Our portal has already touched upon the topic of mobile refueling stations for liquefied household gas. In this material, at the request of readers, we will examine their design in more detail.
The purpose of such equipment is obvious: it allows refueling passenger cars, buses, agricultural machinery, and other vehicles converted to run on methane. Such a station can be installed almost anywhere, as long as there is a household gas pipeline nearby. This could be a private house, a suburban plot, or the territory of a garage cooperative.
It is well known that for the population, the price of gas is significantly lower than at regular CNG filling stations. The opportunity to save considerably on fuel will surely interest many car owners. More details can be found in our article "Refueling your car with methane at home."
Here we will analyze the design of such a mini-station.
In a standard gas pipeline going to a stove, boiler, or water heater, the pressure is maintained at about 0.05 atmospheres. In a high-pressure cylinder, this figure reaches 200 atmospheres. This means a device is needed that can raise the pressure to the required values. This function is performed by a compressor included in the kit of such a refueling station.
Its design differs significantly from conventional household compressors. A typical single-circuit unit can deliver a maximum of 20–25 atmospheres, but filling a cylinder requires all 200. Engineers solved this problem by adding several additional circuits to the system. Essentially, it is a set of sequentially connected compressors, where each subsequent one compresses the gas to a higher pressure than the previous one.
1 Filter for incoming gas. 2 Inlet valve of stage 1. 3 Outlet valve of stage 1. 4 Cooling tube between stages 1 and 2. 5 Inlet valve of stage 2. 6 Outlet valve of stage 2. 7 Cooling tube between stages 2 and 3. 8 Inlet valve of stage 3. 9 Outlet valve of stage 3. 10 Cooling tubes at the final stage of gas outlet. 11 Pressure switch. 12 Activated carbon / molecular filter. 13 Safety valve. 14 Pressure sensor. 15 Outlet to hoses.
Let's analyze how this compressor works using the diagram as an example:
Methane from the household network enters the cylinder of the first circuit through the inlet filter (1) via the inlet valve (3). There it is compressed and directed through the outlet valve (3) along a pipeline with a cooling radiator (4) into the cylinder of the second circuit. At this stage, the gas, already compressed in the first circuit, is additionally compressed to a higher pressure. Then the process repeats in the third circuit. In general, the number of circuits can reach up to five, although in the described scheme there are three. The principle of operation does not change from this.
After reaching the required pressure (in our case 200 atmospheres), the gas passes through the pressure switch (11), is cleaned in the molecular filter, and through the safety valve enters the cylinders of the vehicle being refueled. How long refueling will take depends on the performance of the unit. For home use, units that refuel at a rate of up to 5 cubic meters per hour are currently allowed.
Thus, a cylinder with a volume of 80 liters, holding 18 cubic meters of methane, will be filled in about 3 hours and 40 minutes.
To make the process faster, you can set up a station with a receiver. It works simply: the compressor constantly pumps gas into stationary cylinders, and when you need to refuel a car, methane is transferred directly from them. This way, the refueling time can be reduced to 10–15 minutes.
How such stations will take root in Ukraine is still unclear, but in Europe and America they are already gaining popularity.
