A Novel Hybrid Method Based on Three-Stage Extraction and DEA-CCR Models for Selecting the Optimal Conditions for Citronella Oil Extraction

In citronella oil extraction process by steam distillation, inefficient use of steam is the main cause of excessive energy consumption that affects energy cost and oil yield. This research is aimed to reduce the energy cost and increase the oil yield by studying the steam used in the process. The proposed method is the three-stage extraction model combined with the Data Envelopment Analysis developed by Charnes, Cooper and Rhodes (DEA-CCR model). Although the three-stage extraction model has been widely used, there is no research integrate this model with DEA-CCR model. It is well known that DEA-CCR model is an effective tool to evaluate efficiency of decision making units/alternatives. The advantages of this research were presented as the calculation of the optimum distillation conditions, including the steam flow rate and the distillation time, were achieved as discussed in this article. The study was comprised of 3 parts. Firstly, the three-stage extraction model for citronella oil was formulated. Secondly, the results of the proposed model were calculated under different conditions, classified by steam flow rates from 5,000 to 60,000 cm3/min for the distillation period of 15–180 min. Finally, the DEA-CCR model was utilized to evaluate and rank alternatives. The results expressed that the best condition for producing citronella oil was at the steam flow rate of 40,000 cm3/min and the distillation time of 60 min. The optimal energy cost and percentage of oil yield were equal to 0.440 kWh/mL and 0.7%, respectively. When comparing to the experimental results, the percentage error of optimal energy cost and oil yield were slightly different, with a value of 0.98% and 0.85%, respectively. Moreover, the energy consumption was also reduced by 34.6% compared to the traditional operating conditions.

Syngas Composition: Gasification of Wood Pellet with Water Steam through a Reactor with Continuous Biomass Feed System

Investigations were performed in relation to the thermal gasification of wood granulate using steam in an allothermal reactor with electric heaters. They studied the impact of the temperature inside the reactor and the steam flow rate on the percentage shares of H2, CH4, CO, and CO2 in synthesis gas and on the calorific value of syngas. The tests were conducted at temperatures inside the reactor equal to 750, 800, and 850 °C and with a steam flow rate equal to 10.0, 15.0, and 20.0 kg∙h−1. The intensity of gasified biomass was 20 kg∙h−1. A significant impact of the temperature on the percentages of all the components of synthesis gas and a significant impact of the steam flow rate on the content of hydrogen and carbon dioxide in syngas were found. The highest percentage of hydrogen obtained was 43.3%. The calorific value of the gas depended significantly on the temperature inside the reactor and the correlation between the temperature and the steam flow rate. Its maximum value was 13.3 MJ∙m−3 at 800 °C. This paper also includes an assessment of the mutual correlations of the percentage shares of the individual synthesis gas components.

Syngas production by chemical-looping gasification of waste activated carbon with iron-based oxygen carrier

Waste activated carbon (WAC), as a typical solid waste, can be utilized by chemical looping gasification (CLG) technology with an iron-based oxygen carrier to produce valuable synthesis gas. A series of experiments on WAC of the CLG process have been carried out in a fixed-bed reactor. The operation parameters involving the OC/WAC mole ratio, steam flow rate and reaction temperature during CLG reactions have been investigated in detail. Further, the cyclic performance within 10 cycles has been also discussed. Fresh and cyclic reaction oxygen carrier samples have been analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). In order to obtain high-quality syngas with high carbon conversion, the optimal of OC/WAC mole ratio, steam flow rate and reaction temperature are 0.15, 0.10 mL/min, and 950 °C, respectively. The iron-based oxygen carrier exhibits a stable cyclic performance during the multiple tests, following the reaction path of Fe2O3→Fe0.98O in the individual reduction process. Moreover, the iron-based oxygen carrier could be oxidized almost to its initial state after 10 redox tests. No obvious sintering and agglomeration phenomena are observed. The WAC of CLG presents a new approach for the comprehensive utilization and disposal of solid waste, especially with low volatile feedstock.

Syngas production by chemical-looping gasification of waste activated carbon with iron-based oxygen carrier

Waste activated carbon (WAC), as a typical solid waste, can be utilized by chemical looping gasification (CLG) technology with an iron-based oxygen carrier to produce valuable synthesis gas products. A series of experiments on WAC of the CLG process were carried out in a fixed-bed reactor. The operation parameters involving the OC/WAC mole ratio, steam flow rate and reaction temperature during WAC CLG reactions were investigated in detail. Further, the cyclic performance within 10 cycles was also discussed. Fresh and other representative oxygen carrier samples were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM) characterization methods. The results showed that the optimal OC/WAC mole ratio, steam flow rate and reaction temperature were determined to be 0.15, 0.10 mL/min, and 950 °C, respectively, to obtain high-quality syngas with relatively high carbon conversion. The iron-based oxygen carrier exhibited a stable cyclic performance during the multiple tests, following the reaction path of Fe2O3→Fe0.98O in the individual reduction process. Moreover, the iron-based oxygen carrier could be oxidized almost to its initial state after 10 redox tests, and no obvious sintering and agglomeration phenomena were observed. The WAC of CLG presents a new approach for the comprehensive utilization and disposal of solid waste, especially with low volatile feedstocks.

Optimization of Continuous Solid-State Distillation Process for Cost-Effective Bioethanol Production

To improve the efficiency of bioethanol production, an advanced process was required to extract ethanol from solid-state fermented feedstock. With regard to the characteristics of no fluidity of solid biomass, a continuous solid-state distillation (CSSD) column was designed with a proprietary rotary baffle structure and discharging system. To optimize the operation condition, fermented sweet sorghum bagasse was prepared as feedstock for a batch distillation experiment. The whole distillation time was divided into heating and extracting period which was influenced by loading height and steam flow rate simultaneously. A total of 16 experiments at four loading height and four steam flow rate levels were conducted, respectively. Referring to packing, rectifying column, mass, and heat transfer models of the solid-state distillation heating process were established on the basis of analyzing the size distribution of sweet sorghum bagasse. The specific heat capacity and thermal conductivity value of fermented sweet sorghum bagasse were tested and served to calculate the ethanol yielding point and concentration distribution in the packing. The extracting process is described as the ethanol desorption from porous media absorbent and the pseudo-first-order desorption dynamic model was verified by an experiment. Benefit (profit/time) was applied as objective function and solved by successive quadratic programming. The optimal solution of 398 mm loading height and 8.47 m3/h steam flow rate were obtained to guide a 4 m in diameter column design. One heating and two extracting trays with 400 mm effective height were stacked up in an industrial CSSD column. The steam mass flow rate of 0.5 t/h was determined in each tray and further optimized to half the amount on the third tray based on desorption equation.

Kajian Terbentuknya Scaling pada Komponen Turbin Uap Pembangkit Listrik Tenaga Panas Bumi Skala Kecil

ABSTRACTScaling and corrosion are two major problems in operation of the Small Scale Geothermal Power Plant. This paper discusses some results of the study that was conducted to assess the scaling formation in the Kamojang 3 MW Small Scale Geothermal Power Plant. The result of the study concluded that scaling occurred on the nozzle and steam turbine blade where the main minerals contained in sample A (solid) are Tridymate (SiO2), Pyrite (FeS2) and Chlorite (ClO2). While in sample B (sand) where the main mineral contained in the sample is Tridymate (SiO2), Pyrite (FeS2), Plagioclase (Na,Ca)(Si, Al)4O8 and Chlorite (ClO2). The analysis of this scaling was done by XRD (X-Ray Diffraction) method. Scaling of the nozzle of the steam turbine causes the steam flow rate to decrease, thus lowering the power that the Small-Scale Geothermal Power Plant generates because the power generated by the Small-Scale Geothermal Power Plant is directly a function of the steam flow rate and the enthalpy difference between the inlet side and the outlet side of the turbine. However, scaling does not occur on the exit side of the wellhead KMJ 68 because the concentration of silica is very small that is 0.05 ppm at geothermal steam temperature 200.5°C.Keywords: geothermal steam, scaling, corrosion, Small Scale Geothermal Power Plant ABSTRAKScaling dan korosi merupakan dua masalah yang sangat serius ditemukan pada pengoperasian PLTP Skala Kecil. Tulisan ini membahas sebagian hasil studi yang dilakukan untuk mengkaji pembentukan scaling pada PLTP Skala Kecil Kamojang 3 MW dan pengaruhnya pada daya listrik yang dihasilkan oleh PLTP Skala Kecil. Dari hasil kajian dapat disimpulkan bahwa scaling terjadi pada Nozzle dan sudu-sudu turbin dimana mineral utama yang terdapat didalam sampel A (berupa endapan/padat) adalah Tridymate (SiO2), Pyrite (FeS2) dan Chlorite (ClO2). Sedangkan pada sampel B (endapan lepas/pasiran) dimana mineral utama yang terdapat didalam sampel adalah Tridymate (SiO2), Pyrite (FeS2), Plagioclase (Na,Ca)(Si,Al)4O8 dan Chlorite (ClO2). Analisis scaling ini dilakukan dengan menggunakan metoda XRD.(X-Ray Diffraction). Scaling yang terjadi pada bagian nozzle dari turbin uap menyebabkan laju aliran uap berkurang sehingga menurunkan daya yang dihasllkan PLTP Skala Kecil karena daya yang dihasilkan PLTP Skala Kecil secara langsung merupakan fungsi dari laju aliran uap dan perbedaan entalpi antara sisi masuk dan sisi keluar dari turbin. Akan tetapi, tidak terjadi scaling pada sisi keluar kepala sumur KMJ 68 karena kosentrasi silika sangat kecil yaitu sebesar 0,05 ppm pada temperatur uap panas bumi 200,5oC .Kata kunci : uap panas bumi, scaling, korosi, PLTP Skala Kecil,