JPS5827291B2 - How to remove zinc from zinc-containing carbon black - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a process for removing zinc from zinc-contaminated carbon black, and more particularly to a process for purifying solid carbon black contaminated with at least 3% by weight of zinc, calculated as zinc oxide. .

Carbon black is an extremely useful commodity and is known to be obtained from a variety of sources.

A valuable use of carbon black is in the production of rubber tires.

In fact, apart from rubber, the main component of a rubber tire is carbon black, and it is highly desirable to be able to reuse this type of carbon black contained in rubber.

Recycling carbon black to obtain useful products from the rubber contained in tires serves a dual purpose.

First, it conserves a valuable resource, and second, it eases the problems associated with discarded rubber tires.

For example, at least 200 million rubber tires are discarded each year in the United States.

Moreover, although this type of tire has a relatively small solid waste fraction, the problem of tire disposal is extremely difficult.

When rubber tires are burned, they release large amounts of unburned hydrocarbons that are highly visible and harmful.

Moreover, when tires are used as a mound, the problem of disposing of waste rubber tires remains unsolved, since the tires are difficult to decompose naturally and appear on the surface of the mound, making its appearance undesirable.

To solve the problems associated with waste rubber containing carbon black, for example, rubber tires are pyrolyzed to obtain valuable hydrocarbons.

However, after removing the hydrocarbons, a large amount of solid material remains, and this solid material (commonly known as char, carbonaceous material) is mainly composed of carbon black and inorganic materials mainly consisting of zinc and sulfur.

Unless this type of inorganic material is removed from the carbon black, it cannot be successfully recycled into, for example, rubber tires.

Also, as long as the main metal contained within the inorganic material is zinc, usually as zinc oxide, this valuable metal can be used at the same time as removing the zinc to give a solid material that can be reused to make rubber tires. Preferably, the zinc is recovered for reuse.

The present invention relates to a method or process for removing zinc from carbon black containing 3% or more of zinc (calculated as zinc oxide) (for example, char residue remaining after pyrolysis of scrap rubber).

The process also provides for the recovery and reuse of zinc and the reuse of carbon black-based char, for example for the manufacture of rubber tires or other products using carbon black.

The present invention further provides for the recycling of solid carbon black contaminated with zinc oxide and other inorganic materials such as sulfur, calcium oxide and other trace metals.

It is an object of the present invention to provide a method for removing almost all the zinc or zinc oxide contained in carbon black so that the carbon black can be recycled and the zinc contained in this carbon black can be recovered.

The present invention further aims to provide an economical method for recycling carbon black and retaining zinc oxide in a simple and economical process, for which carbon black is heated to a temperature of at least 732°C, preferably from about 750'C to 1000°C. The volatile zinc chloride produced is separated from the solid carbon black by simple contact with a gas such as chlorine at a temperature of 1200°C or 1200°C.

Other objects of the invention will become apparent from the following detailed description.

All parts and percentages herein are by weight, unless otherwise indicated; likewise, all temperatures are in °C.

As a typical preferred embodiment, the invention is illustrated with char made from scrap rubber.

The main component of this char is carbon blank (for example, 60% to 70% to 85% by weight of carbon black).
90%).

The remainder of the char is commonly referred to as ash, and the main components of ash are zinc as zinc oxide and sulfur.

That is, at least 50% of the ash is zinc and sulfur as zinc oxide.

Generally, zinc oxide comprises at least 3% of the total weight of the char and sulfur usually comprises at least 1% to 2% of the char.

In a typical preferred embodiment, scrap rubber is pyrolyzed to yield spent char by contacting the rubber with a heat-carrying solid in a rotating retort.

During the pyrolysis process, a heat-carrying solid (preferably ceramic) is mixed with the rubber due to the rotation of the retort, and the rubber is crushed in addition to transferring heat from the heat-carrying solid to the rubber, resulting in pyrolysis and crushing. The solid that remains after the process is made into an ultra-fine diameter.

Due to this particle size there is a problem of "dusting".

Therefore, it is common to make pellets from finely divided particles of carbon black to prevent "dusting."

Surprisingly, with the present invention, zinc oxide, for example, can be removed from such carbon black pellets without adversely affecting the physical integrity of the pelletized carbon blank.

That is, after the pelletized carbon black is subjected to an instant process, the pelletized carbon black does not lose its shape.

However, while pelleted carbon black may lose its strength, it does not lose so much that dusting becomes a problem.

It is an object of the present invention to prepare carbon black mixed with zinc oxide and sulfur in finely divided or pelleted form from at least 732°C, preferably from 750°C to about 10°C.
This is achieved by contacting with anhydrous chlorine gas or hydrogen chloride gas at a temperature of 00°C or 1200°C.

Surprisingly, when using chlorine or hydrogen chloride gas at such temperatures, at least 18% of the zinc contaminants in the carbon black can be removed, and in fact more than 99% by weight of zinc can be removed using the method of the present invention. Removed.

Substantially all of the zinc removed can be recovered and recycled.

Although the amount of chlorine gas or hydrogen chloride gas used to purify the zinc or zinc oxide-contaminated carbon black can vary widely, one of the objectives of the present invention is to ensure that all or most of the zinc oxide or zinc oxide is removed. Therefore, it is preferred to contact the carbon black with at least a stoichiometric amount of chlorine gas or hydrogen chloride gas, since the goal is to remove most of the carbon black.

Preferably a stoichiometric excess of chlorine is contacted with the carbon black.

The actual amount of chlorine contacted with the carbon black can be determined by testing the emitted vapor with potassium iodide, which indicates whether free chlorine is present in the volatile gas.

The presence of free chlorine indicates that nearly all of the zinc or zinc oxide has been removed as volatile zinc chloride.

The reaction between zinc oxide and chlorine, in the presence of carbon,
It is as follows.

3ZnO+3C12+2C→3ZnC12+CO+CO
2 It is therefore necessary to use at least 1 mole of chlorine for every mole of zinc oxide present in the ash.

It is also necessary to use at least about 90 parts by weight of chlorine for every 100 parts by weight of zinc oxide.

However, because of the relatively small amount of zinc oxide present, some chlorine will not react with the zinc oxide and at least an equal amount of chlorine must be used for every weight of zinc oxide present.

Generally, for each hundred parts of carbon black containing at least 3% by weight of zinc calculated as zinc oxide, at least 20 parts by weight of chlorine, and preferably at least 3% by weight of zinc.
It is necessary to use 0 or 40 parts by weight of chlorine.

There is no maximum amount of chlorine to use, since once the reaction is complete there is no difference in adding more chlorine, unless of course it is uneconomical to add more chlorine.

However, from a practical standpoint, it is generally not necessary to use more than 100 parts by weight for each 100 parts by weight of zinc-containing carbon black.

A more than stoichiometric excess of chlorine is preferred because a certain amount is retained within the carbon black and a certain amount reacts with the zinc and other oxides present in the carbon black that react with the sulfur if present. It's for a reason.

The above amounts ensure that substantially all zinc oxide and sulfur, if present, are removed.

In particular, gaseous anhydrous hydrogen chloride acts similarly to chlorine in the present invention.

Furthermore, the amount of hydrogen chloride required for use in the present invention is dependent on the amount of chlorine gas, since the molecular weight of hydrogen chloride is approximately half that of chlorine gas, and hydrogen chloride provides half the amount of chlorine as gaseous chlorine. Almost the same amount.

In practice, therefore, at least about 20 parts by weight of hydrogen chloride should be used per part by weight of the carbon black containing zinc oxide and optionally sulfur.

It is preferred to use at least 30, or even 40 parts by weight of hydrogen chloride for each 100 parts by weight of carbon black to ensure that substantially all of the zinc and, if present, sulfur is removed from the carbon black.

Also, as noted above in connection with chlorine gas, the maximum amount of hydrogen chloride that is generally required is 100 parts by weight of chlorine for each 100 parts of carbon black.

As mentioned above, the temperature at which the anhydrous gaseous chlorine or anhydrous gaseous hydrogen chloride contacts the carbon black is at least about 732° C., preferably at least 750° C.
The boiling point of zinc chloride is 732°C).

There is no maximum temperature from purely theoretical considerations, but 1000℃
It was also found that there is no reason to exceed 1200°C.

Since the reaction between zinc oxide and chlorine or hydrogen chloride is an exothermic reaction, it is relatively easy to maintain the temperature.

In the following examples, a type of rubber was used as the starting material to produce the laced carbon blank used in the preferred exemplary examples.

However, tramp carbon black can also be obtained from other sources, and the method of the present invention is effective in treating this type of carbon black.

In a preferred exemplary embodiment, the carbon black contains about 6% by weight zinc oxide and about 3% by weight sulfur, with the balance of the carbon black being carbon with small amounts of other oxides such as calcium oxide.

Since the carbon black was produced by pyrolysis of scrap rubber, all volatile substances were removed from the rubber.

Generally, carbon black was produced as follows.

The raw rubber, either as is or after crushing and drying, is fed to a rotating retort together with a heat-carrying solid.

The temperature of the solids is sufficient to heat the rubber to the pyrolysis temperature for about 3 to 10 minutes, and preferably 5 to 8 minutes.

Generally, the temperature of the heat-carrying solid is about 64°C when it enters the retort.
9°C (approximately 1200°F) and the thermal decomposition temperature achieved by the rubber is approximately 510°C to 538°C (approximately 950°P to
10000F).

After completing the pyrolysis, which is carried out in the absence of oxygen, the produced vapors (generally hydrocarbons) are separated from the solid char material.

This material consists of very fine particles with an average diameter of less than 1 micron, usually less than 0.5 micron, and is substantially free of coke and undecomposed rubber.

Specifically, this char material contains about 6% by weight zinc oxide and 3%
The main component is carbon black mixed with sulfur in weight percent.

Because of the "dusting" problems mentioned above, the fine particle size carbon black is formed into pellets about 3.2 mvt (about 1/8 inch) in diameter.

Reaction temperatures of 750° C. to 1000° C. or 1200° C. can be obtained by heating the carbon black in the reaction zone to a suitable temperature, or by heating the chlorine or hydrogen chloride to a suitable temperature, or both.

In a preferred exemplary embodiment, carbon black pellets obtained as described above are heated at about 375° in a nitrogen atmosphere.
Heat to temperature C.

The reason for using nitrogen or an inert atmosphere is to prevent oxidation of the carbon black, so as not to result in carbon black that is not useful for recycling purposes, such as adding carbon black to rubber to make rubber tires. .

The reaction zone in which the carbon black is placed is a horizontal or vertical furnace with a condenser at the outlet end of the furnace.

As described above, the carbon black is first heated to a temperature of 375°C in an inert atmosphere such as nitrogen.

After this temperature is reached, chlorine is added to the reaction zone (furnace) so that it is in intimate contact with the carbon black pellets placed in the reaction zone.

Generally, free chlorine does not appear until about 60 to 80 minutes later.

In all examples, except for one of the tests treated at 800° C., chlorine addition was continued for an additional 20 minutes after free chlorine appeared before the test was terminated.

One of the tests treated at 800°C was (test number 3 in the following table)
), the test was terminated immediately after free chlorine appeared in the outlet gas.

Table 1 below shows the temperature at which the tests were carried out, the amount of carbon black in parts by weight charged to the reaction zone, the amount of chlorine added in parts by weight, and the length of the run in minutes.

It should be noted that in the tests for free chlorine gas, a potassium iodide scrubber connected to a condenser was used.

This scrubber collects the leaving gas and indicates that chlorine is present.

The reaction temperature is reached by heating the furnace after chlorine gas is actually introduced into the furnace.

In Table 2 below, the results of zinc extraction and sulfur extraction are shown in weight percent.

The feed material carbon black is 6.16 as zinc oxide.
Contains weight percent zinc and 3.06 weight percent sulfur.

From Table 2, it can be seen that almost all the zinc was extracted from the carbon black and about 50 percent of the sulfur was extracted.

Furthermore, the pelletized carbon black in contact with chlorine retains its physical shape and integrity and can be used, for example, in the manufacture of rubber tires.

As described above, volatile zinc and sulfur chloride were produced by the reaction.

Zinc chloride was recovered separately from sulfur chloride by fractional condensation.

Using this type of process, all of the zinc chloride can be recovered and recycled to produce useful products.

To remove chlorine from carbon black, which is not necessary at all for recycling the carbon black, ammonia is added to the carbon black at 800° C. to remove any chlorine retained in the carbon black.

In a preferred exemplary embodiment, only chlorine is used, but similar results can be obtained using gaseous anhydrous hydrogen chloride.

Claims (1)

Claims: 1. In removing zinc and, optionally, sulfur-entrained carbon black pellets from the pellets without adversely affecting the pellets, the method comprises: (a) having an average diameter of about 1 micron or less; forming carbon black pellets from very fine carbon blank particles mixed with 3% by weight zinc calculated as zinc oxide and optionally mixed with at least 1% by weight sulfur; (b) said mixed carbon black; contacting the pellets with an anhydrous gas selected from the group consisting of chlorine and hydrogen chloride at a temperature of at least 732°C to produce gaseous zinc chloride and, optionally, sulfur chloride; (C) carbon black; A method for removing zinc from a zinc-containing carbon blank, characterized in that it comprises the steps of separating gaseous zinc chloride and, optionally, sulfur chloride from the pellets.The contact temperature is between 7328C and 1200C.Claim 1 The method described in section. 3. The method according to claim 2, wherein the contact temperature is 750°C to 1000°C. 4. The method of claim 1, wherein the amount of anhydrous gas is at least 20 parts by weight per 100 parts by weight of carbon black. 5. The method of claim 4, wherein the amount of anhydrous gas is about 20 to 100 parts by weight per 100 parts by weight of carbon black. 6. The method according to claim 4, wherein the anhydrous gas is chlorine. 7. The method according to claim 1, further comprising the step of separating zinc chloride from (c+) sulfur chloride.