Patent GB-768345-A (GB)
Title: Process and apparatus for the recovery of ammonia and pyridine from coke oven gas
IPC: C10K1/10
Filed: 1952-05-01
Abstract: Ammonia and pyridine are recovered as their sulphate, from coke oven gas by passing the gas in succession through a first and second scrubbing spaces, the first space being supplied with a pray of acidulated ammonium sulphate liquor having a relatively small sulphuric acid content, i.e. not greater than 6 per cent, whereby all the ammonia is converted into ammonium sulphate, and the second space is supplied with a spray of acidulated ammonium sulphate liquor having a higher sulphuric acid content, e.g. over 8 per cent, whereby the pyridine is converted to pyridine sulphate.  Acidulated ammonium sulphate liquor and crystals are withdrawn from the first scrubbing space and acidulated ammonium sulphate/pyridine sulphate liquor is withdrawn from the second space.  The pyridine sulphate may be treated with ammonia to obtain pyridine.  Specifications 647,742, [Group III], and 653,325 are referred to.ALSO:<PICT:0768345/III/1> <PICT:0768345/III/2> Ammonia and pyridine are recovered as their sulphates from coke oven gas by passing the gas in succession through a first and second scrubbing space, the first space being supplied with a spray of acidulated ammonium sulphate liquor having a relatively small sulphuric acid content, i.e. not greater than 6 per cent whereby all the ammonia is converted into ammonium sulphate, and the second space is supplied with a spray of acidulated ammonium sulphate liquor having a higher sulphuric acid content, e.g. over 8 per cent whereby the pyridine is converted to pyridine sulphate. Acidulated ammonium sulphate liquor and crystals are withdrawn from the first scrubbing space and acidulated ammonium sulphate/pyridine sulphate liquor is withdrawn from the second space.  As shown in Fig. 1 coke oven gas enters a first scrubbing space A through a pipe B and flows upwards against acidulated ammonium sulphate sprays D1 and D2 into a second scrubbing space I into which ammonium sulphate liquor of greater acid content is sprayed from line N2.  The gases then pass through an acid catcher J2 and JA to leave the apparatus through CA. Ammonium sulphate crystals and liquor are withdrawn from the first scrubbing zone A to a crystallizer F from the lower part of which a portion of the liquor and entrained crystals are pumped through lines G1, G2 to the spray nozzles D, D1 and D2.  A further portion of the liquor and crystals is withdrawn through line G3 and passed to a tank S which feeds the liquor and crystals to a centrifuge T from which the product ammonium sulphate is withdrawn.  The liquor from the centrifuge may be passed through pipe Q and through valves Q2 or Q1 to the ammonium sulphate crystallizer F or the pyridine receptacle O respectively.  As overflow pipe S1 from the tank S similarly feeds through lines S3 or S4 to vessels F and O.  The pyridine sulphate formed in the second scrubbing space by virtue of the ammonium sulphate liquor sprayed through line N2 is recovered in part through line K from the first acid catcher J2 to pass to a pyridine receptacle O and in part through lines leading from the top and bottom of a second acid catcher JA.  The latter consists of a device J4 where the gas is whirled by helical vanes to separate entrained liquor which flows down the wall of the pipe and is deflected by a cone J6 to the pipe L, excess liquor overflowing to the bottom for return to receptacle O.  The spray liquor for the second scrubbing space is withdrawn from the bottom of the pyridine receptacle O and passed by pump N through line N2 to a nozzle I whilst the remainder of the pyridine sulphate liquor is withdrawn through line O3 for a conventional pyridine recovery treatment.  Acid supply lines HA and H respectively are provided in the pyridine receptacle O and ammonium sulphate crystallizing vessel F. Fig. 2 illustrates a modification where the first and second scrubbing spaces are contained in a common vessel.  In this case, coke oven gases entering at B are sprayed in a first scrubbing space by sprays D3 and D4 of ammonium sulphate liquor from crystallizing tank F and line G2 as before.  The gases then rise to a second scrubbing space through inclined overlapping baffles U, U1, U3 where they are sprayed with an acidulated ammonium sulphate liquor through nozzle I which is fed through line N2 from the pyridine receptacle O.  The ammonium sulphate liquor from the first scrubbing space is withdrawn through line E as before and the pyridine sulphate liquor is withdrawn from the second scrubbing space through line KA.  The gases leave through line C and pass through a cyclone acid catcher JB before leaving through CA, the acid liquors so removed passing to the pyridine receptacle O through line MA.  The ammonium sulphate liquor is withdrawn through line G3 and treated as in Fig. 1.  Specifications 647,742 and 653,325 are referred to.