Tanks operations

When tank operators change a stored hquid, care must be exercised. If there is a significant increase in the specific gravity of the new hquid, the effective hydrostatic pressure acting on the tank walls is greater if the design hquid level is not reduced. 

Batch Percolators The batch tank is not unlike a big nutsche filter it is a large circiilar or rectangiilar tank with a false bottom. The solids to be leached are dumped into the tank to a uniform depth. They are sprayed with solvent until their solute content is reduced to an economic minimum and are then excavated. Countercurrent flow of the solvent through a series of tanks is common, with fresh solvent entering the tank containing most nearly exhausted material. In a typical ore-dressing operation the tanks are 53 by 20 by 5.5 m (175 by 67 by 18 ft) and extract about 8200 Mg (9000 U.S. tons) of ore on a 13-day cycle. Some tanks operate under pressure, to contain volatile solvents or increase the percolation rate. A series of pressure tanks operating with countercurrent solvent flow is called a diffusion battery. 

Portable or fixed mixers up to 5hp normally use propellers and run at either direct drive speeds of 1,150 or l,750rpm or at single reduction gear drive speeds between 300 and 420 rpm. They may either be clamped on the rim of open tanks or mounted with a fixed assembly for open or closed tank operation. These mixers are the most economical and are usually used in tanks without baffles. They are rugged and long-lasting. 

Figure 23.10 Heat losses from a feedwater tank operating at 93°C with ambient 21 °C...

The feed tank should always be insulated to reduce heat loss to a minimum. Figure 23.10 illustrates typical heat losses from a feed tank operating at 93°C in an ambient temperature of 21°C with and without 50 mm of insulation. 

A hydraulic system must have a reserve of fluid in addition to that contained in the pumps, actuators, pipes and other components of the system. This reserve fluid must be readily available to make up losses of fluid from the system, to make up for compression of fluid under pressure, and to compensate for the loss of volume as the fluid cools. This extra fluid is contained in a tank usually called a reservoir. A reservoir may sometimes be referred to as a sump tank, service tank, operating tank, supply tank or base tank. 

Liquid is fed continuously to a stirred tank, which is heated by internal steam coils (Fig. 1.21). The tank operates at constant volume conditions. The system is therefore modelled by means of a dynamic heat balance equation, combined with an expression for the rate of heat transfer from the coils to the tank liquid. 

GAS-LIQUID MIXING AND MASS TRANSFER IN BUBBLE COLUMN-TYPE MIXING TANK OPERATION EXAMPLE FOR OXYGEN CONSTANT VL1=300, VL2=100,VL3=600 L... 

A process liquid is pumped from a storage tank to a distillation column, using a centrifugal pump. The pipeline is 80 mm internal diameter commercial steel pipe, 100 m long. Miscellaneous losses are equivalent to 600 pipe diameters. The storage tank operates at atmospheric pressure and the column at 1.7 bara. The lowest liquid level in the tank will be 1.5 m above the pump inlet, and the feed point to the column is 3 m above the pump inlet. 

Consider two CSTRs of unequal sizes, Vx and V2, operating in parallel, as shown in Figure 17.2. The liquid-phase reaction, A - products, is first-order and both tanks operate at the same T. How should the total feed rate, q0, be split (at S) so as to maximize the rate of production in the combined exit streams (at M) ... 

The reactor, an agitated tank, operates under a pressure of 1.5 kN/m2 (15 bar) and at 433 K (160°C). It is charged with a batch of 0.06 m3 of o-xylene and air introduced at the rate of 0.0015 m3/s (5.4 m3/h) measured at reactor conditions. The air is dispersed into small bubbles whose mean diameter is estimated from a photograph to be 0.8 mm, and from level sensors in the reactor, the volume of the dispersion produced is found to be 0.088 m3. Soon after the start of the reaction (before any appreciable conversion of the o-xylene) the gas leaving the reactor is analysed (after removal of condensibles) and found to consist of 0.045 mole fraction O2, 0.955 mole fraction N2. 

J6. An engineer from Catastrophic Chemical Company has designed a system in which a positive-displacement pump is used u> pump water from an atmospheric tank into a pressurized tank operating at 130 psig. A control valve is installed between the pump discharge and the pressurized tank. 

The first tank operates at 2000 kPa at the initial steadystate. There is a pressure drop between the vessels which varies linearly with gas flow rate F,. This pressure drop is 100 kPa when the flow rate is 1000 kg/h. 

Again, the constant density case will be considered with both tanks operating at the same temperature. It will also be assumed that the tanks are of equal volume. 

Mixed Flow L/Any Flow G (tank operations of all types)... 

Soil slurry-sequencing batch reactor (SS-SBR) is a technology for the biological treatment of organic contaminants in soil. The technology has been evaluated in full-scale field tests but is not commercially available. The SS-SBR system consists of a set of tanks operated on a fill-and-draw basis. Each tank is filled during a discrete period of time and operated as a batch reactor. According to the vendor, reaction times are on the order of days. 

Heat transfer coefficients in stirred tank operations are discussed in Section 17.7. 

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