Harvesting System Design and Performance - Engineering and Science of Biomass Feedstock Production and Provision - page 94

Fig. 5.8 Different types of conditioning rollers. Adapted from [ 21 ]

5.3.3 Chopping

Choppingisaprocessinwhichthecutplantsarereducedintosmallpieces.Chopping
is one of the basic operations needed for ensiling moist crops or for preparing bio-
massforcombustioninpowerplants.Choppingalsofacilitatesmaterialhandling
operations during transport and storage. There are two basic types of forage chop-
ping: precision cut and non-precision cut. Precision-cut chopping relies on a cylin-
drical cutter head and a stationary counter shear. Non-precision cut forage chopping
uses a flail cutter for cutting and chopping the standing crop [ 16 ]. The most impor-
tant parameters in the chopping operation are mean cutting length and energy con-
sumption. The mean cutting length depends on rotational speed of the cutting drum,
number of knives on the chopping drum, and incoming biomass feed rate.

5.3.3.1 Forage Harvesters

A forage harvester typically consists of a base machine and harvest head
(see Fig. 5.11 ). The forage head either cuts a standing crop or picks up the wind-
rowed biomass. The biomass is then conveyed to a chopper after which the biomass,
having been chopped into short pieces is conveyed to an accompanying wagon or a
trailed wagon. Forage harvesters may be tractor operated or self-propelled. Self-
propelled forage harvesters offer better maneuverability, operator conveniences,