Scale control in minerals processing plants is needed when the sum of certain ions in solution exceed the solubility in water under prevailing conditions. While a condition of supersaturation of mineral ions in solution may exist, any sudden change in conditions can cause scale to form in the pipe or vessel. Examples of changes which will cause precipitation of solids from the solution include:
1. Mixing of two or more streams with different chemical make up, resulting in a combined stream which generates a precipitate
2. A sudden pressure drop causing gasses to come out of solution, thus changing the chemistry of the stream and causing a precipitate to form. two common examples in processing plants are at the pump suction (generally off the process water storage tank) and immediately following a flow control valve (i.e. butterfly have controlling water addition to a grinding mill.
3. The addition of a chemical to a processing stream which causes supersaturation then precipitation. an example is addition of lime to process water/slurry causing gypsum to precipitate downstream.
Potential scaling issues are best identified and dealt with in plant/process design (i.e. sizing vessels to maintain operational volume between planned shutdowns for cleaning), but unfortunately not often identified and dealt with at this stage. In most cases the issue of scale only arises once a plant is operational, and thus the need for expert advice should be obtained and a plant audit carried out.
In future blogs I will present a series of examples (identities removed) of scaling issues I have encountered, and the solutions I implemented. I also encourage others to contribute in the comments section, and we can have discussions directly too.
Mateo Solutions personnel have extensive experience in the selection and dosing of antiscalants, and may be able to assist you by auditing your current antiscalant program or working with you or your chemical supplier to achieve the optimum program to suit your needs.
Regards,
Roger
1. Mixing of two or more streams with different chemical make up, resulting in a combined stream which generates a precipitate
2. A sudden pressure drop causing gasses to come out of solution, thus changing the chemistry of the stream and causing a precipitate to form. two common examples in processing plants are at the pump suction (generally off the process water storage tank) and immediately following a flow control valve (i.e. butterfly have controlling water addition to a grinding mill.
3. The addition of a chemical to a processing stream which causes supersaturation then precipitation. an example is addition of lime to process water/slurry causing gypsum to precipitate downstream.
Potential scaling issues are best identified and dealt with in plant/process design (i.e. sizing vessels to maintain operational volume between planned shutdowns for cleaning), but unfortunately not often identified and dealt with at this stage. In most cases the issue of scale only arises once a plant is operational, and thus the need for expert advice should be obtained and a plant audit carried out.
In future blogs I will present a series of examples (identities removed) of scaling issues I have encountered, and the solutions I implemented. I also encourage others to contribute in the comments section, and we can have discussions directly too.
Mateo Solutions personnel have extensive experience in the selection and dosing of antiscalants, and may be able to assist you by auditing your current antiscalant program or working with you or your chemical supplier to achieve the optimum program to suit your needs.
Regards,
Roger