Patent GB-828452-A (GB)
Title: Improvements relating to the slaking of lime
IPC: C04B2/08
Filed: 1956-11-01
Abstract: In a process of, and an apparatus for, slaking lime, the proportions of unslaked lime and water mixed together are controlled by device sensitive to the consistency of the mixture so that slaked lime issues at a predetermined consistency. Quicklime passed through a port 24, Fig. 1, is mixed with water from a port 26 within a compartment 10 by paddles 25 carried by shafts 18a, 18b, Fig. 3, rotated in opposite directions through gearing 30 and a belt 33 from an electric motor 32.  The mixture in the form of a paste is moved by the paddles along the compartment and passes through openings 90 over plates 91 formed in an end wall 16, into a dilution compartment 11, the paste being diluted and washed down the plates 91 by water sprays 92. Lime slurry in the compartment 11 flows over a weir 102, Fig. 3, into a chamber 105, provided with <PICT:0828452/III/1> <PICT:0828452/III/2> <PICT:0828452/III/3> an overflow 107 and is discharged through a pipe 106.  Impurities such as grit and stones sink into a trough 93 of the compartment 11 and are removed by rubber scraper, blades 110 carried by an endless chain 113 driven from an electric motor 115 and gearing 116, 117, Fig. 1.  The impurities pass over a point 122 to a discharge shoot 123.  Small particles of lime are removed from the blades 110 by water sprays 96.  Referring to Fig. 5, a pulley 34 driven by the belt 33, Fig. 1, is connected by a shear pin 38 with a crank on a shaft 37 carrying a worm 40 meshing with a worm wheel 41a mounted on a shaft 42a coupled to the paddle shaft 18a by a coupling 31a.  The shaft 42a also carries a gear-wheel 43a meshing with a gear-wheel 43b on a shaft 42b coupled to the paddle shaft 18b.  The loading on the paddles due to the mixture paste causes a reaction thrust on the shaft 37 which is slidable to the left in Fig. 5.  The thrust bearing 47, 48, 49 is carried in a plate 50 supported from the gear housing by a diaphragm 53.  A fork 55 secured by a screw 56 to the diaphragm is pivoted by a pin 57 to a lever 58 the upper end of which is pivoted at 63 to a fork 62 on the shaft 75 of the water supply valve 76.  Movement of the shaft 75 to the left is limited by an adjustment screw 82. The lower end of the lever is pivoted at 61 with lost motion (provided by a slot 64) to a bracket 68 and the lever end is urged to the right as shown by a spring 65 adjustable by a screw 67. The lever engages an adjustment linkage 72, 73 which in turn engages a leaf spring 70 fixed at 71 to the gear housing.  Clearly as the load increases due to a thicker mixture the thrust on the shaft 37 causes the valves 76 to open more and increase the water supply and vice versa.  If the lever engages the screw 82 the lower end can move against the spring 65 due to the slot 64 and operate a switch 87 to stop the motor 32 and the quicklime feed means (not shown).  Lime dust and steam are removed from the compartment 11 by the ejector action of a water spray 95, Fig. 1, in an exhaust pipe 97.  The valve 76 can be by-passed when required by a pipe 125 and valve 126.  With this apparatus which operates with a mixture of approximately two parts of quicklime to one part of water, preheating of the water and thus insulation of the apparatus is unnecessary since the heat of reaction raises the water temperature to or near 212 DEG  F.  Moreover the retention time of the mixture in the compartment 10 is short, e.g. 5 minutes.