US2927063A - Process for maintaining high level of activity for supported manganese oxide acceptors for hydrogen sulfide - Google Patents

Description

J. D. BATCHELOR ET AL A March 1', 1960 2,927,063 PROCESS FOR MAINTAINING HIGH LEVEL OF ACTIVITY FOR SUPPORTED MANGANESE OXIDE ACCEPTORS FOR HYDROGEN SULFTIDE 2 Sheets-Sheet 1 Filed 061:. 28, 1957 HIGH SULFUR FLUE GAS AND so REGENERATED 1 REGENERATION AIR l I G. l

SOLIDS ACCEPTOR SULFIDED ACCEPTOR SOLIDS CARBONACEOUS NET GAS DESULFURIZATION [l6 LOW SULFUR CARBONACEOUS HouRs 0F EXPOSURE TIME AT ELEVATED TEMPERATURE IOO' RECYCLE GAS INVENTORS JAMES D. BATCHELOR GEORGE P. CURRAN EVERETT GORIN March 1960 J. D. BATCHELOR ET AL 2,927,063

PROCESS FOR MAINTAINING HIGH LEVEL OF ACTIVITY FOR SUPPORTED MANGANESE OXIDE ACCEPTORS FOR HYDROGEN SULFIDE Filed Oct. 28, 1957 2 Sheets-Sheet 2 HIGH SULFUR NET CARBONACEOUS FLUE GAS GAS souos AND so 5 REGENERATED H ACCEPTOR 2o E l2 l2 0 g x13 IB L DESULFURIZATION REGENERATION E s 2,9 A I A s I6 I? SULHDED I7 l9 'Q ACCEPTOR LOW SULFUR 8 AIR CARBONACEOUS o 22 souos L E R FRESH 30 I NITRIC ACID I SUPPORTS 2 NON CONDENSI BLE NITRIC ACID GASES 4' 40 E.- A 36 1 24 2 MANGA SAIEJIESE FILTRATE LEACHING VESSEL CONTINUOUS FILTER 33x3 32 REIMPREGNATED 39 ACCEPTOR I Go 2 INVENTORS JAMES D. BATCHELOR GEORGE P. CURRAN EVERETT GORIN ATTORNEY 2,927,063 Patented Mar. 1, 1960 PROCESS FOR MAINTAINING HIGH LEVEL OF ACTIVITY FOR SUPPORTED MANGANESE X- lDE ACCEPTORS FOR HYDROGEN SULFIDE James D. Batchelor, Bethel Park, and George P. Curran and Everett Gorin, Pittsburgh, Pa., assignors to Consolidation Coal Company, Pittsburgh, Pa., a corporation of Pennsylvania Application October 28, 1957, Serial No. 692,865

12 Claims. (Cl. 20231) The present invention relates to a process for maintaining a high state of activity in supported manganese oxide acceptors for hydrogen sulfide. it relates to a process for removing sulfur contamination from carbonaceous solid materials by treatment with hydrogen in the presence of maganese oxide-type solid acceptors for hydrogen sulfide.

Such sulfur removal processes for carbonaceous solid fuels have been described in copending U.S. patent application S.N. 527,705, now U.S. Patent 2,824,047, filed August 11, 1955 by Everett Gorin, George P. Curran and James D. Batchelor, assigned to the assignee of the pres ent invention. A further process relating to surfur removal and calcining of carbonaceous solid fuel briquets has been described in copending U.S. patent application S.N. 635,278 filed January 22, 1957 by James D. Batchelor, Everett Gorin, George P. Curran and Robert J.

taining manganese oxide impregnated on an inert sup port.

More particularly,

According to that process, carbonaceous solid fuels containing sulfur are mixed with a solid material (termed an acceptor) which is capable of absorbing hydrogen sulfide. The mixtureis treated with hydrogen gas at a temperature above about 1100 F. whereby the hydrogen gas combines with the contaminating sulfur to form hydrogen sulfide; the hydrogen sulfide is absorbed in situ by the acceptor. Since the hydrogen sulfide is absorbed almost instantly upon formation, there is only a negligible partial pressure of hydrogen sulfide in the desulfurization zone for inhibiting the reactions whereby sulfur is removed from the carbonaceous solid fuels. The reaction mixture of solids is' separated into (a) product desulfurized carbonaceous solidfuels and '(b) the solid acceptor containing accepted sulfur. The acceptor may be regenerated and heated by contact with air to restore its hydrogen sulfide acceptor properties through elimination of previously absorbed sulfur. The heated regenerated acceptor, when mixed with relatively cool carbonaceous solid fuels preferably provides the heat necessary to raise the solids reaction mixture to a desulfurization temperature.

Where the sulfur-containing carbonaceous solid fuel is V in the form of finely divided particles (e.g., fluidized low Friedrich, assigned to the assignee of the present invention.

The presence of sulfur in carbonaceous solid fuels limits their use in metallurgical applications. Accordingly, most metallurgical fuels are obtained by employing low sulfur content starting materials, e.g., low sulfur coal is converted to low sulfur metallurgical coke. Sulfur removal processes of the type described in the aforementioned patent applications permit the use of high sulfur content fuels as starting materials for preparing low sulfur content carbonaceous fuels for metallurgical use. For example, the sulfur removal process may be provided as a treatment for the solid residue (termed char) resulting from low temperature carbonization of bituminous coal. Where fluidized low temperature carbonization processes are used, the finely divided, low density, porous char product is particularly amenable to those desulfurization treatments. The desulfurization treatment can be applied to any non-caking carbonaceous solid fuel such as cokes and chars. Coke from coal and hydrocarbonaceous residues (pitch coke), coke breeze, low temperature carbonization char from coal and lignite are exemplary. The processes cannot be applied to caking carbonaceous solid fuels such as caking coal since the thermal treatment encompassed in such processes would cause these materials to become sticky and form coked masses which would bind the acceptor solids, thus preventing their recovery for reuse in the process. Further the resulting coke would be contaminated with the acceptor solids; any sulfur transferred from the carbonaceous fuels to the bound acceptor solids would remain in the solid coke. The processes, however, are applicable to the desulfurization of carbonaceous briquets which may contain caking coal inter alia provided the thermal treatment is conducted to avoid severecaking and accompanying formation of large coke masses.

In the aforementioned copending application S.N. 527,705 solid carbonized carbonaceous fuels are desulfurized by treatment at elevated temperatures in the presence of hydrogen and a solid acceptor for hydrogen The equilibrium ratio sulfide. A preferred acceptor in this'proces's is one con- .Carbonaceous solid fuels contain sulfur in at least three forms. Some of the sulfur exists as readily removable sulfur which -is organically bound in the carbonaceous fuel. This organically bound sulfur can be removed from the carbonaceous solid fuels rather easilyby contact with hydrogen. If the readily removable organically bound sulfur is represented as C=S, the desulf ,furization reaction may be represented as follows:

Some of the sulfur-exists as inorganic-ally bound sulfur usually inthe form of metallic (principally iron) sulfide.

This. sulfur may. be-removed rather readily by treating the carbonaceous solid fuel with pure hydrogen gas. The

reaction (assuming iron sulfide) is as follows:

' FeS-l-H eH s-i-Fe for reaction is very low. Hence small quantities of hydrogen sulfide in the gas phase will inhibit the transfer of sulfur from the. solid to thegas. At 1350? F., for example, 0.12

volume percent of hydrogen sulfide in the hydrogen gas is the equilibrium value. At 1600 F., 0.28 volume per-' cent of hydrogen sulfide in the hydrogen gas is the equilibrium value. Thus in orderto remove inorganically bound sulfur effectively, the ratio of ,rnustbe maintained at an extremely low value, i.e., nearly 'purehydrogen must be used.

fur exists in the form of refractory organic material and various inorganic sulfides. While this sulfur theoretically can be removed by treatment of the carbonaceous solid fuels with pure hydrogen gas, nevertheless, even minute traces of hydrogen sulfide are sufiicient to inhibit the transfer of sulfur from the solids to the gas. Removal of the difficultly removable sulfur is not practicable under feasible processing conditions.

The ultimate desulfurization which can be achieved at any temperature depends upon the ratio of in the treating gases without regard to the absolute pressure of the reaction system. While greater absolute pressure increases the rate of desulfurization, it does not affect the ultimate level of sulfur in the treated solids. In accordance with these findings, satisfactory desulfuri zation rates may be achieved at temperatures above about ll F. with atmospheric pressure. Higher pressure accomplishes the same desulfurization in shorter time. A preferred pressure range for the desulfurization is about 1 to 6 atmospheres absolute.

It is possible to maintain a low value for the ratio by employing enormous quantities of hydrogen as a treating gas. For example, the use of 1000 molar volumes of pure hydrogen gas in removing one mol of sulfur would create an environment containing 0.10 volume percent of H 8 in H Alternatively, the ratio may be maintained at a low value by removing the H 8 from the vapor state as quickly as it is formed. The removal of H 8 from the vapor state can be accomplished by providing in a desulfurization zone a solid acceptor which has a greater aflinity for hydrogen sulfide than those materials with which the sulfur is bound in the carbonaceous solid fuels. A preferred solid acceptor is one containing manganese oxide, impregnated on an inert carrier. Suitable carrier materials include silica, alumina and silica-alumina preferably in the form of mullite (containing 75 to 85 percent alumina and the balance silica).

Acceptors containing manganese oxide are preferably prepared by soaking the inert carrier particles in an aqueous solution of a soluble manganese salt which thermally decomposes to leave a residue of manganese oxide. Manganese nitrate is a preferred soluble salt for this'purpose. The concentration of the aqueous solution should be suificient to deposit up to about 10 percent by weight of manganese on the carrier. The soaked carrier thereafter is heated to achieve dehydration and decomposition of the deposited manganese salt to the manganese oxide residue. The resulting acceptor should contain up to about 10 percent by weight of manganese, preferably from about 4 to about 8 percent.

Throughout the specification, the term manganese oxide refers to compounds containing manganese and oxygen, such as MnO, M11 0 Mn 'O MnO which compounds are principally in the form of MnO. The term higher oxides of manganese refers to compounds containing more than one atom of oxygen per ato'm of manganese, e.g., Mn O Mn O MnO- I The reaction of the manganese oxide in the disulfurization treatment is as follows:

MnO

Thus the manganese oxide combines with the generated hydrogen sulfide to form manganese sulfide thereby removing from the vapor phase the hydrogen sulfide formed by desulfurization of the carbonaceous solid :fueL

Thus in the overall process, the sulfur removed from the carbonaceous solid fuels is rejected from the system in the form of sulfur dioxide. So much of the process has been more fully described in the aforementioned application, S.N. 527,705.

The use of H 8 acceptors has been briefly described in relation to desulfurization processes for carbonaceous solid fuels. Such H 8 acceptors also can be used for removing H 5 from any gas stream, regardless of source. For example, elimination of H 8 from petroleum refinery gases, pipeline gas, and the like can be accomplished by passing the gases over an H s-acceptor containing manganese oxide. The H 5 will be absorbed by the acceptor and the manganese oxide converted to manganese sulfide. The sulfided acceptor can be regenerated by treatment with air to release sulfur dioxide and restore the manganese oxide.

The phrase H S-absorbing conditions as employed in this specification refers to a non-oxidizing environment containing H 8 at temperatures Where a favorable equilibrium exists for the reaction.

The preferred temperature range for H s-absorbing conditions is about 1100 to 1600 F. The ability of an acceptor to react with H 3 under fl S-absorbin'g conditions is an important determinant in the efiiciency of the fundamental desulfurization process.

We have found that repeated use of solid acceptors containing manganese oxide impregnated on silica, alumina or silica-alumina carriers results in deactivation of the acceptor. A brief discussion will explain the deactivation phenomenon.

Freshly impregnated acceptor so'lids will remove hydrogen sulfide gas from a vapor stream in intimate contact therewith at a determinable rate. Subsequent regeneration of the acceptor by reaction with air will restore the manganese oxide. However the regeneration necessarily is conducted at elevated temperatures which bring about the deactivation of the acceptor (under H s-absorbing conditions). When the regenerated manganese oxide acceptor is employed to remove hydrogen sulfide from a gas in contact therewith, a lower reaction rate will be observed. Repeated processing of the acceptor through the sulfiding and regenerating processes will result in further deactivation, i.e., a continued lowering in the rate at which the manganese oxide will remove hydrogen sulfide from a gas in contact therewith.

While the regenerated acceptor does not suffer a significant loss in its capacity to absorb hydrogen sulfide, thereis nevertheless a lowering in the rate at which the absorption of hydrogen sulfide occurs. Hence a distinction is made between (a) The capacity of a regenerated acceptor to absorb hydrogen sulfide and (b) The rate at which a regenerated acceptor will absorb hydrogen sulfide.

The capacity for hydrogen sulfide absorption depends upon the quantity of manganese oxide present, whereas the rate at which hydrogen sulfide can be absorbed depends upon a condition which is referred to herein as the acceptors activity under H s-absorbing conditions.

Hence the term deactivation refersto a lowering of'this activity and the term reactivation refers to an increasing of this activity.

Note that it is possible to have a fully regenerated acceptor (one in which all of the manganese sulfide has been converted to manganese oxide) although that acceptor is deactivated, i.e., the regenerated. acceptor will absorb H 8 only at a diminished rate. Should such a regenerated (deactivated) acceptor be exposed to H 8- absorbing conditions for a sufiiciently long period of time, the quantity of H 5 absorbed by it would depend solely on the quantity of manganese oxide which it contains. A reactivated, regenerated acceptor, on the other hand," would absorb the same quantity of H 8 in a shorter period of time. 1

It is believed that this deactivation of manganese oxide impregnated carriers results from'a physical migration of the manganese into the carrier itself The penetration of the manganese into the carrier may sometimes be accompanied by chemical reaction resultingin the formation of manganese silicates and aluminates. Any manganese thus converted is removed from the cyclic MnO-MnSMnOMnS et cetera reactions.

The principal object of the present invention is to pro is to provide a regeneration process for converting the manganese sulfide of a manganese impregnated acceptor to the desired manganese oxide with minimum deactivation of the acceptor. A still further object is'to' provide ;a desulfurization process which employs manganese impregnated acceptors which can be recirculated throughout the pro'cess through sequential sulfur absorbing and sulfur elimination without severe loss of activity (under H S-absorbing conditions).

Another object of this invention is to provide a proc ess for maintaining a high level of activity for manganese oxide acceptors which process also provides fresh acceptor to compensate for any loss of acceptor which may occur.

According to the present invention, a portion of the regenerated manganese acceptor followingfregeneration to the oxide form, is reactivated by leaching with a strong acid solution (preferably concentrated nitric acid) to restore the manganese to an aqueous soluble form for re-impregnation on the inert supports. The leaching is carried out at an elevated temperature of about. 50 to 200 C. in a confined vessel to prevent escape of acid vapors. Substantially all of the manganese contained in v the acceptor is dissolved in the strong acid solution in the form of aqueous soluble manganese salts. The acceptor solids at the same time are soaked in the strong acid solution of manganese salts, and thereby retain the desired quantity of manganese (up to about 10 percent by weight) in the form of manganese salts. 1 The soaked acceptor solids are recovered from the leaching stage and filtered from the manganese salt solution which 'is returned to the leaching stage for reuse. The filtered acceptor solids contain sufficient residual manganese saltsolution to provide the desired impregnation. The moist, filtered acceptor solids are heated to vaporize the residual acid solution and convert the absorbed manganese salts to manganese oxide. The gases and vapors are recovered and condensed. The condensed acid solution is available for reuse in the process. Where nitric acid is employed, some decomposition to non-condensible nitrogen oxide occurs. The uncondensed nitrogen oxides are recovered from the non-condensible gases by a water scrubbing treatment for reuse as nit'ricacid,

If desired, additional manganese compounds such as oxides or salts decomposable to oxides can be added to the acceptor stream under reactivation before or during the leaching treatment.v Additional inert supports also may be added before or during'the leaching treatment. to

"prepare additional acceptor fertile-process."

We prefer to use concentrated nitric acid in the'present process although other strong acids such as sulfuric and hydrochloric can be adapted to the process, Nitricacid is preferred because of the ease of decomposition of manganese nitrate to manganese oxide and further because of the relative ease of recovering the acid and the. nitrogen oxides (formedby its decomposition) for reuse.

Moreover, nitric acid is particularly eflective in the leach{ Figure 1 is a schematic flow diagram illustrating the reactivation process steps embodied in the present invention; and i I Figure 3 is a graphical representation of the activity loss for manganese oxide-type acceptors according to length of exposure to elevated temperatures.

The generalized flow sheet .of Figure 1 illustrates the manner in which an acceptor desulfurization process can be carried out in a continuous manner. A desulfurization zone.10 receives non-caking carbonaceous solids containing sulfur through a conduit 11 and regenerated ac-. ceptor solids through a conduit 12. In this instance, the active ingredient of the acceptor solids is manganese oxide. A. hydrogen-rich treating gas consisting essentially of hydrogen is introduced into the desulfurization zone 10 through a conduit 13'. .Additional gases, consisting of hydrogen gas, are autogenously produced through devolatilization of the carbonaceous solids at the elevated temperature of the desulfurization z one 10. Under preferred operating conditions the autogenously produced devolatilization gases will be in sufficient quantity to provide the full hydrogen requirements for desulfurization so that extrinsic hydrogen production is not required.

The desulfurization zone 10 is maintained at a tem-' perature from about 1100 to about 1600 F. Below about 1100 F., the desulfurization rate is low. Operation above about 1600 F. requires excessive heat and also promotes rapid deactivation of the acceptor. The pressure level preferably is high enough to provide a hydrogen gas partial pressure of at least one atmosphere. A total pressure of from one to 'six atmospheres ispreferred. I v .A typical char (containing sulfur) produced by fluidized. carbonization of Pittsburgh Seam coal at 950 F. yields devolatilization gases containing 58.6 percent .hy- .drogen and 24.8 percent methane at 1.3 atmospheresand 1350 F. The same char yields devolatilization gases containing 48.7 percent hydrogen and 32.9 percent methane at 3 atmospheres and 1350 F. v

- During, passage through the desulfurization zone 10, the treating gases remove sulfur from the carbonaceous solid fuels 'formin-g hydrogen sulfide. The H 8, upon formation, is at once absorbed by the solid acceptor and removed from the gas phase.

Gases are recovered from-the desulfurization zone'10 through a conduit 14 and recirculated through conduit 13 for further contact with carbonaceous solids undergoing desulfurization. A net product gas is removed through a conduit 15; i

The required residence of carbonaceous solids in the ldesulfurization zone 10 depends upon the lability of the contaminating sulfur and also upon the level of 'desul-' furization desired. It must be borne in mind that the 'ult'imate' sulfur level of the product is determined by the level of H 8 contamination which the manganese oxide will maintain. Where the hydrogen partial pressure of the treating gases is about one atmosphere or greater, satisfactory desulfurization can be achieved by subjecting the carbonaceous solids to the desulfurization conditions for a period of about three hours or less. In creased absolute pressure, as already pointed out, promotes more rapid desulfurization.

Desulfurized carbonaceous solids are removed from the desulfurization zone 10 as product through a conduit 16. Sulfided acceptor is removed from a conduit 17 and passed to an acceptor regeneration zone 18. Air is introduced into the regeneration zone 18 through a conduit 19 to raise the temperature of the acceptor through combustion of sulfur along with a portion of the carbonaceous solids commingled therewith and to remove sulfur therefrom through oxidation to sulfur dioxide.

The temperature within the regeneration zone 18 is maintained at about 1300 to 1600 F. Hot flue gases containing sulfur dioxide are removed from the regeneration zone 18 through a conduit 20.

Excessive oxidation in the regeneration zone 18 should be avoided in order to restrict the quantity of higher oxides of manganese produced. Ideally, some of the acceptor solids recovered from the regeneration zone should be in the form of MnS. By maintaining from about 2 to about 15 percent of the manganese as. MnS after regeneration, the oxides of manganese can be main tained principally in the form of MnO rather than as higher oxides such as Mn O or Mn O The presence of higher oxides of manganese in the desulfurization zone undesirably consumes hydrogen gas without accompanying sulfur removal as will be hereinafter described. In general, the amount of oxygen used in the regeneration zone 18 should be within about 20 percent of the stoichiometric quantity, which would be required for oxidizing all of the MnS to MnO according to the equation above.

Regenerated acceptor is returned to the desulfurization zone 10 through the conduit l2 without deliberate cooling to serve therein as a means for removing H 8 therefrom and to supply the heat requirements thereof.

When the desuifurization process is operated as described with an acceptor comprising manganese oxide impregnated on an inert carrier, deactivation of the acceptor will occur as a result of its thermal exposure. Accordto the present process as illustrated in Figure 2, the acceptor deactivation may be retarded. In Figure 2, the elements of the process relating to the desulfurization stage bear numerals corresponding to those of Figure 1. Corresponding numerals identify corresponding elements. Regenerated acceptor solids are introduced into the desulfurization stage 10 through a conduit 12. Sulfided acceptor solids comprising inert carriers containing manganese sulfide and manganese oxide are recovered from the desulfurization stage 10 through a conduit i7. The sulfided acceptor is regenerated in the usual manner by treatment with air at about 1300 to 1600 F. in the regeneration zone 18.

A portion of the regenerated acceptor solids is withdrawn from the conduit 12 through a conduit 21 and cooled in a heat exchanger 22. The cooled regenerated acceptor solids are introduced into a leaching vessel 24 through a conduit 23 either continuously or batchwise. The leaching vessel 24 is constructed of materials resistant to the chemical attack from nitric acid solution and is adapted to confine a slurry of acceptor supports in a nitric acid medium at temperatures from about 50 to about 200 C. The leaching vessel 24 accordingly should be adapted to withstand internal pres-sures of several atmospheres to confine the nitric acid and oxides of nitrogen. A mixing device such as rotatable stirring 8 paddle 25 provides agitation for the contents of the leaching vessel 24.

Strong nitric acid solution, preferably commercial concentrated nitric acid, is introduced into the leaching vessel 24 through a conduit 26. Sufficient nitric acid is provided to assure substantially complete recovery of the available manganese as soluble nitrates. About 1.5 pounds of concentrated nitric acid per pound of manganese is satisfactory, i.e., a slight excess of nitric acid over that determined by stoichiometric calculations for the formation of Mn(NO The concentrated nitric ,acid solution in the leaching vessel 24 also contains dissolved manganese as manganese nitrates in sufficient concentration to provide the desired manganese impregnation on the supports. We prefer that the supports contain from about 4- to about 8 percent of manganese by weight. The acceptor and nitric acid are agitated as a slurry at about 50 to 200 C, for a sufficient period to assure that substantially all the manganese is converted to the soluble nitrate form. At temperatures below about 50 C., the leaching process proceeds slowly. At temperatures above about 200 C., the pressure required to confine the reactants is excessive. About one-half to three hours has been a satisfactory residence period.

Following the leaching treatment, the slurry of supports in a nitric acid solution of manganese nitrate is withdrawn intermittently or continuously from the leaching vessel 24 through a valved conduit 27 and introduced into a continuous pressure filter 28. The solution of nitric acid and manganese nitrate is recovered as filtrate through a conduit. 29 and returned to a. storage vessel 30 providing a surge supply of concentrated nitric acid and soluble manganese salts. The acceptor solids are recovered as a moist filter cake through a conduit 31. The filter cake contains acceptor particles having the desired manganese content, preferably from about 4 percent to about 8 percent by weight.

The moist acceptors are subjected to thermal drying, for example, in a rotary dryer 32.

Hot gases, for example flue gases, are introduced into the dryer 32 through a conduit 33 to supply heat for vaporization of the nitric acid solution and decomposition of the manganese nitrate. When manganese nitrate is thermally decomposed, a residue of manganese oxide remains. The heating gases and dryer vapors are recovered from the dryer 32 through a conduit 34 and are cooled and condensed in a condenser 35. The condensed liquids, principally nitric-acid solution, accumulate in a surge vessel 36 whence they can be recycled through a conduit 37 to the storage vessel 30 for reuse in the process. N 'on-condensib1e gases including the heating gases and nitrogen oxides are separately recovered from the surge vessel 36 through a conduit 38 and are scrubbed with water by a well-known technique for recovery of nitrogen oxides. The nitrogen oxides thus recovered may be reused in the form of nitric acid solution in the process.

Emanat'ing intermittently or continuously from the dryer 32 through a conduit 39 is a stream of reactivated acceptor containing manganese oxide principally in the form of MnO the primary decomposition product of manganese nitrate. The acceptor is in a regenerated state (i.e., sulfur has been eliminated) and also is in a reactivated state (i.e., the manganese is readily available for combination with H 8). However, the acceptor is m a high state of oxidation and should be reduced prior to reuse in a desulfurization stage to avoid unnecessary consumption of hydrogen. Accordingly, the acceptor preferably is returned to the regeneration zone 18 through conduit 39 to re-enter the recirculating acceptor stream. Therein the oxidized acceptor will react with sulfided acceptor undergoing regeneration to effect an oxygen transfer Since only a minor portion of the recirculating acceptor Where desired, the reactivation process may also be employed to prepare fresh acceptor solids. Particles of the support, preferably mullite, are introduced through a conduit 4t into the leaching vessel 24 along with the corresponding quantity of manganese nitrate through a conduit 41. The added manganese nitrate enters the nitric acid solution and is uniformly soaked upon the new as well as upon the reactivated acceptor particles.

In general, only a minor portion (from about 1 to 10 percent) of the total acceptor solids undergoing re.- generation will be subjected to the reactivation treatment of the present invention. The major portion, from about 90 to 99 percent, of the recirculating acceptor solids will be returned directly from the regenenation zone 18 to the desulfurization zone 10 through the conduit 12.

Figure 3 graphically illustrates the effect of thermal exposure on loss of activity of acceptors impregnated with manganese oxide.

To calculate activity of an acceptor, a weighed batch of the acceptor is placed in a container adapted to confine the acceptor in a bed under fluidizing conditions. A stream of gas having a predetermined composition of hydrogen and H 8 is passed upwardly through the bed of'acceptor at a predetermined constant rate as a fluidizing gas. Usually the gas contains about 0.7 percent H 8 in hydrogen. The fraction of entering H S which reacts with the acceptor is measured. Initially substantially all of the entering H S reacts with the acceptor.

Grams of H 8 reacted per hour Grams of unreacted MnO in the acceptor bed A freshly prepared acceptor has an activity which can be expressed as unity. The measured activity of any other acceptor under investigation can be compared with that of the freshly prepared acceptor (expressed as unity)- v To develop the curves of Figure 3, a mullite carrier impregnated with manganese oxide was used. The car-' rier contained 4 percent of manganese. Samples of the acceptor were exposed to elevated temperatures for varying periods of time to illustrate the effect of thermal exposure on activity loss. The activity of each sample was determined and compared with that of a freshly prepared acceptor. The activity values (expressed as a percentage of the fresh acceptor activity) are presented graphically in Figure 3 for each temperature level of thermal exposure. I

The time required for a 50 percent less in activity would be about 5 hours at 1600 F;, about 6 hours at 1500" F., about 87 hours at 1400 F. and about 210 hours at 1350 F. Since the desulfurization processes are operated with an overwhelming excess of acceptor material, maintenance of a maximum activity level is not requisite. Accordingly, full restoration of activity is not required during each regeneration cycle. Thus only a small portion of the recirculating stream of acceptor is subjected to the reactivating treatment of the present invention. For example, from about 1 to 10 percent by weight of the acceptor solids undergoing regeneration would be exposed to the reactivation treatment ofthis invention.

To illustrate the efficacy of reactivation of the present process, an acceptor was selected comprising a mullite carrier containing 4.02 percent by weight of manganese; By virtue of extensive thermal treatment, this acceptor had an activity (under H s-absorbing conditions) only 20 percent of its original activity (under H s-absorbing conditions). About 94 percent of themanganese in the acceptor was in the form of manganese sulfide.

This acceptor was placed in a closed vessel with sufficient concentrated nitric acid (70 percent solution) to cover the particles. The contents of the vessel were heated to 110 C. for four hours. Analysis of the aqueous phase showed that 99 percent of the manganese went into solution from the supports; Subsequent heating of the nitric acid slurry evaporated the liquid constituent and decomposed the residual manganese nitrate to MnO The acceptor was reduced by treatment with hydrogen to convert the manganese to MnO. The activity (under-H,S absorbing conditions) of the reactivated acceptor was indistinguishable from that of freshly prepared acceptori Thus an acceptor which through thermal deactivation had retained only 20 percent of its initial activity (when freshly prepared) was reactivated to a condition where its activity equaled its initial activity (when freshly prepared). Hence we have demonstrated that the present invention counteracts the deactivation effect accompanying thermal exposure of acceptors containing manganese oxide.

According to the provisions of the patent statutes, we have explained the principle, preferred construction, and mode of operation of our invention and have illustrated and described what we now consider to represent its best embodiment. However, we desire to have it understood that, Within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.

We claim:

1. In a process employing solid acceptors for hydrogen sulfide comprising manganese oxide impregnated on an inert support for sequentially absorbing hydrogen sulfide at temperatures above about 1100 F. to form manganese sulfide, followed by oxidizing the manganese sulfide to manganese oxide by reaction with oxygen, the improvement which minimizes loss of the acceptors activity, under H S-absorbing conditions, comprising cooling a minor portion of the stream of recirculating acceptor in the manganese oxide form, contactingsaid minor portion with a concentrated solution ofmineral acid selected from the-class consisting of nitric acid, sulfuric acid and hydrochloric acid, at about 50 to 200 C. to leach out substantially all of the manganese in the form of soluble manganese salt, thereafter heating the supports in contact with the manganese salts in acid solution to vaporize said acid solution, to deposit said soluble manganese salt'on said supports and to convert said manganese salt to manganese oxide, and recovering said supports containing manganese oxide for reintroduction into the recirculating stream of acceptors.

2. In a process employing solid acceptors for hydrogen sulfide comprising manganese oxide impregnated on an inert support for sequentially absorbing hydrogen sulfide at temperatures above about 1100 F. to form manganese sulfide, followed by oxidizing the manganese sultide to manganese oxide by reaction with oxygen, the Improvement which minimizes loss of the acceptors activity, under H S-absorbing conditions, comprising.

cooling a minor portion of the stream of recirculating acceptor in the manganese oxide form, contacting said in nitric acid solution to vaporize said nitric acid solution to deposit said manganese nitrate on said supports and? to convert said manganese nitrate to manganese oxide,

11 and recovering said supports containing manganese oxide for reintroduction into the recirculating stream of acceptors.

3. The improvement of claim 2 wherein the acceptor supports comprise an inert oxide selected from the class consisting of silica, alumina and silica-alumina.

4. The improvement of claim 2 wherein the acceptor supports comprise mullite.

5. The improvement of claim 2 wherein the minor portion of said recirculating stream of acceptor comprises 1 to percent thereof by weight.

6. In the method of removing sulfur from particulate carbonized carbonaceous solids, which comprises preparin g an intimate admixture of said carbonaceous solids and particulate acceptor solids comprising inert carrier hav ing manganese oxide impregnated thereon, subjecting said admixture to treatment at a temperature above 1100 F. in the presence of hydrogen gas until a portion of the initial sulfur has been removed from said carbonaceous solids and transferred to said acceptor solids forming manganese sulfide, separating particulate acceptor solids containing manganese sulfide from low sulfur carbonaceous solids, recovering said low sulfur particulate carbonaceous solids as product, and restoring the H S-absorbing property of sulfided acceptor solids for recirculation in the process, the improvement in the last-mentioned step of restoring the H S-absorbing property of the sulfided acceptor solids comprising subjecting said sulfided acceptor solids to a temperature of 1300 to 1600" F. under oxidative conditions to remove sulfided sulfur therefrom and reform manganese oxide thereby, recovering acceptor solids as a recirculating stream having restored H 3 absorbing property, withdrawing a minor portion or" thustreated acceptor solids, cooling said minor portion and contacting same with a concentrated nitric acid solution at about 50 to 200 C. to leach out substantially all of the manganese in the form of a soluble nitrate, recovering said supports together with said nitric acid solution containing manganese nitrate therein, thereafter heating the supports to vaporize said nitric acid solution, to deposit said manganese nitrate on said supports and to convert said manganese nitrate to manganese oxide, and recovering said supports containing manganese oxide for reintroduction into said recirculating stream.

7. The improvement of claim 6 wherein the inert carrier comprises an oxide selected from the class consisting of silica, alumina and silica-alumina.

8. The improvement of claim 6 wherein the inert carrier comprises mullite.

9. In a process employing solid acceptors for hydrogen sulfide comprising manganese oxide impregnated on an inert support for sequentially absorbing hydrogen sulfide at temperatures above about 1100 F. to form manganese sulfide, following by oxidizing the manganese sulfide to manganese oxide by reaction with oxygen, the improvement which minimizes loss of the acceptors activity, under fi s-absorbing conditions, comprising cooling a minor portion of the stream of recirculating acceptor in the manganese oxide 01m, contacting said minor portion with a concentrated nitric acid solution at about 50 to 200 C. to leach out substantially all of the manganese in the form of soluble nitrate, introducing into the slurry of supports in nitric acid solution additional quantities of acceptor supports and manganese salts yielding manganese oxide when heated, to produce thereby additional solid acceptors for hydrogen sulfide, thereafter heating the supports in con-tact with the nitric acid solution containing the manganese nitrate to vaporize said nitric acid solution, to deposit said manganese nitrate on said supports and to convert said manganese nitrate to manganese oxide, and recovering said supports containing manganese oxide for reintroduction into the recirculating stream of acceptors.

10. In the method of removing sulfur from particulate carbonized carbonaceous solids, which comprises preparing an intimate admixture of said carbonaceous solids and particulate acceptor solids comprising inert carrier having manganese oxide impregnated thereon, subjecting said admixture to treatment at a temperature above 1100 F. in the presence of hydrogen gas until a portion of the initial sulfur has 'been removed from said carbonaceous solids and transferred to said acceptor solids forming manganese sulfide, separating particulate acceptor solids containing manganese sulfide from low sulfur carbonaceous solids, recovering said low sulfur particulate carbonaceous solids as product, and restoring the H s-absorbing property of sulfided acceptor solids for recirculation in the process, the improvement in the last-mentioned step of restoring the H s-absorbing property of the sulfided acceptor solids comprising subjecting said sulfided acceptor solids to a temperature of 1300 to 1600 F. under oxidative conditions in a regeneration zone to remove sulfided sulfur therefrom and reform manganese oxide thereby, recovering acceptor solids as a recirculating stream having restored H S-abSorb-ing property, withdrawing a minor portion of thus-treated acceptor solids, cooling said minor portion and contacting same with a concentrated nitric acid solution at about 50 to 200 C. to leach out substantially all of the manganese in the form of a soluble nitrate, recovering said supports together with said nitric acid solution containing manganese nit-rate therein, thereafter heating the supports to vaporize said nitric acid solution, to deposit said manganese nitrate on said supports and to convert said manganese nitrate to manganese oxide, and introducing said supports into said regeneration zone whereby they are returned to the said recirculating stream in a reactivated condition.

11. The improvement of claim 10 wherein the particulate carbonized carbonaceous solids are carbonaceous briquets and the inert carrier is a finely divided fluidizable size inert support selected from the class consisting of silica, alumina and silica-alumina.

12. The improvement of claim 10 wherein the particulate carbonized carbonaceous solids comprise char obtained by fluidized low temperature carbonization of caking bituminous coal.

References Cited in the file of this patent UNITED STATES PATENTS 1,904,582 Watts Apr. 18, 1933 2,381,659 Frey Aug. 7, 1945 2,397,824 Wanamaker et a1; Apr. 2, 1946 2,663,618 Babbitt et a1 Dec. 22, 1953 2,764,528 Sweeney Sept. 25, 1956 2,779,659 Koslov Jan. 29, 1957 2,824,047 Gorin et al Feb. 18, 1958 UNITED STATES PATENT OFFICE CERTIFICATION OF CORRECTION Patent No 2,927,063

James Du Batchelor et al.

March 1, 196( It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 1, line 27, for "surfur" read sulfur column 6 line 17 for "Figure 1" read Figure 2 s='.'-; column 7, line 11 for "from" read through column 11, line 54, for "following' read followed Signed and sealed this 9th day of May 1961 I (SEAL) Attest:

ERNEST WQ SWIDER DAVID L. LADD Attesting Officer Commissioner of Patents I UNITED STATES PATENT OFFICE CERTIFICATION OF CORRECTION Patent N0 2,927,063 March 1, 1960 James D, Batchelor et a1.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 1, line 27, for surfur" read sulfur column 6, line 17, for ,Figure 1" read Figure 2:5 column 7, line 11, for "from" read through column 11, line 54, for "following" read an followed Signed and sealed this 9th day of May 1961.

(SEAL) Attest: I

ERNEST W SWIDER DAVID L, LADD Commissioner of Patents Attesting Officer

Claims (1)

1. IN A PROCESS EMPLOYING SOLID ACCEPTORS FOR HYDROGEN SULFIDE COMPRISING MANGANESE OXIDE IMPREGNATED ON AN INERT SUPPORT FOR SEQUENTIALLY ABSORBING HYDROGEN SULFIDE AT TEMPERATURES ABOVE ABOUT 1100*F. TO FROM MANGANESE SULFIDE, FOLLOWED BY OXIDIZING THE MANGANESE SULFIDE TO MANGANESE OXIDE BY REACTION WITH OXYGEN, THE IMPROVEMENT WHICH MINIMIZES LOSS OF THE ACCEPTORS ACTIVITY, UNDER H2S-ABSORBING CONDITIONS, COMPRISING COOLING A MINOR PORTION OF THE STREAM OF RECIRCULATING ACCEPTOR IN THE MAGANESE OXIDE FORM, CONTACTING SAID MINOR PORTION WITH A CONCENTRATED SOLUTION OF MINERAL ACID SELECTED FROM THE CLASS CONSISTING OF NITRIC ACID, SULFURIC ACID AND HYDROCHLORIC ACID, AT ABOUT 50 TO 200*C. TO LEACH OUT SUBSTANTIALLY ALL OF THE MANGANESE IN THE FORM OF SOLUBLE MANGANESE SALT, THEREAFTER HEATING THE SUPPORTS IN CONTACT WITH THE MANGANESE SALTS IN ACID SOLUTION TO VAPORIZE SAID

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