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By Dejan Petrović, Pavle Stojković, Jelena Ivaz, Saša Stojadinović

In spite of the fact that flyrock phenomenon represents the real threat for personnel and machinery, it still remains insufficiently investigated. There are efforts, in the mining community, to explain the causes of flyrock, but the models capable to accurately predict flyrock occurrence and define the flyrock distance still do not exist. This article is an attempt to establish such a predictive model. The model utilized the adaptive nature of artificial neural networks and combined it with the accuracy of numerical modeling of physical phenomena. Necessary data were collected by high-speed camera recordings of actual blasts at three different surface mines and processed for further use for artificial network training. The result was a neuro-numerical couple which was capable to predict flyrock occurrence, estimate the launch velocity of flyrock fragments, and calculate the maximum distance of flyrock fragments. The safe distance was then calculated by multiplying the flyrock distance with a factor of safety. The article explains the procedure for data acquisition and processing, artificial network construction, training, and validation. It also explains the principles of flyrock distance calculation and, finally, provides a definition of factor of safety and safe distance. The results showed that the prediction was satisfactorily accurate and reliable.

Oct 22, 2021

By B. Boutilier, R. Mendoza

"First Majestic Silver Corp. (FMS) is a silver mining company founded in 2002 that operates exclusively in Mexico. It has six producing silver mines, one of which is the La Encantada silver mine (La Encantada) located in the state Coahuila. La Encantada is located near the southern United States border and 708 km (440 miles) north of the city Torreon.La Encantada is located in the Sierra Madre Oriental and is a high-temperature carbonate replacement deposit. Mineralization in La Encantada occurs in many different forms such as veins, chimneys, breccia pipes and reefs (mantos). Mineralization is mainly oxides of iron, zinc, lead and manganese, with high concentrations of sulfides at depth relating to two main intrusive events: the Milagros Intrusive and the La Prieta Skarn.Mining began in La Encantada during the 1950s with small vertical shafts, drifts and raises. It focuses on the high-grade silver zones using traditional hoists and extraction methods, before branching into two main separate mining camps: El Plomo and Penoles camp. Penoles, the previous owner, focused mainly on large ore bodies using post pillar cut-and-fill mining method to extract the higher-grade material. Due to the type of ground, irregularity of pillars, and rock conditions, large amounts of high-grade pillars had to be left in situ to ensure the stability of the excavations. The mined-out areas would then be filled with lower-grade material to assist in the stability of the secondary level. These room-and-pillar development entries were 2.5 m x 2.5 m (8.2 ft x 8.2 ft) and spaced every 10 m (32 ft), leaving a vertical pillar of 7.5 m (25 ft). First Majestic acquired La Encantada in 2006. After the acquisition of the mine, the company began the conversion of the surveying reference system from a local grid (Maria Isabel Shaft as 0,0) to the Nav27 coordinate system, and subsequently converted to the WGS84 coordinate system in 2015. Due to the extensive history of the mine, different areas were surveyed with different systems, causing significant challenges when designing the principal extraction levels, pillar heights and ramp locations. To overcome this difficulty, the entire mine was resurveyed and the old workings transposed to the new coordinate system, except for some inaccessible areas due to poor ground conditions or ground collapses. To further ensure pillar height and the safety of the mine workers, probe holes were drilled during the development process."

Sep 1, 2019

In this work, the crystallization of Carnallite from waste brine of Qaidam Basin in Qinghai province was studied based on NaCl-KCl-MgCl2-H2O phase diagram. According to this study, a new crystallization pathway to recycling waste brine was developed. The carnallite salt was formed by using this technology during the waste brine evaporation. The experiment data shows that 5 tons of waste brine was required to form one ton of the carnallite. The average grade of carnallite prepared by using this procedure was about 19.40% of KCl, 16.92% of NaCl, 28.80% of MgCl2, and 0.82% of CaSO4. This study provides an opportunity to utilization of the waste brine.

Jan 1, 2012

By R. W. Kobler

The pelletizing process for low grade iron ores has undergone continual changes since its inception over twenty years ago. These changes have necessitated filtration equipment changes in order to produce a product suitable for balling. With modern techniques it is now possible to produce pellets of 68% Fe from ores containing as low as 26% Fe. Low grade ores require fine grinding to liberate impurities This shift to finer grinds over the years has necessitated major changes in the filtration steps. Techniques are now available for producing suitable product from ores with Blaines as high as 3600 cm2/gram. This has been made possible by the development of high performance filters. Recent developments have reduced maintenance costs and produced higher production reliability. The paper discusses iron concentrate filtration from its beginning to present day design. It will be shown that the dewatering step prior to balling has gone through four generations of filters. Particular emphasis is placed upon hydraulic studies which have allowed today's optimum designs.

Jan 1, 1978

By R. D. H. Bedd

GEOLOGICAL NOTES The area under discussion is situated approximately 150 m north of Loraine No. 3 shaft at ± 1500 m below surface. The block being mined extends from about halfway between 50 and 52 levels to just below 48 level (see Fig. 1). The EB reefs form the lower portion of the EB zone of the Elsburg series and in the 81 line area the various conglomerate bands show the best development. Up to 18 separate reef bands are developed and the distance from the bottom conglomerate band to the top is ± 26 m. The thickness of the quartzite which forms the middling between the various reef bands varies from 0.1 to 2 m. The strike is roughly north-¬south. The reef bands are payable individually. However, owing to the steepness of the reefs and their close prox¬imity, conventional mining would prove very difficult. The nonpayable reef bands all carry varying amounts of gold and the whole area is a massive payable reef body approximately 26 m wide and 60 m high at 300 to 400 m on strike. The major structure of the area consists of a north¬-south trending syncline. The western flank of the syncline has a steep easterly dip, in places approaching the vertical. This flank cuts out against the overlying rocks of the EA zone. The latter forms a noncon¬formity with the underlying EB zone. The eastern flank of the syncline dips to the west at an average dip of 0.17 rad (10°). The 0.1 rad (6°) north-plunging syncline was sub¬jected to severe faulting. The most important are the Nos. 4 and 10 faults, both of which have a roughly north-south strike. The No. 4 fault dips to the west at an angle of 1.04 rad (60°) with a downthrow of approximately 150 m to the west. The dip of the No. 10 fault is 0.69 to 0.81 rad (40° to 50°) west, with the western block having moved 150 m updip relative to the eastern block. The EB reefs are being mined by the sublevel stoping method down from the sub-outcrop position to the cutoff against the No. 4 fault. On the downthrow side of the No. 10 fault, that is just above the 54 level, two reef bands are payable and will be mined conven¬tionally. ROCK MECHANICS From the section in Fig. 1, it can be seen that the area under consideration is surrounded by stoped-out areas. This will naturally change the stress distribution extensively. The only way to calculate the stress field for such a geometry is to use the finite element method. It was established that this method worked for the present geometry and so the method was applied to predict the stress behavior of the final geometry. From the results, it appeared that the effect of the old stopes was to destress the area. There are, however, some areas-such as the 50 and 48 north footwall haulages-which will require continuous attention. In these two footwall haulages, deterioration can take place due to tensile stress which

Jan 1, 1982

By D. E. Healy

In 1989, an autogenous grinding task force was formed to study potential autogenous grinding circuits to replace the existing semi-autogenous grinding (SAG) at the National Steel Pellet Plant in Keewatin, MN. Pilot plant test work, performed by the Hanna Research Center (HRC), indicated that fully autogenous grinding with pebble extraction and crushing could be incorporated into the existing circuits. In 1990, one of the existing 10 grinding mills was converted for an in-plant test incorporating pebble crushing. Full-scale test work were conducted in 1990 and 1991. They verified the pilot plant projections with primary mill throughputs from the fully autogenous circuit using pebble crushing being greater than throughput of the existing SAG mill circuits. The plant produces 5 Mt/a (4.9 million ltpy) of iron ore pellets from 17.6 Mt (17.3 million It) of crude taconite. Crude ore is single-stage crushed by gyratory crushers. Primary grinding is performed by 10 semi-autogenous wet grinding mills. Secondary grinding is performed by five ball mills. Induration is with an Allis Chalmers grate-kiln pelletizing system. The primary grinding circuit consists of 108.2-m-diam x 5.5-m long (27 ft-diam x 18-ft) SAG mills. The mills are charged with 127 mm-diam (5 in.diam) steel grinding balls at from 3% to 5% by volume. Ball consumption rate is about 0.55 kg/t (1.25 lbs/lt) of crude ore feed to the mill. Each SAG mill is powered by two 2.6 MW (3500 hp) motors drawing 5450 kW (7300 hp) at 76% of critical speed. The mills are grate discharge with 16 mm (0.6 in.) slotted grate openings when new. The mill discharge is sized on a trommel screen having 4.5 mm (0.2 in.) openings. The plus 4.5 mm (+0.2 in.) oversize material is returned to the discharge end of the mill by a reverse screw auger located in the center of the trommel. The -4.5 mm (-0.2 in.) trommel screen undersize is pumped to magnetic cobbers.

Jan 1, 1992

By A. Davis

Pit lake chemistry depends on the lithology and hydrologic characteristics of the ultimate pit surface, the availability of buffering capacity in the wall rock versus oxidizable sulfide content, and the alkalinity of recharging ground water. In this paper, we assess the geochemistry of 11 existing pit lakes, ranging from the acidic Red Hill and Berkeley pit lakes (pH 2.6 to 2.8) to the alkaline Yerington Pit lake (pH 8.45). Predicted pit lake chemistry is similar to that in existing pits with the long-term pit lake chemistry lying on a geochemical continuum between end members consisting of influent calcium bicarbonate ground water, and naturally occurring sulfate-rich evaporite playa lakes.

Jan 1, 1996

By Peter Kreisman

This paper and four other papers on the MEQB Regional Copper-Nickel Study, presented today at the 1980 SME-AIME Fall Meeting are based on four years of extensive inter-disciplinary research and impact analysis supported largely by the Legislative Commission on Minnesota Resources. This study produced over 180 technical reports, the results of which are summarized in an Executive Summary available from the Minnesota State Planning Agency, St. Paul, Minnesota. Those wishing to examine the many scientific, engineering, environmental, social or economic issues addressed by the study are encouraged to obtain a copy of the executive summary. The executive summary includes a bibliography of all technical reports produced by the Regional Copper-Nickel Study and describes the five-volume, 26 chapter Regional Copper-Nickel Study Report.

Jan 1, 1980

The National Mining Hall of Fame and Museum (NMHF&M) will celebrate its 25th anniversary on Sept. 22, 2012 when the 2012 class is inducted during a special ceremony in Las Vegas, NV in conjunction with MINExpo 2012. The NMHF&M will induct four men representing the equipment manufacturing, minerals exploration, copper and coal sectors of the mining industry. The diverse cross-section of mining industry giants joining the hall of fame include Glen A. Barton, J. David Lowell, Samuel Newhouse and John Cleveland Osgood. They will join 214 other mining industry pioneers when they are formally inducted into the National Mining Hall of Fame at the 25th Silver Anniversary Induction Banquet & Ceremony. These men were selected for being visionaries, leaders and ambassadors within their own sectors and across the industry at large.

Jan 1, 2013

The market for titanium feedstocks (ilmenite, rutile,synthetic rutile and slag) is driven primarily by offtake from the titanium dioxide (TiO2) pigment industry. The pigment sector depends on the performance of the global economy. Titanium sponge is the first stage of titanium metal manufacture. It constitutes a minor component (3 percent) of overall demand for titanium feed-stocks. Production and consumption TiO2 pigment consumption in 2004 was estimated to be 4.63 Mt (5.1 million st), up 7.6 percent from 2003. It was driven by strong demand in most regions. In the United States, apparent TiO2 pigment consumption rebounded by 5.4 percent (highest growth rate since 1997) to an estimated 1.12 Mt (1.23 million st), following the decrease in demand during 2003. Chinese TiO2 pigment consumption continued its strong upward trend, increasing by 10 percent to 598 kt (659,000 st) in 2004.

Jan 1, 2005

By William S. Alldredge

The Washington Metropolitan Area Transit Authority(WMATA) officially came into existence in February 1967 after the District of Columbia, Maryland, and Virginia joined in a com¬pact pursuant to Federal creative legislation signed the previous November to build a regional rapid rail transit system called METRO (1). The parent organization was the National Capital Transportation Agency (NCTA), a Federal agency, subject to Federal statutes and regulations. Soon after the completion of the transition from NCTA to the new "non-Federal" status of the Authority, the Board of Directors of the Authority formally adopted procurement policies and procedures (2). These are specific statements concerning competition by formal advertising for bids or by solicitation of proposals for negotiation, contracting authority, approval of awards, awards of contract modifications, and processing of claims and disputes. These policies and procedures are silent as to Federal procurement statutes and regulations. But because of the Authority's origin, the sensitive nature of the compact among the several sovereign jurisdictions, Federal financing of two-thirds of the costs, and the resultant surveillance by the General Accounting Office over staff operations, the Authority's procurement practices follow closely Federal regulations adapted to WMATA's needs. This is an important point and is the foundation of contractual relations between the Authority as the owner and its construction contractors. Various constraints and flexibilities of this arrangement with respect to excavation and tunneling contracts will be pointed out in the ensuing discussions.

Jan 1, 1974

By Francesco Chiappalone, Filippo Azzarà, Raffaele Aliberti, Daniele Nebbia, Lance Waddell

As part of the 3RPORT and NEBT Projects, 5-mile Combined Sewer Overflow Tunnels were excavated with a 19 ft diameter Slurry and 26 ft diameter EPB Tunnel Boring Machines. Due to the difficult geological and hydrogeological conditions, both tunnels were excavated maintaining a ground support pressure between 2 and 5.5 bar imposing significant challenges to the projects. The first part of the paper describes the general characteristics of both projects while the second part focuses on the challenges and technical details of the pressurized breakthroughs that took place in deep shafts excavated in urban environment as part of the projects.

Dec 1, 2022

By D. R. Gehring

Effective project management is an excellent technique for meeting a goal through set, well-defined objectives. Even though project management is successfully used throughout the world in various construction projects, underground mining has unique characteristics that require approaches that vary from classical project management theory. Typically, a project includes four main stages: definition, planning, implementation and control. Definition and planning are often the most overlooked stages, but are arguably the most important. This paper addresses practical techniques for the definition and planning of projects for underground construction.

Jan 1, 1996

The National Mining Hall of Fame and Museum (NMHF&M) will induct the 2013 National Mining Hall of Fame class on Sept. 14, 2013. The ceremony will take place at the Brown Palace Hotel in Denver, CO. Representing the domestic and worldwide metal production, education, and health and safety sectors of the industry, this year?s five inductees cover a diverse cross-section of the mining industry. The inductees are: Charles F. Barber, Donald W. Gentry, Patrick H. O?Neill, Milton H. Ward and David A. Zegeer. They will join 218 other mining industry pioneers when they are formally inducted into the National Mining Hall of Fame at the 26th Annual Induction Banquet and Ceremony. They were selected for being visionaries, leaders and ambassadors, both within their own sectors and across the industry at large. Barber was a top executive at leading U.S. metals producer Asarco from 1956 to 1982. During his tenure, Asarco responded successfully to the demanding requirements of new environmental legislation in the United States and to changing concepts of foreign investment in mining, especially in Latin America. Gentry?s career took him from being a working mining engineer, to renowned mining educator, to president and chief executive officer of a mining company. As an educator, he had a positive impact upon hundreds, if not thousands, of new mining engineers and many others who took his short courses in mine economics. During his years in South America, O?Neill did everything from supervising operations of 15-bucket ladder gold dredges to becoming president of International Mining Corp. As an executive, he emphasized provision of education and training to local people working at mine sites for which he had responsibility. Ward?s experience covered the world and spectrum of metals, minerals and ores, ranging from A to Z (antimony to zinc and Australia to Zambia). He was president, chairman and chief executive officer of Cyprus Amax Minerals from 1992 to 1999, and he was president and chief operating officer of Freeport-McMoRan from 1983 to 1992, during which time he was instrumental in developing Freeport?s world-class Indonesian operations. Zegeer dedicated his mining career to protecting the health and safety of miners as a corporate executive, head of the U.S. Mine Safety and Health Administration (MSHA) and community leader. His tenure at MSHA coincided with a period of remarkable progress in U.S. mining safety .NMHF&M Board of Directors Chairman Paul C. Jones said: ?The five outstanding gentlemen being honored this year as inductees into the National Mining Hall of Fame are classic examples of the leadership and work ethic that has made America?s mining industry the world leader in technically sound, environmentally and socially correct, and economical mineral production that sets the standards for mining worldwide. We are very proud to add these five legendary gentlemen, who have demonstrated their sound technical and management skills to advance society on a worldwide basis, to our current list of 218 inductees being honored by the National Mining Hall of Fame.? 2013 Prazen Award winner ? The Nevada Mining Association is the recipient of the 2013 Prazen Living Legend of Mining Award

Aug 1, 2013

By J. Restrepo, N. Ripepi

"The International Organization of Standards defines risk as “the effect of uncertainties on achieving objectives (15).” In mining, many uncertainties can influence the outcome of personal or professional objectives and are often difficult to predict. Risk management, the minimization and control of adverse effects from exposure to identified risks, is a well-established concept that can summarized as “being smart about taking chances” (12). Risk management now consists of management processes unique to numerous organizations across many industries, as varying sectors encounter a variety of needs, including the analysis and mitigation of risks related to physical security, product liability, information security, various forms of insurance, regulatory compliance, and workplace safety (12). The reoccurrence of multiple fatality events in the US mining industry, especially the underground coal sector, suggests an opportunity for improved methods of major safety hazard identification, assessment, and mitigation. A risk management approach would include ready identification and mitigation of these risks, inclusive stakeholder engagement, and rapid integration. While many solutions to reducing the risk of mine disasters have been proposed including stricter regulation and improved technology, a comprehensive risk management approach has yet to be fully integrated in the US mining industry. In December of 2006, R. Larry Grayson of the National Mining Association’s Mine Safety Technology and Training Commission called for “a new paradigm for ensuring safety in underground coal mines, one that focuses on systematic and comprehensive risk management as the foundation from which all life-safety efforts emanate (7).” A risk management approach has already been implemented with success in Australia’s minerals industry as part of a transition during the mid-1990s from a prescriptive based health and safety attitude to a more proactive, duty-of care [risk-based] philosophy (13, 16, 17).FUNDAMENTAL ELEMENTS OF RISK MANAGEMENT TECHNIQUES The fundamental components of a comprehensive risk assessment/management program are well-established within the realm of mining health and safety. Figure 1 depicts the elements of a typical mining hazard management framework. The first step in any safety-based risk management system is to identify and assess hazards by their location, nature, and magnitude within a mine. Next, a decision is made about choosing to eliminate, mitigate, or tolerate each hazard. Ideally, a hazard will be eliminated during the design stages of mining, though dynamic mining conditions often require continuous improvement and reevaluation of existing hazard controls. If elimination is not possible, hazard mitigation actions can consist of methods, rules, equipment, competencies, or other mechanisms. If a hazard is simply tolerated, as many inherent mining hazards must be, then specialized administrative controls must be utilized to minimize losses. During this process, the performance of each action is monitored and modified as needed (13)."

Jan 1, 2015

By Irwan Halim, Seung Han Kim

This paper will describe design of precast segmental tunnel lining for the Pawtucket CSO Tunnel Project in Providence, Rhode Island. The tunnel is 11,700 LF long with 30-foot finished diameter to be constructed in complex sedimentary rocks. Special features of the segments include a large keystone and no connector used on radial joints. The typical segments will be steel fiber reinforced, and hybrid segments with additional steel rebars and shear bicones will be used around the adit openings without use of any structural framing. The important design considerations will be discussed, including special 3D segment to adit connection analyses performed.

Dec 1, 2022

By Landy Stinnett

"When performing a valuation of a mineral property, a developing mine or perhaps an ongoing operation, the appraiser is typically provided with a range of information prepared by the property owner. This information can include ownership records, geological interpretation, assay data, an estimate of the reserves or resources believed to be on site (tons and grade), mine plans, production forecasts, capital and operating cost projections, and so forth.The appraiser familiarizes himself with the data, analyzes the various reports and then prepares the appraisal. There is usually a site visit, and there may be some effort at comparison of the particular mineral deposit with others in the region or with those of similar depositional characteristics, but for the most part, the appraiser is relying on the corporate documents, tempered by his/her experience in the field. Time is usually of the essence, the cost for the assignment has been trimmed, and therefore independent verification of the various components comprising the underlying data base (legal review, redrilling portions of the deposit, collection of new samples, re-assaying, etc.) is unlikely in most situations.In the case of high-value commodities — gold, silver, diamonds, perhaps the platinum-group elements — there have been numerous examples of the property owners attempting to increase the value of their holdings by nefarious methods. Most of these involve salting the deposit in some fashion; i.e., introducing small amounts of the commodity into samples being sent to a laboratory for analysis so that the resultant assay shows a higher grade (Donaldson, 2002; Greeley, 2001; Lechler et al., 2008 and Meech, 2001). Other schemes to enhance the apparent worth of a property include the use of nonstandard assay procedures, incorrect handling or withholding of the underlying information, and false reporting."

Sep 1, 2016

By Raymond Sandiford, Kenneth Xu, Taehyun Moon

Tunnel approach structures situated in slow moving earth flows are subjected to significant earth pressures. The authors have developed a system, utilizing collapsible concrete columns, that limits such loading. The system uses an array of collapsible concrete columns in front of the structure to absorb downslope movement and limit-imposed loads. This concept has been modelled using 3D FEM analyses and a rudimental lab test. For implementation, the collapsible columns would be prefabricated in strengths to mimic the soil strength profile. This concept has merit, and analytical results demonstrate that collapsible columns are a viable means to limit loading.

Jun 23, 2024

By Chiranjibi Santi, Amit Kumar Gorai, VIVEK KUMAR HIMANSHU

Air overpressure (AOp) and peak particle velocity (PPV) are the most undesirable effects of blasting in mines. It is an urgent need to design a predictor model for AOp and PPV for universal applications to minimize environmental effects and damages that occur due to blasting. The present study attempts to design an artificial neural network (ANN) model for the prediction of AOp and PPV in different conditions. In this study, the blast design parameters (number of holes, depth of the blast hole, stemming length, spacing, burden, distance of vibration monitoring location from the blast site, charge weight per delay) of two active mines (coal and iron ore) are considered in four different conditions for training and testing of the model for the prediction of AOp and PPV. The model was trained and tested in four different combinations of data (trained using data of one mine and tested using data of another mine, trained and tested using data of coal mine, trained and tested using data of an iron ore mine, trained and tested using combined data of both the mines) for examining the applicability in different conditions. The results indicate that R2 values are ranged from 0.886 to 0.908 and 0.8728 to 0.8959, respectively, in the prediction of PPV and AOp. A comparative study of the performances of the developed model with the other empirical model is also demonstrated. For this, the site constants of different empirical models were estimated individually for both the mines. The study results indicated that the ANN model performs much better than all the empirical models. It can be inferred from the results that blast vibration cannot be accurately predicted only from charge per delay and distance from the blast hole. The ANN model was considered many other factors and thus can predict the vibration level more accurately.

Jul 30, 2021

By J. D. Miller, R. J. Smith

Earl C. Herkenhoff Publication of the article "The Flotation Behavior of Digested Asphalt Ridge Tar Sands" by R.J. Smith and J.D. Miller has confirmed and again spotlighted a most significant and important development in the field of tar sand and heavy oil mining. This is the ability to recover 95 % of the bitumen in dry tar sands by a hot water process. The initial investigation by Miller and Sepulveda in early 1978, "Separation of Bitumen from Dry Tar Sands," was the first blockbuter. It is disappointing that there has been so little scientific and industry ackowledgement that the authors laid to rest the long entrenched belief that the sand grains had to be "water wetted" for a hot water process to be applicable. Dr. Miller and his researchers at the University of Utah used slightly different mineral dressing terminology in describing their process but it is essentially the old, established technique of high solids attrition scrubbing at elevated temperatures with a conditioner or modifier, followed by dilution and froth flotation. Similar techniques were described in detail for other nonmetallic minerals in the mid-1940s by Stuart Falconer of American Cyanamid Co. The authors used a 15-minute "scrub" period (or in their terminology "digester step") at 73% solids and 95°C (203°F) in a 0.3 m solution of sodium carbonate -about 4 kg/t (8 lb per st) of tar sand. Flotation was at 10% solids. Obviously, the scrub is an expensive step with respect to energy input but the high recovery of bitumen appears to justify it. Two basic questions then arise: • What are the effects of shorter scrubbing time, lower temperature, and less sodium carbonate? • Would a two-stage approach be advantageous? That is, could you get the major proportion of the bitumen with a mild scrub and apply the high power and temperature only to the refractory portion? These variables should be evaluated. Apparently, all results were only for rougher flotation. What would the grade and recovery of bitumen be if multiple cleaner flotation steps were employed? We must concede that a 60-62% grade of bitumen leaves considerable room for upgrading. Finally, it should be noted by all executives who approve funds for heavy oil recovery schemes, most of which are variations of in-situ methods, that mining can yield a 95% recovery of bitumen. That is correct, 95%. Imagine what that does to the total barrels recovered from a heavy oil resource compared with the scrawny 30-35% maximum recovery we are getting now. The conclusion-let's mine heavy oil and tar sands. Reply by R.J. Smith and J.D. Miller We, too, share Mr. Herkenhoff s enthusiasm for the mining of tar sands-heavy oil and continue the development of related processing technology. Specifically, it will be noted that by appropriate control of bitumen viscosity in the feed (probably the most important variable for successful separation) the recovery can be accomplished at low digestion temperature and low addition of alkali. A 91 t/d (100 stpd) pilot plant based on our technology is now being operated by Enercor in Salt Lake City (Hatfield, Oblad, and Miller, 1982). In these same pilot facilities, rougher concentrates containing more than 80% bitumen on a dry basis are being produced from Asphalt Ridge Feed. However, the processing of certain other tar sands results in incomplete digestion of bitumen/sand aggregates as discussed elsewhere (Miller and Misra, 1982). Such undigested aggregates are shown in Fig. 1. In this regard, it is intended that a recycle stream will be installed in the pilot plant to provide for redigestion of middling products. Further details regarding surface chemistry aspects of this tar sand technology have recently been published (Misra, Aguilar, and Miller, 1981). References Hatfield, K.E., Oblad, A.G., and Miller, J.D., 1982, "Pilot Plant Recovery of Bitumen from Oil Wet Tar Sands," Processing, Second International Conference on Heavy Crude and Tar Sands, Caracas, Venezuela, Feb. 7-17. Hatfield, K.E., Oblad, A.G., and Miller, J.D., 1982, "Pilot Plant Processing of Oil-Wet Tar Sands," Symposium, Rocky Mountain Fuel Society, Salt Lake City, Utah, Feb. 18-19. Miller, J.D. and Misra, M. 1982, "Hot Water Process Development for Utah Tar Sands," Fuel Processing Technology, Vol. 6, No. 1, April, pp. 27-49. Misra, M., Aguilar, R., and Miller, J.D., 1981, "Surface Chemistry Features in the Hot Water Processing of Utah Tar Sand, Proceedings, "Symposium of Separation Science and Technology for Energy Applications," Gatlinburg, Tennessee, May 5-8.

Jan 11, 1982