ENHANCED V-GRID TRAYS INCREASE COLUMN PERFORMANCE

Transcription

1 Distillation Honors Session ENHANCED V-GRID TRAYS INCREASE COLUMN PERFORMANCE by Daniel R. Summers, P.E. - Darcy Ehmann - AGP Corn Processors November 4, 2002

2 Background Ethanol already plays an an important role in in today s reformulated gasoline Fuel Grade Ethanol growth is is expected to to continue for the next 5 years Many new plants will be be built and existing plants need debottlenecking. Older plants were built with outdated or or sometimes archaic technology.

3 Typical Plant A typical modern plant has 3 main towers; Beer Mash Tower, the Rectifier and Side Stripper The Beer Mash tower removes all all the solids and most of of the water from the fermenters The Rectifier takes the overhead from the Beer Mash Tower and concentrates the Ethanol up to to the Azeotrope The Side Stripper is is a Beer Tower without the solids

4 Typical Flow Scheme 190 Proof EtOH 30 Trays Rectifier Fusel Draw Feed 22 Trays Beer Mash Still Side Stripper 16 Trays Solids/Water Water

5 Operation A Beer Mash Tower is is a severe fouler Feed contains proteins, fibers, sugars, and suspended solids, as as much as as 14 wgt% Ethanol needs to to be be removed from not only the liquid but from these solids as as well Any stagnation in in these towers results in in solids buildup and premature tower flooding

6 Sight Glasses Tray 12 Sump Section

7 Tray Outlet Area - Old Trays Where the downcomer pipes should be found

8 The Challenge AGP s Beer Mash Tower had an an extraordinarily high Ethanol content in in the bottom at at normal production levels Slight changes in in feed rate or or feed concentration would dramatically increase the amount of of Ethanol in in the bottoms At At times Ethanol in in the bottom was as as high as as 0.2 vol % Typical operating plants see no more than 0.02 vol % Ethanol in in the bottom

9 Bottoms Purity vs. Feed Rate Bottoms Purity, vol% EtOH Feed Rate, gpm

10 Operating Data Oct. 2, vol% Ethanol 11.0 wgt% Solids 206 F 210 F 606 GPM 22 Trays Tray Efficiency to to match the the reboiler duty = 48.1% 7.5 psig 49,700 #/hr steam vol% Ethanol 13.7 wgt% Solids 238 F 374 GPM

11 Observations Low observed Tray efficiency and high sensitivity to to changes in in operation pointed to to a need for more theoretical stages Tray drawings showed that the existing trays had only a 54 flow path length for a 138 diameter tower Pipe Type Downcomers forced liquid to to center of of tower High Efficiency trays that can handle solids were determined to to be be needed

12 Unit Photo Beer Tower Rectifier

13 Options has numerous applications in in this particular service, but never had the challenge of of significantly increasing tray efficiency It It was decided that the SVG Tray would be be used because of of its its extensive experience in in this service. However, an an extra enhancement to to liquid flow would be be added

14 Testing at Nutter/Sulzer Over the past several years many different types of of flow enhancement devices were tested at at One of of these was the Mini Jet Tab Push Valve These devices could force the liquid on the tray to to go go in in directions it it did not naturally wish to to flow.

15 Testing at Nutter/Sulzer By strategically placing these devices on the tray deck, plug flow of of liquid could be be achieved and stagnation eliminated. The device had to to be be large enough to to be be effective with large tray openings such as as the SVG V-Grid valve A lot of of the credit for distribution of of these devices goes to to Dr. Mike Lockett who s work in in this area in in the early 1970 s was applied here.

16 Mini Jet Tab Push Valve ~1

17 Tray Layout with MJT Valves Flow

18 Tray Layout

19 Operating Data Oct. 8, vol% Ethanol 9.5 wgt% Solids 205 F 208 F 649 GPM 21 Trays Tray Efficiency to to match the the reboiler duty = 61% 7.5 psig 53,330 #/hr steam vol% Ethanol 12.6 wgt% Solids F 473 GPM

20 Tray Hydraulics Key Hydraulic Parameters - Not very Loaded Name: Name: TOP TOP BOTTOM BOTTOM Vapor: Vapor: Jet Jet Flood Flood 49% 49% 43% 43% Dry Dry Tray Tray Pressure Pressure Drop, Drop, "H2O "H2O System System Factor Factor Liquid: Liquid: Downcomer Downcomer Velocity Velocity 20% 20% 18% 18% Weir Weir Loading, Loading, gpm/in. gpm/in Downcomer Downcomer Froth Froth Backup, Backup, % 45% 45% 43% 43% Tray Tray Pressure Pressure Drop, Drop, mmhg mmhg

21 Conclusions Old ideas can lead to to significant progress in in new applications. A 27% increase in in tray efficiency was realized through the use of of the push valves and increased flow path length. Run length has increased significantly. In In the past CIP had to to be be applied every few months - this tower now has operated since April with no increase in in pressure drop.