EI CIT .14/IIJR/84

Page

37

of the same planned,rate of grov-rtb. beyoYlcl tlle errd of tIle Plan Period can be accepted as reasoTI201e in the a0s~n6e of an alternative proposal.

In certain ,cases⁹ inc~.ea.~t.~g.._tl'l~§.._~~...g~rQJtl..t.,h....~r~J....-!~~~S ~iJhi.cll_..&.r.edee.med ..--to be

• • .••.••• _ _ _ .. _.~__ •.•••.•• _ , • • . • • • • • • •"T".~:.0..;., _ . . .._ _- •..•~~ '" ...

on the·-·lo~v·,side..~..Gt.fte·r ..~l:l.e el~d of the Flan Period, I.:~~_n also be justified.

For exa-nlpl-e-9" ·the:···grovvth· ..·rc. te of the EthioI.ii&JJ...Pl::-an of-4.•·-J7~·-i,s lower than

·the···-target set by···t-b.e"·Unite--d--Na'ti'ons Develb'l~illent'-"necfa'ae"9'-'-~in;ich--'is'51~~~"'''-''

. Consequently after the 611.d of the Plan Period

(1967),

the lil'i11ilnUlTI annual rate of grolfltll of

590

has been assuflled for tlJ.e period

1967-1975.

A

~ reassessrne'·nt.. of the I(enya DGvelol~j1l1erit 1-Ian is already ta,::cing';~place with -- ··cf:--· ..view ;·t-e:···iricTe_a:s'ing~,·...;-t·_:~.e-' ass^Ufi1ed 'grovrt^h

r a"te

^t·(j'· 'soni'e "6%'~'

....·.._··..

Th-:ls·:;:r;a·~-.e--·

ria's

been assumed fortlie period

1970-1'975.

FirlallY9 for those countries⁹ which either ITave not ela'borated an ..e.GQnornic ...develol:)lllent plan or vlh:ere gr-owth rates ha-ve" 110t been CJ..uantified? tl'le rnini,.lUln rate of

5.6%

^set'by

the ,Utlite.d N'ations Develo;IIlent DelJade haf:3beenassUlned.

8~. Acco~ding to the estimation of Table

5.2,

the averabe _compo~nded anhUalrate of ~'roliJtll'of tlle ~ast .African Sub-reg'ion as a 1'Jhole would be in ~he r~gioh of~9.2%, or a per capita rate

bf

growth of 607%.

These rates of' 2;rOvJth lllig}lt aj)pear to be on the hig11 side if cOlIlpared t.o· trends over th.e l:~~t· five years. Tiley are⁹ h01,v'ever? l011er than the rates of ;rowthnoted in earlier ye&~s within the sub-region, and are·more or less cOillpati~le to those noted for the whole period of

1948-1963

(see Tables

4.1

and

4.2).

It i~ also interesting to compare the rates of (.'Srovrth of C8luent I,.IonslliIll:tion ootc;.ined for the sub-region to those' corresponding to rapidly developing countries in other regions.

Data

on

the total alld IJer cepita consuIllption of" ^C81118nt for I11dia, Brazil1 Greece₉ and the USSR covering the period

1950-1960

are sum~

marized in Table 5-3 below.

E/

CI~.14/II~R/84 Page

38

Table

5.3

Grovrbh of Cement ConsuLlJ;::tion in Selecte,d Co~tri~-;oftheiv-orld'

~.. ~- ..,. -,.--'--_._~.-_.__

._---

~_.----Country Consurnption ^f000 tons AnnLlalRate of Growth

Per Capita Cons~rnp­

tion Annual rate

of Growth

"195° 1960

1950

1960

India

2671 7717 ^11.2 7 ¹⁸ 9·9

Brazil 1780 4442 9.6 ₃₄ 63 6·4

Greece -393

1571 14·9 52 ¹⁹¹ 13.9

10164 16.1

^:.

.-''-~,:.

14.8

USSR 45270 53

²¹¹

Source·~ "WorldCemerrt I\1arket in Figures

1913-1962"?

^Gembureau

~~

--87.

^{'Countries with a} per capita COY1sulnption of cenlent within

the

range of those observ~~c:_ in the c01.lntries of tl'18 su-b-region have .in....

creased\tlleir cons-urJf tion at annual rates of 10 to over 16%. vIith these qualifying remarks₉ the estimates of expected demand of cement by,

1975

can be cOLsid.erecl'as t'easona.l)le assessments of tIle possi'ble expansiol1 of ooneum~ptions, wi tllin ti'le fralrle~vorl( of tl18 overall economic development of the su-O-region.'

88.

A further valid argument that could justij'iaJJly 08 l:ut forward in this C011text is that there is arnple sccf,e for stimulating increased consumption of cernellt. In this rege rd₉ t.b.e expallsiorl of tIle cement based- industries, and sutJstitl:ltion of otl:lCI' mel rials by Ccfil0-nt an.d cemant based pro~usts in oVGrall building a~d construct~onwould raise the relati^VG in-c3Dsi "\TJTI\.:SS of C0Givnt utilization. This aspc~Gt of the

coment r2Ld alliGd indu:3tri :s ;.lill bo tal<:Gn LJ.pag>gip latcr (see Chapter VI) ^G

89.

_~ comparison of total rrojected deInal1d for the sub-region, which would be of the order of

3.5

million tons by

1975

(~abla

5.

2 ), and present

(1965)

installed capacity within the sub-region, which is of

the order

of

1.8 million tons (Table 2.1), shows that

there

would be

a short fall of

1.7

Inilliol"l tons by

1975,

Tllis cOinput<_tion obviously asswnes tllSt t118 rresent installed capacity of tIle sub-region viill be fully utilized in

1975.

This 1nib'ht ^11.0t in practice be realized due

E/

C'N'.14!I111t/84 Page 39

to one or another or a combinatfbn'~f reasons such _as~ for example, uneconomic hau.?-at:?e ~ist~,nces ?etr'een.A,prod1},yi,pg, and n0l}Tproducing coun-tries. The e~~~mate

the minimwn Q~der the

shQr,t fallSl1ould~ tp.e+.efore, b.econsidered as

. .'..".~. '.. ~:~.. '..' .... ~.."~':. ". .~-~:'.::=-..,.._-.~~~;-~~:..~ . '.

cirCDclllstal1Ces. '~lithin the next decade present day installed C2i-iaci_t~I 'vJould have, to ,'be doubli~:a according'to ,t,he

projected estimate of demand in

1975.

Towards the realization of this

$,oall) however, tl18 salie11t fa<Jtores governing' tl'le develo:IHnent of

the

industry lllUSt be exaJ:Lined.

E/CN.14/INR/84

Page

40 '.

CHAPTER VI J

Basic Con~~i~~!~~.~9ns__~E_,.the ,.8x~3,nsion of

the

Cement Ind~~trl in the Ea~i~A.f~.?:.b·an·Sub-region (a) Raw ~1ate.~~ial and Other Input Resources

90. The

process in the manufacture of Portland

Cement

involves burning a finely ground mixture containing calculated qu'an'tities of lime, silica, alumina and iron oxide at high temperature. The lime, which usually

accounts for approximately

80

per cent of t,he rnixture,may be obtained from limestone, chalk, coral, etc_, and the main source of the required silica, alumina and iron and oxide is shale or clay.

91.

Limestone and clay are usually quarrried, ground and blende~j either

by the wet process? which involves mixing in a

slurry

or by the

dry

process, wherein the dry powders are blended. However_J other variations in the

details of processing occur, and semi-dry methods are occasionally used.

In these cases slurries of raw-mixture may be nedulized at about 11 to

15

per cent water content and ei tb.er fed in this state or dried and partly

calcined

on a moving grate through which the gases of

combustion

are expelled.

92.

The factor determining by and large between the wet and dry processes is the water content of the primary raw material. If the water content is high, the wet process is usually chosen. If the water content is very low, the dry process is preferred. Between these two extremities, there is no

hard and fast

rule to decide between one process

or the

other.

In

the

past

the wet process was preferred because it produced more uniform cement than the dry process. This is no longer the case. Dry process equipment can be designed to produce cement which is homogeneous. The following major points enter in the final decision~ the wet process consumes 20 to

25

per cent more fuel per ton than the dry process and very cheap fuel may favour the adoption of the wet processJ. conswnption of power is less

(4-8

per cent) in the wet process~ initial fixed investment costs are about 10 per cent more in the dry process than in the wet process? and less dust is generally

released in the wet process. lI

11

^{Studies in} ~conomics of IndustrY9 United Nations

1963.

•

•

E/CN~14/INR/84 Page

41

93.

The sequence in

the

luanufactlITebf I'ortland" cement can be. summarized as follows. In _~he wet _proce~s, the' wet _·mixtur~ is fed into a slightly sloping rotary kiln, fired at the' lower· and by pulverized coal (charcoal can also be used) or by oil or by gas. The· slurry passes .;throug'h three diff.erentstagE3s a.s it travels by g'ravity f:rom one end of the kiln to the o;ther1 ' first <the ^I.TI..qistur.e i·s~ d,riven. off.9 second the clay is dehydrated and thelimes.tone decomposes into c.ar"Q.on dioxi~o an~ StuicklimG; a.rt.d ~hird, the var·ious·cbi.emicals combine at white heat to form clinker. After c,ooling, the, clinker i-s .fine.Iy g'roU;Ild ,in mills, with the addition .,of some

3-5

per c:e;nt. "of gy~p.s~~:;.to,cQn1;;:rol< .s,E(tting·, and thus become :~h~ or.dinary Portland cement..of·eo.m;merc~,,·whicp-. if? g;enerally .~xpedit~d in p.ap~r bags, but also

in:bulkers'direc~ly,to

con&truotion

sites •

. 94.

,cGeneraily"1.

6

tons :ofl·iIIle'ston·e and

0.3

tons':of cl.ay ':are requir,ed per ·t"011~of the'-"finished

product'.

^'The transport'~problem.andcost .involved in . the'

'movement 6:r

suctl','bulk materials

is

'serious and considerable,' which is

why' cement

is essentially 'a resource..Ltied commodity. The

development

of··the'·'~·iildusiry therefor·e "demands the·availability of these·:basic ,direct

~;'11iatefials"i{l':adequate'quantities and of the a.opropriate quality. "By and

large'it

would'appear that

in the countries of the

sub~region,

the expansion

Dans le document The cement and allied industries in the East African Sub-Region (Page 42-46)