Dynamic gas blending system and process for producing mixtures with minimal variation within tolerance limits and increased gas utilization

Abstract

A dynamic blending system and process to produce a mixture of a desired target concentration with minimal tolerance variation and no waste gas generation is provided. The mixture made from the blending process can be utilized without the need to vent. The inventive system and process enables the ability to perform relatively small adjustments to the concentration of the blended gas mixture. The system and process also includes specifically designed sampling protocols that reduce measurement error.

1 . A method for analyzing a gas mixture in a surge vessel without generating waste gas, comprising:
 regulating a pressure of the gas from the surge vessel using a pressure control device;   regulating a flow rate of the gas mixture from the surge vessel using a flow control device;   sending a predetermined quantity of the gas mixture to a secondary analyzer for measurement of the concentration of the gas mixture;   discharging the predetermined quantity of the gas mixture from the analyzer into a sample collection vessel at a fill pressure that is lower than a fill pressure of the surge vessel; and   supplying the gas mixture from the sample collection vessel to a downstream user at a supply pressure that is greater than or at least equal to a supply pressure of the gas mixture in the surge vessel;   wherein the supplying of the gas mixture to the downstream user occurs in the absence of pressurizing the mixture.   
     
     
         2 . The method of  claim 1 , further comprising maintaining the pressure across the secondary analyzer substantially constant. 
     
     
         3 . The method of  claim 2 , further comprising utilizing a pressure regulation device at a location that is upstream of the secondary analyzer. 
     
     
         4 . The method of  claim 1 , further comprising providing and utilizing a pressure regulation device at a location that is upstream of the secondary analyzer to control a delivery pressure of the sample gas to the secondary analyzer while maintaining a substantially constant gas pressure and a substantially constant flow rate through the secondary analyzer by having a flow control device at a location that is downstream of the secondary analyzer. 
     
     
         5 . A system for reducing mixing variation in a dynamic blending process, comprising:
 an active gas source having a first control valve connected to a first flow controller configured for regulating a predetermined flow rate of the active gas;   a balance gas source having a second control valve connected to a second flow controller configured for regulating a predetermined flow rate of the balance gas;   a mixer configured to received the predetermined flow of the balance gas and the predetermined flow of the active gas and thereafter discharge a blended gas mixture from the mixer;   an in-line analyzer situated downstream of the mixer configured to measure the concentration of the blended gas mixture when the pressure across the analyzer, the flow rate of the active gas and the flow rate of the balance gas each has stabilized to their corresponding predetermined values, said in-line analyzer thereafter configured to generate measurement signals referable to concentration levels of the blended gas mixture;   a first back pressure control device located downstream of the in-line analyzer for maintaining a substantially constant pressure across the in-line analyzer;   a controller in communication with the in-line analyzer and the first control valve and the second control valve, said controller responsive to the measurement signals and configured to minimize variation between the measured concentration of the blended gas mixture and a target concentration of the mixture by dynamically fine-tuning the flow rate of the active gas and/or the flow rate of the balance gas in response to the measured concentration of the blended gas mixture; and   one or more surge vessels located downstream of the in-line analyzer to accumulate the blended gas mixture and thereafter direct said mixture as a product stream to an end-user, or alternatively to direct said mixture to a secondary analyzer.   
     
     
         6 . The system of  claim 5 , further comprising a sample collection vessel situated downstream of the secondary analyzer, said sample collection vessel being sized to receive a sample of the blended mixture at a predetermined first pressure and thereafter direct the sample to the end-user at a predetermined second pressure lower than the predetermined first pressure in the absence of utilizing a pressurization device. 
     
     
         7 . The system of  claim 5 , further comprising a second back pressure control device located downstream of the secondary analyzer with back pressure regulator for maintaining a substantially constant pressure across the secondary analyzer. 
     
     
         8 . The system of  claim 5 , further comprising a flow network supply loop, said supply loop comprising a first leg and a second leg, said first leg in flow communication with the one or more surge vessels, a secondary analyzer and a sample collection vessel, and said second leg in flow communication with the one or more surge vessels and the end-user to discharge the product stream directly from the one or more surge vessels to the end-user. 
     
     
         9 . The system of  claim 5 , wherein the sample collection vessel operates at a fill pressure that is lower than a fill pressure of the surge vessel, and further wherein the sample collection vessel operates at a supply pressure that is greater than or at least equal to a supply pressure of the gas mixture in the one or more surge vessels, thereby allowing substantially all of the blended gas mixture that is sampled by secondary analyzer to be routed to the end-user as the product stream.