Some physical characteristics and heavy metal analyses of cotton gin waste for potential use as an alternative fuel

The use of cotton gin waste as a fuel is an attractive solution to the problems of disposing of a surplus agricultural waste as well as supplementing energy resources. Because a qualified alternative fuel must meet both environmental emission standards and industrial fuel standards, the physical characteristics of cotton gin waste and its toxic element concentrations are important for its initial objective evaluation as a fuel. Constituent components, moisture contents, and ash contents of four separate parts of cotton gin waste were determined and evaluated, closely following the American Society for Testing and Materials (ASTM) test methods. The three most toxic heavy metals, arsenic (As), chromium (Cr), and lead (Pb), chosen for quantitative analyses were also determined by using an inductively coupled plasma atomic emission spectrometry and a microwave oven sample digestion method. This study revealed that the lint component is the leading candidate for fuel, which closely meets both environmental emission and industrial fuel standards.     

Fuel suspensions based on fuel oil,peat, waste wood,and charcoal

The results of experimental studies on the manufacture of suspension fuel based on fuel oil, peat, waste wood, and charcoals prepared by various processes are reported. The effects of concentration, moisture content, ash content, particle size, apparent density, and procedure used for the preparation of the solid phase on the rheological characteristics of dispersions and the quality indices of the suspension fuel were found.     

Characterization of empty fruit bunch for microwave-assisted pyrolysis

Agricultural waste such as oil palm empty fruit bunch (EFB) is of environmental concern to Malaysia as one of the world’s largest oil palm producers. Pyrolysis can be used to treat biomass waste due to its flexibility in producing solid, liquid and gas products. This study attempts to characterize EFB for pyrolysis using microwaves as an alternative heating source. EFB taken from a local oil palm mill was subjected to fuel, chemical and dielectric property analysis. The findings revealed that high moisture and 47% oxygen gave low calorific value of 16 MJ/kg. Notably, high water content is an advantage in microwave heating as water is a good microwave absorber, which results in fast drying. Further, a high volatile content at 70% gave the EFB an advantage of high reactivity. A moderate potassium content of 12.8% could also positively affect microwave absorption. The dielectric properties of EFB were observed to be proportional to the moisture content. Furthermore, the microwave penetration depth was found highest at 20% moisture, i.e. 3.5 cm. However, low values of both dielectric constant and loss of dried EFBs would require the addition of microwave absorbers for pyrolysis reaction. The fuel and chemical characteristics of EFB were found comparable to other biomasses, which indicated a good candidate for microwave pyrolysis treatment.     

Chemical makeup and physical characterization of a synthetic fuel and methods of heat content evaluation for studies on MSW incineration

A well-characterized synthetic fuel is often needed for research related to the efficiency or completeness of combustion and emissions from municipal solid waste incinerators. Knowledge of the chemical makeup, physical characteristics and heat content of such a synthetic fuel is important to establish accurate baseline operating conditions for experiments and to provide a mechanism for verification of data.A synthetic fuel was formulated to be representative of municipal solid waste (MSW) found in the US waste-stream, after some recycling. A majority of the fuel consists of cellulose in the form of paper and wood. Low-density polyethylene is chosen to represent the plastic polymer content, and iron represents the metal content. The waste food organic content is simulated by animal feed. Water and the inert component silica make up the rest of the fuel. The fuel is fabricated in three stages: (i) mixing the components, (ii) size reduction by shredding and (iii) compaction into cylindrical pellets of 2.5 cm diameter and approximate length 5 cm. Chemical analysis of the fuel includes testing its chlorine, nitrogen and sulfur content. The physical characterization includes tests for fixed carbon, ash, volatile matter and moisture content of the fuel. The heat content of the synthetic fuel is determined by three different methods.The first method to determine the heat content is the standard bomb calorimeter method, in which a powdered sample of fuel is burned with excess oxygen in an adiabatic calorimeter. The second method, also experimental in nature, is to apply calorimetry on the individual components of the synthetic fuel. The third method is to investigate literature values for the heat content of the individual fuel components and then multiply them by their mass fractions and sum to find the total heat content. These three values for the heat content are compared, and close agreement is found. The value determined by all three methods is the ‘higher heating value’ (HHV), that is, it includes the latent heat of condensation of water vapor, which is formed during combustion. Thus, in all three methods, among the final combustion products the water content is taken to be condensed (liquid). The data show that any one of the three methods can accurately determine the heat content of a synthetic fuel.     

A Study of Process Optimization of Extraction of Oil from Fish Waste for Use as A Low-Grade Fuel

Waste oils are potentially advantageous over petroleum and virgin vegetable oil based fuels due to waste utilization, and an overall lowering of gases and most other emissions over the life cycle of fuel production, use, and disposal. Waste generated from fish processing plants varies from 10–50 wt% of landed fish depending on the type of fish, product and processing techniques. A portion of this waste contains fish oil and varies significantly depending on the species. The oil recovery process must maximize extraction of oil and at the same time be able to integrate into the existing infrastructure at fish plants. In this study, we have optimized the recovery process developed in our lab (based on a fishmeal processing) and tested with the waste of a variety of fish species. The oil had low impurities (<0.5 wt% moisture) and degradation products, and physical properties suitable for substitution of No. 6 fuel oils and marine distillate/residual fuels. Based on this, pilot scale experiments were performed to determine scale-up challenges and design specifications for eventual costs analysis (e.g. size, residence time, etc.), energy required and waste emissions.     

回转窑热解城市垃圾制造中热值燃气的试验

<正>固体废弃物的热解不仅解决了固体废弃物的处理问题,还可得到气体（燃气）、液体（焦油）和固体（半焦）3种不同形态的产物,根据热值的高低,气体可单独或与其他高热值燃气混合     

On-line monitoring of fuel moisture-content in biomass-fired furnaces by measuring relative humidity of the flue gases

Combustion of biomass for heat and power production is continuously growing in importance, because of incentives for replacing fossil energy resources with renewable ones. In biomass combustion, the moisture content of the fuel is an essential operation parameter, which often fluctuates for biomass fuels. Variation in moisture content complicates the operation of the furnaces and results in an uncertainty in the energy content of the fuel delivered to a plant. The fuel moisture-content in a furnace may be determined either by direct measurement on the entering fuel or by measuring the moisture and oxygen contents of the flue gases deriving the moisture content of the fuel. However, reliable methods of a motivated cost for the small to medium-scale furnaces are today not available. An exception is if the furnace is equipped with flue-gas condenser, which can be used to estimate the moisture content of the flue gases. A limitation of this method is, though, that not all furnaces have flue-gas condensers and that the measured signal has an inherent time delay.In this work, measurement of the relative humidity (RH) of the flue gases from a furnace is investigated as the central component in the on-line monitoring of the moisture content of the fuel in a furnace. The method was analysed with humid air in a laboratory environment and tested for accuracy and dynamical behaviour in two biomass-fired heat-production units, one circulating fluidised-bed boiler (CFB) and one grate furnace. The results show that the method, which is easy to calibrate on site, can be used to predict the moisture content of the biomass fuel in the grate furnace with very good precision (<4% error). Furthermore, the method detects variations in moisture content of the furnace flue gases due to changes in the moisture content of the combusted fuel within the order of seconds. Since the transport time of the flue gases from the furnace to the measurement position is of the same order of magnitude, the total time for detection of a change in the moisture content of the fuel is small enough for the signal to be used to control both the fuel feed and the combustion air in a grate furnace.     

Fruit processing residues as an alternative fuel for drying in Northern Thailand

In this study, the fuel potential of residues from local fruit processing facilities in Northern Thailand was assessed. Facilities were surveyed to determine current processing and waste disposal strategies. In facilities handling large amounts of these fruits particularly, residues are currently disposed of in municipal dumps. Fresh processing refuse such as peels and seeds was sampled and analyzed for fuel properties. The results of proximate analysis showed mean moisture content of wastes were 35-75% wb with ash contents of about 2.2-7.1 wt.% db and high volatile matter ranging 67-73 wt.% db. Higher heating values ranged between 18.3 and 19.3 MJ kg⁻¹. Therefore, wastes showed good fuel potential, but high moisture (>60% wb) and nitrogen (>0.6 wt.% db) contents require attention when considering potential fuel applications.     

Co-firing of coal and cattle feedlot biomass (FB) fuels. Part I. Feedlot biomass (cattle manure) fuel quality and characteristics

The use of cattle manure (referred to as feedlot biomass, FB) as a fuel source has the potential to solve both waste disposal problems and reduce fossil fuel based CO₂ emissions. Previous attempts to utilize animal waste as a sole fuel source have met with only limited success due to the higher ash, higher moisture, and inconsistent properties of FB. Thus, a co-firing technology is proposed where FB is ground, mixed with coal, and then fired in existing pulverized coal fired boiler burner facilities. A research program was undertaken in order to determine: (1) FB fuel characteristics, (2) combustion characteristics when fired along with coal in a small scale 30 kW_t (100,000 BTU/h) boiler burner facility, and (3) combustion and fouling characteristics when fired along with coal in a large pilot scale 150 kW_t (500,000 BTU/h DOE-NETL boiler burner facility). These results are reported in three parts. Part I will present a methodology of fuel collection, fuel characteristics of the FB, its relation to ration fed, and change in fuel characteristics due to composting. It was found that FB has approximately half the heating value of coal, twice the volatile matter of coal, four times the N content of coal on heat basis, and due to soil contamination during collection, the ash content is almost 9-10 times that of low ash (5%) coal. The addition of <5% crop residues had little apparent effect on heating value. The main value of composting for combustion fuel would be to improve physical properties and to provide homogeneity. The energy potential of FB diminished with composting time and storage; however, the DAF HHV is almost constant for ration, FB-raw, partially composted and finished composted. The fuel N per GJ is considerably high compared to coal, which may result in increased NO_x emissions. The N and S contents per GJ increase with composting of FB while the volatile ash oxide% decreases with composting. Based on heating values and alkaline oxides, partial composting seems preferable to a full composting cycle. Even though the percentage of alkaline oxides is reduced in the ash, the increased total ash percentage results in an increase of total alkaline oxides per unit mass of fuel. The adiabatic flame temperature for most of the biomass fuels can be empirically correlated with ash and moisture percentage.     

煤调湿工艺数学模型与计算

以煤调湿反应器为控制体,建立了水分物料平衡和控制体热量平衡数学模型.在理论分析的基础上,计算得到烟道废气量、入口废气温度、出口废气温度、入口煤粉湿度对调湿后煤粉湿度和废气湿含量的影响,计算结果可以作为煤调湿工艺设计和优化的理论依据与参考.     

Advancements in development and characterization of biodiesel: A review

An ever increasing demand of fuels has been a challenge for today’s scientific workers. The fossil fuel resources are dwindling day by day. Biodiesel seems to be a solution for future. Biodiesel is an environmentally viable fuel. Out of the four ways viz. direct use and blending, micro-emulsions, thermal cracking and transesterification, most commonly used method is transesterification of vegetable oils, fats, waste oils, etc. Latest aspects of development of biodiesel have been discussed in this work. Yield of biodiesel is affected by molar ratio, moisture and water content, reaction temperature, stirring, specific gravity, etc. Biodegradability, kinetics involved in the process of biodiesel production, and its stability have been critically reviewed. Emissions and performance of biodiesel has also been reported.     

Conditioning of coal-enrichment waste with high moisture and ash content

The processing of coal-enrichment waste with high moisture and ash content is considered. Existing methods—filtration and thermal drying—are very complex and energy-intensive and have considerable environmental impact. An alternative is adsorption on lignite coke produced in the Krasnoyarsk region by thermal oxidation. Termokoks-KS lignite coke, which is low in ash and sulfur, resembles activated charcoal in its absorption properties. Experiments show that, when mixed with coal wastes, it produces a fuel blend characterized by lower ash content, satisfactory friability, and high energy yields. An industrial technology for such conditioning of coal wastes is described.     

High-pressure compaction of municipal solid waste to form densified fuel

A unique piston-in-mold (punch-in-die) process, developed at the Capsule Pipeline Research Center (CPRC), University of Missouri-Columbia, USA, was used to study the compaction of the combustible components found in municipal solid waste (MSW) stream to produce a densified fuel. The compaction was performed under room temperature without binder and at pressures up to 138 MPa. The materials included waste paper, plastics (both film and hard products), textiles, and wood. They were compacted into 49-mm-diameter logs in different mixtures and under various moisture contents and pressures. The mixtures compacted include: (1) paper and plastic film, (2) paper and hard plastics, (3) paper and mixed plastics (both filmed and hard), and (4) paper, plastics, textiles, and wood. The properties of the logs, including density, abrasion resistance, impact resistance, combustion characteristics, and long-term performance were tested. The results show that the waste paper in the mixtures played a role of binder in the formation of the compacted logs. Moisture content and compaction pressure were two key parameters for producing good logs. For all these mixtures, a moisture content of less than 15% is necessary to produce dense (dry density equal to or higher than 0.8 g/cm³) and strong logs. A minimum compaction pressure of 70 MPa is needed for mixtures 1, 2, and 3, and 100 MPa for mixture 4. The logs made from the mixtures of the combustible wastes have a heating value equivalent to that of subbituminous coal, and can be cofired with coal in power plants.     

Gasification of high moisture rubber woodchip with rubber waste in a bubbling fluidized bed

This study investigated co-gasification of high moisture rubber woodchip (RW) with shredded rubber waste (SR) as an alternative to pre-drying of woodchip and effective utilisation of wastes. The shredded rubber waste was added into the rubber woodchip having originally 27% moisture content at 10 and 20 wt.% based on the dry weight of rubber woodchip. The mixtures were gasified with air in the 100 kWth bubbling fluidized bed gasifier at various equivalence ratios (ER). Operated at the same ER, the SR addition was found to raise the gasification temperature, e.g. an increase from 700 °C without SR addition by ~ 70°C with 20% SR addition. The heating value of synthesis gas generally increased with increasing % SR addition and with decreasing ER. Due to the resulting higher gasification temperature obtained from gasification with SR addition, it is possible to operate gasification at lower ER compared to the case without SR addition leading to the higher CO/CO₂ production ratio. Both ER and SR addition gave a positive effect on the carbon conversion efficiency; while the gasification efficiency was more influenced by the fuel chemistry. The amount and heating value of fly ash were slightly decreased in all mixtures with increasing ER, while increasing the SR addition ratio resulted in the higher fly ash due to the high ash originally present in the rubber waste. Overall, the performance and products from co-gasification were significantly improved compared to those from gasification using the high moisture woodchip alone and almost as good as that obtained when using low moisture woodchip. This implies the direct usability of high moisture rubber woodchip by adding shredded rubber waste without the need of pre-drying and moreover an improvement of the gasification performance and products.     

Determination of particle size distribution of salt crystals in aqueous slurries

A method for determining particle size distribution of water-soluble crystals in aqueous slurries is described. The salt slurries, containing sodium salts of predominantly nitrate, but also nitrite, sulfate, phosphate, aluminates, carbonate, and hydroxide, occur in radioactive, concentrated chemical waste from the reprocessing of nuclear fuel elements. The method involves separating the crystals from the aqueous phase, drying them, and then dispersing the crystals in a non-aqueous medium based on nitroethane. Ultrasonic treatment is important in dispersing the sample into its fundamental crystals. The dispersed crystals are sieved into appropriate size ranges for counting with a HIAC brand particle counter. A preponderance of very fine particles in a slurry was found to increase the difficulty of effecting complete dispersion of the crystals because of the tendency to retain traces of aqueous mother liquor. Traces of moisture produce agglomerates of crystals, the extent of agglomeration being dependent on the amount of moisture present. The procedure is applicable to particles within the 2 – 600 μm size range of the HIAC particle counter. The procedure provides an effective means for measuring particle size distribution of crystals in aqueous salt slurries even when most crystals are less than 10 μm in size.     

Spontaneous ignition of wood, char and RDF in a lab scale packed bed

Many municipal waste combustors use preheated primary air in the first zone to dry the waste. In most cases the preheat temperature does not exceed 140 °C. In previous experiments it is found that at temperatures around 200 °C, in some circumstances, self- or spontaneous ignition can be achieved. Using preheated air can be a powerful tool to control the ignition and combustion processes in a waste combustion plant. To use this tool effectively, the influence of the preheated air on the fuel bed needs to be well understood. The present work is done to investigate in a systematically way the spontaneous ignition behaviour of a packed bed heated with a preheated air stream. Experiments on a lab scale packed bed reactor are carried out for various fuel types. Because MSW is an highly inhomogeneous fuel, wood and char are used as model fuels. To include the inhomogeneous character of MWS, also experiments are carried out with RDF. Parameters such as primary air flow velocity and temperature, addition of inert material, moisture content of the fuel (wood chips) and particle size (char) have been changed to see their effect on the spontaneous ignition temperature and on the minimum air temperature needed for ignition. The spontaneous ignition temperature is defined as the bed temperature at which a transition takes place from a negligible or slow fuel reaction rate to a rapid oxidation of either the volatiles or the solid fuel without an external source such as a spark or a flame. The minimum or critical air temperature is defined as the lowest air temperature at which ignition can be obtained. It is found that the type of fuel has influence on the ignition temperatures. Besides both the critical air temperature needed for the spontaneous ignition and the spontaneous ignition temperature increase with an increase in the primary air velocity (between 0.1 and 0.5  m/s) and increasing the added inert fraction (between 0 and 40 wt%), irrespective of the fuel type. The effect of air flow velocity and temperature and also the effect of inert on both the critical air temperature and the spontaneous ignition temperature can be explained qualitatively by using Semenov’s analysis of thermal explosions. Semenov’s theory is quantitatively applied to predict the spontaneous ignition and the critical air temperatures for wood.     

污泥水热处理制备清洁燃料的研究进展

目前,庞大的污泥产生量是困扰工业与市政工程的一个主要问题,对其减量化与能源化利用是污泥处置的关键。其中,水热技术是一种可直接并有效利用污泥等高含水率废弃物的处理手段。本文首先介绍了污泥的特点以及处理现状,然后总结了国内外近年来关于污泥水热处理工艺的发展历程与工业应用情况。此外,着重讨论了水热处理对污泥能源化利用的各项优势,包括：降低NO_x、酸性气体与飞灰等污染物的排放,固定污泥重金属,改善污泥燃料性能,提高污泥脱水性能以及降低其处理成本等。同时,针对不同种类污泥的不同组分在水热处理过程中的反应过程与影响因素进行了详细讨论。最后,对于污泥水热处理能源化利用的发展前景作出展望,指出深入研究污泥与其他废弃物混合水热或焚烧过程中的协同作用是制备高品质燃料的重要途径。     

Biomass co-firing in a pressurized fluidized bed combustion (PFBC) combined cycle power plant: A techno-environmental assessment based on computational simulations

The co-utilization of coal with biomass and biomass waste in a pressurized fluidized bed combustion (PFBC) system is a promising power generation option for addressing various areas of concern relating to the anthropogenic sources of harmful emissions, the global reliance on fossil fuel and the overall energy supply issues. In this study, coal with a wide range of biomass and biomass waste types such as straw, willow chips and switch grass as well as miscanthus and olive pits are fired in an advanced PFBC system. The produced gases and the evolved heat energy are employed to run a combined cycle. To understand the behavior of the proposed system, detailed computational simulations are carried out utilizing various feedstock mixtures ranging from 100% coal to 40% biomass. The results of the simulations are used to show the effect of co-firing on the technical and environmental performance of the power plant.The results show that the main parameters affecting the overall power plant efficiency are the co-firing ratios and the specific properties of the chosen biomass/waste types. Furthermore, the investigation indicates that the steam cycle output reacts more sensitive to the fuel configurations than the gas turbine cycle. As expected, the increased fraction of biomass or waste significantly reduces net CO₂ emissions, and has a beneficial influence on SO_x emissions. NO_x emissions tend to rise for all biomass types, except the high moisture content willow chips, with increasing co-firing fraction.     

Combustion of bagasse: Use of an agricultural-derived waste

The recent escalation in price of conventional fossil fuels and their uncertain availability has precipitated an intense effort world-wide to develop so called ‘unconventional’ or ‘alternative’ fuels. The waste product from the sugar cane grinding process, termed bagasse, represents an agricultural energy resource which is increasingly used in the sugar industry as a fuel. Currently, the pile burning configuration involving high excess air levels and low combustion efficiencies constitutes the major method of bagasse combustion. This Paper reports on a novel burner which has been developed to burn bagasse efficiently in full-suspension at low excess air levels (down to 5%) thereby generating high combustion efficiencies. To accomplish this excess air level the bagasse was dried to a maximum of 16% moisture and pulverized so that 60–65% passed a 30 US Standard Sieve mesh. A discussion is included concerning optimum methods of bagasse preparation for this system.     

Generalized Titanate Ceramic Waste Form for Advanced Purex Reprocessing

Alternative dissolution processes for spent nuclear fuel lead to highly active waste streams rich in zirconium, iron, chromium, and nickel at levels that vary with fuel assembly design. A titanate ceramic phase assemblage has been developed with the flexibility to accommodate these variations in waste stream composition. Waste loadings range from 42 to 50 wt%. Leach rates are comparable to those from Synroc C.