PRESS RELEASE
April 13, 1995
Environmental requirements
add to the corrosion problems
of pulp and paper mills

As pulp and paper mills close their process loops more and more, or make process changes to increase productivity and avoid environmental pollution, they are faced with the unwanted problem of corrosion.

Closed-loop technology results in higher concentrations of corrosive chemicals, which can have a catastrophic effect on vital parts of the production equipment. In addition, process changes in order to enhance the efficiency of a plant often means higher temperature levels and thereby faster reaction times for corrosive chemicals. Furthermore, there may be difficulties in implementing the chlorine free bleaching method in old equipment. The corrosive effects could in some cases be too strong, depending on process variables and equipment materials.
However, most of the troubles caused by corrosion can be avoided by using specially-developed inhibition techniques.

Corrosion means substantial losses
It is estimated that 3.5 percent of the GNP in industrialised countries is consumed by corrosion. The same US report states that at least 20 percent of corrosion damage can be prevented by using the right kind of protection.
The pulp and paper industry, which is more vulnerable to corrosion than the industry as a whole, has naturally much more than just 20 percent to gain from corrosion protection.
According to the Finnish company Savcor Consulting, vital parts of the production equipment can be corrosion protected by using the latest technology. However, in order to achieve the best possible results, the corrosion environment must be examined thoroughly on-site. This is because every industrial plant or process is unique and needs a customised protection system.
“Since we commenced operations in 1981, we have multiplied the lifetime of plants and equipment by providing the right protection against corrosion,” says Jukka Rautiainen, manager of the company’s corrosion protection division for the pulp and paper industry.
Rautiainen claims that corrosion today causes even greater damage than a decade ago. This is not only a consequence of new processes and closed-loop technology leading to a more aggressive chemical environment. “Today, the efficiency demands on industrial plants are set much higher than earlier. Shut-downs are therefore much more crucial in terms of production losses. The rise in pulp prices has also forced the industry to pay more attention to corrosion than previously.”

Focus on corrosion at the planning stage
The greatest benefits can be achieved when the problem is recognised already at the planning stage of a new production facility. With proper corrosion protection, cheaper materials and lighter constructions can be chosen for production equipment and machine parts. In addition, the routines for operating the protection equipment can immediately be utilised on start-up.
“From a technological point of view, corrosion is no easy problem to deal with, because the chemical reactions associated with the phenomenon are very diverse and vary from material to material and from chemical to chemical. Dealing with corrosion problems, therefore, needs a lot of experience and expertise from many fields of technology,” says Rautiainen.
“When a corrosion protection specialist, such as Savcor Consulting, is engaged already at the planning stage, significant savings can be achieved by choosing appropriate materials and less complex constructions. It is much more difficult and expensive to make the required changes at the stage when corrosion has got a strong foothold.”

Older plants need efficient protection
The corrosion problem is particularly troublesome in older pulp and paper plants, where technological changes have made the processes more aggressive. The equipment is used in conditions for which it was not planned in the first place..
“For a plant and equipment already in use, protection against corrosion can be carried out most effectively by using electrochemical methods, i.e. anodic protection or cathodic protection, depending on process conditions. In most cases these methods save costs and time when compared with alternatives such as welding on new surfaces, changing materials or other forms of coating,” explains Rautiainen.
The shorter time for installing an electrochemical protection system means shorter shut-downs of the plant and thereby smaller production loss. This is especially important for the pulp and paper industry, when the demand is high and when production capacity should be maximised.

From research to start-up
A typical project aimed at preventing corrosion in a new plant or inhibiting further corrosion in an existing facility starts with a thorough study of the process environment. Although process conditions can be simulated, the most effective way is to carry out studies on site.
When a potential or cause of corrosion has been found, the right system for protection has to be chosen, and together with monitoring equipment, installed.
According to Jukka Rautiainen, the whole process from initiating research to the commissioning of a complete protection system normally takes four to six months. Up to the present, the fastest delivery and installation of a complete protection system from Savcor Consulting is less than two months.
A complete corrosion protection system comprises anodes or cathodes for protecting the equipment, reference electrodes for measuring the potential on the protect4ed surface, and rectifiers for the supply of cathodic protection current. Accurate current feed is controlled by a data processing unit with system software responding to process changes.
The whole system can also be connected to a Savcor remote control centre over normal telephone lines. Remote control allows for continuous supervision of the corrosion inhibiting system .


Captions:

1. (Two photos) Severe corrosion damage at the digester wash zone was caused by the aggressive cooking process. This problem can be solved by installing a Savcor anodic protection system.

2. An anodic protection system maintains a passive layer on the inner surface of a digester. Anodic protection is also used to restore damage caused by other corrosion protection methods.

For further information, please contact:
Savcor Consulting Oy
Mr. Jukka Rautiainen
Insinöörikatu 8
FIN-50100 MIKKELI, Finland
Tel: +358 55 760 400 Fax: +358 55 760 4211