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A Rolling Success – part one

World Cement,

As a result of the recent worldwide attention on energy efficiency improvement and CO2 reduction, the number of vertical roller mills (VRMs) adopted for slag/cement grinding has increased. In order to meet this increasing market demand, UBE has been focusing on developing cement mills and has delivered a number of cement VRMs across the world. Among these, a 6-roller cement mill delivered to Wagners Cement in Australia, the UM43.6SCR, has been performing particularly well. This report will examine the operation data of the mill, as well as the latest industry technology.

Actual results of UM43.6SCR

The UM43.6SCR started operation in August 2014 and is capable of grinding both pure slag and cement (OPC). The main features of the mill, which comprises three grinding rollers and three sub-rollers, are a 4300 mm table diameter alongside 3000 kW of motor power. This 2-way grinding system incorporates sub-rollers, making it especially effective for mill vibration suppression and high-efficiency grinding for ultrafine grinding of slag and cement. Additionally, UBE’s original concept, centre chute system, is implemented to prevent slag, a high-moisture material, from sticking to the chute and to allow smooth feeding to the table without clogging the parts.

Table 1 presents the operation data of cement grinding, while Table 2 presents the product quality data. Although the required fineness for normal grade product was at a high level of 4080 cm2/g Blaine, the total power consumption of the mill, separator, and fan was impressive at 30.2 kWh/t. The customer required the products to have an even higher mortar compressive strength and shorter setting time, requiring the grinding of high grade product. This was achieved by limiting the amount of water spray at 1.0% or below versus total material feed. Of the various issues that can affect product quality, the amount of water spray within the mill has the largest impact. Thus, by operating the mill with lowered water spray amount, the grinding of high quality cement was accomplished, as presented in Table 2(b).

Typically, water spray inside the mill is one of the effective methods to suppress mill vibration. Despite the limited water spray amount of the UBE mill, stable and continuous operation was achieved, demonstrating the efficiency of the company’s mill vibration suppression technology development.

This is part one of a three-part article written for World Cement’s February issue and abridged for the website. Subscribers can read the full issue by signing in, and can also catch up on-the-go via our new app for Apple and Android. Non-subscribers can access a preview of the December 2015 issue here.

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