VOCs condensation recovery, especially deep cold condensation (mainly mechanical compression), before we called oil and gas recovery more, this is because VOCs cryogenic equipment was first used in the oil and gas recovery industry, especially the tank truck escape gas and storage tank size breathing away gas high concentration of small air condensation recovery, in addition to achieving environmental protection standards, in terms of economic benefits are also more obvious, which is mainly the economic value of the recovery of some pure solvents. Nowadays, VOCs cryogenic applications are more and more widely used in the pretreatment of the chemical industry. Let's share some of the key points of VOCs condensation recovery device design and operation and maintenance:
First, the key parameters
(1) The operating temperature of the precooler is above the freezing point of each component of the mixed gas, and when the mixed gas temperature of the entering device drops to 4 °C, most of the water can be removed, and the mechanical refrigeration can make most of the VOCs condensed into liquids and recovered; if a lower cold temperature is required, liquid nitrogen refrigeration can be reconnected, thereby improving the recovery rate of VOCs.
(2) During operation, close attention should be paid to the condensation temperature. Reducing the condensation temperature can increase the compressor cooling capacity, reduce power consumption, and improve the refrigeration coefficient. However, the condensation temperature is too low to affect the amount of refrigerant circulation, which reduces the cooling capacity.
(3) R402a and R402b can play a good role as short-term refrigerants, while R404a and R407a can be used as refrigerants for long-term use.
(4) Generally for the integrated process of oil and gas recovery, the temperature of the condensing section can be controlled at -40 ~ -50 ° C (in order to control the emission concentration of the recovery device at a very low level) or -20 ~ -30 ° C (in order to control the investment cost and energy consumption of the recovery device at a low level).
2. Other requirements
Control and adjust the compressor suction pressure, exhaust pressure, refrigerant temperature in front of the expansion valve, etc. within a reasonable range. The following are the requirements for the operation and maintenance of the condensing unit:
Attached: Analysis of the safety distance between VOCs cryogenic recovery equipment and buildings/facilities
1, about the basis for the location of VOCs/oil and gas condensation recovery and treatment devices
(Oil and gas condensation recovery and treatment device - tank farm Class A, B pump or pump room) Q/SH0117-2007 "Oil and Gas Recovery System Engineering Technical Guidelines" Article 3.2: Oil and gas recovery device should be installed near the oil tank truck oil stack. The fireproof distance from other buildings is determined in accordance with the "Class A and B Oil Pump Rooms" in Table 5.0.3 of the Code for the Design of Oil Depots (GB50074-2002). The fire distance between the refinery and other buildings is determined by "tank area Class A and Class B pump or pump room" in Table 4.2.12 of the Code for Designing Fire Protection of Petrochemical Enterprises (GB50160-2008) "Fire Spacing of The General Layout of Petrochemical Plants".
2, "Oil Loading System Oil and Gas Recovery Facilities Design Code" GB50759-2012 provisions
See Chapter 4: Layout, as follows:
3, oil and gas recovery equipment with reference to the "Petrochemical Enterprise Design Fire Code" (GB50160-2008) and other standards in the "tank farm A, B pump or pump room and other building fire distance parameters". Table 4.2.12 of the Code for Designing Fire Protection of Petrochemical Enterprises (GB50160-2008) "Fire Spacing of the General Layout of Petrochemical Plants" in "Parameters of Fire Prevention Distance between Tank Farm Class A and Class B Pumps or Pump Houses and Other Buildings".
Note: 8. Class C pump (room), can be reduced by 25% (except for the torch), but the local combustible liquid storage tank single tank volume is greater than 500m3, should not be less than 10m; the ground combustible liquid storage tank single tank volume is less than or equal to 500m3, should not be less than 8m;
Table 5.0.3 of the Code for the Design of Oil Depots (GB50074-2002) "Fire Distance Between Class A and Class B Oil Pump Houses and Buildings and Structures in Oil Depots" (excerpt), 2014 edition is Table 5.1.3. See the following table.
Combining the above two standard data, the maximum fire protection distance between the oil and gas recovery equipment in the refinery oil depot and other facilities, buildings and structures is 45m from the > 10000 m³ fully refrigerated storage liquefied hydrocarbon storage tank. (This can be considered as a limit distance for the site selection requirements of the oil and gas recovery treatment unit.) ）