*2.3. Research Material*

The research presented in this study concerns the co-firing of sludge with the composition given in Table 2 and hard coal with the composition shown in Table 3. The co-firing process was carried out in the furnace shown in Figure 1 (a fireplace with a fixed grate). The proportion of sludge in the burnt mixture was 15%, and the proportion of moisture in the sludge was 40%. The remaining parameters of the process were as follows: the initial thickness of the fuel layer on the grate was 10 cm, the theoretical ratio of excess air to combustion was 1.4, and the duration of the process was 40 min.

**Table 2.** Selected parameters of sludge used in the tests (d.w.—dry weight).


\* oxygen content = 100%−carbon content %−hydrogen content %−nitrogen content %−sulfur content %−content of noncombustible parts %.


**Table 3.** Selected parameters of coal used in the research.

\* oxygen content = 100%−carbon content %−hydrogen content %−nitrogen content %−sulfur content %−content of non-combustible parts %−humidity content %.

## *2.4. Distribution of Primary Air*

Under the above-mentioned conditions, the tests were carried out for three variants of air stream distribution, which involved the relative version R ∈ [1/6, 5/12, 2/3], which in order to obtain absolute values should be multiplied by T.

In Figure 3, for the aforementioned R values, theoretical air stream distributions, determined according to the Equation (2), taking into account the dependencies (5) and (6), are presented. Figure 4 shows air streams in individual zones during the carried-out tests, which simulate the air flow distribution curves described by the Equation (2), for the R values taken into account. In each variant, the air was fed into 5 zones.

**Figure 3.** Theoretical distributions of air streams for the values R analyzed in the study.

**Figure 4.** Average values of air streams delivered to individual zones during laboratory tests.

*2.5. Sequence of Procedures in the Determination of Gaseous Products of the Combustion Process*


For the values of air streams and concentrations of exhaust gas components resulting from the measurement, from Equation (11), taking into account Equation (9), the emission streams of exhaust gas components were calculated.
