STUDIES ON UREA PULPING OF AGRO BASED RESIDUES - WHEAT STRAW

Abstract

Today agro-based raw materials are playing important role in meeting out more than 50% of the total requirement of 4 million tons of paper and boards in the country. Without a viable chemical recovery unit in most of the small and medium paper mills, huge quantity of sodium hydroxide used in pulping is being drained which generate heavy pollution load. Alternate pulping chemical 'Urea' was tried to replace sodium hydroxide for producing few verities of paper and boards, Earlier urea pulping of rice straw was carried out for its suitability for general grade wrapping paper. Studies are on the urea pulping of wheat straw which was carried out by using 15-30% urea dosage. Unbleachable grade chemi-mechanical pulp of 39% pulp screened yield and 40 K-number could be produced with 20% urea dosage which is of 1.95-2.35 (kPam`lg )burst index and 51.25 Tensile Index, (Nm/g). found the best results in the combination with NaOH and KOH are 10% urea with 5% NaOH/KOH.In this case, urea pulping characteristics of wheat straw were investigated and optimum parameter were found to be: maximum temperature 160°C, time to maximum temperature 55 min, time at maximum temperature 40 min and liquor to straw ratio 6:1. Some properties of wheat straw urea with soda pulp produced at optimum cooking conditions and 10% Urea with 5%NaOH are determined to be: screened yield 44.29%. kappa number 32, SCAN viscosity 0.0278 poise, breaking length 9.8 km, _burst index 1.9 kPa m2/g, tear index 7.84 mNm2/g and Tensile Index, 53.57 Nmlg Consequently, Further studies are on the used urea as a few quantity of additives in the pure soda dosage(18%) which could be produced high tensile index chemi-mechanical grade paper of the range of 50-62 Nm/g. Studies are also, focused on analysis of black liquor in which urea pulping effluent gives low COD,BOD hence low environmental pollution load.