High-temperature Ceramic Filters Research Articles

Multi-objective optimization model of high-temperature ceramic filter

Ceramic filters have been widely used in industrial engineering, such as the Shell coal gasification process (SCGP) and Integrated gasification combined cycle (IGCC), where the performance of the ceramic filter is achieved by the pulse jet. Residual pressure drop and gas consumption are directly related to reverse-flow pulse (RFP) pressure. However, in the process of operation, the RFP pressure is too large and gas consumption is too high. In this study, the effects of RFP pressures on filter’s cleaning efficiency, residual pressure drop, and gas consumption were investigated on a ceramic filter. Within a certain range, the cleaning efficiency gradually increased with increased RFP pressure. When the RFP pressure reached a certain value, the cleaning efficiency did not increase with increased pressure, showing a quadratic relationship between cleaning efficiency and RFP pressure. The residual pressure drop and RFP pressure were also in a quadratic relationship. Besides, the gas consumption increased linearly as increased RFP pressure according to the theoretical model. Based on the research results, a multi-objective optimization model of a ceramic filter was established with the cleaning efficiency as a constraint condition, gas consumption and residual pressure drop as the optimization objectives. A fuzzy decision-making method was used to solve the optimization model and calculate the residual pressure drop and gas consumption, from which the optimal RFP pressure was obtained.

Performance degradation model and prediction method of real-time remaining life for high temperature ceramic filter tube

Performance degradation model and prediction method of real-time remaining life for high temperature ceramic filter tube

Influence of Pulverized Coal on Characteristics of Fly Ash in SCGP

The chemical composition, microstructure and size distribution of pulverized coal and fly ash samples from SCGP(Shell Coal Gasification Process) devices of four different regions were measured using an energy dispersive spectrometer, a scanning electron microscope, and Coulter particle analyzer. The paper aims to analyze the influence of pulverized coal on characteristics of fly ash. The energy dispersive analysis showed the main elements of chemical composition of fly ash and pulverized coal were C, O, Si, Al, and small amounts of metal elements. The difference of chemical composition of pulverized coal samples illustrates the types of coal were different. The similarity in chemical composition of four types of fly ash was due to the same technical process. Scanning electron microscope measurements showed particulate microstructures of four samples of pulverized coal were irregular, however, particulate microstructures of samples of fly ash were all spherical. The surface of most spherical particles had microspheres that were often agglomerated together. This phenomenon indicated that particulate microstructures of pulverized coal had no influence on particulate microstructures of fly ash. The size distribution showed median size of four pulverized coal samples were 31.59μm, 28.85μm, 25.57μm and 20.62μm. Median size of four fly ash samples were 4.07μm, 3.89μm, 3.45μm and 3.04μm. The particle size of fly ash increases with the growth of particle size of pulverized coal. The crests of particle size distribution curves of pulverized coal were not obvious due to the grinding evenness of coal were low. Particle size distribution curves of fly ash were opposite. This phenomenon indicates that uniform degree of fly ash is not affected by coal grinding evenness. In conclusion, the particle size of pulverized coal is the main influencing factor on the characteristics of fly ash while the influences of type of coal, particulate microstructures and grinding evenness of pulverized coal are not so much. Particle size of fly ash has a vital influence on high-temperature ceramic filters in SCGP. Controlling particle size of pulverized coal has a certain guiding significance to reducing the working load and extending the life of filter elements.

Use of a Dielectric Glass to Join Dielectric Ceramics for Microwave Filters

Joining of ceramics with glasses has been widely used for artificial teeth, solid oxide fuel cells, electrical devices, high temperature ceramic filters, structural ceramic components for aeronautic engineering, nuclear reactors, and other applications. This study aimed to explore the possibility of using a dielectric glass to connect a dielectric ceramic resonator to a dielectric ceramic support, in order to make miniaturized microwave filters characterized by higher temperature and environmental stability and low dielectric loss. A mixed powder having Bi2O3-SiO2-Al2O3-MgO-ZnO-CaO glass as a matrix and SiO2-Al2O3-MgO as a ceramic filler was used to join the dielectric ceramic resonators made of the CaTiO3-NdAlO3-Al2O3 system to the dielectric ceramic supports made of the ZnO-TiO2-Al2O3-MgO system. In spite of the strong interfacial bonding obtained, microcracks were observed in the joined bodies, suggesting that not only the dielectric loss of the bonding layer but also the match of the thermal expansion coefficients of the components to be joined should be carefully considered and tailored.

Study on Experimental System for High Temperature Ceramic Filter

High temperature ceramic filter is designed and implemented for purification of hot coal gas, and then an experimental system is build in order to test its filtration performance. The reverse-pulse-jet-cleaning is introduced in detail. Finally, field experiment has been carried out and the results show that the ceramic filter keeps a high dust control efficiency and long on-line stability.

High-temperature ceramic filter for furnace gas analyzer

The manufacturing of the ceramic filters used in a gas analyzer for sampling flue gases at temperatures to 950°C is described. The proposed technology makes it possible to obtain a through porous structure with pore size varying systematically over the filter wall thickness and thereby obtain a long service life.

High Temperature DC-DC Converter Performance Comparison Using SiC JFETs, BJTs and Si MOSFETs

The performance and characterization of SiC JFETs and BJTs, used as inverter switching devices, in a 2 kW, high temperature, 33 kHz, 270-28 V DC-DC converter has been accomplished. SiC and Si power devices were characterized in a phase shifted H-bridge converter topology utilizing novel high temperature powdered ferrite transformer material, high temperature ceramic filter capacitors, SiC rectifiers, and 10 oz. 220oC polyimide printed circuit boards. The SiC devices were observed to provide excellent static and dynamic characteristics at temperatures up to 300oC. SiC JFETs were seen to exhibit on-resistance trends consistent with temperature-mobility kinetics and temperature invariant dynamic loss characteristics. SiC BJTs exhibited positive temperature coefficients (TCE) of VCE and negative β TCEs, with only a 2-fold increase in on-resistance at 300oC. Both SiC power devices possessed fast inductive switching characteristics with τon and τoff ~100-150 ns when driving the transformer load. The SiC converter characteristics were compared to Si-MOSFET H-bridge operation, over its functional temperature range (30-230oC), and highlights the superiority of SiC device technology for extreme environment power applications.

Laboratory Investigation of the Products of the Incomplete Combustion of Waste Plastics and Techniques for Their Minimization

This laboratory investigation aimed at reducing the emissions of pollutants from the batch combustion of three major waste plastics, polyethylene (PE), polystyrene (PS), and poly(vinyl chloride) (PVC). Results are reported herein on the emissions of CO, light aliphatic hydrocarbons, polycyclic aromatic hydrocarbons (PAHs), and particulates. Two-stage combustion of the polymers was investigated, with the first stage (primary furnace) operated at either 600 or 900 °C and the second stage (afterburner) at 1000 °C. Before exiting the afterburner, the effluent passed through a high-temperature ceramic filter, which retained and destroyed particulate products of incomplete combustion (PICs). The effect of the polymer quantity burned was examined, as well as the effect of mixing PS with PVC to explore the influence of chlorine on emissions of PICs. The results indicated that PVC produced the lowest amounts of all PICs, whereas PS produced the highest amounts of PAHs and particulates, and PE produced the highest ...

Emissions of Batch Combustion of Waste Tire Chips: The Hot Flue-Gas Filtering Effect

A laboratory investigation was performed on the emissions from the batch combustion of waste tire chips in fixed beds. Techniques and conditions that minimize toxic emissions were identified. Tire-derived fuel (TDF), in the form of waste tire chips (1 cm in size), was burned in a two-stage combustor. Batches of tire chips were introduced to the primary furnace, where gasification and combustion occurred. The gaseous effluent of this furnace was mixed with streams of additional preheated air in a mixing venturi, and it was then passed through a silicon carbide (SiC) honeycomb wall-flow filter that had been placed inside this furnace. Subsequently, it was channeled into a secondary furnace (afterburner), where further oxidation occurred. The arrangement of the two furnaces in series allowed for independent temperature control; varying the temperature in the primary furnace influenced the type and the flux of pyrolysates. The hot-flue-gas filtering section, ahead of the exit of the primary furnace, allowed the retention and further oxidation of most of the generated particulates and, thus, prevented them from entering the afterburner. Results showed that the combination of the high-temperature ceramic filter with the afterburner treatment was successful in reducing the emissions from the combustion of waste tires. Depending on the temperature of the primary furnace, the final emissions of CO were reduced by factors of 2−6, NOx emissions were reduced by factors of 2−3, particulate emissions were reduced by 2 orders of magnitude (both PM2.5 and PM10), and most individual polycyclic aromatic hydrocarbon (PAH) species emissions were reduced by more than 1 order of magnitude, with the exception of naphthalene, whose reduction was less drastic. The overall combustion effectiveness was enhanced, as evidenced by higher CO2 yields.

Coal topping in a fluidized bed system

A batch-fed bench-scale pressurised fluidised bed combustion (PFBC) facility was built to research the in-bed processes generating fine char particles during PFBC of Australian black coals. Elutriation of such particles is responsible for the combustion inefficiency and their combustion in the filter cake on high-temperature ceramic filters may contribute to the formation of ‘sticky ash’ and consequent cleaning difficulties. Measured carbon elutriation varied from coal to coal and the results agreed qualitatively with large-scale PFBC performance, allowing definition of satisfactory and unsatisfactory performance criteria. Carbon elutriation in PFBC was correlated tentatively with crucible swelling number although the range of values of the crucible swelling number needs to be extended. Carbon elutriation in PFBC did not correlate with volatile matter for the five Australian coals investigated in contrast with previous PFBC pilot plant studies on four Northern Hemisphere coals. The higher swelling coal produced a significantly larger average macro-pore diameter after devolatilisation in PFBC, which caused greater attrition of fine char from the particle surface during the char burnout stage.

Ignition temperature of coal carbonizates

A batch-fed bench-scale pressurised fluidised bed combustion (PFBC) facility was built to research the in-bed processes generating fine char particles during PFBC of Australian black coals. Elutriation of such particles is responsible for the combustion inefficiency and their combustion in the filter cake on high-temperature ceramic filters may contribute to the formation of ‘sticky ash’ and consequent cleaning difficulties. Measured carbon elutriation varied from coal to coal and the results agreed qualitatively with large-scale PFBC performance, allowing definition of satisfactory and unsatisfactory performance criteria. Carbon elutriation in PFBC was correlated tentatively with crucible swelling number although the range of values of the crucible swelling number needs to be extended. Carbon elutriation in PFBC did not correlate with volatile matter for the five Australian coals investigated in contrast with previous PFBC pilot plant studies on four Northern Hemisphere coals. The higher swelling coal produced a significantly larger average macro-pore diameter after devolatilisation in PFBC, which caused greater attrition of fine char from the particle surface during the char burnout stage.

Economics of an Integrated Approach to Control SO2, NOx, HCl, and Particulate Emissions from Power Plants

An integrated approach for the simultaneous reduction of major combustion-generated pollutants from power plants is presented along with a simplified economic analysis. With this technology, the synergistic effects of high-temperature sorbent/coal or sorbent/natural gas injection and high-temperature flue gas filtration are exploited. Calcium-based (or Na-based, etc.) sorbents are sprayed in the post-flame zone of a furnace, where they react with S- and Cl-containing gases to form stable salts of Ca (or Na, etc.). The partially reacted sorbent is then collected in a high-temperature ceramic filter, which is placed downstream of the sorbent injection point, where it further reacts for a prolonged period of time. With this technique, both the likelihood of contact and the length of time of contact between the solid sorbent particles and the gaseous pollutants increase, because reaction takes place both in the furnace upstream of the filter and inside the filter itself. Hence, the sorbent utilization increases significantly. Several pollutants, such as SO2, H2S, HCl, and particulate (soot, ash, and tar), may be partially removed from the effluent. The organic content of the sorbents (or blends) also pyrolyzes and reduces NOx. Unburned carbon in the ash may be completely oxidized in the filter. The filter is cleaned periodically with aerodynamic regeneration (back pulsing) without interrupting furnace operation. The effectiveness of this technique has been shown in laboratory-scale experiments using either rather costly carboxylic salts of Ca or low- to moderate-cost blends of limestone, lime, or sodium bicarbonate with coal fines. Injection occurred in the furnace at 1150 °C, while the filter was maintained at 600 °C. Results showed that 65 or 40% SO2 removal was obtained with calcium formate or a limestone/coal blend, respectively, at an entering calcium-to-sulfur molar ratio of 2. A sodium bicarbonate/coal blend resulted in 78% SO2 removal at a sodium-to-sulfur molar ratio of 2. HCl removal efficiencies have been shown to be higher than those for SO2. NOx reductions of 40% have been observed with a fuel (coal)-to-air equivalence ratio, π, around 2. The filter has been shown to be 97–99% efficient in removing PM2.5 particulates. Calculations herein show that this integrated sorbent/filter method is costeffective, in comparison with current technologies, on both capital cost ($/kW) and levelized cost ($/ton pollutant removed) bases, if a limestone/coal mixture is used as the sorbent for fossil fuel plants. Capital costs for the filter/sorbent combination are estimated to be in the range of $61–$105/kW for a new plant. Because current technologies are designed for removing one pollutant at a time, both their cost and space requirements are higher than those of this integrated technique. At the minimum projected removal efficiencies for HCl/SO2/NOx of about 40%, the levelized costs are projected to be $203–$261/ton of combined pollutant SO2/HCl/NOx and particulates removed from coalfired power plants.

An Experimental Investigation of Alkali Removal from Biomass Producer Gas Using a Fixed Bed of Solid Sorbent

A bench-scale gasifier system composed of a fluidized-bed gasifier, high-temperature ceramic filter, and fixed-bed solid sorbent reactor was used to study the removal of alkali from a hot product gas stream. During a test conducted with an empty solid sorbent reactor, dry gas-phase concentrations of 28 ppmw K, 11 ppmw Na, and 1309 ppmw Cl were measured. Four subsequent tests utilized 2.4−3.4-mm-diameter particles of activated bauxite or emathlite in the solid sorbent reactor. Over these four tests, K concentrations ranged from 0.03 to 0.07 ppmw, and Na concentrations ranged from 0.2 and 0.9 ppmw at the exit of the solid sorbent reactor. Chlorine concentrations at the exit of the reactor were essentially unaffected. Hot-water leaching tests indicated that alkali capture by activated bauxite and emathlite was through physical adsorption and chemisorption, respectively.

Unburnt carbon elutriation from pressurised fluidised bed combustion of Australian black coals

A batch-fed bench-scale pressurised fluidised bed combustion (PFBC) facility was built to research the in-bed processes generating fine char particles during PFBC of Australian black coals. Elutriation of such particles is responsible for the combustion inefficiency and their combustion in the filter cake on high-temperature ceramic filters may contribute to the formation of ‘sticky ash’ and consequent cleaning difficulties. Measured carbon elutriation varied from coal to coal and the results agreed qualitatively with large-scale PFBC performance, allowing definition of satisfactory and unsatisfactory performance criteria. Carbon elutriation in PFBC was correlated tentatively with crucible swelling number although the range of values of the crucible swelling number needs to be extended. Carbon elutriation in PFBC did not correlate with volatile matter for the five Australian coals investigated in contrast with previous PFBC pilot plant studies on four Northern Hemisphere coals. The higher swelling coal produced a significantly larger average macro-pore diameter after devolatilisation in PFBC, which caused greater attrition of fine char from the particle surface during the char burnout stage.

99/02197 Operation results of the first commercial PFBC plant with high temperature ceramic filters: Suga, N. et al. Proc. Am. Power Conf., 1998, 60, (2), 608–613

Trial operation is now successfully underway at Tomato-Atsuma Unit No. 3 of Hokkaido Electric Power Co. (HEPCO) in Japan. This newly built 85 MWe unit is an innovative PFBC plant, which is the first commercial PFBC in Japan, and equipped with full capacity ceramic filters operated at 850 C. The high temperature ceramic filter effectively removes dusts in the hot gas and the dust loading at gas turbine inlet is much less than that of two-stage cyclones, minimizing the cost and time of gas turbine maintenance. The PFBC plant is composed of a pressurized fluidized-bed boiler, cyclones, ceramic filters, a gas turbine, a steam turbine, etc. and all of the equipment were manufactured and supplied by Mitsubishi Heavy Industries, Ltd. (MHI). Joint R and D program between HEPCO and MHI started 7 years ago, based on their own private funding and without any financial supports from public sectors, studying the optimum design of the first commercial PFBC aiming at environmental and economical advantages. And now fruitful results have been achieved. The commercial operation will start in March 1998 or earlier. Several troubles had been experienced during initial trial operation stage including pressure drop increase in ceramic filters. All these problemsmore » were solved one by one by the joint efforts of HEPCO and MHO. Load rejection tests, load swing tests, and automatic power control tests were successfully done in the spring of 1997. And tests with various kinds of coals are scheduled before the commercial operation.« less

99/00640 Effect of dust type and operating conditions on the performance of high-temperature ceramic filters

Fixed-bed hydropyrolysis tests have been conducted on a UK bituminous coal (Gedling), the Wyodak Argonne Premium coal sample and the high-sulfur Mequinenza lignite at a pressure of 15 MPa with heating rates of 5 and 300 K min−1. The tar yields and overall conversions increased markedly by ∼5–20 wt% daf coal as the heating rate was decreased from 300 to 5 K min−1 for final temperatures of 520 and 600°C, both with and without a sulfided molybdenum catalyst. Conversions of > 90 wt% were achieved with slow heating in catalytic hydropyrolysis for all three coals. The small increases in gas yield indicated that tar-forming as opposed to hydrogasification reactions are promoted by slow heating. These results demonstrate the value of slow heating for analytical applications of hydropyrolysis, which include the determination of organic sulfur forms and the covalently bound biomarker hydrocarbons in coals and petroleum source rocks.

Corrosion and Degradation of Ceramic Particulate Filters in Direct Coal-Fired Turbine Applications

High-temperature ceramic filters show considerable promise for efficient particulate removal from coal combustion systems. Advanced coal utilization processes such as direct coal-fired turbines require particulate-free gas for successful operation. This paper describes the various ceramic particulate filters under development and reviews the degradation mechanisms expected when operated in coal combustion systems.