Compression down converting

This technique will allow compression of a 100-femtosecond pulse down to 12 femtoseconds or even to 8 femtoseconds. (A femtosecond is a millionth of a billionth of a second or 1 x 10-15 s.) Pulse compression can be used to study chemical reactions, particularly intermediate states, at very high speeds. Alternatively, these optical pulses can be converted to electrical pulses to study electrical phenomena. This aspect, of course, is of great interest to people in the electronics industry because of their concern with the operation of high-speed electronic devices. It also is of great interest to people who are trying to understand the motion of biological objects such as bacteria. 

Fig. 3.1 outlines the liquefaction of air. Air is filtered to remove particulates and then compressed to 77 psi. An oxidation chamber converts traces of hydrocarbons into carbon dioxide and water. The air is then passed through a water separator, which gets some of the water out. A heat exchanger cools the sample down to very low temperatures, causing solid water and carbon dioxide to be separated from the main components. 

The temperature of the gas thus falls. The cooled air enters the chamber E from below and then goes up as shown. Thus, the gas cools the portion of the compressed air passing down the coil CE. This chilled gas then passes through a jet or throttle J and is further cooled by Joule-Thomson effect on account of expansion. This process goes on till the gas is converted into the liquid state. 

The initial design of the gas producer was such that it could be converted readily to operate either as a downdraft or as an updraft reactor. Also, the air intake could either be by suction from the engine or by forced draft from a compressed air tank. There was only a single air inlet at the side of the producer when it was operated as a down-draft reactor, so that the combustion zone was concentrated in the vicinity of this single air inlet. 

In the case of the stopped flow device (Figure 8.42), two compressed syringes are set up to express small volumes (50-200 pi) at any one time. These syringes are individually loaded with samples as above and small volumes of these samples are then fired together into a mixing chamber and expelled down a flow-tube at constant flow rate (approximately 10 m s ) prior to a mechanical stop. A fixed detector at a distance of 1 cm from the mixing chamber is then positioned to observe solution that is initially 1 ms old at the end of continuous flow. Compression converts continuous into static flow, so spectroscopic and/or physical changes... 

The mixture enters the converter at 26°C and 810 mmHg. We assume a conversion in the reactor equal to 1. The gases are cooled down to 25°C and compressed to 10 atm. During the cooling, NO is oxidized with a conversion of 15% and HNO3 is formed and dissolved in water with a composition of 3.5%. The gas phase is sent to an oxidation tower where the rest of NO is oxidized completely at 7600 mmHg. 

The compressed converter gas is cooled in a series of exchangers and enters an absorption tower where water is added. The tail gas from the absorber is heated through three exchangers and then enters a power recovery-expansion turbine. The absorber tower nitric acid is fed to the top of the bleacher, flowing down countercurrent to the air. The air, which leaves at the top of the bleacher, combines with the converter effluent and is recycled to the absorption tower. The tail gas from the power recovery turbine contains less than 150 ppm nitrogen oxides. 

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