Elemental Partitioning of RDF Through an Advanced Thermal Conversion Technology - Paper Example

Abstract: The participation of the elemental composition of the RDF as a fuel in the Syngas Products group pyrolysis plant, based in Dorset, UK is studied. It is known from operating experience with regards to the process mass balance, burnout behaviour and the productions characterise. This work established the methods for sampling and analysing the plant input and outputs, char, liquids and gasses according to British Standards. A model developed to assess the whole process mass balance. Based on the analysis data, biomass content of the fuel is determined to qualify for support under the Renewable Obligation. The measured and calculated data showed that the plant produced 34 wt% of char, rich in carbon, 24wt% of aqueous effluent rich in water, about 7 wt% of oils with calorific value of 39 MJ/kg and 36wt% of syngas with composition of hydrogen, oxygen, carbon monoxide material plus the wide range of other HCs. The pyrolysis has been identified as the suitable Advanced Thermal Conversion Technology for RDF conversion whereby the syngas produced is applied to a 1MW gas engine to produce heat and electricity. This result also proves that char and oils might be used as fuels.

Keywords: Pyrolysis, Municipality Solid Waste (MSW), Refuse-Derived Fuel (RDF), Syngas, Biomass content

MSW pyrolysis is regarded as a creative and innovative way of treating MSW hence the production of distinct fuels and chemicals. The process involving pyrolysis, it helps in the production of much cleaner as compared the production from the conventional MSW incineration plants as minimum amounts of sulphur oxides, and nitrogen oxides are produced as a result of the inert atmosphere in the pyrolysis processes as well as the opportunity to wash syngas prior its combustion. Additionally, in the reduction of emission of the gas, more prevalent quality of solid residues can also be anticipated to be obtained from the treatment involved in pyrolysis technique for the MSW. Furthermore, the recovering of the waste materials, as well as a substitute for acquiring materials, will enhance the conservation of the resources.

Generally, Pyrolysis is known to be the process of thermal-chemical decomposition that changes the carbon-rich materials into Syngas, bio-oil and char, only at the absence of oxygen. Pyrolysis of MSW has been studied and considered a fascinating alternate to burn for Municipal solid waste (MSW) disposal that facilitates resources and energy recovery; although, it has rarely been practiced with the output of pyrolysis products as the by-products. Pyrolysis as the method of thermal conversion technology has progressively attracted worldwide attention because of its high efficiency together with its eco-friendly adaptability. Pyrolysis technology gives an opening for the conversion of MSW into clean energy. Pyrolysis, and gasification, technologies have been used for many years. Some of the earliest examples were operated during the first and second world wars when fuel was at a premium. The adoption of these processes has been slow due to the easy availability of fossil fuels which has meant that there has not been the investment required to understand or commercialise the process entirely.

The Refuse-Derived Fuel (RDF) represents a fraction of the MSW which is generated after withdrawal of the materials which are recyclable such as glass and ferrous materials. RDF is typically made up of textile, and plastic, cardboard and garden waste. As a result, the RDF constitutes of the highest proposition of the renewable material that can help in the recovery of energy production in the form of the solid, liquid as well as the gaseous fuel. It presents substantial advantages as compared to raw MSW by extended homogeneity and physical composition, excellent heating value and efficient storage.

The current work has been taken on to examine the products and behaviours of the RDF as the feedstock through an advanced thermal conversation technology processes in Syngas Products Group, with the primary emphasis on the evolution of syngas composition, characteristics of liquid bio-oil and the properties of the solid residue. In the process, the RDF is continuously fed into the pyrolyser via a series of conveyors into a feed compactor hopper. The purpose of the compactor is to prevent the ingress of air into the pyrolysis process. Fig.1 shows from the compactor, the feedstock will be continuously fed into the pyrolyser where the feed is indirectly heated, in the absence of oxygen, externally at between 850oC and 1000oC. Under the thermal and chemical conditions within the pyrolysis unit, the feed decomposes to become a synthetic gas (consisting of methane, hydrogen, carbon monoxide and water vapour), leaving a resultant solid carbon char.

The gas from the pyrolysis process is drawn, under negative pressure, through a ceramic filter to remove particulates and to collect the char arising from the pyrolysis process. From there, it passes through a wet quench to rapidly reduce the temperature of the gas and to condense out any tars and oils and prevent the formation of dioxins. The quench system is including a hot water quench which removes the heavy oil tars, and some of the water moisture (Aqueous Effluent) and a cold-water qu...