Chlorine recovery

Chlorine Plant Auxiliaries. Flow diagrams for the three electrolytic chlor—alkali processes are given in Figures 28 and 29. Although they differ somewhat in operation, auxiUary processes such as brine purification and chlorine recovery are common to each. 

Chlorine from HCl. Most organic chlorination reactions consume only half the CI2 to produce the desired product the other half is converted to HCl. Depending on demand and supply of CI2 vs HCl, chlorine recovery from hydrochloric acid is sometimes attractive. Two commercial routes are available electrolysis and oxidation (69). 

Chlorine Recovery System, OxyTech Systems, Inc., Chardon, Ohio, 1988. 

Although there are minor differences in the HCl—vinyl chloride recovery section from one vinyl chloride producer to another, in general, the quench column effluent is distilled to remove first HCl and then vinyl chloride (see Eig. 2). The vinyl chloride is usually further treated to produce specification product, recovered HCl is sent to the oxychlorination process, and unconverted EDC is purified for removal of light and heavy ends before it is recycled to the cracking furnace. The light and heavy ends are either further processed, disposed of by incineration or other methods, or completely recycled by catalytic oxidation with heat recovery followed by chlorine recovery as EDC (76). 

The membrane selectively rejects oxygen and nitrogen. The field test showed a selectivity for chlorine over nitrogen of about ten. That this is so much lower than that obtained in the laboratory is attributed to concentration polarisation. Increasing the rate of flow through the module can alleviate this. At the same time, chlorine recovery can be maintained by adding modules in series. This is precisely what would be done in a commercial unit, and so one can reasonably expect better results in full-scale operation. 

Carbon dioxide permeates the membranes at least as readily as does chlorine. This fact will produce a significant increase in CO2 concentration in a recycle system. For best results at highest chlorine recovery, it will pay to keep the CO2 concentration in the membrane feed-gas low. This can be accomplished in most plants by acidification of cell-feed brine. Acidification is highly recommended in any case when a very high degree of chlorine recovery is required, whether by... 

Next, ways to augment liquefaction and bring chlorine recovery to more than 99% are considered. To eliminate some of the many variables, only the off-gas from a two-stage liquefier, as in Fig. 7.2, condensing 97.7% of the chlorine from a membrane-cell installation is utilised. The gas is available at 800 kPa. 

Figure 7.2 VCM manufacturing with chlorine recovery by HCI oxidation.

Problem 5. Economic Analysis of Chlorine Recovery Systemf... 

The data shown in Table 6 have been obtained for a chlorine recovery system in which all values have been determined at the optimum operating conditions of retention time and recycle rates. 

A chlorine balance in the raw fluff has been reported [2] and chlorine recovery had reached 94.95% as 9.6% hydrochloric acid. Recently, calcium hydroxide is added to the fluff as in the Sapporo Plastic Recycling Center to stabilize the operation. The recovery of HCl decreased greatly from 5.4 to 1.2%, as shown in the material balance in Figure 26.3 and is discarded after neutralization. 

G.7 CHLORINE RECOVERY FROM HYDROGEN CHLORIDE The project... 

Chlorine Recovery (Kel-Chlor Process) Pullman Kellogg, Hydrocarbon Process. 56, 139, Nov. 

The chlorine recovery rate as gaseous HCl is ca. 90 %. The steam production is ca. 4.41 per tonne of residue, which amounts to ca. 85 % heat recovery related to the calorific value of the residues. 

While chlorine has a vapor pressure of about 17 atm at the normal boiling point of bromine, the corresponding number at the boiling point of BrCl is only a bit more than 4 atm. About twice as many theoretical stages are required to effect a given separation of chlorine from the bromine content. The amount of bromine present in most electrolysis salt is too small for the equilibrium to be a serious limitation on chlorine recovery from the suction chiller bottoms. 

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