FI91270C

FI91270C - Process for the preparation of titanium dioxide pigment

Info

Publication number: FI91270C
Application number: FI883782A
Authority: FI
Inventors: Antti Veikko Lahti; Keijo Jaanu; Juho-Pertti Jalava
Original assignee: Kemira Oy
Priority date: 1988-08-15
Filing date: 1988-08-15
Publication date: 1994-06-10
Also published as: GB2221901A; FI883782A0; DE3925833A1; GB8918500D0; FI883782A; FI91270B; GB2221901B

Description

i 91270i 91270

Menetelmå titaanidioksidipigmentin valmistamiseksiA process for preparing a titanium dioxide pigment

Keksinto koskee menetelmåå titaanidioksidipigmentin valmis-5 tamiseksi, jossa a) raaka-aineen sisåltåmå kiinteå titaanidioksidi muutetaan titaaniyhdisteeksi, joka on ei-kiinteåsså olotilassa, b) epåpuhtaudet erotetaan titaaniyhdisteestå, c) titaaniyhdiste saostetaan, 10 d) syntynyt titaaniyhdiste kiteytetåån hydrotermisesti puh-taaksi titaanidioksidiksi hapossa låmmon ja paineen avulla, ja e) puhdas titaanidioksidi erotetaan haposta ja jålkikåsitel-låån tarvittaessa lopullisen titaanidioksidipigmentin ai-15 kaansaamiseksi.The invention relates to a process for the preparation of a titanium dioxide pigment, in which a) the solid titanium dioxide contained in the raw material is converted into a titanium compound in a non-solid state, b) the impurities are separated from the titanium compound into the titanium compound, c) the titanium compound is precipitated in the acid by heat and pressure, and e) the pure titanium dioxide is separated from the acid and further treated, if necessary, to obtain the final titanium dioxide pigment ai-15.

Rutiili- ja anataasikidemuodoissa esiintyvåå pigmenttititaa-nidioksidia (Ti02) valmistetaan kaupallisesti kahdella mene-telmållå; sulfaattimenetelmållå ja kloridimenetelmållå.Pigment titanium dioxide (TiO 2) in rutile and anatase crystal forms is prepared commercially by two methods; by the sulphate method and the chloride method.

2020

Sulfaattiprosessissa hienoksi jauhettu, kuivattu ilmeniitti (FeTi03, joka sisåltåå 40-60 % Ti02:a) ja/tai titaanidioksi-dikuona (synteettisesti ilmeniitistå rikastettua kuonaa, joka sisåltåå 72-87 % Ti02) annetaan reagoida rikkihapon 25 kanssa, jolloin syntyy pååasiassa titanyylisulfaatista (Ti0S04) ja rautasulfaatista (FeS04) koostuva reaktiokakku, joka sitten liuotetaan veden ja valmistusprosessin mydhem-mistå vaiheista palautettujen happoliuosten seokseen. Liuos kåsitellåån pelkiståvållå aineella kuten rautaromulla lås-30 nåolevien ferri-ionien pelkiståmiseksi ferroioneiksi. Pel-kistystå seuraavan selkeytyksen ylite johdetaaan kiteytys-vaiheeseen, jossa liuos jååhdytetåån niin pitkålle, ettå huomattava osa liuoksen sisåltåmåstå raudasta kiteytyy fer-rosulfaattiheptahydraattina, joka poistetaan liuoksesta.In the sulphate process, finely ground, dried ilmenite (FeTiO 3 containing 40-60% TiO 2) and / or titanium dioxide slag (synthetically enriched slag from ilmenite containing 72-87% TiO 2) is reacted with sulfuric acid (mainly sulphate 25). TiSO 4) and ferrous sulfate (FeSO 4), which is then dissolved in a mixture of water and acid solutions recovered from the mydhem steps of the manufacturing process. The solution is treated with a reducing agent such as ferrous scrap to reduce the Ferri ions present to ferro ions. The excess from the clarification following the reduction is passed to a crystallization step in which the solution is cooled to such an extent that a considerable part of the iron contained in the solution crystallizes as ferrous sulphate heptahydrate, which is removed from the solution.

35 Liuos våkevoidåån haihduttamalla ja hydrolysoidaan titanyy-lisulfaatin muuttamiseksi liukenemattomaksi titaanioksohyd-raatiksi, joka suodatetaan ja peståån. Liukenematon yhdiste kalsinoidaan noin 900-1 000°C:n låmpdtilassa rutiili- tai 2 anataasityyppiseksi titaanidioksidiksi. Kalsinointituote jålkikåsitellåån sopivilla jauhatus-, pesu-, kuivaus- ja påållystysvaiheissa hienojakoiseksi ja homogeeniseksi rutii-li- tai anataasityyppiseksi, kaupalliseksi titaanidioksidi-5 pigmentiksi.The solution is concentrated by evaporation and hydrolyzed to convert titanyl sulfate to insoluble titanium oxohydrate, which is filtered and washed. The insoluble compound is calcined at a temperature of about 900-1000 ° C to titanium dioxide of the rutile or 2 anatase type. The calcination product is post-treated in suitable grinding, washing, drying and coating steps to a finely divided and homogeneous rutile or anatase type commercial titanium dioxide-5 pigment.

Kloridiprosessissa kåytetåån puhtaampaa raaka-ainetta, jon-ka Ti02-pitoisuus on yleenså 80-95 paino-%. Raaka-aine se-koitetaan puhtaaseen, hienojakoiseen koksiin ja kloorataan 10 kloorikaasun avulla. Sivutuotteena muodostuu malmin epåpuh-tauksista pååasiallisesti kiinteåå ferrokloridia, joka ero-tetaan titaanitetrakloridista esim. syklonin tapaisen erot-timen avulla. Titaanitetrakloridi erotetaan kloorikaasusta kondensoimalla ja puhdistetaan tislauksen ja kemiallisen 15 kåsittelyn avulla. Puhdistettu titaanitetrakloridi syotetåån hoyrystimen ja esikuumentimen kautta hapetuslaitteistoon, jossa se poltetaan hapen tai hapella rikastetun ilman avulla titaanidioksidiksi, joka on pååasiassa rutiilityyppistå. Hapetuslaitteistoon sydtetty polttokaasu on esikuumennettu 20 noin 1 000°C:een ja laitteistoon syotetåån reaktion edistå-miseksi myds hiekkaa sekå pienempiå mååriå hiilivetyjå. Hiekka erotetaan, kuivataan ja luokitellaan ennen polttojår-jestelmåån palauttamista. Saatu rutiilityyppinen titaani-dioksidi jålkikåsitellåån sopivissa jauhatus-, pesu-, kui-25 vaus- ja påållystysvaiheissa ennen kuin se on valmis kaupal-linen tuote.The chloride process uses a purer raw material with a TiO2 content of generally 80-95% by weight. The raw material is mixed with pure, finely divided coke and chlorinated with chlorine gas. As a by-product, the impurities in the ore form mainly solid ferric chloride, which is separated from the titanium tetrachloride, e.g. by means of a cyclone-like separator. Titanium tetrachloride is separated from chlorine gas by condensation and purified by distillation and chemical treatment. The purified titanium tetrachloride is fed via an evaporator and a preheater to an oxidizer where it is burned with oxygen or oxygen-enriched air to titanium dioxide, which is mainly of the rutile type. The fuel gas injected into the oxidation plant is preheated to about 1,000 ° C and fed to the plant myds sand as well as smaller amounts of hydrocarbons to promote the reaction. The sand is separated, dried and graded before being returned to the incineration system. The resulting rutile-type titanium dioxide is post-treated in appropriate grinding, washing, drying and coating steps before being finished into a commercial product.

Koska edellå mainitut titaanidioksidipigmenttien valmistus-menetelmåt ovat monivaiheisia ja kuuluvat kemian teollisuu-30 den vaikeimpiin prosesseihin, alalia on tunnettu suurta kiinnostusta uusiin prosesseihin ja olemassa olevien proses-sien parannuksiin. US-patenttijulkaisu 4 107 264 koskee pa-rannettua menetelmåå titaanidioksidin erottamiseksi ilme-niittityyppisistå malmeista, jossa malmi uutetaan vesipitoi-35 seen fluorivetyhappoon, syntyneestå liuoksesta erotetaan rautaepåpuhtaudet, hydratoitu titaanidioksidi saostetaan raudattomasta liuoksesta ammoniumhydroksidin avulla ja sakka kalsinoidaan titaanidioksidipigmentin saamiseksi. Japanilai- 3 91270 nen patenttijulkaisu 6 317 221 esittåå alkalisten ionien stabiloimien, kiteisten anataasityyppisten titaanidioksidi-solien valmistamista kåsittelemållå vesiliukoisia titaaniyh-disteitå alkalimetallien hydroksidien, karbonaattien ja/tai 5 ammoniumsuolojen kanssa geelin muodostamiseksi, minkå jål-keen geeli kåsitellåån hydrotermisesti yli 100°C:n låmpoti-lassa. Julkaisun esimerkin mukaan titaanitetrakloridin ve-siliuos kåsiteltiin ammoniumhydroksidilla geelin muodostamiseksi. Pesun jålkeen geeliin sekoitettiin lisåå ammonium-10 hydroksidia ja kåsiteltiin sitten hydrotermisesti 160°C:ssa. Tuloksena saatiin anataasityyppisiå kiteitå sisåltåvåå ti-taanidioksidisolia.Because the aforementioned methods of making titanium dioxide pigments are multi-step and are among the most difficult processes in the chemical industry, there is great interest in the field for new processes and improvements to existing processes. U.S. Patent No. 4,107,264 relates to an improved process for separating titanium dioxide from rhodium-type ores, in which the ore is extracted into aqueous hydrofluoric acid, the resulting solution is separated from iron solution to precipitate iron oxide, and the hydrated titanium dioxide is precipitated from a non-ferrous solution of ammonium. Japanese Patent No. 3,912,701 discloses the preparation of alkaline ion stabilized crystalline anatase-type titanium dioxide sols by treating water-soluble titanium compounds with alkali metal hydroxides, carbonates and / or ammonium salts over a gel to form a gel. n låmpoti-lassa. According to an example of the publication, an aqueous solution of titanium tetrachloride was treated with ammonium hydroxide to form a gel. After washing, additional ammonium-10 hydroxide was mixed into the gel and then hydrothermally treated at 160 ° C. As a result, titanium dioxide diol containing anatase-type crystals was obtained.

Edellå mainitusta kahdesta julkaisusta ilmenee, ettå pigmen -15 tiksi jatkojalostuskelpoista titaaniyhdistettå voidaan saos-taa liuoksesta ammoniakin tai ammoniumhydroksidin avulla. US-patenttijulkaisu esittåå kuitenkin tållaisen saostuksen kåyttåmistå fluorivetyhappoon uutetun titaanin talteenotta-miseksi, jolloin saostettu tuote kalsinoidaan, ja JP-patent-20 tijulkaisu kohdistuu pelkåståån alkalisten ionien stabiloimien titaanidioksidisolien valmistukseen. Siten nåmå jul-kaisut eivåt kykene ratkaisemaan nykyisisså kaupallisissa menetelmisså esiintyviå ongelmia, jotka mm. liittyvåt kal-liiden ja energiaa vaativien kalsinointi- ja polttovaiheiden 25 kåyttoon.It appears from the above two publications that the pigment -15 can be further precipitated from a solution of titanium compound with ammonia or ammonium hydroxide. However, U.S. Pat. No. 4,092,607 discloses the use of such a precipitate to recover titanium extracted into hydrofluoric acid, whereby the precipitated product is calcined, and JP Patent Publication No. 20 is directed solely to the preparation of alkali ion-stabilized titanium dioxide sols. Thus, these publications are not able to solve the problems encountered in the current commercial methods, which e.g. related to the use of expensive and energy-intensive calcination and combustion steps 25.

Esillå olevan keksinnon tarkoituksena on aikaansaada mene-telmå ja laite, jonka avulla mainitut ongelmat voidaan rat-kaista. Keksinnolle on tålloin pååasiassa tunnusomaista se, 30 mitå sanotaan patenttivaatimusten tunnusosassa. On siis oi-vallettu, ettå titaanidioksidivalmistusta voidaan parantaa siten, ettå vaiheen (c) saostus suoritetaan alle 30°C:n låm-pdtilassa; vaiheessa (d) hydroterminen kiteytys suoritetaan låmpdtilassa alle 300°C, paineessa alle 100 baaria ja happo-35 konsentraation ollessa alle noin 15 paino-%; ja titaanidiok-sidista vaiheessa (e) erotettu happo kierråtetåån takaisin hydrotermiseen kiteyttåmisvaiheeseen (d), jolloin saadaan pigmentin valmistukseen sopivia titaanidioksidikiteitå.The object of the present invention is to provide a method and an apparatus by means of which said problems can be solved. The invention is then mainly characterized by what is stated in the preamble of the claims. Thus, it has been found that the titanium dioxide production can be improved by carrying out the precipitation of step (c) at a temperature below 30 ° C; in step (d) the hydrothermal crystallization is carried out at a temperature below 300 ° C, at a pressure below 100 bar and at an acid-35 concentration of less than about 15% by weight; and the acid separated from the titanium dioxide in step (e) is recycled back to the hydrothermal crystallization step (d) to give titanium dioxide crystals suitable for pigment preparation.

44

Hydroterminen kiteytysvaihe on periaatteessa sovellettavissa kaikkiin titaanidioksidipigmenttien valmistusmenetelmiin, joissa suoritetaan titaaniraaka-aineen faasinmuutos, sen pesuoperaatio ja konvertoiminen titaanidioksidiksi. Tållai-5 sia menetelmiå ovat mm. edellå mainitut sulfaatti-, kloridi-ja fluorivetyprosessit. Erityisen edullisia ovat tålldin pa-rannetut sulfaatti- ja kloridimenetelmåt. Sulfaattimenetel-måsså rutiilin valmistus edellyttåå, ettå alkiottomaan muo-toon saostettu titaanihydraattimassa neutraloidaan esim.The hydrothermal crystallization step is in principle applicable to all processes for the preparation of titanium dioxide pigments in which the phase change of the titanium raw material, its washing operation and its conversion into titanium dioxide are carried out. Such methods include e.g. the aforementioned sulfate, chloride and hydrogen fluoride processes. Particularly preferred are the improved sulfate and chloride methods of the general. In the sulphate process, the preparation of rutile requires that the titanium hydrate mass precipitated in the non-embryonic form is neutralized e.g.

10 ammoniakilla ennen sen hydrotermistå kiteytystå. Kloridi-menetelmåsså hydrotermisen kiteytyksen edellytyksenå on, ettå sitå edeltåvå saostusvaihe suoritetaan alkalilla, kuten alkalihydroksidilla, alkalikarbonaatilla, ammoniumhydroksi-dilla ja/tai heikon orgaanisen hapon suolalla, tai laimenta-15 malla vedellå.10 with ammonia before its hydrothermal crystallization. In the chloride process, the hydrothermal crystallization requires that the precipitation step preceding it be carried out with an alkali such as alkali hydroxide, alkali carbonate, ammonium hydroxide and / or a salt of a weak organic acid, or diluted with water.

Esillå olevan keksinndn mukainen menetelmå merkitsee hanka-lan ja kalliin poltto- tai kalsinointivaiheen korvaamista paremmalla vaiheella kaikissa titaanidioksidipigmentin val-20 mistusprosesseissa, joissa on tållaiset vaiheet. Keksinnon suojapiiriin kuuluvat siten kaikki titaanidioksidin valmis-tusprosessien, edullisesti sulfaatti- ja kloridiprosessien variantit siten, ettå tavanomaiset titaaniyhdisteen kalsi-nointi- ja polttovaiheet on korvattu hydrotermisellå kitey-25 tysvaiheella.The process of the present invention involves the replacement of the cumbersome and expensive incineration or calcination step with a better step in all titanium dioxide pigment production processes with such steps. The invention thus covers all variants of the titanium dioxide production processes, preferably the sulphate and chloride processes, such that the conventional steps for calcination and combustion of the titanium compound have been replaced by a hydrothermal crystallization step.

Keksinndn eråån edullisen suoritusmuodon mukainen kloridi-prosessi kåsittåå ensimmåisenå vaiheena korkealaatuisen raa-ka-aineen kloorauksen kloorikaasun avulla koksin låsnåolies-30 sa. Raaka-aineena voi olla mikå tahansa puhdas titaanidiok-sidiraaka-aine, kuten synteettinen tai luonnosta peråisin oleva rutiili (95 paino-% Ti02) ja/tai leukokseeni/hyvin puhdas ilmeniitti ja/tai hyvin puhdas titaanioksidikuona. Yleenså voidaan sanoa, ettå sopiva kloridiprosessin raaka-35 aineen titaanidioksidipitoisuus on vålillå 80-95 paino-%.The chloride process according to a preferred embodiment of the invention comprises, as a first step, the chlorination of a high-quality raw material by means of chlorine gas in the presence of coke. The raw material can be any pure titanium dioxide raw material, such as synthetic or naturally occurring rutile (95% by weight TiO 2) and / or leukoxene / very pure ilmenite and / or very pure titanium oxide slag. In general, it can be said that a suitable titanium dioxide content of the raw material of the chloride process is between 80 and 95% by weight.

Raaka-aine sekoitetaan jauhettuun, erittåin puhtaaseen kok-siin ja klooraus suoritetaan tyypillisesti leijukerrosreak-torissa edullisesti låmpåtilassa 850-1 100°C.The raw material is mixed with ground, very pure coke and the chlorination is typically carried out in a fluidized bed reactor, preferably at a temperature of 850-1,100 ° C.

5 912705,91270

Kloorauksen tuloksena syntyy eksotermisessa reaktiossa raa-kaa titaanitetrakloridia, joka normaaliolosuhteissa on nes-temåinen titaaniyhdiste, mutta reaktio-olosuhteissa kaasu-muodossa. Sivutuotteena muodostuu malmin epåpuhtauksista 5 pååasiallisesti ferrokloridia. Kloorausreaktorin poisto joh-detaan kiintoaine-erottimeen, joka on esim. sykloni ja jossa kiinteåt epåpuhtaudet erotetaan kaasuista. Jååhdyttåmållå kaasua låmpotilaan, joka on juuri titaanitetrakloridin kie-humispisteen ylåpuolella, voidaan kondensoida pois suurin 10 osa muista haihtuvista klorideista, kuten raudan, mangaanin ja kromin kloridit. Pååasiassa titaanitetrakloridista ja kloorikaasusta koostuva reaktiokaasu johdetaan sitten kon-densaatiojårjestelmåån, jossa tltaanltetrakloridl kondensoi-tuu nestemåiseen muotoon ja josta kloorikaasut ohjataan 15 edelleen niiden talteenotto- ja puhdistusyksikkddn. Titaani-tetrakloridi puhdistetaan kolonnitislauksen ja kemiallisen kåsittelyn avulla, jolloin mm. vanadiinin tapaiset metallit erottuvat.The chlorination results in the exothermic reaction to give crude titanium tetrachloride, which is normally a liquid titanium compound, but under the reaction conditions in gaseous form. As a by-product, mainly ferrochloride is formed from the ore impurities. The removal of the chlorination reactor is carried out to a solid separator, which is e.g. a cyclone, where solid impurities are separated from the gases. By cooling the gas to a temperature just above the boiling point of titanium tetrachloride, most of the other volatile chlorides, such as iron, manganese and chromium chlorides, can be condensed off. The reaction gas, which consists mainly of titanium tetrachloride and chlorine gas, is then introduced into a condensing system in which the tetrane tetrachloride condenses into a liquid form and from which the chlorine gases are passed on to their recovery and purification units. Titanium tetrachloride is purified by column distillation and chemical treatment, whereby e.g. vanadium-like metals stand out.

20 Sitten puhdistettu titaanitetrakloridi saostetaan esillå olevan keksinndn mukaisesti esim. ammoniakilla (ammonium-hydroksidilla), natriumasetaatilla, natriumoksalaatilla, tai laimentamalla vedellå kiinteåksi tuotteeksi. Saostus tapah-tuu mielellåån ammoniumhydroksidilla, jonka konsentraatio on 25 10-40 paino-%, edullisesti n. 20-30 paino-%. Låmpdtilaa ei tarvitse nostaa eikå laskea, vaan se on alle 30°C, esim. huoneenlåmpdtila. Saadulle sakalle suoritetaan hydroterminen kiteytys korotetussa låmpdtilassa ja paineessa laimealla, edullisesti epåorgaanisella hapolla, joka voi olla esim.The purified titanium tetrachloride is then precipitated according to the present invention, e.g. with ammonia (ammonium hydroxide), sodium acetate, sodium oxalate, or diluted with water to a solid product. The precipitation is preferably carried out with ammonium hydroxide in a concentration of 10 to 40% by weight, preferably about 20 to 30% by weight. The temperature does not need to be raised or lowered, but is below 30 ° C, eg room temperature. The precipitate obtained is subjected to hydrothermal crystallization at elevated temperature and pressure with a dilute, preferably inorganic acid, which may be e.g.

30 suolahappo, typpihappo, rikkihappo tai fluorivetyhappo. Ha-pon konsentraatio on alle noin 15 paino-%, edullisesti vå-lillå 3-7 paino-%. Låmpdtila on alle 300°C, edullisesti vå-lillå 180-280°C. Paine on alle 100 baaria, edullisesti 5-100 baaria, vielå edullisemmin 5-50 baaria. Nåisså olosuhteissa 35 kiteiden kasvatusaika on edullisesti 1-24 h, vielå edullisemmin vålillå 6-16 h. Hydroterminen kiteytys suoritetaan paineastiassa, johon lisåtåån kiinteå titaaniyhdiste ja laimea 6 happo. Laimea happo voidaan helposti ottaa talteen ja kåyt-tåå oleellisesti sellaisenaan uudestaan, mikå tekee hydro-termisestå kiteytyksestå paitsi edullisen myos ympåristdys-tåvållisen prosessivaiheen. Edellå kuvatulla menetelmållå 5 saadaan titaanidioksidin kidekooksi noin n. 100-300 nm, edulli-sesti 150-250 nm, joten tavanomaisessa prosessissa vålttåmå-ton karkea jauhatusvaihe voitaneen jåttåå pois.30 hydrochloric acid, nitric acid, sulfuric acid or hydrofluoric acid. The acid concentration is less than about 15% by weight, preferably between 3 and 7% by weight. The temperature is below 300 ° C, preferably between 180-280 ° C. The pressure is less than 100 bar, preferably 5-100 bar, even more preferably 5-50 bar. Under these conditions, the growth time of the crystals is preferably 1 to 24 hours, more preferably 6 to 16 hours. The hydrothermal crystallization is carried out in a pressure vessel to which a solid titanium compound and a dilute 6 acid are added. The dilute acid can be easily recovered and reused substantially as such, which makes hydrothermal crystallization not only a preferred but also an environmentally friendly process step. By the method 5 described above, the crystal size of the titanium dioxide is about 100-300 nm, preferably 150-250 nm, so that the coarse grinding step necessary in the conventional process could be omitted.

Edellå kuvatun kloridimenetelmån kiteytyksen olosuhteista ja 10 kåytetystå haposta riippuen voidaan saada puhdasta rutiilia. Suolahapolla saatavan rutiilin Ti02-pitoisuus on låhes 100 %. Valmistettaessa rutiilia kåytetåån edullisesti suola-ja/tai typpihappoa, kun taas anataasin valmistuksessa voidaan kåyttåå my6s rikki- ja fluorivetyhappoa. Nykyåån on 15 tavallista, ettå titaanidioksidin valmistusprosessista saa-tava peruspigmentti xnodifioidaan pintakåsittelyprosessilla sen pigmenttiominaisuuksien parantamiseksi. Tåsså vaihtoeh-toisessa, tekniikan tason mukaisessa vaiheessa saostetaan alumiinin, piin, titaanin ja muiden aineiden yhdisteitå ti-20 taanidioksidihiukkasten pinnalle. Lisåaineiden suhteet ja påållysteen kokonaismåårå såådetåån pigmentin kutakin kåyt-totarkoitusta vårten.Depending on the crystallization conditions of the chloride process described above and the acid used, pure rutile can be obtained. The TiO2 content of rutile obtained with hydrochloric acid is almost 100%. In the preparation of rutile, hydrochloric and / or nitric acid is preferably used, while sulfuric and hydrofluoric acid can also be used in the preparation of anatase. It is now common for the basic pigment obtained from the titanium dioxide production process to be xnodified by a surface treatment process to improve its pigment properties. In this alternative step according to the prior art, compounds of aluminum, silicon, titanium and other substances are precipitated on the surface of the titanium dioxide particles. The proportions of the additives and the total amount of coating are adjusted for each use of the pigment.

Kloridiprosessin lopuksi pigmentti kuivataan ja jauhetaan 25 hienoksi ennen sen pakkaamista såkkeihin.At the end of the chloride process, the pigment is dried and finely ground before packing in sacks.

Keksinnon toisen vielå edullisemman suoritusmuodon mukaisen, parannetun sulfaattiprosessin ensimmåisesså vaiheessa hienoksi jauhettu, kuivattu ilmeniitti tai titaanioksidikuona 30 panostetaan suuriin reaktoreihin, joissa eksoterminen reak-tio rikkihapon kanssa kåynnistetåån nostamalla seoksen låm-pdtilaa tulistetun hoyryn avulla. Reaktiolåmpdtila on titaa-niraaka-aineesta riippuen noin vålillå 150-180°C. Reaktio-tuote saadaan kiinteån, huokoisen kakun muodossa, joka liuo-35 tetaan veden ja valmistusproséssin mydhemmistå vaiheista palautettujen happoliuosten seokseen. Liuottamisen tuloksena saadaan titanyylisulfaatin (Ti0S04) ja rautasulfaattien liuos.In the first step of the improved sulphate process according to another even more preferred embodiment of the invention, finely ground, dried ilmenite or titanium oxide slag 30 is charged to large reactors in which an exothermic reaction with sulfuric acid is initiated by raising the temperature of the mixture to superheated heat. The reaction temperature is between about 150-180 ° C, depending on the titanium raw material. The reaction product is obtained in the form of a solid, porous cake which is dissolved in a mixture of water and acid solutions recovered from the milder steps of the manufacturing process. Dissolution gives a solution of titanyl sulphate (TiSO 4) and ferrous sulphates.

7 912707 91270

Mikåli ilmeniittiå kåytetåån raaka-aineena, ensimmåisestå vaiheesta saatu liuos pelkistetåån edullisesti rautaromun avulla 3-arvoisen raudan muuttamiseksi 2-arvoiseksi. Pelkis-5 tys viedåån niin pitkålle, ettå pieni osa liuoksen 4-arvoi-sesta titaanista saadaan 3-arvoiseksi, mikå takaa sen, ettei 3-arvoista rautaa saostu my6hemmin prosessissa. Liukenematta jååneet epåpuhtaudet poistetaan selkeyttåmållå suurissa såi-lidisså, edullisesti selkeytysapuaineita hyvåksi kåyttåen.If ilmenite is used as a raw material, the solution obtained from the first step is preferably reduced by means of ferrous scrap to convert the 3-valued iron to the 2-valued. The reduction is carried out to such an extent that a small part of the 4-valent titanium in the solution becomes 3-valent, which ensures that the 3-valent iron does not precipitate later in the process. Undissolved impurities are removed by clarification in large scavengers, preferably using clarification aids.

10 Alite eli jåtemutaliete suodatetaan ja peståån liukoisen titaanin talteenottamieksi. Selkeytyksen ylite joutuu kitey-tysvaiheeseen, jossa liuos jåådytetåån niin pitkålle, ettå huomattava osa liuoksen sisåltåmåstå raudasta kiteytyy ferrosulfaattiheptahydraattina. Kiteytetty liuos suodate-15 taan tarvittaessa ja våkevoidåån mahdollisesti tyhj6haihdu-tuksella. Siten saatu liuos siirretåån saostussåilioihin, joissa titaani saatetaan kiinteåån muotoon hydrolyysin avulla.10 The alite, or waste sludge, is filtered and washed to recover soluble titanium. The clarification excess is subjected to a crystallization step in which the solution is frozen to such an extent that a considerable part of the iron contained in the solution crystallizes as ferrous sulfate heptahydrate. The crystallized solution is filtered if necessary and, if necessary, concentrated by evaporation. The solution thus obtained is transferred to precipitation tanks in which titanium is solidified by hydrolysis.

- 20 Hydrolysoitu titaanihydroksidisakka erotetaan, peståån ja uutetaan tarvittaessa rikkihapossa pelkiståvisså olosuhteis-sa viimeistenkin epåpuhtauksien poistamiseksi.- The hydrolyzed titanium hydroxide precipitate is separated, washed and, if necessary, extracted in sulfuric acid under reducing conditions to remove the final impurities.

Tåhån vaiheeseen saakka rutiilin ja anataasin valmistusmene-25 telmåt ovat identtiset, mutta jatkossa menetelmåt eroavat toisistaan. Massaan voidaan tarvittaessa lisåtå pieniå måå-riå lisåaineita, jotka hydrotermmisesså kiteytyksesså ai-kaansaavat haluttaessa anataasia tai rutiilia. Keksinnfin mukaisessa menetelmåsså rutiilia valmistetaan edullisesti 30 siten, ettå titaanihydraattimassa neutraloidaan ammoniakilla (ammoniumhydroksidilla), minkå jålkeen loppuun neutraloitu titaanihydraattisuspensio kiteytetåån hydrotermisesti. Anataasin valmistuksessa tållainen neutralointi ammoniakilla ei ole vålttåmåt5n.Up to this stage, the methods for preparing rutile and anatase are identical, but in the future the methods will be different. If necessary, a small amount of additives can be added to the pulp, which in hydrothermal crystallization provide anatase or rutile if desired. In the process according to the invention, rutile is preferably prepared by neutralizing the titanium hydrate mass with ammonia (ammonium hydroxide), after which the completely neutralized titanium hydrate suspension is crystallized hydrothermally. In the production of anatase, such neutralization with ammonia is not necessary.

88

Puhdistettu ja mahdollisesti kåsitelty titaanihydroksidimas-sa kiteytetåån sitten hydrotermisesti kåsittelemållå se ko-rotetussa, mutta kohtuullisessa låmpdtilassa ja paineessa laimealla, edullisesti epåorgaanisella hapolla, joka voi 5 olla esim. suolahappo, typpihappo, rikkihappo tai fluorive-tyhappo. Hapon konsentraatio on alle noin 15 paino-%, edullisesti vålillå 3-7 paino-%. Låmpotila on alle 300°C, edullisesti vålillå 180-280°C. Paine on alle 100 baaria, edullisesti 5-100 baaria, kaikkein edullisiiranin 5-50 baaria. Nåis-10 så olosuhteissa kiteiden kasvatusaika on 1-24 h, edullisesti vålillå 6-16 h. Hydroterminen kiteytys suoritetaan paineas-tiassa, johon lisåtåån titaanihydroksidi ja laimea happo. Laimea happo otetaan talteen ja kierråtetåån sellaisenaan hydrotermiseen kiteytykseen. Edellå kuvatulla menetelmållå 15 saadaan låhes pigmentin laatuista titaanidioksidia, joten tavanomaisessa prosessissa vålttåmåton karkea jauhatusvaihe voidaan jåttåå pois.The purified and optionally treated titanium hydroxide mass is then crystallized by hydrothermal treatment at elevated but moderate temperature and pressure with a dilute, preferably inorganic acid, which may be e.g. hydrochloric acid, nitric acid, sulfuric acid or hydrofluoric acid. The concentration of the acid is less than about 15% by weight, preferably between 3 and 7% by weight. The temperature is below 300 ° C, preferably between 180-280 ° C. The pressure is less than 100 bar, preferably 5-100 bar, most preferably 5-50 bar. Under these conditions, the growth time of the crystals is 1 to 24 hours, preferably 6 to 16 hours. The hydrothermal crystallization is carried out in a pressure vessel to which titanium hydroxide and dilute acid are added. The dilute acid is recovered and recycled as such to the hydrothermal crystallization. The process 15 described above gives almost pigment-grade titanium dioxide, so that the coarse grinding step which is essential in a conventional process can be omitted.

Sulfaattiprosessin lopuksi hydrotermisesså kiteytyksesså 20 kåytetty laimea happo dekantoidaan ja/tai suodatetaan pois ja sakka peståån tarvittaessa vedellå. Tuotteelle suoritetaan sopivat jauhatus-, pesu-, kuivaus- ja påållystysvaiheet ja valmis kaupallinen titaanidioksidipigmentti pakataan.At the end of the sulphate process, the dilute acid used in the hydrothermal crystallization is decanted and / or filtered off and the precipitate is washed with water if necessary. The product is subjected to suitable grinding, washing, drying and coating steps and the finished commercial titanium dioxide pigment is packaged.

25 Seuraavassa esitetåån ero tavallisten titaanidioksidin klo-ridi- ja sulfaattiprosessien sekå keksinnfin eråiden suori-tusmuotojen mukaisten kloridi- ja sulfaattiprosessien vålillå prosessien eri vaiheita suurin piirtein esittåvien lohko-kaavioiden avulla. Keksinndn mukaiset menetelmåt voivat tie-30 tenkin sisåltåå lisåvaiheita ja/tai korvaavia vaiheita tai niiltå voi puuttua vaiheita.The following is a distinction between conventional titanium dioxide chloride and sulfate processes and between the chloride and sulfate processes of some embodiments of the invention using block diagrams that roughly show the different stages of the processes. However, the methods according to the invention may include additional steps and / or replacement steps or may lack steps.

9 912709 91270

Titaanidioksidin valmistus kloridimenetelmållå; menetelmien vertailu 1. Titaanioksidin (rutiili) 2. Titaanidioksidin 5 valmistus nykyisellå klori- kloridihydroterminen diprosessilla (Kemira Inc) valmistusmenetelmåPreparation of titanium dioxide by the chloride method; Comparison of methods 1. Production of titanium oxide (rutile) 2. Production of titanium dioxide 5 by the current chloride-chloride hydrothermal diprocessing process (Kemira Inc)

Raaka-aineiden kåsittely Raaka-aineiden kåsittely i i 10 Klooraus eli TiCl4 Klooraus eli TiCl4 valmistus (1000-1040°C) valmistus (1000-1040°C) i iProcessing of raw materials Processing of raw materials i i 10 Chlorination or TiCl4 Chlorination or TiCl4 production (1000-1040 ° C) production (1000-1040 ° C) i i

Kondensointi Kondensointi i 4 15 Raaka titaanitetrakloridi Raaka titaanitetrakloridi 4 4Condensation Condensation i 4 15 Crude titanium tetrachloride Crude titanium tetrachloride 4 4

Puhdistus Puhdistus 4 iCleaning Cleaning 4 i

Titaanitetrakloridin h5y- Vedellå laimennetun titaa- 20 rystys ja esilåmmitys nitetrakloridin saostus (150°C<T<500°C) alkalilla kiinteåksi ti- taaniyhdis teeks i 4 iTitanium tetrachloride h5y- Liquidation of water-diluted titrate and preheating of tetrachloride precipitation (150 ° C <T <500 ° C) with alkali to a solid titanium compound 4 i

Hapen esikuumennus <1800°C Pestyn, kiinteån titaani- 25 titaanitetrakloridin hapetusta yhdisteen hydroterminen vårten kiteytys hapossa i iOxygen preheating <1800 ° C Oxidation of washed solid titanium tetrachloride hydrothermal crystals of the compound in acid i i

Titaanitetrakloridin poltto Jålkikåsittely yli 1000°C:n låmpåtilassa 30 "hiekkap01y"-polttimessa i Jålkikåsittely 10Combustion of titanium tetrachloride Post-treatment at temperatures above 1000 ° C in a 30 "sand burner" i Post-treatment 10

Titaanidioksidin valmistus sulfaattimenetelmållå; menetelmien vertailu 1. Titaanioksidin (rutiili tai 2. Titaanidioksidin 5 anataasi) valmistus nykyi- sulfaattihydroterminen sellå sulfaattiprosessilla valmistusmenetelmåPreparation of titanium dioxide by the sulphate process; comparison of methods 1. Preparation of titanium oxide (rutile or 2. titanium dioxide 5 anatase) current sulphate hydrothermal by the sulphate process

Raaka-aineiden kåsittely Raaka-aineiden kåsittely 4 4 10 Uuttaminen rikkihappoon Uuttaminen rikkihappoon 4 4Handling of raw materials Handling of raw materials 4 4 10 Extraction into sulfuric acid Extraction into sulfuric acid 4 4

Liuoksen pelkistys Liuoksen pelkistys 4 4Reduction of the solution Reduction of the solution 4 4

Liuoksen selkeytys ja Liuoksen selkeytys ja 15 puhdistus puhdistus i 4Solution clarification and Solution clarification and 15 purification purification i 4

Liuoksen våkevdinti Liuoksen mahdollinen våkevointi 4 i 20 Hydrolyyttinen saostus Hydrolyyttinen saostus 4 4Concentration of the solution Possible concentration of the solution 4 i 20 Hydrolytic precipitation Hydrolytic precipitation 4 4

Suodatus ja pesu Suodatus ja pesu 4 4Filtration and washing Filtration and washing 4 4

Kalsinointi Hydroteminen kiteytys 25 laimeassa hapossa 4 4 Jålkikåsittely Jålkikåsittely 30 Esimerkki 1Calcination Hydrotemic crystallization in 25 dilute acids 4 4 Post-treatment Post-treatment 30 Example 1

Laimennettua titaanitetrakloridia saostettiin alle 30°C:n låmpdtilassa 25-%:isella ammoniumhydroksidilla kiinteåksi titaaniyhdisteeksi.Diluted titanium tetrachloride was precipitated at 25 ° C with 25% ammonium hydroxide to give a solid titanium compound.

35 16 g kyseistå massaa ja 1,5 g suolahappoa annosteltiin paine- kapseliin, jossa ne sekoitettiin homogeeniseksi suspensioksi.35 g of this mass and 1.5 g of hydrochloric acid were metered into a pressure capsule where they were mixed into a homogeneous suspension.

Painekapseli siirrettiin låmpokaappiin n. 250°C:n låmpotilaan, jossa sitå pidettiin 4-24 h.The pressure capsule was transferred to an oven at a temperature of about 250 ° C, where it was kept for 4-24 h.

91270 1191270 11

Kiteytyksen jålkeen painekapseli jååhdytettiin huoneen låmpo-tilaan ja faasit erotettiin toisistaan sentrifugoimalla. Kiin-toaines pestiin ja sentrifugoitiin ja analysoitiin.After crystallization, the pressure capsule was cooled to room temperature and the phases were separated by centrifugation. The solid was washed and centrifuged and analyzed.

5 Tulokset: rutiilipitoisuus 100 % kuiva-aineen painosta, kide-koko pigmenttikokoa (150-200 nm), jauhautuvuus valmiin pigmen-tin luokkaa.5 Results: rutile content 100% by weight of dry matter, crystal size pigment size (150-200 nm), grindability in the order of the finished pigment.

Esimerkki 2 10 16 g edellå mainitulla tavalla valmistettua titaaniyhdistemas- saa ja 1,5 g jåånnfishappoa (suolahappoa) annosteltiin painekapseli in. Painekapselia pidettiin låmpokaapissa n. 250°C:ssa n. 16 h, jonka jålkeen faasit jålkikåsiteltiin edellå mainitulla tavalla.Example 2 10 g of a titanium compound mass prepared as described above and 1.5 g of glacial acid (hydrochloric acid) were metered into a pressure capsule. The pressure capsule was kept in an oven at about 250 ° C for about 16 h, after which the phases were post-treated as mentioned above.

1515

Tulokset: pigmenttikokoista rutiilia, rutiili-% kuiva-aineen painosta: 100.Results: pigment-sized rutile, rutile% by weight of dry matter: 100.

Tåmå mahdollistaa jåånnoshapon tåydellisen kierråtyksen, mikå 20 tekee menetelmåstå ympåriståyståvållinen.This allows for the complete recycling of residual acid, which makes the process environmentally friendly.

Esimerkki 3Example 3

Painekapseliin annosteltiin Ti-hydraattimassaa ja typpihappoa yhteenså 19,2 g suhteessa 5/1. Painekapselia pidettiin 25 200-260°C:ssa 6-24 h. Kiteytyksen jålkeen jålkikåsittely suo- ritettiin edellå kuvatulla tavalla.A total of 19.2 g of Ti hydrate and nitric acid were added to the pressure capsule in a ratio of 5/1. The pressure capsule was kept at 200-260 ° C for 6-24 h. After crystallization, the post-treatment was performed as described above.

Matalammalla låmpotila-alueella muodostui anataasia ja kor-keammalla låmpotila-alueella muodostui rutiilia.Anatase formed in the lower temperature range and rutile formed in the higher temperature range.

3030

Esimerkki 4Example 4

Sulfaattiprosessin titaanihydraattimassaa (saostomatonta ja saostettua) annosteltiin painekapseliin n. 20 g. Liuosvåke-vyys såådeltiin 4-20 %:ksi joko rikkihapolla tai suolahapolla 35 tai typpihapolla tai fluorivetyhapolla. Painakapselia pidettiin 160-260 C:ssa 16 h, jonka jålkeen reaktorin poisto kåsi-teltiin yllå kuvatulla tavalla. Tuloksena saatiin pigmentin muotoista anataasia.The titanium hydrate mass of the sulphate process (non-precipitated and precipitated) was metered into a pressure capsule of about 20 g. The solution concentration was adjusted to 4-20% with either sulfuric acid or hydrochloric acid or nitric acid or hydrofluoric acid. The pressure capsule was kept at 160-260 ° C for 16 h, after which the removal of the reactor was treated as described above. The result was a pigmented anatase.

Claims

1. F5rfarande for framstållning av ett titandioxidipig-ment, dår a) i ett råmaterial befintlig fast titandioxid omvandlas 5 till en titanfdrening i ett icke-fast tillstånd, b) fororeningarna separeras från titanfåreningen, c) titanforeningen utfålles, d) den uppkomna titanfdreningen kristalliseras hydroter-miskt i syra till ren titandioxid medelst vårme och tryck, 10 och e) den rena titandioxiden separeras från syran och efterbe-handlas vid behov for åstadkommande av det slutliga titan-dioxidpigmentet, kånnetecknat av att utfållningen i steg c) ge-15 nomfors vid en temperatur under 30°C; i steg d) den hydro- termiska kristalliseringen genomfors vid en temperatur under 300°C, vid ett tryck under 100 bar och vid en syrakonsentration under cirka 15 vikt-%; och det från titandioxiden i steg e) separerade syran återcirkuleras till det hydroter-20 miska kristalliseringssteget d), varvid låmpliga titan-dioxidkristaller for framstållning av pigment erhålles.A process for producing a titanium dioxide pigment in which a) in a solid titanium dioxide present in a raw material is converted to a titanium drain in a non-solid state, b) the impurities are separated from the titanium compound, c) the titanium compound is precipitated, d) the resulting titanium compound is crystallized and (e) the pure titanium dioxide is separated from the acid and post-treated if necessary to produce the final titanium dioxide pigment, characterized by the precipitation in step c) being carried out at a temperature below 30 ° C; in step d) the hydro-thermal crystallization is carried out at a temperature below 300 ° C, at a pressure below 100 bar and at an acid concentration below about 15% by weight; and the acid separated from the titanium dioxide in step e) is recycled to the hydrothermal crystallization step d) to obtain suitable titanium dioxide crystals for pigment production.

2. Forfarande enligt patentkravet 1, kånnetecknat av att den ur steg c) genom utfållning erhållna ti- 25 tanforeningen tvåttas fore dess hydrotermiska krystallisering.2. A process according to claim 1, characterized in that the titanium compound obtained from step c) is washed prior to its hydrothermal crystallization.

3. F5rfarande enligt patentkravet 1 eller 2, k å η n e -tecknat av att titandioxiden eventuellt tvåttas efter 30 den hydrotermiska kristalliseringen.A process according to claim 1 or 2, characterized in that the titanium dioxide is optionally washed after the hydrothermal crystallization.

4. Forfarande enligt något av de fdregående patentkraven, kånnetecknat av att syran, som anvåndes vid den hydrotermiska kristalliseringen i steg d) år en oorganisk 35 syra, exempelvis saltsyra, salpetersyra, svavelsyra eller fluorvåtesyra, fåretrådesvis saltsyra eller salpetersyra. 912704. A process according to any one of the preceding claims, characterized in that the acid used in the hydrothermal crystallization of step d) is an inorganic acid, for example hydrochloric acid, nitric acid, sulfuric acid or hydrofluoric acid, sheep wire hydrochloric acid or nitric acid. 91270

5. Fårfarande enligt något av de foregående patentkraven, kånnetecknat av att koncentrationen av den syra, som anvåndes i stegets d) hydrotermiska krystallisering, år under ca 15 vikt-%, fåretrådesvis mellan ca 3 och 7 vikt-%. 5Process according to one of the preceding claims, characterized in that the concentration of the acid used in the step d) hydrothermal crystallization is below about 15% by weight, preferably between about 3 and 7% by weight. 5

6. F5rfarande enligt något av de fåregående patentkraven, kånnetecknat av att trycket i det hydrotermiska kristalliseringssteget d) år mellan 5 och 100 bar, fåretrå-desvis mellan 5 och 50 bar. 10Process according to any of the preceding claims, characterized in that the pressure in the hydrothermal crystallization step d) is between 5 and 100 bar, preferably between 5 and 50 bar. 10

7. Fårfarande enligt något av de foregående patentkraven, kånnetecknat av att temperaturen i det hydrotermiska kristalliseringssteget d) år under 300°C, fåretrådes-vis mellan 180 och 280°C. 157. A process according to any one of the preceding claims, characterized in that the temperature of the hydrothermal crystallization step d) is below 300 ° C, preferably between 180 and 280 ° C. 15

8. Fårfarande enligt något av de fåregående patentkraven, kånnetecknat av att den hydrotermiska kristal-liseringen i steg d) råcker mellan l och 24 timmar, fåretrå-desvis mellan 5 och 16 timmar. 20Method according to one of the preceding claims, characterized in that the hydrothermal crystallization in step d) lasts between 1 and 24 hours, preferably between 5 and 16 hours. 20

9. Fårfarande enligt något av de fåregående patentkraven, kånnetecknat av att den hydrotermiska krystalliseringen i steg d) utfårs i ett tryckkårl, vårs tryck efter steget fåretrådesvis utnyttjas får återcirkulering av 25 utspådd syra.9. A process according to any one of the preceding claims, characterized in that the hydrothermal crystallization in step d) is carried out in a pressure cooker.

10. Fårfarande enligt något av de fåregående patentkraven, kånnetecknat av att efterbehandlingssteget d) innefattar tvått-, malnings-, torknings- och/eller ytbehand- 30 lingssteg.The process according to any of the preceding claims, characterized in that the finishing step d) comprises washing, grinding, drying and / or finishing steps.

11. Fårfarande enligt något av de fåregående patentkraven, kånnetecknat av att steg a) innefattar klorering av råmaterialet till titantetraklorid medelst klorgas i når- 35 varo av kox, steg b) innefattar separation av fåroreningar från titantetrakloriden, steg c) innefattar utfållning av den renade titantetrakloriden till en fast produkt medelst en alkali eller ett salt av en svag organisk syra eller ge- nom utspåddning med vatten samt en eventuell tvåttning av utfållningen, och steg d) innefattar en hydrotermisk krystallisering av utfållningen.A process according to any one of the preceding claims, characterized in that step a) comprises chlorination of the raw material to titanium tetrachloride by chlorine gas in the presence of coke, step b) comprises separation of sheep impurities from the titanium tetrachloride, step c) comprises precipitation of the purified the titanium tetrachloride to a solid product by an alkali or a salt of a weak organic acid or by dilution with water and any washing of the precipitate, and step d) includes a hydrothermal crystallization of the precipitate.

12. Fdrfarande enligt patentkravet 11, kånneteck- n a t av att råmaterialet år rutil.12. Process according to claim 11, characterized in that the raw material is rutile.

13. Fdrfarande enligt patentkravet 11 eller 12, k å η n e -tecknat av att kloreringssteget a) utfors i tempera- 10 turen 850 - 1100°C.13. Process according to claim 11 or 12, characterized in that the chlorination step a) is carried out in the temperature 850 - 1100 ° C.

14. F6rfarande enligt patentkravet 11, 12 eller 13, kånnetecknat av att utfållningen i steg c) ut-f6rs medelst alkalimetallhydroxid, alkalimetallkarbonat el- 15 ler ammoniumhydroxid, vårs koncentration fdretrådesvis år mellan 10 och 40 vikt-%, ånnu hellre mellan 20 och 30 vikt-%.Process according to claim 11, 12 or 13, characterized in that the precipitate in step c) is carried out by means of alkali metal hydroxide, alkali metal carbonate or ammonium hydroxide, our concentration is preferably between 10 and 40% by weight, more preferably between 20 and 30%. weight-%.

15. Forfarande enligt patentkravet 11 eller 12, k å n 20 netecknat av att utfållningen i steg c) genomfors medelst ett salt av en svag organisk syra, foretrådesvis med natriumacetat eller natriumoxalat.15. A process according to claim 11 or 12, characterized in that the precipitate in step c) is carried out by a salt of a weak organic acid, preferably with sodium acetate or sodium oxalate.

16. Fdrfarande enligt något av patentkraven 11-15, k å n -25 netecknat av att utfållningen i steg c) genomfdrs under 30°C, foretrådesvis vid rumstemperatur.Process according to any one of claims 11-15, characterized in that the precipitation in step c) is carried out below 30 ° C, preferably at room temperature.

17. Fdrfarande enligt något av patentkraven 11-16, kånnetecknat av att den utspådda syran i stegets d) 30 hydrotermiska krystallisering år saltsyra eller salpetersy-ra, då rutil framstålles.Process according to any of claims 11-16, characterized in that the diluted acid in the step d) hydrothermal crystallization is hydrochloric or nitric acid when rutile is produced.

18. F6rfarande enligt något av patentkraven 11-16, k å n -netecknat av att steg d) i kloridprocessen utfors 35 så, att den erhållna kristallstorleken hos den rena titan-dioxiden år ca 150-250 nm. 91270Process according to any one of claims 11-16, characterized in that step d) in the chloride process is carried out such that the obtained crystal size of the pure titanium dioxide is about 150-250 nm. 91270

19. Forfarande enligt något av patentkraven 1-11, k å n -netecknat av att steg a) innefattar låsning av råmaterialet medelst svavelsyra och vatten, steg b) innefattar tvåttning och koncentration av den ur steg a) erhållna lås-5 ningen, steg c) innefattar hydrolysering av den koncentrera-de låsningen till en titanhydroxidfållning, tillvaratagning och tvåttning av fållningen, och steg d) innefattar hydro-termisk kristallisering av fållningen. 10A method according to any one of claims 1-11, characterized in that step a) comprises locking the raw material by sulfuric acid and water, step b) comprises washing and concentrating the locking obtained from step a), step c) comprises hydrolyzing the concentrated lock to a titanium hydroxide precipitate, collecting and washing the precipitate, and step d) comprises hydrothermal crystallization of the precipitate. 10

20. Fårfarande enligt patentkravet 19, kånneteck- n a t av att ilmenit utnyttjas som råmaterial.20. Method according to claim 19, characterized in that ilmenite is used as raw material.

21. Fårfarande enligt patentkravet 19 eller 20, k å n -netecknat av att låsningsreaktionen a) genomfåres 15 vid ca 150-180°C.21. Process according to claim 19 or 20, characterized in that the locking reaction a) is carried out at about 150-180 ° C.

22. Fårfarande enligt något av patentkraven 19-21, k å n -netecknat av att låsningen reduceras i bårjan av steg b), ifall råmaterialet år ilmenit eller motsvarande. 2022. A method according to any one of claims 19-21, characterized in that the locking is reduced at the beginning of step b), if the raw material is ilmenite or the equivalent. 20

23. Fårfarande enligt något av patentkraven 19-22, k å n -netecknat av att utfållningen underlåttas genom tillsats av en kristalliseringsinitiator i utfållningssteget c) . 25Process according to any one of claims 19-22, characterized in that the precipitation is failed by the addition of a crystallization initiator in the precipitation step c). 25

24. Fårfarande enligt något av patentkraven 18-23, k å n -netecknat av att den från utfållningen i steg c) erhållna fållningen neutraliseras fåre stegets d) hydroter-miska kristallisering, ifall rutil framstålls medelst fårfa- 30 randet.24. A process according to any one of claims 18-23, characterized in that the precipitate obtained from the precipitation in step c) neutralizes the lower step d) hydrothermal crystallization of the step, if rutile is prepared by the dyeing process.

25. Fårfarande enligt patentkravet 24, kånneteck-n a t av att utfållningen neutraliseras med ammoniak (ammoniumhydroxid) .25. Process according to claim 24, characterized in that the precipitate is neutralized with ammonia (ammonium hydroxide).