Electrolytic On-Site Generator

Abstract

Method and apparatus for a low maintenance, high reliability on-site electrolytic generator incorporating automatic cell monitoring for contaminant film buildup, as well as automatically removing or cleaning the contaminant film. This method and apparatus preferably does not require human intervention to clean. For high current density cells, cleaning is preferably performed by reversing the polarity of the electrodes and applying a lower current density to the electrodes, preferably by adjusting the salinity or brine concentration of the electrolyte while keeping the voltage constant. Electrolyte flow preferably comprises water and brine flows which are preferably separately monitored and automatically adjusted. For bipolar cells, flow between modules arranged in parallel is preferably approximately equally distributed between modules and between intermediate electrodes within each module.

What is claimed is: 
     
         1 . A method for operating an electrolytic cell, the method comprising:
 monitoring a brine flow rate;   monitoring a water flow rate and pressure;   forming an electrolyte by mixing brine and water;   automatically and separately adjusting the brine flow rate and the water flow rate so that a pressure and flow rate of the electrolyte are within predetermined limits prior to electrolysis of the electrolyte; and   electrolyzing the electrolyte.   
     
     
         2 . The method of  claim 1  wherein automatically and separately adjusting the brine flow rate and the water flow rate ensures that a salinity and/or concentration of the electrolyte are within predetermined limits prior to electrolysis of the electrolyte. 
     
     
         3 . The method of  claim 1  further comprising monitoring an electrolyte temperature and/or an oxidant temperature. 
     
     
         4 . The method of  claim 1  further comprising reducing the pressure of the water to an electrolysis operating pressure. 
     
     
         5 . The method of  claim 1  further comprising stopping electrolysis to avoid damage caused by incoming water pressure being too high or too low. 
     
     
         6 . The method of  claim 1  wherein automatically and separately adjusting the brine flow rate and the water flow rate is performed in response to an electrolyte temperature, an oxidant temperature, an electrolysis current density, a water flow rate, a water pressure, a brine flow rate, or combinations thereof. 
     
     
         7 . The method of  claim 1  further comprising:
 selecting a low threshold amount of oxidant in an oxidant tank which signals initiation of electrolysis; and 
 initiating electrolysis of the electrolyte when electricity costs are low even though an oxidant amount in the oxidant tank is higher than the low threshold amount. 
 
     
     
         8 . An apparatus for performing electrolysis, the apparatus comprising:
 a brine input line comprising a variable speed brine pump and an on-off switch;   a water input line comprising a pressure sensor, a flow meter, and a flow control valve;   a connection between the brine input line and the water input line;   an electrolytic cell; and   an oxidant tank.   
     
     
         9 . The apparatus of  claim 8  further comprising a pressure reducing valve on said water input line. 
     
     
         10 . The apparatus of  claim 8  further comprising a check valve on said brine input line. 
     
     
         11 . The apparatus of  claim 8  further comprising a temperature measuring device for measuring an electrolyte temperature and/or a temperature measuring device for measuring an oxidant temperature. 
     
     
         12 . The apparatus of  claim 8  further comprising a controller for separately controlling operation of said variable speed brine pump and said water flow control valve. 
     
     
         13 . The apparatus of  claim 12  wherein said controller operates in response to one or more inputs selected from the group consisting of an electrolyte temperature, an oxidant temperature, a current density in said electrolytic cell, a water flow rate, a water pressure, and a brine flow rate. 
     
     
         14 . A method of cleaning an electrolytic cell, the method comprising:
 lowering a salinity of an electrolyte until a current density of the electrolytic cell falls to or below a predetermined cleaning current density;   reversing a electrode polarity;   maintaining a constant electrode voltage;   ceasing a flow of water into the electrolytic cell;   operating the electrolytic cell until the current density increases to or above the predetermined cleaning current density;   starting the flow of water into the electrolytic cell until the current density decreases to or below the predetermined current density; and   repeating the ceasing, operating, and starting steps.   
     
     
         15 . The method of  claim 14  wherein repeating the ceasing, operating, and starting steps physically dislodges contaminants from the cell. 
     
     
         16 . The method of  claim 14  wherein a flow of brine into the electrolytic cell and a flow of water into the electrolytic cell are independently controllable. 
     
     
         17 . The method of  claim 16  wherein the lowering step comprises stopping the flow of brine. 
     
     
         18 . The method of  claim 14  further comprising increasing a salinity of electrolyte if the current density does not increase sufficiently during the operating step. 
     
     
         19 . The method of  claim 14  performed when an amount of oxidant in an oxidant tank is at or below a predetermined low threshold amount and after occurrence of a predetermined event selected from the group consisting of a time period elapsing, exceeding an operation time of the cell, exceeding an amount of electrolyte flow through the cell, and reaching a contamination level. 
     
     
         20 . The method of  claim 19  further comprising initiating normal operation of the electrolytic cell substantially immediately after cleaning is complete. 
     
     
         21 . The method of  claim 20  further comprising flushing debris from the electrolytic cell once cleaning is complete. 
     
     
         22 . The method of  claim 21  wherein the debris comprises scale flakes. 
     
     
         23 . The method of  claim 14  performed in approximately three to five minutes. 
     
     
         24 . The method of  claim 23  wherein the repeating step is performed approximately every thirty seconds. 
     
     
         25 . The method of  claim 14  performed approximately once per month. 
     
     
         26 . The method of  claim 14  wherein the predetermined cleaning current density and the total cleaning time are chosen to expose the electrolytic cell to a predetermined amount of amp-seconds. 
     
     
         27 . The method of  claim 26  wherein the predetermined amount of amp-seconds is approximately 1800. 
     
     
         28 . A bipolar electrolytic cell comprising:
 a plurality of modules arranged in parallel, each module comprising primary electrodes and one or more intermediate electrodes;   a manifold for distributing electrolyte substantially evenly between each module;   a flow diffuser in each module located inside an electrolyte inlet; and   a gap region in each module or openings in one or more of the intermediate electrodes to facilitate uniformity of electrolyte and oxidant flow in the electrolytic cell;   wherein a general flow direction of electrolyte in each module is parallel to the electrodes.   
     
     
         29 . The bipolar electrolytic cell of  claim 28  wherein the flow diffuser blocks electrolyte entering each module from flowing directly between the electrodes. 
     
     
         30 . The bipolar electrolytic cell of  claim 28  wherein the gap region is formed by the shape of the intermediate electrodes. 
     
     
         31 . The bipolar electrolytic cell of  claim 28  wherein the gap region is formed by the size of an edge protector. 
     
     
         32 . The bipolar electrolytic cell of  claim 31  wherein the edge protector comprises one or more grooves for receiving and holding the intermediate electrodes. 
     
     
         33 . The bipolar electrolytic cell of  claim 31  wherein the edge protector comprises chlorinated polyvinyl chloride (CPVC) or Viton®. 
     
     
         34 . The bipolar electrolytic cell of  claim 31  wherein the edge protector is replaceable by a different size edge protector, thereby enabling a single module housing to accommodate different sizes of intermediate electrodes. 
     
     
         35 . The bipolar electrolytic cell of  claim 28  wherein the openings on an intermediate electrode are staggered or offset from openings in adjacent intermediate electrodes. 
     
     
         36 . A method of operating a bipolar electrolytic cell, the method comprising:
 substantially evenly distributing a flow of electrolyte entering the electrolytic cell between a plurality of modules whose inlets and outlets are connected in parallel;   diffusing a flow of electrolyte entering each module so that electrolyte flow is substantially even between one or more intermediate electrodes present in each module;   mixing the electrolyte flows between the intermediate electrodes in a gap region or via openings in one or more of the intermediate electrodes; and   generally flowing electrolyte in a direction parallel to the intermediate electrodes.   
     
     
         37 . The method of  claim 36  wherein the diffusing step comprises blocking electrolyte entering each module from flowing directly between the intermediate electrodes. 
     
     
         38 . The method of  claim 36  further comprising:
 selecting a low threshold amount of oxidant in an oxidant tank which signals initiation of electrolysis; and 
 initiating electrolysis of the electrolyte when electricity costs are low even though an oxidant amount in the oxidant tank is higher than the low threshold amount.