Ozone process for denim

Abstract

An apparatus and a method for decolorizing a denim fabric with an oxidizing gas is disclosed. The process is initiated by producing compressed air which is processed to generate dry air. The air pressure of dry air is reduced to maintain at 10 psig and thereby generates ozone gas. A negative pressure is maintained to ensure no ozone leak out to ambient from a washer. The denim fabric may be exposed to a controlled amount of ozone gas for a predetermined time such as a process time. Whenever the process time expires, the amount of ozone gas is converted back to oxygen by running a variable speed motor at high speed to create a negative pressure within the processing unit and released to atmosphere. The method also incorporates a means for monitoring the level of ozone concentration in ambient for the safety of operators.

1 . An apparatus for decolorizing at least one denim fabric with an oxidizing gas comprising:
 at least one air compressor for producing compressed air containing approximately of about 21% oxygen and approximately of about 79% nitrogen at an air pressure of about 100 psia;   at least one air separator for producing dry air by removing unwanted elements therefrom;   at least one pressure regulator for regulating the air pressure of dry air at an air pressure of about 90 psia;   at least one oxygen generator for filtering out nitrogen present in the dry air at the air pressure of about 90 psia for producing dry air containing approximately of is about 95% pure oxygen;   at least one pressure regulator for reducing the air pressure of dry air containing approximately 95% of pure oxygen to about 10 psig;   at least one ozone generator for generating ozone gas from dry air containing approximately 95% pure oxygen at an air pressure of about 10 psig;   at least one ozone analyzer for monitoring and analyzing the amount of ozone gas generated in the ozone generator;   at least one proportional integral derivative (PID) control unit designed for controlling the amount of ozone gas for decolorizing the at least one denim fabric;   a plurality of inlet air solenoid valves arranged in connection with at least one washer;   a plurality of outlet solenoid valves being in connection with at least one washer;   a plurality of inlet ozone solenoid valves being in connection with at least one washer;   a plurality of outlet ozone solenoid valves provided in connection with at least one washer;   at least one variable speed motor for creating a negative pressure in the at least one washer;   at least one master control unit designed for setting a regulated period of time;   at least one ozone destruction unit for converting ozone gas to oxygen and releasing oxygen to the atmosphere;   at least one manual air valve for controlling the rate of flow of oxygen released to the atmosphere; and   is at least one ambient ozone monitor for monitoring the ozone concentration in ambient for the safety of operators;   whereby the decolorization rate of the at least one denim fabric can be adjusted by controlling the amount of ozone gas, the duration of the regulated periods of time and thereby applying more abrasiveness on the denim fabric.   
     
     
         2 . The apparatus of  claim 1  wherein the at least one oxygen generator further comprises at least one absorber vessel and at least one oxygen receiver. 
     
     
         3 . The apparatus of  claim 1  wherein the at least one ambient ozone monitor may include at least one ozone sensor for detecting the ozone concentration in ambient. 
     
     
         4 . The apparatus of  claim 3  wherein the at least one ozone sensor may be utilized for shutting down the ozone generator when the ozone concentration in ambient exceeds 0.01 PPM. 
     
     
         5 . The apparatus of  claim 1  wherein the unwanted particles in the compressed air may include oil, moisture or the like. 
     
     
         6 . The apparatus of  claim 1  wherein the at least one PID control unit is in communication with the at least one ozone analyzer for controlling the amount of ozone generated in the at least one ozone generator. 
     
     
         7 . The apparatus of  claim 1  wherein the at least one variable speed motor may be a low speed fan, an exhaust fan or the like. 
     
     
         8 . The apparatus of  claim 1  wherein the at least one variable speed motor is adapted to rotate at high speed and/or low speed for creating the negative pressure in the at least one washer. 
     
     
         9 . The apparatus of  claim 1  wherein the at least one washer may be selected to expose the at least one denim fabric therein. 
     
     
         10 . The apparatus of  claim 1  wherein the apparatus may be utilized for decolorizing a desirable portion of the at least one denim fabric. 
     
     
         11 . The apparatus of  claim 1  wherein the at least one master control unit may be provided in combination with at least one computer. 
     
     
         12 . A method for decolorizing at least one denim fabric with an oxidizing gas comprising:
 a) producing compressed air containing approximately of about 21% oxygen and approximately of about 79% of nitrogen at an air pressure of about 100 psia;   b) producing dry air by removing unwanted elements from the compressed air;   c) regulating the air pressure of dry air at an air pressure of about 90 psia;   d) filtering out nitrogen present in the dry air at an air pressure of about 90 psia for producing dry air with approximately of about 95% of pure oxygen;   e) reducing the air pressure of dry air containing approximately of about 95% of pure oxygen to an air pressure of about 10 psig;   f) generating ozone gas from dry air containing approximately of about 95% of pure oxygen at an air pressure of about 10 psig;   g) analyzing and monitoring the amount of ozone gas;   h) controlling the amount of ozone gas for decolorizing the at least one denim fabric;   i) exposing the at least one denim fabric to a controlled amount of ozone gas for a regulated period of time;   j) creating negative pressure for avoiding the leakage of ozone gas;   k) converting ozone gas to oxygen and releasing oxygen to atmosphere after the completion of the regulated period of time;   l) creating negative pressure to destruct the remaining amount of ozone gas for a regulated period of time; and   m) monitoring the ozone concentration in ambient for the safety of operators.   
     
     
         13 . The method of  claim 12  wherein the method is employed for desirably achieving oxidation of the at least one denim fabric within a predetermined duration of processing. 
     
     
         14 . The method of  claim 12  wherein the method may be utilized in a final stage of laundering operation with oxidizing gases for decolorizing dyes, coloring agents or the like on the at least one denim fabric.