Pulverization Ratio Research Articles

Tailoring self-pulverized low-calcium clinker for CO2 sequestration

To reduce energy consumption and greenhouse gas emissions in the cement industry, this study develops a novel low-calcium clinker with self-pulverization properties. The clinker is synthesized from limestone and sandstone raw materials and comprises dicalcium silicate (2CaO·SiO2 (C2S)) as the primary mineral and rankinite (3CaO·2SiO2 (C3S2)) as the auxiliary mineral. The influence of calcination temperature, cooling rate, and holding time on clinker pulverization and mineral formation is investigated through a series of experiments. The optimal calcination condition involves heating at 1240 °C for 1 h, followed by natural cooling, resulting in a self-pulverized low-calcium clinker (SPLCC) with main mineral is γ-C2S and contains β-C2S, C3S2, and C2AS (Calcium alumina feldspar (2CaO·Al2O3·SiO2)). The self-pulverized clinker exhibits a pulverization ratio of 93.0 %, a specific surface area of 666.4 m2/kg, and an average particle size of 8.2 μm. Additionally, the clinker displays excellent carbonation reactivity, with the compressive strength reaching 69.3 MPa and 82.2 MPa after 4 h and 24 h of CO2 curing, respectively. The carbonation products are identified as calcite and silica gel. SPLCC can reduce and sequester approximately 277.3 kg of CO2 emissions compared to the hydration of Portland cement clinker when considering the preparation and curing stages. The results highlight the potential of SPLCC as a sustainable cementitious material.

An Investigation into the Relationship between Density and Pulverization Ratio for Tannin-Furanic Foam.

Four types of classical tannin-based foam samples were prepared via different methods in the current study with an attempt to find out the impact of each one on the physico-mechanical properties. The results of performed tests showed similarity to the general trend of related research, with typical negative relation between the foam density and mechanical strength. A critical point was found for each type of foam samples, for example, for tannin-formaldehyde foams (TFF), they were in the range of 85-95 kg/m3, while for tannin-glutaraldehyde foams (TGF), mechanically-generated tannin foams (MTF) and steam-driven tannin furanic foams (STDF), they were about 52-62 kg/m3, 53-63 kg/m3, and 73-83 kg/m3, respectively. This implies a significant change for density and mechanical strength, has been dig out by intensive experimental results and analysis. In addition, a non-liner relationship between density and pulverization ratio was obtained by fitting the curves obtained by the experiment results. Finally, visualization using scanning electron microscopy (SEM) together with evaluation of the compression strength presented a deeper insight to illustrate the different factors affecting foam density and pulverization ratio.

Strengthening Granulating and Sintering Performance of Refractory Iron Concentrate by Pre-Pelletizing

May Concentrate Iron ore, as a refractory iron concentrate, deteriorates the permeability of the sintered layer during the sintering process due to its fine particle size and poor granulating performance. Therefore, it cannot be widely used in iron ore sintering. In this study, the strengthening granulation of May Concentrate Iron ore using pre-pelletizing to expand its utilization ratio was proposed. The experiments of conventional granulation, pre-pelletizing granulation and sinter pot test were carried out. Increasing May Concentrate Iron ore (a refractory iron concentrate) proportion was detrimental to conventional granulation, reducing the quasi-particle particle size and strength. May Concentrate Iron granulating and sintering performances were improved by pre-pelletizing. The quasi-particle average size at 36% May Concentrate Iron proportion jumped to 4.92 mm of pre-pelletizing granulation from 3.22 mm of conventional granulation. Meanwhile, the permeability index rose to 0.33 from 0.11, while the falling and drying pulverization ratio fell to 7.05% and 6.11% from 22.59% and 15.88%, respectively. The consolidation mode of matrix materials was liquid phase consolidation, while that of May Concentrate Iron pellets was solid phase consolidation, forming the structure of the pellets embedded in the matrix materials. Furthermore, the partial alkalinity of the matrix materials was increased because of the separation of May Concentrate Iron, generating a large amount of acicular calcium ferrite with better consolidation strength than conventional granulation sintering.

A novel strategy inspired by steaming Chinese steamed bread for preparation of tannin-furanic rigid bio-foam

Tannin-furanic rigid foam material has been receiving extensive attention due to its renewable, easy-preparation, lightweight, thermal insulation, and flame retardancy, that been considering a potential flame-retardants and thermally-insulating materials in construction field. The most fashionable approaches for tannin-furanic foam manufacturing, currently, are the self-blowing expansion with the aid of blowing agent with/without extra heating, and foaming via mechanical stirring in presence of non-environmentally friendly crosslinker. Herein, a novel and green strategy was proposed for tannin-furanic rigid foam preparation without blowing agent and additional crosslinker by steam-driven foaming. The performance of steam-driven tannin-furanic based foam (SDTF) was evaluated systematically and a possible foaming mechanism was suggested. The results indicated that a totally different surface but similar microstructure morphology of SDTF was developed, which displayed a larger cell size and thicker cell wall than standard tannin-furanic-formaldehyde foam (STF). A much lower pulverization ratio (approximately 4.6%) was reached for SDTF with respect to STF even though its compression strength was only less than half. An excellent thermal insulation performance was verified by the thermal conductivity of SDTF, only approximately 0.0286 W/m·K, which is considered ultra-low value that the STF cannot reach or seldom reach after STF modification or/and special structure design. The flame retardancy of SDTF was investigated by LOI and ignition experiment, which demonstrated a strong flame resistance and self-extinguishing nature, rendering it superior to STF. This preparation strategy provides a promising sustainable and environmentally friendly method for fabrication of green tannin-furanic foam for industry applications.

High performance bio-based gelatinized starch-furanic resin derived foam reinforced by microcrystalline cellulose

Sustainable development of bio-based foam implies increasing usage of renewable bio-resources to compensate the rapid consumption of oil-derived resources. Starch and furfuryl alcohol, both originate from crops, are thus considered attractive bio-based precursors for preparation of gelatinized starch-furanic foam. Moreover, the reinforcement of gelatinized starch-furanic foam using microcrystalline cellulose (MCC), originating from forestry, resulted in a stronger chemical network structure. This imparted excellent compressive strength and less pulverization ratio, which is even superior to that of common building insulating materials, such as mineral wool board. Furthermore, the addition of MCC guaranteed a low thermal conductivity, reasonable thermal stability and acceptable limiting oxygen index (LOI), to the produced foam as revealed by the thermal conductivity measurements, thermogravimetric analysis (TGA) and LOI determination, respectively. Meanwhile, scanning electron microscopy (SEM) imaging indicated that the internal cell size and shape of the gelatinized starch-furanic/MCC foam are uniform, while the foam presented more closed cells with suitable cell wall thickness and lacking of cracks or collapse. The developed foam with sources derived from agricultural and forestry imparts the foam excellent thermal insulation and high mechanical strength, which offers a promising potential as biomass foam materials.

Facile Synthesis of Formaldehyde-Free Bio-Based Thermoset Resins for Fabrication of Highly Efficient Foams

Bio-based biodegradable foams were formulated from a crosslinkable network structure combining starch, furfuryl alcohol, glyoxal, and condensed tannin in the presence of p-toluenesulfonic acid (pTSA) and azodicarbonamide (AC) as a foaming agent. More importantly, the reinforcement of gelatinized starch-furanic foam using tannin, originating from forestry, resulted in an excellent compressive strength and lower pulverization ratio. Moreover, the addition of tannin guaranteed a low thermal conductivity and moderate flame retardancy. Fourier transform infrared (FTIR) spectroscopy approved the successful polycondensation of these condensing agents under the employed acidic conditions. Moreover, the catalytic effect of pTSA on the foaming agent induced liberation of gases, which are necessary for foam formation during crosslinking. Scanning electron microscopy (SEM) showed foam formation comprising closed cells with uniform cell distribution and appropriate apparent density. Meanwhile, the novel foam exhibited biodegradation under the action of Penicillium sp., as identified by the damage of cell walls of this foam over a period of 30 days.

Gelatinized starch-furanic hybrid as a biodegradable thermosetting resin for fabrication of foams for building materials

Bio-based biodegradable resin was prepared by condensation of gelatinized starch and furfuryl alcohol, in presence of glyoxal as crosslinker. The resin was blown with different foaming agents and/or flame retardants such as phosphoric or boric acids, to produce environmentally friendly foam structures, given the bio-based nature of the main components, which are both derived from corn. Scanning electron microscopy (SEM) imaging of the samples revealed closed cell structure with a smooth surface. The excellent pulverization ratio and appreciable compression strength compared with the phenol-formaldehyde (PF)-based foam, render them strong candidates for building materials. Different investigations proved characteristics such as low thermal conductivity, good stability against thermal degradation and high limiting oxygen index (LOI) values, support the liability of such structures for application as heat insulating and fire-resistive materials.

Thermal fragmentation and pulverization behavior of lignite during the vibration drying process and its grey relational analysis of multi-factors

Lignite particles are easy to break into smaller particles in the process of thermal drying, which affect the heat and mass transfer inside the particles. Therefore, it is important to study the fragmentation behavior of lignite for optimizing the drying process. In this article, two concepts of degree of fragmentation (F′) and pulverization ratio (R p ) were put forward to describe the overall fragmentation property of lignite after vibration drying. The results showed that the higher the drying temperature, the more favorable it was for the product particles to fragment. The impact of particle size and feeding amount on F′ and R p was relatively small, but it was still not negligible. There was a critical vibration frequency during vibration drying. Once the vibration frequency exceeded critical value, the fragmentation of particles would be greatly promoted. The grey correlation model of lignite was established to quantitatively analyze the influence of five factors on the fragmentation and pulverization of products in the process of multi-factor coupling drying. Following the grey correlation model, five factors, such as the drying time, vibration frequency, drying temperature, feed particle size and feeding amount were ranked according to their influence on F′ and R p .

Preparation and Characterization of Sandwich Structured Materials with Interesting Insulation and Fire Resistance

A cellular material in the form of 3-layered sandwich structure material was prepared via sole use of mechanical stirring without any use of a foaming agent, while Tween-80 was employed as a foam stabilizer via a developed in-situ mold casting. The resulting structure displayed a good appearance with no visual defects. The 3-layered composition of the sandwish structure, “nonporous resin layer-porous foam layer-nonporous resin layer”, was examined in terms of the microstructure, density & density distribution, pulverization ratio, mechanical strength, insulation and flame retardant performance. It was indicated from the results that the bonding between the resin layer and foam layer was tight, while the tensile rupture always occurred in the porous layer. Also, the density of the sandwich structure material was symmetrical with “saddle” distribution, and a uniform density for any given layer. The increase in the density at the interface layer provided a good interpretation for the tensile rupture never occurred at the interface. The brittleness resistance of the developed material was significantly improved, and the pulverization ratio was sharply decreased from 9.93% to 0.31%. The material acquired a thermal conductivity and limiting oxygen index (LOI) of 0.0241 W/m ⋅ K and 29.92%, respectively, indicating potential use of such materials broadly in fields of insulation and flame retardancy.

Lignin demethylation for modifying halloysite nanotubes towards robust phenolic foams with excellent thermal insulation and flame retardancy

AbstractThe demethylation of lignin was conducted under HBr catalysis and microwave irradiation resulting in a demethylation rate of 21.4% as calculated from1H NMR. The demethylated lignin (DL) was applied to modify halloysite nanotubes (HNTs) forming a nano‐hybrid containing 16.5 wt% of DL according to TGA results, and showing rough surfaces dotted with DL particles as observed through TEM. HNTs‐DL was introduced into resol resin synthesis where DL molecules participate in phenol‐formaldehyde polycondensation, functioning as a binder to connect the inorganic HNTs framework and the organic resol resin molecules, giving an increase in flow activation energy as calculated from rheological results. The prepared phenolic foam containing 0.4 wt% of HNTs‐DL shows a significant increase by 37.7% in compressive strength and a decrease by 27.3% in pulverization ratio compared to the neat phenolic foam, and exhibits uniform cells with the highest cell density as observed in SEM, explaining its improved performance in thermal insulation and flame retardancy.

Flame-retardant and thermally-insulating tannin and soybean protein isolate (SPI) based foams for potential applications in building materials

Owing to foreseable extensive shortages in petrochemical resources, energy consumption, and fire safety concerns, recent scientific research in the construction field has been aimed to develop biomass flame-retardants and thermally-insulating materials. Herein, flame-retardant tannin-furanic-SPI bio-foams with outstanding thermal insulation and smoke suppression performance were developed by exploiting the synergistic effect of additives (boric acid, phosphoric acid, and montmorillonite). Their physical and mechanical properties showed that these tannin-based foams are lightweight (82–122 kg/m3), with an acceptable compression strength (0.2–0.35 MPa), and a low pulverization ratio (5.97–12.06%). Moreover, the morphology, thermal stability, thermal conductivity, and flammability were evaluated by scanning electron microscopy (SEM), thermogravimetric analysis (TGA), thermal conductivity tests, limiting oxygen index (LOI), and cone calorimetry, respectively. These foams exhibited closed cell structures, good thermal stability, and low thermal conductivity. Their flammability results showed that higher LOI values were obtained in the range of 37.33–49.05% and that they had a relatively low peak-heat-release rate (PHRR) and total-smoke-produced (TSP). A possible flame retardancy mechanism was suggested. By comparing them to other commercial construction materials, the modified tannin-furanic-SPI foams with integrated properties, such as flame retardancy, thermal insulation, light-weight, environmental-friendliness, and acceptable mechanical properties, show potential applications as thermal insulation for buildings.

Lignin-Based Phenolic Foam Reinforced by Poplar Fiber and Isocyanate-Terminated Polyurethane Prepolymer.

Phenolic foams (PFs) are lightweight (<200 kg/m3), high-quality, and inexpensive thermal insulation materials whose heat and fire resistance are much better than those of foam plastics such as polyurethane and polystyrene. They are especially suitable for use as insulation in chemical, petroleum, construction, and other fields that are prone to fires. However, PFs have poor mechanical properties, poor abrasion resistance, and easy pulverization. In this paper, a polyurethane prepolymer was treated with an isocyanate, and then the isocyanate-terminated polyurethane prepolymer and poplar powder were used to prepare modified lignin-based phenolic foams (PUPFs), which improved the abrasion resistance and decreased the pulverization of the foam. The foam composites were comprehensively evaluated by characterizing their chemical structures, surface morphologies, mechanical properties, thermal conductivities, and flame-retardant properties. The pulverization ratio was reduced by 43.5%, and the thermal insulation performance and flame-retardancy (LOI) were improved. Compared with other methods to obtain lignin-based phenolic foam composites with anti-pulverization and flame-retardant properties, the hybrid reinforcement of foam composites with an isocyanate-terminated polyurethane prepolymer and poplar powder offers a novel strategy for an environmentally friendly alternative to the use of woody fibers.

Efficient improvement for dissociation behavior and thermal decomposition of manganese ore by microwave calcination

Traditional smelting process of manganese ore was plagued with high consume of power and coke, and spraying and slag turning accidents caused by violent decomposition of carbonates and manganese oxides in manganese ore. In the present work, the thermal decomposition mechanism and phase structures of manganese ore were systematically investigated, calcined through microwave calcination approach and characterized by XRD, SEM and EDAX. Results indicated that microwave calcination had a significantly better effect than conventional calcination for manganese ore. An increase in calcination temperature was found to present a more profound effect than calcination duration. The optimum calcination temperature was identified to be 950 °C, with the calcination duration being 30 min, and manganese ore grade increased from initial 30% to 39%–42%, with the pulverization ratio being 8%–9%. Peak intensities of Mn3O4 phase enhanced with calcination temperature increasing, and irregular cracks and pits appeared on the surface of the microwave calcined manganese ore. Meanwhile, the feasibility of decomposition reactions of manganese ore at the considered temperature regime was confirmed by thermodynamics analysis. The upgrading and modified manganese ore by microwave calcination can realize the direct smelting of the concentrate. The work proposes an efficient calcination idea for manganese ore by microwave calcination.

Phenolic Resin Foam Composites Reinforced by Acetylated Poplar Fiber with High Mechanical Properties, Low Pulverization Ratio, and Good Thermal Insulation and Flame Retardant Performance.

Phenolic foam composites (PFs) are of substantial interest due to their uniform closed-cell structure, low thermal conductivity, and good thermal insulation performance. However, their disadvantages of a high pulverization rate and poor mechanical properties restrict their application in building exterior insulation. Therefore, the toughening of these composites is necessary. In this paper, poplar fiber was treated with an acetylation reagent, and the acetylated fiber was used to prepare modified phenolic foams (FTPFs); this successfully solved the phenomenon of the destruction of the foam structure due to the agglomeration of poplar fiber in the resin substrate. The foam composites were comprehensively evaluated via the characterization of their chemical structures, surface morphologies, mechanical properties, thermal conductivities, and flame retardant properties. It was found that the compressive strength and compressive modulus of FTPF-5% respectively increased by 28.5% and 37.9% as compared with those of PF. The pulverization ratio was reduced by 32.3%, and the thermal insulation performance and flame retardant performance (LOI) were improved. Compared with other toughening methods for phenolic foam composites, the phenolic foam composites modified with surface-compatibilized poplar fiber offer a novel strategy for the value-added utilization of woody fiber, and improve the toughness and industrial viability of phenolic foam.

Preparation and Characterization of Bio-oil Phenolic Foam Reinforced with Montmorillonite.

Introducing bio-oil into phenolic foam (PF) can effectively improve the toughness of PF, but its flame retardant performance will be adversely affected and show a decrease. To offset the decrease in flame retardant performance, montmorillonite (MMT) can be added as a promising alternative to enhance the flame resistance of foams. The present work reported the effects of MMT on the chemical structure, morphological property, mechanical performance, flame resistance, and thermal stability of bio-oil phenolic foam (BPF). The Fourier transform infrared spectroscopy (FT-IR) result showed that the –OH group peaks shifted to a lower frequency after adding MMT, indicating strong hydrogen bonding between MMT and bio-oil phenolic resin (BPR) molecular chains. Additionally, when a small content of MMT (2–4 wt %) was added in the foamed composites, the microcellular structures of bio-oil phenolic foam modified by MMT (MBPFs) were more uniform and compact than that of BPF. As a result, the best performance of MBPF was obtained with the addition of 4 wt % MMT, where compressive strength and limited oxygen index (LOI) increased by 31.0% and 33.2%, respectively, and the pulverization ratio decreased by 40.6% in comparison to BPF. These tests proved that MMT can blend well with bio-oil to effectively improve the flame resistance of PF while enhancing toughness.

Enhancement of flame‐retardant and mechanical performance of phenolic foam with the incorporation of cardanol‐based siloxane

ABSTRACTA novel cardanol‐based siloxane (SAECD), which has silicon groups and reactive epoxy groups, was synthesized. Its structure was confirmed by Fourier transform infrared spectrometry and 1H nuclear magnetic resonance. Then, phenolic foams (PFs) modified with different contents of SAECD were prepared. While addition of appropriate amount of SAECD into resin matrix enhances the flexural strength of PFs, incorporation of SAECD into PFs leads to a reduced pulverization ratio. The limiting oxygen index (LOI) increases continuously with the increasing addition of SAECD into PFs. The results of the cone calorimeter test showed that the addition of 3% SAECD could effectively reduce the heat release rate and total heat release of the foam by the condensed phase flame retardant mechanism. The TTI of the modified foam was delayed by 19 s; the PHRR, mean HRR, and THR of the modified foams decreased by 9.10%, 4.11%, and 7.55%, respectively, compared with those of the pristine PF. In addition to the increase in the toughness of the PF, SAECD addition can also improve the flame retardant properties of the PF.

Preparation and mechanism of polyurethane prepolymer and boric acid co‐modified phenolic foam composite: Mechanical properties, thermal stability, and flame retardant properties

In this work, a new kind of co‐modified phenolic foam was synthesized with polyurethane prepolymer (PUP) and H3BO3 by a simple preparation method. Firstly, in order to determine the optimal amount of PUP, the effects of different PUP additions on the mechanical properties, foam microstructure, and pulverization rate of phenolic foam were investigated. Then H3BO3 was added to toughened phenolic foam, in order to reduce its fire hazard. The results showed that the mechanical properties of the PFPUP8 phenolic foam composite were the best when the PUP content was 8 wt%. It had a small and regular cell structure, and its pulverization ratio was reduced by 80% compared with that of pristine phenolic foam. Meanwhile, the flame retardant properties of PFPUP8 were improved in different degrees with an increase in the amount of H3BO3. Particularly, when the addition of H3BO3 was 10 wt%, the peak heat release rate, the total heat release, and the total smoke release values of PFPUP10B were decreased by 35.4%, 42.4%, and 45.2%, respectively, compared with those of PFPUP8. The value of the limit oxygen index was increased by 33.1%. Besides, the addition of H3BO3 had no adverse effect on the mechanical properties and pulverization ratio of PFPUP8. In addition, the specific mechanisms of toughening, flame retardant, and smoke suppression are also discussed in this paper on the basis of an investigation into the thermal properties of the toughened flame retardant foam composites by thermogravimetric analysis in N2 atmosphere.

In situ preparation of intrinsic flame retardant urea formaldehyde/aramid fiber composite foam: Structure, property and reinforcing mechanism

The intrinsic flame-retardant urea-formaldehyde/aramid fiber (UF/AF) composite foam was fabricated via in situ water-based foaming process. At low AF content (<3 wt%), AF can disperse homogeneously in foam and act as heterogeneous nucleating agent, resulting in smaller cell size, narrower cell size distribution, lower porosity. For UF/2 wt% AF foam, the pulverization ratio decreased by 11%, while the compressive strength and modulus increased by 198% and 257% respectively. As the “pillar” structure, AF enhanced the stiffness of the cell wall, while under compressive stress, AF can play a role of bridge between the cracks, preventing further expansion of the crack, increasing the crack propagation path and thus delaying the disastrous collapse of cells. By addition of AF, the decomposition temperature and char yield increased, while the UL-94 tests were classed as a V-0 rating, and during burning, the expansion of the flame was suppressed remarkably for the composite foams.

Intrinsic flame‐retardant urea formaldehyde/graphene nanocomposite foam: Structure and reinforcing mechanism

Based on the industrialized graphene (GN) product, a series of intrinsic flame‐retardant urea‐formaldehyde/graphene‐silane coupling agent (UF/GN‐SA) nanocomposite foams were fabricated via in situ polymerization and water‐based foaming process. It was found that at low GN content, GN sheets dispersed homogeneously in the foams. Compared with neat UF foam, the composite foam exhibited circular cells with smaller cell size, narrower cell size distribution, thicker cell walls, lower porosity, and less water absorption. Introduction of 0.5 wt% GN resulted in about 29.5% decrease in pulverization ratio, 71.8% increase in compressive strength, and 132.6% increase in compressive modulus. The reinforcing mechanism of the UF/GN‐SA nanocomposite foam was explored. Due to the dense cell structure, formation of GN centered network structure, and reinforcing effect of GN, greater compressive stress was required to destruct the foam. UL‐94 V‐0 rating was achieved for the composite foams with remarkably suppressed flame expansion. POLYM. COMPOS., 40:E811–E820, 2019. © 2018 Society of Plastics Engineers

Larch tannin-based rigid phenolic foam with high compressive strength, low friability, and low thermal conductivity reinforced by cork powder

Phenolic foam (PF) has recently been spotlighted because of their excellent flame resistance, low smoke emission, and low production costs. However, PF is mainly prepared from petroleum-based products, and it exhibits poor mechanical strength and high friability. In this study, larch tannin-based rigid phenolic foams (LTPFs) and cork powder was used as filler to prepare cork powder-reinforced LTPFs (CLTPFs). The chemical structure, cell morphology, compressive mechanical properties, friability, thermal properties, and flame retardancy of the foams were evaluated. The results indicated that the LTPFs showed inferior cell morphology, compressive strength and thermal properties, high friability and high flame retardancy as compared with the neat PF. LTPF10 presented the maximal limiting oxygen index (LOI) of 47.8%. As compared with the unreinforced LTPFs, CLTPFs possessed excellent cell morphology, high compressive strength, low thermal conductivity, low friability, and good thermal properties. At a cork powder dosage of 1 wt%, the compressive strength and modulus of CLTPFs increased by 14.84% and 16.18%, respectively; the pulverization ratio and thermal conductivity of CLTPFs decreased by 18.4% and 32.29%, respectively, as compared with those of the LTPF. In addition, the introduction of cork powder improved the thermal stability of LTPFs. The LOI values of the CLTPFs were slightly lower than those of LTPFs. LTPF reinforced with 1 wt% cork powder exhibited the best combination of the features.