The S02 scrubbing tower described in 4.26 is to be used to

Chapter 4, Problem 4.27

(choose chapter or problem)

The S02 scrubbing tower described in 4.26 is to be used to reduce the S02 mole fraction in the waste gas to a level that meets air quality control regulations. The solvent feed rate must be large enough to keep the S02 mass fraction in the exit liquid below a specified maximum value. (a) Draw and label a flowchart of the tower. Along with the molar flow rates and SOz mole fractions of the four process streams, label the feed gas temperature and pressure [TI (OF), PI(psig)], the feed gas orifice meter reading [II] (mm)], the 502 analyzer reading [or the feed gas (Rd, the volumetric feed rate of solvent to the column [V2(m3/min)J, and the SOz analyzer reading for *Computer problem. It is advisable to solve 4.26 before attempting this problem. 100 g Als Encyclopedia Equipment distillation column Encyclopedia Equipment evaporator 165 the exit gas (R3)' (The temperature and pressure units are taken from the calibration curves for the gauges used to measure these variables.) (b) Derive a series of equations relating all of the labeled variables on the flowchart. The equations should include the calibration formulas calculated in part (b) of 4.26. Determine the number of degrees of freedom for the process system. In the remainder of the problem, you will be given values of measured feed gas stream variables [T, (OF), P,(psig), h] (mm), and Rd, the maximum allowed SOz mole fraction in the exit solution [X4], and the specified S02 mole fraction in the exit gas (Y3), and asked to calculate the expected SOz analyzer reading for the exit gas (R3 ) and the minimum volumetric flow rate of solvent (Vz). Part (c) involves using a spreadsheet for the calculation, and part (d) calls for an independent calculation using an equation-solving program. (c) Create a spreadsheet to store input values of T" Pl , hI, R" X4, and Y3 and to calculate R3 and V2 . In the first five rows. insert the values T, = 75, P, = 150. hi = 210, R] = 82.4. X4 = 0.10, and Y3 = 0.05, 0.025, 0.01, 0.005, and 0.001. In the next five rows, insert the same input values except make X4 = 0.02. On a single graph, draw plots of Vz versus Y3 for each of the two given values of X4 (preferably using the spreadsheet program to generate the graph). Briefly explain the shape of the curves and their position relative to each other. (d) Enter the equations of part (b) into an equation-solving program. Use the program to calculate R3 and Vz corresponding to T, = 75. P, = 150, h, = 210. R, = 82.4, X4 = 0.10. and.\'3 = 0.05, 0.025, 0.01, 0.005, and 0.001, and then T, = 75, P, = 150. h] = 210, R, = 82.4, X4 = 0.02, and Y3 = 0.05, 0.025, 0.01, 0.005, and 0.001. If you did not already do so in part (c), draw on a single graph plots of Vz versus Y3 for each of the two given values of X4 and briefly explain the shape of the curves and their position relative to each other.