Ceramic Candle Research Articles

Efficiency of Ceramic Candle Filters towards Purification of Drinking Water

Efficiency of Ceramic Candle Filters towards Purification of Drinking Water

Influence of iron, phosphate, and silicate on arsenic removal from groundwater using a low-cost ceramic filter.

The ceramic filter amended with iron (Fe) has proven to be a potential low-cost method for arsenic (As) removal from groundwater. The presence of Fe, phosphate (P), and silicate (Si) significantly affects the As removal efficiency of the ceramic filter, which has not been passably investigated. The present research aimed to examine the effect of Fe, P, and (or) Si presence as single or in combination on As (III) removal from synthetics groundwater by a low-cost iron amended ceramic filter (IACF). Laboratory-scale filtration experiments at different compositions of Fe, P, Si, and As (III) were conducted by the IACF fabricated with a ceramic candle and iron netting box. Fe (II) in synthetic groundwater positively impacted As (III) removal. At a concentration of 2mg/L of Fe (II), the As levels in the effluent decreased to less than the maximum contamination level (MCL) of 50 μg/L. Groundwater P concentration needed less than 3mg/L or Si concentrations required less than 35 mg/L to effectively reduce As (III) to below the MCL at 5mg/L of groundwater Fe (II). The cumulative effect of P and Si on As removal was found to be more significant than distinct contributions. The presence of 2mg/L P and 35 mg/L or higher Si in the groundwater cumulatively reduced the As removal performance from 92% to 63%, and the MCL was not met. The negative impact of P and Si on As (III) removal followed the order of (P + Si) > P > Si. P competed with As for adsorption sites during the process, while Si inhibited the Fe release and floc formation, significantly reducing As removal performance. The study findings can potentially contribute to optimizing IACF as a low-cost method for As removal from groundwater.

Performance Assessment of Household Water Treatment and Safe Storage in Kathmandu Valley, Nepal

Although many households in the Kathmandu Valley rely on household water treatment and safe storage (HWTS) to obtain drinking water, the safety of treated water has not been evaluated in actual usage. Therefore, we assessed the performance and maintenance of five HWTS methods used in 101 households. The choice of HWTS methods by households was primarily influenced by the raw water source, that is, jarred water users opted for boiling and groundwater users selected reverse osmosis with ultraviolet irradiation (RO-UV). While boiling and electric dispensers (ED) did not remove inorganic contaminants (ammonia nitrogen, arsenic, and manganese), ceramic candle filters (CCF) and RO-UV reduced them moderately. The HWTS methods reduced E. coli and total coliforms (TC) by 95.8 and 84.1%, respectively, but 11.8 and 69.3% of treated water samples remained positive for these two bacteria. Combined methods (CM) and RO-UV showed an inferior TC reduction compared to the simpler HWTS methods, boiling, CCF, and ED, possibly due to difficulties with regular maintenance and storage contamination. Therefore, it is recommended to choose simpler HWTS methods that meet the requirements of the household’s water sources rather than more expensive and difficult-to-maintain methods, which should be chosen only if the raw water contains high concentrations of inorganic contaminants.

Synergic Effects of Bed Materials and Catalytic Filter Candle for the Conversion of Tar during Biomass Steam Gasification

This work concerns the activities of the European project BLAZE that aims to integrate a pilot-scale gasifier unit with a Solid Oxide Fuel Cell (SOFC). The objective is to identify the optimal operating conditions for a gasifier and hot gas cleaning and conditioning unit to produce H2-rich syngas with contaminants levels within the limits for the safe operation of the SOFC (750 mg/Nm3 and 75 mg/Nm3 for toluene and naphthalene, respectively). Experimental tests were carried out on a bench-scale gasification plant with a catalytic filter candle placed in the freeboard, to study the influence of temperature (1032 up to 1137 K), bed materials (olivine or olivine/dolomite 80/20%), and a nickel-based catalyst. The tests with a ceramic filter candle filled with catalyst and the mixture of olivine and dolomite in the bed gave the best results in terms of gas composition and gas yield, but the tar content was still higher than the limits for the SOFC. To increase the residence time of the gas in the catalytic bed a new metallic filter candle was tested. This candle, with almost the same external volume, allowed doubling the amount of catalyst used. Under these conditions, the content of toluene and naphthalene was reduced below 150 and 50 mg/Nm3, respectively.

Three staged integrated community-based water filter system for potable water by effective removal of contaminants from ground water

Potable water scarcity is a dire problem faced worldwide due to contaminated ground water. Microbial contaminants, heavy metals chromium (Cr) and metalloid such as arsenic (As) are some of the major pollutants of ground water and pose serious health hazards. The present work is focused to design a multifunctional three compartment integrated water filtration system for community use and its validation at both lab and pilot scale. The top compartment is mainly for removal of flocculating contamination with improvement of taste and odor of drinking water. The second compartment consists of functionalized sand layers for removal of metal and microbial contaminants and the third compartment comprises of nanoparticle embedded ceramic candles to further eliminate any remaining contaminants. The developed integrated water filter containing various types of materials were characterized through flow rate, scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS) before and after filtration. Moreover, the analysis of various physiological parameters such as pH, turbidity, total dissolved solids and hardness pre and post filtration elucidated stable and improved results. Micro-computed tomography (micro-CT) analysis of baked ceramic candle showed substantial increased porosity of ~83.11 ± 2.17 % in comparison to unbaked candle (26.09 ± 1.33 %). The inductively coupled plasma mass spectrometry (ICP-MS) analysis demonstrated significant reduction of As and Cr levels before and after filtration, which was further confirmed by EDS mapping. Microbial testing showed hierarchal decrease in microbial load after each stage at lab scale. This low-cost, multistage, gravity-based filtration system proved effective in removal of heavy metal and microbial contaminants in water and provides the potable filtrate for daily use. Thus, the integrated system with simple design without requiring major infrastructure and promising results may lead to its potential real-time application for supplying potable water to large populations, particularly in rural populations who cannot afford sophisticated water purification system.

Mini-Review on Hot Gas Filtration in Biomass Gasification: Focusing on Ceramic Filter Candles

Biomass gasification is increasingly attracting interest in the research of biorenewable energy all over the world, as a carbon-neutral supplement to the conventional fossil energy. It can convert biomass to the burnable producer gas for heat and power production or synthesis of fuels and chemicals. However, its commercial applications are seriously interfered by the minor but unavoidable contaminants or impurities in the raw product gas, which cause severe problems in the downstream equipment. This paper reviews the recent progress on the hot gas filtration technologies for removing particulate matters (PMs) and tars from the biomass-derived product gas, focusing on ceramic filter candles, which are widely applied in the biomass gasification systems. Developments of PM characterization, hot gas catalytic filtration, and oxidative filtration as well as the numerical simulation of computational fluid dynamics in hot gas filtration are summarized in detail. It also critically discusses the major challenges and future opportunities in hot gas filtration and concludes that the combined oxidative filtration and catalytic filtration with highly efficient catalyst at moderate temperatures (<600 °C) should be the most economical option for the widespread commercial small-scale biomass gasification systems.

Development of catalytic ceramic filter candles for tar conversion

A catalyst with a high activity in tar conversion, impregnated on the ceramic hot gas filter material was developed. The aim of the experiments was to estimate the light-off temperature of the catalytic filter elements for naphthalene (tar model compounds) conversion and the long-term catalytic stability at a temperature of 700 °C. Configuration of the catalyst was optimized through improvements in coking resistance and long-term stability. The composition and morphology parameters of the filter material were considered. Both the impregnation methods and the composition of the impregnation solution were investigated and validated. The catalyst composed of Ni, Fe, Cr oxides, promoted with Pt (AlSi-Cat43-Pt), and impregnated on the ceramic-fiber filter composed of Al2O3(44%)/SiO2(56%) was found to be the most active catalyst. The designated catalyst was catalytically active at temperatures of about 700 °C, with a naphthalene conversion of around 93% over 95 h without catalyst deactivation. We found that the steam and gas compositions had an influence on the catalytic activity of the filter elements. The same catalytic filter was catalytically active for 115 h at a low concentration of H2O (10 vol%) and H2 (3 vol%) with a naphthalene conversion of 98% at 790 °C without significant deactivation.

English

Due to the erratic nature of microbial contaminants in drinking water, private and municipality water supply systems failed to deliver safe drinking water to households. In Ethiopia, there is lack of data and knowledge on the effectiveness of filter devices used to treat drinking water at household. This study aims to evaluate efficiency of household point of use filter devices (membrane filter, membrane with activated carbon, ceramic candle type filter and hybrid (multistage)) in reducing bacterial contaminants from drinking water. Percent reduction efficiency model was employed in evaluating bacterial removal efficiency. Membrane filter and membrane with activated carbon filter devices had good total coliform removal efficiency on the 1st and 2nd days than hybrid filter device which showed low removal efficiency. Similarly, all filter devices showed better fecal coliform removal efficiency on the 1st day compared to 2nd day but had low heterotrophic bacteria removal efficiency during the three days filtration. Fecal Streptococcus removal efficiency on the 2nd and 3rd days by all filter devices was low except the first day. The result in general showed that using of point of use filter devices for prolonged time could not guarantee in providing risk free drinking water at household level. Key words: Coliform, drinking water, household filters, point of use, removal efficiency.

Permeability and dust filtration behaviour of porous SiC ceramic candle filter

Porous SiC candle filter (∼660 mm L and 75 mm OD) were fabricated by ramming process using commercially available SiC powder (d 50 = 212 μm), with and without alumina and small amount (3 wt%) of clay as the major binder phase additives, following heat treatment at 1400 °C in air. Depending on the composition, porosity of the candle filters varied from 36 to 39 vol% and C-ring strength varied from 15 to 23 MPa. The air permeability and dust filtration efficiency of the candle filter were evaluated using laboratory made test set up. At room temperature, Darcian (k 1 ) and non-Darcian (k 2 ) permeability parameters varied from 1.9 to 2.2 × 10 −12 m 2 and 5.4–9.72 × 10 −8 m, respectively. Airborne fly ash particle filtration tests showed good performance of SiC candle filter with filtration efficiency of >97%.

Purifications of petroleum products contaminated water using modified rice husk ash filters

This study evaluated the effects of different ceramic candle filters made from blends of rice husk ash (RHA), polyethylene glycol (PEG), and clay for effectiveness in purifying petroleum products contaminated water. The filters were characterized for porosity, swellability and water permeability. Performances of the candle filters were evaluated based on the physicochemical analysis of the untreated and purified water samples. The parameters measured include total dissolved solids (TDS), hardness, phosphates, nitrates, and chloride. Results from this investigation indicated that water diffusion in the filters, depends on filter dimensions-as permeability increased with decrease in filter’s surface area. This was also seen in the average flux obtained for the candles. The filter EL4 has a flux of 0.0070 ml/min.cm2, EL3 has 0.0199 ml/min.cm2. Also, the porosity of the filters increased with the amount of porogen used. An improvement in physical appearance of the water samples was seen after purification of the contaminated water. The chloride and TDS content of the untreated water samples were 260.1 ± 7.705 mg/L and 596.7 ± 30.32 mg/L respectively, while the chloride and TDS contents of filtrates obtained from filter made from RHA/Eleme clay and PEG as porogen (EL3) to 246.4 ± 1.915 mg/L and 511.7 ± 13.3 mg/L respectively. All the filters increased the phosphate and nitrate contents of filtrates compared to the untreated water samples. Total polycyclic hydrocarbon was reduced up to 85% by EL4 filter. The values of heavy metals found in the water samples were within the permissible limit for irrigation water. The low preparation cost, ease of preparation and purification results of these candle filters will boost their applications for water remediation in areas with high level of contamination particularly for irrigation and other household purposes but not drinking and cooking.

Developing Zeolite Ceramic Filters For Purifying Open Water Sources In Rural Communities

Access to safe drinking water has been a challenge for most rural dwellers in Sub-Sahara Africa who rely on open water sources for their consumption and domestic activities. In attempt to purify water from these open water sources, this study looked at producing zeolite from kaolin with NaOH concentrations through crystallization process, develop ceramic candle filters and subsequent zeolite filter unit to purify unsafe water. Two procedures were used for the synthesis; pre-treatment or thermal activation of the kaolin at 6500C to get a dehydroxylated product called metakaolin and hydrothermal reaction of metakaolin in alkaline solutions for crystallization of the zeolite. The effect of the zeolite ceramic filter on the users was enormous. Results showed that properties such as turbidity removal, flow rate and coliform removal were within WHO standard after the purification. A pilot study of the zeolite ceramic filter showed improved health standards such as fewer diarrhea, nausea, cramps, vomiting and good skin growth.

Simulation of dust deposition process in ceramic filter under different filtration modes by a novel CFD-based method

In this study, the dust deposition process in the ceramic filter of the updraft, tangential, and downdraft flow filtration mode was modeled by a novel CFD-based method, in which a unique mesh grid zone referred to as “dust cake zone” was created to simulate the actual dust cake layer, and grid cells located in the same line were linked together by a fast neighborhood search algorithm to model the actual dust cake growth path. Next, a simulation of the updraft flow filtration (UFF) mode was first carried on and compared to the related experiment in detail to determine the optimal simulation setting. Then, the simulations of the tangential flow filtration (TFF) and downdraft flow filtration (DFF) mode were performed based on the verified CFD settings of the UFF mode, which was able to reduce the pressure drop relative error to less than 6%. Furthermore, the simulation results of these three kinds of filtration modes were carefully analyzed and compared. It was found that the dust cake distribution varied dramatically among different filtration modes, which was due to different patterns of the vortex-flow forming near the candle surface. Some less-particle-deposition-zones can be found on the ceramic candles’ lower portion, middle-lower portion and upper portion in the UFF, TFF and DFF mode, respectively. Moreover, the TFF mode had the lowest pressure drop growth rate, while the most uniform dust cake layer was formed in the DFF mode.

A novel CFD-based method for predicting pressure drop and dust cake distribution of ceramic filter during filtration process at macro-scale

In this work, a CFD-based method for simulating the real-time pressure drop and dust cake distribution of the ceramic filter at the macro-scale is presented. In this CFD-based method, a unique mesh grids zone, i.e., a dust cake zone, is created to model the particle deposition process on the ceramic candle surface. In the dust cake zone, the mesh grids on the same ray are arranged into a queue to mimic the dust cake growth trajectory, and the pressure drop and porosity of the dust cake layer are modeled by 1-D empirical formulas. In order to determine the exact grid cell for particle deposition, a novel algorithm is developed, and near-wall corrections of the drag and lift force are applied. Then, a steady and a transient simulation were performed and compared to the experimental data. The comparison results of the pressure drop across the ceramic filter show that the deviation of the pressure drop between experiment and simulation is below 3.6% and 6% in the steady and transient simulation, respectively. Additionally, the dust cake thickness at different locations was tested and compared to the simulation results, and the difference is between 3.9% and 12.9%. Moreover, some less-particle-deposition-zones (LPDZs) are found in the middle and lower portion of the ceramic candles. The size and position of these LPDZs are well predicted by the transient simulation, and their forming reasons are carefully analyzed.

Syngas conditioning by ceramic filter candles filled with catalyst pellets and placed inside the freeboard of a fluidized bed steam gasifier

Gasification is a very advantageous conversion process to obtain a fuel gas from organic wastes, however it also generates by-products, such as particulate and tar. These should be removed from the syngas for its smooth utilization in power generation devices and/or biofuels production. In this work, biomass gasification tests were carried out in a bench-scale fluidized bed gasifier with a ceramic filter candle filled with commercial Ni-catalyst pellets integrated in its freeboard, for the abatement of particulate and tar. The activity of catalyst was studied at different operating conditions (temperature and catalyst bed layout) and the results were analysed in terms of residual tar content and composition of the product gas. The catalyst resulted very effective, particularly in tests at higher temperature and with the partially filled candle configuration. Tars were reduced to 250 mg/Nm3 in the best case. The Ni-catalyst did not show deactivation during tests lasting 4 h.

Oxidative filtration for flyash & tar removal from 1.0 MWth fixed-bed biomass air gasification

Experimental campaigns were performed with the aim to study the hot gas filtration process during the pilot-scale biomass gasification at GIEC. This paper gives an overview of the continuous and steady filtration tests performed with stable pressure drop (ΔP) for over 200 h in 400–600 °C, using wood chip and charcoal as the feedstock. The ceramic candles show good long-term filtration performance with a permanent cake layer serving as an extra filtration medium. Tar content is found to be the controlling resistance for the biomass gasification-filtration process. A novel oxidative filtration is reported to lead to a simultaneous removal of carbonaceous flyash particles (CFPs) and tars as well as a dramatic ΔP decrease with no obvious degradation in the heating value of the producer gas, in which a tiny amount of additional air (≤5.5 vol%) is introduced into the producer gas. Under the optimum condition, the CFP removal efficiency is always >99.0% and the tar removal efficiency of 92.2% could be achieved, with ΔP kept within a range of 1000–2000 N m−2 at the gas superficial velocity of 1.5–2.0 cm s−1 and 0.5–1.5% oxygen content of the producer gas (O2%). It is found that filter candles could act as a reactor without any catalyst to partially oxidize tars and CFPs with a little heat generation when hot gas filtration is operated in the presence of low oxygen concentration in 400–600 °C. The efficient CFP removal and tar reduction during the high-temperature oxidative filtration is beneficial for downstream units and their operability.

3D-CFD simulation of catalytic filter candles for particulate abatement and tar and methane steam reforming inside the freeboard of a gasifier

Biomass gasification is a very promising process to produce energy from agricultural wastes; however, tar and particulate have to be removed in order to make the product gas exploitable. Catalytic filter candles inserted in the freeboard of a fluidized bed gasifier, perform hot syngas cleaning from particulate and promote the steam reforming reactions of tar and methane thanks to the addition of Ni-catalyst in their inner space. In this work, a 3D-CFD model is implemented in the FLUENT software, to simulate 6 catalytic candles housing in the freeboard of a pilot scale dual bubbling fluidized bed steam gasifier (100 kWth as biomass input). Main model parameters were derived from experimental results obtained with a bench scale gasification reactor, equipped with a ceramic filtering candle containing a commercial catalyst, to allow conditioning the raw syngas produced on site. Simulations were carried out to study the conversion of tar and methane in a real case application. The temperature drop along the gasifier freeboard causes very low conversion (≈15%) of tar produced inside the gasifier fluidized bed. It was found that small injections of O2 in the freeboard can rise the temperature and increase tar conversion up to 77%. Finally, simulations with raw syngas input subjected to primary tar removal by means of Fe-olivine as fluidized bed material resulted in high conversion rates and residual tar content lower than 1 g/Nm3.

Development and Tests of a Combined Filter for NOx, Particulates, and SO2 Reduction

AbstractThe idea of this innovative filter concept is to combine three individual flue gas technology treatment systems into one product to be more economic and efficient. The central part of the filter is a ceramic filter candle, which is used for common dust separation. The ceramic filter material is activated with modified catalysts to enable selective catalytic reduction at low temperatures (150–200 °C). To reduce acid components while simultaneously increasing dust separation, the activated filter candle surface is precoated with an absorbent. The developed filter is suitable for many applications, especially decentralized applications such as solid biomass combustion or utilization of biofuels in combined heat and power engines, which are target markets. The production of the filter material and the practical test using exhaust gas from a dual fuel engine operating with biofuels are described.

Development of De-NOx selective catalytic reduction catalyst using V2O5 –TiO2 supported on a ceramic filter candle

ABSTRACT This study reports the development of a V2O5-TiO2-based selective catalytic reduction (SCR) catalyst supported on alumina-silicate water filter candles for NOx abatement. The synthesised catalysts have been characterised by thermogravimetry/differential scanning calorimetry, X-ray diffraction, scanning electron microscope and measurement of NOx removal performance. The catalyst synthesised under optimal conditions shows NOx reduction efficiency of >97%. SCR performance has been augmented using O2 as a carrier gas. This simple, reproducible procedure can have wide applications in NOx abatement.

Assessing the Influence of Water Management and Rainfall Seasonality on Water Quality and Intestinal Parasitism in Rural Northeastern Brazil.

Introduction The drought in the Brazilian semiarid region has affected the quality of water. This study assessed the relationships between enteric parasitoses, water management, and water quality, correlating them with pluviometric seasonality. Methods Cross-sectional surveys were carried out in four rural communities at the beginning of the dry season (n=151), at the end of the dry season (n=184), and in the rainy season (n=199), in order to collect sociodemographic data, human fecal samples, and samples of the water used for human consumption for physicochemical and microbiological analyses. In 2015, water filters were provided to 30 households under study. Results There was an increasing trend in detection rates of commensal protozoa and the Entamoeba histolytica/Entamoeba dispar complex at the beginning of the rainy season, with detection rates of 6% in 2014 and 21.6% in 2016. Giardia intestinalis and Ascaris lumbricoides presented distinct temporal distributions, which peaked in 2015: 20.1% and 30%, respectively. The proportion of inhabitants drinking inadequate water was 55% at the beginning of the dry season and 28.8% at the end of the dry season, reaching 70.9% at the beginning of the rainy season. The presence of filters reduced this proportion among those who received the hollow ceramic candle filter. Conclusions Data suggest that the strategies to increase water supply in the Brazilian semiarid region can be ameliorated in order to improve the quality of drinking water.

Effects of temperature, dust concentration, and filtration superficial velocity on the loading behavior and dust cakes of ceramic candle filters during hot gas filtration

Abstract Ceramic candle filters (CFs) are commonly used in power generation processes because of their ability for durable operation at high temperatures. Two ceramic CFs were experimentally and theoretically evaluated in this study, one composed of mullite (30–20) and the other composed of alumina and silicon carbide (F-40), representing filters with high and low collection efficiency for conventional and advanced power generation. The effects of three critical parameters in CF operation (temperature, dust concentration, and filtration superficial velocity) on two performance measures (filter loading behavior and dust cake) were carefully investigated. The revised Endo’s expression was used to evaluate the resistance ( α c ) and porosity ( e ) of dust cakes that formed on a cylindrical CF. An analysis of pressure drops for both CFs and dust cakes revealed that the pressure drops increased with the operation temperature, which was solely due to the increase in air viscosity. However, the resistance and porosity of the dust cakes were still affected by the filtration temperature, even when the influence of temperature on the gas viscosity and volumetric flow rate was considered. Between 473 and 573 K, the overall steady-state α c and e of the dust cakes changed markedly for both CFs. Moreover, for the low-efficiency CF (F-40), improvement in the collection efficiency with the temperature depends on improved diffusional effects and may influence the corresponding dust cake structures.