CONVERSION OF BIOMASS WASTE INTO COAL-LIKE SOLID FUEL VIA HYDROTHERMAL CARBONIZATION WITH CITRIC ACID ADDITION

• Main Author: Eriska Putra, Herlian
• Format: Dissertations
• Language: Indonesia
• Subjects: Teknik saniter dan perkotaan; teknik perlindungan lingkungan
• Online Access: https://digilib.itb.ac.id/gdl/view/43975
• Institution: Institut Teknologi Bandung

Biomass is considered as one of alternative renewable energy source. Although it has a very abundant resource in nature, biomass can be a challenge for scientists to make it as cheap alternative energy. One of the biomass sources that has not received attention is the municipal solid waste (MSW) as an energy source. Municipal waste generally contains organic material (lignocellulose) which has a calorific value high enough to be potentially used as fuel. Due to high moisture content and really season dependant, municipal waste has very difficult to be processed directly by the existing thermal process such as incineration, gasification, and pyrolysis. In this study, waste processing technology has been developed. The process of hydrothermal carbonization (HTC), was able to convert wet biomass waste into solid fuel (char). Unlike gasification or pyrolysis, the process was fairly simple, because it employed temperature typically ranging 180-240 oC. HTC involved subcritical pressure water as process medium, so it is considered very suitable for the characteristics of the MSW in Indonesia which is heterogenic, moist, and easily decomposed. The novelties of this study were the using of citric acid (C6H8O7) with various concentrations as an additive and the kinetics of the degradation reaction of lignocellulose components in biomass waste. The raw materials come from the local waste components that characterize typical waste component big cities in Indonesia, which was represented by one temporary waste disposal (TPS) in the city of Bandung. This citric acid was chosen beacause of its harmless and inexpensive. The additive was used due to its ability to accelate decomposition reaction of waste. Citric acid is organic acid that able to be carbon donors. It also can reduce O/C and H/C ratio. Identification and characterization of the liquid and gas product from the HTC and the kinetics of degradation reaction of lignocellulose in municipal waste typical of developing countries have been done. In the initial stages, the performance and leakage test of the prototype reactor HTC constructed by Research Center for Chemistry LIPI have been done. The lab-scale batch HTC reactor with a volume of 1 L was made of stainless steel 304 equipped with an electric heating mantle. The parameters observed were reactor performance in terms of producing vapor pressure, where the value of the pressure obtained was compared to the steam table. The result was that the coefficient of determination (R2) value of pressure generated from the HTC reactor made was 0.9865, quite similar to the steam table. After making sure the reactor worked properly, a series of HTC experiments has been carried out to obtain the optimum conditions of several parameters, including temperature (190, 210, 230 oC), feed to water ratio (1:3; 1:5; 1:10), and processing time (30 and 60 minutes). HTC experiments were carried out on each waste pseudo-component (sawdust, paper, fruit peel, leaves and twigs, and food waste) and mixed waste. The composition of the mixed waste fraction consists of 15% fruit peel, 10% food waste, 10% paper, 30% leaves and twigs, and 35% sawdust. The results to be observed were the characteristics of mass yield and energy yield of HTC products. Based on the results of HTC's experiments on each component of waste, the optimal temperature was formulated for HTC mixed waste. Characteristics of the mass yield of hydrochar in the HTC process showed the same profile for all biomass feedstocks. The solid mass obtained at the end of the process varied between 30-70%. The energy yield corresponded to approximately 40-80%. The results also showed that hydrothermal treatment of biomass waste for solid fuels gave a higher heating value (HHV) with a value of 24.55; 21.24; 20.08; 24.22 and 22.69 MJ / kg for sawdust, paper, fruit peel, leaves and twigs, and food waste, respectively. The formulation of temperature, feed to water ratio, as well as time for mixed waste and prediction of heating values for the HTC process of mixed waste were carried out on the composition of selected municipal waste biomass components. By adopting the ideal gas model, the operating conditions for the mixed waste are as follows: the temperature was 215 oC, the ratio of raw materials and water was 0.16, and the time was 55 minutes. Validation of the results of the formulation through experiments gave the highest calorific value of 20.24 MJ/kg. The heating value of HTC products obtained through formulation and experimentation did not differ significantly, which was equivalent to the heating value of sub-bituminous coal (19-24 MJ/kg). This optimum operating condition was used in the HTC experiment for mixed waste with and without using the C6H8O7 additive. The variations in the concentration of the additive; 1, 2 and 3% (weight/weight of feedstock). From the experiment, it was found that the addition of additive in small amounts (? 3%) has less increased hydrochar yield. Calorific value has increased around 30% when citric acid presented in HTC process. During process, biomass lost its water molecule so that the pore of biomass was covered by carbon atoms from citric acid. From the reaction kinetics the activation energies of the lignocellulose component degradation were 215,27 kJ/mol (lignin), 142,27 kJ/mol (cellulose), 61,34 kJ/mol (hemicellulose). Studying on kinetics will provide a solid basis for the design of sustainable HTC processes and to get an evaluation of economic studies on scale-up processes. Based on the analysis of benefits and costs of municipal solid waste treatment systems with HTC technology, it was found that the value of the Benefit-Cost Ratio (BCR) was 1.188 which means the project was feasible to be