Fly Ash Transportation Research Articles

Validation on fly ash DEM microparameters based on coarse-grained method

The computational efficiency of the discrete element simulation process is often a limiting factor. However, the use of the coarse-grained method, which employs dimensional analysis to amplify particles, significantly improves computational efficiency. This research utilizes the coarse-grained method to amplify particles and examines the impact of linear models on the mechanical of fly ash. By examining parameters such as magnification, stiffness, sliding friction coefficient, and rolling friction coefficient, we establish the relationship between fly ash cohesion, internal friction angle, and microscopic parameters in discrete element method (DEM) simulation. The simulation results demonstrate that the shear strength of fly ash increases as magnification, stiffness, and sliding friction coefficient increase. The rolling friction coefficient, on the other hand, has minimal effect on shear strength. The elastic potential energy of the system is unaffected by magnification, with stiffness inversely proportional to adaptable potential power. However, sliding and rolling friction coefficients positively impact adaptable potential power. Furthermore, this study proposes a practical simplification method for amplification of materials with small particle sizes. The comparison between numerical simulation and experimental data yields consistent results. As a result, this study provides a foundation for the application of large-scale fly ash transportation, storage, and other engineering purposes.

Optimization of specific energy consumption in the high concentration slurry disposal pipelines for coal ash in thermal power plants

ABSTRACT In thermal power plants, the disposal of coal fly ash is one of the major challenges requiring energy input for its safe disposal, so optimization is needed to minimize the required energy input at maximum fly ash transportation. Present work is focussed on high concentration optimized transportation of ash slurry in thermal power plants using Computational Fluid Dynamics (CFD) which behaves as a Bingham plastic fluid, modeled using Herschel-Bulkley model. Specific Energy Consumption (SEC) is the measure of the energy required for the slurry transportation. Therefore, a parametric investigation to establish the effect of concentration of slurry (Cw), pipe diameter (D), no. of pipes (N), particle size (d) over SEC is conducted. Therefore, these operational parameters need to be carefully selected, as even a minor variation from the desired optimum values may result in huge SEC consumption thereby causing financial consequences. It is found in the current study that the SEC substantially depends on all of the above-mentioned parameters. Mathematical models for prediction of SEC based on the study are also developed for the future designers of such systems.

Research on reuse of shield soil dregs on synchronous grouting materials and its application

Shield tunnel construction will produce a large amount of soil dregs. Transporting soil dregs directly to landfills raises costs and CO2 emissions. In this paper, the shield tunnel of Intercity from Shenzhen to Huizhou is taken as an example, based on the special treating agent of shield soil dregs, the soil dregs were prepared as synchronous grouting material. The working performance and mechanical properties of soil dregs grouting material were studied. The optimal dosage of the treating agent was proposed, and the curing mechanism of the soil dregs synchronous grouting material was analyzed. The soil dregs grouting material was applied to practical engineering, and the application effect was verified by surface subsidence monitoring. The results showed that the setting time, bleeding rate, stone rate and compressive strength of the soil dregs grouting material were better than cement mortar grouting material. The treating agent realized the cementation of soil particles through the synergistic effect of epoxy resin and nano-SiO2, and the optimum dosage is 0.02 % of the solid component. The maximum surface settlement of the soil dregs grouting construction section was 10 mm, which is smaller than the maximum surface settlement of the cement mortar grouting section. Through the life cycle assessment (LCA) method, the CO2 emission reduction capacity of the soil dregs synchronous grouting material was analyzed. The soil dregs grouting material reduced the production and transportation of fly ash and bentonite, and reduces the outward transportation of soil dregs. The use of 1 t soil dregs synchronous grouting material can reduce 59.05 kg CO2 emission.

Environmental impacts and environmental justice implications of supplementary cementitious materials for use in concrete

Abstract As the second most used material after water and the producer of 8%–9% of anthropogenic greenhouse gas (GHG) emissions, concrete is a key target for environmental sustainability efforts. Of these efforts, a main focus has been the use of industrial byproducts as supplementary cementitious materials (SCMs) to replace some of the cement binder, the source of most of the GHG emissions from concrete production. As byproducts, these SCMs are frequently assumed to have limited or no emissions from production. Our goal is to see if this assumption should continue to drive mitigation efforts and to arrive at a clearer understanding of the contribution of SCMs to the environmental impacts of concrete. Needing further examination are: (1) how environmentally beneficial SCMs are if some of the primary process impacts are attributed to them rather than considering them waste products; (2) whether transporting SCMs creates greater environmental impacts than the materials they are replacing; and (3) whether location of primary processes that result in SCMs as well as location of concrete production creates particular burdens on lower income and minority communities. This work focuses on three of the most common industrial byproduct SCMs, namely silica fume, fly ash (FA), and ground granulated blast furnace slag (BFS), exploring both GHG and particulate matter emissions. We show that allocation of impacts from primary processes dramatically increases emissions attributed to SCMs. High levels of transportation of FA and BFS typically do not result in these SCMs having higher GHG emissions than a 95% clinker-content Portland cement. We find that SCMs may be produced in areas with low income or minority populations then used to lower GHG emissions concrete in another location. As such, beyond common environmental impact assessment methods, the role of environmental justice should be incorporated into impact assessments.

Рекомендации по снижению абразивного износа гидротранспортных трубопроводов систем золошлакоудаления ТЭС

In the vast majority of cases, hydraulic ash and slag removal systems are used for conveying ash and slag at the coal-fired thermal power plants (TPPs) in Russia. Such technical solutions related to the evacuation of slag from boilers and transportation of fly ash after electrostatic precipitators have been replicated since the Soviet times. Hydraulic ash and slag removal systems cause significant damage to the natural environment in the area of coal-fired TPPs location. It should be noted, that the average age of TPPs is about 45-50 years. The inter-repair period and reliable operation of pipelines of TPP ash and slag removal systems significantly depend on abrasive wear, which is one of the main problems when transporting fine bulk materials like ash and slag. Abrasive wear or erosion in pipelines leads to a decrease in the reliability of the entire wet ash removal system; there is a need for the unplanned downtime caused by fistulas in pipelines, resulting in the release of ash and slag slurry into the environment. In addition, the thinning of the c'u'u pipeline wall thickness leads to the increase in the diameter of pipes, which, in turn, leads to deterioration in the eco- au'a nomic efficiency of transporting the ash and slag slurry. The article deals with the problem of abrasive wear of slurry pipelines of TPP ash and slag removal systems. Based on the research results, the main measures for extending the service life of straight and shaped sections of pipelines of TPP wet ash and slag removal systems are described. In order to reduce the intensity of abrasive wear, it is possible to apply regime measures that do not require investment in the reconstruction of existing hydrotransport installations. These measures include: turning the straight horizontal and inclined sections of pipelines around their axis; transporting the slurry with optimal parameters. In addition to the mentioned group of measures, constructive measures are considered that require investment in the reconstruction of hydrotransport installations to varying degrees, such as: optimizing the shape of curvilinear sections of pipelines; performing sections of hydrodynamic flow stabilization at the entrance and exit of the curvilinear (shaped) sections of pipelines, taking into account the zone of maximum wear; anti-abrasive inserts in the shaped sections of pipelines; stone-cast products; pipes with an aluminum-thermal coating. The maximum effectiveness of implementing anti-abrasive recommendations is achieved by combining regime and constructive measures.

Statistical variation in the embodied carbon of concrete mixtures

This study presents a refined calculation of the embodied carbon of concrete mixtures via life cycle assessment (LCA) with an explicit focus on three innovations. First, probability distributions that represent process-related variability in the embodied carbon of concrete are calculated using a variety of life cycle inventory data sources. Second, the traditional concrete LCA system boundary (i.e., cradle-to-gate) is expanded to incorporate and analyze estimates of in situ carbon sequestration via concrete carbonation. Third, we analyze the impact of different transportation scenarios on the utility of using fly ash to reduce the embodied carbon of concrete. We use these data to heuristically determine the breakeven transportation distance for fly ash via trucking to be 2655 km for domestic sources of fly ash. However, when fly ash is imported from international sources, reductions to embodied carbon attributed to fly ash replacement can be negligible. The calculated breakeven maritime shipping distance for fly ash equals 15,110 km—beyond which, the anticipated embodied carbon reductions due to fly ash use in concrete are compromised due to transportation. The advancements described herein enable improved scenario-based decision-making for understanding, quantifying, and reducing the embodied carbon of concrete mixtures. In addition, the results highlight the importance of accounting for international transportation of fly ash in LCAs, especially given that domestic sources of quality fly ash are expected to continue to decline and imports are expected to increase in many parts of the world over the next few decades.

Comparative life cycle assessment between imported and recovered fly ash for blended cement concrete in the UK

A UK government report released in 2017 indicated that fly ash (FA) production locally is expected to seize after 2021. This means that for the construction industry to meet its continuously increasing demand for an Ordinary Portland Cement (OPC) replacement, FA would probably need to be either imported or recovered from landfills through energy-intensive processes. Recent reports show that companies in the UK have already started importing FA from several countries from which Germany and China were chosen as case studies to exemplify the closest and furthest respectively. The environmental impact associated with the FA transportation raises concerns about the environmental sustainability of the final concrete product. Therefore, this study focuses on using a life cycle assessment (LCA) tool to analyse the environmental impact of importing FA from Germany and China and compare that to recovering landfilled FA in the UK. The study is the first of its kind to investigate the environmental impact of any of the alternatives. Using a Cradle-to-Gate approach and a mix of primary and secondary data, these alternatives were modelled and compared to conventional OPC and currently available locally sources of FA. Results show that the environmental burden from transporting FA from China to the UK will overcome the environmental benefits of it replacing OPC. It is then concluded that the most promising alternative for cleaner production of blended cement concrete is to recover the 50 million tonnes of landfilled FA from the UK using the Dry-processing technique explained in the study. The second best alternative is to import FA from a country within the Europe region to the UK.

Effect of transportation of fly ash: Life cycle assessment and life cycle cost analysis of concrete

The incorporation of fly ash into concrete may be limited by its quality, local availability, and additional cost incurred due to transportation. The specific objectives of this study are to: conduct an experimental program to evaluate the material properties for the four concrete mix designs considered for analysis (100GU, 25FA, 35FA, 50FA); identify environmental impact categories that are most greatly affected by material transportation; develop a life cycle assessment (LCA) model and a life cycle cost (LCC) model to respectively quantify the environmental and economic benefits and/or burdens that reflect the interplay between concrete mix designs and transportation of fly ash (up to 1000 km by truck). This analysis considers a study period of 100 years and is based on the proposed repair schedule. This study defines the ‘break-even distance’ as the maximum distance at which the LCA or LCC analysis results (i.e. environmental impact or cost) for concrete containing fly ash is lower than corresponding results for the 100GU concrete. Key outcomes of this study are: (i) ‘ecotoxicity’, ‘human toxicity (non-cancer)’, and ‘resources and fossil fuels’ are the most highly affected environmental impact categories by transportation of fly ash. In contrast, global warming potential was minimally affected. (ii) The break-even distance depends on the time to first repair (TFR), total volume of concrete required over 100 years of being in service and the percentage of cement replacement by fly ash. For both the LCA and LCC analysis, the concrete mix, 35FA, has the lowest break-even distance compared to the 25FA and 50FA. The fly ash mix designs ranked in order of least to most environmentally friendly and economically viable are: 35FA, 25FA, and 50FA. (iii) The break-even distances are longer for the LCC analysis compared to the LCA model results which indicates that the environmental impacts associated with the transportation of fly ash are more severe than the cost associated with the process, based on the analysis and assumptions in this study.

Effect of bottom ash at different ratios on hydraulic transportation of fly ash during mine fill

This study examines the suitability of Durgapur Steel Thermal Power Station fly ash and bottom ash for mine fill material based on their physiochemical and rheological properties. The physiochemical properties of both fly ash and bottom ash are suitable for mine fill. Hydraulic transportation of fly ash for mine fill is a challenge for engineers due to its poor flow properties at higher solid concentration. Rheological properties of fly ash are shown that beyond 40% solid concentration hydraulic transportation may not be effective. Therefore an attempt has been made in this study by adding bottom ash to fly ash at various solid to liquid ratios to improve flow behaviour. Viscosity and rheological properties are studied for this purpose. The results show that the mixture of fly ash and bottom ash at 7:3, 6:4 and 5:5 at 50% solid concentration provides the best result by reducing the shear stress and viscosity. These combinations not only improve the rheological properties in terms of energy consumption, but also decrease the use of water for hydraulic transportation. Therefore, the present study shows that the addition of bottom ash can improve rheological properties of fly ash at higher solid concentration.

Toxicity characteristics and durability of concrete containing coal ash as substitute for cement and river sand

The main aim of this study was to investigate the toxicity characteristics and durability of concrete containing bottom ash (BA) and fly ash (FA), as partial or total replacement of fine aggregate and Ordinary Portland cement (OPC), respectively. Concrete mixtures were prepared containing 0, 20, 50, 75 and 100% of BA as a substitute for river sand and 20% of FA as a replacement for OPC. Tests carried out were Toxicity Characteristics Leaching Procedure (TCLP), sulfate and acid attack (change in compressive strength, microstructure and weight) and elevated temperature effects (loss in compressive strength and mass as well as change in pulse velocity). Results showed that submerging coal ash concrete (CAC) mixtures in 5% sulfuric acid solution resulted in less reduction of compressive strength and mass loss compare to that of the control concrete. Moreover, sulfate resistance tests on concrete mixtures indicated that there were no mass loss and no reduction in compressive strength of all the mixtures after submersion in 5% magnesium sulfate solution. CAC showed higher weight loss and greater compressive strength reduction at elevated temperatures. From TCLP results, it is concluded that none of the elements leached higher than the maximum concentration of contaminants for toxicity characteristics. It indicates that transportation, disposal and utilization of BA and FA as clean construction material’s replacement could be utilized to reduce their environmental problems, increase efficiency and reduced unit cost production of concrete.

Greenhouse Gas Abatement Cost of Clinker Substitution in Thailand’s Cement Industry

This research study about the abatement cost of CO2 reduction by using fly ash as a clinker substitute in Thailand cement industry. And also present the sensitivity analysis about the factors that affect the abatement cost. The proportion of quantity to use fly ash as a clinker is equal to 1: 1 ton, therefor will calculate at 1 ton of clinker which make the quantity of mitigated CO2 in this research is equal to 0.825 tonCO2/year. Use the information in year 2015 to analyze, such as the exchange rate, fly ash price and transportation rate. And use average distance of fly ash transportation from the power plant to cement plant to calculate. From the information, the approach to reduce CO2 by this method is without additional investment. Because fly ash is small it can be mixed with clinker before grinding step of the original process. The CO2 abatement cost of this method is equal to -106.16 USD/tonCO2, which is regarded as a worthwhile investment. The factor is the most affect to mitigation cost is transportation rates. The transportation current rate is 0.092 USD/ton/km but if it increases, the abatement cost will also increase accordingly. Moreover we also calculate the maximum distance to decide on the purchase of fly ash from each of power plant.

Influence of Chemical Reagents on Rheological Properties of Fly Ash-Water Slurry at Varying Temperature Environment

About 70% of total electrical energy is generated from thermal power plants in India which in turn release about 160 Mt of fly ash as solid waste annually. Transportation and disposal of such a huge amount of fly ash is a major problem faced by the power plants. Presently fly ash is transported as lean slurry in pipe lines requiring about 80 to 85% of water with high energy input. A major impediment in high volume transportation of fly ash is its high specific gravity as compared to that of water. The objective of the present study was to evaluate the rheological characteristics of high concentration fly ash slurry with and without a chemical reagent at varying temperature environment to facilitate smooth flow of materials in the pipelines. Six different composition of fly ash slurry samples were considered for investigation. The main constituents of the slurry were fly ash, water, a cationic surfactant, and a counter-ion. Detailed rheological properties were determined using a cylindrical coaxial rotational rheometer at shear rates varying from 25s to 1000s for 40% solid concentration (by weight). Temperature was varied from 20uC to 40uC for all the shear rates investigated. Test results showed that all the slurries exhibited shearthinning behaviour in the presence of the surfactant. The influence of cationic tenside on drag reduction of fly ash slurry was also studied. The distinctive reduction of surface tension on colloidal dispersion characteristics of the fly ash slurry was observed in the presence of the tenside. It revealed that the slurry developed in the above manner has a potential to be transported through pipelines with minimal energy consumption. f 2011 The University of Kentucky Center for Applied Energy Research and the American Coal Ash Association All rights reserved. A R T I C L E I N F O Article history: Received 2 September 2011; Received in revised form 5 October 2011; Accepted 8 November 2011

Impact of fly ash content and fly ash transportation distance on embodied greenhouse gas emissions and water consumption in concrete

Background, aim and scope Fly ash, a by-product of coal-fired power stations, is substituted for Portland cement to improve the properties of concrete and reduce the embodied greenhouse gas (GHG) emissions. Much of the world’s fly ash is currently disposed of as a waste product. While replacing some Portland cement with fly ash can reduce production costs and the embodied emissions of concrete, the relationship between fly ash content and embodied GHG emissions in concrete has not been quantified. The impact of fly ash content on embodied water is also unknown. Furthermore, it is not known whether a global trade in fly ash for use in concrete is feasible from a carbon balance perspective, or if transport over long distances would eliminate any CO2 savings. This paper aims to quantify GHG emissions and water embodied in concrete (f′c = 32 MPa) as a function of fly ash content and to determine the critical fly ash transportation distance, beyond which use of fly ash in concrete increases embodied GHG emissions.

Evaluation of the role of a cationic surfactant on the flow characteristics of fly ash slurry

Transportation of fly ash is a major problem in its efficient disposal. The main problem associated with fly ash transportation is that the particles settle down sooner than desired. The primary objective of this research is that not only the fly ash particles should remain floated till it reaches the end but also settle down after that. In this investigation the role of a drag-reducing cationic surfactant and a counter-ion has been evaluated to achieve the objectives. The experimental results show encouraging trends of surfactant helping fly ash particles to remain water-borne. The material exhibited Newtonian behavior. This paper describes these in term of shear rates, shear stress, temperature, concentration and viscosity. Rheological tests were conducted using Advanced Computerized Rheometer. Zeta potential was measured to test the stability of the colloidal fly ash particles using Malvern Zeta Sizer instrument. Surface tension was also measured to know the drag reduction behavior of the fly ash slurry by using Surface Tensiometer. The test results and flow diagrams were generated using Rheoplus software and are presented in this paper. Surfactant concentration of 0%, 0.1%, 0.2%, 0.3%, 0.4% and 0.5% by weight was mixed with equal amount of counter-ion and the slurry was prepared by adding fly ash with ordinary tap water to achieve the desired solid concentration of 20% (by weight).

The Effect of Drag-Reducing Additives on the Rheological Properties of Fly Ash-Water Suspensions at Varying Temperature Environment

Fly ash transportation and disposal is a major problem in India. Presently fly ash is being transported as lean slurry in pipe lines requiring about 80 to 85% of water which, in turn, consumes more energy input. The objective of the present study is to evaluate the rheological characteristics of fly ash slurry at varying temperatures with and without an additive to facilitate smooth flow in the pipelines. Six fly ash slurry samples were prepared from the fly ash obtained from a thermal power plant situated in the southern part of India. The main constituents of the slurry were fly ash, water, a cationic surfactant and a counter-ion. Detailed rheological properties were determined for the six slurries at shear rates varying from 25 to 500s. Temperature was varied from 20uC to 40uC for all the shear rates investigated. The slurry exhibited Newtonian flow behaviour with zero yield stress. The slurry prepared in the above manner has a potential to be transported through pipelines with minimal energy consumption. The distinctive reduction of surface tension on colloidal disperse characteristics of the resulting slurry was observed in the presence of the surfactants. Zeta potential measurements also confirmed that the additive has the capability to keep the fly ash particles water borne during its transportation in pipelines. f 2009 The University of Kentucky Center for Applied Energy Research and the American Coal Ash Association All rights reserved. A R T I C L E I N F O Article history: Received 3 July 2009; Received in revised form 8 September 2009; Accepted 17 December 2009

The Bayswater Fly Ash Transportation System

A power station fly ash transportation system, which moves the ash from a bag house to a mine rehabilitation site, a distance of 12 km, is described. Two pneumatic conveying subsystems move the ash from the bag filters to an intermediate silo and from there to the ash plant (a distance of about I km). Here the ash is mixed with water and pumped to the mine rehabilitation site. The concentration of the ash/water mixture is Cw.∼70%. Comparisons of system characteristics to those obtained on smaller test systems are made for both pneumatic conveying sub-systems and the slurry sub-system. Blockages have been a problem with the pneumatic conveying sub-system 1. The present system effectively demonstrates the dense phase slurry transportation technology and the capability of power station ash to reclaim environmentally damaged land.

Thick suspension technology for fly ash transportation and disposal at a coal fired power plant

Modified technology for fly ash transportation and disposal was tested on a pilot plant at the “Šoštanj” Power Plant. The main advantage of this technology is in reduced water requirements for ash transportation and consequent smaller load on the environment with polluted water. The environmental impact of ash sludge deposited in this way was investigated and is described here.