Characterisation of Wheat Straw Pellets Individually and in Combination with Cassava Starch or Calcium Carbonate under Various Compaction Conditions: Determination of Pellet Strength and Water Absorption Capacity

Abstract

This study aimed to optimise the production conditions of wheat straw (WS) pellets and pellets with the additives of cassava starch (CS) or calcium carbonate (CC) based on the criteria of pellet strength and water absorption by crushed pellets. The pellets produced using a 2–10%-wt/wt additive ratio, material moisture of 10–30% w.b., die height of 66–86 mm, and material temperature of 78–108 °C were tested. The influence these factors on the strength parameters of pellets was different than on the water absorption by the crushed pellets. The pellets made of WS blended with CC additive were characterised by better strength parameters and the compressed pellets were characterised by better water absorption than those with CS. High and positive correlation among specific pellet compression work, elasticity modulus for pellet compression, and tensile strength values were observed. As the strength parameters of pellets showed high correlation with single pellet density, for the consistency of conclusions, the optimal conditions for pellet production were assumed based on the density. For optimal conditions at 4% wt/wt additive ratio, 23% w.b. material moisture, 78 mm die height, and 80 °C material temperature, the specific pellet compression work was 3.22 mJ·mm−2, elasticity modulus was 5.78 MPa, and maximum tensile strength of the pellets was 2.68 MPa; moreover, the water absorption by crushed pellets amounted to 2.60 g H2O·g−1 of dry matter.

The Use of Bread Bakery Waste as a Binder Additive in the Production of Fuel Pellets from Straw

“…According to Matkowski et al [12] and Nath et al [38], who studied the process of straw pelleting with various additives, the optimal range of moisture content for the pelleted mixture was approximately 18-20% due to the formation of durable pellets with the highest bulk density and kinetic strength. Niedziółka et al [37], who examined the process of the pelleting of wheat, rapeseed, and corn straw, indicate that the optimum range of moisture content for the pelleting of material is 18-22%.…”

“…Matkowski et al [12] pelleted wheat straw with the addition of cassava starch and calcium carbonate. They concluded that unit compaction work, relative to dry matter, was the highest for wheat straw without additions, i.e., 18.1 kJ•kg −1 .…”

“…They found that mixing pine sawdust with other types of biomass reduces energy consumption during pelleting and, consequently, reduces the costs of pellet production [11]. Matkowski et al [12] produced pellets from wheat straw as well as pellets with the addition of cassava starch and calcium carbonate testing the strength and water absorption of the pellets. They observed a strong and positive correlation between the values of specific pellet compression work, the elasticity modulus for pellet compression, and tensile strength.…”

Pelletization of Biomass Feedstocks: Effect of Moisture Content, Particle Size and a Binder on Characteristics of Biomass Pellets

“…Maximum strength of spruce pellets (higher than 10 N/mm) was found at MC of 8.3% (at pressure of 300 and 400 MPa) [45]. Another study found the maximum strength of 2.68 MPa for wheat straw pellets at MC of 23.2% [71]. Mohammad Ramezanzade et al [72] recommended the MC of 11.7%, particle size of 1.65 mm and temperature of 100 o C for obtaining the higher quality of biomass pellets (i.e.…”