Soils
The Enviro-Klean technology can process a wide range of soil types. Some soils will be easier than others to work with and will thus increase the throughput of the machine. The feed system on the machine will remove any rocks or chunks over 5cm (2 inches) in size using a trommel screen.
The specifications for the KM-4 for soil classification refer to ASTM: D2487, with the sub-categories GW (well-graded gravel with sand), GP (poorly graded gravel with silt, sand, cobbles and boulders), SW (well graded sand), and SP (poorly graded sand). Combinations of these soil symbols will indicate a mixture of conditions and are the most common occurrences in nature, plus a``clay`` component.
Clay
Clay soil can prove to be a challenge depending on the type of clay present, moisture retention and tendency to lump into larger chunks. A certain amount of clay is usually present in most sub-soils, and the KM-4 can handle this material quite efficiently. The bottom line with clay – this material can slow the throughput down and make feeding the machine more difficult.
Silt
Some clay breaks down into very fine particles and becomes like powder – another concern for thermal remediation as these fines tend to make their way into the filtration system at increased volumes, causing overloading of the filters more quickly. To combat this potential problem, the KM-4 employs a multi-clone rather than a cyclone to remove 90% of the >50 micron particles from the airstream. Usually a by-product of organic clay and sometimes mixed with fine sand, silt is any soil particles that can pass at least 50% through a 200 mesh screen. High percentages of silt should be avoided or these soils should be blended with a larger aggregate material to minimize their adverse affect on the equipment. The soil symbol for silt is ML, while clay is either CL, OL, CH or OH.
Moisture Levels
Hydrocarbons in a soil matrix tend to attach themselves to water molecules. The thermal processor of the KM-4 will evaporate the water as it vaporizes the hydrocarbons. The higher the moisture content, the slower the machine will process the soil, and therefore the more it will cost to operate.
Moisture level in the soil can vary from one area to another by a considerable amount. The lower the moisture level of the soil, the less energy is required to boil the water out of the soil. The KM-4 specifications recommend that the moisture level not exceed 20%, or too much fuel is wasted dealing just with the water. Moisture levels below 15% increase the throughput capabilities greatly. Clays are especially bad when high moisture is present, because they tend to lock the moisture into their matrix and make it harder to remove.
A higher moisture content than desirable can often be remedied by an effective pre-treatment system. Sometimes, simply piling the soil up, covering it with tarps and letting it drain for a period of time, coupled with turning the pile(s) several time will make a major difference. Another method is using a trommel to aerate the soil before piling it up. This can also help to break up lumps in the soil and make it easier to process. The KM-4 includes a trommel with the feed system.
Type/Level of Contaminant
The KM-4 is designed to remove hydrocarbons from soil. The processor is designed with maximum heat-to-soil contact near the bottom of the soil boxes. The heat diminishes as it contacts soil in its rise upward as it gets pulled by the induction fan.
Hydrocarbons found in BTEX or gasoline contamination are much lower on the Carbon Chain than lubrication oils or Bunker C. The lower the Carbon number, the less heat is required to vaporize the contaminants. The less heat that is required, the faster the machine can process it, thus increasing its ``throughput.``
Soil Profile
Soils will quite often contain hydrocarbons ranging from C10 to C40, the latter being to upper range of hydrocarbons allowable through the KM-4. A contractor must be aware of the Soil Profile prior to estimating the throughput and the amount of fuel required to process a given site. The Soil Profile will also indicate the LEVEL of contaminant(s), registered in parts per million, (ppm), or milligrams per kilogram, (mg/kg).
Both these factors have a dramatic effect on the machine throughput, and therefore on the cost for cleaning up a site. The KM-4 is capable of processing up to 25,000 ppm (mg/kg) of hydrocarbon contaminants to Carbon 40, (C40), however, this would be the absolute worst-case scenario and therefore the throughput would be in the range of 12-15 tons per hour, (tph). With more favorable conditions, the throughput could reach 30 tph or more.
Operating Costs
The five factors: soil type, moisture content, contaminant type, contaminant level and clean-up criteria all vary from project to project. Therefore, one can see that the effect of the soil profile on the operating cost can be much different from site-to-site.
Source Emissions Tests
KM-3 tests were conducted in accordance with Environmental Protection Agency (EPA) standards as defined in document Title 40, Code of Federal Regulations, Part 60 (40 CFR 60), Appendix A, Methods 1, 2, 3A, 4, 5 and 25A, and Puget Sound Air Pollution Control Agency (PSAPCA) Method 5 back-half extraction procedures.
The independent testing laboratory, AMTEST, of Washington State ran three (3) 60-minute tests. The TDU processed 11-12 CY of soil per hour during the tests (16 to 18 tons). EPA Method 25A was performed to quantify emissions of volatile organic compounds (VOC) as THC using a flame ionization analyzer (FIA). PSAPCA back-half analysis procedures were used for considerable matter analysis.
