The commonly used dehydration methods in the natural gas industry include expansion cooling, pressure cooling, solid adsorbent adsorption, solvent absorption, etc. The most commonly used method for natural gas dehydration in the world is the glycerol method in solvent absorption, while the commonly used method in China is the triethylene glycol method.9 b Q! t% j1 M
(1) Low temperature condensation dehydration
6 y $| 7 A2 Y% J This method uses various methods to throttle and depressurize high-pressure natural gas for refrigeration, and uses low-temperature separation to recover condensate from natural gas. This method is a natural gas dehydration process that is widely used in domestic gas fields, in addition to the triethylene glycol method. Changqing Gas Production Plant 2, Tarim Kela 2, and others have adopted this method, which has the advantages of simple process and fewer equipment, but also has disadvantages such as high energy consumption and high water dew point.
0 g$ ? +@ # X (J0 P8 s&T! Q (2) J2 T valve and turbine expander' z4 N; v$ l% U; q: L
J2 T valve and turbine expander dehydration belong to low-temperature condensation method dehydration. For high-pressure natural gas, cooling and dehydration are very economical. For example, Daqing Oilfield currently uses many turbine expanders for dehydration, while Wolonghe and Zhongba gas fields in Sichuan use J2T valves for dehydration. The disadvantage of these methods is that: ① a part of the dehydration cycle is within the range of hydrate formation, which is prone to hydrate formation. Therefore, measures such as adding inhibitors to prevent hydrate formation and corresponding inhibitor recovery systems need to be taken; ② When deep dehydration is required, refrigeration equipment should be equipped, which will increase engineering investment and usage costs; ③ Turboexpanders have high-speed moving parts, which are difficult to manufacture and have poor reliability.$ a7 |& q# N0 ?
(3) Triethylene glycol dehydration1 L7 ^% Z% y' m- Q0 r( P+ D
Triethylene glycol dehydration belongs to solvent absorption dehydration and has been widely used in the natural gas industry. This dehydration system includes a separator, an absorption tower, and a triethylene glycol regeneration system. The main problems are: ① The system is relatively complex; ② The energy consumption during the regeneration process of triethylene glycol solution is relatively high; ③ Triethylene glycol solution will be lost and contaminated, therefore it needs to be replenished and purified; ④ Triethylene glycol undergoes oxidation reaction upon contact with air, generating corrosive organic acids. So, the investment and operating costs of glycerol dehydration are relatively high. At present, most of the domestic sled mounted glycerol dehydration systems are imported from abroad. Although the performance is good, there are also many problems. If the one-time investment is relatively large; Various spare parts and consumables are difficult to purchase and expensive; The measurement standards are different from the current standards in China; The measurement system is not suitable for the natural gas properties in China. For example, the sled mounted triethylene glycol dehydration system introduced into the Sichuan Datianchi natural gas transmission trunk line had an average daily consumption of 1119 kg during the trial operation from March 25 to July 27, 1999. Moreover, as the operating time of the device increased, the consumption of triethylene glycol gradually increased. Due to the use of imported triethylene glycol at a price of 36 yuan/kg, the consumption of triethylene glycol has become an important factor affecting production costs.! V7 f: Y1 |. e) e9 u) {! D
(4) Molecular sieve dehydration
&The dehydration of u; I0 j6 f5 F&r'_. J2 X5 ` 8k molecular sieve belongs to solid adsorption dehydration. The dehydration system mainly includes 2 or 3 dryers in dehydration, regeneration, and cold blowing states, as well as a regeneration gas heating system. The molecular sieve dehydration method is more suitable for deep dehydration, and the dew point can be reduced to below -73 ℃. However, for large facilities, equipment investment and operating costs are relatively high. If the dew point required for dehydration is the same, building a treatment station with a processing capacity of 280000 m3/d would require 53% more investment in molecular sieve dehydration than in triethylene glycol. In addition, the regeneration process of molecular sieve dehydration consumes a lot of energy, and the adsorbent in the lower layer of the dryer needs to be replaced frequently.) }8 v6 l: T' E' Z5 u, V9 v
(5) Supersonic dehydration
The supersonic dehydration technology of '\ \+| (R $G) {7 ` 2 G&f/], as a new type of dehydration technology, is mainly studied abroad with the support of Shell Oil Company, including computer numerical simulation, laboratory research, and field experimental research. Basic experimental and numerical simulation research is mainly conducted at several universities in the Netherlands, including Eindhoven University of Technology; On site experimental research is being conducted in natural gas fields and offshore platforms in the Netherlands (1998), Nigeria (2000), and Norway (2002), mainly to verify the system's ability to operate stably for a long time and continuously improve it in practical applications. All studies have achieved satisfactory results. At present, this technology has entered a commercial application state.6 Z.

(6)Membrane separation dehydration0 M: C6 [. }2 A6 u1 H' |
Permea, a division of American Gas Products, specializes in gas separation membranes. They have been researching natural gas dehydration membranes since the mid-1980s, utilizing professional technical expertise. By 1999, they had achieved commercialization of natural gas dehydration membranes using the new Prism gas separation membrane. The separation system can remove 95% of the moisture in natural gas at a pressure of 4-8 MPa, supplemented by 2% to 5% dry gas as the reflux gas, resulting in dry natural gas with a moisture content that meets pipeline transportation standards. Like other membrane separations, membrane natural gas dehydration has the characteristics of simple structure, high reliability, easy operation and maintenance, no environmental pollution, low operating costs and investment. It will become a competitive new process for traditional dehydration methods.

The portable dew point meter MDM300-IS-HZ500 is an intelligent industrial analytical instrument that can be used for gas dew point detection in production processes. It can automatically, quickly, and continuously analyze the water dew point value (℃) of gases in pipelines, and quickly calculate the calculated trace water content (ppm) under natural gas operating conditions. The data can also be processed and stored. The moisture absorbing layer Al2O3 in its sensitive component only responds to the partial pressure of water vapor in the measured medium, and has a direct correspondence with the partial pressure of water vapor in the medium. It is inert to other components in the gas. Good stability, long service life, and easy operation.

The MDM300-IS-HZ500 portable dew point meter for oilfield associated gas has a wide measurement range of -120oC~+30oC, corresponding to a range of 0.1ppb~40000ppm, with measurement accuracy better than ± 2 ℃. Directly measure the moisture content in the gas and calculate the corresponding water dew point. The dew point meter has pressure compensation function and can measure the dew point and ppm water content under normal pressure. The dew point and ppm water content under pressure can be displayed through pressure compensation. Conversely, the dew point and ppm water content under pressure can also be measured under pressure, and the dew point and ppm water content under normal pressure can be displayed through pressure compensation.

MDM300-IS has been approved by BASEEFA (2001) for use in hazardous areas II 1G EEx ia IIC (155 ° C) T3.

Preprocessing system features:

The associated gas of the tested sample is connected to a pressure resistant stainless steel corrugated pipe from the dry gas pipeline at the molecular sieve outlet of the dehydration device, and enters the pre-treatment system mentioned above. Considering the temperature, flow rate, and impurity content of the analyzed associated gas, a membrane filter specially designed by A+company in the United States for filtering liquid impurities in the associated gas was selected. This filter can remove liquid polar particle pollutants and only allow gas to enter the pressure regulating valve and analytical instrument at the back. When the associated gas contains a large amount of liquid, its Liquid Block design can prevent the airflow from flowing to other downstream components and analytical instruments, avoiding liquid pollutants in the sample gas from contaminating the analytical instrument and providing sufficient protection for the analytical instrument.

After filtering through the A+filter in the United States to remove liquid and some solid particle pollutants, the sample gas continues to flow through FITOK's filter that can filter 0.5 micron particles. After the above secondary filtration, it ensures the removal of solid-liquid impurities below 1 um, guarantees the quality and cleanliness of the sample gas, and ensures that the filter element can be used continuously for more than 12 months.

The sample gas after secondary filtration enters the pressure regulating valve, and after being depressurized and stabilized by the pressure regulating valve, it enters the flow regulating valve. According to the indication of the flow meter behind the instrument, the flow rate of the measured sample gas is adjusted to around 0.2-12L/min to meet the requirements of the dew point analyzer for the flow rate of the measured gas.

The preprocessing system also includes a fast response channel, which can increase the gas flow rate of the entire system to shorten the response time, and continuously blow the membrane filter with gas to ensure that the liquid and particulate pollutants filtered by the membrane filter are discharged from the system in a timely manner.

The gas treatment system is designed reasonably and compactly, with all gas contact parts made of 316 stainless steel, which is corrosion-resistant. The entire system is fixed on the corresponding installation base and easy to disassemble and assemble. All joints are connected by front and rear card sleeves and nuts, which can fully ensure their sealing. All equipment and pipelines in the system are leak free, able to adapt to the pressure and temperature range of the sample gas, and corrosion-resistant, without changing the chemical properties of the gas.

Technical specifications of MDM300-IS-HZ500 portable dew point meter for oilfield associated gas

Model: MDM300-IS

Gas Connection: Inlet/Outlet 1/8 "Swagelok ® Coupling joint

Display: LCD

Measurement range: -120~+30 ° C dew point

Verification range: -100~+20 ° C dew point

Accuracy: ± 2 ° C

Resolution: 0.1 ° C dew point (all units are 3 significant digits)

Unit: ° C, ° F, K dew point; ppm(v)； Ppm (w) air, N2, H2, SF6, CO2 natural gas; GM-3 (natural gas); Lb/mmscf (natural gas)

Data storage: Sampling, time and date, tagging, and identification numbers up to 10000 primary and secondary variables

Communication: Bluetooth transmission

Power supply: The internal rechargeable battery pack is charged by an external power charger (provided) and has a rated working time of 24 hours after charging

Outer box: Customized polyurethane box with integrated padding and carrying handle

Size: 250W × 300D × 150H mm (approximately)

Weight: 3 kg

Entrance protection: IP65 (NEMA 12)

Working temperature: -20~+40 ° C

Storage temperature: -65~+65 ° C

Work pressure: 30 MPa (max)

Flow rate: 0.2~1.2Nlmin-1

Intrinsic Safety Certificate: IIG EEx ia IIC (155 ° C) T3

Certified by Baseefa (2001) Limited

Certificate Number: Baseefa03ATEX0090X

FM Certificate Number: J.I.6D0AX

CSA Document Number: LR 114519-1

Gas contact components: 316 stainless steel