TECHNOVACUUM

1) VACUUM CREATING SYSTEMS
based on vacuum hydrocirculating units

Purpose

Vacuum hydrocirculating units (VHC units) are designed to evacuate gas, vapor and gas-vapor-liquid mixtures in order to create vacuum in devices for various purposes (distillation and stripping columns, desorbers, evaporators, deaerators, condensers, reactors, dryers, desalters, systems of oil products refining and other process equipment). The VHC units are alternative to traditional vacuum creation systems such as vacuum pumps, steam ejectors and under certain conditions have sufficiently better operation stability and operating costs.

Application field of vacuum units

• Vacuum distillation columns of refineries.
  
• Vacuum distillation of products in chemical and petrochemical industry.
  
• Vacuum stripping columns, units for lube stock cleaning from solvent.
  
• Vacuum columns for diesel fractions drying.
  
• Vacuum creation in steam turbine condensers.
  
• Vacuum creation in deaerators, desorbers, evaporators, dryers, desalters and other process equipment.
  
• Exhauster systems of high-altitude test benches.
• Vacuum casting in metallurgical production.

Layout of single-stage VHC unit

1 – vacuum creating device 2 - separator 3 - heat exchanger 4 - pump I - gas-vapor mixture from vacuumized vessel II – compressed gas outlet line III – motive liquid excess withdrawal line IV – fresh motive liquid makeup line

Principle of operation

The pumped-out medium is delivered from technological device, e.g. a distillation column, to inlet of the vacuum creating device 1. In the vacuum creating device 1 the gas-vapor mixture is compressed due to energy of the motive liquid jet supplied to the device 1 by the pump 4. One of the process flows, which is allowed to mix with vapor evacuated by the vacuum creating device, can be used as a motive liquid.

In oil refining a diesel fraction or vacuum gas oil is used as the motive liquid. In the caprolactam production the motive liquid is a cyclohexanol-cyclohexanone mixture.

Along with gas-vapor compression the process of vapors condensation on the jet of motive liquid occurs. In this case vapor condensation and gas cooling in the vacuum creating device occurs along the isobar and their compression to the discharge pressure - along the isotherm. It makes the device energy-efficient in comparison with other vacuum pumps, especially in the case of pumping gas-vapor mixtures with a high percentage of vapor.

The generated gas-vapor mixture goes from the vacuum creating device 1 to the separator 2, where gas and liquid separation occurs. The gas compressed to the required pressure is sent for further recycling, e.g. for combustion. After the removal of heat excess in the heat exchanger 3, the motive liquid is delivered to the vacuum creating device 1 by the pump 4. If necessary, the makeup is carried out to refresh the motive liquid. The balance excess of the motive liquid is withdrawn from the system.

Main advantages of VHC unit

The advantages of vacuum creating systems based on the vacuum hydrocirculating unit are given below as compared with

steam ejectors:

• improved environmental safety of the entire unit due to significant reduction of heat energy discharged into the environment, polluted waste water and steam condensate requiring appropriate treatment;
  
• cost savings due to reduction of energy resource consumption (water steam and cooling water);
  
• reduction of valuable products losses entrained by steam condensate;
  
• vacuum stabilization in technological device at the designed level and reduction of process losses caused by decreased performance of steam ejector systems due to intercondenser fouling and steam and cooling water parameters oscillation;
  
• silent operation;
  
• weak dependence of VHC unit suction pressure on cooling water temperature that provides a great advantage, especially under hot climate conditions;
  

mechanical vacuum pumps:

• low sensitivity to liquid and solid particles presence in evacuated gas;
  
• ability to pump explosive and high-corrosive gases;
  
• high level of explosion and fire safety due to absence of moving parts in the jet device;
  
• high reliability, ease of operation and outdoor location of the unit;
  

liquid ring vacuum pumps:

• ability to obtain a higher vacuum;
  
• high reliability, ease of operation;
  
• higher volume flow rate of evacuated gas;
  
• ability of gas cleaning from heavy hydrocarbons.
  

After a slight modification VHC unit can operate as a compressor that compresses various gases and gas-vapor mixtures including polluted and explosive ones.

Other VHC unit application layouts for vacuum creation in columns of refineries

There are various possible layouts of VHC units depending on required capacity, vacuum level, compression ratio, evacuated gas-vapor mixture composition, column operating conditions, equipment layout, Customer requirements and other factors.

Layout of the two-stage VHC unit with hydrocarbon motive liquid;

Layout of the two-stage VHC unit with cracking gases compression to the pressure of refinery fuel header and their cleaning from acid components;

Layout of the two-stage VHC unit with steam and liquid circulation loops
(for creating stable high vacuum of 15-25 mm Hg in refinery vacuum columns and reduction of electric energy consumption);

Layout of the VHC unit with chiller;

Layout of the VHC unit with motive liquid regeneration and hydrogen sulfide removal.

Industrial application experience

For the first time in world practice the VHC unit was introduced at the distillation column VK-1 of Atmospheric-vacuum distillation unit-3 (AVT-3) of Moscow refinery in 1993.

By the beginning of 2023, Technovacuum Ltd. has more than 60 implementations of vacuum creating systems based on VHC unit at vacuum columns of oil refineries, chemical and petrochemical plants in Russia and other countries.

The implementation of vacuum creating systems based on VHC unit at these plants resulted in considerable energy savings, reduction of waste water treatment costs and increased product yield due to holding a stable vacuum level in column.

Based on field experience of VHC units, increase in product yield reaches up to a value of 1.5 %. The payback period of vacuum creating systems revamping is therefore 4-18 months, depending on energy and oil products prices.

In oil-refining industry VHC units are used for vacuum creation in crude distillation units. In chemical and petrochemical industry they are used in units for cyclohexanol-cyclohexanone, alkylbenzene, benzene-toluene-xylene fraction production and other.

Publications and feedback

Features of VHC units performance characteristics

• If certain motive fluids are used, the minimum suction pressure can reach 67 Pa (0.5 mm Hg).
  
• In case of gas evacuation, the volumetric capacity of the VHC unit does not change within the entire range of suction pressure: from atmospheric to almost minimum.
  
• Mass capacity of the unit slightly depends on gas temperature up to 500 ^îC.
  
• In case of gas-vapor mixture evacuation under certain conditions, presence of vapor in gas slightly effects on the unit dry gas mass capacity.
  
• The units with the required capacity and suction pressure are manufactured according to Customer technical specification.

Accepted notation of VHC units

Notation example: VHC-140-2-V-1 (the picture of VHC-140-2-V-1 of Atmospheric vacuum distillation unit-4 (AVT-4) of Ufaneftekhim OJSC)

Description of the VHC unit notation:

The capacity range of the industrial VHC units is 20 m³/min - 350 m³/min. Capacity of VHC units is indicated for dry air at temperature 20 ^îC.

Technovacuum Ltd. constantly improves the VHC units in order to reduce power consumption and decrease the suction pressure.

Equipment layout solutions

The VHC units are easily mounted both at new and existing columns.

Layout of the VHC unit on the separate platform (column K-5 of Atmospheric vacuum distillation unit-4 of Ufaneftekhim OJSC).

Layout of the VHC unit on the existing platform (column K-1 of bitumen unit of Mozyr Refinery).

Layout of the VHC unit on the existing platform (column K-10 of Atmospheric vacuum distillation unit-6 (AVT-6) of Moscow Refinery OJSC).

If you are interested in vacuum creation technology based on VHC unit and you plan to apply it at your enterprise, please fill in the following

Questionnaire.

2) VACUUM CREATING SYSTEMS
based on steam ejectors (steam jet vacuum pumps)

Purpose

Layout of three-stage vacuum creating system based on steam ejectors

1 - steam ejector 2 - condenser 3 - separator I - gas-vapor mixture from vacuumized vessel II - active steam III - compressed gas outlet line IV – condensate outlet line

Main advantages:

• Practically unlimited operation capacity, simple design and reliability.

Disadvantages in comparison with VHC units:

• Considerable consumption of energy and cooling water;
• Strong dependence of vacuum level on cooling water temperature and on fouling rate of heat-exchange surface of inter-stage condensers;
• Contamination of steam condensate by components of evacuated medium and mandatory treatment of this steam condensate;

• Oil processing, petrochemical industry, heat-and-power industry, metallurgy, evaporation and exsiccation technology, fertilizer production, paper and food industry etc.

Questionnaire.

Technovacuum © 2024