Residual Carbon Particles Research Articles

Physicochemical Characteristics of Residual Carbon and Inorganic Minerals in Coal Gasification Fine Slag.

Investigating the physicochemical properties and embedding forms of residual carbon (RC) and slag particles (SPs) in coal gasification fine slag (FS) is the basis for achieving its separation and utilization. An in-depth understanding of their compositional characteristics allows for targeted treatment and utilization programs for different components. In this work, the physicochemical properties and embedding forms of RC and SPs in FS were systematically investigated. An innovative calculation method is proposed to determine the mass fraction of dispersed carbon particles, dispersed mineral-rich particles, and carbon-ash combined particles by using a high-temperature heating stage coupled with an optical microscope. The unburned RC with a rough, loose surface and a well-developed pore structure acted as a framework in which the smaller spherical SPs with a smooth surface were embedded. In addition, the sieving pretreatment process facilitated the enrichment of the RC. Moreover, the RC content showed significant dependencies according to the FS particle size. For FS with a particle size of 0.075-0.150 mm, the mass proportions of dispersed carbon, ash particles, and the carbon-ash combination were 15.19%, 38.72%, and 46.09%, respectively. These findings provide basic data and reliable technical support for the subsequent carbon and ash separation process and the comprehensive utilization of coal gasification slag.

A case study of enhanced flotation of coal gasification fine slag by multiple compound collectors

ABSTRACT The flotation mechanism of multiple compound collectors called ZKC-I for coal gasification fine slag (CGFS) was revealed from the flotation kinetics, adsorption properties, bubble–particle interaction, and froth properties. The results were compared to dodecane, which represents the conventional nonpolar hydrocarbon oil collector. The flotation concentrates yield and rate constant of CGFS treated by ZKC-I were 2–3 times than those of CGFS treated by dodecane. Fourier transform infrared spectroscopy and wrap angle results showed that ZKC-I improved the hydrophobicity of residual carbon because of the synergistic adsorption of fatty acids, esters, and aromatic hydrocarbons in the ZKC-I on the heterogeneous surface of residual carbon particles, which enhanced the adhesion between residual carbon particles and bubble. Due to the strong carrying capacity of the bubble to residual carbon particles, the number of residual carbon particles in the froth treated by ZKC-I was more than that of the CGFS froth treated by dodecane. The high content of carbon particles in the froth resulted in great stability of the flotation froth, and the maximum height and half-life of the froth were higher than that of CGFS treated by dodecane. This study has practical and theoretical significance for the separation of coal-based solid waste.

Insight into the synergism of residual carbon and slag particles in coal gasification fine slag on porous composites preparation for CO2 capture

Coal gasification fine slag (FS), as a by-product of coal gasification process, contains residual carbon (RC) and slag particles (SP). The two components can be used as raw materials to prepare porous materials. Whereas, during simultaneous utilization of RC and SP, their synergistic mechanism remains unclear. The research on the mechanism is beneficial for synthesis of the high performance CO2 adsorbent. Herein, FS was treated by chemical activation followed by hydrothermal treatment to prepare porous composite material (FS-25-HA-HT) which had high surface area of 2194 m2/g and pore volume of 2.095 cm3/g. After chemical activation, the SP could be completely dissolved in alkali solution within around 20 min. The adsorption of porous carbon in alkali solution and strong electrostatic attraction from oxygen groups with the Si, Al-containing groups led to the increase of the concentration of Si (9825 ppm) and Al (2986 ppm) in subnatant during hydrothermal treatment. Thus, the aluminosilicate could deposit on the surface of porous carbon and pile up to form new crystal layer, which could increase the surface area and the CO2 adsorption capacity. The adsorbent met both high uptake (5.32 mmol/g at 0 °C) and fast adsorption kinetics (adsorption equilibrium time of 3 min.). The clarification of synergism during simultaneous utilization of RC and SP offers new routes to prepare high performance adsorbent.

Triboelectrostatic separation of coal gasification fine ash based on different mineralogical characteristics

Unburned carbon particles in coal gasification fine ash can be recycled as fuel for further combustion and ash particles are highly valuable for utilization, which can only be of secondary utilization if the two are separated. Due to the small size of gasification fine ash particles, triboelectrostatic separation has more technological advantages than traditional flotation. In this study, a first attempt has been made to separate carbon and ash particles from coal gasification fine ash by triboelectrostatic separation. It aims to investigate the feasibility of the method and to study how different mineralogical characteristics affect triboelectrostatic separation. Herein, proximate analysis, X-ray fluorescence spectroscopy analysis and X-ray diffraction analysis were adopted to investigate the fundamental nature of raw ash. The triboelectrostatic separation experiments under single conditions were conducted. Carbon enriched products with loss on ignition of 37.45% and ash enriched products with that of 10.32% were obtained whose yield was 29.81% and 32.98%, respectively. Results demonstrated the feasibility of the dry technology to separate residual carbon and ash particles in coal gasification fine ash. Furthermore, triboelectrostatic separation of coal gasification fine ash was significantly affected by differences in particle size and microtopography. Particles of small size were firstly adsorbed by plates in the high voltage electric field. The charge capacity of flake and blocky carbon particles was stronger than that of bonded and flocculated carbon particles allowing them easier to be separated.

Promotion of hydrophobic-hydrophilic separation of coal gasification fine slag through ultrasonic pre-treatment

Coal gasification fine slag (CGFS) is a solid waste byproduct generated during the coal gasification process. However, the high content of residual carbon hinders its potential for resource utilization. The urgent need for an efficient carbon extraction and ash reduction technology is evident. Hydrophobic–hydrophilic separation (HHS) is a technology that enriches hydrophobic particles in the oil phase while hydrophilic particles are in the water phase by stirring, and the different hydrophobic particles are separated by the separation of the oil and water phases. The molecular dynamics simulations revealed that the adsorption of n-heptane onto the residual carbon surface occurred spontaneously and was primarily driven by van der Waals forces. Ultrasonic pre-treatment pulp could enhance the effect of HHS. The fluctuation in tailings ash did not exceed 2% while the concentrate ash was reduced from 31.81% to 18.93% with a continual increase in ultrasonic power. The application of ultrasonic treatment on CGFS facilitated the separation of Carbon-ash molten state, as well as the elimination of ash materials particles residing within the pores of the residual carbon matrix and on its surface. Notably, many residual carbon particles are concentrated in the particle size range of 0.045–0 mm. The heightened hydrophobicity exhibited by particles within this size range enhanced the capture of oil droplets, thereby promoting the efficiency of HHS. This research aims to provide technical support and theoretical foundation for utilizing ultrasonic pretreatment as a means to enhance the HHS efficiency of CGFS.

Graded synthesis of high performance adsorbent from coal gasification fine slag and its application in the removal of methyl blue

The resource utilization of coal gasification fine slag (CGFS) and the harmless treatment of printing and dyeing wastewater are of great significance for the construction of zero-emission industrial system and resource circular economy. In this study, residual carbon and slag particles were separated from CGFS by froth flotation, and their pore structure was modified by alkali activation and acid leaching. Then, the two materials were surface functionalized and applied as adsorbents for the removal of methyl blue (MB) from printing and dyeing wastewater. The results show that optimization of flotation process parameters can achieve efficient separation of residual carbon and slag particles. The adsorption performance of both materials for MB was significantly improved after surface functionalization. The maximum adsorption capacities of modified residual carbon and slag particles for MB were 1708.01 mg·g−1 and 1249.46 mg·g−1, which were 1.4 and 64.6 times higher than before the modification, respectively. The pseudo-second-order kinetic model satisfactorily described the adsorption behavior, which was mainly chemisorption. In addition, the adsorption state of MB on the material surface was analyzed by FT-IR and XPS, and possible adsorption mechanisms were proposed. Based on the idea of high value utilization of solid waste, this research has achieved the resourceful transformation of CGFS into high performance adsorbents.

Solving two industrial waste issues simultaneously: Coal gasification fine slag-based hierarchical porous composite with enhanced CO2 adsorption performance

The coal gasification fine slag (FS) is industrial waste consisting of residual carbon (RC) and slag particles (SP). High-performance hierarchical porous composite (HPC) was synthesized by chemical activation followed by hydrothermal treatment from FS. It has been realized that SP could play the positive role in developing pore structure of HPC which makes CO2 uptake have a sharp increase. Through taking the advantage of SP, HPC has an obvious increase in surface area and pore volume from 914 to 1932 m2/g and 0.617 to 1.332 cm3/g, respectively. The changes of pore structure were mainly attributed to the two factors in a synergetic way. First, hydrothermal treatment could decrease the content of SP which acted as a ballast to reduce the surface area of activated carbon. Second, the formed silicate/aluminosilicate deposits on the carbon surface and forms silicate/aluminosilicate film on internal surface of carbon particles. This makes the meso-macropores change to micro- mesopores leading to the increase of the surface area and pore volume. The porous composites also showed high CO2 adsorption performance. The 4-FSAC-HPC sample exhibits the highest CO2 uptake of 3.25 mol/kg and 1.41 mol/kg at 25 and 50 °C, respectively, which is an increase of around 52% and 83% comparing with that of FSAC sample. Besides, CO2 adsorption up to saturation can be achieved in less than 3 min. CO2 uptake of the 4-FSAC-HPC sample was well regeneration efficiencies above 98% after 10 cycles adsorption/desorption. This work provides a new approach to prepare high-performance porous compositions using the material which contains not only carbon component but mineral matters. Furthermore, it realizes solving two industrial waste issues (fine slag and CO2) simultaneous.

Insight into the role of slag particles in coal gasification fine slag on hierarchical porous composites preparation and CO2 capture

Coal gasification fine slag (FS), classified as an industrial solid waste, is composed of residual carbon (RC) and slag particles (SP). The simultaneous utilization of RC and SP to prepare hierarchical porous composite (HTC) could realize the value-added utilization of FS. The role of SP in FS on HTC preparation is extremely vital and worthy of study. In this paper, FS was successfully used to synthesize HTCs for CO2 adsorption. Orthogonal experiment was conducted to study the effect of SP on the properties of the synthesized HTCs. The changes of impregnation conditions could be effective for developing pore structure of HTCs and the surface area increased by 226 m2/g. Furthermore, the role of SP in FS on HTCs preparation was analyzed. After chemical activation, there was generation of many new pores in SP that the surface area and pore volume could reach 302 m2/g and 0.271 cm3/g. Besides, the leached metallic elements in the process of KOH impregnation could affect the mesopore development. The HTCs also proved to be attractive for CO2 capture. The highest CO2 adsorption capacity of 2.35 mmol/g at 25 °C was achieved with 5-PH-FSHCT sample. It also exhibited good selectivity of CO2 over N2 of 9.5. Furthermore, the sample had not only fast adsorption kinetics that it reached saturation levels in about 1.5 min, but also excellent regeneration efficiency 97% after ten cycles. All results suggest that FS has a great potential to be reused as a high performance adsorbent for practical and industrial CO2 adsorption applications.

Stray particles as the source of residuals in sand filtrate: Behavior of superfine powdered activated carbon particles in water treatment processes

Although superfine powdered activated carbon has excellent adsorption properties, it is not used in conventional water treatment processes comprising coagulation–flocculation, sedimentation, and sand filtration (CSF) due to concerns about its residual in treated water. Here, we examined the production and fate of very fine carbon particles with lacking in charge neutralization as a source of the residual in sand filtrate after CSF treatment. Almost all of the carbon particles in the water were charge-neutralized by coagulation treatment with rapid mixing, but a very small amount (≤0.4% of the initial concentration) of very fine carbon particles with a lesser degree of charge neutralization were left behind in coagulation process. Such carbon particles, defined as stray carbon particles, were hardly removed by subsequent flocculation and sedimentation processes, and some of them remained in the sand filtrate. The concentration of residual carbon particles in the sand filtrate varied similarly with that of the stray carbon particles. The stray and residual carbon particles were similarly smaller than the particles before coagulation treatment, but the residual carbon particles had less charge neutralization than the stray carbon particles. The turbidity of water samples collected after sedimentation was not correlated with the residual carbon concentration in the sand filtrate, even though it is often used as an indicator of treatment performance with respect to the removal of suspended matter. Based on these findings, we suggest that reduction of the amount of stray particles should be a performance goal of the CSF treatment. Examining this concept further, we confirmed that the residence time distributions in the coagulation and flocculation reactors influenced the concentration of stray carbon particles and then the residual carbon particle concentration in sand filtrate, but found that the effect was dependent on coagulant type. A multi-chambered-reactor configuration lowered both the stray carbon particle concentration after coagulation treatment and the residual carbon particle concentration in sand filtrate compared with a single-chambered reactor configuration. When a normal basicity PACl that consisted mainly of monomeric Al species was used, the stray carbon particle concentration was decreased during coagulation process and then gradually decreased during subsequent flocculation process because the monomeric Al species were transformed to colloidal Al species via polymeric Al species. In contrast, when a high-basicity PACl that consisted mostly of colloidal Al species was used, coagulation treatment largely decreased the stray carbon particle concentration, which did not decrease further during subsequent flocculation process. These findings will be valuable for controlling residual carbon particles after the CSF treatment.

Physical properties and microstructures of residual carbon and slag particles present in fine slag from entrained-flow coal gasification

Fine slag (FS) consists of residual carbon (RC) and slag particles (SP). This paper studies the characteristics of SP and RC separately. SP contain a little of pores and mainly consist of spherical particles most of which are solids. RC have a higher pore surface, more continuous and complete pore structure. The chemical structure of inorganic minerals in SP has the following characteristics: According to nuclear magnetic resonance results, the amounts of network structure Q4 and Q3 are more than that of chain structure Q2 and Q1. The 4-coordinated aluminum consists of 74% and the octahedral coordination (Al(VI)) takes up only 11%. SP is a heterogeneous material which contain not only inorganic minerals but also organic carbon. C atom associated in chemical way with the inorganic matter within SP matrix. The predominant groups of organic carbon within SP matrix are C-C and C-O. C-O groups organically bound with inorganic elements in SP forming C-O-M (M: inorganic elements) bands. The predominant components in RC are C-C and C-O.

Chemical characterizations of different sized mineral-rich particles in fine slag from Entrained-flow gasification

Fine slag (FS) is byproduct of the coal gasification process, consisting of mineral-rich particles (MRP) and discrete residual carbon (DRC). MRP were separated using froth flotation method from FS and the ash content of separated MRP was higher than 98%. MRP were sieved into five sized fractions and its properties were studied by SEM/EDS, XPS, XRD, FT-IR and Raman spectroscopy. The results show that MRP are heterogeneous material which contain not only minerals but also residual carbon. The minerals in MRP contain most amorphous glass, together with minor proportions of crystal quartz. The MRP mainly consist of aluminosilicate and smallest (0–23 µm) particles have the most of aluminosilicate. Except for discrete residual carbon particles, there are also another two types of residual carbon within MRP. The first is embedded in the MRP matrix. The second is associated in chemical and/or physical way with the inorganic matter within MRP matrix. Residual carbon within MRP has a low degree of crystalline order. The main functional groups of residual carbon within MRP matrix are C-C, C-H and C-O. C-O which chemically bound with inorganic elements in the MRP forming C-O-M (M represents inorganic elements existing in MRP) groups.

Physicochemical Characteristics of Mineral-Rich Particles Present in Fine Slag from Entrained-Flow Gasifiers

Fine slag (FS), a byproduct of coal gasification, consists of mineral-rich particles (MRP) and residual carbon particles (RCP). The characteristics of the MRP were investigated by laser particle si...

Numerical study of the effect of combustion chamber structure on scavenging process in a boosted GDI engine

The scavenging process is helpful to suppress the super-knock in a 4-stroke turbocharged gasoline direct injection (GDI) engine because it can strengthen in-cylinder cooling and clear suspending residual particles from previous cycles. This paper investigates the effects of combustion system parameters on scavenging process. The simulation results showed that the piston pit with a shallow depth adjacent to the center of cylinder could intensify the scavenging motion and increase the velocity inside the pit, more residual gas and carbon particles could be therefore cleared. The intake and exhaust valve chamfer angle of 45° was beneficial to the scavenging process because more high-velocity scavenging motion occurred in piston pit and less fresh charge flowed into exhaust port directly. The injector location and ground electrode orientation has little influence on scavenging process because of its tiny volume. Finally, an optimum structural shape of combustion chamber was developed and proposed based on the research results.

Combustion Reaction of Pulverized Coal on the Deposit Formation in the Kiln for Iron Ore Pellet Production

The serious deposits on the refractory bricks are found in the grate kiln in iron ore pellet plants, which significantly influence the pellet production. The effect of the combustion reaction of pulverized coal on the deposit formation in kiln during iron ore pellet production was investigated in this work. Hematite iron ore was used as raw material to be pelletized, and the pulverized coal, in general, was used as the fuel. The chemical compositions and microstructures of the deposit samples were detected through the chemical analysis methods, scanning electron microscopy, and energy-dispersive spectroscopy. Effects of different residual carbon contents in coal ash and roasting temperature on the deposit formation were investigated by simulated experiments. Then, the results indicated that the combustion reaction of coal had a significant influence on the deposit formation, under which condition the hematite grains in the preheated pellet were reduced by surrounding residual carbon particles in unburned ...

A Novel Role for Vernix caseosa as a Skin Cleanser

Objectives: Skin cleansing is a complex process involving endogenous and exogenous mechanisms. This study examines the role of vernix caseosa in the process of skin cleansing in the perinatal period. Methods: Vernix was evaluated as an exogenously applied skin cleanser using digitized image analysis which quantified residual carbon particles following a standardized cleansing assay. In addition, the detachment of vernix from human cadaveric skin and Gore-Tex^® supports was investigated following timed exposures to a variety of commonly used commercial surfactants. Detachment was quantified spectrophotometrically as increased turbidity at 650 nm. Results: Image analysis showed that exogenous application of vernix exhibited a cleansing capability comparable or superior to standard skin cleansers. Dose-dependent increases in solution turbidity (vernix detachment) were seen following exposure of vernix-covered Gore-Tex vehicles to sodium laureth sulfate, sodium lauryl sulfate, and cocamidopropyl betaine solutions. Similar results were seen with cadaveric skin. Conclusions: These results demonstrate a role for vernix caseosa as a skin cleanser. Previous views of vernix as a soil or skin contaminant at birth need to be reevaluated.

炭素材の低温酸化に伴うダイオキシン類生成反応

Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) are unintentionally formed and emitted from various industrial thermal processes. So far, many researchers have examined formation/emission behavior and inhibition of PCDD/Fs. Generally, following three routes were pointed out as major formation pathways of PCDD/Fs: (I) through aromatic precursors such as chlorobenzenes and chlorophenols, (II) decomposition reaction of organic compounds having large molecular sizes such as polycyclic aromatic hydrocarbons (PAHs) and (III) via de novo synthesis from macromolecular carbon. In the incineration and other thermal processes, de novo synthesis is now regarded as an important route for PCDD/Fs formation. This reaction occurs on macro structural carbon under oxidation atmosphere at relatively low temperature. Especially, the properties of a small quantity of residual carbon particles, "soot" which suspended the exhaust gas and metallic chlorides seem to have large effect on formation of PCDD/Fs.The present paper introduces the topics concerning PCDD/Fs formation and carbon oxidation. The mechanism of PCDD/Fs formation, the effect of metallic chlorides and various reactions relating to PCDD/Fs formation are reviewed. Further, the mechanism of carbon oxidation at low temnerature and the effect of metallic comnounds are discussed.

A Study of the Reactivity and Formation of the Unburnt Carbon in CFB Fly Ashes

AbstractA comprehensive study was conducted on the reactivify and the turbostratic structure of the unburnt carbon in the CFB fly ashes. The observed deactivation of the unburnt carbon and the pyrolysis chars prepared under various conditions was studied and found to be due to the combination of the loss of catalytic effect of the minerals and the crystalline growth of carbon. Various forms of morphology of the residual carbon particles were examined under a microscope. Both inertinite and vitrinite seem to be possible sources of the unburnt carbon. The formation of the unburnt carbon in the CFB fly ashes was likely caused by the deactivation of char particles and the insufficient residence time of the corresponding fuel particles.

Surfactant adsorptivity of solid products from pulverized-coal combustion under controlled conditions

Most kinetic studies of pulverized coal char combustion have focused on the measurement or prediction of rates of solid-phase mass loss, which determine the ultimate degree of conversion of the solid fuel for a given residence time and gas environment. The strongest motivation for improving the degree of conversion in practical coal combustion systems, however, is not related to the mass of residual carbon, but to its detrimental behavior in concrete mixtures. When fly ash is added to air-entrained concrete as a partial replacement for Portland cement, the specialty surfactants, or air entraining admixtures, can be rendered ineffective by adsorption onto the surfaces of the porous residual carbon particles. This paper presents the first set of measurements of the surfactant adsorptivity of carbon-containing solid products generated during pulverized coal combustion under controlled laboratory conditions. The specific adsorptivity of the carbon is found to vary dramatically over the course of conversion, exhibiting a sharp maximum in the early stages of char combustion. The main features of the data can be explained by considering the concurrent evolution of surface area, pore structure, and elemental composition, especially oxygen content. It is also shown that surfactant adsorptivity can be greatly altered by post-combustion modification of the carbon surfaces in the form of air oxidation at temperatures above about 300°C (reduced activity) or heat treatment at 900°C in argon (increased activity). The combined results are used to describe a mechanism for the competitive adsorption process in concrete mixtures and to discuss implications for combustion systems.

Reaction‐Bonded Niobium Carbide on Graphite via a Novel Solution Impregnation Process

A simple and rapid process has been developed that allows the preparation of NbC‐C composite rods. Graphite rods are impregnated with an ethanolic solution of NbOCl2 and resistively fired (> 1900°C) under an argon atmosphere. The final composite product is found to contain residual carbon particles within a NbC‐C matrix.

Combustion of carbon particles generated from liquid hydrocarbon fuels

The burning rate of residual carbon particles generated from the spray combustion flame of heavy fuel oil droplets has been investigated experimentally. The rate of combustion of a single particle and of a cloud of particles, and the processes of their combustion, have been analysed by electronic computer; the actual particle temperature has been taken into account. The theoretical results agree with the experimental results in their trend (Figs. 7, 10).