The buzz about low-grade heat

June 26 2014 - TI Staff

Extracting waste heat economically has always been a challenge. How low can the waste gas temperatures go before the equipment making power from the gases becomes too complicated and too expensive?
Ener-Core, which uses a microturbine but with a patented oxidizer to burn the waste gases instead of a traditional combustor, recently received a purchase order to test its proprietary gradual oxidation technology with emissions gases from oil sands operations. In addition, it received several memorandums of understanding (MOUs) from companies in a wide range of industries.

Ener-Core has received the order from Cenovus Energy, Inc., a Canadian integrated oil company with operations at the oil sands of northern Alberta, to test the ability of Ener-Core's gradual oxidizer to destroy the waste gases from its oil fields, and convert these gases into power. The testing is expected to take place over the next five months at its testing facility at University of California, Irvine (UCI), with UCI validating the test data.

The MOUs came from a producer of plastics (Saudi Arabia Basic Industries Corporation), a regional supplier of drinking water (Brabant Water in Netherlands), a sewage treatment plant operator and an ethanol producer. Ener-Core recently celebrated the operation of its first installation in Europe by convening a ribbon cutting ceremony along with Attero, the waste management company in the Netherlands.

Alain Castro, CEO of Ener-Core said the company’s target is to cater to a variety of industries, which include landfills, refineries, oil fields, coal mines, distilleries, and industrial manufacturers of plastics and steel.  “This sudden influx of MOUs and the order from Cenovus are testament to the fact that our multi-industry strategy is working.”

"Having a system operating in Europe’s Attero is crucial to our ability to secure additional commercial orders. We are now receiving several requests per week from prospective customers throughout Europe, wishing to schedule site visits to observe the unit in operation,” Castro said.

Ener-Core's technology helps companies to continue to generate electricity with low quality gas from landfills, said Paul Ganzeboom, CEO of Attero. “By generating clean electricity from these sources of waste gas, it reduces our dependency on generating electricity from other sources, such as coal.”

Frans Follings, Director of the Recycling Business of Attero, said gas engines now used on landfills can only operate on gases that contain methane levels of 30 or 40 percent. When the quality of gas falls below that, the engines stop operating. “This issue with low-energy gases is pervasive across other industries, such as the chemical industry and oil industry. Attero has about ten landfill sites where we could use this technology to generate power when the gases become too low to generate power from a traditional engine or a turbine."

Fuel flexibility and pollution control

Ener-Core designs and manufactures systems for producing continuous energy from a broad range of sources, including previously unusable ultra-low quality gas. With its gradual oxidizer matched to gas turbines, Ener-Core offers systems with fuel flexibility and pollution control for power generation. The gradual oxidizer can also be customized for integration with larger existing power generation systems for pollution control, and zero emissions.

Ener-Core’s 250kW Ener-Core Powerstation FP250, and its larger counterpart, the 2MW Ener-Core Powerstation KG2-3G/GO, are designed to transform methane gas, especially "ultra-low-Btu gas" from landfills, coal mines, oil fields and other low quality methane sources into continuous clean electricity with near-zero emissions.

How the FP250 works

The FP250 integrates a modified conventional micro-turbine (Ingersoll Rand MT250, now manufactured by FlexEnergy Energy Systems) with a gradual thermal oxidizer in place of the conventional turbine’s combustor. Gradual oxidation is the 1- to 2-second conversion of a dilute fuel air mixture to heat energy, carbon dioxide and water.

Compared to traditional combustion processes, which occur in milliseconds, the Ener-Core oxidation process is said to be more gradual. The FP250 is able to operate using low heating value fuel sources (theoretically as low as 15 Btu/standard cubic feet [scf]) that would not support operation of conventional gas turbines or reciprocating engines, which require a minimum fuel heating value of 300-500 Btu/scf.

Modifications to improve reliability

Like other turbine-based technologies, the FP250 requires a steady fuel supply with minimum total energy content of about 3.4 million (MM)Btu/hour (higher heating value). In addition, it does not tolerate excessive thermal cycling. A continuous 24/7 operation is recommended, and the number of restarts over the system lifetime should be minimized to avoid excessive maintenance. A sufficient, continuous fuel supply should also be verified during site selection, apart from the reliability of the grid interconnect (if any) at candidate sites.

The FP250 is undergoing minor modifications to improve reliability and operability:

  • Prevention of turbine wear due to particulate breakthrough from the gradual oxidizer
  • A new start-up protocol utilizing the warmer only
  • Full automation of system start-up
  • The capability to continue operation in ‘island mode’ to prevent unnecessary shutdowns due to transient grid faults (applicable to sites with frequent grid interruptions)

Ener-Core is likely to serve several markets globally, including oil fields, biogas, coal mines, natural gas, emissions control, and utility power generation.