Efficient power generation in a sustainable way - a complete boiler plant to ArcelorMittal Energy Ostrava s.r.o., the Czech Republic
Photo: On May 20, ArcelorMittal Energy Ostrava (AMEO) organized a press conference in Ostrava, Czech Republic, where the company announced a boiler plant order from Valmet for the largest steel mill in the country.
Valmet delivers a complete boiler plant to ArcelorMittal Energy Ostrava s.r.o. in the Czech Republic. The new boiler plant will supply steam to existing turbines, which produce electricity and provide process steam to the adjoining ArcelorMittal steel mill. Boiler start-up is scheduled for the mid 2016. The boiler is designed for an energy-intensive industry sector, where cost-efficient energy is essential in order to ensure competitiveness in the global market. The value of the order is approximately MEUR 50.
The need for sustainable power generation with a wide range of coal qualities and operation in accordance with future EU emission limits is taken into account in the boiler design. Simultaneously the mills boiler efficiency will be improved, while maintaining high availability.
Circulating fluidized bed technology
Valmet’s delivery will include an advanced circulating fluidized bed (CFB) boiler plant that features a coal-fired CYMIC boiler, flue gas cleaning, electrical equipment and an automation system. The boiler plant will have a steam production of 320 tons per hour, which corresponds to a thermal capacity of 248 MW. The new unit will replace four old pulverized coal fired boilers.
Efficient emissions control
SO2 emissions are controlled through limestone injection into the furnace. Limestone reacts with SO2, forming solid calcium sulphate that is collected in a baghouse filter. This procedure enables to remove more than 80% of sulphur and to fulfil the EU emission limit of 200mg/Nm3.
The amount of NOx emissions is reduced by means of the Selective Non-Catalytic Reduction (SNCR) system. NO reacts with ammonia that is injected into the cyclone inlet. As a result of this, nitrogen and water vapor are formed. Through this, the EU emission limit of 150 g/Nm3 is fulfilled.
Dust generated in the combustion process is collected in a baghouse filter, the dust removal efficiency of which is over 99.9%. The equipment that enables to fulfil the EU emission limit of 10 mg/Nm3 is designed by Valmet.
High efficiency ratio
The thermal efficiency of the boiler is over 92% with coal, even when the ash content of the coal is high - up to 26%. High efficiency is a result of a high-separation-grade cyclone, which enables to minimize the amount of un-combusted fuel transmitted to the filter. The high efficiency cyclone also enables to minimize limestone consumption.
Heat contained in the bed ash is recovered and utilized in the boiler furnace. This is done by means of special bed ash coolers, in which the ash is cooled by combustion air.
Compact design, high availability
There will be an intermediate hopper installed in the secondary pass (patent pending). This special feature helps to prevent ash collected on the surface of the superheaters from being transmitted onto the denser packages located below and blocking them. Thanks to the intermediate hopper, the boiler design is very compact, and can be implemented without a need to enlarge the boiler building.
High boiler availability is achieved by means of an entirely water-cooled cyclone and loop seal. No heavy refractory or expansion joints are needed.
A heavy-league steel producer
ArcelorMittal Ostrava a.s. is the largest steel producer in the Czech Republic and part of the world’s largest steel and mining group ArcelorMittal. It has an annual production capacity of three million tons of steel, such as hot metal and steel, rolled products. It also produces coke and coke-chemical products. Besides the Czech market, the company sells its products to more than 40 countries around the world. ArcelorMittal Ostrava and its subsidiaries employ more than 7,500 people.
CYMIC is an advanced circulating fluidized bed (CFB) boiler developed by Valmet. It combines high-efficiency combustion of various solid fuels with low emissions, even when burning fuels with completely different calorific values at the same time.
The wide size range of CYMIC covers boilers from 50 to 1200 MW of thermal capacity.
The main advantage of the CYMIC boiler is its superb fuel flexibility. Most of the over 80 references around the world are multifuel boilers that combust biomasses and fossil fuels in continuously varying proportions. Co-combustion is an environmentally benign method of combining excellent reliability and availability with a great potential to optimize operational costs by allowing several fuel alternatives.
In addition to coals and other solid fossil fuels, CYMIC boilers offer ideal combustion technology for recovered fuels, biomasses including fuels derived from agricultural waste streams, and any combination of these fuels.
With CFB technology, the circulating bed material flows together with flue gas through the furnace, after which it is separated from the gas and returned back to the lower part of the furnace with cyclones. This technology provides an even combustion temperature profile, which is optimal for handling a wide variety of fuel properties, for which substantial variation of heating value, moisture, ash content and quality of ash components is typical. The technology also ensures low primary emissions with high combustion efficiency and an excellent utilization of limestone for sulphur removal.