Chia-Chi Chang

Emissions and by-products from manufacturing torrefied solid recovered fuel using pulp industry waste containing wood waste with pulp sludge (WPS) were studied. Two batches of WPS1 and WPS2 were tested. The torrefaction of WSP1 and WPS2 were performed at their respectively optimal temperature of 573 and 593 K and time of 20 min, referred as cases WPST1-573-20 and WPST2-593-20, respectively. WPS1 contained higher fixed carbons and volatile matters but lower ash content than WPS2. The results showed that the solid yields of 56 and 61 wt.%, gas yields of 16 and 16 wt.% and liquid yields of 28 and 24 wt.% for WPST1-573-20 and WPST2-593-20, respectively. The maximal concentration of emissions for WPST1-573-20 and WPST2-593-20 are about 1952.5 and 3743.5 ppmv for CO, 26.5 and 156 ppmv for NO_x and 31.5 and 392 ppmv for SO₂, respectively. The C_CO exceeded the emission standard and required further action. The collected non-condensable gases consisted of hydrocarbons ranging from C1-HC to C6-HC, with C4-HC being the predominant component. Here, Cn-HC represents hydrocarbons with a carbon atom count of n. The GC-MS analysis revealed the primary liquid byproducts. The liquid products can be used directly as pyroligneous liquor in agriculture. Furthermore, with refining techniques, these liquid byproducts can be transformed into high-quality chemicals for applications such as fungicides, pesticides, solvents, surfactants, and as precursors or monomers in the synthesis of other chemicals.

This study examined the application of high-gradient magnetic separation (HGMS) for recycling of super-paramagnetic polymer adsorbent (MPA), namely, polyvinyl acetate-iminodiacetic acid. The HGMS can be incorporated with the adsorption and desorption processes (ADPs) with fresh or regenerated desorbed MPAs and exhausted adsorbed MPAs, respectively. This combines the permanent magnet’s advantage of low running costs with the easy operation using the solenoid to flush the filter in place. The effects of the inlet concentration of MPA in solution (C_LF,i) and the fluid velocity (v₀) or volumetric flow rate (Q_LF) on the performance of the recovery of MPA via HGMS were assessed. The results indicated that the separation efficiency (η or P₀), breakthrough time (t_B) and exhaustion time (t_E) of HGMS reduce as C_LF,i, as well as v₀, increases. Further, the filter saturated capture capacity (σ_S) of HGMS also decreases with increasing v₀. The effect of v₀ on t_B proportional to 1/v₀² is more significant than that on σ_S proportional to 1/v₀. A kinetic model of HGMS shows good agreements for the experimental and predicted breakthrough results, with determination coefficients of 0.985–0.995. The information obtained in this study is useful for the rational design and proper operation of a HGMS system for the recycling and reuse of MPA in ADPs.

This study investigated the torrefaction of de-oiled Jatropha seed residue after a two-stage sequential process consisting of mechanical screw pressing and solvent extraction using n-hexane (denoted as JMS). The optimal torrefaction temperature (T_r) and torrefaction time (t_r) were determined in the ranges of 260–300 °C and 10–60 min, respectively, so to achieve a better heating value and satisfactory energy densification (E_D) with acceptable mass loss. Thermogravimetric analysis was employed to elucidate the thermal decomposition behaviors of JMS. By comparison with the torrefaction of Jatropha seed residue after mechanical oil extraction by screw pressing only (namely, JME_T), the results indicated that the E_D of the torrefaction of JMS yielding the torrefied product JMS_T (two-stage product) was higher than that of the torrefaction of JME giving the torrefied product JME_T (single-stage product). Further, it was found that JME_T contained some tar, which was attributed to a thermal reaction in the residual oil in JME during torrefaction. The tar/oil content of JME_T was about 1.0–1.8 wt.% in the determined optimal conditions. Thus, the enhanced recovery of the residual oil is advantageous not only because it allows obtaining more oil from Jatropha seed residue with a positive net energy gain but also because it prevents the formation of tar in torrefied biomass products.

This research investigated the application of palm shell char as a catalyst for the catalytic steam reforming of tar after the sorption enhanced gasification (SEG) process. The catalytic activities of palm shell char and metal-supported palm shell char were tested in a simulated SEG derived syngas with tar model compounds (i.e., toluene and naphthalene) at a concentration of 10 g m⁻³ _NTP. The results indicated that palm shell char had an experimentally excellent catalytic activity for tar reforming with toluene and naphthalene conversions of 0.8 in a short residence time of 0.17 s at 900 °C. A theoretical residence time to reach the complete naphthalene conversion was 1.2 s at 900 °C for palm shell char, demonstrating a promising activity similar to wood char and straw char, but better than CaO. It was also found that potassium and iron-loaded palm shell chars exhibited much better catalytic activity than palm shell char, while the parallel reaction of gasification of K-loaded palm shell char influenced the conversion with its drastic mass loss. Moreover, contrary to CaO, palm shell char presented relatively low selectivity to benzene, and its spontaneous gasification generated extra syngas. In summary, the present study demonstrated that the low-cost material, palm shell char, can successfully be used as the tar-reforming catalyst after SEG process.

In this study, biomass of rice straw (RS) and wood (WD) and their torrefied biomass (RS_T and WD_T) were used as solid bio-fuel (SBF) for co-firing individually with coal in a commercial continuous chain-grate steam boiler system, which was conducted at fixed input rate of heating value of mixture of SBF and coal and at fixed air flow rate. The effects of key system parameters on the gaseous and particulate pollutions and ash were examined. These include SBF type and blending ratio (R_BL) of biomass (i.e., SBF) in the mixture of coal and biomass based on heating values for co-firing. The results indicated that wood, which possesses high heating value while less amount of ash, is more suitable for co-firing with coal than rice straw. Torrefaction can increase the heating value of biomass and homogenize its property, being beneficial to co-firing. Also, torrefaction can decompose the hydroxyl group of biomass, which makes biomass tending to possess hydrophobicity. This, in turn, helps the storage and transportation of biomass. Generally, adding the RS (with R_BL = 5-10%), WD (2-15%), RS_T (2-10%), and WD_T (2-20%), respectively with coal decreases the emissions of NO_x and SO₂, but increases that of CO (except RS_T). The emission of HCl is little. The addition of biomass also increases the emission of fine particulate matters (PM) especially PM_2.5 in the flue gases, raising PM_2.5/PM₁₀₀ from 34.87 to 78.35 wt.% (Case 50%WD_T). These emissions for the Cases tested satisfy with Taiwanese emission standards of stationary sources which set limitations of NOx, SO₂, CO, and HCl < 350, 300, 2000, and 80 ppmv, while PM < 50 mg/m³, respectively. The results support the use of RS, WD, RS_T, and WD_T for co-firing with coal.

The effects of ultrasonic and ozonation pretreatments on organic solubilization, anaerobic biodegradability, and biogas production were elucidated in this study. Two pretreatment methods for batch anaerobic digestion for biogas recovery with the same material and experimental conditions were the focus for comparison. Anaerobic digestion experiments were conducted at ambient temperature with the solid retention time set to 25 days. The obtained results indicated that the soluble chemical oxygen demand increased from 0.344 without pretreatment to 1.023 and 1.228 g/L with ultrasound and ozone pretreatments, respectively, whereas the yields of biogas production in the 25 days increased by 32.3 and 52.9% via ultrasonic irradiation and ozonation relative to the control case, respectively. The biodegradability of the organic compounds of the samples for the cases of ultrasound, ozone pretreatments, and control achieved 55.9, 64.31, and 39.18%, respectively, in terms of chemical oxygen demand (COD) removal efficiencies. The physicochemical characteristics of sludge flocs were investigated via scanning with particle sizes, which were obviously affected by pretreatments of sonication and ozonation, resulting in finer particles than in the control case.

Combined heat and power production from biogas is now playing an important role in energy and resource utilization as well as pollution control in waste water treatment. This research used biogas from the Bali Sewage Treatment Plant in New Taipei City, Taiwan, as a major source of fuel for the electricity generation. A micro gas turbine electricity generator, Capstone CR-30, which possesses a maximum rated power load (P_WL) of 30 kW, was equipped to convert biogas into electricity. The biogas is mainly composed of CH₄ (56.1 ± 8.0 vol.%), CO₂ (25.5 ± 9.8 vol.%), H₂ (0.5 vol.%), and H₂S (0.99 ± 0.07 ppmv). During the test operation period of the generator, it was found that the thermal efficiency increases from 19.8% to 23.4% kWh_e/kWh_th, while the electricity generation efficiency (η_EB) also rises from 0.93 to 1.09 kWh_e/m³ biogas as the P_WL increases from 10 kW to 30 kW. The results indicated that the generator has a better performance with higher P_WL. At P_WL = 30 kW, the average adjusted concentrations of CO and NOx (adjusted to 15 vol.% O₂) emitted from the generator are 86 ppmv and 17 ppmv, respectively. Both are much lower than the emission standards of stationary sources in Taiwan of 2000 ppmv and 150 ppmv, respectively. Thus, P_WL of 30 kW was selected in cooperation with biogas inflow = 0.412 m³/min and air/fuel ratio (i.e., air/biogas ratio) = 76.0 vol./vol. for the long-term regular operation. At the above setting conditions for long-term operation, the generator continuously consumed the biogas and provided stable electricity generation at a rate of 19.64 kWh_e/h for a 2-year running period. Moreover, the greenhouse gas can be cut off with a rate of 10.78 kg CO₂e/h when using biogas as fuel for electricity generation. Overall, this research proves that the application of a micro gas turbine electricity generator not only has promising performance for using biogas but also gives a significant reduction of greenhouse gas emission, which fits the concepts of the circular economy and environmental protection.

Autoclaving of food wastes (FW) for the resource recovery and reutilization was studied using the pilot plant scale. Experiments were conducted at various temperatures of 408, 428, and 438 K and times of 15 and 60 min. The in-filled steam to the autoclave was supplied by the incineration plant with a gauge pressure of 7 kg/cm² and a temperature of 443 K or above. The results obtained from the experiments show that the less energy- and time-consuming autoclaving conditions (408 K and 15 min, denoted as Case A408-15) are effective. Comparisons of the properties and characteristics of autoclaved FW (FW_A) of Case A408-15 with those of FW are made. The wet bulk volume and wet bulk density of FW _A are dramatically reduced to 15.64% and increased to 313.37% relative to those of FW, respectively. This makes the subsequent processing and reuse for FW_A more convenient than FW. The autoclaving results in an increase of carbon content and a decrease of nitrogen content, and thus an increase of the C/N ratio of FW_A. The contents of sulfur, hemi-cellulose, and cellulose of FW_A are also reduced. All these fluctuations are beneficial for making compost or other usages from FW_A than FW. The autoclaved liquid product (LA) separated from FW_A and liquid condensate (LC) from the released gas possess high COD and TOC. These two liquids can be mixed for use as liquid fertilizers with proper conditioning. Alternatively, further anaerobic digestion of the mixture of FW_A, LA, and LC can offer enhanced biogas production for power generation. All these thus match the appeal of sustainable materials management and circular economy. The emitted gas from autoclaving contains no CO and some hydrocarbons. Suitable air pollution control is needed. The results and information obtained are useful for the proper recovery and reuse of abundant food wastes from domestic households and food industries.

The reduction of high acid value (AV) of inedible jatropha oil (JO) by esterification with isopropanol (IPA), which is a common alcohol solvent waste in Taiwan’s high-tech industry, was studied. The decrease of AV is beneficial for the subsequent transesterification to produce JO biodiesel (i.e., biodiesel of fatty acid isopropyl ester (FAIE)). Acid catalyst (H₂SO₄) and a novel mixing/emulsion technique using ultrasound irradiation (UI) were applied to promote and facilitate the esterification process. The results showed that increased IPA/oil molar ratio (M_IOE) can significantly reduce the AV, kinematic viscosity (KV), density (ρ_LO), and water content (M_W) of esterified JO, while also providing the benefit of enhancing the yield (Y_F) of biodiesel of FAIE. For example, with M_IOE = 5 at esterification temperature (T_E) = 394.2 K (393.8–394.7 K), a reduction of AV of 99.25% with Y_F of 67.15% can be achieved. Free fatty acid (FFA) was reduced from 18.06 wt.% to 0.14 wt.%, indicating 17.92 wt.% out of 18.06 wt.% of FFA was esterified to FAIE. As a result, among the Y_F of 67.15%, 49.23% (= 67.15 wt.% deducting 17.92 wt.%) was contributed by the transesterification of triglycerides. By esterification of high FFA-containing raw JO with acid catalyst, one can not only avoid saponification, but also reduce the loading of the subsequent alkali-catalyzed transesterification. Moreover, increasing T_E from 394.2 to 454.4 K further reduced AV (from 0.27 to 0.084 mg KOH/g) and M_W (from 0.27 to 0.043 wt.%), but, on the other hand, it increased KV (from 14.62 to 25.2 mm²/s) and ρ_LO (from 901.6 to 913.3 kg/m³), while it decreased Y_F (from 67.15 to 25.84%). In sum, IPA was successfully used as a replacement for methanol in the esterification of JO while UI provided mixing/emulsion along with heating resulting from cavitation for the system.

The pulp industry in Taiwan discharges tons of wood waste and pulp sludge (i.e., wastewater-derived secondary sludge) per year. The mixture of these two bio-wastes, denoted as wood waste with pulp sludge (WPS), has been commonly converted to organic fertilizers for agriculture application or to soil conditioners. However, due to energy demand, the WPS can be utilized in a beneficial way to mitigate an energy shortage. This study elucidated the performance of applying torrefaction, a bio-waste to energy method, to transform the WPS into solid bio-fuel. Two batches of the tested WPS (i.e., WPS1 and WPS2) were generated from a virgin pulp factory in eastern Taiwan. The WPS1 and WPS2 samples contained a large amount of organics and had high heating values (HHV) on a dry-basis (H_HD) of 18.30 and 15.72 MJ/kg, respectively, exhibiting a potential for their use as a solid bio-fuel. However, the wet WPS as received bears high water and volatile matter content and required de-watering, drying, and upgrading. After a 20 min torrefaction time (t_T), the H_HD of torrefied WPS1 (WPST1) can be enhanced to 27.49 MJ/kg at a torrefaction temperature (T_T) of 573 K, while that of torrefied WPS2 (WPST2) increased to 19.74 MJ/kg at a T_T of 593 K. The corresponding values of the energy densification ratio of torrefied solid bio-fuels of WPST1 and WPST2 can respectively rise to 1.50 and 1.25 times that of the raw bio-waste. The H_HD of WPST1 of 27.49 MJ/kg is within the range of 24–35 MJ/kg for bituminous coal. In addition, the wet-basis HHV of WPST1 with an equilibrium moisture content of 5.91 wt % is 25.87 MJ/kg, which satisfies the Quality D coal specification of the Taiwan Power Co. requiring a value of above 20.92 MJ/kg.