Electrical Resistance Heating

CES AND ERH - THE PARADIGM SHIFT IN REMEDIATION TECHNOLOGY

Scientists at the Battelle Memorial Institute (BMI) which operates the Pacific Northwest National Laboratory (PNNL) developed ERH with funding from the US Department of Energy which dedicated substantial resources to the National Laboratory system for the research and development of technologies to remediate DNAPL in-situ, and specifically those technologies that would have a wide range of applicability in both permeable and low permeability soils. The technique was developed in the late 1980s and early 1990s. When CES was formed, as part of our operational agreement with BMI/PNNL all the research and development information was transferred to the staff at CES. The primary inventor and author of the ERH patents was William Heath, the full time Chief Operating Officer of CES. Bill not only invented the technology, but also designed and built the original ERH power supplies.

All thermal technologies increase the temperature of the soil and contaminant, causing an increase in the contaminant’s vapor pressure and its removal rate. However, compared to heating by steam or hot air injection, applied electrical fields have the advantage of heating soils internally. Some of the advantages of ERH:

  • Low permeability zones or complex heterogeneous soils can be treated.
  • Electrical heating provides an in situ source of steam to accelerate further removal of volatile organics from soils.
  • Enables higher molecular weight compounds, such as DNAPL, that are not very volatile are removed by simple venting.
  • Removal of soil moisture (as steam) increase the gas permeability of soils and can reduce the mass transfer limitations associated with low permeability soils.
  • ERH is an ideal method for heating soil such as clays. Because of the clay layer's relatively high electrical conductivity, it receives the majority of the current and is where most of the energy is dissipated.

The mechanism of ERH heating is resistive dissipation of the electrical energy. Electrodes are inserted into the ground and conventional single-phase transformers are used to impart standard three-phase electricity to the electrodes arrays. Each electrode is connected to a separate transformer wired to provide it with a separate current phase. An ERH electrode system is typically installed using common drilling equipment and uses conventional non-specialized utility transformers, resulting in low capital cost.

hex heating 1Hex heating 2temps graphtemp graph 2

 

If interested please use the contact us information to request a complete history of the principals and development of sub-surface electrical field propagation and its application in ERH Remediation.