1. Introduction

The total nitrogen water quality online analyzer is a new type of total nitrogen online monitoring instrument developed independently based on magnetic conductivity measurement technology platform, combined with constant temperature optical fiber technology, digestion and spectral measurement integration technology, etc.

The working principle of this product complies with "HJ 636-2012 Determination of Total Nitrogen in Water Quality - Alkaline Potassium Persulfate Dissolved Ultraviolet Spectrometric Method", and it has the characteristics of high reliability, low quantification limit, and good stability. It is widely used in pollution sources, industrial production processes, municipal sewage and other fields.

2. Technical principles

This instrument uses alkaline potassium persulfate digestion ultraviolet spectrophotometry to measure the total nitrogen content in water samples. In aqueous solutions above 60 ℃, potassium persulfate can decompose to produce potassium bisulfate and atomic oxygen. Potassium bisulfate dissociates in the solution to produce hydrogen ions, so the decomposition process can be promoted to complete in an alkaline medium of sodium hydroxide.

The decomposed atomic oxygen can convert the nitrogen element containing nitrogen oxides in water samples into nitrate at (120-124) ℃, and during this process, organic matter is simultaneously oxidized and decomposed. UV spectrophotometry can be used to measure the absorbance A220 and A275 at a wavelength of (220-275) nm, and the corrected absorbance A can be calculated according to the formula A=A220-2A275.

3. Main features

1) The instrument adopts a 7-inch 1024 * 600 touch screen and uses the Android operating system, with a more beautiful interface and smoother operation;

2) The use of strong oxidants at high temperature and high pressure (120-130) ℃ to digest the reaction solution greatly improves the reaction efficiency;

3) The digestion system has complete protection functions, which can effectively prevent possible leakage and other situations under high temperature and high pressure;

4) According to the actual situation, the digestion temperature and time can be adjusted to ensure sufficient reaction;

5) The use of a patented magnetic conductivity quantification method to quantify samples/reagents fundamentally solves the interference of color turbidity, greatly improving the accuracy and reliability of quantification;

6) The single channel integrated distribution valve island reduces the impact of dead volume on quantitative accuracy, and can be disassembled, cleaned, and replaced in a single channel with low maintenance and cost;

7) The instrument has multiple built-in ranges, and can automatically adjust the range according to the total nitrogen content of the water sample, making the measurement more accurate;

8) The instrument can automatically achieve calibration, cleaning and other functions without user intervention, avoiding measurement errors;

9) When the instrument malfunctions, it has self inspection and maintenance functions to ensure personal safety and equipment safety;

10) When a liquid leak occurs, the device's built-in humidity sensor will sound an alarm and automatically lock;

11) All fault information is recorded at the HMI display terminal, allowing users to query and have a clear understanding of the equipment's operating status;

12) The instrument can be extended with remote upgrade function, and remote maintenance and monitoring of equipment can be achieved through Ethernet port, GPRS port, etc;

13) The instrument has rich external interfaces, and various interfaces used on site (such as Ethernet/(4-20) mA input, output/RS485/switch input, output, etc.) are available;

14) The instrument has good scalability, allowing for the addition of device functions according to user needs.

4. Main technical indicators

1) Measurement method: Alkaline potassium persulfate high-temperature digestion, spectrophotometric method (improved method according to national standard GB11894-89)

2) Measurement method: Alkaline potassium persulfate digestion UV spectrophotometry;

3) Measurement range: 0-5/25/50/200 mg/L (expandable);

4) Zero drift: ± 5%;

5) Range drift: ± 5%;

6) Repeatability: ≤ 5%;

7) Indication error: ± 10%;

8) Voltage stability: not exceeding ± 10%;

9) Mean time between failures and continuous operation: ≥ 720h/time;

10) Measurement interval: hourly measurement, interval time measurement, and instrument can also be triggered through Modbus;

11) Calibration: Supports manual and automatic calibration. Calibration cycle and time can be set;

12) Instrument size (mm): 500 * 405 * 1400 (excluding wheel height);

13) Packaging size (mm): 600 * 490 * 1510;

14) Instrument weight (kg): 75;

15) Packaging weight (kg): 90;

16) Temperature for operation and storage: (5-40) ℃, humidity: (65 ± 20)%, no condensation;

17) Power supply and output: (220 ± 22) VAC, (50 ± 0.5) Hz, 200W;

18) Signal output: 1 channel (4-20) mA (expandable to 2 channels), RS232/RS485， 4 multifunctional relays;

19) Signal input: 1 channel (4-20) mA (expandable to 2 channels). 4-channel switch quantity;

20) User maintenance: A single set of reagents can measure 400 samples;

21) Preheating time: 2 hours;

22) Other functions: automatic cleaning, data recording, printing (optional).