Waste Heat into Added Power
What is Recycling Energy?
Energy recycling is the recovery of energy that would normally be wasted in industrial processes by flaring, exhausting to the atmosphere or operating low efficiency equipment, and converting it into electricity or thermal energy (steam or heated water). Combined Heat and Power (CHP) is a form of energy recycling, where processes and equipment are designed to produce power and also supply heat rather than waste it. Energy recycling and CHP can be implemented at industrial sites, manufacturing facilities and large institutions such as hospitals and universities.
In a typical electric power generation plant, input fuel is used to create electricity while excess thermal energy (in the form of steam) is wasted in the process. Many facilities, both commercial and industrial, require a substantial amount of thermal energy for heating, cooling and other low temperature processes. By locating an electric generation plant on-site at a facility that has a significant demand for thermal energy, steam or heated water that is typically wasted can be used by the host. Each CHP plant lowers their host’s energy costs and reduces emissions as compared to buying power off of the grid or burning fuels to produce steam with boilers.
Recycling waste energy streams is accomplished by Primary Energy in two ways:
- Converting industrial waste energy streams into heat and power with on-site generation plants.
- Building CHP facilities near energy users to enable recycling of wasted energy from the production
of electricity to displace boiler fuel.
‘The energy lost in the United States from wasted heat in the utility sector is greater than the total energy use of Japan.’
– U.S. Department of Energy
Industrial Waste Energy Recycling
Many industrial processes produce byproduct energy streams such as (i) hot exhaust gases, (ii) flare gases and (iii) high pressure gases. Hot exhaust gases are generated by facilities such as coke ovens, blast furnaces, petroleum refineries and hot rolled steel ovens, which all have high temperature exhaust gasses that can be converted into electricity and thermal energy. Waste gasses are typically created in industrial processes, such as those that occur in blast furnaces, which reduce iron ore to molten iron and produce byproduct gas that must be flared or disposed of. Finally, energy in the form of pressure drop energy is created when gases, including steam and natural gas, flow from high pressure pipes to low pressure points of use. Electric power and thermal energy can be produced by capturing and recycling these forms of waste energy produced by industrial processes.
The following diagram depicts a typical industrial site, which purchases electricity and fuel, uses the energy to produce finished goods, and emits significant waste energy from the processes.
The following diagram shows the original industrial site with energy recycling added. The site purchases less electricity and less fuel to produce the same quantity of finished goods and, as a result, vents less waste energy.