Spent Acid Compositions

Water rich acids (e.g. methyl methacrylate spent acid) often have part of their water evaporated before they are sent to the H2SO4 decomposition furnace (Rohm and Haas, 2003). This decreases  

H/C atomic ratio 3 occasionally higher These components are decomposed to CO2, H20(g), N2 SO2. 

Outotec (2008) suggests that cutting a spent acid feed s H20( ) content in half doubles the SO2 content (volume%) of the decomposition furnace s offgas. 

Spent acid Alkylation catalyst Methyl methacrylate catalyst 

Spinning cup or spray guns Spray guns Both 

molten sulfur, natural gas Natural gas Molten S and natural gas 

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Representative Nitrating Acid and Spent Acid Compositions for... 

The above conclusions were also reached in an earlier study by Schiemann Kuhne (Ref 21). Their results, including spent acid compositions, are summarized in Table 7... 

Furnace temperature is measured with thermocouples. It is controlled to 1300 K by adjusting fuel combustion rate and air preheat temperature. Feed forward control based on scheduled changes in spent acid composition and feed rate is employed to optimize the process (Rohm and Haas, 2003). 

Figure 52 presents a phase diagram for the system alkylbenzene sulphonic acid - sulphuric acid -water. Before dilution, the sulphonation mixture is represented by a point (P) close to the bottom of the diagram, near or on the lower perimeter of the area of immiscibilily. In diluting with water the composition of the sulphonation mixture "moves up" into the area of immiscibility see dotted line P-L. After dilution into the area of immiscibility, the mixture of alkylbenzene sulphonic acid, sulphuric acid and water will separate into two phases a spent acid phase with very little sulphonic acid (about 0.3%) and a sulphonic acid phase. The composition of the latter is that of the intersection of the appropriate tie line (say the tie line indicated as 80% spent acid composition) with the left hand perimeter of the area of immiscibility (point R). The composition of the spent acid phase is given by the intersection of the same tie-line with the zero percent sulphonic acid line (see point S), since the small amount of sulphonic acid in the spent acid phase is neglected for the purpose of this phase diagram. From S, Q and R, all on the 80% spent acid tie-line, the composition of the sulphonic acid phase and the amounts of sulphonic and spent acid phases can be calculated. 

The purified ziac solution is fed to the electrolyte recirculating stream at a rate that holds the composition of the electrolyte constant, commonly ranging from 100—200 g H2SO4 and 45—70 g Zn/L. Continuous monitoring of the density and conductivity of the spent acid aids ia control. This is important siace the range of acidity is narrow for maximum current efficiency at any given current density. 

Composition of the nitrating mixture, % Composition of the spent acid, % Cellulose to acid ratio 1 j Nitrogen content of nitrocellulose. %... 

This mixture was prepared from 99% nitric acid and sulphuric anhydride. White salt (XVIII) was introduced to the mixture at a temperature of 30°C. The heat evolved during nitration (approximately 500 kcal per kg of cyclonite) was removed by means of a cooling coil. The cyclonite so formed was partly suspended and partly dissolved in the nitrating liquid. Addition of water completely precipitated the product which was separated on a vacuum filter. The composition of the spent acid was ... 

Similar recoveries and waste reductions can be expected for other metal-bearing spent acids, depending on specific compositions. Moreover, because the method uses standard equipment and available technology, it can readily meet immediate needs. 

In practice the nitrating conditions most frequently applied are those which permit the composition of the spent acids after nitration to approximate to the mixture M3. 

The quantitative effect of various additives on the rate of separation of nitroglycerine from spent add has been determined by Moisak and Grigoryev [15]. They found that in the presence of 0.5% ferric sulphate or lead sulphate, the separation rate is halved. Further, they established that the separation rate is related to the composition of the spent acid. The maximum rate of separating was achieved by using add composed as follows ... 

Taking into account only the inorganic components of the spent acid, its composition is as follows ... 

After the cotton has been removed from the nitration tank (Fig. 135) the composition of the acid in the tank is adjusted so that in quantity and strength of it remains unchanged throughout. The waste acid from the centrifuge is low in nitric acid. The regeneration of this spent acid by addition of oleum and fresh nitric acid is uneconomic. Spent acid is denitrated. 

The composition of the spent acid varies, as shown in the graph (Fig. 145). At first it contains a relatively small proportion of nitric acid, the HN03 H2S04 ratio being 0.24, since nitrocotton absorbs more nitric acid than sulphuric acid. This HN03 H2S04 ratio increases significantly when acid partially diluted by water... 

Composition of spent acids used for washing nitrocellulose... 

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