Limestone Sludge Research Articles

High-performance and low-cost electrochemical reactor for limestone decarbonation applied to clinker production – A validation at laboratory scale

Limestone decarbonation to obtain CaO (calcium oxide) and produce cement is an industrial activity with enormous CO2 emissions (CaCO3(s)→CaO(s)+CO2(g)), due to the intrinsic calcination reaction of CaCO3 (calcium carbonate), in addition to the use of fossil fuels. One of the most recent ideas to reduce CO2 emissions in this process has been the electrochemical decarbonation of limestone where Ca(OH)2 (calcium hydroxide) is obtained as an intermediate product that is then used as CaO precursor in clinker synthesis.This study shows the design of a low-cost electrochemical reactor and the optimization of the parameters to produce Ca(OH)2 with high purity and yield from the decarbonation processes of pure CaCO3 and limestone used in the cement industry. In addition, the remaining limestone sludge and electrolytic solutions were analyzed, and it was found that the sludge can be used as a correction material in clinker preparation, and it is also possible to reuse the electrolytic solution twice. Finally, the main finding is the proposal of a new clinker synthesis, which results in a cement with comparable characteristics to those of ordinary Portland cement, using Ca(OH)2 obtained from the electrochemical decarbonation of CaCO3, achieving a reduction in CO2 emissions of approximately 90% compared to the conventional method.

Use of Limestone Sludge in the Preparation of ɩ-Carrageenan/Alginate-Based Films.

The use of processed limestone sludge as a crosslinking agent for films based on Na-alginate and ɩ-carrageenan/Na-alginate blends was studied. Sorbitol was tested as a plasticizer. The produced gel formulations included alginate/sorbitol and carrageenan/alginate/sorbitol mixtures, with tested sorbitol concentrations of 0.0, 0.5 and 1.0 wt%. The limestone sludge waste obtained from the processing of quarried limestone was converted into an aqueous solution of Ca2+ by dissolution with mineral acid. This solution was then diluted in water and used to induce gel crosslinking. The necessity of using sorbitol as a component of the crosslinking solution was also assessed. The resulting films were characterized regarding their dimensional stability, microstructure, chemical structure, mechanical performance and antifungal properties. Alginate/sorbitol films displayed poor dimensional stability and were deemed not viable. Carrageenan/alginate/sorbitol films exhibited higher dimensional stability and smooth and flat surfaces, especially in compositions with 0.5 wt% sorbitol. However, an increasing amount of plasticizer appears to result in severe surface cracking, the development of a segregation phenomenon affecting carrageenan and an overall decrease in films' mechanical resistance. Although further studies regarding film composition-including plasticizer fraction, film optimal thickness and film/mold material interaction-are mandatory, the attained results show the potential of the reported ɩ-carrageenan/alginate/sorbitol films to be used towards the development of viable films derived from algal polysaccharides.

Development of Clay-Composite Plasters Integrating Industrial Waste.

This research investigates the feasibility of developing clay composites using natural materials and incorporating waste by-products suitable for plastering diverse support structures. The study identified a versatile composition suitable for a wide range of support materials and explored the potential of revaluing industrial waste and by-products by reintegrating them into the Circular Economy. The experimental investigation outlines the process of evaluating the influence of different raw materials on the performance of the clay composite. The findings confirm that using limestone sludge and fly ash as additives to clay contributes to reducing axial shrinkage and increasing mechanical strengths, respectively. The optimal percentage of additives for the clay used are identified and provided. Using hydraulic lime as a partial substitute for clay reduces the apparent density of dried clay composites, axial shrinkage, and fissures formation while improving adhesion to the substrate. Introducing dextrin into this mix increases the apparent density of the hardened plaster while keeping axial shrinkage below the maximum threshold indicated by the literature. Mechanical strengths improved, and better compatibility in terms of adhesion to the support was achieved, with composition S3 presenting the best results and a smooth, fissure-free plastered surface after drying.

Characterization of Cu2+ adsorption for eco-hydroxyapatite derived from limestone sludge via hydrothermal synthesis

Characterization of Cu2+ adsorption for eco-hydroxyapatite derived from limestone sludge via hydrothermal synthesis

Critical review of mineral admixture impregnation in bituminous mixes

The effect of different materials in bituminous mixes, as well as their variance in test parameters, are summarised in this paper. Many studies which were carried out earlier were studied to enhance the sustainable parameters from waste materials. Engaging the proper materials usage with precise can make the bitumen more cost-effective and durable one. For user in order to reduce the cost, the engineers started investigation on the usage of treated waste from different industries as filler in the mix. The use of 4–7 percent Fillers is advised because the amount of ash increases the mix's Marshall Stability. It is concluded that stone dust and limestone sludge, cement, coal ash, zeolite powder, limestone, rice husk ash, date seed Ash, broken brick powder, broken tile powder, cow Bone ash, Broken Glass powder, waste brick powder can be used as a filler. All these materials can be used as the filler and combination of these fillers forms a mastic mix of the bitumen and increases durability. The increase in Marshall Properties can be observed by the addition of filler. This critical review research emphasizes the waste material to serve the purpose of increasing the stability, durability and strengthen the mix and to keep the environment clean using these materials gives satisfactory results. According to abundant study, 25% fly ash by total weight of filler bounces with characteristics comparable to traditional Marshall Stability and Flow value of asphalt mix. Apart from these brick dust or stone dust also produce lot of air voids, but it also provide a lot of stability, so it can be used to replace traditional fillers in almost all cases. The Marshall Stability and flow value of the mix design properties after using the above-mentioned fillers are the focus of this study.

The use of limestone sludge for the geopolymer preparation

The study investigates the effect of sludge waste from mining and washing of limestone on the properties of geopolymer binders based on metakaolin and blast furnace slag. The effect of adding two types of limestone sludge on workability, setting time, compressive strengths, durability and pore distribution was investigated. Limestone sludge was dosed in an amount of 0–30 %. Sodium water glass was used as an alkaline activator in the ratio of 5:4. A linear correlation between the flowability and limestone sludge content was observed, and very satisfactory results of compressive strength after 90 days were obtained for samples with sodium water glass (about 55 MPa). The positive effect of CaCO3 on strength was confirmed. The increased content of clay components resulted in a reduction of compressive strength.

Feasibility Analysis and Key Issues of Using Limestone Sludge in Power Plant Desulfurization System

Comparative analysis of limestone sludge in recycled water and desulfurization limestone is made in the chemical composition, reaction activity, crystallization properties and pH of Slurry. The results show that the limestone sludge in recycled water is possible to be used as a desulfurizer. Due to the large amount of impurities and lower reactivity of limestone sludge, the overall performance index values of limestone sludge are lower than that of desulphurization limestone. If it wants to be used as a desulfurizer, the further research on the using conditions of recycled water limestone sludge in desulfurization system and the possible impact of the reuse of desulfurization system on the stable operation of the system are needed.

Feasible utilization of waste limestone sludge as filler in bituminous concrete

The dimensional limestone industries produce a substantial amount of waste limestone sludge during the polishing of stone slabs. The storage and disposal of this non-biodegradable sludge cause issues regarding environmental pollution, shortage of disposal land, increase in transportation cost, and several other associated problems. This study investigated the usability of dried limestone sludge (LS) instead of conventional stone dust (SD) as filler in bituminous concrete mixes. The performance of SD and LS incorporated mixes in several aspects was compared, and the amount of LS needed to ensure optimum bituminous mix behavior is determined. The physical and chemical properties of both fillers were initially explored. Then bituminous concrete mixes having both fillers added at four different proportions (4, 5.5, 7.0, and 8.5% by weight of aggregates) were prepared using the Marshall mix design method and their optimum bitumen contents (OBC) were determined. The performance of both mixes was studied. LS mixes displayed paramount rutting resistance, fatigue resistance, indirect tensile strength, ravelling, and resilient modulus than conventional mixes. It mostly attributed to the fine nature of LS, which ensured its better distribution. LS mixes also had lower OBC than SD mixes due to lower porosity and bitumen extender action of LS. LS displayed a good affinity towards bitumen due to calcite in its composition, which led to excellent adhesion and moisture resistance in its mixes. The test results suggested that the utilization of chosen LS as filler at an optimum filler percentage of 6.45% can result in formation of bituminous mixes with satisfactory engineering properties, lower bitumen content as well as lower greenhouse gas emissions.

Characteristics of Entisol Treated With Pulp Residue and Fertilizer in Eucalyptus Plantation

The purpose of this study was to identify, through multivariate analyzes, the physical and chemical characteristics of the soil that best explain the initial development of eucalyptus treated with limestone and lime sludge. This study was conducted in 2014 in the municipality of Três Lagoas (MS). Three treatments were experimented corresponding to the applications of (i) limestone, (ii) lime sludge, and (iii) control or application of neither limestone nor lime sludge. The principal components analysis identified that Group 1 assembling gravimetric moisture, hydrogen potential, calcium and aluminum and, Group 2 composed of contents of sand, clay, phosphorus and organic matter explained 54.96% of the total variability that showed higher discriminatory power of eucalyptus height and diameter variation at breast height. The treatment with limestone showed a contrast between high pH and high Ca content, but low levels of aluminum.

Properties of Cement Mortar Using Limestone Sludge Powder Modified with Recycled Acetic Acid

One of the various methods of manufacturing low-carbon cement is substituting limestone powder as a raw material or admixture. Limestone sludge powder (LSSP) has the same composition as that of limestone powder. The surface characteristics of LSSP powder modified with recycled acetic acid (RAA) and the characteristics of cement using this modified LSSP as a substitute were investigated in this study. The surface of LSSP modified with RAA was converted into calcium acetate and had a large grain size. When conventional LSSP was used as a substitute for cement, the initial strength increased owing to improved pore filling; however, the strength after 28 days of aging was lower than that of non-substituted cement. In the case of modified LSSP being replaced with cement at up to 10% of the cement weight, however, the calcium acetate on its surface increased the amount of hydration products in the cement, thereby increasing both the initial and the long-term strength.

Steel-Corrosion Characteristics of an Environmental Inhibitor using Limestone Sludge and Acetic Acid

Calcium acetate, which can be used in concrete to shorten the construction period and to improve productivity, was manufactured using limestone sludge and acetic acid. Calcium acetate contains a carboxyl group, and it can provide anticorrosive properties by forming a complex with the steel surface. We evaluated the basic performance of a carboxylic early-strength agent produced from industrial by-products (limestone sludge and acetic acid) as a corrosion inhibitor. A comparative evaluation was performed using calcium nitrate, which is a conventional early-strength agent; the corrosion area ratio, corrosion state, and electrochemical performance of a steel plate immersed in aqueous solutions were evaluated. A steel plate immersed in calcium acetate was not substantially corroded. The electrochemical investigations showed a high corrosion potential based on the impedance characteristics. The corrosion current showed anodic values, and no corrosion occurred on the surface of the steel plate because of the adsorption of carboxyl groups. Scanning electron microscopy indicated that the steel plate was covered by a crystalline coating, which suppressed corrosion. We show that it is possible to develop an environmentally friendly recycling method as an early-strength agent and corrosion inhibitor when manufacturing calcium acetate using limestone sludge.

Utilization of reduction slag and waste sludge for Portland cement clinker production

The feasibility of recycling the reduction slag, limestone sludge, iron‐oxide sludge, and stone sludge produced in the manufacture of cement was investigated through compressive strength testing, differential thermal and thermogravimetric analysis, X‐ray diffraction, and 29Si nuclear magnetic resonance analysis. The major crystalline phases of ecocement clinkers, namely C3S, β‐C2S, C4AF, and C3A, were observed. C3S content decreased and β‐C2S and α‐C2S content increased in the reduction slag. The compressive strength of EcoA pastes (ecocement contain 78% of limestone sludge, 19.51% of stone sludge and 2.49% iron‐oxide sludge) was similar to that of commercial ordinary Portland cement. The Q0 (−70 ppm) species shifted to the Q1 (−80 ppm), and Q2 (−87 ppm) species during curing. The addition of stone sludge, iron‐oxide sludge, and limestone sludge had no negative effect on the hydration of the cement pastes. In contrast, the addition of reduction slag negatively affected the formation of clinker minerals. Cement samples with reduction slag content of 1–7 wt % had lower 28‐, 60‐, and 90‐day compressive strength than did the control mix. © 2017 American Institute of Chemical Engineers Environ Prog, 37: 669–677, 2018

Recycling of spent catalyst and waste sludge from industry to substitute raw materials in the preparation of Portland cement clinker

This study investigated the feasibility of using waste limestone sludge, waste stone sludge, iron oxide sludge, and spent catalyst as raw materials in the production of eco-cement. The compressive strength development of the Eco Cement-A (ECO-A) paste was similar to that of ordinary Portland cement (OPC) pastes. The compressive strength development of the ECO-B paste was higher than that of OPC pastes. In addition, the C2S (Ca2SiO4, C2S) and C3S (Ca3SiO5) minerals in the eco-cement paste were continuously utilized to hydrate the Ca(OH)2 and calcium silicate hydrates gel (Ca6Si3O12·H2O, C–S–H) throughout the curing time. When ECO-C clinker contained 8% spent catalyst, the C3S mineral content decreased and C3A (3 CaO·Al2O3) content increased, thereby causing the structure to weaken and compressive strength to decrease. The results showed that the developed eco-cement with 4% spent catalyst possessed compressive strength properties similar to those of OPC pastes.

Hydration characteristics of recycling reduction slag and waste sludge by co‐sintered treatment produced as eco‐cement

Waste materials have traditionally been discarded in landfills and often dumped directly into ecosystems without adequate treatment. However, possible reuse and recycling alternatives should be investigated and implemented. Recent environmentally friendly approaches have been aimed at achieving sustainable development by conserving natural resources and minimizing the discarding of materials. The objective of the present study was to investigate the hydration characteristics of reduction slag, limestone sludge, stone sludge, and iron‐oxide sludge for fabricating four types of eco‐cement clinkers. The compound raw materials were burned for 2 h at 1400°C to form eco‐cement clinkers. The results showed that the major components of ordinary Portland cement (OPC), namely C3S, C2S, C3A, and C4AF, were present in the eco‐cement clinkers. The compressive strength development of EcoA pastes (containing 78% limestone sludge, 19.51% stone sludge, and 2.49% iron‐oxide sludge) was similar to that of the commercial OPC products. The compressive strength of the EcoD pastes (containing 71% limestone sludge, 19.51% stone sludge, 2.49% iron‐oxide sludge, and 7% reduction slag) decreased as the amount of α‐C2S increased. Mercury intrusion porosimetry indicated that the pore volume of the pastes gradually decreased with an increase in the curing time. Furthermore, the results of physical‐mechanical tests showed that reduction slag, limestone sludge, stone sludge, and iron‐oxide sludge can be used as raw materials in cement production at no cost to the producer, thereby reducing the production costs. © 2017 American Institute of Chemical Engineers Environ Prog, 36: 1466–1473, 2017

The Influence of FGD Gypsum Fabricated from Limestone Sludge on Cement Properties

For the purpose of reducing the amount of limestone, which is used as a desulfurization agent to absorbing SO X gas in thermal power plants, and to recycle limestone sludge generated from a steel mill, limestone sludge was utilized as a desulfurization agent. In this study, cement, made of flue gas desulfurization (FGD) gypsum obtained in a desulfurization process using limestone sludge, was manufactured then, experiments were conducted to identify the physical properties of the paste and mortar using the cement. The results of the crystal phase and microstructure analyses showed that the hydration product of the manufactured cement was similar to that of ordinary Portland cement. No significant decline of workability or compressive strength was observed for any of the specimens. From the results of the experiment, it was determined that FGD gypsum manufactured from limestone sludge did not influence the physical properties of the cement also, quality change did not occur with the use of limestone sludge in the flue gas desulfurization process.

석회석 슬러지의 석회석-석고 습식 배연탈황 공정적용에 관한 연구

배연탈황기술은 화력발전소에 발생하는 <TEX>$SO_2$</TEX> 가스를 제거하기 위한 효과적인 방법이며, 흡수제로 석회석을 사용하고 있다. 본 연구에서는 천연자원인 석회석의 사용량을 저감하고 산업 폐기물의 재활용을 위해, 제철소에서 발생하는 석회석 슬러지를 흡수제로 사용하고자 하였다. 흡수제 원료의 물리 화학적 특성분석을 실시하였으며, 전처리 설비를 구축하여 석회석 슬러지를 사용한 흡수제를 제조한 후 배연탈황 공정에 적용하였다. 제조 흡수제 적용 결과, <TEX>$SO_2$</TEX> 농도 변화상에서의 경향성은 나타나지 않았으며, 흡수탑에서의 운전 제어를 통해 석회석 슬러지를 흡수제로 사용 가능할 것으로 사료되었다. Flue gas desulfurization(FGD) is an effective technique to remove <TEX>$SO_2$</TEX> gases of coal-fired plants. Limestone is usually used as desulfurizing agent. In this study, we use the limestone sludge which is a by-product of steel industry in order to replace desulfurizing agent of FGD process. Physical and chemical characteristics analysis of desulfurizing agent was conducted. Desulfurizing agent using limestone sludge was fabricated by pre-treatment process and, then the agent was used on FGD process. Consequently, the tendency on the <TEX>$SO_2$</TEX> concentration did not appear. And limestone sludge was considered as possible alternative agent for flue gas desulfurization process through absorber control system.

Physical and Chemical Properties of Cement Mortar with Gamma-C2S

Presently, for the cement industry, studies that seek to reduce CO₂, because of the development of the plastic industry and demand for reduction of energy use, have been actively conducted among them, studies attempting to use Gamma-C₂S(γ-C₂S) to fix CO₂ have been actively conducted. The γ-C₂S compound has an important function in reacting to CO₂ and stiffening through carbonatization in the air. The γ-C₂S compound, reacting to CO₂ in the air, generates CaCO₂ within the pore structure of cement materials and densifies the pore structure this leads to an improvement of the durability and to the characteristic of resistance against neutralization. Therefore, in this experiment, in order to synthesize γ-C₂S, limestone sludge and waste foundry sands are used these materials are plasticized for 30 or 60 minutes at 1450°C, and are prevented from being cooled in the temperature range of 30 ~ 1000oC when they are about to be cooled. XRD analysis and XRF analysis are used to determine the effects of this process on γ-C₂S synthesization, the temperature at which a thing is plasticized, and the conditions for cooling that obtain in the plasticized clinker also, in order to confirm the CO₂ capture function, analysis of the major hydration products is conducted through an analysis of carbonatization depth and compressive strength, and through MIP analysis and XRD Rietveld analysis. As a result of these analyses, it is found that when γ-C₂S was synthesized, the clinker that was plasticized at 1450°C for one hour demonstrated the highest yield rate the sample with which the γ-C₂S was mixed generated CaCO₃ when it reacted with CO₂ therefore, carbonatization depth and porosity were reduced, and the compressive strength was increased.

Properties and microstructure of eco‐cement produced from co‐sintered washed fly ash and waste sludge

This study investigated the possibility of recycling washed fly ash, limestone sludge, stone sludge, and iron‐oxide sludge in raw meal for producing Portland cement clinker. All of the major phase components of ordinary Portland cement (OPC)—C3S, C2S, C3A, and C4AF—were identified in each eco‐cement clinker. The compressive strength development showed that the eco‐cement pastes no contained washed fly ash was similar to commercial OPC products. The exothermic peak at 105°C to 440°C corresponded to the coordination change of C‐S‐H gel in the pastes during curing time. The TG/DTA curves showed that the weight loss of the eco‐cement pastes no contained washed fly ash was higher than that of the eco‐cement pastes contained 1% washed fly ash. The Q0 (−70 ppm) species shifted to the Q1 (−80 ppm) and Q2 (−87 ppm) species during curing time. The degrees of hydration of the eco‐cement pastes contained 2 to 4% washed fly ash were lower than that of the eco‐cement pastes no contained washed fly ash. The results of the physicomechanical tests showed that adding the limestone sludge, stone sludge, and iron‐oxide sludge did not negatively affect the quality of the produced cement. © 2016 American Institute of Chemical Engineers Environ Prog, 35: 764–771, 2016

Properties of Calcium Acetate Manufactured with Etching Waste Solution and Limestone Sludge as a Cementitious High-Early-Strength Admixture

Concrete is one of the most widely used construction materials. There are several methods available to improve its performance, with one of them being the use of high-early-strength admixtures (HESAs). Typical HESAs include calcium nitrate, calcium chloride, and calcium formate (CF). Industrial by-products, such as acetic acid and lime stone sludge (LSS), can be used together to produce calcium acetate (CA), which can subsequently be used as a cementitious HESA. In this study, calcium carbonate and LSS were mixed with cement in weight ratios of 1 : 1, 1 : 1.5, and 1 : 2, and the properties of the as-produced CA were evaluated. CA and CF were mixed with cement in different weight ratios (0, 1, 2, and 3 wt%) to obtain CA- and CF-mortars, respectively. The flow behavior, setting time, pH, and compressive strength of these mortars were evaluated, and their X-ray diffraction patterns were also analyzed. It was found that as the CF content in the CF-mortar increased, the initial strength of the mortar also increased. However, it impaired its long-term strength. On the other hand, when 1% CA was mixed with cement, satisfactory early and long-term strengths were achieved. Thus, CA, which is obtained from industrial by-products, can be an effective HESA.

석회석 슬러지의 입도제어에 따른 배연탈황효율에 관한 연구

배연탈황 기술은 화력발전소의 연소가스에서 발생하는 <TEX>$SO_2$</TEX>를 제거하는 기술이다. 발전소에서는 주로 석회석을 이용한 습식 배연탈황공정을 적용하고 있으나, 천연자원인 석회석의 고갈 및 높은 운전동력 소비 등의 문제로 석회석을 대체할 수 있는 흡수제 개발에 매진하고 있다. 따라서 본 연구에서는 제철소에서 발생하는 석회석 슬러지를 흡수제로 적용하기 위해 석회석 슬러지의 입도분포에 따른 탈황성능을 검토하고자 하였다. 탈황효율 검토방법으로는 입도에 따른 석회석 슬러지의 물리 화학적 특성 검토 및 <TEX>$SO_2$</TEX>가스제거시험 등을 시행하였다. Flue gas desulfurization(FGD) is the technique to remove <TEX>$SO_2$</TEX> gas from stack gases of coal-fired plants. Many researcher have studied to replace the desulfurizing agent because FGD systems use a lot of limestone and energy. In this study, we use the limestone sludge which is a by-product of steel industry in order to replace desulfurizing agent of FGD system by control the particle size of limestone sludge. And desulfurization performance test is implemented by investigating <TEX>$SO_2$</TEX> gas removal properties upon the characteristic of the limestone sludge with various particle size.