Kuva kuri Limestone n’ibumba, ukagera kuri portland unyuze kuri farine crue na clinker: Ibyo wamenya ku nzira zinyurwamo ngo haboneke sima dukoresha mu bwubatsi

Sima ni ifu, ifarine ikomeye ikoreshwa mu bwubatsi, ikaba igikoresho gifasha mu guhuza ibindi bikoresho nk’umucanga n’amabuye kugira ngo bigire imbaraga n’ubudahangarwa.

Amateka yayo agaragaza ko ikoreshwa rya sima ryatangiye kera cyane: Abanyamisiri n’Abanyaroma ba mbere bakoresheje ibikoresho bisa na sima mu kubaka ibibumbano n’inyubako zikomeye. Nyuma y’aho, mu kinyejana cya 19, ni bwo habayeho iterambere rikomeye mu gukora sima ya kijyambere (Portland cement), yatumye ubwubatsi bugera ku rwego rwo hejuru.

Uyu munsi, sima ni igikoresho cy’ingenzi mu kubaka inzu zirmo n’imiturirwa igeretse ibinyacumi by’inzi, imihanda, ibiraro amateme n’ibindi bikorwa remezo, bituma ifatwa nk’umutima w’ubwubatsi bugezweho.

Ni muri urwo rwego iyi nkuru ya Virunga Tiday igamije gusobanura neza uburyo sima ikorwa, kugira ngo twumve aho ikomoka n’impamvu ikomeje kugira agaciro gakomeye mu iterambere ry’ibikorwa remezo.

Ni bihe bikoresho fatizo mu ikorwa rya sima

1. Limestone

Limestone ni ibuye rikize cyane kuri calcium carbonate (CaCO₃), iki kinyabutabire akaba aricyo shingiro mu ikorwa rya sima.

– Gutwika mu itanura: Iyo ritwitswe ku bushyuhe bwa 900–1,000°C, ritanga calcium oxide (CaO). Iyo ubushyuhe bukomeje kugera hejuru ya 1,400–1,450°C, calcium oxide ihuza na silice (SiO₂) n’ibindi bikoresho bikomoka mu ibumba,  bigatanga ibuye rikomeye rizwi ku izina rya clinker..
– Ubuziranenge bwinshi  bwa Limestone (purity ya CaCO₃ iri hejuru ya 80–90%)  nibwo butanga  clinker ikomeye, bityo sima ikaba ifite imbaraga nyinshi kandi iramba.

Limestone kandi yoroshye gutwikwa no gusebwa (broyer) bigatuma yihuza n’ibindi bikoresho mu buryo bworoshye, bigatanga sima ifite imbaraga nyinshi.

Ibiye rya Limestone riboneka henshi ku isi, cyane cyane mu misozi yahoze ari inyanja, rikomoka ku bisigazwa by’ibinyabuzima byo mu mazi nka corals na mollusks. Mu Rwanda, riboneka mu duce nka Gishyita (Karongi) na Mpenge (Musanze) Rusizi ndetse no mu bice byinshi by’intara y’i Burasirazuba.

 

2.Ibumba (clay/shale)

Ibumba ni ibuye (roche) rikomoka ku materiaux yirunze munsi y’ubutaka cyangwa munsi y’amazi (sédiment), rikunze kuba rikize kuri silice (SiO₂), aluminium oxide (Al₂O₃), ndetse rikaba rifite n’utundi duce twa iron oxide (Fe₂O₃) n’ibindi bikoresho bito.

– Uruhare mu itanura: Iyo rivanze na limestone mu bushyuhe bwo hejuru (hejuru ya 1,400°C), rifasha mu gutanga ibinyabutabire bikomeye bigize clinker. Ibumba rifasha mu guhuza neza calcium oxide ikomoka muri limestone n’ibindi bikoresho, rikaba ari ryo ritanga imiterere yihariye ya sima ya Portland.
– Ku isi: ibumba rikomoka ku materiaux yirunze mu butaka cyangwa munsi y’amazi (sédiment), rikaba riboneka cyane mu misozi yahoze ari sedimenti.
– Mu Rwanda: riboneka mu bice bya Musanze, Gakenke, no mu Burasirazuba, aho riboneka mu buryo bworoshye kandi rikaba rihagije ku nganda za sima.

Gypsum

Gypsum ni umunyu wa minerali ukize kuri calcium sulfate dihydrate (CaSO₄·2H₂O). ikaba yongerwa muri  clinker mu gihe cy’isya.
-Akamaro kayo ni ako kugabanya  umuvuduko wa sima mu kwiyumisha. Iyo itaba ihari, sima yahita ikomera vuba cyane, bikagora abayikoresha mu kubaka.

Gypsum iboneka henshi ku isi, cyane cyane mu butaka bwahoze ari inyanja cyangwa mu bice by’amakuzimu y’amabuye. Mu Rwanda, hari ahantu hagiye hagaragara gypsum mu bice by’Uburasirazuba ndetse no mu turere twa Bugesera na Nyagatare, ariko inganda zikenera kenshi kuyikura hanze kugira ngo zibone ingano ihagije.

 

Iron ore

Iron ore ifite akamaro k’ingenzi mu nganda za sima, nubwo ikenerwa mu ngano nkeya ugereranyije na limestone cyangwa ibumba.

Akamaro kayo ni :

– Gutanga oxides z’icyuma (Fe₂O₃, Fe₃O₄): izi zifasha mu guhuza neza calcium oxide (CaO) ikomoka muri limestone na silice (SiO₂) ikomoka mu ibumba, bigatanga clinker ifite imbaraga nyinshi.
– Kongera ubushobozi bwo gutwara ubushyuhe mu itanura: iron ore ituma habaho ikoreshwa neza ry’ingufu mu ruganda rwa sima  kuko igabanya ingufu zikenerwa mu itwika ribera mu ruganda.
– Ituma kandi clinker igira ibara ryijimye ryihariye, ikaba ifite imiterere yihariye yifuzwa mu sima ya Portland.

Ku isi: iron ore iboneka mu misozi y’amabuye yirunze hamwe  mu gihe kirekire (sédiment) cyangwa mu misozi yo mukuzimu.
– Mu Rwanda: hari ahantu hagiye hagaragara iron ore mu bice bya Nyamagabe, Rutsiro, ndetse no mu Burasirazuba, ariko inganda za sima zikenera kenshi kuyikura hanze kugira ngo zibone ingano ihagije.

Pozzolana

Pozzolana ifite akamaro k’ingenzi cyane mu nganda za sima, nubwo idakenerwa mu ngano nyinshi nk’uko limestone cyangwa ibumba bikennerwa

Akamaro ka Pozzolana mu nganda za sima
– Kongera kuramba kwa sima: Pozzolana ifasha sima kurwanya ibyangiza birimo amazi n’imyuka ya sulfate, bigatuma inyubako zidashwanyuka vuba.
– Kugabanya ubushyuhe mu kwiyuma: Iyo sima ikomera, isohora ubushyuhe bwinshi. Pozzolana igabanya ubwo bushyuhe, bigatuma sima idacika cyangwa ngo ishiremo ibyuya mu nyubako zikomeye.
– Kugabanya igiciro: Pozzolana iboneka hafi y’ibirunga, ikaba yoroshye kubona. Iyo yivanze na clinker, igabanya ingano ya clinker ikenerwa, bityo igiciro cya sima kikagabanuka.
– Kongera imbaraga mu gihe kirekire: Nubwo sima ivanze na pozzolana ishobora gutinda gukomera mu minsi ya mbere, mu gihe kirekire iba ifite imbaraga nyinshi kurusha sima isanzwe.
– Kurengera ibidukikije: Kuko pozzolana igabanya ingano ya clinker ikenerwa, igabanya n’ingufu zikoreshwa mu itanura, bityo ikagabanya imyuka ihumanya ikirere (CO₂).

Aho iboneka
– Ku isi: mu bice byahoze ari ibirunga (Italiya, Girisi, Mediterane).
– Mu Rwanda: mu misozi y’ibirunga ya Musanze, Burera, na Rubavu, aho ari igikoresho cyoroshye kuboneka kandi gihagije ku nganda za sima.

Coal (amakara)

Ni igikoresho cy’ingenzi mu gutwika itanura: Coal ikize kuri carbon (C), niyo rikoreshwa nk’isoko y’ingufu mu itanura ry’inganda za sima.
Bityo akamaro kayo ni :
– Gutanga ubushyuhe bukenewe: Mu rugendo rwo gukora clinker, itanura rikeneye ubushyuhe buri hejuru ya 1,400–1,450°C. Amakara ni yo atanga ubwo bushyuhe buri hejuru kandi buhoraho.
– Uko amakara aba afite ubuziranenge bwiza (high calorific value), niko atuma itanura rikora neza, rigakoresha ingufu nke mu kugera ku bushyuhe bukenewe.
– Kubera ko amakara aboneka henshi ku isi, ni igikoresho cyoroshye kubona ku nganda za sima, kandi gifasha mu kugabanya igiciro cy’ingufu.
Ikibazo ku bidukikije:
Nubwo amakara ari ingenzi mu rugendo rwo gukora clinker, ni na yo soko ikomeye y’imyuka ihumanya ikirere (CO₂), bityo inganda nyinshi zikaba zishakisha uburyo bwo kugabanya ikoreshwa ryayo cyangwa kuyisimbuza ingufu zisukuye.

Ku isi: amakara aboneka mu bice byinshi by’isi, cyane cyane mu misozi y’amakuzimu y’amabuye (coal deposits).
– Mu Rwanda: amakara aboneka mu bice bya Nyungwe, Gishwati, ndetse no mu turere twa Burasirazuba, ariko inganda za sima zikenera kenshi kuyikura hanze kugira ngo zibone ingano ihagije n’ubuziranenge bukenewe.

Imirimo yo gutunganya Sima

Mu gihe ibikoresho by’ibanze mu itunganywa rya sima bimaze kugezwa mu ruganda, ibyiciro byyo gutunganya sima ni ibi bikurikira:

Intera ya 1: Kuvanga no gusya ibikoresho fatizo

Igikorwa: Kuvanga limestone, ibumba, iron ore.
kigamijwe: Gutegura imvange y’ibi bikoresho  rifite uburinganire bwiza kugira ngo izatwikirwe neza mu itanura.
Uko bikorwa: Ibikoresho bishyirwa  mu mashini isya (crusher na grinder). Iri vang arikorwa neza ( parfaitement dosé , hakagenwa  urugero rukwiye) mu bikoresho bikurikira:  Carbonate de calcium (CaCO₃) rikomoka muri limestone ( 80%) – Silice (SiO₂) ikomoka mu ibumba ( 20%), Alumine na fer (Al₂O₃ + Fe₂O₃) bikomoka mu ibumba n’iron ore ( ku rugero ruto cyane).
Produit iboneka: Haboneka farine crue (ifu y’ibanze), ifu yoroheje cyane, isa n’umucanga w’umweru cyangwa w’icyatsi cyoroheje.

Intera ya 2: Gutwika mu itanura no gukonjesha clinker

Igikorwa: Gutwika farine crue mu itanura rikagezwa ku bushyuhe bwo hejuru ( calcination) , rigahinduka clinker, hanyuma igakonjeshwa.
 Ikigamijwe: Guhindura farine crue mu clinker, shingiro rya sima.
Uko bikorwa: Farine crue itwarwa mu itanura rigezweho (rotary kiln), rigashyirwaho ubushyuhe bwa 1,400–1,450°C hakoreshejwe coal ( amakara) . Calcium oxide (CaO) ihuza na silice, alumina na fer, bigatanga clinker. Nyuma yo gutwika, clinker ihita ikonjeshwa n’umuyaga cyangwa izindi mashini zigezweho (coolers), ikabikwa mu bubiko.
Produit iboneka: Haboneka clinker ishingiro rya sima, akaba ari   amabuye mato y’umukara cyangwa yijimye, asa nk’utubumbe tw’amabuye twum. Clinker  agizwe n’amasilicate , alumina na ferrite ya calcium, kandi buri kinyabutabire gifite uruhare mu guha sima imbaraga, kuramba, no kwiyumisha mu gihe gikwiriye.

Intera ya 3: Kongeramo gypsum

Igikorwa: Kongeramo gypsum mbere yo gusya clinker.
 Ikigamijwe: Kugenzura ukwiyumisha kwa sima (setting time).
Uko bikorwa: Gypsum yongerwa mu rugero ruto (3–5%) kugira ngo sima ijye itinda  gukomera,  bityo byorohe mu ikoreshwa ryayo.
Produit: Haboneka clinker ivanze na gypsum.Ni ifu yoroheje ariko itaragera ku rwego rwa sima, ikaba igizwe na clinker n’utuvanze twa gypsum.

Intera ya  4: Kongeramo pozzolana (amahitamo)
Igikorwa: Kongeramo pozzolana mbere  gusya clinker.
Ikigamijwe: Kugabanya igiciro, kongera kuramba kwa sima, no kugabanya ingaruka ku bidukikije.
Uko bikorwa: Pozzolana ivangwa na clinker na gypsum mu gihe cyo gusya.
Produit: Haboneka ivange rya clinker, gypsum na pozzolana: Ifu yoroheje, isa n’umucanga w’umweru cyangwa w’icyatsi cyoroheje, ikaba ifite imbaraga mu gihe kirekire.

Ni byiza cyane, reka twubake paragraphe yihariye kuri etape ya 5: Gusya clinker hakaboneka sima ya Portland, kuko ari cyo gikorwa cya nyuma cy’ingenzi mu rugendo rwa technique.

Intera ya 5: Gusya clinker hakaboneka sima ya Portland

 Igikorwa: Gusya imvange ya clinker (rimaze gukonjeshwa) hamwe na gypsum, ndetse na pozzolana niba ikenewe.
 Ikigamijwe: Kubona ifu yoroheje cyane yitwa sima ya Portland, ikoreshwa mu kubaka ibikorwa remezo bikomeye.
 Uko bikorwa: Clinker ivanze na gypsum (3–5%) ishyirwa mu mashini agasya (cement mill). Iyo pozzolana ikenewe, nayo ivangwa muri iri gikorwa . Mashini isya iyi vange kugeza ribaye ifu yoroheje cyane.
Produit: Haboneka sima ya Portland, ifu y’umweru cyangwa y’icyatsi cyoroheje, yoroheje cyane, ikaba ifite imbaraga zo kubaka ibikorwa remezo bikomeye. Iyi sima iba igizwe n’amasilicate, alumina na ferrite ya calcium, byaturutse muri clinker, bikagenzurwa n’urugero rwa gypsum, ndetse bikongerwa imbaraga n’uruhare rwa pozzolana niba yifashishijwe.

Icyitonderwa

Grinding cement ni isima  iboneka hifashishijwe clinker yakuwe hanze mu gihe portland cement isanzwe ikorwa mu nganda zifite itanura rikorerwamo clinker imbere mu gihugu.

Igikorwa gitanga clinker ni igikorwa gikomeye cyane cyiharira 70% by’akazi kose mu nganda za sima. Mu Rwanda , ni nkaho inganda zikora gusa grinding cement,  bivuze ko 70%  by’imirimo yo gutunganya sima ikorerwa hanze, isigaye ingana na 30% akaba ariyo ikorerewa mu Rwanda.

Gusa kuri mu Rwanda hari umushinga munini wo kubaka uruganda rukora clinker imbere mu gihugu, uzatuma igihugu kitongera gukoresha cyane clinker ikuwe hanze.  CIMERWA irateganya gushora hafi miliyoni $190 (Rwf275 miliyari) mu mushinga wo kubaka uruganda  ruzakora clinker, uru ruganda rukazubakwa  mu karere ka Musanze, rukazajya rukora toni 60,000 za clinker ku kwezi. Ibi bizagabanya cyane amafaranga igihugu cyoherezaga hanze hatumizwa clinker.