First-Stage Operation

As in the traditional acid extraction process, the feedstock is generally dewaxed solvent refined base stock, since levels of the aromatics, polynuclear aromatics, and nitrogen and sulfur compounds are already reduced relative to a straight-run gas oil. This facilitates hydroprocessing by lightening the load on the catalysts and extending their lives. Equally important is that this is an already dewaxed feed, so the white oil producer does not have to bear the capital costs of crude fractionation and dewax units. 

---

Residual carbamate and CO2 are recovered downstream of the stripper in two successive stages. The first stage operates at 17 bar, and the second stage operates at 3.5 bar. Ammonia and CO2 vapors from the stripper top are mixed with the recovered carbamate solution from the High Pressure (HP) / Low Pressure (LP) sections, condensed in the HP carbamate condenser and fed to the reactor. The urea solution that leaves the LP decomposition stage is concentrated in the evaporation section to make a urea melt110. 

TwinRec A two-stage process for recovering energy and materials from various industrial wastes. The first stage, operated at 500 to 600°C in a reducing atmosphere, separates combustible materials from metallic and inert materials. The second stage, operated at 1350 to 1450°C, produces a molten ash, which solidifies to a granular material suitable for the construction industry. Developed by Ebara Corporation and commercialized in 20 plants in Japan by 2004. 

E4. A distillation column is separating methanol and water at a pressure of 1 atm. Feed rate of the mixture is 100 kmol/h. The feed is 25 mol% methanol and 75 mol% water. The feed is a subcooled liquid. To heat the feed to the boiling point, one mole of vapor condenses on the feed stage for every 10 moles of feed. We desire a distillate mole fraction that is 90 mol% methanol and a bottoms mole fraction that is 2.5 mol% methanol. We operate with a boilup ratio of 1.0. The column is operated with two reflux streams. The reflux to the first stage operates with a flow rate of Lq = 21.4 kmol/h. Sufficient reflux (L ) is returned to stage 2 for the column to operate. Both... 

Vacuum crystallization needs no heat transfer area in the solution, and therefore no incrustation problem occurs. To increase economic efficiency with evaporation crystallization, with respect to steam input, the process is designed for multistage operation with steam heat recovery. The first stage operates under conditions close to ambient pressure, and the final stage under a vacuum, such that the steam is condensed without compression at the temperature of the available cooling water. 

Some hydrotreaters are two-stage hydrotreaters. The first stage operates at low temperature, hydrogenating diolefins and acetylenes. These compounds... 

Filtrate from the second stage is lean in oil and can be used in first stage operation. It may be blended with fresh solvent and used as first stage wash, or it may be added as the final increment of dilution in an incremental plant. Recycling the 2nd stage filtrate reduces the overall solvent usage. 

On the fourth test point, a DC level change is expected if the intensity of the radiation changes. In all other systems pulses should be present on this output if the detector and the first stage operates in response to the radiation. 

---