NO167229B - REGULATOR DEVICE SPECIAL FOR AIR CONDITIONING INSTALLATIONS AND THE USE OF THE REGULATOR DEVICE. - Google Patents

Abstract

The invention relates to a regulator installation, and to the use of the regulator, in particular for air conditioning installation installations. The regulator device is located to regulate the system of the air conditioning system, preferably a valve, and the device consists of a device for supplying pressure medium to apply the regulating pressure to the pressure medium space. The device consists of a stationary frame member (12) and a mobile frame member (13) which is arranged to move in the direction of the center axis (X) of the device and wherein the mobile frame member (13) consists of at least two intermediate spaces (G, Gg. ..) to which the pressure of the medium can be applied to move the Inner mobile frame part (13) to the desired position. The construction according to the invention is accommodated by interconnecting only module units (lia, 11b ...). Depending on the requirements of the regulating force, the module construction can be formed by and connect the desired number of module units to each other end to end.

Description

Process for digestion of lignocellulosic material, especially wood chips

alkaline boiling of material under heat

and press.

The present invention relates to a method for digestion

of lignocellulosic material, especially wood chips, by alkaline boiling of material under heat and pressure after a pre-treatment with hydrogen sulphide in the presence of water under heat and pressure.

In general digestion by the force method, wood chips or other lignocellulosic materials are processed in a cellulose boiler under regulated conditions for temperature, pressure and time, the treatment is carried out with a liquid which essentially consists of an aqueous solution of sodium hydroxide and sodium sulphide. After the completion of digestion, the cellulose mass is separated from the residual liquor, washed and passed on to other processing steps. From the residual liquor, which is generally referred to as "black liquor", the used chemicals are recovered in a . series of steps that make up the recovery and recirculation sequence in the usual procedure. The residual liquor is therefore oxidized to reduce the loss of volatile sulfur compounds, then concentrated in evaporators and finally burned in a combustion chamber, in which, after combustion of the organic components of the liquor, the inorganic components, especially the sodium salts, remain in the form of a melt. The smelt is dissolved in water to form the so-called "green liquor", which is essentially a solution of sodium carbonate and sodium sulphide. After removal of foreign substances, the green liquor is treated with slaked lime as follows

that the sodium carbonate in solution is transferred to sodium hydroxide and calcium carbonate precipitates. The lye now consists of sodium hydroxide and sodium sulphide, which were essentially the composition of the original lye, and it can now be used again for digestion. To compensate for the chemical loss that occurs at various stages in the process, chemicals are added, generally in the form of sodium sulphate. This chemical is generally added to the black liquor which is injected into a combustion chamber.

The hardwood chips contain on average approximately 30% lignin, 65% cellulose and hemicelluloses and 5% ash, resins and extractable atoffers. The purpose of the chemical digestion methods is to remove lignin and extractable substances from the ligno-cellulose material as these compounds are undesirable in the production of many types of paper and other cellulose-containing products. On the other hand, cellulose and hemicelluloses are the desirable constituents. While the lignin is dissolved by the caustic soda, about a third of the cellulose and hemicelluloses in the lignocellulosic material are destroyed. As a consequence of this, only relatively low mass yields are achieved with normal digestion methods. Hemlock fir ("Western hemlock") such as contains 68% cellulose and hemicelluloses gives a yield of kraft pulp of 44%, based on the wood, when the digestion is carried so far that a completely defibrated bleachable pulp is obtained.

Two methods have previously been proposed for increasing the mass yield by the power method. These are the addition of sodium borohydride or polysulphides to alkaline digestion liquors or treatment of the ligno-cellulosic material with one of these chemical compounds before digestion. In general, the use of one percent borohydride based on the dry weight of the ligno-cellulosic material will give an increase in the mass yield of five to six percent based on the wood compared to the power method. Similarly, an increase in pulp yield of approximately one percent based on the wood will be achieved by using one percent polysulfide sulfur based on the wood. The current price of sodium borohydride makes it impossible to use this chemical compound in the kraft digestion. If borohydride should ever be used in kraft digestion, boron compounds will build up in the recycling system for chemicals in the pulp mill. Boron compounds' possible effects on

u

the functioning of the recycling system is not yet known. One of the most important reasons why polysulphide digestion is not yet used industrially is the fact that polysulphide cannot be recovered in the ordinary power - recovery process. Methods have been proposed for the recovery of polysulphides, but they are relatively complicated and consist of a number of work steps. Considerably more air pollution with volatile sulfur compounds can be expected with polysulphide digestion than with power digestion, unless a closed system is used for capturing these sulfur compounds. A 5 percent increase in pulp yield using 5% polysulfide sulfur based on the dry weight of the wood would require approximately 3 times as much sulfur as is typically present in power digestion. This would result in high sulfur losses only in the combustion chamber if there are no possibilities for effective capture of the volatile sulfur compounds. In addition to this, it has been claimed that corrosion of steel is very serious in lye with low polysulphide concentrations.

The purpose of . the present invention is to provide an alkaline digestion method for the production of cellulose pulp with significantly higher mass yields calculated on the dry weight of the ligno-cellulose material than obtained by ordinary power digestion with the same degree of lignin release. Another purpose of the present invention is to provide a method for recycling unused chemicals by this method.

In accordance with the foregoing, the invention concerns a method for digestion of lignocellulosic material, in particular wood chips, by alkaline boiling of the material under heat and pressure after a pre-treatment with hydrogen sulphide in the presence of water under heat and pressure, and the method is characterized by the pre-treatment with hydrogen sulphide takes place in the presence of an alkaline buffer, which is compatible with the digestion liquids and which is added in a sufficient amount to keep the pH of the pretreatment end used between a neutral and a slightly alkaline value, measured after pressure relief.

In a favorable embodiment of the method, the wood chips are first impregnated with said puff and the impregnated chips are then brought into contact with the hydrogen sulphide under heat and pressure. Other features of the method will appear from the following description. Examples of suitable alkaline buffers include diluted power green liquor, sodium carbonate, limestone and lime. The diluted kraft green liquor gives a pH range of about 1Z to 9, while small amounts of lime give a pH range of about 12 to 7.

The ligno-cellulose material can first be impregnated with the puffer and the impregnated material is then introduced into a pressure reactor where it is brought into contact with hydrogen sulphide, or the ligno-cellulose material, the puffer and the hydrogen sulphide can be introduced separately into the pressure reactor for the hydrogen sulphide treatment. The treatment with hydrogen sulphide must take place at a temperature and pressure sufficient to give a careful distribution of the hydrogen sulphide in the ligno-cellulosic material, and good results are obtained when ordinary wood chips are brought into contact with hydrogen sulphide at a temperature in the range of about 93°C to about 166°C and at a pressure in the range from 5.6 kg/cm to 35.2 kg/cm . Particularly good results were obtained at a temperature of about 127°C and a pressure of about 9.8 kg/cm^.

The buffer is generally present in amounts of 0.3 to 4% sodium carbonate, total alkali in the green liquor, calcium oxide or calcium carbonate based on the dry weight of the wood.

Approximately 5 to 20% hydrogen sulphide, based on the dry weight of the wood chip, is generally used in the pre-treatment of the chip with a consumption of approximately 2% hydrogen sulphide. The unreacted hydrogen sulphide is compressed and used again for the pre-treatment of the wood chips. The unused puffer is also reused and can be fed to the power recovery system when the puffer effect ceases. Kraft green liquor or lime from the kraft recausting system can conveniently serve as a source of fresh puffer solution.

It has been shown that approximately 2% less alkali is required to digest wood chips prepared according to the present invention than with ordinary power digestion without pretreatment to achieve a comparable degree of lignin release.

According to a preferred embodiment of the present invention, wood chips are supplied to a pressure reactor and treated with 6.5 - 10% hydrogen sulphide based on the dry weight of the chips in the presence of about 0.1 - 0.2 kg of kraft green liquor or about 0.01 kg of calcium oxide per kg dry wood chips. The temperature in the reactor is raised to around 127°C and as a result the pressure increases to around 9.8 kg/cm . At the completion of the reaction, the pressure is released and the unreacted hydrogen sulphide gas is collected in a gas accumulator, compressed and reused together with fresh hydrogen sulphide for the treatment of chips in the pressure reactor. After the release of the pressure, the part of the puffer solution that has not been absorbed by the tile is separated from the tile, and after the addition of fresh green liquor or lime, it is returned to the pressure reactor. Approximately 0.9 kg of diluted green lye is absorbed per kg dry wood.

The pre-treated wood chips are taken to a cellulose digester and digested under the conditions that are generally used in conventional power digestion. This shows a saving of around 2% of the required kraft-lye compared to the usual kraft method without pretreatment.

in

As an alternative to the pre-treatment described above, the wood chips are impregnated with diluted green liquor or lime in an impregnation vessel. After the impregnation, the free green liquor is separated from the tile and fed back

to the impregnation device. A certain amount of fresh green liquor or lime is added to the recycled solution as a substitute. The impregnated tile is filled in a pressure reactor where it is made to react with hydrogen sulphide gas under conditions similar to those used in the simultaneous treatment with diluted green liquor and hydrogen sulphide. After the pressure treatment, the unused hydrogen sulphide gas is separated from the tile by releasing the pressure, collection in a gas accumulator and compression and is then used again. The treated chip is fed to a cellulose digester and digested by the usual kraft method under normal conditions.

Both the pre-treatment of the tile and the digestion can be carried out as a one-batch process or a continuous process. The kraft digestion step and the recovery method for the usual kraft digestion chemicals are not affected by the pretreatment of the lignocellulosic material with hydrogen sulphide and kraft green liquor. As already mentioned above, approximately 2% less alkali is required, based on the dry weight of the wood, when digesting pre-treated wood chips compared to digestion by the conventional kraft method to achieve the same degree of lignin release. It is of course of significant importance that the unconverted hydrogen sulphide is captured after the pre-treatment of the wood chips in order to achieve economic benefits due to increased mass yield and to reduce air pollution.

The following examples from production in a pilot plant are given to illustrate the method according to the present invention.

Example 1

A 50/50 mixture of Hemlock-fir and Douglas-fir chips with an average water content of 48.7% was placed in a rotatable pressure reactor together with 0.20 kg of kraft green liquor and 4.3 kg of water per kg dry-treated wood. The sodium compounds such as carbonate, hydroxide and sulphide in the green liquor corresponded to 2.0% total alkali based on the wood. A quantity of 0.083 kg of compressed hydrogen sulphide gas per kg of dry-treated wood was then added to the reactor and the temperature was raised to 125°C during 83 minutes by indirect heating. The reaction mixture was held at this temperature level for 79 minutes before the temperature was gradually reduced to 110°C over 41 minutes. The reactor is continuously rotated during the reaction. As a result of the temperature changes, the hydrogen Bulfide pressure increased from 8.86 kg/cm 2 at room temperature to 10.12 kg/cm 2 at 126.7°C after a total reaction time of 205 minutes. At this point the gas was released and the contents of the reaction mixture were cooled to a temperature lower than the boiling point of water. The free puffer solution was then separated from the tile and kraft white liquor containing 16.5% active alkali based on the wood was added to the tile. The kraft digestion was carried out under the following conditions: lye/wood ratio 4.5:1, indirect heating to a temperature of 170°C during 104 minutes and a reaction time of 120 minutes at this temperature. The cellulose pulp was washed, and the permanganate number, which is a measure of the lignin content of the pulp, and the pulp yield were determined. The following results were found: ~

A normal kraft digestion carried out with the same black chip under the same conditions used for the pre-treated chip except that 18.2% active alkali, based on the dry weight of the wood, was used, this gave a pulp yield on. 43.4% and a scrap amount of 0.8% from the sieves, based on the wood at a permanganate number of 22.9. A Valley mill determination gave the following results of pulp from pretreated chips and untreated chips:

The results indicate that the two types of pulp do not differ significantly from each other in terms of quality when the same power consumption is used for grinding.

Bleaching of the two-stage pulp and kraft pulp described above-,- by r a six-stage bleaching treatment (C-E-H-D-E-D) showed that the advantageous pulp yield obtained by this new digestion method is maintained during the bleaching treatment. The bleached pulp yield of the two-stage pulp was 6% higher (46 compared to 40%) based on dry wood compared to that obtained with regular kraft pulp.

Example 2

Chips of Hemlock-fir and Douglas-fir as described in example 1 were treated in a pressure reactor with 0.071 kg of hydrogen sulphide, 0.20 kg of kraft - green liquor and 4.1 kg of water per kg dry wood. The temperature was raised to 125°C by indirect heating over 93 minutes and held at this level for 95 minutes and then gradually reduced to 118.3°C over 25 minutes. The pressure varied from 9.84 kg/cm 2 initial pressure at room temperature to 9.52 kg/cm 2 at 126.7°C in the highest temperature range to 7.59 kg/cm 2 at the end temperature of 118.3°C. At the end of the reaction period of 213 minutes, the pressure was released. The free buffer solution was then removed from the chipboard, and then kraft white liquor containing 16.5% active alkali, based on the wood, was added to the pretreated chipboard. The kraft digestion was carried out under the same conditions as described in example 1. The washed pulp that was produced had:

A conventional power digestion carried out with the same type of chip under the same conditions used for the pre-treated chip, except that 17.5% active alkali, based on the dry weight of the wood, was used, gave a mass yield of 43.3% and a scrap amount from sieves of 0.8%, based on the wood at a permanganate number of 23.5. A Valley mill determination gave the following results of the pulp from pretreated chips and untreated chips:

These results show that there is no significant difference in quality

between the two cellulose masses at a given power consumption during grinding.

Bleaching of the two-stage pulp and the general kraft pulp described in this example, with a six-stage bleaching process showed that this new digestion method gave a 5.3% higher yield of bleached pulp (44.9 compared to 39, 6%, based on the wood) than the normal NOK aft method.

Example 3

Chips of Douglas-fir with a water content of 45.2% were placed in a rotatable pressure reactor together with 0.02 kg of sodium carbonate and 4.2 kg of water per kg dry-treated wood. A quantity of 0.070 kg of compressed hydrogen sulphide gas per kg of dry wood chips were then added to the reactor and the temperature was raised to 125°C during 80 minutes by indirect heating. The reaction mixture was held at this temperature level for 90 minutes before the temperature was gradually lowered to 93.3°C over 30 minutes. The pressure reactor was rotated continuously during the first 80 minutes and only once every 10 minutes during of the remaining 120 minutes. As a result of the temperature changes, the pressure changed from an initial pressure of 9.98 kg/cm 2 at room temperature to 10.74 kg/cm 2 at the highest temperature of 128.3°C to 6.75 kg/cm 2 at the final the temperature of 93.3°C. At the end of the 200 minute reaction period, the pressure was released and the free buffer solution was removed from the chip. Kraft white liquor, containing 15.5% active alkali based on the wood, was added to the tile. Crude digestion was carried out under the same conditions as described in Example 1, except that the ratio between lye and wood was 4.2:1. A washed cellulose mass was obtained with:

A general kr aft-up conclusion which was carried out with the same type of tile under the same conditions used for the pre-treated tile, except that the ratio between lye and wood was 4.5 : 1 and that 17.8% active alkali, based on the dry weight of the trevkrket, was used, gave a mass-v yield of 43.9 and a. scrap amount from the sieves of 1.7%, based on the wood, at a permanganate number of 23.8. A Valley mill determination gave the following results of the pulps made from pre-treated wood chips and untreated wood chips:

The results show that the quality of the two pulp types is not significantly different when the same power consumption is used for grinding.

Example 4

Chips of Douglas fir as described in example 3 were treated in

a pressure reactor with 0.070 kg hydrogen sulphide, 0.005 kg calcium oxide and 4.2 kg water per kg dry-treated wood. The temperature was raised to 125°C over 82 minutes by indirect heating and held at this level for 80 minutes and then gradually reduced to 93.3°C over 40 minutes. The pressure reactor was rotated continuously for the first 82 minutes and only once every 10 minutes during the remainder of the 202 minute reaction period. The initial pressure of 10.19 kg/cm 2 at room temperature increased to 10.4 kg/cm <2>at the highest temperature of 129.4°C and decreased to 7.38 kg/cm 2 at the final temperature of 104, 4°C. After the pressure was released, the free buffer solution was removed and 15.5% active alkali based on the wood was added to the pretreated chip. Crude extraction was carried out under the same conditions as described in example 3. A washed cellulose mass was obtained with:

As mentioned in Example 3, a general force digestion performed with the same chip gave a mass yield of 43.9% and a scrap amount from the sieves of 1.7% based on the wood, at a permanganate number of 23.8. A Valley mill determination gave the following results of pulps from pretreated chips and untreated chips:

The results show that the quality of the two types of pulp is not significantly different when the same power consumption is used for grinding.

Example 5

The mixture of Hemlock-fir and Douglas-fir chips as described

in example 1, was treated in a pressure reactor with 0.067 kg of hydrogen sulphide, 0.089 kg of calcium carbonate and 4.5 kg of water per kg dry-treated wood. The temperature was raised to 125°C by indirect heating in running

one of 87 minutes and held at this level for 80 minutes and then gradually reduced to 111.1°C over 40 minutes. The pressure varied from an initial pressure of 10.19 kg/cm at room temperature to 8.44 kg/cm at 125°C

in the highest temperature range to 6.89 kg/cm at the end temperature of

118.3°C. After the reaction period of 207 minutes, the pressure was released and the free buffer solution was removed from the chip. Next, NOK aft white liquor containing 16.5% active alkali, based on the wood, was added to the pre-treated tile. The Kraft digestion was carried out under the same conditions as described in example 1. A washed cellulose mass was obtained with:

As indicated in Example 2, a general force mas-

see with a pulp yield of 43.3% and with a scrap amount from the sieves of 0.8%, based on the wood, at a permanganate number of 23.5. A Valley mill determination gave the following results of the pulp from pretreated chips and untreated chips.

These results show that there is no significant difference in quality between the two masses at a given power consumption during grinding.

Example 6

Chips of aspen from the Whitecourt area of Northwestern Alberta with an average moisture content of 55% were placed in a stationary pressure reactor with forced lye circulation, together with an aqueous solution containing 16.8% sodium hydroxide, calculated as sodium oxide, and based on dry wood, The temperature of the liquor was raised to 170°C in 105 minutes by circulation through a heat exchanger and was maintained at this temperature for 150 minutes. The contents of the digester were then blown under pressure in one blow tank. The following results were obtained with this conventional soda solution;

Lignin-inducing bleaching of aspen soda ash pulp with an excess of sodium chlorite and acetic acid gave the following results: , A standard grinding degree determination of this pulp using a Valley grinding apparatus gave the following results:

Example 7

The aspen chips described in example 6 were treated in the pressure reactor used in this example with 6.9% hydrogen sulphide and an aqueous solution containing 1.4% sodium carbonate, calculated as sodium oxide, and based on dry wood. The temperature of the lye was raised to 130°C within 33 minutes and this temperature was maintained for 39 minutes. The maximum pressure of 10.1 kg/cm was reached at the maximum temperature. The initial pH of the sodium carbonate solution was 11 and it decreased to 8.3 at the end of the pretreatment. The unconsumed hydrogen sulphide was removed by pressure release and the spent lye was separated from the pre-treated chips by draining. The soda white liquor containing 15.7% sodium hydroxide, calculated as sodium oxide and based on dry wood, was then added to the pre-treated chips. The temperature of the liquor was raised to 170°C in 67 minutes and was held at this temperature for 120 minutes. These times are significantly shorter than those mentioned in example 6 for soda ash without pretreatment. As a result, the pretreatment step and the soda digestion step combined required practically the same time as soda boiling without pretreatment (259 vs. 255 minutes). The following results were obtained with the pretreatment soda ash:

A comparison of these figures with those given in example 6 clearly shows that at the same degree of digestion a 5% greater yield of sifted pulp based on dry wood (55 versus 50%) was achieved with pre-treated aspen chips. In addition to that, the amount of scrap from the sieves decreased from 0.5 to 0.2% calculated on dry wood.

'' A lignin-releasing bleaching of the pretreated aspen-soda digestate with an excess of sodium chlorite and acetic acid gave the following results:

A comparison of these figures with the figures given in example 6 shows that the increase in pulp yield obtained in the pre-treatment was maintained after a complete release of lignin, and due to the stabilization of wood carbohydrates, the comparison also shows that the bleached pre-treated soda pulp had a gloss which was one point higher than a comparable conventional soda ash digester.

A standard grinding degree determination of this pulp using a Valley grinding apparatus gave the following results:

These figures show that the quality of the pretreated soda pulp is slightly better than the quality of the comparable conventional soda pulp described in Example 6. The pretreated soda pulp is easier to grind, which provides power savings in papermaking, and it has a higher mill strength. at 300 ml Canadian standard grinding grade.

Example 8

Alkali sulphite digestion without pretreatment.

A 60/40 mixture of Western Hemlock spruce and Douglas fir chips with a moisture content of approx. 50% was placed in a stationary pressure reactor together with an aqueous solution containing 30% sodium sulphite and 18% sodium hydroxide, calculated on dry wood. The temperature was raised from approx. 21°C to 180°C in 105 minutes by circulating the liquid through a heat exchanger. The temperature was maintained at 180°C for 105 minutes, and the reaction mixture was then blown in a blow tank. The pulp was washed and sieved, and the pulp yield and permanganate number were determined. The following results were obtained:

A determination of the degree of painting in a standard Valley meter gave the following results after 35 minutes of painting:

Example 9

Alkali sulphite digestion with pretreatment.

A mixture of chips of the same kind as used in Example 8 was treated in the same pressure reactor with 7.2% hydrogen sulphide gas and 1.4%

sodium carbonate on wood calculated as sodium oxide. The reaction mixture was heated to 132°C during 30 minutes and the pressure increased to 9.5 kg/

cm. The temperature was maintained at 130°C for 36 minutes. The unconsumed hydrogen sulphide gas was then removed by pressure release and the free lye was separated by decantation. Then an aqueous solution containing 29.0% sodium sulphite and 17.2% sodium hydroxide was added to the pretreated chip and the same temperature cycle as described in example 8 was used. The reaction mixture was then blown. The pulp was washed and sieved and the permanganate number and mass yield were determined. The following results were obtained:

A comparison of these figures with the results given in example 8 shows that the pre-treatment of chips with hydrogen sulphide in the presence of a small amount of sodium carbonate resulted in an increase in the mas se yield of sieved pulp of approx. 6%, calculated on dry wood, and in a reduction of the amount of scrap from the sieves from 1.5 to 0.8% calculated on dry wood. Also, a smaller amount of sodium sulfite and sodium hydroxide was required with pretreated chips to give a pulp with a Tappi permanganate number of 22 to 23.

The determination of the grinding degree of pretreated alkali sulphite pulp on

a standard Valley grinder produced the following results after 35 minutes of grinding:

These figures show that the quality of pre-treated alkali sulphite mass was very similar to the quality of the alkali sulphite mass described in example 8.

Claims (7)

1. Method for digestion of lignocellulosic material, especially wood chips, by alkaline boiling of the material under heat and pressure after pre-treatment with hydrogen sulphide in the presence of water under heat and pressure, characterized in that the pre-treatment with hydrogen sulphide takes place in the presence of an alkaline buffer, which is too similar to the digestion liquids and which is added in a sufficient amount to keep the pH value of the pre-treatment used between a neutral and a slightly alkaline value, measured after pressure relief. 2. Method as stated in claim 1, characterized in that the wood chips are first impregnated with said puff and that the impregnated chips are then brought into contact with the hydrogen sulphide under heat and pressure. 3. Method as stated in claim 2, characterized in that the wood chips are simultaneously brought into contact with said buffer and hydrogen sulphide. 4. Method as stated in claim I -3., characterized in that the buffer is selected from sodium carbonate, calcium oxide, calcium carbonate and kraft green liquor. 5. Method as stated in claim 4, characterized in that the puffer is present in amounts of 0.3 - 4 percent by weight, based on the dry weight of the wood. 6. Method as stated in claims 1 - 5, characterized in that the pre-treatment with hydrogen sulphide is carried out at a temperature in the range between approx. 95°C and 167°C. 7. Method as stated in claims 1(-6), characterized in that the used buffer solution is separated from the tile after the pre-treatment, part of the used solution is transferred to a system for recycling the power chemicals and the rest is brought back to its original concentration and volume by adding fresh puff and then used again.