Not a great specialist in gas supply, but, having personally encountered these gas mixtures a little, I can bring clarity to this issue at the level of the 9th grade of secondary school.
So, for domestic purposes, propane-butane mixtures are usually used. Both propane and butane belong to the group of saturated hydrocarbons (alkanes). The less atomic (more "light") hydrocarbon, the lower its boiling point. Naturally, with decreasing temperature, the volatility of ANY gas decreases, and at a temperature below the boiling point it stops almost completely. Thus, the most "ebullient" and volatile is methane, then - ethane, then - propane, and the next - butane. The next saturated hydrocarbon - pentane - already boils at almost room temperature, and, of course, gas can only be considered conditionally (at temperatures above 30 degrees), the next 15 alkanes - from hexane to octadecane, under normal conditions, are already obvious liquids, and they can be poured into a tank rather than pumped into a cylinder (from which - some of them, in fact, consist of gasoline, kerosene, etc., but here I am not at all competent). Even higher molecular weight alkanes under normal conditions are solids, their mixtures are called paraffins, and everyone has probably seen how paraffin burns.
So, the boiling point of propane is about minus 40 degrees. The boiling point of butane is about 0 degrees. Celsius. Gas workers select the composition of the mixture based on the temperature at which the cylinder is expected to be used. I know that at the time when I was concerned about this issue, there were three gradations of propane-butane mixtures (unfortunately, I won’t name the temperature ranges): low-temperature, normal and high-temperature (relatively), respectively, differing in the ratio of propane and butane - the less propane , the mixture "works" at a lower temperature. Why not use pure propane? But do you need it so that at a temperature of about 30 degrees you have to keep the mixture in a cylinder similar to oxygen? And carry a delayed-action mine in your pocket (aka a lighter), which at any moment can fucking explode on its own ... That's based on ensuring working pressure at a certain temperature environment and the composition of the gas mixture is selected. Unfortunately, I have never seen that the temperature range of the mixture was written on a gas cylinder, including a "lighter" one - this would save a lot of nerves for smokers and tourists.
Now it’s probably clear why the lighter in the cold has to be “crumpled” in the hands for a long time in order to light it up. To some extent, "opening" the valve helps, but at temperatures below 30 degrees, it is completely impossible to light a lighter without "heating" (well, if you only fill it with a gasoline lighter, but then it would be better to leave it on the street, entering the room). The same applies to gas cylinders - especially for those who have a cylinder on the street.
Based on the above, it is clear why methane CANNOT be used as domestic LPG. It will simply be impossible to store it in ordinary gas cylinders- except in oxygen. It is also not used for some other reason (they explained, but now I can’t vouch - either because of the increased explosiveness, or because of the equally increased "poisonousness"). The same goes for ethane.
Now about the rest in the gas cylinder. The volatility of propane and butane, es-no, is different. So, if the cylinder is standing outside at a temperature below 0 degrees, butane practically does not evaporate on its own, and gas combustion stops when all propane evaporates. The higher the temperature, the less the "remainder" of butane (at a normal temperature for the mixture, it should not remain at all). "Linear" saturated hydrocarbons practically do not smell, their isomers smell relatively weakly. That is, it would be practically impossible to detect a leak of domestic gas if ... The smell of the residue mentioned AND YOU, is due to an odorant added specifically to detect gas leaks. As an odorizing agent, a mixture of mercaptans is used (methyl mercaptan, ethyl mercaptan, etc. - they are not specially mixed, they are simply not purified). Mercaptans are added in such a way that they completely burn out along with the gas, but even the slightest leak could be "smelled" by the nose, and the stink of mercaptans is almost unique - milligrams of mercaptans can stink the whole neighborhood so much that even flies will fly away from there (by the way, the presence of microamounts of mercaptans , the smell of a person's "rear exhaust" is also due), so it is not surprising that, having been soaked with "strong" mercaptan from a cylinder, clothes stink for a very long time, and when they appear in such a skin at a party, the owners first rush to the kitchen , and not finding a smell there, they politely (or not politely) are interested in whether everything is in order with your intestines ...
ADDED 02/02/2012 20:00 PM
Uh-umm? When is it NOT done? As far as I know, household gas is always odorized: on January 13, July 13, or on any other day - just open it and forget to light the gas, or press the lighter valve without lighting it - and the nose somehow does not allow you to doubt the presence of mercaptans in gas...
So that such a question does not arise on a hike, it is better to read this note before going to the mountains :)
So, gas burners are powered by a mixture of gases in a gaseous state (one cannot do without a tautology here). In the cylinder, this mixture is in liquid form. Shake the balloon. Do you feel? Liquid splashes inside. Recall the lessons of physics: a liquid begins to evaporate when the temperature of a substance exceeds its boiling point.
Now let's see what happens in summer and winter.
Summer. The air heats the balloon to a relatively high temperatures, above the boiling point of the gas - the gas boils - evaporation is created in the cylinder overpressure- due to pressure, part of the vapor escapes from the cylinder into the burner, mixing with air along the way - efficient combustion of gas occurs at the outlet of the burner. And we get a hot lunch.
Winter. It is cold outside, the cylinder in the backpack has cooled down to a temperature below the temperature required for the gas mixture to boil - the gas remains in a liquid state - there is no pressure - gas does not enter the burner - the burner does not work. And we freeze from the cold, licking frozen food.
Another fact that plays against our hot lunch in winter is the nature of the evaporation process itself. During evaporation, the substance loses a large amount of heat (it is strongly cooled). The gas evaporates very intensively, and therefore cools very strongly. In summer, this does not affect the operation of the burner, because the cylinder is again heated by hot air. And in winter, the balloon only cools down. When the cylinder is full, it is not so noticeable, since the heat loss is distributed over large quantity fuel. And if the cylinder is almost empty, then the temperature of the gas mixture can quickly drop below its boiling point.
Up to what temperature can a gas burner be used?
Drawing conclusions from the above, we need the gas in the cylinder to be heated above the boiling point. But, in fact, this is not enough. If we want to enjoy a hot lunch, then we just need to have enough pressure inside the cylinder to exit a large number gas to the burner. To do this, we need a gap of several degrees.
Gases from our cylinder boil at temperatures:
butane (normal butane, n-butane)…..-0.5°С
isobutane ……-11.73°С
propane…..-42.09°С
This means that if our cylinder contains mainly butane, then it can be effectively used at temperatures above 5 ° C. If only propane with isobutane, then we can go to -10 ° C. There cannot be one propane in a cylinder, because in summer the pressure of the gas inside the cylinder would simply break it.
Very handy! If you decide to refill your cylinder, then never ask or agree to fill up with pure propane. At best, you will see beautiful fireworks while hiking with such a balloon, and at worst, this will be your last trip.
So only down to -10°C? Is there nothing that can be done?
Yes, you certainly may! First, read and memorize. And secondly, take a winter trip
In the country, I use liquefied gas from 50 l cylinders. I always changed an empty cylinder to a full one for a special one. points, and did not know the problems either in summer or in winter. The cylinder was installed outside the house in an iron box and the gas stove worked at any temperature outside.
At the beginning of September, I decided to fill up a cylinder at a car gas station. Freed from condensate, there were 5 liters. Filled with 40 liters of gas. According to the experience of friends with such a gas station, there is enough gas for a longer time, and it turns out a little cheaper.
Finished the introduction.
Winter has come and the gas stove is not working.
Even though the tank is full. I began to study what was the matter and found out that on gas stations gas is summer and winter. It differs in the proportions of propane and butane. “In cold climates (or in winter), LPG, a mixture of propane and butane intended for use as an automotive fuel, should be dominated by propane for better gasification of the mixture” (for details on automotive gas, see link
liquefied petroleum gas
).
And I get summer gas, and at a temperature of -20 ° C it has a saturated vapor pressure of about 0.05 MPa, and liquid gas stoves start working at about this pressure. At lower pressure, the gas exits the nozzle (located inside the burner) at a low speed and does not mix with air. For this reason, it does not want to ignite. Hissing but not burning
.
Here is such a story. Now you have to equip a place for the cylinder in the house, for the time of winter.
To whom this story seemed not interesting or did not discover something new, I apologize.
Alexey M.
Page for konferei ZR.
.
Spring is coming soon! (-)
In two months, without hot, you can turn around. :-) (-)
Alexey M.
Page for konferei ZR.
.
live a century, learn a century, but you will still get there .. (-)
Re: About liquefied gas.
And this is not only at gas stations, sometimes a balloon bottle is brought in in winter such that at least shake it out, it doesn’t even flow out. In 1983, he grew flowers in the winter, so the greenhouse was heated with gas, since it cost 1 rub. 65 kopecks. cylinder, and the cylinder had to be put on an electric stove of 800 watts, then the gearbox worked. The tile worked continuously, on the street in a box for cylinders, and the cylinder stood directly on it. The pressure in the cylinder did not rise above 1-2 atm. The most important thing is not to heat the cylinder with an open fire.
Alexei.
Does not push through the gearbox (-)
V.M. (Casanova retired)
Something is pushing. Hisses from the burners. (-)
Alexey M.
Page for konferei ZR.
.
But still no pressure
It is no higher than in a balloon.
V.M. (Casanova retired)
Uh huh, that's the way it is, it's clear now
where do fire reports come from "...... the cause was a gas cylinder explosion." I kept wondering how it could be done...
Probably heated with a blowtorch :)))
Bon Voyage!
There are probably those. :-)
But ignition of the gas can occur when it flows into the air. At this point, electrolysis of the gas occurs, and a spark is possible because of this. And since this does not happen immediately, a gas explosion may occur in a room filled with it.
Alexey M.
Page for konferei ZR.
.
Re: About liquefied gas. For me, this was news.
All this is fixable: it is necessary to drill a little nozzle, i.e. enrich the mixture. Or buy ready-made with enlarged holes.
Sincerely, Alexander.
You can't do that. Dangerous!!!
For household gas stoves operating on liquefied gas, nozzles with a diameter of 0.9 mm should be used, and on natural gas - 1.2 mm.
The nozzles are sized so that the gas-air mixture burns completely. Fine tuning of the composition of the mixture is done by adjusting the air supply to the concork, the curtains located on it, but this adjustment is not provided for in modern stoves.
So if you replace the 0.9 mm nozzle with a 1.2 mm one, the gas will not burn completely, which can lead to "poisoning" (actually suffocation) or to a gas explosion in the room.
It's not about cutting here. As I wrote, at this temperature, the pressure in the cylinder is 0.05 MPa, and the minimum inlet pressure of the reducer is 0.07 MPa. What passes through the reducer cannot provide the necessary exit velocity of the gas jet from the nozzle, and since the burner is of the injection type, i.e. in order for the gas to mix with air, a certain gas exit rate is needed, and this depends on the pressure in the cylinder.
Alexey M.
Page for konferei ZR.
.
How to fix a gas leak from a high pressure gas cylinder valve or from a system attached to a cylinder?
Situation example. You filled the cylinder at the station, arrived home, connected the reducer, as well as the sleeves, tightened the hex of the reducer on the cylinder, opened the cylinder valve - and you understand that the gas is poisoning somewhere in the upper part of the flywheel. If the cylinder is filled with, for example, carbon dioxide, you will immediately feel an extraneous smell.
Attention! We warn you that the repair of cylinders should be carried out by specially trained and certified specialists! We strongly recommend that you do not self repair high-pressure cylinders, unskilled intervention can lead to tragedy. When conducting repair work described below, you are responsible for the manipulations carried out.
It happens that you need to work, but there is a small malfunction that is quite acceptable to fix on your own.
So, in order to eliminate the breakdown described above, it is necessary to do the following (valid only for the VK-94 valve and its modifications):
- To start, take a 27 mm wrench and try to tighten the nut shown in the photo, clockwise. In most cases this helps.
If, when you try to open the flywheel, the gas begins to poison from its upper part again, it is necessary to unscrew it counterclockwise until it stops, the leak should stop.
If the previous manipulation did not help, then the following must be done (valid only for the VK-94 valve, the procedure should be carried out only with skill):
- Loosen the flywheel nut counterclock-wise and remove it from the bottle.
- Then use a 10mm wrench to unscrew the nut located at the top of the flywheel.
- Remove the stem from the nut - a stuffing box is installed inside it.
- If the cylinder is not the first freshness (and those in our country are 90%), then the gasket will be in the appropriate, “shabby” condition. To eliminate the leak, you need to make the same new gasket from fluoroplast (GOST 15180-86) or paronite (GOST 481-80). You can try to make a gasket from a plastic canister, but this is short-lived and ineffective. The inner hole of the gasket should be no more than 8.5 mm in size, the outer one, respectively, according to the size of the inner diameter of the nut. The stem after replacing the gasket should sit in a tight fit, you will need additional tool to hammer it in (hammer, flat part of an adjustable wrench, etc., etc.) and thus put it back in place. Then the flywheel is installed back and screwed with a nut.
Note. The flywheel nut is not tightened all the way, but so that the spring is tensioned, but not clamped. Otherwise, the flywheel will not rotate.
- Install the assembly back on the cylinder and tighten the nut clockwise with a 27 mm wrench not to the stop (with a force of 5-7 kg).
Note. Similar procedures can be performed only with the VK-94 valve and its modifications.
The valve type VKB cannot be disassembled. If there is gas in the cylinder, even residual pressure, it is strictly forbidden to open the nut. Because apart from it, the pressure in the cylinder does not hold anything! SUCH CYLINDER CAN ONLY BE REPAIRED EMPTY.
There is a small control hole on the back side of the VKB type valve. In the event of a breakdown of the diaphragms that are inside the valve, gas begins to flow from this hole. If gas does not come out of this hole when the gearbox is screwed on and the valve is opened, then the valve is in good condition and they are allowed to work.
VKB is usually installed on cylinders with helium, for all other gases, as a rule, VK-94 is installed.
If the cylinder is expired and needs to be inspected or replaced, pay attention to the following things:
- The cylinder wall should not have dents, rotting shells with a depth of more than 1 mm;
- Pay attention to the date of manufacture of the cylinder, the passport must be read on it;
- Pay attention to the valve, it should not be beaten off (so that it can be unscrewed).
Gas burners, which we so actively and already use everywhere in everyday life, during outdoor recreation, on trips, sometimes help us out a lot. After all, with the help of them you can not only cook food, but also simply heat the seagull to refresh yourself. Let's say, provide yourself with a small snack on the road.
But there is also a “BUT” here, and this “BUT” manifests itself at all at the wrong time. So this article was a kind of derivative from such unplanned circumstances.
All summer long, you can quite actively and successfully use a balloon (such as "Tourist"), and even on the last warm days, a kettle will vigorously boil on it. However, already in the fall, when you once again want to use the cylinder - tiles for their intended purpose, it may turn out that the gas will barely burn or go out altogether. At the same time, you will be sure that all this time the cylinder was stored with the valve closed and the volume of gas in it did not decrease. That is, the bottle is not empty. So what's the deal? Why doesn't the gas burn?
Before answering this question, one must ask what is burning and what processes occur during the operation of such gas cylinders.
What burns in a gas stove
This question is more rhetorical and at first glance very strange, but even such an understanding of the simple does not reach many immediately. Yes, in gas stove gas burns, but where does it come from if the gas was originally refueled in a liquid state? In a gas cylinder, a stove, in fact, first evaporates gas from a liquid state into a gaseous state, and only then it is ignited in a burner. It is precisely because of these circumstances that it is important that the valve from which the gas exits and the burner are at the very top. That is, so that there is enough gas vapor in this place to set them on fire. If, instead of gas, there is liquid in the burner, then it will not burn at all in the burner, but as soon as it pours out and begins to evaporate ...
(depending on evaporation, a gas is formed that just burns. There is evaporation - there is fire, no evaporation - no fire)
So, we mentioned the evaporation of gas not by chance, because each of possible gases in gas cylinders presented in the store may have its own evaporation temperature. This means that it will be able to “work” at its own temperature.
Up to what temperature can a gas burner be used? (summer and winter gas)
Summarizing the above, it is important to have a gas that evaporates best, that is, to ensure that the gas boils in the liquid state. And here, not all used gas cylinders are the same.
If we turn to reference materials, it turns out that gases boil at the following temperatures:
Butane (normal butane, n-butane) ... -0.5 ° C;
- isobutane ... -11.73°C;
- propane…-42.09°С.
For confident evaporation, it would be necessary to overestimate this temperature by another 3-5 degrees Celsius. And here it seems that you use propane, that's all. Then no fear sub-zero temperatures. However, just because of its high volatility, it is not widely used. Indeed, in this case, the balloon will always be very high pressure striving for the worker, and this is potentially dangerous. So, in order to reduce this very potential danger, propane and butane gases interfere. So, it's usually a mixture of gases. It is necessary to look for a middle ground when our mixture will burn, but not create dangerous pressure. In theory, the mixture of gases should be observed according to the following principle. In summer, propane is about 50 percent, no more, the rest is butane, and in winter up to 80 percent propane, the rest is also butane.
However, butane relative to propane, in addition to the minus with volatility, has its own plus. It releases slightly more energy when burned than propane. Here is everything in a nutshell.
Of course, here we can conclude that when choosing gases in a store, be it a Sportmaster or a hardware store on the market, you need to think about what time of the year you plan to use the cylinder. If it is possible to read the ratio of gases, then you will have the opportunity to choose what you need. For the summer we choose with a reduced ratio of propane, for the winter with an increased one.
And then your gas will always burn, and you will not remain hungry without hot tea. Unless you just need to take care of what it is all boiled and prepared from.
Loading...