Production Process

	Bleaching Sequence

The project selected Elemental Chlorine Free (ECF) bleaching system to minimize the environmental impact.  The D1 - E/OP - D2 bleaching sequence causes low AOX (Absorbable Organic Halide) as 0.34 kg/adtp, only a fifth of AOX from conventional Chlorine gas and Sodium Hypochlorate bleaching process. The figure shows in the following table.

Conventional Bleaching Sequence     
EPPCO’s ECF Bleaching Sequence

Cooking Process

Electrostatic Precipitators

The pulp mill has two coal-fired boilers and one chemical recovery boiler. Their flue gas contains tiny particles, which are not allowed to be directly emitted to the air. The ESPs <Electrostatic Precipitators> are installed to collect particles at 99.5% efficiency. Moreover, the coal-fired boilers are equipped with desulphurization system to ensure clean gas emission to the atmosphere.

The bagasse pulp mill has two major sources of wastewater.  First, the bagasse washing water mainly contains lignin and sugar . Such waste water goes to the modern anaero bic sludge digestion process , which consumes very low electricity .  Methane gas produced from bacteria and organic substances is clean fuel for boilers.  Clear water goes back to the bagasse washer and sludge is taken to the further treatment.  Second, the wastewater from pulping process combined with sludge from anaerobic system goes to the activated sludge system to improve water quality to the governmental agencies’ standard before discharged to sugar cane farms and other cultivation.  The wastewater treatment process is designed and supplied by a leading firm from Scandinavian country.

Bleached Bagasse Pulp Production Process

Among the many agricultural fibers used for pulp manufacture, sugar cane bagasse stands out and promises to become a major raw material for the world’s pulp and paper industry. The fibrous bagasse residue, which comes from the processing of the cane in the sugar mill through a series of roller presses to extract the sugar juice, is normally burnt in the bagasse-fired boilers.  In this way, the sugar mill is completely self-sufficient in steam and power.  In-fact, When efficient heat and power balance is established, excess co-generated power can be sold to the local grid.

Moreover, the bagasse has greater economic value when it is processed into pulp, paper, paperboard and/or reconstituted panelboard.  Bagasse has the distinct advantages over other agricultural residues.  The costs of collecting, processing, and washing the sugar cane are borne by the sugar extracting process, and bagasse, when delivered to the pulp mill, is in excellent condition for further processing.

Kaset Thai sugar mill, a major bagasse supplier, will deliver moist depithed bagasse via a belt conveyer system to the adjacent pulp mill with low transportation cost and reliable delivery schedule.

Bagasse Handling

Fresh bagasse from sugar cane crusher will be moist depited.  Pith will be consumed in the boilers of sugar mill as the fuel and depithed bagasse will be conveyed to the storage yard and keep in wet storage system.

Cooking and Washing

Bagasse is reclaimed from storage yard to bagasse washing system,. After three various stages washing, bagasse will be sent to “Cyclone” to separate soil and sand and then to reduce water content by “Dewatering Rotary Screen” bagasse will be sent by “Screw Conveyor,” pass “Magnetic Tramp Iron Separator ” and “Belt Scale” for checking and controlling of bagasse  volume.

Bagasse then will be sent to “Blow Back Valve” and mixed with pressurized steam and NaOH solution in continuous Pandia Digester.  The average cooking time is 20-25 minutes. Next, it will be sent to reduce temperature in “Cold Blow” and to be stored in “Blow Tank.” The cooked bagasse pulp will be sent to “Brown Stock Washer” for cleaning. Unbleached pulp is sent to high pressure screen and centricleaner to remove shive, uncooked fiber, and alien matters and sent to “Brown Stock Decker” to reduce water content and store in  “Unbleached High Density Tower.”

Bleaching

• D1 use Chlorine dioxide as bleaching agent
• E/OP use Sodium Hydroxide, Oxygen and Hydrogenperoxide as bleaching and delignification agent
• D2 use Chlorine dioxide as bleaching agent

Bleached bagasse pulp then passed “Heavy removal and light removal centricleaner” to eliminate sand and plastic and to reduce water content in “Bleached Stock decker” then sent into “Bleached High Density Tower.”

Pulp Drying

Bleached bagasse pulp from “Bleached High Density Tower” will be sent to two pulp machines.

• Dry pulp machine capacity 250 ADT/day produced 10% moisture.
• Wet pulp machine capacity 100 ADT/day produced 52% moistu

Chemical Recovery

"Weak Black Liquor” collected from cooking and Washing of bagasse pulping will be passed through “Black Liquor Filter” and then sent to “Multiple Effect Evaporator” to increase consistency by steam.  The consistency of “Black Liquor” at this stage will be around 45% and sent to “Cascade Evaporator” to increase consistency to 55% .  The “Strong Black Liquor,” as recovery boiler’s fuel, will be injected and burnt in the boiler.

The burnt strong black liquor will become to “Smelt” which dissolve in the water to be “Green Liquor” and mixed with Ca(OH)2 to recover of NaOH.

Wastewater Treatment

The wastewater treatment system is very economic and efficient process in Europe.  The system is combination of Anaerobic Sludge Digestion System and Activated Sludge system.

Anaerobic Sludge Digestion System

wastewater from anaerobic methane system will give methane gas. Estimated volume of Methane gas is 23,000 m3/day which is equivalend to 18,000 liters of grade C bunker oil.

Activated Sludge System

Wastewater from ANAMET and other pulping process will be sent to activated sludge system.  There are 3 principle stage of treatment. 

• pH. Stabilizing (between 5-8) 
• Oxidation and feed nutrient to bacteria 
• Clarification and sludge removing

Treated Wastewater will be distributed to over 5 sq.km. sugar cane farm land.