Lime Slaking Systems
STT knows that no two lime and water combinations are the same, and how these are slaked will have a major impact on the quality of the produced slurry. We can help you select the correct equipment to minimize your lime consumption, material cost and operating cost of your lime slaking system.
The first step toward highly effective slaked lime is selecting the right type of slaker based on your specific parameters.
We design and provide a variety of slaker types, but first collaborates with you to determine the best option for your process and budget. STT takes the time to understand your application, process and site specifics, ensuring you get the type of slaker optimized for your needs.
Lime Manufacturing and the Lime Slaking Process
Quicklime, often referred to as either calcium oxide (CaO) or lime, is manufactured by heating the raw ingredient ‘limestone’ or ‘calcium carbonate’ in large kilns. This process removes CO2 that is trapped in the stone leaving behind CaO and other minor mineral constituents. This CaO molecule is what we consider to be high calcium quicklime.
Quicklime as CaO is not the most useful chemical form for many applications. For applications such as water treatment, flue gas treatment, and when used as a raw ingredient to some chemical applications, the quicklime must first be slaked. Slaking occurs when quicklime is reacted with water to form Ca(OH)2, most commonly called hydrated lime in its dry form or lime slurry or milk of lime in its wet form. The slaking process is exothermic, releasing heat as the quicklime and water mix and chemically combine. A lime slaking system that is not running at its peak could be unsafe, cost you money and potentially shut your process down.
Equipment Used for the Slaking Process
The quality of your slaked lime can have a major impact on your chemical consumption, material cost, and the operating cost of your system. The first step toward avoiding ineffectively slaked lime is selecting the right type of lime slaking equipment based on your parameters, such as pebble size and water temperature. We collaborate with you to determine the best option for your process and budget, offering detention, batch type / mix tanks, vertical ball mill, and mobile lime slakers.
Detention type slakers are relatively inexpensive to install and are well suited to applications where lime quality is reliable. The ZMI Portec Detention Slaker from STT slakes quicklime (particle size up to ¾”) and produces slurry with up to 30% solids. This solids concentration allows any lime added to the slaker to be quickly mixed eliminating hot spots from forming. Our detention slaker produces a highly reactive lime slurry to meet your application needs and maximizes your lime usage.
Research has shown that for any given quicklime source, slaking temperature control is the single most important factor influencing the reactivity of the final lime slurry. Our fully automated temperature control provides a highly reactive slurry and minimizes hot spots.
Batch Slakers / Mix Tanks
Some processes are more simplistic and do not require a high-quality lime slurry. Batch slakers, also commonly referred to as mix tanks, produce a carefully metered slurry and are best suited to applications in which slurry production rate is relatively low and where there are few (if any) changes to the quicklime quality and water sources.
STT can customize batch type slakers / mix tanks with various options to meet your needs. Let STT review your requirements to determine the best fit for your application.
Vertical Ball Mills
When lime or water quality is poor and/or when lime consumption rates are high, STT designs slaking systems utilizing a vertical ball mill. The total grinding process of a vertical ball mill utilizes all residual reaction value, virtually eliminates grit disposal problems, and significantly improves lime usage efficiency.
STT has partnered with Metso to integrate the VERTIMILL® into STT’s complete system package. This, along with our patented lime feed arrangement specifically designed for the Metso VERTIMILL® Slaker, ensures all lime fed to the mill reacts completely with water to produce a highly reactive slurry.
When your environment is demanding or requires grit to be ground and retained in the lime slurry, rather than being screened, collected, and disposed of, STT has the experience to overcome your obstacles and design the right product to achieve your operational goals.
Mobile Lime Slakers
The mobile lime slaker from STT is a self-contained lime detention slaking system that is equipped with all the necessary components needed in a turnkey solution. This lime slaking unit is a plug-and-play slaking plant, no building systems, and with its trailer capability, you can transfer it easily making it both a cost-effective and convenient way to use lime slurry no matter the job and/or location.
Upgrade Your Existing Lime Slaker with New Technologies
Retrofitting your older lime slaker with new technologies can help to make your slaker safer and more efficient at a fraction of the cost of a complete system replacement. STT continually makes improvements to existing components and offers new features that make equipment, like our lime slakers safer, more reliable, and more productive. If you have an existing lime slaker from STT like our ZMI Portec Detention Slaker and METSO® VERTIMILL® Slaker, you can take advantage of these new offerings by contacting us to learn about the retrofits and upgrades available for your specific lime slaker.
Lime Water Treatment
Lime in water treatment is an economical solution for a variety of water treatment applications. Taking advantage of the relatively high pH and alkalinity of the material can contribute to safer and cleaner water.
More specifically, common water treatment applications include:
- Neutralize acidic wastewater
- Aid in the coagulation and removal of organics and pathogens
- Precipitate and remove constituents such as metals and various ions
- Prevent corrosion and leaching in water distribution piping
- Soften hard water sources at water treatment plants
- Stabilize biosolids produced from wastewater processes into sellable products
What is the slaking of lime?
Slaking is the term used for the chemical reaction that occurs when quicklime (CaO) is mixed with water. This reaction is commonly performed with an excess of water, and this creates a slurry of solid calcium hydroxide particles floating in water and this is commonly called ‘Lime Slurry’ or ‘Milk of Lime’. This exothermic reaction releases heat and special reaction vessels called ‘Lime Slakers’ are important to control this process in a safe and efficient manner.
What is slaked lime used for?
Slaked lime has a wide variety of uses including water treatment for municipal drinking water and wastewater, industrial wastewater, acid mine drainage treatment, and flue gas treatment and as a raw ingredient to produce various chemicals and is key in the Kraft paper production process among countless other uses. Slaked lime owes its versatility to its capability to adjust pH and neutralize acids in a relatively safe and cost-effective manner compared to competing chemicals and technologies.
Why is the slaking of lime necessary?
While quicklime is a very economically advantageous form of calcium reagents in terms of potency and shipping, CaO is not immediately useful in a wide range of applications. The most chemically useful form of calcium reagents for pH adjustment is calcium hydroxide (Ca(OH)2) due to this form being immediately chemically available for neutralization of acids in water or waste flue gases. Lime slurry is a chemical base that is already in preparation of fine particles of suspended solids in water that can participate in chemical reactions in the most efficient manner.