Kinetics, thermodynamics, gas evolution and empirical optimization of (co-)combustion performances of spent mushroom substrate and textile dyeing sludge

Study on the effect of biomass on sulfur release behavior from dyeing sludge incineration: Focusing on in-situ sulfur fixation mechanism based on model compounds

Although incineration is a recommended disposal strategy for dyeing sludge (DS), sulfurous gases problem is severe. Wood sawdust (WS) and rice husk (RH) are eco-friendly and CO₂-neutral additives to relieve sulfur emission from DS incineration. However, the interaction between organic sulfur and biomass is uninterpreted. This study explores the effect of WS and RH on the combustion behavior and sulfur evolution from organic sulfur model compound combustion via thermogravimetry (TG) with mass spectrometry (MS). Results indicated that the sulfone and mercaptan combustion activities in DS were more drastic than in other forms. WS and RH additives generally deteriorated the combustibility and burnout performance of model compounds. The combustion of mercaptan and sulfone in DS contributed to most gaseous sulfur pollutants, where CH₃SH and SO₂ were the predominant forms. WS and RH minimized the sulfur release from mercaptan and sulfone incineration, whose in-situ retention ratios reached 20.14 % and 40.57 %. The retention mechanism to sulfur could be divided into: (1) Diffusion stage: the closed structure of biomass residue restrained sulfurous gases from escaping. (2) Chemical reaction stage: multiple sulfation occurred and inhibited sulfur release. Ca/K sulfate and compound sulfates were predisposed and thermostable sulfur-fixing products for the mercaptan-WS and sulfone-RH co-combustion systems.

Bottom slag-to-flue gas controls on S and Cl from co-combustion of textile dyeing sludge and waste biochar: Their interactions with temperature, atmosphere, and blend ratio

S and Cl distribution patterns and their evolution pathways were quantified during the co-combustions of textile dyeing sludge (TDS) and waste biochar (BC). S in the flue gas rose from 10.60% at 700 °C to 45.09% at 1000 °C for the mono-combustion of TDS in the air atmosphere. At 1000 °C, S in the bottom slag and flue gas grew by 2.65% and fell by 2.11%, respectively, for the TDS mono-combustion in the 30%O₂/70%CO₂ atmosphere. The 40% BC addition increased the S retention in the bottom slag by 30.39% and decreased its release to the flue gas by 34.50% by changing the evolution of CaSO₄ and enabling more K to fix S as K₂SO₄. The decomposition of inorganic Cl was the main source of the Cl-containing gases. The 20%O₂/80%CO₂ atmosphere (36.29%) and 40% BC addition (27.26%) had higher Cl in the bottom slag than did TDS mono-combusted at 1000 °C (25.60%) by inhibiting the decomposition of organic Cl. Our study provides insights into the co-combustion of TDS and BC and controls on S and Cl for a cleaner production. Future research remains to conducted to verify scale-up experiments.

Mixed-Combustion Characteristics and Reaction Kinetics of Municipal Sludge and Corn Straw in Micro-Fluidized Bed

With economic development, the output of municipal sludge (MS) continues to increase, and the effective utilization of corn straw (CS) also plays an important role in promoting “carbon neutrality”. The mixed combustion of solid wastes is a very environmentally friendly technology; however, little research has occurred regarding the combustion characteristics and reaction kinetics of MS and CS in a fluidized bed. Therefore, this study used a micro-fluidized bed and process mass spectrometer to evaluate the mixed-combustion characteristics of MS and CS and analyze the effects of the temperature and mixing ratios on the reaction rate. Isothermal kinetics were used to calculate the activation energy, pre-exponential factors, and other kinetic parameters of this reaction. The results showed that with an increasing reaction temperature, the combustion reaction rate of MS and CS under different mixing ratios increased. The reaction rate of mixed combustion of MS and CS was greater than that of MS or CS alone. Compared with the homogeneous model, the shrinking core model is more suitable for analyzing the mixed-combustion behavior of MS and CS. The calculated activation energies of the mixed combustion in different proportions were lower than that of single fuel combustion. When the ratio of MS to CS was 2:8, the activation energy required for the reaction was minimum (28.00 kJ/mol), the pre-exponential factor was 9.06, and the fitting degree was larger than 0.99, which proved the reliability of the results.

Ash-to-emission pollution controls on co-combustion of textile dyeing sludge and waste tea

Given the globally increased waste stream of textile dyeing sludge (TDS), its co-combustion with agricultural residues appears as an environmentally and economically viable solution in a circular economy. This study aimed to quantify the migrations and chemical speciations of heavy metals in the bottom ashes and gas emissions of the co-combustion of TDS and waste tea (WT). The addition of WT increased the fixation rate of As from 66.70 to 83.33% and promoted the chemical speciation of As and Cd from the acid extractable state to the residue one. With the temperature rise to 1000 °C, the fixation rates of As, Cd, and Pb in the bottom ashes fell to 27.73, 8.38, and 15.40%, respectively. The chemical speciation perniciousness of Zn, Cu, Ni, Mn, Cr, Cd, and Pb declined with the increased temperature. The ash composition changed with the new appearances of NaAlSi₃O₈, CaFe₂O₄, NaFe(SO₄)₂, and MgCrO₄ at 1000 °C. The addition of WT increased CO₂ and NO_x but decreased SO₂ emissions in the range of 680-1000 °C. ANN-based joint optimization indicated that the co-combustion emitted SO₂ slightly less than did the TDS combustion. These results contribute to a better understanding of ash-to-emission pollution control for the co-combustion of TDS and WT.

Evaluation of the Thermal Behavior, Synergistic Catalysis, and Pollutant Emissions during the Co-Combustion of Sewage Sludge and Coal Gasification Fine Slag Residual Carbon

The conversion of solid waste into energy through combustion is sustainable and economical. This study aims to comprehensively evaluate and quantify the co-combustion characteristics, synergistic catalysis, and gaseous pollutant emission patterns of sewage sludge (SS) and coal gasification fine slag residual carbon (RC) as well as their blends through thermogravimetry coupled with mass spectrometry (TG-MS). The results showed that the co-combustion of SS and RC can not only improve the ignition and burnout property but also maintain the combustion stability and comprehensive combustion performance at a better level. The kinetic analysis results showed that a first-order chemical reaction and three-dimensional diffusion are the reaction mechanisms during the co-combustion of SS and RC. The synergistic catalysis between SS and RC can well explain the changes in activation energy and reaction mechanism. Furthermore, the blending ratio of SS is recommended to be maintained at 40% because of the lowest activation energy (Ea = 81.6 kJ/mol) and the strongest synergistic effect (Xi = 0.36). The emission of gaseous pollutants is corresponding to the primary combustion stages of SS, RC, and their blends. In co-combustion, the NH3, HCN, NOx, and SO2 emissions gradually rise with the increase of SS proportion in the blends due to the high content of organic compounds in SS.

Experimental study on gasification of oil sludge with steam and its char characteristic

Hydrogen can be prepared by oil sludge (OS) gasification with steam, which is of great significance for industrial hazardous waste treatment and resource conservation. The gasification performance was studied by a tube furnace reactor. The OS gasification was carried out at different temperatures (600, 700, 800 and 900 °C) and with different steam to OS ratio (SOS) (0.1:1, 0.3:1, 0.5:1). During the gasification process, hydrogen production first increased and then decreased, and hydrogen production was faster in 5-15 min. The yield of hydrogen of OS gasification reached the maximum when the SOS was 0.3:1 at 800 °C. The highest hydrogen yield per unit mass OS was 48.50 mL min^-1 g^-1. After gasification, the char yield was high, generally more than 50%. It was necessary to treat the char and incineration was an effective solution for low carbon fuels. Thus particle size distribution, incineration thermogravimetric analysis and heavy metal leaching concentrations analysis were carried out. The results showed that the average particle size of char ranged from 85 to 120 µm. The char incineration process could be divided into three stages: water evaporation, the precipitation and combustion of volatiles, and the combustion of fixed carbon and heavy components. After OS gasification at 800 °C, the leaching concentrations of typical heavy metals (As, Cr, Cu, Ni, Pb and Zn) were all up to the standard. Therefore, OS gasification combined with char incineration was an effective approach for the utilization of solid waste, which can recover hydrogen energy and reduce environmental risks.

Remediation potential of spent mushroom substrate on Cd pollution in a paddy soil

To investigate the remediation potential of spent mushroom substrate (SMS) on Cd pollution in a paddy soil, a rice pot experiment was conducted to study the effects of SMS addition on the availability of Cd in soil and the uptake of Cd in rice tissues. Five percent of SMS from Pleurotus eryngii (SMS-A, treatment: A), SMS from Agaricus bisporus (SMS-B, treatment: B), or SMS-A plus SMS-B (1:1, treatment: A+B) were added into a Cd-contaminated paddy soil before planting, respectively. The treatment of no SMS amendment was set up as the control (CK). At the four main growth stages of rice, the soils and plant samples were collected to detect the soil properties, Cd concentration in soils and rice tissues, and Cd fractions in soils. Results indicated that the application of SMS-A, SMS-B, and A+B significantly increased soil pH by 14.0-22.9, 23.9-32.9, and 22.7-30%, organic matter (OM) contents by 12.9-31.5, 22.1-34.5, and 26.1-36.9% comparing with CK. While cation exchange capacities (CECs) were increased by 3.6-8.5, 4.9-13.1, and 0.4-10.0% in A, B, and A+B treatments, respectively, except those at the maturation stage in A and B treatments. However, the CaCl₂-Cd concentrations in soils were significantly decreased by 64.8-77.9, 76.1-98.9, 73.2-98.9% in A, B, and A+B treatments, respectively, comparing with CK. The reduced availability of Cd was attributed to the changes of Cd from soluble to insoluble fractions in soils amended with SMS and resulted in the decreased Cd uptake in rice tissues. The Cd concentrations in roots significantly decreased by 22.8-36.9, 28.6-36.6, and 26.8-42.6%, while the Cd concentrations in straw decreased by 20.1-46.4, 9.3-41.6, and 16.0-49.1% in A, B, and A+B treatments, respectively. At the maturation stage, the Cd concentrations in brown rice were reduced by 17.7, 15.9, and 19.4% in A, B, and A+B treatments, respectively. Correlation analysis revealed that the Cd concentrations in rice roots, straws, and brown rice were all positively correlated with CaCl₂-Cd concentrations of soils. Moreover, soil pH and OM were significantly negatively correlated with the Cd concentration in rice tissues, except that between soil pH and the Cd concentration in rice straws. Therefore, the reduced Cd availability in soil and uptake in rice plant tissues together with better soil nutrient conditions by SMS application improved the biomass of root and straw at heading, filling, and maturation stages and the rice production by 32.9-38.8% at the maturation stage. The combined application of SMS-A and SMS-B can be used as a potential method for remediation of Cd-contaminated paddy soil.

Multi-response optimization toward efficient and clean (co-)combustions of textile dyeing sludge and second-generation feedstock

The rapid growth of textile dyeing sludge (TDS) necessitates feeding it back into a circular economy in an efficient and clean way. This study aimed to optimize the clean and efficient operational conditions to co-combust TDS and incense sticks (IS). The (co-)-combustions exhibited four distinctive stages of thermal degradation. According to the master-plots method, the reaction mechanisms of reaction order (F2.4 and F1.5), three-dimensional diffusion (D3), and nucleation growth (A1.5) best explained the four stages, respectively. The interaction between TDS and IS exerted an inhibition effect in the range of 400-500 °C and a facilitation effect in the range of 600-1000 °C. At 300 °C as the main reaction temperature, the main evolved gas and functional groups such as CO₂, H₂O, CH₄, C˭O, C-O, and C-H were detected. The addition of IS improved the comprehensive combustion index, inhibited SO₂, but enhanced CO₂, HCN, and NO_x emissions. CaO in IS enabled Fe to remain in TDS and fixed more S in ash. Multi-response optimizations based on the best-fit artificial neural networks revealed the range of 545-605 °C and the co-combustion of 25% TDS and 75% IS as the cleaner and more efficient operational conditions.

Influence of the production environment on the cultivation of lettuce and arugula with spent mushroom substrate

After mushroom production, the substrate plus the cultivated mycelium represents a byproduct, the so-called "spent mushroom substrate" (SMS). We evaluated different SMS types in fresh form, recently taken from the cultivation rooms, for the production of lettuce and arugula in the open field, greenhouse and greenhouse in pot. Three kinds of SMS were used (i - SMS of ABL (Agaricus subrufescens), ii - SMS of POS (Pleurotus ostreatus) and iii - 50% SMS of ABL + 50% SMS of POS) at three doses (1, 2 and 4 kg m-2). For comparison purposes, two commercial soil conditioners, Forth Condicionador® and Visa Fértil Orgânico®, were used. Finally, chicken manure with reference as international organic material was used. A control treatment consisted of a soil plot without any organic material. The application of fresh SMS in the production of LE (lettuce) and AR (arugula) is feasible considering several agronomic parameters evaluated, therefore that in F (field) the superior results were obtained by the ABL dose of 4 kg m-2, in the GR (green house) at a lower dose ABL with 1 kg m-2, POS with 2 kg m-2 and mix with ABL + POS at doses of 2-4 kg m-2, and finally in GR/P (greenhouse pot) it was proved that in a protected environment by rain the combination ABL + POS at dose of 4 kg m-2 is recommended.

Co-combustion behavior of dyeing sludge and rice husk by using TG-MS: Thermal conversion, gas evolution, and kinetic analyses

Co-combustion of dyeing sludge (DS) and rice husk (RH) is a promising energy-from-waste method. The aim of this work was to investigate and quantify the effect of RH additive on combustion performance, gas evolution (especially gaseous pollutants) and kinetics during DS combustion by thermogravimetry-mass spectrometry method. Results revealed that the introduction of RH improved the combustibility, burnout performance and combustion stability of DS. Optimal RH addition (10% RH) reduced the emission of gaseous pollutants (NH₃, NO₂, COS, SO₂ and CS₂). The interaction between DS and RH inhibited the devolatilization reaction and emission of gaseous sulfur substances, and it also restrained NO₂ emission under optimal RH additive amount. A four-interval kinetic model (D₁ → F₃ → D₁ → F₃) was established to describe the co-combustion process (R² greater than 0.9999). RH addition, especially at high doses, led to an increase in activation energy relative to DS.

Multifaceted applications of isolated microalgae Chlamydomonas sp. TRC-1 in wastewater remediation, lipid production and bioelectricity generation

Green microalga, Chlamydomonas sp. TRC-1 (C. TRC-1), isolated from the outlet of effluent treatment plant of textile dyeing mill, was investigated for its competence towards bioremediation. Algal biomass obtained after remediation (ABAR) was implied for bioelectricity and biofuel production. C. TRC-1 could completely decolorize the effluent in 7 days. Significant reduction in pollution-indicating parameters was observed. Chronoamperometric studies were carried out using cyclic voltammetry and electrochemical impedance spectroscopy (EIS). Maximum current density, power and power density of 3.6 A m^-2, 4.13 × 10^-4 W and 1.83 W m^-2, respectively were generated in ABAR. EIS studies showed a decrease in resistance of ABAR, supporting better electron transfer as compared to algal biomass before remediation (ABBR). Its candidature for biofuel production was assessed by estimating the total lipid content. Results revealed enhancement in lipid content from 46.85% (ABBR) to 79.1% (ABAR). Current study advocates versatile potential of isolated C. TRC-1 for bioremediation of wastewater, bioelectricity production and biofuel generation.

Catalytic combustion performances, kinetics, reaction mechanisms and gas emissions of Lentinus edodes

This study aimed to quantify the catalytic effects of CaO, Fe₂O₃, and their blend on the Lentinus edodes stipe (LES) and pileus (LEP) combustion performances, kinetics and emissions in bioenergy generation. Apparent activation energy (E_a) of LES and LEP increased with CaO, decreased with Fe₂O₃ and differed with their blend. The catalysts mainly affected the maximum intensity of volatiles combustion and partly the fixed carbon combustion. CaO, Fe₂O₃, and their blend decreased the release intensity of NO_x from the LES combustion. Fe₂O₃ increased SO₂ emission, while CaO, and the blend narrowed the emission temperature to the range of 200 to 450 °C. Kinetic triplets were estimated via the integral master-plots methods, and the best-fit reaction for the three sub-stages were obtained coupled with the model-free models. Our study provides a reference for the catalyzed biomass combustion in terms of pollution control, bioenergy generation, optimal design of incinerator, and industrial-scale application.

Spent Ganoderma lucidum substrate derived biochar as a new bio-adsorbent for Pb2+/Cd2+ removal in water

The present study firstly reports spent Ganoderma lucidum substrate derived biochars (SLBCS) for the effective removal of Pb²⁺/Cd²⁺ from water. The effects of pyrolysis temperature on the SLBCS characteristics and Pb²⁺/Cd²⁺ adsorption mechanism was studied systematically. The surface physicochemical properties of SLBCS were significantly affected by the pyrolysis temperature. The increase in pyrolysis temperature from 250 to 650 °C resulted in a drastic increase in the biochar surface area and the well development of mesoporous structure, which could provide more effective adsorption sites for Pb²⁺ and Cd²⁺ onto SLBCS. According to the Langmuir model, the obtained maximum adsorption capacity of Pb²⁺ onto SL650 reached 262.76 mg g^-1, while that of Cd²⁺ reached 75.82 mg g^-1. The adsorption capacities of SL650 for Pb²⁺ and Cd²⁺ were even higher than that of other modified biochars. The high adsorption capacity of SL650 for Pb²⁺, attributed to the precipitation supported by high temperature, benefitted the formation of carbonate minerals. Two possible mechanisms involved in Cd²⁺ sorption: carbonate precipitation and coordination with π electrons. Desorption of SL650 showed high efficiency for Pb²⁺, but slightly low efficiency for Cd²⁺. These results indicate that SL650 can be applied for removing heavy metals, especially Pb²⁺, from polluted water.

Parametric assessment of stochastic variability in co-combustion of textile dyeing sludge and shaddock peel

This study aimed at quantification of co-combustion behaviors and kinetic parameters of textile dyeing sludge (TDS) and shaddock peel (SP) in response to blend ratio, heating rate, and temperature. The experimental responses of mass loss (ML) and mass loss rate (MLR) measured using a thermogravimetric analyzer were also estimated using the best-fit multiple non-linear regression (MNLR) models. The independent validations of the models led to high coefficients of determination of 99.8% for ML and 83.8% for MLR. Stochastic uncertainty associated with the model predictors was assessed using Monte Carlo simulations. Our results indicated that the overall cumulative uncertainty was greater in the model predictions of MLR than ML.