Papermaking Wastewater Treatment Project: IC Anaerobic GFS Tank
description
Papermaking wastewater falls into three categories, namely pulping wastewater (black liquor), intermediate washing wastewater and paper machine white water, with vastly different pollutant characteristics.
Alkaline pulping generates wastewater featuring high COD, high alkalinity, high lignin content and strong colority. The dominant biochemical treatment process adopted is anaerobic-aerobic combined treatment, with an IC anaerobic reactor deployed for high-concentration COD wastewater. This process degrades macromolecular lignin and cellulose, and biogas produced can be combusted for heat supply, achieving a COD removal rate of 50% to 70%.
GFS tank composed of Glass-Fused-to-Steel (Glass-lined-steel）sheets meets high-efficiency equipment for treating high-concentration organic wastewater from the paper industry.
The Glass-fused-to-steel (GFS) panel are composed of two materials: glass and steel. The material of properties ensure the super anti-corrosion, designed for high aggressive anaerobic environment of the papermaking industry.
Glass fused to steel is a permanent, molecular bond created by fusing a specially formulated silica-based glass enamel to a base sheet of steel at very high temperatures (around 820°C / 1500°F) ,combines the advantages of both materials -- the strength and flexibility of steel and excellent anti-corrosion properties of glass.
Specification
|
Coating thickness |
250~450um |
|
pH range |
Standard grade 3~11; Special grade 1~14 |
|
Coating process |
Standard 2 coats 2 fire; 3 coats 3 fire available |
|
Hardness |
6.0 Mohs |
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Elasticity |
500KN/mm |
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Service life |
More than 30 years |
Advantages
● Superior Anti-Corrosion Performance Suitable for Severe Corrosive Anaerobic Environment in Papermaking (Core Advantage)
There are three major corrosion sources inside the papermaking IC reactor: hydrogen sulfide generated under anaerobic conditions (which forms sulfuric acid when contacting water vapor), volatile fatty acids (VFAs) produced from lignin degradation, chloride ions from bleaching wastewater, as well as frequent pH fluctuations ranging from 5.5 to 11.
1.The enamel layer is an inorganic glass glaze sintered at a high temperature of 850°C, fused integrally with the steel plate. It features a dense, pore-free structure and outstanding chemical inertness, enabling stable long-term operation under pH conditions ranging from 2 to 12.
2.It fully resists gas-phase corrosion caused by hydrogen sulfide. The gas-liquid interface is a severely corroded zone for lined carbon steel tanks; fiberglass reinforced plastic (FRP) and glass flake coatings will peel off and leak within 3 to 5 years.
3.It resists chloride ions and salts in bleaching wastewater without pitting corrosion or crevice corrosion.
4.The steel plates undergo standardized double-sided enameling and firing in the factory. There are no quality defects caused by on-site welding or lining construction. Special anti-corrosion sealant is applied at welds and joints to prevent medium penetration into the base steel plate.
Smooth inner wall minimizes scaling and ensures stable operation of granular sludge inside the IC reactor.
1.The compact and smooth enamel glaze surface boasts an extremely low friction coefficient, so fibers, lignin and sludge contained in papermaking wastewater are hard to adhere and compact.
2.It reduces the accumulation of biofilm and scale on the tank inner wall, preventing localized anaerobic acidification and aggravated corrosion.
3.The IC reactor relies on the upward flow of biogas to drive internal circulation. The smooth inner wall reduces flow resistance, delivering more stable internal circulation, less loss of granular sludge, and consistent reactor loading capacity.
4.The cleaning frequency is greatly reduced, cutting losses caused by shutdown for flushing.
● Excellent wear and scouring resistance, suitable for papermaking wastewater with high fiber content.
Papermaking wastewater contains a large quantity of fine wood pulp fibers and sediment. The water distribution zone at the bottom of the IC reactor and the area under the three-phase separator are subject to long-term scouring by high-velocity water flow.
1.The inorganic enamel glaze has far higher hardness than epoxy and vinyl ester FRP, offering superior resistance to abrasion from solid-liquid two-phase flow scouring.
2.The scoured areas of carbon steel lined tanks are extremely vulnerable to abrasion penetration that exposes the base steel, while enamel will not suffer rapid damage under long-term scouring.
● Modular assembly design enables fast construction, capacity expansion and relocation.
1.All enameled steel plates are prefabricated and double-side glazed in the factory. Standardized modules are transported to the site for bolted assembly, eliminating on-site welding and anti-corrosion lining work.
2.For IC reactors of the same volume, the construction period is shortened by more than 50% compared with on-site welded carbon steel tanks, which greatly cuts the project schedule and enables earlier commissioning for wastewater treatment.
3.Capacity expansion can be realized by directly adding tank steel plates during production expansion
4.Less high-altitude work is required, resulting in higher safety during assembly construction.
● Excellent tightness achieves zero biogas leakage for safe operation.
The IC reactor is a pressurized anaerobic tank with biogas pressure ranging from 0.01 to 0.3 MPa.
● Extremely low operation and maintenance costs throughout the full life cycle, delivering better economic benefits in the long run.
1.Minimal routine maintenance is required: only regular visual inspection of the enamel surface, with no annual procedures such as rust removal, painting or lining repair.
2.Service life reaches 30 years.
3.After scrapping, the steel plates can be 100% recycled and reused.
It is unlikely to halt production due to corrosive perforation, lowering the risks of excessive wastewater discharge, production restriction and fines for paper mills.
