Patent Application
20070289905
The block diagram of
The cleaning solution comprises a cleaning agent diluted with water. The cleaning agent typically is sodium hydroxide (NaOH) but other types of cleaning agents may be successful.
A basic version of system 10 includes a main tank 23 for holding the cleaning solution. Tank 23 has an outlet port that a duct 45 connects to an inlet port of a pump 30. (The term “duct” refers hereafter to a pipe, hose, or other liquid conduit.) Pump 30 has an outlet port connected to a fermentation tank through a duct 51, an electrically operated valve 40 and an outlet connection 55. Opening valve 40 allows pump 30 to pump cleaning solution to the fermentation tank. An electrically operated valve 70 opens to allow a return pump, not shown, to return the cleaning solution from the fermentation tank to tank 23 through a connector duct 75 and an inlet duct 56.
Closing valve 40 allows pump 30 to pump cleaning solution from tank 23 to a filter 37 through duct 52. Filter 37 removes the contaminants carried in the cleaning solution and previously washed from the fermentation tank in the ethanol plant.
A preferred filter 37 design uses a spring-loaded cleaning disc that travels up and down inside a cylindrical filter medium to remove collected contaminants. One such commercially available filter is the Ronningen-Petter DCF-800 and DCF-1600 Twin mechanically cleaned filters presently available from Eaton Corp., 9151 Shaver road, Portage, Mich. 49024. Web-based information about the DCF is presently available at this URL: http://www.ronningen-petter.com/Ethanol-CIP-Fluids.asp. This information is incorporated by reference into this application document.
A sensing element 34 receives cleaning solution flowing from filter 37 and measures or detects the level of some parameter or characteristic of the cleaning solution. Sensing element 34 provides on a path 58, a condition signal that indicates the level of this parameter or characteristic of the cleaning solution. Cleaning solution flows from sensing element 34 through a duct 35 to the top of tank 23.
Typically, this measured parameter is the concentration of the cleaning agent in the cleaning solution, but the condition signal may indicate the level of a different parameter, or even several parameters. Temperature and the level of fiber concentration, sediment, or dissolved contaminants are other possible cleaning solution parameters that particular types of a sensing element 34 might measure.
Measuring freshly filtered cleaning solution improves the accuracy of the level of the measured parameter, at least where NaOH concentration is the measured parameter. In addition, the constant circulation of the cleaning solution from tank 23 through filter 37 and back to tank 23 stirs the cleaning solution so that the concentration of the various constituents of the cleaning solution are uniform regardless of the type of active cleaning constituents in the cleaning solution.
A preferred sensing element 34 for measuring liquid conductivity has a tyroidal flow-through design, with the liquid flowing through the sensor. One such commercially available sensor is designated the 871FT Series of “Non-Invasive Sanitary and Industrial Flow-Through Conductivity Sensors available from The Foxboro Company, 33 Commercial Street, Foxboro, Minn. 02035-2099. Web-based information about the 871FT series is presently available at this URL: http://www.foxboro.com/us/eng/products/instrumentation/echemanalytical/electrodelessconctivity/models/871FT+Sensors.htm. This information is incorporated by reference into this application document.
The condition signal may in a very simple system, be used by an operator for manually controlling the measured parameter of the cleaning solution. For example, if the condition signal indicates the concentration of cleaning agent present in the cleaning solution, the operator can add water or concentrated cleaning agent to set the concentration of the cleaning agent in the cleaning solution to a desired value. If the condition signal measures contaminants dissolved in the cleaning solution, the condition signal level may indicate to the operator that the cleaning solution must circulate through filter 37 for a longer period before reuse, or cannot be reconditioned for further use.
The preferred system 10 shown in
System 10 operates under the control of a controller 27. Controller 27 may comprise any of the various microprocessor-based devices commonly used for industrial control. Controller 27 receives status signals indicating system 10 performance, such as the condition signal on path 58 from sensor 34, and sends control signals to various valves and other system 10 components that direct flow of the cleaning solution as required to implement the process for cleaning the fermentation tank and reconstituting the cleaning solution.
In this preferred system 10, a tank 13 holds concentrated cleaning solution. Opening an electrically controlled cleaning agent valve 20 allows concentrated cleaning solution to flow into tank 23 through ducts 16 and 43. Valve 20 opens and closes responsive to the state of a cleaning agent valve control signal controller 27 provides on path 22.
In case the concentration of the cleaning solution in tank 63 is too high for one reason or another, or the fluid level in tank 23 is too low, system 10 can add water to tank 23. An electrically-operated valve 60 opens and closes responsive to a control signal that controller 27 provides on path 68. When valve 60 is open, water available at a duct 78 flows through valve 60 and a duct 66 to tank 23.
Controller 27 also manages flow of cleaning solution between tank 23 and the fermentation tank. After fermentation is complete and the fermented liquid has been pumped to the distillation section of the ethanol system, the fermentation tank is cleaned and disinfected using cleaning solution from tank 23.
During startup of system 10 and after tank 23 is emptied because the cleaning solution in tank 23 can no longer be reconstituted, controller 27 sends signals to open both valves 20 and 60 to prepare a fresh volume of cleaning solution. This may occur during a fermentation cycle so no time is lost. Controller 27 holds valve 40 closed during this cleaning solution preparation phase with a closure signal on path 48.
During the cleaning solution preparation phase, pump 30 runs constantly to mix the cleaning solution in tank 23. Because the volume of cleaning solution in tank 23 is quite large, thorough mixing may require that pump 30 circulate the cleaning solution for a substantial period.
Sensor 34 provides a signal on path 58 indicating the concentration of the cleaning solution. Controller 27 opens or closes valve 20 based on the indicated concentration of the cleaning solution, to maintain the proper concentration of the cleaning solution.
A tank level sensor 63 provides a signal on path 65 that specifies the amount of liquid in tank 23. Once the liquid in tank 23 reaches its proper level, controller 27 provides a signal that closes valve 60 to prevent overfilling of tank 23, and a signal that closes valve 20 to maintain the proper cleaning solution concentration.
Preferably, duct 43 includes an extension 43a that empties the concentrated cleaning agent into the cleaning solution well below sensor 63. Injecting concentrated cleaning agent below the surface of the cleaning solution, speeds mixing of the concentrated cleaning agent into the cleaning solution.
When preparing fresh cleaning solution, in general controller 27 should hold valve 20 open only for relatively short periods when adding cleaning agent to the cleaning solution. After valve 20 has been open for a period that may increase cleaning solution concentration by approximately 1%, controller 27 should close valve 20 for a longer period to allow circulation through pump 30 to mix the cleaning agent with the cleaning solution.
After the cleaning solution has been prepared, pump 30 continues to run to cycle cleaning solution through filter 37 and sensor 34. This allows controller 27 to continually receive accurate values of the cleaning solution parameters that sensor 34 monitors, and to change parameters that are not optimal. So for example, temperature of the cleaning solution may be controlled at the same time that cleaning agent concentration in the cleaning solution is controlled.
Since the circulation of cleaning solution through tank 23, pump 30, filter 37, and the various ducts connecting these elements mixes the concentrated cleaning agent with the cleaning solution, the design of all these elements should avoid any dead spots where mixing may proceed slowly. Accordingly, some designs may benefit from returning freshly filtered cleaning solution in duct 35 to near the top of tank 23, or even above the level sensor 63. In this way, additional mixing of the concentrated cleaning agent and the cleaning solution itself may occur within tank 23.
When the time to pump cleaning solution to the fermentation tank arrives, controller 27 sends a control signal on path 48 to valve 40 to open valve 40. With valve 40 open, pump 30 pumps cleaning solution to the fermentation tank. After the proper amount of cleaning solution has flowed to the fermentation tank, controller 27 sets the signal on path 48 to close valve 40.
After an appropriate time interval for the cleaning operation in the fermentation tank or possibly some other criterion, controller 27 sends a control signal on path 72 to valve 70. The pump for returning the cleaning solution to tank 23 then pumps the now-contaminated cleaning solution back to tank 23 through ducts 75 and 56. After nearly all the cleaning solution has flowed to tank 23, controller 27 sets the signal on path 72 to close valve 70.
Flushing or rinsing the fermentation tank follows to remove remaining cleaning solution from the fermentation tank and prepare the fermentation tank for another batch of mash. This requires setting valves to direct feed water in duct 78 to the fermentation tanks that have been just cleaned, and then to drain the water used for rinsing. These operations may be done manually or under control of controller 27, depending on the sophistication of the ethanol plant.
Once the used cleaning solution has been pumped from the fermentation tank to tank 23, the cleaning solution is then reconstituted. Reconstitution includes restoring of the proper concentration of cleaning agent in the cleaning solution. Controller 27 monitors the signal on path 58 that indicates the concentration of cleaning agent in the cleaning solution.
When the concentration of the cleaning agent is too low, controller 27 provides a signal on path 22 that opens valve 20, to allow concentrated cleaning agent to flow into tank 23. Pump 30 runs continuously to circulate the cleaning solution from tank 23 through filter 37 and sensor 34 and back to tank 23. This circulation assures thorough mixing of cleaning agent in the cleaning solution and continues filtering of the cleaning solution. Controller 27 monitors the signal on path 58 that indicates the concentration of the cleaning agent in the cleaning solution.
As mentioned some types of preferred filters 37 require periodic cleaning. This cleaning may be in the nature of a backflush, or may involve mechanical brushing or scraping. Controller 27 may initiate cleaning events using a cleaning control signal on path 81 to filter 37. Controller 27 may issue the cleaning control signal at scheduled times or after a certain number of fermentation tank cleaning events. Or each filter cleaning event may occur whenever fermentation tank cleaning occurs, and no cleaning solution is in tank 23.
As mentioned above, the concentrated cleaning agent preferably flows into tank 23 well below the surface of the cleaning solution. This assures that the cleaning agent quickly mixes with the cleaning solution so that the cleaning agent concentration sensed by sensor 34 is as accurate as possible, or at least is inaccurate for only a short time.
This process continues for each fermentation cycle until the cleaning solution reconstitution is no longer possible or economical. At this point, the cleaning solution in tank 23 is discarded. Controller 27 then opens valves 20 and 60 to allow water and concentrated cleaning agent to flow into tank 23 to form a fresh batch of cleaning solution.
This is a regular application filed under 35 U.S.C. § 111(a) claiming priority, under 35 U.S.C. § 119(e)(1), of provisional application Ser. No. 60/805,291, previously filed Jun. 20, 2006 under 35 U.S.C. § 111(b).
| Number | Date | Country | |
|---|---|---|---|
| 60805291 | Jun 2006 | US |
