Low cost Granulation of lignocellulosic biomass

Transcription

1 Low cost Granulation of lignocellulosic biomass Recipient Organization: University of Georgia Principal Investigator: Sudhagar Mani Project Location: University of Georgia Reporting Period: October 1, 2012 December 31, 2012 Date of Report: January 15, 2013 Written by: Sudhagar Mani 1. Planned Activities: Task 9 Surface properties of liquid binders (extended): The surface tension and the wettability of powders with binder solutions will be continued. The data would be highly useful in identifying the role of binders during granulation and the surface properties of selected biomass powders. Task 10 Testing of various binders for granulating Switchgrass powders: The purpose of this study is to identify the most suitable binder for Switchgrass powder for generating good quality granules with minimal binder use. 2. Actual Accomplishments: Task 9 Surface properties of liquid binders (extended): Surface tension: Surface tension was determined using force tensiometer (DCA-322, Cahn Instruments, WI, USA) by wilhmey plate technique. A platinum plate (19.62 mm 10 mm 0.11 mm) was lowered into the corn starch binder solution that was maintained at a temperature between 50 to 60 C. Force required to pull the plate from the surface of the binder solution was measured using a sensitive balance and used by the software given by the manufacturer to calculate the surface tension using the below equation F g = γ PR cosθ Where, F is interaction force between platinum plate and liquid, g is gravitational constant ( m/sec 2 ), γ is surface tension of sample solution, PR is wetted perimeter of platinum plate, θ is contact angle between platinum plate and sample solution. The procedure was replicated three times. The tensiometer was calibrated with two standard solutions (water and ethanol) having known surface tension values. Surface tension of distilled water at 25 C is mn/m or dynes/cm. Surface tension of ethanol at 25 C is to mn/m or 11

2 dynes/cm. After the calibration, the binder solutions were prepared and the surface tension of the unknown solutions was measured. Results The calibration data for both water and ethanol is reported in Table 1. The surface tension data for both solutions were very close the reported values with less than 2% error. Table 1 also shows the surface tension of binders used in the previous granulation study. The similar operating procedures will be followed for other binders used in this study. Surface tension of binders plays a crucial role in binding of particle together during wet granulation process. The data will be used to formulate low cost binders with selective binder characteristics for a specific application and developing a mechanistic granulation models to predict granule properties and strengths. Table 1. Surface tension of standard solutions/binders measured using a tensiometer in dynes/cm SL. NO Standard Temp. o C Average Std. Deviations Solutions/binders (dynes/cm) 1 Distilled water Ethanol Corn starch (2.5% conc.) Corn starch (5% conc.) Corn starch (7.5% conc.) Corn starch (5%) and sodium alginate (0.5%) Task 10 Testing of various binders for granulating Switchgrass powders: Material: Switchgrass straw was ground in a hammer mill (10HMBD, glenmills, NJ, USA) fitted with 1.58 mm screen and later it was again ground in a knife mill (SM 2000, Retsch, Germany) fitted with 0.25 mm screen. Geometric mean particle size of powder was determined as 180 mm by sieve analysis. Binders: Previous granulation study, calcium lignosulfonate was as a binder for switchgrass in the concentration range of 15-45%. In this study, various combinations of common binders are selected to reduce percent binder and to improve granule quality. Sodium alginate (Will powder, FL, USA), PURE-DENT B880 corn starch NF (grain processing corporation, IA, USA), Calcium Carbonate (analytic grade) and Arabic Gum (Food Grade) were selected and used at various possible combinations. Granulation: Granulation of switchgrass was conducted using a pan granulator and the procedures are similar to previously reported in Q2 Progress Report Results: Table 2 summaries the switchgrass granulation runs conducted using various binder combinations. The primary quality of granules was determined based on granule bulk density and granule (single granule crushing method used by granulation industries). Sodium alginate is commonly used as a binder and as an encapsulating agent. Arabic gum is used as a jelling agent. Figure 1 shows the granules generated 12

3 using various binder combinations. Among all the combination of binders, sodium alginate with corn starch and calcium carbonate binder generated relatively dense and good quality granules. The experimental runs 8 & 9 were conducted with Switchgrass powders pretreated with alkaline solution before granulation. Although the quality of granules was good, the percent binder was significantly higher among all the runs. Both sodium alginate and Arabic gum binders did not generate good quality binders (low bulk density and ). Among all the runs, the combination of sodium alginate with corn starch and calcium carbonate binder is recommended for Switchgrass to generate good quality granules. Pretreatment of Switchgrass may reduce the binder usage without compromising the quality of granules. Mild alkaline pretreatment of Switchgrass is proposed to disrupt the structure of switchgrass and relocate lignin on the surfaces to improve self-bonding of particles during granulation. The experimental plans and results of granulation study are under progress and are presented in the next progress report Figure 1. Switchgrass granules generated using various binder combinations (Note: Number on the picture represents granulation runs and conditions reported in Table 2). 13

4 Table 2. Summary of switchgrass granulation with various binder combinations SL. No. Binder Compositions a powder % (w/w) Total binder to Wet granule moisture content (wb%) Bulk density (kg/m 3 ) Comments 1 2 SA (0.5% w/w), CS (5% w/w), CaC0 3 (5% w/w) (1.14) SA (1% w/w), CS (5% w/w), CaC0 3 (5% w/w) (0.55) Fairly spherical in shape; medium Fairly spherical in shape; medium 3 4 SA (0.5% w/w), AG (1% w/w), CaC0 3 (5% w/w) (1.53) Less spherical in shape; low SA (1% w/w),ag (1% w/w), CaC0 3 (5% w/w) (0.79) Less spherical in shape; low 5 Dry mixing of Arabic gum powder was mixed with switchgrass powder (10% w/w) (0.67) Very spherical and uniform granules; low 6 SA (2% w/w) (0.60) not spherical shape granules; low 7 SA (1% w/v), CaCl 2 (1% w/v) (0.82) medium 8 b CS (5% w/w) (0.66) Uniform and spherical granules; medium 9 b LS (14.7% w/w), AG (2.60% w/w) (1.52) Uniform and spherical granules; medium a Note: SA: Sodium Alginate; CS: Corn Starch; CaCO 3 : Calcium Carbonate; CaCl 2 : Calcium Chloride; AG: Arabic Gum b Switchgrass powder was treated with NaOH (0.5% conc.) and autoclaved for 15 min before granulating with a selected binder. 14

5 3. Explanation of Variance: N/A 4. Plans for Next Quarter: Task 11 Effect of alkaline pretreatment on the granulation of Switchgrass: The purpose of this study is to investigate the effect of alkaline pretreatment on the granulation of switchgrass and to evaluate the properties of pretreated switchgrass granules. 5. Budget: 6. Patents: N/A a. Funds Expended to Date (End of Reporting Period): $160,000 b. Remaining Balance of Funds: $40, Publications / Presentations: Mani, S A novel biomass granulation technology for a modern biorefinery. The Sun Grant Initiative National Conference on Science for Biomass Feedstock Production and Utilization, October 2-5, 2012, New Orleans, LA. Two of the referred manuscripts are under review. 8. Students Funded: Student Name Department Institution Thesis/Dissertation Title Degree Obtained/Date Program Area Vikram Yandapalli Food Science & Technology UGA Granulation of lignocellulosic biomass Fall 2012 M. Sc. In Food Tech. Yifei Vu College of Engg. UGA Systems Analysis of Biomass Granulation Technology Summer 2013 M. Sc. In Agrl. Engg. 15