Fireclay-silica production

Fireclay-silica production - production of refractory materials and articles of them, used in metallurgy for lining furnaces and in other industries. The main industry of refractories is the production of clay, silica, magnesia refractories (for example, magnesite, forsterite), as well as some other refractories (high-alumina, carbon).
Characteristic of all these productions occupational hazards is dust (see). The largest amount of dust is generated when crushing, grinding, preseve and burning of raw materials. Less dust when molding products, their drying, roasting and sorting. Adverse to the body of work is also puregrainaudio or cooling microclimate; in the air furnace departments may contain carbon monoxide and sulfur dioxide. The content of free silicon dioxide (SiO2) the most high in silica and quartzite that serves as raw material for it (over 90%); followed by chamotte (18-30% free and about 50% of the total SiO2) and clay serving as the raw material for its production (respectively 10-15% and 50%), and magnesia refractories (about 1% and 1.5-4%). In such sequence is reduced pneumoconioses dusts of refractories.
The firing, and then operation of refractories furnaces lead to the transformation of quartz in other crystal modifications free silicon dioxide, higher silicotungstic. Therefore, fireclay, according to experimental data, in respect of silicosis is more dangerous than the original clay. However, according to the same data, silicotitanate Dinas not higher, and often lower than the original quartzite; this can be explained by a braking effect generated by the burning of amorphous phase (glass), on the border with which the silica occurs transformation of silica in the cristobalite and tridymite.
Significant physical tension, typical for a number of sites of production of refractories, significantly increasing the volume of respiration, raises the possibility of the development of pneumoconiosis (see). There are experimental data indicate increasing its also influenced by inhalation of harmful gases (CO, SO2) and the cooling effect of the air. In addition pneumoconiosis, with the effect of the dust of refractories can be partly a result of non-specific respiratory diseases (especially chronic bronchitis) and digestive organs (chronic gastritis).
Of the works connected with application of refractories, most unfavourable in hygienically repair of industrial furnaces (especially open-hearth), where a considerable physical and thermoregulatory voltage of the body combined with high concentrations of dust in the air. Dust in the repair Martin contains about 50% of iron oxide and on average about 10-15% free SiO2 (last until relatively recently was much greater, as in the brickwork furnace more than now, was composed of silica and clay and less of magnesia refractories). Among masons-refractory employees found pneumoconiosis, which symptoms, course and morphological characteristics can be attributed to silicosis.
For dusts of various refractories and raw materials in the USSR establishes the following maximum permissible concentration in the air of working premises: quartzite, Dinas - 1 mg/m3; chamotte -2 mg/m3, clay, forsterite - 5 mg/m3; Magnezit - 10 mg/m3. Along with events aimed at the reduction of dust content of air up to these levels (shelter and aspiration equipment, gidroobespylivanie, wet cleaning of premises and other)important health importance transition to roasting products in tunnel furnaces, as well as automation of the charge of raw and other activities that reduce the severity of physical labor. Dusting and other hazards works on repair of a laying of furnaces of refractories while technically not considered fully resolved. The above-mentioned change of the set of refractory brickwork of open-hearth furnaces reduces silicotitanate labour. The ego, however, improvement is not radical as not ultimately solve the issue has already been implemented on the advanced metallurgical plants means of mechanization of repair work. As palliative measures necessary introduction of means of individual protection (air-cooled suits, helmets with supply dust-free air).