Textile Dyeing Sludge Research Articles

Removal performance of Nitrogen, sulfur and chlorine pollutants during chemical looping combustion of textile dyeing sludge using red mud as an oxygen carrier

Textile dyeing sludge (TDS) is a solid waste produced by the textile industry, which contains a large number of N, S and Cl components. Direct heat treatment of TDS will cause a large number of N, S, Cl pollutants to be released. This study verified the possibility of chemical looping combustion (CLC) of TDS using alkaline WS900 red mud (RM) oxygen carrier, which is rich in Na/Ca, to remove N, S and Cl pollutants at the same time. Raising the reaction temperature in the range of 750–900 °C, prolonging the residence time and increasing the oxygen excess coefficient can promote the oxidation performance of WS900 to NOx precursor, while CO2 atmosphere inhibits the oxidation ability. After 10 cycles of CLC, the Cl fixation rate of WS900 is still close to 100% and its S fixation rate is more than 97%. It can maintain more than 90% of carbon conversion and 86% of CO2 selectivity. Compared with the pyrolysis condition, the removal rate of N pollutants is about 67%. Alkaline RM is also neutralized after absorbing acid gases during CLC, which is convenient for its further treatment and utilization.

Co-pyrolytic drivers and volatiles of 3D printing waste and textile dyeing sludge and their multi-objective optimization

Textile dyeing sludge (TDS) disposal poses a critical environmental challenge due to its complex and hazardous nature. This study explored the co-pyrolysis of 3D printing waste (3DPW), comprising photosensitive resin waste (PRW) and polycaprolactone waste (PCLW), with TDS as a potential co-circularity strategy. Drivers, interactions, and resultant products of the co-pyrolysis were characterized through thermogravimetric experiments. Kinetically, the co-pyrolysis process followed a second-order reaction (F2) model. The co-pyrolysis with PRW enhanced the releases of ketones, aldehydes, and esters, with 2-pentene (26.70%) and 2-ethylacrolein (34.67%) as the primary products. Conversely, the co-pyrolysis with PCLW reduced CO emission and generated tetrahydrofuran (27.28%) and cyclopentanone (44.58%). The co-pyrolysis with 3DPW offers a promising approach for mitigating environmental pollution by transforming hazardous wastes into value-added valuable precursors for fuels and organic chemicals.

Energy and exergy analyses, and elemental distribution of microwave-assisted auger pyrolysis of textile dyeing sludge and furfural residue

Microwave-assisted pyrolysis has emerged as a promising treatment method for textile dyeing sludge (DS) and furfural residue (FR), demonstrating the potential to address environmental issues and harness their energy. In this study, microwave-assisted auger pyrolysis of DS and FR was conducted, and the mass balance, elements distribution, energy, exergy and sustainability analysis were investigated. The results indicated that the distribution ratios of carbon (46.14–76.29%), hydrogen (15.04–47.96%), and oxygen (3.62–36.55%) in chars decreased with increasing temperature. As the pyrolysis temperature increased during FR pyrolysis, there was a higher thermal energy loss and a decrease in energy efficiency, energy yield, and exergy efficiency. The pyrolysis temperature and the type of solid wastes are key factors in determining both energy efficiency and exergy efficiency. The energy/exergy utilization efficiencies for FR pyrolysis (57.03–82.24%/55.90–81.82%) surpassed those for DS pyrolysis (26.46–38.93%/23.35–36.65%). The highest energy and exergy efficiencies for DS (i.e. 38.93% and 36.65%) and FR (i.e. 82.24% and 81.82%) were achieved at 450 °C. FR pyrolysis had a lower environmental impact than DS pyrolysis. This study aimed to provide insights into the treatment and disposal of sludge and FR through microwave pyrolysis, considering both energy and exergy aspects.

Microwave co-pyrolysis of industrial sludge and waste biomass: Product valorization and synergistic mechanisms

Microwave co-pyrolysis of textile dyeing sludge (TS) and furfural residue (FR) was investigated in this study. Comprehensive pyrolysis index (CPI) was employed to investigate pyrolysis performance and FR addition significantly improved co-pyrolysis. Product distribution showed that increasing FR ratio enhanced the bio-oil and gas with significant reduction in biochar. For bio-oil, FR addition neutralized the strong alkalinity and inhibited the formation of nitrogen compounds. Moreover, bio-oil maintained a very low oxygenates content (0.97–5.97%). For biochar, co-pyrolysis was favorable for the enrichment of C and H and mitigated the potential contamination. FR addition increased the calorific value and contributed to pore development of biochar. Online inspection displayed that co-pyrolysis drastically restrained the release of sulfur-compounds and nitrogenates in volatile, while enhanced the production of alkanes, aldehydes, and ketones. Moreover, the interaction between TS and FR was influenced by their major components. For heavy metals (HMs), Er was at low risk for most HMs and FR addition ratios of 40 and 80 wt% appeared to be more favorable. Principal component analysis (PCA) showed that FR addition changed the decomposition behavior and affected co-pyrolysis process. This study also evaluated the co-pyrolysis synergistic mechanisms of TS and FR. Overall, microwave co-pyrolysis is a novel and effective method to reduce environmental pollution and produce high-quality products, providing new insights for the low consumption and efficient utilization of industrial solid waste.

Microplastics as emerging contaminants in textile dyeing sludge: Their impacts on co-combustion/pyrolysis products, residual metals, and temperature dependency of emissions

As emerging contaminants in textile dyeing sludge (TDS), the presence and types of microplastics (MPs) inevitably influence the combustion and pyrolysis of TDS. Their effects on the co-combustion/pyrolysis emissions and residual metals of TDS remain poorly understood. This study aimed to quantify the impacts of polyethylene (PE) and polypropylene (PP) on the transports and transformations of gaseous emissions and residual metals generated during the TDS combustion and pyrolysis in the air, oxy-fuel, and nitrogen atmospheres. Thermal degradation of the MPs in TDS occurred between 242–600 °C. MPs decomposed and interacted with the organic components of TDS to the extent that they increased the release of VOCs, dominated by oxygenated VOCs and hydrocarbons under the incineration and pyrolysis conditions, respectively. The presence of PE exerted a limited impact on the concentration and chemical form of metals, while PP reduced the residual amount of most metals due to the decomposition of mineral additives. Also, PP (with CaCO3 filler) reduced the acid-extractable content of cadmium, copper, and manganese in the bottom slag or coke but increased that of chromium. This study provides actionable insights into optimizing gas emissions, energy recovery, and ash reuse, thus reinforcing the pollution control strategies for both the MPs and TDS.

Energetic and environmental optimizations and byproduct valorization of pyrolysis of textile dyeing sludge with FeCl3

Maximizing the circular economy of hazardous wastes is one of the imperatives not to overshoot the biogeochemical limits of Earth. This study aimed to characterize and valorize the textile dyeing sludge (TDS) pyrolysis in response to the addition of FeCl3 conditioner in the N2 and CO2 atmospheres. The increase fraction of FeCl3 decreased comprehensive pyrolysis index (CPI600) from 1.05 to 0.42 in the N2 atmosphere and from 0.71 to 0.41 in the CO2 atmosphere at 20 °C/min. The addition of FeCl3 diminished the pyrolysis performance, with a more pronounced inhibitory effect occurring in the N2 atmosphere than in the CO2 atmosphere. Regardless of the type of pyrolysis atmosphere, with or without FeCl3, all the TDS pyrolysis released CO, CO2, CH4, aromatics, NH3, and SO2. The main pyrolytic byproducts were nitrides and hydrocarbons, represented by ethanolamine (C2H7NO) and benzene (C6H6). Not only did 4 % FeCl3 addition facilitate the transformation of nitrides into hydrocarbons during the pyrolysis, but it also achieved the optimal energetic performance and emission reduction. Our findings provide novel and actionable insights into the byproduct valorization and pollution control during the TDS pyrolysis and the promotion of carbon capture, utilization, and storage.

Technology transition strategies for textile-dyeing sludge management in China from the environmental and economic perspectives

Textile-dyeing sludge reutilization is considered as an effective management scheme in the transition to low-carbon and sustainable development from the conventional incineration or landfilling. However, few studies have focused on its assessment from environmental and economic perspectives. In this study, a bin-to-grave life cycle thinking is applied to compare the environmental and economic performances of four promising and newly industrialized sludge reutilization technologies (i.e., pyrolysis-gasification-incineration, co-combustion in coal-fired power plants, sludge-to-brick, and sludge-to-biochar) with the traditional landfill option. Results indicate that technology transition to sludge-to-biochar option outperforms other transition strategies. The sludge-to-biochar option could gain environmental benefits in 7 categories i.e., primary energy demand (−6.1 × 103 MJ/t sludge), abiotic depletion potential (−4.9 × 10−4 kg antimony eq./t sludge), eutrophication (−0.15 kg PO43− eq./t sludge), ozone depletion(−1.67 × 10−5 kg CFC-11 eq./t sludge), photochemical ozone formation (−2.25 kg NMVOC eq./t sludge), ionizing radiation-human health effects (−3.1 kg U235 eq./t sludge), and ecological toxicity (14.4 CTUe/t sludge). Direct emissions of GHG in sludge reutilization technologies contribute to >70 % of the global warming potential category. Adopting the preferred sludge-to-biochar option at the provincial scale could mitigate approximately 0.81 million t of CO2 eq./year, which is equivalent to the amount of CO2 annually absorbed by 44.1 million trees in China. Feedstock (i.e., chemicals) contributes to about 77.9 %–97.9 % of toxicity-related environmental loads (i.e., human toxicity-cancer effects and ecological toxicity) for sludge-to-biochar, whereas in other utilization technologies, the key factor is heavy metal emission. The sludge reutilization technologies could break even within 3 years except pyrolysis-gasification-incineration (7 years). Meanwhile, contribution, sensitivity, and scenario analyses indicate that reducing primary energy consumption and improving the product quality and yield could effectively alleviate environmental burdens. A reasonable sludge disposal fee could help with the circular regeneration of textile-dyeing sludge. Despite that sludge-to-biochar stands as the foremost advantageous option for the technology transition in managing textile-dyeing sludge, certain aspects (for example, product quality and feedstock consumption) still necessitate further enhancements before its large-scale application in China.

Investigation on ash fusion characteristics during the co-gasification of coal and textile dyeing sludge

Investigation on ash fusion characteristics during the co-gasification of coal and textile dyeing sludge

Study on the pollutant emission characteristics of the co-combustion of high S/Cl waste mixed with recycled papermaking waste

Using solid waste to replace coal for power generation is one of the effective ways to reduce CO2 emissions, but the incineration of some high-sulfur and high-chlorine solid waste will lead to the increase of pollutant emissions. This paper proposed a new way to self-control pollutant emissions by co-incinerating different solid wastes with specific properties. In this work, the recycled papermaking waste residue (RPR) and sludge (RPS) with high calcium content were chosen to co-combustion with high-sulfur and high-chlorine solid waste, and the emission characteristics and control mechanism of pollutants under co-combustion were explored. The primary calcium compound in the recycled papermaking solid waste was CaCO3. When RPR and RPS were mixed at a ratio of 1: 1, HCl could be fully captured, resulting in the least emissions. Pollutant emissions was controlled by adding RPR and RPS to high-sulfur textile dyeing sludge and polyvinyl chloride. The sulfur-fixing efficiency rose from 65 % to 91 % and the chlorine-fixing efficiency rose from 69 % to 93 % with an increase in Ca/(S + 0.5Cl) from 1 to 3. As the reaction temperature rose from 700 °C to 1000 °C, the sulfur-fixing efficiency and chlorine-fixing efficiency initially increased and subsequently dropped. The CaCO3 in the material was rapidly decomposed at 800 °C, which accelerated the positive reaction rate with SO2 and HCl, so that the sulfur-fixing efficiency and chlorine-fixing efficiency reached the maximum, which were 89 % and 92 %, respectively. CaSO4 and CaClOH were the principal reaction products at the temperature range of 700 °C to 1000 °C.

Improvement of waste sludge dewaterability by a novel co-conditioning approach with polyaluminum chloride-sludge based carbon-polyacrylamide

A novel sludge conditioning method incorporating sludge-based carbon (SBC) as a filter aid into the coagulation and flocculation co-conditioning process is proposed to strengthen sludge dewaterability, namely the co-conditioning of polyaluminum chloride (PAC)-SBC-polyacrylamide (PAM). The results show that the co-conditioning method can effectively reduce the specific resistance to filtration (SRF), moisture content (MC) of the filter cake and sludge compressibility coefficient (CC), meanwhile increase the net sludge solids yield (YN) of municipal sludge (MS) and textile dyeing sludge (TDS), resulting in a significant improvement in sludge dewatering performance for two types of sludge. The response of sludge dewatering performance to different conditioning agents and the variation characteristics of sludge EPS in co-conditioning process suggest that the co-conditioning mechanism involves a synergistic effect of coagulation, adsorption, and flocculation, which process includes the aggregation and disintegration of microbial cell flocs caused by PAC, the skeleton-building action and biopolymer adsorption by SBC, and sludge floc agglomeration facilitated by PAM. In addition, SBC also optimizes coagulation by electrostatic neutralization, while strengthening flocculation by bridging biopolymers and PAM. Moreover, co-conditioning exhibits a remarkable ability to eliminate dissolved organic matter from the filtrate, leading to an enhancement in the filtrate quality and a reduction in the downstream burden for sludge filtrate treatment. Consequently, the PAC-SBC-PAM co-conditioning emerges as a promising method for sludge pretreatment.

Optimal metal immobilization of oxygen-enriched co-combustion of Zn/Cd hyperaccumulator and textile dyeing sludge with natural or modified kaolin

Eco-friendly disposal of post-harvest and metal-enriched hyperaccumulator biomass is critical for the industrialization of phytoremediation. The addition of Al/Si-based materials, such as sludge and natural mineral additives, is intended to solve the issue of HM metal stabilization in the oxygen-enriched combustion of hyperaccumulator and slow down ash sintering. This study aimed to quantify and reveal the effects of 10% kaolin or modified kaolin on the oxygen-enriched (co-)combustions of Sedum alfredii Hance (SAH) and textile dyeing sludge (TDS) and their combustion kinetics, metal enrichment rates, and immobilization/stabilization mechanisms. The activation energies for the (co-)combustions of SAH and SAH mixed with 10% additives (ST31) were estimated at 75.84–260.97 kJ/mol and 65.58–327.59 kJ/mol, respectively. The (co-)combustion mechanism model was complex, including phase boundary, diffusion, and chemical reaction order. The co-combustion of SAH with 10% modified kaolin increased Cd and Zn immobilization by approximately 66.6% and 3.2%, respectively, compared with the theoretical data at 550 °C. The co-combustion of ST31 with 10% modified kaolin increased Cd immobilization by approximately 160.9% compared with the theoretical data at 750 °C. Obtained via thermal-acid modified treatment, modified kaolin increased the immobilization efficiencies of Zn and Cd through aluminosilicate reactions to form the stable structures (Ca–Zn–Si, Ca–Zn–Al, K–Zn–Si, Zn–Al, Zn–Si, Cd–Al, and Cd–Si) as well as physical absorption. According to the combination of the experimental, multi-objective optimization, and simulation results, SAH mixed 10% modified kaolin at 550 °C and ST31 mixed with 10% modified kaolin at 750 °C were the ideal co-combustion environment. This study can provide new insights into how to best reduce the environmental risks of the hyperaccumulator disposals through the oxygen-enriched combustion technology.

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.

Co-pyrolysis of textile dyeing sludge/litchi shell and CaO: Immobilization of heavy metals and the analysis of the mechanism

To relieve the secondary contamination of heavy metals (HMs), the synergistic effect of co-pyrolysis of textile dyeing sludge (DS)/litchi shell (LS) and CaO on the migration of HMs was demonstrated in this study. The proportions of Cu, Zn, Cr, Mn, and Ni in the F4 fraction increased to 75%, 55%, 100%, 50%, and 62% at the suitable CaO dosages. When 10% CaO was added, the RI value of DLC-10% was reduced to 7.89, indicating low environmental risk. The characterizations of the physicochemical properties of biochar provided support for the HMs immobilization mechanism. HMs combined with inorganic minerals or functional groups to form new stable HMs crystalline minerals and complexes to achieve immobilization of HMs. The pH value and pore structure also play an important role in improving the immobilization performance of HMs. In conclusion, the results provided a new direction for the subsequent harmless treatment of HMs-enriched waste.

New model for evaluating greenhouse gas emissions from sludge treatment based on fossil and biogenic carbon migration

The treatment and disposal of massive amounts of sewage sludge are potential emission sources of greenhouse gases (GHGs) which strongly depend on the migration of fossil and biogenic carbon into GHGs. Owing to the lack of fossil carbon data and suitable estimation models, CO2 emissions generated from sludge combustion and biodegradation are considered carbon-neutral according to the Intergovernmental Panel on Climate Change (IPCC), increasing the inaccuracy of GHG emissions accounting. Therefore, this study aimed to build a new comprehensive assessment model to accurately evaluate GHG emissions from four typical sludge treatment and disposal approaches. Notably, fossil and biogenic carbon migration were considered, rather than the emission factor method when measuring direct GHG emissions. The results of 14C analysis, which quantified the contributions of fossil and biogenic carbon to the sludge samples, showed significant differences in the average fossil carbon fractions among the four types of sludge: 84.11% for chemical sludge, 25.99% for tannery sludge, 79.19% for textile dyeing sludge, and 45.97% for municipal sludge. According to our model, the route of safely landfilling deep-dewatered sludge possessed the highest GHG emission factors of 1.18–3.75 tCO2eq/t dry sludge. The optimal sludge treatment option was anaerobic digestion followed by land application. This treatment maintained a low and stable level of GHG emissions (0.48–0.54 tCO2eq/t dry sludge) and exhibited low sensitivity to changes in fossil carbon fraction and carbon content according to the sensitivity analysis results. For sludge with a high calorific value and a low fossil carbon fraction, the route of dry incineration + utilization of ash and slag as building materials was carbon-negative and more suitable than anaerobic digestion to achieve carbon neutrality. This study complements the fossil carbon data gaps of sludge in the IPCC Guidelines and provides a more accurate GHG emissions accounting model, which will support the sludge treatment industry in developing effective strategies to reduce GHG emissions.

Kinetics, product properties, and migration of heavy metals during co-pyrolysis of textile dyeing sludge and litchi shells

In this study, the co-pyrolysis behavior, products, and the migration of heavy metals (HMs) during the co-pyrolysis of textile dyeing sludge (DS) and litchi shells (LS) were investigated. Thermogravimetric (TG) analysis was used to identify the pyrolysis stages of mixtures, and the activation energy (Ea) of the main pyrolysis stages was calculated by Kissinger Akahira Sunose (KAS) method. The average of Ea decreased from 326.1 to 232.5 kJ/mol with increasing the proportion of LS. The bio-oil compositions indicated that the interaction effect between DS and LS mainly promoted the generation of phenols and acid compounds and inhibited the production of nitrogenated compounds, ketones, and ethers. The emission characteristics of gases from the co-pyrolysis of three samples were analyzed by TG-FTIR. The results found that the addition of LS could inhibit the generation of NOx precursors. Finally, LS in co-pyrolysis was beneficial to the increase of Cu, Zn, Cr, and Ni stable fractions (F3 +F4) to 96%, 69%, 99% and 80%, and the potential Ecological Risk Index (RI) of biochar was reduced to 7.26. This study provided a cleaner and more efficient idea for co-pyrolysis strategy and resource utilization of solid waste.

Co-thermal conversion, atmosphere, and blend type controls over heavy metals in biochars and bottom slags of textile dyeing sludge and durian shell

The co-thermal conversions of textile dyeing sludge ((TDS) with biomass may be turned into a feasible and green technology to valorize energy and products, but the transformation behavior of heavy metals remains unclear. This study aimed to quantify the migrations and distributions of HMs in biochars and bottom slags and their environmental risks in response to the co-pyrolysis and co-combustion of durian shell (DS) and TDS, atmosphere type, blend ratio, and temperature. The co-combustion interaction of DS and TDS raised the residual HM contents of the bottom slag. Co-pyrolysis reduces the environmental risks of HMs of the TDS, and the effect of CO2 atmosphere is better. In 80N220O2, Cr, Zn, and Cu in the TDS bottom slag had the highest leaching toxicity concentrations at 900 °C. At 800 °C, the leaching toxicity concentrations of HMs were Cr > Cu > Zn > Mn in TDS. The O2 concentration and atmosphere type did not significantly affect the HM morphology and transformation. K increased the temperature of converting solid-phase Ni to slag-phase NiO in DS sample and affected the transformation temperature and strength of Ni, Zn, and Pb in other sample at the high temperature. The combined results of all the three optimizations of HM contents, forms, and risks pointed to add 50 % DS in the N2 atmosphere and add 50 % DS in 50N250O2 and 80CO220O2 atmospheres as the optimal co-pyrolysis/combustion settings, respectively.

Effects of sludge on the ash fusion behaviors of high ash-fusion-temperature coal and its ash viscosity predication

The co-gasification of sludge and coal is a promising way to regulate coal ash fusion characteristics and recover energy from sludge simultaneously. In this paper, the ash fusion behaviors of high ash-fusion-temperature (AFT) Datong coal, textile dyeing sludge (TDS), their mixtures, and the corresponding AFT modification mechanisms on laboratory scale were investigated by an AFT tester, X-ray diffractometer, Raman spectrometer, and FactSage software. The AFTs of Datong coal mixtures decreased slowly when TDS share was in the range of 0–6%, quickly (6–9%), and then nearly stable (>9%) because of its corresponding increasing basic oxide values (the total content of SO3, CaO, MgO, Fe2O3, Na2O, and K2O). The generations of low melting-point minerals of hercynite and anorthite with TDS additions resulted in the AFT decrease. The decreasing intensity of Si–O–Si peak and the increasing ratio bond of bridging oxygen and non-bridging oxygen led to the AFT decrease. Both the decreases in the temperature at which all minerals change into liquid-phase and the continuously increasing liquid-phase content (at the same relative high temperature) in Datong coal mixed ashes with increasing TDS mass ratio were contributed to the variations of AFT. The viscosity-temperature characteristics variation was also predicted using FactSage calculation. The 9.0–12.0% mass ratio of TDS might be suitable for Datong coal entrained-flow bed gasification.

Co-combustion dynamics and products of textile dyeing sludge with waste rubber versus polyurethane tires of shared bikes

The co-combustions of major waste streams such as textile dyeing sludge (TDS) and waste tires of shared bikes may reduce the dependence on fossil fuels, as well as enhance their circular management and the recovery of their value-added products. In this study, the ash-to-gas products, interaction effects, and reaction mechanisms of the co-combustions of TDS and waste tires were characterized. The mono-combustions included the three stages of water evaporation, volatiles release, and mineral decomposition for TDS and the five stages for both rubber (RT) and polyurethane (PUT) tires. The three substages of the main stage of volatiles release for TDS had the activation energy of 124.5, 144.9, and 167.5 kJ/mol and were best explained by the reaction mechanism models of D3, D5, and F2, respectively. The (co-)combustion performance indices rose with the increased heating rate. The blend of 25% TDS with 75% RT (TR) and 75% PUT (TP) led to the best co-combustion performance according to comprehensive combustion index, with TP outperforming TR. The co-combustions of TP and TR reduced the activation energy required for the main devolatilization stage reaction. There was no significant difference in the main reaction mechanisms between the co-combustions. The interaction between TDS and waste tires reduced the applied energy required for the main devolatilization stage. The co-combustions at the low temperature produced O-H, CH4, CO2, CO, SO2, NO, carbonyl products, olefin products, and ketones. The co-combustions increased the production of C-H, reduced SO2 release and the viscosity of their ashes, promoted the complete combustion of substances, and alleviated the scale and sintering issues regardless of TP versus TR and caused the early release of NO from TP. According to the thermodynamic equilibrium simulations, the TR co-combustion promoted the retentions of Ca, S, Si, and Fe, in particular, the fixation of S. The addition of PUT enhanced the combination of Ca and Si into CaSiO3. The optimization based on the artificial neural networks pointed to the temperature range of 400–800 oC and the TR co-combustion as the optimal operational conditions.

Investigations on the iron-rich textile dyeing sludge pyrolysis characteristics: Thermal decomposition behaviors, products, potential mechanisms

The pyrolysis characteristics of iron-rich textile dyeing sludge (TDS) was investigated by combining TG-MS analysis, In-situ-FTIR analysis, Py-GC/MS analysis and bench-scale experiments. The thermal conversion of TDS could be characterized via two main stages, namely primary decomposition and secondary cracking. Primary decomposition occurred in the temperature range of around 150–550 ℃ and it was attributed to the breaking of aliphatic chain and functional groups, producing H2, CO, CH4, H2O, CO2, long carbon chain and residues. With temperature increasing, the reaction was defined as secondary cracking, including dehydrocyclization of aliphatics and carbon reduction of iron oxides. The final products were CO-rich gas, bio-oil and Fe-rich residues, respectively. Noted that when the temperature was 1000 ℃, the gas yield went up to 43.66 wt% and solid yield declined to 47.42 wt%, while liquid yield was only 8.92 wt%, implying that most of organics in TDS has been converted to gas.

Fates of heavy metals, S, and P during co-combustion of textile dyeing sludge and cattle manure

The co-combustion of textile dyeing sludge (TDS) and cattle manure (CM) may enhance circularity in terms of resource and pollution controls. However, the pollutant migrations and transformations of ashes and their characterization during the co-combustion are still unclear. This study aimed to quantify the transformation and migration behaviors of the co-combustion ashes, as well as the interactions involved via thermogravimetric experiments and thermodynamic simulations. The addition of TDS facilitated the conversions of Ni and Cr from the extractable form to the stable one, increasing their environmental safety. P dominated S for the reaction with Ca which promoted the generation of S-containing gas emission and apatite P. The reactions between the minerals in CM and Ca in TDS generated calcium silicate, decreasing the S-fixation ability of Ca, while increasing the emission of S-containing gases. Our findings provide insights into the interactions among the minerals, the heavy metals, and the specific elements and their impacts on pollutant emissions, thus enhancing pollution control strategies.