FI67584C - APPARATUR FOER BLEKNING AV TRAEMASSA - Google Patents

Description

67584

Apparatus for bleaching wood pulp Divided by application 762792

The invention relates to an apparatus for bleaching pulp semi-finished products using an oxygen-containing gas

A reaction vessel designed by Kamyr for treating cellulosic materials with gaseous reagents, such as oxygen-containing gas, is well known in the art. The vessel is divided along its height 10 into several compartments by horizontal rotating intermediate planes. The mass moves from one compartment to another in rotating horizontal planes. the influence.

Equipment for treating a cellulosic material with such a reaction vessel ensures continuous operation by three-phase (solid-liquid-gas) interaction.

The use of such a reaction vessel involves the arrangement of a large number of moving parts within it, as well as a lack of mixing in each compartment, as a result of which the gas is unevenly distributed along the surface of the slurry bed in each compartment.

At the top of the mattress in contact with the gas phase, the gas concentration is relatively high, while it progressively decreases from the surface to the bottom. In addition, this reaction vessel is not suitable for slurries having a low content of cellulosic material, whereby the drop in dissolved gas concentration from the surface to the bottom becomes even greater.

In the reaction vessel developed by Kamyr, a substantial part of the working space is filled, quite uselessly, with a uniform gas phase without any contact with the slurry of this cellulosic material.

67584 In such a reaction vessel, the entire slurry moves unevenly from the upper compartment to the lower. The final product becomes uneven and its quality characteristics are insufficient.

Also known in the art is a spacer for pulsating extraction columns molded into a package of horizontal torn plates in which, to reduce longitudinal mixing of liquid during use, the plate openings are provided with two guide vanes located parallel to each other and inclined against the plate surface.

The angle of intersection between the axes of the vanes of the adjacent plates is 2, which guarantees the interfering helical movement of the currents in the space 15 close to the spacer plates and the reduced mixing of the liquid in the longitudinal direction.

The spacer described above is used in the radiochemical industry, non-ferrous metallurgy, liquid metal urgency, for example, for the treatment of a three-phase system: liquid-solid-20 gas. Equipment with such a spacer has been used in processes which have been effected without the use of overpressures, which did not make it possible to use them as reactors in which the process is effected with aqueous suspensions at a temperature above 100 ° C under overpressure. An apparatus for producing a lignocellulosic product from plant raw materials is further known in the art (cf. FR Patent No. 2,075,111; Cl. D 21c 9/00). It comprises a reaction vessel adapted to operate under overpressure. The upper end of the device has a supply device for supplying raw materials 30, while the lower end has devices for supplying oxygen-containing gas. Apparatus for feeding the basic reagent makes it possible to feed the basic reagent mainly along the entire height of the reaction vessel.

35 The surface of the vessel is partially surrounded by heat exchangers 67584 to change the temperature inside the vessel to initiate a reaction of raw materials, alkaline reagent and oxygen-containing gas resulting in a lignocellulosic product and liquid removed from the bottom of the vessel and waste gas removed from the top.

The reaction vessel is divided into zones along the height, each zone being provided with a specific mixing device.

The mixing devices are designed in the form of impellers, impellers with mechanized blades, remotely controlled mixers, as well as stationary mixing devices that ensure mixing due to the bubbling of gas, or flap mixing devices. The reaction vessel is annular and is located horizontally so that the slurry can rotate and has a dividing surface plane between the slurry and the gas.

The mixing devices used in the reaction vessel have certain disadvantages and do not allow uniform mixing of the three phases for the following reasons: mechanical devices in themselves provide good mixing of the slurry, but do not provide good mixing of the slurry and gas.

When the gas is passed through the bubbles, it passes through the slurry in large bubbles, however, having only a small contact surface with the lignocellulosic feedstock slurry.

The paddle mixers ensure that the gas and sludge are mixed in the pipes without any mixing in the rest of the reaction vessel. In the annular reaction vessel, the contact surface between the slurry and the gas phase is quite small.

30 One of the disadvantages of these devices is that they are otherwise unsuitable for handling coarse particles, since in this case the chips would accumulate as a barrier at the bottom of each zone of the reaction vessel.

Another disadvantage of the prior art devices is that the particles to be treated have different sizes of particles to be treated at the same downward rate in the reaction vessel, regardless of their size, when the processing time of the coarse particles should be clearly longer. In addition, in prior art devices, it is not possible to separate the extracted fibers from the chips and quickly remove them from the reaction zone.

The structural arrangement of the mixing devices in the prior art requires the presence of a continuous gas phase in each zone of the reaction vessel, which increases the volume of the latter without substantially increasing the contact area of the reacting phases.

It is an object of the present invention to provide such an apparatus for bleaching wood pulp by reacting in a three-system system: a solid-liquid gas, the reaction vessel being provided with equipment for feeding basic reagent and additional liquid, oxygen-containing gas inlet and waste gas outlet to ensure lignocellulosic the high quality of the lignocellulosic product obtained and the waste liquor.

These and other objects are achieved by an apparatus comprising a reaction vessel adapted to operate under overpressure and having a feed device at the top of the reaction vessel for feeding raw materials and a device at the bottom of the apparatus for introducing oxygen-containing gas, a device for feeding the reagent substantially height; heat exchangers partially surrounding the reaction vessel and adapted to change the temperatures therein, thereby initiating a reaction between said feedstock, reagent and oxygen-containing gas to form a bleached pulp product and broth which is removed from the bottom of the reaction vessel, and waste gas which removed from the bottom of the reaction vessel, and waste gas removed from the top of the reaction vessel. According to the invention, the reaction vessel comprises a vertical column provided with a series of 67584 horizontal perforated plates mounted in succession, each of the plates being limited in circumferential size to the inner surface of the column. The column is also provided with a device for supplying the additional liquid needed to prevent the lignocellulosic product from accumulating in the column, and the lower part of the column is connected by a pulse line to a pulse device which allows liquid reagents to move reciprocally through the plate openings.

The use of a vertical column with a series of perforated plates mounted in series as a reaction vessel makes it possible to carry out a continuous process by contacting the three phases, solid-liquid-gas, with each other. During the bleaching reaction, the fibers can accumulate in the column, thus preventing the starting materials from interacting with the reagents and the product from moving along the column. The device for feeding an additional amount of liquid makes it possible to wash such fiber agglomerates out of the column, thus preventing deteriorated phase contact.

Connecting the bottom of the column via a pulse line to a pulse device 20 which provides reciprocal movement of the liquid in the column also ensures solid phase movement in the column and also, together with perforated plates, reactivation of the interface between reactive phases without using any moving parts inside and without the reaction vessel. spaces filled by two or three interacting phases.

In the device according to the invention, the openings in the horizontal plates are arranged along concentric circles 30 and are rectangular in shape, in the zone of these openings the end faces of the plates have guide vanes arranged parallel to each other at an angle of 1-60 ° to the surfaces.

The use of rectangular openings arranged along 35 concentric circles and provided with vanes, 6 67584 located in the region of these openings parallel to each other and at an angle of l60 ° to the surface of the plate, ensures rotational movement of the sludge on each plate and dissipation of gas bubbles by impingers . This improves the transport of the solid phase along the column and improves the contact between the reactive phases.

In order to ensure a more precise attachment of the plates to each other and to prevent them from warping during the pulsation of the liquid-10, spacers are provided between the plates in the device according to the present invention. The device includes an amount of additional sludge for supply connected in series with a pulp removal unit, a washing unit for the final product, a pump and pipelines for waste liquor.

In order to increase the rigidity of the plate attachment and to facilitate the disassembly of the reaction column, in the apparatus according to the invention, the horizontal plates are attached to a hollow vertical arm.

In the device according to the invention, this hollow arm is perforated and through these holes an additional amount of liquid or waste slurry is fed to the column along its entire height.

This perforation makes it possible to use the arm as a device for feeding liquid reagents to the column as well as for feeding an additional amount of liquid along the entire height of the reaction column.

The use of horizontal plates in pulp bleaching, where the plates are confined to the entire inner surface of the column, makes it possible to remove the presence of coarse fibers or bundles of fibers from which less lignin has been removed.

30 In the final product, resulting in improved quality of the latter, simplified arrangement of the plates and increased reliability of the column process.

For a better understanding of the present invention, a specific example of its embodiment is given below in the accompanying drawings, of which 67584 Fig. 1 is a schematic diagram showing an apparatus for bleaching pulp according to the invention, and Fig. 2 is an overview of a perforated plate.

The apparatus of the present invention comprises a reaction vessel 1 in the form of a vertical column adapted to operate under overpressure.

At the top of the reaction vessel 1 there is a feed device 2 for feeding wood pulp.

At the bottom of the reaction vessel 1 there is a device 3 for introducing oxygen-containing gas, while the waste gas exits through a device 4 located at the top of the reaction vessel 1.

Reaction vessel 1 is connected to apparatus 5 for the supply of reagent. The heat exchangers 6 are located along the entire height of the reaction vessel 1 and are adapted to change the temperature inside the vessel, thus creating an interaction between the starting raw materials, the basic reagent and the oxygen-containing gas.

Inside the reaction vessel 1, there are horizontal perforated plates 7 mounted in succession and bounding the entire circumference of the inner surface of the column.

In order to prevent the formation of wood pulp accumulations, a device 9 for supplying an additional amount of liquid is arranged in the column 1 and this device is connected to the lower part of the reaction vessel.

In order to make the liquid reagents in the column 1 reciprocal, the lower part of the column is connected to the pulse device 11 by means of a pulse line 10.

The perforated plates 7 have rectangular openings 30 12, in the zone of these openings there are guide vanes 13 arranged parallel and towards each other at an angle of 1-60 ° (Fig. 2), which ensures the disintegration of the gas and the rotational movement of the slurry by the pulse device.

35 Spacers 14 (Fig. 1) are mounted between the plates 8 67584 to ensure that they adhere to each other.

The device 9 for supplying an additional amount of liquid (Fig. 1) comprises a series-connected discharge unit 16, a washing unit 17 for the final product, a pump 18 and pipelines 19 5 for supplying waste liquor to the lower part of the reaction vessel 1 and the hollow arm 20. Discharge is indicated by arrow "A" B ".

The perforated plates 7 are attached to a hollow vertical arm 20 with a perforation 21 through which an additional amount of liquid or effluent is fed to the column along its entire height.

The plates 7 are limited to the entire circumference of the column 1, as a result of which their manufacture and assembly are substantially simplified and their operational reliability is increased.

The operating principle of the device according to the invention is as follows:

The wood pulp is filled by means of a feed device 2 into the reaction vessel 1 to the uppermost perforated level 7 mounted on the vertical arm 20. The reagent solution is introduced into the reaction vessel 1 from the device 5, while steam is fed to heat exchangers 6 to heat the contents of the reaction vessel.

The oxygen-containing gas is fed to the lower part of the reaction vessel 1 via the device 3, this gas decomposes under the action of the guide vanes 13 and the liquid impulses and rises to the low-bogies without, however, forming a uniform gas phase.

Pulsing back and forth from the pulse device 11 along the pulse line 10 is transmitted to the lower zone 23 of the reaction vessel 1. The heart rate of the fluid pulse is 100-600 mm / mi-minute. The pulsation intensity is characterized by the product of the pulsation frequency (pulses / min) and the pulsation amplitude (mm).

As a result of the pulse, the pulp slurry is rotated and the chips from the top plate 7 pass through rectangular openings 12 to the second (from above) plate 7. The distance between two adjacent plates is kept constant by means of spacers 14. In the second plate 7, the lasers rotate in the opposite direction due to the opposite arrangement of the guide vanes 13.

The pulp slurry is removed through the device 9 to supply an additional amount of liquid. First, the slurry passes through a pulp-5 unit 16 and is further delivered to a washing unit for the final product. This washing unit 17 ensures the thickening of the final product, its washing and the production of waste liquor in a concentrated form. A portion of the waste liquor, determined by the liquid ratio in the reaction vessel 1 and the volume of fresh reagent 10 fed to it, as well as the operating conditions of the pulp removal unit 16, is supplied by a pump 13 to the bottom and hollow arm 20 of the reaction vessel 1 via connecting lines 19. At the same time, this broth is used to purify the fractionator 22 and to better separate the non-extractable pulp from the pulp fibers. Another portion of the waste broth is delivered for reuse.

Depending on the selected temperature conditions for the treatment of the chips, the different zones of the reaction vessel 1 can be heated or cooled by means of heat exchangers 6. The waste gas 20 is removed from the upper end of the reaction vessel through the device 4, after which the purified oxygen can be fed again to the device 3, through which fresh oxygen-containing gas is also fed to compensate for its losses and consumption for chemical reactions.

The device according to the present invention does not use a continuous gas phase, as a result of which the working space of the reaction vessel 1 becomes more efficiently used.

The device according to the invention can be used for bleaching with an oxygen-containing gas ascending or descending by transferring the substance in the reaction vessel 1. As the substance to be treated passes down the substance to be treated by means of a feed device 2 to the upper part of the reaction vessel 1 with torn plates 7 with rectangular openings 12 arranged in concentric circular circumferences and provided with guide vanes 13. The treated substance passes down through the openings 12.

67584 The mixing of the substance to be treated with the liquid reagents and the oxygen-containing gas fed to the bottom of the reaction vessel via the device 3, as well as the transfer of the treated raw materials, is effected by transmitting the pulse from the pulse device 11 via the pulse line 10.

The temperature conditions for treating the contents of the reaction vessel are controlled by means of heat exchangers 6. The treated material is removed through a pulp removal unit 16 and delivered to a washing machine 17 for the final product. The waste gas is removed from the reaction vessel 1 via device 4.

As the treated substance passes into the lower part of the reaction vessel 1, the functions of the feed device 2 and the pulp discharge device 16 should be changed. In order to collect the waste gas, the connection point of the device 4 to the reaction vessel 1 should be located higher than the connection point of the supply device 2.

Claims (1)

67584 Claim: Apparatus for bleaching wood pulp, comprising a reaction vessel for operation at overpressure 5, at the top of which a device for supplying raw material and at the bottom a device for conducting oxygen-containing gas, a device for conducting basic reagent mainly along the entire height of the reaction vessel, and heat exchangers which partially surround the surface of this vessel and which are adapted to change the temperature therein to initiate a reaction between the raw materials, the basic reagent and the oxygen-containing gas to form a bleached pulp product and a broth which is removed from the bottom of the vessel; removed from the top of the vessel, characterized in that the reaction vessel (1) comprises a vertical column provided with a series of successively arranged horizontal torn plates (7), each of which is connected peripherally to the inner surface of the column, and that the column is also fitted with a device (9) increased for feeding the amount of obstruction required to prevent the accumulation of mass in the column, that the lower part of the column is connected by a pulsation line (10) to a pulsator (11) which allows liquid reagents to reciprocate through the routing of the plates (7).