Co-firing of palm kernel shell (PKS) into 7 MW existing pulverized-coal boiler has been modeled and analyzed using the computational fluid dynamics (CFD). Co-firing of coal and PKS is a complex chemical reaction involving both gas and solid phases with turbulence effect along the combustor. In numerical simulation, two-steps global reaction mechanisms for homogeneous (volatile matter) and heterogeneous (char) combustion, turbulence and radiation heat transfer are considered. Moreover, five different mass fractions of PKS to coal are observed: 0 (fully coal), 10, 15, 25 and 50 %, respectively. In this study, the analysis is focused on the comparative prediction related to the distribution of temperature, velocity and produced gases of CO2, CO, SO2. As the result, higher PKS mass fraction leads to a favorable combustion in terms of combustion temperature and produced gases exhausted from the combustor.
This study aims at proposing a new and highly-efficient H2 purification system that is able to achieve a low carbon emission level. In general, the conversion of pure hydrogen fuel from syngas requires pressure within a range of 1.0 to 2.0 MPaG. However, the auxiliary power of a compression is quite high, and hence produces a greater eco-burden. In this study, an experimental apparatus is fabricated to observe the performance of a variety of adsorbents in different operating conditions. Based on the results of these tests, this study attempts to propose the design of an optimal system. Next, the observations reveal that a pressure as low as 0.4 MPaG has a high refining efficiency, while the operating temperature is similar to room temperature. Besides, the fabricated apparatus is able to produce a H2 concentration at 97.0 vol.% with a refining efficiency at approximately 55%. In fact, it is close to that of a conventional system. In parallel, CO2 gas can be extracted separately through the system, thus the gas will be available for the cultivation of agricultural products as a growth agent. Then, a further discussion is taken over the experimental results to consider the environmental effects on the basis of life-cycle assessment methodology.
Pyrolysis, a thermal cracking process in inert environment, may be used to produce bio-oil from biomass and plastic waste thus accommodating the use of renewable energy. Abundant amount of biomass wastes in Indonesia are not utilised and plastic wastes are not well processed for clean environment. The aim of present work was to evaluate effect of mass ratio of plastic material to biomass in the feed blend of corn cobs and high density polyethylene (HDPE) of co-pyrolysis on bio-oil yield and chemical composition of bio-oil products. The heating rate of the co-pyrolysis was kept low and residence time was in the order of seconds to accommodate high yield of oil originating from plastic pyrolysis. Corn cobs have high cellulose and hemicellulose content (84%) which is potential to produce bio-oil. The pyrolysis was conducted in a laboratory-scale using a fixed bed reactor with final temperature of 500 °C, heating rate 5 °C/min, flow rate N2 750 mL/min, total weight of biomass and plastic material of 20 g, and hold time after peak temperature of 30 min. Mass ratio of plastics to biomass in the feed blend was varied 0:100, 25:75, 50:50, 75:25 and 100:0. It was found that by increasing HDPE content up to 100% in the feed blend above, the yields of bio-oil decreased, i.e. 28.05, 21.55, 14.55, 9.5, and 6.3 wt%, respectively. Furthermore, for the same variation of the mass ratio, yields of the non-oxygenate mixture of paraffins, olefins and cycloalkanes contained in bio-oil increased, i.e. 0, 28.35, 40.75, 47.17, and 67.05 wt%, respectively. Analysis of the synergetic effect indicates that this effect did work effectively both in bio-oil and non-oxygenate yields due to improper conductive heat transfer from N2 gas to melting plastics, which contained biomass particles. By increasing composition of HDPE in the feed blend, viscosity and pH of bio-oil changed approaching to those of commercial diesel oil.
As tropical country, Indonesia is rich with potential biomass that can be utilized as bioenergy feedstock. Crude palm oil (CPO) is currently the main feedstock used to commercially produce biodiesel in Indonesia. In addition to CPO, various agricultural crops can be utilized as bioenergy feedstocks, such as coconut, jatropha, sugarcane, sago, etc. In order to determine the type of plant potential after oil palm as bioenergy feedstock in Indonesia, an analytical hierarchy process (AHP) was conducted based on seven criteria including 1) food crop with surplus production, 2) plant productivity, 3) yield of biofuel, 4) multipurpose energy plant, 5) plant development readiness, 6) government policy, and 7) uncompetitive land use for food crop/easiness to grow in marginal land. Results of AHP analysis showed that palm oil was the most potential plant for biodiesel feedstock (0.237) followed by coconut (0.179), reutealis (0.147), calophyllum (0.120), pongamia (0.119), jatropha (0.100), and rubber (0.095). It was also shown that sugarcane (0.222) was the most potential feedstock to produce ethanol, followed by sorghum (0.174), sago (0.167), sugar palm (0.152), maize (0.143), and cassava (0.141).
Hydrogen peroxide and CO2 effects on the hydrothermal degradation of biomass are examined using a semibatch reactor. Woody biomass is acquired from Japanese cedar and Japanese zelkova. Cellobiose is also studied as a model biomass. The effects on the sugar yield and the fermentation inhibitor yield are discussed. Hydrogen peroxide decreases the cellulose and hemicellulose decomposition temperature, whereas CO2 exhibits a limited effect on their decomposition.
Thermophilic anaerobic digestion of municipal solid wastes (MSW) was conducted for 6 weeks in a lab-scale semi-continuous digester for investigating the start-up operation of anaerobic digestion treating MSW. The feedstock was a mixture of simulated food waste, paper waste, and in some cases, cow manure. Organic loading rate (OLR) was adjusted 1.14 ～4.00 gVS/kg-sludge/day to biogas production. At the initial stage of thermophilic anaerobic digestion, pH value gradually increased from 8.2 to 8.3 on 17th day from start-up. Free-ammonia concentration in the digester also gradually increased from 361.6 to 412.5 ppm. On 17th day, inhibition of free-ammonia occurs, and biogas generation stopped. After gas generation stopped on day 17, pH and free-ammonia concentration were adjusted to the proper level by adding paper and deionized water. As a result, gas generation restarted on day 21. Then the amount of food waste charged in the digester was decreased and that of paper waste was increased to adjust the total amount of nitrogen invested in the digester. Afterwards, pH value was settled around 7.8, and a stable digestion was achieved till the end of experiment. Inhibition of free-ammonia could be suppressed by adjusting the amount of nitrogen invested in the digester.
Utilization of cellulose nanofiber (CNF) as a substitute for plastic resins to reduce the total vehicle weight is under consideration, even though the total amount of plastic resin used is very small compared to steel. This study aims to investigate the greenhouse gas (GHG) emission effect of the use of CNF as substitutes of plastic resins as composite materials in vehicles. In order to estimate the reduction of GHG effected, two scenarios were proposed: Business as usual (BAU) and CNF-added (CNFa). The amount of GHG emissions from the part of plastic components in a vehicle were evaluated and compared using life cycle assessment (LCA) in the two scenarios. The total GHG emissions in the CNFa scenario declined by about 21.2 per cent compared to the BAU scenario. Although the GHG emissions coefficient of CNF is relatively high compared to plastic resins’, the total amount of GHG emissions decreased probably due to reduction in weight of the part of plastic components in a vehicle by replacing plastic resins with CNF.
Ocean Thermal Energy Conversion (OTEC) is widely expected to be highly practical technology, largely for the reasons of using inexhaustible renewable energy and continuous electricity generation under any weather conditions. One point to be considered in OTEC is the cost of electricity generation, of which a large portion is found to be accounted for the cost of water intake facilities by the analyses of the report for demonstration plant at Kumejima. In this paper, we examined the cost in various settings, including water intake facilities optimization. Against the power generation cost 120.5 yen/kWh at 1,250 kW scale of Kumejima demonstration plant (the intake facilities in business, without the grant), is reduced to 50.5 yen/kWh by optimization of individual components including water intake facilities, and is further reduced to 43.4 yen/kWh by integrating water intake pipes to one pipe. The present findings indicate that an optimized OTEC system will be sufficiently cost competitive against a small scale diesel generator in a small island. Though it is required to further reduce the cost of power generation for the full-scale dissemination of OTEC, there is a limit in the current state of the water intake and power generation technologies under the constraint of the surface water temperature. There is a need to consider economies of scale and the form and effect of the high-temperature side heat source auxiliary equipment.