The heart of the STRATCO lubricating grease manufacturing process is the proprietary. The outstanding feature of the Contactor reactor is its high turbulent circulation in a closed cycle path. All energy input through the mixing impeller is expended within the materials being mixed and there is virtually no pressure differential between the Contactor reactor's inlet and outlet.

The Contactor reactor is first charged with the specified base oil which is at its storage temperature. A hinged opening at the top of the Contactor reactor is used for charging the active chemical ingredients used in the grease formula. Once the specified amount of the raw chemicals is loaded, the charge opening is closed and the Contactor reactor is heated.

The high dispersion mixing in the Contactor reactor is achieved by the hydraulic head assembly. The impeller forces frequent changes in the velocity and direction of flow through the Contactor reactor. The oil and chemical ingredients are pulled down through the inside of the circulation tube via the impeller. Turbulence is established between the stationary shear vanes and the blades of the impeller, resulting in a zone of high shear and intense mixing.

As the material passes through the impeller, its velocity is greatly increased. At the discharge side of the impeller, the stream is impinged against the diffuser vanes. The direction of the flow is reversed at the bottom of the hydraulic head where the vanes force an axial turbulent flow as the dispersion passes through the annular space formed by the circulation tube and Contactor reactor wall. The liquid then flows over the top of the circulation tube and back into the impeller.

Once circulation is established, the Contactor reactor is heated, typically using a hot oil heating system. The Contactor reactor is equipped with two jackets, an external jacket and an internal jacket. Heat transfer oil is circulated in both the internal and external heating jackets. High heat transfer coeffiecients are achieved by the high circulation rates across the heating surface. The saponification reaction is exothermic and the combination of applied heat and reaction heat results in a rapid temperature rise. The entire contents of the Contactor reactor reach a temperature in excess of 400°F (204.4°C) in less than an hour. At this temperature, the saponification reaction is complete.
 
As the saponification reaction proceeds to completion, water is generated as a product of the reaction. Pressures in the range of 70-100 psig (482.7-689.5 Kpa gauge) are typical of those used for efficient and complete saponification. This pressure prevents foaming of the soap concentrate as well as accelerates the saponification reaction. The Contactor reactor pressure is maintained by manually venting or by automatic controls as the temperature rises.

The next step involves the addition of cooling or quench oil used to reduce the temperature below the soap crystallization temperature. At this point, the Contactor reactor's contents are pumped into a finishing kettle. These are large mixing vessels, typically either pressure or open atmospheric types. The kettles are equipped with large slow speed mixing assemblies, whose function is to provide a gentle blending action and aid in cooling of the semi-finished product. Cooling is typically accomplished by cooling water circulation in a shell jacket.

STRATCO provides reliable, equipment and services to maintain our customers' competitive advantage in the global market of lubricating oil and grease.
The development, design, fabrication, and operation of STRATCO process equipment is backed by more than 80 years of experience with over 400 units installed throughout the world. The first STRATCO Grease Contactor™ reactor (installed in 1929) is still in service today. This is indicative of the quality, reliability, and dependability of our equipment.

STRATCO offers to manufacturers around the world a semi-continuous process to manufacture various types of lubricating greases, ranging from calcium, lithium, and sodium to more specialized greases such as aluminum complex, polyurea, etc. The process is similar to that of the conventional kettle process, but more efficient and flexible allowing the manufacturer to minimize unit manufacturing costs while maintaining high standards of quality.

The unique features of the Contactor reactor are its highly turbulent circulation in a closed cycle path and its relatively large heat transfer surface, which contributes to the vessel's enhanced performance as compared with a typical kettle process.

The STRATCO Contactor reactor consists of a pressure vessel, a circulation tube and a hydraulic head assembly complete with the mixing impeller and driver. The Contactor reactor by design has a highly turbulent circulation path.  All energy input through the mixing impeller is expended within the materials being mixed.  The high dispersion mixing in the Contactor reactor is achieved by the proprietary hydraulic head assembly. Frequent and forced changes in velocity and direction of flow occur around the impeller area. This results in a zone of high shear and intense mixing, which reduces the time required to complete the saponification reaction.
Material is pulled down through the center of the circulation tube by the impeller, reversed and then forced up through the annular space. Because the impeller is located on the bottom, dry materials are kept in suspension until they dissolve or are reacted.

The heating medium is circulated through the double-walled circulation tube inside the Contactor. The outside of the Contactor reactor is also jacketed.  An alternate design can be furnished to use high pressure steam.

Because of the double-walled circulation tube and the outside jacket, the Contactor reactor has approximately three times the heat transfer area of an open kettle or other pressure (autoclave) type reactors of the same volume. The flow path, forces the circulating material to remain in contact with the total heating surface area at all times. Also, the heat transfer in the Contactor reactor is enhanced by the high velocity of material flowing past the heat transfer surfaces.

The Contactor reactor’s impeller is connected to a two-speed motor normally turning at 1,200 RPM. The motor is mounted below the vessel and out of the operating area. The shaft is sealed from the process fluid by a mechanical seal which can be replaced from outside the Contactor reactor without removing the head. 
 

Standard Specifications 
The finishing kettle is typically sized between 2 and 2.5 times the working volume of the STRATCO Contactor™ , which are available in a variety of convenient sizes, both commercial scale and pilot plant scale.  Many lubricating grease manufacturers have a grease pilot plant to test formulations, because the correlation between a pilot plant Contactor reactor and a commercial size plant Contactor reactor is around 95%.