ZTM-BPD-CIRCOT

INTRODUCTION:
Conventional chemical processing of pulping involves cooking of cotton plant stalks in a digester under high temperature and pressure in the presence of chemicals (12%- 16%) at 140°C-160°C for about 4 h. The effluents generated are viscous and toxic and cause environmental pollution. Biological processes offer an ideal and appropriate solution in this context. A large number of fungi and bacteria are found in nature, which can degrade lignin as well as other components of plant materials under aerobic as well as anaerobic conditions. Employing these microorganisms for softening of crop residues prior to chemical pulping can result in saving of a lot of energy and chemicals as compared to the conventional chemical process.

CIRCOT’s New Technology:
CIRCOT has standardised a biological anaerobic treatment for softening of cotton plant stalks for the preparation of pulp. The process involves chipping of cotton plant stalks, pretreatment of chips with (2-4%) of sodium hydroxide at 100°C for 30 mm., anaerobic treatment of treated chips with microbial consortium for 7 days, post treatment of digested material with alkali at 100°C for 30 mm. followed by mechanical defibration in a refiner/beater to get pulp of required freeness.

The technology developed and patented was also scaled up in a 100 kg capacity anaerobic digester especially designed and installed for the purpose. The results of the trials clearly indicated that the process of anaerobic digestion is technically feasible and economically viable as evidenced by the significant saving in chemical and electrical energy and that the quality of the paper produced by this new process was on par with that from conventional process. For processing 100 kg of cotton plant stalks by anaerobic process the thermal energy saving was about 106 Mj and the electrical energy saving was about 10 KWh while the chemical saving was about 11 kg/day in comparison with the cost involved in conventional chemical process. The process was also found to be eco friendly as the effluents were less toxic with low BOD and COD values.

Details of techno economic feasibility are given in the following pages:

Digester volume               230 M3
Retention time                  5 days
Capital cost                       Rs.10 lakh

Running Cost

Manpower:
4 persons per day             Rs.450/day
( 1 semi skilled @ Rs.150/day and 3 unskilled @ Rs.100/day)

Chemicals:
200 kg of NaOH daily @ Rs.15/kg     Rs.3000/day