Patent Publication Number: US-4321790-A

Title: Process for increasing the capacity and/or energetic efficiency of pressure-intensifying stations of hydrocarbon pipelines

Description:
FIELD OF THE INVENTION 
     Our present invention relates to the field of pressure-intensifying stations of natural-gas and oil pipelines. 
     BACKGROUND OF THE INVENTION 
     The large production sites for hydrocarbon (natural gas and oil) pipelines serving for the economical long-distance delivery of very large quantities of hydrocarbon. In the interest of economical investment and operation of the pipelines, pressure-intensifying stations are used by (e.g. at 100-150 km distance) which compensate the frictional and other resistance of the pipeline and (in case of natural gas) reduce the volume of the medium to be carried by keeping up the correct pressure. 
     A large number of pressure-intensifying stations are required by a pipeline several thousand km long. On worldwide scale this would amount to several thousand stations. Compressors (pumps) used in the pressure-intensifying stations are driven by power generators operated with the conveyed hydrocarbon. Thus, operation of a large number of pressure-intensifying stations--depending on the length of the pipeline--involves substantial consumption by the delivery system itself, thereby reducing the quantity of the salable hydrocarbon. The main reason for the high internal consumption is that gas turbines of the open circulation type are used nearly exclusively at the present for driving of the compressors (pumps), their energy efficiency being only 20-30%, so that 70-80% of the consumed hydrocarbon is not utilized. The known natural-gas pipeline of Orenburg may be mentioned as an example, along the whose 2800-km length 22 pressure-intensifying stations are operating with consumption of more than 15% (4.5 thousand million m 3  /year) of the carried total natural-gas quantity. 
     OBJECTS OF THE INVENTION 
     Thus, our invention aims at reducing this loss of energy as far as possible. The object of our present invention, therefore, is to provide a process of and means for significantly improving the capacity and/or energy efficiency of the pressure-intensifying stations without the unfavorable alteration of other essential characteristics, such as safety of operation, independence from the surroundings, specific investment cost. 
     SUMMARY OF THE INVENTION 
     According to an essential feature of the invention steam is produced in the boilers heated with the outgoing flue gas of the gas turbines driving the compressors or pumps and the steam is conducted into the steam turbine for driving further compressors or pumps. 
     Main feature of the equipment according to the invention is that the ratio of the simultaneously cooperative gas turbines and steam turbines may vary from the equivalent to tripple value, suitably the ratio is double and the stand-by machine unit is always driven by a gas turbine, a separate flue gas boiler is connected with each of the gas turbines, and the boilers are equipped with a supplementary automatic heater. 
     In order to ensure independence from water for the pressure-intensifying station according to the invention, the steam turbines function with a closed air conditioning system; thus the minimal water requirement can be provided with storage and periodical supply. In the interest of the maintaining water quality and a low gas content in the closed system (boiler water supply) and to avoid the use of a large steam pipeline, the use of indirect air cooling is advantageous. When the small ribbed air cooler is under water pressure, any incidental leakages is recognizable. The mixing condenser of the cooling system is arranged suitably above and along the steam turbine so that the foundation of the steam turbine may be a simple flat base. 
     The process according to the invention solves the problem of cooling of the compressed and heated natural gas and lubricant of the machines, i.e. utilization of the compression and friction heat with heat exchangers built into the water supply system of the boilers. 
     With a small part of the steam produced in the flue gas boilers, heating of the natural gas to be expanded (to prevent water condensation) before the consumers of the pressure-intensifying stations is solved and separate boiler plant is unnecessary, thereby resulting in a saving of natural gas. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     A flow diagram of the process according to the invention is shown in FIG. 1; and 
     FIG. 2 is a block diagram of the layout of the pressure-intensifying station according to the invention. 
    
    
     SPECIFIC DESCRIPTION 
     The two operating and one stand-by compressor units 1 shown in FIG. 1, are driven by gas turbines 2, while one operating unit is driven by the steam turbine 3. Steam for the steam turbine 3 is supplied by the flue gas boilers 4, two of them being operational while one is a stand-by unit. The flue gas boilers can be operated with supplementary natural gas heating or with substitute heating. The flue gas passes out of the flue gas boilers 4 through stacks 5 into the open. The indirect air conditioning system of the steam turbine includes the mixing condenser 6, atmospheric water storage 7, ventilator air cooler 8, and cooling water pump 9. Water supply to the flue gas boilers 4 is ensured from the closed air cooling system by pump 10. For cooling of the natural gas after compression, the water passes through heat exchangers 11. On the other hand with a small proportion of the produced steam the natural gas used for heating of the gas turbines 2 and boilers 4 is preheated prior to expansion with the aid of heat exchanger 12. 
     The main apparatuses of the pressure-intensifying station according to the invention are shown in FIG. 2. The natural-gas pipeline 13 is connected with the pressure-intensifying compressors 1 on the inlet and outlet side, three of the compressors are driven by gas turbines 2, and one by the steam turbine 3. Flue gas of the gas turbines 2 passes to the flue gas boilers 4 through the flue gas ducts 14, the produced steam arrives at the steam turbine 3 through the steam collecting main pipe 15, the mixing condenser 6 is alongside the steam turbine 3, while the air cooler 8, the cooling water storage tank 16 and pump house 17 are shown farther. 
     Advantages of the invention includes the following: 
     reduces the self-consumption by about 1/3rd, 
     improves safety of the pressure intensification, 
     realizable in existing pressure-intensifying stations.