Technical Paper Title: WASTE HEAT RECOVERY POWER PLANT
Authors: SK.ANWAR BASHA, 3rd BTech, EEE
College: Prakasam Engineering College, Kandukur
A large quantity of Flue gases at high temperatures is produced by different parts of the heavy industries. They are purified internally by purifying equipment like Electrostatic Precipitators and are left into atmosphere. At the present condition the heat energy of flue gases is wasted. If we are able to trap the heat and thereby using the heat to produce steam, an efficient electric power generation can be achieved.
As the heavy industries are located independently and in many cases, neither steam nor hot water is needed in their own plants. The recovery in electric power is most effective method. On the other hand, the main advantages offered by the Waste Heat Recovery Power Plant can be listed as follows:
1) Clean power generation
2) No production of green house gases (ex: CO2)
3) No air polluting gases (NOx, SOx).
4) Reduces 10-12% of Global wAarming effect.
The recovery plants can be constructed on the same basis of the thermal power plant with the only difference that flue gases for the production of heat in boilers replace the burning of coal. This difference makes the recovery plant most efficient and clean over conventional plant for same power rating.
Hence this project can be treated as the efficient method of utilization of waste gases for the production of electrical energy and one can hope that the “Waste Heat Recovery “ will play an even great role in the industrial development of 21st century.
WASTE HEAT RECOVERY POWER PLANT
Waste heat recovery is the process of capturing waste heat (thermal) energy for beneficial purposes. Recaptured heat energy is potentially useful for generating electricity. Space heating, water supply and green houses. Heat recovery is a complex system, which requires many parameters to be considered. The exit temperature of the waste heat as well and the application of the regenerated waste heat is key factors in heat recovery systems. There are three temperature ranges of heat recovery. In small, waste heat in industries is recovered from liquids or gases at low temperatures (below 450o F [232oC]). In larger industries, medium temperature recoverable heat (between450o F and 1200o F [232o C–649o C]) may be available for waste heat recovery. High temperature recoverable heat (above 1200o F [649o C]) is usually available only in heat-intensive industries i.e.,
Heavy Industries Generating Waste Heat
• Power and Utility Industries
• Heavy Industries: Steel, Aluminum, Copper, Cement, Pulp & Paper, Glass,
Soda Ash and Waste Recycle
• Refinery, Petrochemical and Gasification plants
• Chlor-Alkali & Vinyl plants
• Incinerators, Waste to Energy
Typical Waste Heat Sources
• Fired boilers, gasifiers, heaters/furnaces (gas, diesel, coal, nuclear, refuse, pet
• Gas turbine exhaust – continuous, standby, peaking, combined cycle units
• Steam turbine exhaust: and vented steam
• Internal Combustion (IC) engine exhaust
The total heat generated in these industries is not utilizing full fledged but 45% is discharged through the exit gases from the preheater and through chimney and the gases which are releasing in to atmosphere through this waste heat are
- NOx & Sox
- Vaporized heavy metals etc..,
And these gases are causing dangerous health problems to people who are leaving surroundings to these industries and indirectly it is forming 10-12% of global warming effect.
If we are able to trap the heat and thereby using the heat to produce steam, an efficient electric power generation can be achieved by this waste heat
The recovery in electric power is most effective method. On the other hand, the main advantages offered by the Waste Heat recovery power plant can be listed as follows:
- Clean power generation
- No production of green house gases (ex: CO2)
- No air polluting gases (NOx, SOx) etc…
The waste heat recovery plants can be constructed on the same basis of the thermal power plant with the only difference that flue gases for the production of heat in boilers replace the burning of coal. This difference makes the recovery plant most efficient and clean over conventional plant for same power rating.
We can place Waste Heat Recovery plant in many heavy industries (Steel, Aluminum, Copper, Cement, Pulp & Paper, Glass, Soda Ash etc..)which are producing huge amount of waste heat.
Suppose if we place “Waste Heat Recovery Power Plant” in Cement industry the layout diagram will be like this.
In Cement plants, about 90% of total energy is used as heat energy in clinker burning process. Out of total heat consumed in the burning process, around 55% of the heat is utilized for clinker burning and rest 45% is discharged as sensible heat through the exit gases from the preheater (PH), Air Quenching Chamber (AQC), as radiation losses and sensible heat carried out by the clinker. Around 8% of heat from the exit gases of preheater and AQC is used effectively for drying the raw materials and coal. The rest 37% is often emitted to the atmosphere without utilization
In Cement industries large portion of the energy consumption for the production of cement occurs in the calcinations process in clinker production. This involves passing the ground raw materials through a pre-heater stack containing cyclone heaters to a long rotating kiln to create clinker and then cooling this in the clinker cooler. Waste heat is typically mainly vented to atmosphere and if captured and used for power generation, as proposed in this Project Activity, can lead to significant greenhouse gas emission reductions.
The layout diagram will be like this:
The production process of this project is an energy conversion process. Feed water recovers the heat energy of low-temperature waste heat exhausted by clinker production line through PH heat recovery boiler and AQC heat recovery boiler, to convert it into superheated steam, and then steam is fed into steam turbine through the steam pipe. The heat energy is converted into kinetic energy in steam turbine to enable turbine rotor to rotate at high speed, and then drive the generator to rotate, and final product – electric energy is generated.
Coming in to operation of W H R in cement industries, the calcinations process of clinker wastes a lot of energy. The amount of the heat contains in the low temperature (lower than 400 °C) waste gas, which is vented by the PH- Boiler and Air Quenching Chamber (AQC), is more than 37 percent of the total amount of the heat consumed in the calcinations process of clinker. The proposed project activity adopts waste-heat recovery technology to utilize waste heat from PH and AQC for power generation
In the project activity, the project entity has equipped a WHR system for the cement clinker production line. The WHR system in the project activity consists of one set of PH boiler, one set of AQC boiler, one steam turbine generator, and water circulation system and dust-removal system etc. The AQC boiler has been installed between the exhaust exit at the middle of the kiln entry clinker and the exhaust electric precipitator at kiln front. The first section of the AQC boiler produces overheated steam and the second section produces hot
water. The PH boiler has been installed between the exhaust exit of the kiln rear pre-heater and the kiln rear high-temperature fan. Steam turbine generator has equipped for the two boilers. The waste heat from PH and AQC will be fed to PH boiler and AQC boiler to generate steam. The steam from SP boiler and AQC boiler will be united and fed to steam turbine generator for power generation.
Expected Power Generation:
- 30% of the plant power consumption is met by the internal generation
through waste heat recovery…
- 40% of the waste heat is recovered…
- Reducing the carbon dioxide emission into atmosphere by about 45,000 tons per year…
- 30% off power is saved for producing ton cement
- Economical for 1 MW to 25 MW Power Plants.
v Electrical Power generation potential from Waste Heat Recovery power plant is below
v Cost comparison of Waste Heat Recovery Power Plant with other sources of Power Plants:
v Cost comparison of Waste Heat Recovery Power Plant with Renewable Energy Recourses
Advantages of Waste Heat Recovery Power Plant (REUSABLE ENERGY):
- Each MW of Power Generation (compared to coal fired plant) Eliminates :
- Each MW of Power Generation (compared to coal fired plant) Eliminates :
21 Tons NOx
59 Tons Sox
8615 Tons of CO2
• Power Generated with Zero Emissions
• Renewable Energy Credits
• Integrated Multi-Pollutant Reduction System
• Zero Emission Power Plants
• Efficient Power from Flue Gas, Steam, Hot Water/Fluids
• Saves Valuable Water Resources
• High Internal Rates of Return
• Supports Distributed Generation
• Solar, Biomass & Geothermal Standalone Power Plants
• Combined Cycle Diesel Engine Power Plants
• Provides Emission Credits
By all this Advantages,
WHY NOT CLASSIFY “REUSABLE ENERGY” AS “RENEWABLE ENERGY”?
Heat recovery technology is an excellent tool to conserve energy. The Waste Heat Recovery brings in related economic benefits for the local community and would lead to sustainable economy and industrial growth in the region. The W H R activity would be able to replace electricity generated by grid-connected power plant thus saving further exploitation and depletion of natural resources – coal, or else increasing its availability to other important process.
The electricity generated from the W H R would help to reduce carbon dioxide emission and other associated pollution at thermal power plats
By placing Waste Heat Recovery power plants in heavy industries which are generating huge amount of waste heat, we can reduce 10-12% of Global Warming effect. This will help full for Nation too…
This project can be treated as the efficient method of utilization of waste gases for the production of electrical energy and one can hope that the “Waste Heat Recovery “will play an even great role in the industrial development of 21st century.