Even modern high-efficiency condensing furnaces produce significant amounts of corrosive acid condensation and unhealthy levels of oxides of nitrogen, carbon monoxide, hydrocarbons and methane. These emissions are generally released into the atmosphere and eventually contaminate the soil, water and air.
Scientists at the Department of Energy’s Oak Ridge National Laboratory have developed affordable complementary technology that removes more than 99.9% of acid gases and other emissions to produce an ultra-clean natural gas furnace. This acid gas reduction technology, or AGR, can also be added to other natural gas equipment such as water heaters, commercial boilers and industrial furnaces.
Just as catalytic converters help reduce emissions from billions of vehicles worldwide, new AGR technology can virtually eliminate troublesome greenhouse gases and acid condensation produced by new and existing residential gas furnaces. Environmentally friendly condensate eliminates the need for corrosion-resistant stainless steel materials for furnace heat exchangers, reducing manufacturing costs.
Zhiming Gao, researcher at ORNL’s Energy Science and Technology Department.
To demonstrate the effectiveness of acid gas reduction in a furnace, the researchers fabricated an AGR catalyst, enclosed it in a metal case, and installed the device in a standard commercially available high-efficiency condensing furnace. Results of a 400 hour reliability and durability test showed that the AGR almost completely eliminated harmful flue gas emissions and produced non-acidic condensate with a neutral pH level.
To examine the internal state and soot distribution of the AGR after the test without damaging the device’s gas flow channels, the scientists used neutron computed tomography at the High Flux Isotope Reactor (HFIR) of the ORNL. Unlike X-rays, neutrons can penetrate the metal casing to record images which are then used to produce 2D and 3D renderings of the device in use.
This knowledge will improve the design of AGR devices to achieve a more uniform and self-cleaning gas flow pattern. It will also help alleviate excessive soot buildup to improve the performance of EGR furnaces.
Zhiming Gao
ORNL’s high-efficiency, ultra-clean condensing natural gas furnace features affordable add-on technology that can remove over 99.9% of acid gases and other emissions. The technology can also be added to other natural gas equipment, such as water heaters, commercial boilers and industrial furnaces.
Soot particles, which usually form due to the incomplete combustion of hydrocarbons, contain a considerable amount of hydrogen. Neutrons are particularly good at detecting and mapping hydrogen and other light elements.
Images and neutron maps obtained after the AGR test provided detailed information on the flow of combustion gases through the AGR, revealing the large accumulation of soot particles in the center of the catalyst.
Yuxuan Zhang, ORNL neutron instrument scientist at HFIR.
AGR technology would allow furnace manufacturers to use more affordable materials than the stainless steels used in most heat exchangers. This increased accessibility could allow furnace manufacturers to sell more high-efficiency furnaces that meet California’s proposed new standards for emissions from residential and commercial furnaces.
Currently, EGR furnaces require off-line regeneration of the device approximately every three years under normal operating conditions. The owner or a technician can remove the EGR unit and take it to a collection and recycling site. This would be similar to how consumers bring their empty natural gas tanks for their outdoor grills to a dealership to exchange them for full tanks.
Zhiming Gao
More information: Add-on appliance makes home ovens cleaner, safer and more sustainable — ScienceDaily
