Impurities from fuels

The SEM-EDS-results of the used bed sanples indicate only little agglomeration in the bed. The small agglomerates were formed solely around quartz particles that were present in the bed as an impurity from fuel, or as a residue of the previous bed. The quartz particles had probably reacted with sodium from the fuel forming sodium aluminium silicates of a low melting point. The coating thus formed may eventually lead to agglomeration. ... 

Krocher O, Elsener M (2008) Chemical deactivation of V20s/W03-Ti02 SCR catalysts by additives and impurities from fuels, lubrication oils, and urea solution I. Catalytic studies. Appl Catal B 75 215-227... 

Organic sulfurs in natural gas and liquid fuels are poison to both the reforming catalyst and fuel cell s electrocatalysts. Many zeolites adsorb organic sulfurs and can efficiently remove these impurities from fuels. Sulfur removal by adsorption... 

Nuclear wastes are classified according to the level of radioactivity. Low level wastes (LLW) from reactors arise primarily from the cooling water, either because of leakage from fuel or activation of impurities by neutron absorption. Most LLW will be disposed of in near-surface faciHties at various locations around the United States. Mixed wastes are those having both a ha2ardous and a radioactive component. Transuranic (TRU) waste containing plutonium comes from chemical processes related to nuclear weapons production. These are to be placed in underground salt deposits in New Mexico (see... 

Pyrolysis has the unique advantage of enabling the removal and separation of most impurities such as sulfur from fuels prior to their combustion. 

The emergence of commercial fuel cell cars will depend on developments in membrane technology, which are about one third of the fuel cell cost. Improvements are desired in fuel crossover from one side of a membrane to the other, the chemical and mechanical stability of the membrane, undesirable side reactions, contamination from fuel impurities and overall costs. 

The concentrations of impurities entering the PAFC are very low relative to diluents and reactant gases, but their impact on performance is significant. Some impurities (e.g., sulfur compounds) originate from fuel gas entering the fuel processor and are carried into the fuel cell with the reformed fuel, whereas others (e.g., CO) are produced in the fuel processor. 

Drying and sweetening is a broad class of processes used to remove sulfur compounds, water, and other impurities from gasohne, kerosene, jet fuels, domestic heating oils, and other middle... 

Although they are more resistant to impurities than other fuel cell types, scientists are looking for ways to make MCFCs resistant enough to impurities from coal, such as sulphur and particulates. 

The adsorber is purged at tail gas pressure with hydrogen recovered from other adsorbers. The gas desorbs impurities from the adsorbent and flows out the tail gas line. The impurity front is returned to the feed end of the adsorbent bed. The tail gas can be used as fuel or for subsequent processing. 

The solid oxide fue( cell (SOFC) have been under development during several decades since it was discovered by Baur and Preis in 1937, In order to commercialise this high temperature (600 - 1000°C) fuel cell it is necessary to reduce the costs of fabrication and operation. Here ceria-based materials are of potential interest because doped ceria may help to decrease the internal electrical resistance of the SOFC by reducing the polarisation resistance in both the fuel and the air electrode. Further, the possibility of using less pre-treatment and lower water (steam) partial pressure in the natural gas feed due to lower susceptibility to coke formation on ceria containing fuel electrodes (anodes) may simplify the balance of plant of the fuel cell system, and fmally it is anticipated that ceria based anodes will be less sensitive to poising from fuel impurities such as sulphur. 

Condensate, however, may not always be usable as boiler feedwater, due to the presence of certain process contaminants (see Table 1). When steam is used for heating, to power equipment, and for varied process applications, condensate comes into contact with oil and other impurities. Contamination from fuel-oil heaters or leaking seals in steam-driven equipment, such as pumps, turbines or compressors, is common. Also, the raw water used as plant makeup, may contain significant levels of solvents, uel oils, gasolines and greases. In addition to these general contamination sources, each industry has its unique one. (Table II). If any of these contaminants become entrained in the returned condensate stream, numerous and sometimes unpredictable problems in the boiler and related systems cs.n occur. 

We see that the incomplete combustion of hydrocarbons yields undesirable products —carbon monoxide and elemental carbon (soot), which pollute the air. Unfortunately, all fossil fuels—natural gas, coal, gasoline, kerosene, oil, and so on—also have undesirable nonhydrocarbon impurities that burn to produce oxides that act as additional air pollutants. At this time it is not economically feasible to remove all of these impurities from the fuels before burning them. 

Removal of dissolved inorganic impurities from methanol Is of Interest from the point of view of utilization of methanol as an alternative to conventional fuels. Reports show that the corrosion rate of metal alloys used for turbines and fuel transportation is greater in methanol than in water in the presence of traces of chlorine and sodium ions ( , 10). Further, ion complexes in trace quantities have been observed in methanol and there is concern that they could alter the reaction kinetics for processes which use methanol as a feedstock or reaction medium (11). Methanol that Is used as a feedstock In the production of single cell protein could be sterilized as well as purified of heavy metals by reverse osmosis which can be integrated in the design of these processes. 

Heating yellow cake in hydrogen gas produces UO2 which in sintered form is used as nuclear reactor fuel. If the UO2 is exposed to F2, IIF4 is obtained ("green salt"), which in a thermite process with calcium metal yields metallic uranium. The metal is slowly oxidized in air at room temperature the metal powder is very reactive at elevated tenqieratures and can then be used to remove practically all impurities from rare gases. 

In addition, for the more conventional uses of coal for power generation and production of coal tar and coke (Part 11), a number of processes have been developed by which solid coal can be converted to a liquid or gaseous form for use as a fuel. Conversion has a number of advantages. In a liquid or gaseous form, the fuel may be easier to transport. Also, the conversion process removes a number of impurities from the original coal (such as sulfur) that have environmental disadvantages. 

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