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Waste gasification plant

Lahti Energia Oy, Lahti (Finland)

Innovative technology saves fossil fuels

Lahti Energia is a versatile energy company which produces energy and offers energy products. The company´s transfer grid covers the areas of Lahti and neighboring communities. Lahti Energia´s main products are electricity and district heat. More information: www.lahtienergia.fi.

Metso is supplying a waste gasification plant to Lahti Energia Oy to Lahti, Finland. Metso’s supply includes waste gasification process, gas boiler and flue gas cleaning system with auxiliary systems and automation system for the whole power plant. The gasification plant represents new type of technology that enables Lahti Energia to convert recycled waste into energy at high efficiency and reduce use of fossil fuels in the city of Lahti significantly.

SSBG and SSB-LCG: maximum firing capacity even under unfavorable conditions

SAACKE's scope for the Lahti gasification project is four pieces of the burner combination SSBG 200 – LCG 1500 for low calorific gas and natural gas with natural gas armatures and cooling air fans. Both gasification gas lines have two burners, each capacity 40 MW. Heat value of the gasification gas is 4,6-5,8 MJ/Nm3 and maximum gasification gas flow per burner 25.000 Nm3/h, so depending on the quality of the fuel (waste) maximum firing capacity is in worst case at least 32 MW. After commissioning of the plant excellent emission values were determined, which fall below nonforfeiture values by factor 3 and thus make an extremely resource-saving and environment-friendly combustion possible.

The benefit for the customer

Waste gasification is a new, innovative technology to utilize recycled waste in energy production in an efficient and environmentally friendly way. “Our power plant project is internationally important. We will build a totally new kind of environmentally friendly technology. Our new plant will increase the total efficiency of the available energy production in the Lahti city area and also ensure sufficiency of electricity and especially heat for increasing needs in this area”, says Mr. Janne Savelainen, Managing Director of Lahti Energia.

Delivery of the burners took place at the end of February, 2011 and the erection should start immediately when the burners arrived to Lahti. At that time of year weather conditions could be quite hard in Finland, like in this year we have had really cold winter and temperature has been under zero (between – 20 and - 30 º C) in Lahti several weeks. This low temperature has to be considered also for the pre-drying of the refractory linings of the LCG chambers before delivery.

Commissioning of the plant will be in autumn 2011 and start of the commercial operation of the plant is scheduled for Q1/2012. 

The process in detail

There will be two gasification lines in the new power plant, and together they will produce 50 MW electricity and 90 MW district heat. The yearly consumption of waste for the gasification plant is approximately 215 000 ton/a in the design point and maximum about 250 000 tonnes. Waste is a mixture of RDF (Refuse Derived Fuel) from households, shops and industries and REF (Recycled Fuel).

Waste is turned into combustible gas in the gasifier in a small over pressure condition and about 900 º C temperature, downstream from the gasifier gas is cooled down to 400-450 º C and cleaned and then combusted in a high-efficiency gas boiler to produce steam for a steam turbine.

Due to the emission requirements for the waste incineration plant NOx emissions was one of the key points in this project and to reach the vales also with this kind of gasification gas with quite a high NH3 content (0,21 vol.%) burners were designed with the additional air staging.

Source: Press release of Metso, press release of Lahti Energia