The paper-making processes generate a variety of corrosive media which have significant effects on the equipment. Before titanium was introduced to the pulp and paper industry, a plurality of materials such as glasses, leads, polyesters, ceramics, rubbers and stainless steels were initially selected to meet the corrosion-resistant requirements. Due to its exceptional corrosion and erosion resistance, titanium, usually unalloyed Grade 2, is widely used in almost every section of the paper-making process nowadays. The higher initial investment costs are soon compensated by increased reliability, extended lifetime of the titanium equipment and low maintenance cost.

Acid-Making Facilities in Pulp & Paper Industry

In the scrubbing system, the high-temperature wet sulfur dioxide flows from the cyclone dusting device through the scrubbing column and venturi tube. The temperature at the inlet of venturi is as high as 400~480°C. Its highest flow rate can reach 60 m/s with an average flow of 2 m³/s along with mineral dusts. Although the temperature decreases to 70°C at the outlet, the sulfuric acid content reaches 0.4%. The harsh conditions in the scrubbing system demand corrosion-resistance performance of a set of the acid-making facilities such as cyclones (isolators), nozzle cylinders, dimesters, U-type bends, venturi tubes, pumps and pipe fittings, etc. Traditional austenitic stainless steels only last for 2~3 months while titanium has proven resistance to these high aggressive circumstances. The titanium blower, which feeds particle-containing sulfuric gases in the boiler system, has been documented more than 10 years normal function without maintenance.

Water Supply Facilities in Pulp & Paper Industry

The pulp and paper industry consume huge amount of water. The natural water shall be flocculated before using. The flocculation agents added are FeCl₃, FeSO₄, AlCl₃, and Al₂(SO₄)₃. The dissolving tank which contains the agents will be heated up to 100°C and is subject to corrosive attacks. Compared to lead, stainless steels and glass fiber materials, commercially pure titanium Grade 2 has proven its superior corrosion resistance to the agents, exhibiting no corrosion.

Bleaching-Agents Making & Bleaching Facilities

The main bleaching agents in pulp and paper industry are chlorine and sodium chlorate, which are made from an electrolytic process. The electrolytic tank is usually made from full structure or lined titanium sheets. The titanium anodes with thin ruthenium oxide surface coatings have replaced conventional graphite anodes. The titanium-based anodes not only offer higher current efficiencies and reduced power consumption, they are also dimensionally stable and cause less contamination of both the cell electrolyte and the chlorine. The titanium pumps used in the production of liquid chlorine and calcium hypochlorite can work with an extended life span without any corrosion. Titanium can not only be used for the manufacture of bleaching agitators of calcium hypochlorite, the titanium cladding or lined steel plates are widely applied for chlorine dioxide bleaching devices.

Cooking and Recycling Facilities

In the acidic cooking process of bleaching, the devices in contact with the bleaching agents, such as heaters, thermowells and feeding pumps(both bodies and blades) shall all be made of titanium. Due to its superior corrosion resistance to alkaline solutions, titanium sewage pumps are used for the recycling of alkalis in paper-making industry. In the cooking process, both the effluent-storage tank and recycling column, that are used for recycling active carbon powder and dark brown lignin, shall be made of titanium materials.