Another reason has been anticipated in the previous sentence: I have been able to send the book to friends and colleagues and have been encouraged by the warmth of their responses. Fuels derived, as waste does in the modern world, have a role that can be related to one or both of these factors, and I hope that anyone who has studied this book will understand why.
Municipal solid waste
Nature and amounts
Introduction
The third row gives the figure for all of China, with a population of 1.4 billion; this translates to a per capita figure of 0.35 kg per day. That for Britain, with a population of 61 million, is in the next row, and this equates to a per capita figure of 1.6 kg per day.
Composition
Calorific values
So for a caloric value in the range 10 to 15 MJ kg-1 the HHV and LHV differ by something like 5%. This is comparable to errors in determining the calorific value of MSW in a bomb calorimeter [10].
Constituents of MSW other than household waste
It is repeated that if the calorific value determination was in a bomb calorimeter, it is CERTAIN to correspond to HHV. Errors would not be as large in laboratory HHV measurement of coal, where much more uniform samples can be obtained for calorimetric work than for MSW.
Carbon neutrality or otherwise of MSW as a fuel
Trade wastes
However, there is a resurgence of interest due to latex's carbon neutrality, particularly in the co-firing of shredded tire waste with coal in electricity generation2. The figure in the fifth row of the table is for paper waste generated in offices.
Concluding remarks
The strength is that it is consistent in composition and in combustion this makes the flame stable. Citrus peels can only lift slightly above their own weight of saturated steam in a bar.
Paper waste is ubiquitous and certainly a significant part of both MSW and commercial waste. Experimental and thermodynamic investigation of sulfur- and chlorine-influenced cadmium transfer during combustion of MSW' Journal of Hazardous Materials.
Municipal solid waste Part II: Incineration
- Introduction
- Examples incinerators and analysis of their operation
- Small-scale waste incinerators
- Concluding remarks
- References
Supposedly the largest waste incinerator in the world is in Detroit3. The iron in the slag is recovered with a recycling magnet, and the rest is removed with ash.
Municipal Solid Waste Part III: Pelletised forms
- Introduction
- Manufacture of RDF pellets
In contrast, carbon in coal was not on any time scale of interest carbon dioxide in the atmosphere, so burning coal increases CO2 levels in the atmosphere. Oxygen in the fuel before combustion means fuel that has already been oxidized, so it must be subtracted from the oxygen demand. Once the gas had cooled, e.g. to 25oC, the water would cease to be in the vapor phase and the total number of moles would be 263 per kg of the burned RDF pellets7.
The adiabatic flame temperature is the temperature reached when all the heat released is retained as enthalpy (sensible heat) in the reaction products. The adiabatic flame temperature for the RDF pellets under consideration is calculated in the shaded area below. In the table in section 3.3.1 we are told that 1 kg of RDF pellet that is released in combustion is, to the nearest whole number, 18 MJ.
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This is called fuel NOx and contrasts with thermal NOx which is due to the reaction of nitrogen and oxygen in the air.
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Coal RDF co-firing
The very high calorific value of RDF pellets is due to their high plastic content and their low moisture content. At the Slough plant, which is second in the table, some of the waste fuel is RDF pellets and some consists of small cubes - typically 3cm on a side - of compressed cellulose waste. The amount of chlorine in the waste-derived fuel is measured, and in experimental trials amounts of calcium (as carbonate as mentioned) in various multiples in molar terms of chlorine are injected into the combustion system.
Various examples of waste-derived fuels examined so far in this book show that fluidized beds are often preferred over, for example, grate combustion when burning waste. The value of the fluidized bed has been explained to countless students in Aberdeen by the following analogy. This ensures a rapid heating rate of the fuel particles and an acceleration of combustion.
Concluding remarks
If an electric iron is set at too high a temperature for the fabric it will be applied to, it will create a hole in it. However, if air at the same temperature as the iron is directed at the fabric, damage is much less likely. With hot iron, heat transfer is by conduction: with hot air, it is by convection.
In the latter case, the substance will never reach the air temperature due to heat transfer from itself to the environment leading to an equilibrium temperature far below that of the air. In a fluidized bed, heat is received to the fuel particles by conduction from the fluidized material which will consist of inert particles, often sand.
Calculations and hypotheses regarding EROEI of hydrocarbon fuels' International Journal of Mechanical Engineering Education. Selected examples of waste fuel consumption and greenhouse implications' Air, Water and Environment International December 2006 pp. 14-18. Emissions during co-firing of RDF-5 with bituminous coal, paper sludge and waste tires in a commercial circulating fluid bed cogeneration boiler' Fuel.
Pollutant Emissions Investigation of RDF Co-Incineration and Coal Waste Management - in press. An investigation of self-heating and spontaneous combustion of RDF during storage' Waste Management - in press.
Miscellaneous Waste-Derived Solid Fuels
- Introduction
- Scrap tyres
- Wood waste
- Selected cellulosic wastes other than wood and paper
- Solid refinery waste
- Concluding remarks
- References
4] 26 million scrap tires are used as fuel each year in the US pulp and paper industry. There is the bonus that some of the steel straps in the tires contribute to the iron content of the product. The use of rice husks on the Indian subcontinent is not surprising: rows three and four of the table provide examples.
In the US, there is currently interest in cotton waste fuels from LA, NC and AZ, among others. The fluidized bed combustion of refinery sludge was affected by water ingress into the sludge, as shown in the table. The application in the third row of the table appears at first glance to be one of those companies.
Principles of Pyrolysis and Gasification
- Introduction
- Heat balance in pyrolysis
- Reactions taking place during total gasification
- The role pyrolysis in combustion
- Plasma gasification
- Concluding remarks
- References
This is because some of the heat used in pyrolysis goes into producing compounds or higher enthalpies than the starting material, which will therefore release more heat. The time in the formulation, of course, refers to gasification, so the nominal value of the gasifier in MWth should not be equated with the rate of heat release of the produced gas fuel after ignition in air. Pyrolysis in combustion will not be complete, so some material will burn "unpyrolized".
Plasma temperatures range from 3000 to 10000 K, which is much higher than those achievable in combustion processes. Each has fuel potential and in a commercial pyrolysis process much will depend on the suitability of individual products for fuel use. When pyrolysis of waste is carried out on an industrial scale, many more such issues must be addressed, and feasibility depends on the nature and marketability of the three product classes.
Examples of Waste Pyrolysis
- Biomass
- Municipal solid waste
- Plastic waste
- Co-pyrolysis
- Concluding remarks
- References
3] Pyrolysis of the paper component only of MSW at 450oC, targeting oil as primary product. In row six of the table, pyrolysis of MSW in pelletized form, i.e. of RDF, functions. In row eight, the calorific value of the paper in the described work has been noted because it is significantly below that of pure cellulose.
The work in the last row of the table deals with the decomposition of an epoxy resin and the Arrhenius parameters are determined. The value of the pre-exponential factor 'A' of 1013 s-1 is also extremely high for the pyrolysis of an organic matter. Is there potential to increase EROEI from co-pyrolysis of kerogen with plastics.
Examples of Gasification of Wastes
- Raw MSW
- RDF pellets as gasification feedstock
- Co-gasification
- Scenes of plasma gasification
- Concluding remarks
- References
As explained in the table, at the moment not all energy is used to produce power, some is used in the production of steam for heating. The reason is that the carbon monoxide except for the dioxide is not completely achieved, and the carbon dioxide thus formed becomes a diluent. The plus is that any carbon neutrality of the RDF will be transferred to the producer gas.
The downside is that since producer gas is made by partial combustion and involves a total reaction of the gas. The results in the next row for the Lurgi gasification of lignite alone and of lignite with tire waste show a very marginal improvement with the co-gasification in terms of calorific value, and there will obviously be some carbon neutrality benefits from the natural rubber component of the tires . The tests in the present work were small scale and a full assessment of the snail was not possible because there was too little of it.
Hydrocarbon Waste
- Introduction
- Incineration
- Pyrolysis and cracking
- Gasification
- Re-refining
- Concluding remarks
- References
The application in the first row of the table is in a remote location in the Middle East that requires self-sufficiency for operations such as oil cleanup. From a product utilization perspective, control of the number of carbon atoms through catalysis clearly has the potential to improve viability on a larger scale. Not only the quantities, but also the compositions of the liquid products differed depending on whether waste lubricating oil was initially present.
Control of the H2/CO ratio was necessary since the end use of the gas was unburned chemical synthesis. Re-refining is widespread and not new, and the content of the table is only a small representative selection. Reference Details [15] Re-refining of used lube oil at the only such facility in the western US.
Incineration of Radioactive Waste
- Introduction
- Units and amounts
- Classifications of radioactive waste
- The performance of a typical radioactive waste incinerator plant
- Concluding remarks
- References
The information in the third row of the table could again have been expressed as 103Bq kg-1 or, more conventionally, 1 Bq g-1. We approximate the composition of the non-radioactive waste that is the fuel to that of cellulose, formula C6H10O5. The value in the calculation of 1000 kBq m-3 significantly exceeds the background level in the atmosphere which, largely due to the radon, is about 1 kBq m-3 (§ 1 Bq g-1).
Radioactive waste disposal planning' Space use policy Fundamentals of radioactive waste management: introduction to management. Nevertheless, it is clear that there is extreme sensitivity in the world's collective consciousness regarding the availability of oil. 26 In modern literature, the term synthetic gas is often used regardless of its intended purpose.
