Södra Näs Vimmerby Energi AB Biomass District Heating Plant, Sweden

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1 Södra Näs Vimmerby Energi AB Biomass District Heating Plant, Sweden Vimmerby Energi AB, a energy company owned by the municipality of Vimmerby. The company Vimmerby Energi AB is serving the municipality of Vimmerby with energy. Vimmerby is a municipality in the south of Sweden. Vimmerby was founded as town about 700 years ago. The number of inhabitants of Vimmerby is about About of the inhabitants are living in the village of Vimmerby. The author Astrid Lindgren is born in Vimmerby. The company Vimmerby Energi AB was founded about 90 years ago. The number of customers has been increasing from 500 year 1998 to 1100 year About 90 % of 1900 flats and about 40 % of detached houses in Vimmerby is connected to the district heating grid. Vimmerby Energi AB owns one production plant named Södra Näs. The company owns three biomass-fired boiler. Two of the boilers were built in 1984 and one in The boilers built in 1984 have a effect of 5 MW each and the new boiler have an effect of 8 MW and 2 MW from a flue gas condenser. In the new boiler is bark and wood-chip used as fuel and in the two old boilers is biomass- briquettes used as fuel. In the plant is also gas from the sewage treatment works used as fuel. The gas plant was taken in operation in For flue gas cleaning to increase the efficiency are the new boiler 1

2 built in 1999 equipped with flue gas condensation. When using the common methods used for calculation of efficiency is the efficiency more than 100 %. There are also four oil-fired boiler effect of 3,5 MW each. The number of employees in the company Vimmerby Energi AB is around 18. For the normal operation of the boiler there are two employees daytime and five to be on duty during other time. Project background The number of connected buildings to the district heating net was increasing and the existing boilers were a limitation for a continued expansion of the district heating net of Vimmerby. The aim of the project was to expand the district heating system and decrease the use of fossil fuel in Vimmerby. The investment in district heating including boilers is made as environmental investment. When the decision was made for the new boiler was one important issue that the fuel should be produced in a circle with in a radius less than 18 km from Vimmerby. The intention was that local suppliers should deliver fuel to the plant. The boiler was opened in January Project description One important issue when the project with the new boiler started was to buy fuel close to Vimmerby. The goal was that the fuel should produced with in a radius of 18 km around Vimmerby. Today the market for biomass is global and biomass are imported to Sweden from other countries. A production of fuel in the neighbourhood of the plant generates social effects such as jobs. In 1999 was the decision made that a new boiler should be built. In spring year 2000 started for heat distribution. The boiler was ordered by Järnforsen a smaller Swedish boiler manufacturer. The main innovation Vimmerby Energi AB built a best practice small-scale biomass-fired boiler for district heating, for year A best practice plant in this case is a plant highly automated with flue-gas condensation. The plant is highly automated to decrease the personnel and equipped with flue gas condensation to give a high efficiency. The plant is not the only of its kind. There are other plants with almost the same data. Plant description The plant is built close to the municipality of Vimmerby. The plant is a district heating plant. There are seven boilers. The boilers are four oilfired boilers, two briquette-fired boilers and on wood ship fired boiler. The newest boiler is a biomass-fired boiler built in 1999 and taken in operation January The new boiler have grate and are equipped with a flue gas condensing. 2

3 Technical details The main fuel in the plant is bark and saw dust. The fuel I delivered by lorries and am dumped in a bin in house. The fuel is transported from the delivery bin to a second bin with a scoop. From the bin is the fuel transported with a scrap conveyer and a conveyer and finally into the furnace with a screw conveyer. The total capacity for the two bins is 3000 m 3, corresponding to four days of operation. The old briquette fired boilers have one bin with scrap conveyers in the bottom. The bin is limited due to the limited usage of briquettes. The plant in Vimmerby contains three boilers fuelled with biomass. The largest boiler is a grate boiler with a output of 8 MW th from the boiler. The outlet temperature from the boiler is 200 o C. After the boiler there are a flue gas condenser. In the condenser is the flue gas temperature decreased to 45 o C. The output from the flue gas condenser is 2 MW th. The operation time, for plant, is 8760 hours a year. When the temperature is above +5 o C is the new boiler is sufficient. With a temperature less than +5 o C must the old briquette fired boilers from 1984 be started. The gas from the sewage treatment works is fired all the year. Thermal power output boiler (MW) 8 Efficiency according to DIN (%) Thermal power output flue gas 2 condenser (MW) Efficiency including heat from flue 110 gas condenser. (%) Combustion equipment Grate Construction pressure (bar) 16 Fuel Bark and wood chip Table 1. Boiler data for the new boiler. Number of persons Total number of employees 18 Personnel for boiler plant 2 Personnel on duty on not office time, 5 in five shifts. Table 2. Number of employees at Vimmerby energy. Annual operating time for plant (h) 8760 Annual operating time for new 6000 boiler (h) Annual operating time for old boilers (h) Annual operating time for gas (h) 3

4 Table 3. Annual operating time for plant and different parts D3b case 2 Fuel storage type Bin Fuel storage size (m 3 ) 3000 Transport equipment for transport of Scoop fuel from fuel inlet. Other transport equipment Scrap, belt and screw conveyers and Table 4. Annual operating time for plant and different parts Picture 1. Interior from boiler house. Energy data The plant is only producing heat for the municipality of Vimmerby. Annual heat production is shown in Table 5 and 6 below. Fuels/Raw material The plant has tree biomass boilers. In the boilers are four different fuels used. The fuels are gas from sewage treatment works, briquettes and not treated biomass such as bark sawdust and wood chips. In the new boiler are bark, wood chips and sawdust used as fuel. Fuel is delivered from the sawmills in the neighbour of Vimmerby. Moisture content in fuel should be 50 %. If the moisture content is less than 50 % water has to be added to the fuel. The lower heating value at 50 % moisture content is approximately kj/kg. Fuel Amount (MWh) Proportion (%) Gas 590 0,8 Bark, wood chip Briquettes Oil Table 5. Fuel usage in the Vimmerby district heating plant. Fuel Amount (MWh) Proportion (%) Gas - - Bark,

5 wood chip Briquettes - - Oil - - Table 6. Fuel usage in new boiler in Vimmerby district heating plant. D3b case 2 Picture 2. Fuel receiving and storage for the new boiler. Picture 3. Fuel receiving and storage for the old briquette fired boilers. The fuel is delivered from different suppliers in the area around Vimmerby. Fuel suppliers to the plant are saw mills, small briquette manufacturer and wood industries. The company have been successful in the aim to decrease the use of fossil fuel. There is only usage 2.2 % of fossil fuel in the plant. There is only one district heating company in Sweden having a higher proportion of biomass in the fuel mix. The average transport distance for the fuel is 37.2 km. During the winter in ordinary days are three to four lorry s delivering fuel to the plant The fuel demand is approximately 300 m 3 a day during the winter season. The fuel is mainly delivered by six companies. Five of the companies are saw mills and three of the sawmills are independent, not belonging to the big forest companies of Sweden. One company is delivering briquettes. The company delivering the briquettes are a small company located close to Vimmerby with four employees named Dalsjö Energi AB. 5

6 Economical data The investment in 1999 was thousand Swedish kronor or approx thousand Euro. The investment include boiler with all equipment for biomass firing and gas production equipment. Environmental impact By firing biomass the CO 2 emissions can be reduced. The concept with gas, biomass and flue gas condensing applies improved efficiency and reduction of SO x. The estimated reduction of SOx compared to before introduction of biomass is 50 tonnes annual. The plant has replaced oil-fired boilers in each building. The plant is estimated to have replaced 7000 tonnes of oil annually. This corresponds to a decrease of tonnes of CO 2 emissions annually. The emissions from the new boiler, delivered in 1999, were as follows in year Emission Amount year 2002 (kg/year) NO x CO Dust Table 7. Annual emissions from the new boiler in Vimmerby. Emission discharge CO 100 mg/mj NO x 90 mg/mj Dust 25 mg/mj Table 8. Emission discharge. Owner of the plant Vimmerby Energi AB is the owner of the plant. The municipality of Vimmerby owns the company. The company owns one plant, named Södra Näs, for production of district heating. Users All energy produced in the plant is delivered to the district-heating grid of Vimmerby. In the village of Vimmerby is about 90 % of 1900 flats and about 40 % of detached houses connected to the district heating grid. The potential for the future is to connect more of the detached houses in the central village of Vimmerby. 6

7 Picture 4. Process scheme. Main manufacturers and service suppliers Supplier Järnforsen Energi System AB Stenvinkelsgatan 3C S Halmstad Sweden Phone: +46 (0) Table of the main data Boiler (or rector) Steam values (if steam boiler) Heat output (process of district heat) Electricity output Annual biomass fuel utilisation Annual heat production Annual electricity production Total investment of the plant Investment aids Other important data (please specify) Type grate, 9.5 MW th Temperature ( o C), pressure (bar), steam (t/h) 8MW th + 2 MW th flue gas condensation 0 MW e 68 GWh 70 GWh 0 GWh kronor and EUR None. 7

8 Additional information Roger Carlsson Managing Director Mats-Lennart Karlsson Plant manager Vimmerby Energi AB S Vimmerby Tel. +46 (0) Produced by OPET Sweden, WSP 1/2004 Rolf Ingman Links to pages of Vimmerby Energi AB and owners: Produced by OPET Sweden, Rolf Ingman. 8