Effects of potassium on solid products of peanut shell torrefaction

ABSTRACT

To investigate the influencing mechanism of potassium on solid products of biomass torrefaction, peanut shell, a typical agricultural waste in China, was selected as the feedstock and the experiments were carried out in the holding temperature range of 200 ~ 300°C, and in the atmosphere of nitrogen. Based on the water-leaching and impregnation (K₂CO₃, KCl and K₂SO₄; impregnation concentration: 0.5%K, 1%K and 2%K) methods, the results showed that the solid product yield of WLPS (water leached peanut shell) torrefaction was higher than that of RPS (raw peanut shell) torrefaction at 200 ~ 300°C. And all these three potassium salts (K₂CO₃, KCl, and K₂SO₄) inhibited solid product yields of torrefaction. Potassium existing in RPS was not beneficial for upgrading the organic content during the torrefaction process. The carboxylate was the key intermediate during the biomass torrefaction conversion process. Besides, the activation energy of WLPS (106.28 kJ·mol⁻¹) was higher than that of RPS (83.34 kJ·mol⁻¹) during the torrefaction. The impregnated potassium salts reduced the activation energy of WLPS torrefaction process. However, the activation energy of potassium salt impregnated WLPS torrefaction was still higher than that of RPS.

KEYWORDS:

• Potassium
• solid products
• peanut shell
• torrefaction
• kinetics

Additional information

Funding

The work was supported by the National Natural Science Foundation of China under Grant No. 51606103; the National Natural Science Foundation of China under Grant No. 51506098; and the Key Laboratory of Efficient & Clean Energy Utilization, the Education Department of Hunan Province under Grant No. 2017NGQ005.