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Licensed for the sole use of the purchaser.See license agreement penalties for distribution. PAGE 4 COMPRESSED GAS ASSOCIATION INC. CGA G-1.5-2015 plus 200 mesh-8%to 12% plus 325 mesh-10%to 20% minus 325 mesh-70%to 80% 5.4.3 Low magnesium content There is only a trace of magnesium in carbide lime because the lime used in making the calcium carbide must be extremely low in magnesium, Low magnesium is desirable for most chemical uses of lime because the re- sulting magnesium products are water soluble while calcium products are insoluble and are readily recovered by filtration. Additionally, some processes are sensitive to magnesium content. 5.4.4 Cost Carbide lime can be an inexpensive high-grade hydrated lime. Carbide time slurry can be particularly economi- cal when used in substitution for dry commercial lime products that must be slurried or slaked before use. De- livery of ready-to-use liquid slurry can reduce or eliminate dry lime product capital equipment and operating costs. 6 Lime processing and handling Lime slurry from a wet generating process has an approximate solids content of 10% to 15%. Since this is too dilute for economical shipment, the solids content is increased by any of the following methods. 6.1 Decanting Decanting systems are normally a series of connected tanks that receive the slurry from the acetylene genera- tors at 10% to 15% solids. The tanks are used to settle the solids permitting removal of the excess water. As the solids settle to the bottom of the tanks, the water will accumulate on the top. By using a pump to add heavy lime from the bottom of one tank to the bottom of another tank, the water on the top of the receiving tank can be decanted to a water holding tank for reuse, or to a holding pond. A consistency of 30% to 40% solids con- tent can be achieved, depending on the time available for the settling process. 6.2 Lime ponds Lime ponds are normally excavations with earthen dike perimeters. As carbide lime slurry is pumped into a pond from the generating process, the solids begin to settle with the excess water rising to the top. After pro- longed settling, a solids content of 50% or more can be obtained.The water from this process can be reused in the acetylene generators, reused in the production of lime slurry for distribution, or discharged in accordance with the appropriate regulatory approvals. Carbide lime slurry can be further concentrated to a putty,firm enough for shoveling, by settling or by additional filtration to remove excess water. In the case of settled carbide lime, additional water and agitation are required to produce a slurry of uniform density. Agitation can be accomplished with a submerged jet of compressed air, steam, or high pressure water applied through pipes, nozzles, or portable equipment such as circulating pumps mounted on barges. Manually operated hoes and power driven rotating paddles can also be used effectively. Slurries of carbide lime containing up to 40% solids can be pumped satisfactorily with centrifugal pumps. 6.3 Membrane filtration Lime slurry can be concentrated by membrane filtration, a filter system with polypropylene plates that operate at pressures of 160 psi to 200 psi (I 100 kPa to 1380 kPa).3 The solids are concentrated on the plates in block form, and the water removed is roused in acetylene generation or suitably treated and discarded. The higher the temperature, the better the filtration and the lower the water content in the block. Lime blocks may be formed with as little as 15% moisture by weight. 3 kPa shall indicate gauge pressure unless otherwise noted as (kPa, abs) for absolute pressure or (kPa, differential) for differential pressure.All kPa values are rounded off per CGA P-11,Metric Practice Guide for the Compressed Gas Industry[4]. This document licensed for the sole use of the purchaser. It may not be shared with any other person or used after the expiration date without the express written permission of the CGA, Any unauthorized use, reproduction, distribution, or modification of this printed page will result in a$5,000 liquidated damages fee plus loss of access to CGA publications for one year for your company.