At present, natural limestone is used for the desulphurization of waste gases from the combustion of fossil fuels. However, it is important to save all primary resources, such as limestone, for the future. The researchers focused on finding alternative sorbents for the purpose of desulphurization in a dry additive method, which would become the alternative for natural limestone. This paper is primarily focused on desulphurization tests of selected substances. Tests were initially conducted on the laboratory scale, followed by pilot and full-scale combustion units.
This paper describes experiments on the application of sodium bicarbonate desulphurisation in the coal-fuel boiler. The boiler has been in operation for several years now and it has refiably fulfilled the original assignment to reduce SO2 emissions from the value of 1200 -1500 mg/Nm 3 to 400 mg/Nm 3 . Higher desulphurisation efficiency is determined only by the ratio of Na/S sorbent dosage. The resulting product of desulphurisation is stored together with fly ash in underground mines, and has no influence on the groundwater. Positive experience of the tests and boiler operation lies in higher reactivity of sodium and sulphur as compared with conventional methods based on limestone. Within the scope of the secondary measures of elimination of sulphur oxides in combustion products, an experimental dry-method desulphurisation of combustion products was performed by blasting an agent containing sodium bicarbonate NaHCO3 (99.6 %) into the flue ways before the electrostatic precipitator in a coal-fuel furnace with the steam output of 220 t/h.
KOLAT PAVEL, KADLEC ZDENĚK: Sewage sludge as a biomass energy source. Acta Universitatis Agriculturae et Silviculturae Mendelianae Brunensis, 2013, LXI, No. 1, pp. 85-91 The major part of the dry matter content of sewage sludge consists of nontoxic organic compounds, in general a combination of primary sludge and secondary microbiological sludge. The sludge also contains a substantive amount of inorganic material and a small amount of toxic components. There are many sludge-management options in which production of energy is one of the key treatment steps. The most important options are anaerobic digestion, co-digestion, incineration in combination with energy recovery and co-incineration in coal-fi red power plants. The goal of our applied research is to verify, if the sludge from waste water treatment plants may be used as a biomass energy source in respect of the EU legislation, which would comply with emission limits or the proposal of energy process optimizing the preparation of coal/sludge mixture for combustion in the existing fl uid bed boilers in the Czech Republic. The paper discusses the questions of thermal usage of mechanically drained stabilized sewage sludge from the waste water treatment plants in the boiler with circulated fl uid layer. The paper describes methods of thermal analysis of coal, sewage sludge and its mixtures, mud transport to the circulating fl uidised bed boiler, eff ects on effi ciency, operational reliability of the combustion equipment, emissions and solid combustion residues.
The exergy concept applied to chemical reactions of combustion and gasification has been presented and discussed in detail. All the essential cases will be taken into account, namely the equimolar and non-equimolarhomogeneous and heterogeneousstoichiometric processes, but also the non-stoichiometric ones. The numerical examples show the expected correctness of the theoretical approach which means, the method can be applied to the complex system analysis containing combustion and gasification processes. The analysis makes it clear that the method can be also used for all the chemical conversion processes in the chemical and process engineering. Abstrakt Exergetická koncepce byla aplikována na chemické reakce spalování a zplyňování a byla předložena a projednána detailně. Všechny základní případy budou brány v úvahu, a sice equimolární a ne-equimolární , homogenní a heterogenní stechiometrické procesy, ale také i ne-stechiometrické procesy. Numerické příklady ukazují na očekávanou správnost teoretického přístupu, což znamená, že metodu lze použít na komplexní systémové analýzy, které obsahují spalovací a zplyňovací procesy. Z analýz je zřejmé, že metoda může být také použita pro všechny chemické konverzní procesy v chemickém a procesním inženýrství.
The carbon dioxide absorption/desorption unit of the Integrated Gasifying Combined Cycle has been detailed described to formulate appropriate model equations for the processes, suitable for further thermodynamic analyzes. There are two principal technologies of the CO 2-removing section, namely the absorption with the following expanding desorption process, and the absorption with the following classical plates (or packing) desorption one. The physics of thermodynamic properties of the water/carbon dioxide solution have been presented thoroughly using hitherto literature data. The Henry's Law has been emphasized as the base for further thermodynamic analyzes. The numerical results of appropriate absorption/desorption units have been compiled presuming fundamental relations, which are also presented. They should be the base for their thermodynamic analyzes. Abstrakt Ve článku je detailně popsána absorpční a desorpční jednotka pro oxid uhličitý integrovaného zplyňovacího kombinovaného oběhu tak, aby se mohl definovat přiměřený matematický model procesu vhodný pro další termodynamickou analýzu. Existují dvě principiální technologie pro extrakci CO 2 jmenovitě absorpce s následným expanzním desorpčním procesem a absorpce s následným klasickým desorpčním procesem. Fyzika termodynamických vlastností roztoku voda/oxid uhličitý je prezentována zatím na základě dat z literatury. Je zde zdůrazněn Henryho zákon jako základ pro další termodynamické analýzy. Numerické výsledky vhodných absorpčních / desorpčních jednotek byly určeny na základě předpokládaných základních vztahů, které jsou také prezentovány. Tyto tvoří základ pro jejich termodynamické analýzy. prof. Ing. Jaroslav KOZACZKA, Dr.
Combustion of coal together with a relative small percentage of waste alternative fuel (WAF) may be a choice for the management of these wastes. Co-combustion coal and their blends of 5%, 10% and 50% (wt.%) with waste alternative fuel were tested in a thermogravimetric analyser (TGA) in the temperature range from ambient to 1000 o C under the heating rate of 10 o C min-1. Combustion characteristics such as volatile release, ignition and burnout were also studied for the fuel blends. The method of direct non-linear regression was used for calculation of apparent kinetic parameters of oxidation processes from thermogravimetric (TG) curves. The coal oxidation is the first-order reaction. The study has been conducted aiming at widening the spectrum of fuels utilised by cocombustion. Abstrakt Spalování uhlí s relativně malým procentem alternativního paliva představuje možnost pro nákládání s těmito odpady. Spoluspalování uhlí a jejich směsí 5%, 10% a 50% (hm%) s alternativním palivem bylo hodnoceno termogravimetrickým analyzátorem v teplotním rozsahu do 1,000 o C a rychlosti ohřevu 10 o C min-1. Spalovací charakteristiky jako těkání, vznícení a zapálení byly také studovány u směsí paliva. Pomocí metody přímé nelineární regrese (PNR) byly stanoveny formální kinetické parametry (aktivační energie, frekvenční faktor) oxidace z TG křivek pro řád reakce roven jedné. Studie byla provedena za účelem rozšíření spektra paliv pro spoluspalování.
The analytical, unified selection method of the converting medium composition is presented as to apply for the oxygenwater steam gasification the recirculation of reaction products. The selected molar fractions of the converting medium components should give the assumed (needed) CO/H 2ratio of the synthetic gas by the chosen process pressure and temperature. The graphical selection methods applying the MOLLIER-HOFFMANN diagram are used for the parameters preselecting of the airwater steam gasification, e.g. if there is any contents of nitrogen from the atmosphere. The presented analytical method refers to the oxygenwater steam without and with gas recirculation. The last assumption allows the presence of CO, H 2 , CO 2 and CH 4 in the converting mediumnew gasifying technologies need the permanent presence of carbon monoxide and hydrogen because of the iron catalyst. The determined values of its molar fractions help to choose the suitable process calculation iterative method. Abstrakt Analytická unifikovaná selektivní metoda přeměny středního složení je prezentována a aplikována pro recirkulaci reakčních produktů zplyňovacího procesu kyslík-vodní pára. Vybrané molární frakce přeměněných produktů dávají potřebný předpoklad určení poměru CO/H 2 syntetického plynu podle tlaku a teploty V daném procesu. Grafická unifikovaná metoda používá MOLLIER-HOFFMANN diagram pro předběžné určení parametrů vzduch-vodní pára U zplyňovacího procesu, jestliže je zde obsažen dusík Z atmosféry. Prezentována analytická metoda se odkazuje na proces kyslík-vodní pára bez a S recirkulaci. Poslední předpoklad dovoluje přítomnost CO, H 2 , CO 2 a CH 4 V přeměňujícím se mediu-nové zplyňovací technologie potřebují S ohledem na katalyzátorželezo, stálou přítomnost CO, H 2. Určené hodnoty těchto molárních frakcí pomáhají vybrat vhodnou výpočtovou iterační metodu. The selection of parameters for the gasifying process can be made using the so-called MOLLIER-HOFFMANN x H2 /x CO diagram, which can be prepared for a chosen fuel, i.e. for hydrogen and carbon contents in it. At the diagram appropriate process temperature can be determined and the needed composition of the converting medium. The last one is the mixture of atmospheric air and water steam, with limits pure water steam and pure atmospheric air. The last component can be enriched with oxygen, but there is not possible to apply the MOLLIER-HOFFMANN diagram to the mixture of water steam and pure oxygen. In the practice, it will be taken into account, that the atmospheric air is highly enriched with oxygen (the so-called technical oxygen).
Plasma technology utilised in power engineering can be divided to: I. High temperature plasma technology. The development of experimental equipment for decomposing the toxic compounds that arise in the pyrolysis or combustion of PCB oils, plastics and other dangerous wastes, by subsequently raising the combustion temperature above the threshold for dissociation of toxic gas molecules. The design of experimental dissociation chamber plant, rated at 100 kg/hour of dangerous waste is presented. II. Low temperature plasma technology is one of the possibilities how to replace efficiently noble fuels (mazut or gas) used for the start-up and stabilization of power stations and utilization in the incineration plants. The output 320 kVA of plasma generator and temperature 6 000 oC for the boiler is sufficient. The operating costs of plasma ignition of coal powders are significantly lower than the start-up of boiler with mazut, and/or the start-up or stabilization with the use of gas. These conclusions have been fully confirmed and verified.
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