TOKYO GAS TOP > Technical development > For the stable production of city gas > DV & M Calorific Value Adjustment System

DV & M Calorific Value Adjustment System

City gas’s calorific value is adjusted at LNG receiving terminals to keep it constant and ensure customer safety. In addition to the gas/gas method of adjusting calorific value by vaporizing LNG and LPG separately and then mixing them in a gaseous state, the direct vaporizing and mixing method, or DV & M for short, is developed, which involves adjusting calorific value by injecting liquid LPG into vaporized LNG. DV & M Calorific Value Adjustment System is widely used in the gas industry.

 

Main Features of DV & M

  
FEATURES OF DV & M
 
 

Comparison of adjustment methods

Conventional method: gas/gas

  • Steam boiler and LPG vaporizer required to vaporize LPG
  • Waste water neutralization unit required for steam boiler
  • Space required for steam boiler and LPG vaporizer
 

DV & M method: liquid/gas

  • Economical as no steam boiler or LPG vaporizer is required
  • Less space required as can be attached to pipes
 
Comparison of adjustment methods
gas/gas liquid/gas

 
 

Construction


The DV & M mixer mixes liquid LPG with natural gas at high speed, with high-speed mixing being achieved by means of a Venturi tube.
 
DV & M mixer construction
 
The Venturi tube is equipped with an LPG spray nozzle to atomize and spray LPG into natural gas. The very fine droplets of LPG produced are rapidly vaporized and mixed in by the sensible heat of the natural gas.

 

Controllability


The conventional gas/gas method tends to exhibit large fluctuations in calorific value when load varies, mainly because of the lag in response of the steam supply for LPG liquefaction. In contrast, the new system has excellent load-following characteristics as only the input of LPG needs to be controlled.
 
Fluctuations in calorific value with changes in load
gas/gas DV & M
 

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