Coal-water slurries containing petrochemicals to solve problems of air pollution by coal thermal power stations and boiler plants: An introductory review

Study on motion behaviour of coal water slurry particles under vibration conditions

This study uses computational fluid dynamics (CFD) to simulate the motion behavior of coal-water slurry (CWS) particles under vibration conditions. Results show that without vibration, the coal particles settle to the bottom of the container due to gravity, forming distinct regions of low, transition, and high concentration. Under low vibration intensity, the slight energy activates particle motion and promotes settlement. Under high vibration intensity, violent reciprocating motion causes severe shaking and uncertainty, resulting in non-uniform particle distribution and back mixing. Particle velocity distribution is significantly influenced by vibration, with higher frequencies and amplitudes resulting in greater velocities. Additionally, particle pseudo-temperature is higher in the near-wall area due to collisions with particles and wall surfaces. Low frequency and amplitude promote particle settlement, increasing compactness in the bottom area and reducing concentration in the top area. The findings provide valuable insights into CWS behavior under vibration conditions, which can be used to optimize the design and operation of CWS handling and transportation systems.

Modified lanthanide-doped carbon dots as a novel nanochemosensor for efficient detection of water in toluene and its potential application in lubricant base oils

A fast and efficient method was developed for obtaining europium(III)-doped surface-modified carbon dots with a hydrophobic coating. This surface functionalization improved the dispersibility of the nanoparticles in non-polar media, as well as modified the accessibility of water molecules to the europium ions. These two features allowed studying the application of doped carbon dots as moisture nanochemosensor, demonstrating high stability over time of both the photoluminescent signal intensity and the stability of the dispersions. The developed nanochemosensor was used to determine water in toluene with a detection limit of 8.5 × 10^-4 M and a quantification limit of 2.4 × 10^-3 M. The proposed system matches and even improves other methodologies for water determination in organic solvents; it has a low detection limit and a fast response time (almost instantaneous) and requires neither expensive material nor trained personnel. The results suggest a promising future for the development of a new sensing phase for moisture determination in lubricant base oil.

Selenite and tellurite reduction by Aspergillus niger fungal pellets using lignocellulosic hydrolysate

The performance of Aspergillus niger pellets to remove selenite and tellurite from wastewater using batch and continuous fungal pelleted bioreactors was investigated. The acid hydrolysate of brewer's spent grain (BSG) was utilized by A. niger as the electron donor for selenite and tellurite reduction. The dilution of BSG hydrolysate using mineral medium had a positive effect on the selenite and tellurite removal efficiency with a 1:3 ratio giving the best efficiency. However, selenite and tellurite inhibited fungal growth with a 40.9% and 27.3% decrease in the A. niger biomass yield in the presence of 50 mg/L selenite and tellurite, respectively. The maximum selenite and tellurite removal efficiency using 25% BSG hydrolysate in batch incubations amounted to 72.8% and 99.5% Two fungal pelleted bioreactors were operated in continuous mode using BSG hydrolysate as the substrate. Both the selenite and tellurite removal efficiencies during steady state operation were > 80% with tellurite showing a maximum removal efficiency of 98.5% at 10 mg/L influent concentration. Elemental Se nanospheres for selenite and both Te nanospheres and nanorods for tellurite were formed within the fungal pellets. This study demonstrates the suitability BSG hydrolysate as a low cost carbon source for removal of selenite and tellurite using fungal pellet bioreactors.

A review of application and development of combustion technology for oil sludge

Oil sludge is a typical hazardous waste in the petrochemical and electric power industry. It has complex components and special properties, and has serious hazards to humans, plants, water, and soil. Therefore, how to realize the effective disposal of oil sludge has become an urgent issue to be solved worldwide. Among the existing oil sludge treatment approaches, combustion has been considered to be a promising technology to realize the large-scale industrial application. In the present work, the characteristics of oil sludge were described in detail. The application and development of oil sludge combustion technology were critically summarized and discussed, including factors affecting combustion, drying process, combustion characteristics, synergistic treatment technology, and formation and control of secondary pollution. Besides, the development of combustion equipment, and integrated thermal treatment technology for oil sludge were prospected. This work can be used for guiding the industrial disposal of oil sludge.

Modeling Challenges for Improving the Heat Rate Performance in a Thermal Power Plant: Implications for SDGs in Energy Supply Chains

Rapid industrialization and the increased use of consumer electronic goods have increased the demand for energy. To meet the increasing energy demand, global nations are looking for energy from renewable sources rather than non-renewable sources, to adhere with the sustainability principle. As energy from renewable sources is still in the experimental stage, there is a need to use available energy sources optimally. Considering this, the present study aims to identify, evaluate, and reveal the interrelationship among critical challenge factors in improving the heat rate performance of coal-fired thermal power plants. The study identifies twenty critical challenges through a comprehensive literature review. Then, to evaluate the identified critical challenges, the grey-DEMATEL (Decision Making Trial and Evaluation Laboratory) technique is used. For evaluating the challenges, this study conducts an empirical analysis in a thermal power plant in India. The findings reveal that air preheater leakage, coal flow balancing, and air heater air outlet temperature are the top three critical challenges hampering the thermal power plant’s performance. Additionally, fourteen challenges come under the cause group, while eight challenges come under the effect group. The findings of the study can assist industrial managers in overcoming problems in their thermal power plants. The results can also guide the development of a robust and reliable framework for mitigating these challenges.

Municipal solid waste management: Dynamics, risk assessment, ecological influence, advancements, constraints and perspectives

Global energy consumption has been increasing in tandem with economic growth, putting pressure on the world's supply of renewable energy sources. Municipal Solid waste (MSW) has been reported contributing immensely to the improvement of a secure environment and renewable sources. Energy scarcity and conventional MSW disposal methods in developing countries lead towards many environmental and economic issues. Scientists have been able to experiment with various waste-to-energy conversion technologies in light of this situation. This communication highlights and reviews WtE technologies to convert MSW and other feedstocks into electricity, hydrogen gas, bioethanol along with other value added products like fertilizer(s), platform chemicals as an environmentally friendly products. This review comprehensively summarized the dynamics, risk assessment, ecological influence, advancements, constraints and perspectives altogether in field of municipal solid waste management and treatment. Stare-of-the-art information on ecological influence and risk assessment in handling and transportation of municipal solid waste has been provided. Advanced trends involved in remediation of emerging pollutants and resources obtained from municipal solid wastes have been uncovered. Lastly, this paper comprises constraints and perspectives for uncovering MSW based circular bioeconomy aspects.

Switching Coal-Fired Thermal Power Plant to Composite Fuel for Recovering Industrial and Municipal Waste: Combustion Characteristics, Emissions, and Economic Effect

Combustion characteristics were studied experimentally for single droplets of fuel slurries based on wet coal processing waste with municipal solid waste components (cardboard, plastic, rubber, and wood) and used turbine oil. We established the ignition delay time for three various groups of fuel compositions in motionless air at 600–1000 °C. The minimum values are 3 s, and the maximum ones are 25 s. The maximum temperatures in the droplet vicinity reach 1300 °C during fuel combustion for compositions with 10% of used oil. The combustion temperatures of fuel compositions without oil are 200–300 °C lower. The concentrations of anthropogenic emissions in flue gases do not exceed those from dry coal combustion. Adding used oils to composite fuels reduces the concentrations of dioxins and furans in flue gases when municipal solid waste in the fuel burns out due to high combustion temperatures. Based on the experimental research findings, we have elaborated a strategy of combined industrial and municipal waste recovery by burning it as part of composite fuels, as illustrated by three neighboring regions of the Russian Federation with different industrial structures and levels of social development. This strategy suggests switching three typical coal-fired thermal power plants (one in each of the regions) to composite liquid fuel. It will reduce the hazard of waste to the environment and decrease the consumption of high-quality coals for power generation. Implementing the developed strategy for 25 years will save 145 Mt of coal and recover 190–260 Mt of waste. The positive economic effect, considering the modernization of fuel handling systems at thermal power plants and the construction of a fuel preparation plant, will make up 5.7 to 6.9 billion dollars, or 65–78%, respectively, of the main costs of three thermal power plants operating on coal within the identical period.

Ignition of Slurry Fuel Droplets with Different Heating Conditions

This paper describes modern research methods of the ignition and combustion processes of slurry fuel droplets. The experiments were carried out using a muffle furnace to ensure the conditions of radiation heating, the hot surface to reproduce the conditions of conductive heating, the high-temperature channel with convective heating, the chamber with the processes of soaring, i.e., a significant increase in the time of fuel residence in the combustion chamber. We identified the differences in combustion modes, threshold ignition temperatures, delay times and durations of combustion processes. We obtained the quantitative differences in the characteristics of the ignition and combustion processes for typical registration methods. It was found that for all heating schemes, the minimum ignition temperatures have comparable values. Minimum ignition delay times were recorded during convective heating. The maximum combustion temperatures were achieved with radiation heating. We determined the values of limiting heat fluxes, sufficient to initiate the combustion of slurries fuels during conductive, convective and radiative heating.

Effective incineration of fuel-waste slurries from several related industries

This study is based on the analysis of a set of industrial sectors (coal processing, wood processing, transport, oil, and water treatment) in order to identify the amount and type of combustible waste suitable for incineration. The main ignition and combustion parameters of these wastes have been experimentally obtained from their direct individual incineration in the original form and as part of a slurry based on wastewater. It has been established that a set of parameters allow waste-derived fuel mixtures to compete with coal dust and fuel oil with an environmental advantage. In particular, the concentration of sulfur and nitrogen oxides in the combustion products of all the tested slurries is 1.5-3 times as low as that of coal dust. Most of the wastes in question do not provide such advantages when burnt individually. We have assessed the fire safety of fuel mixtures and analyzed the prospects of mass waste incineration technologies. The calculations show that about 14-20% of coal and oil can be saved annually by extensively involving industrial waste in the energy sector. The experimental results obtained are the basis for the development of useful technologies for the safe and efficient combustion of waste from different industries.

Prospects of thermal power plants switching from traditional fuels to coal-water slurries containing petrochemicals

The amount of thermal and electric energy produced by coal combustion increases nonlinearly, because the production capacities and consumption of the corresponding energy are on the rise. The prospects of excluding coal from the picture are slim, because it has been traditionally considered one of the most attractive fuels in terms of cost and heat of combustion. What we need is major changes in the energy industry towards environmentally effective use of coals and their processing wastes. In this research, we show the possibility of coal-fired thermal power plants and steam shops switching to coal-water slurries containing petrochemicals (CWSP). Extra calculations are made for fuel oil and natural gas. The scientific novelty of the research consists in the comprehensive consideration of all the possible technological modifications in the fuel feeding, storage, and preparation system. We focus on potential benefits of thermal power plants and steam shops switching from coal, gas, and fuel oil to coal-water slurries containing petrochemicals, while taking into account all the main and most important environmental, economic, and energy performance indicators. Using CWSP instead of coal is much more environmentally friendly. By varying the content of water and additives in CWSP, we can lower the proportion of sulfur and nitrogen and slow down their oxidation. It is also possible to reduce temperature in the combustion zone and improve oxide retention in the ash without its release in the form of anthropogenic emissions. Throughout the world, tens of thousands of fuel oil and coal-fired TPPs with the annual gross electric output of 1.8 TW can switch to CWSP. The integrated performance indicators of CWSP fuels are only inferior to those of natural gas but these slurries are prepared from numerous industrial wastes.

Hazardous waste dewatering and dry mass reduction through hydrophobic modification by a facile one-pot, alkali-assisted hydrothermal reaction

Hazardous waste dewatering is important for volume reduction and further treatment. Hazardous organic wastes with low ratio of free to bound water, and low flash point are difficult to dewater and pose an explosion risk for conventional thermal drying. Here, we develop a facile one-pot, alkali-assisted hydrothermal treatment (AHT) method for cost-efficient hazardous waste dewatering, dry mass minimization and volume reduction. Wet paint sludge (WPS), a hazardous organic waste, was reduced (79% by total weight and 52% by dry mass) by dewatering through AHT hydrophobic modification, and the product was nonflammable. Conversion of bound water to free water enhanced WPS dissolution for further decomposition. Alkali was critical for boosting ether demethylation in the solid phase, and cleavage of ethers forming alcohols that facilitated transfer of solid mass into the liquid phase. Polar functional groups were eliminated through AHT, which increased the relative abundance of hydrophobic functional groups on the surface of solid residues and promoted dewatering. We also demonstrate that AHT can be widely adapted and scaled up to treat various hazardous organic waste streams, which is of significant industrial and environmental interest.

Municipal solid waste recycling by burning it as part of composite fuel with energy generation

In this work, it has been shown that the involvement of composite fuels in thermal power engineering will enable to recycle both industrial and municipal combustible wastes while saving fossil fuels. The ignition and combustion stability of composite fuel droplets up to their complete burnout was experimentally substantiated under the conditions typical of boiler furnaces, using the example of several fuel compositions with wood, food waste, plastic, and cardboard, each added separately. The values of the guaranteed delay times for the ignition of droplets with a size of about 1 mm were established for the considered fuel compositions in a wide range of the ambient temperature variation (600-1000 °C). The minimum values of ignition delay times were about 3 s, the maximum values were about 25 s. It was established experimentally that the concentration of nitrogen and sulfur oxides in flue gases was lower for the fuel compositions containing municipal solid waste (MSW) in comparison with those without it. The maximum difference between NO_x and SO_x concentrations for such fuel compositions was about 60% and 35% (in absolute units about 110 ppm and 45 ppm). As a result of the theoretical analysis, it was found that partial replacement of coal (50% of energy generation) by composite fuel in the amount equivalent in terms of energy generation will save about 1 billion tons/year of high-quality solid fossil fuel in the course of 20 years (the regulated period of safe operation of a boiler in thermal power engineering).

Study connective capabilities of solid residues from the waste incineration

Currently there is increasingly closer interaction between the importance of environmental protection and efficient promoting of scientific and technological progress in the field of waste incineration. Waste is not only undesirable source of pollution, but if it is effectively used it also has great economic importance. In the Czech Republic 34.5 million tonnes of all wastes was produced in 2017, of which 5.7 million tonnes of municipal waste. 50% of the produced municipal waste was used, 38% of which was used for the material and 12% for energy utilization. 45% of municipal waste was deposited in the landfills. The method of waste incineration is among the major tools to reduce the landfill waste. The use or processing of the product which the process of incineration of municipal and hazardous waste generated can be considered as an obstacle to the favorable reception of this process. Apart from flammable components, waste also contains certain amount of dangerous particles. This is especially the sulfur chlorides, fluorine, PCBs and other heavy decomposable organic substances and heavy metals. This fact puts high demands on the gas cleaning processes followed by neutralization of other products that the incinerator leaves, in which these substances can be contained in higher concentrations than in the original waste. For this reason subsequent stabilization of these toxic substances is necessary to ensure new environmental burdens are avoided when not used properly. The major part of the waste combustion process is made up of ash and slag. One of the most common ways of dealing with these solid residues is disposing them to avoid creating new hazardous waste landfills. Other filtering waste also passes hazardous waste stabilization process before landfilling. Currently there is intensive search for new possibilities for utilization of solid residues from incineration. Nowadays there is emphasis on process control of their pretreatment for the production of draft procedure with its management. Appropriate procedures may minimize the instances of improper use.

Studies on CWL with glycerol for combustion process

Findings of more efficient energy recovery methods are focused on composite fuels consisting of coal, water, and waste materials. The use of such slurry fuels has enormous environmental benefits due to the potential for waste utilization and low emissions of harmful oxides to the atmosphere during the combustion process. In this study, we report the effect of waste glycerol on the rheological properties of coal-water fuel (CWS). The addition of glycerol to CWS increases the viscosity (from 45.5 to 184.2 mPa·s at a shear rate of 100 rpm) and density (from 1.08 to 1.11 g/cm³) of these suspensions. The utility of choice of the most favorable parameters is equal to 0.85 for both CWS and CWS with added glycerol. Due to the fact that CWS is dosed to heated chamber, its modification with glycerol results in easier nebulization into the combustion chamber, lowering of the solidification temperature and increasing the calorific value of the resulting fuel. During combustion of CWS with glycerol, the amount of SO₂ and NO_x emitted is reduced by half as compared to the emission of these gases during hard coal combustion.

The influence of liquid plant additives on the anthropogenic gas emissions from the combustion of coal-water slurries

At present, coal is considered one of the main components for the production of cheap, high-energy and environmentally attractive slurry fuels. The latter can be produced on the basis of low-grade coal dust or coal processing wastes. Thus, coal-water slurries and coal-water slurries containing petrochemicals are produced. The involvement of coal and oil processing wastes expands the scope of raw materials, reduces the fuel costs from traditional energy sources and modifies the main economic characteristics of power plant performance. However, it also increases the impact of coal-fired thermal power stations on the environment. In the last 30-50 years, many efforts have been made to decrease the negative impact of human industrial activity on climate. Involving plant-based components in the process of energy generation to save energy and material resources looks very promising nowadays. This research studies the influence of adding typical bioliquids (bioethanol, turpentine, glycerol) on the concentration of anthropogenic emissions from coal-water slurry combustion. Relative mass concentrations of bioliquids varied in a small range below 20%. We focused on the concentration of the most hazardous sulfur and nitrogen oxides from the combustion of typical filter cakes, as well as plant-containing slurries. It was established that the concentration of sulfur oxides can be decreased (as compared to coal) by 75%, whereas that of nitrogen oxides by almost 30%. Using a generalizing criteria expression, we illustrated the main benefits of adding bioliquids to slurry fuels in comparison with coal. Adding 20% of glycerol was found to provide maximum advantages.

Lead Ion Sorption by Perlite and Reuse of the Exhausted Material in the Construction Field

This paper deals with the possibility of using perlite as a lead ion sorbent from industrial wastewater. Dynamic (laboratory column) operations were carried-out using beads, which were percolated by metals in a 2–10 mg·L−1 concentration range. To this purpose, lead ion solutions were eluted in columns loaded with different amounts of sorbent (2–4 g) within a 1–2 mm bead size range, at 0.15–0.4 L·h−1 flow-rates. Tests were performed to complete sorbent exhaustion (column breakthrough). The highest retention was obtained at 0.3 L·h−1, with 4 g of perlite and 10 mg·L−1 of influent, lead ion concentration. Film diffusion control was the kinetic step of the process in the Nerst stationary film at the solid/liquid interface. At the end of the sorption, perlite beads were used as lightweight aggregates in the construction field (i.e., for the preparation of cement mortars). Specifically, conglomerates showing different weights and consequently different thermal insulating and mechanical properties were obtained, with potential applications in plaster or panels.

Impact of Economic Growth and Energy Consumption on Greenhouse Gas Emissions: Testing Environmental Curves Hypotheses on EU Countries

This study analyses the relationship between per capita greenhouse gas (GHG) emissions, gross domestic product, gross inland energy consumption, and renewable energy consumption for a panel of 28 countries of European Union in the period 1990–2016. Two theoretical models, a quadratic and a cubic one, are used to estimate the shape of the environmental curve and to test the Kuznets hypothesis. The panel cointegration approach proved the existence of long-run equilibrium relations among the four macroeconomic indicators. Empirical estimations, using panel data techniques, as well as heterogeneous regression for each individual country in the panel, show non-conclusive evidence for the environmental Kuznets curve (EKC) hypothesis. The least square estimates, with the variables in log per capita form, reveal that the inverted U-shaped EKC hypothesis is verified for the panel and for 17 of the 28 EU countries. Estimates of the cubic model show that the environmental curve has an inverted N-shaped form. These results do not hold when the values are in non-logarithmic form. In addition, the estimations for all models show that an increase of gross energy consumption leads to an increase of GHGs, while an increase of renewable energy consumption leads to a reduction in GHG emissions.

Techno-Economic Analysis of a 600 MW Oxy-Enrich Pulverized Coal-Fired Boiler

Oxy-fuel combustion is one of the most promising methods for CO2 capture and storage (CCS) but the operating costs—mainly due to the need for oxygen production—usually lead to an obvious decrease in power generation efficiency. An “oxy-enrich combustion” process was proposed in this study to improve the efficiency of the oxy-fuel combustion process. The oxidizer for oxy-enrich combustion was composed of pure oxygen, air and recycled flue gas. Thus, the CO2 concentration in the flue gas decreased to 30–40%. The PSA (pressure swing adsorption), which has been widely used for CO2 removal from the shifting gases of ammonia synthesis in China, was applied to capture CO2 during oxy-enrich combustion. The technological economics of oxy-enrich combustion with PSA was calculated and compared to that of oxy-fuel combustion. The results indicated that, compared with oxy-fuel combustion: (1) the oxy-enrich combustion has fewer capital and operating costs for the ASU (air separation unit) and the recycle fan; (2) there were fewer changes in the components of the flue gas in a furnace for oxy-enrich combustion between dry and wet flue gas circulation; and (3) as the volume ratio of air and oxygen was 2 or 3, the economics of oxy-enrich combustion with PSA were more advantageous.