US3536477A

US3536477A - Production of nickel pellets

Info

Publication number: US3536477A
Application number: US683466A
Authority: US
Inventors: George Norman Flint; Stanley Charles Townshend
Original assignee: International Nickel Co Inc
Current assignee: Huntington Alloys Corp
Priority date: 1967-11-16
Filing date: 1967-11-16
Publication date: 1970-10-27
Anticipated expiration: 1987-10-27

Description

United States Patent Office 3,536,477 Patented Oct. 27, 1970 3,536,477 PRODUCTION OF NICKEL PELLETS George Norman Flint, South Ascot, England, and Stanley Charles Townshend, Swansea, Wales, assignors to The International Nickel Company, Inc., New York, N.Y., a company of Delaware No Drawing. Filed Nov. 16, 1967, Ser. No. 683,466 Int. Cl. B22f 9/00 U.S. Cl. 75-5 7 Claims ABSTRACT OF THE DISCLOSURE Carbonyl nickel pellets containing sulfur in controlled amounts and uniformly distributed throughout, which are particularly suitable for anodes in electrodeposition of nickel, are produced by decomposing nickel carbonyl in the presence of a sulfur-containing gas.

The present invention is directed to the production of nickel pellets and in particular to the production of nickel pellets by decomposition of nickel carbonyl.

Carbonyl nickel pellets are produced by the well known Mond process in which nickel carbonyl is thermally decomposed. The term pellets as used herein refers to substantially spherical particles which have average diameters ranging from about 4 millimeters to about 12 millimeters. The pellets derived from the Mond process are normally nickel of remarkable purity, every effort being made to prevent contamination by sulfur, since ths reduces the the ductility of nickel. The sulfur content of the Mond carbonyl pellets is less than 0.001%

It has now been discovered that the usefulness of carbonyl nickel pellets in electroplating processes can be increased by uniformly introducing controlled amounts of sulfur in the pellets.

It is an object of the present invention to introduce controlled amounts of sulfur uniformly throughout carbonyl nickel pellets.

It is a further object of the present invention to provide carbonyl nickel pellets which contain controlled amounts of sulfur uniformly distributed therethroughout.

Generally speaking, the present invention comprises simultaneously introducing nickel carbonyl and a sulfurbearing gas selected from the group consisting of carbonyl sulfide and hydrogen sulfide into a moving bed of nickel pellets preheated to at least the decomposition temperature of nickel carbonyl to produce nickel pellets with sulfur uniformly distributed therethroughout.

The moving bed of preheated nickel pellets can be established in apparatus and in a manner disclosed in UK. Pat. No. 620,287 or as disclosed in U.S. Pat. No. 3,220,875. It is to be understood that the term moving bed of preheated nickel pellets includes nickel powder which is periodically added to nucleate new pellets.

Although other sulfur-bearing gases can be employed, it has been found advantageous to employ carbonyl sulfide since the rate of decomposition of carbonyl sulfide and nickel carbonyl are such that the nickel and sulfur are deposited on the pellets in proportion to the amounts of each gas present. Thus, it is only necessary to introduce a volume of carbonyl sulfide calculated to give the desired sulfur concentration in the pellets. Surprisingly, sulfur dioxide and carbon disulfide are relatively ineffective.

The effectiveness of pellets as anodes is improved by very small amounts of sulfur introduced in this way, and advantageously the sulfur content is at least 0.005%. It is to be noted that all sulfur contents given herein are taken on a weight basis. Higher contents give smoother dissolution but lead to increased non-metallic sludge. Having regard to this, the sulfur content may be as high as 0.07% or even 0.1% but we prefer it not to exceed 0.03%. The optimum sulfur content of the nickel for use as anodes is from 0.012% to 0.014%, and to produce this the volumetric ratio of the nickel carbonyl and the carbonyl sulfide introduced into the decomposer should be from 4540:l to 3780: 1.

In the Mond process the nickel carbonyl is itself formed by the action of carbon monoxide on a roasted and reduced nickel matte or other nickel-bearing material, and the carbon monoxide usually circulates between a volatilizer and a decomposer. The use of carbonyl sulfide thus presents the further advantage that the carbon monoxide produced on decomposition mixes with that produced by the decomposition of the nickel carbonyl and is returned to the volatilizer without diluting the carbon monoxide in the circulating gas.

In an advantageous way of carrying out the Mond process the pellets pass through the decomposer in co-untercurrent to a mixture of nickel carbonyl and carbon monoxide. In one example gas containing nickel carbonyl at 70 C. enters a ceramic-lined decomposing chamber containing a mass of nickel pellets which have been preheated in a top compartment to from about 200 C. to about 240 C. Gas rises from a lower manifold and permeates the mass of pellets. In the process carbonyl is decomposed and the pellets are increased in size and are cooled, until they arrive at the bottom of the decomposing chamber where the temperature is from about C. to C. The gas on reaching the top of the decomposing chamber is withdrawn through an annular manifold. This gas is essentially nickel-free carbon monoxide and it is returned to volatilizing apparatus in which fresh nickel carbonyl is generated. At the bottom of the decomposing chamber there is a central opening which is controlled by a sliding gate. The nickel pellets pass through this opening into a compartment which has a conical bottom with a central opening from which a pipe runs. The pellets move down this pipe and drop onto the inclined bottom of a compartment from which they slide into a collecting chamber at the bottom of a bucket elevator. This takes the pellets up to a hopper from which they enter an inlet pipe and so are returned for further treatment to the decomposing chamber via the top pelletheating compartment when once again they fall in countercurrent to the rising nickel carbonyl gas. Pellets were produced in this way in an example which will now be given.

The gas mixture contained 8.4% Ni(CO) by volume, equivalent to 210 grams of nickel per cubic meter, and was fed at the rate of 90 cubic meters per hour. Carbonyl sulfide was introduced into the inlet gas stream at the rate of 2 liters per hour. Inside the decomposer the temperature of the nickel pellets was 200 C. In 24 hours 1000 pounds of nickel pellets of 0.014% sulfur content were produced.

One advantage of the use of carbonyl sulfide as distinguished from any other sulfur-containing gas such as hydrogen sulfide is that purging of the main carbon monoxide gas circuit between the volatilizer and decomposer to maintain a high carbon monoxide concentration is kept to a minimum, whereas hydrogen sulfide or other gas gives reaction products which have to be purged off together, of course, with some carbon monoxide.

The main advantage of the introduction of the sulfur into the nickel by means of the invention is the uniformity of the distribution of the sulfur with consequent reduction in the amount of sludge when the pellets are used as anodes in the electrodeposition of nickel. This advantage is clearly shown by comparison of the amount of the sludge (both total and metallic) from the dissolution of different sulfur-containing anode materials in electrolytic processes carried on under otherwise identical conditions.

Although the present invention has been described in conjunction with preferred embodiments, it is to be understood that modifications and variations may be resorted to without departing from the spirit and scope of the invention as those skilled in the art will readily understand. Such modifications and variations are considered to be within the purview and scope of the invention and appended claims.

We claim:

1. A process for the production of sulfur-containing carbonyl nickel pellets suitable for use as anodes in the electrolytic deposition of nickel which comprises simultaneouly introducing nickel carbonyl vapor and carbonyl sulfide gas into a moving bed of nickel pellets preheated to at least the decomposition temperature of nickel carbonyl to produce nickel pellets with sulfur uniformly distributed therethroughout.

2. A process as described in claim 1 wherein the nickel pellets preheated to a temperature between about 200 C.

and 240 C. are passed downwardly as a moving bed through a decomposing chamber until the pellets are cooled to about C. to C. and the nickel carbonyl and carbonyl sulfide are passed counter-currently to the downwardly moving bed of nickel pellets.

3. A process as described in claim 1 wherein the volumetric ration of nickel carbonyl to carbonyl sulfide is from about 454011 to 3780: 1.

4. Carbonyl nickel pellets which contain at least about 0.005% and less than about 0.1% sulfur uniformly distributed therethroughout and which are characterized by'smooth dissolution and minimal sludge production when employed as anodes in electroplating processes.

5. Carbonyl nickel pellets as described in claim 4 wherein the sulfur content is less than about 0.07%.

6. Carbonyl nickel pellets as described in claim 4 wherein the sulfur content is less than about 0.03%.

.7. Carbonyl nickel pellets as described in claim 4 wherein the sulfur content is between about 0.012% and 0.014%.

References Cited UNITED STATES PATENTS 3,220,875 11/ 1965 Queneau 117100 2,881,094 4/1959 Hoover 750.5

L. DEWAYNE RUTLEDGE, Primary Examiner W. W. STALLARD, Assistant Examiner US. Cl. X.R. 117-l00