The MPS Coal Pulverizer with SLS (Dynamic) Classifier
and Hydraulically-loaded Rollers
• 30 years of worldwide experience
• Dependable Riley Power Inc. design
• Demonstrated world experience on a variety of coals

There is no other vertical spindle coal pulverizer with more installed combined grinding capacity and range of proven experience worldwide than the MPS Coal Pulverizer. There are now more than two thousand MPS Pulverizers installed, successfully pulverizing all types of coal.

Riley Power Inc., and its licensor, enhanced the original design by investing heavily in the development of pulverizer improvements and upgrades. Riley Power Inc. has the license from Babcock Borsig Power Systems GmbH, to manufacture and sell this improved MPS design in North America.

The new generation of MPS pulverizer is equipped with hydraulic grinding roller loading system. Compared with older spring roller loading designs, the new hydraulic roller loading design increases mill grinding capacity up to 50% and provides optimum characterization of grinding loading vs. mill loading demand. There are two types of classifiers for MPS pulverizers. The illustration shows the MPS pulverizer with a dynamic type of classifier (SLS classifier). The pulverizer can also be supplied with a static type of classifier (SLK classifier). MPS pulverizers with mechanical spring roller loading design were eliminated from our new product line due to their lower operational grinding flexibility, and mill vibration and impact load at low mill load and during mill startup and shutdown. RPI continues to work with the pulverizer users with old spring roller loading designs to improve the pulverizer performance, rebuild grinding roller assemblies and retrofit the pulverizer, as well as to supply wear parts of the pulverizer.

How The MPS Pulverizer Operates
Raw coal is fed through a central coal inlet at the top of the pulverizer and falls by gravity to the rotating grinding table, mixing with classifier rejects returned for re-grinding. Centrifugal action forces the coal outward to the grinding ring where it is pulverized between the ring and three grinding rollers.

Grinding load, transmitted from the tension rods through the loading frame to the roller assemblies, holds the rollers downward against the grinding ring. The rollers adjust vertically as the depth of the coal load increases or decreases.

A nozzle ring on the outside perimeter of the grinding ring feeds primary air to the pulverizer. Pyrites and tramp metal fall through the nozzle ring openings to be scraped into a rejects hopper.

A stream of low-velocity air carries the particles of pulverized coal upward where they enter the classifier inlet vanes. Fine particles travel to the burners in the primary air stream, but the larger, heavier particles are returned to the grinding zone for further pulverization.

Classification is the key to finer coal - and finer coal means better combustion
It is important to maintain close control of the size of the coal particles delivered to the burners. Finer coal burns quickly and efficiently, reducing carbon in the flyash while maintaining low NOx emissions and increasing boiler efficiency. Classification is a closely controlled three-stage process in the MPS Pulverizer, with the capability of producing fineness up to near micronized coal for improved combustion and emission control.

Raw coal is pulverized between the rollers and ring. Primary air enters the mill through an aerodynamically-ported nozzle. The developed swirl air flow induces larger partides to return to the grinding track. During this first stage of classification, fine particles are carried upward in the housing in the stream of air and coarser particles fall back to the table for regrinding.

In the second stage of classification, the velocity in the upper housing decreases and larger particles are dropped out. Particles fine enough to be entrained in the stream of low-velocity air are carried to the classifier. This improved classification results in less fine particles returned for regrinding, thus less pulverizer power consumption.

The most critical classification takes place in the third stage, within the classifier section at the top of the pulverizer. This classification is dependent not only on the velocity of the primary air, but also on the close adjustment of the classifier vanes and the cyclonic action of the primary air/coal mixture that the MPS Pulverizer provides. Even though the particles may be fine enough to be carried into the classifier section, all are not sufficiently pulverized for transport to the burners. Through the centrifugal action in the classifier section, these fall to the bottom of the inner cone and are returned to the grinding zone.

World-class pulverizer technology and Riley Power Inc. know-how works for you
The MPS Pulverizer lends itself to plant upgrades for reducing NOx emissions. Riley  Power Inc.  has already retrofitted MPS Pulverizers to existing boilers to regain grinding capacity and fineness lost as a result of coal switching. On a retrofitted fuel process system in the US, by the high grinding efficiency with a minimal number of fine particles returned to the table for regrinding, MPS pulverizer delivered the pulverized coal at a fineness of greater than 99% through 50 mesh and greater than 80% through 200 mesh at full mill rated output, which reduced the flyash carbon loss enough to increase the boiler efficiency by more than 0.5%.

With Riley Power Inc., you get the benefits of the capabilities of the MPS Pulverizer coupled with our extensive boiler knowledge as a steam generator OEM. Riley Power Inc.'s coal pulverizing experts are ready to engineer the application of this world class pulverizer for you as part of a total plant emissions reduction program.

Grinding Table Segments and Tires for MPS Coal Pulverizers
Grinding table segments and tires are the heart of coal pulverizing efficiency in an MPS mill, and receive the most wear of all the components in the pulverization process. In most applications, the tires are rotating in direct contact with the table until  the mill begins to receive fuel and a  layer of coal is built up.

The materials used in these massive parts must not only have impact resistance, but must also have wear resistance because they operate in a constant stream of pulverized coal and heated air.

Improved long-wearing alloy
Long-wearing grinding table segments and tires from pro-prietary Riloy 38 are available for all MPS mills, regardless of the original manufacturer of  your equipment. Riley Power Inc. offers table segments and tires of Riloy 38, which has typically outperformed commercially available high-chrome materials in pulverizers by 25% or more. Table segments and tires of Riloy 38 have superior wear resistance, higher Brinell hardness, and greater tensile strength than parts cast of conventional ASTM A532 (Ni-Hard 4). This means more efficient pulverization, longer wear life, and fewer planned maintenance outages.

Riloy 38 is a proprietary material with narrow alloy ranges and a proprietary heat treatment. The unique alloy balance coupled with the special heat treatment results in a metallurgical structure with superior hardness and tensile strength. Properties developed in Riloy 38 exceed those that are developed in Ni-Hard 4. The fully transformed microstructure of  Riloy 38 results in a greater bulk hardness, making it a more wear resistant material than Ni-Hard 4.

Conventional Ni-Hard 4 has a tendency to not fully transform because of its higher nickel content. Consequently, Ni-Hard 4 is not as tough or as wear resistant as Riloy 38. For longer life and consistent pulverization in this high stress, abrasive wear application, we recommend Riloy 38 for grinding table segments and tires.

Quality components
Riley Power, Inc.'s certified foundry is a fully integrated manufacturing facility. The entire operation, from pattern making to material selection to machining is carried out on site, under strict quality control. You get the benefit of our metallurgists who follow exacting chemical material specification, and technicians skilled in up-to-date molding technology, fully automated heat treatment, and precision machining.

Riley Power Inc. is a full-service supplier of steam generators, fuel firing equipment, and environmental control systems for electric utilities and industries. With our experience, we offer table segments and tires for MPS mills of all sizes, including those originally furnished by other OEMS.