Pilot-scale Scrubber Research Articles

Desulfurization of H2S‐rich biogas using water scrubbing: Performance in pilot scale scrubber and scale‐up estimation for the concentrated latex factory

AbstractA high about 3% H2S concentration in the biogas produced from concentrated latex process wastewater needs to be removed before further utilization. Water scrubbing is appropriate for the latex factory having plenty of recycled water available. Effects of liquid to gas (L/G) ratios at 0.5–4.0 on H2S removal were tested at 0.06 m3/h biogas flow rate using a pilot scale scrubber. The experimental results were then simulated to validate the scale‐up for the factory, using the process simulation software Aspen HYSYS (HYSYS, Hyprotech and Systems). The highest 99.71% H2S removal was obtained by using L/G ratio 4.0. Interestingly, using L/G ratio 1.0 provided 96.01% H2S removal, which is slightly lower than on using L/G ratio 4.0, but is more practically appropriate for the real volumes of recycled water and biogas generated from the factory. The experimental data agree with the simulations well. The packed column diameter and height were estimated as 0.5 and 3 m for 40 m3/h biogas. Key characteristics of the scrubber effluent were analyzed for further discharge management. The scrubber effluent qualified for direct discharge to the post‐treatment ponds. This work shows that using recycled water for desulfurization of the H2S‐rich biogas is feasible at atmospheric pressure operation.

Advanced Flue-Gas cleaning by wet oxidative scrubbing (WOS) using NaClO2 aqueous solutions

In this work, we investigate the use of a Wet-Oxidative Scrubber (WOS) to simultaneously control SO2 and NOx emissions from exhaust flue-gases.The experiments are performed in a pilot-scale scrubber with a simulated flue-gas containing 500 ppmv of SO2 and 1030 ppmv of NOx, using water doped with 0.25–1% w/w of NaClO2. The results prove that the adopted WOS is able to simultaneously remove SO2 and NOx, and a synergistic effect is observed for the presence of SO2 in the flue-gas, which improves the NOx removal by establishing more effective and faster oxidative mechanisms under acidic conditions.A predictive model of the WOS unit performance based on the experimental dosage of NaClO2, which takes into account for all the operating parameters of the process, is developed to predict the de-SOx and de-NOx efficiencies and also the wash water pH.

Application of palm oil mill waste to enhance biogas upgrading and hornwort cultivation

The potential of oil palm ash (OPA) to enhance H2S and CO2 removal from biogas by scrubbing with maturation pond effluent (MPE), and further the treatment of biogas scrubber effluent (BSE) by Ceratophyllum demersum L. (hornwort) cultivation were investigated in this study. The results show that OPA + MPE solution with pH 9.3 and alkalinity 7525 mg CaCO3/L was obtained with 0.7 kg/L OPA loading. A pilot scale scrubber was used to study the effects of absorbent flow rates of 60–210 L/h on upgrading to 300 L/h field biogas stream. At 210 L/h, the CO2 removal efficiencies were 33% and 53% for MPE and OPA + MPE, respectively. To approach 100% H2S removal efficiency, the minimum flow rates were 120 L/h for MPE and 90 L/h for OPA + MPE. 50–150 g wet weight of hornwort in 30 L diluted POME were loaded to investigate appropriate initial hornwort loading level for hornwort cultivation. The highest specific growth rate of 0.045 day−1 with biomass production of 3.8 g/day were obtained with a 50 g initial loading. Among the wastewaters (MPE, OPA + MPE, and BSE) treatment using hornwort cultivation, the highest 0.035 day−1 specific growth rate and 2.6 g/day biomass production of hornwort were obtained in diluted BSE cultivation, and in 3 weeks of cultivation. COD, nitrate, phosphate, and alkalinity decreased by 76%, 76%, 55%, and 5%, respectively. The Eco-Efficiency concept for palm oil mill waste utilization proposed in this study has a high potential for enhanced biogas upgrading by using OPA + MPE, and hornwort is a good candidate for BSE post-treatment integrated with biomass production.

Evaluation of a pilot-scale scrubber for the mitigation of NH3 emissions from laboratory animal house in the presence of different oxidants

The exhaust air expelled from laboratory animal housing systems is the main source of the NH3 emissions to the atmosphere. On this basis and regarding the environmental impact of NH3 emissions, more insights into the air scrubbers as one of the ways to mitigate the NH3 emission from animal houses are needed. The detailed evaluation of a pilot chemical scrubber system was performed for the elimination of NH3 gas by various oxidants such as NaOCl, H2O2, and KMnO4 over a two months period. The removal performance and elimination capacity were applied as technical indexes for appraisal of pilot-scale function against off-gases. Also, the influence of empty bed residential time (EBRT) and pH of scrubbing solution on the chemical scrubber acting mechanism was investigated. The obtained results indicated that the removal efficiency and elimination capacity of NH3 by scrubber in the presence of H2O2 had more robustness against changes of mass loading rate and empty bed residential time (EBRT) than other oxidants, with a removal efficiency of 99.31 % to 88.12 % in EBRTs of 12.81 to 1.6 s, respectively. Furthermore, for the economic assessment of the oxidants, the oxidant-consumed (mg)/NH3-removed (mg) fraction was obtained for oxidants, which was 7.5–9.2, 1.35–2.5, and 11.5–12.4 for NaClO, H2O2, and KMnO4, respectively. On this basis, employing the hydrogen peroxide oxidant can be beneficial in terms of economic viewpoint. Ultimately, chemical scrubber along with H2O2 oxidant seems to be a more efficient applicable NH3 mitigating method in treating waste gas of animal house.

Removal of odorous compounds emitted from a food-waste composting facility in Korea using a pilot-scale scrubber

ABSTRACTMonitoring and control of odorous compound emissions have been enforced by the Korean government since 2005. One of the point sources for these emissions was from food waste composting facilities. In this study, a pilot-scale scrubber installed in a composting facility was evaluated for its performance in the removal of malodorous compounds. The exhaust stream contained ammonia and methylamine as the major odorants detected by the threshold odor test and various instrumental techniques (GC-FID, FPD, MS and HPLC/UV). For the scrubber operation, the column was randomly packed with polypropylene Hi-Rex 200, while aqueous sulfuric acid was selected as the scrubbing solution. To achieve 95% removal, the scrubber must be operated by using H2SO4 solution with pH at < 6.5, liquid to gas ratio > 4.5, gas loading rate < 1750 m3/m3-hr and contact time < 0.94 s. The scrubber performance was further evaluated by determining the mass transfer coefficients and then monitoring for 355 days of operation. The pilot-scale scrubber maintained > 95% ammonia and methylamine removal efficiencies despite the fluctuations in the inlet (from composting facility exhaust stream) concentration. The optimum operating conditions and scrubber performance indicators determined in this study provides a basis for the design of a plant-scale scrubber for treatment of composting facility gas emissions.

Inactivation of airborne Enterococcus faecalis and infectious bursal disease virus using a pilot-scale ultraviolet photocatalytic oxidation scrubber

High microbial concentrations and emissions associated with livestock houses raise health and environmental concerns. A pilot-scale ultraviolet photocatalytic oxidation (UV-PCO) scrubber was tested for its efficacy to inactivate aerosolized Enterococcus faecalis and infectious bursal disease virus (IBDV). Microbial reduction was determined by the difference in microbial concentrations measured in the upstream and downstream isolators that were connected to the two ends of the UV-PCO scrubber. Two UV irradiance levels were tested by using one or two UV lamps. The theoretical average UV irradiances were 6,595 µ W cm−2 with one UV lamp and 12,799 µ W cm−2 with two UV lamps. At the tested ventilation rate (70 m3 hr−1), the contact time was 1 sec. Reduction rate and other two indexes (k-value and Z-value) that normalized UV radiation were calculated to describe the extent of microbial inactivation. The UV-PCO scrubber eliminated >99.7% of airborne E. faecalis from the incoming airstream under one UV lamp irradiance, and the reduction was further increased by 0.2–0.3% when the second UV lamp was added. The reduction rate for airborne IBDV was 72.4% with one UV lamp. The calculated k-values were 0.501–0.594 cm2 mJ−1 for airborne E. faecalis and 0.217 cm2 mJ−1 for IBDV. The Z-value of airborne E. faecalis to UV irradiance was 9.3 (±1.6) × 10−4 cm2 µ W−1 sec−1. The results indicate that a UV-PCO scrubber can serve as an effective and efficient technology for inactivating airborne bacteria and virus. Scaling up of the pilot-scale scrubber for field use will require considerations such as design air treatment capacity, UV irradiance level, contact time, dust concentration, susceptibility of target microorganisms, and expected reduction rate. Implications: This work demonstrated that a UV-PCO scrubber can be used to inactivate animal-associated airborne microorganisms, thus reducing microbial emissions from livestock houses and minimizing the biological impact to ambient environment. The microbial reduction efficiency by the UV-PCO scrubber varied depended on the level of UV irradiation and the target microbial species. The tested viral species (infectious bursal disease virus) was more resistant to the UV-PCO scrubber as compared to its counterpart bacterial species (E. faecalis).

Simultaneous removal of SO2, NO and particulate by pilot-scale scrubber system

SOx and NOx have both previously been identified as primary precursors of acid rain, and thus the abatement of SOx and NOx emissions constitutes a major target in the field of air pollution control. In this study, the efficacy of a pilot-scale scrubber was evaluated with regard to the simultaneous removal of SO2, NO and particulate with wet catalysts. The removal efficiencies of particulate were measured to be 83, 92 and 97% with catalyst flux of 0.5, 0.8 and 1.5 L/min, respectively. The average removal efficiencies of particulate with different nozzles were approximately 94 and 90% with FF6.5 (5/8 in.) and 14 W (1.0 in.) nozzles, respectively. At least 96–98% of particulate and SO2 were removed, regardless of the stage number of reactor. In a one-stage scrubber, 83.3% removal efficiency of NO was achieved after 48 hours; however, the two-stage scrubber achieved an NO removal efficiency of 95.7%. Regardless of the liquid-gas ratio, SO2 and particulate were removed effectively, whereas NO was removed about 84% and 74% under liquid-gas ratio conditions of 39.32 L/m3 and 27.52 L/m3, respectively. In experiments using STS and P.P. pall ring as packing material, particulate and SO2 removal efficiency values in excess of 98% were achieved; however, NO removal was correlated with the different packing materials tested in this study. With the above optimum operation conditions, even after 20 hours, the removal efficiency for NO stayed at 95% or higher, the removal efficiency for SO2 stayed at 97% or higher, and the removal efficiency for particulate stayed at 92% or higher. In accordance, then, with the above results, it appears that this process might be utilized in scrubber systems, as well as systems designed to simultaneously remove particulate, SO2 and NO from flue gas.

Optimization of Venturi Scrubbers Using Genetic Algorithm

Optimization of a venturi scrubber was carried out using a nondominated sorting genetic algorithm (NSGA). Two objective functions, namely, (a) maximization of the overall collection efficiency ηo and (b) minimization of the pressure drop Δp, were used in this study. Three decision variables, the liquid−gas flow ratio L/G, the gas velocity in the throat Vgth, and the aspect ratio Z were used. Optimal design curves (nondominated Pareto sets) were obtained for a pilot-scale scrubber. Values of the decision variables corresponding to optimum conditions on the Pareto set were obtained. It was found that the L/G ratio is a key decision variable that determines the uniformity of liquid distribution and the best values of L/G and Z are about 1.0 × 10-3 and 2.5, respectively. In addition, Vgth was found to vary from about 40 to 100 m/s as the optimal ηo on the Pareto increased (as did Δp) from about 0.6 to 0.98. The effect of adding a fourth decision variable, the throat length Lo, was also studied. It was found t...