High-pressure preheaters

The second law can also suggest appropriate corrective action. Eor example, in combustion, preheating the air or firing at high pressure in a gas turbine, as is done for an ethylene (qv) cracking furnace, improves energy efficiency by reducing the lost work of combustion (Eig. 4). 

Recommended for high-pressure (>600 psi), high-temperature applications. Tube shape allows extreme temperature differences (AT>250°F) across the bundle. Often used as integral column bottom reboiler and as tank suction heater to preheat product before pumping. Tube side cannot be made single-pass. 

Another example of a cold-wall reactor is shown in Fig. 5.9. It uses a hot plate and a conveyor belt for continuous operation at atmospheric pressure. Preheating and cooling zones reduce the possibility of thermal shock. The system is used extensively for high-volume production of silicon-dioxide coatings for semiconductor passivation and interlayer dielectrics. 

Kumar, K., Mittal, G., Sung, C.J., and Law, C.K., An experimental investigation on ethylene/Oj/diluent mixtures Laminar flame speeds with preheat and ignition delays at high pressures. Combust. Flame, 153, 343, 2008. 

Hydrane A coal gasification process in which coal is hydrogenated directly to methane, using hydrogen gas under pressure, preheated to a high temperature. Developed by the U.S. Bureau of Mines as of 1980 it had not been fully piloted. 

Application of SFE necessitates a CO2 source, a pump to pressurize the fluid, an oven containing the extraction vessel, a restrictor to maintain a high pressure in the extraction line, an analyte collection vessel, and an overall system controller. CO2 is drawn from the bottom of the tank with a dip tube because the liquid is the more dense of the two phases. The substantial vapor pressure of the CO2 at ambient temperature helps to displace the liquid into the pump. CO2 remains a liquid throughout the pumping or compression zones and passes through small-diameter metal tubing as it approaches the extraction vessel. A preheating zone in front of the extraction vessel allows supercritical temperature, pressure, and density conditions to be applied immediately to the analyte matrix in the vessel. 

Tile partially purilied synthesis gas leaves the C02 absorber containing approximately 0.1% CO2 and 0.5% CO. This gas is preheated at the methanator inlet by heat exchange with the synthesis-gas compressor interstage cooler and the primary-shift converter effluent and reacted over a nickel oxide catalyst bed in the methanator. The methanation reactions are highly exothermic and are equilibrium favored by low temperatures and high pressures. 

Fig. I Low-pressure melhanol production. iAi Burner and superheater iBl air preheater it ) lack ID) melhanol converter (Fit separator iF) flash vessel 1(1) crude storage H> topping column, til refining column. HI S - high-pressure sieam LPS = low-pressure steam. Ifiupm n/ Chemitvl Industrie. Ltdt...

The catalytic runs were carried out in a stainless steel tubular flow reactor (length = 100 mm, i.d. 4.6 mm) which was connected to a stainless steel air-cooled condenser. Liquid reactants were fed by means of a Waters M-45 high pressure pump. Typically 0.29 g of the catalyst were placed in the reactor between two layers of granular quartz which acts as a preheater. 

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