TerraTherm has developed an advanced temperature monitoring system that has the ability to let our engineers and our clients know the exact status of their thermal treatment project(s) at all times. It provides a real-time view of temperature performance throughout the target treatment zone (TTZ), while it measures and stores soil temperature data for the life of the project. The system provides a great way to increase understanding and share knowledge of the entire cleanup process, while keeping everyone tuned into the same well-informed data. It is also key to helping us make the fine adjustments that are sometimes required to achieve the target temperature and uniformity throughout the treatment zone, while staying on schedule and using energy wisely.
The success of TerraTherm’s remediation of in situ contamination is primarily accomplished through desorption, volatilization, and vapor extraction of volatile organic compounds (VOCs) and semi-volatile organic compounds (SVOCs). In order to accomplish this, soil temperatures must be raised and maintained nearly to the boiling point of the compounds of concern (COCs), typically 100°C for VOCs and 325°C for SVOCs. Temperature information is used by the engineers and project managers to track the treatment progress, predict completion date, and identify areas of cooling within the treatment zone. The temperature monitoring system provides the data we need to understand and fine-tune the process on a very detailed level, with numerous thermocouples installed in a variety of areas, including representative locations in soil between heater wells, which are the last locations to heat up and thus the coolest zones. Once those locations have heated to the target temperature, we know that all other locations closer to the heaters are at least that hot. In addition, we position thermocouples at specified depth intervals throughout the treatment zone to profile the soil temperature.
Thermocouples operate on the principle of developing millivolts (mV) of potential through two dissimilar metals. Single-point or multiple Type K thermocouples are installed in TerraTherm’s temperature monitoring points (TMPs) due to their low cost, reliability, ruggedness and versatility.
As the thermocouples do their job, the data are sent to remote terminal units (RTU), mounted in TerraTherm-designed wellhead boxes. The RTUs convert the voltage readings to a temperature value and then send the data to a central data hub where the temperatures are logged on a time-interval basis and visually displayed for the operators. Once logged, the temperature data are sent to TerraTherm’s plotter program, which provides a visual image of the current temperatures accessible to our clients. One can click on a particular location and get the data. All of these data are streamed to our client-specific “Thermal Insight” webpage where clients and regulators are able to monitor it daily.
As you might suspect, there are plenty of thermocouples on the job at a TerraTherm site. On typical projects, they are installed in 5 foot intervals within the TTZ, and adjacent to representative heater wells. Operators have the option of adjusting the depth of the thermocouple in the heater well to better profile the heater. An example temperature progression is shown in the following picture, with each line representing the data at one-week intervals.
Having monitored TMPs at every one of our 50+ projects, we have been able to compare actual heating progress in the field against the predictions of our thermal model, and find them to be very reliable. This helps ensure that our thermal designs are optimized to meet project’s goals within its budget and schedule.
TerraTherm’s temperature monitoring system has been developed over the years to become a very user-friendly, easy to install/maintain, reliable system that has proved to be a valuable and unique TerraTherm tool. It is a key player in helping keep the entire team, including clients tuned in to the project, allows for granular adjustments to best achieve results, and keeps all involved “well-aware” of the key temperature variables.