FI67105B - FRAMEWORK FOR THE EXTRACTION OF COCKTAILS AND FOREIGN TRAFFIC MEASURES - Google Patents

Description

1 · 67105

METHOD FOR PREPARING THE SOIL SOLUTION REQUIRED IN ANTHRAULINIC SULFUR ADDED ANTHRAIN

This invention relates to the preparation of a cooking broth for use in neutral sulfite pulp cooking without the need for a causticizing plant.

The sodium-neutral sulfite soup of the present invention is characterized in that anthraquinone or one of its relatives is used as a delignification accelerator and that the cold pH of the cooking solution before cooking is 7 to 12.5 and that the process can produce paper and board pulps in a yield range of 45 to 90%.

The sulfate process is by far the most important of the chemical pulping processes. However, it is known to have certain burdens, which has led it to actively seek to develop an alternative pulping process. The main disadvantages of the sulphate process are its odor of organic sulfur compounds and hydrogen sulphide, its low mass yield and its expensive chemical recovery system.

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The alkaline sulphite cooking process patented by Ingruber (Finnish Pat. No. 53351, issued April 10, 1973), in which NaOH and Na 2 SO 4 are used as cooking chemicals, has been able to eliminate the odor typical of sulphate cooking, but the wood consumption / tonne of the process is in the same order as is more complex than in the sulphate process. This is because the Na 2 S formed in the recovery boiler must be converted to Na 2 SO 4 and Na 2 CO 3 by causticization to NaOH, while only Na 2 CO 3 is converted to NaOH in the recovery of the sulfate process.

Soda soup-based pulping methods have also failed to displace sulfate soup. The reason for this is that the methods have not been able to show any significant improvement over the sulfate process. First, the process is not odorless, although 2.

Na ^ Sia is not actually used in 67105 soup. This is due to the enrichment of the sulfur accompanying the water and wood in the process cycles, which causes a sufficient level of sulfide to form an odor. In addition, the quality of pulp produced by soda ash-based pulping methods rarely reaches the level of sulphate pulp and the process does not provide any significant benefit in terms of wood consumption.

The expansion of the use of pulps made in the acidic pH range has been hindered mainly by their lower strength than sulphate pulp, in particular tear strength.

The neutral semi-chemical sulphite process (NSSC cooking), in which Na 2 SO 4 and Na 2 CO 2 are typically used as cooking chemicals in a ratio of 3: 1, is mainly used to produce the pulp used in the production of the middle layer of corrugated board.

Hardwood is mainly used as a raw material. The application of the method to the production of bleached chemical softwood pulps has been prevented by a slow and very strong cooking process requiring fiberization and, in the final stage of delignification, also by non-selective lignin dissolution.

Nowadays, however, it has been found (e.g. Paper and Wood 61. (1979): 11, 687-700) that by using anthraquinone as an additive in neutral sulphite soup, 0.1-0.5% of wood, coniferous wood can also be advantageously made into chemically fibrous mass. In such a neutral sulfite anthraquinone soup, abbreviated NS-AQ, the cooking conditions are most preferably

- cooking temperature 165 - 180 ° C

- cooking time at maximum temperature 160 - 260 min - total alkali dose 22 - 24% NaOH - 70-95% of the active alkali dose is 70-95%, most preferably 80-85 and the rest Na 2 CO 4 and in some cases a little NaOH (all equivalents) - pH of the cooking medium to be added to the digester 10,5 to 12,5 (at 25 ° C) - anthraquinone dose 0,1 to 0,2 S of wood 671 05 3 '

The pulp produced under the conditions shown is chemically fibrous from high yields, 55-60 S wood in chunk number 35-45, light 40-53 S ISO, relatively easily bleached, rich in hemicellulose containing both xylan and glucomannan, very easily ground and clearly stronger than traditional sulphite pulps a mass with good light scattering ability. Slightly bleached NS-AQ pulp has been found to be suitable e.g. as a chemical pulp component of newsprint as well as semi-bleached sulphate pulp. In addition, the pulp has been found to be suitable for certain wrapping and kraft papers and in high yield as a raw material for liner board almost as well as sulphate pulp. In terms of fiber technology, the biggest advantage of NS-AQ pulp over sulphate pulp is its very good pulp yield. When bleached, the yield advantage is 4 to 8 units and in the production of liner pulp up to 15 to 20 Si units. In other words, from a paper point of view, NS-AQ pulp can be produced bleached in a yield of 48 to 52? Ί: η and a liner pulp in a yield of 70 to 75 5 ».

Thus, NS-AQ cooking is characterized in that the cooking temperature is the same or slightly higher than in sulphate cooking, most preferably 175 ° C, and that the cooking time at the maximum temperature is slightly longer. Thanks to anthraquinone, the total alkali dose of the active chemicals in NS-AQ cooking has been able to be reduced to almost the level of sulphate cooking (19 to 22 S as NaOH).

Another advantage of NS-AQ cooking over sulphate cooking is its odorlessness, as no Na2S is used in the cooking.

One of the biggest burdens in the sulfate process is expensive investment costs. The recovery of chemicals accounts for 25-30% of this, of which about 20% is spent on caustic plant investments. Despite numerous studies, it has not been possible to • develop a substantially cheaper solution for the recovery of chemicals in the sulphate process. Therefore, one of the basic ideas in the development of the NS-AQ process has been to be able to produce cooking chemicals as far in advance as possible, both in terms of operating costs and investment costs. Already at a fairly early stage of the research, it became apparent that current commercial chemical recovery solutions could not produce a cooking solution with the correct chemical ratio and pH without using NaOH in the preparation. The amount of NaOH required became so large that it was not economically possible to carry out the chemical cycle without a causticizing plant. With the current 67105 t equipment solutions, the amount of NaOH required for the production of cooking chemicals can be minimized to 35-45 kg NaOH / ts 90 So when, before the final pH adjustment of the cooking broth (performed with NaOH), the sum of the bicarbonate and bisulfite content of the broth is at a minimum. The preparation of sodium neutral sulfite cooking broth is typically performed by introducing 502 ^ 8 into a Na2CO3 solution until the desired Na2SO4: Na2CO2 ratio is reached. However, the broth used in NS-AQ cooking cannot be prepared directly from N1a2CO2 and SO2 because the optimal pH and S: Na2 ratio for cooking cannot be achieved simultaneously. ; Therefore, in SO 2 absorption, the pH must be lowered to 6.5 to 7.0 to achieve the correct S: Na 2 ratio (0.7 to 0.95) in the broth and to minimize the amount of NaOH required in the final pH adjustment. In this pH range, part of Na 2 CO 3 is present as NaHCO 3 and part of Na 2 SO 4 is NaHSO 4. Thus, NaOH is used to neutralize NaHCO 3 and NaHSO 4, and the finished cooking liquor contains mainly Na 2 SO 4 and Na 2 CO 3, and possibly some NaOH, if more NaOH is added than NaHCO 3 and NaHSO 4. n would have been needed to neutralize. However, from the point of view of cooking, an excess of NaOH is not necessarily needed.

A key aspect of the present invention is that sodium sulfite-bisulfite-carbonate-bicarbonate in a solution prepared, e.g., from sodium bisulfite-sulfite solution by adding ^ 2 - 8.5, the sodium bicarbonate is substantially converted to sodium carbonate by stripping off the above solution with CCl 2 using steam.

Thereafter, the amount of NaOH required for the final pH adjustment of the cooking solution is so small that it can be performed with a make-up chemical. For example, sulphite plants using the Tampella (Finnish Pat. No. 45576) or Rauma recovery system (Finnish Pat. No. 762710,790114, 791015, 791016, 801959, Finnish Pat. No. 57137) would then be easily converted to use the NS-AQ cooking method for recovery. , because causticization is not required for the preparation of the broth.

5.

67105 Stripping according to the present invention means the removal of carbon dioxide from a sodium sulphite-bisulphite-carbonate-bicarbonate solution by the introduction of steam or some other inert gas. nitrogen or a well-washed flue gas with a low content of CO 2, SO 2 and (R 2) countercurrent to the liquid in a device which achieves effective contact between the vapor or inert gas and the liquid, such a device may have fillers and / or a column with intermediate bottoms, the top of which is supplied with a liquid and the bottom with steam or an inert gas.

The stripping of CO 2 can be performed at normal atmospheric pressure, at a reduced pressure of 0.1 to 1.0 bar abs or at an elevated pressure of 1.0 to 5.5 bar abs. The economically optimal pressure is determined by the compound stripping of the stripping to the rest of the surrounding process and the pressure and temperature of the available stripping medium.

The process according to the invention makes it possible to recover concentrated CO 2 in order to utilize CO 2 in the regeneration process of cooking chemicals in the carbonation of solutions such as green liquor. If the stripped CO 2 re-use. requires elevated pressure, pressurization can already be performed in the stripping process at elevated temperature.

An example of the effect of reducing the amount of NaOH required in the preparation of the NS-AQ broth of the present invention is given below.

Case A Preparation of broth without stripping of bicarbonate Composition of the stock solution - pH 7.5 - S: Na2 0.80 - NaHCO3 0.418 mol / l - Na2SO3 1.201 "- NaHSO3 0.07 -Ne ..... 2.890" titratable 'This is used to prepare a broth (pH 11.5) by adjusting with NaOH, whereby NaOH (1-n) is consumed. 50.5 ml / 100 ml of solution. The composition of the broth solution from the regeneration after pH adjustment is 6.

ph 11.5 671 0 5 - S: Na2 0.75 - Nitratable 2'255 Na / l - Na2CO3 0.284 mol / l - Na2SO3 0.844 "The amount of NaOH required for pH adjustment corresponds to a total alkali dose of 22 kg of cooking (NaOH 63.1 kg / ts 90% or 15% of the total alkali.

Case B Preparation of a broth according to the invention using steam stripping and NaOH control Broth as in situation A.

The solution was stripped with steam to pH 10.05, after which the composition was - pH 10.05 - S: Na 2 0.88 - NaUrable 2-890 ml / Na / 1 - Na 2 CO 3 0.129 mol / l - NaHCO 3 0.034 "- Na 2 SO 3 1.271" the pH of the broth was adjusted to 11.5 with NaOH (1-n),

NaOH was consumed in 3.5 ml / 100 ml of solution. The final composition of the solution was - pH 11.5 - S: Na 2 0.869 - Na. .., 2,826 mol / Na / 1 titratable '- Na 2 CO 3 0.185 mol / l - Na 2 SO 3 1.228 "!

Thus, in the example according to the invention, 1.2% of total alkali is required, which corresponds to a total alkali dose of the cooking of 22% NaOH, 5.05 kg of NaOH / i.e. 90%, i.e. the preparation of NS-AQ cooking soups can be carried out by the method according to the invention. Using NaOH and thus without causticization. The ideal number of bases 6.1 has a consumption of stripping steam (100 ° C, 1 bar abs.) Of 0.08 -0.20 t / ts, which means operating costs of FIM 4-9 / ts when the price of steam is FIM 42 / t. If only NaOH was used to neutralize sodium bicarbonate and bisulfite in the preparation of cooking chemicals, and thus the bicarbonate stripping according to the present invention,

Claims (4)

67105 7. the amount of NaOH produced by causticization would be such that the oil cost of the mesa furnace would be approximately in the same order of magnitude as the steam cost of the stripping according to the invention at an oil price of FIM 800 / t. The essential advantage of the method according to the invention compared to causticization is in the investment costs. A process for preparing a neutral sulphite cooking solution and adjusting the pH of the solution from a sodium sulphite / sodium carbonate solution containing sodium bisulphite and / or sodium bicarbonate, characterized in that the pH of said solution is raised to pH 8 to 11, but preferably 9.5 to 10 carbon dioxide from the solution with steam or some other inert gas. Process according to Claim 1, characterized in that the final pH adjustment of the cooking solution is carried out with sodium hydroxide. t Process according to Claims 1 and 2, characterized in that the amount of NaOH required for pH adjustment is less than 11 kg / ts 90 Z, but preferably less than 8 kg / ts 90 Z. Process according to Claims 1 to 3, characterized in that water is condensed from the stripping gas and the CO2 thus concentrated is used in the regeneration cycle of the cooking core to carbonate the solutions.