TECHNOVACUUM

JET COMPRESSION SYSTEMS
for handling of low-pressure gases

Purpose

The jet compression system developed by Technovacuum Ltd. is designed for the compression of low-pressure (e.g., flare) gases produced during processes of oil refineries and petrochemical plants and also during oil-and-gas production.

The use of a jet compression system allows the improvement of ecological conditions at enterprises by reducing of flaring of significant quantities of low-pressure (e.g., flare) gases.

Layout of jet compression system

1 - liquid-gas jet device 2 - separator 3 - heat exchanger 4 - pump I - low-pressure gas II - compressed gas to consumer III - fresh motive fluid makeup IV - excess of spent motive fluid

Principle of operation of jet compression system

The low-pressure gas, e.g., flare gas of refinery, is delivered to the inlet of the jet device 1. The motive fluid is pumped into the jet device by the pump 4. Various fluids present in the process which may be mixed with the pumped gas can be used as an motive fluid.

As result of ejection process in the jet device, the gas-vapor mixture is compressed up to the required pressure. Simultaneously with compression in the jet device, there takes place a process of absorption of vapors contained in the pumped gas by the motive fluid.

The produced gas-vapor mixture after the jet device enters the separator 2, where the separation of gas from motive fluid occurs. The compressed gas is discharged from the separator to downstream operations, as example, it is directed to the fuel system of the plant. The motive fluid from separator is delivered to the cooler 3 for cooling, whereupon it enters to the suction of the pump 4. The excess of motive fluid is discharged from the unit through the level-control valve of separator 2 for further recovering.

It is expedient to use process flows coming for further separation as motive fluid, this allows to extract the absorbed components of low-pressure gas.

In case of variable flow of compressed gas, there are connected several jet devices and operating fluid pumps to one separator.

Capacity control of the jet compression system is carried out by automatic engagement and disengagement of pumps and jet devices. Such scheme allows to respond to changes of gas flow discharge efficiently and to refuse the use of gasholders.

Basic advantages of jet compression systems

As compared with traditionally used mechanical compressors, the jet compression systems have a series of advantages:

• Significant cost-effectiveness by compression of gases absorbed by motive fluid: sufficient quantities of vapors can be absorbed by motive fluid during compression of gas-vapor mixtures, what allows to increase the output of target products and performance of jet compression system;
  
• Possibility of selective treatment of compressed gases with help of motive fluid: as motive fluid there can be used a specially selected absorbent (e.g., monoethanolamine, diethyleneglycol etc.), which allows the removal of aggressive and ecologically dangerous matters from the compressed gas;
  
• Possibility of compression of explosive gases and also gases containing solid particles and liquid drops: this is provided by use of two-phase jet devices, in which gas is compressed with cold liquid;
  
• Automatic adjustment of capacity of jet compression system in the wide range with simultaneous energy saving: this is provided by control system of jet compression system realized on basis of DCS;
  
• High level of explosion and fire safety: this is provided by absence of contact of moving mechanical parts with compressed gas in the jet-devices and by possibility to place the jet-devices on an open site, what allows to exclude formation of explosive mixtures;
  
• High level of operating reliability: this is determined by use of jet devices, separating vessels, centrifugal pumps in jet compression systems, which have a higher level of reliability in comparison with mechanical compressors;
  
• No necessity of specially equipped compressor rooms: the equipment of jet compression systems is placed on an open site, what reduces capital costs.
  

Experience of industrial application of jet compression systems

Jet compression system at Turkmenbashy Refinery

The first jet compression system for handling of flare gases of Turkmenbashy Refinery was developed and put in operation in 2000 (see a picture).

The system has shown the design objectives and at present it is in operation. The maximum capacity of the jet compression system makes up 6000 nm³/h of flare gas compressed up to the pressure of 0.5 MPa. As motive fluid of the jet compression system there is used the light coking gas oil - a feedstock for catalytic cracking.

The hydrocarbon fractions С₃₊ of the flare gas dissolved in the motive fluid are discharged from the jet compression system together with balance excess of motive fluid and delivered to catalytic cracking unit where their recovering occurs.

Main process characteristics of jet compression system at Turkmenbashy Refinery

• gas pressure in the flare collector (at inlet of jet compression system) - 0.10-0.15 MPa abs.;
  
• gas pressure in the fuel system (at outlet of jet compression system) - 0.5 MPa;
  
• actual capacity of the system - 1000-6000 nm³/h depending on the number of operating jet devices.

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