Lime Use

Question

How many operations use lime in their water treatment operations and what are the actual headaches that exist with its use? It seems the "I hate using lime because....." runs a large range.  I'd like to get an understanding of that actual range of dislikes from those  that have a personal complaint.

MOHAMMED NAZEER · Answer

Hello,In SWRO plant we used lime  and kept at silo for LSI to adjust PH.We had plant of 40,000M/day our lime dosing used after Ro and before Storage tank.It required heavy footprint isolated to building.We need to liquid to prepare lime milk is for dosing etc issues.Lime should be kept at good storage and out of sunlight and cool temperature envirnoment is required freezer 93-4 months last).If we keep refrigerator 3-4 weeks and we keep boxes package only 4 days last.
Other than RO for pretreatment of hard water lime softening process should be used expecially biocarbonate hardness removal.Heavy metal removal also lime process will use.

Miguel P. Smurawski Aivasovski · Answer

I work with desalination, and 90% of the problems are related to poor delivery of CO2. However due to inertia, NOBODY goes for advanced technologies such as TOMCO´s PSF. The core issue is that the equipment are rented and the gas suppliers don´t care about performance. In fact they prefer you get poor results: Sales are increased.

Michael Dwyer · Answer

The reason it is used so much is the cost of lime, which often outweighs the handling issues.  Some people now go to a lime/magnesium blend or even magnesium oxide alone.  As stated by others it depends upon what you are using the lime for if it is possible to replace it with something else.

Kris Strom · Answer

I have some experience in lime use at a Kraft pulp mill that also had a water treatment plant using milk of lime during the winter months for softening. 
Regarding quality, the purchased lime we received would vary in quality fairly significantly. We would get layering of high quality and low quality product in our storage silos that caused many issues in keeping the process stable as the supervisory controls and field testing could not adjust the process quickly enough to account for the variation. The physical quality also varied significantly (high quality pebbled lime to powdery and highly reactive crushed lime to low grade undercooked material often containing inert aggregate) which caused many issues in the feed systems; screw conveyor pile ups, erratic solids production in the slakers, and blower system pluggages.
Regarding handling, lime dust gets everywhere. Initial leaks may be localized to a small spot but if there is air movement that dust is travelling and it makes area housekeeping a relative nightmare. Field operators have to wear extensive PPE to stay safe around it and they are never too eager to work around it. Handling systems are difficult to maintain with bag filters fighting pluggages constantly, switching valves wearing out quickly, rotary feeder packing wearing out quickly, transfer lines having holes worn in them at the elbows, silos bridging, rappers on silos needing regular maintenance, and screw conveyors jamming up. We received lime via truck b-trains so unloading in a clean and timely manner was also an issue at times if the system wasn't functioning near top condition. 
Past the slaking stage, there were always safety issues with the heat generated from the reaction. Pumping the lime slurry was also a harsh duty for the pumps and lines requiring regular pipe cleaning and replacement of worn components.
Specific to the water treatment plant, the milk of lime would vary in strength due to the issues mentioned above so maintaining the reaction well pH at 11 or higher was always challenging. The sludge blanket was also difficult to maintain at a constant level due to the erratic quality. A lack of consistent sludge blanket in the clarifier would always result in solids carryover to the gravity filters which would require increased backwash frequency.

Jack Zhao · Answer

This can be a long story. Think that largest user would be Canadian oil sites using warm lime softening to remove hardness and silica from produced water. Other example not directly water but related is water treatment sludge drying/neutralization using lime. 
Yes, some issues from unloading to dosing ,sludge recycle and process control and operation,you can get some more ideas via google above topics.

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