Purity, hydrogen

The purity of hydrogen in the makeup gas to a Hydrocracker will have a major influence on the hydrogen partial pressure and recycle gas/feed ratio. Therefore, the minimum purity on the makeup gas should be set to provide the minimum recycle gas purity allowed. If the hydrogen plant is unable for some reason to produce minimum hydrogen purity product, it may be possible to purge sufficient recycle gas off the high-pressure separator to maintain the recycle gas purity requirements. 

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Figure 10-12. Effect of hydrogen purity and pressure on benzene conversion to cyclohexane. ...

However, the susceptibility to hydrocracking of the non-aromatic intermediates leads to considerable formation of light gases and naphthenes that reduce the xylene yield and the hydrogen purity. 

By 2010, develop and demonstrate technology to supply purified hydrogen (purity sufficient for polymer electrolyte membrane (PEM) fuel cells) from biomass at 2.60/kg at the plant gate (projected to a commercial scale 75,000 kg/day). The objective is to be competitive with gasoline by 2015. 

The secondary reformer vessel is a refractory-lined vessel that has an oxygen burner in its top neck and a fixed catalyst bed. Installation of a secondary reformer usually requires significant changes to the CO2 removal system Hydrogen purity can be increased up to 98%. The economics generally depend on a reliable source of low-cost oxygen172. 

Yield data obtained with the progress of cycle presented in Fig 5 shows the catalyst to possess high stability Increase in WAIT required to produce same RONC reformate is presented in Fig.6 A small increase of 5°C in WAIT was observed during the cycle. Hydrogen purity declined by about 7-8% during the first cycle operation. 

Catalyst deactivated very fast in about three months. Initial reformate yield was lower by about 5 5% wt as shown in Fig,9, RONC dropped from about 88 to 70-68 and hydrogen purity also declined from 75 to 40 %vol. Typical performance data are shown in Fig, 10. Total... 

The plant was restarted following normal procedure. C5+ yield at 88 RONC was 81 6%wt as presented in Fig 9 Hydrogen purity was 75%v The data are in close agreement with the first cycle. Continued performance of the plant had shown the stable activity of the catalyst. 

These caluclations of refinery hydrogen requirements are based on hydrogen consumption data summarized in Table 6 for the various processes that consume and produce hydrogen. These hydrogen consumption data allow for the theoretical hydrogen consumption and 20% excess above that required to maintain the desired hydrogen purity in the process. 

Production of 100 x 10 scf/sd of pure hydrogen. Hydrogen purity is greater than 98% vol. 

Figure 4, presented for illustrative purposes, shows the hydrogen purity achievable for the separation of a 65/35 hydrogen methane feedstock with a final phase separation temperature established by the back pressure of the fuel (methane) stream. 

Hydrogen purity increases with increasing feed pressure, decreasing fuel pressure and decreasing hydrogen recovery. 

The Haldor Topsoe Convection Reformer (HTCR) is a relatively small piece of equipment that combines the radiant and waste heat sections of the conventional reformer. It uses PSA (pressure swing absorption) to make 99.9 percent hydrogen purity. It is best for small and medium-sized hydrogen plants (500 to 10,000 Nm3/hr).75... 

The microalloy tubes allow increased flux rates and higher reformer outlet temperatures. This in turn can make it possible to reduce the steam-to-carbon ratio while the hydrogen purity remains the same.86... 

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