**1. Introduction**

The evolution of energy consumption, based on fossils, has led humanity towards an insecure and expensive energy matrix. This has led many countries to consider the need for profound changes, including an intensification of the use of other energy sources, especially renewable ones, including wood [1].

The energy use of forest biomass also promotes increased use of existing commercial forests, due to the possibility of using forest residues, which are generally left in the field after harvesting and constitute potential sources of energy; in addition, the energy use of forest residues can economically make forest management activities and silvicultural treatments feasible [2].

The main existing barriers to the greater use of renewable energies are of an economic nature. It is considered that one of the most important factors in the use of biomass as an energy input, regardless of the technique used, refers to the cost of harvesting and transporting this raw material [3].

Among the main biomasses lignocellulosic of agricultural and forestry origin, may include rice straw, rice husk, wheat straw, sorghum straw, corn husks, sugarcane bagasse, wood chips, branches and sawdust, grass, etc. In addition, this type of biomass is composed mainly of cellulose, hemicellulose, and lignin [4].

Nowadays, the integration between forest harvesting and pulp mills became closer, always seeking more yield and sustainability in the integrated production chain. Reducing the age of wood, increasing areas for planting and the proportion of total trees destined for the production of pulp keep pushing the consumption of waste generated, both in harvesting and in wood processing. For these residues, the most commonly used destination is burning in power boilers to compose the industrial energy matrix, for internal (or external) use, in addition to completing the wood cycle, completing the total use of the cultivated material.

With the frequent increase in paper production and demand for wood by the Monte Alegre Plant, the availability of this type of material for burning is constantly rising and, consequently, the consumption by power boilers (see **Figure 1**).

The valuation of forest residues for energy purposes supports some critical quality parameters that uniformity of composition is one of them. Since it is a mixed material, the ideal is to maintain the most uniform possible proportions between the various components of residual biomass (wood, bark, branches, thick roots, etc.). When it is just wood chips, it is very important to specify the contents of maximum bark and ash they may contain, in addition to the moisture content that is critical for energy performance [5].

As much as there are technological advances in the ways of harvesting and debarking, there are still several factors that hinder the consumption of forest residues and bark. The main one is based on the physical and granulometric quality of the material itself, which, residues (especially eucalyptus) and bark, have fibrous characteristics, forming the so-called "ribbons" or "strips."

At the Monte Alegre plant (Telêmaco Borba, Paraná, Brazil), there are two biomass-based power boilers to supply the steam demand for the plant. These boilers feature different operating technologies: bubbling fluidized bed (BFB) and

**Figure 1.** *Evolution in the composition of the total biomass consumed in Monte Alegre in the last four years.*

*Reducing Clogs in Power Boiler Biomass Feeding System DOI: http://dx.doi.org/10.5772/intechopen.101991*

#### **Figure 2.**

*Representative drawing of boiler feed system via biomass screws (adapted from Babcock Power España [6]).*

circulating fluidized bed (CFB). In the CFB boiler, biomass is supplied to the power boiler and stored in two silos equipped with continuous level transmitters (weighing cells). Each biomass silo feeds two fuel lines and each silo is discharged by rotating devices with a drag arm and discharge screws. Each fuel line has a discharge screw, which transports the biomass to the metering screws and only in line 1 there is an additional transport screw [6]. **Figure 2** shows the representative design of the described system.

One of the consequences of high waste consumption is the clogging and kinking that this type of material causes. In addition, the fibrous characteristic of this biomass makes the material's specific volume larger, causing the feed screws to work at increasingly higher speeds in order to maintain constant the biomass feed mass rate and, thus, increasing the possibility of entanglements. These factors, linked to the high rate of waste consumption, contributed to one of the power boilers starting to suffer from events of this nature in 2015, increasing the unavailability of the biomass transport screws.

This deviation from an abnormal operating condition brings several problems, which are as follows:


Therefore, the objective of the work was to reduce the occurrence of clogging, increasing the availability of equipment.
