Patent GB-653325-A (GB)
Title: Improvements in or relating to the production of ammonium sulphate and the recovery of pyridine
IPC: C01C1/242
Filed: 1948-02-17
Abstract: <PICT:0653325/IV (b)/1> A process for the recovery of pyridine from gas containing ammonia and pyridine comprises the steps of bringing the gas into contact with dilute sulphuric acid containing ammonium sulphate, the time of contact being sufficient adequately to absorb ammonia but insufficient adequately to absorb pyridine, crystallizing ammonium sulphate in the solution, separating the crystals of ammonium sulphate and incorporating make-up sulphuric acid in the solution; bringing the effluent from this contact into contact with another solution of sulphuric acid which is unsaturated with ammonium sulphate and has a greater affinity for pyridine than the first-mentioned dilute sulphuric acid; and treating both solutions containing pyridine to recover pyridine therefrom and returning the treated solutions to the process.  As shown in Fig. 1, coke, oven gas containing ammonia and pyridine bases is led into a saturator 10 via an inlet 12 and a bell-shaped cracker pipe 14 at or below the normal liquid level.  The saturator solution has a concentration of 1-8 per cent sulphuric acid and a temperature of 35-70 DEG  C.  It is maintained in circulation being withdrawn through a suction head 28 and returned to the bottom of the saturator through a collecting-plate 34 by means of a pump 32.  An overflow 26 controls the liquid level, liquid passing there-through and through a tar skimmer 36 (which receives part of the make-up acid through a line 42) into a storage tank 40.  The balance of the make-up acid is introduced through a line 43 into the saturator.  Ammonium sulphate crystals are withdrawn by a suction head 44, and after settling in a cone 48 and filtration at 52 the filtrate passes to the storage tank. Liquor from the cone 48 overflows into a line 58 and part thereof passes through a line 62 for pyridine recovery at 64, pyridine-free liquor passing through line 56 to the storage tank.  Effluent gases leaving the saturator through an uptake 76 are sprayed with make-up liquors fed from the storage tank via a sprayer 74.  This liquor is maintained below saturation and at a higher acidity by virtue of the make-up acid introduced at 42, and removes the remaining pyridine and ammonia from the gas, the effluent liquor joining the solution in the saturator.  The effluent gas passes out via a spray catcher 80. According to a modification (Fig. 2, not shown), the effluent gas from the saturator is sprayed with ammonium sulphate liquor by-product of the pyridine recovery after it has been acidified with sulphuric acid and the liquid effluent from the scrubber is passed directly into the pyridine recovery unit, thus completing the cycle, whilst the make-up liquor is fed directly to the saturator from the storage tank. Specification 615,641, [Group III], is referred to.ALSO:<PICT:0653325/III/1> A process for the manufacture of ammonium sulphate and for the recovery of pyridine from gas containing ammonia and pyridine comprises the steps of bringing the gas into contact with dilute sulphuric acid containing ammonium sulphate, the time of contact being sufficient adequately to absorb ammonia but insufficient adequately to absorb pyridine, crystallizing ammonium sulphate in the solution, separating the crystals of ammonium sulphate and incorporating make-up sulphuric acid in the solution; bringing the effluent from this contact into contact with another solution of sulphuric acid which is unsaturated with ammonium sulphate and has a greater affinity for pyridine than the first mentioned dilute sulphuric acid; and treating both solutions containing pyridine to recover pyridine therefrom and returning the treated solutions to the process.  As shown in Fig. 1, coke, oven gas containing ammonia and pyridine bases is led into a saturator 10 via an inlet 12 and a bell shaped cracker pipe 14 at or below the normal liquid level.  The saturator solution has a concentration of 1-8 per cent sulphuric acid and a temperature of 35-70 DEG  C. It is maintained in circulation being withdrawn through a suction head 28 and returned to the bottom of the saturator through a collecting plate 34 by means of a pump 32.  An overflow 26 controls the liquid level, liquid passing therethrough and through a tar skimmer 36 (which receives part of the make-up acid through a line 42), into a storage tank 40.  The balance of the make-up acid is introduced through a line 43 into the saturator.  Ammonium sulphate crystals are withdrawn by a suction head 44, and after settling in a cone 48 and filtration at 52 the filtrate passes to the storage tank.  Liquor from the cone 48 overflows into a line 58 and part thereof passes through a line 62 for pyridine recovery at 64, pyridine free liquor passing through line 56 to the storage tank.  Effluent gases leaving the saturator through an uptake 76 are sprayed with make-up liquors fed from the storage tank via a sprayer 74.  This liquor is maintained below saturation and at a higher acidity by virtue of the make-up acid introduced at 42, and removes the remaining pyridine and ammonia from the gas, the effluent liquor joining the solution in the saturator.  The effluent gas passes out via a spray catcher 80. According to a modification (Fig. 2, not shown), the effluent gas from the saturator is sprayed with ammonium sulphate liquor by-product of the pyridine recovery after it has been acidified with sulphuric acid and the liquid effluent from the scrubber is passed directly into the pyridine recovery unit thus completing the cycle, whilst the make-up liquor is fed directly to the saturator from the storage tank.  Specification 615,641 is referred to.