Oilfield associated gas carbon dioxide recovery device

Scale and product indicators of flue gas carbon dioxide recovery device

The processing capacity of the raw gas associated gas in this unit is taken as the average flow rate of 48000Nm3/d from the 3rd to the 14th year, and the CO2 content is also taken as its average content~65%. After purification, separation and other processes, the final products are natural gas and liquid CO2. Operating flexibility of the device: 60% to 110%, annual operating time: 8000 hours.

Technology for recovering carbon dioxide from flue gas

According to the analysis of the composition indicators of the raw gas and product requirements, the raw gas can be purified first and then enter the PSA decarbonization unit, where CH4 is separated and purified, and output as natural gas product. The PSA tail gas rich in CO2 is used as the feed gas for the liquid CO2 device, and the product liquid CO2 is produced through processes such as compression, purification, and low-temperature purification.

Carbon dioxide recovery from flue gasprocess flow

The associated gas from the raw material oil field undergoes coarse filtration, microfiltration, purification, pressure swing adsorption, and separation to produce natural gas as fuel or enter the pipeline network. The compressed and dried carbon dioxide is then liquefied and stored or reinjected. The specific process is as follows

The first stage of the feed gas is gas-liquid separation to separate the free water carried in the feed gas, and then passes through mechanical filters and microporous filters to remove impurities such as heavy hydrocarbons. This filter has a large filter element area, low resistance, and is equipped with a backup filter. Once the resistance increases, it can be switched to another set of filters in a timely manner to replace the filter element without stopping.

The purified associated gas first enters the purification system for desulfurization. The desulfurization system is planned to use two desulfurization towers, which can be connected in parallel or series. The desulfurization tower is filled with room temperature iron oxide desulfurizer, and the H2S content at the outlet of the desulfurization tower is controlled to be less than 20ppm. The remaining trace H2S is removed together during pressure swing adsorption decarbonization and enters the PSA tail gas. The final control product CNG sulfur content is ≤ 15mg/Nm3.

The desulfurized gas enters the pressure swing adsorption decarbonization process.

The pressure swing adsorption decarbonization is planned to adopt a 5-1-3/V process. That is, 5 adsorbers, 1 tower feeding at the same time, 3 times pressure equalization, vacuum desorption process. The entire operation process is carried out at ambient temperature, with each adsorber operating in alternating cycles. Each adsorber must go through the following steps in one cycle: adsorption (A), first equalization (E1D), second equalization (E2D), third equalization (E2D), reverse discharge (D), vacuum pumping (V), third equalization (E2R), second equalization (E2R), first equalization (E1R), final charging (FR), etc. Obtain purified gas with impurities removed at the outlet of the decarbonization adsorber, which is the natural gas product of this unit. Natural gas can be compressed into CNG or integrated into the pipeline network. The desorption gas discharged from the reverse discharge and vacuum extraction steps is mainly composed of CO2, which is collected and sent to the liquid CO2 device to produce liquid CO2.

The PSA decarbonization desorption gas is first compressed to about 1MPa by a compressor and then sent to the pretreatment system for drying treatment. Water and components with boiling points higher than CO2 are removed using temperature and pressure swing adsorption technology. The basic principle is to utilize the characteristic of the adsorbent's adsorption capacity for impurity components, which varies greatly with pressure and temperature. Under the conditions of adsorbent selection, impurities can be adsorbed at high pressure and room temperature, and desorbed at low pressure and high temperature to achieve gas purification. The adsorption purification process consists of three purifiers, one in the adsorption state, one in the heating state, and one in the cold blowing state. Each purifier must go through six steps in one cycle: adsorption (A), depressurization (D), heating (H), isolation (IS), cold blowing (C), and pressurization (R).

Then return to the compressor stage to continue compressing to about 3.5 MPa. The compressed gas is liquefied by the evaporation condenser of the condensation system from room temperature to about -20 ℃ before entering the purification tower. High purity liquid CO2 products are obtained in the tower kettle and directly output to the liquid CO2 storage tank after cooling; The non condensable gas coming out of the top of the purification tower is recovered by a heat exchanger and used as the regeneration gas for the dehydration and drying process. The small amount of waste gas discharged is vented on site or enters the pipeline network to obtain high-purity liquid CO2 products in the purification tower kettle, which are directly output to the liquid CO2 storage tank. The non condensable gas coming out of the top of the purification tower is recovered by the heat exchanger as the regeneration gas for the pretreatment process, and a small amount of exhaust gas is discharged on-site or into the pipeline network. The purification tower kettle uses high-temperature gas from the compressor outlet as the heat source, without the need for external heat supply; The cooling capacity of the tower top condenser comes from the cooling capacity generated by the depressurization flash evaporation of the tower top gas, and no external cooling capacity is required.

The CO2 liquefier of this device uses ammonia as the refrigerant. In the liquefier, liquid ammonia evaporates into gaseous ammonia at low pressure, providing cooling capacity for CO2 liquefaction; Gas ammonia is returned to the refrigeration system for recycling.