Iron Ore Mining (1)

By IonMars

July 25, 2014

I found my thrill
On Blueberry Hill
On Blueberry Hill
When I found you1

A young entrepreneur landing at a Mars village to start up an iron industry will certainly find his thrill on Blueberry Hill. The “blueberries” of Mars are comprised of of nearly pure hematite, one of the richest iron ores to be found in the Solar System. They received this nickname because they looked like blueberries in a muffin. First discovered by The Mars rover Opportunity2 in 2003, these hematite spherules are composed of iron oxide (Fe2O3) 3 commonly called rust. A comparable high-grade iron ore found on Earth was the rich vein discovered in the Masabi Range of Minnesota that contributed the main source of iron to the US steel industry until the 1950s when it petered out. 4

Mars blueberries on Meridiani Plains The Mars blueberries are thrilling because they represent a direct shipping ore, a very high grade that can be shipped directly to a steel-making plant without further treatment. A blast furnace requires an ore grade of 60 percent iron or better to maintain the efficiency of its operation.  But pure hematite, 70 percent iron, can be fed directly into the furnace, which bypasses many of the usual processing steps, thereby realizing a big cost savings.  

To process iron ore in the US today, the ore is first withdrawn from the earth by strip mining.5 The first step in is to remove the overburden, the soil and rock covering the vein of taconite in the ground. Taconite is a lower-grade ore comprised of hematite mixed with various combinations of quartz, chert (fine-grained sedimentary rock), or carbonate. Strip mining is an expensive process, not only because large machinery are employed for extended periods, but also because the spoils area must be reclaimed and replanted with natural vegetation.5 In the case of mining the Mars blueberries, this step can be skipped altogether because the little spherules are found on the surface of the ground. It “only” requires a method for scouring the Meridani Planum or other location of high concentration and collecting them. 

The second step in processing iron ore in the US is beneficiation.6 This step separates the ore from any soil, rock, and other minerals in the vein of ore that Hull Rust strip mine in Minnesotaare waste materials in the iron and steel making process. Considerable processing is required because some of the ores mined today may exhibit a low iron content as little as 15 percent. But the blueberry spherules of Mars, rich as they are, still need to be separated from the surrounding regolith, rocks and stones. At this point the entrepreneur’s thrill may be stifled a bit because the spherules are rather tiny, only 1 to 5 mm in diameter. Entrepreneur Peter will have to pick a pretty pile to fill his bucket of blueberries. 

To separate blueberries from regolith a simple process needs to be found. The budding steel magnate will never be satisfied picking tiny blueberries one-by-one. But some methods of beneficiation can be ruled out.  Magnetic separation, for example, is used on Earth because some of the ores being processed contain magnetite (Fe3O4) rather than hematite. Hematite is only weakly magnetic, so this process would be ineffective for picking blueberries. Another method is washing, which involves a substantial amount of liquid water.  On Mars considerable effort and energy will be required to maintain water in a liquid state, so this method will be avoided, if possible.  

In addition to being concentrated, iron ore that is introduced into a blast furnace must be in small pieces, either pellets or nodules. To meet this requirement, the ore is condensed into pellets. Typically, 99 percent of the pellets will be less than 16 mm in size.7 To produce pellets from ore, the first step is milling, which involves crushing and grinding.  This is followed by filtration and agglomeration (pelletizing, briquetting or nodulizing)5. These processes will not be required for blueberries because the 1 to 5 mm spherules of are about the right size already. 

While magnetic separation, milling, and pelletizing are used today on Earth, other methods have been used historically when adapting to different economic or environmental circumstances. The different circumstances on Mars are the lack of a substantive atmosphere and the extra cost to maintain water in liquid form despite the intense cold. One method of separating rock, sand and soil on Earth is dry classification by means of cyclones.  They are employed in deserts where water is not plentiful to separate particles. Unfortunately, the design of cyclones assumes that the sand can be entrained in air in order to throw and separate the particles.  Almost no air on Mars means almost no use for cyclones in an outdoor environment.

 

Cottage Iron Ore Mining

The pioneering iron industry will begin on a small scale using general-purpose machines that are “low mass and highly effective.” Later, specialized machines can be designed, built and sent to Mars. Alternatively, the iron and steel produced in a cottage industry may be sufficient to construct the larger and more sophisticated equipment required for a larger iron and steel industry.

One type of cottage industry will be based on the mining of blueberries. It will require an effective method of separating blueberries from regolith, such as dry screening. This process employs screens made of steel wire or plastic mesh that are mounted inside a frame and held in a horizontal position. 

Pitbull 2300 in operaton

The Pitbull 2300 demonstrated in the above photo is one example of a portable dual-screen machine. 8 The incoming material passes over the top screen, which is tilted and vibrated to maximize the separation of different sized particles and to prevent the screen from becoming clogged. In the screening operation as shown above, the waste fines drop onto a conveyor, which sends them onto a pile to one side of the operation. The desired particle size range accumulates underneath. This device exhibits a few more features than the EZ-screen described in the article “Pioneer Road Building.” Its higher throughput is purchased at the expense of less mobility. While a ½-ton pickup could tow the EZ-screen, an MEV dump truck will be required for the Pitbull 2300.

To separate blueberries from regolith, two screen sizes will be required.  The first will separate rocks or particles larger than 5 mm as waste.  The rest will pass to the second screen where particles less than 1 mm will pass through to the conveyor and the items of size 1 to 5 mm will be retained. This size range will consist mostly of blueberries, but not entirely. Experience will determine whether this process is sufficient to obtain almost pure hematite that is ready for the blast furnace.  If not, a classification table can be employed to further screen material by particle density rather than size. 

Circular broom under a street sweeper
To make the screening process work properly, the iron spherule-containing regolith should be pre-screened to remove any rocks or glassicles that could foul up a screening procedure. To determine how this could be accomplished consider the environment where screening will take place. For example, assume that the locale is the Meridiani Plains where blueberries were originally discovered. Not only were they found on the surface of the ground but also on rocks. To gather up these spherules, we need to:

1) Sweep blueberries off any hard surfaces onto the regolith. This will require a special tool, such as a spinning brush of the right stiffness to sweep blueberries off irregular surfaces and minor crevices. On a small scale, a general-purpose machine, such as a Mars utility vehicle (MEV) with manipulators could handle a rotary broom. (See the article “Mars Village Vehicle.”). In the photo above a street sweeper is equipped with a wire brush rotary broom that could be placed on the end of a heavy-duty manipulator arm. A colonist in a spacesuit could also carry out the job, but with more difficulty.

2) Comb the spherule-containing regolith to remove larger rocks and glassicles.  A tine rake attachment on a front-end loader will run through the area where the blueberries lie and pull the unwanted debris to one side.

3) Scoop up the pre-screened spherule-containing regolith and deliver it to the spherule-screening station. A front-end loader with a standard bucket will do nicely.

A nice outing on the Mediani Plains for blueberry picking will involve more than a picnic basket. First, an advance exploration foray will survey the plains to determine the areas of higher concentration. A plan will be mapped out whereby the portable sweeping and screening process can be set up as a series of base camps. A minimum crew of four will haul machines and equipment to the site of the first base camp. The first miner will drive an MEV dump truck to haul one front-end loader and tow the Pitboss 2300 (or equivalent). The second miner will drive a second front-end loader and tow a trailer loaded with equipment. A colonist from the village will drive a pickup truck out to the base camp with a Mars Utility Vehicle (with manipulators) carried on the truck bed.  After unloading, he will return to the village, place another MUV on the truck, and make a second delivery to the base camp. The screening machine and auxiliary equipment will be set up at a mining base camp with the intention of collecting spherules within a 1/2-km radius around the camp. 

MEV to HDU adaptor

The mining crew will require overnight accommodations unless a permanent Mars house will be built in a central location for this type of mining venture. 

Otherwise, a Mars Habitation Demonstration Unit (HDU) developed by NASA would be an appropriate overnight lodge for this purpose; it has the capability for housing two explorers (miners) for two weeks away from an exploration base camp or Mars village.9 The HDU has two hatches for connecting to other vehicles and two suitports for going EVA in a space suit, as well as the spacesuits themselves.

To become useful on a mining expedition, one hatch of the HDU will be redesigned to become compatible with MEVs. In case of emergency, for example, there must be a method of evacuation from an MEV to a safe habitat, presumably the HDU. One method of transfer will be the MEV to HDU adapter tube shown in the above photo-sketch.

To deliver accommodations to the base camp, two miners will drive an MEV truck towing a trailer with an HDU from the village out to the base camp. Then they will return and deliver a second HDU to the camp. This will provide overnight protection for four miners.

Tine Rake attachmentA typical two-day mining foray will see three miners driving one front-end loader and two MUVs from the base camp out to a mining area bearing a high concentration of spherules. One miner will stay in camp to conduct equipment maintenance, housekeeping, and communications with the village. One MUV will be equipped with a broom to sweep blueberries from rocky outcrops.  The front-end loader will prepare the spherule-bearing regolith using a tine rake, such as the one in the adjacent picture, or a scarifier attachment. The driver of the second MUV will see to details of outdoors operation that require manipulators. All of them will return to the base camp before dark. 

On the second day the three miners will return to the same area.  They will drive one front-end loader equipped with a standard bucket, the dump truck, and one MUV. They will use the loader to collect regolith to fill the truck and the MUV to manipulate tools in the outdoors, to change a wheel, or ro dislodge a rock from jammed equipment whenever needed. When the truck is loaded, they will return to base camp. Meanwhile, the fourth miner will prepare the screener for operation. The truck driver will dump the load of regolith and the crew will screen it and store the hematite spherules at a nearby location. When enough blueberries have been collected, the truck driver will carry a load to the blast furnace, presumably near the Mars village.

 

Dunes and Meteorites

(In the next two segments Ionmars will address the mining of magnetite iron ore from dunes and the collection of iron-bearing meteorites) 

 

References

 

  1. “Blueberry Hill Lyrics” From the album The Legend of New Orleans Fats Domino Live! (1956).
  2.  “Mars Exploration Rover – Opportunity” (2014) Retrieved June 22, 2014 from http://science.nasa.gov/missions/mars-rovers/
  3. Jolyon, R., “Hematite” (undated) mindat.org, Retrieved 6-22-2014 from http://www.mindat.org/min-1856.html
  4. “Masabi Range” (undated) Retrieved 6-23-2014 from http://en.wikipedia.org/wiki/Mesabi_Range
  5. U.S. Environmental Protection Agency, “Extraction and Beneficiation of Ores and Minerals, Volume 3 Iron,” (1990) EPA 530-R-94-30, Retrieved 6-23-2014 from http://www.epa.gov/osw/nonhaz/industrial/special/mining/techdocs/iron.pdf
  6.  “Iron ore beneficiation,” (Undated) VT CORP VT LTD. Retrieved 6-25-2014 from http://www.vtcorpindia.com/iron-ore-pellet-plant-division/
  7. IKAB Minerals (Undated) “Iron Pellets” Retrieved July 33, 20114 from http://www.lkabminerals.com/en/Products/Iron-Ore-Pellets/
  8. Lake Erie Portable Screeners, “Pitbull 2300” (Undated) Retrieved July 27, 2014 from http://www.pitbullscreeners.com  
  9. “Deep Space Habitat News and Features’” (2012) Retrieved July 12, 2014 from http://www.nasa.gov/explorat”Deep space habitat ion/technology/deep_space_habitat/