SE524318C2 - Purification of unclean condensate emanated from pulp production of chemical or semichemical pulp including evaporation of spent liquor under utilization of a cleaning plant - Google Patents

Abstract

The process steam from the last evaporation stage and the unclean condensate are introduced into the first unit of a combined stripper/condenser while the rest of the steam flows to another condensers. The process steam and unclean condensate are brought to flow in opposite directions to cause a direct heat exchange resulting to the separation of volatile compounds from the condensate. Purification of unclean condensate emanated from pulp production of chemical or semichemical pulp including evaporation of spent liquor under utilization of a cleaning plant having series coupled condensers comprises: (a) the process steam from the last evaporation stage and the unclean condensate are introduced into a combined stripper/condenser in opposite directions to cause a direct heat exchange, resulting separation of volatile compounds from the condensate; (b) the rest of the process steam flows to another condensers while the remaining process steam is cooled down indirectly leading to the contaminated water and turpentine to be condensed and collected together. Methanol is condensed from the first collected condensate that separates from the turpentine content. Turpentine is removed from the plant and the residual condensate leads back to the combined stripper/condenser. Methanol and primary cleaned condensate is collected at the bottom and is removed from the plant or will be further purified. An independent claim is also included for a plant for purifying of unclean condensate emanated from pulp production.

Description

Essay 10 15 20 25 30 35 40 ::: = 45 »in-i 50 524 318 2 The sulphite method or process can be divided according to the base of the cooking liquid used, namely, calcium, magnesium, ammonium or sodium. It is sodium and magnesium cooking liquors that are usually recycled and therefore come into play in this context.

After the lignocellulosic material has been digested to the desired extent, the resulting cooking liquor is separated from the pulp fibers. The boiling liquor is often called black liquor and this black liquor, which in the context of chemical recycling in this position is usually called thin liquor, consists predominantly of water. The dry matter content of thin liquor (lignin, hemicellulose, cellulose, residual chemicals, etc.) is, for example, in the range of 15 - 20%. In order to be able to burn the answer liquor in, for example, a recovery boiler and allow the organic substances to switch to mainly carbon dioxide and water during energy development and allow the inorganic substances to form a residue in the form of a melt and utilize it to produce fresh cooking liquid, the dry liquor dry matter content should be increased. to at least 55%. Such black liquor is usually called thick liquor. Thick liquor is obtained by evaporating the barrel liquor in, for example, five to seven steps. Each step is called effect.

Modern factories for the production of chemical cellulose pulp try to reduce the fresh water consumption and also the amount of liquid that is discharged to the recipient as much as possible. This is done by closing the total fluid system to a greater or lesser degree. This means that effluent from one or more stages in which cellulose pulp is bleached is returned to the process and mixed with the boiling liquor. The thin liquor thus sometimes consists of a mixture of boiling liquor and various bleach liquors.

During said evaporation of the barrel liquor, condensate arises. In some positions the condensate is so clean that this relatively pure condensate can be used in one or more places in the pulp mill. In other positions, impure condensate occurs, including highly contaminated condensate.

According to the invention, it is imperative that such condensate be purified.

In the production of chemical cellulose pulp, another type of impure condensate also arises. The digestion of the lignocellulosic material takes place under pressure, leading to effluent and a gas mixture leaving this vapor consisting of water vapor and various organic and inorganic chemical compounds leaving the digestion vessel (boiler). In conventional batch digestion, the spent liquor leaves the digester together with the resulting cellulose pulp. Said gas mixture is caused to condense and a so-called boiler condensate is formed.

Such gas mixtures are also released and collected in places other than the boiler or boilers in the boiler and are caused to condense, hence the name boiler condensate instead of blue steam condensate. Said boiler condensate occurs both in batch and continuous digestion of lignocellulosic material.

Such crude boiler condensate is usually combined with crude evaporation condensate and this mixture is purified in accordance with the invention. It is possible to purify the two condensates separately, but it is not preferred.

There are several semi-chemical pulp production processes. An example of such is the neutral sulfite chemical method (NSSC). In such mass production, the chemical treatment of the lignocellulosic material is not very far-reaching, which means that a subsequent mechanical defibration of the material is necessary. In some cases the treatment liquid, or cooking liquid if desired, is recovered after the treatment and if this effluent is subjected to evaporation, the present invention is applicable. State of the art In the purification of crude condensate according to conventional technology, at least one step called stripping is used............................... By this is meant that the crude condensate is blown through with steam so that the steam takes with it volatile contaminated chemical compounds from the condensate. According to conventional technology, separate or stand-alone, special stripper systems are used. The steam used is high-quality fresh steam, for example steam originating from and extracted in the recovery boiler or steam from some effect inside the evaporation. Furthermore, such conventional purification of impure condensate is carried out at atmospheric pressure or overpressure.

In Swedish Offenlegungsschrift 7704352-9 (423915) a process is carried out for the recovery of sulfur compounds, volatile alcohols such as methanol and by-products such as turpentine or the like from impure condensate. According to that procedure, stripping is performed in two places, partly in a superstructure on one of the evaporation effects, which leads to an increase in the cost of the evaporation plant and partly in a stand-alone stripper. In the free-standing stripper, lye steam from the last effect of the evaporation is used for stripping unclean condensate. Such use is economically advantageous. However, this use is limited to 20 - 25% of available vapor from the last effect of evaporation. Other available liquor is condensed in a conventional manner in surface condensers. Cold water is usually used as the cooling medium, which results in a low-quality hot water being generated.

Disclosure of the invention Technical problem The hitherto known technique for purifying impure condensate of the type described is uneconomical.

This is primarily due to the use of separate or independent stripper plants and the use exclusively or too much of expensive fresh steam for the performance of the stripping.

The solution The present invention solves this problem and relates to a process for purifying impure condensate emanated in the production of semi-chemical or chemical cellulose pulp including at least evaporation of effluent using a treatment plant having a plurality of series-connected condensers, characterized in that the majority of the lye from evaporation last effect, ie process steam recovered at the power having the lowest vapor pressure, and crude condensate is introduced into a combined stripper and condenser, causing the process steam and the crude condensate to flow in the opposite direction so that direct heat exchange takes place and heat is emitted from the steam to the condensate leading to volatile substances in the condensate are separated from the same and captured by the flowing steam and this during simultaneous indirect cooling leading to condensation of the main part of the process (| out) steam, that the remaining process (liquor) steam flows on to further condensers, whereby the remaining process (| the vapor is gradually cooled indirectly leading to condensed water and turpentine first being condensed and collected together and to methanol being condensed thereafter, the former 10 15 20 25 30 35 35 40 --.- t »n: 45 ß-t-ø 50 524 4318 collected condensate is freed from the majority of the turpentine content, which is removed from the plant and the remaining condensate 1 returned to the combined stripper / condenser and that condensed methanol is removed from the plant, and that substantially purified condensate is collected at the bottom of the combined stripper / condenser and removed from the plant or subjected to further purification. It is highly preferred according to the invention that all the vapor from the last effect of the evaporation, i.e. process steam recovered at the power that has the lowest vapor pressure is introduced into the combined stripper / condenser.

It is optimal if the available process (liquor) steam corresponds to the amount of steam needed to purify the crude condensate in the manner described. A surplus of available process (lye) steam does not pose a problem, since of the surplus, for example, hot water can be produced according to conventional technology. A deficit of available process (lye) steam means that an addition of some other steam, for example fresh steam, is needed for the purification work. In individual pulp mills, a small part of the produced process (liquor) vapor may be bound in the system and therefore not available for purification of crude condensate in the manner described. If a lack of steam for purification arises for this reason, an addition of other steam, for example fresh steam, must be effected. To proceed in such a way is not preferred.

It is suitable that the crude condensate is introduced into a space above and adjacent to the combined stripper / condenser and that process (liquor) steam is introduced into a space below and adjacent to the combined stripper / condenser and that the crude condensate flows in the direction from top to bottom through the combined stripper / condenser, while process (liquor) steam flows in the opposite direction.

Steam from the deaeration of one or more evaporation effects can also be introduced into the space above and in connection with the combined stripper / condenser. In such a case, this vapor does not contribute to the purification of the condensate, but the intention is that contaminated chemicals also condense out of this vapor, so that these do not end up in an inappropriate place and possibly damage the environment.

According to an absolutely preferred embodiment of the invention, the substantially purified condensate is caused to flow down through an underlying extension of the combined stripper / condenser and this is heated indirectly by means of steam from deaeration of one or more evaporation effect (s), which steam is introduced at the lower part of the extension. volatiles remaining in the condensate are separated from the condensate in gaseous form and flow upwards and mix with the upward, newly added process (liquor) steam and the obtained highly purified condensate is collected at the bottom of the extension and removed from the plant.

In a special application of the method according to the invention, said deaeration steam is amplified with fresh steam with variable energy content so that the purity of the condensate which is removed from the plant is regulated in detail.

It is becoming increasingly important to ensure that the purity of the purified condensate is as high as possible. This is caused by the purified condensate being taken to a number of collection points in the pulp mill, for example to different pulp washes and to different places in the bleaching plant, and also to drains, i.e. as emissions to the recipient. The remaining impurities in the part of the purified condensate that go out into the recipient have a direct impact on the environment.

The quantities of condensate used at different collection points often have an indirect environmental impact.

With conventional treatment technology for impure condensate, a degree of purification of 90% is usually what one strives for. Each percentage point above 90% in degree of purification is in many cases sought after and significant. By means of said addition of fresh steam it is possible to ... l - 10 15 20 25 30 35 40 '; 5 n 'so 524 3518 ø- I .. further increase the already very good purification effect achieved with the previously described preferred embodiment of the invention. Degrees of purification of 95% and even above are possible to achieve. Admittedly, the addition of fresh steam is contrary to one of the important principles of the practice of the invention, namely that only inferior, i.e. cheap steam should be used when purifying the crude condensate, but the improvement that can be achieved by such an action may well be worth the extra cost and in comparison with other purification alternatives very advantageous from an economic point of view.

The remaining part of the indirectly heating deaeration steam is taken out at the upper part of the underlying extension and introduced into the treatment plant in the space above and in connection with the combined stripper / condenser. The reason for this has been reported previously.

According to yet another absolutely preferred embodiment of the invention, a negative pressure-creating device is applied at the outlet end of the plant, which has the consequence that inert gases and any foul-smelling sulfur-containing gases are removed from the plant. By inert gases is not meant that these are chemically inert, but they are not condensable and are in gaseous form at the prevailing temperature.

These gases are advantageously fed to a combustion plant for foul-smelling gases, which in itself is completely in accordance with the prior art. By creating a negative pressure in the system where purification of the impure condensate takes place, the process (lye) vapor required for purification can have a temperature which is greatly below 100 ° C.

The temperature of this steam can be, for example, 50-60 ° C.

The purification of the crude condensate takes place as shown in the above in several steps and a suitable number of steps is four. The condensed methanol is collected at the bottom of the last condenser in series and transported away from the plant, whereby part of the methanol is reintroduced into the space above and adjacent to the penultimate condenser in series. The impurities in the crude condensate are taken up as previously stated by the added process (lye) steam and these impurities are then taken care of by condensing them out and in order for this to happen a refrigerant must be supplied in the various steps and further heated refrigerant must be removed in several positions . As for the first condenser, i.e. the combined stripper / condenser, the refrigerant is introduced at the upper part of the condenser and removed at elevated temperature at the lower part of the unit, alternatively approximately at its middle part.

Any refrigerant can be used and the preferred one is cold water.

The invention also relates to a plant for purification of crude condensate, emanated in the production of semi-chemical or chemical pulp including at least evaporation of effluent, comprising a plurality of condensers connected in series, characterized by, a first unit in the form of a combined stripper / condenser having several inserts , by which process (liquor) steam and impure condensate are caused to flow in the opposite direction and in direct contact with each other, which inserts are surrounded by closed space for flow of coolant and to the unit on its upper and lower side connected space, which later space simultaneously serves as the bottom of the unit, means for supplying impure condensate to the space at the top of the unit, means for supplying process (liquor) steam to the space at the bottom of the unit, means for supplying coolant at one end of the unit and means for removing heated coolant at opposite end of the unit, means for removal of substantially purified condensate and further condensers for disposing of non-condensed process (liquor) steam remaining after the first unit, having the plurality of inserts through which only process (liquor) steam and condensate formed by the steam flow, which --..- »10 15 20 25 30 35 45; 45 524 318 6 inserts are surrounded by closed space for flow of coolant leading to condensation in series of contaminated water and turpentine in mixture and methanol and to the respective condenser on its upper and lower side connected space, means for supplying coolant at one end of the condensers and means for removing heated refrigerant at the opposite end of the condensers, means for removing the above-mentioned mixed condensate from the space on the underside of the condenser and for separating the main part of the mixed condensate content and for removing turpentine out of the plant and transporting the remaining condensate the space in the first unit where the impure condensate is introduced, m noble for removing condensed methanol from the space on the underside of the subsequent condenser out of the plant.

Said inserts consist of either tubes or lamellae. The plant may also comprise means for supplying deaeration steam from one or more evaporation power (s) to the space at the first unit where impure condensate is supplied.

According to a preferred embodiment of the plant according to the invention, the first unit in the form of a combined stripper condenser is supplemented with a downward extension having inserts down through which the substantially purified condensate flows, which inserts are surrounded by closed space for flowing primarily of deaeration steam from one or more several evaporation power (s) in the opposite direction to the substantially purified condensate, which extension ends with a bottom, from which highly purified condensate is removed by previously indicated means and further means for supply of steam and removal of the steam remaining after the indirect heating .

The inserts just mentioned consist mainly of tubes.

According to yet another preferred embodiment of the plant according to the invention, a device is arranged at the lower part of the condenser in series for creating negative pressure in the capacitors' inserts and connecting spaces and for removing mainly inert gases and any malodorous sulfur-containing gases.

The number of capacitors connected in series is not critical, but it has proved appropriate with a number of four, with the first in the form of a combined stripper and condenser. The concept of series-connected is that the capacitors are connected to each other.

For example, the first and second may be connected to a space above the condensers themselves and the second and third are connected to a space below the condensers themselves and finally the third and fourth are connected to a space above the condensers themselves. The fourth, or generally the last, capacitor in series can either be located adjacent to the penultimate capacitor or be located at a distance from the penultimate capacitor. In the first case the refrigerant system can be one and the same for all, for example four, condensers, while in the second case there is a special refrigerant system for the last condenser, where the methanol is collected and removed. This makes it possible to use a very strong cooling in the last condenser, which leads to a number of sulfur-containing substances being condensed out and mixed with the condensed methanol. In this way, the volume of residual gas or inert gas, which must be taken care of at the end of the plant, is reduced, at the same time as the volume of liquid in the same position increases slightly. Since the recovered methanol is usually taken to some combustion equipment, it is rational to simultaneously dispose of a number of sulfur-containing substances, which are otherwise present as very bulky gas. 10 15 20 25 30 35 i 40 in: 45 524 318 1 It is preferred to install all capacitors, for example four, in a common enclosing housing. Optionally, the last condenser can be built independently for the reasons stated above. According to an embodiment of the invention, the plant comprises means for extracting a part of the methanol which is removed from the plant and for returning this methanol to the space above the penultimate condenser in series.

To increase the efficiency of the stripping process, it may be appropriate to inside the tubes of the first unit, i.e. the combined stripper and condenser, apply means for increased contact area of the crude condensate vis-à-vis the stripper vapor, i.e. process (lye) steam. The means may consist of two joined, elongate elements, which in cross-section form a cross or a cross. To further increase the effect, the means is rotated along its longitudinal axis leading to a helical shape. The edge portions of the four wings of the agent may be applied close to the inner wall of the tube or at a distance of a number of millimeters from the inner wall of the tube.

It is quite possible to use means consisting of more than two, for example three or four, joined elongate elements, which cross-section forms a star-shaped pattern.

Advantages According to the present invention, it is preferred that the entire amount of steam necessary to purify the crude condensate should be of low value, inexpensive steam, which is available as residual products in the evaporation of effluents. This contributes to the operating costs of the purification process being low. As for the fixed cost, i.e. the investment cost of the treatment plant, it is greatly reduced by the design of a combined stripper and condenser. Furthermore, according to the invention, it is possible to compress the main part of the treatment plant into an object, i.e. all capacitors are enclosed in, for example, a cylindrical building or, if desired, a cylindrical tower. This means, on the one hand, that the material consumption for the plant is minimized, which has a direct effect on the total cost, and on the other hand, that the installation space required is minimized. In pulp mills with a pronounced lack of space, this is particularly advantageous from an economic point of view.

Furthermore, according to the invention, it should be possible to obtain a degree of purification of the purified condensate of 95% and also above, which leads to great environmental benefits. In order to achieve such high degrees of purification, it may be necessary to use a certain amount of expensive fresh steam, but this is outweighed by the possibility of further improving the minimum environmental impact within at least some cellulose pulp production.

Figure description Figure 1 schematically shows an embodiment of a treatment plant according to the invention. Figure 2 schematically shows a preferred embodiment of a treatment plant according to the invention. Figures 3, 4, 5 and 6 show in more detail the central parts of yet another preferred embodiment of a treatment plant according to the invention. ... 11 10 15 20 25 30 35 40 45 50 524 338 Best Mode In the following, the invention is set forth both in terms of method and plant with reference to said figures and furthermore certain circumstances and conditions will be explained in more detail. Figure 1 schematically shows a purification plant according to the invention, by means of which the impure condensate can be purified considerably, i.e. mainly, but not maximally or to a high degree.

Impure condensate, for example a mixture of boiler condensate and evaporation condensate, is passed via lines 1 and 2 to the part of the space 3 located above the combined stripper / condenser 4. The space 3 connects the combined stripper condenser 4 to the immediately following condenser 5.

Through the pipe nozzle 6, process (lye) steam is supplied to the space 7. Inside the combined stripper / condenser there are several inserts in the form of either tubes or lamellae (not shown in the figure). These inserts are surrounded by a space for the coolant, for example cold water. This is supplied via line 8 and after the medium has fulfilled its task and is heated, it leaves the system via line 9. It is repeatedly stated that the space for the refrigerant is closed and by this is meant that the refrigerant surrounding a certain number of tubes does not enter directly contact with the contents of the tubes, but it is an indirect cooling of the contents of the tubes. That the refrigerant is supplied in a line 8 and removed in a line 9 is included in the concept of the end in the described respect.

If the inserts in unit 4 consist of tubes, the following applies. The tubes extend along the entire unit 4 and one open end faces the space 7 and its other open end faces the space 3. Said open ends are surrounded by a connecting unit, for example a plate. The crude condensate is distributed by means of a line 2 over the cross section of the unit 4 and the condensate flows down into the open tubes and is forced by gravity downwards into them. Process (lye) the steam supplied in the space 7, i.e. opposite end of the unit 4, seeks the opening of the tubes and flows upwards and then meets the downstream impure condensate. Then what in technical terms is called stripping, i.e. the majority of the relatively volatile, polluted substances in the condensate leave the condensate and turn into gaseous form and follow the part of the process (liquor) vapor that remains uncondensed upwards and out of unit 4 to space 3. The further down in unit 4 the condensate supplied comes the cleaner the condensate becomes. At the same time as this purification takes place, the indirect cooling of the contents of the tubes leads to a large part of the added process (liquor) vapor condensing inside the tubes. The degree of condensation depends on a number of factors, but the degree of condensation can be, for example, 70 to 75%. This means that only 25 to 30% of the added process (liquor) steam reaches the space 3. The condensate formed in this way is of course mixed with the downflowing purified condensate and this condensate mixture is collected at the bottom of the space 7. The remaining process (liquor) ) the steam flows via the space 3 further down through the tubes, for example, which are in the condenser 5 (not shown in the figure). In this condenser 5 only process (liquor) steam flows into the tubes. However, these tubes are also surrounded by the refrigerant, which leads to a continued condensation of water. 10 15 20 25 30 35 '240; |; »- - -45. 524 šlß Simultaneously and / or before, turpentine and the turpentine are condensed out and the water flows along the main tube walls into the space 10, where these two substances form a mixture, but with the main part of the turpentine forming a layer on top of the water.

The process (liquor) steam remaining in that position flows via the upper half of the space 10 into the third condenser 11 in series. The steam flows up through the tubes, for example, into the condenser 11 (not shown in the figure) and reaches the space 12. This during continued condensation of water and turpentine. The remaining steam flows through the space 12 and down through the condenser 13 and its tubes, for example, (not shown in the figure). In this condenser, methanol is mainly condensed, which accumulates in the bottom of the condenser 13. If the condensate originates, for example, from the production of sulphate pulp and the temperature of the coolant, which is supplied via line 14 and removed in heated form via line 15, is essentially the same as the temperature of mentioned refrigerant, sulfur compounds, such as dimethyl disulfide, are also condensed.

Residual, non-condensed substances are removed in gaseous form from the plant via line 16 and device 17.

The temperature of the process (| out) steam supplied to the plant through the pipe nozzle 6 is directly dependent on the evaporation system for effluent used in the individual pulp mill. There are evaporation plants which operate continuously at overpressure and then the recovered process (| out) steam, which is used in accordance with the invention, has a temperature of at least 100 ° C. In such or such cases, device 17 may consist of a simple valve or possibly a fan. The most common is that the evaporation plant is operated so that recovered process (liquor) steam has a temperature of 60 to 65 ° C. This means that there is negative pressure at the place where said steam is extracted. In those cases, it is necessary that device 17 be constituted by a vacuum-creating device, for example a vacuum pump or an ejector.

The appropriate pressure in the system in those cases is about 10 - 20 kPa (0.1 - 0.2 bar). The temperature of the refrigerant, for example water, which is supplied may vary. 10 ° C is an example of a suitable temperature. Such a temperature is natural at least during the winter in northern countries, such as Sweden. During the summer and in other cases, the water can be cooled down to a temperature of 10 ° C by means of a cooling machine. In the case of an incoming process (liquor) steam with a temperature of 60 ° C, the temperature of the outgoing heated cooling water can amount to 50 ° C. The desired mainly purified condensate leaves the plant via line 18 by means of a pump 19.

Approximately in the middle of space 10 there is an overflow 20 applied, with for instance a toothed upper edge. Since the turpentine condensed out in the condenser 5 settles on the likewise condensed water, the main part of the condensed turpentine flows over the overflow or overflow drain 20 to the right-hand part of the space 10.

This turpentine-dominated condensate is pressed by means of the pump 37 via the lines 21 and 22 to the container 23, in which there is preferably an overpressure created by said pump. Turpentine and water are also layered in this container.

The two-stage decanted turpentine is taken out of the system via the line 24 and to a storage container or collection point.

The contaminated water, which is in the left part of space 10, is transported by means of the pump 25 via lines 26, 27, 28 and 29 back into the system and mixed in freshly supplied unclean condensate, which is introduced into space 3 above the combined 10 15 20 25 30 35 : z40 iz45 »il ~ sl, I 1 524 318 10 the stripper condenser 4 via line 2. The aqueous phase in the container 23 is passed via line 30 to line 26.

It is not necessary to use the overflow drain 20 for the purpose of obtaining a first coarse decanting of the turpentine from water, but it is quite possible to transport from the space 10 a mixture of turpentine and water to a special unit (not shown in the figure) where a careful separation of the turpentine from water is made. These two liquid streams are, in turn, handled in the manner previously described.

A condensate consisting mainly of methanol accumulates at the bottom of the condenser 13. By means of the pump 31, the methanol is discharged from the system via the lines 32 and 33. Usually the methanol is discharged to a combustion site of some kind. In order to optimize the purification process, it is preferable that a part of the methanol which is removed via the lines 33 is caused to be recycled via the lines 34 and 35 to the left part of the space 12, i.e. above the condenser 11.

Since the condenser 13 is independent in relation to the other three condensers 4, 5 and 11 and has its own refrigerant system, it is possible to drive the condensation very far, i.e. so that also several difficult-to-condense sulfur-containing substances are condensed out, for example when impure condensate, formed in the production of sulphate pulp is purified in accordance with the invention.

By means of cooling machines, the temperature of the coolant, for example the water, can be lowered to 0 ° C or a few degrees above.

Via the line 36, the deaeration steam from the evaporation plant can be supplied to the treatment plant where the intention is that the steam is also purified, i.e. the main impurities of the steam are condensed out and taken care of.

Figure 2 schematically shows a preferred embodiment of a treatment plant according to the invention. The two treatment plants are largely consistent and therefore the same reference numerals are used in Figure 2 as in Figure 1 for the objects that are consistent.

The difference between the two treatment plants is that the preferred treatment plant according to Figure 2 has a complementary downward extension 38 to the combined stripper condenser 4. This extension also contains inserts in the form of tubes or lamellae (not shown in the figure). These inserts are surrounded by an enclosed space intended for warming steam. It is primarily venting steam from one or more power (s) in the evaporator, which is supplied via line 39 to the pipe socket 40. In the case that the inserts consist of tubes, the heating steam flows, which may have a temperature of 70 - 80 ° C or slightly above, up along the elongate tubes and residual, non-condensed steam leaves the unit 38 via the pipe socket 41 and the conduits 42 and 43. The latter conduit is connected to conduit 36 and residual deaeration steam is thereby introduced to the space 3 for subsequent purification in accordance with previously stated explanation. .

The substantially purified condensate leaving the combined stripper condenser 4 flows through the space 7 down to the extension 38 and through the tubes, for example, which pass through the extension and open with their open ends in the bottom 44 of the extension. In the opposite direction with the substantially purified condensate on the inside of the tubes flows on the outside of the tubes the indirectly heating steam. Since the condensate in question has a temperature of, for example, 60 to 65 ° C and the heating steam has a temperature of, for example, 70-80 ° C, the condensate heats up slightly as it flows down through the tubes, for example. As a result, some of the pollutants still remaining in the condensate are caused to leave the condensate in gaseous form and this gas flows 10 15 20 25 30 35 fm .-> in '; 45 i imi »f i 1.» i i 524 318 šßï fi š 11: .§ *. ' o o a: u; upwards through the tubes and reaches the space 7 where the gas is mixed with newly supplied process (| out) steam which as previously stated is supplied via the pipe nozzle 6 and this gas mixture then strives upwards through the combined stripper / condenser 4 in the previously stated manner.

The above-described means that the substantially purified condensate is further purified and passes to highly purified condensate, which is collected at the bottom 44.

Via line 18 and with the aid of the pump 19, the condensate in question is removed from the treatment plant.

The supply of deaeration steam from the evaporator is severely limited, at the same time as the amount of condensate flowing down through the extension 38 is large. Although the temperature difference between the two media can be large, the uneven amount ratio leads to the temperature increase of the condensate becoming modest.

However, sufficient for a significant further purification of the condensate.

A portion of the deaeration steam condenses on its way up through the unit 38 and the resulting condensate is collected at the bottom of the previously mentioned closed space including the pipe nozzle 40. The condensate in question is passed via line 45 to line 26 and mixed with the contaminated water returned to the system. in the manner previously described. The handling of the remaining steam in the space 3 and onwards is completely in accordance with what has been stated previously and shown in figure 1. Figures 3 and 4 show the upper part of central parts in a preferred embodiment of a treatment plant according to the invention. These central parts consist of four capacitors enclosed in an elongated cylindrical tower, with the first unit in the form of a combined stripper and condenser. Figures 3, 4, 5 and 6 show neither the unit 38 according to Figure 2 nor other supplementary equipment in the treatment plant according to the invention, as shown in Figure 2 and Figure 1, respectively.

The upper portion of the tower 46 is shown from the side in Figure 3 and in cross section in Figure 4.

Through the pipe nozzle 47, impure condensate plus condensate collected at the bottom of the second condenser in series is supplied. Through the pipe socket 48, a part of the condensed methanol, which has accumulated at the bottom of the fourth condenser in series, is returned.

The coolant, for example cold water, is supplied through the pipe socket 49. The tower 46 contains a large number of tubes 50. These tubes are surrounded by a continuous means 59, for example a plate.

The left part 51 of the tower, which is most clearly seen in the cross section in Figure 4, constitutes a combined stripper and condenser. To the right follows the second capacitor 52 in series.

There is a wall 72 which separates the combined stripper and the condenser 51 from the condenser 52. This wall 72 does not extend all the way to the top of the tower 46, but the process (| out) steam flows up through the tubes 50 in unit 51, over the wall 72 and down through the tubes 50 in the unit 52. This unit is connected at its bottom to the third condenser 53 in series. This condenser is connected at the top of the tower 46 to the fourth condenser 54 in series.

The wall 55 which separates the condenser from both condenser 53 and condenser 54 runs all the way up to the top of the tower 46. The wall 56 which separates condenser 53 from condenser 54 runs as shown in the foregoing, not all the way up to the top of the tower 46.

The number of tubes 50 drawn in the combined stripper and condenser 51 is twelve.

The corresponding number of tubes 50 in condenser 52 is four, while the number of tubes in the third condenser 53 is two and in the fourth condenser 54 one. This is a result of the added process (| out) of the steam condensing as it goes on. This plant is 10 15 20 25 30 35 "40 ._ ~ * 45.. .. .. 524 318 17- so designed that about 2/3 of the supplied process (liquor) steam has condensed in the tubes 50 when the steam reaches the upper end 57 of the tubes in the combined stripper and condenser 51.

The refrigerant is introduced as previously stated in an enclosed space. The space is limited upwards by a means 58, for example in the form of a plate.

The aforementioned means 59, for example a plate, is not applied tightly around the tubes 50. At, for example, four points around the periphery of the tubes 50, said plate rests.

These points are located at the far end of, for example, four crescent-shaped bulges on the plate which force the tube into the exact position. Between the bulges there is a space between said plate and tube, which forces the supplied cold water, for example, to flow along the outside of the tubes 50 down through the tower 46. Such means 59 is applied to the tubes, at one to two meter intervals, down through the tower 46. This serves two purposes. On the one hand, the tubes 50 are cooled efficiently, because cold water constantly flows along the outside of the tubes, and on the other hand, the elongate tubes 50 are braced up in an efficient manner. Figures 5 and 6 show the lower part of the tower 46.

Figure 5 shows a cross section of the tower 46 seen from below. This cross section has been turned from the bottom up by a technical bowl. Process (liquor) steam is fed through the pipe socket 60 into the combined stripper and condenser 51. This is separated at the bottom by means of a wall 61 from both condenser 52 and condenser 53. These are connected to each other at the bottom so that process (liquor) steam can flow freely from condenser 52 up through condenser 53. From there the process (liquor) steam, whose volume decreases for each condenser, flows down through condenser 54. This is at the bottom separated from the condenser 52 by the wall 62 and from the condenser 53 by the wall 63. Via the inlet gases 64 are transported away by inert gases including any malodorous sulfur-containing gases and according to a preferred embodiment of the invention the inlet pipe 64 is connected to a negative pressure generating device (not shown in the figure).

Figure 6 shows the pipe socket 65, through which the heated refrigerant is transported away. The closed space for the coolant is limited downwards by a means 66, for example in the form of a plate. In the bottom of the space 67, purified condensate is collected and it is removed from the plant via the pipe nozzle 68. In the bottom of the space 69 below the condenser 54, condensed methanol is collected and it is removed via the pipe nozzle 70. In the bottom of the space 71, turpentine and contaminated water are collected. pipe nozzle (not shown in the figure) for separation of turpentine and reflux of residual condensate in accordance with what has been repeatedly described previously.

What is shown in Figures 3,4,5 and 6 does not differ from the capacitors 4,5,11 and 13 with associated spaces 7,3,10 and 12, as well as connecting wires including pipe sockets according to Figures 1 and 2, in principle but describes a similar treatment plant, which, however, is extremely compact and requires minimal space.

Claims (1)

1. 0 15 20 25 30 35 '40 45 7 50 524 318/3 PATENT REQUIREMENTS Process for purification of impure condensate, emanated in the production of semi-chemical or chemical cellulose pulp including at least evaporation of effluent using a treatment plant having a plurality of series-connected condensers , characterized in that the bulk of the vapor from the last effect of the evaporation, i.e. process vapor recovered at the power having the lowest vapor pressure, and crude condensate is introduced into a combined stripper and condenser, causing the process vapor and the crude condensate to flow in the opposite direction so that direct heat exchange takes place and heat is emitted from the vapor to the condensate leading to volatile substances in the condensate is separated from the same and captured by the flowing steam and this during simultaneous indirect cooling leading to condensation of the main part of the process (liquor) steam, that the remaining process (liquor) steam flows on to further condensers, whereby the remaining process (liquor) steam gradually cooling indirectly leading to contaminated water and turpentine first condensing and collecting together and then methanol condensing thereafter, the former collected condensate being freed from the majority of the turpentine content being removed from the plant and the remaining condensate being returned to the combined stripper / stripper / t condensed methanol is removed from the plant, and that mainly purified condensate is collected at the bottom of the combined stripper / condenser and removed from the plant or subjected to further purification. Process according to Claim 1, characterized in that all the vapor from the last effect of the evaporation, i.e. process steam recovered at the power that has the lowest vapor pressure is introduced into the combined stripper / condenser. Method according to claims 1-2, characterized in that the crude condensate is introduced into a space above and adjacent to the combined stripper / condenser and that process (liquor) steam is introduced into a space below and adjacent to the combined stripper / condenser and that the crude condensate flows in the direction from top to bottom through the combined stripper / condenser, while the process (liquor) steam flows in the opposite direction. 10. A method according to claim 3, characterized in that steam from deaeration of one or more evaporation power (s) is introduced into a space above and adjacent to the combined stripper condenser. . . . -. . : | . Process according to Claims 1 to 3, characterized in that the substantially purified condensate is caused to flow down through an underlying extension of the combined stripper / condenser and is heated indirectly by means of steam from deaeration of one or more evaporation effect (s), which steam is introduced. at the lower part of the extension, whereby volatiles remaining in the condensate are separated from the condensate in gaseous form and flow upwards and mix with the upward, newly added process (liquor) vapor and a highly purified condensate is collected at the bottom of the extension and removed from the plant. Method according to claim 5, characterized in that the deaeration bed is supplemented with fresh steam with variable energy content so that the purity of the condensate removed from the plant is regulated in detail. Method according to claims 5-6, characterized in that the remaining part of the indirectly heating venting bed is taken out at the upper part of the underlying extension and inserted into the treatment plant in the space above and in connection with the combined stripper / condenser. The method according to claims 1-7, characterized in that inert gases and any malodorous sulfur-containing gases are removed from the plant by means of a negative pressure-creating device applied at the outlet end of the plant. Method according to claims 1-8, characterized therefrom; that purification takes place in four steps comprising four condensers, where the first purification treatment is performed in a combined stripper / condenser. The method according to claims 1-9, characterized in that the methanol is collected at the bottom of the last condenser in series and that the methanol is transported away from the plant, whereby a part of the transported methanol is re-introduced above and in connection with the penultimate condenser in series. Method according to claims 1-10, characterized in that a cooling medium at least at the first condenser, i.e. the combined stripper / condenser, is inserted at the upper part of the condenser and is removed at elevated temperature at the lower part of the unit or approximately at its middle part. Plant for the purification of crude condensate emanated in the production of semi-chemical or chemical cellulose pulp including at least evaporation of effluent comprising a plurality of series-connected condensers, characterized by, a first unit in the form of a combined stripper and condenser (4,51) having the plurality of inserts ( 50), by which process (liquor) steam and impure 10 15 20 25 30 35 "'40 ïmz45 Wtfso 13. 14. 15. 16. 524 318 lS condensate are caused to flow in the opposite direction and in direct contact with each other, which inserts are surrounded of space for the flow of refrigerant and to the unit on its upper side (3) and underside (7,67) connected space, which later space simultaneously serves as the bottom of the unit, means for supplying unclean condensate to the space at the top of the unit (1 , 2,47), means (6,60) for supplying process (liquor) steam to the space (7,67) at the underside of the unit, means (8, 49) for supplying coolant at one end of the unit and means (9 , 65) for removal of upwelling mt coolant at the opposite end of the unit, means (18,19,68) for removing substantially purified condensate from the bottom of the unit (7,44,67), additional condensers (5,11,13,52,53,54), for disposal of non-condensed process (liquor) steam remaining after the first unit, having the plurality of inserts (50) through which only process (liquor) steam and condensate formed by the steam, streams, which inserts are surrounded by closed space for flow of refrigerant conductive to condensation in series of contaminated water and turpentine in mixture and methanol and to the respective condenser on its upper and lower side connected space (3,10,12,67,71,69); means (8,49,14) for supplying coolant at one end of the condensers and means (9,65,15) for removing heated coolant at the opposite end of the condensers, means (26,21,37,22) for removing above-mentioned mixed condensate from the space (10,71) on the underside of a condenser and, means (20,23) for separating the main part of the turpentine content of the mixed condensate and means (24) for removing turpentine out of the plant and, means (25,27,28 , 29,2) for transporting the remaining condensate back to the space (3) in the first unit where the crude condensate is introduced, means (32,31, 33,70) for removing condensed methanol from the space on the underside of the subsequent condenser ( 13.54) out of the facility. The plant according to claim 12, characterized by; that the inserts consist of tubes (50). Plant according to claim 12, characterized by; that the inserts consist of slats. Plant according to claims 12-14, characterized by; that it also comprises means (36) for supplying deaeration steam from one or more evaporation effect (s) to the space (3) at the first unit where impure condensate is supplied. Plant according to claims 12-14, characterized in that the first unit in the form of a combined stripper / condenser is supplemented with a downward extension (38) having inserts (50) down through which the substantially purified condensate flows, which inserts (50) surrounded by closed space for flow primarily of 10 15 20 25 30 35: 40.>. ,, n; 45 'so 17. 18. 19. 20. 21. 22. 23. 23. 524 318 lb vent steam from one or more evaporation effect (s) in the opposite direction to the substantially purified condensate and that the extension ends with a bottom (44), from which highly purified condensate is removed by means previously indicated (18,19) and means (39,40,41,42,43,36) for supplying said steam and removing steam remaining after the indirect heating. Plant according to Claim 16, characterized in that the inserts consist of tubes (50). The plant according to claims 12-17, characterized in that at the lower part of the last condenser (13) in series a device (17) is arranged for creating negative pressure inside the capacitors' inserts and connecting spaces and for removing mainly inert gases and any malodorous sulfur-containing gases. Plant according to claims 12-18, characterized in that the number of condensers (4,5,11,13,51,52,53,54) is four with the first in the form of a combined stripper and condenser (4,51). Plant according to claims 12-19, characterized in that means (34, 35) for withdrawing a part of the methanol which is removed from the plant and for returning this methanol to the space (12) above the penultimate condenser (11) in series , 53) are included. Plant according to Claim 13, characterized in that means for increasing the contact surface of the condensate vis-à-vis the stripper vapor are arranged inside the tubes (50). Plant according to claim 21, characterized in that the means consists of two joined elongate elements, which in cross section form a cross. Plant according to Claim 22, characterized in that the means is rotated along its longitudinal axis leading to a helical shape.