TECHNOVACUUM

VACUUM CREATING SYSTEMS
based on vacuum hydrocirculating units

Purpose

Vacuum hydrocirculating units (VHC units) are intended for exhaust of gases, vapors and gas-vapor-fluid mixtures for vacuum creation in devices of various purposes (distillation and stripping columns, desorbers, evaporators, deaerators, condensers, reactors, dryers, desalters, systems of oil products refining and other technological vessels). The VHC units are an alternative to traditional systems of vacuum creation such as vacuum pumps, steam ejectors and have sufficiently better performance as regards operation stability and operating costs under certain conditions.

Field of application of vacuum units

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

Single-stage scheme of VHC unit

1 - vacuum creating device 2 - separator 3 - cooler 4 - pump I - gas-vapor mixture from vacuumized vessel II - exhaust line for compressed gas III - line of motive fluid excess withdrawal IV - fresh motive fluid makeup line

Principle of operation

The pumpage from process apparatus, e.g. distillation column, is directed to the inlet of vacuum creating device 1. In vacuum creating device 1 there occurs the compression of vapor-gas at the caused by motive fluid energy delivered to device 1 by the pump 4. One of process flows can be used as an motive fluid, there is allowed to mix it with vapors pumped by the vacuum creating unit.

The diesel fraction or vacuum gas oil is used in petroleum refinery as motive fluid. The cyclohexanol-cyclohexanone mixture is the motive fluid in caprolactam production.

The process of vapors condensation on the jet of motive fluid occurs simultaneously with gas-vapor compression. Herewith the vapor condensation and gas cooling in the vacuum creating device occurs on isobar and their compression up to discharge pressure - on isotherm, what makes the device energy-efficient as compared with other vacuum pumps, particularly by pumping of gas-vapor mixtures with large vapor percentage.

The gas-vapor mixture generated goes from vacuum creating device 1 to the separator 2, where the separation of gas and fluid occurs. The gas compressed up to required pressure is directed for further recycling, for example, incineration. After the removal of heat excess in the cooler 3, the motive fluid is delivered to the vacuum creating device 1 by the pump 4. The makeup is carried out for refreshing of motive operating fluid, if necessary. The balance excess of motive fluid is let out of the system.

Main advantages of VHC units

The advantages of vacuum creating systems on basis of vacuum hydrocirculating unit as compared with

steam jet ejectors:

• increased environmental safety of the whole unit thanks to significantly decreased discharge of heat energy, polluted waste water and steam condensate requiring appropriate treatment;
  
• savings on reduction of costs for energy consumption (water steam and cooling water);
  
• decreasing of losses of valuable products with water steam condensate;
  
• stabilization of vacuum in process equipment on designed and reduction of process loss connected with deterioration in operation of steam jet ejector systems by contamination of interstage condensers and by variation in parameters of steam and cooling water;
  
• silent operation;
  
• suction pressure for VHC unit depends only slightly on cooling water temperature, which provides an important advantage, especially under hot climatic conditions;
  

mechanical vacuum pumps:

• low sensitivity to the presence of condensate vapors and solid particles in exhaust gas;
  
• ability to pump explosive and highly deleterious gases;
  
• high level of fire and explosion safety owing to absence of movable mechanical parts in the jet device;
  
• high reliability, ease of operation and external location of unit;
  

liquid ring vacuum pumps:

• possibility to obtain a deeper vacuum;
  
• high reliability, ease of operation;
  
• higher volume capacity of exhaust gas.

The VHC unit can operate in compressor mode - compressing various gases and gas-vapor mixtures including polluted and explosive ones by small design debugging.

Other schemes for vacuum creation on basis of VHC unit in columns of refineries

Depending on required capacity and vacuum depth, compression degree, content of gas-vapor mixture pumped, operating conditions of column, layouts, Customer requirements and other factors, various scheme versions of vacuum hydrocirculating units are possible.

Two-stage scheme of VHC unit with hydrocarbon motive fluid.

Two-stage scheme of VHC unit with compression of cracking gases up to the pressure in fuel collector of the plant and removal of acid components.

Experience of industrial application

First in the world practice, the VHC unit was introduced on distillation column VK-1 of atmospheric vacuum distillation unit-3 (AVT-3) of Moscow Refinery) in 1993.

In 2007, Technovacuum Ltd. already performed over 40 implementations of vacuum creating systems on basis of VHC unit on vacuum columns of refineries, chemical and petrochemical plants of Russia and other countries.

The introduction of vacuum creating systems on basis of VHC unit at these plants resulted in considerable energy savings, reduction of costs for treatment of polluted wastewater and increase of product yield thanks to the maintenance of a stable vacuum level in the column.

Based on field experience of VHC units, the increase of yield reaches up to 1,5 %. The pay-back period of revamping of vacuum creating systems is therefore 4-18 months, depending on prices for energy resources and oil products.

In the oil-refining industry, the VHC units create vacuum in crude distillation units, in the chemical and petrochemical industry - in units for cyclohexanol-cyclohexanone production, alkylbenzene production, in plants for benzene-toluene-xylene cut production and other.

Publications and comments

Operating characteristics of VHC units

• Minimum suction pressure by use of some motive fluids can reach 67 Pa (0,5 mmHg).
  
• Volumetric capacity of unit by gas pumping does not change within the whole range of suction pressure: from atmospheric up to the close to minimum.
  
• Mass capacity of unit only slightly depends on gas temperature up to 800 ë.
  
• The presence of vapor in gas by pumping of gas-vapor mixture under certain conditions weakly affects the mass capacity of the unit on dry gas.
  
• The units are manufactured according to the performance specification of the Customer for necessary capacity and suction pressure.

Accepted notation of VHC units

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

Description of notation of VHC unit:

The capacity of industrial VHC units is 20 m³/min - 350 m³/min. The capacity of VHC units is indicated for dry air with temperature 290 ë.

Technovacuum Ltd. constantly improves VHC units decreasing the power consumption and increasing the vacuum depth.

Layout solutions

VHC units are easily mounted both on new and existing columns.

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

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

Layout of 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 on basis of VHC unit and You plan to apply it on Your enterprise, please, fill in the following

Questionnaire.

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