Energy efficiency when referring to industrial processes is the reduction of energy intensity—the amount of energy used, both from the centralized grid and also from direct on-site combustion of fossil fuels. Energy efficiency reduces the number of emissions from energy use and can be combined with emissions efficiency techniques.
A major part of manufacturing is pumping systems. Pumping systems are used to cool and lubricate machines, transfer fluids, and power hydraulic systems. Making the pipe system more efficient is essential to making the manufacturing process less energy-intensive. Designers should determine the optimal pipe size for products, maximize pressure drops with a piping system layout, and engineer the piping so that they lose less energy en route (low-loss piping).
Compressed air is another major part of manufacturing operations. Leaks can waste 20 to 30% of all input energy. Compressed air systems should be checked for leaks. Operators can also lower the air pressure of systems to lower the flow rate, which leads to fewer leaks.
Motors are a also very important part of manufacturing operations. To improve their efficiency, operators should install a device that automatically adjusts the speed of the motor. By doing so, the motor will operate at an optimal speed. As a result, the system will be more reliable and be more controllable, resulting in higher efficiencies.
Waste heat is heat that escapes before being used and represents 20 to 50% of all input energy. To improve efficiency, waste heat recovery technologies should be employed, with possible efficiency improvements of 50%. One such strategy is "reusing" the waste heat to heat other processes. Recuperators can achieve this through either radiation, convection, or a combination of the two. In general, however, they take the heated waste air and use it to heat other air to use in processes. Similarly, furnace regenerators absorb the combustion exhaust into the brickwork, increasing the temperature of the furnace. Furnace regenerators are often used in glass melting (see below) and coke ovens (see Solution 2, steel). Another type of regenerator is a rotary regenerator, which stores the waste heat in a porous medium. Rotary regenerators rotate the porous medium and combine the waste heat gas with cold gas. Finally, waste heat can be captured and then cooled to prevent it from escaping to the atmosphere and then to reuse.
While these technologies do not directly decrease the emissions from manufacturing, by decreasing the amount of energy they use there is less on-site and electrical burning of fossil fuels, which does cut down on emissions.
Glass accounts for just under 2% of the world's greenhouse gas emissions—60 million tonnes of carbon dioxide. Glass emissions arise from the melting process, a very energy-intensive process. Five possible solutions are discussed here to improve glass melting: oscillating combustion, plasma melters, submerged combustion melting, porous burners, and microwave heating.
Oscillating combustion increases fuel efficiency by forcing fuel to make back-and-forth movements (oscillations) in the furnace. These oscillations cause the fuel to produce more heat and reduce the production of ozone-creator nitrous oxide (30 to 50% fewer emissions of NOx). By producing more heat, less fuel is required. As a result, fuel oscillation can reduce fuel by 2 to 27% and can have an overall efficiency improvement of 6%. These improvements mean that the processes will release less carbon dioxide into the atmosphere. Furthermore, oscillating combustion technologies can be implemented into already-existing furnaces, without retrofitting them.
Plasma melters help with the thermodynamic (heat) efficiency of glass melting. Plasma has a very high heat content (high enthalpy), meaning that it can produce high temperatures quickly. This is because the energy of plasma melting is denser than conventional melting methods. As a result, energy efficiency can improve by 50 to 70%.
In-flight melters disperse the input materials so that they are in direct contact with the flame, allowing rapid heat transfer. Byproduct gases are removed, meaning that emissions are reduced, and it makes the transfer go smoother, leading to greater energy efficiency. In addition, in-flight melters increase the yield of the furnaces, meaning that they could save energy while increasing productivity.
Microwave heating for industrial melting uses the same principles as widespread commercial microwaves. Microwave heating allows the glass to be melted at higher rates but lower temperatures. Microwave heating can also cut down on direct emissions by using electricity to power them, unlike conventional furnaces. Researchers are currently studying how to implement this technology into large-scale industrial applications. By doing so, a study estimates that it will half the energy intensity (double the energy efficiency) of conventional furnaces.
These glass solutions can be combined to multiply energy savings. For instance, in-flight melters can be operating in a plasma melter furnace that employs oscillation combustion. The glass industry is one of the easiest industries to cut emissions, so these technologies must be employed.
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