Читать книгу Petroleum Refining Design and Applications Handbook - A. Kayode Coker - Страница 15

1 1. Fans are used to raise the pressure by about 3% [12 in. (30 cm) water], blowers raise to less than 2.75 barg (40 psig), and compressors to higher pressures, although the blower range is commonly included in the compressor range.

2 2. For vacuum pumps use the following:Reciprocating piston typedown to 133.3 Pa (1 torr)Rotary piston typedown to 0.133 Pa (0.001 torr)Two lobe rotary typedown to 0.0133 Pa (0.0001 torr)Steam jet ejectors1 stage down to 13.3 k Pa (100 torr)3 stage down to 133.3 Pa (1 torr)5 stage down to 6.7 Pa (0.05 torr)

3 3. A three-stage ejector needs 100 kg steam/kg air to maintain a pressure of 133.3 Pa (1 torr).

4 4. In-leakage of air to evacuated equipment depends on the absolute pressure (torr) and the volume of the equipment, V in m3 (ft3), according to W = kV2/3 kg/h (lb/h), with k = 0.98 (0.2) when P > 90 torr, k = 0.39 (0.08) when P is between 0.4 and 2.67 kPa (3 and 20 torr), and k = 0.12 (0.025) at p less than 133.3 Pa (1 torr).

5 5. Theoretical adiabatic horsepower where T1 is inlet temperature in Rankine, R = °F + 460 and a = (k − 1)/k, k = Cp/Cv. Theoretical reversible adiabatic power = mɀ1RT1[({P2/P1}a − 1)]/a, where T1 is inlet temperature, R = Gas Constant, ɀ1 = compressibility factor, m = molar flow rate, a = (k − 1)/k and k = Cp/Cv. Values of °R = 8.314 J/mol K = 1.987 Btu/lb mol R = 0.7302 atm ft3/lb mol° R.

6 6. Outlet temperature for reversible adiabatic process

7 7. To compress air from 37.8° C (100°F), k = 1.4, compression ratio = 3, theoretical power required = 62 hp/million ft3/day, outlet temperature 152.2°C (306°F).

8 8. Exit temperature should not exceed 167–204° C (350–400° F); for diatomic gases (Cp/Cv = 1.4), this corresponds to a compression ratio of about 4.

9 9. Compression ratio should be about the same in each stage of a multistage unit, ratio = (Pn/P1)1/n, with n stages.

10 10. Efficiencies of reciprocating compressors: 65% at compression ratio of 1.5, 75% at 2.0, and 80–85% at 3–6.

11 11. Efficiencies of large centrifugal compressors, 2.83–47.2m3/s (6000–100,000 acfm) at suction, are 76–78%.

12 12. Rotary compressors have efficiencies of 70%, except liquid liner type which have 50%.