Dealing with pest infested wood in the pelleting process

The performance of a pellet plant depends highly on the feedstock quality and the pretreatment. The usual difficulties in operation increase when the wooden raw material is infested with pests and varmints. For the past years, we have been experiencing an increase in infections on a larger and broader scale. This means, more and more forests are experiencing dramatic losses. Infested wood is useless to the timber industry and needs to be removed from the woods to prevent further damage.

Effect of multi-layer feeding of sized green pelletson bed permeability, structure and properties of fired pellets in straight grate induration furnace

Green pellets while indurating in a straight grate induration furnace, pass through different thermal treatments, namely drying, preheating, heating and cooling. The firing of the pellet bed is downdraft using Corex gas and cooling is updraft using ambient air. Coke breeze is used as solid fuel to supplies the necessary heat for uniform heating of the pellet. The physicochemical conditions prevailing in the indurating furnace, i.e., feeding rate, bed height, pellet size, position of the pellets in the bed, temperature, partial pressure of oxygen, amount of fuel, etc. have bearings on the phases and structures of the fired pellets across the core to the shell. The time difference between the reduction and oxidation of the pellet depends on the size of the pellet as well as position of the pellet in the bed. The pellet size as well as the position of the pellet in the furnace has a marked effect on the formation of different phases and microstructure. Usually, mixed pellets of different sizes varying from 8 to 16 mm pellets are fired in duration furnace. The study was aimed at to optimize the pellet bed with different size range of pellets put in layers to make uniform firing and cooling of the pellets throughout the bed to achieve desired micro-structure and properties. The green pellets were divided into three sizes as A − coarse (–16 + 12.5 mm), B − medium (–12.5+10 mm) and C − small (–10 + 8 mm). The bed permeability of pellet plant induration furnace was 91.7JPU (Japanese Permeability Unit). Except permeability of pellet bed with single layer of smaller size pellets (C-C-C), the bed permeability with three layers, two layers & single layer of different size pellets was similar or greater than the bed permeability of pellet plant. From the results of basket trials conducted at pellet plant, it was found that the layer wise pellets like B-A-C, CA-B, AB-C and B-B-B resulted in higher Tumbler Index (TI) and Cold Crushing Strength (CCS) compared to other different size pellets as layer due to better slag bonding and lower pellet porosity. These pellets were exposed to optimum firing temperature as well as the cooling process with the presence of sufficient oxygen for the conversion of magnetite to hematite.

Environmental Sustainability of Heating Systems Based on Pellets Produced in Mobile and Stationary Plants from Vineyard Pruning Residues

The impact of heat production from vineyard pruning pellets has been evaluated in this paper. The study considers two different systems: the first one based on a mobile pelletizer (PS1) and the second one based on a stationary pellet plant (PS2). The analysis conducted is from “cradle to grave”; the systems under analysis includes pruning harvesting, transport to storage area, pelletization (mobile system or stationary production plant), transport to consumer and combustion. The functional unit selected is 1 MJ of thermal energy produced. The impact assessment calculation methods selected are Eco-Indicator 99 (H) LCA Food V2.103/Europe EI 99 H/A with a midpoint and endpoint approach, and ReCiPe Midpoint (H) V1.10. Considering Life Cycle Assessment results, Eco-indicator shows a total impact of 4.25 and 4.07 mPt for mobile pelletizer and stationary pellet plant, respectively. Considering the three damage categories, PS1 has values of 2.4% (Human Health), 3.8% (Ecosystem Quality) and 17.3% (Resources), more impactful than PS2. Contribution analysis shows that direct emissions are the major damage contributor, followed by wood ash management. From a comparison between the baseline scenario and a scenario with an avoided product (wood ash as a standard potassium fertilizer), PS1 and PS2 with an avoided product approach are 41% and 40% less impactful than in the baseline scenarios. When testing the impact of mobile pelletizer while considering transportation as a factor, a reduction of distance for pellet has been evaluated. Reducing the distance from 100 to 10 km, the total impact of PS1 almost reaches the impact of PS2 with a difference of around 4.6% (Eco-indicator 99 method). The most impactful processes are pellet production, direct emissions and ash management, while a less impactful factor is the electricity consumption. Transportation shows the lowest impact. Considering the ReCiPe impact calculation method with a midpoint approach, the results confirm what was found with Eco-indicator 99; the PS1 shows a slightly higher impact than PS2.

The Potential for a Pellet Plant to Become a Biorefinery

The use of bioenergy has increased globally in recent years, as has the utilization of biomaterials for various new product solutions through various biorefinery concepts. In this study, we introduce the concept of using a mechanical dewatering press in combination with thermal drying in a pellet plant. The purpose of the study is to increase the understanding of the effects a mechanical dewatering press has in a pellet production chain and investigate whether a pellet plant could thus become a biorefinery. The evaluations in this study are based on industrial data and initial tests at the university. The results show that the concept of using the mechanical dewatering press together with a packed moving bed dryer reduces energy use by 50%, compared to using only a packed moving bed dryer. The press water could be used as a raw material for biogas, bioplastics, and biohydrogen. Hence, this study points out the possibilities of a pellet plant increasing the efficiency of the drying step, while moving towards becoming a biorefinery.