High Pressure Soil Incineration: Fuel use Optimization for Environmental Remediation for the BAL Process

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High Pressure Soil Incineration

Fuel use Optimization for Environmental Remediation for the BAL Process

A literary/model study of effective fuel use for soil incineration under high pressure conditions, this report studies background and types of earth remediation. It attempts to optimize a new type of soil incineration process, a so-called BAL process.

Calculations were made on fuel types and amounts. This study focuses solely on the combustion and dimensioning of the combustion chamber part of the BAL process and does not attempt to explain/calculate anything before or after the high pressure combustion chamber.

Authors: Arturas Daugela, Oscar Montelius.

Supervisors: Anders Malmquist, KTH.

2015-05-22

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Abstract

Soil incineration is a relatively new subject that has usually had hazardous gas release problems. Incineration has been generally unsustainable. Incineration releases a wide array of gases hazardous to the environment and human health, such as polycyclic aromatic hydrocarbons, volatile organic compounds and dioxins.

The studied so-called BAL process combusts soil to remove pollutants. Waste is removed in slag products and hazardous gases are crystallized. Almost no

hazardous gases are released to the atmosphere. The purpose of this report was to optimize fuel use for the BAL process and to analyze the BAL process from a

Sustainable Development perspective. oil, coal, peat and wood chips were examined.

All fuels were viable. coal and oil required the least amount of fuel but the most amount of air. Peat and wood chips required less air but more fuel. No fuel was chosen as “best in any case”. Other optimization suggestions include: recycling of flue gases, Municipal Solid Waste as fuel and shape of combustion chamber. The BAL process was found to adhere to the Sustainable Development idea. The BAL process increases regional, economic and environmental sustainability. The results of this report may optimize the environmental sustainability of the BAL process even further.

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Sammanfattning

Jordförbränning är ett relativt nytt ämne som vanligtvis har haft problem med giftiga gasutsläpp. Förbränning har generellt varit ohållbart. Förbränning släpper ut ett brett spektrum av gaser som är skadliga för miljön och människor, tex polycyclic aromatic hydrocarbons, volatile organic compounds and dioxiner. Den så kallade BAL-systemet vi har undersökt förbränner jord för att ta bort miljöfarligt avfall. Avfall sorteras ut som slagg och farliga ämnen utkristalliseras ur gasen. Nästan inga farliga gaser släpps ut i atmosfären. Syftet med denna rapport var att optimera bränsleförbrukningen för BAL- systemet och att analysera BAL-systemet från ett hållbarhetsperspektiv. Vi har undersökt olja, kol, torv och flis. Alla bränsletyper var möjliga alternativ. kol och olja krävde minst mängd bränsle och störst mängd luft, torv och flis krävde mer bränsle men mindre luft. Inget bränsle kunde väljas som det bästa alternativet i alla situationer. Andra optimeringsförslag var: Återvinning av avgaser, hushållssopor som bränsle och formen på förbränningskammaren. BAL-systemet innefattas av begreppet hållbar utveckling.

BAL-systemet hjälper ekonomisk, miljömässigt och regional hållbar utveckling.

Resultaten från denna rapport kan underlätta miljömässig optimering.

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Foreword

This report was written for the Sustainable Energy Technology program at KTH during spring of 2015.

Thanks to all who have aided in the process.

Special Gratitude for:

Anders Malmquist Göran Almlöf Weihong Yang Jeevan Jeyasuriya Göran Grönhammar Hans Havtun

Gunnar Bech

Stockholm 2015

Arturas Daugela, Oscar Montelius

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Abbreviations

Abbreviation Meaning Unit

Cp Specific Heat Coefficient kJ/kg^oC

H, h Lower Heat Value kJ/kg

D Density kg/m³

SD Sustainable Development N/A

MSW Municipal Solid Waste N/A

EPA Environmental Protection Agency N/A

PAH Polycyclic Aromatic Hydrocarbons N/A

VOC Volatile Organic Compounds N/A

m% Mass Percentage %

Cp_S Heat Coefficient for soil kJ/kg^oC

Cp_A Heat Coefficient for air kJ/kg^oC

Cp_C Heat Coefficient for coal kJ/kg^oC

Cp_O Heat Coefficient for oil kJ/kg^oC

Cp_P Heat Coefficient for peat kJ/kg^oC

Cp_H₂_O Heat Coefficient for water kJ/kg^oC

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D_C Density for coal kg/ m³

D_O Density for oil kg/ m³

D_p Density for peat kg/m³

D_W Density for wood chips kg/ m³

D_A Density for air kg/ m³

D_S Density for soil kg/ m³

H_C Heat Value for coal kJ/kg

H_O Heat Value for oil kJ/kg

H_P Heat Value for peat kJ/kg

H_WC Heat Value for wood chips kJ/kg

m_A Mass air kg

m_F Mass fuel kg

m_S Mass soil kg

m_C% Mass percentage of coal %

m_H% Mass percentage of hydrogen %

m_S% Mass percentage of sulfur %

m_O% Mass percentage of oxygen %

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E_in Energy going into the system kJ

E_out Energy coming out of the system kJ

El_loss Energy lost from the system kJ

E_sink Energy absorbed by the sink kJ

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1. Introduction

Environmental or earth remediation is a relatively new subject. The high profile of the contaminated earth problem has attracted many engineers and environmentalists.

Already twenty years ago this was a problem. Industry is struggling with waste reduction. Incineration is one of the many types of soil incineration (Brunner, 1993).There are many positive aspects to incineration such as:

 Hazardous components are destroyed by heat.

 Volume is reduced in the form of slag.

 Ease of on-site incineration.

(Brunner, 1993)

1.1 A Brief History of Soil Pollution and Remediation

Industrial pollution of soil, among other things, was brought into the spotlight only late 1993. United Nations Development Organization, the World Bank, United Nations Environment Programme Industry and Activity Centre started by the end of 1993 issuing new pollution abatement/prevention policies. International focus on pollution has always centered on prevention and not remediation.

Previous industry has had many cases of contaminated soil worldwide. An example is Värtahamnen, Sweden, where a gas factory has heavily contaminated the area (Länstyrelsen, 2005), (Wang, 2004). Previous pollution must be remediated. There are now many new methods of remediation which are interesting from a sustainable development perspective. New remediation techniques are largely developed in Holland, Germany and Belgium. Techniques such as vacuum extraction, cadmium washing, and steam stripping etc., this report will focus on incineration techniques.

High temperature incineration is a new and promising lead in soil remediation. Soil is often contaminated by volatile organic compounds and other types of contaminants.

To aid in the pursuit of sustainable development, these contaminants must be remediated (Wang, 2004).

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1.2 Why Earth Remediation and Incineration?

Earth incineration is showing promise as a remediation method. The EPA has recommended more research and funding for the rotary kiln incineration process (Linak, 1988). Recent studies show that destruction of toxic organic waste can reach environmentally sustainable levels (Dellinger, 1998). Incinerator knowledge and technology has come far and is an increasingly viable option for earth remediation (Wang, 2004).

Incineration is 99% energy efficient, and while it has more health and environmental concerns it is still a good option. If done correctly, incineration with post-treatment will not release excessive amounts of contaminated gases. It is one of the best and most economically viable technologies for soil remediation and sustainability of our soils (Li, 2007), (Wolf, 1995).

Incineration can be applied to contamination problems of any size. Companies offering earth remediation via rotary kiln incineration often have a variety of kilns to choose from. Rotary Kilns are mobile and applicable to a wide range of projects, from small projects with less than 5 tonnes of mass to large with up to 500 000 tonnes of remediation (EPA, 2013). The commercial incineration business has a good future.

Even preceding the 21^st century soil incineration was a growing business (Wolf, 1995)

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2. Background

We have chosen to assemble a small background study to give the BAL process some context. It is important to know why this process is vital and why it should be considered as an alternative to other forms of soil remediation. The background study below concerns human and environmental effects caused by incineration, examples of cleanup projects, incineration problems, other types of soil remediation, as well as the studied BAL process. All of these topics have a part in global sustainable development, and it is important to keep this topic relevant. Remediation, optimization as well as the BAL process contributes to Sustainable Development.

2.1 The Sustainable Development Perspective

Sustainable development is one of the greatest challenges that we face today. It is important to keep sustainability in mind throughout this report. We need to sustain human health, the environment and develop, for example, life expectancy. It is therefore important to remediate and clean what we have polluted in the past.

Incineration, in itself, is not a very clean form of remediation. According to environmentalists, it has no place in the 21^st century. In this report we examine the ways that incineration affects both our lives and the environment. However, we also suggest a new type of incineration for remedial purposes (Kates, 2015 and Fulekar et al, 2014). While there are many problems with incineration, it is possible to make incineration sustainable.

2.2 Human Health and Environmental Concerns

Soil incineration is a hazardous form of remediation. It is a complex and controversial issue. Hazardous gases are released due to oxidation, such as heavy metals and dioxins (Taylor et al, 1997). Other areas of concern include stack emissions from destroyed organic vapors and a variety of other contaminant-laden gases (EPA, 1997). All of these emissions are not environmentally sustainable and should be reduced as much as possible.

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4 An example of soil remediation by incineration can be seen at an American chemical treatment plant Baird and McGuire Superfund in Holbrook, Massachusetts. According to a study by the EPA, soil was found to be heavily contaminated by dioxins, VOC’s, PAH’s and a number of other organic compounds. An on-site rotary kiln incineration project took place between 1995 and 1997. During the specified time, approximately 200 000 tonnes of soil has been processed. However this process implied dioxin and other gaseous releases to the atmosphere (Taylor et al, 1997). Contamination of soil is still a significant problem today. Below follows a summary of health effects for some standard gases released due to contaminated soil incineration:

 PAH’s, Polycyclic Aromatic Hydrocarbons. Released due to incomplete organics combustion. Highly toxic, mutagenic, carcinogenic to humans.

Limited bioremediation capabilities (Samanta, 2002).

 VOC’s, Volatile Organic Compounds risk causing respiratory and irritation concerns, asthma in children, other chronic respiratory symptoms (Ware et al, 1993).

 Dioxins, carcinogenic (Travis et al, 1991), dermal toxicity, negative reproductive effects and similar (WHO, 2000).

The environmental effects of these gases are similar as to humans. Organic life and matter is heavily affected by PAH’s, VOC’s and Dioxins. These gases are excessively dangerous in larger quantities. Dioxins, for example, are resistant to most types of degradation and therefore accumulate in the environment. Dioxins are found even in places where they have not previously been used (Deriziotis, 2004).

PAH’s are carcinogenic and mutagenic not only to humans, but to all forms of life (Samanta, 2002).

 PAH’s bind to dust and soot particles to enter the atmosphere. Rain then transfers PAH’s to soil and plant life. Some PAH’s affect aquatic organisms.

Long term environmental effects (Samanta, 2002).

 VOC’s, besides affecting organic life give undesirable ozone smog (Ismail, 2013). Easily accumulate to large concentrations in indoor air (Berglund et al, 1997).

 Similar toxic effect on mammals as the already mentioned human effects (Dobrzynski, 2009).

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2.3 Some Examples of Recent Earth Incineration

There are many examples of soil incineration. The practice is commonplace and effective. Below are just a couple of examples of recent soil incineration for remedial purposes.

Baird and McGuire Superfund in Holbrook.

Contaminant Source: Land disposal.

Contaminants: Dioxins, VOC’s, PAH’s.

Process amount: 210 000 tonnes.

Time: Two years.

Capacity: Approx. 9400kW (EPA, N/A)

Bayou Bonfouca, Los Angeles:

Contaminant Source: Creosote Plant.

Contaminants: PAH’s.

Time: Two Years.

Capacity: Unspecified (EPA, 2000)

Sikes Disposal Pits, Texas:

Contaminant Source: Disposal Plant.

Contaminants: Organic compounds.

Time: Two years.

Capacity: Approx. 35 000kW (EPA, 2000)

Times Beach Superfund, Missouri.

Contaminant Source: Road Oiling.

Contaminants: Dioxins.

Time: One year.

Capacity: Approx. 11 700kW (EPA, N/A)

Figure 1, examples of soil remediation via incineration.

More examples of similar and smaller projects can be found in the Remediation Technology Cost Compendium by the EPA. Extra information is also available on thermal remediation treatments, pricing and kiln types. Above examples are for less common, larger incinerators. For a complete picture of incinerator use, see the 2001 EPA document.

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2.4 Types of Thermal Remediation

There are many forms of soil remediation being used. This report focuses on thermal-based methods. Specifically soil incineration is discussed and optimized, from an energy perspective. Methods of thermal soil remediation most widely used are as follows:

 Thermal Desorption – Using direct or indirect heat, in or ex-situ, to physically separate contaminants from soils. The contaminants together with water vapor must be later treated. This system has risks. Hazardous gas leaks would contain dangerous metals such as Arsenic, Mercury or Lead. Thermal Desorption systems can be mobile or stationary and often use rotary kilns for continuous feeds. The main problem with the desorber system is the large amount of post treatment required (Anderson, 1995). Although post treatment is not the focus of this study, it is worth mentioning that there are better ways of handling it.

 Oxidation (incineration) – Similar to the aforementioned BAL system.

Incineration of soil to oxidize contaminants. This is a controversial method due to release of hazardous materials in gas form (Taylor et al, 1997).

 Catalytic Oxidation – Similar to thermal, but with a catalyst to reduce the required temperature.

2.5 Soil Incineration Methods and Costs

The definition of soil incineration, in its basic form is “use controlled flame combustion to volatilize and destroy organic contaminants to treat a variety of media, including soils, sludge, liquids, and gases.” according to the 2001 EPA Superfund Remedy Report.

There are a number of methods used for soil incineration/oxidation. The Swedish company SAKAB uses a rotary oven at 1200 °C, similar to the recommended 1400

°C of our studied system. Kilns, similar to those for cement hardening, are also used according to Stockholm Recycling Council. Rotary Kilns are most widely used (Shearer, 1991).

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7 The basic incinerator consists of a burner, which ignites a designated fuel type in the combustion oven, which is usually dimensioned project-by-project. The effectiveness of a soil incinerator depends heavily on chamber temperature, cook time and the type of soil.

Thermal destruction of most organic compounds begins at around 600 °C. Yet higher temperatures are needed to release non-organic hazardous compounds (EPA, 2013).

The cost of on-site soil incineration, according to 17 case studies, prepared by the Federation Remediation Technologies Roundtable, and summarized by the EPA are as follows:

 No correlation in quantity of soil by unit cost was found.

 Total cost for treatment ranged between 300-400USD per tonne. This cost is for soil with standard contaminants such as PAH’s or propellants.

 Aforementioned soils were mainly Sediments/Sludge/Organics.

 Aforementioned soils were incinerated using rotary kilns.

 Dates of projects were between 1991 and 1997.

(EPA, 2001)

2.6 Current Earth Incineration Problems

Current problems with the aforementioned incineration types and techniques are:

 Release of hazardous gases, such as VOC’s, PAH’s or Dioxins to the atmosphere (Dellinger, 1988).

 Human health concerns of the aforementioned gases.

 Fuel consumption. Current rotary kilns and incinerators use large amounts of, usually fossil, fuel (Johnke, 2003)

 CO² and other greenhouse gas release from use of fossil fuels (Johnke, 2003).

As earlier mentioned, these problems lead to an unsustainable remediation process.

This report studies a new, high-pressure incineration process, the so-called BAL process. This innovation is patented by inventor Göran Almlöf.

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2.7 The BAL Process

This report puts forward a new process of earth remediation. The BAL system, by patent-holder Göran Almlöf, is a complex system. It includes, in systematic order:

 Air compression to 5 bars.

 High-pressure incineration at 5 bars and 1400 °C.

 Expansion (cooling).

 Crystallization of hazardous gases.

 District cooling/energy extraction.

Figure 2, The BAL process. Taken from Patent No. SE 7908565-0 in the Swedish patent database.

Legend:

1 Steam Boiler 11 Combustion Chamber

2 Cooler 12 Vaporizer

3 Compressor 13 Steam Drum

4 Cooler 14 Superheater

5 Expansion Device 15 Steam Turbine

6 Receptacle 16 Economizer

7 Chimney 17 Gas Scrubber

8 Shaft 18 Gas Cooler

9 Motor 19 Condenser

10 N/A 20 Water Cooling Circuit

Note: Not all legend entries are present in figure.

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9 The main point of the BAL process, as recognized by this report, is to incinerate pollutants present in soil. Soil is combusted by a flow of fuel and air. After compression, air at a temperature of 187 °C enters the chamber. In a separate flow, fuel at room temperature, either solid (see 2.8), liquid or gas, enters the chamber.

The fuel combusts together with the required amount of air and releases energy into the soil, which acts as a heat sink. Once the chamber and soil are heated to around 1400 °C, the soil forms slag and most pollutants escape via flue gas.

Virtually all hazardous airborne particles should be crystallized for easy disposal.

This is done by expanding the flue gases, therefore substantially reducing their temperature, down to -80 °C. The gases crystallize. This should nullify all gas release and sustainability concerns. No contaminants such as PAH’s, VOC’s or Dioxins are released into the atmosphere. Instead they are separated and stored. All mineral or other solid particles are reduced to slag. Through a system of compressors and expanders, gases can be used for District Cooling. This process also generates net power (Almlöf, 1983). According to the idea and patent by Almlöf, the combustion process includes airborne pollutant remediation. The purpose of this invention is to combine a combustion process with complete exhaust emission control. This report will henceforth focus solely on the combustion process of the BAL system, as illustrated by Fig. 2.

The BAL system removes many concerns regarding soil incineration. Concerns such as human health, environmental contamination, and hazardous gases should be completely removed. Slag is contained and easily stored. According to the patent holder, most gases are separated and sorted. Net energy is extracted or used for District Cooling. Fuel environmental concerns become more or less irrelevant due to that all gases, including fuel combustion gases, are separated and stored (Almlöf, 1983).

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2.8 Solid Fuels

There is an inherent problem using solid fuels in a pressurized chamber. We have assumed a “flow” of solid fuels, but this of course is not possible under standard circumstances. As a solution for this problem we have examined gating, which is a way to systematically add coal and achieve a flow of the fuel.

Gating, as represented by figure 4, is a way to pressurize solid fuels and obtain a mass flow. This removes the need to add fuel via batches. This method is used in Värtaverket in Sweden, and was suggested and described to us in person by Göran Grönhammar, an engineer at Gamleby Innovators.

Figure 3, The Gating process.

Solid fuels will enter the system in small pieces, and then it will pass two gates into a pressurized chamber. These gates will make sure no pressure is lost. This fuel, now pressurized, then enters a rotator and is spread evenly into a pipe through which compressed air flows and propels the fuel into the combustion chamber, generating a mass/volume flow of a solid fuel.

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3. Objective and Method

3.1 Objectives and Limitations

The purpose of this report is to examine the combustion process of the BAL invention. To optimize fuel use, fuel choice and other aspects of the combustion. To achieve the specified temperatures and pressures, a number of results are to be analyzed. Combinations of fuel, air and soil are to be determined per fuel type. These are to be presented in a table. Other combinations of volumes and fuel types are to be presented in tables in the appendix. Discussions are to be made on availability/price of the chosen fuels. Discussion will also be put forward regarding sustainable development and how the BAL system interacts with this field.

The purpose of this report excludes examination of the rest of the BAL process other than in the introduction, chapters 1 and 2. Economy considerations, availability or environmental effects of chosen fuel are also mostly excluded. High-detail simulations of the BAL process or its combustion phase are also excluded. This report does not take into account the small chemical contents of soils that might contribute to or subtract from the combustion process. Meaning any type of pollutants that might contribute heat to the combustion reaction.

Our study is centered on the combustion part of the BAL process, as seen in fig. 5.

The BAL process is a large and complex process and this report makes an assumption that other parts of the process function flawlessly. We focus strictly on the combustion and combustion chamber, flow and fuel.

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3.2 Method

This report begins with a literature study of the current situation with soil incineration processes, policies, health concerns, environmental concerns and costs.

Literature was acquired through a wide array of sources, such as:

Scopus, KTHB, Google Scholar and

EPA Reports. Calculations were done based on a variety of assumptions and delimitations.

The entire work process is illustrated by Figure 4.

Calculations consisted of determining and solving the energy balance (eq 1-3) for the combustion chamber. Stoichiometric calculations (eq 4-13) were done to identify the amount of theoretical air needed for a full combustion to take place. The reason as to why these calculations need to take place is to determine the total air and fuel requirements for a given amount of soil.

These results will then be discussed and optimization suggestion will be put forward. Future research suggestions will also be made.

Figure 4 Flow chart over our work process.

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3.3 Other Investigative Methods

Discussions with other lecturers/engineers at KTH were performed, especially to assume proper delimitations. Discussions with the supervisor and the innovator Göran Almlöf at Gamleby have been ongoing during the span of the project. The outcomes of these discussions are incorporated in the relevant sections of this report.

3.4 Calculations

Equations were taken from books that have waste incineration as their subject and other incineration reports. Calculations were done strictly in Matlab code. Plots were done strictly in Matlab code. Heat values, densities, stoichiometric values and other material facts were taken from various sources discussed in 3.5.

The first task was to create and balance an energy equation. According to the law of conservation of energy, energy is never destroyed or otherwise lost. All energy added via a combustion must leave or be absorbed in some way. In this case, energy that was added by fuel combustion was absorbed by the heat sink and lost through the chamber walls or via the escape of flue gases. Once the mass balance equations (eq. 1-3) were complete, the stoichiometric equations were needed to determine the minimum amount of air required for combustion.

The stoichiometric equations consist of basic reactions during the combustion of fuels, and besides for the ratios of elements and molecules, are the same for all fuels. In a fuel it is the Carbon, Hydrogen and Sulfur elements that react with oxygen to release heat. These are rather simple reactions that can be balanced for a specific amount of fuel with ease.

Below follows all energy balances equations and stoichiometric equations, with an energy balance image (Figure 5) to illustrate the energy balance workflow.

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Figure 5. The incineration chamber of the BAL process.

Eⁱⁿ is the total energy of Air at 186 °C and the total energy of the Fuel. This energy was calculated with Specific Heat Coefficient values according to our sources (Table 2) and temperature differences specified in the BAL process patent.

Heat loss through walls was estimated with help from Weihong Yang, a KTH professor, to 2-10 %. For calculation purposes we have chosen that the loss is 10 %.

E^loss therefore is 10 % of Eⁱⁿ. The energy absorbed by the soil is E^sink. The soil absorbs a large amount of energy and is released in the form of slag products. This was calculated with temperature differences and the specific heat coefficient for soil (Table 2).

The Energy balance Equation is (1), and with all of the energies expressed and above calculations included leads to eq. (2), and when solved for mass of air leads to eq. (3).

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𝐸_𝑖𝑛= 𝐸_𝑜𝑢𝑡+ 𝐸𝑙_{𝑙𝑜𝑠𝑠}+ 𝐸_{𝑠𝑖𝑛𝑘} (1)

𝑚_𝐴∗ 𝐶𝑝_𝐴∗ ∆𝑇₁+ 𝑚_𝐹∗ 𝐶𝑝_𝐹∗ ∆𝑇₂= 0,1 ∗ (𝑚_𝐴∗ 𝐶𝑝_𝐴∗ ∆𝑇₁+ 𝑚_𝐹∗ 𝐶𝑝_𝐹∗ ∆𝑇₂) +0,8 ∗ 𝑚_𝑆∗ 𝐶𝑝_𝑆∗ ∆𝑇₃+ 0,2 ∗ 𝑚_𝐻₂_𝑂∗ 𝐶𝑝_𝐻₂_𝑂∗ ∆𝑇₃+ (𝑚_𝐴+ 𝑚_𝐹) ∗ 𝐶𝑝_{𝐹𝑙𝑢𝑒}∗ ∆𝑇₄

(2)

𝑚_𝐴 =0,1 ∗ 𝑚_𝐹∗ 𝐶𝑝_𝐹∗ ∆𝑇₂+ 0,8𝑚_𝑆∗ 𝐶𝑝_𝑆∗ ∆𝑇₃+ 0,2 ∗ 𝑚_𝑆∗ 𝐶𝑝_𝐻₂_𝑂∗ ∆𝑇₃+ 𝑚_𝐹∗ 𝐶𝑝_{𝐹𝑙𝑢𝑒}∗ ∆𝑇₄ 0,9 ∗ 𝐶𝑝_𝐴∗ ∆𝑇₁− 𝐶𝑝_{𝐹𝑙𝑢𝑒}∗ ∆𝑇_{𝐹𝑙𝑢𝑒}

(3)

The variables for equations 1-3 are as follows:

 𝑚_𝐴 = 𝑀𝑎𝑠𝑠 𝑎𝑖𝑟 (𝑘𝑔)

 𝑚_𝐹 = 𝑀𝑎𝑠𝑠 𝑓𝑢𝑒𝑙 (𝑘𝑔)

 𝑚_𝑆 = 𝑀𝑎𝑠𝑠 𝑠𝑜𝑖𝑙 (𝑘𝑔)

 ∆𝑇₁ = 1600 − 187 (℃)

 ∆𝑇₂ = 1600 − 20 (℃)

 ∆𝑇₃ = 1400 − 20 (℃)

 ∆𝑇₄ = 1200 − 200 (℃)

 𝐶𝑝_𝐴, 𝐶𝑝_𝐹, 𝐶𝑝_𝑆, 𝐶𝑝_{𝐹𝑙𝑢𝑒}=

𝑆𝑝𝑒𝑐𝑖𝑓𝑖𝑐 ℎ𝑒𝑎𝑡 𝑣𝑎𝑙𝑢𝑒𝑠 𝑓𝑜𝑟 𝐴𝑖𝑟, 𝐹𝑢𝑒𝑙, 𝑆𝑜𝑖𝑙 𝑎𝑛𝑑 𝐹𝑙𝑢𝑒 𝑔𝑎𝑠 _{𝑘𝑔∗𝐾}^𝑘𝑗

This energy balance equation was used to calculate the needed mass of air and fuel for every given amount of Soil. The equation was solved using Matlab. This equation was later plotted together with the stoichiometric calculation for the air needed.

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16 The stoichiometric equations are:

𝐶 + 𝑂₂ ^{𝑦𝑖𝑒𝑙𝑑𝑠}→ 𝐶𝑂₂ (4)

1𝐶 +32

12𝑂 ^{𝑦𝑖𝑒𝑙𝑑𝑠}→ 44

12𝐶𝑂₂ (5)

1𝑘𝑔 𝐶 + 2.67𝑘𝑔 𝑂 ^{𝑦𝑖𝑒𝑙𝑑𝑠}→ 3.67𝑘𝑔 𝐶𝑂₂ (6)

2𝐻₂+ 𝑂₂ ^{𝑦𝑖𝑒𝑙𝑑𝑠}→ 2𝐻₂𝑂 (7)

1𝐻 +32

4 𝑂 ^{𝑦𝑖𝑒𝑙𝑑𝑠}→ 36

4 𝐻₂𝑂 (8)

1𝑘𝑔 𝐻 + 8𝑘𝑔 𝑂 ^{𝑦𝑖𝑒𝑙𝑑𝑠}→ 9𝑘𝑔 𝐻₂𝑂 (9)

𝑆 + 𝑂₂ ^{𝑦𝑖𝑒𝑙𝑑𝑠}→ 𝑆𝑂₂ (10)

1𝑆 +32

32𝑂 ^{𝑦𝑖𝑒𝑙𝑑𝑠}→ 64

32𝑆𝑂₂ (11)

1𝑘𝑔 𝑆 + 1𝑘𝑔 𝑂 ^{𝑦𝑖𝑒𝑙𝑑𝑠}→ 2𝑘𝑔 𝑆𝑂₂ (12)

The purpose was to calculate the stoichiometric mass of air needed to combust the chosen amount of fuel. To do this we used basic stoichiometric equations. Equation 4 describes the process where Carbon combines with oxygen and creates carbon- dioxide. Using the atomic weight we know that 1mole C weighs 12 g and 1 mole O weighs 16 g, divided to get one C gives equations (5-6). Now we can simply insert any mass since we know it follows a linear correlation.

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17 Equation (7) describes how hydrogen combines with oxygen and forms water. We do the same with this process as before and we know that the atomic weight of one mole hydrogen is 2 g. This gives, by the same logic as before, equations (8-9).

Equation (10) describes how sulfur combines with oxygen and forms sulfur-dioxide.

In the same way we calculated previously, we know that the atomic mass of sulfur is 32 g/mole. This is shown by equation (11-12).

These calculations combined and the fact that only 23.3 % of the air is pure oxygen gives us equation (13), which describes the stoichiometric amount of air needed to combust any given amount of fuel.

𝑇ℎ𝑒𝑜𝑟𝑒𝑡𝑖𝑐𝑎𝑙 𝑎𝑖𝑟 𝑟𝑒𝑞𝑢𝑖𝑟𝑒𝑑 𝑓𝑜𝑟 𝑐𝑜𝑚𝑏𝑢𝑠𝑡𝑖𝑜𝑛 =2.67 ∗ 𝑚_𝐶%+ 8 ∗ 𝑚_𝐻%+ 1 ∗ 𝑚_𝑆%− 𝑚_𝑂%

0.232

(13)

The theoretical air requirement equation is now known (eq. 13). The next step is to determine the Coal, Hydrogen, Sulfur and Oxygen content for our four fuels. Table 1 represents the mass percentages for the mentioned elements.

Table 2 represents where the source data was taken from for densities, heat coefficients, heat values and mass percentages.

Fuel 𝒎_𝑪% 𝒎_𝑯% 𝒎_𝑺% 𝒎_𝑶% 𝒎_𝑨

𝒎_𝑭

Coal 0.861 0.046 0.006 0.03 11.13

Oil 0.859 0.12 0.005 0.007 13.76

Peat 0.42 0.039 0.01 0.231 5.10

Wood Chips 0.50 0.052 0.003 0.43 5.56

Table 1. Stoichiometric Balance.

With these results we were able to acquire the optimal amount of fuel and air depending on the amount of soil combusted. After this the mass and volume flows of fuel, air and flue gases were calculated by using the specific heat coefficients and densities for the fuels. The fuels that we have analyzed are oil, coal, wood chips and peat.

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18

3.5 Thermodynamic Source Data

The data for densities, specific heat coefficients and heating values were taken from various sources. A source widely used was a database called Engineering Toolbox. It is worth mentioning that we were unable to fact check this data. The data appears to be valid, but in a further iteration of this study it is suggested that this data would be experimentally acquired. Even though the data is generally trusted, approximations were made. The thermodynamic data and sources are represented by table 2:

Data Constant Unit Source

𝐶𝑝_𝑆 0.8 _{𝒌𝒈 ∗ 𝑲}^𝒌𝑱 Alnefaie Et Al, 2013

𝐶𝑝_𝐴 1.2 _{𝒌𝒈 ∗ 𝑲}^𝒌𝑱 Urieli, 2014

𝐶𝑝_𝐶 1.8 _{𝒌𝒈 ∗ 𝑲}^𝒌𝑱 Tomeczez, Et Al, 1996

𝐶𝑝_𝑂 1.8 _{𝒌𝒈 ∗ 𝑲}^𝒌𝑱 Watlow, 2015

𝐶𝑝_𝑃 1.88 _{𝒌𝒈 ∗ 𝑲}^𝒌𝑱 Engineering Toolbox

𝐶𝑝_𝐻₂_𝑂 1.9 _{𝒌𝒈 ∗ 𝑲}^𝒌𝑱 Radmanivoc Et Al, 2014

𝐷_𝐶 1500 ^𝒌𝒈_𝒎𝟑 Engineering Toolbox

𝐷_𝑂 920 ^𝒌𝒈_𝒎𝟑 Engineering Toolbox

𝐷_𝑝 310 ^𝒌𝒈_𝒎_𝟑 Engineering Toolbox

𝐷_𝑊 360 ^𝒌𝒈_𝒎𝟑 Engineering Toolbox

𝐷_𝐴 5500 ^𝒌𝒈_𝒎𝟑 Engineering Toolbox

𝐷_𝑆 2600 ^𝒌𝒈_𝒎_𝟑 Loganathan, 1987

𝐻_𝐶 32500 _𝒌𝒈^𝒌𝑱 Trent Et Al, 1982

𝐻_𝑂 42700 _𝒌𝒈^𝒌𝑱 Wang, 1999

𝐻_𝑃 17000 _𝒌𝒈^𝒌𝑱 Stockholm Convention Organic Pollutants

𝐻_𝑊𝐶 18500 _𝒌𝒈^𝒌𝑱 Sustainable Energy Authority of Ireland

m_C% N/A ^% Trent Et Al, 1982 (Coal) , Haanel, N/A (Peat) Francescato Et Al, 2008 (Oil, Wood Chips)

m_H% N/A ^% Trent Et Al, 1982 (Coal) , Haanel, N/A (Peat) Francescato Et Al, 2008 (Oil, Wood Chips)

m_S% N/A ^% Trent Et Al, 1982 (Coal) , Haanel, N/A (Peat) Francescato Et Al, 2008 (Oil, Wood Chips)

m_O% N/A ^% Trent Et Al, 1982 (Coal) , Haanel, N/A (Peat) Francescato Et Al, 2008 (Oil, Wood Chips) Table 2. Thermodynamic data and sources.

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19

4. Results

For the results we have chosen the following attributes:

 Combustion Chamber – 60 m³. The furnace should be mobile; a rough estimation of volume was taken from a standard sized, 40’ shipping container, which is 67 m³and should fit the furnace (Direct Logistics, N/A).

 Soil Combusted – Between 1 and 30 m³of soil were examined, with intervals of 2 m³.

 Fuels examined – Oil, Coal, Wood Chips and Peat.

 Air needed – The air needed varies fuel by fuel. Air flow and compression is outside the limitations of this report, but it is worth noting that the air requirement for the chamber is very large.

Figures 6-9 represent the optimal amounts of air and fuel for five given soil volumes as well as conditions when using one of the four fuels that are examined. The results will be further explained following each figure. Where the stoichiometric equation line crosses the energy balance line is the optimal air/fuel ratio. After an intersection there is not enough stoichiometric air for the combustion to take place. Under non- theoretical circumstances it would be recommended to increase the air flow beyond the required amount, more on this in chapter 5.

The heat loss, E^loss, was assumed to be 10% according to Weihong Yang. This will later be varied to assert the range of possible losses and how this affects fuel use.

Other types of errors will be discussed in the error analysis chapter.

Time to heat up the combustion chamber and soil is assumed at one hour, as per discussion with supervisors.

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20

4.1 Fuel and Air Consumption Graphs

Below are the graphs of fuel and air requirements. Each intersect represents the optimal air and fuel consumption . The volumes V^s represent the volume of combusted soil.

Coal yielded the most moderate results of all the fuels. It needs a moderate mass and requires a

relatively high amount of air to burn, similar to oil below.

Further intersections and exact values are

represented by table 3. For variations of values see chapter 5 and appendix B.

Figure 6. Stoichiometric air vs energy balance calculation for coal.

Oil obtained similar results to coal, needing high amounts of air flow but less fuel mass.

Further intersections and exact values are represented by table 4. For variations of values see chapter 5 and appendix B.

Figure 7. Stoichiometric air vs energy balance calculation for oil.

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21 Unlike oil and coal, peat and wood chips required significantly less airflow per

amount of fuel. These two fuels are of lower densities, meaning that per volume unit of fuel, the amount of air is significantly higher.

When comparing the graph for peat with graphs for oil and coal, it can be gauged that, for example, 2 m³of soil (the first intersection) take more mass of fuel to combust Further intersections as well as exact values are represented by table 5. For variations of values see chapter 5 and appendix B.

Figure 8. Stoichiometric air vs energy balance calculation for peat.

Wood chips performed similarly to peat. However they required even more mass to combust the same amount of fuel. Further intersections as well as exact values are represented by table 6. For variations of values see chapter 5 and appendix B.

Figure 9. Stoichiometric air vs energy balance calculation for wood chips.

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22

4.2 Coal

Coal yielded the most moderate results of all the fuels. It needs a moderate mass and requires a relatively high amount of air to burn, unlike peat or wood chips. The volumes of soil that were examined are between 2 and 30 m³, until half of the 60 m³ chamber was filled. According to our model, the amount of Coal required to combust 6 m³of soil is 7 699 kg. 38 495 m³ of atmospheric air is required to combust.

Table 3. Intersection points of Figure 6, Mass flow air and fuel required for combustion using Coal.

4.3 Oil

As previously mentioned, oil was the only liquid fuel examined. Results show that oil required the least amount of mass per unit soil to combust, but required large amounts of air. The volumes of soil that were examined are between 2 and 30 m³, until half of the 60 m³chamber was filled.

Volume of Soil (𝒎^𝟑)

Volume of Air After compressio

n (𝒎^𝟑)

Volume of Air before compressio

n (𝒎^𝟑)

Mass of Fuel (kg)

Volume Flow of Air after compressio

n (𝒎^𝟑/s)

Volume Flow of Air before compressio

n (𝒎^𝟑/s)

Mass Flow of Fuel (kg/s)

2 2 566 12 831 1 285 0,71 3,56 0,35

4 5 133 25 664 2 537 1,43 7,13 0,70

6 7 699 38 495 3 805 2,14 10,69 1,05

8 10 265 51 327 5 073 2,85 14,26 1,40

10 12 832 64 160 6 341 3,56 17,82 1,76

12 15 398 76 992 7 609 4,28 21,39 2,11

14 17 965 89 824 8 877 4,99 24,95 2,46

16 20 531 102 655 10 145 5,70 28,52 2,81

18 23 098 115 491 14 130 6,42 32,08 3,39

20 25 664 128 318 12 681 7,13 35,64 3,52

22 28 231 141 155 13 949 7,84 39,21 3,87

24 30 796 153 982 15 217 8,55 42,77 4,22

26 33 364 166 818 16 485 9,27 46,34 4,57

28 35 929 179 645 17 753 9,98 49,90 4,93

30 38 496 192 482 19 021 10,69 53,47 5,28

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23 According to our model, the Oil required to combust 6 m³of soil is 8 033 kg. 40 164 m³ of atmospheric air is required to combust. All volumes of soil, fuel and air required are represented by Table 4.

Table 4. Intersection points of Figure 7, Mass flow air and fuel required for combustion using Oil.

4.4 Peat

According to stoichiometric calculation Peat requires much less air since there is air trapped within the fuel. This fuel has a lower Heating Value however and contains less carbon per unit of mass, so more fuel is needed. The volumes of soil that were examined are between 2 and 30 m³, until half of the 60 m³chamber was filled.

Volume of Soil (𝒎^𝟑)

Volume of Air After compression (𝒎^𝟑)

Volume of Air before compression (𝒎^𝟑)

Mass of Fuel (kg)

Volume Flow of Air after compression (𝒎^𝟑/s)

Volume Flow of Air before compression (𝒎^𝟑/s)

Mass Flow of Fuel (kg/s)

2 2 678 13 388 1 323 0,74 3,72 0,36

4 5 355 26 775 2 646 1,49 7,44 0,73

6 8 033 40 164 3 969 2,23 11,16 1,10

8 10 710 53 551 5 292 2,98 14,88 1,47

10 13 388 66 939 6 615 3,72 18,59 1,83

12 16 098 80 490 7 938 4,47 22,36 2,20

14 18 744 93 718 9 261 5,21 26,03 2,57

16 21 420 107 100 10 584 5,95 29,75 2,94

18 24 098 120 491 11 907 6,69 33,47 3,30

20 26 776 133 882 13 230 7,44 37,19 3,67

22 29 453 147 264 14 553 8,18 40,91 4,04

24 32 131 160 655 15 876 8,93 44,63 4,41

26 34 809 174 045 17 199 9,67 48,35 4,77

28 37 485 187 427 18 521 10,41 52,06 5,14

30 40 164 200 818 19 844 11,16 55,78 5,51

High Pressure Soil Incineration: Fuel use Optimization for Environmental Remediation for the BAL Process