Your Guide to Raw Water Treatment and Why Your Industrial Facility Needs It

Cleaning the water used by industrial facilities through chemicals involves extensive services from fresh construction to continual maintenance. Chemical cleaning is especially useful for raw water treatment. Raw water is water found in nature that has not been treated for content like particles, ions, minerals, parasites, or bacteria. 

Treatment of raw water is typically done in industrial or commercial settings since it is vital to ensure that raw water is effectively treated before it makes its way to the general public. The suitable design of raw water treatment plants will help any industrial facility avoid losses in the future. Good design can help prevent costly fees for renovation.

Various factors like the varieties and amount of chemicals used play a huge role in how the raw water is treated. Some of the items removed by the raw water treatment system include suspended and colloidal solids, silica, iron, hard matter, pathogens etc.

New construction facilitiesmostly undergo cleaning before becoming operational. Vessels and piping may be full of oils, oxides, scale and debris, which require removal for the effective running of the plant.

To resume operating at peak efficiency, pipelines, vessels and process systems must be maintained at the highest levels of cleanliness. A few of the typical by-products of operating processes include deposits like sludge and scale, metal deposits and precipitates. Such kinds of build-up foul the piping and vessels and can reduce the efficiency of the system substantially, leading to plugging and failure of the unit.

What are the categories of chemical cleaning?

The two main categories of chemical cleaning are pre-operational and post-operational cleaning. Pre-operational is part of commissioning or pre-commissioning activities. Post-operational is maintenance cleaning, a part of regular work with shut-down.

●    Pre-operational cleaning
It consists of the removal of any foreign material left by construction activities either on the system fabrication or piping. Leading considerations in this phase include construction debris like protective coatings, dirt, sand, grease, oil, corrosion products, mill scale etc. 

●    Post-operational
It is conducted for many reasons, such as reduced transfer of heat, safety, reduced flow, reduced surface area, accessibility to complete inspection and many more. The frequency and kind of such chemical cleaning differ as per system design, operating needs and history of water treatment and operation.

Methods of chemical cleaning

●    Fill and Soak mode

It is mostly used for cleaning internal surfaces of big volume pipes and vessels where it is not feasible to have proper circulation. The system is filled with a chemical cleaning solution and drained after some time has elapsed. When needed, this can be repeated multiple times till the equipment is clean. Such mineral acids can react with metal deposits with minimal or no agitation. Such cleaning can be used for both pre and post-operational cleaning.

●    Fill and circulate mode

This mode comprises of filling a system with a solution for chemical cleaning and circulating this using a pump. This method is the most commonly used one in industries. It is vital to keep fluid velocity within a certain range to avoid corrosion. Additionally, the temperature and concentration of the cleaning solution have to be monitored throughout the whole operation.

●    Cascading cleaning

In case big vessels are not designed to sustain full levels of liquids, this method of chemical cleaning is the perfect solution. Chemicals are added at the top of the vessel, and the level at the bottom is maintained as a common method in the cleaning of towers.

●    Slug flow mode

This mode of cleaning is particularly suitable for piping work. In this, a slug of liquid chemicals is applied in between two separators. Either gas or liquid can be used as a driving force to move the slug via the pipeline.

●    Vapour phase mode

In this mode, the process of plant cleaning is completed in a single, fast, efficient and economical way. ‘Process plant’ refers to interconnected piping, exchangers, reactors and big process vessels. This is an upgraded process of steaming where chemicals are infused in a stream of steam. Though this mode is diverse, it is used mostly in post-operational cleaning for removing contaminants like ammonia, benzene, H2S, mercaptans etc.

●    Boiler boil-outs

Experts recommend the removal of organic matter from internal surfaces for the efficient and safe start-up of equipment for steam generation. Compounds of construction grease and oil may result in foaming and reduce heat transfer on the tubes, which can lead to failure of tubes. Boiler boil-outs are recommended as preventive measures before the start-up of operations. This is an alternative alkaline method to clean systems of steam generation.

●    Foam cleaning

Instead of using high volumes of concentrated chemical solution, a gas combined with the same concentration of chemicals is used in this method. This is ideal for systems featuring a large ratio of area to volume. This would provide exact or similar results with a substantially reduced amount of used chemicals and generated waste.

●    Nozzle cleaning mode

This is another method used when the ratio of volume to surface area is high. Instead of filling the complete system with expensive chemicals, a nozzle with a 360-degree rotating head is used to spray the walls of the vessel and keep the volume of chemicals low. This permits the maintenance of temperature and flow of chemical solution in the range that is recommended.

In sum, these are the major methods of using chemicals for raw water treatment.