Costain process

Silver azides made by both the Taylor and the new process were compared and found to be chemically and explosively (see Chapter 5 and Table VI) the same. The product of the Costain process is coarser in granulation and of a different appearance, as can be seen in the microphotographs (Figures 16 and 18). 

With the Picatinny Arsenal apparatus, one batch of silver azide made by the Costain process (Chapter 1) was almost as sensitive as the RD1333 lead azide (Figure 12). However, two other samples (one made by the Taylor process and the other by the Costain process) were significantly less sensitive. A difference between the two groups of over 25 in. was evident in heights that caused 50% of the samples to react under the action of a 2-kg weight. 

SILVER AZIDE - -COSTAIN PROCESS -TAYLOR PROCESS -COSTAIN PROCESS... 

In the ball-drop test the RD1333 lead azide and the Costain process silver azide had practically the same impact sensitivities, but the other two silver azides, although still less sensitive, showed a wider disparity (Figure 13). 

A method of preparing a reduced sensitivity SA introduced in USA is called the Costain process after Thomas Costain who improved the original procedure for RD 1336 developed in England in the ERDE laboratories shortly after World War 11 [96]. In the Costain process, aqueous solutions of silver nitrate and sodium azide are added to the dilute aqueous ammonia (or an aqueous solution of sodium azide is added to an aqueous solution of silver nitrate and ammonia). The reaction mixture is then heated and part of the ammonia is distilled from the solution. When the first silver azide precipitate appears, a small amount of acid (e.g., acetic acid) is added to induce crystal seeding and results in profuse nucleation ( shock crystallization ). The distillation of ammonia then continues and the precipitation of silver azide is total. Costain reported several improvements for his product, first of all bulk density 1.4 g cm [96]. Hirlinger and Bichay later reported a further improvement leading to a product with density 1.6 g cm [97] (vs. 1.0 g cm for original ERDE silver azide). Further, concentration and addition parameters are not as critical as for the ERDE process [96]. Not much has been published about the Costain process but some details have been published in [98]. 

Three years after publication of the Costain process in the USA, McGuchan published a conference paper summarizing areas of primary explosives research at PERME in UK which included production of improved SA— product RD 1376 [95]. The increased solubility of SA by addition of ammonia was confirmed as a best option (all other substances performed worse). The neutralization of the ammoniacal solution of SA was recognized as a major aspect. The type of acid was found to affect the nucleation process and even weak acids (e.g., acetic acid)... 

PetroFlux A refrigeration process for removing liquid hydrocarbons from natural gas. Developed by Costain Engineering. Twenty three plants had been operating by 1992. Hydrocarbon Process., 1996, 75(4), 132. 

The inversion barriers calculated in this way show that the Costain-Sutherland model is far superior to the earlier Kincaid-Henriques one. The agreement with experiment is satisfactory within certain limits the results seem to be more reliable for AX 3 systems than for less symmetrical pyramidal or planar XAY systems (for an extensive study and a list of calculated barriers see 140>). Thus this spectroscopic model may provide a satisfactory estimate of barrier height in a given compound, but says nothing about the physical process itself. 

It is easy to account for what has been called Costain s errors [7,5] by adding to each variance 02(/i ]) on the diagonal of Arm an additional variance term (A/j 11)2. Costain has estimated the uncertainty of a / -coordinate with absolute magnitude h (in pm) as A/i = 15/17/1 pm (when the reduced mass of substitution is assumed as 1). Errors so introduced would be correctly propagated to any further processing of Arm. There is still another, perhaps more fundamental way, to... 

The principal application of the Kraitchman equations [Eq. (9)1 is for the determination of the atomic coordinates, at, bSi and cs. From a study of the rotational spectrum of the parent and of a species with single isotopic substitution the coordinates of the substituted atom may be determined. These coordinates are referred to as substitution coordinates or rs coordinates. Each new species yields new coordinates, and since all of the coordinates are in the same coordinate system, the calculation of substitution or rs bond distances and bond angles is a simple process. Costain,s demonstrated that there are definite advantages to the use of the Kraitchman equations to obtain molecular parameters. These advantages are sufficient to make the use of Kraitchman s equations the preferred method of structure determination from ground-state rotational constants. 

Figure 5.5 A schematic of the Costain nitrogen removal process. I) heat exchanger, 2) heat exchanger (subcooling), 3) subcooler by low pressure nitrogen, 4) low pressure column, 5) condenser/reboiler, 6) high pressure distillation column, 7) hydrocarbon pump. Source [11].

Figure 5.4 shows a schematic of the Ciyoplus process [76] for the removal of nonhydrocarbon contaminants, and Figure 5.5 shows a flow diagram of the Costain nitrogen removal process [77], The Costain double-column process is sufficiently flexible to handle natural gas with nitrogen concentrations of 5—80 mol%. Feed natural gas above 27 bar can be directly processed without any compression. 

Costain, T.S. Process for producing silver azide. US Patent 3,943,235, 1976... 

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