KR20000074829A - Process for production gas fuel from Landfill gas and the system therefor - Google Patents

Abstract

PURPOSE: A method for refining Landfill Gas (LFG) and system therefor are provided, which are characterized in that VOC (Volatile Organic Material) generated from landfill is adsorbed in adsorption tower packed with activated carbons, followed by desorption. In this method, obtained landfill gas mainly composed of CH4 is directly applicable to domestic use after mixed with LPG and/or to industrial use after refined further. CONSTITUTION: The system is consisted of: a dewaterer (1) having packing material inside for increasing contact area and a drain port for discharging water; a gas receiver tank (2); a compressor (3); a first gas holder (4) with a drain port to remove condensation water; an adsorption tower (5) packed with molecular sieve for water-removal; an adsorber (6) packed with activated carbon for impurity-removal; a second gas holder (7); a gas mixer (8); a blower (9); a heater (10) to dry activated carbon and molecular sieve for reuse; and a gas-supply pipe (11).

Description

Process for producing gas fuel and landfill gas and the system therefor}

The present invention relates to a method and a system for gas fuelizing LFG. More specifically, the present invention provides a novel LFG gas fueling method and system capable of removing impurities from landfill gas and having combustion characteristics and calorific value of existing city gas level for practical use of landfill gas in landfill. .

Landfill gas or biogas generated from landfill (hereinafter referred to as "LFG") contains a lot of methane gas (CH ₄ ) that can be used as gas fuel and carbon dioxide (CO ₂ ), which is an inert gas, depending on the conditions. It accounts for more than 90 mol% of the landfill gas. In addition, LFG contains a large number of trace harmful components in ppm, including nitrogen, oxygen, moisture, hydrogen sulfide, and nitrogen and oxygen due to air entering the landfill gas collection system or penetrating into the landfill.

Conventional methods of using LFG capture include the use of naturally occurring pressure of landfill gas or a vacuum suction device, and the extracted LFG treatment and utilization are collected by incineration of pipe manifold buried in landfill, or electric power production. It has been used as fuel for or burned as a heat source.

Considering that the main component of natural gas used as city gas is methane gas, LFG containing a large amount of methane gas is an important resource that can be considered as an alternative fuel. However, since LFG contains less methane than natural gas, it is relatively low in calories. Therefore, in order to utilize LFG directly as an industrial or general household gas fuel, it is necessary to raise the calorific value to some level and remove moisture and harmful substances in advance. There has been a problem.

In the adsorption method, VOC vapor is adsorbed using adsorption, and desorption and VOC recovery using steam, vacuum, or an organic solvent are widely used. If steam is used in the desorption process, it is cooled again after desorption and the VOC is recovered therefrom.

If VOC is incompatible with water, it will be easily separated by phase separation, and if miscible, additional separation is required. The most important property of the adsorbent is the affinity for the specific surface area and the adsorbent, and the greater the specific surface area and the affinity, the greater the effect of adsorption. Activated carbon and activated carbon fiber are mainly used as adsorbents. In addition, polymer materials, silica gel, alumina and molecular-sieve carbon (CMS) are used.

Effective methods of using LFG include the use of electric power through the generation of gas engines, gas turbines and steam turbines using LFG, and the use of direct fuel by refinement and distillation to natural gas levels. As another method of use, the city gas is mixed with LFG. In this case, although the calorific value of the mixed fuel is lower than that of city gas, there is an advantage in that combustion and stability, which are disadvantages of LPG, can be improved. Such LFG mixed fuel may be useful for power plants, cogeneration plants, district heating and the like as large plants.

Accordingly, an object of the present invention is to provide a method of gas fueling using LFG. Another object of the present invention is to provide a gas fueling system of LFG for achieving the above object effectively.

The above object of the present invention was achieved by gasifying LFG generated in landfills, identifying general combustion characteristics of LFG mixed fuel, and then examining its functionality in a utility burner.

1 is a process diagram briefly illustrating a method and system thereof.

Figure 2 shows the chemical equilibrium temperature according to the equivalent ratio of the various mixed fuels of the LFG.

3 shows the flame stability of the LFG mixed fuel.

4 is a view showing the combustion speed of CH4, LPG and LFG.

5 is a view showing the combustion rate of the LFG mixed fuel.

6 is a view showing another combustion rate of the LFG mixed fuel.

7 and 8 show the combustion characteristics of the practical burner of LFG mixed fuel.

<Description of Symbols for Major Parts of Drawings>

1: dehydrator 2: gas supply tank

3: compressor 4: gas reservoir

5: Water removal adsorption tower 6: Impurity removal adsorption tower

7: second gas reservoir 8: gas mixer

9: blower 10: heater

11: gas supply pipe

The present invention provides a pre-treatment method and system for removing water, hydrogen sulfide, trace harmful substances, etc. contained therein to utilize LFG as a gaseous fuel, and a method for increasing the temperature after pre-treatment to be used in existing domestic and industrial combustion devices. It consists of a system. The pretreatment process consists of extraction, compression storage, water removal, and impurity removal processes. The steaming process mixes the gas that has undergone pretreatment with gas such as LPG, which has a higher calorific value than that of city gas or city gas. It is a process of increasing the heat amount to have a calorific value of.

The specific configuration of the gas fuelization system of the present invention is described in FIG.

The LFG extracted from the landfill is introduced into the dehydrator 1 through the gas supply pipe 11 in the state containing impurities and water, and after the water is removed, the gas tank 2 through the pipe 12. Flows into. The packing material of the dehydrator is to increase the contact area to the LFG to have a lot of active points, and to install the drain port (not shown) at the bottom of the dehydrator to discharge the removed water. The LFG of the gas supply tank is compressed by the compressor (3) and flows into the gas holder (4) through the pipes (13) and (14). Here, the drain port (not shown) is also installed to compress the process. To remove condensate. Meanwhile, the LFG in the gas reservoir is transferred to the Molecular Sieve adsorption tower 5 by the pipe 15 in a compressed state, and after residual moisture is removed, the LFG is transferred to the activated carbon adsorption tower 6 through the pipe 16 to be traced harmful substances. This was to be removed. The heater 10 is a drying apparatus for regenerating and utilizing the activated carbon and the molecular sieve. The LFG from which water and trace harmful substances are removed through the process on the system is transferred to another second gas reservoir through the pipe 17 and then stored. The pure LFG stored in the second gas reservoir is connected to the place of use through the discharge pipe 31 when directly used as fuel, and the gas mixer through the pipe 19 when there is insufficient heat to use as fuel. (8) was fed to the city gas or LPG with high calorific value through a pipe 25 so as to have a constant ratio, so that the calorific value could be increased to the level of city gas or industrial gas and supplied to the user through the pipe 32. .

In the present invention, since the heater 10 can transmit the heat of 300 ° C. through the pipe 21 of the blower 9, the heater 10 is composed of a device suitable for dry regeneration of the Moleculer Sieve adsorption tower 5 and the activated carbon adsorption tower.

Data on the composition and process conditions of the landfill gas flow at various stages of the process will be supplemented later. Hereinafter, the specific configuration and operation of the method of the present invention will be described.

The disclosure material LFG of the method of the present invention was obtained from a landfill in Incheon Metropolitan City, and the combustion characteristics and city gas or LPG of the purified LFG which removed moisture, harmful substances such as H ₂ S and VOC, and the city gas or LPG were refined according to the present invention system. The combustion characteristics of the mixed LFG mixed fuel will be described with examples.

Example 1 Combustion Properties

Table 1 calculates the calorific value, Webbe Index, air-fuel ratio, specific gravity and flame temperature necessary for combustion management when LPG or NG is properly mixed with the average LFG composition (LFG 100%). will be. Here, LFG 50% + LPG 50% is the case of matching the city gas and Weber index (WI = 13A), LFG 70% + LPG 30% is the case of city gas and calorific value (WI = 10A). LFG 30% + NG 70% assumes that LFG is properly mixed with city gas and used in large plants.

FIG. 2 compares chemical equilibrium temperatures according to equivalent ratios of representative LFG mixed fuels shown in Table 1 with commercial fuels NG and LPG. In Figure 2, although pure LFG contains a large amount of inert gas, as shown in Table 1, since the air-fuel ratio is small, the flame temperature is more than 2000K, it can be seen that the flame temperature can be used in various hot air.

In addition, LPG 50% mixed fuel shows the same temperature distribution as the existing city gas, LPG 30% also shows that the temperature is slightly lower than the existing city gas can be substituted for the city gas.

Thermodynamic Characteristics of LFG Mixed Fuels division LFG100% LPG 100% 100% city gas LFG 70% + LPG 30% LFG 50% + LPG 50% LFG 50% + City Gas 50% LFG 30% + City Gas 70% Furtherance CH ₄ 54.5 0.0 89.78 38.15 27.25 72.14 79.20 C ₂ H ₆ 0.0 0.0 7.48 0.00 0.00 3.74 5.24 C ₃ H ₈ 0.0 100.0 2.02 30.00 50.00 1.01 1.41 C ₄ H ₁₀ 0.0 0.0 0.70 0.00 0.00 0.35 0.49 CO ₂ 37.5 0.0 0.00 26.25 18.75 18.75 11.25 N ₂ 7.0 0.0 0.02 4.90 3.50 3.51 2.11 O ₂ 1.0 0.0 0.00 0.70 0.50 0.50 0.30 High calorific value (HHV: Kcal / ㎥) 5207.62 23826.9 10528.5 10793.4 14517.2 7868.09 8932.28 Weber Index (Kcal / ㎥) 5.33 19.27 13.35 10.17 13.03 8.89 10.51 Air-fuel ratio (㎥ Air / ㎥ Fuel) 5.14 23.80 10.49 10.74 14.47 7.82 8.89 Specific gravity (SGAir = 1.0) 0.9542 1.5286 0.6224 1.1265 1.2414 0.7883 0.7220 MaximumTemp. (K) 2115.7 2290.9 2254.2 2229.2 2257.7 2205.8 2228.2

Example 2 Flame Stability of Mixed Fuels

In this example, the flame stability of LFG mixed fuel was investigated.

3 shows a comparison of the stabilization region of LFG mixed fuel with CH ₄ . The result is a fractional diffusion flame with a fuel nozzle inner diameter of 2.95 mm. However, the LFG fuel alone was not stable and the experiment could not be performed because the flying phenomenon occurred in the ambient flow of 0.1 m / s. In the stabilization zone of pure CH ₄ , blowout does not occur until the flow velocity reaches near 40 m / s after the liftoff occurs near the fuel nozzle flow rate of 10 to 15 m / s in the region where the flow velocity is small. However, as the flow velocity gradually increased, the liftoff and blowout zones dropped drastically and the occurrence of blowout was accelerated. When the flow velocity reaches 0.8m / s, the liftoff and blowout meet, and if the flow velocity increases, the flame does not form. This ambient flow rate is the critical velocity at which no flame is formed. Next, when looking at the stabilization region of the LFG + LPG mixed fuel, it can be seen that as the LPG addition ratio increases, the blowout and attachment points become higher but lower than CH ₄ . And it can be seen that the critical flow rate increases with increasing LPG addition ratio but lower than that of CH ₄ . As such, the LFG + LPG mixed fuel was found to have a poor flame stability compared to the CH ₄ flame.

Example 3 Burning Rate Measurement

In the embodiment of the present invention, the combustion rate of LFG (average composition) and LPG used in the mixed fuel was compared with the combustion rate of CH ₄ corresponding to the city gas. The experimental results are shown in FIG. 4, and the maximum combustion speed of LPG is about 45 cm / s at the equivalent ratio φ = 1.1, which is about 4 cm / s higher than that of pure CH ₄ , but the tendency of the combustion rate according to the equivalence ratio is almost the same. LPG has a high value.

The maximum burning rate of LFG is about 31cm / s at equivalent ratio φ = 1.1, about 10cm / s lower than pure CH ₄ , and the change in combustion rate according to the equivalent ratio is slightly slower than CH ₄ . The lower the equivalence ratio, the more unstable the flame, and the measurement was possible up to the equivalence ratio 0.8.

Example 4 Combustion Rate of LFG Mixed Fuels

In the embodiment of the present invention was compared with the combustion rate of pure CH ₄ by measuring the combustion rate for the LFG mixed fuel made by adding LPG so that the LFG having a different composition is the same as the city gas and the Weber index. The experimental results are shown in FIG. 5, and the maximum combustion rate is the same as that of CH ₄ when the urban gas and the Weber index are the same using LFG having an average composition of 54.5% CH ₄ concentration in the LFG, but in lean or over-concentrated areas. It can be seen that the mixed fuel is high.

Even when the concentration of CH _{4 in the} LFG is 30%, the maximum combustion rate is slightly lower than that of CH ₄ , but the difference in combustion rate between the two fuels is smaller in the lean or over-concentrated region. These results indicate that even when the CH ₄ content in LFG is low, the mixed fuels with consistent Weber's index have a similar combustion rate as the city gas under lean or excessive conditions, so that the mixed fuel can be used as an alternative fuel for city gas. Is showing.

On the other hand, Figure 6 shows the comparison with the combustion rate of pure CH ₄ by measuring the combustion rate for the mixed fuel made the same as the city gas and the calorific value using LFG of different composition. In this case, the maximum combustion rate was somewhat lower than CH ₄ in all cases. In particular, when the concentration of CH _{4 in} LFG is 30%, the maximum combustion rate is about 10 cm / s lower than CH ₄ . As described above, other trends are similar to the previous case, except that the maximum combustion rate is slightly lower than the fuel which made the same Weber index described earlier. In this case, the mixed fuel is also likely to be fully utilized as a substitute for city gas.

Example 5 Applicability of Utility Burner

In this embodiment, in order to examine the combustion characteristics of the LFG mixed fuels in the practical burner, the cooking gas range was improved to control the equivalent ratio and the amount of the mixer, and the stable combustion region was observed while changing the equivalent ratio and the flow rate. In the figure, the stable combustion zone was divided into flashback, liftoff, and yellow tip (Yellow Tip). These classifications were judged by direct observation.

7 is measured for the same mixed fuel as in Example 4, the horizontal axis in the figure is the value of the calorific value of the mixed fuel divided by the square root of the specific gravity, the calorific value per hour of the gas range that is generated when the fuel supply pressure is the same, that is, Weber Corresponds to the index. The figure shows that even if the CH ₄ content in the LFG changes, the stable combustion tendency of the mixed fuel with the same Weber index is almost the same. As can be inferred from the stable combustion zone of CH ₄ , the optimum combustion conditions in this practical combustor correspond to an equivalence ratio of 1.4 and an output of 700 KJ / hr, which can stably burn even in the case of all mixed fuels. Therefore, it can be seen that these mixed fuels are compatible with the city gas without any problem.

8 is a measurement of another mixed fuel of Example 4, the horizontal axis in the figure was used as the calorific value of combustion differently from the previous figure. In the figure the amount of heat generated in the case of using the mixed fuel is the same as in the case of most of CH _4, in the case of LFG CH ₄ content of 54.5% is rather it can be seen that can generate more heat.

In this case, however, in order to generate the same amount of heat, the proportion of mixed fuels is higher than that of CH ₄ , so the fuel supply pressure must be increased or the salt holes must be increased. Such adjustment can be made relatively simple. Therefore, it was found that even in the case of the mixed fuel in which the calorific value coincides with the city gas, it can be sufficiently used as an alternative energy of the city gas by simple improvement of the fuel supply condition or the combustor burner.

As can be seen from the above embodiments and the detailed description of the invention, the method of the present invention has the effect of providing the LFG gas fueling method and system thereof and the excellent effect of providing the purified or LFG for home or industrial use. It is a very useful invention.

Claims (3)

A method of LFG gas fueling, characterized by dehydration from landfill gas and compression to remove condensate, passing through a Molecular Sieve adsorption column and activated carbon adsorption column to remove moisture and harmful substances, and then mixing it with city gas or LPG for vaporization. The LFG containing water and harmful substances are introduced into the dehydrator (1) having a drainage outlet at the bottom through the gas supply pipe (11) to remove water, and introduced into the gas supply tank (2) through the pipe (12), and then Compressed by the Lesser (3) and flows into the gas reservoir (4) having a drain at the bottom through the pipes (13) and (14), and the compressed gas introduced into the Molecular Sieve adsorption tower (5) through the pipe (15). LFG gas fuel system, characterized in that to remove the harmful substances by passing the activated carbon adsorption tower (6) through another pipe (16). 3. The LFG gas fueling system according to claim 2, further comprising a drying heater (10) for regenerating the Molecular Sieve and activated carbon.