Innovative energy conservation technology at coal-fired power plants
Published on 21 December 2020
Romania
Sud-Vest Oltenia
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About this good practice
CET Govora is a cogeneration power plant - CHPP that uses, as a basic energy resource, the lowest grade coal, lignite - from the coal basin of Oltenia. Thermal energy is produced as industrial steam and primary thermal flow for district heating.
The slag is a coarse solid waste resulted from the process of burning lignite on the post-combustion grills located below the coal boiler hearths.
Normally, the slag is first crushed and hydraulically driven through water channels to the solid combustion by-products evacuation system and to the landfill.
The slag contains combustible materials due to incomplete combustion from a mechanical and chemical point of view, unburned which represents on average approx. 3% of the amount of lignite that feeds the boiler hearth. The unburned carbon particles are concentrated in the molten slag discharged below the boiler’s hearth into a special tank, where it is cooled in the water flow and continuously discharged with the help of inclined scraper strips.
The proposed process for the energy recovery of unburned slag, by creating a recirculation flow in the main fuel supply stream, is carried out with minimal transport and investment costs, applicable to all lignite coal boilers, but some technological constraints must be considered.
In homogeneous mixture with biomass and coal, when the slag is introduced controlled in a continuous regime in the boiler’s hearth, the fuel mass from the slag burn in suspension.
The slag is a coarse solid waste resulted from the process of burning lignite on the post-combustion grills located below the coal boiler hearths.
Normally, the slag is first crushed and hydraulically driven through water channels to the solid combustion by-products evacuation system and to the landfill.
The slag contains combustible materials due to incomplete combustion from a mechanical and chemical point of view, unburned which represents on average approx. 3% of the amount of lignite that feeds the boiler hearth. The unburned carbon particles are concentrated in the molten slag discharged below the boiler’s hearth into a special tank, where it is cooled in the water flow and continuously discharged with the help of inclined scraper strips.
The proposed process for the energy recovery of unburned slag, by creating a recirculation flow in the main fuel supply stream, is carried out with minimal transport and investment costs, applicable to all lignite coal boilers, but some technological constraints must be considered.
In homogeneous mixture with biomass and coal, when the slag is introduced controlled in a continuous regime in the boiler’s hearth, the fuel mass from the slag burn in suspension.
Resources needed
The total project budget was 1,634,234 €, of which 61.8% represented the co-financing of Govora CHPP. From the state budget, through the INNOVATION program, the project benefited from a grant of 624,277.5 € (38.2% of the total value of the investment).
At this project worked approx. 100 specialists
At this project worked approx. 100 specialists
Evidence of success
The amount of slag recovered at each boiler was on average 5 tons of slag / h / boiler and in the third year of operation amounted to a quantity of 36,140 tons of slag, of which the amount of 30,047 t of slag was recirculated to boilers.The primary energy from recovered and recycled slag controlled in the third year was 35,115 Gcal / year, representing a quantity of 23,244 t of lignite saved.As a result, a reduction in carbon dioxide emissions of approx. 2.1 thousand t CO2 was obtained.
Potential for learning or transfer
The proposed process, carried out with minimal handling and investment costs, can be applied to all lower grade coal-fired boilers in the country, but certain technological restrictions must be taken into account:
- if the discharged slag is soaked with water in the cooling process - the excess soaking water must be drained so that it is not reintroduced into the boiler’s hearth;
- the fuel mass content of the slag is variable depending on the quality of the burned coal, the efficiency of the coal grinding process and the loading regime of the boiler;
- the slag has a combustible material content, but does not contain volatiles which contribute to ignition, so that the dosage must not exceed 10% slag in lignite.
- if the discharged slag is soaked with water in the cooling process - the excess soaking water must be drained so that it is not reintroduced into the boiler’s hearth;
- the fuel mass content of the slag is variable depending on the quality of the burned coal, the efficiency of the coal grinding process and the loading regime of the boiler;
- the slag has a combustible material content, but does not contain volatiles which contribute to ignition, so that the dosage must not exceed 10% slag in lignite.
Further information
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Good practice owner
You can contact the good practice owner below for more detailed information.
Organisation
Regional Development Agency South West
Romania
Sud-Vest Oltenia