GAS-JET PLANT FOR MILLING NONPLASTICS

A. A. I v a n o v , V. I . G o r o b e t s , L . Z h . G o r o b e t s , G. P . T r o p i n , V. S. T e r n o v s k i i , V. I . Z a i t s e v , A. D. G e r t i k , a n d V. V. K o n s t a n t i n o v

UDC 666.3.022.2:621.926

Inc reas ing the efficiency of mil l ing raw m a t e r i a l s is one of the means of inc reas ing the volume of product ion in c e r a m i c products and increas ing labor product ivi ty . The t radi t ional method of p repa r ing s l ips for building c e r a m i c s includes wet combined grinding of the nonplast ics in per iodic ba l lmi l l s . Al- though ensur ing the n e c e s s a r y deg ree of grinding and blending the components it has ce r ta in drawbacks , such as the i r r e g u l a r i t y of the g r a i n - s i z e composi t ion of the mi l led product , the high consumption of grinding bodies, the low speci f ic output, and the cycl ic na ture of the p r o c e s s , h inder ing i ts comple te auto- mat ion.

A p r o g r e s s i v e method of grinding is the jet technique cha rac t e r i z ed by low meta l consumption for the equipment employed, un i form g r a i n - s i z e composi t ion of the mil led m a t e r i a l , and a lso the possibi l i ty of complete automation.

Invest igat ions c a r r i e d out by the Dnepropet rov Mining Inst i tute showed that it is poss ib le to reduce the energy content of jet mil l ing by se lec t ing an economic energy c a r r i e r and also making cer ta in design decis ions , etc.

Tes t s done by DGI toge ther with the Verkhnednepropet rov Mining-Metal lurgical Combine on the i r g a s - j e t mil l [1], and a lso a mil l using a jet engine as the sou rce of gas energy c a r r i e r [2], showed the ad- vantages of using them in the product ion of building c e r a m i c s .

In the Volgograd Ce ramic Fac tory in 1971 a s t a r t was made on the industr ia l development of this method for grinding s lag which is one of the components in sl ip bodies.

Fig. 1

Dnepropet rov Mining Inst i tute . Volgograd Ceramic Factory . T rans la t ed f rom Steklo i Keramika , No. 1, pp. 23-25, January , 1974.

�9 1974 Consultants Bureau, a division of Plenum Publishing Corporation, 227 ff/est 17th Street, New York, N. Y. I0011. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, microfilming, recording or otherwise, without written permission of the publisher. ,4 copy of this article is available from the publisher for $15.00.

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TABLE 1

Factors Calculated Attained

2,5 2.0-2.2 Output, tons/h Dimensions, m:

length

width

height Weight, tons Rating of electric

motor, kW Specific consumption

(in normal conditions), mS/ton:

air gas

Pressure in combustion chambers, kg]cm z

Temperature in com- bustion chambers, ~

90

1000 20

4. 0

600

3.8 3.2 5.8 5.0

90

I140-1250

2~6-25.0

3.7-3.8

570-650

Certain physical proper t ies of the slag make it neces sa ry to find new technical ideas for creat ing a sys tem of mill loading and dust extraction.

On the basis of tes ts which were ca r r i ed out recommendat ions have been made of a scheme (see Fig. 1) specifying pre l iminary drying of the raw mater ia l s and dry dust extract ion of the milled product with final wet purif icat ion of the gases leaving the mill .

The grinding of the slag is done with a contraflow gas- je t mill tested at the Verkhnednepropetrov GMK. The sources of energy c a r r i e r consis ted of the highly efficient combustion chambers of jet engines redesigned for burning natural gas in them. Gas fed f rom the main pipeline of the factory and air f rom the c o m p r e s s o r were fed into the combustion chambers .

The slag del ivered from the stock is dried in a drum dr i e r 1 and fed to the hopper -accumula tor 2. Then it is gravi ty fed into the original mater ia l hopper of the gas - je t mill 3, and then into the loading units of the injectors 4. The par t ic les impelled into the injectors a re ground as a resul t of the mutual collision in the grinding chamber 5, and a re removed in the impac t -vor tex c lass i f ie r 6 where they are separa ted in t e rms of s ize. The undermil led mater ia l is re turned to the loading chambers of the in jectors , and the finished product is ca r r i ed away to the dust-set t l ing cyclone 7. The ground mater ia l passes through the subeyclone hoppers 8 having sluice valves, and auger feeder 9, and the elevator 10, and enters the finished- product hopper 11. The final purif ication of the gases taken from the mill with the fan 12 is done in the wet dust ex t rac tor 13 of the type PVM8A with ext rac tor fans 14.

The scheme of the gas - je t mill being examined is compact, easi ly fitted into the body-prepara t ion division, and facil i tates rapid convers ion to the continuous method of grinding nonplastic components of the body.

The equipment was selected in accordance with the production of the gas - je t mill in t e rms of gas and hard mater ia l . The production requi rements a re established with re fe rence to the output of the mill in

TABLE 2 TABLE 3

~9

650 570 480 400 340

1Specific con~ t '~ Isumption in I - . ~ ]norm l con-] ,.

3,8 3,7 3,6 3,5 3,5

1140 23,6 2,2 1250 25,0 ] 2,0 1530 28.2 [ 1,7 2160 32,3/ 1,3 2800 36,0/ 1,0

1,91 1,12 2,08 2,1 4,2

A ~ ~ ~ V

] 5,6 40,2 29,8 18,8 5,6 1 2 ] 2,0 31,0 36,0 11,4 19,6

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TABLE 4 I~ r

o ~, - Grmdlng method

z ~

1 Gas-jet 2 2 2 ~ 2 ,"I 2 Ballmill

.O ~ .

O '>

2130 2120 2480 2440 2340 4270

Grain s i z e , qo

60 p 40-60p < 10 p

3,3 1,91 1,12 2,08 2,0 2,26

13,1 17,23 2,0 2,79 2,24 9,06

2o-40~ i0-20~

56,4 18,0 51,02 22,68 62,7 23,09 61,4 23,00 68,37 18,38 32,34 30,62

9,2 7,16

l1,09 10,73 9,01

25,72

t e r m s of hard mater ia l , on which in turn depends its output (in t e rms of gas) and the geometr ical dimen- sions of the components. When the equipment was being adjusted it turned out that the compres so r station at the factory could not guarantee the provis ion of the neces sa ry quantity of gas energy c a r r i e r so as to achieve the calculated output of the mill . Therefore it was neces sa ry that the p resc r ibed output of the mill, in t e r m s of finished production, be achieved with an unchanged gas consumption.

The basic element determining the effectiveness of operating the gas - je t mill is the grinding unit, in- cluding the injector devices and the grinding chamber i tself . We established the geometr ical dimensions of the grinding unit, and fixed the value of the mill output in t e rms of finished product. The pa rame te r s of the gas before ejection were var ied as follows: t empera tu re 340-650 ~ and p r e s s u r e 3.5-3.8 kg / cm 2. Slag from phosphorus production was the mater ia l being ground.

The charac te r i s t i cs and technical factors of the gas - je t mill a re given in Tables 1 and 2, The best working factors for the mill were achieved with an initial gas p r e s s u r e of 3.7-3.8 kg / cm 2, and a t empera - tu re of 570-650 ~ .

With gas - je t grinding of quartz sand which is widely used as a nonplastic component in ce ramic bod- ies, the output of the mill , other conditions being equal, increases ; while the specific consumption of energy c a r r i e r is reduced by a factor of 1.4-1.5.

The resul ts of test ing prototypes of the gas - je t mill at the Volgograd Ceramic Factory and a i r - j e t mills at the Slavyansk Ceramic Combine [3] showed that there is a reduction in the energy capacity of the je t -mi l l p rocess with a higher specific output f rom the mill as a resul t of using the h igh- tempera ture energy c a r r i e r .

Tables 3 and 4 give the g ra in - s i ze composit ions and specific surface of the original and milled slag respect ively . This shows that the gas - je t method of milling ensures the production of a m o r e uniform (in t e r m s of gra in-s ize) product, content of grains measur ing 10-40~ = 74-87% (63% when grinding in ball- mills) , and the content of the finest f ract ions, 10~, is less by a factor of 2.3-3.6 compared with the p ro - duct ground in a ballmill .

This opens up yet another possibi l i ty for speeding up p rocesses in the manufacture of ce ramics . Ac- cording to data f rom the labora tor ies of the Volgograd Ceramic Factory the use of slags milled by the gas- jet technique would reduce the mois tu re content of the slip and the consumption of e lect rolytes . The slip has a lower congealing capacity and can be s tored for longer per iods. The tiles made f rom slag milled in a gas - je t mill have proper t ies that cor respond in all respec t to the requirements of GOST.

The tes ts made at the Volgograd Ceramic Factory with the gas - je t mill for grinding nonplastics show the advantages of this type of grinding. It improves the quality of the slip, speeds up the p rocess of p re - par ing glazes, and opens up the possibil i ty of creat ing a continuous production technology for ce ramic ti les and completely automating it, which means that we can recommend the method for wide introduction into the ce r amic industry.

At present work is being done to inc rease the output of the gas- je t mill and to reduce the consump- tion of energy c a r r i e r per ton of mil led products; and also labora tory process ing of a production scheme for continuous methods of obtaining tiles and elements for its automatic control are being developed.

i.

LITERATURE CITED

V. I. Gorobets et al., Authors' Patent No. 314545.

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2. V. I. Gorobets, L. Zh. Gorobets, G. P. Tropin, and L. A. Sil'chenko, in: Thermomechanical

Methods of Breaking up Minerals [in Russian], Naukova Dumka, Kiev (1972).

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