical scheme co-processing of red mud and scale

Elaboration and implementation of effective technologies of utilization of alumina production wastes (red mud) is a rather actual task. Various variants of red mud and oiled rolling scale agglomeration considered aimed at their utilization at sinter and blast furnace plants to obtain conditional marketable cast iron. As the object of the study, red mud of OJSC RUSAL and oiled rolling scale of Sinarsky pipe manufacturing plant were used. It was shown, that their joint processing enables to obtain an agglomerated product having iron content more than 50%, which meets the modern requirements to the burden materials for blast furnaces. To determine the optimal scheme of the processing in the blast furnaces, various variants of studied materials agglomeration were calculated – an oxidizing roasting to obtain pellets and briquetting with application of burnt lime as a binder. The components interrelation in the mixture was selected to have iron content in the agglomerated product high enough at maximal possible volume of red mud utilization. The calculation analysis showed that interrelation 50% of red mud and 50% of oiled rolling scale meet the requirement. Calculated blast furnace heat indicators presented while applying briquettes and pellets from red mud and oiled rolling scale in the burden.