Liquefied gas as a backup fuel. Reserve fuel as an energy-saving factor

How is the problem of reserve fuel solved?

Due to prevailing stereotypes, the solution of issues of reserve and emergency fuel, if it arises when drawing up a technical assignment for design, then most often falls on the shoulders of designers. The customer usually does not delve into the development of such solutions, considering the issue of secondary importance, and minimizes the cost of solving it. Designers conscientiously fulfill the will of the customer and put into the project the cheapest, from the point of view of starting costs, options for reserve fuel economy: fuel oil or diesel fuel. These solutions have been template solutions specified in outdated SNiP for many decades.

When the time comes for the operation of a power facility and it turns out that the current costs, for example, for heating fuel oil, theoretically amount to more than 7-10% of the total generated thermal energy (in fact, up to 20%), then it is too late and expensive to redesign the reserve fuel system. Diesel fuel turns out to be quite expensive, and the prices for it jump after the prices for motor fuels.

These are obvious facts. But for the customer they become obvious after the first operating experience, it is more convenient for the designer not to see them - not to complicate his life. In addition to those mentioned, the disadvantages of such solutions should be indicated, for example, dual-fuel burners have different efficiencies when switching from one type of fuel to another (if one fuel is gas, and the second is heavy oil products), a low level of process automation, especially for domestic equipment.

What should be an effective backup fuel?

Today, having experience in the construction of energy facilities with autonomous gas supply, where gas is used as the main and as a backup fuel, we can talk about urgent need break stereotypes in the issue under discussion. It should be taken into account that, in terms of consumer properties, gaseous reserve fuel has many positive aspects: first of all, it is economic efficiency and environmental friendliness.

Perhaps there is a need to consider these arguments in more detail. Why gas? Because its consumer properties are immeasurably higher than the same properties of other types of fuel. It is thanks to the use of gas as a reserve fuel that the operation of power plants is fully automated. A number of technological processes in various types production does not allow the use of other types of fuel. For example, gas drying in high-speed printing machines for glossy printing or the process of processing non-ferrous metal scrap, in which gas is used as a reserve fuel, etc.

Another typical example of fuel reservation is a gas turbine power plant (GTPP). No other fuel as a backup provides such high reliability and economic efficiency other than liquefied petroleum gas (LPG) or liquefied natural gas (LNG), using natural gas as the main fuel. In Yekaterinburg, the construction of a gas turbine power plant is being planned, at which two gas turbine units of 9 MW each will use propane-butane as a backup fuel. Such a decision to use gas as a reserve fuel is likely to become typical for other regions of the country.

If progressive gas infrared heating systems or direct-acting gas-air curtains are used at an enterprise for heating high-altitude industrial premises, then the only correct way out in terms of choosing a backup fuel is liquefied gas.

The level of consumer and technological comfort when using gaseous fuels is one of the most important arguments when talking with customers today. The potential of this fuel market is quite large.

What types of gas fuel can be discussed for use as a reserve? First of all, liquefied petroleum gas (LHG), known to everyone as propane-butane, it is also possible to use liquefied natural gas (LNG) - liquefied methane (due to the low storage temperature (-164 ° C), its use as a backup fuel is very limited). For one of the projects, studies were carried out on efficient use LNG as a damper-accumulator when installing gas liquefaction equipment at gas distribution stations on the territory of the enterprise, storage and regasification to cover peak and emergency loads. This project is characterized by a weekly cycle of fluctuations in gas consumption with "busts" in working time and the possibility of efficient accumulation of liquefied gas at night and weekends. To improve the efficiency of the functioning of the entire system as a whole, it is proposed to use liquefied methane for the needs of gasification of residential buildings in nearby settlements. The LNG market in our country is still being formed, so this is a rare and not yet very typical project.

With the use of LPG, everything is the other way around. It is a liquefied gas, consisting of two thirds of propane and one third of butane, as well as methane, related to paraffinic hydrocarbons. Unlike LNG, it is transported and stored for a long time at natural temperatures, so it is well suited for backup. It is more familiar as household gas to the population. The LPG market is quite developed and dynamic. It is, to some extent, focused on market prices. motor types fuel and oil products and is little dependent on the dynamics of prices for natural gas.

To burn propane-butane, there is no need to replace burners, a simple adjustment in the gas line or a separate own gas line for the burner is enough. This is due to the fact that the calorific value of 1 m3 of the vapor phase of this gas is 2.8 times higher than the calorific value of methane, and if combustion of 1 m3 of methane requires 9.5 m3 of air, then combustion of 1 m3 of a propane-butane mixture requires 25, 9 m3.

There is a very serious question regarding the reliability of heating the factory area. If suddenly something happens to the old boiler house, production facilities will remain without heat, not to mention the administrative and household sector.

Not so simple.
To do this, "Schedules for the transfer" to reserve fuel must be drawn up, which include all organizations that are required to have reserve fuel facilities according to their fuel regimes. The number of tanks should usually be at least two to store reserve fuel. In some cases, storage in one container is allowed. The duration of operation on reserve fuel is regulated.
In addition, the procedure for switching to reserve fuel must be specified in the specifications of the company providing gas connection and supply.
And this is just the beginning...

Reserve fuel for boiler plants

There are usually no problems with fuel oil and diesel, but there are many of them with gas. Firstly, it will be necessary to organize a place to store this very gas, and the volumes are huge! You need a gas tank no less. The room must be underground or semi-underground with protection against static discharges, etc. I recommend reading what is said in the norms for ensuring emergency heat supply.

Reserve fuel for boiler plants

Guest wrote: What to do if the gas is turned off? Where can you keep a supply of it, at least for the first day, until the accident is eliminated?

Yes, indeed, here we are talking about gas tanks, and not about an alternative type of fuel ...
But always, when situations are considered related to the disconnection of boiler plants from gas supplies for one reason or another, the question arises not about the use of additional gas reserves, but about the transition of boiler plants to reserve fuel, which is a supply of liquid fuel stored in special tanks.
In general, the issue of reserve fuel should be resolved at the design stage of boiler houses. The customer considers this to be secondary, insignificant and seeks to minimize costs under this item. Designers put into the project the cheapest, in terms of costs, options for reserve fuel economy. And then fair questions arise during the operation of the boiler room ...
Gas as a backup fuel???
Why gas? Because its consumer properties are immeasurably higher than those of other types of fuel. Thanks to the use of gas as a reserve fuel, full automation of the operation of power plants is ensured. A number of technological processes in various types of industries do not allow the use of other types of fuel.
Therefore, it may be worth considering the option with a gas tank ...

Reserve fuel for boiler plants

There is an option to make an additional burner, for example, on diesel fuel, but the burner is not ordinary, but a burner of low power. If a sudden shutdown of the main gas supply happens, just run an alternative option.
Diesel is easier to store. There is only one problem with the rearrangement of the burner, it is necessary to somehow figure out how to do it quickly and without problems. may be an additional small boiler to provide.

Reserve fuel for boiler plants

A catastrophe will not happen if the factory is heated not at 25C, but at 17C. If anyone is cold, they simply turn on additional electric heaters. And where there is a responsible production - there to provide regular heating devices on the electrical principle of operation. In responsible production, everything must be duplicated many times for greater reliability.

Reserve fuel for boiler plants

Guest wrote: There is a very serious question regarding the reliability of heating the factory area. If suddenly something happens to the old boiler house, production facilities will remain without heat, not to mention the administrative and household sector.
What to do if the gas is turned off? Where can you keep a supply of it, at least for the first day, until the accident is eliminated?

Is there anything that can happen??? Even without any accident, batteries are barely warm in winter ... They are far, far away from their relatives 50 C! So maybe, if there is a danger of defrosting the system, do not rack your brains with an additional supply of "firewood" for heating, but provide for an emergency drain of water from the system and turn on emergency emergency air heating on electricity. We have a combined system with forced ventilation at our ball production. So this ventilation has never been turned on for 20 years ... And the employees warmed themselves with their own heaters ...

Reservation of gas fuel.

Lecture 7

Reservation of LPG facilities. Propane air technology. Reservation schemes. Methods of influence on the torch.

All consumers of gas fuel according to consumption conditions are divided into:

1. Enterprises and installations designed only for the combustion of natural gas. These include thermal furnaces with radiant tubes, some types of shaft furnaces, and apparatus designed specifically for burning gaseous fuels (furnaceless).

2. Enterprises and installations with duplicate or combined devices for burning both gas and other types of fuel. These include industrial furnaces, boiler units equipped with gas-oil burners or separate gas burners and oil burners. Dual fuel leads to:

1. More expensive system

2. The thermal regime during the transition from one type of fuel to another changes noticeably

3. Units, the main type of fuel of which is liquid or solid, and gas is a reserve, then these consumers are called buffer (thermal plants, large heating boilers, etc.).

Combined burners have a high metal consumption, they work with a large α (1.2-1.25). If the coefficient α is larger, then the efficiency becomes lower.

The most commonly used heating oil grades 40,100,200.

Reservation with liquefied gas has significant advantages over other types of fuel, because. allows you to save all gas-using equipment, gas distribution system and automation, as well as combustion conditions.

As a backup fuel for technical installations, technical propane is convenient (both with artificial evaporation of propane and with natural evaporation due to heat environment). The pressure of technical propane at a temperature of -20°C is 0.2 MPa, at a temperature of 40°C it is 1.6 MPa.

When using a propane-butane mixture, the scheme should include an evaporator with a steam or water heater (with artificial evaporation).

If liquefied gas without additives is used instead of natural gas, then the entire gas supply scheme and gas equipment must be redesigned. To maximize the preservation of gas equipment, a mixture of liquefied gas with air is used, which has the same Wobbe number as natural gas.

This circuit allows you to maintain a given Wobbe number with an accuracy of 5% when the load changes from 100 to 25%.

Propane-Air technology

One of the key issues in the design of heat supply systems is the reliability of fuel supply. Lack of attention to this problem can lead to large-scale economic losses in the event of interruptions in the supply of basic fuel; This situation can be especially critical for production processes with a continuous technological cycle.
Typical risk factors for systems using natural gas as the main fuel are: a gas supply interruption caused by an accident on the main pipeline, or a pressure drop in the pipeline due to increased consumer load.

One of the effective and widely used options for "backup" fuel, suitable for most natural gas consumers, is a propane-air mixture (propane-air).
The use of liquefied hydrocarbon gas (propane or propane-butane) as a backup fuel is advisable for many reasons. The undoubted advantages of this type of fuel include its environmental friendliness, ease of transportation and storage, and price stability for LPG. From a technical point of view, the disadvantage of propane-butane as a backup fuel is its difference from natural gas in terms of physical and chemical properties, which is why equipment designed to run on natural gas cannot be “directly” converted to use propane-butane. However, this problem has an effective technological solution. Propane acquires optimal properties, almost similar to those of natural gas, when mixed with air. The typical composition of such a mixture is about 57% propane and about 43% air.
The use of a propane-air mixing plant avoids the downtime and costs associated with switching gas equipment to another type of fuel. The performance of such systems varies widely. The range of their possible applications is limited only by the availability of propane-butane, as well as the specific nature of a number of production processes that do not allow the use of gas with an admixture of nitrogen.

For these reasons, Propane-Air technology is popular both among industrial users and in many other areas (agricultural, commercial, social). The range of manufactured products is very extensive both in terms of performance and the principles of operation, design, applied control and safety systems.
Most manufacturers offer combined options (“vaporizer-mixer”) that combine the functions of an LPG evaporator and a mixing unit. Such qualities as compactness, modularity, high efficiency, reliability and ease of use, as well as ample opportunities for their refinement and adaptation to the needs of the consumer, ensure the popularity of combined evaporative-mixing plants, especially as a ready-made technical solution for low power systems.
Capital costs for a Propane-Air system vary widely. Difficult conditions for the location of the facility, requiring non-standard design solutions, increase capital costs. The calculation of the benefits from using the Propane-Air system is also individual for each consumer.

Prospects for technology in Russia.
In Russia, this technology has not yet received distribution. Despite the fact that natural gas is the most widely used type of fuel in our country, ranking first in the structure of consumption of fuel and energy resources, the issue of its effective replacement in case of possible accidents or interruptions in its supply at most enterprises is still not given sufficient attention. . In recent years, however, the situation has begun to change. Industrial consumers of natural gas in Russia have begun to realize the importance of effectively solving the problem of reserve fuel. This is facilitated by the state of the network main gas pipelines and gas distribution networks in Russia is unfavorable. Many sections are already characterized by a high degree of wear and tear, and with an increase in traffic load, the probability of accidents will increase.

Practice shows that the operation of gas supply systems operating on natural gas, in some cases, is associated with a number of difficulties. Sudden drops in gas pressure in the system, the appearance of water condensate in pipelines; "Rolling" shutdowns - all this leads to forced shutdowns of the equipment of enterprises and the risk of large production losses.
The autonomous gas supply system (both main and backup), being equipped with a mixing plant, allows for the replenishment of systems operating on natural gas without the need to stop the working process and any adjustment work. The use of mixing plants is most justified in the following situations:
- reserve gas supply of systems operating on natural gas;
- coverage of peak loads when consuming natural gas;
- use both in new and existing LPG networks at facilities with an increased risk of condensate formation in the gas pipeline.
Any industrial or municipal consumer (for example: a glass factory or a cottage settlement) receives undeniable advantages when using a backup gas supply system equipped with a mixing plant.
The use of a propane-air mixing plant allows you to avoid downtime and costs associated with the need to quickly switch gas equipment to another type of fuel. Switching the system to alternative fuel takes from 3 to 60 seconds. At the same time, the transition of the system to gas supply with propane-butane occurs automatically, without intervention. service personnel and does not require expensive commissioning.
Standard technology system Secondary fuel supply system based on Propane-Air technology includes the following main components:

· storage for liquefied gas (in most modern projects, underground placement of LPG tanks is accepted in accordance with the requirements of the current regulatory legislation);

a pump for supplying liquefied gas to the evaporator;

LPG evaporator (installation for transferring propane-butane from liquid phase into the gas phase before being fed to the inlet of the mixing plant);

air compressor (for installations operating on compressed air);

Propane-air mixing plant (propane-air mixer).

Mixing plants FAS 4000 are divided into two types:
- low pressure systems - ND
- high pressure systems - HD
Low-pressure systems (with an outlet pressure of not more than 500 mbar) are quite economical in operation and less capital-intensive during construction compared to high-pressure systems.
High pressure systems with automatic tuning the caloric content of the gas-air mixture are more complex units, and are produced depending on the actual operating conditions for each individual gas supply facility.

To replace natural gases, it is necessary to prepare a mixture of "butane-air" (47% butanes and 53% air) and "propane-air" (58% propane and 42% air). Such mixtures have calorific values ​​of 55902 and 52080 kJ/m3, respectively. They can be transported at low pressure (up to 5 kPa) and temperature (down to -18°C for butane and -53°C for propane). It is possible to prepare gas-air mixtures with more low temperature condensation, down to -37°C for butanes (mixture meets the safety limit). However, in this case it is necessary to use special gas burners. Gas-air mixtures are prepared in automatic mixers. Monitoring Their operation is controlled automatically depending on the calorific value, the Wobbe number or the density of the mixture. In some sources, a mixture of propane with air is called "artificial natural gas" (synthetic natural gas, SNG).

The need for reserve or emergency fuel for the boiler house is due to the objective need to ensure the uninterrupted operation of the boiler house in the event of a shutdown or non-delivery of the main fuel. To fulfill this task, an unreduced supply of reserve (emergency) fuel is created at the boiler house in accordance with regulatory documents. The documents regulating the need for reserve fuel for boiler houses are:

• Rules technical operation thermal power plants approved by Order of the Ministry of Energy Russian Federation dated March 24, 2003 No. 115, (clause 4.1.1);
• Rules for the use of gas and the provision of gas supply services in the Russian Federation, approved by Decree of the Government of Russia dated May 17, 2002 No. 137, (p. 49);
• SNiP II-35-76 "Boiler plants", approved by the Decree of the State Committee of the Council of Ministers of the USSR for construction of December 31, 1976 No. 229, (clause 4.1);
• SP 89.13330.2012 "Boiler plants". Updated version of SNiP II-35-76”, approved by Order of the Ministry regional development of the Russian Federation dated June 30, 2012 No. 281, (clause 4.5).

The type of fuel and its classification: basic, and if necessary, emergency, is established taking into account the category of the boiler house, based on local operating conditions, and is determined in agreement with the regional authorized authorities.

Energy saving in modern conditions has proven its relevance. Owners of large and small businesses pay great attention to energy efficient projects and their implementation in the enterprise. And it's not just about the constant rise in energy prices. Important here is such an advantageous moment as the possibility of reducing the cost of the goods produced, which, under equal conditions, gives an advantage in the competitive struggle in the sales market.

However, behind all this excitement, in the matter of energy saving, a very important issue is overlooked, namely, reserve fuel. Today we have either outdated use of fuel oil, or we have nothing at all. And the second, unfortunately, is more common. Plant managers are often reluctant to invest in a backup power system, basing their reluctance on the wrong conclusions.

The price of a mistake in energy security planning

Many believe that since today the percentage of gasified enterprises is high, and most new enterprises are designed to use natural gas, the gas supply system is a priori reliable and there is no need to introduce a backup power supply system. And this is far from true! The cost of such a mistake can be very high. Let us consider just one example of the fallacy of such an opinion.

In September 2005, as a result of an accident that occurred on the section of the Ural-Bukhara gas pipeline, one of the largest cities Sverdlovsk region- Kamensk-Uralsky - was left without gas. leader of one of industrial enterprises of this city appealed to Gosgortekhnadzor with a demand to compensate for the damage caused. In response, he was asked to file a lawsuit against the gas workers. To this, an answer came from Uraltransgaz LLC that everyone should have reserve fuel except for the population.

This example eloquently shows that one should not rely on the reliability of gas pipelines. Many of them are worn out and require repair, and backup gas pipelines are not always available. Therefore, the presence of reserve fuel at the enterprises is mandatory. And, therefore, it is worth considering this issue in more detail.

What is reserve fuel and why is it needed

Considering from the position of gasified enterprises, this is an alternative to natural gas. It is used in the event of a gas supply failure, in order not to interrupt the production cycle. As you can see from the example above, the lack of alternative energy supply can lead to serious losses.

For example, a large food processing enterprise uses steam from 7 to 10 tons per hour according to the technology. After spending necessary calculations, it was found that when idle, up to 40 thousand dollars are lost every day. And these are only direct losses, without loss of the cost of damaged raw materials. For metallurgical enterprises, the amount of losses increases several times. In addition, at metallurgical enterprises there is a risk of ruining production altogether if the metal solidifies at certain stages of production. All this shows that it is necessary to pay maximum attention to solving the problems of alternative fuel, and hence energy security.

How to solve the problem of reserve fuel now

Owners of enterprises, as a rule, have little interest in the efficiency of the energy-replacing system. When ordering the development of such a project, they put forward the only condition: minimum cost. Designers willingly fulfill this wish and opt for outdated systems using fuel oil or diesel fuel. Then, when it comes time to use the reserve, such short-sighted leaders realize that the effectiveness of outdated systems is low. It takes up to 20% of the generated heat to warm up fuel oil, and the cost of purchasing diesel fuel, given the scale of consumption, is huge. However, there is no time to remake the energy substitution system.

What efficiency properties should reserve fuel have?

After analyzing the situation with energy substitution, we came to the conclusion that liquefied gas is the best alternative for gasified enterprises. LPG (liquefied petroleum gas - propane-butane mixture) or LNG (liquefied natural gas). And that's why:

• high consumer properties;


• economic efficiency;


• environmental friendliness.

Consumer properties. It is with gas as a reserve fuel that full automation of the transition from the network to the reserve and vice versa is possible. Same burner type, same Chemical properties fuel. Plus, at some enterprises it is impossible to use any other fuel other than gas. An example is the work of a non-ferrous metal smelter. The production line - furnaces, converter, lances, chutes, waste heat boiler, drying stands, etc. - is designed for the use of gas fuel. Applying another, in this case, would violate technological process production.

It turns out that the cost of introducing an energy substitution system for a large gasified enterprise is less than the losses from unplanned downtime. The benefit from the introduction of a reserve of liquefied gas is direct. Considering that the service life of the backup power substitution system is practically unlimited and directly depends on the quality and timeliness of the repair service, we can safely say that investments in it will pay off more than once.