NOVEL CONCEPT TO TREAT

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EXAMENSARBETE INOM MATERIALTEKNIK, AVANCERAD NIVÅ, 30 HP

STOCKHOLM, SVERIGE 2016

NOVEL CONCEPT TO TREAT

WEEE FOR ENERGY AND METALS RECYCLE BASING ON PYROLYSIS PROCESS

KHILOD SHILTAGH

KTH

SKOLAN FÖR TEKNIKVETENSKAP

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www.kth.se

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Khilod Shiltagh. N ovel concept to treat weee for energy and metals recycle basing on pyrolysis process

Supervisors:

Dr. Weihong Yang

PhD student Panagiotis Evangelopoulos

Royal Institute of Technology

School of Industrial Engineering and Management Department of Material Science and Engineering Division of Energy and Furnace Technology SE-100 44 Stockholm

Sweden

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Abstract:

For the time different challenges are facing the world to stop the environment impacts and availability of vital resources. Electrical and electronical Equipment (EEE) are contained harmful compounds which considered to be a major threat for living organisms and might cause long term impacts on environment (Md. Abdur Rakib, 2014). Furthermore, evolution of technology leads to production of a huge amount of electronic waste globally, which need to be treated by innovative technologies in order to minimize their environmental impact and simultaneously maximize their recovery rates.

Pyrolysis is a promising method for treating these fractions of waste because it can potentially convert these waste into energy and metals.

Waste of Electrical and electronical Equipment (WEEE) contains both valuable and harmful materials, industrial waste are various physically and chemically from household waste. To avoid the opposite influence on environment and human health, presuppose particular recycling and treatment technique depending on the waste type (Gkaidatzis, Aggelakoglou, & Aktsoglou, 2009).

Two types of WEEE have been processed using typical pyrolysis (Nitrogen) and pyrolysis (steam) at 600 °C, Fixed bed reactor was used in addition to a separate boiler for producing steam. Two samples were investigated Printed circuit board- main body and -sockets.

The main focus of this work was to investigate the influence of steam presence on pyrolysis for recovering energy and metals from recycling WEEE.

The comparison between pyrolysis at inert atmosphere and steam pyrolysis results of two various fractions of E-Waste were prepared, in addition to literature investigation related to recycling of E- waste and traditional routes which are followed in recovering materials nowadays was done. The results of this study provides the incentive to continue experiments around pyrolysis process by using other methods.

Key words: WEEE. PCB. Pyrolysis. Steam. Nitrogen. Recycling metal & plastics

Acknowledgements

This work is dedicated to the soul of my dear father.

I would especially like to thank my supervisors Dr. Weihong Yang and PhD student Panagiotis Evangelopoulos from the Royal Institute of Technology (KTH) for their generous support and precious guidance which were extremely valuable for my study both theoretically and

practically.

To my brother who encouraged me to go back to study after interruption about 25 years, to you Ghassan, thank you. I would like to thank my family and friends.

To all of you thank a lot for the unlimited support given to me.

Khilod Shiltagh Stockholm October 2016

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TABLE OF DIAGRAMS

Figure 1- Estimated global quantity of E-waste between 2010 and 2018 ... 6

Figure 2- Saving energy for making certain elements by using recycling ... 7

Figure 3- Classification of E-waste generated globally in 2014 (UNU-IAS, 2014) ... 9

Figure 4- Average composition of the plastics fraction in EU-2012 ... 10

Figure 5- Composition of typical Printed Circuit board and the metal fraction ... 11

Figure 6- Composition of collected E-waste (Evangelopoulos, ... 12

Figure 7- Composition of critical material in collected E-waste ... 13

Figure 8- The traditional ways for recovering metals from E-scrap ... 15

Figure 9- Thermal decomposition of organic material in differ temperature ... 22

Figure 10- Required feedback energy loop for sustained burning ... 23

Figure 11- Closing the loop by recovering energy and metals through pyrolysis process ... 27

Figure 12- An image of experiment facility ... 35

Figure 13- Sketch of laboratory pyrolysis facility ... 36

Figure 14- Vertical semi-batch type cylinder reactor covered by electrical heater utilized in experiments ... 37

Figure 15- Image of Balance scale that used for samples and tar measurement vessels ... 37

Figure 16-Image of tar collection equipment ... 38

Figure 17- Weight scale used for tar measurement vessel in steam pyrolysis ... 40

Figure 18- Gas measuring vessels connected to other buckets ... 40

Figure 19- Agilent 490 micro- GC ... 41

Figure 20- Schematic drawing shows increasing temp of samples according to time ... 42

Figure 21- The GC-FID/MS analyzer used for liquid analysis ... 42

Figure 22- A separatory funnel ... 44

Figure 23- Results of Pyrolysed PCB mb by N2 and steam ... 46

Figure 24- Products of treating PCB sockets by N2 & steam pyrolysis ... 46

Figure 25- Amount of outcome gases is different according to sample & experiment type... 48

Figure 26- Comparison of gases produced by pyrolysis PCB - mb using N2 & steal ... 48

Figure 27- Comparison of gases produced by pyrolysis PCB sockets using N2 & steam... 49

Figure 28- Amount of produced oil from pyrolysis PCB- mb ... 50

Figure 29- Amount of produced oil from pyrolysis PCB- sockets ... 50

Figure 30- Comparison of amount of phenol as shared product among all experiments ... 51

Figure 31- Differ in products amount was resulted from typical & novel pyrolysis ... 52

Figure 32- Illustrate differ dominate phase in the four experiments ... 53

Figure 33- Different in amount of pyrolysis products according to experiment´s type ... 54

LIST OF TABLES

Table 1- Technique halogenated fire retardant (Diaz & Friedrich, 2015) ... 14

Table 2- Proximate composition analysis of printed circuit boards both samples ... 34

Table 3- Required time to approach elevated temp in both pyrolysis... 41

Table 4- Different agents used to prepare liquid samples before GC-FID/MS analyzer ... 43

Table 5- Experimental conditions for the two types of pyrolysis ... 45

Table 6- The difference in mass loss percentage of solid residue at 600 °C ... 47

Table 7- Mass balance of the four experiments ... 52

Table 8- Illustrates proportion of higher yield according to sample- and experiment –type ... 54

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1. INTRODUCTION

A great deal of interest is generated by combination pyrolysis as thermal process to recover energy and metals from the recycling of Electrical and Electronical Equipment (Tuncuk, Yazici, Akcil, & Deveci., 2012). Acording to previous studies, pyrolysis process has higher potential for decreasing air pollution and increasing resource recovery compared with the existing recycling techniques which help to recover a limit number of metals (Lewis, 1967). Furthermore these conventional ways are incapable in recovering critical high-tech metals like gallium (Ga), germanium (Ge) and tantalum (Ta). (Hense, Reh,

& Franke, 2015).

As a result of the revolution of informatics technology, the innovation cycles become shorter and hence high amount of Electrical and Electronic Equipment are produced over the world. Moreover the variation in user patterns, economic growth and the expansion of markets in differ parts of the world, is the reason that the useful life of these devices become shorter and thus globally increasing in quantities of E- waste is generated. (Abdul Khaliq, 2014) (Hense, Reh, & Franke, 2015)

In the industrial countries the amount of WEEE is growing faster, since the collected amount of WEEE in the EU-27 is increased in about 7 wt. % per year between 2007 and 2012 (Hense, Reh, & Franke, 2015). In Sweden the amount of collected E-waste was 697,500 tons from 2004 to 2008 with increasing about 39 % between these two years (Elretur, 2009). The production of E-waste is expected to increase by 45% in Europe between 1995 and 2020. (Abdul Khaliq, 2014).

The total global quantity of WEEE that generated in 2014 is estimated by 41.8 million metric tons (Mt) and the essential materials value of gold, copper and plastics contents in this WEEE is evaluated to be 48 billion euro (UNU-IAS, 2014).

According to previous studies, different metals, critical metals and polymers are found in collected WEEE, in addition to complex compounds which are hazardous to both environment and human health (Hense, Reh, & Franke, 2015).

That´s why huge challenges are facing proposed process of pyrolysis such as made better both of the recovery of valuable metals as well as the process control, increasing recycling capacity and better control of hazardous substances. (Diaz & Friedrich, 2015)

Printed circuit boards (PCBs) are common part in different electric systems that create for various usages (Jinhui Li, 2010). The volume of PCB in the mobile phone represent between 2% and 30% of the total weight. (Tangea Lein, 2004)

The characteristics of plastic such as toughness, easy fabrication, flexibility, physical properties, low electrical and thermal conductivity, make them in the beginning of rival materials that employed in important applications (Singh & Sharma, 2007) (Bhaskar, 2004). In this case the environmental impact is higher if these materials end up on landfills (Bhaskar, 2004).

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Negative or positive effects are associated with the way of handling E-waste (Md. Abdur Rakib, 2014).

In other words the treatment ways of E-waste has an important role to decrease the impact of pollutants elements on environment for instance dioxins that produced by burning a cable at low temperature is higher 100 times than household waste combustion (Gkaidatzis, Aggelakoglou, & Aktsoglou, 2009).

The traditional recycling routes that followed during last two decades leads to loss the precious metals and that influence the process economy (Abdul Khaliq, 2014). Some of critical metals such are Tungsten (W), Gallium (Ga), Palladium (Pd) and Cobalt (Co) are not recovered yet which means losing a secondary resource to supply these metals from E-waste (Abdul Khaliq, 2014). While base metals like Iron (Fe), Aluminium (Al) and Copper (Cu) are recovered by different routes (Hense, Reh, & Franke, 2015). The total demand in the EU to the critical metals is about 2000 ton/year that can be covered by recovery E-waste. The value of amount of Pd and Co that find in E-waste according to current market data in 2014 is equivalent to 215 Mio. €. (Hense, Reh, & Franke, 2015)

Precious metals (PMs) available in E-waste is more than that found in their primary ores for instance the recovered gold from one tonne of personal computers classified as scrap is more than that extracted from 17 tonne of gold ore. I.e.The recovery of PMs is the vital reason to encourage the recycling of all amount of E- waste (Abdul Khaliq, 2014). In this case recycling of WEEE has been chosen as beneficial way for recovering metals and saving energy compared to the extraction of virgin ore (Kantarelis, Evangelopoulos, & Yang, 2015).

Diagram (1) below shows estimated global quantity of E-waste in Mt between 2010 and 2018, according to the United Nation University report 2014, a great challenge is facing both developed and developing countries for creating the particular E-waste collection and treatment systems (UNU-IAS, 2014).

Figure 1- Estimated global quantity of E-waste between 2010 and 2018 (UNU-IAS, 2014)

33,8 35,8 37,8 39,8 41,8 43,8 45,7 47,8 49,8

0 10 20 30 40 50 60

10 11 12 13 14 15 16 17 18

E-waste (Mt)

year

GLOBAL QUANTITY OF E- WASTE

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The total amount of E-waste that declared is not included the E- waste that are discarded along with household. Which means actually higher amount of WEEE is generated over the world (Md. Abdur Rakib, 2014), and environmental problems are exacerbated (Gkaidatzis, Aggelakoglou, & Aktsoglou, 2009).

The purpose of this report is to create awareness among the importance of pyrolysis as process that can be more effective compared with current applied techniques such as incineration, acidic leaching or direct leaching for small electronic devices after mechanical separation process (Lewis, 1967). Pyrolysis is a thermo-chemical conversion process (Hense, Reh, & Franke, 2015), the thermal decomposition is happened by using the action of heat in absence of oxygen. The organic compounds yields from the process are Char, liquids, fuel gas and water in liquid or gaseous phase depends on the process final conditions. (Lewis, 1967)

Typical pyrolysis is a lab scale process and not applied in the industrial sector yet. Some of the reasons behind that is that the use of inert gas (nitrogen) required can increase the cost as well as the technological demands are hard to overcome (Jasminská, Brestovič, & Čarnogurská, 2013); Nitrogen loss its feature as inert gas after 1000 °C (Wojkiewicz, 2015). In addition to perform the process compare with the value of outcome products, the process was applied in fixed bed reactor, i.e low capacity and high cost. That´s why there is an urgent need to develop a new pyrolysis process with less cost and higher value products (Jasminská, Brestovič, &

Čarnogurská, 2013).

According to the U.S Environmental Protection Agency using recycled materials is an important manner to save energy compared to extraction of virgin materials. The diagram (2) below shows percentage of saved energy for certain metals and materials (Abdul Khaliq, 2014).

Figure 2- Saving energy for making certain elements by using recycling (Abdul Khaliq, 2014)

Aluminum copper Iron &

steel Lead Zinc Paper Plastics

1 2 3 4 5 6 7

Energy saving (%) 95 85 74 65 60 64 80

0 10 20 30 40 50 60 70 80 90 100

The percentage of energy saving from recycling compare with extraction of virgin materials

Energy saving (%)

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2. OBJECTIVES OF THIS WORK

1) Literature investigation including recycling of WEEE as well as the traditional methods that are followed nowadays in recovering metals.

2) Making a comparison between the results of using Nitrogen and Steam during thermal treatment (Pyrolysis) for two various fractions of PCBs- main body and -sockets in 600°C is the another aim of this work. The following tasks are taken into consideration:

 Experimental investigation for the two types of pyrolysis to enhance the understanding of the fundamentals of WEEE thermal conversions.

 Make mass balance for two processes of pyrolysis to determine composition of pyrolysis products.

 Experiments performed at low temperature 600°C, nevertheless the usage of steam is considered as pyrolysis.

3. WASTE OF ELECTRIC AND ELECTRONIC EQUIPMENT

WEEE includes a wide range of electric and electronic equipment with different sizes, purposes and applications, which are worthless to their owner. (Abdul Khaliq, 2014) Diagram (3) in the next page shows various devices generated globally in 2014 (UNU-IAS, 2014). All items of electrical and electronic equipment (EEE) that unwanted by their owner as well as not intend to re-use them are classified as E-waste.

In general, the term E-waste covers ten categories provided by the Directive 2002/96/EC on E-waste as in bellow (Gkaidatzis, Aggelakoglou, & Aktsoglou, 2009) (Kantarelis, Evangelopoulos, & Yang, 2015):

I. Large household appliances (Gkaidatzis, Aggelakoglou, & Aktsoglou, 2009), including cooling and freezing equipment (refrigerators, freezers, heat pumps and air conditioners (Abdul Khaliq, 2014) as well as washing machines are also the typical equipment) (Kantarelis, Evangelopoulos, & Yang, 2015).

II. Lighting equipment (Gkaidatzis, Aggelakoglou, & Aktsoglou, 2009) (Kantarelis, Evangelopoulos, & Yang, 2015). Typical equipment comprises straight fluorescent, fluorescent lamps, compact fluorescent lamps, LED lamps (light-emitting diode) and high intensity discharge lamps.) (Abdul Khaliq, 2014)

III. Consumer equipment and photovoltaic panels (Gkaidatzis, Aggelakoglou, & Aktsoglou, 2009) (Kantarelis, Evangelopoulos, & Yang, 2015).

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(Typical equipments are copying equipment, photovoltaic panels and clothes dryers (Abdul Khaliq, 2014)

.

Added to these Products and equipments for the purpose of recording, reproducing sound or images (Kantarelis, Evangelopoulos, & Yang, 2015).

IV. Small household appliances (Gkaidatzis, Aggelakoglou, & Aktsoglou, 2009). Typical equipment microwaves, toasters, electric kettles, radio sets, small electrical and electronic tools and electric shavers (Abdul Khaliq, 2014). In addition to appliances that are used for sewing, knitting, and weaving (Kantarelis, Evangelopoulos, & Yang, 2015).

V. IT telecommunication equipment (Gkaidatzis, Aggelakoglou, & Aktsoglou, 2009).

Typical equipment are comprises mobile phones and televisions, personal computers, pocket calculators, telephones and printers (UNU-IAS, 2014) (Kantarelis, Evangelopoulos, & Yang, 2015) (Abdul Khaliq, 2014).

VI. Electrical and electronic tools, stationary industrial tools are accepted from this category (Gkaidatzis, Aggelakoglou, & Aktsoglou, 2009) As well as tools for welding, shearing, screwing and nailing (Kantarelis, Evangelopoulos, & Yang, 2015).

VII. Automatic dispensers (Gkaidatzis, Aggelakoglou, & Aktsoglou, 2009). Include all appliances that used in this sector (Kantarelis, Evangelopoulos, & Yang, 2015).

VIII. Medical appliances (Gkaidatzis, Aggelakoglou, & Aktsoglou, 2009). Devices that used in medical employment (Kantarelis, Evangelopoulos, & Yang, 2015).

IX. Toys and sports equipment (Gkaidatzis, Aggelakoglou, & Aktsoglou, 2009). Including all electrical toys and video games (Kantarelis, Evangelopoulos, & Yang, 2015).

X. Monitoring and control devices (Gkaidatzis, Aggelakoglou, & Aktsoglou, 2009). Different appliances that used in household and industrial installations such as adjusting devices, heating regulators, smoke detectors, and measuring weight (Kantarelis, Evangelopoulos,

& Yang, 2015).

Figure 3- Classification of E-waste generated globally in 2014 (UNU-IAS, 2014)

Lamps Screens Small IT Small

equipment

Large equipment

Cooling &

freezing equipment

1 6,3 3 12,8 11,8 7

0 2 4 6 108 12 14

Amount in MT

E-waste type

Amount of global E-waste 2014

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3.1 Polymers High Complex Fraction

The complex fraction of polymers that can be associated with environmental and health hazards (Richards, 2015) is consist of different kinds of plastic components such as polycarbonate-ABS (PCABS), polystyrene (PS), polyethylene (PE), acrylonitrile-butadiene-styrene (ABS), styrene acrylonitrile (SAN), polyvinyl chloride (PVC) or ethylene-propylene-diene monomer (EPDM) as in diagram (4) below which shows collected WEEE in Europe for year 2012 contains plastics in about 22 wt. % of the total amount (Hense, Reh, & Franke, 2015). The polymeric matrix also includes quantities of halogen compounds which employed as flame retardants (Diaz & Friedrich, 2015).

Figure 4- Average composition of the plastics fraction in EU-2012 (Hense, Reh, & Franke, 2015)

3.2 Printed Circuit Boards

PCBs are a common part in all Electronics Equipment and have the most complex fraction of the waste electrical and electronic equipment.

Production of PCBs is increased over the past several decades according to the rapid development and expansion in the electronic industry (Jinhui Li, 2010). For that reason the importance of recovering PCBs is increased in time hence the volume of PCBs is growing worldwide from 90,000 metric tons (mtons) in 2003 up to 156,000 mtons in 2009 (Tangea Lein, 2004).

PCBs scraps are generally classified into three groups according to type of precious metal content. They are indicated in H (high-grade), M (medium-grade) and L (low grade) scrap (Goosey & Kellner, 2002):

1- Low grade material (L): include television boards, laminate Offcuts and power supply units that structured of heavy ferrite transformers and large aluminum heat sink.

8,9

6 , 3 1

3, ,7 1

1 , 1

9 0, 0,6 0,5

, 03

1,2

Composition of the plastics fraction in collected E-waste

ABS PS PCABS PE PVC PP SAN PC EPDM

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2- Medium grade scrap (M): high precision apparatus that content precious metal with little aluminum.

3- High grade material covers high precious metal content boards, optoelectronic devices, integrated circuits (ICs) with gold-containing and special components such as gold pin boards, palladium pin boards and thermally coupled modules from mainframes (Goosey & Kellner, 2002).

According to the recycling process, PCBs are divided into two various fractions, the main body of the printed circuit boards (PCBs mb), this part contains metals used for connecting the different components of the PCBs, plastic resign used to enhance the strength of the PCBs and the ceramic base of the PCB (Evangelopoulos, 2015). The high conductivity of tin, silver and copper is the reason for usingthem in coating the PCBs (Abdul Khaliq, 2014).

The second fraction is plastic sockets (PCBs sockets) which is used for connecti ng the independent elements and components of the computers” conductors, CPU and ram memory” (Evangelopoulos, 2015). Pyrolysis is used as a pre-processing method for both fractions of PCBs to allow a better separation of the metallic and non-metallic fraction. (Diaz & Friedrich, 2015)

The waste of PCBs consist of various hazardous components in addition to the precious metals that is why the treatment and recycling of PCBs by using traditional methods cause a negative impact for the environment (Mankhand, Singh, Gupta, & Das, 2012). The various in types of electric and electronic appliances, manufacturers and ages of these devices have the main role for the differences in composition of PCBs. The typical PCBs as in diagram (5) below includes 40% of metals, 30% of organics and 30% ceramics (Luda, 2011). In addition the metallic fractions in PCBs are being made up of about 16% copper, 4% solder (tin-lead), 2% nickel along with 3% iron and ferrite, precious metals:

0.03% gold, 0.05% silver, and 0.01% palladium, while tantalum are usually linked with plastic cover or ceramic (Diaz & Friedrich, 2015) (Luda, 2011).

Figure 5- Composition of typical Printed Circuit board and the metal fraction (Abdul Khaliq, 2014) (Luda, 2011)

% 40

% 30

Printed circuit boards contents

metals plastics ceramics 0% 5% 10% 15% 20%

Copper Solder Nickel Iron Gold Silver Palladium

Composition of metal fraction in PCB

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3.3 Compositions of WEEE

Different metals, critical metals and polymers are found in collected WEEE that is profitable when they are recycled, in addition to complex compounds which are hazardous for both environment and human health (Hense, Reh, & Franke, 2015).

The type and age of the electronic equipment lead to change chemical composition of E-waste (Gkaidatzis, Aggelakoglou, & Aktsoglou, 2009). Diagram (6) below illustrates the average composition of the collected WEEE according to Swedish Environmental Protection Agency, 2011 (Evangelopoulos, Efthymios, & Yang, 2015).

Figure 6- Composition of collected E-waste (Evangelopoulos, Efthymios, & Yang, 2015)

The analysis of E-waste components shows that different compounds are present such as plastic and other organic polymers as well as the metals like lead, iron, copper, aluminium, nickel, cadmium, chromium, selenium etc. Some electronic components such as [resistors, transistors] were found to be suitable for reuse and other metals can be converted by separation from solid residue (Antrekowitsch &

al, 2006).

Metallic fraction in WEEE includes a mixture of different metals; Diagram (7) in the next bage shows the proportion of these metals as well as plastic fraction and amount of refractory oxides that found in collected E-waste (Gramatyka, Nowosielski, & Sakiewicz., 2006).

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Figure 7- Composition of critical material in collected E-waste (Gramatyka, Nowosielski, &

Sakiewicz., 2006)

3.4 Flame retardants

Problems that occur in recycling process of E-waste are related to flame retardants which represent about one quarter of E-waste plastics. One third of quantity amount of these flame retarded are based on halogens. The amounts of halogens Br & Cl in plastic fraction represent about 10.9 wt. % and 57.8 wt.

% respectively of the total plastic weight of WEEE.

Different toxic substances such as poly-brominated dibenzo dioxins and furans (PBDD/F), polyhalogenated aromatic hydrocarbons (PHAH) and polycyclic aromatic hydrocarbons (PAH), are created by degradation of those halogenated flame retardants (Hense, Reh, & Franke, 2015).

The use of poly-brominated biphenyls (PBB) and poly-brominated diphenyl ethers (PBDE) as flame retardant in producing EEE are limited in Europe according to the Directive 2011/65/EU. Despite many materials which mainly phosphorous- or nitrogen -based are developed to replace hazardous substances, however the fabrication of halogenated flame retardants is growing (Hense, Reh, & Franke, 2015).

The use of flame retardants is necessary and the reason is when solid polymers are heating, thermal degradation is currying out which is equivalent to burning of non-organic materials. Smaller molecules in the gas phase are resulted from this degradation;

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This reaction would be exothermic in presence of oxygen. The purpose of adding flame retardants elements to polymer is hydrogen halides are released in gas phase and thus it captures the active radicals and replaces them by less active halogen radicals. This procedure leads to regenerating of hydrogen halides as shows in table (1) below (Diaz & Friedrich, 2015):

Table 1- Technique halogenated fire retardant (Diaz & Friedrich, 2015)

𝑓𝑙𝑎𝑚𝑚𝑎𝑏𝑙𝑒 𝑔𝑎𝑠𝑒𝑠

?→𝐻°+𝑂𝐻°→ 𝐻𝑒𝑎𝑡

Halogenated fire retardant  HXg X=Br, Cl HX + H°  H2 + 𝑋° flame poisoning

HX + OH° H2O + °𝑋 flame poisoning RH + 𝑋°  𝑅°+ HX regeneration

Increasing the temperature leads to thermal decomposition of halogenated flame retardants (Hense, Reh,

& Franke, 2015) and form toxic PBDD/F from the poly-brominate diphenyl ethers (DBPE and TBPC) whichform a part ofthe additive flame retardants (Diaz & Friedrich, 2015), that causes the formation of highly toxic hydrocarbons and dioxins (Hense, Reh, & Franke, 2015).

The substrate and pyrolysis conditions decide if halogens Br and Cl plus antimony are collected in pyrolysis products (gas, oil and solid residue). (Diaz & Friedrich, 2015)

Inorganic compounds like antimony trioxide (Sb2O3) and magnesium hydroxide Mg(OH)2, or aluminium hydroxide Al(OH)3, are often incorporated with the halogenated flame retardants. For example, catalysts for recombination of hydroxyl, hydrogen and oxygen are formed by the decomposition of Sb2O3. In both the condensed and the gaseous phase of a flame, (Sb2O3) is working as synergist (Hense, Reh, & Franke, 2015).

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4. TRADITIONAL METALLURGICAL PROCESSES FOR THE RECOVERY OF METALS FROM E-WASTE

At present time industrial processes of recycling of E-waste are divided into two main routes pyro- metallurgical- and combined pyro- hydrometallurgical -process (Navazo, Méndez, & Peiró., 2013).

Energy needed to recover metals by using pyro-metallurgical and combined pyro-hydrometallurgical is 7,763 and 7,568 MJ/tone of mobile phones, respectively. The both methods are consumed almost the same amount of energy (Navazo, Méndez, & Peiró., 2013). Various treatments are proposed for recovery of metals from WEEE, because this type of west are heterogeneous and complex (Tuncuk, Yazici, Akcil,

& Deveci., 2012).

Recycling facilities are choosing carefully with highest level of development in order to recover precious metals as well as to isolate dangerous materials professionally. In this case choosing a suitable recycling facility leads to close the loop of precious metals in addition to minimize the environmental impact that appeared from large quantities of E- waste (Abdul Khaliq, 2014). Diagram (8) below shows traditional methods that followed in recovery of metals from E- waste (Tuncuk, Yazici, Akcil, & Deveci., 2012).

To take out pure metals from BMs, better to combine both of pyro- and hydrometallurgical process, starting with pyro. where partial recovery and purity take place then followed by hydro and electrochemical methods (Abdul Khaliq, 2014).

Figure 8- The traditional ways for recovering metals from E-scrap (Tuncuk, Yazici, Akcil, & Deveci., 2012)

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4.1 WEEE Standard Mechanical Pre-processing

Mechanical pre-treatment step is needed for the recycling of valuable metals from E-scrap by

hydrometallurgic methods (Tuncuk, Yazici, Akcil, & Deveci., 2012). Recycling and recovering metals that the E- waste contains requires special pre-processing techniques because of the diversity and complexity of WEEE materials (Diaz & Friedrich, 2015).

In general, Through recycling of E-waste mechanical separation occurs to segregate Iron, Aluminum, and Plastic parts, this operation leads to higher a risk of losing the PMs, because the PCBs are designed that PMs is fixed with non-ferrous metals and plastics. In this case, better recovering of PMs obtains when pieces of Fe, Al, and plastics are taking with the copper fraction.

Higher environmental efficiency creates when the mobile phones is direct smelting comparing with fragmented mobile phones components. ( i.e smelt PCBs in furnace directly will leads to increase the recovered PMs because PMs are mostly treated in copper smelters, moreover combustion of plastic will supply energy that will replace coke partially in addition this will be a good reason to recycle Ewaste and in this case the loop of metal will be closed. Take into account separating batteries in both cases to release hazardous materials that emit from batteries (Abdul Khaliq, 2014).

In other words it is not favourable to apply standard mechanical pre-processing in case of recovery precious metals from PCBs because under strong shredding process these metals are converted to dust (Diaz & Friedrich, 2015).

During mechanical processing the metals fraction is separated from E-waste. To regain the residual metals, the major processes such as Hydro- Pyro- and electro- metallurgical methods are utilized after mechanical separation (Abdul Khaliq, 2014). Standard Mechanical Pre -processing is doing according to the following steps:

1- First step is dismantling and sorting processes (Kantarelis, Evangelopoulos, & Yang, 2015) is covered of E-waste sorting and separating into various fractions such as hazardous elements (capacitors, batteries, LCDs, PCB), plastic, metals (iron, aluminum, copper, etc.) (Diaz &

Friedrich, 2015) (Tuncuk, Yazici, Akcil, & Deveci., 2012). This step is important to improve recycling capacity, increase of economic potential of E-waste by pre-concentrating of precious metals as well as to get rid of hazardous components (Tuncuk, Yazici, Akcil, & Deveci., 2012).

2- Shredding and Grinding (Kantarelis, Evangelopoulos, & Yang, 2015) or Size reduction stage to tear and fragment E-waste by using shredders, mills (ball or hummer) (Diaz & Friedrich, 2015) (Tuncuk, Yazici, Akcil, & Deveci., 2012). The size of shredded E-waste is generally below 5 mm or 10 mm (Kantarelis, Evangelopoulos, & Yang, 2015); the second step is performed to collect metal bearing components before metal recovery process (Tuncuk, Yazici, Akcil, &

Deveci., 2012). Type of recovery route determines the extent of size reduction in second stage.

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Hydro-metallurgical method is probable to use for fine size reduction to get efficient recovery of metals from E-waste. On the other hand pyro-metallurgical is appropriate for relatively coarse metals (Tuncuk, Yazici, Akcil, & Deveci., 2012).

3- Physical separation or mechanical separation is subsequent stage where depends on principle that various materials have differ physical properties (Diaz & Friedrich, 2015) (Tuncuk, Yazici, Akcil, & Deveci., 2012). The physical characteristics such as shape, density, weight, magnetic characteristics and electric conductivity are performed in the E-waste sorting during this step (Kantarelis, Evangelopoulos, & Yang, 2015). The traditional methods that used for separation of material are (Diaz & Friedrich, 2015) (Tuncuk, Yazici, Akcil, & Deveci., 2012):

a) Magnetic separation to separate ferrous parts from nonferrous materials.

b) Eddy current separation, this route is used to release nonmagnetic metals.

c) The third method step is gravity or density separation to separate heavier materials from lighter.

4.1.1 Boliden

Extraction of metals from WEEE has been done by using the traditional routes through the Rönnskär Smelters and the Kaldo furnace at Boliden, Sweden. (Abdul Khaliq, 2014) The process that followed in Boliden is pyro- metallurgical process, which includes a smelter, and converter, then anode furnace, and electrolytic refining (Navazo, Méndez, & Peiró., 2013). During process is used differ scrap consist of electrical industry and nonferrous, that added in different stages according to the purity and the final product requirement (Abdul Khaliq, 2014).

The Kaldo furnace is utilized to combust PCB and nonferrous fraction of WEEE while the electric smelting furnace is used to treat the copper rich concentrate fraction of crushed WEEE (Kantarelis, Evangelopoulos, & Yang, 2015). Drying, roasting, smelting, converting and refining are the main steps in the Rönnskär Smelter (Abdul Khaliq, 2014).

The required process energy is gained from degradation of plastic. A mixture of elements such as Cu, Ag, Au, Pt, Pd, Ni, Se, and Zn, are produced through the Kaldo furnace (Kantarelis, Evangelopoulos,

& Yang, 2015).

Utilized farther treatments are done through the anode casting plant, the electro-refinery, and the precious metals plant to recover these elements (Kantarelis, Evangelopoulos, & Yang, 2015). More than 100,000 tons/year of waste (including E-waste) are recycled at Boliden. Scrap contain high copper content is fed into converter directly, while in Kaldo furnace is fed E-waste with low grade. Kaldo furnace feed are mix lead concentrate and E- waste, they combusted with the supply of oxygen and oil (Abdul Khaliq, 2014).

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4.2 Pyro- metallurgical process (Thermal treatment)

Pyro- metallurgical process has been utilized as traditional technology for recovering metals from different waste materials in last two decades (Abdul Khaliq, 2014). This route consists of pre-treatment of E-waste (Tuncuk, Yazici, Akcil, & Deveci., 2012) then incineration and smelting of enriched metal by using blast furnace or plasma arc furnace (Gramatyka, Nowosielski, & Sakiewicz., 2006) to obtain copper bullion, (Tuncuk, Yazici, Akcil, & Deveci., 2012) thereafter to get high purity copper the last product undergo to electrolytic refining and then collect slims from copper electrorefining.

While recovering of precious metals such as Ag, Au, Pt, Pd, Ru, Ir and Rh is done after that (Tuncuk, Yazici, Akcil, & Deveci., 2012), the process is followed by further refining through drossing, sintering, melting and high temperature reactions in a gas face (Gramatyka, Nowosielski, & Sakiewicz., 2006) in order to reduce environmental problems that creates from halogenated flame retardants which utilized in production of PCBs (Tuncuk, Yazici, Akcil, & Deveci., 2012).

The process includes a combustion in a furnace to get rid of plastics and other organic materials which are converted to volatile compounds or slag in refractory oxides, in addition to generate a solid residue with concentrate metal in it. Only alloys are obtained by pyro- metallurgical process (Havlik, o.a., 2010).

The strong oxidation tendency of Aluminum is the reason to ending it in slag when the metallurgical process of copper is used in recovering metals. In this case recovery of Al is not viable because it should recovered from Cu before melting by using mechanical separating ways, to prevent losing Al element with slag as oxides (Diaz & Friedrich, 2015).

Treatment of E-waste by using pyro- metallurgical process can be considered appropriate where organic constituents are exploited to replace coke that used as fuel and reducing agent (Tuncuk, Yazici, Akcil, & Deveci., 2012). The energy recovery by incinerating of plastic in a mobile phone to replace fuel is about 10% and the residue is utilized in metal recovery process (Tangea Lein, 2004).

Degradation of halogens that form a part of plastics in E-waste occurs at high temperature. In this case the presence of Oxygen causes a high temperature combustion which is a reason of hazardous gaseous emissions during this process (Havlik, o.a., 2010).

The releasing of valuable metals in Pyro- metallurgical process achieved by smelting in furnace at high temperature compare with hydrometallurgical process which is done through leaching by using strong acids, crushing or grinding. (Abdul Khaliq, 2014)

4.2.1 Disadvantages of pyro-metallurgical process

• Not easy to recover Iron and Aluminum because they transform to oxides and change to slag phase (Abdul Khaliq, 2014) (Kantarelis, Evangelopoulos, & Yang, 2015).

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• Particular mechanisms of isolating hazardous are required to reduce environmental contamination that take place by emission of hazardous. During smelting of feed materials generate dioxins (Kantarelis, Evangelopoulos, & Yang, 2015), when halogenated flame retardants in plastics are burned (Abdul Khaliq, 2014). One tone of shredded mobile phone waste during smelting process generates approximately 440 kg emission. Organic and plastic matters represent 44% of E- waste which means high amount of hazardous (Navazo, Méndez, & Peiró., 2013). Therefore not possible to recover plastic by using pyro- metallurgical process (Abdul Khaliq, 2014).

• Pyro-metallurgical route is applied in large scale for economy point of view because the process required large facilities such as integrated smelters (Navazo, Méndez, & Peiró., 2013).

• Fine dust of E- waste non- metallic fraction is burning immediately before reaching the metal bath in blast furnace. To employ energy content and reduce health risk created by fine dust particles, forming pellets by agglomerating these fractions is necessary (Abdul Khaliq, 2014). Which influences the total cost.

• The risk of losing PMs (Au, Ag and Pd) from the base metals BMs (Cu, Al, Ni, Sn, Zn,Pb and Fe) occurs by increasing the volume of slag in furnace that generated by feed material from ceramic components (Abdul Khaliq, 2014).

• The feedstock (E- waste) are compound and that causes difficulty to manage the process of smelting and refining (Abdul Khaliq, 2014).

4.2.2 Copper smelting route

Solid residue outlet from combinations of pyro- and hydrometallurgical processes is applied in copper smelter in order to recover copper cathodes as the main product. Copper smelters are used in Boliden, Sweden to recover precious metals ((CRI), 2014). E-waste recycling is dominating by copper smelting route because PMs are collected in copper matte or black copper (Abdul Khaliq, 2014). The recycle and extract PMs from E-waste occur by utilizing primary and secondary copper smelting routes. Lead smelting routes is generated toxic gases, which mean copper smelting is more environmentally friendly.

In this case the facilities of copper smelting can put near populations that is enhanced the recycling economy by reducing the cost of WEEE transportation (Abdul Khaliq, 2014). Recovering of PMs occurs in this process where they segregated in slims by using conventional electrorefining process (Abdul Khaliq, 2014). The input of smelting process is copper ore, WEEE and copper scrap ((CRI), 2014) Primary copper smelting or called sulfur- based route, is utilized to produce 40% of copper matte and 98.5% of blister copper.

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At the end to produce pure copper using fire refining of blister copper. Secondary copper smelting or called the black copper route, take place through reduction process form crude copper and used a converter to refine it by oxidation.

Secondary copper route is important because there used oxidation to remove high levels of impurities consist of Iron (Fe), Zinc (Zn), and Tenn (Sn). Secondary smelting process contain reduction and oxidation cycles. The separations of impurities into vapor phase occur to settle them later in the off gas (Abdul Khaliq, 2014).

4.3 Hydro- metallurgical process

Extraction of Au, Ag, Cu, Pb, and Zn from WEEE is done by traditional technologies of Hydrometallurgical process. Processing of E- waste includes two main stage of extraction by using leaching, first the base metals are extracted and then valuable metals. Hydrometallurgical process steps are starting with mechanical pre-treatment in order to granulate the total fraction (Kantarelis, Evangelopoulos, & Yang, 2015) of E- waste since plastic or ceramic materials cover the metallic elements in PCBs (Tuncuk, Yazici, Akcil, & Deveci., 2012), leaching of wanted dissolution of metals by using appropriate filter (Tuncuk, Yazici, Akcil, & Deveci., 2012) (Abdul Khaliq, 2014) to isolate the interest metal from the solution (Gramatyka, Nowosielski, & Sakiewicz., 2006).

The utilized acid or caustic leaching solvents are mainly HCl, NaOH, H2SO4 and H2O2 or HNO3. In order to increase the metal yield, a small grain size is required in this process (Gramatyka, Nowosielski,

& Sakiewicz., 2006). Followed by purification through separating the pregnant solution and removing impurities (Abdul Khaliq, 2014) (Tuncuk, Yazici, Akcil, & Deveci., 2012), where the enrichment of metal content is a result. Then using the solvent extraction to separate (Abdul Khaliq, 2014), and to concentrate this metal (Gramatyka, Nowosielski, & Sakiewicz., 2006) followed by adsorption and ion exchange enrichment process (Abdul Khaliq, 2014).

Extra benefits of hydro- compare with pyro- metallurgical are getting more exact, expectable results, and easy to control the process, (Abdul Khaliq, 2014) no hazardous gases or dusts that result from incinerating of E- waste which means less environmental impact,add to that the process is applied in small scale (small facilities) with low capital cost while leads to high metal recoveries (Tuncuk, Yazici, Akcil, & Deveci., 2012).

The leaching solvent that used to recover PMs from their primary ores is consisting of halides, cyanides (CN), thiourea (CH4N2S) and thiosulfates (S2O32- ). Metals dissolution from their primarily ores are controlled by amount of PH, Temperature, and stirring of the process (Abdul Khaliq, 2014).

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To recover PMs from E-waste a hydro metallurgical method was suggested by previous study, utilizing Aqua regia (HNO3 + 3 HCl) as leaching agent with choosing ratio of metals to leachant is 1 / 20. During the first stage recovered 98% of Silver and 93% of Palladium. To extract gold applied liquid - liquid extraction method with toluene to recover 97% of gold (Abdul Khaliq, 2014).

4.3.1 Disadvantage of hydrometallurgy

• Recovering in all hydrometallurgical methods go slow and thus takes longer time (Abdul Khaliq, 2014). Relatively high voltage (3 V) is needed which means high electricity is required (Navazo, Méndez, & Peiró., 2013), that influence the recycling economy (Abdul Khaliq, 2014), in addition to the overall recycling scheme (Kantarelis, Evangelopoulos, & Yang, 2015).

• To obtain an efficient dissolution, takes longer time to reduce feedstock size by applying mechanical process on E- waste. (Abdul Khaliq, 2014) Furthermore 20% of precious metals are lost during this process (Kantarelis, Evangelopoulos, & Yang, 2015).

• The extracting of gold from E- waste need special equipment that made of Al and rubber because the process is performed by using a Halide leaching. Where strong corrosive acids and oxidizing conditions are applied, difficult to use ordinary metals. (Abdul Khaliq, 2014)

• High safety standards should take into account when using a hazardous leachant such as Cyanide. Problems of environment contamination and human health are causing by this leachant. (Abdul Khaliq, 2014) (Kantarelis, Evangelopoulos, & Yang, 2015).

• The overall recovered metals are susceptible to loss during dissolution and later steps. (Abdul Khaliq, 2014) and that also influence the process Economist (Kantarelis, Evangelopoulos, &

Yang, 2015).

4.4 Electrochemical treatment

At the end utilized electro-refining or chemical reduction process (Abdul Khaliq, 2014). The method is done in aqueous electrolytes or in molten salts to refine the metal that recovered via hydro -metallurgical treatment (Gramatyka, Nowosielski, & Sakiewicz., 2006). The small voltage that´s needed in the process is from 0,2 to 0,3 V (Navazo, Méndez, & Peiró., 2013).

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5. THERMAL DEGRADATION OF PLASTICS

5.1 The Mechanism of Thermal Degradation of plastics

Flammable volatiles are generated through chemical processes while decomposition and variation of material burning characteristics for instance melting and charring is considered as physical changes (L.

& Hieschler, 2002). Diagram (9) illustrates organics suffer various thermal cracking at high temp.

Figure 9- Thermal decomposition of organic material in differ temperature (Diaz & Friedrich, 2015)

Through the pyrolysis process, mechanism of degradation (thermal cracking) is done by the following four steps:

I) End-chain scission (depolymerisation): Consider as the main method for plastic pyrolysis (Diaz & Friedrich, 2015), the split of polymer occurs at the end groups consecutively and the corresponding monomers are yielding as a result of the breaking up (Buekens & Huang, 1998) (Diaz & Friedrich, 2015). In this step input energy as a result from heat is a reason to loss hydrogen atom from the polymer chain which cause unstable polymer (Zeus &

technical whitepaper, 2005).

II) Random-chain scission. Fragments of unequal length are formed when the polymer chain is split up (Buekens & Huang, 1998)(Diaz & Friedrich, 2015) randomly along the chain (Diaz

& Friedrich, 2015).

III) Chain-stripping. Different reactions are involved in this step (Zeus & technical whitepaper, 2005). A Cracking product and charring the polymer are resulted when side group and reactive substitutes are eliminated from the polymer chain (Buekens & Huang, 1998) (Diaz

& Friedrich, 2015).

IV) Cross-linking. The cross link and polymer embrittlementare a result when two polymer chain become linked together (Zeus & technical whitepaper, 2005). Increasing the temperature, a chain network is formed for thermosetting polymers (Buekens & Huang, 1998) (Diaz & Friedrich, 2015).

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Gaseous fuel vapours that generated by the chemical decomposition of solid material, can burn above the solid material and cause thermal decomposition. Self- sustaining process can approach when the production of volatile or gaseous fuel vapour is continued as well as the burning of material is uninterrupted, in this case a sufficient heat from burning gases feed back to the material is necessary (L.

& Hieschler, 2002).

Flammable volatiles are generated when heat is transferred to the polymer. The reaction between the oxygen in the air above the polymer and volatiles causes heat generation. The process continues when a part of generated heat is transferred back to the polymer (L. & Hieschler, 2002). Diagram (10) below is a schematic sketch illustrated that:

Figure 10- Required feedback energy loop for sustained burning (L. & Hieschler, 2002)

5.2 Gasification

Thermal degradation Process of material that takes place in exists of air, oxygen and steam as oxidizing medium. The purposes of gasification process are: (Richards, 2015)

o An intermediate gas is produced which has many usages.

o Carbon conversion degree is increased during gasification.

To perform stoichiometric combustion (the ideal combustion process where fuel is burned completely) during gasification process, one important thing is keeping the equivalent ratio at the right level to avoid excess oxygen in the outgoing gases when producing CO2 and H2O from incoming fuel.

The equivalent ratio is the amount of oxygen supplied in relation to what is needed for a theoretical combustion (Richards, 2015).

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To increase the incoming fuel temperature and to prevent the happening of endothermic reactions, the needed heat is generated by exothermic reaction or supplied externally.

When the material is heated, pyrolysis process occurs first regardless the present of an oxidizing medium (Richards, 2015).

In case of using polymers as feedstock, basically the original material of solid polymer is volatile. For easily vaporized smaller molecules are needed and they maintained by breaking down large molecules.

A number of differ chemical species form the smaller molecular fragments with differ equilibrium vapour pressure for each fragment. The vaporization of lighter molecular fragments are occurred immediately after their creation, while for some time will stay the heavier molecules in the condensed phase (solid or liquid). During this time further decomposition of these heavier molecules are taken place to create lighter fragments.

Virtually the solid residue will not remain when polymers decompose completely. In case when solid residues are left, not all the original fuel becomes fuel vapour. The solid residue divided into char (carbonaceous), inorganic or a mixture of the two. The physical properties of original materials and their chemical composition are the main factors that influence the rate, mechanism, and product composition of thermal decomposition processes (L. & Hieschler, 2002).

5.2.1 Advantages of gasification

 Liquid product (oil) is more suitable for using in Otto engine, gas turbine, and Rankine cycle, since it produced during second stage which takes place with a low presence of contaminants.

 Lower emission levels can be reached.

 Applying high temp is the reason to produce less amount of slag.

 As a result of the above, minimized the possibility to form toxic substances (such as dioxins and furans) (Richards, 2015).

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5.3 Pyrolysis technology

Chemical and thermal reaction utilizes to degrading organic materials (Hense, Reh, & Franke, 2015) in absence of oxygen with ratio of air content in the system to the total stoichiometric combustion require air 𝜆 is equal to zero (Diaz & Friedrich, 2015). Inert gas for instance nitrogen is used in typical pyrolysis in order to create a non-oxidative atmosphere (Jasminská, Brestovič, & Čarnogurská, 2013). Pyrolysis leads to separate valuable metals from plastic matrix as well as produce gaseous and liquid fuel at the same time (Hense, Reh, & Franke, 2015).

In general Pyrolysis is carried out at temperature range from 250 °C to 1100 °C, and can be classified into three categories according to the temperature during running the process as follows (Jasminská, Brestovič, & Čarnogurská, 2013):

1- Low temperature pyrolysis, process temperature is from 250 °C up to 500 °C.

2- Middle temperature pyrolysis, reaction occurs when temperature between 500 °C and 800 °C.

3- High temperature pyrolysis, when reaction temps higher than 800 °C.

The pyrolysis process employs to degrading organic materials in absence of oxygen (Hense, Reh, &

Franke, 2015) at temperature in between 450°C to 750 °C (Tangea Lein, 2004). Applying pyrolysis in recycling plastics leads to convert solid organic into solid cokes and gaseous components. Condensable gases will transfer into liquid (oil state) and non- condensable gases are form gaseous components (Diaz

& Friedrich, 2015).

Primary output products of pyrolysis process are char coal, oil and gas. There are three intervals during pyrolysis process (Jasminská, Brestovič, & Čarnogurská, 2013):

1- Endothermic process at temp up to 200 °C, where water steam is formed while samples materials are being dried.

2- Dry distillation occurs between 200°C and 500 °C when side chains are split off from high-molecular organic matters and leads to convert macromolecular structures into liquid and gas organic products in addition to solid carbon.

3- Temp range of last interval is from 500°C up to 1200 °C to fission and transform the second interval products and create gas from differ compounds such as H2, H2S, CO, CO2, CH4, C2H4, C3H6 and other light hydrocarbons in addition to non-condensed organic elements .

At low temperature pyrolysis is endothermic and becomes exothermic at higher temperature. The sum of the heating value in the original material and the added energy during pyrolysis process represents the pyrolysis heating value (Lewis, 1967).

According to the desired product, the technology of pyrolysis is divided into slow and fast pyrolysis (Richards, 2015).

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5.3.1 Slow pyrolysis:

Low heating rate with a long residence time is applied in this process for the solid material in order to guarantees a mild treatment that causes converting of low amount of material into gas phase. The process results in a solid char contain a higher amount of oxygen and hydrogen.

Low energy is required when low temperature process at around 500 °C is applied, as well as during gas de-volatilization, less violent reaction than in high temperature process.

The gas phase contains fewer amounts of tars when applying the process at higher temperature above 700 °C as well outcome char is more rich carbon.

Both the low- and high-temperature processes start with pyrolysis as first stage. First the separating of solid residue occurs directly after pyrolysis and then treating of solid takes place separately from other products. While in the later continue applying higher regular temperature on the solid that also separated from gas phase to guarantee the complete melting.

Rotary furnace is suitable to carry out the slow pyrolysis and in case of utilizing a tube furnace, an external force is necessary for better transportation

(Richards, 2015)

.

5.3.2 Fast pyrolysis:

Fast pyrolysis is applied at 510°C in order to obtain the highest liquid yield, thereafter the yield is decreased by lifting up the temp.

Actually there are no large-scale workshops that employed in order to focus on producing oil pyrolysis.

In this case only slow pyrolysis is working at this time (Richards, 2015).

5.3.3 Pyrolysis Factors:

Pyrolysis outcome composition of the solid, liquid, and gas products and final yield, (Kantarelis, Evangelopoulos, & Yang, 2015)(Lewis, 1967) as well as amount of emission, are influenced by number of variables (Hense, Reh, & Franke, 2015).

 Chemical composition of material (Lewis, 1967)  the composition of raw materials as well thermal decomposition of polymer influence the outcome from pyrolysis process (Kantarelis, Evangelopoulos, & Yang, 2015).

 Pyrolysis temperature and heating rate (Lewis, 1967)  Formation of smaller molecules frequently take place at higher- heating rates and –temperatures (Kantarelis, Evangelopoulos, &

Yang, 2015).

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 Residence time  Gas yields, coke, and tar formation are increased during secondary reaction at longer residence time.

 Reactor type  Type of reactor has major role in setting the rate of heat and mass transfer as well the residence time of the products.

 Pressure  less coke and heavy ends formation are created at lower pressure as a result of reducing the condensation reactions between the reactive vapours (Kantarelis, Evangelopoulos,

& Yang, 2015).

5.3.4 Advantage of pyrolysis

 The process has a max thermal efficiency, That related to combustion of fuel gases is done in a separated chamber from the E-waste, which result in a complete combustion at high temp and low excess oxygen (Lewis, 1967)

 The three products of the process are: Solid residue includes concentrated metals, liquid tar and volatile metal compounds are stayed in the gaseous fraction. (Havlik, o.a., 2010) I.e. thermal treatment of E waste leads to reduce the mass and volume of WEEE and hence reduce landfill space, and the environmental load will be decreased by demolition the organic contaminants and saving resources (Richards, 2015).

Figure 11- Closing the loop by recovering energy and metals through pyrolysis process (Evangelopoulos, Efthymios, & Yang, 2015)

 Pyrolysis is a promising method to recover the critical metals that are not recovered yet such as gallium (Ga), germanium (Ge) and tantalum (Ta) in addition to that, the pyrolysis is used to generate energy through producing high calorific gases and liquids (Hense, Reh, & Franke, 2015).

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 Another advantage of pyrolysis is the liquid products can be utilized for chemical or power industry (Abdul Khaliq, 2014). In other words, enable an energetic utilization of organic materials (Hense, Reh, & Franke, 2015)

 During this thermo-chemical process contained metals are not oxidized due to the inert atmosphere (Hense, Reh, & Franke, 2015). I.e. they stay in their original form where they were in E-waste. (Havlik, o.a., 2010)

 Since the two phases (liquid oil & gaseous output) have homogeneous composition, the thermal energy that formed by these phases is performed easily and in better environmental conditions compare with direct incineration by using e.g. a blast furnace (Tangea Lein, 2004).

 Lower potential for air pollution compared with traditional methods of thermal processing (Lewis, 1967).

 During pyrolysis process lower unsaturated hydrocarbons are created while the higher saturated hydrocarbons are cleaved. (Havlik, o.a., 2010)

 Pyrolysis process does not produce slag (Evangelopoulos, Efthymios, & Yang, 2015), while using traditional method (smelter) resilts 396 kg of slag from treatment 1 tonne of mobile phones (Navazo, Méndez, & Peiró., 2013).

 Laboratory research shows that a problem of incomplete combustion is occurred in case of applying thermal treatment in presence of oxygen (Havlik, o.a., 2010).

 Pyrolysis is promising method to recover material and energy from polymer scrap, since the energy needed to convert plastic waste into valuable hydrocarbon products is estimated by about 10% of available energy in the waste plastic (Bhaskar, 2004).

 The need for pre-treatment of liquid product is reduced by using pyrolysis process before combustion as well as increasing the opportunity to separate solid residue for instance refining more iron and aluminium before the combustion at high temperature (Richards, 2015).

 Pyrolysis is used as a pre-processing method to separate two different fractions e.g metallic and non-metallic in case of PCB. (Diaz & Friedrich, 2015)

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5.3.5 Pyrolysis technology and reactors

Different types of technologies and reactors are employed to perform pyrolysis process relying upon the required output (Richards, 2015). Due to the difference of heat and mass transfer with time, the residence time of the products is altered according to the type of utilized reactor (Kantarelis, Evangelopoulos, &

Yang, 2015). Depending on the method of operating, these reactors divided into:

Fixed bed, fluidized bed, or entrained flow. A high quality syngas is produced by using the entrained flow type but the operation is done in large scale (i.e. not laboratory scale) and the pre-treatment needs to be in high level (Richards, 2015).

5.3.5.1 Fixed bed gasification

The direction of gas flow inside the fixed bed reactor is the reason to divide operation systems into updraft or downdraft. In both type of gasifier the feedstock is added from the top.

Downdraft when the flow of gas is in same direction to the solid material. Higher quality gases are produced as well as the damage of gas turbine is avoided by utilizing this type which is easy to clean, while the complex design and more control are required. The opposite direction is used for updraft kind which produces gases with high amount of tars since the reactor is suitable for treating different qualities of feedstock. In general advantages of updraft gasifier are considered as a high energy efficiency unit and the produced gases are cleaned first then cooled.

The difficulty of controlling gases outcome from large diameter reactor is the reason of using this type of reactor to produce small amount of products (Richards, 2015).

5.3.5.2 Fluidized Bed (FBR) (Richards, 2015)

Fast and efficient heat and mass transfer inside the reactor is the reason to distribute the fuel and raises mixing in this type of reactors.Utilized bed material is formed from sand in small particles that needed to add in FBR as well as the largest dimension of used west (feedstock) is around 5 cm. i.e. The feedstock should prepare before the adding.

Two types of fluidized bed gasifiers are representing by either circulating (CFB) or bubbling (BFB) fluidized bed according to the velocity of gas flow.

Certain minimum amounts of fluidizing medium such as air, steam, or oxygen are needed to apply during fluidization. Sand with smaller size around 0.25 mm is used in case of bubbling (BFB) than in circulating fluidized bed (CFB). Smaller sands particles are easier entrained and the gas flow will be more uniform and not being channeled.

NOVEL CONCEPT TO TREAT