If a Renewable Energy solution isn't appropriate for your application, There’s still a way to reduce greenhouse gas emissions while you wait for one!
Renewable Energy sources like wind, solar, and biomass are currently being taken advantage of to reduce our dependance on fossil fuels and reduce the effects of combusting fossil fuels for power. We have all seen the push to eliminate burning fossil fuels in the hopes that we can clean our air and environment for the future of our planet.
Most of us, though, have no real idea of what this implies or how we reach this goal. Sure, we have all seen solar panels on roofs and fields collecting energy from the sun and converting it into electricity. Great advancements have been made to store that electricity for use when the sun is not shining. The same goes for vast farms of wind turbines spinning to harvest the energy in the wind and convert it to useable electricity. In locations where wind is consistent and sunshine plentiful year-round, these technologies help to supplement, and in some cases, replace the power generated by burning gas, oil or coal to make steam and turn turbines for electricity production.
For electricity generation to power our devices, air conditioners, motors and machines wind and solar power are as clean as it gets. Storing and moving that electricity is still a challenge but one that we have in our sights to overcome.
Where electricity is not the final form of energy to be used, renewable energy sources become a bit more difficult to rely on. Consider a hospital or university. Every dorm, classroom, hall, operating room and office needs to be heated. Heating with electricity is very inefficient which is why most of these facilities use centralized heating plants that generate steam for heating. Steam is an excellent medium to move energy, especially heat. Some plants are powered by biomass to generate steam and can be considered “green” renewable energy, but most utilize a fossil fuel as a primary energy source for heat.
Industrial processes requiring large amounts of heat are also less likely to use electricity as a primary source of energy. For example, in the paper-making process, heat is required to breakdown the fibers in pulp as well as dry the processed pulp into paper or boxboard. In refining, heat is necessary to separate light and heavy constituents for petroleum-based products. In agriculture, heat is required to extract oils from grain and seeds. All of these processes depend on steam generated by fossil fuels or biomass that will not soon easily be replaced by wind or solar power.
Until the time when these heat-related processes can be satisfied with renewable energy, the answer to reduced emissions is efficiency. With heating processes, efficiency typically brings to mind insulation-ensuring the heat is kept in the process rather than losing the heat to the atmosphere. It is true, Insulation is a key to reducing carbon emissions, but there is another, more beneficial solution available.
Before we explain this relatively simple solution, it’s important to know a bit about the combustion process. When we burn fuel for heat or to generate steam, the fuel combines with air releasing heat and forming CO2 and water vapor. There can be a substantial amount of water in the exhaust, especially when burning natural gas. This water is vaporized and leaves the stack as an invisible gas, until it cools enough to create a white cloud or plume. On cold days you can see the white plume from stacks passing natural gas exhaust into the atmosphere. The white plume is nothing more than water vapor condensing in the cold air.
If you consider that the water from combustion absorbs heat energy to vaporize before leaving the stack, you realize that some of the energy in the fuel is being used to vaporize the newly created water. These BTU’s are locked in the water vapor, a byproduct, carrying some of the energy you purchased when buying every cubic foot of natural gas, and they are leaving the stack without adding to any process or heating load- this means wasted energy and money.
Knowing that a portion of the energy you purchased is being wasted out the stack, actually up to 15% of the total energy content, there must be a way to capture this lost energy in a way that makes every cubic foot of natural gas much more valuable. And there is, through condensing waste heat recovery!
A condensing heat recovery system uses the energy in exhaust gas streams, both in the temperature and locked in the water vapor to heat cold liquid streams that otherwise would use steam, gas or electricity to heat. By cooling the exhaust gas before it leaves the stack, we can condense the water vapor and capture the energy it took to vaporize it during the combustion process.
When you heat a cold liquid stream, you release cooler exhaust carrying less water and you capture water that would otherwise leave the stack and enter the atmosphere as water vapor.
(And by the way, water vapor is also considered a greenhouse gas like CO2!)
In the past few years, there has been a lot of news about condensing boilers and how efficient they can be. This is true, as long as they are heating cold water that reduces the exhaust temperature below the dew point. In residential and small commercial applications, the technology works because water going to the boiler is straight from the city pipe or well at an average temperature of about 65 degrees which is perfect for condensing exhaust.
In larger industrial applications though, part of the method for saving energy is to return hot condensate back to the boiler so that not as much energy or fuel is needed to re-vaporize the returned water to steam. This condensate comes back, in many cases, too hot to drive exhaust gas temperatures below the dew point.
The Condex Condensing Waste Heat Recovery system is designed to go behind any existing boiler, turbine, engine, incinerator, oven or dryer outputting hot exhaust gas. The Condex takes in liquid streams like boiler make up water, process water, domestic hot water, condensate return, swimming pool water, or glycol and other liquids to be heated using the energy remaining in the exhaust gas.
With this technology, it is possible to save 12-15% on fuel use, which means you’re not only saving cost but also reducing the amount of greenhouse gas emitted to the atmosphere without reducing the steam or heating load. The team at Combustion & Energy have installed systems in many different types of applications including district heating, food manufacturing, pharmaceuticals, refineries, schools and universities, hospitals, paper making, brewing and distilling and other general industrial applications.
So, with all these great benefits, why aren’t condensing economizers more widely used? There are a number of reasons, many of which are losing importance with time. The primary reason is the low cost of fuel. With Natural Gas prices as low as they currently are, the return on investment may take longer than most companies are reasonably willing to accept. However, newer utility incentives are helping to reduce the payback period and sometimes, the amount is based on this time period.
Second, without a financial incentive, protection of the environment has not been a strong enough driver to push for lower emissions until recently. By installing a condensing waste heat recovery system, it is possible to claim a reduced environmental footprint for the exact same output. Going “green” and being a good steward to the environment has never had as much impact.
Third, some applications just aren’t right for condensing waste heat recovery. A plant that brings back all or most of their high temperature condensate to the boiler has very little cold make up water to heat and may have no other cold “heat sink” to absorb energy from flue gas.
Last, making a condensing heat recovery system that works and, more importantly, lasts is difficult. Hardware design and materials selection are critical to maintaining a long-lasting system that does not rapidly decay in the slightly corrosive environment created when combustion gases are cooled and mixed with water. 20 years and more than 200 systems installed have proven the knowledge and expertise of the Condex engineers who design every application to the specific requirements for construction and material selection of that application.
If you would like to know more about the technology or have an application to heat a cold liquid stream, we would be happy to review the application to see if condensing heat recovery is a good choice. Our goal is to reduce gas use, reduce your operating costs and reduce the emission of greenhouse gases. The local utilities in many area’s of the country like the technology too. We have helped our customers obtain incentive money for many of our projects that defray the installed cost by reducing the amount of gas use and we always work with our customers and their local utilities to take advantage of similar programs.
For more information please contact us at info@combustionandenergy.com or call 603 910-5174.