A study on lignin characteristic as internal binder in hot briquetting process of organic municipal solid waste

Municipal solid waste has the potential to become renewable energy resource. As solid fuel however, municipal solid waste has many problems caused by its low bulk density. Briquetting process is widely used to overcome the problem of low bulk density in solid fuel. Organic fraction of solid waste is benefited with lignin as one of its constituent which could be utilized as internal binder in hot briquetting process. To provide better understanding of lignin characteristic as internal binder, briquetting research was commenced in two stages using dry leaves as the representation of organic fraction in municipal solid waste, which contains 35.14% lignin. First stage was aimed to search the opportunity for evaluating lignin characteristic with variance of briquetting pressure. The second stage was used to investigate the binding characteristic of lignin as briquetting temperature increased in the range of lignin phase transition from glassy to liquid phase. The mechanical strength of produced briquette was measured using drop shatter test. Experiment results show that briquetting pressure of 500 bar could be utilized to evaluate the lignin characteristic in briquetting process. Highest performance of lignin as internal binder in briquetting was obtained at temperature 164 °C. In this temperature, briquette with DSI as high as 83% could be provided. The improved quality of lignin in green strength condition was probably caused by mechanical interlocking and adhesion effect that appeared during hot briquetting process.