Engineering Tips

Mechanical cleaning and hydroblasting are more effective than chemical cleaning, however access to the exchange surfaces is necessary.

Be sure to survey the condensate level glasses on your evaporator effects ahead of the next shutdown and schedule maintenance as needed. Level glasses are an excellent troubleshooting tool but only effective when functional. Give your operators the tools needed to troubleshoot problems.

Overdosing of anthraquinone, an additive which is used to improve digester yield, can result in evaporator fouling. AQ scale can be identified as an off-white film found on the vapor side heat transfer surface of condensers and the final evaporator effect. To remove the scale wash the heat transfer service with sodium hydrosulfide.

If you find an evaporator effect operating with higher than normal condensate level check for a vacuum leak in the condensate outlet line. Alternatively, there may be a blockage in the outlet nozzle due to an impingement baffle failure. When all else fails, disconnect and inspect.

Consider weak liquor rather than condensate to boil out concentrators. Using a weak liquor reduces the volume of spills generated and can effectively increase the overall evaporator capacity in a mill that is evaporator limited.

It is recommended that you avoid the introduction of mill water into the liquor cycle. The exclusion of mill water reduces the build up of non-process elements such as calcium and manganese within the liquor cycle. Keeping the water out can significantly improve mill operations.