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INTEGRATED ENERGY MANAGEMENT FRAMEWORK IN WASTE TO ENERGY, INTEGRATION OF OTHER

RENEWABLES

PhD Thesis

Zsófia FODOR

Supervisor:

Prof. Dr. Jiří J. Klemeš Co-supervisor:

Dr. Petar S. Varbanov

Doctoral School of Information Science and Technology University of Pannonia

Veszprém 2013

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INTEGRATED ENERGY MANAGEMENT FRAMEWORK IN WASTE TO ENERGY, INTEGRATION OF OTHER RENEWABLES

(A KÜLÖNBÖZŐ ENERGETIKÁJÚ RENDSZEREK INTEGRÁLÁSA, A NEM HASZNOSÍTHATÓ ENERGIA ÉS A MEGÚJULÓ ERŐFORRÁSOK FELHASZNÁLÁSA)

Értekezés doktori (PhD) fokozat elnyerése érdekében Írta:

Zsófia FODOR

Készült a Pannon Egyetem Informatikai Tudományok Doktori Iskolája keretében

Témavezető: Dr. Jiří J. Klemeš

Elfogadásra javaslom (igen / nem)

...

(aláírás) Témavezető: Dr. Petar S. Varbanov

Elfogadásra javaslom (igen / nem)

...

(aláírás) A jelölt a doktori szigorlaton ... %-ot ért el,

Veszprém

...

a Szigorlati Bizottság elnöke Az értekezést bírálóként elfogadásra javaslom:

Bíráló neve: ... igen / nem

...

(aláírás)

Bíráló neve: ... igen / nem

... (aláírás) Bíráló neve: ... igen / nem

...

(aláírás)

A jelölt az értekezés nyilvános vitáján ... %-ot ért el Veszprém,

...

a Bíráló Bizottság elnöke A doktori (PhD) oklevél minősítése: ...

...

Az EDT elnöke

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ACKNOWLEDGEMENTS

The research work presented in this thesis has been carried out at the Research Laboratory of Process Intensification and Integration (CPI2) at the Department of Computer Science and the Faculty of Information Technology, University of Pannonia, Hungary. First and foremost I offer my sincerest gratitude to my supervisor, Prof Dr Jiří J. Klemeš, who supported me throughout my thesis with his patience and knowledge, whilst allowing me the space to work in my own way. Special words go to my co-supervisor Dr Petar Varbanov. Thank you for all your advice, scientific support, and also for flexibility, steady support and guidance.

I would also like to thank Prof Ferenc Friedler, the Rector of the University of Pannonia for welcoming me to the Department from the very beginning, Dr Rozália Pigler-Lakner, the Dean and also the Secretary of The Information Technology PhD School, and Ms Orsolya Ujvári, the School’s Project Officer for their administrative support and endless helps.

Furthermore, I would like to thanks, Prof Petr Stehlík from Brno University of Technology, Czech Republic and Dr. György Kozmann from University of Pannonia, who gave helpful support and advice in preparing me for the comprehensive examination.

In my daily work I have been blessed with a friendly and cheerful students. I would like to take this opportunity to show heartfelt thanks to my colleagues, Mr Mate Hegyhati and Gábor Kiczenkó who provided useful guidance in mathematical programming and Ms Andreja Nemet for her friendship and support.

The financial support from (i) EC project Marie Curie Chair (EXC) MEXC-CT-2003-042618

“Integrated Waste to Energy Management to Prevent Global Warming – INEMAGLOW” is gratefully acknowledged.

Finally, I would like to express my great gratitude to my parents, family members and my husband.

Thank you for your love, understanding and selfless support, as the time needed to complete this thesis has been taken mainly from them.

Mrs Zsófia Závodi-Fodor

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Table of contents

1

 

Introduction... 1

 

1.1  Problem area ...3 

1.1.1  Waste management ...5 

1.1.2  Total Site Integration...6 

1.1.3  Renewable Energy Sources...7 

2

 

Literature review and state of the art ... 9

 

2.1  Classification of waste...10 

2.2  Waste generated by households...14 

2.2.1  Biogas from landfilling ...18 

2.2.2  MSW Incineration ...18 

2.2.3  Ash ...21 

2.3  Industrial and construction waste ...22 

2.3.1  ISW utilization ...22 

2.3.2  Cryogenics...26 

2.3.3  Pyrolysis and gasification...26 

2.3.4  Fuel Cells...29 

2.4  Biodegradable waste...30 

2.4.1  Anaerobic Digestion...30 

2.4.2  Hydrolysis ...33 

2.4.3  Biomass waste gasification ...34 

2.5  Hazardous waste ...35 

2.5.1  Developments in advanced technology design ...36 

2.6  Process Integration ...40 

2.6.1  Pinch Analysis...41  III

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2.6.2  The Problem Table Algorithm ...43 

2.6.3  Grand Composite Curve...45 

2.6.4  Total Site Integration with the traditional method ...46 

2.7  Renewable Energy Sources ...50 

2.7.1  Variability of demands ...53 

2.7.2  Demand and supply properties...54 

2.7.3  Handling the variability...54 

2.7.4  Integration approach...55 

2.7.5  Potential tools to be used for handling renewables supply variability...56 

2.8  State of the art analysis, focus of the thesis...56 

2.8.1  Waste as an alternative fuel...56 

2.8.2  Total Site Integration...59 

2.8.3  Renewable Energy Sources...59 

3

 

Total Site Integration including Renewables ... 61

 

3.1  Classification of the energy demands...62 

3.2  Variability of renewable resources ...64 

3.3  Suggested Integration approach...66 

3.4  Demonstration case study...67 

3.5  Total Site Targeting with Time Slices...71 

3.6  Analysis of the targets ...76 

3.7  Section Conclusion ...76 

4

 

Extended Pinch Methodology - Total Site targeting with process-specific Minimum Temperature Difference ... 77

 

4.1  Process specific procedure for Total Site Targeting with flexible ΔTmin specifications ...79 

4.2  Demonstration case study...85 

4.3  Process-level targeting using the traditional procedure...88 

4.4  Process-level targeting using the modified ΔTmin procedure...90  IV

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4.5  Total Site Targeting comparing the traditional and modified ΔTmin methodology ...91 

4.6  Discussion of the results ...94 

4.7  Section Conclusion ...95 

5

 

Extended Pinch Methodology - Total Site Targeting with Stream Specific Minimum Temperature Difference ... 98

 

5.1  Stream specific targeting procedure ...99 

5.2  Industrial Case Study with stream specific targeting ...102 

5.3  Section Conclusion ...107 

6

 

Software implementation for the different Total Site targeting procedures 108

  6.1  Input-output operations...108 

6.2  Total Site Targeting ...109 

6.3  Comparison of the traditional and the new procedure...114 

6.4  Section Conclusion ...115 

7

 

Collaboration with industry... 117

 

7.1  Industrial problem typical for developing countries...117 

7.2  Optimal stream discharge temperatures for an idustrial dryer operation ...122 

8

 

Summary of Accomplishments ... 131

 

8.1  Original Contributions...131 

9

 

References ... 138

 

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List of Figures:

Figure 1. Enhanced integration of the whole system, forming a Locally Integrated Energy

Sector (Perry et al, 2008. LIES)...5 

Figure 2. Waste hierarchy (after European Union, 1991)...6 

Figure 3. Enhanced integration of the whole system, representing the main focuses ...10 

Figure 4. Advantages of Waste to Energy (Fodor et al., 2011a.) ...11 

Figure 5.Pyrolysis process advantages (Fodor et al. 2011a). ...27 

Figure 6. Thermodynamic limitations of heat recovery (after Klemeš et al., 2011)...42 

Figure 7. Constructing a composite curve from two hot streams (after Klemeš et al., 2011) ...42 

Figure 8. Shifting Temperatures (afterKlemeš et al., 2011) ...43 

Figure 9. The Problem Table (after Klemeš et al., 2010) ...44 

Figure 10. Heat Cascade (after Klemeš et al., 2011) ...45 

Figure 11. Grand Composite Curve (after Klemeš et al., 2011)...46 

Figure 12. Construction of a Total Site Profile with original Methodology (after Klemeš et al., 2011)...48 

Figure 13. Total Site Composite Curves (after Klemeš et al., 2011) ...49 

Figure 14. Heat recovery targeting for the Total Site (after Klemeš et al., 2011)...49 

Figure 15. Typical residential electricity demands within a 24 h cycle (Bance et al., 2012)...53 

Figure 16. Four areas are integrated into a Total Site (Varbanov et al.,2010) ...67 

Figure 17. Time Slices for the example (after Varbanov et al.,2010)...72 

Figure 18. Time Slice 1: Site Composites for inter-process heat recovery (Varbanov et al., 2010)...73 

Figure 19. Time Slice 1: Site targets including the solar heat – initial placement (Varbanov et al., 2010) ...73 

Figure 20. Time Slice 1: Site targets for solar heat capture and storage (Varbanov et al., 2010) ...74 

Figure 21. Time Slice 2: Site targets for solar heat capture and storage (Varbanov et al., 2010) ...75 

Figure 22. Time Slice 3: Site targets for solar capture and storage (Varbanov et al. ,2010) ...75 

Figure 23. Mapping of the process-specific ΔTmin values accounting for different heat transfer types (Fodor et al., 2010) ...81 

Figure 24. Modified Total Site targeting procedure (Varbanov et al., 2012)...84 

Figure 25. Selection of ΔTmin specifications (Varbanov et al., 2012) ...85 

Figure 26. Configuration of the considered system (Varbanov et al., 2012)...85 

Figure 27. Problem Table for Process A (Varbanov et al., 2012)...88 

Figure 28. Utility targets for Process A, uniform ΔTmin = 12 °C (Varbanov et al.,2012) ...89 

Figure 29. Problem Table for Process B ...90 

Figure 30. Utility targets for Process B for ΔTmin,PP,B = 5 (Varbanov et al.,2012)...91 

Figure 31. Heat Source Segments (Varbanov et al., 2012)...93 

Figure 32. Total Site targets obtained with the modified procedure (Varbanov et al., 2012)...94 

Figure 33. Comparison of the targets ...95 

Figure 34. The Modified Stream Specific Total Site targeting procedure (Fodor et al., 2012) 102  Figure 35. Examined different sites of the dairy factory (Fodor et al., 2012)...103 

Figure 36. Data entry interface...109 

Figure 37. Problem Table ...110 

Figure 38. Heat Cascade ...111 

Figure 39a. Grand Composit Curve (GCC);   b. GCC without pocket(s)...112 

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Figure 40. Total Site with the traditional targeting ...113 

Figure 41. Traditional Total Site targeting with option to utility placement...113 

Figure 42. Utility entry interface ...114 

Figure 43. Utility dependent ΔTmin limitation ...115 

Figure 44. Process specific targeting using utilities on different level...115 

Figure 45. Process flowsheet (Fodor et al.,2011)...119 

Figure 46. Process Grid Diagram (Fodor et al., 2011)...120 

Figure 47. Problem Composite Curves (Fodor et al.,2011) ...121 

Figure 48. Utility, Q, and utility cost, Cu, for a range of TWC,out and TEA,out set at 63 °C. (Walmsley et al., 2012)...126 

Figure 49. Grand Composite Curve for various TWC,out with TEA,out constant at 63.0 °C. Pinch temperatures include 10.5 and 53.0 °C. (Walmsley et al., 2012)...127 

Figure 50. TWC,crit, Qrec and Cu for a range of TEA,out. (Walmsley et al., 2012)...127 

Figure 51. Total heat exchanger network area, left, and change in cost (referenced to the cost when TEA,out = 75 °C, i.e. no heat recovery from EA stream), right, for a range of TEA,out and TWC,crit. (Walmsley et al., 2012) ...128 

Figure 52. The minimum total cost, heat exchanger number and discharge stream temperatures for various process modifications. Modifications: (A) Two fluidised bed air streams and the liquid concentrate are heated by utility, (B) WC streams are combined, and (C) Hot water demand is doubled. (Walmsley et al., 2012) ...129 

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List of Tables:

Table 1. Composition of waste by treatment type (Fodor et al., 2011a)...13 

Table 2. Parameters of Municipal Waste (Fodor et al., 2011a) ...15 

Table 3. MSW management technology options (Fodor et al., 2011e)...17 

Table 4. Comparison of the IWT (Fodor et al., 2011a) ...25 

Table 5. Energy flow demand variability (Varbanov and Klemeš, 2010)...53 

Table 6. Waste treatment matrix diagram (used:

9

; not used:

8

) (Fodor et al., 2011a)...57 

Table 7. Streams for Process A ...69 

Table 8. Streams for Process B ...69 

Table 9. Streams for Process C...70 

Table 10. Streams for Process D...70 

Table 11. Heating and cooling demands for Chemical Plant (process A)...86 

Table 12. Heating and cooling demands for Food plant (process B) ...86 

Table 13. Heating and cooling demands for Hospital (process C)...87 

Table 14. Heating and cooling demands for Residential Area (process D) ...87 

Table 15. Cost and operating parameters...87 

Table 16. ΔTmin matrix for the case study, all values in °C...88 

Table 17. Processes utility requirements - comparison ...89 

Table 18. Process utility cost comparison ...91 

Table 19. Steps 4 and 5 of the modified procedure applied to processes A and B ...92 

Table 20. Comparison of the targets after identifying utility recovery...94 

Table 21. Heating and cooling demands for D4 ...104 

Table 22. Heating and cooling demands for D5 ...105 

Table 23. Heating and cooling demands for Casein...105 

Table 24. ΔTcont specification (°C) according to different heat exchangers inside the all the processes ...106 

Table 25. ΔTcont matrix for the case study, all values in °C ...106 

Table 26. Processes utility requirements - comparison ...107 

Table 27. Extracted cold streams...119 

Table 28. Extracted hot streams...119 

Table 29. Stream data (Walmsley et. al., 2012) ...125 

Table 30. Utility data (Walmsley et. al., 2012) ...125 

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Abstract

Effects of the utilization of fossil fuels, such as global climate change, world energy conflicts and energy source shortages, have increasingly threatened the world stability. The need for a novel approach for better energy saving technologies that complements also environmental and financial considerations is essential. In this study clearly addressed different energy optimisation techniques with the introduction of further developed new concepts:

1. The thesis evaluates the economic and environmental implications of using waste as an energy source through Waste-to-Energy (WtE) technologies. It focuses on the world general energy management, the environmental aspects of waste management part and the opportunities for integrating the WtE processes. It discuss how WtE and recycling are compatible as different waste treatment options.

2. Review the novel extensions of Total Sites to Locally Integrated Energy Sectors (LIES).

Further examine the implementation of the renewable energy sources into the Total site Profiles. The work propose tools for handle the variability of the renewables with suggesting Time Slice model, as these energy sources availability is changing by year, month and even over the day.

3. Improve the Total Site targeting procedure for allowing individual minimum temperature differences between the heat source / sink profiles on the one hand and the utility generation / use profiles on the other. The new methodology deals with an extension of traditional Total Site Integration. Process Heat Integration (based on traditional Pinch Analysis) aims to minimise the amount of energy mostly used in industrial processes. It is still an open question how to solve the Total Site targeting problem when different values for the minimum allowed temperature differences (ΔTmin) are specified for each process on the site.

A single uniform ΔTmin for all processes integrated in a Total Site, as practiced to date, cannot be generally optimal. Such an assumption may be too simplifying and lead to inadequate results due to imprecise estimation of the overall Total Site heat recovery targets.

The modified Total Site targeting procedure, called Proces Specific targeting, proposed in this paper, allows obtaining more realistic heat recovery targets for Total Sites. It is illustrated with a case study for Locally Integrated Energy Sectors, also providing a

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comparison with the traditional targeting procedure and the advantages offered by the modified one.

4. The further extension of

the Process Specific Total Site Integration methodology to produce more meaningful utility and heat recovery targets for the process design called Stream Specific targeting methodology. The previous extension was on the introduction of using an individual minimum temperature difference (ΔTmin) for different processes so that the ΔTmin is more representative of the specific process. Further the new extension deals with stream specific ΔTmin inside each process by setting different ΔT contribution (ΔTcont) and also using different ΔTcont between the process streams and the utility systems. The paper describes the further extended methodology called Stream Specific targeting methodology. A case study applying data from a real diary factory is used to show the differences between the traditional, process specific and stream specific total site targeting methodologies. The extended methodology gives more meaningful results at the end of the targeting with this avoiding the over or under estimated heat exchanger areas in the process design.

5. Creation of an in-house

computational tool incorporating the improved procedure. Several proprietary and open source software exist to address the optimisation subjects, however these implementations lack the capability to calculate with separate ∆Tmin values per process and per utility at the Total Site level. This results inaccurate profiles. In order to get closer to real-life values, software was written that resolves these shortcomings. The software is able to handle virtually unlimited streams and processes. It updates all result charts in realtime. The chosen language for this task was C#, with MSVS2010 environment. It has been shown that with the novel calculation method, both Process Specific and Stream Specific, the results are more accurate.

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Kivonat

A Föld egyensúlyát egyre inkább veszélyeztetik a fosszilis tüzelőanyagok, mert csökkenő készletük energia válsághoz vezet és felhasználásuk jelentős hatással van a globális klímaváltozásra. Ennek tükrében rendkívül fontosak a hatékonyabb energia felhasználására irányuló kutatások, amelyek a környezeti és gazdasági tényezőkre is tekintettel vannak. A dolgozatban egyértelműen bemutatásra kerülnek az energia optimalizáló eljárások, illetve azok továbbfejlesztett modelljei:

1. A dolgozat felméri a hulladék, mint energiaforrás felhasználásának (ezek az un. Waste-to- Energy technológiák) gazdasági és környezeti hatásait. Részletesen foglalkozik a világ energia politikájával, a hulladékgazdálkodás környezeti hatásaivalés annak integrációs lehetőségeivel. Bemutatja, hogyan lehetnek kompatibilisek a különböző, újrafeldolgozásra vagy energiaként való felhasználásra kidolgozott, hulladék kezelési eljárások.

2. Kutatja és kiterjeszti a legújabb energia optimalizálási és hőintegrációs folyamatok lehetőségeit (Total Site – LIES). Továbbá vizsgálja a megújuló energiaforrások integrálását a már meglévő hőintegrációs rendszerekbe. A megújuló energiaforrások rendelkezésre állása az időben más és más, évente, havonta de akár egy nap leforása alatt is változhat. A dolgozat eszközöket javasol a változások időbeli követésére és kezelésére az un. Time Slice modell bevezetésével.

3. Az új eljárás az un. hagyományos Total Site eljárás olyan továbbfejlesztése, ami lehetővé teszi a meleg / hideg áramot felhasználó rendszerek jobb optimalizálását különbőző egyéni minimum hőméséklet különbségek bevezetésével (ΔTmin). Az eljárás (Pinch methodology) célja hogy minimalizálja főleg az ipari területen felhasznált energiát. Jelenleg is kérdéses hogyan oldható meg az a hőcsere integrációs probléma, amikor a folyamatokban az áramok közötti termodinamikai hajtóerő különbözik (ΔTmin). A jelenleg alkalmazott módszerrel a termodinamikai hajtóerő (ΔTmin) egységesítése a folyamatokban nem ad optimális megoldást. Egy ilyen feltételezés túlzottan leegyszerűsített és hibás eredményhez vezet. A dolgozatban javasolt (Process Specific) számolási metódus lehetőséget ad a különböző folyamatokhoz tarozó termodinamikai adatokkal való számításra és ezzel jobban megközelíti a valóságot. A bemutatott esettanulmányban egyértelműen látszik a két optimalizálási eljárás közti különbség, illetve a Process Specific előnye.

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4. A Process Specific eljárás tovább fejlesztésére (Stream Specific targeting) azért volt szükség hogy a rendszereken belül folyó áramokhoz is meghatározható legyen a különböző termodinamikai hajtóerő a hőcsere során. Ennek érdekében bevezetésre került az egyes áramokhoz tartozó hajtóerő fogalma - ΔT contribution (ΔTcont). A dolgozat leírja a kiterjesztett eljárás lépéseit egy tejipari üzem példáján keresztül. A kapott eredmények sokkal jobban megközelítik a valós üzem működését. Ezzel a továbbfejlesztett módszerrel elkerülhető a hőcserélő rendszerek felületének túlzott alul illetve túlméretezése.

5. Kifejlesztettünk egy

szoftvert, amely alkalmazza a javasolt változásokat. Létezik több más nyílt forráskódú program is, de ezek egyike sem képes a rendszerek / áramok termodinamikai megkülönböztetésre, így pontatlanok. Annak érdekében hogy a valósághűbb eredményeket kapjunk szoftverünk kiküszöbölte az előzőekben felvázolt hibákat. A program képes végtelen számú rendszereket és áramokat kezelni és frissítenivalós időben. A program C#

programnyelven fut MSVS2010 környezetben. Használata során bizonyítást nyert, hogy a mind a két módszerrel (Process Specific és Stream Specific) elvégzett számításai sokkal pontosabb eredményeket adnak.

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摘要

过度使用化石燃料导致如全球气候变化,世界能源冲突和短缺的问题,威胁世界的稳定性。

因此,一种能够全面顾及环境和经济方面的新节能技术,是必须的。这项研究清楚地针对不 同的能源优化技术的引入并进一步研发新概念:

1. 本文同时考虑经济和环境的因素,审核运用废废物转化为能源(WTE)技术作为一种 能源来源。它侧重于的国际能源,环境与废物管理,并集成了绿化垃圾焚烧过程的机 会。本文也比较垃圾回收利用-焚烧与其他的废物处理方案。

2. 本文概览评介了由总合盘(Total Site)扩展的局部性能源综合组合(Locally Integrated Energy Sectors - LIES。

进一步研究,如何实施可再生能源于总合盘里。本研究提出,处理可再生能源波动的 工具- 时段模式 (Time Slice Model),因为能源波动都会随着,年,月,日而变化。

3. 提高总合盘的允许热源分布,

提供/接纳还有生成/使用的最低温度之间的差异。新的方法是传统的集成的扩展。过 程热集成(根据传统的夹点分析)的目的,是在于工业生产过程中使用的能量降至最 低。如何解决时指定的网络上的每个进程允许的最低温度差异的不同的值(ΔTmin) 定位仍然是一个悬而未决的问题。总合盘的所有进程整合在一个单一的统一ΔTmin, 很难被优化。这样的假设可能过于简化,导致不充分的结果不精确的估计的总热能回 收目标。修改后的总网络定位的过程,称为具体过程目标(Proces Specific

targeting),本文提出的具体目标,能获得更真实的热网总数的热回收目标。这可以 通过LIES案例来说明,并还比较传统与修改后的优势。

4. 进一步展延具体总合盘集成方法以产生更有意义的工具和热回收的过程,

称为具体流量目标方式(Stream Specific targeting methodology。

之前的研发使用的最低温度的差异(ΔTmin)为不同的进程,ΔTmin的具体过程是比较 有代表性的。此外,新的扩展处理每一个过程,通过设置不同的ΔTmin的贡献 

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(ΔTcont)和使用的过程流和公用工程系统不同ΔTcont之间流的特定ΔTmin内。本文介 绍了进一步的扩展方法称为称为具体流量目标方式方法。本论文通过一个真实的工厂 案例显示传统过程中与具体流量目标的总网络定位方法之间的差异。这扩展的方法,

给出了更有意义的结果,尤其避免错误估计热交换器在工艺设计领域的定向。

5. 创建一个内部的计算软件工具,以改进过程。现有的几个专有优化学软件和开放优化 软件仍缺乏计算每个进程的的独立ΔTmin值。这样的结果不能反映真实的问题所在。

为了更贴近真实的值,我们的软件,解决了这些缺点。该软件能够处理几乎无限的数

据流和流程。它的实时更新所有图表。此任务所选择的语言是C#,与MSVS2010。

它已被证明,新颖的计算方法结果是更准确的。

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Introduction

1 Introduction

1

The major primary energy sources are petroleum (oil), natural gas, coal, nuclear, and renewable energy in the world. These major primary energy sources have been widely used and the largest consumers are transportation with 28 %, industry with 20 %, residential areas and business complexes (hotels, restaurants etc.) with 11 %, and electric power generation with 39.6 % (Energy Information Administration, EIA, 2012). The energy use in industry is increasing due to the growing consumption of industrially processed food and a growing demand for a greater range of various products. These changes in customer behaviour, together with raising energy prices, policy instruments and harder price competition, stimulate the interest in saving energy in industry.

By the estimation from the Energy Information Administration (EIA) the world industrial energy demand is expected to further increase with rising industrialisation of developing nations and the population growth at an average annual rate of 1.3 % until 2035. The industrial sector accounted for a majority of the reduction in energy use in 2009 caused by the recent economic downturn. Long- term growth of industrial sector energy demand occurs in non-OECD countries. Non-OECD economies consume 60 % of global delivered energy in the industrial sector. Industrial energy use in non-OECD countries is predicted to grow by an average of 1.8 %/y, compared with 0.2 %/y in OECD countries. This means that the industrial energy usage in the non-OECD countries would have grown by 95 % until 2035. Over the 28 year projection, worldwide industrial energy consumption would grow from 194.13·1012 MJ in 2007 to 276.42·1012 MJ in 2035 (EIA, 2012). To keep up with this growth without further serious damage to the environment effective energy reduction solutions are needed. In Europe the greenhouse gas emissions should be reduced by 20%

compared to 1990 (Europe 2020 indicators, Eurostat). The share of renewable energy sources in final energy consumption should be increased to 20%. Energy efficiency should improve by 20% In Europe the primary energy consumption since 2005 until 2012 was decreased 5% (Europe 2020 indicators, Eurostat). Besides, the share of the renewable energy in gross final energy consumption is increasing with it from 8.5% (2005) to 12.5% (2011) in the 27 EU countries, in Hungary the same data was from 4.5% to 8.7% by 2011, which is a good projection to the “green” future of the country. Although, with the growing share of the renewable energy sources, the greenhouse gas emissions are not decreasing with the same rate year by year as the regulations are expected (Eurostat, 2012). There should be combined with other energy saving technologies to reach the expectations.

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Introduction

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Waste, defined by Directive 2008/98/EC Article 3(1) as ‘any substance or object which the holder discards or intends or is required to discard’, potentially represents an enormous loss of resources in the form of both materials and energy. In addition, the management and disposal of waste can have serious environmental impacts. Landfills, for example, take up land space and may cause air, water and soil pollution, while incineration may result in emissions of dangerous air pollutants, unless properly regulated. EU waste management policies therefore aim to reduce the environmental and health impacts of waste and improve the EU’s resource efficiency. The long-term aim of these policies is to reduce the amount of waste generated and when waste generation is unavoidable to promote it as a resource and achieve higher levels of recycling and the safe disposal of waste.

In 2010, the total generation of waste from economic activities and households in the EU (Eurostat, 2012) amounted to 2,570 Mt, this was slightly higher than in 2008 but lower than in 2004. The relatively low figures for 2008 and 2010 may, at least in part, reflect the downturn in economic activity as a result of the financial and economic crisis. Among the waste generated in the EU in 2010, 3.7 % of the total was classified as hazardous waste. There is a large variation between countries which may be linked to the differences in economic structures. For example, the high level of waste generated in Bulgaria, Finland, Estonia, Sweden and Romania was strongly influenced by large quantities of mineral wastes from mining and quarrying activities, whereas in Luxembourg, mineral waste from construction was largely responsible for the high amount of waste generated. In 2010, 2,366 Mt of waste was treated in the EU; this includes the treatment of waste that was imported into the EU. Almost half (48.2 %) of the waste treated within the EU in 2010 was subject to disposal operations other than waste incineration (this was predominantly landfills). A further 46.3 % of the waste treated was sent to recovery operations (other than energy recovery).

The remaining 5.4 % of the waste was sent for incineration (with or without energy recovery).

The energy efficiency, the improved unit operation, the system integration applying advanced Process Integration (PI) and the reliable waste management and treatment options are the key element of achieving the energy savings. PI allows industries to increase their profitability through reduction in energy, water and raw material consumption, reduction in greenhouse gas (GHG) emissions, and waste generation. Among PI methodologies, Pinch Analysis is certainly the most widely used for process integration. This is due to the simplicity of its underlying concepts and especially to the spectacular results it has obtained in numerous projects worldwide. Nowadays the mostly used applications are:

Heat Exchanger Networks for recovering heat from process product streams,

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Introduction

3

Waste-heat recovery from a gas turbine,

Optimal scheduling of reactor usage,

Integration of a number of production units, and

Complete the integration of the whole industrial complex.

The presented PhD work focuses on:

Discover the applications related to increase the Waste to Energy (WTE) technologies pro and con.

Improve the energy connections between the different system concerning the energy efficiency which covers the improved unit operations and better process unit integrations.

Increase the usage of the renewable energy sources and implementation of them into existing systems.

Develop in-house software for the quick graphical representation of different unit integrations.

Representation of case studies from collaboration with different industries.

Figure 1 represents the above mentioned main parts of the thesis. Energy efficiency implementation means searching for better heat recuperation inside the examined systems and redesigns the whole process by suggesting changes on heat exchanger network to reach better heat recovery. The process units mainly use fuel based power as the main energy source and generate huge amount of different type of waste. The thesis aim is also to replace these fuel based energy sources by reducing the fuel consumption and the emission with increasing the renewables usage, generate more energy from waste through Waste to Energy (WTE) technologies and increase the heat recovery inside each process and for process to process.

1.1 Problem area

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Introduction

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The thesis deals with topics, which has strong influence on the energy saving methodologies and technologies. It provides an overall framework and analyses of the energy systems for different processes and further improving the traditional Pinch methodology to be more realistic and also extending the system with connections to other energy sources besides the fuel based like renewables and waste (Figure 1). Locally Integrated Energy Systems (LIES) is a representation for Total Site at constant demand and supply rates in the different energy consumption sectors. Total Site targeting was put forward as a means of integrating heating and cooling requirements between individual units in a total processing plant. The method also forms the basis for a target-based design sequence for the overall site utility system that is required to meet heating and cooling demands through the steam-based system and power requirements. The Total Site targeting method allows waste heat from processes to be used as a source of heat in other processes. The waste heat sources are converted to hot water, steam, sometimes hot oil and then passed to processes that are in heat deficit through utility system.

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Introduction

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Figure 1. Enhanced integration of the whole system, forming a Locally Integrated Energy Sector (Perry et al, 2008. LIES)

The main issue is reducing the fuel based energy demand, by promoting energy efficiency both within the energy sector itself and at the end-use (EUR-Lex, 2007). The majority of the energy systems – industrial, service, business, and residential – are still dominated by fossil energy sources.

They are equipped with internal combustion engines (e.g. gas turbines and diesel generators), boilers, steam turbines, and water heaters. These different sectors are produce different waste streams, some of these waste streams can be further utilized as alternative fuels and reused in the system elsewhere for another sector as energy supply. As baseline the traditional pinch methodology is used to make sure the examined units of the systems are energy efficient. The uses of the renewable energy sources also seems to be as a key element in the energy policy, reducing the dependence on fossil fuel, reducing emissions from carbon sources, and decoupling energy costs from oil prices. The most actual and important challenge is to increase the share of these renewables in the primary energy mix could be met by integrating solar, wind, biomass as well as waste from different sectors with fossil fuels.

1.1.1 Waste management

The cornerstone of a successful planning for waste management program is the availability of reliable information about the quantity and the material type of the waste being generated.

Management systems and techniques have been developed to reduce the environmental burden of waste generation and at the same time to address possibilities of the conversion of waste to energy.

However waste treatment still can provide a viable possibility for energy production, but this option needs to be analysed with specific tools to assess its environmental impact. The type of waste treatment strongly depends on the waste characteristics (Eurostat, 2011). The first step is to organise the various waste treatment methods in a waste hierarchy (Figure 2). The waste hierarchy classifies some methods to handle waste as more efficient than others from an environmental and also an economic point of view. A general waste hierarchy presented by the EC directive (PO EU, 1991) summarises the main waste management strategies. The aim of the waste hierarchy is to extract the maximum practical benefits from products and to generate the minimum amount of final non- recoverable waste. A strong driver for improving the energy supply from WTE plants is the Waste Framework Directive - Directive 2008/98/EC (PO EU, 2008), which defines and allows high efficiency WTE installations to benefit from a status of “recovery” rather than “disposal”. It is more

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Introduction

6

important that the technologies are defined by the actual regulations and fitted on the updated waste management policy.

Figure 2. Waste hierarchy (after European Union, 1991)

Designing and planning for effective waste management is important for numerous reasons, including the need to estimate material recovery potential, to facilitate design of processing equipment, to estimate physical, chemical, and thermal properties of the waste and to maintain compliance with national law and European directives. The composition of the generated waste by the different sectors is extremely variable depending on season (autumn, winter, spring, and summer), lifestyle, demographic, geographic, and legislation impacts. Gidarakos (2006) shows that there has been a significant decrease in organic wastes due to the increase of packaging materials, as a result of a change in consumption patterns. Different waste categories such as organic wastes, paper and plastics, a high fraction of glass and a seasonal variation of aluminum indicate a strong correlation of waste composition with certain human activities, such as tourism. This variability makes defining and measuring the composition of waste more difficult and at the same time more essential.

1.1.2 Total Site Integration

Heat Integration using Pinch methodology was introduced by Linnhoff et al., 1982. Traditional Pinch Analysis can be used to set the minimum utility targets, to inform thermo-economic analysis of potential recovery and project integration, and to identify heat exchanger network design and synthesis opportunities. Total Site analysis can be conducted to establish the overall energy targets for the site (Klemeš et al., 2010). The targets generated from the traditional total site approach can be misleading because it assumes that the whole site operates with the same minimum allowed temperature difference (ΔTmin) for both direct and indirect integration. The traditional pinch methodology assumes the same values for ΔTmin also inside the process and between different sites

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Introduction

7

through the utility system. Process streams with different heat transfer characteristics require different ΔTmin values for process to process heat exchange. For adequate design of the heat recovery systems, ΔTmin specifications are needed for several types of heat transfer: process to process, hot streams to cold utility, and hot utility to cold streams. If different types of plants are integrated on a site – for instance oil refinery, food processing plant, brewery, hospital, football ground and stadium – rather different ΔTmin values could be the optimum for each plant. All these specifications should be available as degrees of freedom to the system designers.

1.1.3 Renewable Energy Sources

Renewable energy is energy that is derived from natural processes (e.g. sunlight and wind) that are replenished at a higher rate than they are consumed. Solar, wind, geothermal, hydro, and biomass are common sources of renewable energy. Renewable sources of energy have been the driver of much of the growth in the global clean energy sector. Recent years have seen a major scale up of wind and solar photovoltaic technologies. Other renewable technologies – including hydropower, geothermal and biomass – continued to grow from a strong established base, adding hundreds of GW of new capacity worldwide. Success of wind and solar has been driven by policy support, which has grown considerably in the last decade (EIA, 2012). Policies continue to evolve to address market developments and costs reductions. In the case of solar energy, at least ten countries now have sizeable domestic markets. Both utility scale and rooftop solar photovoltaic generation have seen a major scale up in the past few years, resulting from market creating policies that led to an extraordinary decline in the cost of solar photovoltaic modules. Wind power also experienced dramatic growth over the last decade; global installed capacity at the end of 2011 was around 240 GW, up from 18 GW since the year 2000.

Despite this good news, worldwide renewable electricity generation since 1990 grew an average of 2.8 % /y, which is less than the 3 % growth seen for total electricity generation. While 19.5 % of global electricity in 1990 was produced from renewable sources, this share fell to 19.3 % in 2009.

This decrease is mainly the result of slow growth of the main renewable source, hydroelectric power, in OECD countries. Achieving the goal of halving global energy related CO2 emissions by 2050 will require a doubling (from today’s levels) of renewable generation by 2020.

The challenge to increase the share of the renewables in the energy mix could be met by integrating solar, wind, biomass, geothermal energy as well as some types of waste. The renewables availability, the energy demands (heating, cooling and power) of the different sites like industrial, residential, service, business etc. all vary significantly with time of the day, period of the year and

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Introduction

8

location. Some are not predictable and highly variable in both frequency and/or magnitude. Some are changing in very regular time intervals – as day and night, summer and winter for solar energy but the wind-generated energy is less predictable.

Renewable resources availability in time is usually well below 100 % varying with time and location. Consumer demands for heating, cooling and power also vary significantly with time. The variation of supply and demand are partly predictable and some form stable patterns – e.g. day and night for solar energy. Availability of wind and solar generated energy can be predicted for a short period only by advanced metrological forecasts. This is caused by the changing weather and geographic conditions. The design of energy conversion systems using renewable resources is more complex compared with fossil fuels.

A system combining the supply and the demand of the individual users may serve industrial, residential and service–sector customers (hotels, hospitals), where the demand levels will depend on the occupancy rate and some less predictable features. They could typically utilise various energy carriers and the task is to account for the variability on both the demand and supply sides. This requires applying the advanced Process Integration methodology using the time as another problem dimension is a potential solution to deal with this problem.

The availability of some renewable energy sources are close to the performance of fossil fuels and can be well stored for energy generation – e.g. biomass, where the supply varies by bio-waste availability. The other renewable sources as wind and solar vary faster – in hours and even minutes.

These types of variation present an integration challenge where the time horizons of the changes are diverse. The two main issues are the system operability and the appropriate performance targeting procedures. The operability challenges imposed by renewable integration also need attention.

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Literature review

2 Literature review and state of the art

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The thesis structure follows the main sections - as it is highlighted in the Figure 3- such as:

Review of the various waste classification according to the latest waste management regulation and treatment technologies (Chapter 2),

Integration of the renewable energy sources into other energy systems (Chapter 3),

Using different optimization for the different energy consumption units (LIES) (Chapter 4, 5),

Develop in-house software for the quick and better graphical representation for the unit integration results

(Chapter 6) and

Results from the collaboration with industries based on the improved unit integrations (Chapter 7)

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Literature review

Cooling Utility Hot water Steam Electricity

Unit 4- Residential area Unit 3- Hospital

LIES – Distributed Area, District Heating / Cooling

Electricity – National Grid Fuel

Emissions

Raw material

Non- Recyclable Waste

WASTE ENERGY

Chapter 3

Chapter 4, 5, 6, 7

Chapter 2

Unit1 - Chemical Plant A

process B process C process

Unit 2- Food Industry

A process

B process

Figure 3. Enhanced integration of the whole system, representing the main focuses

Further, according to the original research part there is a related in-house software implementation (Chapter 6) and results from the collaboration with industries (Chapter 7).

2.1 Classification of waste

Waste-to-Energy (WTE) is an area dealing with the technologies for the combined waste processing and energy generation. It is part of the overall waste management hierarchy (Figure 2 from the introduction). Managing waste properly follows the established priorities of minimising generation and maximising the reuse, recycling and recovery of materials followed by utilisation of the waste energy value treatment and safe disposal (EUROPA, 2011). Also important is to minimise the pollution caused by waste treatment and usage of fossil energy sources. Exploiting WTE generation can be advantageous (Figure 4) by reducing further the amount of waste intended for disposal while simultaneously decreasing the consumption of fossil energy sources (Fodor et al., 2011a) and the related Carbon Footprint - CFP (UK POST, 2006).

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Literature review

Figure 4. Advantages of Waste to Energy (Fodor et al., 2011a.)

Pires et al., (2011) made a comprehensive literature review of advantages and disadvantages of waste management practices in 31 European countries including. They thoroughly reviewed models and tools illuminating possible overlapped boundaries in waste management practices in European countries and encompassing the pros and cons of waste management practices. Their conclusions where that:

The Southern EU countries (e.g. Portugal, Greece, Spain) need to develop further measures to implement more integrated solid waste management to comply with EU directives.

The Central EU countries (e.g. Germany, Austria, The Netherlands, United Kingdom and France) and certain Northern countries (e.g. Norway) need models and tools with which to rationalise their technological choices and management strategies.

Considering systems analysis models and tools in a synergistic way would certainly provide opportunities to develop better solid waste management strategies leading to conformity with current standards and foster future perspectives for both the waste management industry and government agencies in EU.

The reviewed energy recovery techniques include thermal treatments such as incineration, gasification, pyrolysis, cryogenics and hydrolysis, in addition to non-thermal techniques such as anaerobic digestion, microbial fuel cells and the utilisation of biogas from landfilling. The novel technologies offer enhanced material recovery, efficient energy recovery and contribute to the reduction of the landfilling. A proper understanding of waste properties and composition is needed to select the most efficient WTE technologies (Fodor et al. 2011e).

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Literature review

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Every second year, information is collected on the generation and treatment of waste in the EU on the basis of the regulation on waste statistics (EUR-Lex, 2011).The most recent are from 2010:

About 2.6 106 Mt of waste was generated in the EU, of which 101 Mt constituted hazardous waste (Eurostat, 2011).

The waste classification provided by Fodor et al. (2011a) proposes the most appropriate waste treatment technologies:

Waste generated by households (Section 2.2)

Industry and construction waste (Section 2.3)

Biodegradable waste (Section 2.4)

Hazardous waste (Section 2.5)

The type of waste treatment depends on the waste characteristics - Table 1 (Fodor et al., 2011a).

The recovery includes all treatment of biodegradable matter (composting). A further waste category relevant for disposal is household waste. Other significant categories include sorting residues and used oils. However, these categories add up to less than 60 % of the incinerated total.

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Table 1. Composition of waste by treatment type (Fodor et al., 2011a)

Recovery 1091 Mt

Mineral waste 55 %

Metallic waste 6 %

Animal and vegetal waste 5 % Paper and cardboard waste 3 %

Other 31 %

Incineration 130 Mt Household and similar waste 40 %

Sorting residues 9 %

Chemical waste 8 %

Mixed and undifferentiated materials 3 %

Other 40 %

Disposal 1149 Mt

Mineral waste 75 %

Household and similar waste 8 %

Common sludge 3 %

Sorting residue 2 %

Other 12 %

Eurostat (2011) defines almost 10 % of waste for incineration as hazardous, of which 3 % can be recovered or disposed. Incineration is a suitable treatment operation for hazardous waste that can’t be recovered or disposed.

Dealing with raw material variability is always a challenge. The composition of a specific type of waste also varies throughout the year and also from location to location. Variations are manifested in flow rate, total dissolved solids, chemical oxygen demand, total organic carbon, Fe, and Mn (Ragle et al., 1995). Monitoring these changes is a required guideline in waste management options.

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Literature review

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2.2 Waste generated by households

The EU households generated 445 kg of waste per capita (Eurostat, 2011). It is important to distinguish the concept of municipal waste from the concept of waste generated by households.

Municipal waste includes waste produced by households, but also similar waste from offices, small businesses, services, depending on the arrangements in a municipality. On the other hand, some municipalities do not collect some specific waste categories, such as discarded vehicles, construction waste and hazardous waste. For this reason, waste produced by households usually has a larger amount than waste generated by municipalities.

Effective waste management through municipal solid waste composition studies is important for numerous reasons, including the need to estimate material recovery potential, to facilitate design of processing equipment, to estimate physical, chemical, and thermal properties of the waste and to maintain compliance with national law and European directives. The composition of generated waste is extremely variable depending on season (autumn, winter, spring, and summer), lifestyle, demographic, geographic, and legislation impacts. Gidarakos (2006) shows that there has been a significant decrease in organic waste generation due to the increase of packaging materials, as a result of a change in consumption patterns. Different waste categories such as organic wastes, paper and plastics, a high fraction of glass and a seasonal variation of aluminium indicate a strong correlation of waste composition with certain human activities, such as tourism. This variability makes defining and measuring the composition of waste more difficult and at the same time more essential.

If municipal solid waste is to be used as a fuel, it is usually pre-treated, which involves crushing, homogenisation, and often mixing with other fuels, including refuse derived fuels (Frey et al., 2003). The particle size of the fuel determines the combustion method as smaller size increases the combustion rate (Haas and Weber, 2010). The heating value of MSW depends also on its moisture content. Its magnitude varies from time to time and location to location. In the US (Ruth, 1998) cited about 10.4 MJ/kg with 25 % moisture content, in Central Europe (Frey et al. 2003) quoted 8.3 MJ/kg with 29 % moisture, and in India it is 10.1 MJ/kg with 42 % moisture (Kumar and Goel, 2009). As an example of the average values of various municipal waste parameters are listed in Table 2 (Fodor et al., 2011a). Besides legislation, these parameters define the treatment method of

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15

the waste, e.g. waste with high moisture content cannot be incinerated with reasonable calorific value, and requires pre-treatment methods. The heating value further depends on the oxygen content, the ratio of hydrogen and carbon in the waste.

Table 2. Parameters of Municipal Waste (Fodor et al., 2011a) Parameters of Municipal Waste Value

Moisture content 42.05 %

Total solids 58.36 %

Volatile solids 19.63 %of total solids

Fixed solids 80.35 %of total solids

Organic carbon 8.91 %

COD (Chemical Oxygen Demand) 0.158 mg O2/mg of solid waste

Calorific value 10,008.24 kJ/kg

Municipal solid waste modelling approaches were identified aimed at present and future waste generation (Beigl et al., 2008). Jankowitsch et al. (2001) examined another important feature - the environmental and economic assessment of waste treatment alternatives under uncertainty. The model for determining the cheapest legal treatment paths for a given waste stream has been extended by an assessment measuring the environmental impact resulting from the treatment itself as well as from the remaining emissions allowing a comparison of treatment policies.

About 14 % of municipal waste was incinerated in 1998 but this proportion had risen to 19 % by 2008 (Eurostat, 2011). The amount of sewage sludge has been increasing due to municipal development and with it waste disposal. Sewage sludge has mainly been handled via landfill and ocean disposal, but these measures will be completely restricted due to the London protocol from 2012. The treatment of sewage sludge through fertilization, composting, and incineration have been performed. EC Directive (PO EU, 2000) defined incineration as the thermal treatment of waste with or without recovery of the generated heat. The MSW incineration had been reaching the share of around 20 - 35 % produced in the EU countries (200 Mt/y) in over 400 installations (BREF, 2006).

The average net efficiencies in an incineration plant are ~ 18 % of power, ~ 63 % heat production, ~ 43 % CHP (PO EU, 2000).

Comparison of the major municipal solid waste management technology options is presented on the Table 3 (Fodor et al., 2011e). To select the best applicable technologies all advantages and disadvantages have to be compared.

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Table 3. MSW management technology options (Fodor et al., 2011e)

Technology Advantages Disadvantages

Landfilling

Universal solution that provides waste disposal

Relatively low cost and easy to implement

Complements with other technology options for handling residual waste It can derive landfill gas as a by- product for household and industrial uses

Requires large area of land; Cost incurred as landfill expands

It does not achieve the objectives of reducing volume of and converting MSW into reusable resources

Result in secondary pollution problems, including groundwater pollution, air.

pollution, and soil contamination Due to public acceptance and space limitation, landfills are often far away from the places where waste is generated, necessitating long distance transport of the waste

Composting

It converts decomposable organic materials into an organic fertilizer It reduces the amount of waste to be landfilled and integrates well with landfilling and materials

recovery/recycling

It needs more space than other MSW technologies

It is costly to implement and maintain It has not large environmental or economic advantages compared to incineration

It requires waste size reduction and degree of waste separation/processing Public perception, such as bioaerosol emissions during the composting process, and insects

Products may cause soil pollution by heavy metals and pathogens

Incineration

Optimal land usage

Provides substantial reduction (by 90%) in the total volume of waste requiring disposal in landfill Requires minimal pre-processing of waste; The bottom ash is biologically clean and stable, can be used in road building and the construction industry

Combustion heat can be used as energy source for CHP

The facilities can be located near residential areas reducing costs of MSW transporting. Air emissions can be well controlled

The most modern facilities are operating in cooperation with waste recycling and/or material recovery

High capital, operational and maintenance cost

Significant operator expertise is required Air pollution control hardware is required to treat the flue gas, and the fly ash needs to be disposed in hazardous waste landfills

Public perception is sometimes negative, primarily due to dioxins emission

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Literature review

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2.2.1 Biogas from landfilling

Landfill is defined (Eurostat, 2011) as the depositing of waste into or onto land, including specially engineered landfills, and temporary storage of over one year on permanent sites. Landfilling has been the most common waste disposal option for many years. About 57 % of municipal waste in 1998 was landfilled in Europe, dropping to 39 % by 2008. Alternative ways of treatment have become more prevalent. Landfilling can be considered as a WTE technology only when the generated biogas is captured and utilised for energy generation.

A mixture of municipal and industrial waste, but excluding significant amounts of concentrated specific chemical waste is frequently treated as landfilled. Due to the leaching high environmental impact the landfill leachates have to be characterized as a water-based solution of four groups of contaminants:

Dissolved organic matter (alcohols, acids, aldehydes, short chain sugars etc.)

Inorganic macro components (common cations and anions including sulphate, chloride, iron, aluminium, zinc

and ammonia)

Heavy metals (Pb, Ni, Cu, Hg)

Xenobiotic organic compounds such as halogenated organics, dioxins, etc.

Again a proper classification could provide help in the waste treatment technology selection and to reduce the release of pollution and effluents. The European Union in an early Directive (1991) required waste management option, where the landfilling of the hazardous waste should the lowest priority. Other waste treatment solutions should displace landfilling reducing the harmful impact on the environment and lower energy (electricity) generation during the biogas treatment.

2.2.2 MSW Incineration

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Since most of the burned waste has sufficient heating value, it is frequently classified as a renewable (and/or alternative) energy source, which allows the saving of fossil fuels as a primary energy source (Stehlík, 2009). However the classification still varies under legislation in various countries. Incineration is a kind of thermal treatment of waste between 400-1100 °C in a specifically designed plant (Stehlík, 2009). Thermal treatment requires the burning of waste with recovery of energy for generation of heat and/or power and processing of released pollutants.

Combustors are widely used for waste treatment because of their high availability, flexibility and efficiency.

The process converts the waste to flue gas, heat, metal, and ash. Incombustible parts (such as rocks, bricks, etc,) should be separated before the process, otherwise they reduce efficiency. The heat can be used to supply district heating systems or further used for electricity production with a turbine at high pressure. The condensed water can be reused after electricity production. The non-separated waste fraction has a lower heating value of 8.85 MJ/kg and can generate 1.29·1010 J of energy (Cherubini et al., 2009).

As an example, for each ton of MSW that is incinerated, 15–40 kg of hazardous waste is produced, requiring further treatment and landfill as hazardous waste. Harmful emissions of MSW incineration come from bottom ashes and flue gas treatment ashes. They are usually sent to landfills. Haiying et al. (2010) developing a methodology for the thermal characterization of municipal solid waste incineration’s (MSWI) fly ash. They found that the content of crystal phases first increases between room temperature and 800 °C and then decreases between 800 °C and 1200

°C, while that of glass phases registers a reverse trend. Fly ash registers a SiO2–Al2O3–metal oxides system and its content of glass phases is around 57 %. Leachate toxicity analysis shows that toxicity of As, Cd, Cu, Hg, Pb, Ni and Zn decreases with increase of sintering temperature from 600 °C to 1200 °C. On the other hand, the toxicity behaviour of Cr is different – it decreases with increase of temperature from 600 °C to 800 °C and then increases as it rises from 800 °C to 1200 °C.

The waste is thermally decomposed and the energy contained is released and recovered in heat exchangers, where the combustion products are cooled down (Lam et al. 2010). The combustion exhaust gas is pre-treated to remove pollutants. The lime is used to absorb acid gases, activated carbon to fix combustion by-products and ammonia to remove NOx. However, this leads to production of further waste although its quantity is considerably lower.

The following subsystems generally can be found in present up-to-date MSW incineration plants:

waste feeding, combustion (i.e. incineration), heat recovery, off-gas cleaning. Incineration is

Ábra

Figure 3. Enhanced integration of the whole system, representing the main focuses
Table 2. Parameters of Municipal Waste (Fodor et al., 2011a)  Parameters of Municipal Waste  Value
Figure 9. The Problem Table (after Klemeš et al., 2010)
Table 5. Energy flow demand variability (Varbanov and Klemeš, 2010)
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