Hakkpuidu kasutamine Tallinna linna kaugküttesüsteemis

Kaugküte on tiheasustusega asulates mõistlik küttelahendus, kuna see on keskkonnasäästlik. Kaugkütte suurimad ohud Eestis on praegu tarbijate hulga langus asulates ja kallite kütuste kasutamine. Need ohud ei võimalda ehitada uusi efektiivsemaid torustikke või renoveerida vanu. Seepärast peab väga tõsiselt hindama investeeringuid kaugküttevõrku. Kaugküte sobib kohtadesse, kus on piisav tarbijate hulk ja võimalus investeerida. Tallinn on kaugkütte seisukohalt kõige suuremate võimalustega ja tarbijate vähesuse probleemi ei ole. Küll aga on tarbijad hinnatundlikud, seepärast peab otsima odavamaid küttemeetodeid. Praegu kasutatakse Tallinna linna kütteks enamasti maagaasi, kuid sel on mitmeid poliitilisi ja majanduslikke ohte ja nii ei saa maagaasile kui jätkusuutlikule kütuselahendusele lootma jääda. Teine, enamasti reservkütusena kasutatav, põlevkiviõli on kallis ja seda saab kasutada ka mitmetel teistel, kasulikel eesmärkidel, kui lihtsalt kütteks ära põletada. Hakkpuidu kasutuselevõtt on väga aktuaalne teema ja erinevad hinnangud näitavad, et kütuse reservi on. Arvestades karmistuvaid euronõudeid heitmetele, erinevaid riiklikke plaane ja tarbijate hinnasurvet on mõistlik Tallinna varustamiseks mõelda hakkpuidu katlamajade peale. Nüüd aga tuleb arvestada plaanitavate investeeringute pikaajalist tasuvust. Tallinnasse tahetakse ehitada katlamaju, mis lähevad seaduse mõistes suurte põletusseadmete termini alla. Lisaks peab renoveerima olemasolevaid rajatisi. Hakkpuidukatlamajad on keerulised ehitada ja nõuavad väga suurt alginvesteeringut. Tuleb otsustada, kas tarbimist on piisavalt, et nii suured investeeringud ära tasuksid. Soojustarbimise tipud on talvel, kuid kas suvel on koormust piisavalt, et katlamaju töös hoida. Hakkpuidu katlamaja tühjana seismas hoida ei ole mõistlik ning lisanduvad ka katelde sisse – välja lülitamise kulud. Suurtel katlamajadel ei ole kütuse kvaliteedile suuri nõudmisi, paigas peab olema kütuse niiskus ja tüki suurus Materjalis ei tohi olla rohelist massi, mineraalset ainet ega kivisid. Erinevad allikad näitavad, et selliste puidujäätmete, st energiapuidu reservi on. Kuna majanduslikud kaalutlused on osutunud tugevaks, on metsamaterjalile ka turgu ja sellist materjali kogutakse ning müüakse. Samas on Eestis väga palju looduskaitsealust metsa, kus selline puit jääb lihtsalt metsa vedelema. Väga suur reserv võib olla ka kändudel, kuid nende töötlemistehnoloogia on hakkpuidu tootmisest erinev ning peamiselt looduskaitselistel põhjustel ei ole kändude juurimine paljudes kohtades lubatud.

The work aims to address the possibilities of using woodchips for heat production in Tallinn and the advantages of using wood chips, especially environmental. Fossil fuel combustion plants are some of the major polluters of the environment and pollution charge payers. Several companies offer district heating in Tallinn. Amongst them, only Tallinn Power Plant uses woodchips. The first chapter introduces the condition of district heating system in system in Estonia and particularly in Tallinn, which is the biggest and developing area of district heating. The use of woodchips has been compared to another most common fuel in district heating system, natural gas statistically. The second chapter focuses on the Tallinna Küte, which is the largest operator of district heating system in Tallinn. The company has to modify its operating to be more environmentally sustainable and economically profitable. It has a number of plans including construction of new woodchips boiler and renovation of existing equipment. Woodchips have a number of advantages, for example combustion plant does not have to pay pollution charge for carbon dioxide emissions, the most important greenhouse gas. It is considered as carbon neutral fuel, the trees have already absorbed carbon dioxide during growth. The natural gas and woodchips boiler plant emissions have been shown in order to show how the use of woodchips will help to reduce emissions. Residual ash from combustion of woodchips has not been discussed, as regulations in Estonia classify ash as non-hazardous waste, which must be properly stored in a landfill. Tallinn Power Plant provides some of the ashes for stuffing material and for fertilizers. Also, the chapter deals with what the heat prices for consumers are consisting of and what kind of benefits the development of the use of woodchips will give to consumers. The third chapter gives an overview of one supplier who supplies Tallinn Power Plant with woodchips. It also gives an introduction to Estonias Timber. Overview of the Forestry Development plan and statistical data should provide sufficient image of whether there is a reserve of woodchips in Estonia and how price will change. Import and export of wood material that is used for heating is not considered. The review includes materials, which cannot be used in manufacturing including chopped and other wood waste, which are inexpensive. The work has been compiled on the basis of data from Tallinn district heating system companies that generate heat from woodchips or are planning to do so. In addition, text has taken into account Estonia District Heating Act and materials from Tallinn University of Technology and Estonian University of Life Sciences. District heating is a viable solution for cities and other densely populated areas. District heating creates preconditions for the wide use of domestic renewable fuels, including low-quality woodchips. The use of woodchips also helps to limit the use of imported fuels (especially natural gas), lowers the price of heat produced and reduces greenhouse gas emissions. Tallinn has good conditions for further developing the district heating system and unlike several Estonian rural settlements there is no problem of a decrease of customers. However, consumers are price sensitive, so it is wise to think about cheaper heating solutions. Given the stricter European standards for emissions, the various national plans and consumer price pressures, AS Tallinna Küte has found that it is cheaper to cover the base load of Tallinn with woodchips boiler plant. The companys natural gas boiler plants remain in reserve. There are two major projects in work in Tallinn. AS Tallinna Küte wants to build one 100 MW wood chip boiler in its boiler plant at Mustamäe. Ltd. Auragen 76,5 MW boiler plant is expected to start in 2015. Boiler plants in Tallinn are under the term of large combustion plants, so they have to consider a variety of European and national legislative acts. In addition to a new woodchip boiler, AS Tallinna Küte has to renovate existing facilities. Wood-based fuel combustion technologies are well developed, but large woodchips boiler plants are difficult to build and require a large initial investment. Large woodchips boiler plant must operate continuously and at a constant power level, so that the efficiency of the plant would be very high. Woodchip boiler plant standing empty is not rational, and in addition there will be boiler switching off and on costs. Chips used in boiler plants have to be uniform in size with suitable moisture content of the material. There may not be green mass, mineral matter, or stones. Various sources indicate that there is a reserve of such wood waste that could be used in district heating plants. Since the use of woodchips has proven to be commercially profitable, the wood waste is being collected, prepared and sold as fuel. Estonia has a great number of forest conservation grounds where this kind of timber is just lying around in forest. The reserve can also be stumps, but their processing is different from regular wood and mainly because of forest conservation reasons uprooting the stumps is not allowed in some forests in Estonia.