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Overall and structural design of rotary dryer
1 Introduction
The drying operation involves almost all sectors of the national economy and is widely used in production and life. The so-called dry is generally from solid materials make the evaporation and separation of a liquid (usually water) operation, including from the evaporation of the liquid or slurry material to remove moisture, in order to achieve solid in the loss of moisture. The purpose is to remove some of the raw materials, semi-finished and finished products in the water or solvent, in order to facilitate the processing, use, transport, storage, etc..
Drying is a great deal of heat consumption, today in the strict demands on energy saving and heat source for drying, if the heat source of cheap gas and residual steam as the direction, the dryer itself, even with reduced thermal efficiency, but on the whole, the economy is still. In addition, before entering the drying process, the former treatment process can be used to reduce the water method is economical.
For dry operation, the choice of the dryer is a very difficult and complicated problem. Due to the characteristics of dry materials, heating methods and materials - the fluid dynamics of the system must be fully considered. Due to the variety of dry materials, different requirements, it is impossible to have a universal dryer, can only choose the best drying method and dryer form.
The main body of the rotary dryer is a cylinder which is slightly inclined and can rotate. Wet material from the upper part of the left join, through the inner cylinder, and through the inner cylinder hot air or heated wall surface of effective contact is dried, dried products from the lower part of the right end of the collection. During the drying process, the material is rotated slowly by the aid of the cylinder, moving from the higher end to the lower end under the action of gravity. The inner wall of the cylinder body is provided with a parallel plate (or similar device), which continuously throws the material from the surface of the thermal contact surface of the material to increase, in order to improve the drying rate and promote the material moving forward. The heat carrier used in the drying process is generally air, flue gas or water vapor, etc.. If the heat carrier, such as hot air and flue gas directly in contact with the material, after drying, usually with cyclone separator in gas entrained fine grained material capture set down, non air is after Cyclone vent. Rotary dryer is one of the oldest drying equipment, but it is still widely used in metallurgy, building materials, chemical industry and so on because of the high efficiency and the high efficiency of economic and practical work.
2 Overview
2.1 the purpose of drying
The drying operation involves almost all sectors of the national economy and is widely used in production and life.
The so-called dry is generally from solid materials makes the operation of evaporation and separation of a liquid (usually water), including from the evaporation of the liquid or slurry material to remove moisture, in order to achieve solid in the loss of moisture. The purpose is to remove some of the raw materials, semi-finished and finished products in the water or solvent, in order to facilitate the processing, use, transport, storage, etc..
Drying is a great deal of heat consumption, today in the strict demands on energy saving and heat source for drying, if the heat source of cheap gas and residual steam as the direction, the dryer itself, even with reduced thermal efficiency, but on the whole, the economy is still.
In addition, before entering the drying process, the former treatment process can be used to reduce the water method is economical.
2.2 Main composition and function of rotary dryer
Rotary dryer is mainly composed of the following main parts. The cylinder is a main part, need in reaction or operation space determines the overall size. The cartridge is empty or has a copy board, and also has a chain, to achieve the purpose of increasing heat transfer and crushing material.
A rolling ring is arranged on the cylinder, the weight of the material in the barrel body and the barrel is passed to the supporting wheel of the supporting seat through the rolling ring. A gear ring is arranged on the cylinder body of a block wheel seat near the support wheel. Gear mounted on the shaft of the reduction gear box is connected with the gear ring, and the gear box and the motor form a transmission mechanism.
In the end of the drum material, is provided with a chamber for unloading of materials and incoming or the introduction of gas extraction. The outlet end of the cylinder is sealed with a sealing device (a labyrinth or an end face seal).
At one end of the cylinder is provided with a discharging device, which is used for loading and unloading the processed solid material.
The processed material and the air flow can flow in the rotating drum, and can also be counter current. If due to processes or reactions of must be heated, the heat can be directly offered by gas; also can be introduced by the cylinder wall; due to the cylinder of the material being handled by the release of heat of reaction; also by in cylinder direct fuel supply. The method of gas heating and the maximum temperature are determined by the properties of the solid material and the factors such as whether it is allowed to be dirty and so on.
It is usually made of circular cross section in terms of manufacturing convenience, high mechanical strength and low material consumption. But a small rotating cylinder, there are also made of hexagonal or polygonal, and even some of the ends of the cone made of.
The size of the contour of the cylinder decided to the required production capacity, the material in the barrel stay time and through the maximum cylinder gas to allow the speed.
2.3 rotary drum dryer working principle
The main body of the rotary dryer is a cylinder which is slightly inclined and can rotate. Wet material from the upper part of the left join, through the inner cylinder, and through the inner cylinder hot air or heated wall surface of effective contact is dried, dried products from the lower part of the right end of the collection. During the drying process, the material is rotated slowly by the aid of the cylinder, moving from the higher end to the lower end under the action of gravity. The inner wall of the cylinder body is provided with a parallel plate (or a similar device), which continuously throws the material from the surface of the thermal contact surface of the material to increase, so as to improve the drying rate and cause the material to move forward. The heat carrier used in the drying process is generally air, flue gas or water vapor, etc.. If the heat carrier, such as hot air and flue gas directly in contact with the material, after drying, usually with cyclone separator in gas entrained fine grained material capture set down, non air is after Cyclone vent. Rotary dryer is one of the oldest drying equipment, but it is still widely used in metallurgy, building materials, chemical industry and so on because of its great economic and practical work.
2.4Classification and application scope of drum dryer
2.4.1 direct heating
(1) conventional direct heating rotary dryer
The material in the drying device is directly contacted with the hot air in the drying process, and the drying process is carried out by the method of convective heat transfer. According to the flow direction between the hot air and the material, the flow direction is divided into parallel flow and counter flow. The hot air and the material moving direction are the same in the flow type, and the hot air with high temperature at the entrance is in contact with the material with high moisture content. Because the temperature of material is in the stage of surface vaporization, the temperature of the product can still keep the wet bulb temperature. Although the temperature at the outlet side of the material increases, but at this time the hot air temperature has been reduced, so the temperature of the product will not be too large, so the choice of higher hot air inlet temperature, will not affect the quality of the product. For the heat sensitive material drying including those contains easy volatile material drying is very suitable for; for high temperature materials using counterflow drying, heat utilization rate is high. The air outlet temperature of the dryer is generally higher than that of the material outlet temperature of 10, 20. In the counter flow type, if not clearly defined, the general use of 100 degrees as the temperature of the outlet is more reasonable.
The diameter of the cylinder is generally 0.4 - 3M, and the ratio of the length to the diameter of the cylinder is 4 - 10 -. The circumferential velocity of the dryer is 0.4 0.6m/s, the air velocity is in the range of 1.5 - 2.5m/s.
(2) vane type wear circulation tube dryer
In accordance with the hot air blowing the blade wear transfer dryer is divided into surface blowing type and side blowing type two. Above is a diagram of a face blowing type, the cylinder is horizontally arranged, the distance along the cylinder wall circumferential direction with many leaves (blinds) from the end surface of the side inlet outlet side of tilt, hot air from the end into a rotary cylinder bottom, only from the lower part of the layer material part of the blade gap blowing tube in, so it can effectively ensure the drying in the full contact of the hot air and raw materials, does not appear short circuit phenomenon. The material is moved by the side of the inlet side of the outlet side, and the retention time of the material is moved by the side of the inlet side. Side blowing type and end blown into a pattern of different cylinder body slightly inclined installation is, most of the hot air from the open has many small holes in the barrel body, blowing tube, at right angles to the direction of movement of the material in the direction and the tube and then through triangular blades of shutter holes into material layer. A box shaped shell is arranged around the inner wall of the rotary drum body, and is divided into 3 and 4 independent chambers along the length direction of the rotating cylinder. Each chamber has an independent blower, an air heater, an air inlet and an exhaust port. The hot air temperature and the circulating air volume and the air volume can be adjusted automatically. This type of dryer volumetric heat transfer coefficient is big, about 349 - 1745w/ (m); the drying time is short, about to 10, 30min; materials filling rate is larger, about 20% -- 30%; device volume is relatively small, material layer resistance for 98 - 588pa; channel wind speed is generally 0.5 -- 1.5m/s; cylinder speed for the conventional direct heating transfer dryer 1 / 2 or so; use of the hot blast temperature 100 -- 300 DEG C. In industry often use the dryer for drying granular, lump or flaky materials, materials such as coke, compressed dry beans, sugar and avoid damage. In addition, like plastic particles are a class must be dried to very low moisture of material and like materials with small density ten pieces, low pulp slag can to use it to dry.
(3) ventilation tube rotary dryer
The dryer design and installation and conventional type is the same, different is cylinder is internally provided with a mounting board copy, material from the inlet end to the outlet end of the mobile process, always in a rotating cylinder at the bottom of the space, a stable material layer is formed, thus reducing the dust. The hot air enters from the end of the center pipe which is not rotated with the cylinder body, and is high speed, and is ejected from the small hole of the powder pipe which is buried in the material layer, and is in strong contact with the material. The volumetric heat transfer coefficient of the vent tube dryer is about two times of that of the conventional type. The circumferential speed of the rotary drum is about the conventional 1/2. Under the same production capacity, the length of the drying tube is only the conventional 1/2, so the cost of the equipment is greatly reduced.
24.2 indirect heating rotary drum dryer
1 conventional indirect heating rotary drum dryer
The dryer cylinder is built in the furnace, and the shell is heated by the flue gas. A concentric cylinder is arranged inside the cylinder. The flue gas enters the annular space between the outer shell and the furnace wall, and passes through the connecting pipe into the central tube of the drying cylinder. The conventional direct heating rotary dryer is especially suitable for drying the materials with longer drying stage. Because it can be quite stable in the drying temperature, so that the material has enough residence time, at the same time can be the use of rotary drum rotation, effectively prevent the agglomeration of materials. This dryer is suitable for drying heat sensitive materials, but not suitable for high viscosity, easy to agglomerate special material.
2 steam tube indirect heating rotary drum dryer
circle heating pipe is arranged in a concentric circle in a drying cylinder, one end of which is arranged on the drainage separation chamber of the collecting pipe box at the outlet of the dryer; the other end is provided with a heat expansion structure. The material in the dryer is heated by the opening and stirring of the heating tube and is dried, and with the help of the dryer's inclination to move from the higher to the lower end, the discharge from the end of the row hopper. The dryer with conventional indirect heating transfer all the advantages of the dryer, it per unit volume of drying capacity is about 3 times of that of the conventional direct heating type, thermal efficiency as high as 80% - 90%, the material filling rate of 0.1 - 0.2.
2.4.3 double heating rotary dryer
The dryer is mainly composed of a rotary drum and a central inner tube. The hot air enters the inner cylinder, and the material outlet end is folded into the outer cylinder, and the material is discharged from the raw material supply end. Material moves in the annular space along the outer wall of the housing and the inner wall of the central wall. The required heat, part by the hot air passing through the inner wall of the cylinder heat transfer surface, heat conduction to material; another part through the hot wind and materials in the shell wall and the central tube annular space in a countercurrent contact, by convection heat transfer to materials. The structure has the advantages that the air is first passed through the inner tube, and the entrained dust can be reduced, and the heat loss to the surrounding environment can be reduced, and the effective utilization rate of the heat energy is improved.
轉(zhuǎn)筒干燥器的總體與結(jié)構(gòu)設(shè)計
1 引言
干燥的操作幾乎涉及到國民經(jīng)濟的所有部門，廣泛用于生產(chǎn)和生活之中。所謂干燥，一般是指從固體材料中使液體（主要是水份）揮發(fā)和分離的操作，也包括從液體或泥漿狀的物料中蒸發(fā)除去水分，以達到固體中失去水分的操作。其目的是除去某些原料、半成品以及成品中的水分或溶劑，以便于加工、使用、運輸、儲藏等。
干燥是消耗大量熱量的操作，在嚴格要求節(jié)省能源的今天，干燥所使用的熱源，若能把利用廢氣及剩余蒸汽等廉價的熱源作為方向，對于干燥機本身來說，即使熱效率降低，但對整體而言，還是經(jīng)濟的。另外，在進入干燥工序之前的前處理工序，能采用降低水分的方法是經(jīng)濟的。
對于干燥操作來說，干燥器的選擇是非常困難而復(fù)雜的問題。因被干燥物料的特性、供熱的 方法和物料 — 干燥介質(zhì)系統(tǒng)的流體動力學(xué)等必須全部考慮。由于被干燥物料的種類繁多，要求各異，決定了不可能有一個萬能的干燥器，只能選用最佳的干燥方法和干燥器形式。
轉(zhuǎn)筒干燥器的主體是略帶傾斜并能回轉(zhuǎn)的圓筒體。濕物料從左端上部加入，經(jīng)過圓筒內(nèi)部時，與通過筒內(nèi)的熱風或加熱壁面進行有效的接觸而被干燥，干燥后的產(chǎn)品從右端下部收集。在干燥過程中，物料借助于圓筒的緩慢轉(zhuǎn)動，在重力的作用下從較高的一端向較低的一端移動。筒體內(nèi)壁上裝有順向抄板（或類似的裝置），它不斷地把物料拋起又灑下，使物料的熱接觸面表面增加，以提高干燥速率并促進物料向前移動。干燥過程中所用的熱載體一般為空氣，煙道氣或水蒸氣等。如果熱載體（如熱空氣、煙道氣）直接與物料接觸，則經(jīng)過干燥后，通常用旋風除塵器將氣體中所夾帶的細粒物料捕集下來，非空氣則經(jīng)旋風除塵器后放空。轉(zhuǎn)筒干燥器是最古老的干燥設(shè)備之一，但由于經(jīng)濟實用工作量大，效率較高，目前仍被廣泛使用于冶金、建材、化工等領(lǐng)域。
2 概述
2.1 干燥的目的
干燥的操作幾乎涉及到國民經(jīng)濟的所有部門，廣泛用于生產(chǎn)和生活之中。
所謂干燥，一般是指從固體材料中使液體（主要是水分）揮發(fā)和分離的操作，也包括從液體或泥漿狀的物料中蒸發(fā)除去水分，以達到固體中失去水分的操作。其目的是除去某些原料、半成品以及成品中的水分或溶劑，以便于加工、使用、運輸、儲藏等。
干燥是消耗大量熱量的操作，在嚴格要求節(jié)省能源的今天，干燥所使用的熱源，若能把利用廢氣及剩余蒸氣等廉價的熱源作為方向，對于干燥機本身來說，即使熱效率降低，但對整體而言，還是經(jīng)濟的。
另外，在進入干燥工序之前的前處理工序，能采用降低水分的方法是經(jīng)濟的。
2.2 轉(zhuǎn)筒干燥器的主要組成及作用
轉(zhuǎn)筒干燥器主要有以下主要部分組成。筒體是一主要部分，其外廓尺寸決定于反應(yīng)或操作所需要的空間。筒內(nèi)是空的或裝有抄板，也有裝著鏈子的，以達到增加傳熱和粉碎物料的目的。
筒上裝有滾圈，筒體及筒中所裝物料的重量，通過滾圈而傳給支座的托輪，支座裝有防止筒體作軸向竄動的裝置。靠近托輪一擋輪座的筒體上，裝有齒圈，以帶動筒體回轉(zhuǎn)。裝在減速箱軸上的齒輪與此齒圈相連，減速箱和電動機構(gòu)成一傳動機構(gòu)。
在轉(zhuǎn)筒的物料端，裝有一個小室，為卸出物料及傳入或引入引出氣體而用。筒的出料端用密封裝置（迷宮或端面式的密封）加以密封。
在筒的一端設(shè)有卸料裝置，用以加卸出被處理的固體物料。
被處理的物料與氣流在轉(zhuǎn)筒內(nèi)即可以并流，也可以逆流。如果由于過程或反應(yīng)的進行必須加熱，則此熱量可由氣體直接供給；也可由筒壁傳入；可由于筒內(nèi)被處理物料所放出的反應(yīng)熱；也可由在筒內(nèi)直接燒燃料供給。氣體加熱的方法及其最高溫度決定于被處理固體物料的性質(zhì)及是否允許被弄臟等多種因素。
從制造方便、機械強度大及材料消耗少等方面考慮，轉(zhuǎn)筒通常做成圓形截面。但是小的轉(zhuǎn)筒，也有做成六邊形或多邊形的，甚至有的將兩端做成錐形的。
圓筒的外廓尺寸決定于所需的生產(chǎn)能力、物料在筒內(nèi)所停留的時間以及通過圓筒的氣體的最大允許速度。
2.3轉(zhuǎn)筒干燥器的工作原理
轉(zhuǎn)筒干燥器的主體是略帶傾斜并能回轉(zhuǎn)的圓筒體。濕物料從左端上部加入，經(jīng)過圓筒內(nèi)部時，與通過筒內(nèi)的熱風或加熱壁面進行有效的接觸而被干燥，干燥后的產(chǎn)品從右端下部收集。在干燥過程中，物料借助于圓筒的緩慢轉(zhuǎn)動，在重力的作用下從較高的一端向較低的一端移動。筒體內(nèi)壁上裝有順向抄板（或類似的裝置），它不斷地把物料拋起又灑下，使物料的熱接觸面表面增加，以提高干燥速率并促使物料向前移動。干燥過程中所用的熱載體一般為空氣、煙道氣或水蒸氣等。如果熱載體（如熱空氣、煙道氣）直接與物料接觸，則經(jīng)過干燥后，通常用旋風除塵器將氣體中所夾帶的細粒物料捕集下來，非空氣則經(jīng)旋風除塵器后放空。轉(zhuǎn)筒干燥器是最古老的干燥設(shè)備之一，但由于經(jīng)濟實用工作量大、效率較高，目前仍被廣泛使用于冶金、建材、化工等領(lǐng)域。
2.4 轉(zhuǎn)筒干燥器的分類及適用范圍
2.4.1 直接加熱式
（1）常規(guī)直接加熱轉(zhuǎn)筒干燥器
該干燥設(shè)備中被干燥的物料與熱風直接接觸，以對流傳熱的方式進行干燥。按熱風與物料之間的流動方向又分為并流式和逆流式。在并流式中熱風與物料移動方向相同，入口處溫度較高的熱風與濕含量較高的物料接觸。因物料溫度處于表面汽化階段，故產(chǎn)品溫度仍然大致保持濕球溫度。出口側(cè)的物料雖然溫度在升高，但此時的熱風溫度已經(jīng)降低，故產(chǎn)品的溫度升高不會太大，因此選用較高的熱風入口溫度，不會影響產(chǎn)品的質(zhì)量。這對于那些熱敏性物料的干燥包括那些含有易揮發(fā)物料的干燥是很適宜的；對于耐高溫的物料，采用逆流干燥，熱利用率高。干燥器的空氣出口溫度在并流式中一般應(yīng)高于物料出口溫度的10——20℃。在逆流式中，如沒有明確規(guī)定，一般采用100℃作為出口的溫度較為合理。
常規(guī)直接加熱轉(zhuǎn)筒干燥器的筒體直徑一般為0.4——3m，筒體長度與筒體直徑之比一般為4——10。干燥器的圓周速度為0.4——0.6m/s，空氣速度在1.5——2.5m/s范圍內(nèi)。
（2） 葉片式穿流轉(zhuǎn)筒干燥器
按照熱風的吹入方式將葉片式穿流轉(zhuǎn)筒干燥器分為端面吹入型和側(cè)面吹入型兩種。上圖是端面吹入型的簡圖，其筒體水平安裝，沿筒體內(nèi)壁圓周方向等距離裝有許多從端面入口側(cè)向出口側(cè)傾斜葉片（百葉窗），熱風從端部進入轉(zhuǎn)筒底部，僅從下部有料層的部分葉片間隙吹入筒內(nèi)，因此能有效地保證干燥在熱風與物料的充分接觸下進行，不會出現(xiàn)短路現(xiàn)象。物料在傾斜的葉片和筒體的回轉(zhuǎn)作用下，由入口側(cè)向出口側(cè)移動，其滯留時間可用出口調(diào)節(jié)隔板調(diào)節(jié)。側(cè)面吹入型與端面吹入型不同的是筒體略帶傾斜安裝，大部分熱風從開有許多小孔的筒體外吹入筒內(nèi)，其方向與筒內(nèi)物料的移動方向成直角，再穿過三角形葉片的百葉窗孔進入料層。在回轉(zhuǎn)筒體內(nèi)壁四周裝有箱形殼體，并沿回轉(zhuǎn)筒體長度方向分成3——4個獨立的室。每個室都有獨立的鼓風機、空氣加熱器以及進氣口和排氣口。熱風溫度以及循環(huán)風量、排氣量均能自行調(diào)節(jié)。這種類型的干燥器體積傳熱系數(shù)大，約為349——1745w/（m）；干燥時間短，約為10——30min；物料的填充率較大，約為20%——30%；裝置容積相對較小，料層阻力為98——588pa；通道風速一般為0.5——1.5m/s；筒體的轉(zhuǎn)速為常規(guī)直接加熱轉(zhuǎn)筒干燥器的1/2左右；使用的熱風溫度為100——300℃。在工業(yè)上常采用這種干燥器干燥粒狀、塊狀或片狀物料，例如焦炭、壓扁干豆、砂糖等忌破壞的物料，此外，像塑料粒一類必須干燥到很低水分的物料以及像十片、低漿渣等密度小的物料，都可以用它來干燥。
（3）通氣管式轉(zhuǎn)筒干燥器
該干燥器的設(shè)計和安裝與常規(guī)式相同，不同的是筒內(nèi)設(shè)有安裝抄板，物料自進口端向出口端移動的過程中，始終處于轉(zhuǎn)筒的底部的空間中，形成一個穩(wěn)定的料層，因而減少了塵土的飛揚。熱空氣從端部進入不隨筒體轉(zhuǎn)動的中心管后，高速地從埋在料層中的粉質(zhì)管小孔中噴出，與物料強烈接觸。通氣管式干燥器的體積傳熱系數(shù)約是常規(guī)式的兩倍。轉(zhuǎn)筒的圓周速度約為常規(guī)式的1/2，在相同的生產(chǎn)能力下，干燥筒體的長度僅是常規(guī)式的1/2，因此大大降低了設(shè)備的費用。
24.2 間接加熱轉(zhuǎn)筒干燥器
1.常規(guī)間接加熱轉(zhuǎn)筒干燥器
該干燥器筒體砌在爐內(nèi)，用煙道氣加熱外殼。筒內(nèi)設(shè)置一個同心圓筒。煙道氣進入外殼和爐壁之間的環(huán)狀空間后，穿過連接管進入干燥筒內(nèi)的中心管。常規(guī)直接加熱轉(zhuǎn)筒干燥器特別適用于干燥那些降速干燥階段較長的物料。因為它可以在相當穩(wěn)定的干燥溫度下，使物料有足夠的停留時間，同時可以借助轉(zhuǎn)筒的回轉(zhuǎn)作用，有效的防止物料的結(jié)塊。該干燥器適用于干燥熱敏性物料，但不適用于粘性大，特別易結(jié)塊的物料。
2.蒸汽管間接加熱轉(zhuǎn)筒干燥器
在干燥筒內(nèi)以同心圓方式排列1——3圈加熱管，其一端安裝在干燥器出口處集管箱的排水分離室上；另一端用可以熱膨脹的結(jié)構(gòu)安裝在通氣頭的管板上。物料在干燥器內(nèi)受到加熱管的開舉和攪拌作用而被干燥，并借助干燥器的傾斜度從較高一段向較低一端移動，從設(shè)在端部的排料斗排出。該干燥器具有常規(guī)間接加熱轉(zhuǎn)筒干燥器的所有優(yōu)點，它的單位容積干燥能力是常規(guī)直接加熱式的3倍左右，熱效率高達80%——90%，物料的填充率為0.1——0.2。
2.4.3 復(fù)式加熱轉(zhuǎn)筒干燥器
該干燥器主要由轉(zhuǎn)筒和中央內(nèi)管組成。熱風進入內(nèi)筒，由物料出口端折入外筒后，由原料供給端排出。物料則沿著外殼壁和中央內(nèi)壁的環(huán)狀空間移動。所需的熱量，一部分由熱空氣經(jīng)過內(nèi)筒傳熱壁面，以熱傳導(dǎo)的方式傳給物料；另一部分通過熱風與物料在外殼壁與中央內(nèi)筒的環(huán)狀空間中逆流接觸，以對流傳熱的方式傳給物料。該結(jié)構(gòu)的優(yōu)點是：熱風先通過內(nèi)筒，可以把夾帶的粉塵沉降下來，同時減少了對與周圍環(huán)境的熱損失，提高了熱量的有效利用率。
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