Addition Of Sludge Research Articles

Mixture Design Identification of Admissible Tannery Sludge Incorporation in Fired Bricks

Pollution problems caused by industrial production of leather tanneries are an important environmental issue. In the present paper we propose to study effects of tannery sludge (TS) addition in manufactured clay bricks applying a mixture design formed by different proportions of four components: Clay, two types of sand and TS. The analysis leads to an optimal practical mixture of around 10% of TS, 20% of sand and 70% of clay and this to remain with an acceptable aspect, an admissible water absorption below 15%, an admissible total shrinkage (drying and after fire) lower than 8%, a tensile strength higher than 5MPa and a thermal conductivity of 0.93 Wm-1K-1, 15% lower than the reference mixture with 0% of TS. Experimental results indicate that a temperature cycle firing up to 950°C can lead to higher tensile strength and lower water absorption compared to a cycle that reaches only 850°C. Furthermore, incorporating (TS) in the fired brick manufacturing process can lead to significant energy saving. Additionally, it was observed that a moderate inclusion of TS can enhance evaporation process. Keywords : Mixture design, Tannery Sludge (TS); Clay bricks ; Evaporation ; Strength; Water absorption; Shrinkage; Leaching; Energy.

Mechanism study of the effect of superplasticizers in alkali-activated materials containing sludge

To realize the safe disposal of solid waste containing heavy metals, sewage sludge jointly with slag and metakaolin was used to prepare alkali-activated materials (AAMs), and the effect mechanism of polycarboxylate acid superplasticizer (PCE), naphthalene superplasticizer (NS) and aliphatic superplasticizer (AS) in AAMs were studied. The results showed that both the fluidity and strength of AAMs decreased with the addition of sludge. For the NaOH + Na2SiO3 activated mortar specimen, the incorporation of sludge can reduce their fluidity and strength from 206 mm and 80.25 MPa to 193 mm and 42.43 MPa, respectively. However, the addition of superplasticizers into sludge-containing AAMs leads to a reduction of 3–9% of the fluidity. Interestingly, it can enhance the strength of the AAMs, especially the NS and AS, which increase the strength by approximately 25%. This is attributed to the increase of particle dispersion by superplasticizers. However, the free water released in the process is reabsorbed by the sludge, which increases the local alkali concentration and promotes the activation of the activity. The dispersed sludge particles can play the role of physical filling, making the structure denser. HIGHLIGHTS Sludge is adverse effects on both the fluidity and strength of alkali-activated materials (AAMs). The addition of superplasticizers (SPs) increases the strength of AAM with sludge. SPs do not affect improving the fluidity of AAMs with sludge, even slightly bad. The dispersion effect of SPs on the sludge is beneficial to promote its activity in AAMs.

Geochemical Evaluation of Manganese Neutralization Sludge for Mn-Containing Mine Drainage Treatment

Conventional neutralization treatment for manganese (Mn)-bearing mine drainage provides a challenge of cost-efficiency, and new approaches should be explored for efficient removal of Mn. We focused on Mn neutralization sludge, a by-product of the Mn-bearing drainage treatment process, which was assumed to be useful as a water purification material. Mn and zinc (Zn) removal tests in simulated drainage were performed using Mn neutralization sludge, and the reaction mechanism was elucidated using geochemical modeling and X-ray absorption fine structure (XAFS) analysis. The results showed that the addition of sludge enabled to lower the Mn and Zn concentration below Japanese effluent standard (10 mg dm−3 for Mn; 2 mg dm−3 for Zn) within 1 h. Furthermore, heavy metal immobilization was achieved at neutral pH (7–8) with the sludge addition, while the conventional neutralization process without adding the sludge requires higher pH (>10) to lower Mn concentration. These removal behaviors were not explainable by considering only well-known phenomena: hydroxide precipitation, surface complexation reaction onto δ-MnO2, and autocatalytic Mn oxidation. Hence, we advanced the geochemical model for simulation, suggesting that a surface complexation reaction onto γ-MnOOH greatly contributed to the removal of Mn. Besides, Zn was calculated to be predominantly precipitated as ZnMn2O4. Solid residue analysis by XAFS measurement supported the result of above calculation, validating the reliability of the constructed geochemical model. Overall, we concluded that the advanced geochemical model would be useful in predicting the Mn and Zn behavior during mine drainage treatment with Mn neutralization sludge.Graphical abstract

Oil sludge addition enables prediction of biomass pyrolysis product profiles by synergistic behaviors between biomass components and oil sludge

The complex composition of biomass leads to wide variations of pyrolysis products, which makes the prediction of pyrolysis product profiles greatly difficult. This study firstly found that biomass co-pyrolysis with oil sludge (OS) made product profiles well-predictable. Co-pyrolysis of three biomass components, hemicellulose (Hemi), cellulose (Cel), and lignin (Lig) with OS increased the comprehensive pyrolysis index compared to OS pyrolysis alone. Moreover, co-pyrolysis with OS led to a weaker intensity of gas release (CH4, H2O, CO, and CO2) and lower apparent activation energies than pyrolysis of individual biomass components. OS/Hemi and OS/Cel co-pyrolysis promoted the formation of char and gaseous products as well as the generation of oxygenates in oil products. On the other hand, OS/Lig co-pyrolysis enhanced gas production and contributed to the formation of hydrocarbons like long straight-chain alkanes with less oxygenates formation. Using co-pyrolysis results of OS/Hemi, OS/Cel, and OS/Lig, the product yields and oil compositions of OS/real biomass co-pyrolysis (woody biomass and rice straw) were successfully predicted based on only Hemi/Cel/Lig composition ratios of the biomass. Because direct interactions between OS and biomass components might be prior to pyrolytic interactions among biomass components, it enables the excellent predictability. It also proposes that OS or other appropriate materials might facilitate the industrial applications of miscellaneous biomass pyrolysis owing to reliable predictions of product profiles based on the biomass composition ratios.

Study on the mechanism of action of methane production by co-fermentation of sludge and lignite.

To improve the methanogenic efficiency of lignite anaerobic fermentation and explore innovative approaches to sludge utilization, a co-fermentation technique involving lignite and sludge was employed for converting biomass into biomethane. Volatile suspended solids were introduced as a native enrichment of the sludge and mixed with lignite for fermentation. The synergistic fermentation mechanism between sludge and lignite for biomethane production was analyzed through biochemical methane potential experiments, measurement of various parameters pre- and post-fermentation, observation of bacterial population changes during the peak of reaction, carbon migration assessment, and evaluation of rheological characteristics. The results showed that the addition of sludge in the anaerobic fermentation process improved the microorganisms' ability to degrade lignite and bolstered biomethane production. Notably, the maximum methane production recorded was 215.52mL/g-volatile suspended solids, achieved at a sludge to coal ratio of 3:1, with a synergistic growth rate of 25.37%. Furthermore, the removal rates of total suspended solids, and total chemical oxygen demand exhibited an upward trend with an increasing percentage of sludge in the mixture. The relative abundance and activity of the methanogens population were found to increase with an appropriate ratio of sludge to lignite. This observation confirmed the migration of carbon between the solid-liquid-gas phases, promoting enhanced system affinity. Additionally, the changes in solid-liquid phase parameters before and after the reaction indicated that the addition of sludge improved the system's degradation capacity. The results of the study hold significant implications in realizing the resource utilization of sludge and lignite while contributing to environmental protection endeavors.

Asphalt Concrete Production Technology Using Oil Sludge from Zhaik Munay LLP

Oil sludge exhibits a compositional similarity to bitumen, a pivotal constituent in asphalt concrete mixtures. This similarity underscores the potential applicability of oil waste in the production of asphalt concrete, serving not only as an organic binder to fortify indigenous soils but also as a binding agent for the fabrication of organomineral mixtures. The incorporation of oil sludge in road construction endeavors holds promise for the conservation of natural resources, the amelioration of the environmental landscape, and a concurrent reduction in the cost of construction materials. The focus of this study encompasses a comprehensive examination of the physical and mechanical properties pertaining to asphalt concrete of Grade I, Type B. To enhance the performance attributes of asphalt concrete, an additive in the form of oil sludge sourced from ZhaikMunay LLP (Uralsk) was introduced. Various proportions of oil sludge, namely 5%, 10%, and 15%, were incorporated into the asphalt concrete mixture. The utilization of 5% oil sludge elicited negligible alterations in the properties of the asphalt concrete. However, with a 15% addition of oil sludge, discernible reductions were observed in maximum compressive efficiency (0.03% by volume) and shear resistance, indicated by the internal friction coefficient efficiency (0.01% by volume).

Effects of Wastewater Sludge Addition on Fired Clay Bricks: Enhancing Performance and Sustainable Construction Practices

This study explores the impact of incorporating wastewater sludge into fired clay bricks to improve their performance and promote sustainable construction. Physical, mechanical, and environmental properties of the sludge-amended bricks are investigated to assess their suitability as an alternative construction material. Lab tests are conducted to characterize the sludge and clay, and brick samples with varying sludge content are produced. Physical properties such as water absorption, are analyzed to determine the influence of sludge addition on the bricks' structural characteristics. Mechanical tests, including compressive and flexural strength evaluations, assess the performance of the sludge-amended bricks compared to traditional clay bricks. Additionally, environmental aspects are considered to evaluate the sustainability of the sludge-amended bricks. Life cycle assessment and carbon footprint analysis quantify the environmental benefits and drawbacks associated with their production and use. The findings of this study contribute to the knowledge of sustainable construction materials by exploring the potential utilization of wastewater sludge in fired clay brick production.

Cultivation of the coupling bacteria for simultaneous autotrophic nitrogen and sulfur removal and its remediation effect on the river sediment

The coupling bacteria for simultaneous autotrophic nitrogen and sulfur removal was cultivated by supplying sulfide to an Anammox biofilter treating low-strength wastewater. The results showed that sulfide-driven autotrophic denitrification (SAD) was successfully induced, and the total nitrogen (TN) removal increased from 83.0% to 94.4% when the sulfide concentration was increased to 25 mg L−1, with complete sulfide removal. Mass balance analysis suggested that 30.5% of the generated nitrate was reduced to nitrite while the rest was converted to nitrogen gas. The relative abundance of Anammox bacteria (Candidatus Kuenenia) increased from 9.16% to 18.8%, and the SAD bacteria (Thiobacillus) increased from 0.07% to 2.00%, both contributing collaboratively to nitrogen and sulfur removal. The coupling bacteria demonstrated a significant remediation effect on river sediment, increasing the TN removal activity by 10 times with a sludge addition ratio of 1:20. The results provide indications for enhancing the nitrogen and sulfur cycle in aquatic environments.

Co-applications of Rhizobium and arbuscular mycorrhizal fungi synergistically alleviate heavy metal uptake and toxicity in lentil plants (Lens culinaris Medik.) grown in sewage sludge amended soil

Reusing sewage sludge as a mode of nutrients and an organic amendment may be a viable choice for the appropriate treatment of organic waste. This study examined the impact of symbiotic microbes such as Rhizobium and two selected arbuscular mycorrhizal fungi (AMF), Funneliformis caledonius (Nicolson & Gerd.) and Glomus bagyarajii (Mehrotra), on the growth, photosynthetic pigments, biochemical content, microbial population, and heavy metal uptake in lentil plants grown in soil mixed with 20 % sewage sludge. Lentil seeds were inoculated with Rhizobium prior to sowing and with either of the AMF (Funneliformis caledonius or Glomus bagyarajii) in pots filled with soil-sewage sludge mixture. The results showed that the tested microbial inoculum enhanced the growth and productivity of lentil plants. Lentil plants inoculated with Rhizobium and AMF had better nodulation and root colonization, leading to an increase in the nitrogen, phosphorus and potassium (NPK) content and a decrease in the stress marker, proline, in plant parts. In addition, the inoculated microbes also improved the photosynthetic and biochemical contents of the plant. Lentil plants grown in sewage sludge-amended soil when inoculated with Rhizobium and either of AMF were found to be more effective in accumulating Cd, Cr, Pb, Ni, and Zn in the roots, while restricting their translocation to the above-ground parts of the plant, thereby improving plant health. Overall, the study outcomes provide evidence that Rhizobium and AMF have the potential to tolerate heavy metal stress caused by the addition of sewage sludge to soil, which has important implications for sustainable agriculture practices. The study also highlights the importance of microbial inoculants, such as Rhizobium and AMF in enhancing growth and yield, particularly under heavy metal stress in economically important lentil.

Sustainable treatment and recycling of oily sludge: Incorporation into gel -system to improve oil recovery.

Oily sludge is very difficult to treat in solid waste, how to achieve on-site treatment and recycling of the sludge is rarely reported. This research proposes a new treatment method for oily sludge by adding the oily sludge into the gel water plugging system designed for low-performing oilfields-sludge re-injection technology. The gel system of oily sludge can resist dehydration for 150 days at a high temperature up to 140 °C and a salinity of 2.11 × 105 mg/L, and its strength reaches grade I. The microstructure of the gel was revealed using scanning electron microscopy (SEM). The addition of oily sludge made the gel system microstructure develop a dense three-dimensional network structure, which can effectively improve the strength and temperature resistance of the gel system. Differential scanning calorimetry (DSC) experiments show that the gel with oily sludge can maintain temperature resistance even at 188 °C. Laboratory displacement experiments show that the breakthrough pressure of the gel system can reach 3418 kPa/m, and the plugging rate is above 98%. The performance of the system was improved by adding oily sludge into the gel as an enhancer, which provided a research idea for harmless treatment, resource utilization and clean production of oily sludge.

ИССЛЕДОВАНИЕ УТИЛИЗАЦИИ NI2+-СОДЕРЖАЩЕГО ОТХОДА В КАЧЕСТВЕ КАТАЛИЗАТОРА ПРОЦЕССА ОКИСЛЕНИЯ УГЛЕВОДОРОДОВ

The feasibility of utilization of spent galvanic solutions containing high concentrations of heavy metal ions as a catalyst for hydrocarbon oxidation process is shown. Characterization of the studied sulfur-alkaline wastewater (SAWW) and spent Ni2+-containing electroplating solution is presented. It is established that the sludge isolated as a result of joint treatment of SAWW from sulfide ions and spent Ni2+-containing electroplating solution from nickel (II) ions contains a significant amount of impurities of organic substances. The method of obtaining Ni2+-containing catalyst from the sludge obtained as a result of joint treatment of wastewater from chemical and galvanic production - high-temperature heat treatment at 900 °C is proposed. It is shown that 15 minutes heat treatment of sludge in air medium at 900 °C leads to almost complete removal of organic impurities from it. Diffractometric method established that the main component of heat-treated sludge is nickel (II) oxide. It has been experimentally shown that treatment of SAWW with an ozone-air mixture for 60 minutes leads to a decrease in the Chemical Oxygen Demand (COD) value by only 1604 mg O/dm3, which corresponds to a purification degree in terms of COD value equal to 11.9 %. Addition of NiO-containing sludge obtained from the joint purification of SAWW and spent Ni2+-containing galvanic solution in the concentration of 200 mg/dm3 allows to significantly intensify the process of oxidation of organic pollutants of SAWW. It has been established that the use of heat-treated NiO-containing sediment as a catalyst leads to a decrease in the COD value by 3438 mg O/dm3. At the same time the degree of purification by COD value reaches 28.1 %. It is revealed that the efficiency of treatment of SAWW by COD value as a result of ozonation process using the obtained heat-treated sludge is 16.2 % higher in comparison with non-catalytic oxidation.

Enhancing Anaerobic Biodegradation of Phenanthrene in Polluted Soil by Bioaugmentation and Biostimulation: Focus on the Distribution of Phenanthrene and Microbial Community Analysis

The remediation of polycyclic aromatic hydrocarbon (PAH)-contaminated soils has received much attention in recent years, and most of the contaminated sites are in anaerobic environments, such as deep soils and flooded soils. We simulated the natural flooded soil environment, selected phenanthrene (PHE) as a model PAH contaminant, and designed batch experiments run for 63 days to comprehensively investigate the effects of the combined addition of anaerobic sludge and granular biochar on microbial community and function and the anaerobic biodegradation of PHE. Firstly, the residue, distribution, and removal of PHE in the flooded soil environment were quantified for each group. Secondly, the effects of bioaugmentation of soil indigenous microorganisms by the addition of anaerobic activated sludge and biostimulation of biochar on the removal of PHE from the soil were analyzed against each other. Lastly, the changes in the structure of the microbial community under the effect of bioaugmentation and biostimulation were illustrated by sequencing analyses. The results of this study showed that the removal efficiency of PHE reached 72.0% after the addition of anaerobic activated sludge. The incorporation of anaerobic activated sludge and biochar resulted in a 25.3% increase in PHE removal compared to a single soil, suggesting that the combination of bioaugmentation and biostimulation can have a synergistic effect on the anaerobic biodegradation of PHE in contaminated soils. The results of sequencing analysis further indicated that the introduction of an exogenous microbial community changed the dominant genera associated with PHE degradation and introduced methanogenic archaea, which enriched the metabolic pathways of the carbon cycle in the system. On this basis, the addition of biochar resulted in higher anaerobic microbial community diversity, functional dominant species were enriched, and the direct interspecies electron transfer (DIET) process between electroactive bacteria (Bacteroides, f_Geobacteraceae) and Methanosaeta was facilitated, which accelerated the degradation of PHE by anaerobic microbial communities. The results of this study provide regulatory tools and basic data support for enhanced bioremediation of PAHs in flooded soils.

Removal of Diclofenac in Wastewater by Activated Sludge in Batch and Moving-bed Biofilm Reactor Experiments

This study aimed to determine the diclofenac removal in wastewater by sludge taken from an operating wastewater treatment facility. Laboratory experiments were conducted in two parts: batch and moving-bed biofilm reactor (MBBR) experiments. Results from batch experiments showed that 0.1–2 mg L-1 of diclofenac could be removed more than 80% within 72 h, and the removal efficiency reduced to less than 60% for higher concentrations. The increase in the removal rate from 0.00058 to 0.16527 mg L-1 h-1 was observed when the initial diclofenac concentration increased from 0.1 to 10 mg L-1, respectively. The average first-order rate constants of 24-h and 72-h degradation were calculated as 4.71 × 10-2 and 1.99 × 10-2 h-1, respectively. The removal of diclofenac by sludge was mainly from biodegradation by microorganisms in sludge, followed by the adsorption onto the sludge biomass. The addition of various metal ions in the studied range did not significantly increase the diclofenac removal; however, the addition of Ca2+, Co2+, Fe3+, Mn2+, and Zn2+ tended to increase both diclofenac removal rate and efficiency. This positive effect was reduced when the metal ion concentrations were increased up to 0.75 ppm. Lastly, results from an initial phase of continuous MBBR showed that sludge addition during the start-up also extended the diclofenac removal efficiency to one week compared with 3 days in the experiment without sludge addition. In conclusion, the findings show the capability of using activated sludge in diclofenac wastewater treatment by the traditional or alternative systems.

Co-combustion of bituminous coal and industrious sludge under non-isothermal and isothermal conditions: Thermal behaviors, kinetic analyses, and heavy metals migration

Considering the environmental pollution caused by the direct stacking or landfilling of various sludge, the combustion characteristics of bituminous coal, Fe-rich industrious sludge, and their blend were studied using thermogravimetric analysis at non-isothermal and isothermal conditions. It was found that the volatile matter in sludge with low C/H ratios will be released and burned in the low-temperature stage, then the generated heat will promote extra heat for the combustion of fixed carbon in coal when the addition of sludge was greater than 60%. The used Flynn-Wall-Ozawa and Kissinger-Akahira-Sunose methods were more accurate for coal, sludge, and their blend with low sludge addition. After comparing the activation energy, a suitable addition of sludge was found to improve the combustion and kinetic characteristics of fixed carbon but do less help to volatile matter in coal. As to the heavy metals emission, the synthetic effect of the blend combustion enhanced the Pb emission when sludge addition was more than 60% but almost did not affect Cr, Ni, Zn, and Cu. By sampling dynamically during the co-combustion, it was found that the leaching toxicity of heavy metals was greatly related to the combustion degree. The stabilization of Al, Ca, Cr, and Zn was finished as their leaching toxicity decreased to a constant value before the burnout of fixed carbon (100∼120s) while that of Ni was slightly delayed, especially when the coal was added. Besides, the leaching concentration of Cu gradually increased with combustion time and its stabilization cost more time. Such a time-controlled combustion strategy may also be worthy of further research to help dispose of other solid wastes with similar composition.

The influencing mechanism of AD-MEC domesticated sludge to alleviates propionate accumulation and enhances methanogenesis

Anaerobic digestion combined with microbial electrolysis cell (AD-MEC) could maintain stable reactor operation and alleviating the anaerobic digestion (AD) propionate accumulation. In this study, the addition of sludge to AD-MEC was examined as a way to enhance system performance and explore the microbial interaction mechanism after electric field domestication. The results showed that under 1000 and 4000 mg/L propionate, the methane production of the sludge from AD-MEC increased by 34.29 % and 9.70 %, respectively, as compared to the AD sludge. Gompertz fitting analysis showed that sludge after electric field domestication enhancing its continuous methanogenic capacity. Further analysis showed that sludge extracellular electron transfer capacity was enhanced in AD-MEC and that its domesticated granular sludge formed a microbial community function with acid-degrading synergistic methanogenesis. The results of the study may provide theoretical support and optimization strategies for the application of AD-MEC system.

Utilization of treated wastewater dry sludge for lightweight concrete and the use of treated waste water as a curing medium

The increasing generation of sludge from wastewater treatment plants and the growing concerns over sustainable waste management have led to a demand for innovative and eco-friendly approaches. This abstract presents a novel approach that addresses two significant environmental challenges: the utilization of dry sludge as a partial replacement for cement in concrete production and the use of wastewater as a curing medium for concrete. Concrete, being the most widely used construction material worldwide, has a significant environmental impact due to its extensive consumption of natural resources and high carbon emissions. To address these challenges, researchers have explored various sustainable alternatives, one of which is incorporating sludge, a byproduct of wastewater treatment plants, into concrete production. This abstract presents a comprehensive overview of the utilization of sludge as supplementary cementations material (SCM) in concrete, highlighting its potential benefits and challenges. Sludge, rich in organic and inorganic compounds, possesses properties that can enhance the performance of concrete. As a SCM, It can partially replace cement thereby reducing its demand and minimizing the carbon footprint associated with cement production. Additionally, sludge in corporation in concrete promotes waste management and offers a sustainable solution for the disposal of this abundant by product. The abstract examines the effects of sludge on various concrete properties, including workability, strength development, durability and environmental impacts. Studies have shown that sludge addition can enhance the workability of fresh concrete, leading to improved cohesiveness and reduced water demand. Furthermore, the pozzolanic and filler effects of sludge contribute to the strength development of hardened concrete, with potential improvements observed in both early age and long-term strengths. Moreover, the inclusion of sludge in concrete can enhance its durability performance, such as resistance to chloride ion penetration, sulfate attack and alkali-silica reaction. The abstract also discusses the potential environmental benefits, including reduced carbon emissions, energy saving and conservation of natural resources, resulting from sludge utilization in concrete production. Overall , in corporation sludge into concrete presents a promoting opportunity to enhance the sustainability of the construction industry; further research and development efforts are required to fully understand the long term performance and environmental implication of sludge-based concrete and to overcome the associated challenges. By embracing sludge as valuable resources, the construction sector can move towards a more circular economy and contribute to a greener and more sustainable future.

Impact of the Addition of Sugar Beet Lime Sludge on the Composting of Argan Oil By-Products

Impact of the Addition of Sugar Beet Lime Sludge on the Composting of Argan Oil By-Products

Preparation and performance of non-sintered lightweight aggregates derived from textile sludge and coal fly ash

The feasibility of preparing non-sintered lightweight aggregate using textile sludge and coal fly ash as the main raw materials was investigated. Extensive experiments were conducted to analyze the effects of different coal fly ash/sludge ratio, sodium silicate addition and curing time on the performance of non-sintered lightweight aggregates (NSLWAs). The optimal preparation parameters were determined as follows: coal fly ash/cement ratio of 2.2, textile sludge addition of 20%, sodium silicate addition of 10%, and curing time of 28 days. Under these optimal preparation conditions, the cylindrical compressive strength of NSLWAs was relatively high. The test results of Zn leaching toxicity test and S content all met the relevant standards and environmental safety requirements. NSLWA has a dense internal structure with uniformly distributed grains. By analyzing the hydration reaction mechanism during the NSLWAs preparation, it can be obtained that part of Zn<sup>2+</sup> was stabilized by conversion into insoluble Ca(Zn(OH)<sub>3</sub>)<sub>2</sub>･2H<sub>2</sub>O, while the remaining part was solidified and stabilized through encapsulation and adsorption of hydration products. Furthermore, it was discovered that pozzolanic admixtures played a crucial role in the hydration and hardening process of NSLWAs, and the presence of C-S-H gel and Mullite contributed to the increase in cylinder compressive strength of NSLWAs.

Regulation Mechanism of Solid Waste on Ash Fusion Characteristics of Sorghum Straw under O2/CO2 Atmosphere

Co-combustion of solid waste and biomass can alleviate biomass ash-related problems. To investigate the effects of solid waste on the ash fusion characteristics of biomass and its variation mechanisms under an oxidation atmosphere, an X-ray diffraction, thermogravimetric analyzer (TG), scanning electron microscope (SEM), and FactSage calculation were used to examine the ash fusion behaviors of sorghum straw (SS) with the addition of textile dyeing sludge (TDS) or chicken manure (CM). The ash fusion temperature (AFT) of SS increased gradually with the TDS ash addition; with CM ash addition, the AFT of SS mixtures increased rapidly (0–20%), decreased slightly (20–30%), and finally increased slowly (30–60%). The generations of high melting point (MP) minerals (e.g., KAlSi2O6, Fe2O3, and Fe3O4) led to an increase in the AFT of TDS-SS mixtures. The K+ in silicate was gradually replaced by Mg2+ or Ca2+, which caused the generations of high-MP minerals (e.g., Ca3MgSi2O8, Ca2MgSi2O7, and CaMgSiO4). The TG analysis showed that the additions of TDS or CM ash slowed down the weight loss of SS mixed ash due to the formation of high-MP minerals. The SEM and FactSage calculations were also explained with the AFT change and their variation mechanisms. The result provided effective references for the AFT regulation during the co-combustion of biomass and solid waste.

A comparative study of the reaction mechanism for deep reduction hydrogen production using two special steel solid wastes and a chemical looping hydrogen production scheme

Pickling sludge (PS) and presintered waste (PW) are two special steel solid wastes that have potential as oxygen carriers due to their Fe content. Using these raw materials to produce hydrogen allows for the resource utilization of solid waste, which has good environmental effects. Here, we studied the deep reduction-hydrogen production characteristics. Specifically, the effects of temperature, papermaking sludge (PMS) blended ratio, and reaction time on the deep reduction characteristics of Fe in pickling sludge and presintered waste were studied. On this basis, the study also aimed to investigate the effects of temperature and PMS blended ratio on hydrogen production. The results indicated that when exposed to high temperature, PMS shows the ability to effectively reduce pickling sludge and presintered waste. The maximum Fe recovery rate can reach 65.63 and 96.94 % in a fixed bed reactor operating at 700 °C and a blended ratio of approximately 10 %. Under the conditions of 900 °C and 15 %/50 % papermaking sludge addition, the Fe content within pickling sludge and presintered waste was reduced to FeCr2O4 and FeO, respectively. Subsequently, during the reaction with steam, Fe2O3 and Fe3O4 were generated in PS and PW, respectively. The hydrogen production per unit mass of Fe2O3 in pickling sludge is higher due to the existence of the FeCr2O4 spinel structure in the reduction product of pickling sludge. According to the above results, two hydrogen production strategies of PS and PW through different deep reduction paths are proposed.