Bum cleanly

Jet fuel is classified as aviation turbine fuel, and in the specifications, ratings relative to octane number are replaced with properties concerned with the ability of the fuel to bum cleanly. Jet fuel is a light petroleum distillate that is available in several forms suitable for use in various types of jet engines. The exact composition of jet fuel is established by the U.S. Air Force using specifications that yield maximum performance from the aircraft. The major jet fuels used by the military are JP-4, JP-5, JP-6, JP-7, and JP-8. 

Figure 19 shows the slow coke profiles for the top and bottom zones obtained when 0.0, 0.1, and 0,2% fast coke is present. When no fast coke is present, the catalyst does not bum clean ( 0.2% residue carbon at kiln exit). This is consistent with the rapid rise in bum-off distance at 875 F (469°C) seen in Fig. 17. However, the presence of 0.1% fast coke gives an essentially clean catalyst, using only 0.6 of the bottom zone. Only a quarter of the bottom zone is needed when 0.2% fast coke is present. This improvement in bum-oflf distance is caused by the temperature boost obtained from the rapidly burning fast coke. This temperature boost is shown by the temperature curves in Fig. 20b. The temperature of the catalyst at the top of the upper bed has increased from 875°F (741 K) to 900°F (755 K). This is sufficient to make a large improvement in bum-off distance as shown by Fig. 17.

It is well known that the boiling point of hydrocarbon molecules will generally increase as the number of carbon atoms increases. It is also known that in order for fuel to bum cleanly and completely, enough oxygen must be present to react with all carbon atoms to form either C02 or CO. Therefore, if a fuel contains a greater number of carbon atoms, more oxygen will be required to completely combust this fuel to C02 or CO. 

Natural gas will be the premium fuel for this century for three reasons (1) while we wish to use hydrogen as a fuel, we are economically restricted from obtaining it by reforming light hydrocarbons (with attendant inefficiencies) until we learn to efficiently electrolyze water, (2) gas bums cleanly, causes few pollution problems and, relative to oil or coal, produces less carbon dioxide, and (3) liquid fuels are better used as feedstocks for petrochemicals. 

This gives a fine color, bums clean and ia inexpenaive. 

European settlers used the tangled roots of saw palmetto as scrub brushes, and the roots were burned to create potash salts as a source of alkali. The seeds yield a fixed oil (a nonvolatile vegetable oil), which bums cleanly with a blue flame that gives off a peculiar coffee-like odor. A wax extracted from the leaves was investigated as a source of industrial vegetable wax, but it was found to be less useful than already available sources. 

Jet fuels must bum cleanly and remain fluid and free from wax particles at the low temperatures experienced in high-altitude flight. The conventional freeze-point specification for commercial jet fuel is -50°C. The fuel must also be free of any suspended water particles that might cause blockage of the fuel system with ice particles. Special-purpose military jet fuels have even more stringent specifications. 

Because natural gas bums cleanly, the nation s domestic natural gas resources, and the presence of supporting infrastructure, the development of domestic shale gas reserves will be an important component of the United States energy coffer for many years. Recent successes in a variety of geologic basins have created the opportunity for shale gas to be a strategic part of the nation s energy and economic growth (IPAMS, 2008). 

Most plastics bum cleanly, producing emissions of carbon dioxide, nitrogen oxides, and water vapor, but some produce unwanted by-products such as polyvinyl chloride (PVC). However, PVC and such other by-products can be safely burned at high temperatures of 980 to 1,650°C (1,800-3,000°F), using controlled oxygen input, sufficient cycle (residence) time, typically i to 2 minutes, and appropriate auxiliary equipment like scrubbers and solid salts. However, most U.S. incinerators operate below 87°C (1,600°F) and use only limited auxiliary equipment. For example, incinerated PVC generates undesirable chlorine (and bleached paper generates much more chlorine). Exhaust scrubber systems must be used to remove this chlorine. 

Natural gas is an excellent fuel which bums cleanly with little or no residue. The main problem with its use is its low energy density—it is not readily stored in sufficient quantities to power a vehicle for the normal distance of 300 00 km. The simplest storage method is as a compressed gas in cylinders. Buses in Vancouver have such storage cylinders on the roof. It has been shown that by filling a cylinder with active carbon, it is possible to double the amount of CH4 which can be stored in the cylinder. However, this still limits the use of compressed natural gas (CNG) to fleet vehicles which can routinely refill the cylinders with compressed gas. Buses mn on natural gas in Vancouver (British Columbia, Canada) during the last 2010 Winter Olympic Games. This is shown in Fig. 6.6. 

To reduce smog, ozone, and carbon monoxide by requiring automakers to sell autos that bum clean alternative fuels in cities with bad air pollution. 

North Sea gas bums cleanly, with no smoke or fumes. 

These fuels are highly desired because they bum cleanly, producing little air pollution. 

These polymers, with number average molecular weights of about 50,000, have decomposition temperatures of 220-250°C and good to excellent tensile properties. The poly(alkylene carbonates) decompose and bum cleanly to yield mainly the appropriate cyclic carbonate with minimal ash residue and only trace levels of contaminants. Because of these clean burning characteristics, suggested applications include use as a ceramic binder metal-casting material. 

---