Scrubber System Research Articles

Payback Period for Emissions Abatement Alternatives: Role of Regulation and Fuel Prices

As of January 2015, the new maximum limit of fuel sulfur content for ships sailing within emission control areas has been reduced to 0.1%. A critical decision for ship owners in advance of the new limits was the selection of an abatement method that complies with the regulations. Two main options exist: investing in scrubber systems that remove sulfur dioxide emissions from the exhaust and switching to low-sulfur fuel when sailing in regulated waters. The first option would involve significant capital costs, while the latter would lead to operating cost increases because of the higher price of the fuel used. This paper presents a literature review of emissions abatement options and relevant research in the field. A cost–benefit methodology to assess emission reduction investments from ship owners is also presented. A study examined the effects of recent drops in bunker fuel price to the payback period of a potential scrubber investment. The results show that lower prices would significantly delay the payback period of such investments, up to two times in some cases. The case studies present the emissions generation through each option for representative short sea shipping routes. The repercussions of low-sulfur policies on large emission reduction investments including cold ironing are examined, along with implications of slow steaming for their respective payback periods. Recommendations are made for research in anticipation of future regulations and technological improvements.

Absorber modeling for NGCC carbon capture with aqueous piperazine.

A hybrid system combining amine scrubbing with membrane technology for carbon capture from natural gas combined cycle (NGCC) power plants is proposed in this paper. In this process, the CO2 in the flue gas can be enriched from 4% to 18% by the membrane, and the amine scrubbing system will have lower capture costs. Aqueous piperazine (PZ) is chosen as the solvent. Different direct contact cooler (DCC) options, multiple absorber operating conditions, optimal intercooling designs, and different cooling options have been evaluated across a wide range of inlet CO2. Amine scrubbing without DCC is a superior design for NGCC carbon capture. Pump-around cooling at the bottom of the absorber can effectively manage the temperature of the hot flue gas, and still be effective for CO2 absorption. The absorber gas inlet must be designed to avoid excessive localized temperature and solvent evaporation. When the inlet CO2 increases from 4% to 18%, total absorber CAPEX decreases by 60%; another 10% of the total absorber CAPEX can be saved by eliminating the DCC. In-and-out intercooling works well for high CO2, while pump-around intercooling is more effective for low CO2. Dry cooling requires more packing and energy but appears to be technically and economically feasible if cooling water availability is limited.

The innovation inducement impact of environmental regulations on maritime transport: a literature review

Maritime transport is facing wide-ranking challenges due to stricter environmental regulations. It has been positioned that these stricter environmental regulations will significantly hamper the competitiveness of the shipping industry and other export/import oriented industries. However, contrasting views, arguing that environmental regulations will, in fact, enhance firms' competitiveness by inducing innovation, have also been voiced. Here, this issue is examined through a literature review on the innovation inducement impact of environmental regulations (i.e., the Porter Hypothesis), in general, and the economic impacts of environmental regulations (here Annex VI of the MARPOL Convention) as it applies to shipping in Northern Europe, in particular. According to the review, the literature is still inconclusive and lacks a clear consensus on the economic and innovation inducement impacts of environmental regulations on maritime transport. Therefore, the review concludes in suggestions for further studies on the use of marine scrubber systems as an illustrative case study example.

The effect of selenite on mercury re-emission in smelting flue gas scrubbing system

Recently, the mercury re-emission from the scrubbing solution has become a hot topic in wet flue gas desulfurization process (WFGD). Selenite is one of the most important matters in the solution. It is discovered that selenite have great effect on the mercury re-emission in the WFGD process in this paper. Several important parameters, such as selenite concentration, pH value, temperature and chloride concentration, and reaction mechanisms were studied on the Hg0 re-emission. The experimental results indicate that mercury reduction and re-emission can be effectively inhibited with high selenite and chloride concentrations, low temperature and pH value. The mechanisms for inhibition of mercury reduction and re-emission are proved to be different under acid and alkaline conditions respectively. Under acid condition, it is the formation of stable HgSe that decrease Hg0 re-emission. However, the formation of more stable HgSeO3SO32- or Hg(SeO3)22- than Hg(SO3)22- contributes to avoid the oxidized mercury reduction by sulfite ions and then the mercury re-emission under the alkaline condition. In addition, it is also found that Cl- ions can further enhance the inhibition effect and suppress Hg0 re-emission by the formation of stable HgSeO3Cl- and HgSeO3Cl22- complexes.

Algae scrubbers for phosphorus removal in impaired waters

Algae scrubbers are a developing technology used for nutrient removal from many different impaired waters, including: agricultural runoff, wastewater, and animal operation waste. Algae thrive in environments with high flow velocities, allowing treatment of large volumes of nutrient-rich water. This adaptation helps overcome space issues associated with other biological treatment systems. Although algae scrubbers have shown promise for recovering phosphorus (P), no detailed studies have been completed to research conditions for maximum total P (TP) removal. Previous studies have suggested that faster flow rates and pulsed inflow conditions are necessary for high biomass production. Studies have also theorized that the calcium-phosphorus (Ca-P) co-precipitation is the driving TP removal mechanism. As a result, the goal of this study was to determine the effect of the following operating parameters on TP removal: (1) flow rate, (2) pulsed versus constant inflow, (3) calcium addition to inflow water, (4) calcium seed addition, and (5) 24-h versus 12-h operation. Results show that 12-h operation significantly increases TP removal in algae scrubber systems from an average of 24g/m2/y to 52g/m2/y. The high TP removal rate can be attributed to the stabilization of Ca-P minerals during 12-h operation. Algal photosynthesis increases daytime pH values (9–9.5) driving Ca-P co-precipitation, and 12-h operation prevents these minerals from re-dissolving at night as the pH decreases back to neutral (7–7.5). The maintenance of an algal seed on the scrubbers significantly decreased the amount of time necessary between harvests, increasing algal productivity.

Selecting and implementing a fuel blend for scrubbed units at a pulverized coal power plant

The DTE Power Plant includes four boilers, each generating up to 5.7millionlbs/h of supercritical steam, and each supporting the generation of up to 800MWe (net) of electricity. At the time of the testing two units were equipped with both scrubber and selective catalytic reduction systems in addition to electrostatic precipitators. Over a two year period, the Plant modeled and tested a wide variety of fuels and fuel combinations with a base fuel of Wyoming Powder River Basin (PRB) subbituminous coal and Central Appalachian bituminous coal. Fuels incorporated into the blend included petroleum coke, northern PRB subbituminous coal, and northern Appalachian bituminous coal. Various blend combinations were considered and/or tested. Operation with 100% PRB was also tested. The objective was to optimize the fuel blend from both technical and economic perspectives. The blend proven to be optimal from both technical and economic perspectives included 10% petroleum coke with PRB coal and, as necessary, Central Appalachian coal. This blend was implemented.

Utilization of Effluent Water from Wastewater Treatment as a Flue Gas Scrubbing Liquid in a Sewage Sludge Incineration Plant

Compared to common, medium sized wood firing biomass power plants, sewage sludge incineration plants need quite complex systems for flue gas cleaning, as they have to deal with higher amounts of acidic gases like sulfur dioxide (SO2) and hydrochloric acid (HCl). Because of the quite high nitrogen content in the sludge as well nitrogen oxides (NOx), especially nitrogen monoxide (NO), have to be considered. During the current work, a scrubber system was developed, which fulfills the needs of such a plant, using water from the adjacent wastewater treatment plant as a scrubbing liquid. The water is taken from the effluent of the wastewater treatment plant and is returned to the bioreactor of this plant for regeneration after usage. During the extensive testing of the scrubber system, removal efficiencies of up to 99.5 % for HCl and 95 % for SO2 have been achieved. As expected, an increased liquid-to-gas ratio as well as scrubbing liquid recirculation has a positive influence on the removal efficiencies. A major finding was that the nitrite concentration of the fresh scrubbing liquid effects the NO removal efficiency. Nitrite concentrations below or above a certain range resulted in poor NO removal efficiencies, while under ideal conditions removal efficiencies of more than 50 % have been reached. Based on the gained experiences, this system can be developed further and used for flue gas treatment in similar applications. Given that the effluent water is available for free from the wastewater treatment plant, it has very low operational costs, as no additional chemicals are needed.

Exploration of anionic inhibition of the α-carbonic anhydrase from Thiomicrospira crunogena XCL-2 gammaproteobacterium: A potential bio-catalytic agent for industrial CO2 removal

The α-class carbonic anhydrase (CA) from the thermophilic gammaproteobacterium Thiomicrospira crunogena XCL-2 (TcruCA) has been recently proposed as a candidate enzyme for carbon dioxide removal (CDR) in flue gas scrubbing systems. However during this process, the enzyme may be exposed to anionic impurities which can limit the use of CA for CDR. The inhibition of TcruCA by various anions, some of which are found in flue gas, is reported. The majority of the anions tested display weak (mM) inhibition but some, such as the metal poisons and anionic acids, exhibit stronger (μM) inhibition. Most relevant to the use of CA in CDR is the inhibition by SOx, NOx, and Hg2+, which can be removed through a pre-scrubbing treatment. In addition, the active site structural architecture of TcruCA is compared with other α-class CAs and differences in catalytic efficiency and anion inhibition are discussed. This study provides information regarding anionic inhibition of CAs as bio-catalytic CDR agents and the results should therefore be considered in the design of CA-mediated flue gas scrubbing systems.

Green shipping: Marine engine pollution abatement using a combined catalyst/seawater scrubber system. 1. Effect of catalyst

A marine engine pollution abatement system was constructed and tested on a 1.5MW auxiliary marine engine. The integrated system, designed to abate all of the currently legislated emissions from marine engines, consisted of a monolithic Pt/Al2O3 oxidation catalyst and a seawater scrubber, both of suitable dimensions for the engine size. The test results obtained showed the general validity of the approach adopted, as significant abatement of emissions was achieved. However, under the conditions used, the system showed some limitations with regard to the sulphur content of the fuel. On the basis of the results obtained, the system can be used with fuel sulphur content of up to 0.4%, while problems were encountered when a fuel with a sulphur content of 2.0% was used. Whereas the catalytic section operated satisfactorily, fine tuning of the scrubber operating conditions is necessary to improve abatement of NOx and increase the range of fuel sulphur which can be used with the system.

The fleet renewal problem with regional emission limitations: Case study from Roll-on/Roll-off shipping

In this paper, the maritime fleet renewal problem (MFRP) is extended to include regional limitations in the form of emission control areas. The motivation for including this aspect is that strengthening of emission regulations in such areas is expected to be challenging for deep sea shipping in the years to come. In the proposed model, various means to cope with these stricter emission regulations are evaluated for new vessels, and the possibility of upgrading existing vessels with new emission reduction technology is introduced. We consider future fuel prices to be important for the problem, and have chosen to treat them as uncertain, and thus, a stochastic programming model is chosen. A fleet renewal problem faced by the liner shipping operator Wallenius Wilhelmsen Logistics, concerning whether to use low sulphur fuel or have an exhaust gas scrubber system installed to comply with sulphur regulation in emission control areas from 2015, is used as a case study. Furthermore, tests show that the savings from including the aspect of emission control areas in the MFRP are substantial.

Technological and life cycle assessment of organics processing odour control technologies

As more municipalities and communities across developed world look towards implementing organic waste management programmes or upgrading existing ones, composting facilities are emerging as a popular choice. However, odour from these facilities continues to be one of the most important concerns in terms of cost & effective mitigation. This paper provides a technological and life cycle assessment of some of the different odour control technologies and treatment methods that can be implemented in organics processing facilities. The technological assessment compared biofilters, packed tower wet scrubbers, fine mist wet scrubbers, activated carbon adsorption, thermal oxidization, oxidization chemicals and masking agents. The technologies/treatment methods were evaluated and compared based on a variety of operational, usage and cost parameters. Based on the technological assessment it was found that, biofilters and packed bed wet scrubbers are the most applicable odour control technologies for use in organics processing faculties. A life cycle assessment was then done to compare the environmental impacts of the packed-bed wet scrubber system, organic (wood-chip media) bio-filter and inorganic (synthetic media) bio-filter systems. Twelve impact categories were assessed; cumulative energy demand (CED), climate change, human toxicity, photochemical oxidant formation, metal depletion, fossil depletion, terrestrial acidification, freshwater eutrophication, marine eutrophication, terrestrial eco-toxicity, freshwater eco-toxicity and marine eco-toxicity. The results showed that for all impact categories the synthetic media biofilter had the highest environmental impact, followed by the wood chip media bio-filter system. The packed-bed system had the lowest environmental impact for all categories.

Mercury Removal from Flue Gas by Aqueous Precipitation

Mercury has drawn the public’s concern due to its bio-accumulative nature and its adverse impact on human health. At the same time, concern for greenhouse gas release has also grown, leading to a range of carbon capture strategies. Previous mercury removal studies, however, focused on either dry techniques or acidic solution conditions, and a major uncertainty is how high alkalinity (which is used in carbon mineralization capture methods) may result in a different mercury removal mechanism. To examine this question in detail, in this study, a lab-scale liquid-gas scrubbing system is manufactured and installed, based on the carbon mineralization by aqueous precipitation (CMAP) process for CO 2 sequestration. Sodium hydroxide solution is selected as a typical candidate to remove mercury. Based on the test results, the CMAP process, like most other capture methods, has relatively low elemental mercury removal efficiency, i.e. less than 20%, but it can remove oxidized mercury with more than 90% efficiency. This performance is very similar to that of the traditional flue gas desulfurization processes which are operated under acidic conditions, at pH from 4 to 6. Equilibrium calculations by Visual MINTEQ predict the speciation of mercury equilibrium in the liquid phase, and the result is in agreement with the experimental findings.

습식 스크러버의 분무유량, 형상비 및 충진율 변화가 스모크 저감에 미치는 영향

There has been increased amount of atmospheric pollutants including NOx and SOx which cause acid rain and photochemical smog as a result of increased use of fossil fuels. In order to reduce the amount of pollutants produced by fossil fuel, wet scrubber system is introduced in this experiment. Wet scrubber system is applied to a diesel engine (3,298 cc) and the amount of smoke is measured before and after the application in terms of aspect ratio, filling rate, and flow rate. The result showed a lot of smoke reduction when wet scrubber system was applied, and also the aspect ratios and water spray flow rate were the important factors to improve smoke reduction.

Integration of a Water Scrubbing Technique and Two-Stage Pressurized Anaerobic Digestion in One Process

Two-stage pressurized anaerobic digestion is a promising technology. This technology integrates in one process biogas production with upgrading and pressure boosting for grid injection. To investigate whether the efficiency of this novel system could be further increased, a water scrubbing system was integrated into the methanogensis step. Therefore, six leach-bed reactors were used for hydrolysis/acidification and a 30-L pressurized anaerobic filter operated at 9 bar was adopted for acetogenesis/methanogenesis. The fermentation liquid of the pressurized anaerobic filter was circulated periodically via a flash tank, operating at atmospheric pressure. Due to the pressure drop, part of dissolved carbon dioxide was released from the liquid phase into the flash tank. The depressurized fermentation liquid was then recycled to the pressurized reactor. Three different flow rates (0 L·day−1, 20 L·day−1 and 40 L·day−1) were tested with three repetitions. As the daily recycled flashed liquid flow was increased from 0 to 40 L, six times as much as the daily feeding, the methane content in the biogas increased from 75 molar percent (mol%) to 87 mol%. The pH value of the substrate in the methane reactor rose simultaneously from 6.5 to 6.7. The experimental data were verified by calculation.

Design and development of a bench scale vegetable oil based wet packed bed scrubbing system for removing producer gas tar compounds

The overall goal of this study was to design, fabricate and evaluate a vegetable oil based wet packed bed scrubbing system to study the removal of model producer gas tar compounds, i.e., benzene, toluene, and ethylbenzene. The designed column was 0.5m diameter by 1.1m tall and contained 6-mm raschig rings. Soybean and canola oils were used as solvents. These oils were not statistically (p>0.05) different in removal efficiencies of benzene, toluene and ethylbenzene. Packing specific constants of Billet and Schultes (1999) correlation (CV=0.80 and CL=2.40) were found experimentally. These constants can be used to predict height equivalent to a theoretical plate (HETP) of laboratory or pilot scale vegetable oil based wet packed bed scrubbing systems. The pressure drop across the column was in the range of 6.7 to 18.8mm of water column.

Selection of Exhaust Scrubber: Concept for Optimal Solution

The International Maritime Organization (IMO) through Annex VI of Marpol Convention sets 0.1% sulphur oxides (SO x ) limits by 2015 in the Emission Control Area (ECA) and globally 0.5% by 2020. These restrictions will bring not only considerable financial problems but also technical challenges for shipowners. In order to comply with the said limits and achieve the best possible economic and technological results it is very important to make a well-founded decision both for existing ships and new ships in the conceptual design phase. According to ship characteristics, the design of a scrubber system will be determined by its operating profile. There is no way to avoid extra ship operation, administration and organisation costs no matter which solution will be chosen. Therefore, the most efficient solution in the context of a particular ship is of paramount importance. The article proposes a concept to be used for (SO x ) scrubber system selection in the conceptual design phase, by analysing technical parameters, relevant to particular ship. DOI: http://dx.doi.org/10.5755/j01.erem.70.4.7490

습식세정장치에서 발생되는 마이크로버블을 이용한 음식물쓰레기 발생 복합악취 처리

The objective of this work was to treat complex mal-odor of food waste with micro-bubbles from enhanced wet scrubber system, where the pilot plant was operated. Micro bubbles from the enhanced reactor of venturi scrubber were successfully generated through the air atomizing process with high velocity more than 60 m/sec and played an important role in the removal of mal-odor. Mal-odor was effectively changed into the micro-bubble and treated with washing chemicals together. Through establishing two series connection of the reactors, 85.2 % removal efficiency of complex mal-odor was obtained in case of average 940 times of input air. 0.35 kg/hr of sulfuric acid, 0.188 kg/hr of sodium hydroxide and 0.043 kg/hr of hypochlorite were injected for chemical washing.

Vegetable oil as a solvent for removing producer gas tar compounds

The objective of this study was to evaluate the performance of vegetable oil as a solvent in a wet packed bed scrubbing system for removing model producer gas tar compounds. Solvent type, column bed height, solvent temperature and solvent flow rate were varied to assess the performance in terms of tar removal efficiency. Soybean and canola oils were used as solvents. Benzene, toluene and ethylbenzene were used as model tar compounds. Testing was conducted using a bench scale packed bed column, 5.25cm diameter by 1.1m height, filled with 6-mm raschig rings as packing material. Statistical analysis showed that soybean and canola oils provide comparable removal efficiencies of tar compounds. The analysis also revealed that bed height and solvent temperature had highly significant effects on tar removal efficiencies. Bed height, solvent temperature and solvent flow rate had highly significant effects on liquid holdup and pressure drop across the column.

Equilibrium stage based model of a vegetable oil based wet packed bed scrubbing system for removing producer gas tar compounds

This study was aimed to develop and validate equilibrium stage based absorption model to investigate the removal of model producer gas tar compounds using vegetable oil as a solvent. The absorption model was developed using split (φ/γ) approach and a “RadFrac” block in Aspen Plus™. The model used Peng–Robinson equation of state (EOS) and non-random two-liquid (NRTL) activity coefficient model to predict the fugacity coefficients (φ) for vapor phase and activity coefficients (γ) for liquid phase. The developed model was validated using the extreme conditions of the experimental test range. The model predictions showed best fits with the experimental data within 6% for benzene, 4% for toluene, and 2% for ethylbenzene at the solvent temperature of 30°C. Packing specific constants of Billet and Schultes (1999) correlation (Ch=2.52 and CP,0=2.93) were found experimentally. These constants can be used to predict pressure drop across the column for vegetable oil based wet packed bed scrubbing systems. The average deviation of predicted pressure drop across the column compared to experimental data was within 5%. The developed absorption model and packing specific constants would be beneficial in the design, optimization, and economic evaluation of vegetable oil based wet packed bed scrubbing systems.

Design and Construction of a Water Scrubber for the Upgrading of Biogas

This paper discusses the results of studies conducted on raw biogas produced from a prototypic biogas production plant located at the Teaching and Research Farm, University of Ibadan, Ibadan. This setup consists of a mixing chamber, a biogas digester and a stabilizing unit, locally designed and fabricated. It further discusses preliminary and detailed design coupled with the construction of an effective and efficient technology used in purifying raw biogas generated from the prototypic biogas production plant; this technology is otherwise known as the Water Scrubbing technology. The Scrubbing system consists of the Water scrubber with iron wool packed bed connected to a 500 litre water tank, and two tyre tubes which were used in storing the pre scrubbed (raw) biogas and the scrubbed (purified) biogas. The water scrubber has an inlet for the entry of the raw biogas and a discharge for the exit of the scrubbed biogas. Raw biogas from the plant was stored in a tyre tube and directly fed into the Water scrubber housing the iron wool packed bed, the purified biogas from the exit was also collected into another tyre tube. The samples of the gas mixture were taken before and after scrubbing and analyzed with Pascal Manometric Glass Tube technique. Results indicated that methane content of the scrubbed/ purified biogas was raised from 58% to 82% due to the reduction of Carbon dioxide and Hydrogen Sulphide. CO2 was reduced from 31% to 14% while H2S was reduced from 1% to 0.4%. The corresponding Energy content of the purified biogas was evaluated to be 41MJ/kg which is higher than that of the raw biogas which was evaluated to be 29MJ/kg.