DE2151465A1 - Method and apparatus for the production of polysulphide - Google Patents

Description

OR-WfLLRATH DR WEBER

215U65

Docket 5221

Οϊρί.-PHYS. SEIFFERT 'II / Wh

Patent attorneys 62 WIESBADEN Gustov-Freytog-Sft-οββ 25 Pot compartment 13 »Tel. 372720

The Mead Corporation, Talbott Tower, Dayton, Ohio 45 402, USA

Method and apparatus for the production of polysulphide

Priority: U.S. Serial No, 87 504 dated Nov. 6, 1970

The invention relates to a system for the production of sodium polysulphide for use in treating lignocellulosic materials and especially a new redox system for the simultaneous recovery of sodium polysulphide and sodium hydroxide with a minimal amount of thiosulfate by-product Sodium sulfide or sodium hydrogen sulfide.

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A large number of fundamentally different methods are known in which sodium polysulfide is obtained, either as Main product or as a smaller by-product quantity. These methods are, for example, electrochemical methods and redox methods and catalytic processes.

U.S. Patent 3,249,522 describes the use of hydrogen sulfide gas as a fuel in an electrochemical Fuel element, the products being sulfur, sulphides, polysulphides and the electricity generated. The fuel element itself includes an anode and a cathode separated therefrom by an ion exchange membrane, the anode being made with Platinum-catalyzed carbon and the cathode is made of nickel-catalyzed carbon. Hydrogen sulfide is in the anode compartment and oxygen is introduced into the cathode compartment, the electrolyte being alkaline. The method includes one Oxidation of the hydrogen sulfide at the anode and a reduction of oxygen at the cathode.

U.S. Patent 3,409,520 describes an electrochemical system for removing hydrogen sulfide gas from a Natural gas mixture, the system being of an electrolytic nature. The electrolytic cell contains an anode that is separated from the cathode is spaced and separated by a diffusion barrier. With an acid electrolyte, that is anodic oxidation product Sulfur, while hydrogen gas is formed at the cathode. When the electrolyte is basic, the anodic oxidation product is polysulfide, while hydrogen gas is formed at the cathode will. This system requires the application of electricity from an outside source.

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The catalytic oxidation of hydrogen sulfide in an alkaline solution with the formation of sulfur is in the United States patent 3 471 254. The catalyst is a phthalocyanine complex that is soluble in aqueous sulphide and in sulphide-free is insoluble in aqueous solutions, the catalyst being recovered as a clot and recycled.

U.S. Patent 2,135,879 describes the air oxidation of calcium hydrogen sulfide, i.e. the reaction product of lime or calcium hydroxide and hydrogen sulfide, using a nickel sulfide catalyst, with polysulfide, thiosulfate and sulfate being formed in a ratio of 74: 73: 17. Around To increase the amount of polysulfide, 0.1 to 1.0% hydrogen sulfide gas is mixed with the air oxidizer to to get an excess of hydrogen sulfide in the oxidation state.

In the processing of pulp, it is known that the use of sodium polysulphide (hereinafter referred to as polysulphide) increases the yield in the cooking liquor (see US Pat. No. 3,216,887 and the patents and publications discussed therein) . Different processes for the formation of polysulfide are discussed there, such as the dissolution of sulfur in aqueous sodium hydroxide or a sulfide solution. The production of polysulphide by air oxidation of neutral sodium hydrogen sulphide is also discussed. In the USA patent it is also established that white liquor is strongly alkaline and that its sulfide is not easily oxidized by air will. In addition, the oxidation of white liquor does not produce any sodium

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polysulfld, but sodium thiosulphate. The US patent suggests mixing white liquor and black liquor and oxidizing the sulfide to form polysulfide and thiosulfate. However, the values shown make it clear that the amount of polysulfide formed, measured in grams of Na ₃ S ₂ 3 ^e liters, is less than the amount of thiosulfate, expressed as grams of NapS20o per liter.

Canadian Patent 814,882 and the references cited therein also describe the benefits of polysulfide treatment of pulp and specifically an adsorption process for the production of polysulphide pulp treatment liquor by Hydrogen sulfide gas is adsorbed on activated carbon in the presence of air or oxygen, with the hydrogen sulfide is oxidized to elemental sulfur, which is deposited on the coal. If the coal once with sulfur When saturated, the sulfur is leached out by an alkaline solution. Saturation gives the best results the hydrogen sulfide with water vapor before contact with the coal and by removing the sulfur formed alkaline leaching to neutralize some alkaline residue for the sulfuric acid formed during the reaction to leave behind.

U.S. Patent 3,470,061 describes the formation of polysulfide using insoluble manganese oxide compounds that act as oxidizing agents and after use Heating in air can be regenerated by the manganese oxidizer is raised to the next higher oxidation level.

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This latter patent also discusses the disadvantages of the methods described in U.S. Patent 3,216,887 as well the processes described in U.S. Patents 3,210,235 and 2,944,928,

On the catalysis field, it is known that certain finely divided materials increase the reaction rate. For example, finely divided nickel and cobalt have been used as catalysts in the hydrogenation of vegetable oils. Improved results are obtained when using thin foils or plates, remain äispergiert as a fine powder which is easier (see US patent ore i £ t 1 0P3 31 * 0) _o

The United States patent specification 1 14S 363 describes the use of vc: i coal in granulated form as a catalytic or cleaning agent, the coal being in a column or a scolator in which the liquid is passed through a Sdkrlaht granulated coal .

The USA patent 2 365 723 describes the Os ^ idabion of an acidic solution of iron (II) sulfate to Eissn-IxI-söIfat _P indeiu granulated, activated carbon, cli © absorbed oxygen oclsr air contains _{r used} as a catalyst *: £ reU Di © Eoßl © will! The liquid is suspended and the oxidizing agent is bubbled through the suspension, or the oxidizing agent is dispersed throughout the liquid with the aid of a carbon diffuser, or the liquid and oxidizing agent are "flowed" in cocurrent through a packed column packed tower

£ ■■■■■ ' δ * & y ί

The benefits of polysulfide treatment of lignocellulosic material are known in the art. Currently there is at least one pulp mill using a polysulfide treatment Pulp, with sulfur being converted to sodium sulfide with the formation of polysulfide is added. The sulfur added from the outside is lost in the chemical extraction process. With the one Mill reported to improve on polysulfide treatment of pulp, the addition of 2.2% elemental sulfur increases the yield by 3 to 4%, based on the dry wood chips.

The present invention now provides a simple and efficient polysulfide generating system in response to a need the pulp treatment industry by using a polysulphide formation and recovery system obtained in connection with currently used kraft pulp treatment and recovery processes and systems can be used.

According to the present invention, sodium polysulfide and sodium hydroxide are produced by a reduction-oxidation process, in the case of sodium sulfide or sodium hydrogen sulfide in an aqueous solution in the presence of a solid electronic conductive material to be oxidized, The oxidizing agent is

Oxygen, air or a mixture of oxygen with other gases, while the reducing agent is the sulfide or hydrogen sulfide is in an aqueous solution. The electronically conductive material that is chemically opposed to the oxidizing agent as well is relatively inert to the reducing agent, has the function of removing electrons from the reducing agent

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molecules or ions to form oxidizing agent molecules in contact or to conduct ions and thus to accomplish the electron transfer of the reaction. In contrast to well-known

-en
Electrochemical system, such as electrolysis or fuel elements, in which the anode and cathode are separated from one another by partitions or membranes and in which the oxidation takes place on one electrode and the reduction takes place on another electrode, the system according to the present invention includes adjacent oxidation and Reduction reactions on the electronically conductive material and does not require the use of membranes or partitions.

The reactions which involve oxidation of sulfide are known to tend to be predominantly thiosulfate instead of forming polysulphide, especially if the reducing agent is strongly alkaline. In contrast, the new ones produce Redox systems according to the invention mainly polysulphide, the formation of thiosulphate being minimal. This is done according to the Invention by having the oxidizing agent and the reducing agent simultaneously in contact with the electronically conductive Material and brings into contact with each other, but the contact of the oxidizing agent with the reducing agent to a minimum with the exception of the point where both are in contact with the electronically conductive material. In such systems According to the invention, the oxidizing agent and the reducing agent form an interface, the electronically conductive Material is at the interface and at the same time in contact with both the reducing agent and the oxidizing agent is held.

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An important aspect of the present invention is that it is prevented that the electronically conductive solid material is only in contact with the liquid reactant, i.e. the reducing agent. In the same way, the electronically conductive solid material must not be exclusively in Be in contact with the gaseous reaction partner, i.e. the oxidizing agent. If help in describing the invention the term "flooded" is used, then that term means that the electronically conductive material is exclusively in contact with either the clsm oxidizing agent or with the reducing agent stands. When the electronically conductive material of the present invention is flooded, the preferred listen Polysulphide-yielding reaction for all practical purposes.

It may be useful now to consider the invention in more detail in terms of catalysis and electrochemistry. For example, if the electronically conductive material according to the present invention is viewed as an electrode, whether-

Probably none. . / wires connected to it to make electrical To add or remove power, both oxidation and reduction take place on the same "electrode"; a part acts as both an anode and a cathode, and both the oxidation product and the reduction product are turned on formed the same "electrode" part. Although such a part may be referred to as a "mixed potential electrode", 1st the kinetics of the system according to the present invention are not sufficiently defined or understood to be complete

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To give an explanation of the reaction mechanism. In view of the solid nature of the conductive material, elements appear to be more heterogeneous Catalysis is present because the effect of the present system is to increase the rates of polysulfide forming Responses are significantly increased compared to those that are possible in the absence of the solid electronically conductive material are. However, labeling with an expression, such as heterogeneous catalysis, does not provide a complete explanation either and does not fully understand the mechanism of the reaction.

Regardless of whether the explanation of the reaction mechanism is based on catalysis, electrochemistry or a combination of both the results obtained give the following general rules applicable to the present invention:

a) The oxidizing agent and reducing agent should be able to form an interface,

b) a flood of the electronically conductive material should be avoided,

c) Oxidizing agents and reducing agents should be in contact with each other and stand with the electronically conductive material and

d) a mixing of the oxidizing agent and reducing agent outside the place or the range of the electronic Conductive material should be avoided.

The methods and system of the present invention encompass a fundamentally new concept and fundamental new way of working in the production of chemical materials

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through a reduction-oxidation reaction from reactants one which contain chemical elements of the desired product, but in a valency which is different from that in the desired product Product is different. This new process involves the controlled contact of a flowable oxidant and a flowable reducing agent, the contact mainly at the interface in the area of an electronically conductive solid material, the latter limited contact being an essential element of the System is. This controlled contact is in contrast to a mixing of the reactants, such as gas bubbles in a liquid, for example with a diffuser, and the reaction takes place at the point of contact between the oxidizing agent, the reducing agent and the electronically conductive solid material. For the sake of simplicity the following term was chosen to identify the process and its essential elements.

"Contacogen" means the electronically conductive solid material that forms the place of the interface contact for the reducing agent and oxidizing agent and that at the same time with them in Contact should be made to give the desired response.

Of particular interest is the fact that the present system has unique advantages in the manufacture of polysulfide for use in the treatment of lignocellulosic material «. This unique advantage is due to the fact that Polysulfide can be produced easily and continuously at ambient conditions, although higher pressures and higher

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Temperatures below the decomposition temperature of the reactants or products can be used, and polysulfide is formed simultaneously with sodium hydroxide without the need to regenerate the oxidizer.

Accordingly, it is a primary object of the present invention to. a System for the production of polysulphide with minimal formation of thiosulphate to get what a complete represents a new concept and a new way of working for redox processes.

Another object of the invention is to produce polysulfides on a batch basis or on a continuous basis through a reaction in which the oxidizing agent is a gas and the reducing agent

so-

tion agent is an aqueous solution and the / probably the oxidizing agent as well as the reducing agent in interfacial contact with each other and at the same time in contact with an electronic one conductive solid material.

Another object of the present invention is to provide a relatively simple apparatus for the production of polysulfide by to obtain an implementation in which an electronically conductive material, i.e. the Contacogen, in a non-flooded Condition, but is kept in contact with both the oxidizing agent and the reducing agent, the latter with one another are essentially only in contact with the Contacogen in the area or at the place of their contact.

Another object of the invention is a system for forming polysulfide for treating pulp of lignocellulosic materials,

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wherein both polysulphide and sodium hydroxide are formed the.

Another one. The aim of the invention is to provide a system and an apparatus for the production of polysulphide and sodium hydroxide by a reaction in which these reaction products are formed on the same part and in which the membranes and partitions used in electrochemical processes are avoided will.

In the drawing means

Fig. 1 is a schematic representation of a generator according to the present invention,

FIG. 2 is a schematic representation of a generator according to FIG

two
Invention in which / separate zones for the production of the

Product are provided,

3 shows a simplified representation of a generator according to the invention, in which moisture-resistant, finely divided ¹ Contacogen material floats on the surface of the reducing agent,

Fig. 4 is a schematic illustration of a continuously operating Generator according to the invention, in which the Contacogen at the interface between the oxidizing agent and the reducing agent is held,

5 is a schematic representation of another form of continuously operating generator according to the invention; in which a variety of soils are used and in which the contacogen on the surface of the reducing agent swims,

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Fig. 6 is a cross section taken along line 6-6 in Fig. 5;

7 shows a schematic representation of a closed tower generator according to the invention with parts broken away to show the internal components,

8 shows an enlarged partial section along the line 8-8 in FIG. 7;

9 shows an enlarged partial section along the line 9-9 in FIGS. 7 and

10 shows a schematic representation of the use of the generator according to the invention in a pulp eye extraction system.

The reduction-oxidation system according to the present invention includes, in the case of sodium sulfide, the following reactions: an oxidation:
S ⁼ } S ° + 2e (1)

Reduction:

2H ₂ O + O ₂ + 4e 3> 40H ~ (2)

Together:

2Na ₂ S + 2H ₂ O + O ₂ -> 2S + 4 NaOH (3)

The elementary sulfur then combines with the sodium

S fid with formation of Na ₀ S, the latter being polysulfide, In which the value of χ is above 1 and can be as high as 4.5. However, these materials can also react in the following ways:

2Na ₂ S ₂ + 3O ₂ > 2Na ₂ S ₂ O ₃ (4)

2Na ₂ S + 2O ₂ + H ₂ O> Na ₃ S ₃ O ₃ + 2NaOK (5)

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In the case of polysulfide for use in treating lignocellulosic material, it is desirable to reduce the amount of thiosulfate to a minimum and, if possible, to prevent its formation altogether. Thiosulfate is not an effective pulp treatment chemical in alkaline pulp treatment and therefore represents an undesirable burden on the extraction system.

In the case of sodium hydrogen sulfide, which is formed by the absorption of hydrogen sulfide gas in an alkaline solution can, for example, the following reactions take place:

H ₂ S + NaOH ^ NaHS + H ₂ O (6)

NaHS + O ₂ -> 2S + 2NaOH (7)

The three essential components of the system according to the present Invention are an oxidizing agent, a reducing agent and a contaogen, the oxidizing agent can be any gas, that contains elemental oxygen, such as air, pure oxygen or mixtures of oxygen and small amounts of chlorine and the like, although the amount of gases such as ozone should be limited if they attack the electronically conductive solid material or dismantle. The reducing agent is an aqueous solution of sodium sulfide or hydrogen sulfide and is also an ionic one conductive phase, although it is believed that the conductivity of this phase is not so essential in the invention Factor as in electrochemical fuel elements or elec trolysis systems is. The oxidizing agent and the reducing agent are also characterized by the formation of an interface, when the two are brought into contact with each other.

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The electronically conductive material, i.e. the Contacogen after of the invention, is a solid that is substantially inert to the oxidizing agent, the reducing agent and the Products in the sense that it does not react chemically with them or is not attacked by them. One material with one high surface area to weight ratio is preferred as it gives greater interfacial contact. The resistance of the Material should be such that it allows transfer of the electrons involved in the reaction. materials resistance less than about 10 ohms / cm can be used, but are preferred materials a resistance of 10 ohms / cm or less.

In order to initiate and control the reaction according to the present invention, the reducing agent and the oxidizing agent are used brought into contact with each other and with the contacogen and held in such a relationship that the oxidizing agent and the reducing agent is in contact with each other only in substantially the same area where they are simultaneously also be in contact with the Contacogen. An essential aspect of the present invention is that the Contacogen is prevented from being overrun by either the reducing agent or the oxidizing agent. If that Contacogen is flooded by the liquid reducing agent, the liquid film reduces the diffusion rate of the Oxidizing agent to the surface of the contacogen is essential. On the other hand, when the contacogen is flooded with the oxidizer the reducing agent is prevented from affecting the upper

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to achieve surface of the Contacogen in the manner desired according to the invention. When with a non-flooded condition

how
is worked / was described above, it is observed that the formation of thiosulfate reduced to a minimum, if not even completely eliminated. This is particularly important with regard to prior publications that strongly alkaline sulfide solutions are not easily oxidized by air, the oxidation forming thiosulfate rather than polysulfide. The system of the present invention is thus a controlled oxidation in which sulfide is oxidized preferentially to sulfur rather than thiosulfate so that a reaction product is obtained which consists mainly of polysulfide as far as sulfide conversion is concerned.

Since the reaction zone includes a gas, a liquid and the contacogen, the contacogen must be in contact with the gas and to be wetted by the liquid, but without being flooded by either of the two, flooded here means that the contact angle between the contacogen and the liquid is small, i.e. less than about 90 ° and approximately zero. If the contact angle is high, such as greater than 90 ° and approximately 180 °, then the liquid tends to pulling away from the surface of the contacogen, and the The surface of the contacogen is essentially only in contact with the gas, i.e. it is flooded with the gas. On the other hand, if the surface of the contacogen is slightly wetted by the liquid, i.e. with a contact angle of approximately 0 between the contacogen surface and the liquid

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speed, the liquid tends to hit the surface of the contacogen to cover completely, so that the surface is then essentially only in contact with the liquid, i.e. of the liquid is flooded. One method of preventing the fluid from flooding is by treating the Contaaogens, which is known as "wetting". This method adds a smaller portion of a to the Contacogen inert substance that is not wetted or moistened by the liquid reactant, so that the contact angle between this inert additive and the liquid is greater than about 90 °.

In the case where porous materials are used as Contaoogen, this is _f understood so that the oxidant gas can not be forced through the pores of the Contaoogerts in the sense

kl should that a porous part as a diffuser forming / a Oxidant gas bubbles are used, which mix in contact with the liquid.

Typical electronically conductive materials that can be used as Contacogen are carbon, activated carbon, platinized asbestos, nickel © carbon or activated carbon, inclusions such as nickel, iron, cobalt, Silver, platinum, palladium, manganese oxides, such as manganese dioxide, manganese sulfides, iron oxides and hydrated iron oxides, nickel oxide, Contain kickelsulfide and cobalt sulfide or mixtures thereof, Of the above materials, carbon and more appear to be activated Carbon or activated coal dare the best performance relatively large surface-to-weight ratio and because of

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to the ease with which inclusions of metals and metal compounds can be introduced into the material, as well as the degree to which carbon can be finely divided. Plus, this is an easily available one Material that can be obtained in a wide variety of particle sizes and surface areas. Types of coal from different Sources often lead to different reaction rates. These variations are easily made by simple procedures certainly. Typical of the types of coal that are useful in accordance with the present invention are carbon black, furnace black, sewer black or types of carbon, which can be obtained by known methods from various Sources such as wood, corn on the cob, beans, nutshells, bagasse, lignin, types of coal, tar, petroleum residues, Bones, peat and other carbonaceous materials win.

can

The particle size / from 9 m, u to relatively large sizes, such as Vary 2.5 cm or more, and usually the charcoal or carbon is used as a mixture of different particle sizes fed. The surface of the carbonaceous

2 2

Materials can vary from 3 m / g to greater than 950 m / g as characterized by gas absorption using the BET method will.

The carbon can be provided in various physical arrangements, such as a porous nickel substrate with powdered platinum, covered with powdered carbon and a moisturizing agent, all on one Place of the nickel substrate are available, as described in "Fuel Cells", Prentice Hall, 1969, pages 402 to 403,

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a porous carbon plate or tube, made moisture-proof, to prevent flooding, or a mass of moisturized carbon granules or powders left on the Surface of the reducing agent float, or a layer of contacogen particles deeper than the capillary slope of the reducing agent when the contacogen is in contact with the surface of the reducing agent.

The carbon can be made moisture resistant in the following ways:

Polytetrafluoroethylene (PTFE) in emulsion form is made with finely divided carbon mixed in an amount of 0.1 to 100% based on the solid carbon. The mixture is heated to remove the carrier and dispersant for the PTFE. Another moisturizing method is that you finely divided carbon with linear polyethylene in a ratio treated by 1 g of polyethylene per 10 g of carbon. The polyethylene is used in the proportion of 1 g of polyethylene per 100 g dissolved hot toluene and poured over the carbon. After the treatment, the carbon is heated to around 105 ° C to reduce the temperature To evaporate toluene. The particles are not uniformly moisture-repellent, however, most of them are sufficiently moisture repellent to last for several hours to several days swim.

Using the method described above can be finely divided Carbon also with polystyrene, fluorocarbon resins, Polyethylene emulsions, silicones or other hydrophobic materials

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materials can be made moistureproof by any suitable method which allows complete encapsulation by hydrophobic Prevents materials from being impermeable to the reactants or educated products. Other materials that can be used are chlorotrifluoroethylene, prepolymerized Silicone oils and high vacuum silicone grease.

Another method is to sublime a chlorinated paraxylylene dimer in a vacuum chamber and sublime the vapors on materials such as fine particle carbon and porous sintered Nickel precipitates and thus a poly (chloro-pxylylene) forms what is known as "parylene".

In the case of materials such as finely divided platinum in an asbestos base, moisture resistance or water repellency is achieved by using a 1% solution of polyethylene in toluene, wetting the asbestos base material with the solution, Drain excess liquid and then dry in an oven to evaporate the toluene.

In another example, paraffin wax is used in an amount ranging from one-half gram to 2 grams per ten Carbon varies. The paraffin is dissolved in a solvent such as hexane or toluene, the carbon in the Mixture introduced, heated and then the solvent evaporated »Cetyl alcohol can also be used and in the same way be applied. One of the paratoluenesulfonamides, polydichlorotrifluoroethylene and octadecylamine can also be used and by mixing with the carbon and heating the mixture,

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to cause the treatment material to adhere to the carbon. Any of the above materials will work satisfactory in the new systems, as can be demonstrated by the polysulphide production which is visually observable is.

The finely divided carbon can be mixed with a carboxylated styrene-butadiene latex be bound, which is used in an amount of 5 g of a 25% pesticide dispersion per 10 g of carbon will. The resulting material is a sheet that is placed at the interface of a sodium sulfide solution and the air The reaction can be observed through the formation of the yellow color that is characteristic of polysulphide is. In another example, polyethylene was dissolved in toluene, the polyethylene in a ratio of 5 g per 10 g granulated carbon was used and the toluene was removed by floating the mixture on boiling water. The result was a bound product that was sufficiently porous to allow passage of the oxygen-containing gas, and that was sufficiently moisture repellent to swim in.

In Fig. 1, a preferred embodiment of the generator cell Illustrated in accordance with the present invention is a polypropylene container 10 having an inlet 12 and an outlet 14 for Introduction of aqueous reducing agent and intended to remove reaction products. In the container is a contacogen 15 forming one wall of the container and a porous nickel substrate with platinum carbon deposited thereon, powdered carbon and moisture repellant,

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on the side of the substrate with the reducing agent is in contact. The container 10 is also provided with an inlet 16 for gaseous oxidant as well as an outlet 17 equipped for this. The gaseous oxidizing agent first comes into contact with the nickel side of the contacogen 15.

In operation, a 2 molar solution of sodium sulfide was made a storage container, not shown, through the solution space 19 and then back to the same storage container with the aid of a pump not shown circulates. The solution was kept at a temperature of 50 ° C, and gaseous oxidizing agent, such as oxygen, was admitted to the gas space 20 from a pressure cylinder using a water column, to apply a pressure of about 0.04 atmospheres (16 inches of water) to the gas in the headspace, excess and unreacted Oxygen was withdrawn through outlet 17. The free

The surface of the contacogen was 48 cm after 65 hours Operation was 72.2 g of polysulfide sulfur along with 232 g Sodium hydroxide is formed. No thiosulfate had formed. This means a 50% conversion of sulfide to sulfur.

In another embodiment of the present invention the Contacogen 15 was a 0.6 cm thick porous carbon electrode, which had been made water-repellent as described. The operating conditions were as described above, and after During 23 hours of operation, 40.6 g of sulfur had formed together with 112 g of sodium hydroxide and 5.7 g of thiosulphate. this represents a 68% conversion of sulfide to sulfur and a 4% conversion of sulfide to thiosulfate.

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It can be seen that the apparatus shown in FIG. 1 can also be oriented so that the contacogen 15 is horizontal is placed above the reducing agent by simply turning the entire apparatus through 90 °. In this form the liquid level becomes held in the solution space so that the solution is in contact with the carbon surface, but not that whole part 15 flooded. With such an orientation of the apparatus it may be unnecessary to have a pressure system for the oxidizing agent held in contact with the part 15.

In the form shown in Fig. 2, if possible the same Reference numerals have been used, a variant is explained in which two separate cotacogen parts 15 and 15a are used to form cladding walls of the container 10. The space between them forms the solution space 19, the reducing agent is introduced through inlet 12 and the reaction products are removed through outlet 14. The part 15a has one Oxidant inlet and outlet 16a and 17a, respectively, the member 15a being of the type described above. After 4 hours of operation, as described in connection with the apparatus of Figure 1, there was 26.6 g sulfur and 83.6 g sodium hydroxide educated. No thiosulfate had formed. In each case, however, the formation of sulfur was revealed by the occurrence a yellow color, and with increasing formation of the sulfur formed in the sodium sulfide to form the polysulfide the color deepened. The nature of the reaction products was confirmed by analysis.

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A simple arrangement for the batchwise implementation of the present The invention and for the evaluation of contacogens is illustrated in FIG. 3, in which a container 25 contains a reducing agent contains. The Contacogen 29 is in the form of particles floating on the surface of the reducing agent and which at the same time are in contact with the oxidizing agent gas, such as air.

In one example, sodium sulfide solution was introduced into the container and carbon was used as the contacogen had been removed from the front of a fuel electrode. The activity was evident from the appearance a yellow color, and heat developed at the interface. Analysis of the carbon showed the presence of Fluorocarbon resin, copper, nickel, cobalt and iron, the latter Metals in trace amounts. The reducing agent solution originally contained 62 g Ie liters of sulphide sulfur and 169 g per liter Total alkali expressed as NaOH. There was also a trace of thiosulfate. This solution was left without stirring Stand room temperature for 3 days, with the carbon floating on the surface of the reducing agent, after which it is analyzed became. The results were 9 g / l sulfide sulfur, 30.7 g / l polysulfide sulfur, 34.5 g / l sulfur in the form of thiosulphate (SjO, ""). The total alkali was 142 g / l calculated as sodium hydroxide. For the present invention, each polysulfide ion, S ~, is said to consist of one atom of sulfide sulfur defined, i.e. as S ~, and with χ - 1 atoms of polysulfide sulfur, i.e. S,. The value of X is calculated from the amounts of sulfide sulfur and polysulfide sulfur according to the following formula

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X - 8 "+

i.e. from the ratio of sulphide sulfur plus polysulphide sulfur to sulphide sulfur.

A second sample of the same reducing agent solution was used, and after one hour and 15 minutes at room temperature the analysis showed the following results: 47.2 g / l sulphur, 11.2 g / l polysulphide sulfur and no thiosulphate (S ₃ O ₃ " Total alkali was 161.6 g / L as NaOH. After 4 hours the analysis was 29.3 g / L sulfide sulfur, 21.1 g / L polysulfide sulfur and no thiosulfate (S ₃ O ₃ "). Total alkali was 157.2 g / l, expressed as NaOH,

The above results are compiled in the table below .

Time ⁺ S * * ^S x-1 * ^S 2 ° 3 X value

1.25 hours 47.2 11.2 0.0 1.24

4.0 hours, 29.3 21.1 0.0 1.75

72.0 hours 9.0 30.7 34.5 4.23

Concentrations in g / l as sulfur,

Activated charcoal suitable for water treatment became water repellent made by using polyethylene as described above. It became the system with a floating layer used according to Fig. 3, the values were as follows:

Time ^{+ s = 450} XI * ^S 2 ° 3 ~ X value 5 hours 56.1 5.6 0.0 1.10 24 hours 40.3 22.2 0.0 1.55

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By using pillars made with finely divided carbon were packaged, it was demonstrated that a sufficiently high level of moisture repellant properties were one Prevents flooding and maintains continuous polysulphide production even under hydrostatic loading. Comparisons of carbon in this way showed that there was essentially no polysulfide with non-moisture repellant made coal was developed, while in this case large amounts of thiosulfate were produced. That Basic procedure used 100 g of 2M sodium sulfide solution in a 2.5 cm diameter glass column with a glass diffuser in the ground. Air was blown at a speed of 250 cm / min. bubbled into the column for 2 hours. The values obtained were the following:

liquid _

Repulsive - "= + S, + S ₉ O.

such Contacogen participates =

1 none not

2 g? Off ⁿ ~ not

^{2% PTFE 20% PTPE}

53.8 0 ,1 10 , 2 g / i 1.00 51.0 1 , 2 11 , 9 g / i 1.02 20.2 34 , 6 9 , 6 g / i 2.69 48.4 15th ο 1.32

These * values indicate that the system is operating optimally according to the present invention occurs when the contacogen is at the interface of the oxidizing agent and reducing agent and the oxidizer is kept in contact with a non-flooded surface of the contacogen will,

⁺ Concentrations in g / l as sulfur,

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Whatever the explanation for these unique results, it is clear that by flooding the surface of the contacogen the rate of oxidation is significantly reduced. aside from that the results are unique in that such oxidation as occurs when the surface of the contacogen is flooded, the oxidation level of the sulfur is too high, namely to thiosulfate, while the desired reaction, that with the non-flooded, water-repellent made Contacogen runs quickly, the oxidation level of sulfur only increases to the point of polysulphide. An explanation of this behavior in a column using a non-water repellent material, making polysulphide production negligible and thiosulfate production is greater, it may be that a direct reaction between the oxidizing agent and dent Reducing agent takes place, which does not include the Contacogen.

It has been observed that if the sulphide solution is kept in the vicinity of the oxidative region for too long, the oxidation product will be the product of the oxidation loaded to an undesirable extent from thiosulfate

the
stands, where / amount of thiosulfate increases with the reaction time. In a column, the reaction time can be controlled by the throughput rate of the sulfide solution, the faster the throughput, the shorter the reaction time. The following analyzes of effluent solutions from the bottom of a special column, through which air flowed upwards on the countercurrent principle, show that with a certain contacogen the throughput should be kept above the value at which thiosulphate is formed. The following values show that the oxidation rate

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1.9 8.5 50.5 3.7 11.8 42.8 9.9 31.8 21.7 25.4 32.8 0.0 31.8 26.8 0.0 36.6 17.9 3.2

is comparatively very low if the Contacogen has not been made water-repellent.

Throughput + "o + _{Q n} =

In ccm / hour ⁺ S ~ ^b x-1 ^b 2 ^u 3

Carbon with 10% PTFE • Made water-repellent

the same carbon untreated

The amount of moisturizing material with which the Contacogen should be treated can vary from less than 1% of the contacogen weight to more than 99% of the same. Lower or higher percentages of the moisture repellant material do not appear to have any useful purpose to serve, since the contact surface available for one flowable phase compared to that which is then the other flowable Phase is available, being excessively scaled down. The exact proportions of the water-repellent material

Concentrations in g / l as sulfur,

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57.3 1.0 2.6 63.2 0.5 0.0 58.9. 0.8 2.6 63.4 1.0 0.0

The best way to determine the material is through experiments for a special one Contacogen to be used in special equipment, depending on the practical results desired.

For example, the amount of was used to treat activated Carbon PTFE used varies, with the various water-repellent made carbon charges in glass columns from 5 cm thick and 40 cm long. Sodium sulfide solution at an approximately 2 molar concentration was added with passed down through the columns at a set and measured volume velocity, and a large chemical excess air was passed upwards in the countercurrent trinssip at a constant volume velocity. In separate experiments the flow rate of the sulfide solution was adjusted to various values, and after the operation for a long time When enough had occurred to achieve constant conditions, samples of the effluent solution were collected and analyzed. The following Table shows the analytical values of these experiments with the respective values of the amount of water repellent PTFE on the carbon and the dwell time in the column, the latter is inversely proportional to throughput and is reported in minutes, which in these experiments equals 43,440 divided by ecm per hour.

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% PTFE used to make the carbon water repellent

Dwell time ° _ ^{2 5 10}

in minutes S x-1 2 3 x-1 2 3 S x-1 2 3 S x-1 2 3

33 - 40.6 14.1 1.3 - -

46 - 48 - 32.3 24.3 2.6 35.2 21.4 2.6 36.2 24.6 0.0

53 - 54 50.6 1.9 0.0 - - 25.9 28.2 9.0 -

O-64 ~ ~ - ■ 27.2 29.1 0.0

OCf 69 ~ 18.2 25.9 10.2 ~

^ To / 2 ■ * "" "" "" "·" —.-.— —— · -—.- - ~ - 17.9 32.6 16, ο "**" ——— - —ι—

«Ο ¹ 77 53.1 1.6 1.3

The values in the table are concentrations in g / l as sulfur. The dashes mean that no values were recorded.

215U65

This table shows that when the minimum residence time in the column is a primary criterion and the maximum polysulfide sulfur production a secondary criterion is either 2, 5 or 10% moisture repellant PTFE on the carbon produces roughly the same results. On the other hand, if the maximum polysulfide sulfur production is a primary criterion and the coagulated thiosulfate sulfur production is a secondary criterion then 10% moisture repellant PTFE on the carbon gives the best results in these experiments. In two experiments, the column was operated with activated carbon with no moisture repellant material, and the above results show that the production of oxidized sulfur products was greatly reduced compared to that which was obtained when PTFE in amounts of 2, 5 or 10% the coal was available.

A simple arrangement for practicing the present invention batchwise and for the evaluation of contacogens is explained in FIG. 3, in which the container 25 contains the liquid reducing agent 26 includes. The contacogen 29 is in the form of particles deposited on the surface of the liquid reducing agent float and are carried by this and which are at the same time in contact with the gaseous oxidizing agent. The particular arrangement of Figure 3 can be used with a contacogen carried at the interface and a convenient and effective means of accomplishing this is to make the contacogen moisture repellant, such as with finely divided coal made water-repellent. On the-

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This way you get a floating layer in which the Contacogen is held at the interface between the two reactants.

In Fig. 4 there is a container 30 with an inlet 31 for introducing the reducing agent 32 and with an outlet 33 for removal

around

the reaction products and unsettled reducing agent provided. In the container 30 there is a sieve element 34 which, with respect to the level of the reducing agent 32 in the container 30 is arranged such that the reducing agent is in contact with the underside of the sieve 34. The thickness of the Contacogen material layer 35 is proportioned so that its vertical height is greater than the capillary slope of the reducing agent so that the contacogen is flooded by the Reducing agent is prevented. Thus, the free surface portion 36 of the contacogen material is contiguous with the oxidizing agent Exposed to (air) and works in essentially the same way as a floating layer. The Contacogen 35 can take various forms in the arrangement of FIG. 4, for example that of a porous carbon plate interconnected porous carbon particles either from a sieve or from other suitable means be worn. Depending on the size, the cross-section and the strength of the plate, it can also be designed to be self-supporting eliminating the use of support screens and other devices. This arrangement like the one above has been described, ensures that oxidizing agent, which is in contact with the reducing agent, also in contact with must come to the Contacogen.

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215H65

Another form of apparatus is shown in Figs. 5 and 6, in which the generator 45 includes a plurality of vertically layered trough members 46 which are spaced from one another by the parts 47 being held. In the embodiment shown four troughs are provided, although the number of troughs used can be larger or smaller. Each trough has several spaced apart separating elements 48 which extend from a wall 49 of the trough. The dividers 48 end just before the opposite wall 51. From the opposite wall 51, several also extend Separating elements 53, and these end just before the wall 49. Reducing agent is introduced into the trough through an inlet 55, and due to the arrangement of the partitions 48 and 53, the reducing agent flows in a serpentine manner to the trough outlet 56, the allows the reductant material to flow into the next trough below. In this way the reducing agent migrates from one trough to the next and is finally withdrawn through a drain line 57.

The reaction takes place in the presence of a Contacogen, for example with polytetrafluoroethylene (PTFE) made water-repellent finely divided carbon can be that on the surface of the Reducing agent floats in practically the same manner as described in connection with FIG. The apparatus 5 and 6, however, constitute a continuous system in which fresh reducing agent is introduced into inlet 55 and removed at outlet 57. The contacogen, which is in finely divided form, is attached to it by baffle plates 60

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215H6S

prevents wandering through the generator, and these baffles are so placed in the path of the flowing reducing agent, that they allow the reducing agent to flow underneath while the contaceogen is held in place will. The oxidizing agent is air that is circulated between the troughs.

In a typical experiment, there were 8 troughs measuring 60 χ 120 cm operated in series continuously for 5 1/2 hours. The feed rate was 430 to 490 cc / min. for one aqueous sodium sulfide solution containing about 64.6 g / l sulfide expressed as sulfur. The feed temperature was about 54 ° C (130 ° F), and the outlet from each trough was taken into account the concentration, the percentage conversion of the X-value analyzed. The values obtained are in the following Table compiled:

trough ⁴ S = ^s ° x-: L ^S 2 ° 3 ~ conversion ^h X value Loading
ski-
kung 64.6 O 1.00 1 59.0 5.1 0 8.2 1.09 2 51.0 12.5 0 19.4 1.24 3 43.9 19.9 0 31.0 1.45 4th 34.6 28.2 0 44.8 1.81 5 31.1 33.0 0 51.5 2.06 6th no values certainly 7th 27.2 36.2 0 57.0 2.33 8th 25.3 37.2 0 59.5 2.47

⁺ Concentrations in g / L as sulfur ⁺⁺ Total percentage of sulfide converted to polysulfide

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"2151463

In a second series of tests, a loading speed of 400 ccm / min. at a feed temperature of 49 ° C (120 ° F) was used with the unit operated continuously for 28 hours. The values were determined as above and were the following:

trough 31.9 ^{+ S} ° x-1 ^{+ S} 2 ° 3 ⁼ conversion X value Loading
kung 25.8 _— —— 0 1.00 1 20.4 5.9 0 18.7 1.23 2 17.0 10.9 0 34.6 1.53 3 14.9 14.2 0 45.6 1.84 4th 13.3 15.9 0 51.5 2.06 5 12.3 16.5 0 55.3 2.24 6th 11.5 18.4 0 59.8 2.49 7th 10.7 19.1 0 62.4 2.65 8th 19.9 0 65.0 2.85

Concentrations in g / l as sulfur

Total percentage of sulfide converted to polysulfide

These values are important because of the large amounts of polysulphide formed without thiosulphate when using a generator in the Figs. 5 and 6 were used. It is also important that the generator 45 operate continuously for a long time without that a loss of activity of the contacogen was observed, which would have made regeneration necessary.

A closed tower generator 75 is shown in FIGS and includes several vertically stacked

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215U63

Trough elements 76 a. Four of these are shown in the drawing, although more or less can also be used if desired. In this construction, each trough contains Polypropylene, stainless steel, or other suitable material has a plurality of spaced apart separators 77 which extend from one end wall 78 and terminate shortly before the other end wall 79. From the wall 79 extends a second row of spaced-apart separating elements 80 which end shortly before wall 78. The separators 77 and 80 form Flow channels for the reducing agent and the oxidizing agent. The oxidizing agent is through inlet 81 in the upper Blanket 82 is introduced while reducing agent is introduced through inlet 84 also in the upper blanket. A reducing agent inlet chamber 85 is formed by baffles 86 and 37, which the space between the adjacent side walls and span the adjacent separating element 80. The baffles end just before the ceiling 82 and thus provide a space for the passage of oxidizing agent, while the baffle plate 87 is spaced from the bottom of the trough, allowing the reducing agent to flow under the baffle. In Adjacent to the reducing agent inlet chamber is an oxidizing agent inlet chamber 88 is provided, which is delimited by the baffle plate 86 and the end wall 79.

Unreacted reducing agent and product and some residual oxidizing agent are removed from an outlet 89 in chamber 85a subtracted, which is formed by baffle plates 86a and 87a corresponding to the baffle plates 86 and 87. The upper end of the outlet

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215U65

This 89 extends beyond the lower end of the baffle 87a, as shown in Fig. 9, around the reducing agent level in such a way that the contacogen 90 in the form of finely divided, water-repellent made coal is prevented from to flow from one trough to the next. Oxidizing agent arrives over the upper edges of the baffle plates 86a and 87a to an oxidant outlet chamber 88a and through the outlet 91 to the next lower trough. For the sake of simplicity, this trough has essentially the same construction, with the passageways 89a and 91a are plugged or sealed at the inlet end of the trough as shown in FIG. If thus reducing agent and oxidizing agent flow into the next trough below, oxidizing agent and reducing agent migrate in one Direction opposite to that in the trough above and they exit through chambers which correspond in location and construction to chambers 85a and 88a. In which The last trough is unused oxidizing agent, if any is still present, and the remaining gases from the Tower outlet 92 withdrawn while unused reductant and products are withdrawn from trough outlet 93.

The ceiling 82 is so tightly connected to the uppermost trough by sealing elements that a continuous flow channel is formed between the separating elements and walls, as FIG. 7 shows. The bottom of the top trough forms the ceiling for the next trough below, while only the top trough is provided with an additional cover. The troughs are separated by sealing elements 95, which can have different shapes.

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seals. In the form shown in Figures 7-9, the sealing members are resilient members which adhere to the top of the dividers 77 and 80 and to the top of the side walls and end walls of each trough. In this way control of the oxidant feed rate can be maintained and the system can be pressurized if necessary
be set.

Using a tower generator of the type shown in Figures 7 to 9, air was fed in as the oxidizing agent at a rate of 44 l / min, while reducing agent at a rate of 400 cc / min. was fed. That
The reducing agent was an aqueous sodium sulfide solution with a content of 61.5 g / l sulfide sulfur, while finely divided carbon made water-repellent with PTFE was used as the contacogen and floated on the surface of the reducing agent. the
Values were as follows:

Inlet temperature, + _q o + „ _n = * Conversion trough temperature QC S ~ ^a x-1 2 ^U 3 treatment% X value

chic

kung 61, g g / l

1 59 62.1 g / l 0 0 0 1.0

2 58 60.5 g / l 0 0 0 1.0

3 64 57.4 g / l 1.6 0 3.0 1.03

4 84 52.5 g / l 3.5 0 6.5 1.07

5 91 45.1 g / l 11.2 0 20.0 1.25

6 89 28.2 g / l 28.5 0 50.2 2.01

"•" Concentration in g / l as sulfur

209820/0901

The oxidant was air with an oxygen content of about 21% and it was found that the oxygen content of the outlet 92 withdrawn gas was about 9%. The dwell time was about 90 minutes for the six troughs or 15 minutes for each Trough. The total trial time was about 6 hours in continuous Operation.

The closed apparatus according to FIGS. 7 to 9 provides advantages in practicing the present invention. For example, the heat developed during the exothermic reaction can be used as a low temperature heating source by using a heat exchange device connected to the tower used. In addition, the reaction conditions and the reaction temperature can be adjusted by adjusting the feed rates for the oxidizing agent and reducing agent are controlled. The oxidizer compositions can to be controlled. Countercurrent flow can optionally be used. Part of the tower can be heated to the Increase reaction speed by applying heat, which is developed in other part of the tower, or by using a separate heating source. Cooling is also certain Parts of the tower possible if this proves advantageous. Of course, the tower can also have other shapes accept.

In view of the fact that the reaction is exothermic, it can be seen that when made moisture repellant materials can be used as a Contacogen, the moisture repellant made material stable at the applied temperature should be.

209820/0901

Other variables affecting the operation of that shown in FIGS Affect the apparatus, for example, the oxidizing agent concentration, the feed rate and the amount of the oxidizing agent charged, the degree of moisture-repellent properties of the finely divided coal or another contacogene. Because the amount of oxygen is noticeable is reduced when air is used as the oxidizing agent, the gas generated can continue to use the system after of the present invention can be treated to obtain an inert gas composition that is rich in nitrogen and oxygen is depleted, although other systems can be used to remove the remaining oxygen. For example For example, the exhaust gas can be passed through a second generator of the type shown in FIG. It is also possible to use the Reaction conditions for the effectiveness of oxygen reduction rather than controlling for the effectiveness of polysulfide production.

The speed and / or effectiveness of the system according to the present invention can be increased by adding inclusions or the like. used in the Contacogen. For example, inclusions of metals and metal compounds appear in the finely divided charcoal increase the reaction rate compared with the same charcoal without inclusions. The inclusions can be provided as follows:

Cobalt sulfate was in water in a proportion of Dissolve 0.5 g / 100 ml of water. Finely divided charcoal was added in an amount of 10 g / 100 ml of solution. The resulting ge

209820/0901

«Μ

The mixture was heated to the boil and then dried in an oven at 110.degree. The solid material was then washed with sodium hydroxide treated to precipitate an insoluble cobalt material, the solids were then filtered off and washed with 0.1 η sodium hydroxide solution washed. The charcoal was then soaked in sodium sulfide solution for 4 hours, then filtered and 3 times washed with hot water and then dried again at 110 ° C.

Manganese-II-nitrate was in slightly acidic solution in a quantitative ratio of 0.5 g / 100 ml of water acidified with 0.1 g of nitric acid. The rest of the treatment was the same as described in connection with cobalt sulfate.

The same procedure as just described was also repeated except that the inclusion of ferric sulfate was brought about, which was dissolved in 0.1 η sulfuric acid.

Nickel sulfate, silver nitrate and chloroplatinic acid were also used individually and as described above to form Inclusions processed.

It has been observed that all such inclusions increase the speed of the reaction compared to the reaction rates obtained without inclusions.

One of the main advantages of the system according to the present invention lies in the use of this system for the recovery of polysulphide pulp treatment liquor for the processing of lig-

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215H65

nocellulosic material such as wood for paper pulp and the like Fig. 10 shows an alkaline pulp treatment system in which chemically Boiled pulp is withdrawn from a digestion vessel 100 through a blow vessel 102. The pulp and spent liquor are then treated in a washer 103, the pulp being separated from the spent liquor as indicated, and the latter is called black liquor. As is customary in the pulp treatment industry, the black liquor is treated to produce it Obtain pulp treatment chemicals for reuse.

This processing typically consists of feeding the black liquor to a multi-action evaporator 105, with the output of the evaporator being fed to a recovery cooker where the organic solids are consumed to produce heat and an inorganic sulphide-containing melt which is then fed into a Melt dissolving container 109 is introduced. The output of the container dissolving the melt is green liquor, which is an aqueous solution containing mainly sodium sulfide and sodium carbonate. The green liquor is fed to a container 111 into which calcium oxide from a roasting furnace 112 is also introduced. The mixture from this container passes to a caustic container 115 in which the precipitation of calcium carbonate and the formation of sodium hydroxide are completed. The resulting mixture is fed to a clarifier 117, in which the lime sludge, which consists mainly of calcium carbonate, is removed. The sludge is passed through a filter 120 and then to a grate

209820/0901

oven 112, which converts the calcium carbonate into calcium oxide. The latter is returned to the container 111 to be in
Calcium hydroxide to be converted. The output of the clarifier 117 is white liquor, an aqueous solution mainly
of sodium hydroxide and sodium sulfide.

The polysulfide generator according to the present invention can
can easily be incorporated into the system shown in Fig. 10 by taking the discharge of the clarifier 117 and through
conducts a polysulfide generator of the type described above -as indicated at 125. The feed of the generator 125 is white liquor. The outlet of the generator is an aqueous one
Solution mainly of polysulfide and sodium hydroxide that can be used as pulp treatment liquor.

The pulp treatment liquor from the generator can be used directly in the digestion tank if the desired pulp treatment conditions require a liquor of the chemical formed
Require content, or the content and concentration of the lye from the Geifrator can be adjusted by adding chemicals. For dilution, controlled amounts of water can be added continuously, or the lye from the generator can be fed to a borax tank and the concentration can be increased by adding water or the like. can be set. Supplemental chemicals can also be added to the system to improve the
to obtain the desired composition. For example, can
.alkali, sulfur, hydrogen sulfide gas or sodium sulfide to the reducing agent before it enters the generator or

209820/0901

be added to the liquor formed before or during entry into the digestion vessel or else separately therefrom be added to the digestion tank. Sodium carbonate can be added before the causticizing system, while sodium sulfate can be added above the recovery boiler. Sodium hydrogen sulfide and sodium polysulfide can be used in either Point where sulfur can be added, although either sodium sulfite or sodium thiosulfate can also be added can be added to the recovery boiler. For the professional

ig

it will be understood that the above modifications can and will be made alone or in combination with one another other materials can be added, such as penetration aids or / and pitch control agents.

The lye from the generator can also be used for pretreatment of the cossettes or in semi-chemical pulp treatment or for odor removal from exhaust gases. According to the invention it is also possible to add white liquor, green liquor or black liquor or mixtures thereof from the generator mix. The feed to the generator can be white liquor,

Sodium sulfide with or without sodium hydroxide, black liquor, green or
lye / be a mixture thereof. The starting reducing agent can come from any source of the pulp treatment system since all that is required is a source of sulfide or hydrogen sulfide. For example, Kraft black liquor fortified with sodium sulfide solution was treated in accordance with the present invention. Analysis of this fortified black liquor showed 58 g / l sulphide sulfur, no polysulphide sulfur and 154 g / l gel

820/0 901

MS

total alkali as NaOH. 1 g activated, finely divided charcoal, treated with polyethylene, was made to float on the surface of the resulting mixed solution, and with air as an oxidizing agent the reactants stood undisturbed for 12 hours. At the end of this time the following analysis values were found: Sulphide sulfur 41.2 g / l, polysulphide sulfur 12.3 g / l and alkali as NaOH 174.4 g / l. The presence of black liquor bothered them usual determination of thiosulphate. However, it was evident that the oxidation of sulfide to polysulfide promoted by Contacogen progressed with the existing black liquor.

In another example, 500 grams of Kraft black liquor containing residual sulfides was poured into a trough to about 2 cm thick layer to be gained. The surface of the black liquor was activated with fine-particle activated carbon of 8 χ 30 mesh,

ο treated with 2% PTFE, in an amount of 22 g per 645 cm of the

Lye surface covered.

3DO g of black liquor were poured into a similar trough and used as a control.

The progress of the sulfide oxidation was followed analytically with the following results:

Contacogen control - no Contacogen reaction time 0 12 0 1 2

SuIfid ⁺ 2.1 0.22 ^ IJJ "2.1 0.80 0.29

Polysulphide sulfur 0.0 0.33 0.22 X-WGrt 1.0 1.45 -

Odor of the sample strong "^ concentration in g / l as sulfur

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0.0 Ο, ΟΟ 0.00 1.0 1.0 1.0 strong strong weak

These values show that from the sulfide in the black liquor, polysulfide had only been formed in the presence of the contacogen and that the rate of sulfide oxidation was in its presence was very quick. Again, the intense color of the black liquor interfered with the precise determination of the thiosulfates present.

Kraft black liquor is usually malodorous as a result of the Presence of mercaptans and organic sulphides, and paper mills serve over great lengths to eliminate this odor. The amount of these malodorous compounds in the black liquid oxidized in contact with the Contacogen can be severe be reduced. The odor tests were carried out by three people who individually measured the odor of the air layer directly assessed over the caustic layer.

The ability to process black liquor is essential, since it is also possible according to the present invention to adjust the polysulfide concentration control in the cooking liquor in the digestion vessel by adding some of the cooking liquor used is recirculated through a polysulfide freezer, which is arranged on the digestion vessel that part of the cooking liquid withdrawn therefrom, passed through the polysulfide generator and then reintroduced into the digestion container. Independent Because of the special arrangement it is advantageous to avoid the introduction of air into the polysulphide liquor otherwise there is a tendency to convert polysulphide into thiosulphate.

The following examples illustrate the use of polysulphide pulp treatment liquors, the using systems according to

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of the present invention. Between 1% and about 10% polysulphide sulfur, based on the oven dry weight (OT) of wood chips, can be used with different types of wood chips. Cooking liquid is over Pour the chips into the digestion vessel, and add water to bring the ratio of lye to wood to about 4: 1 up to 4.5: 1. The digestion container is tightly closed and the lye is heated to 100 ° C as quickly as possible, by circulating it through a heat exchanger. Entrained air is released and cooking continues, as stated. The assessment is preferably carried out with batches of around 50OO g (OT) wood chips.

example 1

A mixed wood chip mass was prepared as follows:

Chestnut oak 20% Tulip poplar 8th % Scarlet oak 15% Hard and soft maple 6% White oak 10% Ash 2% Black oak Elm 2% Red oak 2% beech 1 % other oaks 5% plane 1 % hickory 15% other hardwoods 5%

The cooking conditions were as follows:

18% active alkali expressed as N ₃

20% suIfidity, expressed as Na _? 0 and defined by the

following ratio

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Na ₂ S ⁰ + 100 NaOH + Na ₂ S

Ratio of lye to wood 4: 1 (l / kg)

3% polysulphide sulfur (based on the dry wood weight OT)

90 minutes from 100 to 163 ° C

60 minutes at 163 ° C

After boiling, the digestion container is blown off and filled with hot water and then blown off again. The fibers are washed free of black liquor and sieved through a sieve with slots 2 mm wide. Typical values for a boil of this type are the following:

Percent screened pulp 51.5%

Percent of the screened splinters 0.8%

Total percentage 52.3%

The permanganate number (K) averages 14.5. The pulp is bleached as follows: chlorination, caustic extraction, Hypochlorite and chlorine dioxide. The resulting pulp is cleaned and handsheets are made according to TAPPI Standard T 205m-58 and T 227-m-58 and assessed according to TAPPI-Standard T 220 m ~ 60 and T 425m-6O. Typical values for according to the above Process obtained pulp are the following:

CS. Degree of grinding 550 9 440 340 250 Tear factor 1OO, 6th 84.5 82.0 80.5 Bursting factor 33, 49.0 55.8 59.7 Crushing length (BLM) 533O 72OO 8160 8630 x-fold 33 135 338 636

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Mass 1.60 1.48 1.38 1.33

Opacity 74.0 70.9 68.3 66.3

Basic weight (OT) 59.6 59.3 59.3 59.6

Example 2

A mixture of oak chips was made as follows:

I & stanie oak 33%

Scarlet Oak 25%

White oak 17%

Black oak 13%

Red oak 3%

other oak 8%

The schnitzel mass was cooked under the following conditions:

23% active alkali as Na ₀ O

4Lt

19.1% sulfidity

Ratio of lye to wood 4: 1

Polysulphide sulfur (calculated on the dry wood weight OT) 5%

90 minutes from 100 to 170 ° C 45 minutes at 170 ° C

Typical sieving and result values for this type of cooking were obtained according to Example 1 in the following way:

Percent sieved pulp 50.1% percent sliver on one

Sieve with slots of 2 mm 0.3%

Total percentage 50 _f 4%

Mean value for K 11.9

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5 € Γ 5t)

The evaluation of handsheets gave the following typical values for such a pulp:

CS. Man lung s gr ad 550 43Ο 360 250 Tear factor 87.2 84.6 81.5 78.7 Bursting factor 25.9 36.1 40.3 46.7 Crushing length 5255 641Ο 7243 793Ο x-fold 15th 65 122 355 Dimensions 1.72 1.58 1.51 1.41 Basic weight (OT) 58.7 59.0 59.7 61.0 Example 3

A mass of hardwood chips was made as follows:

Quivering aspen 13.3% Hornbeam 12th large-toothed aspen 6.7% Yellow beech 12th Hard maple 37.5% beech 6th Soft maple 12.5%.

The schnitzel mass was cooked under the following conditions:

23% active alkali as ₃

20% sulfidity

Ratio of lye to wood 4: 1 (l / kg)

Polysulphide sulfur (calculated on the dry weight of the wood OT) 6%

90 minutes from 100 to 152 ° C
60 minutes at 152 ° C.

Typical fourths obtained for this type of cooking are the following:

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si

Percent sifted pulp

Splinters screened off with a sieve with a slot width of 2 mm

Total yield
Mean value for K

58.3%

1.3% 59.6% 11.65

Hand sheets of each pulp gave the following typical values in the evaluation described above:

CS. Degree of grinding 580 44O 360 200 Tear factor 96.0 87.2 85.0 81.2 Bursting factor 31.4 49.8 56.6 65.6 Crushing length 553O 744O 873O 9200 x ~ fold 22nd 171 485 1196 Hate 1.59 1.46 1.39 1.30 Basic weight (OT) 61.36 6O, 9O 61, O 60.72 Example 4

A mass of pine chips was prepared from 20% frankincense pine, 40% slotted pine and 40 % long-leaved pine. The schnitzel mass was cooked under the following conditions:

22% active alkali as Na ₂ O 2O % sulfidity

Ratio of lye to wood 4: 1 Cl / kg) Polysulphide sulfur (calculated on dry wood weight OT) 6%

90 minutes from 100 to 152 ° C 90 minutes at 152 ° C

Percentage of total yield 58.9%

Mean value for K 32.4

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Sl

The evaluation of such a pulp gave the following typical results:

CS. Degree of grinding

Tear factor, burst factor, breaking length x times

Dimensions

Basic weight (OT)

Example 5

530

460

340

240

149 13? 119

58.0 61.9 67.6 68.7

7649 8473 9052 8934 467 580 730 663 1.95 1.94 1.88 1.76

59.3 59.3 60.8 61.6

Using the pine pulp mass as in the previous one Example, the following conditions were applied:

26% active alkali as ₃

20% sulfidity

Ratio of lye to wood 4: 1 (l / kg) polysulfide sulfur (calculated on dry wood weight OT) 9.65 %

90 minutes from 100 to 164 ° C

90 minutes at 164 ° C

Typical values for material treated in this way were as follows:

Sieved yield (calculated on dry weight OT)

of wood 54.8%

Splinters on a sieve with slots of 3.5 mm 1.0% Total yield 55.8 "

Mean value for K 24.5

Example 6

The liquor used in this example was Kraft pulp treatment liquor from an industrial source and fortified by adding 125 g / l of technically pure Ha2S flakes. The analysis of the amplified liquor showed a concentration of active alkali of 126.8 g / l, at Gesamtaslkali of 132.7 g / l and Na S ₀ of 77.5 g / L, all expressed as Ka ₀ O. This liquor was then treated in a polysulfide generator in accordance with the present invention, the generator being of the construction generally shown in FIGS. An alkali of the following concentration was obtained:

Na ₉ S as Na ₂ O 34.1 g / L

Polysulfide sulfur 12.0 g / l

NaOH as Na ₂ O 76.9 g / L

A mass of softwood chips was prepared as follows:

Balsam fir 38%

Red pine 16%

Shrub pine 19%

White pine 19%

Hemlock 8%

Following the usual procedures, Na _? S and alkali added in an amount sufficient to obtain the indicated sulfides and indicated active alkali. The schnitzel mass was then cooked under the following conditions:

20% active alkali as Na ₃ O

25% suIfidity

Ratio of lye to wood 4: 1 (l / kg)

Polysulfide Sulfur (calculated on a wood dry weight basis OT) 1.75%

90 minutes from 100 to 170 ° C
90 minutes at 170 ° C

Seven gave the following fourths:

Percent sifted pulp (sieve with slots of

3.5 mm width) 48.73%

Percent of screened chips O, 42%

Overall yield 49.15%

Mean value for K 22.0

The washed pulp was subjected to chlorination, alkaline extraction, bleached with chlorine dioxide, alkaline extraction and treatment with chlorine dioxide. After bleaching the pulp was cleaned, and handbows obtained therefrom were rated. The following values were obtained:

CS. Degree of grinding

Tear factor, burst factor, tensile strength, breaking length x-fold

Dimensions

Opacity gloss

Basic weight, OT

535

460

330

270

100.6 93.6 87.9 81.9 80.3 84.3 87.7 86.8 2O, 9 21.8 23.1 22.4 10488 10774 11485 11327 1460 2092 2597 2866 1.35 1.33 1.29 1.32 61.6 57.8 56.9 53.2 84.8 84.0 82.2 79, O 60.26 61.19 60.82 59.80

2 0 9 8? D / n.9.0 1

S5

⁺ ΤΛΡΡΙ T 452 m-58

The upper limiting amount of polysulfide sulfur that can be formed depends on the amount of ^T <i sodium sulfide contained in the reducing agent and can be as much as about 100 g / l. Obviously there is no lower limit for the ^{size of} the polysulphide sulfur. The production of sodium hydroxide varies in proportion to the production of polysulfide sulfur. Of practical importance is the fact that the use of polysulfide in amounts as little as 1 % based on the kiln dry weight of the wood gives an increase in yield compared to Kraft processes. Here is a unique advantage of the present invention in a system for the production of polysulfide which is useful for the treatment of lignocellulosic material, since compared to known systems it is relatively simple and offers the advantage of being adapted to currently existing kraft pulp treatment systems and caustic recovery systems can.

Although the description of the present invention refers primarily to the conversion of sodium sulfide or sodium hydrogen sulfide, the present invention can also be practiced using hydrogen sulfide gas since the hydrogen sulfide can be absorbed in sodium hydroxide to form sodium sulfide or sodium hydrogen sulfide. In the pulp processing area, hydrogen sulfide is obtained from dissolved melt, carbonated liquor, the 7Mii ^: 3chlußbehiilter, the front dam, the Blnstank and dom black]; iuffo.oxjdntionsturm.

? η η η? η / ο η ο 1

BAD ORIQiNAL

The treatment of lignocellulosic materials is not on
fully restricted to chemical cooking. The product of the system of the present invention can also be used in semi-chemical processing, chip impregnation and any other chip treatment and the like which normally heat
be to partial or complete separation of lignins
and cellulose, or used for any other preparatory treatment.

209870/0901

Claims (2)

Claims 1. Process for the production of Iodium polysulphide and sodium hydroxide from sodium sulfide or sodium hydrogen sulfide, thereby characterized in that one has a gaseous oxidizing agent and one of an aqueous, sodium sulfide or sodium hydrogen sulfide containing solution existing reducing agent in contact with a Contacogen, which is relatively chemically inert to the oxidizing agent and reducing agent, and bringing into contact with each other, wherein the oxidizing agent and the reducing agent are able to form an interface on contact with one another, and the contacogen at the same time and in intimate contact with the oxidizing agent and the reducing agent and so on the Contacogen at the same time the reduction of the oxidizing agent with the formation of sodium hydroxide and the oxidation of Sulphide ions or hydrogen sulphide ions with the formation of sodium polysulphide causes. 2. Device for performing the method according to claim 1, characterized through a container containing a contacogen, means that cooperate with the contacogen and a Prevent flooding of the contacogen with the reducing agent, devices that keep the oxidizing agent in contact with the reducing agent and so raw the oxidizing agent as well as the reducing agent in contact with the contacogen and such a thing Cause oxidation with the formation of sodium polysulphide and a reduction with the formation of sodium hydroxide on the Contacogen, and facilities for the extraction of unreacted reduction agent! L and the products the redox process. 209820/0901 lee rs e ite