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Pyrolysis oil is known to be unstable due to polycondensation reactions that negatively affect properties, such as increased viscosity and water content, lower heating values, and phase separation. Filtration of particulates and solid content out of the pyrolysis oil has been proven to increase stability, thus a filtration system was designed for pilot scale testing for the Mississippi State University Sustainable Energy Research Center (SERC). A literature review was conducted to determine potentially effective methods and eliminate methods likely to not improve the pyrolysis oil properties and stability. An in-line centrifuge system was identified as a useful and cost effective way to remove solids from the pyrolysis oil with an added benefit of potentially removing water content through a three-phase separation configuration. Lab-scale testing of centrifugation on pyrolysis oil indicated both two phase (solid + oil phases) and three phase (solid + aqueous phase + oil phases) separations could be obtained depending on feedstock and pyrolysis oil characteristics, and that centrifugation was a viable option for the removal of solid content. KiOR, Inc. pine clear wood derived pyrolysis oil (formerly known as ReCrude™) was characterized to determine physicochemical properties in comparison to literature results. Aging tests were also performed to investigate stability. In comparison with literature data, the properties for the KiOR product indicated significantly lower water content, particulate matter loading, and viscosity coupled with higher heating and pH values, indicating a product much closer in composition to fossil fuel oils than other pyrolysis oils. The KiOR ReCrudeM™ oil also demonstrated a much higher degree of stability versus other pyrolysis oils; however, there are still some stability issues with the aged samples resulting in slightly higher water content and viscosity values and lower heating and pH values. It is recommended that stability testing (aging) be performed on aliquots separated using a method such as rotary evaporation to more accurately determine what mechanisms are resulting in the properties changes observed over time in response to elevated temperature and/or pressure.

[pt] Caracterização Reológica de Fluidos para Perfuração com Gerenciamento de Pressão. Forças Hidráulicas desempenham uma função importante em muitas operações de campo de petróleo, incluindo perfuração, completação, fraturamento, acidificação, workover e produção. Em aplicações de Perfuração com Gerenciamento de Pressão (Managed Pressure Drilling - MPD), onde as estimativas de perdas de pressão são críticas para controlar o poço dentro da janela de operacional, é necessário utilizar a reologia correta para a modelagem matemática precisa do comportamento do fluido. Os métodos API (American Petroleum Institute) empregam para os cálculos de hidráulica os modelos reológicos de Herschel-Bulkley (H-B), Power Law (PL) ou plástico de Bingham. Este trabalho resume os resultados de um estudo aprofundado sobre as questões e os aspectos relevantes relacionados com o equipamento e os métodos utilizados para caracterizar os fluidos de perfuração para aplicações MPD, bem como as implicações operacionais que divergem das práticas convencionais. Uma comparação da caracterização reológica de fluídos é feita usando reômetros de alta precisão contra métodos convencionais tais como o viscosímetro FANN35. Subsequentemente, é apresentada uma comparação da seleção do modelo reológico proposto por API 13B em contrapartida com o método de Regressão Não Linear (NLR). Investigações detalhadas das faixas de taxas de cisalhamento são apresentadas para geometrias de um poço anular MPD típico, calculadas através de Dinamica de Fluidos Computacional (CFD) e comparadas com as fórmulas sugeridas na API RP 13D. Para concluir, é apresentada uma discussão sobre os efeitos das medições, do tratamento de dados (Curve Fit) e do meio ambiente (observações de laboratório em comparação com experiências de campo) na precisão da obtenção da reologia do fluido e as consequências na estimativa das perdas de carga no anular. / [en] Enhanced fluid rheology characterization for Manage Pressure Drilling. Hydraulics play an important role in many oil field operations including drilling, completion, fracturing, acidizing, workover and production. In Managed Pressure Drilling (MPD) applications, where pressure losses become critical to accurately estimate and control the well within the operational window, it is necessary to use the correct rheology for a precise mathematical modelling of fluid behavior. The standard API methods for drilling fluid hydraulics employ Herschel-Bulkley (H-B), Power Law (PL) or Bingham plastic as rheological models. This work summarizes the results of an extensive study on issues and relevant aspects related to the equipment and methods used to characterize the drilling fluids for MPD applications, as well as the operational implications that diverge from conventional practices. A comparison of fluid rheology characterization is made using high precision rheometers versus conventional FANN35 methods. Subsequently, a comparison of rheology model selection proposed by API 13B and by Non Linear Regression (NLR) is presented. Further investigation of shear rate ranges is presented in a MPD typical annular geometry. Results obtained via Computational Fluid Dynamics (CFD), and with the formulas suggested in API RP 13D are compared. To conclude, the effects of measurements, data treatment (Curve Fit), and environment (laboratory observations versus field experiences) in the accuracy of fluid rheology characterization and annulus pressure loss estimation are presented and discussed.

This study focuses on the effects of mixing temperature, binder content, and dust content on the performance of Stone Matrix Asphalt (SMA). Mixes produced at different mixing temperatures and with or without added polymer modified binder (Pb) and/or bag house dust (BHD) were evaluated. Two different types of specimens: laboratory mixed laboratory compacted, and plant mixed laboratory compacted were evaluated by Cantabro Mass Loss (CML) testing in an unaged condition or after a laboratory conditioning protocol (CP) was applied. Additional Pb and BHD were added to plant produced mixes in the laboratory before mixing. Results showed that mixing temperature affected behavior in some cases. Specimens with lower air void (Va) levels performed better than those with higher Va levels. Additional polymer modified binder and BHD, when added together, meaningfully improved mixture results in terms of CML values.

The mining industry is a major economic driver and job creator for many countries. However, mining is associated with geo-hazards and environmental issues, such as the disposal of large volumes of waste, acid mine drainage, and ground subsidence. As a result, efficient mining waste management is crucial for sustainable development. The geotechnical, economic, and environmental benefits of cemented paste backfill (CPB) have piqued the interest of researchers and academicians worldwide, making it an essential aspect of underground mining management. CPB is a thickened cementitious combination of dewatered tailings (70 - 85 wt.%), binders (usually 3 to 8% wt.%), and water used to backfill mine waste into underground mining stopes. Despite being used in small amounts, the cost of cement makes up to 80% of the cost of backfilling operations. In addition, clinker production accounts for 5-8% of global human created carbon dioxide (CO₂) emissions. This predicament necessitates the development of a viable alternative to cement. Partially substituting cement with supplementary cementitious materials like fly ash, blast furnace slag, natural pozzolans, and other materials has been increasingly prevalent in CPB. It is evident that the addition of slag to cement can increase the mechanical strength of CPB at the advanced ages but decreases the strength and suction development due to the slow reaction kinetics in the CPB at the early ages, which may negatively affect the mechanical stability of the CPB, mining cycle, and safety of mineworkers. Moreover, the supply of these materials is limited and may not be enough for the future needs of the industry. Furthermore, there has been a surge in interest in using limestone powder (LS) owing to its abundance, low cost, and lack of environmental costs which are associated with Portland cement - Type 1 (PCI). The addition of LS accelerates hydration at the early ages, thus resulting in high early strength, but the dilution effect can reduce the late strength. The combination of LS and slag in a ternary blended cement can be potentially used as a binder for CPB with acceptable strength development at the early and advanced ages while lowering the cost of the CPB and the carbon footprint of the mining industry. Nevertheless, the rheology, mechanical strength, and stability are important key performance quality criteria for CPB; however, the effect of ternary cement blends on these parameters is not well known. In this research program, the impact of the binary and ternary cement blends on (i) the fresh properties of CPB, such as the rheological properties (yield stress, viscosity) and setting time, and (ii) the strength and suction development of CPB are investigated. To understand the effect of substituting slag with LS in the binary binder in the first phase of the study, binary binders with two differ-ent PCI: Slag proportions of 50/50 and 80/20 are examined with no limestone, followed by replacing slag with an increasing amount of LS from 0 to 20 wt. % of the total binder, with a constant cement content, over a period of 4 hrs (0, 0.25, 1, 2, and 4 hrs) of curing at room temperature. In the second phase, the effect of a ternary binder (PCI-Slag- LS) with varying proportions on the suction development and the mechanical behavior of hardened CPB is investigated over a curing period of up to 90 days. The changes in strength of these binary and ternary binders on the CPB sample are tested for 1, 3, 7, 28, 60, and 90 days. An unconfined compression test (UCS) is conducted to evaluate the strength development. The microstructure of the mixes is examined through mercury intrusion porosimetry (MIP) for changes are validated through monitoring for the development of hydration and suction, electrical conductivity (EC), and temperature, which is carried out for up to 30 days. This is followed by a microstructure analysis with a thermogravimetric/differential thermogravimetric test on fresh and hardened samples. The results of the first phase show that an increase in the percentage of substituted cement in the binary binder (from PCI/Slag 80/20 to 50/50) increases the yield stress of the CPB but decreases the viscosity of the mix. However, the addition of LS as a substitution for slag shows a considerable decrease in the yield stress of the control mix with an increase in viscosity with increasing dosages of LS, thus indicating an improvement in the flowability of CPB. The second phase results indicate that the slow hydration kinetics of slag influences early age suction and strength changes in the binary sample with a high slag content (50/50); however, its latent hydraulic and pozzolanic properties enhance strength gain after 28 days. The addition of 5% limestone to the ternary blend increases the strength gain by up to 7 days compared to the binary control samples. Indeed, the presence of LS influences the rate of hydration of cement and slag through both physical (filler, nucleation, dilution) and chemical (hydrate) effects. However, substituting more than 10% LS for slag affects the mechanical performance at all ages. Overall, up to 50 wt.% slag and 10 wt.% limestone with cement as a ternary binder can be used without significant compressive strength loss. This study demonstrates that the partial substitution of ordinary Portland cement (OPC) with varying percentages of slag and LS is complementary, and overall, the interaction of slag and LS is observed. The optimal use of LS and slag in a ternary system may serve as a sustainable alternative to the commonly used OPC and PCI/Slag binders, thereby reducing the energy consumption and carbon footprint associated with cement. The findings of this study will ultimately help to develop a better understanding of the impact of ternary blends with increasing percentages of LS on the rheology and setting time of CPB mixes and mechanical strength changes in designing an efficient mixing plant, particularly its transport system.

Cemented paste backfill (CPB) is a highly advantageous method of backfill that has been increasing in use in recent decades as it provides many environmental, economic, and practical benefits. When combined with cement and water, it recycles a portion of the dewatered tailings produced from mines as backfill for underground stopes. CPB is transported from the plant on the surface through pipes to the stopes, sometimes over several kilometers, and then placed in underground mining cavities (stopes) to support the ground or rock mass. Therefore, it must meet certain rheological, setting time, and strength gain performance requirements. Additionally, as many mines around the world are located in areas of freshwater scarcity, and societies are holding corporations to ever higher standards for humanitarian and environmental responsibility, many mines are seeking to utilize locally available, saline groundwater or seawater as mixing water in backfill. The impacts of this decision on the rheological, setting, and strength properties of CPB must be better understood to allow for the confident selection of this convenient solution, as the risks associated with improper design include huge costs due to pipeline clogging and death or injury due to backfill failure and ground subsidence. NaCl is a contributor to natural groundwater and seawater salinity and may be present in concentrations of up to 300 g/L. An additional cost-saving measure favoured by mines is to replace some of the costly Portland cement with much cheaper supplemental cementitious materials such as blast furnace slag. Therefore, this thesis examines the impacts of NaCl concentration and binder composition on the yield stress, viscosity, initial and final setting time, and strength development of CPB. A robust experimental program has been undertaken in which CPB was subjected to the above-mentioned tests in addition to pH and MIP testing, SEM, TG/DTG, XRD, and zeta potential analyses, and electrical conductivity, suction, and water content monitoring. CPB samples were made with synthetic silica tailings, Portland cement, and water with NaCl concentrations of 0 g/L, 10 g/L, 35 g/L, 100 g/L, and 300 g/L and CPB made with 35 g/L and slag replacement percentages of 0%, 25%, 50%, and 75%. Additional samples tested were made with natural gold tailings, Portland cement, and NaCl concentrations of 0 g/L and 35 g/L for verification. Rheological testing was conducted at 0 minutes, 15 minutes, 1 hour, and 2 hours after mixing, and UCS testing was conducted after 1 day, 3 days, 7 days, 28 days, and 60 days of curing. Additional tests or analyses were performed on selected mixes and curing times for optimum insight and monitoring was conducted from 0 to 28 days after curing. It was found that low concentrations of NaCl (10 g/L and 35 g/L) generally had favourable impacts on the UCS and setting times of CPB, while higher concentrations had negative impacts. The impacts of slag replacement on UCS development of saline CPB were also generally favourable. However, the impacts of slag replacement on initial setting time were generally negative, and favourable at higher replacements (50% or more) for final setting time. Low NaCl concentration led to slightly negative impacts on yield stress, especially at longer curing times (1-2 hours), but high concentrations greatly reduced the yield stress. NaCl concentration had minor impacts to viscosity, with any concentration leading to a slightly higher initial viscosity but slightly lower viscosity at longer curing times. Slag replacement content had negligible effects on yield stress, but led to favourable decreases in viscosity over longer curing times. The combination of positive and negative impacts indicates that care must be taken to knowledgeably prioritize or balance critical properties in mix design, though there is indication of opportunities for overall improvement. Supplemental testing provided useful information to explain the mechanics behind the results which will allow designers to carefully select the required components for the desired properties.