Figure 1.
![Scheme of the SS-3 test stand for testing the compaction process [18]: 1 – press, 2 – base, 3 – compaction chamber, 4 – thermostatic element, 4a – heating band, 5 – chamber bottom, 6 – compacting piston, 7 – stub pipes, 8 – displacement sensor, 9 – multi-channel recorder, 10 – temperature controller, 11 – computer](https://sciendo-parsed.s3.eu-central-1.amazonaws.com/64706e6e83f1392090d696f0/j_acee-2018-031_fig_001.jpg?X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Content-Sha256=UNSIGNED-PAYLOAD&X-Amz-Credential=AKIA6AP2G7AKOUXAVR44%2F20251107%2Feu-central-1%2Fs3%2Faws4_request&X-Amz-Date=20251107T072122Z&X-Amz-Expires=3600&X-Amz-Signature=085eab5030b4358af67cac570d46485c3ce10c8f191f420473c6b7133cc241fc&X-Amz-SignedHeaders=host&x-amz-checksum-mode=ENABLED&x-id=GetObject)
Figure 2.

Figure 3.

Figure 4.

Results of rye straw compaction process with 20% hard coal addition
| Independent variables | Dependent variables | ||||||
|---|---|---|---|---|---|---|---|
| x1=tp [°C] | x2=w [%] | Average force under the piston [N] | Maxiumum agglomeration pressures [MPa] | Avrerage agglomeration pressures [MPa] | Work of agglomeration [J] | Pellet density [kg·m-3] | |
| 1 | 30 | 15 | - | - | - | - | - |
| 2 | 30 | 20 | 1036.54 | 36.39 | 16.45 | 38.35 | 1139.82 |
| 3 | 30 | 25 | 430.04 | 20.65 | 6.83 | 15.91 | 871.37 |
| 4 | 50 | 15 | 846.60 | 29.93 | 13.44 | 31.32 | 970.58 |
| 5 | 50 | 20 | 796.01 | 31.04 | 12.64 | 29.45 | 1066.91 |
| 6 | 50 | 25 | 362.93 | 16.25 | 5.76 | 13.43 | 737.95 |
| 7 | 70 | 15 | 428.58 | 16.16 | 5.48 | 16.29 | 908.03 |
| 8 | 70 | 20 | 925,05 | 26.30 | 14.68 | 32.23 | 1063.69 |
| 9 | 70 | 25 | 417.93 | 14.98 | 6.63 | 15.46 | 715.48 |
| 10 | 90 | 15 | 41.77 | 1.82 | 0.66 | 15.45 | 578.48 |
| 11 | 90 | 20 | 470.29 | 14.53 | 7.46 | 17.40 | 1004.47 |
| 12 | 90 | 25 | 541.39 | 14.78 | 8.46 | 20.03 | 756.82 |