RU2028369C1 - Fuel for power plant - Google Patents

Abstract

FIELD: hydrogen-containing fuel. SUBSTANCE: composition containing the following components is utilized, vol.%: air 0.25-1; unsaturated C₁-C₄-hydrocarbon 2-27, and hydrogen - up to 100. This fuel composition decreases concentration limits of air excess from 0.76 to 0.59. EFFECT: enhanced exploitation property of fuel. 2 tbl

Description

 The invention relates to the fuel industry and can be used in gas internal combustion engines and gas turbine units.

 Hydrogen is considered as a promising fuel for an internal combustion engine (ICE). This is due to two circumstances. Firstly, hydrogen fuel is economical compared to hydrocarbon fuel. Secondly, hydrogen is produced by nuclear plants by electrolysis of water, which ensures a favorable operating mode of the reactor due to constant load, creating greater safety of nuclear power plants.

 Hydrogen fuel in production is still more expensive than hydrocarbon fuel, but over time, as technologies for the production and operation of hydrogen improve, as well as an increase in the price of hydrocarbon fuel (depletion of reserves in nature), hydrogen will be cheaper than hydrocarbon fuel. The modern approach to economic valuation, which requires taking into account the costs of preserving nature, now already shows that the total costs of using hydrogen fuel should be significantly lower than that of hydrocarbon ones.

 The use of hydrogen as fuel (2) in internal combustion engines with external mixture formation (the usual type of gas engine that is in wide use) is hindered by two negative features of the working process during the combustion of hydrogen in the engine.

 The first is "rigidity" in operation, the engine experiences a sharp shock load, in appearance resembling a detonation load, which reduces reliability and power. The second is the ignition of a mixture of hydrogen with air in the suction pipe, which violates the stability of the work and causes the engine to stop. It is believed that both of these features of the operation of internal combustion engines on hydrogen are associated with a high rate of combustion of a hydrogen-air mixture (up to 270 m / s) compared with the rate of combustion of a gasoline fuel mixture (up to 30-40 m / s).

 A fuel based on a hydrogen-gasoline mixture (1) is known, which does not have the indicated disadvantages, but when using it, power plants have a complex structure, since they require separate tanks and highways for storing and supplying gasoline and hydrogen.

The proposed fuel based on a mixture of hydrogen with unsaturated hydrocarbons as additives (in%) that inhibit hydrogen during combustion does not have the disadvantages inherent in these hydrogen fuels. The use of unsaturated hydrocarbons (propylene) as not a fuel, but as an inhibitor of the combustion process of H ₂ with O ₂ , i.e. additives that breaks the reaction chains cannot be equated to the known method of adding saturated hydrocarbons to hydrogen, because the latter, to reduce the ignition limits of hydrogen to the required value, must be added in large quantities (Le Chatelier rule), because do not have the properties of an additive that breaks the reaction chains. Hence, the environmental properties of this fuel mixture will be significantly worse, approaching fuel using natural gas or propane.

 The aim of the invention is to improve the quality of fuel by eliminating explosive (detonation) combustion, reducing the induction time and increasing the calorific value.

 This goal is achieved in that the fuel contains 0.25-1.0 air mixed with hydrogen, with 2.0-10.0% of gaseous low molecular weight hydrocarbon (GNU) added to the specified mixture.

+

-

(1) Газообразное топливо является, обычно, смесью различных горючих и инертных газов. Количество воздуха, которое теоретически необходимо для сгорания 1 кг моль(м³) газообразного топлива имеет вид
L

=

0,5(CO)-H₂+2CH₄+

n +

-

c

(2)
Сгорание топлива с теоретически необходимым количеством воздуха является частным случаем сгорания топлива с воздухом в энергетической установке. В других случаях на каждый кг топлива количество воздуха L, необходимого для сгорания, может быть больше или меньше теоретически необходимого L_о. В обоих случаях (при L > > L_o и L < L_о) отношение действительного количества воздуха к теоретически необходимому L_оназывается коэффициентом избытка воздуха
α =

(3)
Расчет по формулам (1) и (2) дает следующие результаты: Топливо

Водород/Н₂ 1,19 2,38 Этилен/С₂Н₄ 0,51 14,28 Пропилен/С₃Н₆ 0,51 21,43 Бутилен/С₄Н₈ 0,51 28,57
Наиболее энергоемкой, а следовательно, и наиболее опасной является смесь при α = 1.If the content of individual elements in 1 kg of fuel (i.e., the elemental composition) is characterized by weight fractions, denoting these mass fractions by the signs of the corresponding elements, then
C + H + O = 1 kg
The amount of air that is theoretically necessary for the combustion of a fuel of this composition is expressed from stoichiometric ratios of:
L _o =

+

-

(1) Gaseous fuel is usually a mixture of various combustible and inert gases. The amount of air that is theoretically necessary for the combustion of 1 kg mol (m ³ ) of gaseous fuel has the form
L

=

0.5 (CO) -H ₂ + 2CH ₄ +

n +

-

c

(2)
Combustion of fuel with a theoretically necessary amount of air is a special case of combustion of fuel with air in a power plant. In other cases, for every kg of fuel, the amount of air L required for combustion may be greater or less than the theoretically necessary L _about . In both cases (for L>> L _o and L <L _o ) the ratio of the actual amount of air to the theoretically necessary L _o is called the coefficient of excess air
α =

(3)
The calculation according to formulas (1) and (2) gives the following results: Fuel

Hydrogen / H ₂ 1.19 2.38 Ethylene / C ₂ H ₄ 0.51 14.28 Propylene / C ₃ H ₆ 0.51 21.43 Butylene / C ₄ H ₈ 0.51 28.57
The most energy-intensive, and therefore the most dangerous mixture is at α = 1.

 Studies have been conducted on the inhibition of ignition and combustion of hydrogen by gaseous unsaturated hydrocarbons for this particular composition. Table 1 shows the experimental data.

The initial temperature of the gas in the reaction chamber, the “bomb,” is 295 K, and the initial pressure of the mixtures is 1 atm. After each experiment, the reactor was pumped out to 10 ^-2 atm, air was let in and pumped out again. Ignition was recorded by chemiluminescence and by pressure jump.

= const, находим P_к= P

= 1 ·

. Получим Р_к

9,9 абс атм или Δ P = 8,9 атм, что по существу совпадает с экспериментальным значением Δ Р = 8,5 ати. В то же время значение Δ Р = 3,8 абс или 3,3 атм соответствует значительному снижению температуры реакции, т.е. наличию заметного ингибирующего эффекта, вызванного добавкой пропилена.We come to a similar conclusion based on the analysis of Δ P. values. As is known (/ 1 /, p. 35), the temperature of combustion of a hydrogen-air mixture at α = 1 is approximately 2900 K. Considering that heat transfer practically does not have time for explosive combustion , i.e.

= const, we find P _k = P

= 1

. We get P _to

9.9 abs atm or Δ P = 8.9 atm, which essentially coincides with the experimental value of Δ P = 8.5 atm. At the same time, the value Δ P = 3.8 abs or 3.3 atm corresponds to a significant decrease in the reaction temperature, i.e. the presence of a marked inhibitory effect caused by the addition of propylene.

 Thus, there is a complete basis, not approaching the maximum content of the inhibiting additive of propylene, which prevents explosive combustion of the hydrogen-air mixture, to vary the amount of additive within the conservation range α = 1, which allows to achieve a higher percentage of hydrogen in the fuel.

 Experiments were also carried out on other ratios of the components of the fuel and the mixture, i.e. at other values of the coefficient of excess air α. The experimental results are presented in table.2.

 It follows from the experiments that the positive effect is achieved with an inhibitory addition of propylene in the fuel in the range from 2 to 27%, while with a larger amount of inhibitor there is a complete suppression of flammability, and with a smaller one, a significant increase in the combustion rate, usually limited in power plants.

 To reduce the induction time, which mainly depends on the quality of the mixture formation, as was established during the experiments, it is necessary to add at least 0.25 vol.% Air to the fuel, which corresponds to the lower limit of hydrogen ignition at the ignition temperature. The addition of air in excess of 1% of the amount of hydrogen leads to a loss of usable volume in the fuel tank, no longer affecting the induction time.

 The resulting fuel has a greater mass and volumetric calorific value, since the addition of propylene (ethylene or butylene) increases this ability by an average of 18% compared with a mixture of pure hydrogen with air. Fuel allows you to work stably at α <2 up to α = 0.9-1.0, thereby increasing the specific power of the power plant by 2 times.

Claims (1)

FUEL FOR POWER INSTALLATIONS based on hydrogen with the addition of air and hydrocarbon, characterized in that, in order to increase the fuel performance, it contains unsaturated hydrocarbon C ₁ - C ₄ in the following ratio of components, vol.%:
Air - 0.25 - 1.0
Unsaturated hydrocarbon C ₁ - C ₄ - 2 - 27
Hydrogen - Up to 100

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