The history of the development of the drying parts of paper machines. Ergashev Karim Ergashevich, Sadriddinov Bakhtiyor Badriddinovich, Rakhmatov Makhmud Norboevich Pulp and paper production equipment Recommended as a textbook. Cylinder paper machines

A paper machine is a combination of continuous production sections, as a result of which paper and cardboard are obtained from a fibrous suspension. There are two types of this...

The paper machine is the combination of continuous production sections, as a result of which paper and cardboard are obtained from a fibrous suspension. There are two types of this unit: canteen (with a flat mesh) and cylinder (with a round mesh).

More common table paper machine, with which the main types of paper are made.

The main sections of this design are: mesh, press, drying and finishing parts.

Grid part

The grid part is an endless grid made of synthetic materials or various copper alloys. In this section, a paper web is formed from a highly diluted slurry and the first part of the excess water is removed. These stages occur due to the free flow of the suspension and the suction effect of the register rollers. Further dehydration is carried out using special vacuum pumps.

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press part

After passing through the wire section, the paper web with a dryness percentage of approximately 18-22% enters the press section. Here, excess water is removed by mechanical extraction. The paper is passed through 2-3 roller presses arranged in series under the simultaneous action of vacuum and pressure. At the same time, its bulk density and strength increase, while the absorbency and porosity, on the contrary, decrease. The pressing process takes place between wool felts, which absorb moisture and transport the web, and also perform an important function of protecting the weak paper web from destruction. In order to achieve an increase in the density and smoothness of the paper, additional smoothing presses are often installed.

Drying part

The paper web enters the drying section with a dryness of about 45%. This section of the paper machine consists of rotating cylinders staggered and heated by steam. At this stage of production, the paper web is pressed against heated cylinders with the help of felts, which prevents its wrinkling and warping. Its movement occurs from the lower cylinder to the upper one, then again to the lower one located nearby, etc. The paper in the drying section is dried to a moisture content of 5–7%.

Finishing part

In the finishing section there are 5-10 cast iron chilled rollers located one above the other. The paper, pre-moistened with cold water, moves from top to bottom between the rollers. After passing through this stage, the paper web acquires a flat, smooth surface and uniform thickness. To prevent wrinkling, the canvas is wound into rolls on the reel. If it is necessary to release paper of increased smoothness, additional moisturizing equipment is installed above the reel. The resulting rolls are then fed to a slitting machine, where they are cut into pieces with the required parameters.

Special equipment

The paper machine is also equipped with a large number of automatic devices that ensure its continuous operation. The task of this additional equipment is to regulate the technological parameters of the entire process. For the manufacture of various kinds the paper web, its technically justified parameters are set, namely the operating speed and width of the machine. The paper machine can be narrow or wide.

Narrow machines with a web width of 1.6 to 4.2 m are mainly intended for the production of special technical, high-quality bond papers. Wide machines with a web width of more than 6 m are used for the production of sack and newsprint. The operating speed of the paper machine in the production of newsprint and tissue paper is much higher than the speed in the manufacture of high-quality papers. The presence of special equipment and automatic devices contributes to the accuracy of the paper machine and reduces the number of workers serving it to 3-8 people.

Manufacturing Process Improvement

To further improve the paper production process, it is necessary to change the production technology, increase the productivity of the machine due to the width and speed, and modernize the device of the machine and its components.

To increase the productivity of the paper machine due to speed and width will help:

special high-speed flow distributors that release the fibrous suspension onto the mesh at the speed that is necessary with the increased speed of the mesh;
hydroplanki and register rollers, increasing the removal of moisture;
various types of presses such as hot and multi-shaft presses, presses with wide suction chambers;
suction rolls fixed in the middle, grooved corrugated rolls, suction vacuum cloth washers;
reels of peripheral type with pneumatic paper web clamp, used for winding a roll of 2200–2500 mm in diameter.

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For the drying section of a paper machine, the following can also be successfully used: siphon removal of condensate, new layouts of steam distributors, higher steam pressure, replacement of dryer felts with dryer nets. At present time runs active search for new types of drying, in order to replace traditional look to a more advanced one, which would increase the uniformity of the drying process and significantly reduce the working area of the drying section. New types of drying such as infrared irradiation, hot air drying, dielectric drying and vacuum drying have good prospects for the future.

The principle of operation of the paper machine

The paper machine is used to make paper from fibrous mass by casting a layer of fibers, followed by dewatering, pressing and winding into a roll. IN tsarist Russia such units began to be used from the second half of the nineteenth century. They were distinguished by low productivity, poor water separation, and manual control. Repairs required stopping the machines, but they were highly reliable and simple in design. At the Slavuta paper mill, such a unit was installed in 1864 and worked until the end of the 20th century.

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The principle of the machine

There are 2 types of paper machine: canteen - the pulp is distributed on a flat endless grid and cylinder - with a round grid. Table units are mainly used, cardboard and some types of paper are made on cylinder units. The machine is made according to the principle of sequentially installed continuously operating sections:

grid;
press;
drying room;
finishing.

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In addition, there are many auxiliary systems and mechanisms that provide and control a continuous cycle of paper production. The speed of the paper web varies from 40 m/min in the production of thin capacitor paper, up to 1000 m/min in newsprint. This is a very energy-intensive unit that consumes up to 30 MW of electricity and 45 tons of steam. A process control system is used to control the technological process. At such speeds, manual control and adjustment of parameters is impossible.

The paper manufacturing process begins with the preparation of raw materials. For this, a mixing chamber is used, into which the crushed and previously cleaned of foreign objects that are not involved in the process (metal, stones, adhesive tape, etc.) are fed paper components - waste paper, rags. If wood is used, then pre-prepared chips are boiled in a solution of caustic substances until completely dissolved.

The finished stock is pumped from the mixing section to the paper machine pool. The concentration of the incoming medium is 3-4%. In the tank there is a constant mixing of the solution to maintain a homogeneous state of the paper pulp throughout the volume. By supplying recycled water containing cellulose inclusions, the concentration of the prepared solution is adjusted to 0.15-1.5%, it is sent to the treatment equipment. For this, knot catchers, centrifuges and others are used. After that, the paper mass through the inlet device enters the grid.

The quality of the material produced depends on the synchronism of the speeds of the mesh and the outflow of the suspension. The lag of mass movement from the grid should not exceed 5-10%. The deviation of the parameters in one direction or another leads to an uneven distribution of the fibers over the grid area and their orientation in the direction of the web movement. This is reflected in the density, uniformity and strength of the manufactured products.

Paper forming

Sheet shedding is a filtration process in which, as water is removed, a fibrous layer is formed. After passing through the register part of the grid table, a sheet with a mass concentration of about 3% is formed. When such values are reached, the “mirror of the bay” ends and the concepts of “paper, paper web” and its dryness are introduced. The ebb process is most intensive in the register part, located in the first third of the table. Errors made at this stage can no longer be corrected during paper production and will be considered a product defect.

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The quality of the paper ebb and the position of the fibers relative to the direction of flow depend on the nature and concentration of the mass, the speed of the mesh and the outflow of the colloidal solution, and the intensity of water filtration. In turn, these parameters depend and are determined by the purpose of the manufactured products.

In some cases, it becomes necessary to increase the rate of dewatering of the web, for example, to prevent flocculation, that is, the formation of clumps of fibers. The course of this process is largely influenced by the concentration of the mass. At low values, active water filtration occurs, which greatly reduces the likelihood of flocculation.

On the other hand, too much water separation leads to the washing out of fibers, especially fine fractions. Intensively this process occurs in the initial stage of leaf formation. Ultimately, this leads to a decrease in the content of the filler in the lower (grid) side of the sheet. This defect is eliminated by reducing the filtration rate.

The change in the intensity of water separation occurs with an increase in sheet thickness and filtration resistance. This leads to the need to use forced methods of dehydration of the fibrous layer. For this, suction boxes are used. A vacuum is created in them with special pumps, which allows removing moisture that did not have time to drain in the initial stage of paper formation.

The mesh table ends with a device called a suction couch roll. A vacuum of 30-70 kPa is maintained in its chamber, which makes it possible to effectively suck out moisture. Under the couch-shaft there is a bath, into which water is drained and the so-called wet waste is discharged. These are the cut-off edges of the paper web, breaks from the press part, the contents of the mesh table when the paper breaks. An agitator located in the bath conveys the mixture to the transfer pumps, which return the solution to the receiving tank for recycling.

press part

After the couch roll, the paper web with a dryness of 15-20% is transferred by a vacuum transfer device to the press section of the paper machine for further mechanical dehydration. It usually consists of 2-3 twin-shaft presses. The upper shaft is made of granite, the lower one is metal lined with rubber. Between them, together with the paper web, the cloth moves, protecting the surface of the wet paper from damage.

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The design of the press mechanism allows the use of sequential passage of different sides of the web between the shafts. This ensures that both sides of the paper are smoothed evenly. A cloth washer is used to remove fibers adhering to the fabric. After successive passage of the press section, the dryness of the paper is 30-40%.

In this section of the machine, not only dewatering takes place, but also the web is compacted. This increases the area of contact and adhesion between the fibers. In addition, paper properties change: strength increases, porosity decreases, transparency increases, etc. The press part must operate at full load, since an increase in dryness by 1% reduces the steam consumption for heating the drying cylinder by 5%. The intensification of these processes can significantly reduce the overall energy consumption, which ultimately affects the cost of products.

Drying the paper web in the press section is 10 times cheaper than in the dryer. Of the total volume of removed water, about 95% falls on the wire part, 3-4% on the press part, and the rest on the drying part. Therefore, the first 2 parts are called wet. To remove the remaining 1-2% of moisture, most of the energy intended for dehydrating the paper web is expended.

Drying part

This section of the machine consists of 2 rows of successively staggered cylinders covered by a drying cloth. The device of the drying cylinder is a hollow cylindrical container, heated from the inside with steam. The pressure of the working environment is 0.35 MPa. The diameter of the drying cylinder is 1500 or 1800 mm, depending on the type of paper being produced.

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The number of cylinders depends on the product type and machine speed. For the manufacture of capacitor paper, 5-8 drums are installed, and for newsprint and bag paper - 50-80. Drying cylinders are combined into 3-5 independent groups, which allows for separate regulation and maintenance of temperature in separate blocks. The scheme of movement of paper and felts provides heating and evaporation of moisture not only when it comes into contact with the heating surface of the drying cylinder, but also during free running. The use of an individual drive for each of the groups allows you to synchronize the speeds of neighboring blocks to ensure the smooth movement of the paper web.

Each group provides for the installation of a drying cylinder for felts designed not only to absorb moisture, but also to transport the paper web through this part of the unit. In machines with a high paper speed, the dryer section is completely covered with a hood, which allows you to keep warm without additional use energy. It is equipped with a forced ventilation system and heat exchangers-recuperators. The heated moist air, before being released into the atmosphere, with its heat heats the supplied medium, which is heated up on the heat exchanger and enters the airflow of the web.

Depending on the type of paper produced, the temperature of the cylinders is 80-115 °C. During the drying process, up to 2.5 liters of moisture is removed from 1 kg of paper, which is 60-80 times less than on the wire and press parts of the machine. An increase in the heating rate of the drums speeds up the drying process, so it should be carried out at the maximum values of this parameter, which does not affect the quality of the finished product. In drying hoods of high-speed machines, nozzle blowing of the web with heated air is used. This speeds up the dehydration process and reduces energy costs.

The finishing part consists of a calender and a reel. It is installed between the drying part and the reel and consists of 5-8 horizontally arranged shafts. The lower ones are driven and provide the passage of paper between them. At the same time, it is additionally compacted and smoothed. On the reel, the paper is formed into rolls by weight or diameter and then sent for cutting.

This completes the papermaking process. The use of advanced technologies and automation of the manufacturing process, at web speeds of 1000 m/min and more, made it possible to reduce the maintenance of the unit to 5-8 people.

I bring to your attention my debut article in a new way. In it are given general principles work of the paper machine for a more comfortable entry of the translator into the topic.
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paper machine(paper machine) - multi-section unit continuous (continuous) of the action on which of strongly diluted (diluted) water fibrous suspension (fibrous suspension) get paper and some kinds cardboard (board).
There are 2 main types of paper machines: flat mesh / table (four-drinier machine) used to make the main types of paper, and circular/cylinder (vat machine), which produce a limited range of paper and cardboard. These types have different release devices paper pulp (paper/papermaking pulp or stock) on the grid (wire) paper machine and low tide (formation) of the paper web, the design of the remaining nodes, as well as the technological process of making paper, are similar.
The finished paper pulp with a concentration of about 3-4% is fed with a pump ( feed) from mass preparation department (stock preparation department) in machine pool (machine chest), from where it enters the paper machine. Permanent mixing (agitation) the masses in the engine pool achieve alignment degree of grinding (beating/refining degree) and mass concentration throughout the volume. It is pre-diluted recycled water (white/back water) received from dehydration (dehydration) paper pulp on the grid of the paper machine, to a concentration of 0.1-1.5% and passed through treatment (screening) equipment - knotters ( screen/strainer), centriccleaners (centricleaner), centriscreens (centriscreen), etc., where various foreign inclusions and coarse particles of mineral and fibrous origin are removed. From the cleaning equipment, the paper pulp enters the headbox (headbox), which provides expiration (discharge) mass with a certain speed (rate) and the same thickness jets (jet) over the entire width of the grid.

The paper machine consists of the following main parts:

grid (wire section), where a dilute suspension is continuously molded paper canvas (paper web ) and the first part is removed from it excess water (excess water );
press (press section), where dehydration is performed and seal (compacting) paper webs:
drying room (dryer section), in which the moisture remaining in the paper web is removed:
finishing (finishing section), where the canvas is subjected to the necessary processing to give gloss (glaze), density (density), smoothness (smoothness) And wound in rolls (wind to rails ).

Grid part - an endless mesh woven from threads of various copper alloys or synthetic materials. The grid drive is carried out from couch shaft (couch roll). On new machines with vacuum transfer devices (vacuum pick-up arrangement), the drive shaft is also the main shaft of the grid. To prevent the paper pulp from flowing, the edges of the grid are installed restrictive rulers (guides). The dehydration of the paper pulp and the formation of the paper web occur due to the free flow and suction action (suction) register rollers ( table roll). For a more uniform web of paper in longitudinal (machine/grain direction) And transverse directions (c ross direction ), when the machine speed is not more than 300 m/min, the register part is sometimes subjected to shaking (shake) in the transverse direction. Further dehydration occurs over suction boxes (suction box) under the action of a vacuum created by special vacuum pumps (suction pump). When developing high-grade papers (fine paper) above them are often installed easy comparative roller (Dandy roll). Leveling roller for application watermarks (water marks) is called egutere (egoutteur). After that, the paper web still contains a relatively large amount of moisture (88-90%), to remove which the mesh, together with the paper web, passes over the couch shaft, which has from one to three suction chambers (vacuum chamber). Couch-shaft - perforated hollow cylinder (drum) of bronze alloy or stainless steel (perforation area is about 25% of the shaft surface). Inside the body is a stationary vacuum chamber with graphite seals, which are pneumatically pressed against the inner surface of the cylinder. The vacuum chamber is connected to a continuously operating vacuum pump. The couch roll completes the shaping and dewatering (to a dryness of 18-22%) of the paper web on the wire of the paper machine.

Further dehydration occurs in the press section mechanical extraction under pressure and vacuum by passing the web through several (2-3, less often 4-5) roller presses (roll press) arranged in series (often the first and second presses are combined into double press - two-roll press). At the same time, they increase bulk density (specific density), strength properties (strength properties), transparency (transparency), decrease porosity (porosity) And absorbency (absorption) paper. Pressing is carried out between woolen cloths (felt), which protect the still weak paper from destruction, absorb the squeezed moisture and at the same time transport the web. Each press has its own cloth. On all new high-speed paper machines, the lower press rolls are made perforated (perforated) (like couch shafts). They are covered special rubber (rubber cover), which improves dehydration and increases service life. On some paper machines, instead of lower suction shafts (bottom roll) are set shafts with special grooved corrugation (grooved roll). On powerful paper machines, the lower rolls of the first and second presses are made suction (similar to the couch shaft). Often, in addition to presses with felts, they also install smoothing (or offset) presses (second nip) without felt to compact the paper and make it smooth. Then the paper web with a dryness of up to 45% enters the drying section.

Finishing part is a calender calendar), consisting of 5-10 located one above the other chilled cast iron shafts (cast chilled iron roll). In order to make it more elastic and soft, the paper is preliminarily cooled and slightly moistened on a refrigerating cylinder (through the hollow necks of which cold water). When moving between the shafts from top to bottom, the web becomes smoother, compacted and leveled in thickness. Then the paper is wound with an endless tape into rolls on a forcibly rotated cylinder, against which the roller with the paper wound on it is pressed - reel. To moisten the paper when additional finishing it on supercalenders (supercalender) (to obtain paper with increased smoothness, gloss and bulk) is installed above the reel humidifier (rewetting device). Next, the roll is cut into slitting machine (longitudinal cutter) to the required formats. At the same time, the paper is sorted cliffs (break) that have arisen during its development are glued together. When releasing paper in sheets, the rolls for cutting are fed to the paper web cutting machine - self-tapping screw (sheeter/sheet cutter).

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Ministry of Education and Science

Federal State Budgetary Educational Institution

higher professional education

St. Petersburg State Forest Engineering University named after V.I. CM. Kirov

faculty of secondary vocational education

College of Forestry Automation

course project

discipline "Wood processing equipment"

PROJECT OF THE DRYING PART OF A PAPER MAKING MACHINE FOR PRODUCING DRAWING PAPER

Artist T-211 Sukhanova V.R.

Head Lotsmanova E.M.

St. Petersburg

Introduction

1. Theoretical part

1.1 Composition of the drying part of the paper machine

1.2 The principle of operation of the dryer part of the paper machine

2. Calculation of the drying part of paper machine

2.1 PM performance

Conclusion

Introduction

The production of paper on a paper machine consists of several technological stages, one of which is the process of drying the web. After the presses, the residual moisture in the paper can only be removed by drying with heat. The first dryers for paper machines appeared in the twenties of the 19th century. Since then, they have been continuously modified and improved. Despite the fact that drying is the most energy-intensive part of the paper machine, one of the main parameters of paper quality - humidity - depends on it.

The basis of any paper is cellulose fibers, which can be obtained from wood, straw, cotton, cane, hemp, rice or waste paper. Most paper used today contains a mixture of hardwood (birch, aspen) and softwood (spruce, pine) wood species.

Drawing paper is intended for making drawings in watercolor, pastel, pencil or charcoal; produced in accordance with GOST 7277-54 of two grades: grade B - the highest quality, grade O - ordinary. Depending on the type of drawing paper, its surface can be smooth, velvety, fine-grained, coarse-grained, or, if necessary, specially embossed. Drawing paper weighing 80 g/m2 is watermarked.

The purpose of the course work is theoretical and practical study dryer section of the paper machine.

Based on the goal, it is necessary to solve the following tasks:

To study the composition of the drying part of the paper machine;

To study the principle of operation of the drying part of the paper machine;

Calculate the dryer part of the paper machine.

1. Theoretical part

1.1 Composition of the dryer section of the paper machine

The drying part has a receiving cylinder, two rows of paper drying cylinders and several dryers. An after-drying cylinder is installed at the end of the drying section. The drying section is divided into groups. Each drying group includes in the upper and lower rows several paper drying cylinders, at least one felt drying cylinder, tension, straightening and accelerating rollers, several felt and paper rollers and one common cloth. Each group has an independent drive from a variable speed transmission or from a separate engine, which allows the group to start and stop independently from the rest of the machine, as well as independently control the speed of its movement. Paper after wet presses is fed to the receiving cylinder. This cylinder has no cloth. Its value is reduced to a slight increase in the temperature of the passing paper. Next, the wet paper passes in turn each next lower and each next upper paper drying cylinder.

The main element of the drying part is the cylinder. It is a hollow drum rotating around a horizontal axis. Saturated steam with a pressure of more than 0.07 MPa enters the cylinder through the pipe and fills it. The heat of the steam is transferred to the wall of the cylinder and through it to the paper, which tightly covers approximately two-thirds of the surface of the cylinder. To increase heat transfer from the outer wall of the cylinder to the paper, the side surface of the cylinder is ground and polished. Cylinders are made of special cast iron.

Another important element of the multi-cylinder dryer section are nets and felts, which serve to transport the paper web and create tight contact between the wet paper web and the heated surface of the cylinder. Drying felts or nets press the paper web tightly against the heated surface of the cylinders, thereby ensuring good contact between them. This prevents the formation of wrinkles and folds on the surface of the paper web.

1.2 How the dryer works

dryer paper machine

In the dryer section of the paper machine, the paper web is dehydrated to a final dryness of 92 - 95%. During the drying process, 1.5 - 2.5 kg of water is removed per 1 kg of paper, which is about 50 - 100 times less than on the wire and press parts of the machine. During drying, further compaction and convergence of the fibers occur simultaneously. The result is increased mechanical strength and smoothness of the paper. The volumetric weight, absorbency, air permeability, transparency, shrinkage, wet strength, degree of sizing and coloring of the paper depend on the drying mode.

Drying of paper on the drying cylinder consists of two phases: on the heated surface of the cylinder under the felt and in the free running area, i.e. when the paper web passes from one cylinder to another. In the first phase, under the cloth, the main amount of moisture evaporates: on low-speed machines up to 80-85%, on high-speed machines up to 60-75% of all moisture evaporated in the drying part of the machine. In the second phase, in the free running areas, the moisture evaporates from both sides of the paper due to the heat absorbed by the paper in the first drying phase. In this case, the paper, depending on the speed of the machine, undergoes a decrease in temperature by 4 - 15°C. When the temperature drops, the drying speed decreases, especially on low-speed machines, since the temperature drop of the paper web is greater on them than on high-speed machines. As the speed of the machine increases, the amount of evaporated water in the paper free play area increases. With a decrease in the amount of water in the paper web, the intensity of drying in the free area decreases.

The temperature of the drying cylinders is increased gradually, which helps to improve the quality of the paper and complete the sizing process. At the end of the drying section, the temperature of the surface of the cylinders is reduced, since the high temperature at a low moisture content of the paper acts destructively on the fibers.

The wet paper web, guided from the press section of the paper machine, is threaded between the heated surface of the first drying cylinder and the drying mesh (cloth). At the initial stage of movement, the drying mesh (cloth) accompanies the dried web in the free area between the upper drying cylinders and the lower vacuum rollers. This is a feature of this paper web filling scheme. This refilling reduces the risk of paper web breakage.

Drying cylinders are hermetically sealed with a ventilation hood, from which exhaust moist air is removed. Part of the exhaust air in the heat trap is mixed with fresh shop air, heated in the air heater and fed through the drying air duct to the drying part of the paper machine through the air distribution channels. Exhaust and shop air, water from the scrubber, is directed to the general exchange ventilation of the shop. After processing in a calender, the paper web dried to the standard humidity is wound into a roll on the reel.

2. Settlement part

Calculation of the drying part of the paper machine

Data for calculation

Paper - drawing

B0 = 4200 mm -- cutting width

V = 500 m/min -- PM speed

q \u003d 120 g / m2 - mass of 1 m2 of paper produced

w \u003d 14 kg / m2 * h - specific water removal from the working drying surface

Тk = 95% - final dryness of paper (after drying part)

Tn = 42% - initial paper dryness (before the drying part)

tн = 45оС - paper temperature in front of the drying section

tk = 95оС - paper temperature after the drying section

t? \u003d 95 ° C - the average temperature of the paper web in free areas

tv \u003d 85 ° C - ambient air temperature

tn1 \u003d 95 ° C - steam temperature in the first drying

tн2 = 123оС - steam temperature in the second drying group

tн3 = 115оС -- steam temperature in the third drying group

sun \u003d 0.6 -- coefficient of girth of paper drying cylinders with a grid

wb \u003d 0.63 - coefficient of girth of paper drying cylinders with paper

d \u003d 0.0275 m - thickness of the end cap of the cylinder

d1 = 0.00035m -- paper thickness

d2 = 0.005m -- mesh thickness

db = 0.025m - thickness of the side wall of the drying cylinder

l1 \u003d 0.0465 W / (m * deg) - coefficient of thermal conductivity of paper

l2 \u003d 0.058 - the coefficient of thermal conductivity of the grid

l \u003d 62.8 W / m2 * deg - coefficient of thermal conductivity of the wall material, for cast iron

n1 = 15n/100pcs -- number of drying cylinders in the first group

n2 = 30n/1000pcs -- number of drying cylinders in the second group

n3 = 55n/100pcs -- number of drying cylinders in the third group

2.1 PM performance.

Qh.gross=0.06*BnVq, kg/h

where: 0.06 is a coefficient that takes into account the conversion of grams to kilograms and minutes to hours;

V -- paper machine speed, m/min;

q -- weight of 1m2 of produced paper, g/m2

Bn -- uncut paper width, m

Bn=B0+100, mm

Bn=4200+100=4300mm=4.3m

Qh.gross=0.06*4.3*500*120=15480kg/h

Qs.gross=(Qh.gross/1000)*24, t/day

Qc.gross=(15480/1000)*24=371.52t/day

Qs.n.=Qs.gross*Kef, t/day

Qs.n \u003d 371.52 * 0.86 \u003d 319.507 t / day

where: Kef - the total utilization rate of the PM (from the table = 0.86)

Qyear=Qs.n*Z, t/year

Qyear=319.507*345=110229.984t/year

where: Z is the number of days of PM operation per year according to design standards, 345 days

2.2 Calculation of the number of paper drying cylinders and the heat balance of the drying process

n=19.1*(V*q*(TK-Tn))/d*b*Tn*w, pcs

n=19.1*(500*0.12*(95-42))/1.5*0.65*42*14=106pcs

where: b - coefficient of girth of drying cylinders with paper (from 0.60 to 0.67);

d -- diameter of paper drying cylinders = 1.5m;

q -- mass of 1 m2 of produced paper, kg;

w -- specific water removal from the working drying surface, kg/m2*h;

Tc -- final dryness of paper, %;

Tn -- initial dryness of paper, %;

w accept [No.] p.605, tab.65.

2.3 Calculation of heat and steam for drying

Total heat and steam consumption for paper drying

Qgen.=Qpol.+Qpot., kJ/h

Useful heat consumption for paper drying

Qpol.=G*C*(tk-tн)+Wн*Св*(tk-tн)+W*(i-Св*tс), kJ/h

where: G is the mass of absolutely dry paper, kg/h;

C - heat capacity of absolutely dry paper, kJ / kg * deg (ranging from 1.22 to 1.30);

tn and tk - paper temperature before and after the drying section, °C

Wn - the mass of water in the wet web of paper supplied for drying, kg / h;

St - heat capacity of water \u003d 4.19 kJ / kg * deg;

tc -- average drying temperature = tk, °C;

G=15480*0.95=14706kg/h

Comes for drying moisture with paper:

Wn=G*((100-Tn)/Tn), kg/h

Wн=14706*((100-42)/42)=20308.286kg/h

Moisture leaves with air-dry paper:

Wк=G*((100-Тк)/Тк), kg/h

Wc=14706*((100-95)/95)=774kg/h

W=Wн-Wк,kg/h

W=20308.286-774=195304.286kg/h

Qpos.=14706*1.25*(95-45)+20308.286*4.19*(95-45)+19534.286*(2677.5-95*4.19)=919.125+4254585.917 +44527428.223=48782933.265kJ/h

or 48782933.265/15480=3151.352 kJ/kg

Heat loss

Qpot=q1+q2+q3+q5+q7+q8+q9, kJ/h

Free sections of paper web

q1=3.6*Fb*b*(tb-tw), kJ/h

where: Fb is the surface of free sections of the paper web on both sides, m2

b -- heat transfer coefficient of paper in air, W/(m2*deg)

tb -- average temperature of the paper web in free areas, °C

tv -- ambient air temperature, оС

Fb=2*l*b*n, m2

Fb=2*1.2*4.3*106=1093.92m2

where: l is the length of the free section of paper between the cylinders (ranges from 1.1 to 1.2 m, for a drying cylinder with a diameter of d = 1.5 m)

b - paper web width

The heat transfer coefficient b can be determined by the empirical formula:

b=5.58+3.95*V, W/(m2*deg)

V=500m/min=500/60=8.33m/s

b \u003d 5.58 + 3.95 * 8.33 \u003d 38.5 W / (m2 * hail)

q1=3.6*1093.92*38.5(95-85)=1516173.12kJ/h

Free sections of drying nets

q2=3.6*Fs*b*(tb-tw), kJ/h

Fc \u003d 2 * Sun * [ Lc- (P * d * n * wb)], m2

Where: Sun-standard grid width, m

Where: Lc - drying mesh length, m

n - total number of paper drying cylinders

k - experience factor = 5

Lc=1.5*106*5=795m

Fс=2*4.7*=4660.559m2

The heat transfer coefficient is determined by the empirical formula for a rough surface:

b=6.16+4.187*(V/60), W/m2*deg

b \u003d 6.16 + 4.187 * (500/60) \u003d 41.052 W / m2 * deg

q2=3.6*4660.559*41.052*(95-85)=6887709.65

Bottoms of paper drying cylinders

q3=3.6*2*F*K[(tn1- tv)* n1+(tn2- tv)* n2+(tn3- tv)* n3], kJ/h

where: F - end surface of one cylinder, m2

K - coefficient of heat transfer of steam to air through the end wall of the cylinder, W / m2 * deg

n1,n2,n3 - number of drying cylinders by groups (drying section is divided into three drying groups)

n1=(106*15)/100=16pcs

n2=(106*30)/100=32pcs

n3=(106*55)/100=58pcs

tn1, tn2, tn3 - steam temperature in drying groups, °C

The heat transfer coefficient is calculated by the formula:

K=1/(1/b1+ d/l+1/b2), W/m2*deg

Where: b1 - heat transfer coefficient from steam to the wall of the drying cylinder, 5815 W/m2*deg

d - thickness of the end cover of the cylinder, m

l - coefficient of thermal conductivity of the wall material, for cast iron 62.8 W / m2 * deg

b2 - heat transfer coefficient from the end wall of the air cylinder, W/(m2*deg)2

v \u003d 500 / (60 * 2) \u003d 4.167 - since two end surfaces

b2=5.58+3.95*4.167=22.05W/(m2*deg)2

K=1/(1/5815+0.0275/62.8+1/22.05)=21.76W/m2*deg

F=(3.14*1.52)/2=1.77m2

q3=3.6*2*1.77*21.76*[(95-85)*16+(123-85)*32+(115-85)*58]=864097.96kJ/h

Open side surface of paper dryer cylinders:

q5=3.6*K*P*d[(1-wb)*Bn+(1/sun)*(Bc-Bn)*[(tn1-tv)*n1+(tn2-tv)*n2+(tn3-tv )*n3], kJ/h

Where: sun - coefficient of girth of paper drying cylinders with a grid

wb - coefficient of circumference of paper drying cylinders with paper

Bn - average paper web width, m

Bc - standard mesh width 4.7m

tv - ambient air temperature, оС

We calculate the heat transfer coefficient by the formula:

K=1/(1/b1+ db/l+1/b2)

K=1/(1/5815+0.025/62.8+1/22.05)=21.77

q5=3.6*3.14*1.5*21.77*[(1-0.63)*4.3+(1-0.6)*(4.7-4.3)]* [(95-85)*16+(123-85)*32+(115-85)*58]=2014027.011kJ/h

Side surface of paper dryer cylinders covered with paper and mesh:

q7=3.6*K*P*d*Bn*vb*[(tn1-tv)*n1+(tn2-tv)*n2+(tn3-tv)*n3], kJ/h

K=1/(1/b1+db/l+d1/l1+d2/l2+1/b2), W/m2*deg

Where: d1 - paper thickness, m

l1 - coefficient of thermal conductivity of paper

d2 - mesh thickness, m

n2-mesh thermal conductivity

K=1/(1/5815+0.025/62.8+0.00035/0.0465+0.005/0.058+1/22.05)

q7=3.6*7.02*3.14*1.5*4.3*0.63*[(95-85)*16+(123-85)*32+(115-85)*58 ]=1004769.78kJ/h

Side surface of paper dryer cylinders covered with mesh but not covered with paper:

q8=3.6*K*P*d*Bn*(db-ds)*[(tn1- tv)* n1+(tn2- tv)* n2+(tn3- tv)* n3], kJ/h

K \u003d 1 / (1 / b1 + db / l + d1 / l1 + 1 / b2), W / m2 * deg

K=1/(1/5815+0.025/62.8+0.00035/0.0465+1/22.05)=18.7 kJ/h

q8=3.6*18.7*3.14*1.5*4.3*(0.63-0.6)*[(95-85)*16+(123-85)*32+( 115-85)*58]=127453.437kJ/h

Side surface of paper dryer cylinders, covered with mesh, but not covered with paper:

q9=3.6*K*P*d*(Bc- Bn)*sun*[(tn1- tv)* n1+(tn2- tv)* n2+(tn3- tv)* n3], kJ/h

K \u003d 1 / (1 / b1 + db / l + d2 / l2 + 1 / b2), W / m2 * deg

K \u003d 1 / (1 / 5815 + 0.025 / 62.8 + 0.005 / 0.058 + 1 / 22.05) \u003d 7.43 W / m2 * deg

q9=3.6*7.43*3.14*1.5*(4.7-4.3)*0.6*[(95-85)*16+(123-85)*32+( 115-85)*58]=94215.376kJ/h

The total losses during drying are:

Qpot=q1+q2+q3+q5+q7+q8+q9, kJ/h

Qpot=1516173.12+6887709.65+864097.96+2014027.011+1004769.78+127453.437+94215.376=12508446.334 kJ/h

12508446.334/15480=808.039kJ/kg

Qgen.=Qpol.+Qpot., kJ/h

Qtotal=48782933.265+12508446.334=61291379.599kJ/h

Or Qsp \u003d 61291379.599 / 15480 \u003d 3959.391 kJ / kg

Thermal coefficient useful action drying part of the machine? equals:

?=(Qpol/Qtotal)*100%

?=(48782933,265/61291379,599)*100%=79%

Specific steam consumption:

Dsp=Qsp/(Ip-Ik),kg/kg of paper

Where: Ip - steam enthalpy \u003d 2708.44 kJ

Ik - enthalpy of condensate = 502.42 kJ/kg

Dsp=3959.391/(2708.44-502.42)=1.8kg/kg of paper

Conclusion

IN term paper the drying part of the PM was studied.

The following tasks were also solved:

The composition of the drying part of the paper machine has been studied;

Studied the principle of operation of the drying part of the paper machine;

The calculation of the drying part of the paper machine was made.

In the first chapter, the composition and working principle of the dryer part of the paper machine were studied.

In the second chapter, it was possible to calculate the dryer part of the paper machine, and it turned out that, based on a high thermal efficiency of 79%, the operation of the dryer is beneficial. The dryer part produces a large amount of paper, its productivity was 110229.984 tons/year. And the specific consumption of steam is small, it is equal to 1.8 kg of steam/kg of paper.

List of used literature

1. Ivanov S.N. paper technology. 2nd edition, revised. Publishing house " timber industry", 1970, 696 p.

2. Mazarsky S.M., Malinsky I.Z., Epshtein K.Yu. Pulp and paper production equipment.M. - Forest industry, -1969. 452 p.

3. Sokolova L.M., Ovdeichuk V.P., Samson M.V. Tutorial on course and diploma design of technological processes of pulp and paper production: Textbook for technical schools. - M. "Forest industry" - 1982, 160 p.

4. Technology of pulp and paper production. Reference materials. St. Petersburg. SPbLTA publishing house. Volume 1. part 1. 2002. 420 p.

5. Technology of pulp and paper production. Reference materials. St. Petersburg. SPbLTA publishing house. Volume 1. Part 2. 2003. 632 p.

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PURPOSE, DEVICE OF THE DRYING PART OF PM AND KDM

DRYING PROCESS OF PAPER AND CARDBOARD. CALCULATION METHOD

NUMBERS OF DRYING CYLINDERS, THEIR LAYOUT IN

DRYING PART

Lecture plan

Characteristics of the dryer section, its role in the overall process of paper production. Possible methods of drying paper, their advantages, disadvantages. Mechanism of contact drying of paper on cylinders, factors of contact drying. Method for calculating the number of drying cylinders during the warm-up period, in the first period, in the second period.

Possibilities of eliminating the shrinkage of the paper web and the layout of the drying cylinders along the length of the drying part.

Drying part of machines producing sanitary papers.

After the press section, the dryness of the paper is typically between 28 and 45%. Further dewatering to a final dryness of 92 - 95% takes place in the dryer section of the paper machine. The amount of water evaporated here is determined by the dryness of the paper entering and leaving the drying section. It ranges from 1.3 to 2.5 kg of water per 1 kg of paper, which is about 50 to 100 times less than the amount of water removed on the wet part of the machine.

Of all the parts of the paper machine, the dryer part is the longest. The number of drying cylinders, depending on the speed of the machine, the weight of 1 m 2 and the type of paper, can be from 60 to 80 (diameter 1500 mm). The weight of the drying part, excluding auxiliary equipment, is approximately 60 - 70% of the weight of a high-speed machine, and the cost reaches 50% of the cost of the entire machine. The operating costs associated with the operation of the dryer are also significant: the cost of steam for drying and ventilation is 5 - 15% of the cost of paper; the power consumed by the dryer is approximately half of the total power consumed by the machine (excluding the power consumed by the vacuum pumps). Removal of water on the dry end is much more expensive than on the wet end. In this regard, the expediency of the maximum possible increase in the dryness of the paper entering the drying section is obvious, since this reduces the steam consumption and the required number of drying cylinders.

Currently, the main method of drying paper on a paper machine is the contact method. In order to avoid the formation of wrinkles (warping), the paper should be pressed against the cylinders by the felts during drying.

The cylinders are heated by steam. There are designs of drying cylinders heated by organic heat carriers, gas burners and electric heaters, but they have not yet found wide application.

Contact drying of paper in comparison with other methods has a number of significant advantages, the main of which are high economic indicators and high quality of the dried web, in particular, high bilateral smoothness. On the drying part, the sizing of the paper web ends. For good paper sizing, the paper temperature must be brought to 70 - 80°C before the dryness of the paper reaches 50%.

The disadvantages of multi-cylinder drying include high metal consumption (about two thirds of the mass of the entire machine) and insufficient intensity of the process.

In parallel with contact drying in paper and board machines, convective drying with heated air is used. Despite the fact that convective drying, as a rule, has higher energy costs than contact drying, it is used on all modern paper and board machines.

The advantages of the convective drying method include the simplicity of the design, the wide possibilities of controlling the humidity along the width of the paper web, and also, in some cases, the greater intensity of the process compared to contact drying. The highest drying intensity is achieved when using speed drying hoods with nozzle blowing of the moving web.

Along with contact and convective drying of moving webs, combinations of the first two with drying in energy fields, vacuum drying and drying with thermal mechanical removal of moisture are also known.

IN Lately devices with thermal mechanical removal of moisture have found wide application abroad for drying paper and cardboard. With this drying method, not only the evaporation of moisture occurs due to the supply of heat, but also its mechanical displacement and replacement in the pores of the material with a gaseous agent. Drying with the suction of air or gas has a very significant intensity. A drying intensity of about 140 kg/(m2×h) was achieved, which is about 10 times higher than the average drying intensity in the multi-cylinder dryer section.

During contact drying, when a wet web of paper or cardboard comes into contact with the hot surface of the drying cylinder, contact heat transfer begins. Some heat is also transferred by radiation, since there is no absolutely complete contact between the paper and the surface of the cylinder.

paper machine

a multi-sectional unit of continuous operation, on which paper and some types of cardboard are obtained from a fibrous suspension highly diluted with water ( rice. one ).

Two main types of paper are distinguished: flat-grid (table) paper, which is used to produce the main types of paper, and round-grid (cylinder) paper, which is used to produce a limited assortment of paper and cardboard. These types have different devices for discharging paper pulp onto the paper web and for casting the paper web, while the design of the remaining units, as well as the technological process of making paper, are similar (with the exception of the “dry forming” machine).

On fig. Figure 2 shows a diagram of a flat-grid paper machine, which, along with the machine itself, includes auxiliary equipment designed to prepare paper pulp before feeding it to the wire. The types of auxiliary equipment and their design are extremely diverse.

The finished paper pulp with a concentration of about 3-4% is pumped from the pulp preparation department to the machine pool, from where it enters the paper mill. By constantly stirring the stock in the machine pool, the degree of grinding and mass concentration throughout the entire volume are equalized. It is preliminarily diluted with recycled water (from dehydration of the paper pulp on the B. m. grid to a concentration of 0.1-1.5%) and passed through the cleaning equipment (knotters, centric cleaners, centric screens, etc.), where various foreign inclusions are removed and coarse particles of mineral and fibrous origin. From the cleaning equipment, the paper pulp enters the headbox, which ensures the outflow of the pulp at a certain speed and the same jet thickness over the entire width of the grid.

B. m. consists of the following main parts: mesh, where a sheet of paper is continuously formed from a diluted suspension and the first part of excess water is removed from it; press, where the paper web is dehydrated and compacted; dryer, where the moisture remaining in the paper web is removed; finishing, where the web is subjected to the necessary processing to give gloss, density, smoothness and is wound into rolls.

Grid part- endless mesh (woven from threads of various copper alloys or synthetic materials). The mesh drive is carried out from the couch-shaft. On new machines with vacuum transfer devices, the driving shaft of the mesh is also driven. To prevent the paper mass from flowing, restrictive rulers are installed along the edges of the grid. The dehydration of the paper stock and the formation of the web of paper occur due to the free flow and suction action of the register rollers. To obtain a more uniform web of paper in the longitudinal and transverse directions, at a machine speed of not more than 300 m/min, the register part is sometimes subjected to shaking in the transverse direction. Further dehydration takes place above the suction boxes under the action of a vacuum created by special vacuum pumps. When producing high-grade papers, a light leveling roller (eguter) is often installed above them. It also serves to apply watermarks to paper (See Watermark). After that, the paper web still contains a relatively large amount of moisture (88-90%), to remove which the mesh, together with the paper web, passes over the couch shaft (on low-speed couch press machines), which has from one to three suction chambers. Couch-shaft - a perforated hollow cylinder made of bronze alloy or stainless steel (perforation area is about 25% of the shaft surface). Inside the body is a stationary vacuum chamber with graphite seals, which are pneumatically pressed against the inner surface of the cylinder. The vacuum chamber is connected to a continuously operating vacuum pump. The couch-shaft completes the formation and dehydration (to dryness of 18-22%) of the paper web on the B. m grid.

Further dehydration occurs in the press section mechanical extraction under the action of pressure and vacuum by passing the web through several (2-3, less often 4-5) roller presses arranged in series (often the first and second presses are combined into a double press). At the same time, the volumetric mass, strength properties, transparency increase, the porosity and absorbency of the paper decrease. Pressing is carried out between woolen felts, which protect the still weak paper from destruction, absorb the squeezed moisture and at the same time transport the web. Each press has its own cloth. On all new high-speed B. m., the lower rolls of the presses are made perforated (like couch rolls). They are covered with special rubber, which improves dehydration and increases the service life. On some B. m., shafts with special grooved corrugations (grooves) are installed instead of the lower suction shafts. On powerful B. m., the lower shafts of the first and second presses are made suction (similar to the couch shaft). Often, in addition to presses with felts, smoothing (or offset) presses without felts are also installed to compact the paper and make it smooth. Then the paper web with a dryness of up to 45% enters the drying section.

Drying part(largest in length) consists of rotating cylinders heated from the inside by steam and usually arranged in 2 rows in a checkerboard pattern. The web is pressed against the heated surface of the cylinders with the help of felts, which improve heat transfer and prevent warping and wrinkling of the paper surface during drying. The upper and lower rows of drying cylinders have separate felts, and one cloth covers several cylinders at once (a group of drying cylinders). The paper web moves from the upper cylinder to the lower one, then to the neighboring upper one, and so on. The paper is then dried to a residual moisture content of 5-7%. On modern paper machines, a two-shaft gluing press is usually placed in the second half of the drying section for surface sizing of the paper and for applying a surface layer. The drying section of some paper machines is equipped with automatic regulators for supplying steam to the cylinders, devices for automatically threading the web of paper onto the drying cylinders, and so on. The steam is collected under a hood located above the entire drying part of the B. m., and then it is removed by exhaust fans to the outside. Heat is used in heaters and heat exchangers.

Finishing part is a calender consisting of 5-10 chilled cast iron shafts arranged one above the other. In order to make it more elastic and soft, the paper is preliminarily cooled and somewhat moistened on a refrigerating cylinder (cold water is supplied and removed through the hollow necks of which). When moving between the shafts from top to bottom, the web becomes smoother, compacted and leveled in thickness. Then the paper is wound with an endless tape into rolls on the reel (a forcedly rotated cylinder, against which the roller with the paper wound on it is pressed). To moisten the paper during its additional finishing on supercalenders (to obtain paper with increased smoothness, gloss and bulk density), a humidifier is installed above the reel. Next, the roll is cut on a slitting machine into the required formats. At the same time, the paper is sorted, the breaks that have arisen during its development are glued together. When releasing paper in sheets, the rolls for cutting are fed to the self-cutting machine.

BM also has a large number of various equipment necessary to ensure its continuous operation, and automatic devices that regulate technological parameters. For each type of paper, technically and economically justified paper width and working speed are established. The narrowest paper paper (with a paper web width of 1.6-4. m) are designed for the production of the thinnest capacitor papers, special technical, high-quality photographic and document papers. Wide B. m. (over 6 m) are used to produce newsprint and sack paper. The working speed of B. m. in the production of capacitor paper is 40-150 m/min, newsprint - up to 850 m/min, sanitary papers - about 1000 m/min and more. Productivity B. m., manufacturing capacitor paper with a thickness of 4-12 micron, is 1-4 t/day, newsprint - 330-500 t/day and more. The length of the B. m. for the production of newsprint reaches 115 m, weight about 3500 T, height of individual parts up to 15 m, power of all electric motors (including paper stock preparation equipment) about 30,000 kW. The drive of individual sections of the B. m. is carried out by DC motors. Within 1 hour, such B. m. consumes up to 45 T pair. Automatic devices regulate the processes of casting and drying paper at high speeds. The high level of equipment with automatic devices and the accuracy of adjustment and execution of the BM make it possible to reduce the number of workers directly servicing it to 3-8 people.

Many new designs of paper materials are being developed, differing mainly in the methods of forming the web of paper. In inverform-type paper (England), a sheet of paper is cast and molded between two grids - the lower and the upper ( rice. 3 ). The pulp from the headbox is fed into the gripper between the lower and upper screens, which creates pressure on the fluid flow. Some of the water passes down through the deposited layer of fiber on the bottom wire and the rest is removed through the top wire. From the inner surface of the mesh, water is removed by a scraper equipped with a knife made of plastic material and a tray for draining water. Further dehydration is carried out on conventional and "inverted" suction boxes with a vacuum not exceeding 12 kn/m 2 (0,12 kgf / cm 2). A press is installed behind the suction boxes, and the squeezed water is sucked off through the upper grid with a scraper. When producing multilayer paper, there are several upper grids (according to the number of layers). Water is practically removed only through the upper screens along the scrapers and into the “inverted” suction boxes.

In B. m. of the vertiform type ( rice. 4 ) the paper web is dehydrated on both sides between two vertically moving grids using scrapers and suction boxes, which ensures that fibers of the same fraction are deposited on both sides of the paper web. In this case, short and thin fibers are deposited first, as a result of which a surface is formed that is most suitable for printing, and large fibers appear in the middle of the sheet, which increases the strength of the paper web.

There is a trend towards the use of circular wire machines for paper casting, where the formation of the paper web is carried out on cylinders covered with a net and located in a bath or without a bath, where the paper pulp is fed. In a rotoformer machine ( rice. five ) the headbox and the mesh part are made in one compact unit, and dehydration is carried out using a suction chamber located inside the rotating shaft. The speed of such machines is up to 300 m/min. They can work with low concentrations, which is important when making papers from artificial fibers.

In the production of long-staple papers made from cotton, asbestos and synthetic materials, “dry forming” of the paper web is used, based on the principle of deposition on the grid of fibers dispersed in the air stream. It is possible that such molding will be widely used for the production of technical and special types of paper.

A further increase in the efficiency of papermaking is associated with a change in the technology of paper production, an improvement in the design of the machine and individual components, and an increase in productivity due to speed and width. A sharp increase in the speed and width of the machine will provide: flow distributors and headboxes of a closed type, allowing you to release the mass onto the grid at a speed corresponding to the increased speed of the grid; register rolls of grooved and mesh type, hydroplanks, two- and three-chamber suction couch-rolls that intensify dehydration; new types of presses (reverse suction presses, presses with a wide suction chamber, multi-shaft and hot presses); rubberized suction rolls and rolls fixed in the middle, rolls with grooved corrugation, presses with underlay mesh, vacuum suction cloth washers, rolls, calender-mounted open bed with articulated arms, fixed in the middle (lower and upper), floating, not needing bombing to compensate for deflection; peripheral type reels for winding rolls with a diameter of up to 2200-2500 mm with pneumatic clamping of the roll and automatic transfer of it from filling to working supports, etc. In the drying part of the B. m., the use of more than high pressure steam, new schemes of steam distributors with steam circulation, siphon removal of condensate, completely closed hoods over the dryer section, installation of dryer nets instead of dryer felts and so on. In addition to the widespread and relatively cheap drying through the contact of the surface of the drying cylinders of the machine with the paper web, new types are being sought that would significantly reduce the working area of the drying part and increase the uniformity of drying. New types of drying are promising: dielectric (due to high-frequency current passed through the paper web); irradiation with infrared rays; hot air blowing; under vacuum.

Lit.: IvanovS. N., Technology of paper, M.-L., 1960; Eidlin I. Ya., Paper-making and finishing machines, 2nd ed., M., 1962; Jahn K., Arbeit an der Papiermaschine, 4 Aufl., Darmstadt, 1958; Hardman H. and Cole E. I., Papermaking practice, Manch., 1960.

V. A. SMIRNOV