Читать книгу Petroleum Refining Design and Applications Handbook - A. Kayode Coker - Страница 25

1 1. Long tube vertical evaporators with either natural or forced circulation are most popular. Tubes are 19–63 mm (0.75–24.8 in.) in diameter and 3.66–9.14 m (12–30 ft) long.

2 2. In forced circulation, linear velocities in the tubes are in the range of 4.57–6.09 m/s (15–20 ft/s).

3 3. Elevation of boiling point by dissolved solids results in temperature differences of 3–10°F between solution and saturated vapor.

4 4. When the boiling point rise is appreciable, the economic number of effects in series with forward feed is 4–6.

5 5. When the boiling point rise is small, minimum cost is obtained with 8–10 effects in series.

6 6. In backward feed the more concentrated solution is heated with the highest temperature steam so that heating surface is lessened, but the solution must be pumped between stages.

7 7. The steam economy of an N-stage battery is approximately 0.8 N-lb evaporation/lb of outside steam.

8 8. Interstage steam pressures can be boosted with steam jet compressors of 20–30% efficiency or with mechanical compressors of 70–75% efficiency.