As shown in
Exemplary materials of construction include high-density polyethylene and Teflon with Hastelloy where necessary although metal parts are preferably kept to a minimum. Corrosive-resistant materials, include but are not limited to, high-density polyethylene, polyvinyl fluoride, Hastelloy, and/or Teflon. The wetted interior of the processing vessel 11 is suitable large so as to receive a diffraction grating, e.g. approximately 100×60×30 cm in dimension. In this regard, an inclined platform nominally 100×50×10 cm will support the optic. While any incline of 1-90 degrees is possible, preferably the incline is about 2-3° draining to the sump 12 (shown as a lower channel) at the bottom of the vessel. For the above mentioned dimensions, the sump may be approximately 10 L capacity, and is used as the reservoir for processing liquid to be recirculated during the cleaning step. With these preferred dimensions, large optics, such as 95×45×10 cm, may be treated with this solution. However, it is only one face, i.e. top surface of this optic that requires this cleaning step. The vessel 10 also includes a fill inlet 21 where cleaning agents, such as Nanostrip 2X may be supplied into the vessel, as well as an exhaust line 20 for evacuating any potentially toxic vapors that may be present inside the vessel.
As shown best in
Preferably the fluid line 15 connects to a collection tank 31, shown schematically in
It is appreciated that the waste storage container is preferably a separate standalone unit. In the alternative, however, the waste storage container may be an integral component of the system of the present invention, i.e. as a temporary waste holding tank. In any case, cleaning solution waste drained from the sump 12 and recirculation line 14 via valve 32, is preferably measured, such as by measuring the difference in weight of the acid waste carboy after waste collection. This determination is used later for dispensing the neutralizing agent.
As shown in
The described apparatus and system is preferably automated, such as by using a controller (e.g. programmable logic controller PLC) for controlling the fluid fill, circulation, and drainage functions in the various stages of operation of the present invention, so as to perform multi-step cleaning of the top surface of the diffraction grating. A level sensor 44 is also shown provided to determine when the collection tank needs to be purged.
An exemplary process illustrating the method of cleaning a diffraction grating using the apparatus and system of the present invention is described as follows:
Optic to be cleaned will be transferred from its PETG container into the processing station using the overhead crane and an approved lifting fixture.
5 gal. acid waste carboy placed into position
Acid to be added to process weighed and weight recorded.
Collection tank charged with approx. 50 gal of city water.
Lid closed and startup sequence initiated through PLC
Acid solution will be introduced into process through manual pour into funnel designed for this purpose
Recirculation initiated. Acid will be pumped from reservoir onto surface of optic, continuously recirculating, for approximately 1 hr.
Acid waste valve opened; acid pumped into waste carboy.
Acid waste valve closed. Weight of collected acid recorded automatically using scale.
Mixer started in collection vessel. Weight of NaOH needed to neutralize known amount of acid is metered into collection vessel.
DI water rinse initiated with recirc pump running and drain valve closed. Process tank filled to overflow.
Drain valve opened, process tank contents drained to collection tank.
Drain valve closed. TMAH-based (pH˜12) developer solution added to reservoir (1-2 gal).
Recirc pump started to rinse part surface with TMAH solution, approx 5 min.
Drain valved opened, DI rinse begun, approx 2 min.
Drain valve closed. Solution pumped up from collection tank to fill process vessel to overflow.
Drain valve opened, pumping from collection tank stopped, and final DI rinse begun. Approx 5 min.
With regard to acid/base balance, it is estimated that that between 100-200 ml of concentrated acid residue will remain adhering to process vessel walls, optic surfaces and in liquid lines following pumping of the acid waste to the waste carboy. This amount will be precisely known by measuring (such as by weighing) the amount introduced and amount collected in waste container. The amount of base needed to neutralize this known amount will be metered into ˜50 gallons of water in the collection tank during the rinse process. The resulting solution at the end of the rinse process will be within the pH limits for disposal to sewer. This will be monitored by pH meters and sampling.
The neutralization of 250 ml of concentrated H2SO4 by NaOH in 50 gal of water releases heat sufficient to raise the temperature of this amount of water by less than 1 degree C. (based on a reaction enthalpy H+OH→H2O(aq) of −79.9 kJ/mol).
It is important from a safety standpoint to neutralize the rinsewater as part of the process. This is in part due to compatibility with other processes in the facility. A sol-gel dip tank for AR coating, containing ˜100 gallons of ethanol solution, shares the same secondary containment pit as this proposed equipment. Concentrated sulfuric acid and ethanol do not mix, and so neutralizing the acidic rinse stream immediately as it enters the collection tank will assure that no mixing of these chemicals is possible in the event of an emergency situation.
Additional devices, such as sensors and interlocks may be employed for operating the apparatus and system, such as in a preferably automated manner. For example a proximity switch may be used to sense lid closure, and enable acid recirculation and DI water rinse. An airflow switch may be used for exhaust airflow, and enable acid recirculation, and DI water rinse. A float switch may be used to detect collector tank level and enable DI water rinse. A pH meter may be used to measure collecter tank pH, and enable NaOH charging into the collection tank and enable drain pumping.
Acid handling by operators will preferably include manually filling the reservoir with 1 to 2 gallons of Nanostrip2X, poured from HDPE 1-gal containers they were received in, into the top of the strip station through the funnel in the top of the container placed for this purpose. The operator will also remove and place a lid on the 5 gal carboy containing the acid waste from the process. While handling acid, the operator will wear the following: Full face shield, Butyl rubber or neoprene gloves, Lab cleanroom suit, Tyvek (HDPE) apron.
While particular operational sequences, materials, temperatures, parameters, and particular embodiments have been described and or illustrated, such are not intended to be limiting. Modifications and changes may become apparent to those skilled in the art, and it is intended that the invention be limited only by the scope of the appended claims.
This application claims priority in provisional application filed on Sep. 8, 2006, entitled “Apparatus and Process for Aqueous Cleaning of Diffraction Gratings with Minimization of Cleaning Chemicals” Ser. No. 60/843,462, by Jerald A. Britten et al, and incorporated by reference herein.
The United States Government has rights in this invention pursuant to Contract No. W-7405-ENG-48 between the U.S. Department of Energy and the University of California for the operation of Lawrence Livermore National Laboratory.
Number | Date | Country | |
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60843462 | Sep 2006 | US |