The conceptual, technical and technological approaches to creation of    natural gas equipment in Scientific –cum-Technical Complex  “  CRYOGENIC  TECHNIKA” ( Omsk City, Siberia)                                       
                                           
                                                 
                             An abstract from the article by:

                 by L.V. Popov, T.I. Rogalsky, Yu.I. Schelkonogov

 
                                       INTRODUCTION

 The role of  natural gas has been  increasing  lately. In Russia  even now  the consumption of  gas  as an energy source ( in percentage)   is more than in European countries and the demand for natural  gas is ever growing. That creates new problems:

 1)      The pipe line gasification programs in many regions of Russia proved that  traditional  pipe lines have their limitations because of  the high costs and low efficiency in distant regions with  a low density of population,  also in places with very  hard  conditions for laying pipe lines.

2)      Increasing demand for natural gas makes it necessary to develop new  sources of gas extraction  from sources    in very distant  and untraditional  locations  like Arctic sea shelf  where new approaches to gas transportation to the mainland are  needed. 

3)      It is necessary to begin to replace  oil motor fuels with gas  fuels as the  production of oil in Russia will  fall in near future with drying up of the existing  oil wells. 

 Alternative  technologies in transportation and utilization of natural gas 

 An alternative to  traditional pipe line  gas transportation systems   becomes a must  if we want to solve the problems mentioned above.  It is possible to transform  natural gas (NG)  by chemical methods into other products, like methanol, for example.  There are  also two  main technologies to convert NG by non-chemical methods – to compress NG and to liquefy NG.

Today a CNG technology  is more popular in Russia than a LPG one  because CPG equipment is relatively  simple and relatively  inexpensive . It uses the same principles as in traditional gas industry and  any gas specialist can handle it without  serious additional training.  Yet a CPG  technology has  many  weak points as well.

  First of all, - high pressure cylinders which are used in this high pressure technology  are very heavy. It is particularly  noticeable  if CNG is used  for  On Board  Fuel Systems ( Gas Tanks)  in  Gas Filling Vehicles ( Mobile  Gas  Filling Stations). Besides, CNG vehicles have to be refueled  more often, CNG filling time  is quite long, the filling coefficient is low if it is a filling from  a  Mobile  Gas  Filling Station ( by gas  pressure difference in  tanks of the MGFS and   the vehicle to be filled with CNG). CNG is  also inconvenient if  the daily consumption of  CNG  is uneven  at  a stationary  auto gas filling-cum-compressing station.

In case of an accident CPG is highly inflammable and  explosive.

 All this factors seriously  limits use of CNG  as Gas Motor Fuel and even  more  in using this technology for  gas transportation purposes.

 От the other hand LPG has some unique features. At the atmospheric pressure  it is a cryogenic liquid with a temperature at 110-115 K, containing  600 times  more  natural  gas in the  same volume of  cryogenic storage vessel as compared with ordinary natural gas. The same  volume of LPG at a normal pressure contains 3 times more gas as compared with CNG at 15  Bar pressure. It enables LPG to compete with CNG as a motor fuel, especially  for  heavy  trucks.  Yet  LPG as a motor fuel is not used  much in Russia yet.  First of all,  LPG equipment is expensive  as LPG technology as such is not widely used in Russia and therefore there is  no mass (serial) production of this equipment in Russia which could make prices much lower. Besides, unlike CNG technology in LPG sphere  there is lack of trained specialists to handle and service LPG  equipment.  As a result, both  technologies – CNG and LPG ones are developed in Russia today. Each is used  in a sphere where it is more applicable.

  MAIN  APPROACHES   IN   CREATION   OF    LNG    EQUIPMENT

 -         If small scale LNG production is required than from both economic and thermodynamic points of view  the  liquefiers schemes should be based on  a turbodetander  which is  located at a Gas  Distribution Station ( GDS) and uses the energy of  compressed  natural gas coming to a GDS from the in feeding  gas  pipe line. The liquefiers installed  at  this kind of cryogenic complex  should produce  no less than 0,5 tons  LNG per hour.

-          -         - the invested money is returned  more quickly if LNG  is used as a motor gas fuel than for   other purposes.

-          -         the basic variant of the LNG producing complex  should  be  based on LNG   liquefiers with  production output  of 1 ton   in hour. If it is  necessary to create a bigger complex then a number of these basic productivity liquefiers (up to 1.5 tons  output each) should  be installed at he larger  complex.

-          -         In this case it is possible to ensure:

-          -          a stage by stage  LNG output regulation  without  deterioration of  thermodynamic parameters  if demand for LNG is low  or if  out coming  from GDS  natural gas  consumption  by natural gas  end users  is less than usual;

-          -          more reliability for a  LNG  production complex as  a whole  and the possibility to have a smaller volume of LNG storage vessels   at such  a complex,  making  the storage system  less costly;

-          -         a stage by stage installation of basic liquefiers in blocks  ( depending on the demand for LNG, including  low demand at  the initial stage) thus ensuring  faster money return.  It is calculated that in case of a stage by stage installation  it is possible to save up to 30% in investments and  up to 5% in invested money return. However,  usually  the real saving effect is even more noticeable. ( The authors do not explain why it is so).  

 Usually  the most efficient LNG producing complexes  have productivity of up to 3 tons  per hour.

  Further the  authors of the article describe  production possibilities of their company.  It is noted that  an  ordinary  gas storage vessel    volume of 8 cubic meters,  traditionally produced at their plant  for oxygen or nitrogen  storage purposes  is  insufficient  today  for LNG storage vessels. Besides, LNG  equipments  must be  more fire and explosion proof in comparison  with  the ones  used for air separation units.

Now the company produces 3,  8,  16 and  25  cubic meters  stationary  cryogenic storage vessels for above the earth level installation. It is planned to produce also a 30 cubic meters  stationary storage vessel.  If necessary these can be installed in a storage complex with a  total volume up to  250 cubic meters,  fully equipped with cryogenic pipe lines,  regulation and safety valves,  etc. 

  Today the Company produces  regasification systems  with a volume up to 100 cubic meters  This vaporizing system  yield  of natural gas  is up to 1500  cubic meters per hour at pressure  ranging from  1 to  16 Bar which enables to supply  natural gas  in  volumes enough  for work  of a   14 Megawatt.  Boiler Station.

 Further, the  authors of the article dwell on  LNG transportation problems.  It is  a standard opinion that the larger volume of the cistern installed on a Semi-Trailer is,  the more efficient   LNG transportation  from a LNG producer to its consumers will be. The authors claim that it not right in  any cases. It is true only when the volume of produced LNG is big or if the road conditions ( or the distance to be covered)  does not enable  fast turnover of  gas auto carriers. In  fact the efficiency of transportation  by auto roads is dependant on many factors: on the volume of LNG production, on the distance of transportation, on the road conditions, on the quantity  of consumers and their territorial distribution.  Depending on this factors auto carriers may have very different volumes of their cisterns. The  authors  provide tables illustrating this  in simple cases of LNG transportation.

 At present, as the authors claim,  a 16 cubic  meters Semi-Trailer is  efficient enough  for transportation  of 16 Bar pressurized   LNG in very many cases. Such  a Semi-Trailer has been  serially  produced  as a LNG carrier for quite a long time  and it has a good record of its exploitation. However, despite the positive results of the usage of such auto carriers,  the authors note that  16 Bar pressure makes  the cistern thick walled and heavy / Fs a result  these are costly  while the volume of transported LNG is noticeably diminished by the weight of the  cistern.  The authors consider that 7-8 Bar pressure is optimal for such carriers and  such a  carrier – a cistern installed on a Semi-Trailer is being prepared for  serial production.

 At the same time the authors write that for big consumers  at least  27-30  LNG cubic meters  carrier is needed and such  a  Semi-Trailer is being designed at their company. Yet to make it а financially viable project there  must be a  greater demand for such carriers.

  If there is a Government program to convert auto transport for LNG motor fuel,  the company will  produce serially cryogenic cisterns with a cheap thermo insulation for LNG transportation purposes on a daily  basis. (  If LNG supply is required  as a motor fuel every day  by many consumers  located  not far from a  LNG production plant then the problem of evaporation loss  caused by long time storage becomes not so important while the possibility  to buy a relatively cheap  LNG Semi-Trailer will  remain  very important for  LNG  future distributors as usually.

 In the second part of their article the authors dwell  on  equipment for CNG.

 
                     
                       Cryogenic Semi-Trailer produced in Ukraine by a New  Zeland Company
                        Cryogenic vessel  ( a cistern installed on a Semi-Trailer) - 19,59 cubic                                 meters for carrying 20,52 tons of liquid oxigen. Vacuum-shield thermo
                        insulation, cryogenic pump.