Pressure hydrocarbon partial

Product Distribution. In addition to ethylene, many by-products are also formed. Typical product distributions for various feeds from a typical short residence time furnace are shown in Table 5. The product distribution is strongly influenced by residence time, hydrocarbon partial pressure, steam-to-od ratio, and coil outlet pressure. 

Advanced Cracking Reactor. The selectivity to olefins is increased by reducing the residence time. This requires high temperature or reduction of the hydrocarbon partial pressure. An advanced cracking reactor (ACR) was developed jointly by Union Carbide with Kureha Chemical Industry and Chiyoda Chemical Constmction Co. (72). A schematic of this reactor is shown in Figure 6. The key to this process is high temperature, short residence time, and low hydrocarbon partial pressure. Superheated steam is used as the heat carrier to provide the heat of reaction. The burning of fuel... 

Tlie feedstock is mixed witli steam before entering tlie pyrolysis reactors. Steam reduces tlie hydrocarbon partial pressure, acts as a heat transfer... 

As with gas feeds, maximum olefin yields are obtained at lower hydrocarbon partial pressures, pressure drops, and residence times. These variables may be adjusted to obtain higher BTX at the expense of higher olefin yield. 

Fig. 4. Comparison of activity patterns of the group VIII noble metals for cyclopropane hydrogenation and ethane hydrogenolysis. The activities were all determined at hydrogen and hydrocarbon partial pressures of 0.20 and 0.030 atm, respectively (63).

Many processes in a refinery use steam as a stripping medium in distillation and as a diluent to reduce the hydrocarbon partial pressure in catalytic or thermal cracking [37]. The steam is eventually condensed as a liquid effluent commonly referred to as sour or foul water. The two most prevalent pollutants found in sour water are H2S and NH3 resulting from the destmction of organic sulfur and nitrogen compounds during desulfurization, denitrification, and hydrotreating. Phenols and cyanides also may be present in sour water. 

Low hydrocarbon partial pressure with higher steam rate (total pressure of about 12-15 psig and steam usage of 25 wt% of the feed)... 

Data used to develop the deactivation kinetics consisted of over 50 balances in the isothermal fixed bed reactor. Experimental conditions were 756 and 794 K isothermal reactor temperature, 551-1378 kPa H2 partial pressure, 137-344 kPa hydrocarbon partial pressure, and 1-26 liquid hourly space... 

Once the deactivation rate coefficients at reference conditions were determined, activation energy, hydrogen partial pressure, and hydrocarbon partial pressure parameters were estimated from data at 756 and 794 K, 551 to 1378 kPa hydrogen partial pressure, and 137 and 344 kPa hydrocarbon partial pressure. 

A Diagonal matrix of catalyst state veclor Mj Hydrocarbon partial pressure exponent in deactivation kinetics... 

CN Weight average C6. product carbon number P Hydrocarbon partial pressure vector in deactivation kinetics... 

D Deactivation rate constant matrix P tc C6. hydrocarbon partial pressure,... 

A steam stripper, as shown in Fig. 10.1, works in the same way. The diesel-oil product drawn from the fractionator column is contaminated with gasoline. The stripping steam mixes with the diesel-oil product on the trays inside the stripper tower. The steam reduces the hydrocarbon partial pressure and thus allows more gasoline to vaporize and to escape from the liquid phase into the vapor phase. The heat of vaporization of the gasoline cannot come from the steam, because the steam (at 300°F) is colder than the diesel oil (at 500°F). The heat of vaporization must come from the diesel-oil product itself. 

Pressure effects are, in general, not significant in the range of commercial pyrolysis interests. For hydrocarbon partial pressures of 0.2 to 2.0 x 105 Pa, few differences are seen. When pressures are increased to the range of 50 to 100 x 105 Pa, however, the global rate constants sometimes double. 

The activity of granulated rhenium catalyst, obtained from copolymer carbonisate, has been investigated in reactions of cyclohexane or ethylbenzene dehydrogenation in bed -packed quartz tube reactor at the plug flow conditions at temperatures from 650 to 900 K, the reagents feed of 30 - 100 ml/min and initial hydrocarbons partial pressure of 0.5 kPa. 

Ethane enters the pyrolysis section, which comprises a series of cracking furnaces. The ethane is heated as quickly as possible to the cracking temperature and maintained at this temperature for the minimum residence time. In order to lower the hydrocarbon partial pressure and mitigate coke forming in the pyrolysis tubes, steam is added to the ethane prior to entering the pyrolysis section (not shown). 

Cracking yields are highly influenced by cracking parameters thus, better yields require better cracking conditions. Main cracking parameters are hydrocarbon partial pressure, residence time, and temperature. 

Hydrocarbon Partial Pressure. For naphtha, the influence of hydrocarbon partial pressure on different components is shown in Figure 1. For other feed stocks, this influence is similar. This is also shown in Figure 1 for the ethylene yields from kerosene and hydro-converter residue. 

In general, with decreasing hydrocarbon partial pressure, unsaturated components such as acetylene, ethylene, propylene, and butadiene increase whereas BTX, pyrolysis fuel oil, and saturated components such as methane, ethane, and propane decrease. Low hydrocarbon partial pressure can be attained either by high steam dilution or by low absolute pressure in the cracking coil, which is determined by furnace outlet pressure and pressure drop in the cracking coil. For each specific case there is an optimum steam dilution. Reduction of steam dilution influences yields, utilities, running times and, in the case of a new ethylene plant, of course, investment costs—but in different ways, either positive or negative. Thus, an optimization has to be carried out to identify the most economic steam dilution. 

Figure 1. Yields as a function of hydrocarbon partial pressure (N) naphtha, (K) kerosene, (HCR) hydroconverter residue.

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