Moving Bed Granular Filter Research Articles

Filtration for nano/micron-sized particulates with a moving bed filter

Particulate Matter (PM) pollution has attracted much attention as it represents a serious threat to public health. Granular bed filtration is a highly efficient gas cleaning technique at high temperatures. A counter-current moving bed granular filter with novel internal components was proposed to capture fine particulates. The effects of the moving bed filter on removing the fine dust particulates with various sizes (micron and nanometer scale) were investigated. The experimental results indicate that dust is easily captured under a low superficial gas velocity or a high capturing particle moving velocity. In a moving bed filter with the counter-current flow, diffusion is the dominant collection mechanism for the nanometer dust; on the other hand, the micron dust capturing is a combined effect with multiple mechanisms including diffusion, sedimentation, interception, and impaction. An efficiency calculation model was constructed based on the experimental results and the single-particle filtration mechanism.

Filtration characteristics with parameter variation for dust removal from syngas

BackgroundGranular bed filter technology is a newly emerging field, and the science is in its infancy. There is a lack of background information on these consistencies. This study provides new insights into clean processing, which is useful in hot gas cleanup technology. MethodsWe employed a moving granular bed filter, which is evaluated in two separate performance studies: (1) optimization of particle removal efficiency and bed pressure drop under different movement velocities of silica sand; and (2) high temperature model simulation conducted dust and Silica sand flow rates and superficial velocity. Besides, this evaluated the filter system's dynamic characteristics by measuring variations in the outlet concentration and size distribution of dust particulates. Significant findingsThe results indicated that the filtered dust in the silica sand considerably affected the dust via inertial impaction and diffusion. With higher movement velocity of silica sand, the higher specific resistance coefficient of k1 and k2 caused better performance of collection mechanism, thereby enhancing the removal efficiency. Consequently, this study observations indicated that at a high movement velocity of silica sand, the gas velocity favors dust attachment on the silica sand particle surface, facilitating dust removal.The purpose of this study is to investigate the efficiency of moving granular bed filter (MGBF) in high-temperature environment under different operation conditions. The effects of the test temperature and movement velocities of silica sand on the dust size distribution and removal efficiency were studied; further, an experimental system comprising a high-temperature environment of 600 °C was established for a filter system. The removal efficiency was enhanced at a test temperature of 25 °C when considering a gas velocity of 500 mm/s and a movement velocity of silica sand of 1.95 mm/s. The test results showed that an improvement in the movement velocity of silica sand decreased the temperature of the bed, increasing the removal efficiency. Furthermore, this study could be used in different high-temperature filter systems for gas cleanup.

Study of the heat transfer characteristics and waste heat recovery of hot gas with coagulative particles flowing through a moving granular bed filter (MGBF)

The moving granular bed filter is a promising technology for handling the challenges of hot gas clean-up and waste heat recovery in various fields. The purpose of this study was to investigate the heat transfer characteristics and waste heat recovery of a moving granular bed filter during hot gas clean-up. The novelty of this study lies in its investigation of the heat transfer performance of coagulative particles. Experiments were carried out to study the influence of the flue gas inlet temperature, granular velocity, and filtration superficial velocity. The results revealed that increasing the superficial velocity and inlet temperature and reducing the granular velocity are beneficial for improving the heat storage capacity of granules in terms of single factor. However, moderate granular velocity and superficial velocity are recommended to achieve a high waste heat recovery efficiency considering multiple factors. In the present study, a granular velocity of 2 cm∙min−1 and a superficial velocity of 0.3 m∙s−1 are optimal. The superficial velocity is the main factor affecting the comprehensive heat transfer coefficient. The results reveal that the melting and solidification processes of the coagulative particles affect the heat transfer. They also reveal that improving the heat transfer performance is necessary for enhancement of waste heat recovery. The focus of the present study is essentially the development of a moving granular bed filter that contains coagulative particles for use in the metallurgy industry. The results are significant for the design and evaluation of a moving granular bed filter in practical applications that can improve energy efficiency.

Experimental study on filtration performance of the moving bed granular filter with axial flow

The filtration performance of the moving bed granular filter with axial flow (MBGF-AF) is investigated through a large cold experiment. The effect of different operation parameters on the filtration performance (collection efficiency, pressure drop) of the axial-flow moving bed filter is investigated in combination with the dust deposition effect and the mechanism of trapping dust by the capturing particles. The results show that the collection efficiency of MBGF-AF is enhanced by decreasing the superficial gas velocity, increasing the inlet dust concentration properly, or decreasing the moving velocity of the capturing particles. A model covering the above operation parameters is established to calculate the collection efficiency of the moving bed granular filter. It is used in a wide range of operating parameters for the MBGFs.

Study of Flow Patterns in Two-Stage Mode of Moving Granular Bed Filter

ABSTRACTThe use of moving granular bed filters (MGBFs), which hold an important role in the gasification or combustion of coal and biomass, has been growing. Furthermore, these filters have great potential to be developed for the high-temperature gas cleanup of advanced power generation systems. However, the creation of a stagnant zone due to defective designs in MGBFs can cause serious issues such as plugging. Therefore, in order to minimize these problems, flow-corrective inserts for filter vessels have been researched, most of which use mono-sized filter granules. This study proposed a new method that introduced two granule sizes in one filter vessel, called the two-stage filtration mode. Nevertheless, the design theory of a mass flow vessel by Johanson could not be satisfied by using two sizes of filter granules to diminish the stagnant zone. The flow patterns in a two-dimensional and cross-flow moving granular bed were evaluated in six test configurations based on different geometric designs in a filter. The two kinds of filter granules consisted of coarse and fine silica sands. The findings revealed that the flow patterns of filter granules were influenced by the vessel geometry. The optimal design for two-stage filtration diminished the stagnant zone in 165 minutes.

Effect of pyrolysis and moving-bed granular filter temperatures on the yield and properties of bio-oil from fast pyrolysis of biomass

Fast pyrolysis of biomass in a fluidised-bed reactor incorporated with a moving-bed granular filter is carried out to investigate the effects of pyrolysis and filter temperatures on product yields and bio-oil properties. The results showed that increasing the pyrolysis temperature reduced organic bio-oil and increased reaction water. When the temperature was increased from 400 to 500°C, the char decomposed to permanent gas and reaction water. Further increase to 550°C caused the organics to transform to gas. The proportion of CO2 reduced with pyrolysis temperature, while other gases increased. The increase of the filter media temperature from 350 to 380°C resulted in the decomposition of char to reaction water. Bio-oil water content increased with both pyrolysis and filter temperatures, whereas opposite trend was found with the viscosity. Increasing the filter temperature could lower the bio-oil solids content. Both temperatures did not affect the bio-oil pH and density.

Hot gas clean-up technology of dust particulates with a moving granular bed filter

The purpose of this study is to investigate the efficiency and stability of moving granular bed filter (MGBF) in high-temperature environment with various operation conditions. Experiments were carried out to study the influence of various parameters, such as test temperature, mass flow rate of filter granules and filtration superficial velocity. The experimental facilities include an air fan, flow ducts, heaters of gas and filter granules, a screw feeder of dust particulates, a measurement system for size distribution of dust particulates, a filter granules supply device, a rotary valve, and a granular bed filter filled with filter granules. The results of this study indicate that this type of method can be useful to applications in different cross-flow filter systems for gas clean-up. From the results, with the conditions of filtration superficial velocities at 0.2 and 0.35 m/s, and the mass flow rate of filter granules at 0.01 kg/s, the better collection efficiency and the smaller-sized distribution of dust particulates were obtained for the case with operating temperature of 20 °C. The experimental results show that an average increase in operation temperature of 100 °C resulted in a decrease in average collection efficiency of 1.74%. The focus in the current study is essentially the development of an MGBF that can be applied in the industrial environment. The results are expected to serve as the basis for future research.

Hydrodynamic behavior in a moving granular bed filter for modeling on char separation during the biomass fast pyrolysis process

Moving granular bed filters (MGBFs) are the promising approach to improve the quality of pyrolysis oil by removing char particles from fast pyrolysis vapor streams. To minimize the commercial MGBF system, the inner MGBF structures were modified, resulting in differential granular media velocities between inlet and outlet gas stream. The modified structure was applied to increase the removal efficiency under the same superficial gas velocity. The experiments were conducted at room temperature and the designed parameters included the insert length and angle of inserted plates in the bottom of MGBF. In this study, the insert plates were used to distinguish the MGBF into two particle flow streams in the same section. The section area was the function of particle response angle, insert length, insert angle, and angle of the MGBF boundary plate. An accurate equation for determining the mass flow rate of the bed material particle and section area was proposed in this study. In addition, cold model filter tests were conducted on differential designs for three sets of flow fields. These results show that differential flow field designs can effectively enhance filtration efficiency. Under the same filtration pressure decline or loss, the filtration efficiency can be increased from the baseline of 95.4% to 99.9%.

Filtration of fast pyrolysis char fines with a cross-flow moving-bed granular filter

A cross-flow moving-bed granular filter was investigated for its performance to filter the fast pyrolysis char-laden gas with an aim to elucidate the influence of the number of filtration stages, the filter media size and mass flow rate on the collection efficiency of the filter and the pressure drop across the bed. The results showed that the two-stage filtration gave higher collection efficiency than the one stage, especially for small filter media size. The decrease of the filter media size significantly increased the collection efficiency, while slightly increased the pressure drop. In addition, the increase of the mass flow rate led to the reduction in the collection efficiency. Within the scope of the parameters investigated, the maximum collection efficiency of the granular filter was 99.79% which occurred when applying single stage filtration with the filter media size and the mass flow rate of 0.425–0.600 mm and 8 g/min, respectively.

Effect of filter media size, mass flow rate and filtration stage number in a moving-bed granular filter on the yield and properties of bio-oil from fast pyrolysis of biomass

Fast pyrolysis of cassava rhizome was performed in a bench-scale fluidised-bed reactor unit incorporated with a cross-flow moving-bed granular filter. The objective of this research was to examine several process parameters including the granular size (425-1160 μm) and mass flow rate (0-12 g/min) as well as the number of the filtration stages (1-2 stages) on yields and properties of bio-oil. The results showed that the bio-oil yield decreased from 57.7 wt.% to 42.0-49.2 wt.% when increasing the filter media size, the mass flow rate and the filtration stage number. The effect of the process parameters on various properties of bio-oil is thoroughly discussed. In general, the bio-oil quality in terms of the solids content, ash content, initial viscosity, viscosity change and ageing rate could be enhanced by the hot vapour granular filtration. Therefore, bio-oil of high stability could be produced by the pyrolysis reactor configuration designed in this work.

The influence of granular flow rate on the performance of a moving bed granular filter

The goal of this study is to evaluate the effect of granular flow rate on the performance of a moving bed granular filter designed for hot gas filtration of fine char particles (dust) produced during fast pyrolysis of biomass. The filter employs a counter-current configuration, in which down-flowing granular material spreads out at the bottom of the filtration vessel to form an interfacial area where the dusty gas enters the granular bed and much of the gas cleaning is hypothesized to occur. This study uses a real-time particle counter to measure the instantaneous filtration efficiency during cold flow tests of the filter. Differential pressure measurements at various locations within the granular bed are used to assess the level of char dust hold-up over time. These experiments reveal a critical granular residence time below which the filter must be operated to achieve filtration efficiencies exceeding 99%. Operating above the critical value causes the filter to “clog” and decrease in efficiency. The clogging is characterized by a critical dust volume fraction as determined through a fixed bed filtration test. The filter is found to accumulate most of the dust at the interfacial region. Also the interfacial region is more efficient than the downcomer section of the granular bed in removing dust. Decreasing residence time of granular material in the filter reduces the hold-up of char dust in the filter, which is expected to mitigate coking reactions of organic vapors when the filter is used to remove char from fast pyrolysis gas streams.

Experimental study of the gas flow behavior in the inlet of a granular bed filter

The Moving Granular Bed Filter (MGBF) is an important apparatus being developed for filtration of the hot gas. Our research group demonstrated a good solution to diminish stagnant zones in MGBF during the filtration process. However, there still remain some systematic problems that have to be worked out prior to commercializing a whole facility. The design of the gas inlet component of the granular bed filter is important for achieving a uniform gas distribution and higher usage rate of the filter media. Non-uniformity may lead to a lower usage rate. The new gas inlet component design uses baffle devices in order to achieve a more uniform gas velocity distribution. Fixed bed and moving bed conditions were studied. The uniformity of the gas velocity distribution can be characterized by the standard deviation definitions and the differences in the mean velocities between the two filtration surfaces. The baffle lengths and angles affected the uniformity of gas velocity in inlet and filtration surfaces. The optimal experimental parameters were found by using different baffle lengths, angles and mass flow rate of filter media. The uniform gas velocity distributions were obtained by a series experiments. Furthermore, the results give important information about IGCC system that will be helpful for designing better models of moving granular bed filters in the future.

Similitude study of a moving bed granular filter

The goal of this study was to evaluate the performance of a moving bed granular filter designed for hot gas clean up. This study used similitude theory to devise experiments that were conducted at near-ambient conditions while simulating the performance of filters operated at elevated temperatures and pressures (850 °C and 1000 kPa). These experiments revealed that the proposed moving bed granular filter can operate at high collection efficiencies, typically exceeding 99%, and low pressure drops without the need for periodic regeneration through the use of a continuous flow of fresh granular filter media in the filter. In addition, important design constraints were discovered for the successful operation of the proposed moving bed granular filter.

Behaviour of powder during movement of feed shoe in die filling : M.Kondoh, S.Takemoto. (Toyota Motor Corp, Toyota, Japan.) J. Jpn Soc. Powder Powder Metall., vol 44, no 5, 1997, 487–491. (In Japanese.)

The purpose of this study is to investigate the efficiency and stability of moving granular bed filter (MGBF) in high-temperature environment with various operation conditions. Experiments were carried out to study the influence of various parameters, such as test temperature, mass flow rate of filter granules and filtration superficial velocity. The experimental facilities include an air fan, flow ducts, heaters of gas and filter granules, a screw feeder of dust particulates, a measurement system for size distribution of dust particulates, a filter granules supply device, a rotary valve, and a granular bed filter filled with filter granules. The results of this study indicate that this type of method can be useful to applications in different cross-flow filter systems for gas clean-up. From the results, with the conditions of filtration superficial velocities at 0.2 and 0.35 m/s, and the mass flow rate of filter granules at 0.01 kg/s, the better collection efficiency and the smaller-sized distribution of dust particulates were obtained for the case with operating temperature of 20 °C. The experimental results show that an average increase in operation temperature of 100 °C resulted in a decrease in average collection efficiency of 1.74%. The focus in the current study is essentially the development of an MGBF that can be applied in the industrial environment. The results are expected to serve as the basis for future research.

97/05162 Dust collector with annular moving-bed granular filter: Seto, H. Jpn. Kokai Tokkyo Koho JP 09,239,221 [97,239,221] (Cl. B01D46/38), 16 Sep 1997, Appl. 96/78,193, 5 Mar 1996, 16 pp. (In Japanese)

The method previously developed for the determination of phenols by chromatography and spectrophotometry of their methyl ethers has been applied to their determination in wood smoke, Phenol, o-cresol, m-cresol,p-cresol, 1-naphthol, 2-naphthol and the three isomeric dihydroxy-benzenes have all been detemined in microgram amounts. Guaiacol, and possibly other methyl ethers of the phenols are also present.La méthode, décrite précédemment pour le dosage des phénols par chromatographie et spectrophotométric de leurs éthers méthyliques, a été appliquée au dosage de ces composés dans la fumée de bois. Phénol, o-crésol, m-crésol, p-crésol, 1-naphtol, 2-naphtol et les trois isomères du dihydroxybenzène ont pu être dosés à l'échelle microchimique. Le gaïacol et peut-être d'autres éthers méthyliques des phénols sont également présentsDie früher entwickelte Methode zur Bestimmung von Phenolen durch Chromatographie und Spektrophotometric ihrer Methyläther wurde zur Bestimmung dieser Verbindungen im Holzrauche angewendet. Phenol, o-, m- und p-Kresol, 1- und 2-Naphtol und die drei isomeren Dihydroxybenzole wurden in Mengen von der Ordnung des Mikrogramms bestimmt. Guajakol und möglicherweise auch andere Methyläther der Phenole sind ebenfalls gegenwärtig