Regeneration of alkanolamine absorbing solution in gas sweetening processes

Claim 2

IN COMBINATION WITH AN AQUEOUS ALKANOLAMINE ABSORPTION/DESORPTION PROCESS WHEREIN INDUSTRIAL GASES ARE SWEETENED BY REMOVAL OF ACID GASES INCLUDING HYDROGEN CYANIDE AND SULFIDE GASES, A PROCESS FOR PREVENTING IRREVERSIBLE DETERIORATION OF THE ALKANOLAMINE SOLUTION COMPRISING: MAINTAINING SUFFICIENT AMMONIUM IONS IN THE ALKANOLAMINE SOLUTION DURING ABSORPTION TO INSURE A CONTINUED PRESENCE OF SAID AMMONIUM IONS IN THE ALKANOLAMINE SOLUTION DURING THE ABSORPTION PROCESS, SAID AMMONIUM ACTING AS A DETERRENT WITH RESPECT TO THE FORMATION OF THIOCYANATES WHEREBY IRREVERSIBLE DETERIORATION OF SAID ALKANOLAMINE SOLUTION BY SAID THIOCYANATES IS SUPPRESSED.

Claim 3

The process of claim 1 in which the industrial gas is coke oven gas.

Claim 4

The process of claim 1 in which the ionizable form of ammonia supplied is substantially ammonia.

Claim 5

The process of claim 1 in which the ionizable form of ammonia is substantially an aqueous solution of an ammonium salt of a weak acid.

Claim 6

The process of claim 2 in which the ionizable form of ammonia supplied is substantially ammonia.

Claim 7

The process of claim 2 in which the ionizable form of ammonia is substantially an aqueous solution of an ammonium salt of a weak acid.

Claim 8

The process of claim 2 in which the ionizable form of ammonia is ammonia in an amount of at least about 0.2 mole percent of the industrial gas.

Claim 9

The process of claim 2 in which the ionizable form of ammonia is an aqueous solution of an ammonium salt of a weak acid in the amount of about 0.2 to 1 weight percent of the absorbing solution.

Claim 10

The process of claim 7 in which the alkanolamine is substantially monoethanolamine.

Claim 11

The process of claim 8 in which the alkanolamine is substantially monoethanolamine.

Claim 12

The process of claim 1 in which at least part of the ionizable ammonia is supplied by recirculating desorbed solution.

Claim 13

An improved gas sweetening process for removing acid gases from industrial gases containing hydrogen cyanide and sulfide components by means of aqueous alkanolamine absorbing solutions without irreversible deterioration of the absorption capacity of the alkanolamine solution due to combination of the alkanolamine with thiocyanates comprising: a. absorbing the acid gases into the alkanolamine solution in the presence of ammonium ions, b. desorbing the acid gases from the alkanolamine to regenerate the solution and recirculating the regenerated and undeteriorated alkanolamine solution back to the absorbing step.

Claim 14

An improved gas sweetening process for removing acid gases from industrial gases containing hydrogen cyanide and sulfide components by means of aqueous alkanolamine absorbing solutions without irreversible deterioration of the absorption capacity of the alkanolamine solution due to combination of the alkanolamine with thiocyanates comprising: a. absorbing the acid gases into the alkanolamine solution in the presence of ammonium ions, b. desorbing the acid gases from the alkanolamine to regenerate the solution and recirculating the regenerated and undeteriorated alkanolamine solution back to the absorbing step.

Claim 15

An improved method of gas sweetening according to claim 12 wherein ammonium ions are maintained in both the absorption and desorption steps of the gas sweetening process.

Claim 16

An improved method of gas sweetening according to claim 13 additionally comprising: c. recovering ammonia from the foul gases leaving the desorption step of (b) and recycling said ammonia to the absorption step of (a).

Claim 17

An improved method of gas sweetening according to claim 13 wherein the ammonia is recycled to the absorption step of (a) along with the recirculated alkanolamine solution from the desorption step of (b).

Claim 18

An improved method of gas sweetening according to claim 12 wherein the ammonia is provided in excess of the molar amount which would theoretically be necessary to form thiourea from thiocyanates.

Claim 19

An improved method of gas sweetening according to claim 16 in which solution of the elevated temperature in the desorption step is sufficient to decompose thiourea if present, to gaseous carbon dioxide and hydrogen sulfide.

Claim 20

In combination with an alkaholamine absorption/desorption process wherein industrial gases are sweetened by removal of acid gases including hydrogen cyanide and sulfide gases, a process for preventing irreversible deterioration of the alkanolamine solution comprising: a. providing prior to the absorbing process, an aqueous alkanolamine containing solution for the absorption of acid gases therein; b. providing ammonia in ionizable form; c. absorbing acid gases into said alkanolamine solution in the presence of said ammonia whereby thiourea is formed; d. desorbing said solution including reacting said thiourea with water to generate gaseous carbon dioxide and hydrogen sulfide and removing desorbed gases to purify said solution.

Claim 21

In combination with an alkaholamine absorption/desorption process wherein industrial gases are sweetened by removal of acid gases including hydrogen cyanide and sulfide gases, a process for preventing irreversible deterioration of the alkanolamine solution comprising: a. providing prior to the absorbing process, an aqueous alkanolamine containing solution for the absorption of acid gases therein; b. providing ammonia in ionizable form; c. absorbing acid gases into said alkanolamine solution in the presence of said ammonia whereby thiourea is formed; d. desorbing said solution including reacting said thiourea with water to generate gaseous carbon dioxide and hydrogen sulfide and removing desorbed gases to purify said solution.