2006 Slag Grinding With MPS Vertical Roller Mills

IntroductionGebr. Pfeiffer AG, a medium-sized family business, has been a supplier to the cement, lime and gypsum industry for over 140 years. The company’s product range compris-es machines and equipment for the grinding, classification and drying of diverse materials and for slaking quicklime and calcining gypsum, which are sold worldwide.

The company, headquartered in Kaiserslautern, employs 260 staff and maintains manufacturing facili-ties as well as a foundry of its own. Gebr. Pfeiffer AG has an annual turnover of around Euro75m. With over 2000 MPS vertical roller mills in use around the world today for grinding cement raw material, coal, clinker, granulated blast furnace slag, pozzolana, limestone, clay, gypsum and various other materials, the MPS technology repre-sents the company’s major source of revenue.

In the cement industry, MPS vertical roller mills grind-ing cement raw materials and cement or granulated blast furnace slag with installed powers of over 5000kW are currently in operation or on order.

Pfeiffer’s MPS vertical roller millThe structure of the MPS BC series, to which all mills

producing cement or blast furnace slag powder belong, basically corresponds to that of the MPS vertical roller mills that have been used for cement raw material and coal grinding since the 1960s: the statically determinate 3-roller-system, which is pressed against the grinding bed by a pressure frame, external pull rods and the hydraulic system, is a characteristic feature of the mill. The grinding rollers can be lifted with the help of the tensioning cylin-ders during start-up or for maintenance purposes.

An SLS high-efficiency classifier sits on top of the grind-ing zone. The supply of fresh material is integrated in such a way that the fresh material and the grits from the clas-sifier mix well and the material drops onto the centre of the grinding table.

The MPS BC model range distinguishes itself from raw mills through its process-related design, which is par-ticularly characterised by the increased grinding force, an adapted, reduced speed of the grinding table and lower gas velocities.

SLAG GRINDING WITH MPS VERTICAL ROLLER MILLS

Since 1980 a vertical roller mill MPS 3750 C near Hannover supplied by Gebr. Pfeiffer AG produces cement types CEM III A and CEM III B with a slag content between 40% and 80%. Actually an MPS 5600 BC with 5300kW installed main drive is under erection. The guarantee values for grinding blast furnace slag in this mill are 120t/h at a fineness of 5000cm²/g (Blaine) and 170t/h at a fineness of 5000cm²/g (Blaine).

July 2006 21 GLOBAL SLAG

lobal lobalGGSLAG

S L A G G R I N D I N G

BY YORK REICHHARDT

GEBR. PFEIFFER AG

MPS 5600 BC for Tenghui Cement, China. Under erection 120t/h slag 5000 Blaine, 170t/h slag 4000 Blaine (250t/h OPSC 3000)


The mechanical design is tailored to the higher abrasiveness of the mate-rial to be ground. The noz-zle ring and other parts exposed to increased jet wear in the area of the grinding table are made of Ni-hard IV. The area of the classifier is provided with a ceramic lining, and the rotor of the clas-sifier is hardfaced. The wear parts of the rollers and the grinding table normally are made of chromium alloy cast iron and will be hardfaced at a later stage, when knowing the exact wear profile. The hardfacing can be carried out inside the mill with-out the rollers having to be removed from the mill. The rollers are lifted up for this purpose, and, while it is being welded, the grind-ing plate is turned with the help of a variable-speed maintenance drive, which is integrated in the gear. Then the rollers are low-ered again, driven by the grinding table and welded using several weld heads simultaneously. With an

MPS 5600 BC for 170t/h slag powder like the one currently under erection, downtime for the entire hard-facing can be kept as short as 110 hours, approx-imately, if work is organised accordingly. The hardfacing is expected at this mill to be necessary each 2000 hours based on a production of 170t/h slag at 4000cm2/g acc. to Blaine. MPS mills are in operation which are hardfacened more than ten times. In total this leads to comparatively low mainte-nance costs.

Plant concept The entire grinding plant consists of

• equipment for meter-ing, supplying the wet slag to the mill and for metal

GLOBAL SLAG MAGAZINE SLAG GRINDING

MPS 3750 C 3750 C 4250 BC 4250 BC 4250 BC

country Germany Germany Ecuador Italy Italy

commissioning 1980 1980 2002 2004 2004

clinker (%) 20 95 67 64 89

blast furnace slag (%) 75 18

pozzolana (%) 30 6

limestone (%) 6 5

gypsum (%) 5 5 3 6 6

specific surface (Blaine) (cm/g)

4300 3000 4600 4400 3800

specific power con-sumption (mill, clas-sifier, fan) (kWh/t)

45 29 28 2334

(guarantee)

throughput rate (t/h) 45 78 118 126103

(guarantee)

dust collection in cyclone

yes yes yes no no

MPS 2500 BC 2500 BC 2500 BC 2500 BC 3750 C

country India India Czech Republic Czech Republic Germany

commissioning 2000 2000 2002 2002 1980

clinker (%) 48 97 96 43

blast furnace slag (%) 48 100 52

pozzolana (%)

limestone (%)

gypsum (%) 4 3 4 5


3600 3100 3800 4300 3600

specific power con-sumption (mill, clas-sifier, fan) (kWh/t)

31 27 31 38 32

throughput rate (t/h) 22 26 23 21 70


yes yes no no yes

Table 1, above: MPS vertical roller mill for the grinding of cement and blast furnace slag.Left: References in the cement industry from 1994 onwards.

Table 2: MPS vertical roller mill for the grinding of cement and blast furnace slag.


extraction upstream of the mill• the MPS BC vertical roller mill• the external material circulation system

with a complementary metal extraction system especially aimed at the already dried and liber-ated pig iron

• the process gas routing• bag filter for dedusting and product

removal.For drying the wet slag in the mill either

process gases like clinker cooler exhaust gases or hot gases from a hot gas generator may be used. Gebr. Pfeiffer AG’s scope of supply may

be in between just the vertical roller mill or the complete machinery and the electric part of such a grinding plant.

Operating data The first industrial-scale vertical roller mill for slag cement, an MPS 3750 C, went into operation in Hannover 25 years ago [1] and is still in operation. It produces 70t/h CEM III A and 45t/h CEM III B with slag content between 50 and 80% and fineness of 3600cm2/g and 4300cm2/g. The cement quality meets all the requirements of the German market. For 100% slag at a fineness of 4100cm2/g the capacity of this mill is 60t/h. Also newer mills of the

MPS BC series produce slag cement and slag powder in this range of composition and fineness.

Today more than 20 MPS vertical roller mills of the BC series for slag, cement and binding agents with capaci-ties of up to 150t/h [2-5] are used or under contract for slag powder and the produc-tion of virtually all cements of various compositions commonly used worldwide. The mills achieve finenesses ranging from 2000cm2/g to


MPS 4250 BC 16x4250 BC 5600 BC 5600 BC

country Italy Iran China China

commissioning 2004

clinker (%) 29 95

blast furnace slag (%) 65 100 100

pozzolana (%)

limestone (%)

gypsum (%) 6 5


4000 3000 5000 4000

specific power con-sumption (mill, classi-fier, fan) (kWh/t)

45(guarantee)

18(guarantee)

38(mill drive)

30(mill drive)

throughput rate (t/h)75

(guarantee)120

(guarantee)120

(guarantee)170

(guarantee)


no yes no no

Above: a MPS 2500 BC vertical roller mill at Sagar Cement at Bayyavaram works, India.Table 3, to the left: MPS vertical roller mill for the grinding of cement and blast furnace slag.

Above: Grinding of slag.Right: Design of MPS BC cement/slag mill by Gebr. Pfeiffer AG.


7000cm2/g in the case of binding agents which contain cement. The operating data are proving, that the sales arguments in favour of the MPS technology for the eco-nomic production of slag powder and cement are true. The actual development goes to bigger units with higher capacity.

Actually an MPS 5600 BC with an installed power of 5,300kW is under erection. It is guaranteed for 120t/h of granulated blast furnace slag at a fineness of 5,000cm2/g or 170t/h with a fineness of 4,000cm2/g. Start of produc-tion is scheduled for spring 2006.

References[1] Steinberg, H.,

Hoffmann, R.: Production

of slag cements in a

vertical roller mill, ZKG

International 51 (1998)

No. 3, pp.101-109

[2] Jung, O.: MPS vertical

roller mills for blended

cements, Wold Cement

Vol. 20 (1989) No. 9

[3] Reddy, S.A, Reichardt,

Y.: Production of slag

cement with an MPS verti-

cal roller mill at the cement

plant of Sagar Cements in

Bayyavaram, India,

ZKG International 54

(2001) No. 9, pp. 492-497

[4] Reichardt, Y., Link,

G., Gilabert, H.: Cement

finish grinding with an

MPS vertical roller mill

at the San Rafael cement

plant in Ecuador, ZKG

International 55 (2002)

No. 11, pp. 54-57

[5] Reichardt, Y., The use

of MPS vertical roller mils in the production of

cement and blast furnace slag powder, Cement

International (2005) No. 2m pp.64-69

GS


Above: Grinding of slag with a MPS 2500 BC at Cemex/RMC in the Czech Republic.Left: MPS 3750 C vertical roller mill at Teutonia AG, Germany.

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2006 Slag Grinding With MPS Vertical Roller Mills