**3. Results and discussion**

*Fillers - Synthesis, Characterization and Industrial Application*

processes taking place.

**2. Experiment**

up to 4 dm3

**Table 1.**

(SC-T)

**Table 2.**

Shale coke > heated at 250 C

*Characteristics of the fillers.*

characteristics.

The prototype of method [16] is the method for determining the sintering ability of coals [18]. Caking coal is used instead of pitch, and anthracite is used instead of coke. It should be noted that in the prototype, the determination temperature reaches 600°C, which has a decisive influence on the physics-chemistry of the

In our opinion, for pitches as caking binders, it is important to evaluate the adhesive strength of their contact with fillers. In this case, the activity of the fillers will be the "sintering strength" and/or the "sintering capacity" of the pitch [19]. By the strength characteristics of the pitch composites, quantitative estimates of the quality of pitch as a binder relative to the selected filler can be obtained, as well as evaluation of the activity of the fillers with respect to the selected pitch. It is assumed that the use of this approach will allow to determine the optimal mass ratios of the binder-filler. In this case, the transition of the pitch to a solid state must be irreversible. Only then will it fully reproduce the physicochemical processes of interaction between the binder and the filler that occur during the production of the composite.

In our work, we used industrial pitches as binders. Pitch samples were taken

; the pitches were mixed, quartered, and sieved through a sieve

*V* **B1**

**%**

**C H**

in the production conditions of coke plants. The volume of the sample was

Softening point, °C 85.0 72.0 Yield of volatiles, % 53.8 59.0 Quinoline insoluble, % 10.5 8.2 Toluene insoluble, % 33.2 28.2 Ash, % 0.11 0.13

**Samples W<sup>a</sup> Vdaf A, % dt, g/cm3 Elemental composition,** 

Pitch coke (PC) 3.0 0.8 0.3 1.53 96.5 0.45 Shale coke (SC) 2.8 0.9 0.25 1.50 97.2 0.22

Anthracite (A) 3.0 5.5 4.0 did not determine 94.0 4.1 Strained glass 0 0 did not determine 2.6 did not determine

Washed sand 0 0 1.51

0.9 0.5 did not determine 2.0 did not determine

**Characteristics Pitch mark**

*Characteristics of the pitches that were used as a binder.*

to a laboratory sample with a fraction of 0.5–0.25 mm. **Table 1** presents their

**20**

The photographs of the surface of the filler grains (**Figure 1**) clearly show the difference in their structure. For shale coke (**Figure 1a, b** and **e,f**), there are at least two types of structures: sponge (**Figure 1a**) and layered fibrous structures (**Figure 1b**). The grain sizes with a spongy structure in **Figure 1a** are about 180–450 μm, and the grains of shale coke with a layered structure are 100–300 microns in diameter and 800 μm in length. The thickness of the layers in the grains of the layered structure according to optical microscopy is <2–5 μm. The surface of the pitch coke grains is most rough with numerous pores (**Figure 1c, g** and **i**), which coincides with the data [20]. Lamellar anisotropic structures are visible on the pitch coke (**Figure 1g**). In the case of good wettability, the caking can give a strong adhesive bond and a significant proportion of adhesion due to the capillary penetration of the pitch in the pores of the filler.

The surface of anthracite grains is the smoothest. It is well visible that the surface is sometimes chipped with folded structures. Anthracite grains have a large variation in size from 20 μm to 100–160 μm. Anthracite dust is present on the surface of the grains in the photographs (**Figure 1d**).

Samples of composites for mechanical testing were prepared as follows. Mixtures of pitch and an inert filler (anthracite, sand, glass, pitch coke (PC), shale coke (SC), and shale coke after heat treatment (SC-T) at 250°C) in different proportions (from 1:1 to 15:1) are charged in cells of ceramic cassette (**Figure 1**), preliminarily placed in a special coking chamber (**Figure 2**). One loading of the cassette camera allows to receive 14 samples of char from the pitch composites. The heat input in the coking chamber was carried out from below, since radial heating of the cylindrical sample has a temperature gradient along the radius of the cylindrical charge—the outer layers of the charge in the coking chamber undergo heat treatment for a longer time than in the central part. With one-sided heating (from below), the temperature gradient in the loading of the coke composition is available in the height of the load. Therefore, semicoke samples of the pitch composite for mechanical testing had a gradient of strength in height, but in the fracture region, samples were prepared at the same temperature (500°C).

Isothermal aging at the final treatment temperature is designed to increase the homogeneity of the composite in the radial plane.

Mechanical test samples of solid residue from the pitch composites are carried out according to the procedure described in [4], using a cassette chamber (**Figure 2**).

Each semicoke sample of the pitch composite was placed in the test cell (**Figure 3**), and mechanical strength tests were carried out so that the fracture region of all samples was in the semicoke plane heated to a temperature of 500°C. All the samples in the fracture region had the same final heating temperature, and the strength of the semicoke sample of the pitch composite was determined in an isothermal layer.

We believe that since the strength of the coke (filler) is higher than that of the semicoke matrix, the destruction of the sample during our tests was mainly carried out on the pitch matrix (cohesive failure), and the filler grains were not destroyed.

**Figure 1.**

*Structure of filler surface (SEM): a – shale coke (×200); b – shale coke x 100); c – pitch coke (×200); d – anthracite (×200). Optical microscope, polarized light, ×500): e, f – shale coke; g, h – pitch coke.*

**23**

**content**

**Figure 3.**

**Figure 2.**

concentration maximum.

we calculate the discriminant and determine the roots.

*Test machine and test cell for testing composite for strength.*

*Determining the Filler Activity in the Sintering of Pitch Composites*

**3.1 Determining the filler activity by the positive root of the parabola equation, which describes the dependence of the pitch composite strength on the filler** 

*Coking chamber for samples of pitch composites: 1 – cassette of ceramic cells; 2 – coking chamber; 3 – heater.*

The dependence of the pitch composites of the semicoke's strength on the mass ratio of the pitch and filler is investigated. As a rule, an extreme dependence of the strength on the degree of filling was observed, characterized by the presence of a

A second-order equation is a reasonable approximation. For all the equations,

**Table 3** shows the equations of the second-order curves describing the dependence of the strength of the semicoke from the pitch composites on the composition

*DOI: http://dx.doi.org/10.5772/intechopen.82012*

*Determining the Filler Activity in the Sintering of Pitch Composites DOI: http://dx.doi.org/10.5772/intechopen.82012*

## **Figure 2.**

*Fillers - Synthesis, Characterization and Industrial Application*

**22**

**Figure 1.**

*Structure of filler surface (SEM): a – shale coke (×200); b – shale coke x 100); c – pitch coke (×200); d – anthracite (×200). Optical microscope, polarized light, ×500): e, f – shale coke; g, h – pitch coke.*

*Coking chamber for samples of pitch composites: 1 – cassette of ceramic cells; 2 – coking chamber; 3 – heater.*

**Figure 3.** *Test machine and test cell for testing composite for strength.*
