Process for the manufacture of sodium silicate

Claim 2

A process for the manufacture of a sodium silicate solution in a continuous manner from a silicon dioxide-containing material, comprising continuously adding to a reaction zone a stream of said silicon dioxide-containing material and a stream of a sodium hydroxide-sodium carbonate solution, reacting said silicon dioxide-containing material and said sodium hydroxide-sodium carbonate at a temperature of from about 225° to 245° C. and pressure of from about 27 to 32 bars for a time of from about 20 to 35 minutes, and recovering said sodium silicate solution from the reaction zone.

Claim 3

The process of claims 1 or 2 wherein the sodium hydroxide-sodium carbonate solution contains NaOH in a concentration of 180 to 230 grams/liter and Na 2 CO 3 in a concentration of 15 to 20 grams/liter.

Claim 4

The process of claim 1 wherein the silicon dioxide containing material is quartz sand which is placed into suspension with a portion of said sodium hydroxide-sodium carbonate solution prior to being added to said reaction zone.

Claim 5

The process of claim 3 wherein the remainder of said sodium hydroxide-sodium carbonate solution is heated to a temperature of about 250° to 280° C. prior to being added to said reaction zone.

Claim 6

The process of claim 4 wherein the weight ratio of SiO 2 /total NaOH being reacted is from about 1.7-2.6.

Claim 7

A process for the manufacture of a sodium silicate solution in a continuous manner comprising forming a suspension of quartz sand having a grain size below 1 mm in a portion of a solution of sodium hydroxide-sodium carbonate containing 180 to 230 grams/liter of NaOH and 15 to 20 grams/liter of Na 2 CO 3 , heating the remainder of said sodium hydroxide-sodium carbonate solution to a temperature of 250° to 280° C., continuously adding a stream of said quartz sand suspension and a stream of said heated solution to a reaction zone to form a reaction mixture, maintaining said reaction zone at a pressure of 27 to 32 bars and the reaction mixture at a temperature of 225° to 245° C., and recovering a sodium silicate solution from said reaction zone after the reaction has continued for 20 to 35 minutes.

Claim 8

A process for the manufacture of a sodium silicate solution in a continuous manner comprising forming a suspension of quartz sand having a grain size below 1 mm in a portion of a solution of sodium hydroxide-sodium carbonate containing 180 to 230 grams/liter of NaOH and 15 to 20 grams/liter of Na 2 CO 3 , heating the remainder of said sodium hydroxide-sodium carbonate solution to a temperature of 250° to 280° C., continuously adding a stream of said quartz sand suspension and a stream of said heated solution to a reaction zone to form a reaction mixture, maintaining said reaction zone at a pressure of 27 to 32 bars and the reaction mixture at a temperature of 225° to 245° C., and recovering a sodium silicate solution from said reaction zone after the reaction has continued for 20 to 35 minutes.