Drum hydration

Moderate and even low reactivity quicklimes can be used in the drum hydration process, because of the pressurised hydration stage (see section 13.2, Fig. 13.3, and Annex 1 for explanations of these terms). The reactivity of quicklimes used for the silo hydration process should be moderate to high , depending on the silo residence time. For both of these processes, the quicklime should be finely ground (e.g., with 90 % less than 75 pm) to ensure efficient dispersion and hydration. 

In a typical gas oil design, the lighter products overhead from the quench tower/primary fractionator are compressed to 210 psi, and cooled to about 100°F. Some Q plus material is recovered from the compressor knockout drums. The gases are ethanolamine and caustic washed to remove acid gases sulfur compounds and carbon dioxide, and then desiccant dried to remove last traces of water. This is to prevent ice and hydrate formation in the low temperamre section downstream. 

Flare systems must be protected against any possibility of partial or complete blockage by ice, hydrates, solidification, etc. Seal Drums and Y-seals requiring winterizing should be provided with temperature-controlled steam injection to maintain the seal water temperature at 4 to 10 C. This limits the quantity of water vapor entering the flare stack. 

Chloral Hydrate. (An ethane derivative.) Chloral hydrate is one of the easiest drugs to make in this entire book. It is an effective hypnotic, that is rapidly absorbed from the stomach, and produces dulled sensoiy and motor functions, that last for 6 to 8 hours. The dose is from 250 mg to 1,500 mg. Chloral can be purchased at most any chemical supply house, eliminating the need for performing the first part of this synthesis. Chloral is not very suspicious (unless you re buying it by the 55 gallon drum), so you should have no trouble in making chloral hydrate directly from chloral. 

Crystallization at temperatures between 1.8 and 48°C yields heptahydrate, MgS04 7H20. Below 1.8°C, a dodecahydrate, MgS04 12H20 crystallizes out. Above 48°C crystals of lower hydrates form. The anhydrous salt is obtained by heating the heptahydrate at about 500°C in a rotary drum or dehydrating above 150°C in the presence of sulfuric acid. 

Uhen Na was available at 60X of stoichiometry, a second zirconate salt, NayZrgFj, formed. The NayZrgF3 salt is believed to hydrate, forming a wetter cake that may liberate freestanding liquid when the cake is placed in a drum. Using 90X or greater stoichiometry of Na will produce a drier eake that does not contain free water. 

Drum dryers potatoes, cereals, buttermilk, skim milk, dextrins, yeasts, instant oat meal, polyacylamides, sodium benzoate, propionates, acetates, phosphates, chelates, aluminum oxide, m-disulfuric acid, barium sulfate, calcium acetate-arsenate-carbonate-hydrate-phosphate, caustic, ferrous sulfate, glue, lead arsenate, sodium benzene sulfonate, and sodium chloride... 

A drum of styrene oxide was punctured and the spillage absorbed into an hydrated silate absorbent, the combination swept up and drummed up for disposal. The drum became hot and started emitting copious white fumes. It was not possible to duplicate this behaviour in the laboratory unless acid or base catalyst was also present [1], Absorbents may be inert, epoxides are not but contain considerable strain energy which will be liberated by autoreaction or nucleophilic substitution by, e.g. water. Only a catalyst is needed neither silicates nor floor-sweepings can be guaranteed free of these [2]. 

A drum dryer (Fig. 6.4) consists of one or more heated metal rolls on which solutions, slurries or pastes are dried in a thin film. The thin film dries in less than one revolution of the slowly revolving rolls and is scraped off by a doctor blade to form a product in flake, chip or granular form. Drum dryers are widely used in chemical processing frequently to dry hydrates, carbonates, arsenates, acetates, phosphates, clays and food products [11]. 

Neutralizing a spill often consists of mixing fnll-strength bleach with hydrated lime and working this mixture into the spill site with a coarse broom. Fresh absorbent material is then spread over the spill site to soak np the nen-tralizing liquid. This material is swept up and placed in a plastic drum or bag for disposal. You may be instructed to repeat the process several times to make sure that the site is thoroughly neutralized. 

Electrolysis [5.30]. The principle of the method is to have the tungsten scnq> as anode in an electrolyte like sodium hydroxide or sodium carbonate aqueous solution. The tungsten atoms are oxidized electrolytically to the hexavalent state. The resulting solution contains sodium tungstate besides insoluble oxides or oxide hydrates of flie other constituents. Rotating drum or disk electrolytic cells are the applied equipment. 

The zinc oxide may be added to the hydrazine during manufacture to prevent its decomposition at any stage where the concentration is greater than that of hydrazine hydrate. It may be added to finished 95% hydrazine as it is loaded into drums or tank cars for storage or shipment. The insoluble excess zinc oxide is easily removed by settling and decanting or by filtration, and the hydrazine product may be distilled prior to use if necessary or desirable. 

The thermodynamics of this process are described in detail in references (67 —72, 80,81). Let us examine a typical methanol injection system. In a typical methanol injection and recovery system for a cold-oil absorption or turboexpander plant, feed gas passes through a free-water knockout drum and into a gas-gas exchanger with methanol being sprayed on exchanger tube-sheets. Methanol inhibits hydrate formation and aqueous methanol condenses in the exchanger (and the chiller following it) and is pumped to a primary separator. The methanol-water solution is then flashed in a flash drum and filtered into a methanol still to recover methanol. Normally, methanol dissolves in the hydrocarbon liquids and is distilled as a mixture of propane and methanol. Some of the methanol is recovered as the overhead product to recover the methanol dissolved in the heavier solution, the bottoms of the methanol still (propane product or hydrocarbon liquids from the demethanizer)... 

Five key variables influence the drum dryer performance. They are (1) steam pressure or heating medium temperature (2) speed of rotation (3) thickness of film (4) feed properties (e.g., solids concentration, rheology, temperature, etc.) and (5) method of removing dust flakes by scraper or knife. Because they allow control of the temperature, drum dryers may be used to produce a precise hydrate of a chemical compound rather than a mixture of hydrates. 

Fig. 6.7-45 shows the manufacturing process of (hollow) building blocks made from lime and sand. Milled burnt lime and sand are mixed and hydrated in a batch drum... 

Fig. 6.7-45 Diagram of the manufacturing process of (hollow) building blocks made from lime and sand. 1, lime ball mill 2, elevator 3, wind sifter 4, 9, 11, silos 5, metering bucket 6, screw conveyor 7, sand feed 8, screen 10, batch mixing and hydration drum 12, proportioning 13, elevator 14, stone press 15, block cart 16, transfer platform 17, post-treatment (hardening) chambers 18, steam production Fig. 6.7-46 Sketch of a manual pusher furnace [B.28, B.97j...

The ground quicklime is stored in a bunker and discharged through a similar mechanism to that described for hydrated lime (section 26.10.2). The quicklime is hydrated using either the drum, or the silo hydration process. 

Internally chilled rotating drum crystallizers (see Figure 8.24) are normally associated with melt crystallization (section 8.2), but have also found occasional application for crystallization from solution. Sodium sulphate and barium hydroxide hydrates, for example, have been produced commercially in this manner. 

---