Wet-End Manufacturing Process for Bitumen-Impregnated Fiberboard

Abstract

A process for manufacturing fiberboard by preparing a fiber slurry mixture including containing cellulose fibers and water then atomizing a liquid bituminous material, such as asphalt. The liquid bituminous material is atomized by mixing it with a pressurized gas, such as compressed air, forming a mist comprising droplets of bituminous material having a diameter between 20 microns and 50 microns. A water spray solidifies the bituminous material droplets thereby forming bituminous particles which fall into the fiber slurry within the spray chamber. From there the slurry is sheared, dewatered, and dried, forming a finished fiberboard.

1 . A process for manufacturing fiber board comprising the steps of:
 preparing a fiber slurry mixture by adding a material containing cellulose fibers to water and agitating the fiber slurry mixture;   transferring the fiber slurry mixture to a spray chamber;   heating a bituminous material to a temperature between 300 and 440 degrees F., wherein the bituminous material is in a liquid state;   atomizing the liquid bituminous material within the spray chamber by mixing the liquid bituminous material with a pressurized gas, forming a mist comprising droplets of bituminous material having a diameter between 20 microns and 50 microns;   solidifying the bituminous material droplets by spraying water into the mist thereby forming bituminous particles which fall into the fiber slurry within the spray chamber;   shearing the slurry containing cellulose fibers and bituminous particles;   dewatering the slurry containing cellulose fibers and bituminous particles, leaving a wet mat containing fibers and bituminous material;   drying the wet mat thereby forming a fiber board; and   optionally, further including the step of applying a coating to both major sides of the dried fiberboard.   
     
     
         2 . The process of  claim 1 , wherein after heating the bituminous material, including the additional step of heating the bituminous material to a temperature between 400 and 450 degrees F. 
     
     
         3 . The process of  claim 2  wherein the additional step of further heating the bituminous material is performed in a heat exchanger, wherein mineral oil heated to a temperature of approximately 600 degrees F. is circulated about the heat exchanger as the bituminous material passes through the heat exchanger. 
     
     
         4 . The process of  claim 1  wherein the bituminous material is atomized by mixing with a gas, optionally compressed air, which may be heated to a temperature between 200 degrees F. and 300 degrees F., wherein the gas has a pressure of between approximately 10 psi and 50 psi; alternatively, wherein the gas has a pressure of between approximately 20 psi and 40 psi. 
     
     
         5 . The process of  claim 1  wherein the material containing cellulose fibers is selected from the group consisting of wood pulp, sugar cane, switch grass, straw, and recycled paper pulp. 
     
     
         6 . The process of  claim 1  wherein the solid content of the slurry is less than about 10% weight but greater than about 8% weight. 
     
     
         7 . The process of  claim 1  wherein the asphalt content of the slurry is less than about 30% weight but greater than about 10% weight. 
     
     
         8 . The process of  claim 1  further including the step of adding a wax to the slurry wherein the wax content is greater than about 1.0% weight but less than about 2.5% weight; optionally, further including the step of adding a starch to the slurry wherein the starch content is greater than about 1.0% weight but less than about 3.0% weight; optionally, further including the step of adding aluminum sulphate to the slurry wherein the aluminum sulfate content is greater than about 1.0% weight but less than about 2.0% weight; optionally, further including the step of adding a solvent-based or water-based dye to the slurry wherein the dye content is greater than about 0.001% weight of the slurry but less than about 2.0% weight of the slurry. 
     
     
         9 . The process of  claim 8  wherein the dye has a pH between about 6 and about 8. 
     
     
         10 . The process of  claim 1  wherein the coating is selected from the group consisting of asphalt, flux oil, and fuel oil. 
     
     
         11 . The process of  claim 10  wherein the total content of the coating is between about 1% and about 10% weight of the fiber board. 
     
     
         12 . The process of  claim 1  wherein the total bitumen content of the fiberboard is between about 10% and 40% by weight. 
     
     
         13 . A process for producing bituminous particles by atomizing a molten bituminous material comprising the steps of:
 heating a bituminous material to a temperature such that the bituminous material is in a liquid state;   passing the liquid bituminous material through a nozzle, the nozzle having a liquid passage and a plurality of gas passages, and an atomization chamber, wherein the liquid bituminous material and a pressurized gas provided through the plurality of gas passages are mixed together within the atomization chamber forming a mist of liquid bitumen droplets;   solidifying the liquid bitumen droplets by spraying with water;   wherein the bituminous material is heated to a temperature between 300 and 440 degrees F.; and   wherein the bituminous material is atomized by mixing with a gas having a pressure of between approximately 10 psi and 50 psi; alternatively, wherein the bituminous material is atomized by mixing with a gas having a pressure of between approximately 20 psi and 40 psi.   
     
     
         14 . The process of  claim 13  further including the step of additionally heating the bituminous material to a temperature of between 400 to 450 degrees F. 
     
     
         15 . The process of  claim 13  wherein the pressurized gas is compressed air. 
     
     
         16 . The process of  claim 15  wherein the compressed air is heated to a temperature between 200 degrees F. and 300 degrees F. 
     
     
         17 . A process for manufacturing fiber board comprising the steps of:
 preparing a fiber slurry mixture by adding a material containing cellulose fibers to water and agitating the fiber slurry mixture,   the material containing cellulose fibers being selected from the group consisting of wood pulp, sugar cane, switch grass, straw, and recycled paper pulp, and wherein the solid content of the slurry is less than about 10% weight but greater than about 8% weight;   heating a bituminous material to a temperature between 300 and 450 degrees F., wherein the bituminous material is in a liquid state;   atomizing the liquid bituminous material within the spray chamber by mixing the liquid bituminous material with a gas,   wherein the gas is supplied at a pressure between 20 psi and 40 psi, and   wherein the gas is supplied at a temperature between 200 degrees F. and 300 degrees F.,   producing a mist comprising droplets of bituminous material having a diameter between 20 microns and 50 microns;   solidifying the bituminous material droplets by spraying water into the mist,   the water having a temperature between 45 degrees F. and 55 degrees F., thereby forming bituminous particles having a diameter between 20 microns and 50 microns which fall into the fiber slurry within the spray chamber, wherein the asphalt content of the slurry is less than about 30% weight but greater than about 10% weight;   shearing the slurry containing cellulose fibers and bituminous particles;   dewatering the slurry containing cellulose fibers and bituminous particles, leaving a wet mat containing fibers and bituminous material; and   drying the wet mat thereby forming a fiber board, the finished fiber board having a total bitumen content between about 10% and 40% by weight.   
     
     
         18 . The process of  claim 17  wherein the gas is compressed air. 
     
     
         19 . A process for producing bituminous particles from a molten bituminous material comprising the steps of:
 heating a bituminous material to a temperature such that the bituminous material is in a liquid state;   passing the liquid bituminous material through a liquid passage for receiving an adjustable flow of liquid bituminous material thereby forming liquid bitumen droplets; and   allowing the liquid bitumen droplets to enter a slurry and solidify in the slurry, wherein the slurry comprises a material containing cellulose fibers and water.   
     
     
         20 . The process of  claim 19  wherein the liquid passage is disposed within a nozzle, the nozzle including a plurality of gas passages configured to allow flow of a pressurized gas and further comprising the step of mixing the flow of liquid bituminous material with the flow of pressurized gas to form a mist of liquid bitumen droplets; and wherein the bituminous material is atomized by mixing with the pressurized gas having a pressure of between approximately 10 psi and 50 psi; alternatively, wherein the bituminous material is atomized by mixing with the pressurized gas having a pressure of between approximately 20 psi and 40 psi. 
     
     
         21 . The process of  claim 20  wherein the pressurized gas is compressed air that is optionally heated to a temperature between 200 degrees F. and 300 degrees F. 
     
     
         22 . The process of  claim 19  wherein the bituminous material is heated to a temperature between 300 and 440 degrees F. 
     
     
         23 . The process of  claim 22  further including the step of additionally heating the bituminous material to a temperature of between 400 to 450 degrees F. 
     
     
         24 . The process of  claim 19  wherein the material containing cellulose fibers is selected from the group consisting of wood pulp, sugar cane, switch grass, straw, and recycled paper pulp, and wherein the solid content of the slurry is less than about 10% weight. 
     
     
         25 . The process of  claim 19  wherein the bituminous material content of the slurry is less than about 35% weight of total solids but greater than about 10% weight of total solids.