Research: Environmental uses
1. Phosphorus Adsorption
1.1 Cost-Effective Phosphorus Removal from Secondary Wastewater Effluent through Mineral Adsorption. Executive Summary
1.2 Town of Willsboro Explores Innovative Technologies: Abstract
1.3 Phosphorus removal by wollastonite: A constructed wetland substrate
Abstract: Wollastonite, a calcium metasilicate mineral mined in upstate New York, is an ideal substrate for constructed wetland ecosystems for removing soluble phosphorus from secondary wastewater. Design parameters, required for designing a full-scale constructed wetland, were measured in vertical upflow columns with hydraulic residence times varying from 15 to 180 h. Secondary wastewater was pumped vertically upward through eleven soil columns, 1.5 m in length and 15 cm in diameter and influent and effluent concentrations of soluble phosphorus were monitored for up to 411 days. Greater than 80% removal (up to 96%) was observed in nine out of 11 columns and effluent concentrations of soluble phosphorus ranged from 0.14 to 0.50 mg:l (averaging 0.28 mg:l) when the residence time was \40 h. Columns with a decreased residence time averaged 39% removal. A direct relationship between residence time and soluble phosphorus removal was established.
1.4 Evaluation Of Filter Media For Treating Stormwater Runoff
1.5 Evaluation Of Specialized Permeable Media For Phosphorus Removal
1.6 Determining Design Parameters For Recovery For Aquaculture Wastewater Using Sand Beds
2. Metals Remediation
3.1 Fight Global Warming By Boosting Calcium Silicates In Soil – Theory
3.2 Disposing Of Greenhouse Gases Through Mineralization Using The Wollastonite Deposits Of New York State
Abstract: This project explores the potential for mineral sequestration of carbon dioxide (CO2) in a carbonation reactor using wollastonite, a calcium silicate mineral found in large quantities in New York State. The project team will attempt to determine the optimum conditions for CO2 mineralization, including an assessment of the potential use of chemical additives. The results will be used to design multi-phase reactors to be employed for each stage of the process. The overall mass and energy balance of the process will be calculated, and mineral production and reserve data will be analyzed to estimate the carbon mineral sequestration capacity for New York State.
Findings: Wollastonite samples procured for this project were mostly mining tailings with a large particle size distribution. To obtain a uniform particle size for the kinetic studies, wollastonite samples were ground and separated by size. The average particle size for the fine wollastonite sample was 51.2 micrometers (μm). The particle density of the wollastonite sample was found to be 2.68 grams per millilitre (g/ml). Current project tasks include continuing the characterization and dissolution studies of the wollastonite samples and developing an efficient carbonation process.
See related topics and documents: Disposing of Greenhouse Gases through Mineralization – Update
3.3 Viability of Storage Options of CO2 in Ca Silicates
This report investigates a direct aqueous route of mineral carbonation of wollastonite under elevated pressure and temperature. Choice of the wollastonite was made based on its high reactivity rate and the method was determined by a catalytic effect of water on the adsorption kinetics. To improve the process and limit duration of the step where CO2 diffuses in solution before attaining the solid surface, most of the experiments were dedicated to carry in a moistened sample. As a result it could benefit from the catalytic effect of water and transport of CO2 was fast enough due to pressure equilibration. To investigate the influence of the water content of the sample, the experiments for this research were carried out with different water fractions.
See related topics and documents: http://repository.tudelft.nl/search/ir/?q=title:”Viability of Storage Options of CO2 in Ca Silicates”
3.4 Mechanisms Of Aqueous Wollastonite Carbonation As A Possible C02 Sequestration Process
Abstract: The mechanisms of aqueous wollastonite carbonation as a possible carbon dioxide sequestration process were investigated experimentally by systematic variation of the reaction temperature, C02 pressure, particle size, reaction time, liquid to solid ratio and agitation power. The carbonation reaction was observed to occur via the aqueous phase in two steps: (I) Ca leaching from the CaSi03 matrix and (2) CaC03 nucleation and growth. Leaching is hindered by a Ca-depleted silicate rim resulting from incongruent Ca-dissolution. Two temperature regimes were identified in the overall carbonation process. At temperatures below an optimum reaction temperature, the overall reaction rate is probably limited by the leaching rate of Ca. At higher temperatures, nucleation and growth of calcium carbonate is probably limiting the conversion, due to a reduced (bi)carbonate activity. The mechanisms for the aqueous carbonation of wollastonite were shown to be similar to those reported previously for an industrial residue and a Mg-silicate. The carbonation of wollastonite proceeds rapidly relative to Mg-silicates, with a maximum conversion in 15 min of70% at 200 °C, 20 bar C0 2 partial pressure and a particle size of <38 Jl.ID. The obtained insight in the reaction mechanisms enables the energetic and economic assessment of C02 sequestration by wollastonite carbonation, which forms an essential next step in its further development.
Conclusions: The aqueous carbonation of wollastonite for mineral C0 2 sequestration occurs in two subsequent steps via the aqueous phase (i.e., Ca-leaching and CaC0 3 precipitation). A key process variable is the specific surface area of the wollastonite particles. The applied C0 2 pressure determines the optimum reaction temperature at which maximum conversion is reached. At temperatures below the optimum, the overall reaction rate is probably limited by the leaching of Ca from wollastonite into the water phase, which is suggested to be controlled by diffusion of Ca through a Ca depleted silicate rim formed by incongruent leaching. At higher temperatures, a reduction of the bi(carbonate) activity probably causes the nucleation and growth of calcium carbonate to limit the conversion. The aqueous carbonation mechanisms of wollastonite, olivine and steel slag were shown to be generally similar. Wollastonite carbonates rapidly compared to Mg silicates, with a maximum convers ion in 15 min of 70% at relatively mild conditions (d<38 )liD, T = 200 °C and pc02 = 20 bar). However, resources of wollastonite are limited, relative to those of Mg-silicates. The process conditions required to sequester C02 by the aqueous carbonation of wollastonite seem technically feasible. However, the energy consumption and costs associated particularly with the grinding to a small particle size (e.g. <38 )liD or D[3,2] = 8 )llTI) are likely to be substantial. Therefore, an essential step in the further development of this process is an assessment of the energetic and economic feasibility of aqueous wollastonite carbonation as a possible C0 2 sequestration process.
See related topics and documents: Mechanisms of aqueous wollastonite carbonation as a possible CO2 sequestratin process
3.5 Aqueous Mineral Carbonation As A Possible CO2 Sequestration Process: Energetic Efficiency And Costs
Abstract: Aqueous mineral carbonation is a potentially attractive sequestration technology to reduce CO¬2 emissions. In this paper, the energy consumption and costs of this technology were assessed using either wollastonite (CaSiO3) or steel slag as feedstock. The major energy-consuming process steps were found to be the grinding of the feedstock and the compression of the CO2. Within ranges of experimentally investigated process conditions, optimum energetic CO2 sequestration efficiencies were 79 and 74% for wollastonite and steel slag, respectively. It was shown that the energetic performance for both feedstock might be improved up to >90% by e.g. further grinding of the feedstock and reducing the amount of process water applied. At energetically optimized process conditions, a preliminary cost estimate was made of 93 and 66 €/ton CO2 avoided for wollastonite and steel slag, respectively (sequestration costs excluding possible capture). For wollastonite, major costs were associated with the feedstock and the electricity consumption (51 and 20 €/ton CO2 avoided, respectively). A sensitivity analysis showed that additional influential parameters with regard to the sequestration costs include the liquid-to-solid ratio applied in the carbonation reactor and the possible commercial value of the carbonated product.
Conclusions: The presented system study of an aqueous mineral carbonation process has shown that the measures taken to increase the carbonation rate (i.e., grinding, heating and compression of CO2) were, in principle, energetically favourable. Within ranges of experimentally investigated carbonation conditions, the optimum energetic CO2 sequestration efficiencies were found to be 79 and 74% for wollastonite and steel slag, respectively. The sequestration efficiency can be further improved to >90% by e.g. further grinding of the feedstock and increasing the solid content in the carbonation reactor.
At energetically optimized process conditions, sequestration costs of 93 and 66 €/ton CO2 avoided were estimated for wollastonite and steel slag, respectively. State-of-the-art aqueous mineral carbonation seems a relatively expensive CO2 sequestration technology compared to both other CO2 storage technologies and (expected) CO2 market prices. Further research on cost reduction should focus on the major costs within the process (e.g., in the case of wollastonite, the feedstock and electricity consumed with 51 and 20 €/ton CO2 avoided, respectively). A sensitivity analysis showed that additional influential parameters on the sequestration costs include the liquid-to-solid ratio applied in the carbonation reactor and the possible commercial value of the carbonated product.
See related topics and documents: Aqueous Mineral Carbonation as a Possible CO2 Sequestration Process
3.6 Carbonation of wollastonite [CaSiO3] exposed to variably hydrated supercritical CO2 (scCO(2)) at 50, 55 and 70 degrees C and 90, 120 and 160 bar.
Abstract: Reports from University of Central Missouri Advance Knowledge in Greenhouse Gas Control 2013 JUN 17 (VerticalNews) — By a News Reporter-Staff News Editor at Global Warming Focus — Researchers detail new data in Greenhouse Gas Control. According to news reporting from Warrensburg, Missouri, by VerticalNews journalists, research stated, “Subsurface injection of CO2 is commonplace in certain industries, yet deployment at the scale required for emission reduction is unprecedented and therefore requires a high degree of predictability. Accurate modeling of subsurface geochemical processes related to geologic carbon sequestration requires experimentally derived data for mineral reactions.”
The news correspondents obtained a quote from the research from the University of Central Missouri, “Most work in this area has focused on aqueous-dominated systems in which dissolved CO2 reacts to form crystalline carbonate minerals. Comparatively little laboratory research has been conducted on reactions occurring between minerals in the host rock and the wet supercritical fluid phase. We studied the carbonation of wollastonite [CaSiO3] exposed to variably hydrated supercritical CO2 (scCO(2)) at 50, 55 and 70 degrees C and 90, 120 and 160 bar. Reactions were followed by three novel in situ high pressure techniques, which demonstrated increased dissolved water concentrations in the scCO(2) resulted in increased wollastonite carbonation approaching similar to 50 wt.%. Overall, the X-ray diffraction and infrared and magic angle nuclear magnetic resonance spectroscopies experiments conducted in this study allow detailed examination of mechanisms impacting carbonation rates. These include the development of amorphous passivating layers, thin liquid water films, and amorphous hydrated carbonate phases.”
According to the news reporters, the research concluded: “Collectively, these results emphasize the importance of understanding geochemical processes occurring in wet scCO(2) fluids.”
For more information on this research see: Insights into silicate carbonation processes in water-bearing supercritical CO2 fluids. International Journal of Greenhouse Gas Control, 2013;15():104-118. International Journal of Greenhouse Gas Control can be contacted at: Elsevier Sci Ltd, The Boulevard, Langford Lane, Kidlington, Oxford OX5 1GB, Oxon, England. (Elsevier – www.elsevier.com; International Journal of Greenhouse Gas Control –www.elsevier.com/wps/product/cws_home/709061)
See related topics and documents: http://global-warming.verticalnews.com/articles/9617631.html
3.7 Mineral Carbonation And Industrial Uses Of Carbon Dioxide
Executive summary: This Chapter describes two rather different options for carbon dioxide (CO2) storage: (i) the fixation of CO2 in the form of inorganic carbonates, also known as ‘mineral carbonation’ or ‘mineral sequestration’, and (ii) the industrial utilization of CO2 as a technical fluid or as feedstock for carbon containing chemicals.
In the case of mineral carbonation (see Section 7.2), captured CO2 is reacted with metal-oxide bearing materials, thus forming the corresponding carbonates and a solid byproduct, silica for example. Natural silicate minerals can be used in artificial processes that mimic natural weathering phenomena, but also alkaline industrial wastes can be considered. The products of mineral carbonation are naturally occurring stable solids that would provide storage capacity on a geological time scale. Moreover, magnesium and calcium silicate deposits are sufficient to fix the CO2 that could be produced from the combustion of all fossil fuels resources. To fix a tonne of CO2 requires about 1.6 to 3.7 tonnes of rock. From a thermodynamic viewpoint, inorganic carbonates represent a lower energy state than CO2; hence the carbonation reaction is exothermic and can theoretically yield energy. However, the kinetics of natural mineral carbonation is slow; hence all currently implemented processes require energy intensive preparation of the solid reactants to achieve affordable conversion rates and/or additives that must be regenerated and recycled using external energy sources. The resulting carbonated solids must be stored at an environmentally suitable location. The technology is still in the development stage and is not yet ready for implementation. The best case studied so far is the wet carbonation of the natural silicate olivine, which costs between 50 and 100 US$/tCO2 stored and translates into a 30-50% energy penalty on the original power plant. When accounting for the 10-40% energy penalty in the capture plant as well, a full CCS system with mineral carbonation would need 60-180% more energy than a power plant with equivalent output without CCS.
The industrial use of CO2 (see Section 7.3) as a gas or a liquid or as feedstock for the production of chemicals could contribute to keeping captured CO2 out of the atmosphere by storing it in anthropogenic carbon products. Industrial uses provide a carbon sink, as long as the pool size keeps growing and the lifetime of the compounds produced is long. Neither prerequisite is fulfilled in practice, since the scale of CO2 utilization is small compared to anthropogenic CO2 emissions, and the lifetime of the chemicals produced is too short with respect to the scale of interest in CO2 storage. Therefore, the contribution of industrial uses of captured CO2 to the mitigation of climate change is expected to be small.
See related topics and documents: Mineral carbonation and industrial uses of CO2
3.8 Emission Reduction Of Greenhouse Gases From The Cement Industry
Abstract: 5% of global carbon dioxide emissions originates from cement production. About half of it from calcination and half of combustion processes. A wide range of options exists to reduce CO2 emissions considerably.
Conclusions: In 1994 cement industry consumed 6.6 % of primary energy, corresponding with 2% of world energy consumption. Worldwide 1126 Tg CO2 or 5% of the CO2 production originates from cement production. The carbon intensity of cement making amounts to 0.81 kg CO2/kg cement. In India, North America, and China the carbon intensity is about 10% higher than on average. Specific carbon emissions range from 0.36 kg to 1.09 kg CO2/kg cement mainly depending on type of process, clinker/cement ratio and fuel used. On average a little above 50% of the emissions originates from the calcination step.
To reduce the carbon intensity the following options are identified: improving energy efficiency, shifting to more energy efficient process, shifting to lower carbon fuels, shifting to lower clinker/cement ratio, shifting to mineral polymers and removal of CO2.
Seventeen different energy efficiency improvement options are identified. The improvement ranges from a small percentage to more than 25% per option, depending on the reference case (i.e type of process, fuel used) and local situation. The use of waste instead of fossil fuel may reduce CO2 emissions by 0.1 to 0.5 kg/kg cement (varying from 20 to 40%). On average blended cements may reduce carbon emissions from 0.81 kg to 0.64 kg per kg cement (20%). Global potential of blended cements reducing carbon emissions is at least 5% but it is estimated to be as high as 20%. An end-of-pipe technology to reduce carbon emissions may be CO2 removal. Probably the main technique is combustion under oxygen while recycling CO2. However, considerably research is required to all unknown aspects of this technique.
See related topics and documents: Emission Reduction of Greenhouse Gasses from the Cement Industry