Constant pressure drop filtration

Constant-pressure drop filtration can result in saturation or blockage of the filter medium. The network of pores within the filter medium can become blocked because of one or a combination of the following situations ... 

This equation applies to the case of constant-rate filtration. For the more common case of constant-pressure-drop filtration, A, AP, s, a , w, VF, and p can all be assumed to be constant with change in V, and Eq. (37) can be integrated between the limits of zero and V to give... 

During constant pressure drop filtration of an incompressible cake, how does filtrate flow rate vary with time ... 

For a constant pressure drop and temperature filtration process all the parameters in Equation 9, except V and x, are constant. Integrating Equation 9 over the limits of 0 to V, from 0 to x, we obtain ... 

CHE 440 Filtration Experiment... find the parameters (discussed below) that govern constant pressure drop cake filtration... 

The system described in question 4 has an auxiliary time of = 1800 sec. Determine the total filtration time at constant pressure drop, cake thickness and filtrate volume. 

A rotary drum filter 6 ft in diameter and 8 ft long is to be used to filter a slurry. The drum rotates at 0.5 rpm, and one-third of the drum s surface is submerged in the slurry. A vacuum is drawn in the drum so that a constant pressure drop of 10 psi is maintained across the drum and filter cake. You test the slurry in the lab by pumping it at a constant filtrate rate of 20 gpm through 1 ft2 of the drum filter screen and find that after 1 min the pressure drop is 8 psi and after 3 min the pressure drop is 12 psi. How long will it take to filter 100,000 gal of filtrate from the slurry using the rotary drum ... 

A rotary drum filter is used to filter a slurry. The drum rotates at a rate of 3 min/cycle, and 40% of the drum surface is submerged in the slurry. A constant pressure drop at 3 psi is maintained across the filter. If the drum is 5 ft in diameter and 10 ft long, calculate the total net filtration rate in gpm that is possible for a slurry having properties as determined by the following lab test. A sample of the slurry was pumped at a constant flow rate of 1 gpm through 0.25 ft2 of the filter medium. After 10 min, the pressure difference across the filter had risen to 2.5 psi. The filter medium resistance may be neglected. 

A rotary drum filter is to be installed in your plant. You run a lab test on the slurry to be filtered using a 0.1 ft2 sample of the filter medium at a constant pressure drop of 10 psi After 1 min you find that 500 cm3 of filtrate has passed through the filter, and after 2 min the filtrate volume is 715 cm3. If the rotary drum filter operates under a vacuum of 25 in.Hg with 25% of its surface submerged, determine ... 

B. 4-Phenyl-l-carbethoxysemicarbazide. In a 1-1. three-necked round-bottomed flask equipped with a liquid-sealed mechanical stirrer (Note 3), a constant-pressure dropping funnel, and a reflux condenser fitted with a drying tube containing silica gel is placed a solution of 52 g. (0.5 mole) of ethyl hydrazine-carboxylate in 550 ml. of dry benzene (Note 4). The solution is cooled in an ice bath, and the stirrer is started. To the solution is added 59.7 g. (55 ml., 0.5 mole) of phenyl isocyanate (Note 5) dropwise over a period of 45 minutes. After about one-half of the isocyanate has been added, a white precipitate of the product appears, and the reaction mixture becomes progressively thicker. After addition is complete the ice bath is removed, and the mixture is stirred at room temperature for 2 hours and then is heated under reflux for 2 hours. The suspension is allowed to cool to room temperature, and 4-phenyl-1-carbethoxysemi-carbazide is isolated by suction filtration, washed with 500 ml. of benzene, and dried in a vacuum desiccator. The yield is 108 g. (97%), m.p. 151-152°. The product is not further purified before being used in the next step. It may be recrystallized from ethyl acetate to yield white crystals, m.p. 154-155°, vmax 1645, 1687, 1797, and 3300 cm.-1 (Note 6). 

Filtration tests with a given sluny have indicated that the specific cake resistance a is 157 h2/lb. The fluid viscosity is 2.5 lb/(hXft), and 3 lb of dry cake is formed per cubic foot of filtrate. The cake may be assumed to be noncompressible, and the resistance of the filter medium may be neglected. If the unit is operated at a constant pressure drop of 5 psi, what is the total filtering area required to deliver 30 ft3 of filtrate in j h ... 

A plate-and-frame filter press is used to filter a known slurry mixture. At a constant pressure drop of 10 psi, 50 ft3 of filtrate is delivered in 10 min, starting with a clean filter. In a second run with the same slurry and filter press, 40 ft3 of filtrate is... 

Pilot-scale particle collection efficiency has been found to be similar to the cold and dry experiments over 300 hours filtration time, Figure 12 presents a relatively constant pressure drop over time for the hot and dry experiments conducted on the pilot-scale filter under a gas flowrate of 20 Nm /h (80 Nm /hr/m ), with a particle load of 3000 mg/Nm and using Ottawa sand as the filtering media. Deep holes on Figure 12 are air pulses to back-flush the solids plugging the exits. 

Example 30.2. Laboratory filtrations conducted at constant pressure drop on a slurry of CaCOj in H2O gave the data shown in Table 30.2. The filter area was 440 cm, the mass of solid per unit volume of filtrate was 23.5 g/L, and the temperature was 25°C. Evaluate the quantities a and as a function of pressure drop, and fit an empirical equation to the results for a. 

The slurry of Prob. 30.3 is to be filtered in a press having a total area of 8 m and operated at a constant pressure drop of 2 atm. The frames are 36 mm thick. Assume that the filter-medium resistance in the large press is the same as that in the laboratory filter. Calculate the filtration time required and the volume of filtrate obtained in one cycle. 

The filter of Prob. 30.7 is operated at a constant rate of 0.6 gal/ft -min from the start of the run until the pressure drop reaches 70 Iby/in. and then at a constant pressure drop of 701by/ln. until a total of 1400 gal of filtrate is obtained. The operating temperature is 70°F. What is the total filtration time required ... 

From the Hagen-Poiseuille relation (Equation 39) replacing Wj in Equation 40 with constant filtration rate W and substituting APj for constant pressure drop AP we obtain ... 

If the suspension were a clean liquid, all the parameters in equations 9.1 and 9.2 would be constant, resulting in a constant flow rate for a constant pressure drop and the cumulative filtrate volume would increase linearly with time, as shown in Figure 9.4. 

A suspension of incompressible solids at a concentration of 300 kg m of slurry is to be filtered at constant pressure drop. Estimate the filtration area necessary to produce 50kgh of dry solids. 

For filtration at constant pressure drop we use Equation (6.27), which indicates that if we plot t/V versus V a straight line will have a gradient... 

A laboratory leaf filter has an area of 0.1 m, operates at a constant pressure drop of 400 kPa and produces the following results during a test on filtration of a slurry ... 

The filter in the preceding problem is operated at a constant rate of 0.5 gallons/ft min from the start until the pressure drop reaches 5.44 atm. Next operation is at a constant pressure drop until 200.5 ft of filtrate is produced. How long is the total required filtration time ... 

The material described in Problem 14-22 is to be processed in a press (total area 10 m, frames 40 mm thick). Constant pressure drop is 2 atm. Determine filtration time and filtrate volume obtained in one cycle. 14-24. A continuous rotary filter (submergence of 25 percent, speed 2 rpm) with a pressure drop of 0.7 atm is used to obtain the same production as that of Problem 14-23 (slurry as described in Problem 14-22). 

At constant pressure drop, Ap, the volume of filtrate collected depends on the drum speed according to the relation... 

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