Thermal Disposal Research Articles

Comparison of Environmental Footprint for Per‐ and Polyfluoroalkyl Substances Liquids and Solids Treatment Technologies

ABSTRACTPer‐ and polyfluoroalkyl substances (PFAS) contamination is a critical worldwide issue due to their widespread industrial use and persistence in the environment. PFAS treatment technologies are being applied to address the challenges associated with these substances. Selection of the appropriate treatment technology requires the assessment of many variables before full‐scale implementation. Factors such as cost, effectiveness, availability, and expected treatment duration are commonly considered; however, it is important to also consider the environmental footprint, which is the impact on the environment from the energy and materials used in implementing the treatment technology itself. The low PFAS treatment levels promulgated thus far, such as US Environmental Protection Agency drinking water Maximum Contaminant Levels of 4 ng/L for perfluorooctane sulfonate and perfluorooctanoic acid, as well as future low cleanup standards for other compounds and impacted media, will require long‐term remedial actions. Understanding the environmental impacts for PFAS treatment technologies can provide additional insights to be considered during the remedy selection. The authors conducted a comparison study of a wide range of PFAS treatment technology types for both liquids and solids, operating under limited but realistic hypothetical scenarios. The results present the approximate expected greenhouse gas (GHG) emissions of each technology type and scenario, compared to one another for the treatment of two key target compounds: perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA). The liquid treatment technology types considered in this evaluation include technologies that concentrate or separate PFAS from the liquid media (such as ion exchange, granular activated carbon, and foam fractionation), technologies that destroy PFAS (such as supercritical water oxidation and electrochemical oxidation), and landfill disposal via solidification. In practice, remedial solutions for a given site might include both a concentration/separation step and a destruction step. These combinations were not evaluated in this comparison. The solids treatment technologies considered included thermal desorption, soil washing, soil stabilization, and excavation and disposal at a landfill. The factors included in each scenario were material production, material and equipment transportation, equipment and energy use, and material disposal, as these were considered to be the largest contributors to GHG emissions.

Finishing bench tests for thermal neutralization of marine oily waters

The studies conducted on the ship's oily water thermal disposal test bench demonstrated, on the one hand, the suitability of the bench for research work, and on the other hand, revealed several unaccounted aspects in the design of the bench and its measuring system. Specifically, the nozzle was replaced to ensure finer atomization of the oily water into the flue. Additionally, it was previously established that lower pressure than originally designed was sufficient for proper atomization, necessitating the replacement of the control manometer and the electronic pressure sensor, followed by their calibration. To enable the calculation of the thermal energy characteristics of the thermal disposal process, a correlation between the pressure in the tank and the flow rate of the oily water through the nozzle was established. In a series of fine-tuning tests, data were collected on the temperature distribution along the length of the flue without and with the injection of both clean and oily water. The results indicate additional heat release when oily water is injected into the flue. The environmental characteristics of the thermal disposal process were monitored using a gas analyzer. In all the tests, the decrease of carbon monoxide concentration to almost zero was noted. Based on the results of the fine-tuning tests, it was concluded that the bench is ready for the following experiments: screening and interpolation.

Radioactivity of Technosols on thermal power station ash disposal sites: Assessment of potential radiological human‐health risk

AbstractSoil radioactivity is a poorly recognized form of land degradation; however, there are regions all around the world where it can be dangerous to the environment and human health. The aim of the study was to analyze the radioactivity of Technosols developed on thermal power station (TPS) ash disposal sites. Total concentration of uranium (U), thorium (Th), and cesium (Cs), as well as the radioactivity of select radionuclides in Technosols were determined to recognize the level of radioactivity and to assess the potential radiological health risk. Total U, Th and Cs concentrations in Technosols were in ranges 1.5 to 11.3, 4 to 22.9, and 0.2 to 21.3 mg·kg−1, respectively. The radioisotope activities in Technosols (in Bq·kg−1) were in the 1.6–25.5 (137Cs); 29.2–1265 (40K); 26.2–99.9 (228Th); 27.9–100 (228Ra); 20.5–134. (226Ra); 32.8–177 (210Pb); 23.9–144 (238U); 1.2–7.0 (235U) ranges. The activity concentrations were slightly higher than the activities of non‐contaminated soils. Technosols developed from bituminous coal ash had higher 40K, 228Th, and 228Ra activity concentrations than soils developed from lignite ash. Artificial 137Cs occurred in surface horizons of Technosols due to fall of atmospheric dust enriched in 137Cs. Annual effective dose (AED) in Technosols amounted 0.07–0.16 mSv·a−1 and was somewhat higher than the global and Polish average (0.06 and 0.07 mSv·a−1, respectively) for outdoor external terrestrial radiation. The radioactivity of the investigated Technosols is slightly above the average radioactivity of native soils. The radiological human‐health risk related to the analyzed soils is low.

Emission Characteristics of PCDD/Fs, Heavy Metals, and Nuclides during Incineration of Waste Resins Containing Nuclides

The waste resins generated from nuclear power plants contain radioactive substances, such as 137Cs and 60Co. The treatment of nuclear power plant waste resins is more challenging compared to conventional resins. In this study, the migration and emission characteristics of heavy metals, PCDD/Fs, and nuclides were investigated in relation to the incineration temperature and addition ratio of waste liquid. The results of tube furnace incineration experiments showed that when the resin was incinerated at 900°C, the PCDD/F concentration in the flue gas was 3.02 ng m−3 (0.31 ng l-TEQ m−3), dominant by polychlorinated dibenzofurans (PCDFs). Furthermore, the low nuclide concentration was observed in the flue gas. Almost no solid residue was generated due to sufficient incineration in the tubular furnace. In the pilot scale experiment, when the resin was incinerated at 900°C, the PCDD/F concentration in the flue gas was 16.97 ng m−3 (0.8 ng I-TEQ m−3). In addition, the majority of the nuclides were solidified in the solid residue produced during incineration, and only trace amounts presented in the solid residue. The total amount of nuclide in the flue gas was 49.5 mg m−3, while it reached 33.269 g kg−1 in the solid residue. This accounted for approximately 76.14% of the initial nuclide content of 218.46 mg kg−1 in the reactant. This study verifies that during the thermal disposal process, most of nuclides and heavy metals in the waste resin will migrate to the solid residue.

Experimental study on thermal bridge effect of steel-concrete-steel tunnel elements under fireproof board insulation schemes

Steel embedded parts welded on the surface of steel-concrete-steel tunnel elements serve as thermal bridges in tunnel fires. Their influence on temperature field and macroscopic thermal damage of steel-concrete-steel structure were investigated through fire tests, and their heat transfer forms were analyzed. Then, a thermal bridge disposal scheme was proposed and examined. The results show that steel embedded parts significantly cause an increase and an uneven distribution of steel shell temperature in tunnel fires. As time exposed to fire increases, the extent and range of these influences grow. Thermal bridges raise the average temperature by 45.2 % inside the steel-concrete-steel structure, worsen the unevenness of temperature distribution in horizontal and vertical directions. Thermal bridges worsen surface macroscopic damage, lengthening cracks by more than 32.5 % and widening them by more than 22.6 times. Within a distance of 30 cm from the embedded part, heat provided by embedded parts accounts for over 79.9 % of the steel shell's total heat, and heat conveyed along the steel shell through thermal conduction accounts for over 53.7 %. GX-3 high-temperature adhesive is an effective method for thermal bridge treatment. These detailed findings offer new insights into the design of fire insulation schemes for the steel-concrete-steel structure.

Oxidation Study and Mechanism Analysis of Desulfurization Ash in Dense-Phase Tower

Dense-phase-tower desulfurization technology is an emerging semi-dry flue-gas desulfurization ash process, i.e., the flue gas is allowed to enter the desulfurization tower from the bottom up and, at the same time, is sprayed with a desulfurizing agent that undergoes an acid–base reaction with the flue gas in the ascent process. The calcium sulfite and calcium sulfate produced by the reaction and the part of the desulfurization agent that is not involved in the reaction will enter the subsequent dust removal system, and what is retained is the by-product desulfurization ash. This desulfurization ash contains a large amount of calcium sulfite, which leads to its unstable nature; it is easily oxidized and expands in volume, and, if used in the field of building materials, it will lead to cracking and other problems, so it is difficult to effectively use it. In order to solve this problem, XRF, XRD, and iodometric and other analytical methods were used to determine the specific composition of desulfurization ash, and the muffle furnace and vertical tube furnace were used to study the thermal oxidative modification of calcium sulfite in desulfurization ash, to investigate the effects of the oxygen content, reaction temperature, medium flow rate, and chloride content on the oxidation of calcium sulfite, and to analyze the thermodynamics in the high-temperature oxidation reaction. The results showed that the oxidation rate of calcium sulfite increased with higher reaction temperatures. Increased oxygen content promoted the oxidation rate, particularly at low oxygen levels. The oxidation rate of calcium sulfite correlated positively with the medium flow rate until a rate of 75 mL·min− was reached. At a reaction temperature of 420 °C and a gas flow rate of 85 mL·min−1, the oxidation conversion efficiency exceeded 89%. Chloride content significantly reduced the oxidation rate of calcium sulfite, although this inhibition weakened at temperatures above 500 °C. Kinetic analysis suggested that the oxidation reaction of calcium sulfite predominantly occurred below 500 °C. These findings have both theoretical and practical implications for the thermal oxidation treatment and disposal of desulfurization ash.

Numerical study of particle behaviours and heat transfer in a complex rotary kiln

Rotary kiln is widely used for thermal disposal of solid waste due to its effectiveness and high efficiency in recent years. To further improve the processing efficiency, a newly designed rotary kiln with three-section structure is proposed, and the behaviours of particle motion and heat transfer are investigated. Firstly, a lab-scale rotary kiln is manufactured, and experiments are carried out. Verified by experimental data, a CFD-DEM numerical model is developed to analyze the particle motion and heat transfer characteristics with the effects of inlet flue gas temperature, feeding rate and rotating speed. The results show that the outlet temperature increases linearly with the flue gas temperature, while it is negatively correlated with the feeding rate and rotating speed. In addition, the volumetric heat transfer coefficient in this complex rotary kiln is analyzed, the overall heat transfer coefficient is between 200 and 700 W/(m3 K).

Effects of thermal disposal of oil-water residues on operation heating plant boiler

Industrial zones are often the source of specifically polluted waters, depending on type of industry. These waters are usually not in the limits for outtake into public sewers and it is necessary to dispose them externally or build-up technologies for their pre-treatment. The article is about the real case of an industrial. A separate sewage network is built for oily water. Solid impurities are separated from the oily water and oily water is treated by evaporation technology. The evaporator produces two types of products - condensate and concentrate. Condensate is a water with high organic content, and it is necessary to purified it by a chemical treatment plant in next step. Evaporator technology remove from water the most of metal content and significantly decrease organic and water content in concentrate. Concentrate is oily stream with lower water content. Water content in concentrate decreased in next technology steps to ca. 40-50 %. The final product is certificated technological fuel, and its final elimination is in the heating plant fluidized bed boiler. The article is detailed focused on the influence of concentrate combustion. A local temperature increases around 10-15 °C extending across the combustion chamber was confirmed. There was also an increase in HF concentration in flue gas. CO concentrations were higher in the first moments of combustion, but the control system responded by increasing the combustion air supply, and CO concentrations were finally lower at the level of 3 mg·m-3. During combustion, there was no provable increase in concentrations of NOX or other substances, and the co-combustion did not have a significant effect on the operation of the boiler, so this way was evaluated like technically and economically effective.

INCREASING THE EFFICIENCY OF FUEL-FIRED PLANTS WITH DUSTY WASTE GASES

The results of a set of thermal calculations of the air-heating heat exchanger of the dusty waste gases of the thermal disposal of household waste are given. The initial data for the calculations were taken in the practical range when incinerating 1t/h of household waste from the experience of using the specified installations. The heat-recovery unit is designed to heat air for combustion by recovering the heat of the exhaust gases leaving after the turbine of this installation. Its design solution is characterized by the possibility of cleaning work surfaces from deposits of technological dust. The thermal indicators (temperatures of coolants and heat productivity) of the proposed heat-recovery unit under the conditions of its use for waste incineration plants were investigated. Calculations were performed in different modes of operation of the heat-recovery unit during the year, namely: at inlet temperatures of air and exhaust gases in the range from -20 to +20 ºС and from 200 to 300 ºС, respectively, the coefficient of excess air in waste gases from 1.5 to 2, 5 and different levels of dust on the heating surface. The influence of dustiness on the thermal parameters was characterized by the coefficient k, which determined the level of reduction in the thermal efficiency of the heat exchanger as a result of dust deposits on the specified surface and varied in the range from 1 to 0.5. Under the considered conditions was established, that use of the proposed air heater it provides heat output of 72 ÷ 263 kW, cooling of flue gases to a temperature of 107 ÷ 245 °С and heating of air to 96 ÷ 220 °С. At such levels of flue gas cooling, the efficiency of the thermal disposal of household waste increases by 2 ÷ 5%. In the case of a decrease in the heat-recovery capacity of the heat-recovery unit to technologically unacceptable levels, it is necessary to carry out its forced cleaning with compressed air, as provided for in the technical solution of such an air heater.

HOSPITAL WASTE – LEGISLATIVE FRAMEWORK AND MANAGEMENT DIFFERENTIATIONS IN AUSTRIA, BELGIUM, GERMANY AND GREECE

In this paper, the differences regarding hospital waste management, specifically regarding the legal and technical situation and the definition of hazardous hospital waste in four member states (Austria, Belgium, Germany and Greece) are presented. All countries follow the legal guidelines of the European Union, but the technical situation, especially the possibilities for thermal waste disposal in incineration plants are different. Also, the definition and categories of hazardous medical wastes is different in the aforementioned four EU member states. The annual production amounts of medical waste in selected countries are presented, as well as criteria that lead to their classification as hazardous medical waste.

IMPROVED LEVEL OF TECHNOGENIC SAFETY IN PLANTS INTENDED MUNICIPAL SOLID WASTE INCINERATION

Solid municipal waste can be an alternative and renewable type of fuel. Waste incineration provides effective disposal, significant volume reduction and utilization of the energy potential of the carbon waste part. In order to protect the components of the biosphere and service personnel from harmful substances that are formed in the furnace space, it is first necessary to assess the chemical composition and volume of emissions. The purpose of the work is to study the process of burning municipal waste, determine the heat energy obtained, determine the amount of air required for the complete combustion reaction, and determine the volume of flue gases produced as a result of combustion. To achieve the goal of the research, a complex of methods of system analysis and the method of data analysis was applied. An analysis of modern international literary sources, an analysis of the morphological composition of the combustible part of solid household waste, and an analysis of the interaction of chemical substances was carried out. For the research, several components of waste were collected, which were conditionally divided into two main groups - paper and plastic. The first group includes waste, which includes wood, cardboard, and paper. The second group (plastic) includes waste, which includes plastic in the form of scraps of polyethylene film, disposable dishes. As a result of the research, a theoretical volume of combustion products was obtained for the further design of the system of protection of the environment and service personnel from emissions of thermal disposal of solid household waste. Research results can be used in the design of municipal waste incineration equipment. The system of using the heat of flue gases generated after burning waste to dry the waste before feeding it to the furnace is of great importance for saving additional fuel.

Термическая утилизация отработанных масел

Pollution of the environment with petroleum products is a serious environmental problem. There are several ways to dispose of used oils: regeneration, burial and incineration. The burning of waste oils is widespread both in Russia and abroad. One of the significant disadvantages of the method is the entry of harmful substances into the atmosphere. The results of research on the development of a more advanced installation of thermal utilization of waste oils, ensuring the completeness of combustion and reduction of harmful emissions, are presented. The unit for thermal disposal of waste oils consists of a furnace and an emulsion nozzle. The furnace from the furnace chamber and the afterburning chamber of the flue gas provides two-zone, two-stage oil gorenje. Oil is burned in the combustion chamber (1st gorenje zone with t ≈ 600–700 оC). Then the smoke enters the afterburning chamber, where it is completely burned due to the supply of additional air (2nd gorenje zone with t ≈ 1200–1300 оC), due to the increase in temperature, toxic substances contained in the smoke are transformed into harmless due to their complete oxidation. The emulsion nozzle consists of intersecting grooves, which, when air and heated oil are fed into it, provide finely dispersed oil spraying by forming gas-liquid vortices in the oncoming grooves. Using the ANSYS program, the calculation of the flame angle of the emulsion nozzle was carried out. It is established that to change the range of the spraying torch and the use of emulsion nozzles in furnaces of different volume and power, it is necessary to change the angle of the screw direction. This research contributes to the development of the industry of processing of production and consumption waste. The proposed solution allows the installation to be used not only in industrial centers where significant volumes of waste oils accumulate, but also in sparsely populated areas, and also ensures the completeness of combustion of oil waste and reduces the negative impact on the environment.

Synergistic co-combustion of carbon-rich fraction from coal gasification fine slag and corncob char: Performance, mechanism, kinetics, and thermodynamics

Coal gasification fine slag (FS) is a coal-based solid waste with high carbon content, and landfill-based disposal causes water-soil-gas composite pollution. Co-combustion is a common method of solid waste thermal disposal, and corn cob is used as an auxiliary fuel for co-combustion because of its energy density and ease of handling and processing. In this paper, the thermal degradation characteristics, interaction mechanism, kinetics, and thermodynamics of co-combustion RC (carbon-rich fraction obtained by flotation) and CC (corncob char) were studied. The results showed that physicochemical properties suggested that RC and CC will complement and promote each other in the combustion process. The addition of CC reduced the RC ignition temperature and improved the overall combustion performance. The interaction effect was mainly due to metal catalysis, the effect of the porous carbon structure, the thermal effect, and the hindering effect of ash. The activation energy was reduced due to the blending of RC-CC, and the activation energy was lowest (132.19 kJ/mol) when the RC adding ratio was 60%. The co-combustion process was controlled by the F3 model (chemical third-order reaction kinetics), and it was a typical gas-solid phase reaction with a progressive process from the outsides toward the insides. Thermodynamic analysis showed that the co-firing process was an extremely complex multi-stage reaction. The results of this study provide a theoretical reference for the synergistic resource utilization of coal gasification fine slag and waste biomass.

Free radical formation via BDE-209 thermolysis in the precalciner of a cement kiln: Simulation and DFT study

To deeply understand the formation mechanism of polybrominated dibenzo-p-dioxins/furans (PBDD/Fs) in the thermal disposal process of polybrominated diphenyl ether (PBDE)-containing waste, this paper studied the formation pathways of key intermediates (free radicals, FRs) in the formation process of PBDD/Fs. BDE-209, the most common PBDE in the environment, was selected as the object of study to analyze FR formation by simulating the key conditions such as temperature (850 °C) and Fe-based materials when PBDE-containing waste entering cement kiln precalciner. Electron paramagnetic resonance (EPR) spectroscopy and density functional theory (DFT) calculations were used to study the reaction. The result of simulation experiments revealed carbon-centered radicals, and DMPO-OH analysis further confirmed the generation of FRs. The findings confirmed previous calculations predicting the existence of radical intermediates during the formation of PBDD/Fs from BDE-209. DFT calculations revealed the existence of an inner ortho-position CBr bond in BDE-209. The priority order of the bond breaking of BDE-209 was ether bond, inner ortho-position CBr bond, and outside ortho-position CBr bond. BDE-209 can further form three kinds of FRs, namely, oxygen-centered radicals of single benzene rings, carbon-centered radicals of single benzene rings, and carbon-centered radicals of double benzene rings. The specific processes of FR formation were inferred: high-temperature homogeneous cleavage of chemical bonds, electron transfer, and chemisorption, where electron transfer and chemisorption may be more important pathways. The proposed inner ortho-position cleavage within BDE-209 provides new insights into the degradation of PBDEs and the formation of PBDD/Fs; the results regarding BDE-209 generation radicals further elucidate the synthesis mechanism of dioxins, which is important for controlling dioxin generation and emission during the treatment and disposal of waste containing PBDEs.

Release characteristics of chromium and sulfur during cothermal disposal of waste tires and sludge: An experimental and DFT study

Chromium (Cr) and sulfur-containing pollutants (S) are released during thermal disposal of municipal sludge (MS) and waste tires (WTs). In this paper, the effects of the mixing ratio, temperature, atmosphere, and CaO on Cr release were determined, and the mechanism for Cr trapping during CaO sulfation was revealed with density functional theory (DFT). The MW (MS and WTs) thermal decomposition behavior, sulfur-containing pollutant release, and kinetic parameters were analyzed. The results showed that the thermal disposal of MW at 850 °C under flue gas immobilized the Cr, and the relative enrichment (RE) for Cr reached 92.66 % when the proportion of WTs was 50 %. DFT calculations revealed the effect of CaO sulfation on Cr adsorption. The energies for CrOOH adsorption on the (001) surface of CaO, and the (001) surface of CaSO4 decreased sequentially. The products of the CrOOH transformations in the flue gas, CrCl3 and CrO2Cl2, also diminished in that order for the corresponding surfaces. Typical decomposition steps were observed, including volatilization of water and small hydrocarbons, cracking of hydrocarbons, and transformations of inorganic materials at higher temperatures. H2S, SO2, CH3SH, and COS were the main sulfur-containing pollutants released during thermal disposal.

ENVIRONMENTALLY SAFE OPERATION OF MUNICIPAL WASTE INCINERATION

The technology of waste incineration makes it possible to solve the issue of obtaining an alternative type of fuel and eliminate the problem of the excess waste in landfills. A multi-stage emission cleaning technology has been proposed to protect the environment and service personnel. The chemical processes that take place in the furnace space have been considered.
 The purpose of the research is to develop the concept of control systems for the technological cycle of the installation of thermal disposal of solid household waste to protection of the environment from these toxic substances: dioxins, carcinogenic hydrocarbons, products of incomplete combustion, in particular, polycyclic aromatic hydrocarbons, nitrogen and sulfur oxides. A complex of methods of system analysis and the method of data analysis was applied to achieve the goal of the research. An analysis of modern international literary sources, an analysis of the morphological composition of solid household waste, an analysis of the interaction of chemical substances, and experimental studies at a research and industrial facility were carried out. As a result of the research, the scientific and applied task of improving the system of protection of the environment and service personnel from emissions of thermal disposal of solid household waste was formulated and substantiated.
 Research results might apply to designing equipment for waste incineration, for choosing rational parameters of the furnace, location of fuel supply burners. General recommendations for the use of chemical properties of harmful substances in the design of cleaning equipment have been provided. The effectiveness of the method of supplying an inert medium (flue gases) to the combustion zone at a temperature below the flame temperature was evaluated. Effective thermal destruction of dioxins is possible in modern waste incineration plants, provided high temperatures, excess air and sufficient residence time followed by a catalytic cleaning. Homogeneous and heterogeneous formation of polychlorinated dibenzodioxins and polychlorinated dibenzofurans formed and released in zones with relatively low temperatures.

Chemical Speciation Distribution and Thermal Stability of Heavy Metals along Flue Gas Cleaning Systems in a Hazardous Waste Incinerator

Hazardous heavy metals may release from incineration residues in the utilization concerning heat treatment or landfills, which would cause great harm on the environment. The evaluation of chemical speciation and thermal stability of heavy metals are of great significance for the control of heavy metal pollution during heat treatments. In this study, chemical speciation distribution and thermal stability of heavy metals (As, Cd, Cr, Cu, Pb, Se, Zn, and Hg) along flue gas cleaning systems were investigated in a hazardous waste incinerator located in Zhejiang, China. The chemical speciation and thermal stability of heavy metals, environmental risk evaluation, and morphological and mineralogical characteristics of incineration residues were assessed before and after heat treatments. Results indicated that the chemical speciation of heavy metals in the bottom slag, burn-out chamber ash, boiler ash, and bag filter ash varied significantly. The thermal stability of heavy metals in the incineration residues was significantly influenced by chemical speciation, and the thermal stability of the chemical speciation decreased basically in the order of residual form > reducible form > oxidizable form > acid soluble form. As, Cr, and Se showed high thermal stability due to the fact that they were involved in the crystallization reaction, and heat treatment would promote the transformation from mobile fractions into the residual fraction. Hg and Cd displayed the worst thermal stability, and high-temperature heat treatment would contribute to secondary volatilization from the incineration residues. More attention should be paid to the secondary volatilization of Hg and Cd during thermal disposal. Cu, Pb, and Zn had moderate thermal stability, and heat treatment would cause the volatilization of mobile fractions and the transformation from mobile fractions into the residual fraction. Pretreatments such as water-washing or adding a chemical stabilizer would be conducive to reducing the volatilization of heavy metals during thermal disposal.

Feasibility of thermal disposal masks in domestic waste incinerators: a study on the combustion characteristics, gaseous pollutant emissions characteristics and control of masks

ABSTRACT Discarded disposable medical masks generated due to the COVID−19 epidemic are overwhelming the current medical waste disposal facilities. Thermal disposal masks in domestic waste incinerator can both utilize the heat energy released by their combustion and dispose of the headache-inducing masks in a harmless manner. The masks are divided into 6 parts: white inside (WI), filter (FI), blue outside (BO), bonding of 3 parts (BP), ear strap (ES) and nose wire (NW). The highest burnout temperature (Tb) of each part of the mask was only 481.2°C and had a high HHV of 40.47 MJ/kg, which has a high energy potential as an energy source. The NOx, SO2, and HCl emission characteristics of each part of the masks were evaluated in a fixed-bed reactor. BP, BO, and ES contradict SO2 and HCl emission limits in China. The SO2 and HCl emission peaks of the masks with the addition of 10 wt% Ca(OH)2 did not exceed 60 mg/m3, which made the combustion emissions of the masks comply with GB 18,485–2014. Considering subsidies for disposal of masks and power generation, blending masks with a 1%−5% ratio enhances the subsidy revenue of waste incineration power plants by 12.63%−63.13%.

Thermal Disposal of Post-processing Water Derived from the Hydrothermal Carbonization Process of Sewage Sludge

Hydrothermal carbonization is a suitable method for sewage sludge management due to great improvements in its dewaterability and the successful application of its solid product, hydrochar, in different sectors. However, the resulting liquid product requires special treatment due to the amount of undesirable compounds it contains. The main purpose of this work is to study the use of distillation as a method of post-processing liquid purification. In addition, the influence of vacuum depth on the properties of liquid products was investigated. A number of chemical and physical parameters were determined to confirm the validity of this treatment method: TOC, COD, total nitrogen Kjeldahl content, ammonium nitrogen content, phosphorus, magnesium, calcium, selected heavy metals content and phenol index. Distillation under atmospheric pressure caused reductions in the following parameters: COD, TOC, phenol index, heavy metals, chlorine by more than 90%: removal of 95% COD and TOC, 99.5% of PO4-P, 93% of Phenol, over 90% of heavy metals, and over 97% of free and total chlorine. In the case of distillation under -0.3 bar pressure, the following reductions were obtained: 97% of COD, 98% of TOC, 99.9% of PO4-P, 94% of Phenol, c.a. 98% of heavy metals, and more than 98% of free and total chlorine. Decreasing the pressure to − 0.5 bar did not producee any significant effects as the results were similar to distillation under atmospheric pressure. Both methods, distillation and distillation under lower pressures, can be used as an appropriate method of post-processing water utilization.Graphical

Повышение эффективности пиролизной переработки твердых коммунальных отходов

The disposal of waste by direct combustion method is prohibited in the Russian Federation due to the negative impact on the environment. An alternative option is solid waste pyrolysis technology, which allows not only to significantly reduce the amount of waste that requires disposal, but also to obtain various types of energy carriers. Existing installations allow recycling waste with humidity up to 30–35 %. An increase of humidity over 40 % requires additional energy sources for the drying process. To increase the efficiency of waste recycling by pyrolysis, it is necessary to improve the technology and to design an energy-efficient waste disposal plant. The use of the heat of combustion products in the heat exchanger to heat the air going into the drying chamber will increase the range of processing of wet waste. To determine the efficiency of the furnace for thermal waste disposal, the method of material and thermal balance is used. It allows determining the efficiency of the installation and selecting its operating mode with its maximum value. The paper proposes a new design of a waste disposal furnace with separate drying and pyrolysis chambers, as well as a mathematical model based on the equations of thermal and material balance. The design feature of the installation allows you to organize the controlled drying of wet waste and reduce losses with combustion products by using a heat exchanger for air heating. The proposed installation allows the waste recycling process to be carried out at a relative humidity of 0 to 60 % without additional energy sources. The efficiency of the waste varies from 61,5 to 80 % when the plant is operating on dry waste and from 42 to 62 % when operating on wet waste.