**3.7. Distribution of nanoparticles in the premises of the continual casting equipment**

## *3.7.1. Measuring point a)*

446 Atmospheric Aerosols – Regional Characteristics – Chemistry and Physics

**Figure 29.** Measuring point at the slab continual casting

described below.

**Figure 30.** Measuring point in the steelworks dispatching section (at the scarfing machine)

Measurements of particles trapped in personal cascade impactors were performed in the convertor hall of the steelworks in 2 selected locations under the technological conditions

The average flow rate in the first location was 0.12 m·s-1 (determined with TESTO 445 with a thermal probe). 6 spectrums were measured in total with the distribution of size of aerosol particles ranging from 14 to 736 nm. The distribution of the size of aerosol particles obtained by averaging the collected spectrums is shown in the diagram in Figure 31, Table 9.

**Figure 31.** Distribution of aerosol particles in the measuring location a)

The mode of the collected spectrum is around 20 nm. The presented spectrums indicated presence of particles under 10 nm, which may be estimated from the size distribution


**Table 9.** Measured physical values of nanoparticles – point a)

## *3.7.2. Measuring point b)*

The average flow rate in the location was 0.27 m·s-1. The distribution of size of aerosol particles obtained in this measurement location is shown in the diagram in Figure 32, Table 10.

The higher flow rate has probably also affected the uneven distribution of the size of aerosol particles. The different technological development of the operation during which the measurement was performed also played a role.

Experiences with Anthropogenic Aerosol Spread in the Environment 449

**Conversion into volume concentration (mg/m3)** 

**(mg)** 

A 2.5 0.12 2.40 B 1.0 0.15 3.00 C 0.5 0.09 1.80 D 0.25 0.12 2.40 < 0.25 0.18 3.60 **Total 0.66 13.20** 

A 2.5 0.38 7.60 B 1.0 0.35 7.00 C 0.5 0.45 9.00 D 0.25 0.33 6.60 < 0.25 0.38 7.60 **Total 1.89 37.80** 

**Sampling point Sorting level (µm) Trapped particles a)**

**Pourover into the pre-treated melt** 

**Pourover of raw iron** 

a) air flow rate 10l/min. for a period of 5 minutes.

**Table 11.** Individual trapped fractions of aerosols in the first impactor

trapped in the filter by sorting levels are shown in Figures 33 and 34.

small crystals which came into immediate contact in the atmosphere.

the presence of non-reacted iron in the particle core.

Samples of trapped particles at the pourover of raw iron were submitted for electron microscope analysis. The images made by the electron microscope based on the particles

Pictures made by a scanning electron microscope show visible particles from several hundreds of nanometers to ca. 5µm. The evaluation of the sizes of the observed particles has made it possible to estimate that the most numerous particles were in the range from 1 to 2µm. The prevailing majority of trapped particles in fine atmospheric aerosols were spherical; see Figure 33. In agreement with the generally accepted theory, particles of the size of units of micrometers are formed directly by the solidification of finely dispersed liquid aerosol of liquid iron. If the cooling rate is sufficient, round particles with some signs of crystalline structure of atoms on the surface appear instead of crystalline formations. On the contrary, if the conditions for a transition into a solid state are different, particularly in terms of the cooling rate, then fairly interesting crystalline formations can be found between the particles, as shown in Figure 34. The resulting product is actually an aggregate of very

The entire process of formation of the fine aerosol is accompanied by a chemical reaction in which melted iron particles are in a thermodynamic imbalance with oxygen from the atmosphere, and therefore an intense exothermic chemical reaction occurs on the surface of the particles which produces oxidation products of iron. The resulting formations are shown in the pictures. A chemical analysis of particles with EDS has confirmed the variable values of the Fe/O ratio. In some cases the atomic ratio Fe/O was > 3/2, which may be explained by

**Figure 32.** Distribution of aerosol particles in the measuring point b)

The maximum peak of the doublet shape in the area around 20 nm corresponds to the distribution measured in the measuring point a) but the concentration of the particles was higher. Another area with an increased number of particles is around 120 nm, while this phenomenon was not observed in the previous case. The overall concentration of particles in the nano area is by one order of magnitude higher, the weight of the particles 5x higher than in the previous case.


**Table 10.** Measured physical values of nanoparticles – point b)
