15 which passes it to filter element 16 the cyclic urea degradation product accumulates on the filter and is thereby selectively removed from the lean solution when the ultimate buildup of the insoluble material on the filter causes a pressure drop of for example about 25 psi a secondary filter 17 is cut in to allow continued operation of the process during the cleaning of the segregated filter the lean solution passes out of filter 16 via line 23 and joins with some of the other lean solution in line 21 which was not cooled by exchanger 19 these two streams combine and enter the top of the absorber the purified gas passes out of absorber 2 via line 24 hot water having a temperature of about 230 u00b0 f is passed via line 20 into filter element 16 in order to wash the cyclic urea from the filter and to permit its effective reuse the following is a summary of several examples which describe the invention a gas treating solution was prepared which had the following composition 30 wt k 2 co 3 with 10 as khco 3 6 0 wt cyclohexyl 1 3 propane diamine 6 1 wt pipecolonic acid 56 2 wt water and 1 7 wt cyclic urea i e 1 cyclohexyl hexahydro 2 pyrimidinone as disclosed in copending application ser no 930 222 filed aug 2 1978 incorporated herein the solution at 200.