Solid adipic acid concentration

Oxidation In Solids Adipic acid Concentration In Solution (ppm) Acipid Acid Concentration In Solids (ppm) [Ad]s/[Ad] ... 

Add 10 ml. of concentrated sulphuric acid cautiously to 45 ml. of water contained in a 200 ml. round-bottomed flask, introduce 3 g. of Nylon 66 polymer into the hot solution, and heat imder reflux for 6 hours. Allow to stand for 1 hour and cool in ice for a further hour. Filter off the solid and keep the filtrate. RecrystaUise the solid (adipic acid) from water m.p. 152°. 

This correlation indicates that the adipic acid degradation rate, normalized by the S02 removal rate, is roughly proportional to the percent oxidation of the solids times the square root of the adipic acid concentration. A graph of the above correlation is shown in Figure 2. 

Figure 2. Correlated relationship between the adipic acid degradation rate, the liquid phase adipic acid concentration, and the percent solids oxidation for the baseline data set. 

The effect of liquid phase adipic acid concentration on adipic acid concentration in the scrubber solids, and... 

Table V. Summary of Test Results tor Various Adipic Acid Concentration and Solids Oxidation Levels...

The batch precipitation tests show dramatic effects of adipic acid slurry concentration and solid phase oxidation fraction on coprecipitation of adipic acid in scrubber solids. Real world scrubbers would probably never operate at adipic acid concentrations as high as those tested and would also not likely ever produce pure phase calcium sulfite hemihydrate. Therefore, the magnitude of the results observed is somewhat a product of the laboratory test conditions. The results do, however, establish the potential importance of adipic acid coprecipitation and, hence, the need for analysis of scrubber solids for adipic acid when determining adipic acid chemical degradation rates by a mass balance calculation approach. 

Large amounts of adipic acid were coprecipitated or occluded in the scrubber solids. The concentration of adipic acid in the solids was a function of both the liquid phase adipic acid concentration and the oxidation fraction in the solids. 

The run was controlled at a nominal limestone stoichiometric ratio of 1.2 and 1,500 ppm adipic acid concentration in the slurry liquor. Slurry solids concentration was controlled at 15 percent. The flue gas flow rate was varied between 20,000 and 30,000 acfm (8.4 to 12.5 ft/sec superficial gas velocity) as the boiler load fluctuated between 100 and 150 MW. The slurry recirculation rate was fixed at 1,200 gpm (L/G = 50 to 75 gal/Mcf). The effluent hold tank residence time was only 4.1 minutes. 

It should be noted that under the operating conditions chosen for Run 951-2E, the major SO2 scrubbing species was calcium adipate because there was little sulfite available, both in liquor or solids, normally the major scrubbing species in an unenhanced lime system without forced oxidation. Higher SO2 removal than the 82 percent in Run 951-2E should be achievable by simply raising the adipic acid concentration beyond the 1,330 ppm tested. 

Onstream hours Fly ash loading Adipic acid concentration, ppm (controlled) Scrubber gas velocity, ft/sec Liquid-to-gas ratio, gal/Mcf Slurry solids concentration, wt % (controlled) Scrubber inlet pH (controlled) Oxidation tank level, ft Oxidation tank residence time, min Effluent hold tank residence time, min Average percent SO2 removal Average inlet SO2 concentration, ppm SO2 make-per-pass, m-moles/liter Percent oxidation of sulfite to sulfate Air stoichiometry, atoms oxygen/mole SO2 absorbed Oxidation tank pH Percent limestone utilization Scrubber inlet liquor gypsum saturation, % Filter cake solids content, wt % 1,688 High 1,300 1,700 5.4- 9.4 85 150 15 5.0- 5.1 18 2.8 8.3 93.4 2,660 4.0- 8.9 99.8 1.4- 2.4 4.9 92.6 93 86... 

Fig. 4 Comparison of the different solid-phase extraction columns tested for the extraction of adipic acid, 1,4-butanediol, and the internal standards glutaric acid and 1,5-pentanediol from water. Relative intensities were compared for a sample concentration of 300ng/p.l. Reprinted from [92] with permission of Elsevier. Elsevier (2004)...

The addition of adipic acid to limestone-based FGD wet scrubbers results in improved limestone utilization and enhanced S02 sorption kinetics. The use of adipic acid was first proposed by Rochelle (1) and has been tested by the EPA in pilot systems at the Industrial Environmental Research Laboratory, Research Triangle Park, North Carolina and at the TVA Shawnee Test Facility at Paducah, Kentucky. Adipic acid in the concentration range of 1,000-2,000 mg/1 has been found effective as a scrubber additive. During scrubber operation, however, adipic acid is lost from the system in the liquid and solid phase purge streams and by chemical degradation (2,3). 

At the start of each run, various materials were added to the hold tank. These materials included deionized water, adipic acid, calcium sulfite seed crystals, NaCl, MnS( H20, Fe2(S( )3, fly ash, etc. depending on the purpose of the test. The resulting thin slurry was circulated through the scrubber where it was contacted with flue gas. This procedure was continued for several hours, allowing time for the mass of solids in the hold tank to increase and the concentration of ionic species (particularly S03) to reach a constant level. At this point, a quantitative amount of slurry was withdrawn from the hold tank. 

The cake analysis was corrected for the amount of adipic acid calculated to have been associated with the water in the wet cake based on weight percent solids in the cake and the measured concentration of adipic acid in the slurry liquor. A summary of test results is given in Table IV. 

Figure 6. Normalized concentration of adipic acid in solids vs. percent sulfate in...

Solids from the batch precipitation tests were also examined by scanning electron microscopy. In tests where no adipic acid was added, the calcium sulfite solids formed a single platelet crystal. However, upon addition of 3,000 ppm adipic acid prior to solids precipitation, the calcium sulfite crystals formed as platelet clusters or rosettes. As the concentration of adipic acid was increased the crystals became smaller and less plate-like until at 10,000 ppm adipic acid in the slurry solution the crystals were submicron in size and resembled popcorn shaped spheres (5). These results suggest that adipic acid effects the nuclea-tion rate of calcium sulfite and certainly can drastically change the particle size distribution and crystal morphology of precipitated solids. 

Losses of adipic acid in liquid associated with the filter cake can also be expected to be site-specific due to differences in solids dewatering equipment. The percent solids achieved in the filter cake may also be affected by the concentration of adipic acid. 

Coprecipitation of buffer with CaSC>3 may be an important additional source of buffer losses. Radian has shown that adipic acid is present in significant concentrations in CaS03 solids, especially with low concentrations of CaSO in the solids (35). 

Bleed stream oxidation of unenhanced lime or limestone slurry is usually not feasible because the pH rise caused by the residual alkali in the oxidation tank makes it difficult to redissolve the solid calcium sulfite. With adipic acid-enhanced limestone scrubbing, however, this constraint is removed because of the low operating pH and low residual alkali in the bleed slurry. Thus, the oxidation tank can be maintained at a low pH for good sulfite oxidation, while achieving high SO2 removal efficiency with a sufficiently high concentration of adipic acid in the scrubber liquor. 

Reliability Run 932-2A, which was made with fly ash, discharged a sludge containing 61 percent solids, and required a makeup of 17.5 lb/ton S02 When these data are normalized to a fly-ash-free basis, at equal limestone utilization, and equal sludge moisture, they yield the same makeup rate of 10.7 lb/ton SO2 for a concentration of 1500 ppm adipic acid in the scrubbing liquor. 

Horizontal basket, pusher discharge 20-120 cycles/min cake formation, wash, discharge. Cake buildup rate 1000-10000 g/s m area per unit 0.1-1.8 m cake thickness < 75 mm. Basket diameter 0.2-1.2 m 300-600 G. Power 40-60 kW/m filter area or 7-15 kj/kg salt (about 3000 g/s m ). Keep feed solids concentration > 40% w/w for optimum. Example data adipic acid, urea 1.4 kg/s m crude sodium bicarbonate 1.45 kg/s m phosphate rock,... 

Thus in the production of nylon 6,6, the first step consists of the neutralization of an aqueous solution of adipic acid by addition of hexamethyl-enediamine the exact end-point is determined electrometrically. The aqueous salt solution is then concentrated to 60—75% solids content before transfer to the polymerization reactor. In an alternative procedure, approximately equivalent quantities of adipic acid and hexamethylenediamine are mixed in boiling methanol, from which the 1 1 salt is precipitated. The salt is isolated by filtration and then dissolved in water and the solution fed to the polymerization reactor. The nylon salt, hexamethylenediammonium adipate may be represented as follows ... 

Hi. Other dicarboxylic acids. Aqueous solutions of malonate CH2(C00 )2, adipate (CH2CH2COO )2, succinate (CH2COO )2 12, 573, 598), and mercaptosuccinate 516) with aqueous zirconium(IV) solutions leads to the precipitation of solids with composition [ZrO(CH2)K(COO )2]. The 1 1 adipate and succinate species do not dissolve in excess carboxylic acid solution indicating that the dianionic species are not formed. At metal ion concentrations of (1 to 2) x 10 M and hydrogen ion concentrations between 0.087-0.350 M, malonic and succinic acids establish the equilibrium defined by the equation... 

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