This study investigated the combustion characteristics of coal gasification fine slag (CGFS) before and after particle size classification. The research focused on combustion loss, burnout characteristics, gaseous pollutant emissions and fine particulate matter emissions of the raw sample (FS1), size-classified samples (FS2 similar to FS5), and sample ground to below 100 & micro;m (FS6). At low heating rates, combustion characteristics are enhanced as particle size decreases, and are also influenced by ash content. Under high heating rates, the combustible consumption fraction increases significantly with decreasing particle size, from 10.18% for FS2 (particle size > 500 & micro;m) to 98.86% for FS5 (particle size < 100 & micro;m). Under the present preheating combustion conditions, grinding CGFS to below 100 & micro;m is recommended for complete burnout. Moreover, grinding treatment enhances the positive effect of preheating temperature on burnout performance. As particle size decreases, char particles react more readily. The enhanced char reactivity strengthen local reducing reactions and promote NOx reduction. NOx emission concentrations for both FS1 and FS6 are positively correlated with combustion zone temperature and excess air coefficient, but negatively correlated with preheating temperature. The mass distribution of submicron particulate matter produced during FS6 combustion follows a unimodal curve, with a peak around 0.06 & micro;m. Over 98% of the submicron particles are distributed below 0.274 & micro;m, and sulfur is identified as their dominant component. Submicron particulate emissions are positively correlated with preheating temperature, combustion zone temperature, and excess air coefficient.

Amid the comprehensive utilization of coal gasification fine slag (CGFS), its abundant metallic elements (Al, Fe, Ca, Mg) remain underutilized, yet these are key constituents of layered double hydroxides (LDHs). This study innovatively proposes using CGFS-derived metals to synthesize CO2-adsorptive LDH for resource enhancement of solid waste. The effect of ultrasonic acid leaching on metal separation from CGFS's ash-rich fraction (LFS) was analyzed, the conditions for synthesizing LDHs using leachate as feedstock were optimized, the CGFS-based LDHs were characterized, and their CO2 adsorption capacity, cycling stability, and adsorption behavior were evaluated. Results show that factors affecting leaching rates follow HCl concentration > ultrasonic power > leaching time > leaching temperature, the leaching rates for Al, Fe, and Ca under optimized conditions were 76.68%, 80.96%, and 80.35%, respectively. Saucer-shaped LDHs via alkaline hydrothermal method and nanosheet-shaped LDHs via urea hydrothermal method were synthesized, with the latter having a multi-level pore structure including ultramicropores, micropores, and mesopores. This LDH exhibits a CO2 adsorption capacity (0.65 mmol/g) comparable to that of LDHs synthesized from pure reagents, with excellent cycling stability, via a hybrid mechanism of basic site-dominated chemisorption and multi-level pore-facilitated physisorption. The study establishes the synthesis-structure-performance relationship and three-stage mechanism of element separation, LDH synthesis, CO2 adsorption of CGFS-based LDHs, proposes approaches to boost its CO2 adsorption performance, which provides a novel pathway for CGFS's high-value utilization and carbon reduction, advancing clean coal use and carbon-neutral technologies.

With the municipal sludge production increasing annually, co-disposal of municipal sewage sludge (SS) has become the choice of more and more power plants. In this paper, municipal solid waste (MSW), sewage sludge as well as fly ash and slag were sampled from a power plant that actually co-disposed municipal sludge. The ash fusion characteristics and compositions of MSW and SS at different mixing ratios were investigated and analyzed. The simulation of mineral evolution under different sludge mixing ratios was also carried out using Factsage software. The experimental results showed that the ash melting temperature of MSW was lower than that of sludge. When SS was mixed at a low ratio (SS10%), the ash melting temperature of the ash samples decreased significantly. When the mixing ratio gradually increased, the fly ash melting temperature gradually increased. XRD analysis results showed that when SS mixing ratio was small, the Fe content in the ash samples was low, and Fe mainly existed in the form of FeO, which led to the decline of the ash melting point of SS10%. When the sludge mixing ratio was gradually increased to 20%, the Fe content in the ash samples increased. The reaction of Fe with SiO2 and Al2O3 generated high melting point Fe-containing minerals such as Ca4FeO3, CaFeO4 and Ca4Fe9O17, which led to an increase in the ash melting point of the ash samples. The Factsage results also showed that MSW ash samples in the three-phase diagram moved gradually from the Ca2P2SiO12 region to the CaAl2Si2O8 region and the mullite region with the increase of sludge mixing ratio, so the ash melting point was higher. Through the slag and fly ash analysis of the power plant, it is found that the fly ash and slag are both dominated by silica-aluminate such as calcium feldspar and mullite, where slag also contains a small amount of iron-containing minerals such as Ca4Fe9O17. The Fe in the sludge is mainly residual in the slag. It indicates that the mixing of sludge in small proportions mainly affects the fly ash of the power plant, and does not have much effect on the slag of the power plant. The experimental results can contribute to the actual waste power plant in terms of reasonable sludge mixing, avoiding boiler slagging and improving boiler efficiency.

This study conducted a theoretical analysis on the hydrodynamic factors of surface cleaning and then carried out detection on the surface physicochemical properties of coarse/fine coal particles after surface cleaning. Results show that the desorption degree of fine slimes does not increase monotonically with the impeller speed. Within the range of conventional high-intensity conditioning rotation speeds, a medium impeller speed of 1600-1900 rpm was the appropriate speed for surface cleaning. The cleaning effect depended on the impeller speed rather than the cleaning time. Surface cleaning increased the contact angle, single-bubble loading capacity, and induction time by 18.67%, 65.96%, and 28.99%, respectively. XPS analysis results indicated that when the cleaning impeller speed was 1600 rpm, the content of C-C/C-H on the surface of +75 mu m coal samples increased by 4.10%, while the content of hydrophilic groups such as C-O-C/C-OH decreased by 15.23%. SEM-EDS analysis results showed that, after surface cleaning, the content of C element on the surface of coarse coal and fine coal increased by 34.48% and 25.51%, respectively; the contents of O, Al, and Si elements in coarse coal decreased by 57.16%, 88.79%, and 83.85%, respectively, while those in fine coal decreased by 32.22%, 62.79%, and 55.42%, respectively.

Innovation in collector is pivotal to overcoming bottlenecks in the flotation separation of coal gasification fine slag (CGFS). The combination of oil-based reagents with surfactants represents an effective approach to enhancing flotation performance. However, the mechanism by which nonionic surfactants enhance the effectiveness of oil-based collectors in CGFS flotation remains unclear. This study employed n-dodecane (n-D) as the base oil agent, which was blended with three nonionic surfactants of ODEA, Span 80, and TX-100 to prepare composite collectors. Their effects on CGFS flotation were investigated through flotation experiments and kinetic modelling, whilst their microscopic mechanisms were elucidated from an adsorption perspective via characterization tests (zeta potential, FTIR, XPS) and molecular dynamics simulations. The results indicate that the composite collectors exhibit superior flotation performance compared to n-D alone. The combustible recovery rates and flotation rates are ranked as n-D/TX-100 > n-D/Span 80 > n-D/ODEA > n-D. The composite collector reduces the electronegativity of residual carbon surfaces in CGFS, masks hydrophilic groups and enhances bubble adhesion. n-D covers the hydrophobic regions of the residual carbon, whilst surfactants cover the hydrophilic regions; their synergistic adsorption enhances the collector's diffusion coefficient and interfacial adsorption energy, restricting the wetting and spreading of water molecules. This facilitates hydrophobic modification of the residual carbon surface and improves its floatability. This research can provide theoretical support for refining the CGFS flotation theory and developing highly efficient collectors.

Municipal solid waste incineration (MSWI) fly ash is rich in hazardous substances such as heavy metals and dioxins, posing significant challenges to environmental safety and disposal. High-temperature vitrification effectively immobilizes these pollutants, but the process requires high temperatures and substantial energy consumption. Therefore, developing efficient fluxing systems to lower the melting temperature of fly ash and promote its resource utilization has become an important area of research. This study aims to explore the effects of composite fluxing agents on the melting characteristics and mineral transformations of MSWI fly ash, and to develop an optimized fluxing system suitable for low-temperature sintering and resource recovery. Using thermodynamic simulations and repeated experiments, The study examines the impact of primary fluxing agents (SiO2 and Al2O3) and auxiliary fluxes (B2O3, P2O5, and CaF2) on the melting temperature, mineral composition, and structural evolution of sintered fly ash ceramsites. The results indicate that SiO2 significantly lowers the melting temperature and narrows the melting range, demonstrating the strongest fluxing effect. Al2O3 lowers the initial softening temperature at high additions but expands the melting range and limits flow. B2O3 promotes early liquid phase formation and the generation of low-melting calcium borosilicates. P2O5 aids early softening but forms stable calcium phosphate crystals, limiting flow. CaF2 improves flowability at low additions and enhances densification. This study clarifies the mechanisms of different fluxing agents, providing compositional design guidelines for low-temperature sintering of fly ash and offering new approaches for the resource utilization of fly ash.

Coal gasification generates fine slag with high residual carbon, but its porous structure hinders efficient separation. This study investigates carbon–ash separation of gasification fine slag using a spiral chute. Particle size and pore structure jointly determine separation outcomes. Effective separation was achieved for +0.125 mm and 0.125–0.045 mm fractions, which exhibit developed porous carbon skeletons, yielding concentrate ash of 20.22% and 39.50%, respectively. Conversely, the −0.045 mm fraction (41.16% of feed) consists predominantly of mineral microspheres with poorly developed pores, leading to high feed ash (80.73%) and poor separation (concentrate ash 76.35%). Pore structure governs separation by reducing effective density through water absorption: high-porosity particles behave as light products and report to concentrate. Optimal conditions (10% concentration, 1.96 m3/h) achieved 64.67% carbon recovery and 52.92% concentrate ash. A Bagnold-based model reveals that radial particle position is co-determined by effective density and particle size, with fine particle entrainment limiting separation precision.

In this study, to examine the applicability of prediction models when dealing with long-term and large-scale industrial on-site data, a total of 26,225 pieces of industrial flotation data were collected continuously for 45 days from an industrial site. The prediction of the Random Forest (RF), eXtreme Gradient Boosting (XGBoost), Deep Neural Network (DNN), Long Short-Term Memory (LSTM), Gated Recurrent Unit (GRU), as well as the hybrid models DNN-LSTM and LSTM-DNN for flotation reagent dosage were compared. The results show that when predicting with a single model, the MRE of RF for the dosage of collector and frother are 5.94% and 8.11%, respectively, which achieves the best performance. However, the prediction performance of the hybrid model outperforms that of the single DNN, LSTM, or RF models. The MRE of LSTM-DNN model for the collector and frother reached up to 4.39% and 6.26%, respectively. This indicates that neural network models are applicable for training with large-scale data in actual flotation industries.

In-plant washing, granulation, and recycling through sintering is a promising method for the disposal of municipal solid waste incineration (MSWI) fly ash. This study focused on the effects of deacidification, washing, and flux additives on the ash melting characteristics, heavy metal content and leaching behavior during the thermal treatment of fly ash. The results demonstrate that chloride salts in the fly ash volatilize predominantly above 700 degrees C. Certain heavy metals (e.g., Hg, Cu, Pb) similarly volatilize at elevated temperatures. Following water washing and dechlorination, the volatilization rates of heavy metals in the fly ash decrease significantly. The high calcium content (35.20 %) of fly ash adversely affects sintering/melting processes, necessitating a flux addition exceeding 40 %. In contrast, fly ash prior to deacidification tower, with lower calcium (23.44 %) and chlorine (15.72 %) contents, requires only 10 % flux. After 1000 degrees C thermal treatment, the contents of Cu, Pb, and Cd in the fly ash decrease markedly. Furthermore, the quantity of fly ash prior to deacidification is approximately 54 %-70 % of the fly ash downstream of the deacidification tower, indicating that fly ash removal before the deacidification tower could significantly reduce processing requirements. By implementing simple modifications to the incinerator, such as adding a high-temperature dust collector before deacidification tower, the cost of thermal treatment can be reduced, and the feasibility of engineering applications for fly ash thermal treatment can be improved.

The utilization of Jurassic bituminous coal as a chemical feedstock is constrained by its high inertinite content, and the separation of vitrinite from inertinite is the basis for its fractional utilization. In this study, enhanced flotation tests were conducted on macerals from two typical Shendong coal samples, using n-dodecane-based oily bubbles modified with methylnaphthalene (MN), octylphenol polyoxyethylene ether (OP-4), and oleic acid (OL). The characteristics of the coal samples and modified n-dodecane were analyzed using Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), Zeta potential, surface tension, and viscosity measurements. The interactions between modified oily bubbles and coal macerals were investigated via induction time tests and the extended Derjaguin-Landau-Verwey-Overbeek (EDLVO) theory. The results indicated that the surface of vitrinite-rich coal is more hydrophobic than that of inertinite-rich coal. Meanwhile, when MN was used as the modifier, selective enrichment of vitrinite was achieved. It was found that the excellent flotation separation effect arises from the ability of MN-modified n-dodecane oily bubbles to selectively increase the mineralization energy barrier between the oily bubbles and inertinite-rich coal, while widening the flotation difference between vitrinite-rich and inertinite-rich coal. This study provides experimental evidence and theoretical support for the separation of vitrinite from inertinite.

Incineration technology has emerged as the predominant approach for the safe disposal of municipal solid waste in China, generating a significant amount of fly ash as a byproduct. However, the primary landfill method currently employed in China, chelation stabilization coupling, falls short of reliability in terms of environmental standards. Consequently, the safe and effective disposal of fly ash containing high concentrations of chlorine salts, heavy metals, and dioxins is of critical importance. This study proposes a synergistic approach for the dechlorination and sintering of fly ash (FA) generated in waste incineration plants. This method entails the washing of FA with leachate and concentrate, followed by pelletizing and in-furnace sintering. The results indicated that treatment with leachate reduced the residual chlorine concentration in FA to 7 % at a liquid-to-solid ratio of 10 mL g-1, while subsequent treatment with concentrate further lowered it to 4 %. FA also adsorbed impurities from the leachate and concentrate without substantially altering critical water quality parameters, enabling the treated liquids to be reintegrated into the leachate treatment system. Aspen Plus simulations demonstrated that in-furnace sintering had a negligible impact on furnace temperature, even when fly ash constituted 0-3 % of the total waste processed. Additionally, the plant's leachate and concentrate output lives up to FA washing requirements. Overall, our study provides fundamental information and establishes a novel model for a low-cost and eco-friendly "waste to treat waste" approach to dispose FA via leachate/concentrate washing in concert with in-furnace sintering.

Pellet molding technology is widely used for biomass and coal fuels due to its advantages in transportability, storage, and energy density. Coal gasification fine slag, a coal-based solid waste rich in carbon, presents significant application potential. Through separation technologies, this slag can be further refined to produce a high carbon fraction. In this study, the high carbon product derived from coal gasification fine slag was blended with biomass to produce centimeter-grade pellet fuel. Preparation conditions varied across pressures (5 similar to 25 MPa), temperatures (20 similar to 250 degrees C), residence times (5 similar to 50 min), and biomass blending ratios (20% similar to 80%). Combustion characteristics were evaluated using a self- constructed flat flame macro thermogravimetric reactor, simulating high temperature, high heating rate conditions, which can be used for the thermal analysis of large sample masses. Results indicated that increasing the biomass blending ratio enhanced volatile release and reduced the overall combustion time. Elevated flue gas temperatures accelerated volatile release and combustion, improving overall combustion efficiency. Higher mold temperatures led to faster volatile combustion and reduced total weight loss. These findings provide valuable insights for the large-scale industrial application of pelletizing technologies for coal-based solid waste energy recovery.

Co-combustion of coal gasification fine slag (CGFS) with sewage sludge (SS) is a promising method for achieving low-cost and large-scale disposal of both solid wastes. However, the impact of co-combustion of these low-grade solid wastes on burnout and emissions remains unclear, and the feasibility and safety of this process need validation. This study establishes a two-stage preheating and combustion reactor to investigate the effects of sludge type, blending ratio and temperature on burnout, gas pollutant and heavy metal emissions during the cocombustion of CGFS with SS. The results show that the unburned carbon content in the ash is less than 1.4 % at 900 degrees C, meeting the expected targets for decarbonization and reuse. This value decreases further to below 0.3 % at 1000 degrees C and 1100 degrees C. NOx emissions remain below 135 ppm under all conditions, with the conversion ratio of fuel nitrogen to NOx staying below 4 %. Additionally, comparative ecological risk analysis reveals that compared to the sole combustion of CGFS, the co-combustion of SS does not adversely affect the disposal of postcombustion ash. Conversely, it helps reduce the potential ecological risks of heavy metals. This study provides guidance for the practical application of large-scale co-disposal of CGFS and SS.

Particle size is crucial for sedimentation processes. However, there is limited research on how varying particle sizes influence the sedimentation of fine‐grained particles. This study examined the aggregation behavior of two types of montmorillonite particles with different sizes under different concentrations of Al 3+ . The findings indicated that the sample of fine particles exhibited a more rapid reduction in turbidity and a greater increase in the absolute value of surface potential across various Al 3+ concentrations. Despite this, both samples achieved comparable final supernatant turbidity, sediment layer height, and residual particle size, suggesting that the enhancing effect of Al 3+ on the sedimentation of fine‐grained montmorillonite is limited by particle size. Different concentrations of Al 3+ result in the formation of hydroxyl compounds and hydroxides that adsorb onto mineral surfaces, promoting the sedimentation of finer‐grained montmorillonite in the sample of fine particles. DLVO theory confirmed that the electrical double layers of the samples of coarse and fine particles gradually diminished under the influence of Al 3+ , effectively enhancing the aggregation of montmorillonite. Furthermore, thermodynamic analysis suggested that particles smaller than 500 nm do not settle further, even with the addition of aluminum ions.

In coal slime water treatment, traditional anionic polyacrylamide (APAM) faces challenges including difficulties in balancing charge density with hydrolysis degree and inadequate hydrophilicity. This study developed a plasma-modified APAM (P-APAM) and systematically investigated its enhancement mechanism for kaolinite particle flocculation and sedimentation. Experiments were performed with 5-20 s plasma treatments on APAM solutions, analyzing P-APAM properties such as viscosity, pH, conductivity, molecular chain structure, and functional group configuration. Parallel flocculation-sedimentation tests evaluated kaolinite treatment performance through settling velocity, supernatant turbidity, floc size, and Zeta potential measurements. Results revealed that 5 s plasma treatment strengthened hydrogen bonding while altering oxygen-containing functional group composition and arrangement in P-APAM molecules. The treatment promoted oxidative degradation of hydrophobic groups (-CH3/-CH2-), boosting hydration capacity and hydrophilicity while optimizing molecular chain flexibility and surface adaptability. The modified P-APAM formed compact floc structures (SK value = 0.612), achieving superior sedimentation rates, larger floc sizes, and enhanced flocculation efficiency at reduced dosages. Comprehensive experimental analysis confirmed that plasma-modified P-APAM substantially improved kaolinite flocculation and sedimentation performance. This research presents an innovative plasma-modified flocculant approach for clay mineral treatment in slime water, establishing an effective technical pathway for developing high-performance green flocculant systems with significant reference value for sustainable mineral processing.

The co-processing of coal gangue and locally sourced biomass enables energy recovery while enhancing the resource utilization potential of ash residues, resulting in significant economic and environmental benefits. The application of preheating combustion facilitates the disposal of low-grade coal gangue, which is otherwise difficult to combust, thereby improving the overall disposal efficiency. In this study, the synergistic disposal potential of low-grade coal gangue (CG) and Salix (SA) through preheating combustion was evaluated, with particular focus on burnout performance, NOx emission characteristics, and submicron particulate matter (PM1) formation. The results show that blending 30% SA reduces the unburned carbon content by 41.4%. At a preheating temperature of 900 degrees C, the unburned carbon content decreases by 36.3% for pure CG and by 58.4% for the CG/30%SA blend, while NOx emissions decrease by 36.8 ppm and 43.9 ppm, respectively. Increasing the SA blending ratio from 10% to 30% initially increases the total yield of submicron particulate matter to 3.45 mg/g fuel, then decreases it to 3.02 mg/g fuel. Submicron particulate matter generated during preheating co-combustion of CG and SA was primarily composed of sulfur and aluminum. The formation of submicron particulate matter is a result of both combustion intensity and the original inorganic element content in the fuel.

Gasification fine slag, a carbon-rich solid waste produced during coal gasification, is currently disposed of through conventional landfilling methods. Its high-water content hampers resource utilization by reducing its calorific value. This study employs low field nuclear magnetic resonance (LF-NMR) analysis to investigate the water occurrence states in a filter cake with 70.7% moisture content derived from fine gasification slag of the Ningxia coal water slurry furnace. The analysis reveals that free water constitutes a major proportion (68.28%), while combined and capillary water accounts for 2.62% and 2.33%, respectively. The removal of moisture from the coal gasification fine slag filter cake is significantly affected by the drying temperature. The drying rate initially increases and then decreases with different temperatures. For drying temperatures of 60, 70, 80, 90, and 100 degrees C, the maximum drying rates are achieved at 1.09, 1.23, 2.18, 3.86, and 4.01%/min, respectively, with corresponding durations of 40, 40, 25, 30, and 35 min. The T-22 relaxation peak area continually decreases and shifts leftward on the coordinate axis. The behavior of the T-23 and T-22 peaks follows a similar pattern, indicating that water with higher mobility is easily eliminated during drying, while the T-21 peak exhibits a robust signal strength throughout the drying process. At a drying temperature of 100 degrees C, the proportion of free water (A(22)) decreases from 87.3% to 0, the A(23) fluctuates between 0 and 5.3%, and the bound water peak area (A(21)) increases from 10.4% to 94.7% as drying time prolongs. A relationship model is developed between the moisture content of the coal gasification fine slag filter cake and the total integral area of the LF-NMR test, enabling rapid detection and analysis of the total moisture content and distinct occurrence states in the filter cake.

Coal gasification is one of the most promising clean coal technologies. However, gasification process also produces a huge amount of solid waste of high carbon content, named coal gasification fine slag. The coal gasification fine slag is mainly handled by landfilling, which is not only a hazardous pollution, but also wasting the energy from residual carbon. Developing a technology to utilize coal gasification fine slag and recover the residual carbon is becoming essential for an eco-friendly coal chemical industry. In this paper, the enrichment behavior of residual carbon in coal gasification fine slag by a spiral separator is studied. The raw coal gasification fine slag sample and separator products are characterized on particle size distribution, size-depending ash content, reactivity, micromorphology and porous structure. The experimental results show that the spiral separator is efficient to remove ash and enriched carbonaceous components in coal gasification fine slag by separating feed (100%) into concentrate (81.2%), middlings (8.8%), and tailings (10.08%), where the ash content in tailings is up to 90%, accounting for 18.5% of total ash in feeding. The beneficial product "concentrate" has a good distribution of size-depending ash content, that most combustibles are enriched in these particles of diameter >100 μm. After spiral separator, the concentrate products have a more pure and developed porous structure with the surface area increasing from 199.8 m2/g (feeding) to 231.8 m2/g, as well as a better combustion reactivity of lower ignition temperature compared with feedings. Accordingly, an economic and feasible combination process of spiral separator connecting sieve can produce an enriched-carbon product of ∼45% yield and ∼80% carbonaceous content. The Iodine adsorption ability of sieved products increases by 47.6% compared with feed, and reaches up to about half of industry activated carbon. The finally sieved concentrate products have a good market prospect as fuel and adsorbent.

Coal gasification fine slag is a kind of solid waste with high carbon content produced in the process of coal gasification. There is an urgent need to analyze the various pore sizes and their characteristics, and then design a proper method for dewatering gasification fine slag. In this study the low-temperature adsorption analysis, high-pressure injection analysis (mercury porosimetry) as well as the two types of filter press are used to first analyze the gasification slag pore characteristics and then dewatering efficiency, respectively. Results show that the full pore size combined analysis method portray that the pore size increases rapidly between 100 similar to 2000 nm, which is significantly different and larger than the pore size at low-temperature nitrogen adsorption analysis (4.37 nm). As a result, the combined pore size method of high-pressure mercury injection and low-temperature nitrogen adsorption predicts more precise results. Micropores, transition pores, mesopores, and macropores account for 6.62%, 7.84%, 18.46%, and 67.08% of the total. A filter press with a diaphragm plate and frame is an efficient dewatering device for fine coal gasification slag. The final filter cake moisture is 50.87%, which is significantly lower than the vacuum belt filter with 69.22%. A new option for coal gasification fine slag dewatering equipment is the ultra high-pressure filter press; the moisture content of filter cake obtained is 44.70%, and the dewatering effect is outstanding. This study will help to better design the dehydration methods of the wet slags. Ultimately, it will help recycling the water, reducing the ash quantity as well as the cost of the ash landfill.