Differential liberation

This process is called differential vaporization, differential liberation,... 

Oil viscosity is measured in a rolling-ball viscosimeter or a capillary viscosimeter, either designed to simulate differential liberation. Measurements are made at several values of pressure in a stepwise process. The liquid used in each measurement is the liquid remaining after gas has been removed at that pressure. See page 6 of Table 10-1. 

Measurement of gas viscosity is very tedious. Obtaining accurate measurements on a routine basis is difficult. Thus, gas viscosity is estimated from correlations using the values of gas specific gravities measured in the differential liberation. Gas viscosity correlations as given in Chapter 6 or Appendix B are used. 

Why is the relative volume of a flash liberation equal to 1.0000 at die bubble point Why is the relative oil volume of a differential liberation not equal to 1.0000 at the bubble point ... 

If the pressure is released from a sample of reservoir crude oil the quantity of gas evolved depends upon the conditions of liberation. There are two basic types of gas liberation fiash and differential. In a fiash liberation the pressure is reduced by a finite amount and after equilibrium is established the gas is bled off, keeping the pressure constant. In a differential liberation the gas evolved is removed con-... 

Fig. 56. Typical plot of r versus P showing differences obtained by flash and differential liberation of gas.

In order to obtain compounds with Ti-O-P and Zr-O-P units, the hexaethoxy-derivative, NsPaCOEOg, was treated with titanium and zirconium tetrachlorides. In each case, hygroscopic solids of the type NaPaCOEOiOaMCU (M = Ti or Zr) and ethyl chloride were obtained. The degree of polymerization of these solids was 1.6—1.8, and on the basis of their i.r. and n.m.r. spectra, two alternative structures, (46) and (47), were proposed. In an alternative route to the same type of compound, N3P3CI6 was treated with tetra-n-butoxytitanium in o-xylene. Butyl chloride was liberated and a solid was obtained which has been assigned the structure (48). Its thermal decomposition was studied by differential thermal analysis. 

Although there are other ways, one of the most convenient and rapid ways to measure AH is by differential scanning calorimetry. When the temperature is reached at which a phase transition occurs, heat is absorbed, so more heat must flow to the sample in order to keep the temperature equal to that of the reference. This produces a peak in the endothermic direction. If the transition is readily reversible, cooling the sample will result in heat being liberated as the sample is transformed into the original phase, and a peak in the exothermic direction will be observed. The area of the peak is proportional to the enthalpy change for transformation of the sample into the new phase. Before the sample is completely transformed into the new phase, the fraction transformed at a specific temperature can be determined by comparing the partial peak area up to that temperature to the total area. That fraction, a, determined as a function of temperature can be used as the variable for kinetic analysis of the transformation. 

Once the well is drilled, the oil is either released under natural pressure or pumped out. Normally crude oil is under pressure (were it not trapped by impermeable rock it would have continued to migrate upward), because of the pressure differential caused by its buoyancy. When a well bore is drilled into a pressured accumulation of oil, the oil expands into the low-pressure sink created by the well bore in communication with the earth s surface. As the well fills up with fluid, a back pressure is exerted on the reservoir, and the flow of additional fluid into the well bore would soon stop, were no other conditions involved. Most crude oils, however, contain a significant amount of natural gas in solution, and this gas is kept in solution by the high pressure in the reservoir. The gas comes out of solution when the low pressure in the well bore is encountered and the gas, once liberated, immediately begins to expand. This expansion, together with the dilution of the column of oil by the less dense gas, results in the propulsion of oil up to the earth s surface As fluid withdrawal continues from the reservoir, the pressure within the reservoir gradually decreases, and the amount of gas in solution decreases. As a result, the flow rate of fluid into the well bore decreases, and less gas is liberated. The fluid may not reach the surface, so that a pump (artificial lift) must... 

Ammonia evolved in coal gasification usually is washed out with water, taking with it H2S, CC>2, and HCN. Phenols and basic nitrogen compounds are also present if a pyrolyzing gasifier is used. Such water usually is purified by steam stripping, which liberates a vapor mixture of NH3, H2S, CO2 with some HCN. Usable ammonia may be separated by fractional distillation (the WT process) or by differential absorption (the Phosam process) in these cases a rich H2S is prepared for Claus processing. 

---