Ethanol Facility Water Treatment

LIME SLAKING SYSTEMS FOR WATER TREATMENT

Lime Slaking System for a Water Softening Unit at an Ethanol Facility

Equipment & Technology Offered: Bulk Quick Lime Storage Silos (Welded or Bolted) Silo Discharge and Metering Devices Pneumatic Dilute Phase Conveying System Lime Slaker Lime Slurry Mix Tank Lime Slurry Pumping System PLC Based Control Systems
Photo: Lime Make Down System for an Ethanol Facility Requiring a Cold Water Softening System Prior to Reverse Osmosis Purification

Lime is the most widely utilized chemical in the treatment of industrial wastewater effluent. Most people don't realize that Lime is also used in the treatment of process water when the water is a feed material to a "Clean" process such as an Ethanol facility. In this particular example, the local water supply was extremely high in dissolved minerals which would place a high burden on the process equipment. In order to increase the efficiency of the RO water pre-treatment system this client, utilized a process called "Cold Lime" water softening. The term "Cold Lime Water Softening" refers to the process temperature conditions for the precipitation of the dissolved Silica and other minerals. In some cases a combination of Hydrated Lime or Ca(OH)², and Magnesium Oxide MgO are required to get the desired amount of Silica to precipitate. The ratio of Si to Mg in precipitation is 1:1. The facility receives the Lime as CaO or Quicklime in a bulk truck which transfers the material to the bulk silo. Inside the bottom of the bulk silo a Lime Slaker is utilized to hydrate the material to Calcium Hydroxide that is required by the process. The hydrated lime is then made into slurry of known concentration which can be fed into the water flow at a fixed rate to accomplish the precipitation of the dissolved minerals. The preparation of the slurry can be accomplished by either a continuous or batch process depending upon the desired quantity and philosophy of the plant operator. This type of system can also incorporate a mixing tank and the metering systems all located in the base skirt of the Hydrated Lime silo. Usually this type of process requires a second storage tank for the accumulation and storage of the prepared slurry prior to being dosed into the treatment process. This second storage tank would be located outside of the silo skirt area.

Dilute phase pneumatic conveying systems can be utilized in the case where the slurry is being prepared in a mix tank located remotely from the bulk Quick Lime storage silo.

The equipment design expertise for these types of systems is available from Semco Systems Limited.