Propane-butane recovery

In 1997, a plant with capacity for natural gas of 3.0 billion m³/year was commissioned in Karshi, Uzbekistan, it was developed by LENNIIHIMMASH specialists for production of 68 thousand tons per year of propane-butane-mixture.

Source gas parameters:

 
Products of processing are:

• propane-butane mixture according to GOST R 52087-2003
• liquefied hydrocarbon gases
• high-pressure methane fraction returned to gas-main pipeline after compression

Propane-butane mixture recovery process is continuous; it uses the method of natural gas cooling and partial condensation by means of source gas expansion effect in a turbo-expander followed by rectification of the produced condensate. External sources of cold are not used.

The plant consists of the following units of:

• Fine filtration
• Pre-cooling
• Expander
• Deethanization
• Production of target products
• Drainage tanks
• Auxiliary equipment – pipeline and metal structures

Heat exchange processes in the plant take place in vertical heat exchangers with twisted tubes and rigid core and in horizontal apparatus with straight tubes (water coolers). There are also heat exchangers with twisted (reboilers) and straight (dephlegmators) tubes built into columns. For cooling of hot streams, air coolers are provided. Mass exchange processes take place in two tray-type rectification columns.

Separators, reflux tank and condensate collection tanks are used as vessels for storage of process fluids during shutdown, and drainage. The size of the site occupied by the plant is 70x30 m².
In July 2006, the construction of associated petroleum gas processing plant with capacity of 3 billion m³/year (UPG-3), implemented based on LENNIIHIMMASH technology and project, was completed at OAO Surgutneftegaz, the plant was commissioned and ramped up.
During creation of separation technology, the energy-saving method of associated petroleum gas separation with usage of the turbo-expander unit, developed by LENNIIHIMMASH (Patent of Russia # 2225971, dated 20.03.04) was applied.

The produced market products are as follows:

• methane fraction according to industry standard OST 5140-93 – 2,8 billion nm³/year
• propane-butane, technical grade according to GOST R 52087-2003 – up to 203 thousand t/year
• LPG according to TU 38.101524-93 – 27 thousand t/year
• natural stable gasoline according to GOST 20448-90 – up to 47 thousand t/year.

The rated capacity of electrical equipment - 465 kW, that is in 3-5 times less than at the gas separation with usage of propane cooling cycle.

Major process equipment of the plant was also supplied by LENNIIHIMMASH.

The plant consists of the following units:

• initial separation
• dehydration and purification (gas treatment)
• pre-cooling with a turbo-expander
• rectification
• fired heaters
• heat-transfer fluid system

Today the design has been finished and construction of the integrated plant for ZAO Severorgsinez is carried out in Novy Urengoy, including gas processing line with capacity of 1.2 bln m³/year, tank farm, truck loading and a number of auxiliary facilities.