Hang Seok Choi

Investigation of chemical modifications of micro- and macromolecules in bio-oil during hydrodeoxygenation with Pd/C catalyst in supercritical ethanol

Miscanthus bio-oil was subjected to hydrodeoxygenation (HDO) with Pd/C at different temperatures (250, 300 and 350°C) and times (30, 45 and 60 min) to investigate the chemical modification of micro- and macromolecules in bio-oil. Four main products - char, gas and two immiscible oils (light and heavy oil) - were obtained from the HDO reaction. Yields of heavy oil as a targeting product of HDO varied from 60% to 13%, whereas those of gas and char were ranged from 7% to 36% and 6% to 17%, respectively. Water content was estimated to<1% and heating value was 26-31 MJ kg(-1). Reduction of unstable oxygen-containing compounds such as acids (2-hydroxy-butanoic acid), aldehydes (furfural), alcohols (butanedial) and sugars (levoglucosan) were characteristic in heavey oil. Apart from hydrogenation and deoxygenation, micromolecules in bio-oil were plausibly modified to stable ketones, esters and saturated components via demethoxylation, dealkylation, decarbonylation, dehydroxylation and ring opening. Macromolecular lignin fragments (referred to as pyrolytic lignins in bio-oil and phenol polymers in heavy oil) were extracted and subjected to several analyses. Approximately 60% of the pyrolytic lignins were decomposed into low molecular weight compounds during HDO reaction. Moreover, essential functional groups, OCH3 and phen-OH groups attached to pyrolytic lignin, were severely modified during HDO reaction.

A numerical study on biomass fast pyrolysis process: A comparison between full lumped modeling and hybrid modeling combined with CFD

Abstract This study focuses on process modeling and simulation of a biomass fast pyrolysis system. For the simulation of the biomass fast pyrolysis process, two types of simulation models were developed: lumped model and hybrid model. Employing the above models, the effect of reaction temperature on reaction rate and final product yields were analyzed. It was found that the hybrid model exhibited a peculiar characteristic of displaying multiphase reacting flow occurring in fluidized bed. This behavior of hybrid model could have attributed for the difference in product yields of the models (hybrid and lumped). For the yields of the tar and NCG, hybrid model prediction was very consistent with the experimental results than the lumped model. However, for char yield, the results of both the lumped model and the hybrid model were close to that of experimental results.

Influence of process conditions on product yield of waste tyre pyrolysis- A review

Waste tyres have become a grave concern as their accumulation is aggregating every year. Not only the size of waste tyre has to be reduced, but also some useful energy has to be recovered out of it as the world badly requires energy from alternate sources. Pyrolysis is one such method to extract energy potential products from waste tyres. It is extensively used to generate carbon black (solid product), tyre-oil (liquid product) and syngas (gas product) from waste tyres. In that connection, this article discusses the effect of various parameters on the product composition of pyrolysis of waste tyres. The current usage of pyrolysis products and their typical characteristics are also discussed in this critique. Of late, extraction of high value added products, such as activated carbon from carbon black, and limonene from tyre-oil is gaining attention. The article also throws some light on the application and generation routes of activated carbon and limonene from waste tyres.

Evaluation of hydrodeoxygenation reactivity of pyrolysis bio-oil with various Ni-based catalysts for improvement of fuel properties

Three Ni-based catalysts were prepared for hydrodeoxygenation (HDO) of bio-oil with three different support materials (active carbon, SBA-15 and Al-SBA-15) and their catalytic effects were tested with crude bio-oil at 300 °C and under 3 MPa H2 pressure for 60 min. After the HDO reaction, gas, liquid phase (light oil and heavy oil) and char were obtained as the primary products. Heavy oil was produced at a yield of 45.8–48.1 wt%, with no significant differences among the three catalysts. Mesoporous silica-supported catalysts (Ni/SBA-15 and Ni/Al-SBA-15) produced large amounts of char (16.3–18.6%), while Ni/C yielded 8.5 wt% char. Active carbon-supported catalysts (Ni/C) yielded more gas (27.7%) than the Ni/SBA-15 and Ni/Al-SBA-15 catalysts (6.6–8.9%), due to high surface area and low char deposition on the active carbon-supported catalysts. The HDO reaction led to improvement in the fuel properties of crude bio-oil. The water content, acidity, viscosity and oxygen content decreased via de-moisturization, i.e., dehydration, as well as dehydroxylation, resulting in an increase in heating value. The heavy oil obtained from HDO with Ni/Al-SBA-15 exhibited a low water content (9.3 wt%), while that of Ni/SBA-15 revealed a high HHV (22.8 MJ kg−1), energy efficiency (62.8%), and degree of deoxygenation (54.9%). A major factor of bio/oil instability is unstable oxygen-containing compounds, such as acetic acid, furfural, vanillin and levoglucosan, which were obviously reduced in the heavy oil in this study.

Heat transfer of bio-oil in a direct contact heat exchanger during condensation

Rapid quenching of volatiles in fast pyrolysis is important for achieving high yield and quality of the bio-oil product, but few studies have examined the condensation of volatiles and their related heat exchangers. Accordingly, we have studied the condensation characteristics of volatiles by varying heat transfer conditions in a direct contact heat exchanger. As the mass flow rate ratio of quenching oil to pyrolysis gas increased, the heat transfer rate and yield of bio-oil increased. The heat transfer rate and yield of bio-oil reached a maximum value at an intermediate air-to-quenching oil mass flow rate ratio. Additionally, the heat transfer rate and yield of bio-oil decreased as the temperature of the quenching oil increased. Experiments were also conducted to derive an empirical relationship for the volumetric heat transfer coefficient for direct contact heat exchangers.

A numerical study on the performance evaluation of ventilation systems for indoor radon reduction

Numerical simulations were conducted using computational fluid dynamics to evaluate the effect of ventilation conditions on radon (222Rn) reduction performance in a residential building. The results indicate that at the same ventilation rate, a mechanical ventilation system is more effective in reducing indoor radon than a natural ventilation system. For the same ventilation type, the indoor radon concentration decreases as the ventilation rate increases. When the air change per hour (ACH) was 1, the indoor radon concentration was maintained at less than 100 Bq/m3. However, when the ACH was lowered to 0.01, the average indoor radon concentration in several rooms exceeded 148 Bq/m3. The angle of the inflow air was found to affect the indoor air stream and consequently the distribution of the radon concentration. Even when the ACH was 1, the radon concentrations of some areas were higher than 100 Bq/m3 for inflow air angles of 5° and 175°.

Numerical Study for Heat Transfer Characteristics Varying Cross-Sectional Shape of a Tube

Numerical study has been carried out to investigate heat transfer and pressure drop characteristics for streamlined shape tubes. The flow and thermal fields are investigated with varying diameter ratio of the tube ranging from 0.4 to 2.5 and Reynolds number ranging from 10,000 to 30,000. The results show that heat transfer per unit fan power is maximum at

Co-gasification characteristics of palm oil by-products and coals for syngas production

D_2/D_1

Utillization of automobile shredder residue (ASR) as a reducing agent for the recovery of black copper

Large amounts of empty fruit bunches (EFB) are generated annually during the palm oil manufacturing process; however, they are still treated as waste. In this study, gasification experiments were conducted using EFB in a fluidized bed reactor (throughput=1 kg/hr) at an experimental temperature range of 700 to 1,000 oC to assess the use of EFB as a renewable energy resource. To overcome the issues of an unstable EFB supply, co-gasification experiments using EFB with coal were conducted. The resulting syngas yield was approximately 70 vol%, similar to that from EFB gasification. The heating value of syngas was a magnitude of three-times higher than that of EFB gasification. However, the dry gas yield and cold gas efficiency were lower than those of EFB gasification. A coal mixing rate of 20 wt% and 0.6 of ER would be appropriate conditions for continuous production of stable syngas.

Numerical Study on Indoor Dispersion of Radon Emitted from Building Materials

The physicochemical characteristics of automobile shredder residue (ASR) and its melting slag were investigated: In particular, the applicability of ASR as a reducing agent to the black copper recovery process. ASR is classified into three types after the shredding process: heavy fluff, light fluff and glass and soil. In this study, the portions of heavy fluff, light fluff and glass and soil in the ASR were 89.2 wt%, 8.1 wt% and 2.7 wt%, respectively. Physicochemical analysis revealed that moisture and fixed carbon content were low in heavy and light fluffs, and combustible content was the highest. The higher heating value (HHV) of light fluff was 6,607 kcal/kg, and the HHV of heavy fluff was 5,312 kcal/kg. To sum up, the separation of black copper and discard slag mostly seems to be affected by the melting temperature. Therefore, if basicity and melting temperature are properly controlled, the ASR can be used as a reducing agent in the smelting process of black copper recovery. Moreover, the possibility of black copper recovery from ASR and heavy metal poisoning is evaluated.