W pracy przedstawiono dotychczasowe konwencje i dyrektywy, w których poruszano problematykę emisji rtęci do atmosfery ze spalania paliw stałych w elektrowniach. Wszystkie dotychczasowe regulacje obowiązujące na terenie Unii Europejskiej (UE) nie zawierały dopuszczalnych poziomów emisji rtęci do atmosfery. Nowe regulacje BAT przyjęte w ubiegłym roku, które mają zacząć obowiązywać od roku 2021, zawierają już dopuszczalne poziomy emisji rtęci, a także zmuszają elektrownie do przeprowadzania regularnych pomiarów emisji rtęci (dla bloków o mocy poniżej 300 MWth), lub też do ciągłego monitoringu emisji rtęci (bloki o mocy powyżej 300 MWth). Dla pokazania, jaki wpływ będą miały tak ustalone dopuszczalne poziomy, emisji przedstawiono obliczone poziomy emisji z dziesięciu polskich elektrowni opalanych węglem kamiennym. Spośród tych elektrowni osiem to bloki o mocy poniżej 300 MWth, a dwa o mocy powyżej 300 MWth. W żadnym przypadku nie stwierdzono przekroczenia obowiązujących w przyszłości norm emisji rtęci. W przypadku elektrowni o mocy powyżej 300 MWth, które są nowoczesnymi elektrowniami oddanymi do eksploatacji w XXI wieku, emisja rtęci była znacząco niższa, niż w przypadku elektrowni o mocy poniżej 300 MWth, które w większości to wyeksploatowane jednostki z lat siedemdziesiątych i osiemdziesiątych. Pokazuje to, jak ważna jest budowa nowoczesnych jednostek o dużej mocy, które to są w stanie spełnić wymagania stawiane nawet nowym obiektom. Oznaczać może to również brak konieczności inwestycji w specjalne metody usuwanie rtęci, a konieczność tylko optymalizacji istniejących urządzeń do oczyszczania gazów.
Work is being carried out on possibilities of limiting the content of mercury in hard coal products by gravity concentration of run-of-mine coal in the Branch of the Institute of Mechanized Construction and Rock Mining in Katowice and on the Faculty of Energy and Fuels of the AGH University of Science and Technology in Krakow. Under domestic industrial conditions, gravity concentration is carried out with heavy medium liquids and in jigs. Preliminary - pilot studies have shown the possibility of mercury removal also by using the dry deshaling method involving vibratory air separators. Mercury is mainly found in the pyrite and the rubble formed by the mineral carbon, but also in the organic carbon. Some of it is located in layers of coal roof fields, which in the course of their exploitation go to coal. The mercury removal efficiency during the gravity concentration process will depend on the decomposition of the listed components in the density fractions. The paper presents the results of investigations of total mercury and total sulphur content in the separated coal fractions from four mines. These contents were determined in fractions: –1.5 g/cm3 (conventionally clean coal – concentrate), 1.5–1.8 g/cm3 (conventionally middlings) and +1.8 g/cm3 (conventionally rock – waste). The results are summarized in Tables 3–5 and in Charts 1–4. Conversely, graphs 5-8 show the relationship between mercury content and total sulphur content in the tested coal samples. The study, which can be called a preliminary analysis of the susceptibility of the coals to gravity concentration, showed that the dry deshaling method on the vibratory air separators would allow significant amounts of mercury accumulated in the middlings and waste fractions to be removed.
Obowiązująca dyrektywa IED, a co za tym idzie bardzo rygorystyczne wymagania względem rtęci (Hg) stawiane przez BAT/BREF, zmuszają polską energetykę do poszukiwania nowych wydajnych technologii oczyszczania spalin z gazowych jej form. Obecnie żadne z metod pierwotnych ani wtórych usuwania związków Hg w kraju nie jest w stanie sprostać tym restrykcjom. Wymagań tych nie spełniają nawet powszechnie stosowane metody z wykorzystaniem węgla aktywnego modyfikowanego bromem lub jodem czy też nowoczesne metody stosowane w innych krajach wykorzystujące moduły polimerowe. Związane jest to z dużym zanieczyszczeniem rtęcią paliw kopalnych stosowanych w krajowej energetyce. Dlatego też w ramach projektu pt. „Hybrydowe układy adsorpcyjne do redukcji emisji rtęci z zastosowaniem wysokoefektywnych komponentów polimerowych”, akronim HYBREM, podjęte zostały próby zbudowania innowacyjnej linii technologicznej łączącej kilka technik oczyszczania spalin ze szkodliwych związków rtęci. Do budowy instalacji pilotażowej wykorzystano technologie bazujące na modułach polimerowych oraz iniekcji różnych sorbentów stałych. Zaletą budowanej instalacji będzie jej mobilność, przez co może być testowana na różnych obiektach energetycznych. Otrzymane wyniki oczyszczania spalin przy użyciu zaprojektowanej instalacji pilotażowej pozwolą określić czy zbudowany prototyp jest efektywny w każdych warunkach dla polskich elektrowni opalanych węglem. Wiedza na ten temat pozwoli efektywnie rozwinąć technologie przemysłowe pod kątem oczyszczania spalin z rtęci spełniając jednocześnie wymagania stawiane przez konkluzje BAT/BREF.
The issue of mercury emission and the need to take action in this direction was noticed in 2013 via the Minamata Convention. Therefore, more and more often, work and new law regulations are commencing to reduce this chemical compound from the environment. The paper presents the problem of removing mercury from waste gases due to new BREF/BAT restrictions, in which the problem of the need to look for new, more efficient solutions to remove this pollution was also indicated. Attention is paid to the problem of the occurrence of mercury in the exhaust gases in the elemental form and the need to carry out laboratory tests. A prototype installation for the sorption of elemental mercury in a pure gas stream on solid sorbents is presented. The installation was built as part of the LIDER project, financed by the National Center for Research and Development in a project entitled: “The Application of Waste Materials From the Energy Sector to Capture Mercury Gaseous Forms from Flue Gas”. The installation is used for tests in laboratory conditions in which the carrier gas of elemental mercury is argon. The first tests on the zeolite sorbent were made on the described apparatus. The tested material was synthetic zeolite X obtained as a result of a two-stage reaction of synthesis of fly ash type C with sodium hydroxide. Due to an increase, the chemical affinity of the tested material in relation to mercury, the obtained zeolite material was activated with silver ions (Ag+) by an ion exchange using silver nitrate (AgNO3). The first test was specified for a period of time of about 240 minutes. During this time, the breakthrough of the tested zeolite material was not recorded, and therefore it can be concluded that the tested material may be promising in the development of new solutions for capturing mercury in the energy sector. The results presented in this paper may be of interest to the energy sector due to the solution of several environmental aspects. The first of them is mercury sorption tests for the development of new exhaust gases treatment technologies. On the other hand, the second aspect raises the possibility of presenting a new direction for the management and utilization of combustion by-products such as fly ash.
In the processes of coal mining, preparation and combustion, the rejects and by-products are generated. These are, among others, the rejects from the coal washing and dry deshaling processes as well as the coal combustion by-products (fly ash and slag). Current legal and industry regulations recommend determining the content of mercury in them. The regulations also define the acceptable content of mercury. The aim of the paper was to determine the mercury content in the rejects derived from the coal cleaning processes as well as in the combustion by-products in respect of their utilization. The mercury content in the representative samples of the rejects derived from the coal washing and dry deshaling processes as well as in the coal combustion by products derived from 8 coal-fired boilers was determined. The mercury content in the rejects from the coal washing process varied from 54 to 245 μg/kg, (the average of 98 μg/kg) and in the rejects from the dry deshaling process it varied from 76 to 310 μg/kg (the average of 148 μg/kg). The mercury content in the fly ash varied from 70 to 1420 μg/kg, (the average of 567 μg/kg) and in the slag it varied from 8 to 58 μg/kg (the average of 21 μg/kg). At the moment, in light of the regulations from the point of view of mercury content in the rejects from the coal preparation processes and in the coal combustion by-products, there are no significant barriers determining the way of their utilization. Nevertheless, in the future, regulations limiting the maximum content of mercury as well as the acceptable amount of leachable mercury may be introduced. Therefore, preparing for this situation by developing other alternative methods of using the rejects and by-products is recommended.
Nowadays, actions allowing for a reduction of anthropogenic mercury emission are taken worldwide. Great emphasis is placed on reducing mercury emission from the processes of energochemical coal conversion, mainly from the coal combustion processes. One of the methods which enable a reduction of anthropogenic mercury emission is the removal of mercury from coal before its conversion. It should be pointed out that mercury in hard coal may occur both in the organic and mineral matter. Therefore, a universal method should allow for the removal of mercury, combined in both ways, from coal. In the paper, a concept of the hybrid mercury removal process from hard coal was presented. The idea of the process is based on the combination of the coal cleaning process using wet or dry methods (first stage) and the thermal pretreatment process at a temperature in the range from 200 to 400 °C (second stage). In the first stage, a part of mercury occurring in the mineral matter is removed. In the second stage, a part of mercury occurring in the organic matter as well as in some inorganic constituents characterized by a relatively low temperature of mercury release is removed. Based on the results of the preliminary research, the effectiveness of the decrease in mercury content in coal in the hybrid process was estimated in the range from 36 to 75% with the average at the level of 58%. The effect of the decrease in mercury content in coal is much more significant when mercury content is referred to a low heating value of coal. So determined, the effectiveness was estimated in the range from 36 to 75% with the average at the level of 58%.
Coal combustion processes are the main source of mercury emission to the environment in Poland. Mercury is emitted by both power and heating plants using hard and brown coals as well as in households. With an annual mercury emission in Poland at the level of 10 Mg, the households emit 0.6 Mg. In the paper, studies on the mercury release in the coal and biomass combustion process in household boilers were conducted. The mercury release factors were determined for that purpose. For the analyzed samples the mercury release factors ranged from 98.3 to 99.1% for hard coal and from 99.5% to 99.9% for biomass, respectively. Due to the high values of the determined factors, the amount of mercury released into the environment mainly depends on the mercury content in the combusted fuel. In light of the obtained results, the mercury content in the examined hard coals was 6 times higher than in the biomass (dry basis). Taking the calorific value of fuels into account, the difference in mercury content between coal and biomass decreased, but its content in coal was still 4 times higher. The mercury content determined in that way ranged from 0.7 to 1.7 μg/MJ for hard coal and from 0.1 to 0.5 μg/MJ for biomass, respectively. The main opportunity to decrease the mercury emissions from households is offered by the use of fuels with a mercury content that is as low as possible, as well as by a reduction of fuel consumption. The latter could be obtained by the use of modern boilers as well as by the thermo-modernization of buildings. It is also possible to partially reduce mercury emissions by using dust removal devices.
This article presents the effects of the application of the passive method of flue gas purification from mercury compounds emitted during combustion. The research was carried out on a fluidized bed installation using coal. The dry method of acid gas pollutants reduction was applied during the combustion with the use of 9 modified sodium sorbents. They were fed into a gas jet of 573 K in two molar ratios (sodium contained in the sorbent to the sulphur contained in the fuel). The mercury emission level into the atmosphere was determined based on the mercury content in the solid substrates of the combustion process (in the fuel and the sorbent) and the solid products (fly ash and bottom waste). The combustion process was accompanied by mercury emission 14.7 μgHg/m3. During the removal of acid pollutants from fumes, a decrease in mercury concentration was achieved. The degree of the mercury reduction depended on the type the sorbent used, the manner of modification and the molar ratio in which they were fed into the installation (2 Na/S = 0.5; 2.1). Each time, the more the sorbent was fed into the installation, the bigger the reduction of the mercury emission level. Among the unmodified sorbents, the lowest emission level was achieved for the raw bicarbonate – 3.7 μgHg/m3. For baking soda it was 9.7 μgHg/m3. The application of mechanically modified compounds based on baking soda resulted in the reduction of the Hg emission in fumes up to 2.5–2.6 μgHg/m3. The determined mercury concentration levels in the gases during the purification of the fumes were compared with the accepted Hg emissions contained in the BAT conclusions for large combustion plants. As for all of the existing and newly built plants with a heat capacity below 300 MW, satisfactory effects would be achieved by the use of mechanically modified sorbents in the molar concentration of 2 Na/S = 2.1.