The problem related to the management of post reclamation dusts generated in the reclamation process of waste moulding sands with organic binders is presented in the hereby paper. Waste materials generated in this process are products hazardous for the environment and should be utilised. The prototype stand for the utilisation of this dangerous material in its co-burning with coal was developed and patented in AGH in Krakow. The stand was installed in one of the domestic casting houses. As the utilisation result the transformed waste product is obtained and its management in the production of ceramic materials constitutes the subject of the presented publication.
The paper, especially dealt with problems of reclamation of used furan sand, carried out in new, vibratory sand reclamation unit REGMAS developed by researches from AGH-University of Science and Technology, Faculty of Foundry Engineering in Cracow (Poland). Functional characteristics of reclamation unit as well as the results of reclamation of used sand with furfuryl resin are discussed in the paper. The quality of reclaim was tested by means of the LOI and pH value, dust content in the reclaim and at least by the the quality of the castings produced in moulds prepared with the use of reclaimed matrix.
The results of the efficiency of the primary reclamation process as well as the influence of the used sand temperature and other process parameters on it are presented in this paper. A separate stand realized on a reduced scale was built, which is an analogous process of the primary reclamation treatment of spent foundry sands. The used sands were introduced to the crushing process in an agglomerated form in the way typically used in industrial devices. The primary reclamation process was realized on a set of four horizontal sieves with decreasing mesh clearances while maintaining their geometrical dimensions applied in the Regmas industrial device. The model system consists of a vibratory drive mounted on the table, allowing us to control the supply frequency of the vibratory motors within a range of 40-60 Hz as well as the computer system for measuring the vibration parameters and drive power. The used sand on the quartz matrix with the KALTHARZ U404 resin and 100T3 hardener was used in our investigations. The used sand was prepared under the following conditions: cubic-shaped elements made of the applied furan sand was compacted by vibrations then hardened and subjected to heating under controlled conditions (as a “simulation” of the overheating process taking place in the mold after pouring). Time functions of the crushing and sieving process in dependence of the overheating degree of the reference sand samples (100°, 200°, and 300°C) were investigated at various table vibration frequencies and feed loads of the sieve set. The relative index of the crushing ability was determined.
The results of mechanical reclamation of waste moulding sands with furfuryl resin and activators of new generation are presented. The aim of the research described in this study was to determine what effect the addition of reclaim obtained in the process of dry mechanical reclamation could have on the properties of furan sands. The sand supplied by one of the domestic foundries was after the initial reclamation subjected to a two-step proper reclamation process. The following tests were carried out on the obtained reclaim: pH, S and N content, loss on ignition and comprehensive sieve analysis. The obtained reclaim was next used as a component of moulding sands with furfuryl resin, wherein it formed 50% and 80% of the base moulding material, respectively. The strength properties of the ready sand mixtures (bending strength Rg u and tensile strength Rm u ) were determined after the hardening time of 0.5, 1, 2, 4 and 24 hours.
The results of investigations of spent moulding sands taken from the mould at various distances from the surface of the produced casting, are presented in the paper. The casting mould was made with an application of the cooling system of the metal core in order to increase the cooling rate of the ladle casting. As temperature measurements in the mould indicated the heat flow from the metal did not create conditions for the complete burning of a moulding sand. The analysis was performed to find out changes of spent moulding sands caused by degradation and destruction processes of organic binders. Conditions occurring in the casting mould were discussed on the bases of testing: ignition losses, dusts contents, pH reactions and the surface morphology of the moulding sand samples. Factors limiting the effective mould degassing were pointed out. Operations, possible for realization, which can limit the reasons of a periodical occurrence of increased amounts of casting defects due to changing gas evolution rates being the result of the technological process, were also indicated.
The results of investigations of thermal reclamation of spent moulding sands originating from an aluminum alloy foundry plant are presented in this paper. Spent sands were crushed by using two methods. Mechanical fragmentation of spent sand chunks was realized in the vibratory reclaimer REGMAS. The crushing process in the mechanical device was performed either with or without additional crushing-grinding elements. The reclaimed material obtained in this way was subjected to thermal reclamations at two different temperatures. It was found that a significant binder gathering on grain surfaces favors its spontaneous burning, even in the case when a temperature lower than required for the efficient thermal reclamation of furan binders is applied in the thermal reclaimer. The burning process, initiated by gas burners in the reclaimer chamber, generates favorable conditions for self-burning (at a determined amount of organic binders on grain surfaces). This process is spontaneously sustained and decreases the demand for gas. However, due to the significant amount of binder, this process is longer than in the case of reclaiming moulding sand prepared with fresh components.
For the reason of environmental problems connected with the use of furan binders, attention is increasingly being paid to self-setting mixtures using alkali resols. A resol binder stabilized with KOH, NaOH is hardened by liquid esters with the formation of alkaline salts. The increase of their concentration affects the shortening of the mixture bench life, it also decreases strength, increases abrasive wear to moulds and cores, and results in uneconomical dilution of the reclaim with expensive new base sand. The length of life (bench life) of mixtures plays an important role in the manufacture of huge and voluminous moulds and cores in self-setting mixtures. This study aims at analyzing the function of reactive alkaline salts in the reclaim, monitors the consequences of its thermal exposure on the properties of selfsetting mixtures, and deals with development of methods evaluating its qualities.
The paper summarizes research realized by the author in laboratory and industrial conditions (foundries of cast steel and cast iron, castings up to 50 tons) on the effects of the chemically hardened molding sands regeneration using hard/soft rubbing in the dry reclamation. A reference was simultaneously made to advisability of application of the thermal regeneration in conditions, where chromite amount in the circulating (reclaimed) molding sand goes as high as above ten percent. An advisability of connecting standard and specialized methods of examination of the reclaimed sands and molding sands made using it was pointed out. A way of application of studies with the Hot Distortion Plus® method modified by the author for validation of modeling of the thermo-dynamic phenomena in the mold was shown.