Fired Clay Research Articles

Применение экспериментально-статистического моделирования процесса термообработки полиминеральных глин, вводимых в цементные композиты

The article presents a method of producing an active mineral additive by firing polymineral clay. The authors show the possibility of obtaining cement composites with increased strength characteristics both due to the introduction of clay additive and due to the optimisation of the clay firing conditions. The authors used experimental and statistical modelling techniques to determine the appropriate clay firing conditions to produce an active mineral additive for cement composites.

Brownish Green Fired Clay Tiles Produced by Valorizing Green Glass Cullet and Sediment Soil

This paper aims to valorize waste materials for producing eco-friendly fired clay tiles. Green glass cullet and the water supply process waste; sediment soil have been utilized. In addition, local white clay is used to mix with waste materials for promoting the plasticity and easily forming of specimens. The Triaxial diagram has been employed to construct the formulas. Mixture’s formulation of this experiment consists of 23 formulas. Test samples are fired at temperature 950 °C. Physical properties of fired specimens are carried out and compared with Thailand Industrial Standards. The results show that formula A6 can pass TIS. 2508-2555 wall tiles of medium water absorption series. However, A6 only utilize 10% of sediment soil. Therefore, increasing sintering temperature to 1,050 °C for utilizing higher content of sediment soil has been examined. Twelve formulas of group A and C are selected to be further investigated. Results show that formula A6 and C6 can achieve TIS. 2508-2555. Formula C6 utilizing 30% and 60% of sediment soil and green glass cullet obtain the highest strength and lowest water absorption. Analyzing microstructure of this formula by Scanning Electron Microscope has found glassy phases. Furthermore, Wollastonite 2M, Nepheline and Albite are identified by X-Ray Diffractometer. It can be summarized that sediment soil mixed up with green glass cullet and local white clay can develop brownish green color fired clay tiles which can be further applied to the production of local ceramic factory.

Between Scientific and Sensory Knowledge: Exploring the Enactment of Clay Sensibilities Among Clay Artists in Singapore

This article explores how clay artists in Singapore utilize both their scientific and sensory knowledge of clay-making in producing clay works. Based on a study of the biographies and sensory experiences of clay artists, clay artists rely simultaneously on their scientific knowledge and understanding of clay firing processes, temperatures, and glazing, together with their sensory judgment and experience of the same set of processes, to produce clay works of different design, effect, and form. Thermoreceptive understanding and knowledge of how clay reacts and behaves toward the different styles of firing are deployed by clay artists through both a scientific calibration of temperature, as well as one’s sensory evaluation—including visual and sonic judgments—of fire-control toward producing intended textures and forms. Through making sense of how scientific and sensory knowledges are concurrently enacted but not without contradictions, we make a case for how creative clay work-making straddles across different domains of learning, knowledge use, teaching, and evaluation emerging through kairotic moments. The article contributes to extant debates on art worlds, material culture, sensory knowledges, and embodied experiences through clay work as a medium of analysis.

Evaluation and application of Moroccan clay materials in ceramic tiles: Composition and technological behavior

This paper aims to assess the suitability of various Moroccan clay materials for application in ceramic tile production. Six clay samples (S1–S6) sourced from cities including Fez-Meknes, Safi, Berrechid, and Benslimane were collected and subjected to comprehensive characterization to elucidate their chemical and mineralogical composition, as well as their morphological and thermal behavior. The impact of sintering temperatures ranging from 900 to 1100 °C on parameters such as bulk density, porosity, water absorption, shrinkage, flexural strength, and chemical resistance was investigated. Results revealed elevated levels of Fe2O3 (>3 %), indicative of dark firing clays across all samples. Additionally, the samples exhibited a composition comprising clay minerals, quartz, feldspars, and carbonates. Based on the findings, it was determined that these clay materials are suitable for the production of cottoforte and majolica falling within the BIIb and BIII ceramic classes (ISO 13006). The study underscores the potential of these materials for utilization in industrial ceramic products, given their demonstrated characteristics.

Effect of Calcination Atmosphere on the Acid Leaching Recovery of Rare Earth Elements in Coal-Byproducts

ABSTRACT Thermal treatment of coal byproducts has been shown to improve leaching characteristics of rare earth elements (REEs) in bituminous coal sources due to its influence on the associated minerals. This study investigated the impact of the calcination atmosphere on REE leaching behavior in different density fractions of Baker and Fire Clay seam coarse refuse sources using a thermogravimetric analyzer to create an oxidizing or reducing atmosphere at a desired temperature for 2 h. The effect on leaching characteristics was evaluated using 1.2 M sulfuric acid at 75°C for 5 h at 1% w/v solid concentration. Rare earth element (REE) recovery for the 2.2 specific gravity (SG) sink fraction improved by approximately 15 absolute percentage points at 1000°C relative to the 600°C calcined sample in an inert atmosphere and equilibrated within 10 min from the start of the test. Contrarily, thermal treatment at 1000°C under oxidizing atmosphere significantly reduced the REE recovery due to sintering of the clays, which limited access to the RE minerals for leaching. In general, thermal treatment of heavier fractions in both atmospheres significantly improved the light REE (LREE) recovery while the increase in heavy REE (HREE) recovery was relatively less. As common clay minerals in the coal sources, kaolinite and illite samples were tested under the same conditions and using a digital scanning calorimeter. The findings confirmed that the improvement observed in REE leaching through thermal treatment at 600°C was due to decarbonization for the lighter density fractions and dehydroxylation of clays.

Revolutionizing Construction - Harnessing the Power of Brick Kiln Dust as a Sustainable Cement Alternative

Abstract: The concrete industry stands as the preeminent colossus within the realm of industrial domains. The building and construction industry, a primary contributor to environmental issues, is constantly seeking innovative approaches to enhance sustainability. Bricks forming the building block of the building structures are being manufactured worldwide. A substantial volume of fine particle dust is produced during the production step in the form of leftovers. This dust is the by-product of firing clay bricks at high temperature and the residual ash of the induced fuel. Brick Kiln dust poses environmental challenge due to disposal complexities. Commonly, the only established method of disposal is through land-filling, which can contribute to environmental concerns. This experimental investigation explores the transformative potential of utilizing Brick Kiln Dust as sustainable alternative to convention cement. BKD, obtained from a kiln situated in District Budgam, Jammu and Kashmir, was incorporated into concrete mixes at varying proportions (5%, 10%, 15%, 20%, and 25%) as a replacement for cement. Through the use of rigorous testing on mix samples, this study examined the effect of BKD on concrete workability as well as compressive and split tensile strength. The results were compared to identify the optimal dosage for achieving a balance between reduced cement consumption and maintaining structural integrity. The results showed that adding BKD not only significantly decreased the amount of cement used, but also demonstrated that it was a workable and sustainable substitute. This research not only addresses the environmental concern associated with BKD but also contributes to the ongoing efforts to develop sustainable construction practices.

Effects of Fe2O3/SiO2 Molar Ratios in the Fe-Silica on the Compressive Strengths and Microstructural Properties of Geopolymer Materials Derived from Waste Fired Clay Brick and Metakaolin

Effects of Fe2O3/SiO2 Molar Ratios in the Fe-Silica on the Compressive Strengths and Microstructural Properties of Geopolymer Materials Derived from Waste Fired Clay Brick and Metakaolin

A Study of Performance of Compressed Earth Brick Incorporation with Waste Fire Clay Brick as a Filler

This study examines the use of waste fire clay brick as a filler in compressed earth brick production. The purpose of this study is to determine the compressive strength and water absorption of the compressed earth brick incorporation with waste fire clay brick as a filler. The optimum amount of waste fire clay to utilize as a filler is also being studied. A total of 72 compressed earth bricks were produced with the brick size of 125 mm x 250 mm x 100 mm which consist of a mix of sand, soil and cement with mix proportion of 1:4:4. A few tests were conducted which are compressive strength test and water absorption test. The waste fire clay bricks were utilized in this study and replace by volume fraction percentage of 10%, 20%, 30%, 40% and 50% while 0% is set as the control. The findings obtained show that the compressive strength of the bricks was increasing. The percentage of water absorption were decreasing along with the increases of percentage of waste fire clay brick as a filler.

Optimizing calcination of coal by-products for maximizing REE leaching recovery and minimizing Al, Ca, and Fe contamination

High-temperature calcination is effective in improving the leaching characteristics of rare earth elements (REEs) from conventional REE-bearing minerals by transforming them into more leachable forms. However, the recovery of contaminants such as Al, Fe, and Ca also increases significantly. The objective of the study was to maximize the REE extraction while minimizing the concentration of contaminant ions (Al, Ca, and Fe) in the leach solution. Representative density fractions of the coarse refuse from the Baker and Fire Clay seam coal refuse were pulverized to a top size of 180 μm and used as a feedstock for the study. All the samples generated from thermal treatment were leached at 1% (w/v) using 1.2 mol/L sulfuric acid at 75 °C for 2 h. Test results from a parametric program based on a Box-Behnken design were used for modeling and optimization of three operating parameters associated with the lab-scale calcination process. The parameters included temperature (400–800 °C), ramp rate (2–10 °C/min) and holding time (0–120 min). It was determined that the calcination temperature was the most significant parameter influencing REE recovery. The majority of the heavy rare earth elements (HREEs) were found to be present in an insoluble form in the calcination products and were marginally affected by thermal treatment. A strong correlation between light rare earth elements recovery (LREEs) and Al suggested a possible association with clays. The optimum operating conditions for high REE recovery with comparatively lower contaminant concentration for 1.6 specific gravity float and 2.2 sink fractions of Baker and Fire Clay seam material were determined to be at 776, 800 °C and 407, 800 °C, calcining temperatures, respectively. A higher optimum temperature of 1.6 float fraction of Baker seam relative to Fire Clay seam material was due to elevated pyrite concentration in Baker seam material. Thermal treatment at 400 °C converted pyrite into a soluble intermedium iron oxide, resulting in a high Fe content in the leachate. Calcining at 776 °C converted most of the soluble iron oxide into insoluble α-hematite, considerably reducing the Fe concentration in the solution.

Investigation of Indoor Air Quality by Incorporating Sewage Sludge Waste into Fired Clay Brick

Generally, the production of sewage sludge waste has increased due to rapid growth of the population. Due to that, the disposal method has become crucial issues nowadays. Therefore, this research focuses on the investigation of indoor air quality of fired clay brick incorporating with sewage sludge. The bricks were incorporated with 0% and 5% of two type of sewage sludge and fired at 1050°C with heating rates 1°C/min. The experiment of Indoor Air Quality was obtained by measuring gases emissions of total volatile organic compound (TVOC), carbon dioxide (CO2), carbon monoxide (CO), ozone (O3), formaldehyde (HCHO) and particulate matter (PM10) and were compared with Industry Code of Practice on Indoor Air Quality requirement standard. From the result shows that by incorporation of 5% of sewage sludge into fired clay brick complied with the standard requirement for building material usage with no negative effect to the environment. As the conclusions, the use of sewage sludge as clay replacement reduces the waste disposal in landfills and produce the low-cost building materials.

Rare Earth and Critical Element Chemistry of the Volcanic Ash-fall Parting in the Fire Clay Coal, Eastern Kentucky, USA

Abstract In the search for rare earth and other critical elements in coal measures, the coals are emphasized with lesser consideration for the accompanying rocks. In this investigation, the focus is on a lanthanide-rich, 315–317 Ma (after Machlus et al., Chemical Geology, 539, art. no. 119485, 2020) volcanic ash-fall trachyandesite to trachyte tonstein which occurs in association with the Middle Pennsylvanian Duckmantian-age Fire Clay coal in eastern Kentucky. The tonstein was deposited largely during peat accumulation, although it is known to occur at the base of the coal or within the underclay. The mineralogy is dominated by kaolinite with illite and quartz as minor to major minerals. A number of accessory minerals, as detected by X-ray diffraction + Siroquant XRD software and scanning and transmission electron microscopy (S/TEM), include REE-bearing phosphates (apatite, crandallite, florencite, monazite), and Y-bearing zircon. The highest rare earth element + Y concentrations occur in the weathered tonsteins, probably due to the concentration of these minerals after weathering of kaolinite from the rock.

Pretreatment of Bituminous Coal By-Products for the Hydrometallurgical Extraction of Rare Earth Elements

Low-temperature plasma (LTP) oxidation has been widely used to study the mineralogy of the mineral matter existing in coal sources. The current study investigated the potential of LTP oxidation as a pre-treatment method to improve rare earth element (REE) leachability from coal and its by-products. Representative density-fractionated samples of Baker and Fire Clay coarse refuse seam materials were ground to a top size of 180 µm and subjected to low-temperature plasma oxidation. Subsequently, the treated samples were leached at 1% w/v solids concentration and 75 °C for 5 h using (i) de-ionized (DI) water, (ii) 0.1 mol/L of ammonium sulfate, and (iii) 1.2 mol/L of sulfuric acid. It was determined that LTP treatment improved REE leaching characteristics, especially the leaching of heavy REEs (HREE), existing in the lighter density fractions of the Baker seam coarse refuse material. For instance, the HREE recovery for the 1.6 specific gravity (SG) float fraction increased from 8% to 33% using 0.1 mol/L of ammonium sulfate solution after 32 h of LTP treatment. This finding indicated that HREEs associated with the organic matter were released by the LTP treatment and adsorbed onto the surfaces of highly negative charged mineral matter and was exchanged with ammonium to allow their recovery. Similarly, when using 1.2 mol/L of sulfuric acid, the HREE recovery increased from 23% to 53% for the 1.6 SG float fraction. Interestingly, LTP oxidation did not provide significant improvement in REE recovery from the 2.2 sink density fractions, which was likely due to its lower organic content. No significant benefits were observed when treating the Fire Clay coarse refuse material, which was likely due to the lack of organic affinity and the difficult-to-leach REE minerals associated with the coal source such as monazite, xenotime, and zircon. Conversely, high-temperature oxidation within a temperature range of 600–750 °C significantly improved REE leaching characteristics for both coal sources. Improvement in REE recovery was due to decarbonization of the material, clay dehydroxylation and subsequent conversion of liberated REE-bearing minerals into a more leachable form. However, increasing the temperature above 800 °C decreased REE recovery due to the conversion of meta-kaolinite into mullite, which is chemically stable.

Mechanical behavior in terms of shear and bending performance of reinforced concrete beam using waste fire clay as replacement of aggregate

In this experimental and analytical study, waste fire clay (WFC) was consumed by the use of replacing fine aggregate (FA) in confident amounts. It is targeted to remove the current sustainable complications by confirming the consumption of WFC in reinforced concrete beams (RCBs) as raw materials. For this purpose, FAs were partially replaced with WFC in proportions of 0 %, 10 %, 20 %, and 30 %. Based on this motivation, a series of experimental studies were performed on 12 + 12 small-scale bending and shear RCBs of 100×150×1000mm, considering altered WFC and stirrup spacing. While the percentage of WFC in the RCBs was selected as 0 %, 10 %, 20 %, and 30 % by weight, correspondingly, the longitudinal reinforcement was taken into account as Ф12, Ф10, Ф8. Besides, while the longitudinal tension and compression reinforcements of constant 2Ф12 and 2Ф6, the stirrup spacing was chosen as 160 mm, 200 mm, and 270 mm. As a result of the study, increasing the tensile reinforcement ratio has made the WFC less effective. Similarly, as stirrup spacing decreases, stirrup dominates the behavior, and as stirrup spacing increases, WFC determines the behavior. Finally, while the WFC content for bending RCBs increases the ability at the maximum level for the range of 20 %−30 %, it can be said that the optimum WFC content for shear RCBs is 20 %. The experimental results were obtained with the prediction of ACI-318 and the reason for the difference between the expected and actual values can be explained in detail.

Effect of agricultural biomass wastes on thermal insulation and self-cleaning of fired bricks

This research investigates the feasibility of using dry crushed pomegranate peel waste as thermal insulator to produce light clay bricks. Pomegranate peel waste (PW) is used with different substitution levels of 0%, 5%, 7.5%, 10% and 15% of clay weight. The clay bricks were heated at temperatures of 700, 800, and 900 °C, that resulted in the formation of internal pores due to the combustion of PW. The bulk density, water absorption, porosity, shrinkage, and compressive strength are examined to evaluate the effect of using PW on the physical and mechanical properties of thermal insulation bricks. Also, the investigation of the effect of photocatalytic activity of bricks under sunlight irradiation is carried out. The use of PW increased the thermal conductivity up to 21% at 900 °C, water absorption from 22.6% in cold water to 29.1% in boiling water, density from 2.5% at 800 °C to 7.6% at 900 °C, and shrinkage from 4.3% in linear drying shrinkage to 5.4% in linear firing shrinkage. The heated brick samples at 700 °C showed greater photodegradation efficiency than firing clay at 800 °C and 900 °C. Moreover, the compressive strength decreased with the increase in replacement rate, reaching up to 74% for 15 wt% PW. This study confirms that lightweight heated bricks with low thermal conductivity and a reasonable compressive strength can be made using PW as a pore-forming agent.

MESOZOIC DELTAIC SYSTEM AND SEQUENCE STRATIGRAPHIC MODEL OF THE LOWER JURASSIC DATTA FORMATION ALONG THE WESTERN SALT RANGE, PAKISTAN

In this research, the Early Jurassic Datta Formation from three outcrop sections of the western Salt Range has been extensively studied to elucidate facies architecture, sedimentary features, diagenetic features, sequence stratigraphy, and depositional model. Datta Formation is well exposed with massive thickness in the western Salt Range and the Trans Indus Ranges, while tapering in the central Salt Range further eastward, it dies out. Its mainly dominated by variegated sandstone, siltstone, shale, fire clays, laterites, and carbonates. Seven lithofacies has been identified and interpreted in the Datta Formation, i.e., (i). Fluvial Meandering Lithofacies (JDL-01), (ii). Braided Fluvial Lithofacies (JDL-02), (iii). Lateritic Lithofacies (JDL-03), (iv). Flood Plain Lithofacies (JDL-04), (v). Siliciclastic Lagoon Lithofacies (JDL-05), (vi). Carbonates dominant Lagoon Lithofacies (JDL-06), (vii). Swamps related Deltaic Lithofacies (JDL-07). Sequence stratigraphic analysis is primarily based on recognizing sequence surfaces, finning-coarsening upward trends, and types of facies. Two transgressive-regressive cycles are identified in the south-eastern section (Kassan Nala and Kaowali sections), while four sequences are identified in the Nammal Gorge section. These sequences are started with the underlying sequence boundary of LST and ended with the sequence bounding surface after HST. Datta Formation is possibly deposited in fluvial to deltaic environments in the study area, revealing a prograding delta with a shoreline oriented in the SW-NE direction and the siliciclastic detritus fed the fluvial system running over the Indian cratonic basement in the direction of N-NW. The lower part of the formation is deposited in fluvial settings, probably in the incised valley. The point bar sequences result from meandering channel facies and show association with overlying flood plain/overbank facies. Moreover, the lagoonal facies mainly covered the upper part of the formation and displayed mixed lithologies of delta plain to delta front setting. However, the repetition of these lithofacies in the study area at several points indicates the recurrence of depositional phases. The carbonaceous shales and coal streaks are evident by the presence of swamp or marshy lands. These conditions meet the criteria of deltaic settings. Furthermore, several laterites and fire clay horizons are also argue periodic sub-aerial exposure of the depositional area. Thus it is concluded that the depositional area lies in a fluvial to deltaic setting with major distributary channels and their flood plain in the adjoining delta plain to delta front part.

ЖАРОСТОЙКИЙ ФОСФАТНЫЙ ГАЗОБЕТОН НА СВЯЗУЮЩЕМ ИЗ ТЕХНОГЕННОГО АЛЮМОСИЛИКАТНОГО СЫРЬЯ

A modified aluminophosphate binder has been technogenically developed using aluminosilicate. Waste – a by-product of production firing of refractory clays from the Nizhne-Uvelskoye deposit – was used for obtaining the raw materials for the binder. Нeat-resistant phosphate aerated concrete was developed based on the modified aluminophosphate binder. Its density was 600–800 kg/m3 and the temperature of application about 1400–1450 °C. The main heat-resistant properties of aerated concrete were investigated and aerated concrete using a modified aluminophosphate binder is not inferior to cellular materials based on known aluminophosphate binders.

The effect of clay on initial and residual saturation of hydrogen in clay-rich sandstone formation: Implications for underground hydrogen storage

Understanding wettability in rock-brine-hydrogen systems is essential for dependable predictions of capillary/residual trapping in clay-rich sandstone formations. Despite being the most used technique, wettability assessment based on contact angle measurements is confronted with inherent uncertainties that limit its reliability. In contrast, core flooding techniques provide a more direct and realistic picture of wettability and its time evolution. Nuclear Magnetic Resonance (NMR) allows us to evaluate the initial and residual hydrogen saturations and distribution along the core specimen. It is a fast, reliable, and effective way of inferring the impact of wettability on hydrogen migration, and residual trapping in prospective geo-storage rock formations. Recent publications have reported the evaluation of wettability in a brine-hydrogen-rock system where the rock is a clean sandstone (no clays). Here we evaluate the impact of the presence of clays in a sandstone, which has not been reported yet. NMR monitoring was employed to characterize the initial and residual hydrogen saturations in the Bandera Grey (BG) sandstone. To investigate the impact of clay minerals on hydrogen saturation, same rock sample was characterized in its natural state, and after heating it to 700 °C for 12 h in an air environment to burn off clay minerals, During the NMR core flooding experiments, ten pore volumes (PVs) were injected/withdrawn during the drainage/imbibition cycles at a fluid injection rate of 2 mL/min under room temperature and 1000 psi confining pressure. Due to the hydrophilicity of quartz and clay, the tested BG sandstone (clay-rich sandstone) shows a significant residual/trapped saturation (∼3.5% can be reproduce); therefore, clay-rich sandstone may not be ideal for hydrogen storage unless cushion gas is used.The results show that initial and residual hydrogen saturations were slightly changed after firing (from 16% to 18% for initial and from 14% to 13% for residual). This also suggests that the wettability of the BG sandstone-brine-hydrogen system is slightly impacted by clay content and type. We also observed that clay firing at 700 °C has little effect on the porosity and gas permeability of the BG sandstone. Moreover, X-ray powder diffraction (XRD) results showed that quartz content increases from 68.1% to 76.2%, Kaolinite transformed into illite and clinochlore disappeared. The disappearance of chlorite after firing suggests that it is transformed into another clay type.

Mechanical and microstructural characterization of aluminium metal matrix composite reinforced with bottom ash and fireclay

In this experimental investigation, bottom ash and fireclay are added to reinforce aluminium 7075 (Al7075) making use of stir casting technique, at different compositions to generate flat castings. Three plates having Al7075, varying composition of fire clay and bottom ash will be developed. Upon fabrication, tests are done on the plates for evaluating the mechanical and microstructural properties. Mechanical properties like microhardness, ultimate tensile strength and yield strength are tested and then compared. Scanning Electron Microscopy Imaging (SEM) and X-ray Diffraction technique (XRD) are employed to investigate the distribution pattern of the reinforcement particles. The results of mechanical and microstructural evaluation will provide information whether there is an enhancement in properties with change in reinforcement composition.

Petrology and geochemistry of the Fire Clay coalbed, Martin County, Inez 7 ½′ quadrangle, Kentucky, USA

The Middle Pennsylvanian Duckmantian-age Fire Clay coal in the vicinity of Inez, Martin County, Kentucky, USA, is about 80-km northeast of the intensely studied Fire Clay coal in central eastern Kentucky. The moderate-ash, high-S, high volatile B bituminous Martin County Fire Clay coal does not have an obvious volcanic ash parting, one of the major contributors to the rare earth element (REE)-rich central eastern Kentucky Fire Clay coal, and is further from the Pine Mountain thrust fault, the primary driver of hydrothermal metamorphism in the region. Terrigenous input and infiltrational mode of REE emplacement and redistribution were likely factors in the development of the REE chemistry of the Martin County coals, but, without the tuffaceous and strong hydrothermal influences, the overall level of the REE concentration is generally below the levels seen in many other central Appalachian coals.

Coal Feed-Dependent Variation in Fly Ash Chemistry in a Single Pulverized-Combustion Unit

Four suites of fly ash, all generated at the same power plant, were selected for the study of the distribution of rare earth elements (REE). The fly ashes represented two runs of single-seam/single-mine coals and two runs of run-of-mine coals representing several coal seams from several mines. Plots of the upper continental crust-normalized REE, other parameters derived from the normalization, and the principal components analysis of the derived REE parameters (including the sum of the lanthanides plus yttrium and the ratio of the light to heavy REE) all demonstrated that the relatively rare earth-rich Fire Clay coal-derived fly ashes have a different REE distribution, with a greater concentration of REE with a relative dominance of the heavy REE, than the other fly ashes. Particularly with the Fire Clay coal-derived fly ashes, there is a systematic partitioning of the overall amount and distribution of the REE in the passage from the mechanical fly ash collection through to the last row of the electrostatic precipitator hoppers.