PROCESS AND APPARATUS FOR SLAKING LIME AND DISSOLVING SCALE

摘要

Process and apparatus is disclosed for providing a chemical reaction between calcium oxide containing grit particles to produce calcium hydroxide and heat, capturing the heat of hydration and using it to preheat water initially at ambient temperature, to rise to an elevated temperature to increase the amount of lime present in the water to a supersaturated lime suspension level, with the chemical reaction running to completion, followed by cooling. Heat from a water jacket may be used to raise the temperature in the lime slaker. A process and apparatus is also provided for dissolving scale on internal surfaces of a lime slaker, a lime aging tank, grit separation device and piping and dosing sub-systems, by adding acid into the system with rinse water. A pressurized delivery system that is substantially closed to the atmosphere delivers treating doses of slaked lime slurry under sufficient pressure conditions to maintain a relatively constant back pressure, by means of valving.

主权项

1. A process for producing slaked lime slurry comprising the steps of:
providing a slaking vessel having at least one support location that is provided with at least one load cell, wherein the load cell provides a signal indicative of a total weight of the slaking vessel and its contents; charging a predetermined weight of water to the slaking vessel by using the signal from the load cell to stop charging water to the slaking vessel when the signal from the load cell indicates that the predetermined weight of water has been charged to the slaking vessel, wherein the water has a temperature; charging a predetermined weight of lime feed stock to the slaking vessel by using the signal from the load cell to stop charging lime feed stock to the slaking vessel when the signal from the load cell indicates that the predetermined weight of lime feed stock has been charged to the slaking vessel, wherein the lime feed stock comprises calcium oxide (CaO), and wherein said step of charging a predetermined weight of lime feed stock to the slaking vessel is performed after said step of charging a predetermined weight of water to the slaking vessel is completed; allowing the calcium oxide to undergo a slaking reaction with the water in the slaking vessel at least until the slaking reaction substantially reaches completion, wherein the predetermined weight of water charged to the slaking vessel is in excess of the weight of water required by stoichiometry of the slaking reaction for hydration of all the calcium oxide in the predetermined weight of lime feed stock charged to the slaking vessel; controlling the temperature of the water such that the water is at a temperature within a predetermined range before the lime feed stock is charged to the slaking vessel, the predetermined temperature range of the water being selected such that the contents of the slaking vessel are at a temperature in the range of 175° F. to 195° F. at least when the slaking reaction substantially reaches completion, and wherein no cooling or dilution water is added to the contents of the slaking vessel after said step of charging a predetermined weight of water to the slaking vessel and before the slaking reaction substantially reaches completion; and discharging the slaked lime slurry from the slaking vessel after the slaking reaction substantially reaches completion.