Drying & Torrefaction to produce 10 Tons per Hour of Torrefied Wood (TW)
| Superheated Steam Drying at Atmospheric Pressure | ||
| Green Wood Chips | 50,000 | lbs per hour |
| Moisture Content | 50% | MC |
| Water in Wood | 25,000 | lbs/hr |
| Dry Wood | 25,000 | lbs/hr |
| Moisture Content after Drying | 8% | MC |
| Wood for TW & Charcoal | 27,174 | lbs/hr |
| Water Removed in Dryer | 22,826 | lbs/hr |
| Heat Load for Drying | 1,500.85 | Btu/lb water |
| Total Heat Load for Drying | 34.3 | MMBtu/hr |
| Dryer Inlet Steam Temp | 428 | F. |
| Dryer Inlet Steam Enthalpy | 1,253.18 | Btu/lbm |
| Dryer Outlet Steam Temp | 302 | F. |
| Outlet Steam Enthalpy | 1,193.56 | Btu/lbm |
| Change in Enthalpy | 59.62 | Btu/lbm |
| Steam Recirculated | 574,581 | lbm/hr |
| Steam Vented at 302 F. | 22,826 | lbs/hr |
| Superheated Steam Torrefaction | ||
| Wood for Torrefaction | 27,174 | lbs/hr |
| Water in Wood | 2,174 | lbs/hr |
| Water Enthalpy at 90 C. (194 F.) | 162 | Btu/lbm |
| Steam Enthalpy at 280 C. (536 F.) | 1,305 | Btu/lbm |
| Difference | 1,142 | Btu/lbm |
| Heat to Dry Wood to 0% MC | 2.48 | MMBtu/hr |
| Bone Dry Wood | 25,000 | lbm/hr |
| Temperature of Wood into Torrefaction (110 C.) | 230 | F. |
| Torrefaction Temperature (280 C.) | 536 | F. |
| Temperature Difference | 306 | deg. F. |
| Specific Heat Capacity of Bone Dry Wood | 0.30 | Btu/lbm-deg F. |
| Heat Input to Torrefy Dry Wood | 2.30 | MMBtu/hr |
| Incl 20% for Structural Losses | 2.87 | MMBtu/hr |
| Indirect Heater Load for Torrefaction | 2.87 | MMBtu/hr |
| Torrefaction Steam at 280 C. (536 F.) | 2,199 | lbs/hr |
| Summary | ||
| Yield of TW |
80% |
|
| TW | 20,000 | lbs/hr |
| Heating Value | 8,500 | Btu/lb |
| Heat Load for Drying | 34.26 | MMBtu/hr |
| Heat Load for Torrefaction | 2.87 | MMBtu/hr |
| Total Heat Load | 37.13 | MMBtu/hr |
| Calculation of Heat Input to Dryer | ||
| Heat 1 lb of moisture from 68 F. to 212 F. | 144 | Btu/lbm water |
| Heat 1 lb of dry wood from 68 F to 212 F Cp = 0.3 | 43.2 | Btu/lbm dry wood |
| Evaporate 1 lb water at 100 C. | 970.4 | Btu/lbm water |
| Superheat 1 lb of vented steam from 212 to 302 F. | 43.08 | Btu/lbm steam |
| Moisture Content of Feed | 50% | |
| Heat Water | 72.00 | |
| Heat Wood | 21.60 | |
| Evaporate. Water | 485.20 | |
| Superheat Steam | 21.54 | |
| 600.34 | Btu/lb of wet Wood | |
| 1200.68 | Btu/lbm water | |
| Incl. 20% for Structural Losses | 1500.85 | Btu/lbm water |
Two Stage Drying to Remove Free & Bound Water
| Superheated Steam Drying at Atmospheric Pressure | ||||
|
Remove Free Water |
Remove Bound Water |
|||
| Wood for TW | 50,000 | lbs per hour | 35,714 | lbs per hour |
| Moisture Content | 50% | MC | 30% | MC |
| Water in Wood | 25,000 | lbs/hr | 10,714 | lbs/hr |
| Dry Wood | 25,000 | lbs/hr | 25,000 | lbs/hr |
| Moisture Content after Drying | 30% | MC | 8% | MC |
| Wood Out of Dryer | 35,714 | lbs/hr | 27,174 | lbs/hr |
| Water Removed in Dryer | 14,286 | lbs/hr | 8,540 | lbs/hr |
| Heat Load for Drying | 1,575.38 | Btu/lb water | 1,266.85 | Btu/lb water |
| Total Heat Load for Drying | 22.5 | MMBtu/hr | 10.8 | MMBtu/hr |
| Dryer Inlet Steam Temp | 750 | F. | 428 | F. |
| Dryer Inlet Steam Enthalpy | 1,408.38 | Btu/lbm | 1,253.18 | Btu/lbm |
| Dryer Outlet Steam Temp | 428 | F. | 302 | F. |
| Outlet Steam Enthalpy | 1,253.18 | Btu/lbm | 1,193.56 | Btu/lbm |
| Change in Enthalpy | 155.20 | Btu/lbm | 59.62 | Btu/lbm |
| Steam Into Dryer | 145,009 | lbm/hr | 181,462 | lbm/hr |
| Steam Out of Dryer | 159,295 | lbs/hr | 190,002 | lbs/hr |
| Outlet Steam Enthalpy | 1,253.18 | Btu/lbm | ||
| 199.6 | MMBtu/hr | |||
| Steam Vented | 22,826 | lbs/hr | ||
| Calculation of Heat Input to Dryer | ||||
| Temperature of Wood Chips into Dryer | 68 | F. | 300 | F. |
| Heat 1 lb of moisture from 68 F. to 212 F. | 144 | Btu/lbm water | 0 | Btu/lbm water |
| Heat 1 lb of dry wood from 68 F to 212 F Cp = 0.3 | 43.2 | Btu/lbm dry wood | 0 | Btu/lbm dry wood |
| Evaporate 1 lb water at 100 C. | 970.4 | Btu/lbm water | 970.4 | Btu/lbm water |
| Superheat 1 lb of vented steam to outlet temp. | 102.71 | Btu/lbm @ 428 F | 43.08 | Btu/lbm @ 302 F. |
| Moisture Content of Feed | 50% | 30% | ||
| Heat Water | 72.00 | - | ||
| Heat Wood | 21.60 | - | ||
| Evaporate. Water | 485.20 | 291.12 | ||
| Superheat Steam | 51.35 | 12.92 | ||
| 630.15 | Btu/lb of wet Wood | 304.04 | Btu/lb of wet Wood | |
| 1260.31 | Btu/lb water | 1013.48 | Btu/lb water | |
| Incl. 20% for Structural Losses | 1575.38 | Btu/lb water | 1266.85 | Btu/lb water |
