Knowledge Platform » Pulp & Paper Sector » Pilot Examples/Case Studies » Acidic Sizing (Alum & Rosin) Replaced by Surface Sizing  · 

Acidic Sizing (Alum & Rosin) Replaced by Surface Sizing

Description

Sizes are applied to the surface of the paper sheet (surface sizing) to avoid dusting (linting) of the paper in offset printing processes. Surface sizing increases the surface strength of the paper. In surface sizing, the web is passed through the sizing liquor pond. As a result, the paper web absorbs the sizing liquor.This case study describes the economic as well as environmental benefits that could be accrued through replacement of the Acidic Sizing by Surface Sizing.

Surface sizing techniques replaces the internal acidic sizing and therefore eliminates consumption of chemicals such as Alum and Rosin which are a major cause of TDS formation in process water.

Implementing Industry

R. A. Shaikh Paper Mills Pvt Ltd. is a small scale manufacturer of Machine Grade kraft paper located in Vapi GIDC. Industry was established in 1997, with present production Capacity of 80 TPD with an Annual Turnover of 40 crores.

Implemented technology / technique

BEFORE:

  • In kraft board & MG kraft paper industries, alum & rosin are used for sizing process, which reduces drainability, and supports fibre retention.
  • Acidic sizing disables manufacturing of high GSM paper. It also increases total dissolved particles in effluent.
  • In chemical chest, alum and rosin were added about 30 Kg/Ton and 8 Kg/Ton respectively as sizing agent.
  • Aluminium sulphate (alum) combines with the Sodium rosinate to form Aluminium rosinate (the water-repellent size), along with the ions of sodium sulphate and sulphuric acid.
  • The acidic material is responsible for deterioration of cellulose and decreased paper permanence.  It is also observed that rosin-sized paper has a lower thermal decomposition temperature and reduced paper strength.
  • Due to acidic nature, COD and TSS are also increased in the effluent.

AFTER:

  • Surface sizing of paper refers to the application of starch by means of a size press or film press which is placed after the M.G. Cylinder and 6 nos. Dryers. This process replaces the acidic sizing to neutral sizing.
  • In surface sizing, Retention Aid K-301 150 gm/Ton and PAC (Poly Aluminium Chloride) 15 Kg/Ton are added as sizing agent to both sides of the paper web, as it passes through rollers that press the size on the sheet and remove excess size.
  • It Increases internal and surface strength from 16-18 BF (Burst Factor) to 24 BF, improved printing quality and paper stiffness. Surface sizing also affects the printing process by altering paper absorbency, flatness, density, fibre consolidation.

Economic benefits

The Capital cost invested by the industry was Rs. 54,00,000 and a total revenue increase due to product quality improvement was estimated as Rs. 35,32,500 per annum giving simple payback in 19 months.

Contact details 

Mr. Miskin Diwan (Plant In charge); Mobile No.: +91-9925013186