Mines Repository (Colorado School of Mines)
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Salty solutions: tapping geothermal brines for rare earth elements
No full textAs ever changing policies strain trade relationships between the U.S. and China, rare earth elements (REEs) provide China with leverage in negotiations, adding renewed urgency to seek alternative, domestic sources of these high-value materials. REEs are essential to the development and manufacturing of electric vehicles, wind turbines, semiconductors, and defense technologies, and are integral to the transition to cleaner energy. However, their extraction is not low impact. REE mining is accompanied by environmental contamination risks and potential impacts to human health, necessitating new solutions for sustainable mining practices
Estimating jacking force in vertical-curved microtunneling
No full textIncludes bibliographical references.2025 Spring.Subsurface construction methods, such as microtunneling, are effective in minimizing surface disruptions during installation of pipelines or other utilities. As urban environments become increasingly complex, Vertical-Curved Microtunneling (VC-MT) has emerged as a viable solution for navigating subsurface obstacles, natural or manmade, while reducing the required depth of launch / receiving shafts, potentially lowering the cost of the project and project completion time. A critical aspect of VC-MT design and execution is the accurate estimation of jacking force (JF), which involves additional complexities compared to traditional Straight-Line Microtunneling (SL-MT). However, limited studies have been conducted on this topic, mainly due to limited availability of field data for VC-MT.
This study presents analysis of limited available data on VC-MT to develop predictive models for JF estimation using empirical method and machine learning techniques. Data from seven VC-MT projects were used in the analysis. Additionally, 23 datasets from SL-MT projects were analyzed and applied to the testing data for comparison. The proposed models were further evaluated against existing jacking force equations from Pellet (2002), Najafi (2004), Staheli (2006), Ma (2008), and Cheng (2017), which seem to overestimate JF by a notable amount.
The best-performing model incorporated key factors such as drive length (L), pipe diameter (D), depth of cover (Hs), unit weight of the soil (γ), height of groundwater (Hw), and frictional coefficient (μ). The proposed model achieved the highest coefficient of determination (R² = 0.822) and demonstrated the smallest deviation from actual jacking force values observed in the field when applied to testing data.
The findings indicate that the proposed VC-MT model in this study offers a more accurate and reliable estimation of jacking force, with reduced overestimation compared to existing equations. The results could help the industry in sizing the jacking equipment as well as a more realistic assessment of the need for the intermediate jacking stations (IJS) which could ultimately reduce the cost and risks involved in microtunneling operations. The analysis also showed that additional efforts have to be made to characterize and estimate the frictional coefficient between pipe and the ground for more accurate estimation of jacking forces
Resource recovery with membrane processes: overcoming limitations and increasing performance and economics
No full textIncludes bibliographical references.2025 Spring.Resource recovery from water and wastewater is of increasing importance due to stressors such as climate change, which decreases water availability, especially in the western United States. Several solutions to mitigate water stress have been proposed and are being implemented, and membrane processes offer unique benefits and high potential for enhancing both water supplies and recovery of valuable resources.
This thesis examines two ways in which membrane processes can be utilized to increase resource recovery. The first focuses on increasing resource recovery in membrane desalination processes. The goal was to increase water recovery in a closed-circuit reverse osmosis system by implementing a scaling detection system, which enables a water recovery of over 90% from a gypsum-rich solution without scaling occurring by detecting crystal growth as it occurs in solution. From the highly concentrated brine, gypsum was recovered, which can be reintroduced to the economy. The second focus was on utilizing membranes for the recovery of nitrogen from nitrogen rich streams. Anaerobic digester centrate was collected, analyzed and a pretreatment process developed. Nitrogen was then recovered from the pretreated centrate through a membrane contactor process. This was done in lab-scale experiments at 1.5 L/min with up to 30 L batches to optimize conditions for pilot-scale testing at 75 L/min with over 5,500 L batches. Pilot-scale testing was then implemented with an ultrafiltration pilot system as a pretreatment process. The ultrafiltration system removed solids and foulants from the centrate, before nitrogen was recovered with a membrane contactor system. The pretreatment process combined with the membrane contactors system allowed for >80% of nitrogen recovery without nitrogen recovery performance declining.
The economic viability of the pretreatment and membrane contactor processes for a 20 MGD wastewater treatment facility was investigated in a techno-economic analysis, with data from piloting applied for the economic evaluation of the process in a model. The results indicate large economic benefits for wastewater treatment facilities larger than 10 MGD. Sensitivity analysis of key parameters for the economic viability of the process for a 20 MGD wastewater treatment facility was conducted. Base (NaOH) cost, aeration demand, and electricity cost were found to have a large impact on economic viability of the process
Barite
No full textPhotographed by Ron Wolf.Flat white books of barite crystal on a matrix of smaller white blade-like crystals
Native silver
No full textPhotographed by Ron Wolf.Mass of metallic native silver with slight gold sheen, Gowanda, Ontario, Canada
Electrical initialization and readout of triplet excitons generated via room temperature singlet fission
No full textIncludes bibliographical references.2024 Summer.Molecular quantum systems are of rapidly growing interest, but there remains an open question as to the optimal choice of organic framework and spin generating mechanism for each specific quantum application. In this work, we outline and test the viability of a room temperature singlet fission system using opto-electronic initialization and readout for use as a generic quantum system with a focus on quantum sensing. The framework of the triplet-charge interaction can be used to probe the spin state of the triplet exciton in the Zeeman basis by producing either scattering or quenching events. Because the ratio of these two events are fundamentally field dependent, the magnetoconductance response of the system constitutes a fast and convenient room temperature ensemble spin readout without the need for bulkier optical probes. Initialization in the short-term is achieved by the inherent spin biasing present in the singlet fission phenomenon in the linear acenes, causing the neutral triplet sublevel to be preferentially populated at steady state. Direct manipulation of the triplet sublevel spins can be achieved by driving the sublevel transitions on resonance with the appropriate microwave-magnetic field in electrically detected magnetic resonance (EDMR) experiments. Incorporating a host-guest architecture of two linear acenes, we were able to successfully drive sublevel transitions as a function of applied field within isolated guest triplet excitons boasting sufficiently low hopping diffusivity. We conclude with predictive simulations of pulsed resonance experiments that would provide indisputable evidence of the governing spin species present, quantify the amount of doublet-triplet coupling, and allow for reasonable measurement of decoherence processes. These ideas present a convincing route for future work, as we have successfully exhibited the first steps of building a functional room temperature quantum system utilizing singlet fission as the spin initialization mechanism and the triplet-charge interaction as the electrical manipulation and readout scheme
Developing computational models for spiritual care in online support communities
No full textAs mental health has become more understood as an integral part of wellness, spiritual health–or one’s sense of meaning and purpose–is still largely neglected. Spiritual care providers, or chaplains, have assiduously provided this form of care through providing immediate human connection that can aid patients to grapple with questions of meaning, purpose, and mortality. Although human-computer interaction research has explored the ways how online communities buttress individuals through difficult times, there remains a gap in the understanding of chaplains within these communities. Thus, the aim of this research is to classify users based on their original posts into categories regarding their role through machine learning models like a LSTM with GloVe embeddings and fine-tuning a BERT model. Of the 386 users classified with the final model with 84% cross-validation accuracy, we find that chaplains (48 users) and medical professionals (79 users) are extremely difficult to classify due to conflation with users who may use spiritual or medical concepts in general terms, which led to many false positives. Moreover, we note the common occurrence of people exhibiting symptoms (273 users), receiving care (42 users), and expressing care (127 users) throughout these communities which all were classified with high accuracy. Finally, we lay the groundwork for future inquiries into the behaviors of different roles within these communities through computational methods
Modeling and analysis of a H₂-H₂O driven reversible solid oxide cell system for electrical energy storage applications
No full textIncludes bibliographical references.2024 Summer.The future of renewable energy resources, such as solar and wind is heavily reliant on energy storage. Solid oxide cells (SOCs) with bidirectional operation have advantages over other types of energy storage systems since they may be deployed in time-shifting, long-duration, and seasonal storage applications while having lower life cycle environmental impacts and can be manufactured from readily abundant elements and materials. This research examines the technical and economic viability of grid-scale energy storage systems based on high-temperature, stand-alone reversible solid oxide electrochemical systems at the 1 MW (8 MWh) scale using H2-H2O chemistry. A multi-scale modeling approach is employed that moves from one-dimensional cell-level models for stack performance estimation to full-scale systems with balance-of-plant models and equipment cost equations. The one-dimensional cell model is developed and calibrated using test data from an advanced, anode-supported SOC from a project industry partner. Process engineering and equipment selection of various ReSOC system configurations is examined and down selected based on energetic and economic considerations. The system performance sensitivity to various design parameters, including current density, stack temperature and pressure, and recirculation ratios on both the air and fuel sides of the stack, is explored and parameters selected through optimization studies of various objective functions. It is demonstrated that increasing the operating current density of the electrolysis stack leads to thermoneutrality while only minimally enhancing system efficiency. The results show that by carefully selecting the system design and operational parameters, it is possible to achieve 50.4% round-trip efficiency (RTE) with a levelized cost of storage (LCOS) as low as 13.5 ¢/kWh. Because of thermal management challenges associated with maintaining ReSOC stack operating conditions in either the highly endothermic or exothermic operating modes, approaches for integration of various thermal energy storage (TES) technologies are investigated towards improving the system RTE while trying to limit increases in LCOS. Both low- and high-temperature sensible and latent TES approaches are examined through a combination of heat transfer fluid type screening, phase-change materials assessment, and system simulation. The results show that a ReSOC combined with a steam accumulator which stores low-grade thermal energy (<150°C) during exothermic fuel cell operation achieves the highest system RTE (57%), representing a 6.6% point improvement over scenarios without TES. Despite the addition of new system components, the LCOS remains largely unchanged when compared to the base case. Technology attribute comparisons with conventional EES technologies are made. Lastly, the impact of mode-switching on the thermal dynamics of the ReSOC is evaluated under various inlet flow configurations using a dynamic 1-D Model
The future of carbon dioxide removal
No full textAt Nomadic Venture Partners (NVP), we are focused on enabling decarbonization across heavy industries like mining, manufacturing, and heavy-duty transportation. As climate professionals, we also recognize the role that removal of atmospheric carbon will play in a global net-zero roadmap