Instrument Keywords: Proportional Nitrogen Flow Distributor   Chlorine Calibration Method   Unattended Operation

 
A high-chlorine wastewater COD digestion instrument that uses an imported proportional adjustment distributor to control nitrogen flow velocity;
A fully compliant high-chlorine wastewater COD digestion instrument meeting the national standard HJ70-2025 "Water Quality - Determination of Chemical Oxygen Demand - Chlorine Calibration Method" testing standard; 
 
Product Development Background:
For the determination of COD in industrial wastewater, the national standard "Water Quality - Determination of Chemical Oxygen Demand - Potassium Dichromate Method" (HJ828-2017) is generally referenced. However, for industrial wastewater containing high concentrations of chlorides, such as from petroleum, dye chemicals, organic chloride industries, and salt lake extraction, the chloride ions are easily oxidized by potassium dichromate under strong acidic conditions during COD determination, affecting the accuracy of results. Therefore, for high-chlorine industrial wastewater with concentrations between 1000mg/L and 20000mg/L, the standard HJ70-2025 "Water Quality - Determination of Chemical Oxygen Demand - Chlorine Calibration Method" is generally required.
 
Method Principle:
Add a known amount of potassium dichromate solution and sulfuric acid silver solution to the water sample, use silver sulfate as a catalyst under strong acidic conditions, reflux for 2 hours, then use 1,10-phenanthroline as an indicator, titrate the unreacted potassium dichromate with ferrous ammonium sulfate, and convert the consumed amount into oxygen mass concentration, representing the apparent COD. The chlorine gas formed by chloride ions in the sample is absorbed by sodium hydroxide solution, then potassium iodide is added, the pH is adjusted to about 3~2 with sulfuric acid, starch is used as an indicator, and the solution is titrated with sodium thiosulfate standard solution. The consumed sodium thiosulfate is converted into oxygen mass concentration, representing the chloride ion correction value. The difference between the apparent COD and the chloride ion correction value is the true COD of the sample.
 
Instrument Application:
Used for dechlorination and digestion of COD samples in high-chlorine water bodies (water and wastewater, chloride concentration greater than 1000mg/L and less than 20000mg/L).
 
Applicable Industries:
Oil fields, coastal refineries, oil depots, chlor-alkali plants, steel plants, power plants, pesticides, food, textile printing and dyeing enterprises, and COD determination in high-chlorine wastewater discharged into deep sea. 
 
Product Main Advantages:
1.  Heating unit adopts far-infrared ceramic heating technology, stable and controllable heating rate;
2.  Digestion unit: 1-6 positions, each can be independently controlled;
3.  Nitrogen flow control uses imported proportional adjustment distributor, ensuring uniform flow distribution and stable velocity;
4.  Digestion time is controlled by computer program, freely adjustable, and stops automatically upon completion;
5.  Cooling system uses built-in compressor cooling, with automatic internal circulation, no need for external cooling water;
6.  Main unit has an automatic nitrogen anti-suction unit to prevent liquid backflow after heating;
7.  The entire machine adopts PLC module control, with touch-screen LCD computer, enabling remote operation for convenience and speed