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Calorific value fluctuation control system for LNG satellite terminals

Small LNG satellite terminals use air-heated or hot-water-heated vaporizers that the state of LNG from liquid to gas before supply. The fluctuations in the calorific value of the gas produced by the vaporizers are normalized by storing the gas into a buffer tank before supply. Using adsorption technology, Tokyo Gas has developed a calorific value fluctuation control system that can control calorific value fluctuations at roughly 1/30 the size of a conventional buffer tank. 
 

Objective


The calorific value of gas supplied by small LNG satellite stations fluctuates constantly due to impact from (1) vaporizer switching and (2) inflows of boil-off gas (BOG) inside the LNG tank. To prevent such variation from affecting gas-consuming appliances, sharp fluctuations in calorific value are controlled using a buffer tank. However, buffer tanks are a piece of large equipment that is costly and takes up a large area of the LNG satellite terminal. To address this issue, we look to reduce the size of buffer tanks using adsorption technology.

 

Development overview

Calorific value fluctuation control system based on adsorption technology


Filling the buffer tank with an adsorbent that selectively adsorbs various hydrocarbons, which are a constituent of natural gas, we were able to confirm a calorific value fluctuation control effect equivalent to 30x in volume terms. Following field tests carried out over more than one year, we confirmed a reduction in calorific value fluctuation control performance without any powdering of the adsorbent. 
 
Illustration of LNG satellite terminal and calorific value fluctuation control facility
Illustration of LNG satellite terminal and calorific value fluctuation control facility


Calorific value fluctuation control methods
 
Method Overview Characteristics
Adsorption tank Calorific value is controlled by installing a tank filled with a material that adsorbs and desorbs some constituents of city gas and thus controls calorific value fluctuations
  • 1/30 size of the conventional buffer tank
  • Low-cost
Buffer tank Calorific value is normalized by installing a buffer tank, where the gas is stored and its calorific value normalized
  • Strong track record in terms of actual on-site deployment
  • Large facility


 

Design of adsorption tank size


The installation of an adsorption tank at a LNG satellite terminal requires technology that estimates the optimal adsorption tank size for the to ensure costs are kept to a minimum. Accordingly, we are developing a simulator that estimates tank size using basic gas adsorption properties for key constituents of natural gas ranging from methane to butane, and a plug flow reactor model that can express multi-component competitive adsorption.
By inputting the composition of the vaporized gas sent by the vaporizer, data on how calorific value changes over time, pressure, flow, and targeted tolerated values for calorific value, the simulator is able to design the optimal adsorption tank size. 

 
Screen of adsorption tank size simulator for input and output
Screen of adsorption tank size simulator for input and output

 

Perspective


We aim to contribute effective utilization of natural gas by establishing a system to swiftly provide proposals on Tokyo Gas’ proprietary, low-cost, calorific value fluctuation control systems that are tailored to customer needs, geared specifically toward customers who are considering the installation of new LNG satellite terminals or the deployment of gas-consuming appliances such as co-generation that utilizes gas supplied by an LNG satellite terminal.

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