Partial Oxidation Process

This invention relates to the partial oxidation of ash-containing liquid hydrocarbonaceous materials, ash-containing petroleum coke, or both to produce gaseous mixtures comprising H.sub.2 +CO. More particularly it pertains to the partial oxidation of ash-containing fuel comprising a liquid hydrocarbonaceous material, petroleum coke or both to produce synthesis gas along with molten petroleum coke ash having a reduced ash fusion temperature.

The partial oxidation of liquid hydrocarbonaceous fuels such as petroleum products and slurries of solid carbonaceous fuels such as coal and petroleum coke as well known processes. The foreseeable trend for petroleum reserves is that the produced crude will be increasingly heavier and of poorer quality. To compensate for this trend, refiners must employ more "bottom of the barrel" upgrading to provide the desired light products. The current industry workhorse to provide this upgrading is some type of coking operation (either delayed or fluid). A good deal of current refinery expansion includes the installation or expansion of coker units, and thus, coking will be a process of general use for some time to come.

A major drawback for coking is the disposal of the product coke. With a reasonably clean coker feed, the product coke has been substituted for applications requiring only relatively pure carbon, such as electrode manufacture. However, with the feed crudes becoming poorer, there are compounding factors affecting coker operations. First, since the crudes contain more contaminants, i.e. sulfur, metals (predominately vanadium, nickel and iron), and ash, and these contaminants are concentrated in the product coke, this coke is of a much poorer quality and is excluded from its normal product applications. Second, because the crudes are heavier, i.e., contain more coke precursors, more of this poorer quality coke is produced from each barrel of feed crude. The manufacture of petroleum coke pellets by a delayed coking process is described in coassigned U.S. Pat. No. 3,673,080. A fluid coking process is described in U.S. Pat. No. 2,709,676.

The Texaco partial oxidation gasification process offers an alternative processing route for the coke. For example, water slurries of petroleum coke are reacted by partial oxidation in coassigned U.S. Pat. No. 3,607,157. Gasification is often cited as a convenient means of coke disposition. The decision to use gasification as a coke disposal means is generally based on economics. The expected rise in energy costs and legislation (primarily Canadian) requiring total use of feed crude should bring about a greater utilization of petroleum coke feeds to the partial oxidation gas generator.

Previous gasification runs with delayed coke gave rise to some unexpected operating problems. The ash, which normally melts and is discharged from the gasifier as a slag, was not melting completely and being discharged from the gasifier as a slag, but was building up on the walls of the refractory. The use of fluxing additives normally used for coal operations did not alleviate the problem. By the subject invention, the ash from the liquid hydrocarbonaceous fuel and/or solid carbonaceous fuel is combined with an ash fusion temperature reducing agent and the total ash produced from this combination of materials is easily removed from the partial oxidation reaction zone as molten slag at a lower temperature.

In accordance with the invention there is provided a process for the production of gaseous mixtures comprising H.sub.2 +CO comprising: (1) mixing togehter (i) an ash fusion temperature reducing agent principally comprising about 50.0 wt. % or more, such as least 50.0 wt. %, say about 50-80 wt. % of a manganese compound, and the remainder of said agent comprising a silicon compound with (ii) ash-containing fuel comprising a liquid hydrocarbonaceous material and/or ash-containing petroleum coke; wherein the particle size of said mixture is preferably such that substantially all of the material passes through a sieve of the size in the range of ASTM E11 Standard Sieve Designation 425 .mu.m (microns) to 38 .mu.m (microns), or below, and the weight ratio of said ash fusion temperature reducing agent to ash in said ash-containing fuel is in the range of about 0.5-10; (2) reacting said mixture from (1) at a temperature in the range of about 2100.degree. F. to 2700.degree. F. and a pressure in the range of about 1 to 200 atmospheres in a free-flow partial oxidation reaction zone having a refractory lining with a free oxygen containing gas in the presence of a temperature moderator to produce a hot raw effluent gas stream comprising H.sub.2 +CO along with molten ash having a reduced ash fusion temperature; and (3) separating said molten ash from said hot raw effluent gas stream. In another embodiment of the invention, the comminuted ash fusion temperature reducing agent is mixed with an ash-containing heavy liquid hydrocarbonaceous material and coked. The resulting ash-containing petroleum coke containing dispersed throughout said ash fusion temperature reducing agent is then introduced into the partial oxidation reaction zone in (2) above. By the subject process, the initial ash fusion temperature for the ash derived from the partial oxidation of the ash-containing liquid hydrocarbonaceous material and/or ash-containing petroleum coke may be reduced in the range of about 100.degree. F. to 600.degree. F. Partial oxidation gas generators may now be run in the slagging mode at lower temperatures. The life of the refractory lining of the reaction zone is thereby extended at a great cost savings.

Closer study of the ash derived from the partial oxidation of liquid hydrocarbonaceous fuels and/or pertroleum coke shows that they are largely composed of oxide and sulfide compounds of vanadium, nickel, iron, along with some normally occurring mineral matter species similar to that found in coal mineral matter. The metals present in the ash provide a system that is significantly different from that occurring in coal. A further factor is that the total ash content of the petroleum coke may only be about one half to 5 weight percent, whereas coal typically contains 10-20 weight percent ash. The comparatively low ash concentration in petroleum coke apparently is the reason that the ash removal problem is only noticed after prolonged gasifier runs. The chance for effective ash/additive mixing that is necessary to achieve ash fusion temperature modification is therefore greatly reduced. Moreover, it is theorized that in the liquid hydrocarbonaceous material and petroleum coke systems, a good deal of the ash materal is liberated as individual molecular species. This is because upon vacuum distillation or coking, the metallic species in the crude, which are generally presented as porphyrin type structures (metal atoms, oxides or ions thereof confined in an organic framework), are entrapped within the collapsed carbon matrix. This invention provides an improved ash fusion temperature reducing agent. Further, a means of introducing this agent into the system to give maximum effectiveness is provided.

By definition, the term ash-containing liquid hydrocarbonaceous material or fuel is a petroleum or coal derived fuel selected from the group consisting of virgin crude, reduced crude, vacuum tower bottoms or feeds, residual fuel oil, decanted oil from a catalytic cracker, heavy fuel oil slurry, heavy gas oils, asphalt, tar sands bitumen, shale oil, coal derived oil, and mixtures thereof.

A preferred embodiment of the subject invention involves mixing the improved communicated ash fusion temperature reducing agent with ash-containing liquid hydrocarbonaceous fuel, or comminuted ash-containing petroleum coke, or both and introducing the mixture into the partial oxidation gasifier. In another embodiment the comminuted ash fusion temperature reducing agent is mixed with the liquid hydrocarbonaceous material and first fed into a coker. By this means, the finely ground agent may be intimately mixed throughout the petroleum coke product. The petroleum coke contains uniformly dispersed therein sufficient ash fusion temperature reducing agent to provide a weight ratio of ash fusion temperature reducing agent to the ash in the ash-containing fuel in the range of about 0.5 to 10.0. The preferable particle size of the mixture of comminuted ash fusion temperature modifying agent, the comminuted petroleum coke and mixtures thereof is such that substantially all e.g. about 95 wt. % or more of the material passes through a sieve of the size in the range of ASTM E-11 Standard Sieve Designation about 425 .mu.m to 38 .mu.m, or below. In another embodiment, the ash-containing petroleum coke is ground together with the ash fusion temperature reducing agent. Intimate mixing of the materials is thereby achieved, and the particle sizes of each material are substantially the same. The ground mixture is then mixed with water or a liquid hydrocarbonaceous material or both to produce a pumpable slurry. Alternatively, the solid materials may be wet ground with the liquid slurry medium. This slurry is then introduced into a partial oxidation gasifier. The mixture of ash fusion reducing agent and ash-containing fuel is introduced into the free-flow partial oxidation zone and reacted at a temperature in the range of about 2100.degree. F. to 2700.degree. F. and a pressure in the range of about 1 to 200 atmospheres with a free-oxygen containing gas in the presence of a temperature moderator to produce a hot raw effluent gas stream comprising H.sub.2 +CO e.g. synthesis gas along with molten ash having a reduced initial deformation temperature in comparison with that of the molten ash produced by the partial oxidation of the ash-containing fuel without being mixed with ash-fusion temperature reducing agent. Preferably, the communuted mixture of ash fusion reducing agent and ash-containing fuel is introduced into the gasifier as a pumpable slurry including water or liquid hydrocarbonaceous fluid, or mixtures thereof. The solids content of the slurry is in the range of about 50-68 weight percent. Alternatively, the mixture may be entrained in a gaseous transport medium. The gaseous transport medium may be selected from the group consisting of steam, CO.sub.2, N.sub.2, free-oxygen containing gas, and recycle synthesis gas.

In the embodiment where the ash fusion temperature reducing agent is mixed with the liquid hydrocarbonaceous material and fed into a coker, the actual operation can be accomplished for example by mixing the agent into the ash-containing petroleum liquid feed to the vacuum distillation tower, which normally precedes the coker unit. In either unit operation (coking or distillation), the agent should predominately stay behind in the desired bottoms stream. In other words, there should be little, if any, carry over of agent with the lighter products. A possible advantage for mixing the agent into the vacuum tower feedstream in preference to the bottoms stream (i.e. coker feed) is that the feed to the vacuum tower is significantly less various than the bottoms from the vacuum tower. A more thorough mixing may be thereby effected.

In one embodiment a mixture of high boiling liquid petroleum i.e. liquid hydrocarbonaceous fuel and comminuted coke ash fusion temperature reducing agent at a temperature in the range of about 650.degree. F. to 930.degree. F. is introduced into a delayed coking zone, such as shown and described in coassigned U.S. Pat. No. 3,673,080, which is incorporated herein by reference. At a temperature in the range of about 800.degree. F. to 895.degree. F. and a pressure in the range of about 20 to 60 psig, uncondensed hydrocarbon effluent vapor and steam are removed overhead and petroleum coke is removed from the bottom of said delayed coking zone. Alternatively, the mixture of high boiling liquid petroleum and comminuted coke ash fusion temperature reducing agent at a temperature in the range of about 550.degree. F. to 750.degree. F. may be introduced into a fluidized bed coking zone for example by way of line 31, such as shown and described in U.S. Pat. No. 2,709,676, which is incorporated herein by reference. At a temperature in the range of about 1000.degree. F. to 1200.degree. F. and a pressure in the range of about 10 to 20 psig, uncondensed hydrocarbon effluent vapor and steam are removed overhead and said petroleum coke is removed from the bottom of said coking zone.

By definition, ash from liquid hydrocarbonaceous material or petroleum coke ash comprises mostly the oxides and possibly the sulfides of Ni, V, Fe, Al and Ca along with the oxides of Si and a minor amount of the oxides selected from the group consisting of Ti, Cr, and mixtures thereof. While the metal concentrations in the liquid hydrocarbonaceous material may comprise Ni 0.5 to 610 ppm (parts per million), V 2.0-1500 ppm, Fe 0.5 to 750 ppm, along with Si, Al and Ca 0.5 to 750 ppm each; the metal concentrations in the petroleum coke product may comprise Ni 2.0 to 3100 ppm, V 8.0 to 7400 ppm, Fe 2.0 to 380 ppm, and Si, Al and Ca 2.0 ppm or more. For example, the silicon content of petroleum coke made from syncrude derived from heavy oil sands may be greater than 7,000 ppm.

Another aspect of this invention is that the ash fusion modifying agent involved may be selected on the basis of serendipitous catalytic properties in addition to their primary function of ash fusion modification. They may act to produce more and/or better quality light products from the coker operation. They may also aid in the gasification reactions either by increasing the reaction rate and thus the throughput capacity of the gasifier or by increasing the conversion of the soot and thus the overall efficiency of the process. Again, however, this invention does not depend on the catalytic properties of the agent.

It was unexpectedly found that a preferred ash fusion temperature reducing agent for mixing with the ash-containing fuel comprising liquid hydrocarbonaceous material and/or petroleum coke comprises a comminuted pyrolusite ore in admixture with a comminuted silicon compound. The following elements are present in a typical pyrolusite are in weight percent (basis ore): manganese in the range of about 50-75, calcium in the range of about 0-10, silicon in the range of about 0-3.0, magnesium in the range of about 0-10, and aluminum in the range of about 0-1.0.

Thus, the comminuted ash fusion temperature reducing mixture principally comprises about 50.0 wt. % or more, such as at least 50.0 wt. %, say about 50-80 wt. % of a manganese compound, and the remainder comprises a silicon compound. The manganese compound may be selected from the group consisting of oxides, carbonate, nitrate, acetate, silicate, sulfate, sulfide, and mixtures thereof. MnO is a preferred oxide. The silicon compound may be selected from the group consisting of silica, quartz, volcanic ash, and mixtures thereof. SiO.sub.2 is preferred. The particle size of said coke ash fusion temperature mixture is such that preferably substantially all e.g. about 95 weight percent, or more of the material passes through a sieve of the size in the range of ASTM E-11 Standard Sieve Designation 425 .mu.m to 38 .mu.m, or below.

The weight ratio of ash fusion temperature reducing agent to ash in the ash-containing fuel comprising liquid hydrocarbonaceous material and/or petroleum coke is in the range of about 0.5 to 10, such as about 1 to 3. In the aforesaid ratio, the ash-containing fuel to be analyzed for ash is ashed under standard conditions and ignited to constant weight e.g. American Society For Testing and Materials (ASTM) D482 and D3686. The weight ratio of MnO to SiO.sub.2 in the molten ash from the partial oxidation gasifier is about 1.0 to 4.0, such as about 1.3 to 3.0.

In other embodiments, this invention may be applied to other similar petroleum processes that produce a stream suitable for gasification. Any "bottom of the barrel" process that does not upgrade the bottoms or residue stream to extinction must ultimately produce such a stream. These streams, either liquid or normally solid but pumpable at elevated temperatures will produce the same gasification problems as discussed for coke. Thus, the invention of introducing an ash fusion temperature reducing agent as part of the petroleum processing prior to gasification should, depending on the specific process, produce a gasified feed that will be free of the gasification problems mentioned above. Most of these processes employ vacuum distillation as pretreatment. Accordingly, as described above, the ash fusion temperature reducing agent may be mixed into the vacuum distillation feed. The agent then will emerge from the distillation in the bottoms stream. In turn the bottoms stream is the feed stream for the upgrading process. This incorporation of the agent should not adversely affect these processes, and the agent should ultimately emerge with the residue stream from each respective process. In all of these processes, this residue stream should be suitable for gasification by partial oxidation.

The ash-containing fuel and ash fusion temperature reducing agent are reacted with a free-oxygen containing gas e.g. air, oxygen-enriched air, substantially pure oxygen, in the presence of a temperature moderator e.g. H.sub.2, CO.sub.2, N.sub.2, in the refractory lined partial oxidation synthesis gas generation zone at an antogenous temperature in the range of about 2100.degree. F. to 2700.degree. F., such as about 2150.degree. F. to 2400.degree. F., and a pressure in the range of about 1 to 200 atmospheres, such as about 6 to 60 atmospheres. The molten slag droplets are readily separated from the hot effluent gas stream leaving the reaction zone by gravity or by quenching and/or scrubbing the gas stream with water or other gas scrubbing medium. By this means, synthesis gas substantially comprising in mole % dry basis H.sub.2 25 to 45, CO 20 to 50, CO.sub.2 5 to 35, CH.sub.4 0.06 to 8.0, and CO.sub.2 +H.sub.2 S 0.1 to 2.0 may be produced in a free-flow partial oxidation reaction zone, such as that shown and described in coassigned U.S. Pat. No. 3,607,157, which is incorporated herein by reference. The molten ash entrained in the hot raw effluent gas stream comprising H.sub.2 +CO has an initial ash deformation temperature in the range of about 2100.degree. F. to 2700.degree. F., such as about 2150.degree. F. to 2400.degree. F. This is a reduction in the range of about 100.degree. F. to 600.degree. F. in comparison with the initial deformation temperature of the molten ash produced by the partial oxidation of the ash-containing fuel without admixture with ash-fusion temperature reducing agent.

Advantages of the present invention are illustrated by the following specific examples. These examples are set forth for purpose of illustration and should not be construed as limiting the invention.

Run No. 1--The initial deformation temperature of ash produced by the partial oxidation of aqueous slurries of petroleum coke and referred to hereafter as "coke ash from the gasifier" was determined to be greater than 2700.degree. F. when tested according to ASTM Test Method D-1857. The petroleum coke feed to the partial oxidation gas generator was derived from the delayed coking of Alaskan heavy crude. The particle size of the ash-containing petroleum coke feed to the gas generator was such that substantially all of the material passed through a sieve of the size in the range of ASTM E-11 Standard Sieve Designation 425 .mu.m to 38 .mu.m, or below. The ash content of the petroleum coke was 0.4 wt. %.

Run No. 2--As shown in Table I, column 2, various other materials were prepared and tested such as 100 wt. % SiO.sub.2, 100 wt. % pyrolusite, and mixtures thereof. These materials were tested for ash fusion temperature and the results are reported in columns 3-5.

In accordance with ASTM Test Method D-1857, the initial deformation temperature, was determined for the coke ash from the gasifier (No. 1) and the components of the additive (Numbers 2 and 3). Further, the initial deformation temperature, softening and fluid temperatures were determined for the additive mixture (No. 4) and the mixture of 3 parts by weight of additive for each part by weight of coke ash from the gasifier (No. 5). The data show that the initial deformation temperature of coke ash from the gasifier of greater than 2700.degree. F. is reduced by about 432.degree. F. by the addition of the subject petroleum coke ash fusion temperature reducing agent.

Accordingly, when the subject ash fusion reducing mixture are introduced into a partial oxidation gas generator in admixture with the ash-containing coke feed, gaseous mixtures comprising H.sub.2 +CO and molten ash having a reduced ash fusion temperature are produced. The gas generator may now be run in the slagging mode at lower temperatures. The subject ash fusion reducing mixture has a minimal interaction with the liner during shut down where the partial pressure of oxygen is high. The life of the refractory lining of the reaction zone is thereby extended at a substantial cost savings.

Although modifications and variations of the invention may be made without departing from the spirit and scope thereof, only such limitations should be imposed as are indicated in the appended claims.