Lead bath reactor

Heat transfer calculations show that when 15% of the coil has been traversed, the oil temperature is within 5°F of the lead bath. It will be assumed that no significant conversion has occurred in the preheat section and that the reaction is substantially isothermal in the remaining 85% of the reactor volume. 

The vapor-phase contact oxidation of toluene was conducted in a conventional flow system. The reactor was made of a steel tube, 50 cm long and 1.8 cm I.D., mounted vertically and immersed in a lead bath. Air or a mixture of oxygen and nitrogen was introduced from the top of the reactor, with toluene being injected into the preheating section of the reactor by means of a syringe pump. 

Catalyst Evaluation. Experiments were conducted in a stainless steel reactor containing 150 mL of catalyst. The catalyst bed measured 15 in. in length. A 3-point thermocouple was placed in the middle of the catalyst bed to monitor the temperature at the inlet, center, and outlet of the reactor. A lead bath was used to heat the reactor, attempting to achieve an isothermal operation, which frequently was attained. However, temperature rises were observed when good performance was achieved. 

Based on this engineering study we concluded that further laboratory studies should be made more fully to define the primary reactor catalyst loadings required to approach equilibrium conversion of sulfur dioxide to sulfur vapor over the range of pilot plant operating conditions. The reactor used in this additional study duplicated as nearly as possible the geometry of the proposed pilot plant reactor. The laboratory reactor was fabricated of type 304 stainless steel pipe. An electrically heated molten lead bath maintained the desired operating temperature. 

The usual cleaning bath reactor (Figure 22.12a) suffers from the fact that there are air gaps between the transducer (usually flat) and the reactor wall (usually circular) leading to inefficient energy transmission to the liquid inside the reactor. This problem can often be overcome by using a hexagonal cross-sectional reactor, in which contact occurs between flat faces. 

Direct smelting processes provide alternatives to the sinter plant-blast furnace above, up to the stage of crude bullion production, but still require the addition of refining operations to produce high-grade lead. Three alternatives have been evaluated - the Kivcet process, the QSL process and the Isasmelt process - as typical of the top submerged lance slag bath reactor. Evaluations are based on comparable feeds, predominantly lead concentrates with low residue inputs. 

The reaction of propionic acid and HCHO was carried out with a continuous-flow system. The reactor was made of a steel tube (50 cm X 1.8 cm I.D.) mounted vertically and immersed in a lead bath. Nitrogen was fed in from the top of the reactor at a fixed rate of 140 ml/min (at 20°C) as the carrier or the diluent, and a mixture of trioxane [(HCHO) ] and propionic acid was introduced into the preheating section of the reactor by means of an injection syringe pump. The feed rates of propionic acid, HCHO, and nitrogen were 33.6, 16.8, and 350 mmol/h, respectively. The other procedures were the same as those described previously [3,4,9]. The yield (mol-%) was defined as 100 times (moles of methacrylic acid)/(moles of HCHO fed). 

The niter and fresh caustic soda, required to maintain the fluidity of the salt bath in the reactor chamber, are added gradually. When the color of the saturated salts turns from a dark gray to white, the impurity metals are at their highest state of oxidation, and the lead content of the spent salts is very low. In a modification, the arsenic and tin are selectively removed as sodium arsenate and sodium stannate, followed by the removal of antimony as sodium antimonate. 

Two processes, developed for the direct processing of lead sulfide concentrates to metallic lead (qv), have reached commercial scale. The Kivcet process combines flash smelting features and carbon reduction. The QSL process is a bath-smelting reactor having an oxidation 2one and a reduction 2one. Both processes use industrial oxygen. The chemistry can be shown as follows ... 

Closely related to the superheating effect under atmospheric pressure are wall effects, more specifically the elimination of wall effects caused by inverted temperature gradients (Fig. 2.6). With microwave heating, the surface of the wall is generally not heated since the energy is dissipated inside the bulk liquid. Therefore, the temperature at the inner surface of the reactor wall is lower than that of the bulk liquid. It can be assumed that while in a conventional oil-bath experiment (hot vessel surface, Fig. 2.6) temperature-sensitive species, for example catalysts, may decompose at the hot reactor surface (wall effects), the elimination of such a hot surface will increase the lifetime of the catalyst and therefore will lead to better conversions in a microwave-heated as compared to a conventionally heated process. 

The pyrolysis apparatus consists of a vertical, electrically-heated Vycor tube (25 mm. I.D.) packed with 6-mm. lengths of Pyrex tubing (10 mm. O.D.) and mounted in an electric furnace about 45 cm. long (Notes 1 and 2). Attached to the top is a 100-ml. dropping funnel with a pressure-equalizing side arm that has an inlet for nitrogen (Note 3). A thermocouple well inside the tube holds a movable thermocouple and extends to the bottom of the heated section (Note 4). The bottom of the reactor is fitted to a 500-ml. side-arm flask packed in ice. The side arm leads to tw o traps in series cooled in ice and to a final trap cooled in a bath of dry ice and acetone (Note 5). 

Figure 8 (Top) Electrochemical flow cell for the oxidation of phenol and aniline (a) Pb anode feeder (b) packed bed of 1-mm lead pellets (c) stainless steel cathode plate (d) Nation membrane (e) stainless steel screen (f) Luggin capillary (g) glass beads (h) gasket (i) reactor inlet (j) reactor outlet. (Bottom) Schematic of apparatus (a) electrochemical reactor (b) peristaltic pump (c) water bath (d) heater (e) anolyte reservoir (t) gas sparging tube (g) C02 adsorbers. (From Ref. 39.)... 

For the depolymerization of PMMA, molten metal bath, dry distillation, extruder processes and fiuidized-bed processes are used [19], The depolymerization reactor of a molten metal bath consists essentially of a gas- or oil-heated metal bath. The metals used are those which have a low melting point such as tin and lead. The PMMA regrind is fed from the storage silos onto the stirred metal bath. Bath temperature and a residence time of some minutes are important for good yield and quality of the MMA. 

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