Effect of Carboxymethyl Cellulose Binder on the Quality of Biomass Pellets

Abstract

Quality and energy efficiency are two critical concerns associated with the production of biomass pellets. This study elaborates methods to improve the quality of biomass pellets by using a new additive solution (carboxymethyl cellulose (CMC)) and its influence on pellet physical and mechanical properties during the densification of three types of agricultural waste (cotton stalks, wheat straw, and rape straw). Simultaneously, the cohesion and binding mechanisms were analyzed with attenuated total reflectance infrared spectra (ATR-FTIR) and light microscopy (LM). The results show that adding CMC lowers the energy consumption and increases the pellet quality by improving relaxed density, compressive strength, and durability for cotton stalks and wheat straw. However, adding CMC to rape straw decreased the pellet quality. Our results showed that addition of CMC leads to electrostatic forces among the particles that might be responsible for the cohesion strength of biomass pellets, which may be attributed to the formation of polyelectrolytes. The electric dipole from water molecule in biomass and OH groups on the CMC formed the hydrogen bond. In addition, strong bonds, similar to solid bridges, were formed at the interfaces between CMC and biomass solid particles. These interactions enhance interparticle bonding in the pellets, thereby improving the product quality and providing an efficient means to convert agricultural waste into biomass energy.

Recent Developments of Carboxymethyl Cellulose

“…In some recent studies, CMCs have been reported as a cost-efficient binder in biomass pellets that considerably enhanced the quality, durability, and compressive strength of the biomass pellets and reduced the energy consumption extent shells [ 70 , 362 ]. On the other hand, due to the presence of cation-enticed carboxyl groups, CMCs can be hybridized with various metal ions such as Fe 2+ , Ca 2+ , Al 3+ , Mg 2+ , etc., via cross-linking processes to synthesize numerous aerogels with tunable physiochemical and morphological characteristics [ 363 ].…”

Pellet Production from Woody and Non-Woody Feedstocks: A Review on Biomass Quality Evaluation

“…Other binders which have been shown to increase the mechanical characteristics of pellets are sugar beet molasses [99], Persea kurzii kosterm powder [100], carboxymethyl cellulose [101], calcium carbonate [102], and cow dung [103]. Cashew nut shell decreases the mechanical characteristics but increases the LHV of pellet of approximately 1 and 0.5 cal•g −1 in comparison with the use of Persea and dammar as binders, respectively.…”

Pelletization of Sunflower Seed Husks: Evaluating and Optimizing Energy Consumption and Physical Properties by Response Surface Methodology (RSM)

“…To the best of our knowledge, there is no ISO standard for energy consumption for pelletization. However, many researchers have focused on this index [24,25,33,47,50,[59][60][61]. According to Equation (1), the curve of the force (F 1 , F 2 ) and displacement (x 1 , x 2 ) can be obtained by a single pelletizer.…”

“…As reviewed in Figure 8, during the pelletization process, the average energy consumption of wood pellets is around 40 kJ/kg, and the energy consumption of straw pellets is generally in the range of 13-25 kJ/kg. That is, the energy consumption of wood pellets is much higher than that of straw pellets, which is mainly because straw plants contain more cellulose and hemicellulose [61]. These natural binders are easier to form and agglomerate, resulting in lower energy consumption for the pelletization of straw [65].…”