Introduction to Energy Conservation Fundamentals
Energy conservation is essential for businesses and homes around the world. By reducing energy consumption, not only will you save money, but you can also help to reduce your environmental footprint. To achieve these goals, it is important to understand the fundamentals of energy conservation. This includes understanding the basics of energy balance and the data needed to build a reliable energy balance.
What is Energy Balance?
Energy balance is crucial in energy conservation. It is the process of measuring and tracking all energy inputs and outputs of a given system, such as a furnace or boiler. By doing so, energy losses can be calculated and identified, and steps can be taken to reduce them.
To carry out a successful energy balance, it is important to identify all operations in which energy is either introduced or removed from the balance object. This includes tracking energy streams such as steam, hot and cold water, liquid and gaseous fuel during transmission, as well as energy used by the application itself.
Data Needed for Effective Energy Balance
To build a reliable energy balance, it is important to have access to the necessary data. This includes measurements of product flow and temperature, flue gas composition and temperature, fuel flow rate and heating value, combustion air temperature and flow, furnace surface temperature, and mechanical equipment electric consumption.
How to Calculate Energy Consumption for Processing Plants
Energy consumption is an important factor to consider when designing and operating a processing plant. It is the quantity of energy necessary to produce a unit of the product, and is calculated by taking into account the efficiency of the process. In this article, we will discuss the calculation methods for energy consumption, combustion efficiency, and the different categories of combustion losses.
Fuel Energy, Mechanical Work, and Specific Gas Consumption
The energy and mass balance for a processing plant provides several metrics that can be used to calculate energy consumption. These include fuel energy, mechanical work, and specific gas consumption. Fuel energy is the amount of energy available in the fuel, expressed in kilojoules per kilogram of product. Mechanical work is the energy required to produce a unit of the product, expressed in kilojoules per kilogram of product. Specific gas consumption is the amount of gas required to produce a unit of the product, expressed in cubic metres per kilogram of product.
In addition, it is important to consider the proportion of natural gas used for energy purposes and the proportion used as raw material. Generally, 43.2% of natural gas is used for energy purposes, while 56.8% of natural gas is used as raw material.
Calculating Combustion Efficiency
Combustion efficiency is a measure of the ability of a fired system to convert fuel into useful heat. It is calculated by comparing the efficiency computed from the balance with a benchmark performance. This benchmark is not fixed or constant over time and across processes, and must take into account actual operating procedures and technological evolution.
Combustion efficiency can be calculated using either a direct or an indirect method. The direct method calculates combustion efficiency as the total fuel energy minus the total flue gas energy divided by the total energy available in the fuel. The indirect method calculates combustion efficiency as 100 minus the sum of the combustion losses expressed as a percentage. The indirect method is more widely used in practice.
η c = Useful Heat/ Total Energy Available in Fuel
Combustion Losses
Combustion losses arise principally in three categories: heat carried out of the stack by dry flue gas, heat carried out by hot water vapor, and unburned fuel and products of incomplete combustion (e.g., carbon monoxide and hydrocarbons). It is important to take these losses into account when calculating combustion efficiency, as they can significantly reduce the efficiency of the process.
η c =(Total Fuel Energy- Total Flue Gas Energy )/Total Energy Available in Fuel
And indirect method, where η c =100- (sum of combustion losses %). The later method is
more widely used in practice.
Energy consumption is an important factor to consider when designing and operating a processing plant. It is calculated by taking into account the efficiency of the process, and is expressed as fuel energy, mechanical work, and specific gas consumption. Combustion efficiency is a measure of the ability of a fired system to convert fuel into useful heat, and is calculated using either a direct or an indirect method. Combustion losses arise from three categories, and must be taken into account when calculating combustion efficiency.
Introduction to Flue Gas Calculation
Flue gas calculation is a method used to determine the amount of excess air and flue gas losses in combustion systems. It is an important tool used in assessing the combustion efficiency of different types of fuels. In this article, we will discuss the basics of flue gas calculation, the first law of thermodynamics, and principles of PV work and enthalpy.
Excess Air and Flue Gas Losses
Excess air and flue gas losses can be calculated using measurements of oxygen and carbon dioxide levels in the exhaust gas, as well as the flue gas temperature. Charts can be used to obtain the excess air and flue gas losses if the oxygen or carbon dioxide levels and the temperature of the flue gas are known. Different fuels will have their own unique charts.
The charts used for flue gas calculation are usually based on an ambient temperature of 20°C. If the ambient temperature is different from 20°C, a correction for the flue gas temperature must be made. The corrected flue gas temperature is calculated by subtracting the difference between the ambient temperature and 20°C from the flue gas temperature.
The combustion efficiency ηc can then be calculated using the % flue gas losses. The combustion efficiency is equal to 100 minus the % flue gas losses.
If Ta is different from 20°C, correction for the flue gas temperature Tfg, should be introduced, accordingly: Tfg, corrected= Tfg- [Ta-20]
The First Law of Thermodynamics
The first law of thermodynamics is the law of conservation of energy. This law states that the net increase in the energy content of a system over a given period is equal to the energy content of materials leaving the system, plus the work done on the system, plus heat added to the system.
Systems can be either closed or open. A closed system does not allow mass to cross the boundary of the system, such as in piston engines. An open system, on the other hand, allows mass as well as energy to cross the boundary. Examples of open systems include turbines, boilers, and pumps.
PV Work and Enthalpy
PV work, also known as flow work, is work done when a system undergoes a change in volume. Enthalpy is the sum of internal energy and flow work. It is the total energy a system contains, and is used to evaluate the changes in a system.
What Is Specific Heat?
Specific heat is a measure of the amount of energy needed to raise or lower the temperature of a material by one degree. It is an important property of materials, as it is used to calculate the amount of energy required to heat up an object or the amount of energy released when it cools down. Specific heat is measured in units of energy per unit mass (J/kg) or energy per unit volume (J/m3).
ΔH= m Cp (To-Tin)
Where; m: is the mass flowrate and Cp is specific heat under constant pressure.
The Second Law of Thermodynamics
The first law of thermodynamics states that energy cannot be created or destroyed, but the second law of thermodynamics helps to explain the limitations of this law. The second law of thermodynamics states that it is impossible to convert all the available energy into a desired form of work, meaning that a portion of the energy must be rejected to a lower temperature level. This rejected energy is at a minimum if all the processes are reversible.
The second law of thermodynamics also highlights the concept of irreversibility, which states that heat cannot be transferred from a low temperature source to a higher temperature level without an input of work. Other sources of irreversibility, such as surface and internal friction, also contribute to the concept of irreversibility.