SU744212A1

SU744212A1 - Hearth pipe

Info

Publication number: SU744212A1
Application number: SU782590571A
Authority: SU
Inventors: Вениамин Васильевич Антонов; Григорий Саввич Якименко; Вячеслав Леонидович Дзюба; Николай Антонович Кияшко
Original assignee: Донецкий научно-исследовательский институт черной металлургии
Priority date: 1978-03-13
Filing date: 1978-03-13
Publication date: 1980-06-30

Description

(54) ПОДОВАЯ ТРУБА(54) GRADE PIPE

II

Изобретение относитс к технике нагрева металла, преимущественно к технике двухстороннего нагрева на охлаждаемых опорах и может быть использовано в металлургической и машиностроительной промышленности .The invention relates to metal heating technology, mainly to double-sided heating technology on cooled supports and can be used in the metallurgical and engineering industries.

Известны подовые трубы, охлаждение которых осуш,ествл етс либо проточной водой , либо с помощью испарительного охлаждени 1. С целью уменьшени потерь тепла с охлаждающей водой и улучшени качества нагрева металла, наружную поверхность труб изолируют либо специальными огнеупорными блоками, либо рейтерами из жаропрочной стали.Bottom pipes are known whose cooling is dried either by running water or by evaporative cooling 1. In order to reduce heat loss from the cooling water and improve the quality of metal heating, the outer surface of the pipes is insulated either with special refractory blocks or heat resistant steel reaters.

Недостатком известных подовых труб вл етс в случае вод ного охлаждени - низка стойкость труб из-за прогаров вследствие выпадени накипи и отложени шлама, а также большие потери тепла с охлаждающей водой и существенное охлаждение вли ни на металл в области контакта заготовок с трубами, а в случае испарительного охлаждени - неудовлетворительна стойкость труб из-за локальных прогаров вследствие неравномерного распределени охлаждающей воды по трубам и низкие энергетические параметры пара, что затрудн ет использование пара в технологических процессах .A disadvantage of the known bottom pipes is in the case of water cooling — low pipe resistance due to burnout due to precipitation and sludge deposition, as well as large heat losses from the cooling water and substantial cooling of the effect on the metal in the contact area of the billets with the pipes. in case of evaporative cooling, the pipe resistance is unsatisfactory due to local burnout due to the uneven distribution of cooling water through the pipes and low energy parameters of steam, which makes it difficult to use steam in technological processes.

Наиболее близким по технической сущности и достигаемому эффекту к предлагаемому вл етс печной ролик, состо щий из герметично закупоренного корпуса с жидким теплоносителем, холодильником и внутренней трубы с перегородками и отверсти ми 2. Ролик обладает более высокой стойкостью по сравнению с роликом, охлаждаемым проточной водой. Кроме того, потери тепла через предложенный ролик меньше, а КПД печи больше, так как температура наружной поверхности ролика выше.The closest to the technical essence and the achieved effect to the proposed is a furnace roller consisting of a hermetically sealed housing with a heat-transfer fluid, a cooler and an inner tube with partitions and holes 2. The roller has a higher resistance compared to a roller cooled by running water. In addition, the heat loss through the proposed roller is less, and the efficiency of the furnace is greater, since the temperature of the outer surface of the roller is higher.

Недостатком известного ролика вл етс то, что при применении его в стационар15 ном положении, т.е. без вращени будет создаватьс неравномерное распределение температуры в корпусе и возникать термические напр жени , так как жидкий теплоноситель заполн ет не всю полость корпуса ролика , а лишь 1/4-1/5 часть объема или сег20 мента с дугой 120-130°. Увеличение объема жидкого теплоносител свыше 25Vo нецелесообразно , так как жидкой фазой будет перекрыватьс часть поперечного сечени .A disadvantage of the known roller is that when applied in a stationary position, i.e. without rotation, an uneven temperature distribution in the housing will be created and thermal stresses will occur, since the heat-transfer fluid does not fill the entire cavity of the roller body, but only 1 / 4-1 / 5 of the volume or segment with an arc of 120-130 °. An increase in the volume of the liquid coolant above 25Vo is impractical, since the liquid phase will overlap part of the cross section.

через которое движетс газообразна фаза, вследствие чего ухудшаетс циркул ци теплоносите 1 и снижаетс эффективность охлаждени . Поэтому при применении конструкции известного ролика в стационарном положении, т.е. при отсутствии вра1цени , ухудшаетс стойкость опорного устройства. Цель изобретени - увеличение стойкости трубы и повышение эффективности использовани тепла при стационарном режиме .through which the gaseous phase moves, as a result of which the circulation of heat carrier 1 deteriorates and the cooling efficiency decreases. Therefore, when applying the design of a known roller in a stationary position, i.e. in the absence of a momentum, the stability of the support device deteriorates. The purpose of the invention is to increase the resistance of the pipe and increase the efficiency of heat use in stationary mode.

Поставленна цель достигаетс тем, что внутренн труба смещена вниз относительно оси корпуса на 0,08-0,12 внутреннего диаметра корпуса и выполнена с диаметром, равным 0,7-0,8 внутреннего диаметра корпуса, причем торцы ее заглушены, а отверсти на внутренней трубе расположены в верхней части ее в пределах дуги 40-50°.The goal is achieved by the fact that the inner pipe is displaced downward relative to the axis of the housing by 0.08-0.12 inner diameter of the housing and is made with a diameter equal to 0.7-0.8 of the internal diameter of the housing, with its ends plugged and the holes on the inside The pipe is located in the upper part of it within an arc of 40-50 °.

На фиг. 1 схематически изображена нодова труба, продольный разрез; -на фиг. 2 - разрез А-А на фиг. 1; на фиг. 3 - разрез Б-Б на фиг. 1.FIG. 1 shows schematically a node tube, a longitudinal section; in FIG. 2 shows section A-A in FIG. one; in fig. 3 shows a section BB in FIG. one.

Труба состоит из корпуса 1, представл юшего собой толстостенную трубу. Участки трубы, выступаюшие из печи и наход шиес в теплообменниках 2, выполнены из тонкостенной трубы. Дл интенсификации теп лооб.гена и у.меньшени габаритов теплообменников эти участки трубы оребрены. Внутри корпуса находитс жидкий теплоноситель, воздух откачан. В корпусе установлена внутренн труба 3 с перегородками 4, отверсти ми 5 в середине трубы и отверсти ми 6 на участках, наход щихс в теплообменниках . Перегородки 4 перекрывают полностью верхнюю часть кольцевого канала до уровн воды. Отверсти 5 и 6 выполнены в верхней поверхности трубы в пределах дуги 40-50 дл предупреждени затекани воды во внутреннюю трубу. В корпусе 1 выполнено отверстие 7, в которое, в цел х обеспечени безопасной работы под давлением, ставитс либо клапан, срабатываюпшй при повышеНИИ давлени выше допустимого, либо устанавливаетс пробка из сплава, те.мпература плавлени которого на 20-50° выше максимально допустимой те.мпературы внутри трубы . К теплообменникам 2 подсоединены патрубки 8 и 9, служащие дл подвода воды и отвода либо воды, либо пара, либо паровод ной смеси. В стенке теплообменников со стороны печи предусмотрены уплотнительные фланцы 0, служащие дл поддержани в теплообменниках необходимого давлени и перемещени трубы вследствие температурных расширений.The pipe consists of body 1, which is a thick-walled pipe. The pipe sections protruding from the furnace and located in the heat exchangers 2 are made of a thin-walled pipe. In order to intensify the heat gene and reduce the dimensions of the heat exchangers, these sections of the tube are ribbed. Inside the case there is a liquid coolant, the air is pumped out. An internal pipe 3 with partitions 4, openings 5 in the middle of the pipe and openings 6 in areas located in heat exchangers is installed in the housing. Partitions 4 overlap the entire upper part of the annular channel to the water level. Holes 5 and 6 are provided in the upper surface of the pipe within the arc 40-50 to prevent water from flowing into the inner pipe. In case 1, a hole 7 is made, in which, in order to ensure safe operation under pressure, either a valve actuated when the pressure is raised is higher than the allowable pressure, or an alloy plug is installed, the melting temperature of which is 20-50 ° above the maximum allowable temperature. The temperature inside the pipe. The heat exchangers 2 are connected to the pipes 8 and 9, which are used to supply water and discharge either water, steam, or steam-water mixture. Sealing flanges 0 are provided in the wall of the heat exchangers on the furnace side to maintain the required pressure in the heat exchangers and displace the pipe due to temperature expansion.

При работе вода из теплообменников 2 по кольцевому каналу движетс к середине подовой трубы, охлажда стенки корпуса 1, нагрева сь и испар сь. Движению пара навстречу конденсата преп тствуют перегородки 4. Поэтому практически весь пар движетс к середине подовой трубы и через отверсти 5 поступает во внутреннюю трубу. При испарении происходит повышение давлени , вызывающее движение пара в полость внутренней трубы. Пар но внутренней трубе движетс к теплообменникам, где истекает через отверсти 6, растекаетс по стенкам теплообменников и конденсируетс . При конденсации происходит уменьшение давлени , что также способствует перемещению пара в зону охлаждени . Движение воды из зоны конденсации в зону испарени происходит под действием силы т жести. Нагрев, испарение , охлаждение и конденсаци , а также перемещение теплоносител (воды) происходит непрерывно. При кипении и конденсации создаютс весьма высокие коэффициенты теплоотдачи , что обеспечивает эффективное равномерное охлаждение корпуса и эффективный отвод тепла. При работе внутренн полость трубы находитс под давлением в несколько атмосфер, что также способствует эффективности теплообмена, так как коэффициенты теплоотдачи с повышением давлени до определенного уровн при прочих равных услови х увеличиваютс . В трубе практически полностью отсутствует опасность образовани накипи и выпадени щлама, так как в обороте находитс один и тот же объем воды. Создание давлени внутри трубы вызывает повышение температуры. Например, температура кипени воды при давлении 10 ата составл ет 179°С. Поэтому температура внутренней и, как следствие, наружной поверхности корпуса выще, чем в случае охлаждени трубы проточной водой, а при создании специальных условий выше, чем в случае испарительного охлаждени .During operation, the water from the heat exchangers 2 moves through the annular channel to the middle of the bottom tube, cooling the walls of the housing 1, heating and evaporating. Partitions 4 prevent movement of steam towards condensate. Therefore, almost all of the steam moves to the middle of the bottom tube and through holes 5 enters the inner tube. During evaporation, an increase in pressure occurs, causing the vapor to move into the cavity of the inner tube. The vapor inside the tube moves to the heat exchangers, where it flows through the openings 6, spreads along the walls of the heat exchangers and condenses. During condensation, the pressure decreases, which also contributes to the movement of steam into the cooling zone. The movement of water from the condensation zone to the evaporation zone occurs under the force of gravity. Heating, evaporation, cooling and condensation, as well as movement of the heat carrier (water) occurs continuously. During boiling and condensation, very high heat transfer coefficients are created, which ensures efficient uniform cooling of the casing and efficient heat removal. During operation, the internal cavity of the pipe is under pressure of several atmospheres, which also contributes to the efficiency of heat transfer, since heat transfer coefficients increase with pressure to a certain level, ceteris paribus. In the pipe there is practically no danger of scaling and sludge falling out, since the same volume of water is in circulation. Creating pressure inside the pipe causes a rise in temperature. For example, the boiling point of water at a pressure of 10 atm is 179 ° C. Therefore, the temperature of the inner and, as a result, outer surface of the housing is higher than in the case of cooling the pipe with running water, and in creating special conditions it is higher than in the case of evaporative cooling.

Оптимальное соотношение диаметров корпуса и внутренней трубы, а также эксцентриситета определ етс при следующих услови х .The optimum ratio of the diameters of the casing and the inner tube as well as the eccentricity is determined under the following conditions.

Пространство между корпусом и внутренней трубой в нижней части должно обеспечивать беспреп тственное удаление пузырьков и подвод жидкого теплоносител . Диаметр внутренней трубы должен быть таким, чтобы при ее опускании уровень жидкости поднималс до хорды сегмента с дугой 200240° корпуса и над этим уровнем оставалс участок внутренней трубы с дугой 60-90°. Объем полости над уровнем жидкости должен обеспечивать беспреп тственное движение газообразного теплоносител к середине трубы.The space between the casing and the inner tube in the lower part should ensure the smooth removal of bubbles and the supply of heat-transfer fluid. The diameter of the inner tube should be such that when it is lowered, the liquid level rises to the chord of the segment with the 200240 ° arc of the body and the section of the inner pipe with the arc of 60-90 ° remains above this level. The volume of the cavity above the level of the liquid must ensure the unimpeded movement of the gaseous coolant to the middle of the pipe.

Claims

The rationale for these limits of the relationship between the diameters of the body and the inner pipe, as well as the eccentricity is confirmed by the example of a bottom pipe with a diameter of 121 mm and a wall thickness of 20 mm. The length of the section in the furnace is 20 m. The average heat flux to the surface of the pipe is 120,000 kcal / m. The average pressure inside the pipe is 10 atm. The diameter of the inner tube is 60 mm, the wall thickness is 3.mm. Heat transfer is carried out entirely by evaporation and condensation. The heat carrier is water. Two-way heat removal, i.e. heat exchangers are installed at both ends of the pipe. The amount of heat removed. Q qf q2лrl 120000.23,14-0,06-20 904320 kcal / h, where q is the average heat flux to the surface of the pipe, kcal / m h; f is the area of the outer surface of the pipe section located in the furnace, g is the pipe radius, m; 1 is the length of the pipe section located in the furnace, m. The water flow is 1875.8 kg / h V | rrife-v 1875.8 Yu, 001126 2.112, where gp and Vg-, respectively, the mass and volume consumption of water, kg / h, i - the heat of vaporization is hidden, kcal / kg; V is the specific volume of water,. It is assumed that the length of the pipe sections located in the heat exchanger is 5 m (2.5 m each). The total length of the pipe is 25 m, the volume of the cavity is 0.1287 m, the volume of water is 20% or 0.02575 m. With a uniform filling of the pipe along the length, water occupies a segment with an arc of 121 °, the area of which is 0.001 m. Minimalin is the size of the gap between the body and the inside the pipe should be at least three times the diameter of the vapor bubbles at the operating parameters. The diameter of vapor bubbles at a pressure of 10 atm is 0.3-0.5 mm. However, taking into account that with a decrease in heat loads of the furnace, a decrease in pressure inside the pipe occurs and, accordingly, an increase in the diameter of the bubbles, we take the gap size equal to 2.5 mm. The axis of the inner tube with respect to the axis of the housing is displaced down by 8 mm or by 0.099 of the inner diameter of the housing. The downward displacement of the inner pipe causes the water level to rise by such a magnitude that the water occupies an annular channel with an arc of 220 ° relative to the inner circumference of the housing, and the inner pipe segment with an arc of 86 ° remains above the water level. (The cross-sectional area of the housing cavity to 0; 005153 is the cross-sectional area of the inner tube with respect to the outer diameter fgrO, 00283 the cross-sectional area occupied by water fgO, 00103 is the inner tube segment area with an arc of 86 ° fgV 0.00022 the cross-sectional area of the inner tube is below water level 0 , 00261, the cross-sectional area of the hull is below the water level f to, 0.00364 m 2; the hull cross-sectional area is higher than the water level, f is 0.001513 arc of the segment washed by water, 220 °; the free cross-sectional area of the hull is higher than the water level ) 0.001293 m2). It is assumed that the heat removal is carried out uniformly to both heat exchangers. Then the water consumption per heat exchanger mg l / 2mj 1875.8 937.0 kg / h; Vi j-Vi ,, - 2, 056M l4 Water velocity in the annular channel Vj1,056 3600-fgS600-0.00103 0.285 m / s. Steam is formed (based on one heat exchanger) V; i rng-Vn 937.9-0.198 185.7 0.0516 m3 / s, where V is the specific volume of dry saturated steam,. The steam velocity in the annular channel A is 39.9 ° / s. The area of the holes in the wall of the inner tube is equal to the cross-sectional area of the inner tube. The steam velocity in the inner tube Wn -) -, 5 m / s. f6T0.00225 where fg is the cross-sectional area of the pipe according to the inner diameter, m. The given example shows that the use of the proposed device allows to increase the perimeter of the pipe wetted by the heat-transfer fluid up to 220 ° or 1.8 times, which allows to increase the service life bottom pipes. The movement of water and steam inside the pipe occurs at relatively low speeds, which is quite feasible due to the pressure drops that occur during evaporation and condensation. The geometrical ratios of the diameters and the eccentric system may vary within very narrow limits due to the fact that an increase in the diameter of the inner tube causes a decrease in the cross-sectional area above the tube for the passage of steam. The diameter of the inner tube should not be greater than 0.8 of the inner diameter of the housing. The decrease in the diameter of the inner tube causes a decrease in the arc of the segmentation washed by the heat-transfer fluid. The minimum value of the inner tube is 0.7 of the inner diameter of the housing. The decrease in eccentricity causes a decrease in the degree of rise of the level of the liquid coolant and a decrease in the arc of the segment washed by the coolant. The minimum value of the eccentricity is 0.08 of the inner diameter of the case, the perimeter wetted by the coolant is 200 °. The increase in eccentricity causes the misery between the hull and the pipe in the lower part. The minimum gap should be 3-4 times the diameter of the vapor bubbles with operating parameters. This value, when used as a heat transfer fluid, is 2.5 mm for pipes with a diameter of up to 100 mm and 4 mm for pipes of large diameter. The maximum eccentricity value here is 0.12 of the inner diameter of the housing. The internal cavity of the pipe is filled with: a liquid heat carrier, for example, water. During operation, the main part of the pipe is located in the working space of the furnace, the pipe ends are removed from the furnace and are located in heat exchangers. The cooling of the tube, the circulation of the coolant and the transfer of heat inside the tube is carried out in the same way as in the known roller. A distinctive feature is that for a more uniform cooling of the housing with a heat-transfer fluid, its volume in the tube cavity is left the same, and the level is raised so that the heat-transfer fluid will wash the surface with an arc of about 200-240 °. For this, the inner pipe relative to the body is installed eccentrically with a shift downwards, and the ends of the pipe behind are damped. The downpipe pipe displaces the liquid in the annular channel upwards, higher; The body wash stump increases with liquid heat carrier, improves the uniformity of temperature distribution in the cross section of the case, decreases thermal stress, as a result of which the resistance of the pipe increases. The inner tube, as in the known roller, serves as a channel for the movement of the gaseous coolant, the liquid coolant moves along the annular channel. The partitions installed in the area between the high-temperature zone and the heat exchangers overlap completely the cross section of the annular channel above the level of the heat-transfer fluid. To prevent the coolant from flowing into the inner tube, the inlet and outlet openings for the coolant gas are made in the upper surface of the inner tube. The proposed device also makes it possible to increase the efficiency of using the heat entering the pipe. The advantages are that the steam parameters in the heat exchanger may differ from those inside the pipe. In addition, the device allows to obtain superheated steam, which is unattainable in the widespread evaporative cooling system. To this end, the heat exchanger is divided into several sections: in some, water evaporates, in others, steam overheating. The effectiveness of the proposed bottom tube is to increase the resistance of pipes, reduce the specific fuel consumption for heating and increase the degree of use of heat entering the pipe. The invention of the billow tube, comprising a sealed housing with a heat-transfer fluid and an inner tube with holes built into it, heat exchangers installed along the ends of the tubes and partitions placed in the gap between the tubes in front of the entrance to the heat exchangers, characterized in that the durability of the pipe and increase the efficiency of heat use in stationary mode; the inner pipe is shifted downward relative to the axis of the body by 0.08-0.12 inner diameter of the body and is made with a diameter of 0.7-0.8 internal its case diameter, and its ends are plugged and the holes in the inner tube are located in the upper part of it within an arc of 40-50 °. Sources of information taken into account during the examination 1. Reference book of the designer of furnaces for rolling production. Ed. Tymchak V.M., Metallurgi, 1970, Vol. 2 p. 825-836.

2. USSR author's certificate according to the application 2464892 / 29-02, cl. F 27 D 3/02, 1976.

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