Densification of untreated crops

Goals and scope of task

The goal of this task was to improve conventional densification processes – both from equipment and operating point of view – to make these more suitable for woody as well as grassy energy crops. Although the focus was on briquetting technologies, a general comparison was made between briquetting technologies and standard pelletizing technologies for both woody and grassy energy crops.

Main results and reports

Optimized briquetting and pelletization recipes for the nine woody and grassy energy crops investigated in Logist’EC are given in Deliverable 3.1, which is based on a literature review, and Deliverable 3.2, and Deliverable D3.3 based on single-pellet and bench-scale tests, respectively.

The following 1-page poster gives a quick overview of these results, which are also summarized below.

In total twelve biomass samples (from seven different species) were tested. Samples were ground using the same hammer mill after receiving, particle size distribution and moisture content were determined for each sample. Single-pellet press was used to study the pelletizing properties of different biomass. First, each biomass has been adjusted to three different moisture contents, and the friction between pellet and press channel during pelletizing and pellets’ densities were determined to choose the optimal moisture content for each biomass. Second, the influence of pellet press temperature on the friction during pelletizing was measured for each kind of biomass in order to find the optimal die temperature in real pellet production. It was found different biomass has different desired temperature for pelletizing. In the end, three kinds of biomass (fresh miscanthus, triticale, and fescue) have been pelletized in a bench-scale pelletizer to test the proposed theory of die temperature influence. The results showed good consistency with our theory, a steady pellet production requires die temperature reaching a certain level, which is dependent on biomass species.