MIXING SYSTEM UNCONDENSABLE REFINERY GAS-AIR, FOR DISTRIBUTION NETWORK SERVING TOWN mixture 53 MJ/ncm 2,500 scm/h 500 mbar OPERATING SINCE 1985
LPG-AIR MIXING SYSTEM, AT AIR ASPIRATED, FOR DISTRIBUTION NETWORK SERVING TOWN mixture 53 MJ/ncm 2,500 scm/h 430 mbar OPERATING SINCE 1991
GASHOLDER A GUARD HYDRAULIC 200 mbar, FOR GAS-AIR SYSTEM AND MECHANICAL PROGRAMMER
PNEUMATIC PROGRAMMER STEPPING-STEPPING CONTROL MIXERS OPERATING SINCE 1991
MIXING SYSTEM UNCONDENSABLE GAS REFINERY-AIR AND LPG-AIR, AT AIR BLOWN, INSTRUMENTAL. FOR DISTRIBUTION NETWORK TOWN mixture 53MJ/ncm 3,700 scm/h 0,6 bar
ELECTRONIC PROGRAMMER FOR CONTROL MIXING SYSTEM
MIXING PLANTS UNCONDENSABLE GAS-AIR and LPG-AIR. PLANT ONLY ONE IN EUROPE IN ITS GENRE.
The company Procogi of Luigi Morelli has realized, with its own know-how, plants for blending uncondensable gas-air and LPG-air, at air suction and at air blown to supply the urban network gas distribution of the City of Sannazzaro de 'Burgondi (PV) Italy, about 2,000 users.
The City of Sannazzaro de 'Burgondi in the years 1968/1969 decided to provide the territory of the urban network with gas distribution, entrusting the concession to a private company (exercise initially led by Luigi Morelli).
Given the difficulty in connecting to the methane network, they chose to distribute a LPG-air mixture (Gross Calorific Value 53 MJ/nm3, variable pressure 140 to 200 mbar) interchangeable with natural gas.
In 1969 gas distribution to the town was started and subsequently it was extended to the neighboring town of Scaldasole.
The municipality, bought-back the plant from the company in 1983, made an investigation in order to look for cheaper sources of gas to supply the urban network.
The source of supply was identified in the uncondensable gas of refinery (mixture CH4 - C2H6 - C3H8 - C4H10 - H2) with Gross Calorific Value 73.7÷81.7 MJ/nm3.
Once the supply from the local refinery was obtained, it was identified a mixture of uncondensable gas-air (70/30% to 68/32%) interchangeable to the mix LPG-air, which satisfied the requirements for the proper functioning of the equipment of domestic and industrial users.
The municipality commissioned to Procogi the realization of the new condensable gas-air mixing plant, which had to interact with the existing LPG-air.
Project data:
- Capacity 1,500 m3/h (double the range of the existing LPG-air)
- Constant supply pressure 200 mbar
- Gross Calorific Value 53 MJ/m3.
We proposed and realized a mixing plant at air suction, consisting of a battery of injectors governed by a hydraulic guard gasometer with mechanical programmer. The operation of the system is pneumatic and employs the same gas, so it is autonomous without the use of any external energy. The existing LPG/air mixing plant was kept in operation in stand-by, with the aim to intervene in an automatic and immediate way in order to always ensure the gas supply to the urban network, for the possibility of interruptions in the supply condensable gas, caused by breakdowns in the production facilities.
The plant was started in late 1985.
Due to a disservice of the existing feed-out LPG vaporization plant, we realized a new feed-back LPG vaporization plant with a new overheating/decompression group, with flow rate of 2,500 kg/h at a pressure of 2,5 bar.
The plant was started in late 1986.
To cope with the increasing demand for gas, we realized :
- The strengthening of the uncondensable gas-air mixing plant with the installation of an new injector, the adaptation of the existing plants governed by pneumatic programmer. Capacity 2,500 m3/h at a pressure of 480 mbar.
- The installation of a new air suction LPG-air mixing plant, consisting of a battery of injectors governed by pneumatic programmer with emergency pneumatic pressure switches, for a flow of 2,500 m3/h at a pressure of 430 mbar; plant on stand-by for the reasons described above.
The plants were started in 1991.
With the purpose of adapting to new safety regulations the LPG storage, a radical operation was performed:
- installation of a new underground tank of 100 m3 in place of the two tanks of 50 m3 above ground,
- reconstruction of the point of loading with the installation of metal arms,
- realization of new thermal power plant of 450 kW,
- realization of a new firefighting pressurizing unit with water reserve of 200 m3.
Work carried out in 2002
In order to meet the needs of users during periods of greater consumption, to boost the pressure and the flow rate and make an easier and quicker correction of the Gross Calorific Value of the uncondensable gas-air mixture (due to the significant changes in the composition of the uncondensable gas), we have realized a blown air mixing plant, with flow rate 3,700 m3/h at a pressure of 600 mbar with Gross Calorific Value 53 MJ/nm3, in parallel to the air suction systems.
The plant, at the discretion of the conductor, will be activated only in the winter season and during the hours of the day with higher consumption, while at night and during other periods of the year the air suction mixers will continue to operate (without energy expenses), with significant energy savings.
The priority gas to use for the production of the gas-air mixture to be delivered to the urban network is in any case, being cheaper, the uncondensable gas, while the mixture LPG-air remains the replacement emergency gas in case of interruption of the supply of uncondensable gases.
The air blown mixing plant is constituted, in its essential parts, by:
- blowing top
- three lines of measurement and control, one for each fluid, uncondensable gas, LPG and air
- mixer
- adjustment of supply pressure
- system alarms and locks
- electronic controller command
- group of measurement of the delivered mixture.
The plant is scheduled to be started and stopped automatically in time.
In the startup phase the pressure of the mixture is gradually increased up to the value of exercise, while the air suction plant in service is stopped.
In the stopping phase the pressure of the mixture is gradually reduced to the value of the operating pressure of the air suction system, and, after this value or a flow rate of 10% is reached, it is stopped. In this phase the air suction system is put to regime with flow rate from the 0 to the flow rate required by the urban network.
If during the period of production of the mixture (uncondensable gas-air) the uncondensable gas supply is stopped, this line is excluded and, automatically together with an alarm, the LPG line is activated, without any inconvenience for the user.
The gross calorific value mixture produced is determined by the gas-air ratio, whose theoretical value is set by the driver on the electronic controller, that can always be corrected during operation in relation to the value indicated by the calorimeter (with the future installation of a new calorimeter, the GCV will be corrected automatically).
In conjunction with the installation of this system, new groups of uncondensable gas preheating-decompression, with increase up to 2,700 m3/h, and of LPG vaporization-heat-decompression, with an increase up to 4,000 kg/h, were built in order to adapt to the new requirements . In addition in order to prevent that the condensate in the uncondensable gas can be brought to the mixing plants, due to faults to production installations, an alarm and supply block system has been installed.
The plant was started in late 2013.
