Strength and permeability properties along with microstructural evolution of hardened slurries composed of fly ash from fluidal bed combustion of brown coal and an addition of OPC/BFSC is assessed in this paper. An increase in the amount of fly ash in slurries influences the development of mechanical strength and a decrease of hydraulic conductivity. SEM, XRD, and porosity analyses confirmed formation of watertight microstructures. The structure of slurries is composed of ettringite, C-S-H phase, AFt, and AFm phases. Ettringite crystallises as relatively short needles forming compact clusters or intermixed with the C-S-H phase. The occurring C-S-H phases are mainly of type I – fibrous and type II – honeycomb
According to a fuel flexibility, fluidized bed boilers are considered as appropriate for biomass combustion as cofiring. But the burning of fuels such as forest and agricultural biomass raises a number of operational problems. Most important of these problems are bed agglomeration and deposition. Deposition appears when biomass contains significant amounts of alkali elements, such as sodium and potassium. The purpose of the work is to select a fuel additive to overcome these operational problems. Investigations were conducted in two stages at a pilot scale 0.1 MWth laboratory circulating fluidized bed reactor. As the fuel, the mixture of biomass contained forest residues, sunflower husks, straw and wood pellets from mixed woods was selected. In the first stage biomass was burnt without any additives, while in the second one the fuel was enriched with some additive. The additive (liquid mixture of chemicals) was added to the fuel in amounts of 1 dm3 per 5-10 Mg of fuel. The following operational parameters were examined: temperature profiles along the height of the circulating fluidised bed column, pressure profiles, emissions. After the tests, the laboratory reactor was inspected inside. Its results enables expression of the following conclusions: there was no agglomeration during fuel additive testing, and the deposition was reduced as well. Moreover, the parts (heating surfaces, separator) of the laboratory reactor were coated with a protective layer. The layer covered microcracks and protected the parts from deposition for a long period after the operation.
Petrographic and physico-chemical analyses of ashes are carried out on a large scale and presented in numerous scientific papers. The mentioned ashes are obtained from filters and electrostatic precipitators mounted in large industrial installations. The large-scale analysis of the ashes obtained directly from grate furnaces or blast furnaces mounted in low-power boilers started with combating smog and low-stack emissions. The collection of ash samples from household furnaces usually involves the analysis of the combustion of waste in low-power boilers. This is justified in the case of old type boilers, which were designed to use virtually any fuel. Currently, new types of boilers, designed to burn dedicated fuels, are offered on the market. The aim is to use only renewable fuels (biomass) or fossil fuels with high quality parameters, which are more environment-friendly, e.g. eco-pea coal, lignite briquettes, or peat briquettes. The authors of the study focused on examining the ash obtained from boilers for burning wood pellets by performing microscopic analysis of residues after biomass combustion. The above mentioned analysis provides a comprehensive information on the efficiency of the combustion process, the content of contaminants remaining in the ash, and the suitability of ash for other applications. The entire process, from the moment of collecting the samples to the execution of the analysis takes up to 12 hours, which ensures a quick decision on furnace adjustment or fuel change. The ash components were determined based on the results obtained by the Fly-Ash Working Group of the International Committee for Coal and Organic Petrology (ICCP). The mentioned classification has been supplemented with new key elements occurring in ashes resulting from the combustion of wood pellets in household boilers. This allowed determining the percentage content of characteristic components in the tested material, which can be used as a specific benchmark when issuing opinions on the quality and efficiency of the boiler and the combusted pellets.
The article concerns computer modelling of processes in cooling systems of internal combustion engines. Modelling objectives and existing commercial programs are presented. It also describes Author’s own method of binding graphs used to describe phenomena in the cooling system of a spark ignition engine. The own model has been verified by tests on the engine dynamometer. An example of using a commercial program for experimental modelling of an installation containing a heat accumulator is presented.
Wood pellets are classified as a solid biomass type. They are one of the most popular bio-heating fuels used in Europe, especially in the small heating sector, where pellets are burned in low-power domestic boilers. The pellets and automatic pellet-fired heating devices gained popularity due to the increasing air pollution (smog) problem and the low emission limiting campaigns associated with it. Wood pellets are formed as a result of small forestry particles mechanical compression (mainly conifers originated) and they are listed among renewable energy sources. The purpose of the presented studies was to compare the quality of wood pellets used for pellet-fired boilers and to identify, qualitatively and quantitatively, impurities marked in the samples obtained from the domestic market. The application of petrographic analyses, applied so far in relation to fossil fuels, is a presented work innovation for wood pellets. The microscopic analyses were performed on both certified (ENplus/DINplus) and uncertified wood pellets available on the market. Unfortunately, the analysis revealed that the quality requirements were not met, because of the unacceptable contamination presence. The unacceptable organic inclusions in the analyzed samples are fossil coals and their derivatives, coke, and polymeric materials of natural origin. Unacceptable inorganic inclusions determined in the analyzed samples were: glass, slag, rust, pieces of metal, stone powder, plastic, and polymeric materials of inorganic origin.
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/Nm3 to 400 mg/Nm3. 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.
The aim of the paper is a comparative study of co-firing high shares of wooden and agro-biomass with hard coal under oxy-fuel and air conditions in the laboratory scale reactor for pulverised fuels. The investigations of co-combustion behaviour NOx and SO2 emission and burnout were carried out for selected blends. Detailed investigations were concentrated on determining the effect of dosing oxygen method into the burner on NOx emission. The paper presents the results of co-firing blends with 20 and 50% share of biomass by mass in air and oxy-combustion condition. Biomass oxy-cofiring integrated with CCS (CO2 capture) technology could be a carbon negative technology. The reduction of NOx emissions in the conditions of oxy-co-firing is dependent on the concentration of oxygen in the primary stream of oxidiser. A significant reduction of NOx was achieved in the case of low oxygen concentration in the primary stream for each investigated blends. Co-firing of biomass with coal in an oxygen enriched atmosphere enhances combustion behaviour, lowers fuel burnout and as a result increases of the boiler efficiency.
Fly ashes from the combustion of lignite coal are suitable materials for the creation of suspensions in which CO2 is bound by mineral carbonation. Considering their limited economic uses, mineral sequestration, as a stage of the CCS technology in lignite coal power plants, can be a way of recycling them. Mineral sequestration of CO2 was researched using fly ashes from the combustion of lignite coal in the Pątnów power plant, distinguished by a high content of CaO and free CaO. Research into phase composition confirmed the process of carbonation of the whole calcium hydroxide contained in pure suspensions. The degree of CO2 binding was determined on the basis of thermogravimetric analysis. A rise in the content of CaCO3 was found in the suspensions after subjecting them to the effects of carbon dioxide. Following carbonation the pH is lowered. A reduction in the leaching of all pollutants was discovered in the studied ashes. The results obtained were compared to earlier research of ashes from the same power plant but with a different chemical composition. Research confirmed that water suspensions of ashes from the combustion of lignite coal in the Pątnów power plant are distinguished for a high degree of carbonation.
The article presents the results of tests of the application of magnetic fuel activators, which improve the efficiency of metallurgical furnaces and positively affect the ecological aspects of their work. Energy indicators for metallurgical furnaces during operation before and after installation of magnetic fuel activators as well as the results of composition and concentration of emitted pollutants are included in the paper. The magnetic activation of liquid and gaseous fuels modifies their structure. As a result of the activation, the fuel mixture is selectively saturated with oxygen in the zone of free fuel flow. The combustion conditions were close to optimal, which is confirmed by the reduction of pollutants in the exhaust gases. Fuel saving in the combustion process is also a measurable economic effect. The tests included ovens of several types: pusher furnace, one and two chamber furnaces and a furnace with a rotary shaft. Several-month measurement cycles were carried out on each of them. The experiments consisted in the analysis of gas and heat consumption per month in individual furnaces before and after the use of magnetic fuel activators. The effectiveness of using activators was determined on the basis of the results of the tests carried out. As a result of a twelve-month test cycle on the pusher type furnace, a 36% reduction in gas consumption and a 22% reduction in heat consumption were achieved. After a seventeen-month measurement cycle on chamber furnaces, a 35% reduction in gas consumption and 6% in heat consumption were achieved. The tests on furnaces with a rotary shaft lasted fourteen months and showed a reduction in gas consumption by 8%. An improvement in the composition of fumes in the furnace atmosphere was achieved in all units with magnetic activators installed, as well as a reduction in the emission of harmful pollutants into the atmosphere from the installation.
Natural gas combustion was carried out in air enriched with oxygen in the amount of 25 and 29% with addition of CO2 in place of part of nitrogen. The research was carried out at different flow rates of gas and oxygen excess ratios. The concentration of CO and NOx was analyzed. It has not been proved that the increased oxygen concentration influences significantly the CO concentration. However, the addition of CO2 caused a substantial variability of CO concentration in the exhaust gas, in contrast to the concentration of NOx which decreased monotonically. Model calculations, performed with use of FactSage, indicate an increase in the concentration of CO not only for the air enriched with oxygen, but after adding CO2 too, as well
CO, NO, NO2 and dust concentrations from combustion of deciduous wood (birch, beech, lime-tree) logs and pellets in two heating boilers (15 and 25 KW), situated in a heat station were investigated. Time dependences of pollutant concentrations as well as the impact of temperature in the combustion chamber and oxygen concentration on pollutant concentrations were presented. Pollutant emission indices have been estimated.