A novel method of removing heat released during hydrate formation

Reporter : Xiaofei Song

Supervisor : Feng Xin

The background of the subject

Introduction of several literatures and patents

Several methods of removing heat

A process flow chart

Thought and plan

Contents

The background

The application of gas hydrates: carbon dioxide sequestration; transportation of natural gas; seperation of gas mixtures.

The main issue: slow formation rate.

To design a novel reactor for rapid and in continuo production of hydrates.

Several reactors

L.-W. Zhang, G.-J. Chen, , C.-Y. Sun, S.-S. Fan,Y.-M. Ding. X.-L.Wang, L.-Y.Yang∗ . The partition coefficients of ethylene between hydrate and vapor for methane+ethylene+water and methane+ethylene+SDS+water. Chemical Engineering Science 60 (2005) 5356 – 5362.

Kazuya Fukumoto, Jun-ichiro Tobe, Ryo Ohmura, and Yasuhiko H. Mori.Hydrate Formation Using Water Spraying in aHydrophobic Gas: a Preliminary Study. Yokohama 223-8522, Japan

Ryo Ohmura,*,† Shigetoyo Kashiwazaki, Saburo Shiota, Hideyuki Tsuji, and Yasuhiko H. Mori. Structure-I and Structure-H Hydrate Formation Using Water Spraying. Energy & Fuels 2002, 16, 1141-1147

Thermoelectric module assembly

US 2012/0082590 A1

Several methods of removing heat A solution :Adding sodium chloride or ethylene glycol to the liquid to be treated to lower the freeing point of the liquid .merits: it can make a good use of the high heat capacity of water and can be operated easily. Problems existed: how to obtain the specific temperature needed ,for example

263K,if heat exchanger is to be choosed, the exteral shell of the heat changer could freeze ,thus hindering the heat diffusion.

it was showed that even 3% （ mass percentage )of the sodium chloride extended greatly the hydrate formation time,while the freezing point of the solution is just about 271K.

guess:all substances which can lower the freeing point of the liquid could inhibit the formation of gas hydrates since freezing and hydrates formation have some similarities!

B solution:Absorb the heat released during the process by solid melting . merit:there is no need to consider the effection on the inside pressure of the reactor after adding the solid.

Problems existed: To find the solid whose melting point is between 273K-277K. The sizes of the solid paticles. If there are residues of the solid in the reactor ,their effection on hydrates ,such as density ,viscosity,must be considered.The seperation of hydrates from the solid is a ploblem ,too. Refrigeration system must have sufficient capacity to cool the solution when we recycle the solid . How to get the solid out from the refrigeration system.

C solution: absorb the heat released during the process by gasification of a specific liquid . Merits:it is easy to add the liquid and recycle the liquid . problems existed: To find the specific liquid or liquid mixture whose saturated vapor pressure is 3MPa at 277K. the exteral shell of the heat changer could freeze. Pressure .Supercondensation: if there is a limitation of the content of the specific liquid in the reactor. how to operate the condition to change the phase state of the specific material.

As relative supersaturation increases ,the rate of reaction increases but the gas separation efficiency decreases .

With increasing subcooling,the rate of reaction increases,but that the degree of gas separation decreases as the less-preferred formers, rates increase faster than the more-preferred formers, rates.

the presence of the catalyst initially was found by us to promote the formation of a dense ,heavy foam during dissociation.the foam makes processing of the products extremely difficult and more than offsets the increase in formation reaction rate afforded by the catalyst.

US 20100113845A1

It was found that experiments in the SPS resulted in hydrates consistently forming at lower overpressures and in shorter induction times than equivalent experiments in the Parr vessel.

Scott D. McCallum, David E. Riestenberg, Olga Y. Zatsepina, Tommy J. Phelps. Effect of pressure vessel size on the formation of

gas hydrates. Journal of Petroleum Science and Engineering 56 (2007) 54–64.

Question Which one should be given more attention ,seperation or

reaction speed?the reactor alone or the whole process?

Will we still design a small reactor ?(1-1000ml)

The plans

To consult more articles about heat transfering during the hydrate formation.

To acquire more knowledge about supercondensation.

To consult more liquids about their properties.

To calculate on the energy balance and show its validity.

Thank you!