Wet Carbon Research Articles

Upcycling sintering red mud waste for novel superfine composite mineral admixture and CO2 sequestration

To utilize the sintering red mud waste（SRM）on a large scale and sequester CO2, a room temperature in-situ wet carbonation method was proposed for activation of SRM. The wet carbonation reaction process of SRM was investigated, and the evolution of phase composition, microstructure and pore structure during carbonation of the SRM was revealed by XRD, TG/DTG, FT-IR, NMR, SEM and nitrogen adsorption. Moreover, the feasibility of carbonated SRM (C-SRM) as a high value-added mineral admixture was explored. The results showed that the carbonation of SRM produced a large number of fine calcite crystals and silica-alumina gel with high polymerization. After 3 h of carbonation, the SRM achieved a CO2 sequestration rate of 15.3%, calcite (Cc) yield of 86.5% and Na+ leaching rate of 81.8%. The C-SRM possessed a high pozzolanic reactivity and fine particle size, showing its potential as a cement mineral admixture.

Corrosion product formation on zinc-coated steel in wet supercritical carbon dioxide

In a wet supercritical carbon dioxide atmosphere, carbon dioxide is dissolved into water and causes corrosion of zinc-coated steel. The first corrosion products appeared in singular nano-scale initiation sites, which gradually grew in number and size and ultimately covered the whole surface. Zinc hydroxy carbonate was detected as a rapidly forming needle-like corrosion product, which prevailed at short exposure times (from minutes to hours). A prolonged exposure caused conversion of zinc hydroxy carbonate to anhydrous zinc carbonate with high crystallinity and a stable, dense layer was formed on zinc. The chemical transition from zinc hydroxy carbonate to anhydrous carbonate was reported for the first time and is in the light of current literature unique for wet scCO2 atmosphere.

Ionic Interactions at the Crude Oil-Brine-Rock Interfaces Using Different Surface Complexation Models and DLVO Theory: Application to Carbonate Wettability.

The impact of ionic association with the carbonate surface and its influence toward carbonate wettability remains unclear and is an important topic of interest in the current literature. In this work, a triple layer model (TLM) approach was used to capture the electrokinetic interactions at both calcite–brine and oil–brine interfaces. The developed TLM was assembled against measured ζ-potential values from the literature, successfully capturing the trends and closely matching the ζ-potential magnitudes. The developed TLM was compared to a diffused layer model (DLM) presented in previous works, with the DLM showing a better match to the ζ-potential values for seawater brine solutions. The ζ-potential values predicted from both surface complexation models (SCMs) were used to calculate the total interaction energy (or potential) based on the Derjaguin, Landau, Verwey, and Overbeek (DLVO) theory. It was observed that low Mg2+ and high SO42– concentrations in modified composition brine (MCB) made the calcite–brine interface more negative. However, at the oil–brine interface, low Mg2+ made the oil–brine interface more negative but high SO42– concentrations slightly shifted the oil–brine ζ-potential toward negative. At the crude oil–brine–rock (COBR) interfaces, low Mg2+ and high SO42– concentrations in the MCB were observed to generate a greater repulsive interaction energy, which could trigger carbonate wettability alteration toward water wetness. The absolute sum of the ζ-potential at both interfaces was observed to be correlated to the total interaction potential at a 0.25 nm separating distance. Thus, an increase in the absolute sum of the ζ-potentials would generate a greater repulsive interaction potential and trigger wettability alteration. Therefore, these SCMs can be applied to design modified composition brine capable of triggering a repulsive interaction energy to alter carbonate wettability toward water wetness.

Continuous, pilot-scale production of carbon fiber from a textile grade PAN polymer

Presented here is an investigation into the successful wet spinning and carbonization of a low-cost textile grade (TG-PAN) polyacrylonitrile (PAN) polymer blended with a more traditional carbon fiber (CF-PAN) grade precursor. Both wet spinning and carbonization were performed using continuous pilot scale facilities directly analogous to larger scale industrial processes which provide validation for further scale-up. The blended precursor fibers (TG-CF) showed consistently uniform cross-sections with the benchmark CF grade PAN precursor exhibiting mechanical properties similar to a commercially available precursor fiber. Despite a TG-PAN only precursor failing to adequately stabilize, the benchmark CF-PAN and the blended (TG-CF) precursor fibers and carbon fibers produced are high quality and exhibit uniform properties. The corresponding TG-CF carbon fiber containing 70 wt% of TG-PAN has a tensile strength of 2.2 GPa, a tensile modulus of 210 GPa and a 1% elongation to failure. Although less than the CF-PAN carbon fiber, the mechanical properties of TG-CF affirm that this approach has the potential to develop scalable low-cost carbon fiber suitable for a range of important applications.

A review of carbon monitoring in wet carbon systems using remote sensing

Carbon monitoring is critical for the reporting and verification of carbon stocks and change. Remote sensing is a tool increasingly used to estimate the spatial heterogeneity, extent and change of carbon stocks within and across various systems. We designate the use of the term wet carbon system to the interconnected wetlands, ocean, river and streams, lakes and ponds, and permafrost, which are carbon-dense and vital conduits for carbon throughout the terrestrial and aquatic sections of the carbon cycle. We reviewed wet carbon monitoring studies that utilize earth observation to improve our knowledge of data gaps, methods, and future research recommendations. To achieve this, we conducted a systematic review collecting 1622 references and screening them with a combination of text matching and a panel of three experts. The search found 496 references, with an additional 78 references added by experts. Our study found considerable variability of the utilization of remote sensing and global wet carbon monitoring progress across the nine systems analyzed. The review highlighted that remote sensing is routinely used to globally map carbon in mangroves and oceans, whereas seagrass, terrestrial wetlands, tidal marshes, rivers, and permafrost would benefit from more accurate and comprehensive global maps of extent. We identified three critical gaps and twelve recommendations to continue progressing wet carbon systems and increase cross system scientific inquiry.

Phase assemblance evolution during wet carbonation of recycled concrete fines

In this work, recycled concrete fine (RCF), one of the major products generated from waste concrete recycling process, was carbonated in water. The carbonation mechanism of RCF is investigated, aiming to bring forward the basic understanding of carbonation mechanism and develop value-added products. It was found that the CO2 dissolution and calcite precipitation limited the carbonation process for the initial stage. Afterwards, the kinetics was dominated by the dissolution of RCF. Portlandite was firstly consumed and the decalcification of C-S-H involved three steps associated with pH development of the aqueous environment. The main carbonation products were calcite, amorphous calcium carbonate (CC), alumina-silica gel, silica gel and alumina gel. The formed CC was turned from a poorly-crystalline layer into aggregated calcite grains. Meanwhile, a silica-rich layer was still located at the outermost surface of carbonated RCF. The carbonated RCF had a significantly high pozzolanic reactivity, being reused as supplementary cementitious materials.

An Electrokinetic Study of Amino Acid and Potential-Determining Ions for Enhanced Waterflooding in Carbonate Reservoirs

Summary Reservoir rock wettability plays an important role in waterflooding especially in fractured carbonate reservoirs because oil recovery tends to be inefficient from the mixed-wet or oil-wet rock matrix. Improved oil recovery has been observed by adjusting the concentrations of potential-determining ions (PDIs) to alter the wettability of carbonate rocks. Our previous study showed that the oil recovery from carbonate reservoirs by waterflooding can be enhanced by the addition of glycine, the simplest amino acid. The interaction of glycine anion and oil-wet carbonate surfaces was confirmed in contact angle measurements and yielded the incremental oil recovery in imbibition experiments. This paper presents a surface complexation model (SCM) for the interaction between glycine and oil-wet carbonate surfaces that considers the impact of temperature, pH, salinity, and the concentrations of PDIs. The proposed SCM was tuned based on the zeta potential (ZP) data reported for synthetic calcite in glycine solutions. The tuned model predicts that the strong affinity of glycine for the oil-wet carbonate surface causes the carboxylic acids to desorb from the surface. The concentration of adsorbed carboxylic acids was in qualitative agreement with the water-wetting state of carbonate rocks inferred from the reported contact angle and spontaneous imbibition experiments. Moreover, the model indicates that glycine’s performance as a wettability alteration agent improves significantly at high temperatures. It also suggests that enhanced oil recovery (EOR) by formation brine (FB) with 1 to 3 wt% glycine at high temperatures should be similar to the injection of low-salinity seawater (LSW). The proposed SCM supports glycine’s potential to change the wettability of oil-wet carbonates at high salinity, high hardness, and high temperature.

Preparation of Reactive Urchin-Like Recycled Concrete Aggregate by Wet Carbonation: Towards Improving the Bonding Capability of the Interfacial Transition Zone in Recycled Aggregate Concrete

Preparation of Reactive Urchin-Like Recycled Concrete Aggregate by Wet Carbonation: Towards Improving the Bonding Capability of the Interfacial Transition Zone in Recycled Aggregate Concrete

Surfactant and surfactant-polymer effects on wettability and crude oil liberation in carbonates

Surfactants and polymers are used in enhanced oil recovery (EOR) to reduce interfacial tension and increase the viscosity of displacing fluid, respectively. For oil-wet to mixed-wet systems, especially carbonates, which tend to be heavily fractured, wettability becomes a key parameter that strongly affects oil recovery. Therefore, studying the impact of surfactant and surfactant-polymer chemicals on carbonate wettability is important to understand the underlying mechanisms responsible for incremental oil recovery in surfactant-polymer flooding. In the present study, liberation kinetics of crude oil from carbonate surfaces were investigated by using a liberation cell at both ambient and elevated temperatures (70 °C). The liberation cell is equipped with an optical microscope for monitoring oil liberation. In addition, a custom-designed integrated thin film drainage apparatus (ITFDA) was used to measure adhesion forces between carbonate substrates and crude oil droplets. The chemical solutions were prepared in a representative high salinity brine. Two types of surfactants: a nonionic and an amphoteric were used and a sulfonated polyacrylamide polymer was selected. The chemical solutions were prepared at dilute concentrations of 1000 mg/L and 500 mg/L for the surfactant and polymer, respectively. Besides the main experimental data, i.e., adhesion forces and liberation kinetics, interfacial tensions and zeta potentials were also measured for different solutions. In the zeta potential tests, carbonate particle suspensions in brine, surfactant, polymer and surfactant-polymer solutions were used. Oil liberation from carbonate surface is the lowest with brine and the polymer increased the degree of oil liberation. The amphoteric surfactant showed better efficiency to liberate more crude oil from carbonate surface over the nonionic surfactant. Polymer and surfactant addition to brine resulted in an oil liberation degree that is much higher than those obtained by each of the chemicals when applied individually. For solutions containing brine, polymer, surfactant, and surfactant-polymer, oil liberation degree increased at elevated temperature. Adhesion forces were very consistent with the observed oil liberation results. Adhesion force was strongest in brine, and both the polymer and surfactants further lowered the adhesion force. Accordingly, the lower adhesion force between carbonate and crude oil in aqueous solutions containing surfactant and polymer contributed to the increased oil liberation. The higher oil liberation degree obtained with the amphoteric surfactant can be explained by its ability to lower oil/water interfacial tension by two to three orders of magnitude. In addition, the surface charges of carbonate particles were found to be increasingly negative in aqueous solutions containing surfactant and polymer, thereby contributing to enhanced wettability alteration in crude oil-brine-carbonate systems. These microscale results indicate that trapped-oil mobilization in carbonates is governed by both wettability and capillarity; in other words, wettability alteration as well as reduction in oil/water interfacial tension would lead to increased oil liberation. This experimental study has characterized, for the first time, surfactant, and surfactant-polymer effects on wettability and crude oil release from carbonate surface at microscale through adhesion force and dynamic oil liberation measurements. Such enhanced understanding obtained on the microscale interactions of surfactant, and surfactant-polymer chemicals at carbonate/brine/oil interfaces can provide some guidance on how to optimize EOR formulations for carbonate reservoirs. • Higher negative surface charge for carbonate particles in surfactant and surfactant-polymer solutions. • Two to three orders of magnitude reduction in interfacial tension with amphoteric surfactant. • Lowest adhesion forces for crude oil on carbonate surface in surfactant, and surfactant-polymer solutions. • Better efficacy of amphoteric surfactant over non-ionic surfactant to liberate crude oil from carbonate surface. • Trapped-oil mobilization in carbonates is governed by both wettability and capillarity.

Biogas upgrade using modified natural clay

• The biogas upgrade using clay slurry resulted in pH decrease from 9.2 to 6. • Activation of clay with NAOH increased CO 2 uptake by more than 5 folds. • The highest CO 2 capacity achieved was 5.72 mmol/g activated clay. • The breakthrough curves for column adsorption fitted best into Yan Model. • H 2 S was eliminated from biogas using clay slurry. The pollutants in biogas reduce its calorific value and limit its application in machines by causing corrosion and wear in metallic parts. The commercial technologies of biogas upgrade are expensive for small digesters. Natural adsorbents present cost-effective and locally available materials for purification of biogas but the process has not been satisfactorily investigated for most materials. The current study for the first time compared upgrading of biogas by removing CO 2 contaminants with clay through dry adsorption and wet carbonation processes. Natural and modified clay was characterized using X-ray fluorescence. Biogas composition was analysed using gas chromatography and digital biogas analyser. The adsorption equilibrium, kinetics isotherm and breakthrough curves of carbon dioxide removal were investigated using CAVS adsorption software. The optimum slurry temperature and clay/water ratio for CO 2 uptake by carbonation process were 75 °C and 1:3 respectively. The carbonation process resulted in pH decrease from 9.2 to 6. Furthermore, activation of clay using 2 M NaOH decreased the silica to alumina (SiO 2 /Al 2 O 3 ) ratio from 11.2 to 8.5 and enhanced the CO 2 uptake by more than 5 folds. The equilibrium and the kinetics data of CO 2 removal by carbonation process fitted best into Freundlich isotherm and pseudo-first order equation respectively. In addition, the breakthrough curves for column adsorption fitted best into Yan model. The highest CO 2 uptake capacity for modified clay was 5.72 mmol/g. Furthermore, complete removal of hydrogen sulfide was achieved. The CO 2 uptake decreased on increasing the ratio of adsorbent mass to biogas volume. However, the CO 2 removal efficiency increased to maximum of 93.8% at 7 g/l ratio. Therefore, modified clay is a potential candidate for biogas purification.

Investigation of anionic in place of cationic surfactants onto oil wet carbonate surfaces for improving recovery

This paper depicts the utilization of sodium dodecyl sulphate (SDS) that replaces and enhances traditional use of cationic surfactant that is acetylene tri alkyl bromide (CTAB) for improving oil recovery. The SDS was assessed in Alkaline Surfactant Polymer (ASP) slugs containing regularly utilized surfactants with polymers. The impact of SDS on interfacial tension (IFT), adsorption and recovery was contrasted with that of a CTAB in these applications. The SDS was seen as good with saline solutions containing high total dissolved salt and greater volumes of double cations. They can be utilized in saline solutions without the requirement for softening and they give preferable outcomes over traditional CTAB in frameworks where either can be utilized. The SDS has the favourable position of improved recovery with unsoftened saline solution. Their non-reactive properties make them especially appropriate for ecologically delicate applications at on land and offshore oil fields.

Can Wet Aggregate Stability and Texture Regulate Organic Carbon Stock in Alluvial Soils of East Champaran (Bihar)?

Aims: Here in this experiment, the investigation was done for the relationship among the various soil health parameters i.e., soil organic carbon (SOC), soil texture, and wet aggregate stability (WAS).
 Place and Duration of Study: Sample: Collection of soil samples were done from 0-15 cm depth from East Champaran is situated in Bihar and is located at 26038’N and 84054’E in the year 2019-2020.
 Methodology: Soil texture: 14g (+/- 0.1g) of sieved soil was added to a 50 ml centrifuge tube holding 42 ml of a dispersant 3% sodium hexametaphosphate solution follwed by 2 hr shaking and 0.053 mm sieved. Water stable aggregates: Each 0.25-mm sieve contained 4g of air-dried, 2-mm aggregate soil. Each sample's precise weight was recorded. The soil samples were dispersed for 3 minutes with 100 mL distilled water and then for 10 minutes with a 2 g/L sodium hexametaphosphate solution. Pre-weighed filter sheets were used to filter both solutions. Each filter paper was weighed after being oven-dried at 105°C.
 Soil organic carbon: The amount of soil organic carbon (SOC) was calculated using the Walkley and Black technique (1934).
 Results: Wet aggregate stability and soil organic carbon storage were shown to have a strong positive connection. Soil carbon stock in soils of East Champaran varied between 5.27-19.60 Mg ha-1 with an average of 12.98 Mg ha-1. WAS ranged from 3.82 to 36.43% with a mean of 16.11%. The results revealed that WAS increased with increase in SOC stock. This experiment also revealed that clay (%) and silt (%) directly affect WAS and hence enhance SOC storage.
 Conclusion: So, it can be concluded that WAS and soil texture directly and positively impact SOC storage in soils of East Champaran, Bihar.

Land management effects on wet aggregate stability and carbon content

AbstractLand management affects soil structure and many other soil properties and processes. Our objectives were to evaluate soil organic C (SOC), aggregate size distribution, aggregate‐associated C, and soil structure as affected by long‐term land management and slope. A chronosequence of 38 on‐farm sites with low to high (5–18%) slopes was selected to evaluate 5–40 yr of management. The sites were classified as business as usual (BAU) cropland (BAU‐Crop), BAU pasture (BAU‐Past), newly established conservation reserve program (CRP) areas (CRP‐New), and established CRP (CRP‐Old). Soil samples were collected from the 0‐to‐5‐ and 5‐to‐15‐cm depth increments and processed for soil property measurements including fractionation by wet sieving into five aggregate size classes (>2,000, 1,000–2,000, 500–1,000, 250–500, and 53–250 μm). Within the surface 5 cm, mean weight diameter (MWD) and geometric mean diameter (GMD) were used to characterize soil structural stability. The BAU‐Past and CRP‐Old sites had 79% more macroaggregates (>2,000, 1,000–2,000, and 500–1,000 μm), 123% higher MWD, 38% higher GMD, and 47% higher SOC than BAU‐Crop or CRP‐New sites. The 5‐to‐15‐cm depth increment showed a similar but lower magnitude response. Aggregate‐associated C was quantified using a constant soil mass that reflected aggregate size distribution to prevent overestimating C content. Lower‐slope locations had more SOC, more macroaggregates, more C associated with macroaggregates, and higher GMD and MWD compared with high‐slope locations across all management classifications and soil depths. The results support our hypothesis that the high‐slop soils may benefits from specific management decisions than the lower‐sloping soils as a function of landscape property. We recommend reestablishing grassland on sloping land that is susceptible to excessive soil erosion, although those practices will likely take a long time to restore soil structural stability and SOC content to precultivation levels.

Efficiencies of carbonation and nano silica treatment methods in enhancing the performance of recycled aggregate concrete

This study compared the efficiencies of five recycled aggregate treatment methods (pressurized gas–solid carbonation (PC), flow-through gas–solid carbonation (FC), wet carbonation (WC), nano-silica (NS) spraying and combined PC with NS spraying (PCNS)) in enhancing the performance of recycled aggregate concrete (RAC). Mechanical properties, durability and microhardness of RACs were evaluated. The results showed that PC method recorded higher enhancing efficiency than both FC and WC method. NS spraying method caused higher improvement in mechanical properties of RAC than three carbonation methods. Because of the synergistic effect of enhanced old mortar and new ITZ, PCNS method recorded the highest efficiency.

Wetting Kinetics of Molten Carbonate on Carbon.

The wettability of molten carbonate on carbon determines the electrochemical performances of high-temperature direct carbon fuel cells (DCFCs). However, a universal method to measure the high-temperature wettability of molten carbonate is absent and the wetting kinetics is not well understood. Herein, we develop a dispensed drop (DD) method to measure the wetting kinetics of molten carbonate (Li2CO3-Na2CO3-K2CO3, 43.5:31.5:25.0, molar ratio) on the carbon substrate at 450-750 °C under controlled atmospheres (100%Ar, 100%CO2, and 1%O2-99%N2). The measured contact angles under different conditions reveal that increasing the O2- concentration in the gas-liquid-solid (GLS) interface decreases the contact angle. In addition, elevating the temperature, introducing O2 in the gas atmosphere, or pretreating the carbon substrate can enhance the wetting kinetics of molten carbonates. The molten carbonate completely wets the carbon substrate in 150 min in Ar gas atmosphere and in 30 min in 1%O2-99%N2 gas atmosphere at 600 °C. Further, it takes only 30 min to completely wet the pretreated carbon substrate in Ar atmosphere at 600 °C. Overall, this paper offers the DD method to study the wettability of molten carbonate on the carbon substrate, which is helpful to understand the underlying wetting mechanism and engineer the electrode design for DCFCs.

Automated Fabrication of Perovskite Photovoltaics Using Inkjet Printing and Intense Pulse Light Annealing

Rapid chemistry and processing development has increased the performance of perovskite solar cells (PSCs) in an unprecedented manner, yet postdeposition annealing impedes high‐throughput manufacturing. Herein, SnO2 and carbon charge transport films are fabricated entirely through an integrated robotic setup utilizing inkjet printing and intense pulse light (IPL) as a high‐speed postprocess annealing method; hence, process optimization is crucial for successful fabrication of PSCs. This work investigates the role of inkjet deposition parameters as well as IPL annealing on the morphology and uniformity of films with aid of spectroscopy and spectrophotometry. Initially PSCs exceeding 13% efficiency are developed by only fabricating the SnO2 film through the robotic setup, but spin coating all other films followed by IPL annealing to demonstrate successful fabrication of SnO2 layer. Finally, SnO2 and carbon back contact films are entirely fabricated through the integrated robotic setup in a high humid ambient environment (>60%), resulting in PSCs exceeding 5% efficiency. Unlike successful direct annealing of SnO2 wet films, IPL annealing of wet carbon severely damaged the phase and morphology necessitating rapid solvent removal before IPL annealing. This work establishes pioneering steps towards utilizing IPL in an entirely automated fabrication line, allowing for scalable fabrication of PSCs through non‐roll‐to‐roll.

Assessment of aggregate stability and soil organic carbon sequestration in Alfisols of Guinea Savanna

Soil aggregate stability is a vital indicator for improving soil quality and controlling soil losses. This study aimed to assess the effect of fallow forage legumes and fertilizer application on wet and dry stability aggregate and soil organic carbon on Alfisols of Guinea Savanna, Nigeria. The study was conducted at the Institute for Agricultural Research (IAR) experimental field, Samaru Zaria. Treatment consisted of 3 plots (Centrosema pascuorum (Cp planted), Macrotyloma uniflorum (Mu planted) and control-natural vegetation regrowth). The soil samples collected were dried at room temperature and then separated into six aggregate fractions. Aggregate stability assessment results showed that dry stable aggregate fraction was significantly influenced by fallow management practice where Cp planted fallow recorded the highest amount in soil aggregate sizes of 2000 μm (0.99 g kg-1). Concerning wet stable aggregate, the proportion of 2000 μm sized aggregate fraction had the highest value (0.22 g kg-1) under treatment Cp. However, 0 kg N ha- 1 -1 produced the highest quantity in 2000 μm (0.23 g kg ) sized stable aggregates, and there was no significant difference in Nitrogen and Phosphorus application rates. The wet mean weight diameter (MWD) was significantly affected by forage legume with Mu planted fallow having the highest value (0.40 g kg-1) while the dry MWD aggregates with Cp recorded the best value (1.37 g kg-1). Cp planted fallow sequestered more carbon (0.65 g kg-1) in the 500 µm aggregates fraction. NVR contributed the highest carbon (0.80 g kg-1) under 50 µm sized aggregates. For carbon content in <50 µm sized aggregates, Mu produced the highest carbon (0.72 g kg-1) in the fraction. Conclusively, the type of management practices affects the soil aggregation size fractions, which increased soil organic carbon sequestered.

Synthesis of amorphous nano-silica from recycled concrete fines by two-step wet carbonation

In this work, a two-step wet carbonation process was developed to synthesize amorphous nano-silica by extracting the silicon phase from recycled cement fines (RCF), aiming to convert RCF into value-added products and sequester CO2. The phases evolution and their microstructure during carbonation were investigated. The results indicated that the RCF was carbonated rapidly to form a mixture of calcite and amorphous silica gel, followed by the formation of silica bearing gel containing aluminosilicate gel and silica gel after two-step wet carbonation. An amorphous silica with a purity of 98.8% and in the form of aggregated nanoparticles (<10 nm) was successfully prepared, and another calcium carbonate-rich material was produced as a by-product. The proposed approach tackled several issues such as sequestration of CO2 (0.27 g CO2 per 1 g RCF), converting RCF into value-added nano-silica and promoting the recycling of RCF, which has good potential to be industrialized.

Fast enhancement of recycled fine aggregates properties by wet carbonation

Accelerated carbonation for recycled concrete aggregate (RCA) was one of the effective and economic solutions for improving the quality of RCA and its concrete products. Previously, a fast wet carbonation method was developed and proved to be effective for property enhancement of the coarse fraction of RCA by transforming the carbonation reaction from a gas-solid phase to a liquid-solid phase. Fast carbonation is essential for providing a cost effective and practical method of enhancing the properties of recycled aggregates by waste CO2. In order to investigate the feasibility and effectiveness of the wet carbonation for fine RCA (i.e. < 5 mm), this study presents the results of an experimental investigation by using both laboratory-prepared well-hydrated cement paste particles (RCP) and a real fine RCA derived from demolished concrete. The test results of RCP revealed that a quick 10-min wet carbonation densified the surface layer of the particles, significantly reduced the volumes of the pores less than 10 nm, and increased the carbonation products by 2.6–3.5%. Moreover, the mortar specimens prepared by the carbonated fine RCA showed a 32.6% increase in compressive strength and a 6.4% reduction in drying shrinkage. Replacing 50% river sand by the carbonated fine RCA in the new mortar would not result in significant property deterioration.

Research on the integration of flue gas desulfurization and dust removal in oil shale refining

The flue gas of oil shale retort is characterized by high humidity, low sulfur content and tar content, which makes it impossible for traditional flue gas desulfurization facilities to deal with such flue gas normally. By collecting flue gas parameters at the inlet and outlet of the original desulfurization tower of oil shale dry distillation flue gas, and combining with computational fluid dynamics numerical simulation, this paper analyzes the fault reasons of each step in the process of desulfurization of oil shale dry distillation flue gas. Through experimental study, the flocculation characteristics of suspended solids and petroleum substances in desulfurization circulating liquid were analyzed. The results show that the low concentration of Na2CO3, Ca(HO)2, CaO desulfurizer can promote the flocculation, Ca(HO)2, CaO desulfurizer is beneficial to the removal of petroleum substances. The original wet limestone-gypsum desulfurization system was transformed into the wet sodium carbonate desulfurization and dust removal integrated system. The method of flocculation and sedimentation is used to remove sludge and petroleum substances, which can ensure the normal operation of the system and the emission of flue gas up to the standard.