**3. Results**

A large survey carried out over the year 2015 (see **Figure 4**) showed that position M710 was the main responsible for the blockages of the biomass system (35% of the total occurrences), being, therefore, the position chosen for the study and solution of the problem. **Figure 5** shows the simplified schematic drawing of the main components of the equipment in the M710 position.

**Figure 4.** *Number of cloggs per position in 2015.*

#### **Figure 5.**

*Schematic drawing of the M710 thread and main items.*

The initial analysis of the work on the position defined as the focus aimed to identify external factors that could contribute to the clogging being recurrent or severe. Some indicators such as average precipitation, average steam generation load, and possible operational variations between groups or work shifts did not show influence with the occurrences. As already known, the particle size quality of biomass was a point of attention, but not directly addressed, as the actions for this topic are medium and long term.

Through the "5 Whys," it was possible to observe that the biggest challenges of the M710 position were the "empty spaces" and the obstructions present in the path taken by the biomass. The actions focused on solving these root causes were:

### **3.1 Manhole readjustment**

The manhole present in the screw fall duct was misaligned with the fall wall profile. This misalignment generated an "empty space" inside the pipeline, serving as support for the deposition of biomass, which, over time, totally obstructed the transverse profile of the pipeline, causing clogging. Thus, the simple solution was to fill the empty space with metallic material, welded to the manhole, which would eliminate the space and keep the walls of the entire duct in the same profile, as shown in **Figure 6**.
