JPS5844281B2 - Nenshiyouhouhou - Google Patents

Description

[Detailed Description of the Invention] In order to efficiently burn clean fuel, the present invention
Concerning methods for comprehensive control.

LNG (liquefied natural gas), LPG (liquefied petroleum gas), and hydrogen, which are attracting attention as clean energy, do not contain sulfur or other corrosive components, so in prime movers and stationary combustion equipment that use these as fuel, exhaust gas humidity can be reduced. It is possible to design the temperature to be sufficiently low to increase the efficiency of the thermal cycle.

However, since these fuels contain a large amount of moisture in their exhaust gas (LNG: about 17 volumes, hydrogen: about 34% by volume), if the exhaust gas temperature is kept too low, the moisture will condense and become water, producing white smoke.

In this case, since the exhaust gas temperature is low, the buoyancy rise height of the flue gas is small, and the housing is not favorable from the viewpoint of exhaust smoke diffusion.

However, in recent years, the installation location of the prime mover has been subject to various restrictions.
Depending on the location, it is becoming difficult to secure make-up water or on-board water, and this trend will only accelerate as the number of prime movers increases in the future.

In the case of cased LNG and hydrogen fuel, although they are clean energy, they emit a considerable amount of NOx and produce white smoke and KN at the same time.
It is essential to take measures against Ox.

Furthermore, in the case of hydrogen fuel, hydrogen embrittlement of transportation pipes and hydrogen fuel equipment materials, especially when used as household equipment, the explosion range, extremely high combustion speed, and low ignition energy are obstacles to practical application. Therefore, there is a demand for the development of technology to control these.

In order to solve the above-mentioned problems, the present inventors have carried out research aimed at the following.

1) Keep the exhaust gas temperature low and improve the heat recovery rate of the cycle.

2) Preventing exhaust gas from turning into white smoke.

3) Moisture recovery that does not require new energy (water supply method) 4) Control of NOx in exhaust gas 5) Customized control of combustion of easily flammable fuels (explosion range, combustion speed, ignition energy, etc.) 6) Combustion equipment materials Prevention of Hydrogen Embrittlement The inventor noticed that in the case of clean fuels, exhaust gas that has been treated in a combustion management chamber or treated can be directly used as an oxygen-insulating inert gas.

For example, in the case of hydrogen combustion, the theoretical combustion exhaust gas is N2 and H2
Consists only of 0.

When N20 is INm″/Nm3, the theoretical air amount is 2
．． 38 Nms/Nm", N2 is 1.88 Nm"/Nm
3, so the total of N2 and N20 in the exhaust gas is 2.88
N m3/N m3.

In the case of LNG, the components in the exhaust gas are approximately N27
2%, H2O 17%, CO28%, Article 023.

Therefore, we first considered 1) installing a moisture recovery device to recover moisture from exhaust gas and at the same time recover heat.

2) by circulating a portion of the almost pure N2 gas from which moisture has been removed into the fuel gas to adjust the flow rate, or by injecting a portion of the recovered water into the high temperature combustion zone for mixed combustion; The idea was to perform comprehensive control such as a) effective reduction of NOx in exhaust gas, b) prevention of hydrogen embrittlement of combustor equipment, and c) control of the combustion characteristics of easily flammable fuel.

That is, the present invention is a comprehensive exhaust gas utilization method that improves the purity of the effective inert gas in the exhaust gas through water recovery, and recirculates it to control polluting components and combustion characteristics. Regarding a system that combines pollution-free combustion and energy recovery, in a system that burns fuel that produces a relatively large amount of water, a moisture recovery device is installed in the combustion exhaust gas passage section of the fuel to recover moisture at the same time. The main feature of this combustion method is that part of the moisture in the combustion exhaust gas downstream of the moisture recovery device is recirculated to the combustion chamber where the fuel is combusted.

The present invention will be explained in more detail with reference to FIG.

A moisture recovery device 3 is installed in the exhaust gas system in the combustion chamber or furnace 1 of various combustors and its exhaust gas/duct system 2.

After fuel is sent from the fuel supply pipe 4 to the combustion chamber IK and burned, the exhaust gas enters the exhaust gas duct system 2Fc.

The exhaust gas system moisture recovery device 3 includes an air type water cooler 5 and a cooling system 6.
Condensation occurs on solid or liquid surfaces that are maintained at a salinity lower than the dew point of the exhaust gas, leaving the entire exhaust gas unsaturated. ! 1 is discharged.

The exhaust gas leaving the water recovery device is discharged outside from the chimney 8 through line 7, but a branch pipe 9 is taken in the middle of line 7.
A portion of the exhaust gas is recirculated to the fuel supply pipe 4 via the recirculation blower 10 and the flow control valve 11.

The amount of circulating waste is controlled by a flow control valve 11.

Alternatively, a part of this exhaust gas may be directly supplied to the combustion chamber.

On the other hand, the condensed moisture in the exhaust gas recovered by the moisture recovery device 3 can be used as hot water for heating, bathing, etc., but some of it is injected into the combustion chamber 1 via the recovered water tank 12 and the flow control valve 13. Combustion can also be controlled.

Air is passed through an air-type water cooler 5 connected to a water recovery device 3 in a housing, and is sent to a fuel supply pipe 4 via an air blower 14 and an air preheater 15 to be used as combustion air.

By adopting the above method, the following effects can be achieved.

1) Moisture in the exhaust gas is removed by a moisture recovery device, so no white smoke is produced even if the exhaust gas is used for heat in the olden days when the temperature was low.

(High thermal efficiency) b. Almost pure water can be recovered.

There is no corrosion or rust due to moisture after the C0 moisture recovery device.

d. The exhaust gas after the water recovery device becomes an inert gas whose main component is N2 gas.

2) Since the moisture button on the downstream side of the moisture recovery device recirculates the inert gas from which water and water-soluble components have been removed and mixes it with fuel gas, it is possible to control NOx in the exhaust gas. When active gas is circulated, intermediate combustion products (radicals, such as HCN, etc.) and 02 compounds in the exhaust gas are reduced.

If there is a large amount of 0□, the intermediate combustion products will interact with 02 and become NO.
x, and if 02 is small, it directly produces N2.

Therefore, if there are fewer intermediate combustion products and 02, less NOx will be produced.]

Particularly in the case of hydrogen combustion, the mixed combustion with N2 has a great effect, and as shown in FIG. 2, NO can be reduced to less than 1/10 by adding just 28 times more N2.

In FIG. 2, the dotted line shows hydrogen, and the solid line shows the NO generation rate when hydrogen is mixed with 28% nitrogen and combusted.

It has been confirmed that the same effect can be obtained even if LNG, LPG, etc. are used as fuel.

b. In the case of high-purity hydrogen, low-flow hydrogen embrittlement of the material becomes a problem, but hydrogen embrittlement is prevented at the same time as the temperature increases by mixing the exhaust gas and fuel.

In the case of easily flammable fuels such as CO hydrogen, the factors that govern safe combustion, such as explosion limits, combustion speed, and ignition energy, are
It can be freely controlled by adjusting the mixing ratio with inert gas.

3) By mixing and burning a portion of the recovered water with fuel,
Furthermore, the water recovery rate can be increased.

Due to the mixed combustion effect with water, the latent heat of vaporization of water (540ca
e/f! ) Since a large amount of heat is consumed during combustion, the combustion temperature is significantly lowered, and NOz and smoke can be further reduced.

Furthermore, reduction of smoke reduces the amount of 02 supplied for combustion, and as a result, the combustion temperature also decreases, contributing to the NOx reduction effect.

4) By recirculating inert gas and water into the combustion chamber, a synergistic effect of 2) and 3) above is obtained, and the amount of NOx produced is significantly reduced.

That is, the recirculation of water lowers the combustion temperature, and the recirculation of inert gas lowers the combustion temperature without promoting the chemical reaction due to the constant pressure specific heat CpO difference.

Moreover, by supplying a low source of water force and inert gas to the combustion zone, the NOx production rate coefficient becomes small, and NOx
This results in a decrease in the amount of x produced.

[Brief explanation of the drawing]

FIG. 1 is a flow sheet showing one embodiment of the present invention. FIG. 2 is a diagram comparing the amount of NO generated when hydrogen is combusted by the method of the present invention and the conventional method.

Claims (1)

[Scope of Claims] 1. In a system that burns fuel that produces a relatively large amount of water, a moisture recovery device is installed in the combustion exhaust gas passage section of the fuel to recover moisture, and at the same time collect water from the moisture. A portion of the combustion exhaust gas downstream of the moisture recovery device is burned with the fuel. A combustion method characterized by recirculation into the combustion chamber.