US2814588A - Purification of petroleum coke - Google Patents

Description

Nov. 26,v las/7 LE Rol E. HuTcHlNGs PURIFICATION OF PETROLEUM COKE Filed May 10, 1956` United States Patent PURIFICATION OF PETROLEUM COKE Le Roi E. Hutchings, Crystal Lake, Ill., assignor to The Pure Oil Company, Chicago, Ill., a corporation of Ohio Application May 10, 1956, Serial No. 584,059

3 Claims. (Cl. 202-31) This invention relates to a method of purifying petroleum coke and, more particularly, to the removal of Sulfur and nitrogen compounds from petroleum coke by hydrogenation at temperatures of at least about 900 F. and pressures greater than 1000 p. s. i. g.

Naturally occurring sulfur and nitrogen compounds found in petroleum coke are known to have a deleterious effect when the coke is used in certain applications such as metallurgie electrodes. For this reason it is desirable that the sulfur compounds and nitrogen compounds be removed. However, little is known as to the form in which sulfur exists in petroleum coke, but there is evidence to show that compounds such as mercaptans, suldes, thiophanes, thiophenes and disuldes are the products of the decomposition of different high molecular weight sulfur compounds originally present in the crude oil. The amount and kinds of sulfur compounds present in petroleum coke depend upon the amount of total sulfur in the asphalt from which the coke is prepared and the manner of its preparation. When asphalt is converted to coke there is a general degradation of the majority of sulfur compounds with the evolution of hydrogen sulfide, leaving a residual quantity of sulfur and nitrogen compounds which is diicult to remove and is highly undesirable as far as the end characteristics of the coke are concerned. Numerous methods have been proposed for the production of low sulfur, solid carbonaceous fuels. In general, many of these methods relate to coal desulfurization and the principal problem is sulfur removal without excessive conversion of the coal into gas or vapor. Furthermore, the pressures and temperatures used are not sufficient for the treatment of petroleum coke and these processes are concerned with the preparation of a non-coke product. In addition, these processes directed to the desulfurization of coal do not effect a sucient reduction in the sulfur and nitrogen content to vbe effective for use in petroleum coke desulfurization.

It is reported in the prior art that coke may be desulfurized by the use of a catalyst and through treatment at temperatures ranging from 1340" to 1600 F., using oxidizing, reducing or inert atmospheres. Such materials as nitrogen, carbon 4dioxide, carbon monoxide, methane, ethylene water gas, anhydrous ammonia, and hydrogen have been used and studied in connection with sulfur reduction. It has been reported that hydrocarbon gases are most eicient in this respect. However, carbon is formed from these gases and interferes with subsequent sulfur determinations. I have been unable to reproduce the data reported in the art except when samples known to be contaminated with such outside carbon have been analyzed. Several other investigators concerned with the use of various atmospheres for the reduction of sulfur in petroleum coke have concluded that the presence or absence of an oxidizing or reducing atmosphere does not influence the reaction one `way or the other.

In accordance with the present invention, it has been found that petroleum coke can be elfectively desulfurized by the use of hydrogen at relatively low temperatures and under high pressure. I have found further that the other desulfurizing atmospheres described in the prior art are ineffective. For example, ethylene when used at atmospheric pressure and temperatures of about l700 F. is an ineffective desulfurizing atmosphere. The same may be said for oxygen and the other gases enumerated when used at pressures under atmospheric pressure and under conditions of elevated temperature. It has been found that the greatest amount of desulfurization per unit of time takes place when the coke is subjected to high hydrogen pressures of at least 1000 lbs. per square inch at the reaction temperature, While the coke is maintained at temperatures of at least about 900 F. and preferably about 1000 F. The degree of removal of sulfur and other compounds is directly related to the temperature, the hydrogen pressure and the Contact time. A further advantage of the invention is that in addition to reducing the sulfur and nitrogen contents, the present process yields hydrocarbon liquids, gases, semi-liquids, or highly viscous fluids and ammonia as by-products. If the higher temperatures disclosed in the prior art were used, many of these valuable compounds would be destroyed. The process is also effective for the removal of water and volatile materials originally present in the coke. Accordingly, a primary object of the invention isY to provide a process for the removal of `sulfur compounds from petroleum coke by high pressure hydrogenation at temperatures of at least 900v F.

A second object of the invention is to provide a process for the removal of sulfur compounds and nitrogen compounds from petroleum coke by treatment with hydrogen at temperatures between about 900 F. and 1050 F. using hydrogen pressures of at least 1000 lbs. per square inch at the reaction temperatures.

A further object of the invention is to provide a process for preparing coke for use in the manufacture of metallurgie electrodes which contains a certain minimum amount of sulfur compounds. v

These and further objects of the invention will be described or become apparent as the description thereof proceeds.

The drawing is a simplified schematic flow diagram `that may be used to illustrate the process.

.chamber 6. The residencetime in the reaction vchamber 6 may vary from less than 1 hour to several hours, depending on the temperature and degree of desulfurization desired. The reaction chamber is Well insulated and all heat is supplied by the circulating gases from line 8. The gases and reaction products pass out through the top of the reactor via line 11 and to condenser 12, which is operated at about atmospheric or elevated pressure and at about 500 F. If desired, a dust separator (not shown) may be provided within line 11 to separate any coke particles that may be carried over and return same to the reactor. Waxy and resinous materials are removed in condenser 12 as indicated at line 13. The gases from condenser 12 pass via line 14 to Warm condenser 15, which is operated at about 212 F. for the removal of any heavy liquid products at line 16.` 'Ihe remaining gaseous products pass through line 17 to cold condenser 18 operated at normal cooling water temperatures. Condenser 18 may be refrigerated to recover light liquids and a water solution of NH3 and H28, which pass via line 19 `to separator 20 wherein the water solubles collect as a lower phase and the light liquids as an upper phase. Additional water may be used to scrub these gases. The water solubles are collected through line 21 and the light liquid at line 22. The remaining gases, comprising principally hydrogen, are drawn ol at line 23 for recycle via line 24 through compressor 25 and line 26 to furnace 7.` Part of the oil-gases may be discarded via line 27 to prevent a build-up of inerts and methane. Additional hydrogen is added via makeup H2 line 28. In the furnace the gases are heated to the desired temperature, i.\e., about 1200 F. The amount of gas recirculated depends upon the heat losses, but in general will be about 4,000 s. c. f. per 100 pounds of coke. The temperature of the gases leaving reaction chamber 6 should be at least about 700 F. to prevent deposition of the heavier components` therefrom.

In order to demonstrate the invention, a series of experiments was `conducted wherein a petroleum coke was treated under various reaction conditions. The coke used in these experiments was largely from a sour crude obtained by coking a reduced crude in a normal refinery processing operation. Samples were ground to 100 mesh and iiner and treated with hydrogen in a rocking autoclave. The conditions were adjusted so that the time in minutes at which each sample was held at a particular temperature could be recorded. The results are shown in the following table:

Table Run No Feed 1 2 3 4 5 Time (min.) at:

Time, total, mmm- 140 205 285 490 225 Max. press., p. s. i. g.. i, 175 2,650 2, 475 2, 440 2,350 Sulfur, wt. percent--- 2.88 2. 88 1. 0.85 0. 1. 30 Nitrogen, wt. percent 1. 28 1.05

The pressure in the autoclave rose to the indicated maximum pressures during heating and then gradually decreased as hydrogen was consumed in the reaction. Inrun #4, of the grams of coke charged, containing 2.88% sulfur, about 15.6 grams of product were recovered which contained 0.53 weight percent of sulfur. This reduction was effected by the consumption of 2.8 grams of hydrogen at about 1000 F. and 2440 lbs. per square inch pressure for a total reaction time above 800 F. of 490 minutes. This represented the best product that was obtained. It will be observed from the foregoing experiments that, contrary to the prior art, low temperatures and very high pressures do effect a reduction of the sulfur content. It is apparent from the f t 4 experiments that the longer the coke is maintained at temperatures between about 1000 to 1015 F. the greater will be the desulfurization, provided the pressure is suiciently high, that is, at least about 1000 p. s. i. g. and preferably over 2000 p. s. i. g.

In carrying out the process of the invention, it is only necessary to bring the coke into intimate contact with an atmosphere containing at least about 10% by weight of hydrogen per unit weight of charge under conditions such that the coke and hydrogen are contacted at temperatures of at least about 800 F. to as high as 1050 F. within a reaction zone at a pressure of at least about 1000 lbs. per square inch at the reaction temperature. The coke may be grounded or pulverized into a granular or finely divided form and passed into the top of a reaction zone. Hydrogen under pressure and preheated to a temperature of about 900 to 1100 F. is introduced into the reaction zone at the bottom or at a plurality of points therein. The reaction zone may be fitted with independent means for bringing the coke to the reaction temperatures. The reaction, once under way, is endothermic, and heat must be supplied to maintain the reaction temperature and pressure. The desulfurized coke may be removed from the bottom of the reaction zone and passed to a cooling zone and then to conveyors for storage. The process may be carried out batchwise or in a continuous manner, using in the rst instance a static bed and in the latter a homogeneous or tluidized bed of coke in the reactor. One advantage of the process using high pressures is that it is amenable to continuous and cyclic ow of reactants through the reactor which makes industrial application economically attractive.

What is claimed is:

1. The method of desulfurizing petroleum coke containing about 3 Weight percent of sulfur which comprises subjecting said coke to hydrogenation at a temperature between about 900 F. to 1050 F. in the presence of at least about 10 weight percent of hydrogen per unit weight of said coke and maintaining said reaction at a temperature of about 985 F. to 1015 F. for a period of time ranging from about 2 hours to 6.5 hours at a pressure between about 2000 p. s. i. g. to 3000 p. s. i. g. during said reaction and recovering a desulfurized petroleum coke having a sulfur content of about 1.3 weight percent of sulfur or less.

2. The method in accordance with claim 1 in which said reaction is maintained at a temperature of 985 to l0l5 F. and a pressure of about 2475 p. s. i. g. for at least about 3 hours and a petroleum coke having a sulfur content of about 0.85 weight percent is recovered.

`3. The method in accordance with claim 1 in which said reaction is maintained at a temperature of 985 to 1015 F. at a pressure of about 2440 p. s. i. g. for at least about 6.5 hours and a petroleum coke having a sulfur content of about 0.53 weight percent is recovered.

McKinley et al. Dec. 6, 1955 Iahnig Apr. 24, 1956

Claims (1)

1. THE METHOD OF DESULFURIZING PETROLEUM COKE CONTAINING ABOUT 3 WEIGHT PERCENT OF SULFUR WHICH COMPRISES SUBJECTING SAID COKE TO HYDROGENATION AT A TEMPERATURE BETWEEN ABOUT 900*F. TO 1050*F. IN THE PRESENCE OF AT LEAST ABOUT 10 WEIGHT PERCENT OF HYDROGEN PER UNIT WEIGTH OF SAID COKE AND MAINTAINING SAID REACTION AT A TEMPERATURE OF ABOUT 985*F. TO 1015*F FOR A PERIOD OF TIME RANGING FROM ABOUT2 HOURS TO 6.5 HOURS AT A PRESURE BETWEEN ABOUT 2000 P. S. I. G. TO 3000 P. S. I. G. DURING SAID RACTION AND RECOVERING A DESULFURIZED PETROLEUM COKE HAVING A SULFUR CONTENT OF ABOUT 1.3 WEIGHT PERCENT OF SULFUR OF LESS.

Images