Možnost využití pyrolýzy v oblasti nakládání s komunálním odpadem.

Abstract

The dissertation work is focused on verification of pyrolysis utilisation as a possibility of municipal solid waste and sewage sludge disposal. With respect to required reduction of biodegradable waste deposited in landfills is necessary to explore feasible utilisation of these wastes. The results of municipal solid waste and sewage sludge laboratory pyrolysis are presented in this work. Three samples with different moisture content (0 %, 30 % and 65 %) of municipal solid waste was prepared for tests. 65 % moisture content represents standard conditions of raw municipal waste in landfill. The samples was pyrolysed for three hours with heating rate 3,47 °C/min and the material was pyrolysed for another one hour after reaching 650 °C. The pyrolysis products was then analysed and the results was evaluated. Pyrolysis of dry municipal solid waste produces approximately same amount of organics, gas and solid residue. Increasing the moisture content results in higher yield of pyrolytic gas in relation to pyrolytic oil and char. Pyrolytic gas from municipal solid waste consists of CO2 (25-59 % wt.), hydrocarbon gases CxHy (25-58 % wt.), CH4 (6-11 % wt.), CO (4,35-8,61 % wt.) a H2 (0,65-0,86 % wt.). The concentration of CH4 released from municipal solid waste with 65 % moisture content decreased more than 50 % relative to the dry matter, concentration of CO2 increased more than 50 %. The analysis shows that higher the sample moisture content higher the ash content in pyrolytic char. Reversely the content of carbon, hydrogen and nitrogen in char decreased with higher moisture. Also heating value decreased. Liquid organic fraction has a wax character. The results show that the separation and segregate pyrolysis of bio and plastic wastes is preferable in term of pyrolysis products utilisation The pyrolysis of sewage sludge was held in smaller apparatus and the research was concerned in the influence of sludge moisture and hygienisation on the gas yield and composition. Sludge without liming and limed sludge from the Central Wastewater Treatment Plant in Ostrava and sludge from the Wastewater Treatment Plant in Sviadnov was pyrolysed. The tests were carried out with dry sludge and with wet sludge from the Central Wastewater Treatment Plant in Ostrava (natural moisture content cca. 70 %). The final temperature of the pyrolytic process of dry sludge was 850 °C, and this temperature was maintained for two hours after reaching this value. Final temperature of pyrolysis of wet sludge was 750 °C. The pyrolysis was realised in a nitrogen atmosphere and the flow rate of nitrogen was set at 25 ml/min. The concentration of H2, CO2, CO, a CH4 were determined at intervals of 3-5 minutes. The release of gases during pyrolysis was in the sequence of CO2, H2, CH4 and CO. It was found that sample moisture results in gasification reaction. Secondary reactions of char gasification have to be promoted by accentuated residence time prolonging. The content of CaO in sludge increases their reactivity during pyrolysis; it supports cracking of volatile organic compounds. CaO is active especially in the splitting of oxygen-containing functional groups and the production of carbon dioxide. As a consequence of a higher amount of CO2, higher amounts of CH4 and CO are formed in the pyrolytic process of limed sludge.