Polyamide (PA) 6 in waste incineration plant; waste-to-energy plant with dry flue gas treatment, without collection, transport and pre-treatment; production mix (region specific plants), at plant; 32.0 MJ/kg net calorific value
The modeled Waste-to-Energy plant (WtE) is defined based on the treatment of average municipal solid waste (MSW) in Europe. The thermal treatment of a single waste fraction like paper or plastic or even specific wastes like Polyamide 6 is not done in reality in a WtE plant. The waste is always homogenized to obtain a relative constant calorific value and to comply with the emission standards. Nonetheless the used model and the used settings for the average MSW allows to attribute the environmental burden (emissions and also resource consumption of auxiliaries) energy production as well as the credits (metal scrap recovery) to a single fraction or specific waste incinerated within an average MSW. Therefore the LCI data is valid for the thermal treatment of the specific waste within an average MSW. The following technology description explains the settings and technology of the average WtE plant used to generate the LCI data set. The data set covers all relevant process steps for the thermal treatment and corresponding processes, such as disposal of air pollution control residues or metal recycling. The inventory is mainly based on industry data and is completed, where necessary, by secondary data. The system is partly terminated (open outputs electricity and steam). Electricity and steam flows has to be connected and adapted to local specificities in order to take into account these credits. Credits for recovered metals are already included. The data set represents an end of-life inventory for the thermal treatment of a specific waste fraction in an average Waste-to-Energy (WtE) plant with dry flue gas cleaning. The data set includes the emissions and resource consumption for the thermal treatment of waste. The behavior of bottom ash and air pollution control residues on a landfill are considered. Credits for recovered metals are included. Produced electricity and process steam are unconnected (partly terminated). Electricity and steam flows has to be connected and adapted to local specificities in order to take into account these credits. It should be considered that this data set is an approximation to reality. The used model of an average European WtE plant and the average composition of MSW do not exist in reality and efficiencies, emission values, transfer coefficients and elementary composition will differ if a specific WtE plant is used. This data set can be used for the incineration of the mentioned and specified waste.
The data set represents the incineration of Polyamide (PA) 6 waste with a net calorific value (NCV) of 32.0 MJ/kg. The incineration is done in waste-to-energy plants (WtE) for the thermal treatment of municipal solid waste (MSW) in Europe with dry flue gas cleaning and selective catalytic reduction (SCR) for NOx-removal to meet the legal requirements. Environmental impacts for waste collection, transport or any pretreatment of the waste are not included in the data set. The modeled plant consists of an incineration line fitted with a grate and a steam generator.
The average efficiency of the steam production is about 82%. Produced steam is used internally as process-steam and the balance is used to generate electricity or exported as heat or steam to industry or households. . The energy balance for the plant was modeled country/region specific using data from the "CEWEP Energy Report 2004-2007" (2008) representing 231 waste-to energy plants in Europe. The energy balance for the average combusted waste (44% net efficiency, 27% of the energy output is electricity, 73% is steam) is extrapolated to the heat input of the specific waste and the waste specific differences on the own consumption of energy (steam and waste) and auxiliaries. The own consumption is partly independent of the waste type (handling of waste before combustion) and partly depending of the waste composition (flue gas volume, treatment of specific emissions etc.).
The flue gas treatment system uses a dry technology with adsorbent and a SCR system for NOx-reduction. The NOx reducing agent ammonia is directly injected into the furnace and reacts with the NOx to nitrogen and water. The flue gas is conditioned, adsorbents added and filtered with fabric filters. Lime milk and small parts of hearth furnace coke are used as adsorbents; a part of the adsorbents is re-circulated. The fly ash together with the adsorbent is mixed together with the boiler ash (treatment of APC residues see below).
For the emissions HCl, HF, NOx, VOC, N2O, CO, NH3, SO2, dust, dioxin and the heavy metals As, Cd, Co, Cr, Ni and Pb mean emission values per cubic meter of cleaned flue gas published in the BREF document "Waste Incineration" of the European Commission are used. Due to the wide range of emissions for some elements and substances the mathematical mean values are adjusted with additional real plant data. The emission of all other elements and the distribution of all elements and substances into the different residues are calculated by means of transfer coefficients.
The bottom ash is quenched, ferrous scrap and partly non-ferrous metals (aluminum, copper, brass, zinc, lead) are recovered and a three month ageing process is done to stabilize the bottom ash. The produced bottom ash after metal recovery and ageing is reused as construction material (and will leave the system as bottom ash for reuse). The APC residues including boiler ash, filter cake and slurries are disposed in underground deposits salt mines. The disposal in underground deposits without free water and contact to ground water reservoirs was modeled as emission free. The operation of the underground deposit is included. Transports for bottom ash and APC residues independent of the different routes are considered.
All important utilities and auxiliaries used in the waste incineration plant are included in the system. To calculate the credits for the recovered ferrous metal scrap a "value of scrap" data set was used, i.e. the environmental burdens for the remelting and processing of the scrap are taken into account in the system boundaries. Credits for an eventual recovery of non-ferrous metals are not given.
GaBi (source code, database including extension modules and single data sets, documentation) remains property of thinkstep AG. thinkstep AG delivers GaBi licenses comprising data storage medium and manual as ordered by the customer. The license guarantees the right of use for one installation of GaBi. Further installations using the same license are not permitted. Additional licenses are only valid if the licensee holds at least one main license. Licenses are not transferable and must only be used within the licensee's organisation. Data sets may be copied for internal use. The number of copies is restricted to the number of licenses of the software system GaBi the licensee owns. The right of use is exclusively valid for the licensee. All rights reserved.