The reaction stage is the heart of CMC and PAC production and takes place across two kneader reactors operated in series. Pulverised cellulose is first charged into the alkalization kneader together with liquid caustic soda (NaOH) and ethanol solvent, forming alkali cellulose under tightly controlled cryogenic conditions. The alkali cellulose is then transferred to the etherification kneader, where it reacts with monochloroacetic acid (MCA) at high jacket temperature to form the final carboxymethyl cellulose ether.
Degree of substitution (DS) and the degree of polymerization (DP) of the finished CMC or PAC — the two parameters that govern viscosity and product grade — are set almost entirely by the temperature control, mixing uniformity, and sealing performance of these two reactors.
Vessel design temperature reflects the minimum design metal temperature (MDMT) rating for the vacuum-rated 304 stainless vessel; the jacket carries the process heating/cooling duty in each stage.
The two kneaders in a CMC or PAC production line sit at opposite ends of the process temperature spectrum. The alkalization kneader processes a mixture of cellulose, ethanol, and liquid caustic soda under cryogenic conditions — jacket temperature as low as −15°C using chilled water — to control the exothermic alkalization reaction and preserve cellulose degree of polymerization (DP). The etherification kneader then processes the alkali cellulose together with ethanol and monochloroacetic acid (MCA) under a high-temperature steam/circulating water jacket reaching 170°C, driving the etherification reaction to the target degree of substitution (DS).
Both vessels are fabricated in 304 stainless steel for corrosion resistance against NaOH, ethanol, and MCA, with carbon steel jackets rated for their respective thermal duties. Each reactor is fitted with a twin-shaft agitator drive to maintain uniform mixing of the highly viscous cellulose mass throughout the reaction cycle.
Dimensions listed as Length × Width × Height (overall footprint including jacket and drive). Vessel diameter and tangent-to-tangent length available on request.
- Cryogenic alkalization jacket protects degree of polymerization: The alkalization reaction between cellulose and NaOH is exothermic. Without active cooling, localized overheating accelerates cellulose chain scission, reducing degree of polymerization (DP) and final product viscosity. The chilled water jacket, rated to −15°C design temperature, removes reaction heat and holds vessel temperature near −1°C during the alkalization cycle.
- High-temperature etherification jacket drives reaction completion: The etherification reaction between alkali cellulose and MCA requires sustained heat input to reach target degree of substitution (DS) within cycle time. The steam/circulating water jacket, rated to 170°C design temperature, maintains vessel temperature at 80°C — the level required for complete, uniform etherification across the batch.
- Twin-shaft sigma-blade agitation: Both kneaders use a twin-shaft drive configuration — 37 kW / 37 kW on the alkalization kneader and 30 kW / 30 kW on the etherification kneader — providing the high torque and mixing uniformity required to process the highly viscous alkali cellulose mass without dead zones.
- 304 stainless steel product-contact surfaces: Vessel walls, blades, and all product-contact components are fabricated in 304 stainless steel, resistant to the caustic soda, ethanol, and monochloroacetic acid present across both reaction stages.
- Vacuum-rated vessels: Both vessels are rated to −0.09 MPa.G, allowing operation under negative pressure — used to control ethanol vapour and manage the reaction atmosphere in both the alkalization and etherification stages.
- Matched jacket pressure ratings: The alkalization jacket is rated to 0.4 MPa.G for chilled water circulation; the etherification jacket is rated to 0.6 MPa.G to accommodate steam heating, giving each reactor an appropriate safety margin for its thermal duty.
| Parameter | Alkalization — Vessel | Alkalization — Jacket |
|---|---|---|
| Medium | CMC, ethanol, liquid caustic | Chilled water |
| Operating Temperature | −1°C | −8°C |
| Operating Pressure | −0.09 MPa.G | 0.3 MPa.G |
| Design Temperature | −15°C | −15°C |
| Design Pressure | −0.09 MPa.G | 0.4 MPa.G |
| Volume / Dimensions | 3,000 L | 4500 × 1900 × 2200 mm |
| Power | 37 / 37 kW | — |
| Material | 304 stainless steel | Carbon steel |
| Weight (single unit) | 12,000 kg | — |
| Parameter | Etherification — Vessel | Etherification — Jacket |
|---|---|---|
| Medium | CMC, ethanol, MCA | Circulating water / steam |
| Operating Temperature | 80°C | 145°C |
| Operating Pressure | −0.09 MPa.G | 0.4 MPa.G |
| Design Temperature | 9°C (MDMT) | 170°C |
| Design Pressure | −0.09 MPa.G | 0.6 MPa.G |
| Volume / Dimensions | 2,500 L | 4400 × 1800 × 2200 mm |
| Power | 30 / 30 kW | — |
| Material | 304 stainless steel | Carbon steel |
| Weight (single unit) | 11,000 kg | — |
Parameters shown are from a completed reference project and represent typical values for this equipment class. Vessel volume, power, and dimensions are engineered to match your target production capacity.
| CMC Production | Alkalization and etherification of refined cotton or wood pulp cellulose with NaOH and monochloroacetic acid. Suitable for all CMC grades — food, industrial, oilfield, paper, ceramic, and textile grades. |
| PAC Production | Production of polyanionic cellulose (PAC) for oilfield drilling fluid applications. Process conditions similar to CMC but tuned for higher DS and specific viscosity targets. |
| HPMC / HEC Production | Applicable in hydroxypropyl methylcellulose and hydroxyethyl cellulose production lines where kneader reactors are used for the alkalization and etherification stages. |