Abstract
The authors have developed a method, named “Simdcap”(Simple distillation of digested liquid to concentrated liquid, ammonia liquid and purified water) to reduce methane fermented liquid supernatant by a simple vacuum distillation. The Simdcap method separates the supernatant into concentrated liquid, ammonia liquid and purified water.
In this paper, a method to predict the ammonia concentration removed by Simdcap was clarified. The prediction method calculates the distillation time for a specific ammonia concentration and ammonia liquid volume with an initial ammonia nitrogen (NH4-N) concentration of supernatant at a determined distillate rate. For instance, 1, 500mg ·l-1 initial NH4-N and a 2%·h-1of the distillate rate indicate that 9.6h are required to obtain the ammonia concentration. The ammonia liquid is 19% of the initial supernatant volume in the distiller. The distillate rate “%” is the rate of distilled liquid volume to initial supernatant volume in the distiller.
In addition, the weight of clinging residuals as related to concentration of the supernatant in the distiller was examined. Clinging residual ratio was below 0.5% and the average water content of the clinging residuals was 95% while concentration rate of the supernatant was below 90%. Clinging residual ratio increased in proportion to the concentration rate, the average clinging residual ratio was 0.93% and the average water content of the clinging residual was 48% while the concentration rate was above 90%.
The clinging residual weight in the second turn was less than in the first turn when 90 % concentration of the supernatant was redistilled. The outflow of concentrated liquid in the second turn seemed to wash out some of the clinging residuals during the first turn. The distiller must be able to efficintly remove the clinging residual.
