Waste Management 50 (2016) 86–92
Contents lists available at ScienceDirect
Waste Management journal homepage: www.elsevier.com/locate/wasman
Fluidized bed gasification of industrial solid recovered fuels Umberto Arena a,b,⇑, Fabrizio Di Gregorio b a b
Department of Environmental, Biological and Pharmaceutical Sciences and Technologies, Second University of Naples, Via Vivaldi, 43, 81100 Caserta, Italy AMRA s.c.a r.l. – Analysis and Monitoring of Environmental Risk, Via Nuova Agnano, 11, 80125 Napoli, Italy
a r t i c l e
i n f o
Article history: Received 2 September 2015 Revised 21 January 2016 Accepted 8 February 2016 Available online 16 February 2016 Keywords: Solid recovered fuel Fluidized bed Gasification Cellulose Plastic waste Nappies
a b s t r a c t The study evaluates the technical feasibility of the fluidized bed gasification of three solid recovered fuels (SRFs), obtained as co-products of a recycling process. The SRFs were pelletized and fed to a pilot scale bubbling fluidized bed reactor, operated in gasification and co-gasification mode. The tests were carried out under conditions of thermal and chemical steady state, with a bed of olivine particles and at different values of equivalence ratio. The results provide a complete syngas characterization, in terms of its heating value and composition (including tars, particulates, and acid/basic pollutants) and of the chemical and physical characterization of bed material and entrained fines collected at the cyclone outlet. The feasibility of the fluidized bed gasification process of the different SRFs was evaluated with the support of a material and substance flow analysis, and a feedstock energy analysis. The results confirm the flexibility of fluidized bed reactor, which makes it one of the preferable technologies for the gasification of different kind of wastes, even in co-gasification mode. The fluidized bed gasification process of the tested SRFs appears technically feasible, yielding a syngas of valuable quality for energy applications in an appropriate plant configuration. Ó 2016 Elsevier Ltd. All rights reserved.
1. Introduction The study is a part of a European project (‘‘Virgin” project, LIFE 12 ENV/IT/000611) aimed to demonstrate the technical feasibility and quantify the environmental performances of a recycling scheme for wastes generated by the utilization of absorbent hygiene products, typically indicated with the acronym AHP (Arena et al., 2015). The AHP wastes are first sterilized by steam in an autoclave, and then treated in a sorting machine that separates the plastic fraction, ready for the ordinary recycling chain, and the cellulosic fraction, containing large part of the hydrogel used as absorbent. The sterilized cellulosic fraction is sent to a bubbling fluidized bed air gasifier (BFBG), where is converted in a low heating value fuel gas (‘‘syngas”), which can be burned in a boiler for energy recovery. The aim is to utilize the energy content of AHP cellulose fraction to produce the steam necessary for the sterilization stage, so avoiding the consumption of fossil, non-renewable energy sources, like natural gas. The paper focuses on the main process aspects of the fluidized bed air gasification (Basu, 2010; Arena, 2013; Gómez-Barea et al., 2013) of the secondary recovered fuel (SRF), obtained from the cellulosic fraction generated by ⇑ Corresponding author at: Department of Environmental, Biological and Pharmaceutical Sciences and Technologies, Second University of Naples, Via Vivaldi, 43, 81100 Caserta, Italy. E-mail address: [email protected] (U. Arena). http://dx.doi.org/10.1016/j.wasman.2016.02.011 0956-053X/Ó 2016 Elsevier Ltd. All rights reserved.
sterilization and sorting treatments of AHP waste. To this end, a series of experimental tests have been carried out under different operating conditions in a pilot scale reactor, having a size large enough to avoid any scale-up effects.
2. Materials and methods 2.1. Solid recovered fuels The experimental investigation involved three SRFs obtained as co-products of the recycling process of AHP wastes. The first fuel, to which this study is specifically dedicated, was essentially made of cellulose, doped with absorbent grains of a specific hydrogel. A second SRF was made of mixed plastics, mainly polyolefins. The last was a mixture of the first two materials, with about 80% by weight of mixed plastics and 20% of cellulose: it has been utilized to simulate operation in co-gasification mode. The three SRFs, generated as flakes during the sterilization and sorting treatments, were pre-treated by means of a pelletizing machine producing cylindrical pellets having an ID of 1 cm and a length of 1 cm for the cellulosic fraction of the original AHP waste, and an ID of 5 mm and a length of 3 cm for the plastic wastes (Fig. 1): this allowed increasing the density of material to be fed into the gasifier and avoiding any effect related to fuel size. Table 1 reports the ultimate analysis of the SRF pellets, obtained by means of a
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U. Arena, F. Di Gregorio / Waste Management 50 (2016) 86–92
Fig. 1. The three SRFs as obtained after the sterilization and pelletization treatment. Cellulosic SRF_1 (left), plastic SRF_2 (middle), plastic–cellulosic SRF_3 (right).
Table 1 Chemical and physical characterization of the three solid recovered fuels utilized for the experimental tests.
Table 2 Ash composition as obtained by means of XRF and ICPMS analyses (only for chlorine) for the three SRFs. DL = Detection Limit.
SRF_1
SRF_2
SRF_3
#
SRF_1
SRF_2
SRF_3
Unit
DL
Main components
cellulose
plastics
80% plastics 20% cellulose
Ultimate analysis, %wt C H N S O (by difference) Moisture Ash
30.18 4.76 – – 32.29 29.00 3.77
76.54 12.84 0.20 – 7.91 0.47 2.04
66.58 10.14 0.10 0.03 16.07 1.51 5.57
Heating value, MJ/kgfuela HHV LHV
Al2O3 CaO Fe2O3 P2O5 MgO K2O SO3 SiO2 Na2O Zn Cl
Contents lists available at ScienceDirect
Waste Management journal homepage: www.elsevier.com/locate/wasman
Fluidized bed gasification of industrial solid recovered fuels Umberto Arena a,b,⇑, Fabrizio Di Gregorio b a b
Department of Environmental, Biological and Pharmaceutical Sciences and Technologies, Second University of Naples, Via Vivaldi, 43, 81100 Caserta, Italy AMRA s.c.a r.l. – Analysis and Monitoring of Environmental Risk, Via Nuova Agnano, 11, 80125 Napoli, Italy
a r t i c l e
i n f o
Article history: Received 2 September 2015 Revised 21 January 2016 Accepted 8 February 2016 Available online 16 February 2016 Keywords: Solid recovered fuel Fluidized bed Gasification Cellulose Plastic waste Nappies
a b s t r a c t The study evaluates the technical feasibility of the fluidized bed gasification of three solid recovered fuels (SRFs), obtained as co-products of a recycling process. The SRFs were pelletized and fed to a pilot scale bubbling fluidized bed reactor, operated in gasification and co-gasification mode. The tests were carried out under conditions of thermal and chemical steady state, with a bed of olivine particles and at different values of equivalence ratio. The results provide a complete syngas characterization, in terms of its heating value and composition (including tars, particulates, and acid/basic pollutants) and of the chemical and physical characterization of bed material and entrained fines collected at the cyclone outlet. The feasibility of the fluidized bed gasification process of the different SRFs was evaluated with the support of a material and substance flow analysis, and a feedstock energy analysis. The results confirm the flexibility of fluidized bed reactor, which makes it one of the preferable technologies for the gasification of different kind of wastes, even in co-gasification mode. The fluidized bed gasification process of the tested SRFs appears technically feasible, yielding a syngas of valuable quality for energy applications in an appropriate plant configuration. Ó 2016 Elsevier Ltd. All rights reserved.
1. Introduction The study is a part of a European project (‘‘Virgin” project, LIFE 12 ENV/IT/000611) aimed to demonstrate the technical feasibility and quantify the environmental performances of a recycling scheme for wastes generated by the utilization of absorbent hygiene products, typically indicated with the acronym AHP (Arena et al., 2015). The AHP wastes are first sterilized by steam in an autoclave, and then treated in a sorting machine that separates the plastic fraction, ready for the ordinary recycling chain, and the cellulosic fraction, containing large part of the hydrogel used as absorbent. The sterilized cellulosic fraction is sent to a bubbling fluidized bed air gasifier (BFBG), where is converted in a low heating value fuel gas (‘‘syngas”), which can be burned in a boiler for energy recovery. The aim is to utilize the energy content of AHP cellulose fraction to produce the steam necessary for the sterilization stage, so avoiding the consumption of fossil, non-renewable energy sources, like natural gas. The paper focuses on the main process aspects of the fluidized bed air gasification (Basu, 2010; Arena, 2013; Gómez-Barea et al., 2013) of the secondary recovered fuel (SRF), obtained from the cellulosic fraction generated by ⇑ Corresponding author at: Department of Environmental, Biological and Pharmaceutical Sciences and Technologies, Second University of Naples, Via Vivaldi, 43, 81100 Caserta, Italy. E-mail address: [email protected] (U. Arena). http://dx.doi.org/10.1016/j.wasman.2016.02.011 0956-053X/Ó 2016 Elsevier Ltd. All rights reserved.
sterilization and sorting treatments of AHP waste. To this end, a series of experimental tests have been carried out under different operating conditions in a pilot scale reactor, having a size large enough to avoid any scale-up effects.
2. Materials and methods 2.1. Solid recovered fuels The experimental investigation involved three SRFs obtained as co-products of the recycling process of AHP wastes. The first fuel, to which this study is specifically dedicated, was essentially made of cellulose, doped with absorbent grains of a specific hydrogel. A second SRF was made of mixed plastics, mainly polyolefins. The last was a mixture of the first two materials, with about 80% by weight of mixed plastics and 20% of cellulose: it has been utilized to simulate operation in co-gasification mode. The three SRFs, generated as flakes during the sterilization and sorting treatments, were pre-treated by means of a pelletizing machine producing cylindrical pellets having an ID of 1 cm and a length of 1 cm for the cellulosic fraction of the original AHP waste, and an ID of 5 mm and a length of 3 cm for the plastic wastes (Fig. 1): this allowed increasing the density of material to be fed into the gasifier and avoiding any effect related to fuel size. Table 1 reports the ultimate analysis of the SRF pellets, obtained by means of a
87
U. Arena, F. Di Gregorio / Waste Management 50 (2016) 86–92
Fig. 1. The three SRFs as obtained after the sterilization and pelletization treatment. Cellulosic SRF_1 (left), plastic SRF_2 (middle), plastic–cellulosic SRF_3 (right).
Table 1 Chemical and physical characterization of the three solid recovered fuels utilized for the experimental tests.
Table 2 Ash composition as obtained by means of XRF and ICPMS analyses (only for chlorine) for the three SRFs. DL = Detection Limit.
SRF_1
SRF_2
SRF_3
#
SRF_1
SRF_2
SRF_3
Unit
DL
Main components
cellulose
plastics
80% plastics 20% cellulose
Ultimate analysis, %wt C H N S O (by difference) Moisture Ash
30.18 4.76 – – 32.29 29.00 3.77
76.54 12.84 0.20 – 7.91 0.47 2.04
66.58 10.14 0.10 0.03 16.07 1.51 5.57
Heating value, MJ/kgfuela HHV LHV
Al2O3 CaO Fe2O3 P2O5 MgO K2O SO3 SiO2 Na2O Zn Cl
