Heating with Steam

Therefore, its process gain varies inversely with flow. Its time constant, dead time, residence time, and period of oscillation also vary with flow. 

Where Q = Heat-Transfer Rate Fs = Steam Mass Flow AHs = Latent Heat of Vaporization F = Feed Rate Cp = Heat Capacity of Feed T0 = Steam Supply Temperature Pt = Steam Supply Pressure P2 = Steam Valve Outlet Pressure Ps = Condensing Pressure Tj = Inlet Temperature T2 = Outlet Temperature A Tm = Log Mean Temperature Difference Ts = Condensing Steam Temperature 

The feedback control of a steam-heated exchanger and its characteristic equation. 

This cycling can be eliminated by mounting the control valve in the condensate pipe, but this creates new problems, because when the load decreases, the process is slow steam has to condense before the condensate level is affected, and when the load increases, the process is fast, because blowing out liquid condensate is fast. With such nonsymmetrical process dynamics, control is bound to be poor. A better option is to use lifting traps to prevent condensate accumulation. These pumping traps will make temperature control possible even when the heater is under vacuum, but will not improve the problem of low rangeability, and the possible use of two control valves in parallel can still be necessary. 

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For off-site transportation, the phosphoms is loaded into railcars for transfer to the sites where it is used directly as a raw material or burned and hydrated to phosphoric acid. During shipping, the phosphoms is allowed to soHdify in the cars. The railcars are commonly double walled with a jacket that can be heated with steam or hot water so that the phosphoms can be remelted on-site for transloading to local storage tanks. For overseas shipping, tanktainers with reinforced superstmcture for safe handling are used. Formerly, full tanker ships were in use. 

Complete removal of water from the pyrolysis gas is achieved with molecular sieve dryers. Typically, there are two dryers one is in normal operation while the other is being regenerated. The dryers are designed for 24 to 48 hours between successive regenerations and high pressure methane heated with steam at 225°C is the preferred regeneration medium. Activated alumina was used in older plants, but it is less selective than molecular sieves (qv). 

Preparation. On a coml scale the nitration of naphthalene is carried out in two steps using a cylindrical jacketed reactor 1.6 x lm with a conical bottom. It is fitted with a discharge pipe 8cm in diameter and a stirrer which can be rotated at 85—90rpm. The jacket can be heated with steam or cooled with cold w. The cover is provided with an opening for the addn of naphthalene and a vent for the removal of gaseous prods... 

The drums are usually heated with steam, and steam economies of 1.3 kg steam per kg of water evaporated are typically achieved. 

The reactor is followed by a gas-liquid separator operating at 30 bar from which the liquid phase is heated with steam to decompose the catalyst for recovery of cobalt by filtration. A second gas-liquid separator operating at atmospheric pressure subsequently yields a liquid phase of aldehydes, alcohols, heavy ends and water, which is free from propane, propylene, carbon monoxide and hydrogen. 

Neostar A process for destroying waste organic chlorides (e.g., polychlorinated biphenyls) by heating with steam and hydrogen at over 1,000°C. The products are methane, ethane, other chlorine-free hydrocarbons, and hydrochloric acid. Developed by Cerchar, France. 

Weldon An early process for making chlorine by oxidizing hydrochloric acid (from the Leblanc process) with manganese dioxide. The mixture was heated with steam in stone tanks. Manganese was recovered from the liquor by precipitation with calcium hydroxide and subsequent oxidation by air ... 

Cobalt. Appreciably less reactive than Fe. It is stable, unless heated, to atmospheric oxygen. It is oxidized first to C03O4 and then (above 900°C) to CoO. It dissolves slowly in diluted mineral acids (giving Co11), it reacts on heating with steam, the halogens and several non-metals (B, C, P, As, S). 

A medium, which flows through an 80 mm i.d. stainless tube at a flow rate of 1.0 m h , is to be continuously sterilized by indirect heating with steam. The temperature ofthe holding section is maintained at 120 °C. The number of bacterial spores of 10 rn in the entering medium must be reduced to 0.01 m . The specific death rate of the bacterial spores in the medium, medium density, and medium viscosity at 120 °C are 180 h , 950 kgm , and 1.0kgm h , respectively. 

As a rule fusible mixtures are prepared in metallic kettles heated with steam or water jackets and fitted with stirrers, which are emptied either by tilting or through a valve placed in the bottom of the vessel. 

It must be borne in mind that generally aromatic nitro compounds are not highly sensitive to impact and friction, but become more sensitive at elevated temperatures as they melt (changes in the sensitiveness of TNT are discussed in Vol. I, p. 319). If, therefore, a mechanical device is used for the preparation of mixtures by melting, its construction should be such as to exclude any possibility of friction or impact. It is probably best to use a converter heated with steam or water jackets and fitted with a stirrer that can be lifted out by a special arrangement. After the stirrer has been removed, the contents are poured out by tilting the vessel. 

ShelI l..oadi ng with 80/20 Amatol, Part of the mixt maintained in the kettle at 90—95° (See above under Preparation) was transferred to the hopper of an extruder which was provided with a stirrer and jacket heated with steam at 3—5 lbs pressure. The extruding machine consisted of a steel tube in which a worm screw rotated slowly. This... 

Furfural occurs in many essential oils and is produced in small quantities in many organic reactions,1 particularly those involving the decomposition of various carbohydrate materials. Pentoses when subjected to the action of hydrochloric acid are decomposed to give practically quantitative yields of this aldehyde.2 It is well known that carbohydrate materials such as corn cobs, wood, bran, etc., when heated with steam under pressure or distilled with dilute hydrochloric or sulfuric acids, yield appreciable quantities of furfural.3 Particularly good yields, however, are obtained from ordinary corn cobs, and this material therefore appears best for the production of large amounts of furfural in the laboratory. Improvements in the production of furfural from carbohydrate material have appeared recently in the patent literature 4 but those do not appear as satisfactory as the ones described.5... 

The mixture of two liquid phases is cooled in water cooler E-103 and then separated in brine decanter V-103. From that vessel the lighter phenol phase proceeds (P-108) to a basket type evaporator D-101 that is heated with steam. Overhead vapor from... 

Because of the elevation of boiling point by dissolved solids, the difference in temperatures of saturated vapor and boiling solution may be 3-10T which reduces the driving force available for heat transfer. In backward feed [Fig. 8.17(b)] the more concentrated solution is heated with steam at higher pressure which makes for lesser heating surface requirements. Forward feed under the influence of pressure differences in the several vessels requires more surface but avoids the complications of operating pumps under severe conditions. 

Feed to a spray dryer contains 20% solids and is to be dried to 5% moisture at the rate of 500 lb/hr of product. Pilot plant data show that a residence time of 6 sec is needed with inlet air of 230T, H = 0.008 lb/lb, and exit at 100°F. Ambient air is at 70°F and is heated with steam. Enthalpy loss to the surroundings is 10% of the heat load on the steam heater. The vessel is to have a 60° cone. Air rate and vessel dimensions will be found. 

In a 5-I. flask, placed on a steam bath and fitted with a mechanical stirrer, a separatory funnel, a thermometer well (Note 1) and a calcium chloride tube, is placed 182 g. (7.5 moles) of magnesium turnings. To this is added a crystal of iodine and 100 cc. of a solution of 1133 g. (7.5 moles) of 2-bromo-pentane (Note 2) in 750 g. of -butyl ether (Note 3). The stirrer is started and the flask is heated with steam until the reaction starts. This may take from fifteen minutes to one hour, but the flask must be watched quite closely because the reaction, when once started, is very vigorous and evolves a large amount of heat. As soon as the reaction has started, 750 g. of w-butyl ether is added and then the balance of the solution of 2-bromo-pentane in w-butyl ether is added at such a rate that the temperature is kept at 50-60°. External cooling is used in order to allow more rapid addition of the 2-bromopentane. After addition is complete (about three hours), the mixture is heated on a steam bath for one hour. 

A pharmaceutical intermediate was initially produced at a scale of 500 kg (product) per batch in a 2.5 m3 reactor. The reaction was the condensation of an amino-aromatic compound with an aromatic chloride to form a di-phenyl amine by elimination of hydrochloric acid. This acid was neutralized in situ by sodium carbonate, forming water, sodium chloride, and carbon dioxide. The manufacturing procedure was very simple The reactants were mixed at 80 °C, a temperature above the melting point of the reaction mass. Then the reactor was heated with steam in the jacket to a temperature of 150 °C. At this temperature, the steam valve had to be closed and the reaction left to proceed for a further 16 hours. During this time, the temperature increased to a maximum of 165 °C. Several years later, the batch size was increased to 1000 kg per batch in a 4 m3 reactor. Two years after this a further increase to 1100 kg was decided. 

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