Effect of Different Types of Chemicals, Cooking Time and Chemical Concentration on the Quality of Sludge and Pulp Appearance

Abstract

Pulp and paper production process releases different types of wastes into the environment and pulp mill sludge is one of the major wastes from pulp and paper mill. The environmental awareness has led to more attention being given to the process of paper production and the raw materials and chemical usage. In this study, we analyzed the effect of chemical, concentration and cooking time on the characteristics of sludge and physical appearance of pulp obtained from pulping kenaf stem. The stem was pulped with 20%, 60% and 90% concentrations of formic acid and sodium hydroxide at 1 hour, 2 hours and 3 hours intervals to determine the parameters of their sludge as well as pulp appearance. The parameters considered include carbon, nitrogen, turbidity, phosphorus, ash and moisture. Sludge from sodium hydroxide pulping showed lowest value (0.02) of carbon with 60% concentration and highest (4.30) with 90% after 1hr cooking. Formic acid sludge that reported zero carbon with 20% concentration gave lowest value (1.77) at 60% after 1hr and highest value (8.73) after 3hrs with 90% concentration. Both formic acid and sodium hydroxide sludge recorded highest values (0.29 & 39.77) of nitrogen at 60% concentrations. The sludges of the two chemicals were most turbid at 90% and less at 60% concentrations with highest phosphorus values at the same concentrations. Both sludges reported lowest moisture contents at 60%. Sodium hydroxide showed highest ash at 20% after 1hr cooking while the highest value for formic acid was recorded at 90% after 3hrs cooking. The 60% formic acid at 2 hours gave a better pulp on physical examination and the sludge from the same process can also be reused.