On the detection of non-methane total hydrocarbons by gas chromatography - Master's thesis - Dissertation

Generally refers to all volatile hydrocarbons other than methane (mainly C2~C8), also known as non-methane total hydrocarbons. NMHC in the atmosphere exceeds a certain concentration. In addition to being directly harmful to human health, it can produce photochemical smog under sunlight under certain conditions, causing harm to the environment and humans. There are many ways to monitor NMHC in ambient air and industrial waste gas, but most countries [1, 2] use gas chromatography. The total hydrocarbon and methane content were measured by gas chromatography with a two-column double hydrogen flame ionization detector, and the difference between the two was NMHC content. The NMHC measured under the specified conditions is the total amount of hydrocarbons other than methane, which is apparently responsive to the gas chromatographic hydrogen flame ionization detector, in terms of carbon. Nature: Refers to all hydrocarbons (hydrocarbons) except methane. Because it is different from methane, it has a large photochemical activity and is a precursor for the formation of photochemical smog. There are many types, the most emissions of which are terpenoids released by natural plants, accounting for about 65% of the total NMHC, the most important of which are isoprene and monoterpene, which will be in urban and rural areas. Photochemical oxidants and aerosol particles are formed in the atmosphere by photochemical reactions. The anthropogenic sources of NMHC are mainly gasoline burning, incineration, solvent evaporation, petroleum evaporation and transportation losses and waste refining, which account for about 96% of the anthropogenic emissions of hydrocarbons.

The gas chromatographic method of Junqi instrument for the determination of non-methane total hydrocarbons in fixed-source exhaust gas:

1

GC9890A gas chromatograph host (220V, 50HZ)

*Imported HP high sensitivity FID detector

* packed column inlet

* packed column inlet

*Double six-way injection valve

* Five independent temperature control system, intelligent rear door

*With data power-off protection function, fault self-diagnosis

*Installing accessory kit

2

V2008 Chromatography Data Station

Dual channel capture card and software

(Double channel, gas-liquid universal) analysis software

3

Column

Total hydrocarbon analysis packed column

*Main features
1. The main machine comes with two-way valve control system, which is convenient for online automatic injection.
2. The inter-column compensation circuit electronically compensates for drift in the baseline during program temperature operation, reducing the complexity of the second column, detector, and auxiliary flow system.
3. The signal of the detector, the value of the heater, the furnace temperature, the flow sensor reading or the stored column compensation baseline signal can all be assigned to an analog output channel.
4, self-machine detection and fault diagnosis, power-off protection stored experimental data, stopwatch and running timer, keyboard lock function.

5, can be connected to the counter-control workstation, real-time control, and can store 100 sets of experimental conditions and spectrum.

6, can be installed in the United States HP-5890 gas chromatograph micro-thermal conductivity detector, to achieve complete docking.
7, can install two flow sensing channels, two single column compensation channels.

* Heating furnace system temperature range: ambient temperature +5 ° C ~ 400 ° C third-order program temperature, heating rate 0 ~ 50 ° C / min; increase

The amount is 0.1 ° C / min. Temperature control accuracy ± 0.05 ° C, the user can re-correct the furnace temperature, and set the maximum temperature.

The intelligent rear door opening system has stepless variable inlet and outlet air volume, which shortens the system stable balance time after rising/lowering. The time taken for the oven to drop from 300 ° C to 50 ° C is < 6 min.

*Injection system

1. Packed column sampler: suitable for various caliber packed columns and large diameter capillary columns

2. Capillary injector: optional split/distributed system controlled by programmed valve

3, optional with the company's headspace sampler and thermal analyzer.

*Detector system
1. Hydrogen flame ion detector (FID):

Easy to disassemble and install, easy to clean or replace nozzles, easy to operate; input signal can be logarithmically amplified, reducing interference, high sensitivity, good linearity and wide measuring range.
Sensitivity: Type A Mt ≤ 5 × 10-11g / s (n-hexadecane)
Baseline noise: ≤6×10-12A/H
Linear range: ≥105
Stabilization time: <0.5h

2. Thermal Conductivity Detector (TCD):

Sensitivity: Type A: ≥4000mv•ml/mg (n-hexadecane)

Baseline noise: ≤30μv (helium gas with a carrier gas of 99.999)
Stabilization time: A type <1.5h gas barrier protection

For specific national standards and configuration methods, please call 021-57786311