Normally the characteristic of coal aerification reaction of high temperature high pressure asks in aerification furnace in-house beard is added set fireproof material liner. Normally cent is aerification furnace structure 3: The layer is insulation material layer among the; of fireproof material layer that the layer in furnace interior is medium of direct contact high temperature; Of lining outer body of heater is stainless steel furnace casing. Besides the crucial technology such as reactor structure and accessory equipment, because temperature, pressure reachs the requirement of the condition such as other reaction operating mode, the choice of material of its reactor liner and the crucial technology that carbonado making also is to matter to craft success or failure. The service life of fireproof material liner is opposite liner aerification furnace long cycle is stable moving influence is tremendous. Coal aerification craft is planted because of used coal various, character each different, operating mode of the reaction inside fluid-bed aerification furnace is mixed, accompany the atmosphere that high temperature oxidation, vulcanization, hydrogen sulfide, carbonization, chloridize waits to corrode normally, the craft that coal is planted or adds alkali metal activator to tall alkali metal at the same time introduces possibly still alkaline corrode wait for a problem, this a little bit erode the service life that affected fireproof data badly, and move to the safe stability of high temperature device cause undesirable effect. The happening that corrodes inside aerification furnace makes the choice of fireproof material and service life equipment get attention.
One, the sort of fireproof material
The classified level with fireproof material different according to has different classification. Specific and OK according to chemistry different cent reachs acidity and fireproof material for alkalescent, neutral; Differ according to offerring goods form, cent is finalize the design fireproof material and adventitious fireproof material; Whether does the basis pass fire, cent is firing with did not burn fireproof material; Also but according to be able to bear or endure material chemistry composition differs cent is: Silica is able to bear or endure material, aluminous silicate is able to bear or endure material, magnesium is able to bear or endure character material, carbon is compound be able to bear or endure material.
What fireproof material uses operating mode is complex reach abominable sex to decide, differ according to use environment need to put forward different function to ask to fireproof material, include its to fight temperature to damage function of function, heatproof strain crack to reach fight environmental medium aggressivity to be able to wait.
As a result of each its manage turns fireproof material function is put in bigger difference, should join environment of reactor characteristic, work and specific utility, choose appropriate fireproof data. To fluid-bed aerification furnace, the attaint of fireproof material basically divides liner to be eroded for chemistry, heat is eroded, machinery erodes 3 kinds big. Chemistry erodes what can cause function of fireproof material composition to reduce, increase then thermodynamic erode the influence that reachs machinery to erode pair of material wear-resisting performance.
The choice of material needs to combine craft characteristic adequately. The run that attention requires when normally material is chosen changes index to include compression to fight fold intensity, wear-resisting and thermal shock stability, heavy burn a line to change rate. The material that leaves an alternative when reaction operating mode, be like pouring makings did not amount to place to require firing temperature, criterion intensity can be reduced greatly, need to assure what to choose fireproof material to have better strength below working temperature above all, the intensity of the material when when perhaps beginning drying-out, carbonadoing to what achieve material to pledge firing temperature moves with assuring operating mode is higher. Additional, fireproof material reachs drying-out process in the construction that make, installation medium unreasonable also can bring about be able to bear or endure the attaint of material. Accordingly, must ensure manufacturer asks strictly in the construction process that make to undertake construction according to the design, make sure whole process is contented at the same time be able to bear or endure the material construction requirement that timber production manufacturer raises. Ensure the water that contains in material divides transgression of vapor of complete translate into, the exceeds material because of the vapor pressure in fireproof material tensile strength after avoiding furnace ignition to move causes liner then statified, break down, bring about furnace liner to collapse fall.
2, fluid-bed aerification furnace and alkali resistance erode mechanism
2.1 fluid-bed boiler uses the current situation of fireproof material
Normally fluid-bed can divide by action with fireproof material liner it is 3 kinds: Wear-resisting material; Fireproof material; Insulation material. The fireproof data that existing fluid-bed uses includes: Phosphate is able to bear or endure material; Carborundum is able to bear or endure material; Corundum is able to bear or endure material; Nitrogen changes silicon to combine carborundum product to wait.
Phosphatic brick applies to 1200 ～ limits of 1600 ℃ temperature, do not bake bricks for what heat treatment of 500 ℃ low temperature gets, already applied in cement kiln old, boiler liner also uses inchoate circular fluid-bed this material. But inside the moving temperature limits in circular fluid-bed boiler (850 ～ 900 ℃ ) , phosphate is able to bear or endure material performance is not steady, wearability is poor, but because of price advantage, its are inchoate more application is had in fluid-bed.
Carborundum is able to bear or endure material has exceedingly good wear-resisting and thermal shock stability. But to coal aerification craft, suffer because of oxidisability atmosphere is being taken to bring about its to use slightly inside reactor be restricted. The report points out, the United States is forbidden carborundum is chosen to be able to bear or endure in circular fluid-bed boiler material, and the use that higher cost also restricted carborundum.
Siliceous aluminous simple fireproof stuff (Al₂O3-SiO₂ fastens) , basic and chemical composition is Al₂O3, SiO₂ . This department is able to bear or endure the application in material is more reach corundum for Molaishi fireproof material. Because Mo Laishi is fireproof degree tall, fight it is creep, good to fight chemical aggressivity, loading bate temperature is tall, heatproof better, bulk stabilizes shake function performance is good and insulating property is strong, make good fireproof material. But chemical composition of Molaishi is not stable, include 2Al₂O3 · SiO₂ and 3Al₂O3 · 2SiO₂ two kinds of forms.
Corundum is fireproof in material, al₂O3 content prep above 90% and advocate brilliant photograph is α - Al₂O3. Corundum has thermodynamic strength sex of good, heatproof shake reachs tall, chemical stability fight abrasiveness capability of action of good, counteractive reducer is strong wait for function, because this serves as the important raw material of fireproof material.
Integrated the consideration of each respect element such as afore-mentioned material function and price, coal aerification furnace chooses corundum to regard liner as fireproof material normally, the variety that uses normally has He Zonggang of Bai Gangyu, tall aluminous corundum jade.
To coal aerification furnace, choose be able to bear or endure what material composition reachs design construction is different bring about be able to bear or endure of material liner fight coal ash to erode ability each different. Coal ash is right of fireproof material erode mechanism namely coal ash is mineral with fireproof data reaction, erodent process. Consider to make clear, coal ash is able to bear or endure to tall aluminium of material erode strong, carborundum is able to bear or endure material take second place, fireproof material fights corundum erode ability stronger.
2.2 different and fireproof material are fought alkaline corrode characteristic research
Each atmosphere is corroded in aerification furnace in, alkaline erode to be able to bear or endure the destruction of material liner action especially strong. The alkali metal inside furnace evaporates, agglomeration comes firebrick lining, especially aperture place, amid rich collect, permeate, bring about bricky line to corrode, craze, be able to bear or endure material liner is sufferred destroy.
Current, be opposite in alkali metal of fireproof material corrode a respect, began a large number of works domestic and internationally. Blast furnace worker made fireproof material fight level of state of method of alkaline function experiment, its are fought high with low porosity alkalescent for the target, developed small stomatic product; Xu Guotao differ through inspecting alkali metal to be opposite of fireproof material caustic, those who study fireproof material falls in different condition is alkaline erode a process, put forward to be able to bear or endure material improves the way to deal with a situation; Li Wei in carbon hot the reproducibility conditions issues those who studied silicon aluminium fastens fireproof material to corrode behavior, the corrosion resistance that discovers tall aluminous brick can be good, and the accretion of alkali metal aggravate of fireproof material erode, additive adds quantity change to erode aggravate; Zhou Shizhuo studied what material and carbolic material expect to all sorts of silicon aluminium are able to bear or endure character fight alkaline aggressivity can, discover alkali metal to be able to bear or endure character to silicon aluminium of material because formed high volume of nepheline of leucite, Potassium to expand,eroding is material, caused bricky line volume thereby expand, reach corundum is able to bear or endure character of material fight alkaline caustic can stronger; The height made an on-the-spot investigation to contain alkaline coal ash to reach aggressivity in the wetability of different firebrick surface, discover corundum brick gets erode weaker; Stjernberg studied Molaishi / corundum is able to bear or endure material and the reaction that contain alkaline material, discover alkali metal and firebrick reaction made nepheline and leucite appearance, of appearance of this somes of substance generate bring about the journey inside the brick certain volume expands, quickened fireproof material then mar. It is certain to contain fireproof stuff to cause damage, guide thereby generation " alkaline splitting decomposition " . In addition, contain alkaline material to be able to form felt content to damage then fireproof material, especially easy form sulfur - alkaline compound, attaint is able to bear or endure the felt structure of material. Consider to make clear, the alkaline corrode under 900 ℃ contains alkaline material together for fireproof material immediate reaction is caused, and below high temperature because will contain potassium compound,eroding is reductive into made potassium steam, produce migratory oxidation reaction to cause then. Those who contain alkaline operating mode to issue commonly used and fireproof data face to fight below alkaline caustic have detailed introduction:
(1) silicon aluminium fastens fireproof material
The basic and chemical composition that Al₂O₃-SiO₂ is fireproof material is alumina and 2 oxidation silicon, the discretion of content of according to alumina, silicon aluminium department fireproof material differentiates to express a few kinds 1.
Expressing 1 silicon aluminium is fireproof material classification
Using Al₂O₃-SiO₂ is fireproof material, the chemical reaction that contains alkaline compound to happen to it is as follows:
Orthoclase of A₃S₂+16SiO₂+3K₂O → 3KAS₆() leucite of A₃S₂+10SiO₂+3K₂O → 3KAS₄()
Nepheline of square Potassium of 2A₃S₂+8SiO₂+6K₂O → 6KAS₆()
11Al₂O₃+K₂O+Na₂O → (corundum of β of K · Na)A11()
Gesso of Potassium of H₂O(of · of K₂SO₄ of · of 2CaSO₄ of → of K₂SO₄ · 2CaSO₄+H₂0)
Gesso of anhydrous Potassium of K₂SO₄(of · of 2CaSO₄+K₂SO₄ → 2CaSO₄ )
Alkali metal is qualitative to Al₂O₃-SiO₂ of fireproof material because formed nepheline of leucite, Potassium, β ,eroding is - corundum, its generate bring about be able to bear or endure material liner volume happens expand, the result can bring about the happening of phenomenon of alkaline splitting decomposition eventually. Reaction child depends on the content of the Al₂O₃ in alkaline chroma and fireproof material, SiO₂ . Alkali metal pledges to all sorts of silicon aluminium fireproof material expands destructive degree each are not identical.
Tall aluminous brick (Mo Laishi composition) fireproof material is poorer, damaged expands relatively serious. Alkali metal is the same as Molaishi to react, in 700 ～ 110 ℃ generate nepheline, those who contain alkaline content photograph build meeting generation 20% ～ the bulk of 25% expands, bring about material to mar.
It is better that corundum pledges fireproof material fights alkali metal function, bulk change is minor. Alkaline erodent mechanism is: Crystal boundary material and contain alkaline material to produced reaction to produce new material, and this material produced certain volume to expand, bring about corundum to be able to bear or endure the disintegrate of material test block, namely the process that the K₂O below constant temperature, pressure and Al₂O₃ fashion solid solution Potassium, chemical reaction is as follows:
Al₂O₃)(S of · of 1/11K₂O(S)+Al₂O₃(S) → 1/11(K₂O)
Additional, alkali metal is right the corrodes function to accept form of time of specific response temperature, atmosphere, reaction and alkali metal existence influence of fireproof material. Different aerification craft is choosing aerification furnace liner when fireproof material, should combine oneself craft characteristic and condition of craft of use place, specific inside aerification furnace response (atmosphere, temperature) , K configuration those who wait is different and choose different fireproof material. But fall in high temperature and chroma of tall alkali metal, nonexistent the silicon aluminium that can fight alkali metal completely to erode is qualitative fireproof material. Accordingly, accumulate serious blast furnace circularly to alkali metal, bottom should not use tall aluminous liner, additional, air hole is spent is one of crucial factors that affect fireproof material to fight alkali metal function.
(2) contains chromic fireproof material
Magnesian chromic qualitative, chromic corundum is fireproof material is fireproof degree tall, high temperature strength is great, heatproof shake sex is admirable. Because its fight alkaline function goodly to reach admirable high temperature resistant characteristic, magnesian chromic simple fireproof stuff uses as for a long time alkaline reclaim furnace lining is able to bear or endure material. Contain the Cr₂O₃ in chromic fireproof material, especially the Cr₂O₃ in matrix is helpful for increasing material density and strength of the union that heat up voice, reduce porosity, improvement fights broken bits aggressivity. But Cr₂O₃ and chromic mine are easy below oxidation atmosphere with alkali metal oxide (the 6 price chromate that reaction of K₂O, Na₂O) makes low melting point, its react form is as follows:
2(Cr₂O₃)+O₂+R₂O → 4(R₂CrO₄)(R-K, Na)
The happening of this reaction, destroyed the structure of Cr₂O₃ and chromic mine not only on one hand, and formation low frit content still is met inside infiltration brick; On the other hand chromate R₂CrO₄ is compound of a kind of weak oxidisability, chemical stability is taller, 6 price chromium is poisonous can cause cancer, consider to make clear in great quantities: Ulcer of a few skins and respiratory tract disease all are concerned with Cr6+ , and the pollution that can cause to the environment is had durative. As the buildup of environmental protection consciousness, already will handle " chromic social effects of pollution " mentioned the order of the day.
(3) aluminium acerbity calcium fastens fireproof material
Two important compound include in CaO-Al₂O₃ binary system, namely 6 aluminous acid are 2 aluminous acerbity calcium, calcic. Because of good water ability of hardening capacity, decarbonization reachs high temperature performance characteristics, apply in the industry such as building materials, metallurgy, national defence extensive. 6 aluminous acid are calcic (CaAl₁₂O₁₉ or CaO · 6Al₂O₃ , logogram is CA₆ , mineral name: ) of black aluminous calcic rock, because of relatively the manage of beautiful turns performance in recent years times get attention. Its are in CaO-Al₂O₃ binary system, fight to hydrate sex better, melting point (upper limit makes an appointment with 1830 ℃ high to decompose melt) . CA₆ crystal anisotropy grows, can form 6 an appearance of shape crystal form, this brilliant have small hole structure, and agglomeration is affected in internal energy of constant temperature limits, the apparent pore rate that carries data is basic and fixed, lower coefficient of thermal conductivity. Be worth what carry is, CA₆ and Al₂O₃ are had very good comfortable match a gender, both because make the same score soaking coefficient of expansion to be close to very, can make deserving to compare and won't be caused arbitrarily expand break match. In the meantime, because CA₆ melting point is high, good in the stability below high temperature reducing atmosphere, it is better to be had in alkalescent environment fight erode ability. Prospect of progress of 6 aluminous acerbity calcic material is good. Below high temperature condition, corundum, CA₆ reacts jointly with K₂O. Corundum and oxidation Potassium reaction generate β - corundum, companion expands as larger volume, this is one of main reasons that cause fireproof liner to destroy. But the crystal structure of CA₆ and β - Al₂O₃ crystal structure is similar, embed Ca2+ in layer shape alumina, alkali metal ion can be absorbed between the layer, and volume won't produce apparent change; Additional, the bulk density of CA₆ (the bulk density of 3.38g/cm3) and KA11 (3.37g/cm3) close, become so CA₆ by alkaline when eroding, the fireproof data phase with other is compared, its bulk stability is taller.
(4) magnalium pointed spar fastens fireproof material
Magnalium pointed spar (MgO · Al₂O₃ or MgAl₂O₄ , logogram is MA) is compound of existence of the stability in MgO-Al₂O₃ binary system. Magnalium pointed spar is the octahedral structure of isotropy, be united in wedlock with electrovalent bond between Al-O, Mg-O, its are electrostatic key intensity is same, the structure is stable. Structure of this kinds of crystal made sure MA is able to bear or endure the thermal shock stability with superior material and wear-resisting function, and fall in oxidation reducing atmosphere, have to the SO₂/SO₃ of free and K₂O/Na₂O relatively of beautiful fight aggressivity, accordingly, MA applies in fireproof data industry extensive. Additional, melting point of magnalium pointed spar is high (2135 ℃ ) , coefficient of thermal conductivity is low, hot coefficient of expansion small, intensity tall, hardness is big, fight concussion, fight alkaline erode ability strong, and very stable also to the action of the oxide of iron.
(5) composite material
It is better to all be had in view of CA₆ and MA fight alkaline corrode function, and the close of hot coefficient of expansion of CA₆ and MA, consistence is good, OK and aleatoric scale cooperates, nonexistent expand break compound a problem. Accordingly, can consider two kinds of material compound use, already developed a CA₆-MA at present compound light qualitative aggregate, have good thermal shock stability via considering to make clear its, be able to bear or endure function of aggressivity, wear-resisting reachs the good aggressivity that fight broken bits.
(6) aluminous charcoal fastens fireproof material
Aluminous charcoal fastens fireproof material to apply on blast furnace more, if be being put in the molten iron pretreatment of alkaline corrode,reductive furnace is having furnace, melt to apply or apply foreground potentially. Among them SiAlON(carborundum kind) the crucial and fireproof material that combines corundum material to become large blast furnace to go up character. Below reducing atmosphere, contain a lot ofwhat the blast furnace slag of alkali metal combines corundum brick to SiAlON to erode speed lesser, its erode mechanism to generate potassium nepheline for SiAlON and alkaline steam reaction, shared silicate glass photograph generate; The reaction such as natrium of the oxidation ferrous in corundum grain and grey broken bits, oxidation and oxidation Potassium makes iron aluminium pointed spar and a few acicular β - alumina. But SiC is used below oxidisability operating mode, siC oxidation becomes SiO₂ , can generate alkaline silicate, produce photograph of high temperature felt, with synchronism of exterior layer reaction, easy form the layer that hang broken bits. This on one hand may process of slow down alkaline corrode, but the existence of photograph of felt of this high temperature is met at the same time conglutinate is fireproof material and grey broken bits, the likelihood generates nepheline etc low temperature further in all frit content, cause matrix fragile change mar.
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