According to data of the Central Statistical Ofﬁce, the amount of sludge produced in municipal wastewater treatment plants in 2010 amounted to 526000 Mg d.m. The forecast of municipal sewage sludge amount in 2015 according to KPGO2014 will reach 642400 Mg d.m. and is expected to increase in subsequent years. Signiﬁcant amounts of sludge will create problems due to its utilization. In order to solve this problem the use of thermal methods for sludge utilization is expected. According to the National Waste Management Plan nearly 30% of sewage sludge mass should be thermally utilized by 2022. The article presents the results of co-combustion of coal and municipal sewage sludge in a bubbling ﬂuidized bed boiler made by SEFAKO and located in the Municipal Heating Company in Morag. Four tests of hard coal and sewage sludge co-combustion have been conducted. Boiler performance, emissions and ash quality were investigated.
The aim of the paper is the petrographic characterization of coal from the Wieczorek mine and the residues after its gasification. The coal was subjected to gasification in a fluidized bed reactor at a temperature of about 900°C and in an atmosphere of oxygen and CO2. The petrographic, proximate, and ultimate analysis of coal and char was performed. The petrographic composition of bituminous coal is dominated by macerals of the vitrinite group (55% by volume); macerals of inertinite and liptinite groups account for 23% and 16.0%, respectively. In the examined char, the dominant component is inertoid (41% vol.). Mixed dense and mixed porous account for 10.9% and 13.5% vol., respectively. In addition, the examined char also contained unreacted particles such as fusinoids, solids (11.3% vol.), and mineroids (5.1% vol.). The char contains around 65% vol. of low porosity components, which indicates a low degree of carbon conversion and is associated with a low gasification temperature. The char was burned and the resulting bottom and fly ashes were subjected to petrographic analysis. Their composition was compared with the composition of ashes from the combustion of bituminous coal from the Wieczorek mine. Bottom ashes resulting from the combustion of bituminous coal and char did not differ significantly in the petrographic composition. The dominant component was mineroid, which accounted for over 80% vol. When it comes to fly ash, a larger amount of particles with high porosity is observed in fly ash from bituminous coal combustion.
The objective of this investigation was comparing the penetration of chloride ions in ordinary and air-entrained concretes containing a waste material Fluidized Bed Combustion Fly Ash (FBCFA). All concretes were tested with 15% and 30% cement replacement by FBCFA, with the same water-binder ratio of 0.45. Two kinds of fly ash coming from fluid bed combustion in two power plants in Poland have been used. In this study the rapid chloride permeability test – Nordtest Method BUILD 492 method – was used. The microstructure of the concrete was analyzed on thin polished sections and the measurement of air voids sizes and their distribution, using digital image analysis, was carried on according to PN-EN 480-11:2008. Obtained results have shown a significant influence of partial cement replacement by FBCFA on the chloride ions movements in concrete. It has been found that this kind of addition reduced considerably the chloride ion penetration. The influence of air entrainment on the chloride diffusion coefficients was also measured and it was shown that application of air-entraining admixture for concretes with FBCFA reduce the chloride diffusion coefficient but it should be used with caution.
Combustion technology of the coal-water suspension creates a number of new possibilities to organize the combustion process fulfilling contemporary requirements, e.g. in the environment protection. Therefore the in-depth analysis is necessary to examine the technical application of coal as a fuel in the form of suspension. The research undertakes the complex investigations of the continuous coal-water suspension as well as cyclic combustion. The cyclic nature of fuel combustion results from the movement of the loose material in the flow contour of the circulating fluidized bed (CFB): combustion chamber, cyclone and downcomer. The experimental results proved that the cyclic change of oxygen concentration around fuel, led to the vital change of both combustion mechanisms and combustion kinetics. The mathematical model of the process of fuel combustion has been presented. Its original concept is based on the allowance for cyclic changes of concentrations of oxygen around the fuel. It enables the prognosis for change of the surface and the centre temperatures as well as mass loss of the fuel during combustion in air, in the fluidized bed and during the cyclic combustion.