Defining Black: Characterization of Soot Reactivity with Thermogravimetrical Methods

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Defining Black: Characterization of Soot Reactivity with Thermogravimetrical Methods

Adarsh Roy Choudhury

Examiner

Prof. Joydeep Dutta

Supervisors Abdusalam Uheida

Anders Ersson Francesco Regali

December 2020

KTH Royal Institute of Technology School of Engineering Sciences,

Department of Applied Physics SE-100 44 Stockholm, Sweden

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Abstract

Exhaust emissions in a vehicle has to flow through an exhaust aftertreatment in a diesel vehicle. In a diesel engine, the exhaust emissions are treated with Diesel Oxidation Catalyst (DOC), Diesel Particulate Filter (DPF), and Selective Catalytic Reduction (SCR). Every engine produces a different kind of soot depending on the drive cycle. In this thesis, a study was made on the soot oxidation in DPF so as to reduce the net fuel consumption and hence optimising the engine.

This project focuses on DPF, where the soot and ash are trapped on the walls of the filter when the emissions flow through the DPF. Over a period of time, the soot accumulates and causes the pressure inside the filter to increase. To reduce the backpressure due to soot accumulation, soot has to be removed from the filter which is done by a regeneration process in which soot is oxidized. To understand the soot oxidation in the DPF, we study the chemical kinetics of the soot.

The soot reacts with NO2, O2, and N2 in a Thermogravimetric Analysis (TGA) instrument, in isothermal conditions. Two soot samples, SORT-1 and FORCED 360 were analyzed with TGA, the rate equations were derived from using Arrhenius type kinetics and the data was processed by MATLAB. The rate at which the soot is oxidized by NO2 and O2 for SORT-1 is higher than for FORCED 360. This trend is observed similarly when both the soot samples react with only O2. When soot oxidation reaction takes place with O2 and NO2 they require a lower temperature of 250 °C-400 °C than compared to samples reacting with only O2 with a temperature of 350 °C - 500 °C. To understand the conditions that affect soot oxidation, the concentration of oxygen was varied and it was found that at higher oxygen concentration the soot oxidized is almost constant. Then soot kinetics were analysed by finding the rate of the reaction, the order of the reaction, and finally the activation energy. The order of the reaction for FORCED 360 and SORT-1 vary and slope of the graph, logarithm of reaction constant vs logarithm of mass shows a non-linearity in the former due to the slower rate of the reaction in SORT-1 than in FORCED 360. The activation energy was found to be 39.3 kJ/mol for SORT-1 and FORCED 360 is 60.8 kJ/mol.

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Acknowledgments

This thesis work would not be possible without the help of my supervisors. The project is dedicated to everyone who has helped me during the period of my thesis.

Firstly, I would like to thank Scania CV AB to allow me to do my thesis work. A warm thank you to my supervisor Anders Ersson and Francesco Regali for their guidance and support during my journey. With their expertise and help, I was able to learn and enjoy the work done in this project. I would also like to thank my supervisor at KTH, Abdusalam Uheida for his support and guidance to complete my project successfully.

A special thanks to Ph.D. student Andres Suarez for his help and his mentor on learning the concept as well as working on the MATLAB. Without him, this project would have become arduous and incomplete.

I would like to thank Group Manager Martina Levin for her help and participation to carry out the experiments in the department YTMC. Your support and knowledge made this project interesting and educational.

Thanks also to the staff for caring for my health during the COVID-19, without them, I would not have safely performed the experiments.

Finally, I would like to thank my family and friends who encouraged and believed in my confidence and helped me conquer greater heights.

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Nomenclature

TGA Thermogravimetric analysis PM Particulate matter

FORCED 360 soot type with lower ash content SORT-1 soot type with higher ash content DOC Diesel oxidation Catalyst

SCR Selective Catalyst Reduction DPF Diesel Particulate Filter SOF Soluble Organic Fraction HC Hydrocarbons

CSF Catalysed Soot Filters VOF Volatile Organic Fraction

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A kinetic model was designed by Svante Arrhenius. The soot data using this model which was assessed by using MATLAB 2019b that can solve the Arrhenius equations and hence to calculate the activation energy. The data interpretation was used to check the data validity with other soot samples in the isothermal region.

The characterization of the soot was done by using the data that was collected from an earlier work that was done at Scania. The experimental part was cut short due to the coronavirus situation. The kinetics of the soot was calculated using MATLAB can be used for the prediction of the soot oxidation during regeneration of a DPF in the engine control system and thereby potentially minimizing the back pressure and hence the fuel consumption. Moreover, this could lead to extended lifespan of the filter.

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1 Introduction

1.1 Diesel engine

The first commercial internal combustion engine was produced by an American named George Brayton. In early 1863 the Frenchman Etienne Lenoir designed a gas turbine engine; it had undergone testing but proved to be inefficient and unsuitable for assembly and driving. The engine was developed by Nikolaus August Otto, a 4-stroke engine which had a magneto-ignition and operated with liquid fuel and proved to be much easier in its applications.

A breakthrough for the development of Diesel engines came from a theoretical design of Rudolf Diesel [1].

Rudolf Diesel was a very innovative and ambitious person, who was born in Paris, he wanted to become an engineer from his early days. He designed an engine that had higher efficiency than the steam engine, it followed Carnot’s cycle principle. This was done based on theoretical explanation and his aim was to make the theoretical idea to a practical application. His engine design was accepted by the Imperial Patent Office in Berlin for a patent called “New rational thermal engines” in the year 1892. It was only present on paper during that time even though many experts were skeptical about it.

Eventually, he got an opportunity to work with Maschinenfabrik Augsburg- Nürnberg (MAN) and they designed a working prototype. This engine was developed for production and had higher efficiency.

In 1897, Maschinenfabrik Augsburg-Nürnberg (MAN) and Rudolf Diesel came up with a working prototype that would run on heavy fuel oil. This prototype was about 4,5 tonnes and 3 m high which made it unsuitable for use on roads.

1.1.1 Uses of Diesel engine

Nowadays, a diesel engine is being used in various fields. The engine has a higher efficiency and better fuel economy than any other internal combustion engine and hence it is one of the most widely used engines in the world today.

Some of the major areas of application are 1. Cars and light commercial vehicles 2. Heavy-duty vehicles

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3. Construction and agricultural machinery 4. Railway Locomotives

5. Ship industry 6. Military

Stationary Diesel Engine [1]

1. Generators to provide electric power 2. Auxiliary power production

3. Pumping Stations

1.1.2 Characteristics of Diesel engine

Mentioned below are important features that help in designing a basic engine.

1. Engine power

2. Specific power output

3. Operational safety

4. Production costs

5. Economy of operation

6. Reliability

7. Environmental compatibility

8. User-friendliness

9. Convenience

1.2 How does a Diesel Engine Function?

A diesel engine is composed of three parts the inlet, compression chamber, and outlet. These three components work together in a four-stroke engine. Four different processes take place in a Diesel engine. Starting with (a) induction stroke, (b) compression stroke, (c) ignition stroke, and (d) exhaust stroke which are described schematically in Fig 1.1 [1]. These processes are explained in detail below.

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Fig 1.1. The functioning of a Diesel Engine[1]

1. The air is passed into the chamber and is compressed in the chamber.

2. The compression of air in the chamber yields a higher temperature which is used to ignite the diesel fuel spontaneously when the fuel is sprayed in it.

3. After the combustion, chemical energy released is converted to kinetic energy which is used to move the crankshaft to produce a torque.

4. The exhaust exits the exhaust valve and is then subjected to exhaust aftertreatment processes.

1.3 Diesel Exhaust

Exhaust gases are nowadays subject to statuary legislation and the most prominent regulated emissions in the exhaust from diesel engines are unburned hydrocarbons (HC), carbon monoxide (CO), nitrogen oxides (NOX), and particulate matter (PM).

Certain legislations need to be followed in their jurisdiction. These legislations become stringent year after year, to be environment friendly and hence it is important to understand the exhaust systems to follow these legislations. European legislations are given in Table 1.1 which gives an idea of how every governing body control emissions [2].

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Table 1.1. European Emission legislations [2]

1.4 Basic components of exhaust aftertreatment

There are three main components of the exhaust aftertreatment system as shown in Fig 1.2 and their function is to remove emissions that cause harm to the environment.

Fig 1.2. Exhaust aftertreatment system [3]

The first component in an aftertreatment system is the Diesel Oxidation Catalyst, removal of hydrocarbons and CO is managed by using a Pt or Pd catalyst (at low- temperature reactivity and hydrocarbon conversions). In this technology, the catalyst used is made to oxidize the HC and CO to convert them to CO2 and H2O.

The oxidation in DOC is dependent on the exhaust gas composition, flow velocity and light of temperature of 170 °C-200 °C. It can remove most of the SOF (soluble organic fraction), HC, and CO by three reactions. One other function of DOC is conversion of NO to form NO2[4, 5].

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𝑆𝑂𝐹 + 𝑂₂ → 𝐶𝑂₂ + 𝐻₂𝑂 (1.1) 𝐶𝑂 + 𝑂₂ → 𝐶𝑂₂+ 𝐻₂𝑂 (1.2) 𝐻𝐶 + 𝑂₂+ → 𝐶𝑂₂+ 𝐻₂𝑂 (1.3)

The second stage is the DPF, where filters trap the particulate matter that consists of soot and ash.

In Diesel Particulate Filter (DPF), the material used to make the filter is a porous ceramic material made of Cordierite which is used to trap particulate matter on the walls of the ceramic as they are porous. DPF will be discussed in detail below.

SCR (selective catalytic reduction), NH3 as a reductant reduces NOX (Nitrogen oxides) to N2 which is shown in the chemical equation 1.4 [6, 7].

6𝑁𝑂 + 4𝑁𝐻₃ → 5𝑁₂+ 6𝐻₂𝑂……….(1.4)

1.5 Diesel Particulate Filters

Mercedes had initiated the DPF in the market in the year 1985 and later it was discontinued as it was not successful for cars. Later several companies worked on different types of DPF, companies like Dow chemicals and Emitec Gmbh. In 2001, Navistar made the first fitting of DPF in Heavy-Duty Vehicles [1, 3].

DPF is a ceramic material made of Cordierite. This filter is designed in a way that it has inlet and outlet channels that are plugged alternatively in a honeycomb structure as shown in Fig 1.3 and Fig 1.4. The red arrows in Fig 1.3 represent the flow of ash/soot from the engine to the filter. This formation represents a checkerboard pattern having an approximate density of 100-400 cells per square inch. It also has a wall thickness ranging from 0.4 mm-0.6 mm[8]. The estimated pore size is approximately is 0.001 mm - 0.015 mm[8]. Soot particles are approximately of 0.003 mm – 0.005 mm which can are filtered. The soot and ash are trapped on the walls of the filter. It is pivotal as an increase in soot and ash layer will help in filtration but also increases backpressure in DPF [9]. The DPF is also coated with a Pt/Pd catalyst layer, to help oxidation of NO into NO2 during the process of regeneration which is explained in the below section.

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Fig 1.3. Flow of soot/ash in a DPF filter [3]

Fig 1.4. Honeycomb cordierite filter[10, 11]

1.6 Regeneration of DPF

Regeneration is a process of cleaning the filter from time to time by removing the soot.The backpressure inside the filter increases as soot/ash accumulates, this increase in backpressure causes lower fuel efficiency of the engine. As the soot gets accumulated slowly, it may lead to a fire hazard due to a rise in the exhaust temperature. Hence, oxidation or removal of the soot becomes important. Regeneration of filter in any vehicle depends on the amount of soot

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in the filter, only if the quantity of soot present is increasing then the process should be triggered at the correct time [12].

There are two types of regeneration processes that can be used to decrease the pressure drop over the filter by removing the soot in it. They are active and passive regeneration.

1. Active regeneration: It is a regeneration process in which temperature inside the filter increases for the oxidation of soot to takes place. This temperature increases over a normal operating temperature of 300 °C- 500 °C. The temperature inside is increased either by adding fuel that will be converted over DOC or through engine runs in a way that the exhaust temperature increases above 600 °C. Here the main oxidant that takes part in active regeneration is oxygen. This regeneration has to be carried out when the engine is idle to increase the temperature of the engine gradually [1].

2. Passive regeneration: In this process, the regeneration occurs at a lower temperature. The major reactants are NO2 and O2, in which NO2 plays a major role during the oxidation of soot in this process. It is a slow process and it takes place simultaneously during the drive cycle. To get sufficient NO2, a catalyst (preferably noble metals) is coated on the walls of the filter, which is used for oxidizing NO to NO2. The temperature at which passive regeneration is carried out at 350 °C -450 °C [1, 13]. The regeneration of the soot with NO2 at lower temperature takes place as NO2 is regarded as stronger oxidant than O2.

During passive regeneration process the soot oxidises with NO2 which yields different intermediates.

The first intermediate is when the carbon radical reacts with NO2, where NO2 is adsorbed on its surface of the carbon forming C-(NO2). The C-(NO2) undergoes decomposition in which, it desorbs NO to form C-O intermediate. After this the NO2 molecule further attacks the C-O intermediate to form C-(ONO2) which lowers the activation energy of the C-(O) decomposition due to the breaking of the C-C bonds[14]. The intermediates formed in this reaction are obtained at a lower temperature than when the soot reacts with only oxygen during the active regeneration. In this complete process the intermediates show a higher reactivity [15].

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2 Soot

Soot also called as lamp black or carbon black. They are amorphous from of carbon that consists of poly aromatic hydrocarbons. They are formed by incomplete combustion of fuel. IT consists mainly of carbon but due to combustion of other lubricants there are traces of metals, hydrogen, oxygen, sulphur and hydrogen is formed on the surface of the soot.

2.1 Structure and Formation

Soot is formed when hydrocarbons undergo combustion. In a soot formation, the soot’s dominant part is the (Poly aromatic Hydrocarbon) PAH which is stable hence soot formation takes place via PAH. The structure of these aromatic rings formed is seen in the next section as formation of aromatics, it is done by a radical chemical mechanism which has a largely planar structure as proven from previous studies. The mechanism signifies that the reason for having a condensed, planar structure [16]. The radical mechanism is the formation of PAH radical by abstraction of hydrogen, then collision of another PAH radical and then finally an internal rotation of the PAH structure formed.

These structures determine how fast the soot structure is formed [17].

Fig 2.1. The formation of soot particles on hydrocarbon combustion which involves stacks, primary particles, and the fractal aggregates [16].

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In this thesis work, we will be considering the soot released during the combustion of diesel fuel. The diesel soot undergoes agglomeration and the primary particle contains a graphene-like domain [18].

Steps for soot formation. The major steps that are involved are homogenous nucleation of soot, particle coagulation, particle surface reactions, and particle agglomeration. This is represented by a graph showing the C/H ratio versus molecular mass. The C/H ratio shows the amount of carbon and hydrogen present in the particles during the soot formation. Ratio of carbon rich compounds mass increases as the soot formation is in process. The PAH is has a lower mass but with lower carbon constituents but as it undergoes aggregation and agglomeration the molecular mass of the soot increases.

These aggregates in the soot and are shown in Fig 2.1. These will be explained in detail in the next section.

2.1.1 Formation

The soot formation is based on soot chemistry where the first step of soot nucleation is the formation of the first aromatic ring. This has many rate determining steps that have to be considered. Condensed particles that are formed are mainly dominated by the entropy driven process. Carbon phases like graphene or graphite is formed from saturated alkenes releasing H2 which causes an increase in entropy [18].

For a soot formation, there is a need to form the first aromatic ring. It is done in the following 2.1 chemical reaction

𝑛 − 𝐶₄𝐻₅+ 𝐶₂𝐻₂ → 𝐶₆𝐻₆+ 𝐻…………(2.1)

where the benzene ring formed which will be subjected to the growth of aromatics.

2.1.2 Growth of aromatics

From the literature studies the growth of aromatics was done by using HACA (Hydrogen abstraction and C2H2 addition) HACA mechanism is used for explaining the growth of soot with soot chemistry. Fig 2.2 shows a representation of the growth of soot by the HACA mechanism.

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i) Removal of a hydrogen atom from the hydrocarbon (Benzene) by a gaseous H2 atom forming a radical site

ii) Adding an acetylene molecule to the radical site formed [19].

Fig 2.2. HACA mechanism [20]

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3 Chemical kinetics

A branch of physical chemistry that deals with rates of a chemical reaction. There are concepts mentioned below that constitute the chemical kinetics for this project.

3.1 Reactivity

It is a part of the chemical kinetics that is defined as how fast or slow does a reaction takes place in a chemical reaction.

3.2 Rate law

The rate of a reaction is defined as the concentration of reactants produced per unit of time. For any, the reaction rate is defined by [21].

𝑟𝑎𝑡𝑒 (𝑟) = −𝑐ℎ𝑎𝑛𝑔𝑒 𝑖𝑛 𝑐𝑜𝑛𝑐𝑒𝑛𝑡𝑟𝑎𝑡𝑖𝑜𝑛 (𝑡𝑖𝑚𝑒)

𝑟 = ±1

𝑉 𝑑𝑛

𝑑𝑡 (𝐸𝑞 3.1)

where n is moles of component i, V is the volume of the reacting substance, and t time taken. The rate of a reaction is positive for products and negative for reactants a shown in equation 3.1.

Below is a graph showing change in concentration versus time and the slope of the graph in Fig 3.1 shows the rate of the reaction.

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Fig 3.1. Rate of the reaction is the slope of the graph[21]

The rate law is defined as the relation of the reactants and the rate of the reaction. The concepts that control the rate law are the Law of Mass Action, Potential Energy surfaces, and energy barriers, and Fraction of Molecular collisions that have sufficient energy to react.

1. Law of mass action – It is defined as the rate of the reaction that increases with an increase in the concentration of reactants because of an increase in molecular interactions.

2. Potential Energy surfaces and energy barriers- The minimum potential energy of the system that is required for the reaction to reach the intermediate and then go to the products.

3. Fraction of Molecular Collisions that have significant energy to react- The energy required to cross over the barrier and react.

From the postulate 1 we can derive an equation with respect to the rate law for a given reaction

𝐶 + 𝑂₂ → 𝐶𝑂₂ ……….(3.1) Hence, the rate of the reaction is given by

-r = k[C]ⁿ[O2]^m

where n and m are the order of the reaction and k is the reaction rate coefficient.

Rate of the reaction depends on certain factors, they are [22].

i. Concentration of the reactants- As the concentration of the reactants increases the rate of the reaction also increases.

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ii. Temperature- An increase in temperature increases the rate of the reactiom. Usually, for every 10 °C increase in temperature the rate of the reaction increases two fold or three fold.

iii. Catalyst- They are substances that increase the rate of the reaction by lowering the activation energy.

iv. Physical states of the reactants and surface area- Reactant molecules exist in different phases, the rate is are limited by surface area of the phases. For example, two reactants one is in gaseous phase and other is in solid phase leads to the the reaction happening on the surface of the solid surface and how much area of the solid surface is exposed to the gaseous reactant.

3.3 Activation energy

When reacting molecules in a chemical reaction create hindrance due to collisions between the molecules. Hence, the minimum energy to overcome the hindrance is called activation energy.

The A,B and C reactants require a potential energy which is created due to the steric hindrance given by an energy barrier EB. To overcome this energy barrier the reactants need a minimum potential energy which is called the activation energy(Ea). Fig 3.2 indicates that when reactants A,B and C react which is depicted in the graph of potential energy versus reaction coordinate [21].

Fig 3.2 Activation energy barrier of a reaction[21]

It is given by the rate coefficient in the rate law equation 𝑘 = 𝐴𝑒𝑥𝑝(^𝐸^𝑎

𝑅𝑇)………..(Eq 3.2)

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A is the Arrhenius Constant or pre-exponential factor, Ea is the activation energy, R is the universal gas constant and T is the temperature.

3.4 Arrhenius Law

Svante Arrhenius, found the dependence of temperature and rate of the reaction which is given by an Arrhenius law. It states that for evey 10 °C increase in temperature, the rate of the reaction is doubled. This is observed in most biological and chemical reactions [23].

To find the activation energy natural logarithm is applied on both sides of Eq 3.2 and then we observe the slope and the intercept [24]. This has been explained in detail in section 8.4.

This means that for any chemical reaction obeying Arrhenius law the slope of the Arrhenius plot will give the activation energy. It is done by plotting logarithm of k (reaction coefficient) vs 1/T (temperature). Here, there is a representation of the Arrhenius plot of a reaction in Fig 3.5 [24].

In Fig 3.5, the slope gives the Ea/R value whereas the intercept gives the pre- exponential factor (A).

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3.5 Soot oxidation kinetics

Soot oxidation kinetics has been researched over a long period of time. They have been found in diesel filters, flames, oil refineries, grills, burning agriculture waste also few other important sources of soot are incomplete combustion of oil, wood, paper and coal [12].

Soot oxidation studies for this project are specific to only soot oxidation in the DPF during regeneration. The soot oxidation in this project is withO2 and NO2. The soot in this case is predominantly carbon.

In the chemical reaction as described Eq 3.3 is used to derive the order of the reaction and then the Arrhenius plot [15].

Rate of the reaction for soot oxidation with O2 and NO2

𝑟 = 𝑘(𝑚_𝑐)^𝑛(𝑁𝑂₂)^𝑚(𝑂₂)^𝑙……….(Eq 3.3)

Fig 3.5. Arrhenius plot of a typical chemical reaction [25]

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where n, m and l are the reaction orders of C, O2 and NO2; r is the rate of reaction; k is the reaction constant; mc, NO2 and O2 are the mass of the carbon, concentration of nitrogen dioxide and concentration of oxygen respectively. The unit to represent the rate is mg/min.

Order of carbon is derived from the plot rate vs mass change by applying logarithm on both sides of the Eq 3.3

ln (^𝑑𝑚

𝑑𝑡) = ln 𝑘′ + 𝑛𝑙𝑛(𝐶) ………(Eq 3.4)

Due to pseudo first order reaction, that is when the there is not a significant change in the reaction due to the either excess of reactants or if they are present in constant concentration. In this project the of reactants like NO2 and O2 are maintained at a constant concentration throughout the whole reaction. Hence, the equation takes the form pseudo first order constant k’=k[NO2][O2] which is then represented in the Eq 3.4 [26-28]. Previous literature studies have referred to order of the is carbon as unity during regeneration reaction[29].

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4 Instruments

4.1 TGA (Thermogravimetric Analysis)

TGA is a method where the change in mass is measured as a function of temperature or time. In this project, the mass loss is with respect to the time as the experiment is carried out at isothermal conditions. The loss of mass can happen due to various effects.

Examples of different effects that can be studied in a TGA are:

1. Evaporation of volatile constituents.

2. Oxidation of metals in air or oxygen.

3. Oxidative decomposition of organic substances in air or oxygen.

4. Thermal decomposition in an inert atmosphere with the formation of gaseous products.

5. Heterogeneous chemical reactions

4.2 Design and measuring principle

Components of TGA are the sample holder, furnace, thermocouple and balance.

The components are shown in Fig 4.1.

To design the measuring of the balance, three different types of thermobalances can be used. They are top loading, hang down loading and horizontal loading measurements. To protect any external factors effecting the balance, there is purged gas or protective construction material. Secondly, depending on the resolution of the balance they are semi-micro (10µg), micro(1µg) and ultramicro(0.1µg) balances [30].

The reactants used in the TGA are in form of a gaseous phase which can be regulated in the device. Moreover, in this project the gases NO2 and O2 are regulated in different concentrations.

4.3 Sample preparation

Sample preparation for TGA experiments is based on how the sample is measured and how accurately and precise the results can be obtained. Some factors are important during sample preparation

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1. To have precise measurements the mass of the sample should be taken in adequate amounts.

2. The analyzed material should be representative of the sample.

3. Prevent any contaminants to enter the sample which avoids other unrelated processes to be part of this analysis.

Fig 4.1. Schematic diagram of TGA[31]

4.4 Measurements

Mass loss in the TGA is caused due to certain parameters. Some of the parameters are given below which effect the mass loss [32].

1. Making method parameters like heating rate or atmosphere.

2. Preparing a sample and hence choosing the size, homogeneity and morphology of the sample.

3. Choosing the crucible for the experiment as this would prevent the reactivity of the sample with the crucible.

4. Some samples are reactive at certain temperatures and this can lead to samples being thrown out of the holder and to prevent this, it can be done by grinding the sample.

5. For every sample, there are physical properties that are taken during the analysis.

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6. Finally, some of the internal aspects of measurements like buoyancy and gas flow effects can also affect measurements.

4.5 How to interpret the TGA data or the terminology used in the TGA?

The TGA analysis data can be used by observing certain changes, there are different curves used in the graph, such as [32];

1. First derivative curve is the rate of change of mass.

2. SDTA curve shows the exothermic and endothermic events as shown in Differential scanning calorimetry.

To read and understand the TGA data an example is shown in Fig 4.2 is of Calcium oxalate monohydrate in non isothermal condition.

Fig 4.2 TGA data for Calcium oxalate monohydrate

The initial TGA analysis, the curve shows the decomposition of volatile substances at 100 °C Fig 4.2. After, the initial loss volatile substances the calcium carbonate undergoes further decomposition to form calcium oxide and evolution of carbon monoxide. Finally, after the multilevel decomposition process there is a formation of calcium oxide with carbon dioxide at a higher temperature of 800 °C.

In this case we can see that as the temperature increases the conversion also increases showing that the reaction rate is faster initially but as the temperature is lower the reverse process happens and rate of the reaction reduces.

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5 Experimental

5.1 Soot samples preparation

In this study soot samples from two different types of soot were used. The soot samples compared were denoted SORT1 and FORCED 360. These two samples were prepared from an earlier thesis work [33]. Due to the COVID-19 situation most of the TGA data used originated fro earlier measurements done at Scania.

5.2 SORT-1

SORT-1 soot’s was produced from a simulation test cycle of a bus in heavy urban traffic. Ash content was found to be 39% in SORT-1.

5.3 FORCED 360

Forced soot was generated by employing a previously known stationary point with substantially reduced fuel injection rail pressure, which resulted in a high engine-out soot flow [33]. Ash content was found to be 23%.

5.4 Elemental analysis of the soot

The soot samples are present have a compostion of carbon, oxygen, nitrogen and hydrogen. This is shown in Table 5.1[33]

Table 5.1. Soot samples elemental constituents

Constituents SORT-1 FORCED 360

Carbon(w%) 57.2 72.1

Nitrogen(w%) <0.3 <0.3

Hydrogen(w%) <1.0 <1.0

Oxygen (w%) 11.9 9.21

Ash (%) 39 23

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5.5 Soot sampling & storing

The soot sample was extracted from the DPF (Diesel Particulate Filters). The soot sample was cooled overnight and afterward the soot was brushed off from the filter and collected in a plastic. The soot is removed by air pressure and then stored. More information about the sample soot can be found in reference [33].

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6 TGA Soot oxidation experiments

TGA setup was done in a TGA8000 instrument using Pyris and a Perkin Elmer software as shown in Fig 6.1.

Fig 6.1. TGA 8000 [34]

6.1 Equipment used for this analysis

This device has an additional gas mixing device (GMD8000) which helps in mixing different reactant gases. The purge gas used is N2, O2 and NO2 are used as reactants.

6.2 TGA Set up

The TGA can be performed in two different conditions. One is the isothermal and second is non isothermal condition. In isothermal conditions the sample is kept at a constant temperature for a defined period of time and data is retrieved from that region only. Whereas in nonisothermal the temperature is varied with different heating rates.

In this project only isothermal condition were used during the data collections as the kinetic parameters can be derived easily. Soot samples were subjected to different conditions as shown in Table 6.2. To set up the TGA certain conditions were needed to be followed:

1. Hold for the soot sample for 2mins at 50 °C.

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2. Heat the sample from 50 °C to target temperature at 100 °C/min.

3. Hold it again for 10 min at target temperature.

4. Hold the sample at target temperature for 120 min. (Isothermal region)

In table 6.1, shows the samples that have undergone the TGA analysis.

Table 6.1 Soot samples with NO2 and O2

Experimental conditions SORT-1 FORCED 360 Conclusions

Concentration of NO2 2000ppm Reaction with

NO2, O2 and N2

Concentration of O2 0%,5%,10% and 15% Reaction with O2 and N2

Temperatures 250 °C, 300 °C, 350 °C, 400 °C Temperatures varied in all the experiments

Mass of sample 1-1.8 mg Constant for all

experiments

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7 Methodology

Calculations of the model was done using MATLAB R2019b in which the TGA data imported to calculate the kinetic parameters. The steps that were used are given below in Fig 7.1.

Fig 7.1. Schematic diagram of the process flow

To analyze the TGA data, a specific flow was followed. Starting from importing the data in MATLAB and formulating the plot conversion rate vs time by subtracting the ash content of 23% for FORCED 360 and 39% for SORT-1. Using that data, the rate law was formulated for the soot oxidationThen the order of the soot was derived which was done by plotting the logarithm rate of the reaction vs logarithm mass. After which the Arrhenius plot was obtained from the Arrhenius expression. Finally, deriving the activation energy from the Arrhenius plot.

Extract isothermal TGA soot data

Derive the rate of the reaction

Calculate the order of the reaction by plotting the rate of the reaction vs mass

Data is analysed to plot the Arrhenius Equation

Slope of Arrhenius plot gives

the Activation energy

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8 Results

8.1 Reactivity of soot with O

2

/NO

2

Soot oxidation with 10% O2 and 2000ppm NO2

TGA measurements in this experiment will give information about the oxidation of the soot. We observe a certain mass loss, which is given by unconverted soot vs time graph. The mass percentage represented in the graph is the amount of soot that is left after the reaction. In Fig 8.1 and Fig 8.2, two soot samples are SORT 1 and FORCED 360 are taken to calculate the soot oxidation rate.

In Fig 8.1, the isothermal TGA results for the oxidation of FORCED 360 the presence of oxygen and NO2, are shown. At lower temperature 250 °C the amount of soot oxidized is only 6.5% after 120 minutes of soot oxidation. As the temperature increases, the amount of soot oxidized also increases. This is seen when the soot is subjected to 300 °C the amount of soot oxidized is 15.4% and similarly, as for 350 °C, the amount of soot oxidized is 37.7% at 120mins. The highest soot oxidation in these conditions observed was at 400 °C where the amount of soot oxidized was found to be 64.7%. This trend was similarly seen for soot oxidation with SORT-1 as shown in Fig 8.2.

In Fig 8.2, the isothermal TGA results in the oxidation of SORT-1 soot in oxygen and NO2. Higher temperatures of SORT-1 which are 400°C, have 88.2% soot is oxidized after 120mins. Comparing the reaction of soot with temperatures less than 400°C, it is observed that at the lowest temperature of 250°C, the amount of soot oxidized was found to be 8.1 % after 120 minutes. For temperature of 300 °C the amount of soot that was oxidized was 25.2 % and as the temperature increased the amount of soot oxidized increased as seen at a temperature of 350°C where the amount of soot oxidized was 58.1 % after 120 mins of soot oxidation.

Comparing two soot’s in Fig 8.1 and 8.2, some differences are observed between the soot samples. It is seen that SORT-1 has more soot oxidized than of FORCED 360. While at higher temperatures, above 250 °C, in FORCED 360 soot in Fig 1a shows lower soot oxidation compared to that of SORT-1.

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8.2 Reaction soot with 10% oxygen

In these experiments, the soot was oxidized with 10% oxygen without any NO2

and this yielded the results shown in Fig 2a and 2b.

In Fig 8.3, FORCED 360 soot oxidized in 10% oxygen and N2 as balance. The soot was oxidized at temperatures ranging from 350 °C-500 °C. For FORCED 360, maximum soot oxidation occurs at 500 °C where almost 19.03 % of the soot is oxidized. As seen in Fig 8.3 at 350°C and 400°C the amount of soot oxidized is 1.2% and 2.3% respectively.

From Fig 8.4, SORT-1 reacts with 10% oxygen and N2 as a balance. Here, the maximum soot oxidized is at 52.3% at 500°C. As the temperature reduces to 450

°C, only 16.5 % of the soot is oxidized compared to 500°C. But for 350°C and 400°C only 2.7 % and 6.6 % respectively of the soot is oxidized.

Results of Fig 8.3 and 8.4 compared to Fig 1a and 1b shows the difference in soot oxidation when soot is oxidized with O2 and NO2 and when soot is oxidized with

Fig 8.1. Unconverted soot (Mass percentage) vs Time (min) of FORCED 360 Isothermal, 2000ppm NO2, 10% O2 and N2 as balance

Fig 8.2. Unconverted soot (Mass percentage) vs Time (min) of SORT-1

Isothermal, 2000ppm NO2, 10% O2 and N2 as balance

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only O2. Comparing the two sets of soot samples in Fig 8.1 and Fig 8.2, the amount of soot oxidized at 350 °C with O2 and NO2 was 37.7 % whereas in Fig 8.3 the soot oxidized at the same temperature is only 5%. There is a higher conversion in case of FORCED 360 with NO2 +O2 at 350 °C and 400 °C as shown in Fig 8.1 when compared to reactions with only O2 as shown in Fig 8.3 at those temperature. These results were similar to soot SORT-1 when it reacts with O2

and NO2 and with only O2 at 350 °C and 400 °C.

8.3 Soot oxidation with 0%,5%,10% and 15% oxygen concentration, 2000ppm NO

2

and 350°C

Next experiment was to see how the soot reacts with 2000 ppm NO2 and with different oxygen concentration. The temperature was held at 350 °C during the tests which were to show the effect of oxygen concentrations on the soot oxidation.

In Fig 8.5, the TGA results for Sort 1 with 2000 ppm NO2 and oxygen concentration of 0%, 5%, 10% and 15% at 350 °C were plotted for unconverted

Fig 8.3. Soot oxidation at 250 °C,300

°C,350 °C and 400 °C. The soot is oxidised with 2mg soot, 10%

oxygen and N2 balance.

(FORCED360)

Fig 8.4. Soot oxidation at 250 °C,300

°C,350 °C and 400 °C for graphs. The soot is oxidised with 2mg soot and 10%

oxygen, N2 balance. (SORT1)

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36

soot vs time. The soot oxidation observed at 0% oxygen concentration resulted in a mass loss of 32.8% after 120 min. When the soot was oxidized with a higher oxygen concentration of 10% and 15%, the amount of soot oxidized remains constant and with 5% oxygen concentration certain difference was observed.

The amount of soot oxidized for 5% oxygen concentration was 51.8 % and subsequently as the concentration increased for 10% and 15 % which was around 56% of the soot oxidized. In conclusion, as concentration increased there was no change in terms of soot oxidation.

Fig 8.5. Mass vs Time isothermal experiment with 2000ppm NO2 and 0%, 5%, 10% and 15%

8.4 Kinetics of the soot oxidation reaction

To find the kinetics of soot oxidation there is a procedure that is followed.

Following is the procedure that is followed in the model 1. Find the order of the reaction

2. Calculate the k from the log (dm/dt) vs log m.

3. Using the value of k plot the Arrhenius plot ln k vs 1/T.

4. The slope of the Arrhenius plot gives the activation energy.

Order of the reaction

First, the order of the reaction is to be calculated. To calculate the order of the reactants as in Eq 1

𝑟 = 𝑘(𝑚_𝑐)^𝑛[𝑁𝑂₂]^𝑚[𝑂₂]^𝑙 ….. (Eq 1)

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37

Here, r is the rate of the reaction(dm/dt), k is the reaction constant, mc is the mass of carbon and n,m,l are the orders of their respective reactants.

Order of NO2 and O2 are assumed to be zero as they are present in a constant concentration in the TGA experiment. The order of reaction of carbon is calculated. This is done by forming a linear line equation in Eq 2.

Line equation is given by

𝑦 = 𝑚𝑥 + 𝑐

where y is the y-axis intercept, x is the x-axis intercept, m is the slope of the line and c is the constant.

Taking ln on both sides of Eq 1 we get a linear expression that is used to find the order of the reaction.

ln (^𝑑𝑚^𝑐

𝑑𝑡 ) = ln 𝑘 + 𝑛𝑙𝑛(𝑚_𝑐)…..Eq (2)

From Eq 2 it is important to get a linear plot for carbon to verify the results with the literature studies. In equation 2 which is representative of a linear line equation which determines the order of the reaction as 1 for carbon from Fig 4a and Fig 4b. Hence, the slope of the line is the order of carbon, x-intercept is log C, y-intercept is ln (dm/dt) and ln k is the constant which will be used further.

From equation 2 we can determine the value of k. Then value of ln k is taken and used to plot an Arrhenius Plot. Using the order of the reaction and k as the reaction constant, the Arrhenius equation can be derived as given in the next section.

Arrhenius Equation

From the values of ln k obtained from

Arrhenius equation for the reactants is given by 𝑘 = 𝐴 𝑒⁽^−𝐸^𝑅𝑇^𝑎⁾… . Eq 3 Putting ln on both sides of Eq 3.

ln 𝑘 = ln 𝐴 − 𝐸_𝑎 𝑅𝑇

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This equation is similar to the linear line equation and slope of this line will give activation energy in kJ/mol.

Here, the Arrhenius plot from equation 3 gives a linear line which intercepts from the plot ln k vs (1/T). With this linearity observed in Fig 8.8 and Fig 8.9 we can evaluate the activation energy (Ea) in kJ/mol.

Following are the activation energy of the soot when it reacts with O2 and NO2

which coincide with the literature studies.

To find the kinetics of the soot as shown in the experimental procedure, it is vital to know the order of the reaction. To calculate the order of the reaction, it is required to find a linear relationship between the rate of the reaction and mass.

The reaction order for the carbon as shown in Table 8.1. For lower temperatures of 250 °C and 300 °C, both the soot samples show non-linear slope when compared to the soot reaction at a higher temperature which is linear.

In Fig 8.7, at 250°C the slope of the graph is non-linear and at 400 °C at highest temperature, the linearity of the slope was found to be 0.4. As for 300 °C and 350 °C, the order slope of the line is linear as it corresponds to the order of reaction to be 2.1 and 0.8 respectively. For the 250 °C, there was a large deviation which showed an order of 9.1.

Comparing Fig 8.6 and 8.7, it can be seen that for both soot samples, the non- linearity is prominent during lower temperatures and is linear as the temperature increases. Order of carbon is shown in Table 8.1 at different temperature.

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Fig 8.6. Order of the reaction FORCED 360 with 2000 ppm/10%, NO2/O2

Fig 8.7. Order of the reaction SORT1 with 2000 ppm/10%, NO2/O2

Table 8.1: Order of the carbon when soot reacts with 10% O2 and 2000ppm NO2

FORCED 360

Temperature(°C) Order

400 0.18

350 0.3

300 2

250 14.9

SORT-1

Temperature(°C) Order

400 0.4

350 0.8

300 2.1

250 9.1

The next experimental procedure is to determine the Arrhenius equation, the Arrhenius plot of ln k vs 1/T is as shown in Fig 8.8 and 8.9. In Fig 8.8, there is deviation at 250 °C when compared to other temperatures of 300 °C,350 °C and 400 °C. From Fig 8.9, it is a linear slope and is similar to literature studies. The only difference between the two as observed is at lower temperatures.

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Table 8.2. Activation energy of two soot sample

Soot Sample Activation Energy

SORT1 39.3 kJ/mol

FORCED 360 60.8 kJ/mol

Fig 8.8. Arrhenius Plot FORCED 360 with 2000ppm/10%, NO2/O2

Fig 8.9. Arrhenius plot SORT-1 with 2000ppm/10%, NO2/O2

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9 Discussion

Soot samples FORCED 360 and SORT-1 are different in their composition.

FORCED 360 has an ash content of 23% and SORT-1 has an ash content of 39%.

In FORCED 360 and SORT-1 there is an unequal amount of soot oxidized after 120 minutes when it reacts with 10% O2 and 2000ppm NO2. Oxidation of SORT- 1 is higher than in FORCED 360. There might be many reasons for this observation as there only two different types of soot taken in this project.

The most potential reason is that the ash content and volatile organic fraction in SORT-1 is higher than that of FORCED 360. The effect of volatile organic fraction on SORT-1 yields a slower rate of the reaction than that for FORCED 360. In isothermal reaction, as the soot oxidation initiates the number of active sites for surface oxygen complexes are hindered due to the presence of the volatile organic fraction of SORT-1. Hence, we observe a curve in the graph for SORT-1 than for FORCED 360.

When soot reacts with 10% O2 and 2000 ppm NO2 it shows a higher oxidation rate compared to the soot reacting with only 10% O2 at the same temperatures.

When the soots react with two different reactants O2/NO2 it reacts faster than with the only O2. This is because NO2 is known to be a more potent oxidizer than O2.

When the soot reacts with 0%,5%,10% and 15% oxygen concentration with 2000ppm NO2, the amount of soot oxidised is same as the concentration of the oxygen increases. This happens because when 2000ppm NO2 reacts with the soot, it creates the surface oxygen complexes on the surface of the soot for the oxygen to react. But as the concentration of oxygen increases, the amount of surface oxyen complexes remains the same due to constant NO2 concentration.

Hence, this creates a saturation for the reaction of the O2 with the surface oxygen complexes.

To derive the order of carbon when the soot reacts with O2/NO2, to determine the kinetics a graph was derived to define the order of carbon (log dm/dt vs log m). The two samples show different orders which change with respect to the temperature. The two soot samples undergo oxidation at different temperatures and the way to identify the order of the reaction is to find a linear relationship in

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the plot. When SORT-1 reacts at 350 °C and 400 °C we see the fitted lines to be linear. But at the lower temperature, the plot becomes more non-linear. This variation is because the soot reacting at 250 °C and 300 °C has more external factors influencing it like evaporation or presence of more carbon species that react faster than the carbon. This soot oxidation can be made more prevalent on the plot if the evaporation could take place with longer soot oxidation.

Activation energy is derived from Arrhenius expression by using the Arrhenius plot of ln k vs 1/T. In this, the activation energy is similar to what was found in the literature studies for soot oxidation with O2/NO2 [36]. Activation energy of FORCED 360 is 39.3 kJ/mol is lower than for SORT-1 which is 60.8 kJ/mol. This tells us about the rate of desorption of the products from the surface of the soot whichis slower in case of SORT-1 that blocks the intake of fresh ions on the surface of the soot. Hence, the reaction proceeds at slower rate. In case of FORCED 360 the rate of the reaction is faster than that of SORT-1 as shown in Fig 8.8 and Fig 8.9 [21].

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10 Conclusions

• The two soot samples oxidize at a lower temperature when O2 and NO2

are reactants than when compared with soot's reacting with only O2. This was because NO2 is a stronger oxidizer than O2 for soot oxidation.

• SORT-1 has a higher soot oxidation rate than FORCED 360. This is likely due to the soot composition which resulted in having a higher amount of ash content as seen in SORT-1 than in FORCED 360.

• This order of carbon helped it finding the kinetic parameters in the soot.

• The activation energy of the SORT-1 is 39.3 kJ/mol and for FORCED 360 it is 60.8 kJ/mol. This information will help in finding whether the fuel consumed during the drive cycle and then the engine can be optimised.

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11 Future Work

For the project to be more precise further work can be carried out in the soot oxidation.

• To measure the ash content for each sample which could be achieved by increasing the temperature at the end of each run burning off the remainder of the soot.

• The algorithm in MATLAB can be optimized by using more soot types and see the outcome of the algorithm.

• The impact of storage time on the soot oxidation can be verified using this data.

• The kinetic calculations of the soot oxidation can be improved by getting more results from TGA, e.g. at additional temperatures

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12 References

1. Reif, K., Diesel Engine Management Systems and Components. 2014: Wiesbaden : Springer Fachmedien Wiesbaden : Imprint: Springer Vieweg.

2. Diesel soot standards. [cited 2020 18/11]; Available from:

https://dieselnet.com/standards/eu/ld.php.

3. Lakshminarayanan, P.A. and A.K. Agarwal, Design and Development of Heavy Duty Diesel Engines: A Handbook. 2019, Singapore: Singapore: Springer.

4. Reif, K., Diesel Engine Management: Systems and Components. 2014, Wiesbaden: Springer Vieweg: Wiesbaden.

5. Mollenhauer, K. and H. Tschöke, Handbook of Diesel Engines. 1st ed.. ed. With contributions by numerous experts. 2010: Berlin, Heidelberg : Springer Berlin Heidelberg : Imprint: Springer.

6. Nova, I. and E. Tronconi, Urea-SCR Technology for deNOx After Treatment of Diesel Exhausts.

1st ed. 2014.. ed. 2014: New York, NY : Springer New York : Imprint: Springer.

7. Majewski, W.A. Selective Catalytic Reduction. 2005 2005; SCR]. Available from:

https://dieselnet.com/tech/cat_scr.php.

8. Adler, J. and U. Petasch, Chapter 8.1 - Diesel Particulate Filters. 2013, Elsevier Inc. p. 585-606.

9. Heck, R.M., Catalytic air pollution control : commercial technology. 3rd ed.. ed, ed. R.J. Farrauto and S.T. Gulati. 2009: Hoboken, New Jersey : Wiley.

10. Coderite for DPF. Available from:

https://lh3.googleusercontent.com/proxy/AfKQSHG3YlLHAv40Ue5sUoTefFX2gZZT34Jp0aPO8 v2l2yKBQ9w1PlraAzYfy32PJoXDC9VG-14U38zmfhOg9fbXqvS5KzKRha7885-z.

11. engine system. Available from: https://www.dieselforum.org/about-clean-diesel/what-is-scr.

12. Raghavan, K., J. Johnson, and J. Naber, An Experimental Investigation into the Effect of NO2 and Temperature on the Passive Oxidation and Active Regeneration of Particulate Matter in a Diesel Particulate Filter. Emission Control Science and Technology, 2018. 4(1): p. 45-63.

13. Shangguan, W., Simultaneous Catalytic Removal of Diesel Soot and NOx. 1st ed. 2019.. ed, ed.

G. Zou and Z. Jiang. 2019: Singapore : Springer Singapore : Imprint: Springer.

14. Li, Z., et al., Mechanism of accelerating soot oxidation by NO2 from diesel engine exhaust.

Environmental pollution (1987), 2020. 264: p. 114708-114708.

15. Lapuerta, M., J. Rodríguez–Fernández, and J. Sánchez-Valdepeñas, Soot reactivity analysis and implications on diesel filter regeneration. Progress in Energy and Combustion Science, 2020.

78: p. 100833.

16. Jacobson, R.S., et al., The Molecular Composition of Soot. Angewandte Chemie International Edition, 2020. 59(11): p. 4484-4490.

17. Semenikhin, A.S., et al., On the mechanism of soot nucleation. II. E-bridge formation at the PAH bayElectronic supplementary information (ESI) available: Rate coefficients of the most relevant reactions considered. See DOI: 10.1039/d0cp02554b. Physical chemistry chemical physics : PCCP, 2020. 22(3): p. 17196-1724.

18. Wang, H., Formation of nascent soot and other condensed-phase materials in flames.

Proceedings of the Combustion Institute, 2011. 33(1): p. 41-67.

19. Frenklach, M., Reaction mechanism of soot formation in flames. Physical chemistry chemical physics : PCCP, 2002. 4(11): p. 2028-2037.

20. Bockhorn, H., Soot Formation in Combustion Mechanisms and Models. 1st ed. 1994.. ed. 1994:

Berlin, Heidelberg : Springer Berlin Heidelberg : Imprint: Springer.

21. Fogler, H.S., Elements of chemical reaction engineering. 4. ed.. ed. 2010, Harlow: Harlow : Pearson.

22. BALL, J.A.K.A.D.W., Introductory Chemistry- 1st Canadian Edition. 2011, Canada: British Columbia Ministry of Advanced Education. 1005.

23. Arrhenius theory. 2014.

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46 24. Cantor, B., The Equations of Materials. 2020, Oxford: Oxford: Oxford University Press.

25. Skinner, G.B., Introduction to chemical kinetics. 1974, New York: New York : Academic Press.

26. Teixeira-Dias, J.J.C., Chemical Kinetics. 2017, Cham: Springer International Publishing: Cham.

p. 83-111.

27. Antonio, P.T., et al., An Experimental and Computational Study of the Pressure Drop and Regeneration Characteristics of a Diesel Oxidation Catalyst and a Particulate Filter. SAE transactions, 2006. 115: p. 115-135.

28. Soren, A., A. Claes, and B. Micael, Low Pressure EGR Calibration Strategies for Reliable Diesel Particulate Filter Regeneration on HDD Engines. SAE transactions, 2002. 111: p. 1572-1579.

29. Prasad, R. and V. Rao Bella, Isothermal Kinetics of Catalyzed Air Oxidation of Diesel Soot.

Bulletin of chemical reaction engineering & catalysis, 2011. 5(2): p. 95-101.

30. Gabbott, P. and P. Gabbott, Principles and applications of thermal analysis. 2008, Hoboken:

Hoboken: WILEY.

31. TGA. [cited 2020 16th July]; TGA]. Available from: https://www.netzsch-thermal- academy.com/en/advanced-materials-testing/methods/thermogravimetric-analysis/.

32. Wagner, M., Thermogravimetric Analysis. 2018, Hanser Publishers. p. 10-349.

33. Boström, T., Diesel soots – which gasifies faster and why? 2014, Uppsala University.: Scania CV. p. 83.

34. PerkinElmer, TGA 8000, T. 8000, Editor. 2020, Perkin Elmer Perkin Elmer.

35. Liang, W., et al., Effect of Ash on Coal Combustion Performance and Kinetics Analysis.

Combustion science and technology, 2020: p. 1-16.

36. Tighe, C.J., et al., The kinetics of oxidation of Diesel soots by NO2. Combustion and flame, 2012.

159(1): p. 77-90.

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13 Appendix

FORCED 360

Forced 360 iso.pdf farr.pdf fdmdt.pdf forced 360

withoutno2.pdf

SORT-1

SORT-1iso.pdf sort1dmdt.pdf sarr.pdf sort1 without no2.pdf

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48 TRITA-SCI-GRU 2020:369

www.kth.se

Defining Black: Characterization of Soot Reactivity with Thermogravimetrical Methods

Defining Black: Characterization of Soot Reactivity with Thermogravimetrical Methods

Adarsh Roy Choudhury

Abstract

Acknowledgments

Nomenclature

Contents

Aim

1 Introduction

1.1 Diesel engine

1.2 How does a Diesel Engine Function?

1.3 Diesel Exhaust

1.4 Basic components of exhaust aftertreatment

1.5 Diesel Particulate Filters

1.6 Regeneration of DPF

2 Soot

2.1 Structure and Formation

3 Chemical kinetics

3.1 Reactivity

3.2 Rate law

3.3 Activation energy

3.4 Arrhenius Law

3.5 Soot oxidation kinetics

4 Instruments

4.1 TGA (Thermogravimetric Analysis)

4.2 Design and measuring principle

4.3 Sample preparation

4.4 Measurements

4.5 How to interpret the TGA data or the terminology used in the TGA?

5 Experimental

5.1 Soot samples preparation

5.2 SORT-1

5.3 FORCED 360

5.4 Elemental analysis of the soot

5.5 Soot sampling & storing

6 TGA Soot oxidation experiments

6.1 Equipment used for this analysis

6.2 TGA Set up

7 Methodology

Extract isothermal TGA soot data

Derive the rate of the reaction

Calculate the order of the reaction by plotting the rate of the reaction vs mass

Data is analysed to plot the Arrhenius Equation

Slope of Arrhenius plot gives

the Activation energy

8 Results

8.1 Reactivity of soot with O

/NO

8.2 Reaction soot with 10% oxygen

8.3 Soot oxidation with 0%,5%,10% and 15% oxygen concentration, 2000ppm NO

and 350°C

8.4 Kinetics of the soot oxidation reaction

9 Discussion

10 Conclusions

11 Future Work

12 References

13 Appendix