氧化鋁耐火磚生産工藝Production process of alumina refractory brick

 行業動态    |      2019-06-05

     耐火磚是一種建築材料磚類,具有抗熱震性、抗渣性、耐火性等性能。雖然很多人不認識它,但是它經常出現在我們的生活中,例如房屋建築、煤爐等,那麼耐火磚應該怎麼選用呢?下面我們就“耐火磚設計選用注意事項以及氧化鋁耐火磚生産工藝”來詳細了解下。
    1:廢氣焚燒的基本條件
    為了确定某個工藝過程中産生的廢氣是否能夠采用焚燒的辦法進行淨化,首先我們必須從焚燒的基本條件進行分析,我們認為廢氣焚燒的基本條件包括焚燒溫度、停留時間和空氣需要量三要素。
    焚燒溫度。焚燒溫度指廢氣中有害組分在高溫下氧化分解以至破壞所需要達到的溫度。焚燒溫度不同于着火度(燃點),它比着火溫度高出許多,是爐襯耐火磚選材及耐火磚厚度設計的重要依據。
    一般而言,提高焚燒溫度有利于廢氣中有害成分的分解破壞。但是,過高的焚燒溫度不僅會對爐襯材料的選擇和工藝厚度提出更高的要求,增加燃料消耗和環保費用,更會增加焚燒産物中氧化氮的組分含量上升,造成二次污染。
    合适的焚燒溫度是在一定的停留時間下通過實驗的方法确定的,在生産實踐中,決定多數有機廢氣的焚燒溫度範圍在800℃~1100℃左右,通常涉及選擇在800℃~900℃。
    停留時間。停留時間指有害組分在焚燒溫度下,發生分解燃燒、轉化為無害組分所需要消耗的時間。停留時間直接影響焚燒的完善程度,是決定爐膛容積尺寸的重要依據。
    停留時間對于廢氣焚燒而言,并非越長越好。因為設計的停留時間過長,不僅會造成爐體的結構過于龐大,增加爐體的占地面積和構築成本,而且可能會造成爐膛溫度不夠,使焚燒不能完全分解。
    廢氣在爐内的停留時間是由多方面的因素決定的。對于工業中産生的一般廢氣,停留時間通常在1~2秒。
    2:焚燒爐爐膛的設計要點
    廢氣焚燒爐的爐膛尺寸主要是由燃燒時的容積熱強度和廢氣焚燒是在高溫爐膛内所需的停留時間兩個因素決定,廢氣容積熱強度值一般可取(20~25)X104Kcal/(m³·h),較合适的數據應根據不同的物料、來判斷選用合适爐襯耐火磚。
    3:焚燒爐爐襯耐火磚的選用
    爐襯耐火磚首先應根據爐膛溫度高低選用能承受焚燒溫度的耐火材料和隔熱材料,同時應考慮焚燒廢氣對爐襯的腐蝕性,乃選材料按照其耐酸堿程度可以分為三種:對酸性抵抗較好的耐火磚。
    如矽磚:對堿性抵抗能力較強的耐火磚,如鎂鋁磚、鎂磚、白雲石磚,對酸堿抵抗效果都可以的中性耐火磚如:高鋁磚、剛玉磚、碳化矽磚及碳磚等。按照其比重分耐火磚分為輕質磚和重質磚。
    輕質磚氣孔率高,抗渣性差,機械強度低,穩定性差,而重質磚則與之相反,對于1200℃以下的爐膛溫度,在一般情況下,選用重質三級高鋁磚即可,其荷重軟化溫度可以達到1350℃,并且造價也相對較低,但是,如果焚燒爐采用架空設計,則需要選用輕質耐火磚或者纖維折疊塊,以減輕爐體重量、降低鋼結構建造成本,增加美觀度。
    焚燒爐襯在處理廢氣的過程中,不可避免的會有腐蝕和損壞情況的發生,因此,設計應考慮爐襯的操作方便,通常情況下,每2-3年就需要小型維修一次。
    1.結合劑的選擇
    制造高鋁磚通常采用軟質粘土做結合劑。粘土在配料中的主要作用是改善泥料的成型性能,并使成型和幹燥後的坯體具有一定的強度。但是,在燒成過程中,粘土中的遊離SiO2與高鋁礬土熟料中的遊離A12O3發生二次莫來石化反應,該反應随着結合粘土加入量的增多而加劇。
    二次莫來石化反應愈強,燒後高鋁磚氣孔率則愈高,強度和體積密度下降的可能性也愈大。從這點出發,應盡量減少結合粘土在配料中的加入量。配料中粘土粉的加入量一般為5%。
    為了制得體積穩定型夏等高鋁磚,可采用高鋁礬土微粉作高鋁結合劑;或用高鋁礬土微粉和粘土粉按預定比例配合,制備合成莫來石作結合劑,均可制得無二次膨脹的體積穩定型高鋁磚。
    2.顆粒組成的确定
    高鋁礬土熟料的顆粒組成對成型操作、坯體密度、高鋁磚密度、強度有着重要的影響。因此,根據不同的成型方法确定合理的顆粒組成是穩定工藝操作、提高高鋁磚質量的重要工藝因素。
    确定顆粒級配的原則是形成良好的堆積密度,對高鋁磚性能和外觀質量無不良影響。對于夏等磚來說,還應考慮到二次莫來石化反應所産生的體膨脹。
    高鋁磚通常采用粗、中、細三級配料。但是,也可采用二級或四級配料。當采用三級配料時,各粒級的臨界尺寸為:粗顆粒3—0.5mm,中顆粒0.5—0.1mm,細粉<0.1mm。
    生産實踐表明,确定顆粒尺寸時适當增大粗顆粒尺寸和數量可提高泥料的堆積密度,而且易于成型。燒成時,由于大顆粒料的比表面積較小,減弱了物料周圍的二次莫來石化反應,有利于坯體的燒結。進而使高鋁磚氣紮率降低,荷重軟化溫度和耐壓強度有所提高,熱穩定性能有所改善。

    本公司長期出售高鋁磚、粘土磚等,價格合理,質量優。電話:0086-13608670776

Firebrick is a kind of building material brick with thermal shock resistance, slag resistance, fire resistance and other properties.Although a lot of people do not know it, but it often appears in our life, such as building, coal stove, so how should firebrick be chosen?Below we on the "refractory brick design selection considerations and alumina refractory brick production process" to understand in detail.

1. Basic conditions for waste gas incineration

In order to determine whether the waste gas generated in a certain process can be purified by incineration, we must first analyze the basic conditions of incineration. We believe that the basic conditions of exhaust gas incineration include three elements: incineration temperature, residence time and air demand.

Burning temperature.Incineration temperature refers to the temperature required for the oxidation decomposition and destruction of harmful components in waste gas at high temperatures.The burning temperature is different from the ignition temperature (ignition point), which is much higher than the ignition temperature.

Generally speaking, increasing incineration temperature is beneficial to decomposition and destruction of harmful components in waste gas.However, too high incineration temperature will not only put forward higher requirements on lining material selection and process thickness, increase fuel consumption and environmental protection costs, but also increase the content of nitrogen oxide in incineration products, causing secondary pollution.

The appropriate incineration temperature is determined by experiment under a certain residence time. In production practice, most organic waste gas incineration temperature ranges from 800℃ to 1100℃, usually involving the selection of 800℃ to 900℃.

Stay time.Residence time refers to the time consumed for decomposition and combustion of harmful components into harmless components at incineration temperature.Residence time directly affects the perfection of incineration and is an important basis for determining the size of furnace volume.

The residence time is not the better for waste gas incineration.Because the residence time of the design is too long, it will not only cause the structure of the furnace is too large, increase the floor area and construction cost of the furnace, but also may cause the temperature of the furnace is not enough, so that the incineration cannot be completely decomposed.

The residence time of waste gas in furnace is determined by many factors.For the general waste gas produced in industry, the residence time is usually 1~2 seconds.

2. Design key points of incinerator chamber

The chamber size of waste gas incinerator is mainly determined by the volumetric thermal intensity of combustion and the residence time required by waste gas incineration in the high-temperature chamber. The thermal intensity value of waste gas volume is generally (20~25) X104Kcal/ (m ^ 3 ·h). The appropriate data should be determined according to different materials and the selection of appropriate lining firebrick.

3: selection of firebrick lining for incinerator

Furnace lining refractory brick should first choose according to the temperature of the furnace chamber can withstand the temperature of refractory materials and heat insulation materials, at the same time should consider the corrosion of burning waste gas on the furnace lining, is the choice of materials according to its acid and alkali resistance can be divided into three kinds: good resistance to acid refractory brick.

Such as silicon brick: to alkali resistance ability of strong fire brick, such as magnesia aluminum brick, magnesium brick, dolomite brick, acid and alkali resistance effect can be neutral fire brick such as: high aluminum brick, corundum brick, silicon carbide brick and carbon brick.According to its specific gravity fire brick is divided into light brick and heavy brick.

Light brick high porosity, slag resistance, low mechanical strength, poor stability, while heavy brick, on the other hand, for furnace temperature below 1200 ℃, in general, choose heavy level 3 high alumina brick, its load softening temperature can reach 1350 ℃, and the cost is relatively low, however, if the incinerator adopts the design of overhead, you will need to choose lightweight brick or fiber folding, in order to reduce body weight, decrease the cost of steel structure construction, increase the aesthetic.

In the process of treating waste gas, corrosion and damage will inevitably occur in the incineration furnace lining. Therefore, the design should consider the convenience of operation of the furnace lining. Usually, small maintenance is needed every 2-3 years.

1. Selection of binder

High alumina bricks are usually made with soft clay as a binder.The main function of clay in batching is to improve the molding performance of clay and make the formed and dried green body have certain strength.However, in the firing process, the free SiO2 in clay and the free A12O3 in high alumina clinker have a secondary mullite reaction, which intensifies with the increase of the amount of binding clay added.

The higher the secondary mullite reaction, the higher the porosity, the higher the strength and the higher the volume density.Starting from this point, the amount of bound clay in the ingredients should be reduced as much as possible.The amount of clay powder in the batching is generally 5%.

In order to produce volume-stable high alumina bricks, small powder of high alumina bauxite can be used as high alumina binding agent.Or synthetic mullite can be prepared by using high-alumina powder and clay powder in predetermined proportion.

2. Determination of particle composition

The grain composition of high alumina clinker has an important influence on molding operation, blank density, high alumina brick density and strength.Therefore, the determination of reasonable particle composition according to different molding methods is an important process factor to stabilize the process operation and improve the quality of high alumina bricks.

The principle of determining particle gradation is to form a good stacking density without any adverse effect on the properties and appearance quality of high alumina bricks.For xia and other bricks, the volume expansion produced by secondary mullite petrochemical reaction should also be considered.

High alumina bricks are usually made of three grades: coarse, medium and fine.However, secondary or secondary ingredients may also be used.When three grade ingredients are used, the critical size of each grain size is: coarse particle 3 -- 0.5mm, medium particle 0.5 -- 0.1mm, fine powder <0.1mm.

The production practice shows that increasing the size and quantity of coarse particles can increase the density of the mud, and it is easy to form.During sintering, the secondary mullite reaction around the material is weakened due to the small specific surface area of the large particle material, which is beneficial to the sintering of the green body.Furthermore, the gas binding rate of high alumina brick is reduced, the softening temperature under load and compressive strength are improved, and the thermal stability is improved.

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