Closed, indirect vacuum drying system for ethanol-wet CMC and PAC cake. Integrated rake dryer, vapor condenser, plate heat exchanger, transfer silo, and water ring vacuum pump recover solvent vapor during drying rather than venting it. Engineered to your production capacity.
The Rake Dryer system is installed after the centrifuge (first-wash) stage and performs both drying and solvent recovery in a single closed system. It is the preferred drying route where the wet cake still carries significant residual ethanol and venting solvent vapor to atmosphere is not acceptable.
Unlike the steam stripping dryer or vibrating fluidized bed dryer, the rake dryer operates as a fully closed vacuum system: ethanol vapor driven off during drying is condensed and recovered rather than discharged, making it well suited to plants prioritizing solvent recovery economics and emissions control.
Ethanol-wet CMC or PAC cake is charged into the vacuum rake dryer vessel, where a rotating rake agitator continuously turns the material bed. The vessel is held under vacuum while the surrounding steam jacket heats the vessel wall indirectly — there is no direct contact between steam and product.
As the ethanol evaporates under vacuum, the solvent-laden vapor is drawn through two parallel shell-and-tube condensers, where cooling water condenses the vapor back to liquid ethanol for recovery. A plate heat exchanger provides additional cooling capacity on the same water circuit, maintaining consistent condensing performance across the drying cycle.
The system vacuum is maintained by a water ring vacuum pump handling the ethanol vapor stream. Once drying is complete, the dried product discharges from the rake dryer into an agitated transfer silo, which buffers material flow ahead of the downstream crusher and blending stages.
Dimensions listed as Length × Width × Height (overall footprint including jacket and drive).
The rake dryer is supplied as a complete drying and solvent recovery system. In addition to the main vacuum rake dryer above, the standard reference configuration includes the following equipment:
| Component | Specification |
|---|---|
| Transfer Silo (1 unit) | Horizontal agitated buffer vessel, 4,000 L, CMC medium — 50°C operating / 90°C design, atmospheric operating pressure / 0.09 MPa.G design pressure, 37 kW drive, 304 stainless steel, 5,000 kg |
| Water Ring Vacuum Pump (1 unit) | Liquid circulation type, ethanol service — ambient operating temperature, −0.03 MPa.G operating pressure, explosion-proof design, 22 kW, 304 stainless steel, 380 kg |
Component counts and specifications above reflect a completed reference project. Configuration is engineered to your target production capacity and site utility conditions.
| Parameter | Rake Dryer — Vessel | Rake Dryer — Jacket |
|---|---|---|
| Medium | CMC, ethanol | Steam |
| Operating Temperature | 78°C | 150°C |
| Operating Pressure | −0.09 MPa.G | 0.4 MPa.G |
| Design Temperature | 90°C | 155°C |
| Design Pressure | −0.09 MPa.G | 0.5 MPa.G |
| Volume / Dimensions | 4,000 L | 4900 × 1600 × 2400 mm |
| Power | 22 kW | — |
| Material | 304 stainless steel | Carbon steel |
| Weight | 8,000 kg | — |
| Parameter | Condenser — Shell (×2) | Condenser — Tube |
|---|---|---|
| Medium | Ethanol vapor | Cooling water |
| Operating Temperature | 78°C | 20°C |
| Operating Pressure | −0.05 MPa.G | 0.3 MPa.G |
| Design Temperature | 90°C | 65°C |
| Design Pressure | −0.09 MPa.G | 0.4 MPa.G |
| Area / Dimensions | 40 m² | 800 × 3000 mm |
| Material | 304 stainless steel | — |
| Weight (each) | 600 kg | — |
| Parameter | Plate HX — Shell Side | Plate HX — Tube Side |
|---|---|---|
| Medium | Ethanol vapor | Cooling water |
| Operating Temperature | 78°C | 20°C |
| Operating Pressure | −0.05 MPa.G | 0.3 MPa.G |
| Design Temperature | 90°C | 65°C |
| Design Pressure | −0.09 MPa.G | 0.4 MPa.G |
| Plate Material / Rating | 316 stainless steel | PN10 |
| Weight | 300 kg | |
| Parameter | Transfer Silo | Vacuum Pump |
|---|---|---|
| Type | Horizontal agitated vessel | Liquid circulation, water ring |
| Medium | CMC | Ethanol (vapor handling) |
| Operating Temperature | 50°C | Ambient |
| Operating Pressure | Atmospheric | −0.03 MPa.G |
| Design Temperature | 90°C | Explosion-proof rated |
| Design Pressure | 0.09 MPa.G | Explosion-proof rated |
| Volume / Configuration | 4,000 L | — |
| Power | 37 kW | 22 kW |
| Material | 304 stainless steel | 304 stainless steel |
| Weight | 5,000 kg | 380 kg |
Parameters shown are from a completed reference project and represent typical values for this equipment class. Vessel volume, area, and power ratings are engineered to match your target production capacity.
Standard delivery time is approximately 120 days from down payment. ZHAOYUAN can also arrange these excluded items and full installation as part of an EPC project scope — contact us to discuss.
| CMC Production Lines | Closed-loop drying and ethanol recovery for CMC after the washing stage, where solvent recovery economics or emissions requirements favor a fully closed vacuum system. |
| PAC Production Lines | Vacuum drying with ethanol recovery for polyanionic cellulose. Compatible with both PAC-HV and PAC-LV production processes. |
| Cellulose Ether Production | Applicable across CMC, PAC, and related cellulose ether lines wherever ethanol vapor recovery is a priority over lower-capital-cost open drying routes. |
| Plant Revamping | Retrofit of solvent recovery capability into existing cellulose derivative plants as part of emissions control or raw material cost reduction projects. |
After washing, wet CMC or PAC cake still carries significant residual ethanol. The rake dryer system dries this cake under vacuum inside a steam-jacketed vessel while a rake agitator turns the bed, and simultaneously condenses and recovers the ethanol vapor driven off — combining drying and solvent recovery in one closed system rather than venting the solvent.
All three are drying options at the same stage of the line, but they trade off differently. The steam stripping dryer combines stripping and drying in one vacuum vessel. The vibrating fluidized bed dryer uses hot air and is the lowest capital cost option once solvent is already removed. The rake dryer system adds a full condenser and vacuum pump train specifically to recover ethanol vapor as liquid solvent, making it the preferred choice where solvent recovery economics or emissions limits are the priority.
Running two shell-and-tube condensers in parallel, each with 40 m² of shell-side area, gives sufficient condensing capacity and built-in redundancy for continuous operation. The plate heat exchanger sits on the same cooling water circuit and adds further heat rejection capacity, helping the system keep pace with vapor generation during the peak of the drying cycle.
CMC and PAC powder can bridge or compact in a static hopper, causing flow interruptions to downstream crushing and blending equipment. The 4,000 L agitated transfer silo keeps dried product moving, decoupling the batch-cycle timing of the rake dryer from the continuous operation of downstream equipment.
The standard package includes the vacuum rake dryer with jacket and agitator, two shell-and-tube condensers, the plate heat exchanger, the agitated transfer silo, and the water ring vacuum pump. It does not include the electrical control cabinet, frequency converter, cooling water supply, installation labor, or interconnecting piping between units — these are typically sourced locally or supplied by the customer to match site utilities and layout. ZHAOYUAN can also supply these items and full installation as part of a complete EPC project.
Yes. The specifications on this page reflect a completed reference project (4,000 L rake dryer, 2 condensers at 40 m² each, 4,000 L transfer silo). Vessel volume, condenser area, and pump/motor power across the whole system are engineered to match your target production capacity. Contact ZHAOYUAN with your requirements for a tailored system specification.