Water Scrubbing Research Articles

Current Status of Biological Biogas Upgrading Technologies

To limit global warming, ratio of renewable sources in the energy mix has to be considerably raised in the following years. While application of e.g. wind and solar power usually generates fluctuations in the electric grid, biogas produced in anaerobic processes is an easy-to-store renewable energy source. Raw biogas contains generally ~55–70% methane and ~30–45% carbon-dioxide. Although raw biogas can be utilized directly for combustion or combined heat and power generation (CHP), its methane content can be raised to >95% by upgrading technologies, thus it can be valorized. By upgrading and cleaning, the quality of the upgraded biogas may reach the quality of the natural gas and it may be injected to the gas grid or used as fuel for devices optimized for natural gas. Several physico-chemical upgrading methods are available on the market (e.g. high pressure water scrubbing, pressure swing adsorption, membrane technology, etc.) to remove the carbon-dioxide content of the biogas. Opposite to the physico-chemical methods, where basically the CO2 removal is the main goal, in biological biogas upgrading technologies microorganisms are applied to convert the carbon-dioxide content of the biogas to methane (chemoautotrophic upgrading), or algal biomass (photoautotrophic upgrading). The expectations are high towards biological biogas upgrading technologies in the field of energy storage linked with carbon-dioxide capture. In this paper, latest research results concerning biological biogas upgrading are summarized, viability and competitiveness of this technology is discussed together with the most important future development directions.

Hand hygiene adherence at entrances and exits of healthcare facilities in two rural districts of Uganda

Background: During the COVID-19 pandemic, the World Health Organization (WHO) has recommended hand hygiene (HH) stations (ie, with soap and water for handwashing or alcohol-based hand rub or ABHR) at entrances and exits of every public or private commercial building, including healthcare facilities (HCFs). Methods: Enumerators observed the HH materials present at the entrances and exits of 37 public HCFs in the Moroto and Kotido districts and patient and visitor use of those HH materials. When handwashing stations were nonfunctional or out of water, no HH observations were made. Results: Of the 37 HCF entrances and exits assessed, 4 (11%) met the recommended guidance for HH materials: 3 (8%) had water and soap, and 1 (3%) had ABHR and water and soap. In other HCFs, 12 (32%) had no HH station present, 13 (35%) handwashing stations had no water, and 8 (22%) had water but not soap. Of 180 persons observed, 52 (29%) attempted HH and only 10 (6%) used appropriate HH technologies (4 with ABHR and 6 with water and soap). Of 52 people who attempted HH, 42 (81%) used only water without soap. All HH observed occurred when entering facilities; no HH occurred when exiting (0 of 68). Of those 52 who performed HH, 48 (92%) performed HH for the recommended time of >20 seconds. However, only 9 (5%) of 180 adhered to suggested HH technologies and length of time (used water and soap scrubbing for ≥20 seconds or used ABHR). Conclusions: We detected poor HH practice by patrons at entrances and exits of HCFs, which may be due to lack of appropriate HH materials, particularly lack of soap. Optimal strategies for adherence to WHO-recommended HH practices at entrances and exits of public and private commercial buildings, including HCFs, should be explored.Funding: NoneDisclosures: None

Thermoeconomic Analysis of Biomethane Production Plants: A Dynamic Approach

This work analyses the two most diffused technologies for biogas upgrading, namely water scrubbing and membrane separation. In order to carry out such analysis, these two technologies are coupled with photovoltaic panels and an electric energy storage system. The optimal water scrubbing renewable plant achieves a primary energy saving of 5.22 GWh/year and an operating cost saving of 488 k€/year, resulting in the best plant. It was compared to a reference system based on a cogenerator unit, directly supplied by biogas, producing thermal and electric energy, and delivered to the district heating network and to the electric grid. The profitability of both plants depends on the electric energy and biomethane exporting price. The proposed bigas upgrading plant achieves a payback period lower than 10 years with a biomethane selling price greater than 0.55 €/Sm3 and a primary energy saving index around 25–30% with a null share of thermal energy exported by the cogeneration plant.

Deployment of treated and compressed biogas as a sustainable fuel for ceramic kiln firing

Inefficiency, emission of greenhouses gases and the deleterious effects of carbonaceous fuels on both human health and the environment are responsible for the increased in exploration and adoption of eco-friendly and sustainable fuels to various aspects of human development and production processes. This study was aimed at the generation, treatment and compressing of biogas into Liquefied Petroleum Gas Cylinder (LPGC) for deployment to firing ceramic kiln. The methodology involved the anaerobic digestion of cow dung and the treatment of the generated gas using water scrubbing technology. The results of the study showed an increased in methane content from an untreated value of 43.5% to 93.98%, the elimination of CO2, and H2S; reduction in volume of gas used in firing a ceramic kiln to 1030 °C from 22,300 L of untreated biogas to 492 L of treated biogas, as well as the prevention of 108,000 g of methane, 124,00 g of CO2, 74,400 g of CO and 173.6 g of NO2 from venting into the climate system.

An innovative integrated CCHP system with water scrubbing‐based biogas upgrading unit and molten carbonate fuel cell

AbstractThe main purpose of this study is to develop an integrated structure of simultaneous generation of electricity and refrigeration as the main product and hot water as a by‐product. This proposed structure consists of a water scrubbing biogas upgrading process, molten carbonate fuel cell (MCFC) unit, gas/steam power (GSP) cycle, and absorption refrigeration (AR) system. In this regard, 10.71 kg/s untreated biogas enters the integrated system and 158,351 kW net power is produced. Wasted heat of the structure is utilized to generate cooling of 253.9 kW at a temperature of 243.6 K by applying the AR system and the rest of the heat is used to generate 8.391 kg/s hot water as the system byproducts. The process integration between the different parts has led to an increase in the thermal efficiency of the whole system so that the electrical and overall efficiencies are 78.68% and 79.86%, respectively. The investigation of the exergy study demonstrates that the exergy destruction of the entire structure is 71,859 kW, of which the turbine/compressor/pump section with 24,700 kW (with a share of 34.37% of the total) and MCFC/reformer section with 22,285 kW (with a share of 31.01% of the total) have the most irreversibility. The exergy efficiency of the hybrid structure is 71.06%. Through a parametric study, the present integrated system in various conditions is assessed. One of the results of main outcomes is the increase of overall efficiency up to 83.39% due to the reduction of inlet biogas methane mole content up to 50%. Rising the methane in inlet biogas, although leading to more production of system products, reduces the efficiencies of various parts of the system, including the MCFC unit and GSP cycle, as well as integrated system total efficiency.

Rate-based modeling approach for High Pressure Water Scrubbing with unsteady gas flowrate and multicomponent absorption applied to biogas upgrading

Biogas upgrading aims to increase the methane concentration in biogas by removing carbon dioxide. Upgraded biogas can then be used as a renewable energy resource. Among the technologies used for biogas upgrading, High Pressure Water Scrubbing (HPWS) is one of the most widespread. HPWS is identified as fulfilling all the requirements for farm-scale anaerobic digesters, presenting several levers to reduce operational and installation costs. One possible remedy is to optimize operating parameters to reach targeted gas specifications, without applying excessive treatment or energy consumption. The purpose of this study is to develop an efficient modeling tool that can predict methane purity and its recovery for different operating conditions of gas and liquid. This original model integrates the decrease of gas flow along the packing height and the concomitant absorption of carbon dioxide and methane. The model is based on mass transfer and hydrodynamics to explain and anticipate the performance of HPWS in order to facilitate its implementation on the field. Model results retrieved from a homemade environment on Excel are compared to those of experiments conducted on a farm-scale biogas upgrading plant and show very good agreement. The model demonstrates great adaptability regarding variations of parameters. It can thus be used to anticipate HPWS performance and to optimize running parameters in order to reach targeted purities while making energy consumption more flexible. Water regeneration is identified as the key parameter for compliance with gas injection standards, achieving a purity over 97% and a recovery ratio of 93% at a desorption pressure of 0.2 bar. Results highlight that a rate-based model giving access to molar fraction variation along the column is crucial to adjust operating parameters in order to reach optimal economic and environmental performances. More accurate operating conditions could be the key to lowering costs of production and attaining financial viability for biogas upgrading at farm scale.

Process simulation and evaluation for NH3/CO2 separation from melamine tail gas with protic ionic liquids

Melamine production is known to produce a tail gas with a significant amount of NH3 and CO2. The most common separation methods applied to melamine tail gas are water scrubbing and urea co-production technology. With good stability, non-volatility and tailored properties, ionic liquids (ILs) are regarded as vital potential solvents for gas separation. Therefore, two new process technologies, one is the ionic liquid-based process (IL-0), and the other is the enhanced ionic liquid process (IL-En) was employed and evaluated for energy and cost efficiency. The IL-En employs stripping on the treatment of melamine tail gas. The protic ionic liquid named 1-butyl imidazolium bis (trifluoromethylsulfonyl) imide ([Bim][NTf2]) was selected for the evaluation of the melamine tail gas cleaning process. Thermodynamic data were fitted to the NRTL equations. Three full process flowsheets were simulated in Aspen Plus V11 TM. A basic and an enhanced ionic liquid process (IL-0 and IL-En), a conventional water scrubbing (WS) technology as a comparison, process sensitivity analysis and energy/economic evaluation were carried out. The results showed that the total separation cost of the IL-En can be reduced by 61% compared to that of the WS process. Moreover, the IL-based flowsheet is simpler than WS and avoids wastewater discharge.

AN OVERVIEW: ENVIRONMENTAL AND ECONOMIC STRATEGIES FOR IMPROVING QUALITY OF SHIPS EXHAUST GASES

In spite of the fact that most of different transport means have achieved a significant reduction of their emissions quantity during the last few years; maritime field still suffers from the steady increase in the quantity of exhaust gases emitted from ships. As a result, the International Maritime Organization was prompted to issue a set of regulations for facing the seriousness of those emissions. The present paper handles the different methods which can be used to reduce the environmental damage caused by ship emissions. Through the study of the advantages and disadvantages of ships, emission reduction strategies; use of natural gas, selective catalytic reduction and sea water scrubbing systems have appeared as the best ways that can be utilized to reduce the environmental harms caused by ship emissions. Applicability of these methods aboard ships could vary from ship to another. Two high-speed passenger ships of different age were studied to evaluate the importance of applying these strategies. The results showed the possibility to attain valuable emission reduction percentage by using of selective catalytic reduction and sea water scrubbing systems, but they will be of high initial cost and will increase operating cost of both ships. On the other hand using of LNG as alternative fuel will be more convenient from the point of view of environment and economic issues for the newer existing ship.

Economic and environmental assessment of organic waste to biomethane conversion

Biomethane and biofertilizer production by anaerobic co-digestion of organic waste serves a promising method for reducing the environmental footprint of organic waste management. This study evaluated the techno-economic feasibility and environmental impacts of organic waste to biomethane development in Glasgow, UK using net present value (NPV) analysis and life cycle assessment. Four different biogas upgrading technologies (pressurized water scrubbing, chemical scrubbing, membrane separation, and pressure swing adsorption) were compared. The membrane separation technology-based biomethane production meets 0.8% of the gas demand for Glasgow households with a conversion efficiency of 83%. The organic waste to biomethane development saved up to 264 kg CO2-eq annually per tonne of waste treated, with an NPV ranged between £-9.0 million and £-12.0 million based on the upgrading technology. High costs for waste collection and transportation are primarily responsible for the negative NPV. Carbon taxes between £31.30 and £58.02 per tonne of CO2 are needed for economically viable biomethane production.

Significance to the Horticulture Industry

Significance to the Horticulture Industry

Purified biohythane (biohydrogen+biomethane) production from food waste using CaO2+CaCO3 and NaOH as additives

The current work focuses on biohythane (biohydrogen + biomethane) production from waste biomass by utilising CaO2+CaCO3 and NaOH as additives and purification in a novel purification and mixing column with water and NaOH scrubbing. The production process indicates an enhanced hydrogen content of 33.85% with CaO2+CaCO3 as an additive from the fermentative reactor. The methanogenic reactor produces an improved methane content of 67.24% by utilising NaOH as the alkali reagent. During purification, NaOH scrubbing results in the highest purification of 87.43% hydrogen and 91.27% methane. In contrast, the water scrubbing system produces a maximum purity of 76.18 and 82.36%, respectively. Further, the variation of gas flow rate illustrates improved biohydrogen and biomethane purity up to 97.85 and 98.39%, with a gas flow rate of 0.12 m3 h−1. While producing biohythane, a gas flow rate of 0.12 m3 h−1 produces the optimum concentration of hydrogen and methane at 31.08 and 66.17%, respectively.

“Human elephant conflict in changing land-use land-cover scenario in and adjoining region of Buxa tiger reserve, India”

The land use land cover changes (LULCC) in and around wildlife habitat are one of the major driving forces behind frequent human elephant conflict (HEC). The present study aims to determine the spatiotemporal LULC changes and its impact on Human – Elephant conflict in and adjoining Buxa Tiger Reserve (BTR). Landsat TM and OLI images of 1990, 2000, 2010, and 2019 were used and supervised classification using maximum likelihood classification algorithm applied to classify the LULC attributes. Each sign of elephant presence was recorded using GPS used for corridor mapping. The recorded sign of conflict was collected, used for settlement based human elephant conflict probability zone identification mapping by areal interpolation method. We found that (1990 - 2019) dense forest, surface water bodies, scrub land and agricultural fallow land decreased by 184.04 sq km, 21.94 sq km, 142.48 sq km, and 130.21 sq km respectively. On the other hand crop land, sparse vegetation, tea garden, open forest, degraded forest and built up areas increased by 119.74 sq km, 90.96 sq km, 87.05 sq km, 57.02 sq km, 19.07 sq km and 32.21 sq km respectively. The visual overlay method was performed between LULC map, and settlement based HEC probability map, therefore impact of spatiotemporal LULC change on HEC was determined. It finds out moderate to very high HE conflict settlement zone lies where nearby forest tract either degraded or large areas of open forest, scrub land replaced into crop fields and settlements. In addition, elephant sign along the broad gauge rail line were collected on foot, recorded using GPS used to prepared accident prone susceptibility map by Inverse Distance Weighting (IDW) interpolation technique to estimate where accidents were more likely to occur due to the concentration of elephant activity. It finds out high to very high accident prone susceptible zone lies in between Rajabhatkhawa station (st) – Damanpur st, Gorapara st- Rajabhatkhawa st, and railway line within Hamiltonganj range. The study wants to draw attention to the concerned authority and policy makers on that there is a need of long term land use planning to save BTR forest and its biodiversity as well as need for proper mitigate method for HE conflict for peaceful coexistences of both the species.

Modelling of Physical Method for Tar Elimination from Producer Gas at Low Temperature

Combining a methanation step with biomass gasification requires an intensive tar removal process that reduces its content down to 1 mg/Nm3. In this paper, low temperature processes are suggested for treating tar and reducing its content to the acceptable limit. However, the gas must be pre-treated prior to the low temperature process in order to reduce its temperature, its moisture content and the heavy tar fraction. Two water scrubbers are placed prior to the low temperature tar removal process. Benzene and toluene remains in the producer gas after the scrubbers. Those two components can be valorised if separated from the producer gas at low temperature. The tar removal, at low temperature, induces the water vapour frosting remaining in the producer gas. The simultaneous frosting and condensation takes place over a cold plate. Modelling simultaneously the multi-component frost growth and condensation requires complex mathematical approach. A parametric study is completed to assess the impact of the wall temperature and the producer gas flow rate on the tar removal process function of time and plate length. Results showed that a wall temperature of -20 (C is required to lead to the benzene frost formation for an initial molar fraction of 0.024. After one hour, the thicknesses of benzene and ice frost layers reach 1.5 and 2.5 mm, respectively. Therefore, the heat transfer between the gas and the cold surface is reduced.

Methane Refinement by Iron Oxide, Packed Column Water Scrubbing, and Activated Charcoal Scrubbing Techniques

Methane Refinement by Iron Oxide, Packed Column Water Scrubbing, and Activated Charcoal Scrubbing Techniques

Recent Technology Developments in Biogas Production from Waste Materials in Malaysia

AbstractSolid waste management towards the sustainable process is one of the major undertakings of the Malaysia Solid Waste Management Department. Hence, development towards biofuels including biogas production from wastes has been escalating in Malaysia. There have been some major innovations in biogas production, including design and operation of the reactor, the presence of an additive, change in mixing regime, supporting unit, measurement, and monitoring systems, since the technology has developed. The sections mainly included are types of digesters, strategies such as upstream, mainstream, and downstream. In upstream strategies, the hydrothermal pretreatment of anaerobic digestion showed a higher improvement of biogas by an increase of 222 % of methane content. The mainstream strategies showed that co‐digestion was the best method to increase the methane yield to 305–445 mL g−1 VS. In downstream system, methane content can be upgraded from 60 to 90 % by applying water scrubber. This paper aims to discuss the recent trends and innovations in biogas production from waste and their pathways in details.

Effect of Mg Electrodes Wired in Series in Electrolysis to Alkalize EGR Scrubber Water

Exhaust gas from ships becomes a problem as a causative substance of air pollution. Scrubber water is used for EGR that is an exhaust gas purifying device to absorb harmful matter. However, it cannot be reused since its alkalinity decreases after absorbing SOx. Therefore, an electrolytic device with Mg electrodes connected in series was developed. In this report, the current as a function of the applied voltage and the voltage between electrodes were measured. We also investigated the effect of the electrolytic device connected in series by comparing its alkalinity and energy efficiency with those of a device connected in parallel. It was shown that the output voltage from a power supply was divided between electrodes. The energy efficiency of the former device was equivalent to that of the latter. In the case of a 6.5 MW engine, the voltage and current of the later device were estimated as 7.9 V and 468 A, respectively. On the other hand, those of the former were 79 V and 46.8 A.

SIMULATION AND OPTIMISATION FOR PRODUCTION OF BIOGAS FROM PALM OIL MILL EFFLUENT (POME) USING ASPEN PLUS

POME undergoes anaerobic digestion to produce biogas, and when it is purified, the biomass can be used as a fuel. This work aims to create a model to simulate the production of biogas and identify the key parameters of the water scrubber using Aspen Plus. The production of biogas was successfully simulated with a relative difference of less than 5%. The key parameters of scrubber in order of percentage contribution to the purity of biogas is as follows, the temperature of water (38.34%), column pressure (35.29%), water flow rate (23.75%) and lastly, number of stages (2.62%). By employing the optimum values, biogas with 99.3% methane purity was obtained.
 Keywords: Palm oil mill effluent, biogas upgradation, water scrubbing, Aspen Plus, optimisation

Heating Performance and Ammonia Removal of a Single-Stage Bioscrubber Pilot Plant with Integrated Heat Exchanger under Field Conditions

In this study, biological exhaust air treatment was combined with a recuperative heat exchanger in one process stage. The aim of this plant development and testing is not only to reduce ammonia from the exhaust air of pig houses but also to recover thermal energy at the same time. This is intended to offset the high operating costs of exhaust air treatment with savings of heating costs in cold seasons and to use the plant more efficiently. This system was tested for the first time under practical conditions in a pig fattening house in southern Germany. Three different assembly situations of the heat exchanger were examined for 13 days each and then compared with each other. The heating performance of the plant is primarily dependent on the outside air temperature and secondarily on the scrubbing water temperature. Depending on the assembly situation of the heat exchanger, an average heating performance of between 6.0 and 10.0 kW was observed; the amount of recovered thermal energy was between 1860 and 3132 kWh. The coefficient of performance (COP) ranked between 7.1 and 11.5. Furthermore, ammonia removal up to 64% was demonstrated. A long-term investigation of the system under practical conditions is recommended to validate the data collected in this study.

Effects of seawater scrubbing on a microplanktonic community during a summer-bloom in the Baltic Sea

The International Maritime Organization (IMO) has gradually applied stricter regulations on the maximum sulphur content permitted in marine fuels and from January 1, 2020, the global fuel sulphur limit was reduced from 3.5% to 0.5%. An attractive option for shipowners is to install exhaust gas cleaning systems, also known as scrubbers, and continue to use high sulphur fuel oil. In the scrubber, the exhausts are led through a fine spray of water, in which sulphur oxides are easily dissolved. The process results in large volumes of acidic discharge water, but while regulations are focused on sulphur oxides removal and acidification, other pollutants e.g. polycyclic aromatic hydrocarbons, metals and nitrogen oxides can be transferred from the exhausts to the washwater and discharged to the marine environment. The aim of the current study was to investigate how different treatments of scrubber discharge water (1, 3 and 10%) affect a natural Baltic Sea summer microplanktonic community. To resolve potential contribution of acidification from the total effect of the scrubber discharge water, “pH controls” were included where the pH of natural sea water was reduced to match the scrubber treatments. Biological effects (e.g. microplankton species composition, biovolume and primary productivity) and chemical parameters (e.g. pH and alkalinity) were monitored and analysed during 14 days of exposure. Significant effects were observed in the 3% scrubber treatment, with more than 20% increase in total biovolume of microplankton compared to the control group, and an even greater effect in the 10% scrubber treatment. Group-specific impacts were recorded where diatoms, flagellates incertae sedis, chlorophytes and ciliates increased in biovolume with increasing concentrations of scrubber water while no effect was recorded for cyanobacteria. In contrast, these effects was not observed in the “pH controls”, a suggestion that other parameters/stressors in the scrubber water were responsible for the observed effects.

Removal of Tar Contents Derived from Lignocellulosic Biomass Gasification Facilities Using MgAl-LDH@clinoptilolite

Gasification of lignocellulosic biomass requires the effective removal method of tar. This study focused on the application of specially designed Mg/Al-layered double hydroxides clinoptilolite (Mg/Al-LDH@clinoptilolite) to improve the removal efficiency of tar, which would eventually lead to enhancing the power efficiency of gasification, preventing damage to facilities, and deducing durability improvement plans. Zeolite-layered double hydroxides impregnated with clinoptilolite, a natural zeolite, and Mg/Al-layered double hydroxide incorporated into conventional water scrubbers were prepared to enhance the removal efficiency of the tar and improve the quality of the syngas produced during the gasification process. The simultaneous removal of moisture and CO2 in the syngas was also investigated during the removal of the tar. The drastic decrease in tar and CO2 concentration was confirmed, which triggered a relative increase in the effective content of inflammable gas. The findings of the present study provide a practical approach to increasing power efficiency and durability during the gasification of lignocellulosic biomass.