DK172101B1

DK172101B1 - Process and installation for producing mineralised cement clinkers

Info

Publication number: DK172101B1
Application number: DK024894A
Authority: DK
Inventors: Hans Erik Borgholm
Original assignee: Smidth & Co As F L
Priority date: 1994-03-03
Filing date: 1994-03-03
Publication date: 1997-10-27
Also published as: DK24894A

Description

i DK 172101 B1in DK 172101 B1

Opfindelsen angår en fremgangsmåde og et anlæg til fremstilling af mineraliserede cementklinker, som omfatter opberedning af råmel for eksempel ved findeling, homogenisering og/eller tørring af råmaterialer, hvorefter råmelet forvarmes, kal-5 cinéres og brændes, for til sidst at blive afkølet.The invention relates to a method and plant for the production of mineralized cement clinkers which comprises the preparation of raw flour, for example by comminution, homogenization and / or drying of raw materials, after which the raw flour is preheated, calcined and burned, to be eventually cooled.

Fra britisk patent nr. 1 498 057 kendes en fremgangsmåde til fremstilling af mineralisexede klinker. Ved denne fremgangsmåde tilsættes fluor og svovl, almindeligvis i form af CaF2 og CaS04, 10 til råmaterialerne inden de underkastes blanding og eventuel formaling. Det tilstræbes at opnå et fluor indhold på ca. 0,25 % og et S03 indhold på ca. 2,5 %. Fremgangsmåden i dette skrift er rettet mod anvendelse i en roterovn af vådtypen, der var meget udbredt i 1975, men som idag anses for yderst uøkonomisk 15 på grund af de store energimængder, der bruges til tørring og det har vist sig at være særdeles vanskeligt at overføre metoden til nye og energimæssigt økonomiske ovnsystemer med forvarmer og kalcinator.British Patent No. 1,498,057 discloses a process for producing mineralized clinker. In this process, fluorine and sulfur, usually in the form of CaF2 and CaSO4, are added to the feedstock before being subjected to mixing and optional grinding. We aim to achieve a fluorine content of approx. 0.25% and a SO3 content of approx. 2.5%. The method of this publication is directed to use in a wet-type rotary kiln, which was widely used in 1975, but which today is considered extremely uneconomical due to the large amounts of energy used for drying and has proved to be extremely difficult to transfer the method to new and economically economical oven systems with preheater and calciner.

20 Så på trods af de meget store forbedringer i cementkvaliteten der kan opnås (se f eks Moir, Phil Trans Roy Soc, 1983, A310) med metoden ifølge britisk patent nr. 1 498 057, er det bemærkelsesværdigt, at den har vundet så ringe udbredelse. Dette skyldes formodentligt, at der er driftmæssige vanskelig-25 heder ved at udføre fremgangsmåden, både med hensyn 'til at styre produktionen af klinker og med hensyn til påbagninger i cykloner og stigrør.20 So despite the very large improvements in cement quality that can be achieved (see, e.g., Moir, Phil Trans Roy Soc, 1983, A310) with the method of British Patent No. 1,498,057, it is notable that it has won so little dissemination. This is probably due to the fact that there are operational difficulties in carrying out the process, both with regard to controlling the production of clinker and with regard to the baking of cyclones and riser pipes.

Formålet med opfindelsen er således at anvise en fremgangsmåde 30 og et anlæg til fremstilling af mineraliserede cementklinker, hVor anlægget er af en sådan type, at forvarmning og en del af kalcinering foregår udenfor ovnen og hvor man undgår de problemer, der er i forbindelse med den kendte teknik.The object of the invention is thus to provide a method 30 and a plant for the production of mineralized cement clinkers, where the plant is of such a type that preheating and part of calcination takes place outside the furnace and where the problems associated with it are avoided. prior art.

35 En første driftsvanskelighed er at finde ud af hvordan man kan regulere mængden af tilsat mineralisator og samtidigt opnå den nødvendige homogenitet i råmelet. Af britisk patent nr. 1 498 057 fremgår det, at mineralisatoren blandes med råmaterialerne DK 172101 B1 2 inden disse brændes (side 5, linie 89 - side 6, linie 43).35 A first operating difficulty is figuring out how to regulate the amount of mineralizer added and at the same time achieve the necessary homogeneity in the raw flour. British Patent No. 1 498 057 states that the mineralizer is mixed with the raw materials DK 172101 B1 2 before burning them (page 5, line 89 - page 6, line 43).

Såfremt mineralisatoren tilsættes på denne måde, sikrer man ganske vist en stor homogenitet, men det er ikke muligt at 5 udføre en hurtig regulering af mængden af tilsat mineralisator i forhold til råmaterialerne og på denne måde styre driften af ovnen og de færdige cementklinkers egenskaber, da mineralisatoren udgør en fast procentdel af den samlede mængde af råmaterialer.If the mineralizer is added in this way, a high homogeneity is assured, but it is not possible to perform a rapid regulation of the amount of added mineralizer relative to the raw materials and thus control the operation of the furnace and the properties of the finished cement clinker, since the mineralizer constitutes a fixed percentage of the total quantity of raw materials.

1010

Specielt ved fremstilling af mineraliserede klinker med højt indhold af sulfat kan det være vanskeligt at styre temperaturvariationer i brændezonen. Dette skyldes at sulfaten har tendens til at dekomponere til S02 i brændezonen og kondensere 15 i de koldere dele af ovnen. Når brændezone temperaturen øges, øges fordampningen af S02. Dette medfører forhøjede koncentrationer af sulfater i de koldere dele af ovnen og det kan blive så galt, at videre ovndrift bliver umulig på grund af ringdannelser i ovnen eller påbagninger efter ovnen, hvis sulfat-20 tilførslen fra råmelet ikke kortvarigt reduceres eller helt indstilles.Especially when producing mineralized clinker containing high sulfate content, it can be difficult to control temperature variations in the burn zone. This is because the sulfate tends to decompose to SO 2 in the burn zone and condense 15 in the colder parts of the furnace. As the burn zone temperature increases, the evaporation of SO2 increases. This results in elevated concentrations of sulphates in the colder parts of the furnace and it may become so wrong that further furnace operation becomes impossible due to ring formation in the furnace or baking after the furnace if the sulphate supply from the feedstock is not shortened or completely stopped.

Med fremgangsmåden ifølge opfindelsen, som angivet i krav 1, undgår man disse problemer, da det er muligt at bruge mængden 25 af tilsat mineralisator som en regulerbar parameter ved fremstillingen af de mineraliserede klinker, hvorved man kan forhindre situationer med stærkt varierende koncentrationer af forskellige stoffer i brændezonen i at opstå. Samtidigt har det vist sig, at det ikke er nødvendigt med nogen særlig homogeni-30 sering af råmel og mineralisator, når mineralisatoren tilsættes on-line.The method according to the invention, as claimed in claim 1, avoids these problems, since it is possible to use the amount 25 of added mineralizer as an adjustable parameter in the preparation of the mineralized clinker, thereby preventing situations with widely varying concentrations of different substances. in the burn zone of arising. At the same time, it has been found that no special homogenization of raw flour and mineralizer when the mineralizer is added on-line.

Eventuelt kan man vælge at tilsætte en del af mineralisatoren til råmelet inden formaling og homogenisering, og bruge den 35 resterende del af den nødvendige mængde af mineralisator til at styre processen med. I nogle tilfælde vil råmaterialerne have et naturligt indhold af mineralisator, men såfremt indholdet ikke er for højt, kan det fortsat lade sig gøre at styre procesforløbet ved mineralisatortilsætning.Optionally, one may choose to add a portion of the mineralizer to the raw flour prior to grinding and homogenizing, and use the remaining portion of the required amount of mineralizer to control the process. In some cases, the raw materials will have a natural mineralizer content, but if the content is not too high, it can still be possible to control the process of mineralizer addition.

3 DK 172101 B13 DK 172101 B1

En anden driftsvanskelighed, som er velkendt ved brænding af almindelige klinker af Portland cement med et højt indhold af 5 mineralisator, særligt S03 og F, i råmelet, er dannelsen af faste udfældninger eller påbagninger når materialet passerer et temperaturområde på omkring 700-900eC. Årsagen er formodentligt at mineralisatoren katalyserer dannelsen af spurrit (2C2S *CaC03).Another operating difficulty well known in burning ordinary clinker of Portland cement with a high content of 5 mineralizer, especially SO3 and F, in the feedstock, is the formation of solid precipitates or coatings when the material passes a temperature range of about 700-900eC. The reason is probably that the mineralizer catalyzes the formation of spurrite (2C2S * CaCO3).

10 I amerikansk patent nr. 5.183.506 har man valgt at løse dette problem ved at anvende en særlig gipsblanding.In U.S. Patent No. 5,183,506, this problem has been resolved by using a special plaster mixture.

For at reducere eller helt undgå problemerne med påbagninger 15 kan mineralisatoren hensigtsmæssigt tilsættes til det trin hvor kalcineringen starter, det vil sige efter at råmelet er forvarmet til mere end 700'C. Herved sikrer man, at der ikke opstår tilstopninger og påbagninger i forvarmercyklonerne og stigrørerne mellem cyklonerne.To reduce or completely avoid the problems of baking 15, the mineralizer may conveniently be added to the step at which the calcination starts, that is, after the raw flour is preheated to more than 700 ° C. This ensures that no clogging and baking occurs in the preheater cyclones and riser pipes between the cyclones.

2'2 '

Herved undgår man desuden problemer med at få råmelet til at bevæge sig jævnt igennem forvarmeren, da råmelets flydeegenskaber kan blive væsentligt dårligere, når mineralisatoren tilsættes før forvarmeren, afhængigt af hvilken mineralisator 25 der vælges.This also avoids problems with the raw flour moving smoothly through the preheater, as the flow properties of the raw flour can become significantly poorer when the mineralizer is added before the preheater, depending on which mineralizer 25 is selected.

Mineralisatoren kan i et forkalcineringsanlæg med efterfølgende køler, så som en ristekøler endvidere hensigtsmæssigt tilsættes tertiærluftledningen, hvorigennem opvarmet luft ledes fra 30 køleren til kalcinatoren. Luften i tertiærluftledningen sørger ved denne løsning for transport af mineralisatoren til kalcinatoren .Furthermore, in a pre-calcination system with subsequent cooler, such as a shaker cooler, the mineralizer may also be suitably added to the tertiary air line through which heated air is conducted from the cooler to the calciner. The air in the tertiary air conduit provides this solution for transporting the mineralizer to the calciner.

Eventuelt kan mineralisatoren først tørres i overskudsluft fra 35 køleren, hvorefter den tilsættes tertiærluftledningen.Optionally, the mineralizer can first be dried in excess air from the cooler and then added to the tertiary air line.

Som mineralisator kan anvendes et ikke-brændbart svovlholdigt produkt og sammen med dette kan eventuelt anvendes et hjæl DK 172101 B1 4 pestof indholdende fluor eller kobber- eller zinkoxid. Ofte vil det dog ikke være nødvendigt at tilsætte et sådant hjælpestof, fordi det allerede er tilstede i råmaterialerne.As a mineralizer a non-combustible sulfur-containing product can be used and together with this an auxiliary pesticide containing fluorine or copper or zinc oxide may optionally be used. Often, however, it will not be necessary to add such an excipient because it is already present in the raw materials.

5 Det ikke-brændbare svovlholdige produkt kan blandt andet være et sulfat-, sulfit- eller sulfidholdigt afsvovlingsprodukt fra røggasrensning, gips (CaS04· 2H20), hemihydrat (CaS04· ^jHjO) , anhydrit (CaS04) eller andre svovlholdige mineraler indeholdende calcium eller magnesium.The non-combustible sulfur-containing product may include, among other things, a sulfate, sulfite or sulfide-containing desulphurisation product from flue gas purification, gypsum (CaSO 4 · 2H 2 O), hemihydrate (CaSO 4 · 2 .

1010

Afsvovlingsprodukterne opstår når røg f.eks fra kraftværker renses for S02. Ved semitør røggasafsvovling produceres et restprodukt af calciumsulfit og -sulfat, som endvidere kan indeholde flyveaske og andre bestanddele. Ved moderne våde af-15 svovlingsmetoder kan der produceres en meget ren gips, der dog i første omgang foreligger som en våd slam eller filterkage.The desulfurization products occur when, for example, smoke from power plants is purified for SO2. In semi-flue gas desulphurization, a residual product of calcium sulphite and sulphate is produced, which may also contain fly ash and other constituents. In modern wet desulfurization methods, a very clean plaster can be produced, but initially available as a wet sludge or filter cake.

Det sidstnævnte produkt kan efter tørring afsættes til f.eks gipspladefremstilling eller anvendes i stedet for naturgips til 20 fremstilling af cement på den måde, at det samformales med klinkerne i cementmøllen. Det afsvovlingsprodukt, der fremkommer ved semitør afsvovling, har for tiden ikke fundet nogen udbredte anvendelser, og deponering af det er endvidere vanskeligt på grund af produktets uheldige rheologiske egen-25 skaber.The latter product can, after drying, be deposited for, for example, gypsum board manufacture or used instead of natural gypsum for the manufacture of cement in that it is co-milled with the clinker in the cement mill. The desulfurization product resulting from semi-desulphurisation has at present found no widespread uses, and depositing it is moreover difficult due to the unfortunate rheological properties of the product.

Et andet interessant restprodukt, er den anhydrit, forurenet med CaF2 og H2S04, som opstår ved fremstilling af flussyre ud fra flusspat og svovlsyre.Another interesting residual product is the anhydrite, contaminated with CaF2 and H2SO4, which is produced by the production of hydrofluoric acid from fluoride and sulfuric acid.

3030

Et tredje restprodukt kan i fremtiden opstå, når asbest skal destrueres: det er foreslået at opløse det i flussyre (HF) og dernæst neutralisere med brændt kalk, hvorved <3er fremkommer et produkt bestående af MgO, Si02, CaF2 og noget CaS04.2H20. Endelig 35 kan mulighederf for at anvende phospho-gips (dvs. det gips der er restproduktet fra - fremstilling af phosphorsyre ud fra råphos-phat og svovlsyre) overvejes.A third residual product may arise in the future when asbestos is to be destroyed: it is proposed to dissolve it in hydrofluoric acid (HF) and then neutralize with burnt lime, resulting in <3s a product consisting of MgO, SiO2, CaF2 and some CaSO4.2H20. Finally, the possibility of using phospho-gypsum (i.e., the gypsum from which the residual product - production of phosphoric acid from crude phosphate and sulfuric acid) can be considered.

DK 172101 B1 5DK 172101 B1 5

Med fremgangsmåden ifølge opfindelsen er det nu muligt at sluse disse affaldsprodukter ind i cementfremstillingsprocessen på en hensigtsmæssig måde, da det har vist sig, at de omtalte driftsvanskeligheder kan undgås når affaldsprodukterne ikke 5 opberedes sammen med råmelet, men doseres separat til processen.With the method according to the invention, it is now possible to incorporate these waste products into the cement-making process in an appropriate manner, since it has been found that the mentioned operating difficulties can be avoided when the waste products are not stored together with the raw material but are dosed separately for the process.

Opfindelsen forklares nærmere i det følgende under henvisning til tegningen, som viser et udførelseseksempel på opfindelsen.The invention is explained in more detail below with reference to the drawing which shows an exemplary embodiment of the invention.

ioin Island

Tegningen viser et cementovnsanlæg af almindelig kendt type, der omfatter en forvarmer 1, som på figuren udgøres af tre cykloner, en kalcinator 2 med en udskillecyklon 3 og en roterovn 4 med klinkerkøler 5.The drawing shows a cement kiln plant of the prior art comprising a preheater 1, which in the figure is comprised of three cyclones, a calciner 2 with a separator cyclone 3 and a rotary kiln 4 with clinker cooler 5.

1515

Fremstillingen af cement i et anlæg som dette foregår ved, at cementråmel tilføres ved indløbet 13 øverst i forvarmeren 1 og ledes gennem denne i modstrøm med røggassen fra ovnen 4 og kalcinatoren 2. Røggassen bringes op gennem forvarmeren 1 og ud 20 ved 14 ved hjælp af en ikke vist røggasventilator. Råmelet ledes fra forvarmeren 1 via en ledning 7 ned i kalcinatoren 2, hvor det kalcineres og i suspension føres videre til udskille-cyklonen 3. Her udskilles det kalcinerede råmel fra røggassen og ledes ved hjælp af en ledning 6 til roterovnen 4, hvor 25 råmelet ved hjælp af varme fra brænderen 9 brændes til klinker. Klinkerne falder herefter ned i køleren 5, hvor de afkøles med luft. En del af den herved producerede varme luft går til roterovnen, en anden del gennem tertiærluftledningen til kalcinatoren. Resten af den i køleren indblæste køleluft 30 bortledes ved 10.The production of cement in a plant like this takes place by supplying cement raw flour at the inlet 13 at the top of the preheater 1 and passing through it countercurrently with the flue gas from the furnace 4 and the calciner 2. The flue gas is brought up through the preheater 1 and out 20 at 14 by means of a flue gas fan not shown. The raw flour is passed from the preheater 1 via a conduit 7 into the calciner 2, where it is calcined and in suspension is passed to the separator cyclone 3. Here the calcined raw flour is separated from the flue gas and is passed by means of a conduit 6 to the rotary kiln 4, where the raw flour using heat from burner 9 burns to clinker. The tiles then fall into the cooler 5, where they are cooled with air. Part of the hot air thus produced goes to the rotary kiln, another part through the tertiary air conduit to the calciner. The remainder of the cooling air blown in the cooler is discharged at 10.

Et let håndterligt ikke-brændbart svovlprodukt på pulverform, som kun indholder sulfat og som ikke ødelægger råmelets flydeegenskaber, kan principielt tilsættes overalt efter at 35 råmelet har forladt det lager, hvor det er blevet opbevaret og eventuelt homogeniseret, og gennem et doseringsapparat er tilført processen.In principle, an easily manageable non-combustible sulfur powder product containing only sulfate and which does not destroy the flow properties of the raw material can, in principle, be added anywhere after the raw material has left the store where it has been stored and possibly homogenized, and through the dosing apparatus is added to the process. .

DK 172101 B1 6DK 172101 B1 6

Et mere vanskeligt håndterligt svovlprodukt, som f.eks det der kan fremkomme ved afsvovling af røggas, kan hensigtsmæssigt tilsættes kalcinatoren enten direkte via ledningen 12 eller ved at tilsætte mineralisatoren til tertiærluftledningen 8 via 5 ledningen 11, således at mineralisatoren transporteres af den varme luft fra køleren til kalcinatoren.A more difficult to handle sulfur product, such as that which may be produced by flue gas desulphurization, may conveniently be added to the calciner either directly via line 12 or by adding the mineralizer to the tertiary air line 8 via line 5, so that the mineralizer is transported by the hot air from the the cooler for the calciner.

Når mineralisatoren således sendes ind i kalcinatoren og den efterfølgende udskillecyklon, vil kalcinatoren og cyklonen virke som en blandemaskine og forårsage en meget fin fordeling 10 af S03 i råmelsstrømmen.Thus, when the mineralizer is sent into the calciner and the subsequent excreting cyclone, the calciner and cyclone will act as a mixer, causing a very fine distribution of SO3 in the feed stream.

Indeholder restproduktet svovl i et lavere oxidationstrin f.eks sulfit eller sulfid, kan det hensigtsmæssigt tilsættes ved 11 og 12 for at disse svovlforbindelser kan blive oxideret til 15 sulfat i kalcinatoren. Ved tilsætning ved 13 vil der dannes en smule S02, som kommer med røggassen.If the residual product contains sulfur in a lower oxidation step, for example sulfite or sulfide, it may conveniently be added at 11 and 12 for these sulfur compounds to be oxidized to sulfate in the calciner. Upon addition at 13, a little SO2 will be formed which comes with the flue gas.

Hvis det findes nødvendigt at cøire mineralisatoren inden anvendelsen kan der udtages varm overskudsluft fra køleren ved 20 10, som kan anvendes i et vilkårligt tørreapparat.If it is necessary to run the mineralizer before use, hot excess air can be withdrawn from the cooler at 20 10, which can be used in any dryer.

Claims

A process for producing mineralized cement, which comprises preparing raw flour, for example by comminution, homogenization and / or drying, after which the raw flour is preheated, calcined and burned to finally be cooled. , after the feedstock is dosed for the process and before the feedstock has passed through the burn zone. 10

Process according to claim 1, characterized in that the mineralizer is dosed to the raw flour after the raw flour is preheated to more than 700 ° C.

3. A method according to claim 2, characterized in that the mineralizer is dosed to the tertiary air line passing from the cooler to the calciner.

4. A process according to claims 1-3, characterized in that the mineralizer is a non-combustible sulfur-containing product, for example gypsum, hemihydrate, anhydrite or other sulfur-containing minerals containing calcium or magnesium.

5. A process according to claims 2-3, characterized in that the mineralizer is a non-combustible sulfur-containing product, for example a sulfate, sulfite or sulfide-containing desulphurisation product from flue gas purification.

A process for disposal of a non-combustible sulfur-containing product during the simultaneous production of mineralized cement, which comprises the preparation of raw flour, for example by comminution, homogenization and / or drying, after which the raw material is preheated, calcined and burned to eventually be cooled FEATURE that the non-combustible sulfur-containing product is added to the feedstock after the feed is dosed for the process and before the feed has passed through the burn zone. DK 172101 B1 8

Process according to claim 6, characterized in that the non-combustible sulfur-containing product is a waste product which is obtained, for example, by desulphurisation of flue gas.

8. Plant for the production of mineralized clinker, comprising an approach for prepared raw flour, a preheater, a calciner, an oven, and a cooler FEATURED THAT the plant has an approach (11,12,13) for a mineralizer located after that point , to which raw flour is dosed. 10

Installation according to claim 6, characterized in that the inlet (11,12) for the mineralizer is located after the preheater (1).

Plant according to claim 7, characterized in that the inlet (11) for the 15 mineralizer is located in the tertiary air line (8).