KR102388063B1 - Apparatus For Reducing Pollutants From Exhaust Gases OF Small Ships - Google Patents

Abstract

A cost-effective exhaust gas pollutant reduction device for small ships is introduced. According to the present invention, the exhaust gas of a ship engine (1) is discharged to the outside through a selective catalytic reactor (SCR) module (20) and a dust collector (30) sequentially, and pollutants such as nitrogen oxides (NOx), hydrocarbon (HC), carbon monoxide (CO), and particulate matters (PM) are removed in the process. After the exhaust gas and a reducing agent are mixed in a mixer (21), the mixture is uniformly diffused in a diffuser (22) and introduced into the SCR module (20). In the dust collector (30), a diesel particular filter (DPF) module (31), a soot blower (32), and a diesel oxidation catalyst (DOC) module (33) are sequentially stacked.

Description

Apparatus For Reducing Pollutants From Exhaust Gases OF Small Ships

The present invention relates to a hazardous substance treatment apparatus, particularly an apparatus for reducing harmful substances contained in the exhaust gas of a small ship.

In addition to land transport vehicles, the level of demand for reducing pollutant emission from ships operating in the sea is being strengthened. The International Maritime Organization (IMO) has strengthened NOx emission regulations at sea to Tier III since 2016, and at IMO 2020, fuel sulfur content standards for all ships around the world have been significantly strengthened.

Ships using low-grade heavy fuel oil (HFO) emit large amounts of pollutants such as sulfur oxides (SOx), nitrogen oxides (NOx), hydrocarbons (HC), carbon monoxide (CO), and fine dust (PM) during operation. SOx can be reduced to some extent through the use of low-sulfur oil, and since NOx is naturally generated in the combustion process of fossil fuels, it is removed using a treatment device such as an exhaust gas recirculation device (EGR) or a selective catalytic reduction device (SCR).

EGR is a method of reducing NOx contained in the exhaust gas by cooling a part of the exhaust gas generated during the fuel combustion process of the engine, mixing it with fuel, and re-injecting it into the engine for combustion. Although EGR can reduce NOx emissions, there is a limit in that the overall efficiency decreases due to an increase in fuel consumption rate.

SCR is an exhaust gas post-treatment device that reduces and separates NOx contained in exhaust gas into nitrogen (N) and water (H ₂ O) using a reducing agent and a selective catalyst. Usually, urea solution is sprayed into the exhaust gas to evaporate, pyrolyze, and hydrolyze urea water by the heat of the exhaust gas to generate ammonia (NH ₃ ) as a reducing agent, and the generated NH ₃ turns NOx into N under the catalyst. ₂ and H ₂ O.

In order to cope with the regulation of marine exhaust gas, the application of natural gas engines is gradually expanding in the case of large ships, and in the case of existing large ships, a separate post-processing device such as SCR is being installed. In the case of small ships mainly used in the offshore, legal regulations are not yet complete, but cost-effective measures for reducing harmful substances in exhaust gas are required in line with the gradually tightening regulatory trend.

The present invention is based on the recognition of the prior art as described above, and an object of the present invention is to provide an apparatus capable of efficiently reducing harmful substances contained in exhaust gas of small ships.

Another object of the present invention is to provide a device for reducing harmful substances in exhaust gas for small ships that can remove PM, HC, and CO in addition to NOx.

The problems to be solved in the present invention are not necessarily limited to the above-mentioned matters, and other problems not mentioned before may be understood by the matters described below.

In an exhaust gas hazardous substance reduction device for small ships according to the present invention for achieving the above object, a reducing agent, for example, urea is injected into the exhaust gas introduced from a ship engine, and then the exhaust gas containing the reducing agent is sequentially applied to the SCR module and the dust collector. It is configured to be discharged to the outside through the

According to the present invention, a device for reducing harmful substances in exhaust gas for small ships includes a diffuser disposed at the front end of the SCR module, and a mixer disposed at the front end of the diffuser and having rotating blades. In order to increase the NOx reduction efficiency in the SCR module, the efficiency at which the element supplied as a reducing agent is converted into NH ₃ must be high. The urea is uniformly mixed with the exhaust gas in the mixer and converted to NH ₃ , which is then decelerated in the diffuser and introduced into the SCR module.

According to the present invention, the dust collector includes a filter layer in which a DPF module and a soot blower are sequentially stacked from below, and the exhaust gas from the SCR module is configured to flow upward from the bottom of the filter layer. The sootblower operates periodically or at preset times to remove contaminants that have accumulated on the DPF module.

According to the present invention, the DOC module is disposed on the sootblower. The exhaust gas that has passed through the filter layer passes through the DOC module to remove CO and HC.

According to the device for reducing harmful substances in exhaust gas for small ships according to the present invention as described above, the exhaust gas and the reducing agent are uniformly mixed in the mixer, so that the selective catalytic reduction reaction by the catalyst in the SCR module is efficiently performed.

In addition, according to the present invention, since the diffuser is disposed in front of the SCR module, the pressure and speed of the exhaust gas flowing into the SCR module can be controlled to a certain level even when relatively strong stirring is performed in the mixer, thereby improving the removal efficiency of harmful substances do.

In addition, according to the present invention, since it is possible to uniformly mix the reducing agent and the exhaust gas using a mixer and a diffuser, the harmful substance reduction device can be designed more compactly, and it can be applied to small and medium-sized ships with many space restrictions.

In addition, according to the present invention, NOx contained in the exhaust gas is intensively removed from the SCR module, and PM, HC, and CO contained in the exhaust gas are additionally removed from the dust collector, so ship exhaust in the Emission Control Area (ECA) It can respond to environmental regulations on gas.

1 is a schematic diagram of a device for reducing exhaust gas harmful substances for small ships according to an embodiment of the present invention.
Figure 2 is a schematic diagram of a device for reducing exhaust gas harmful substances for small ships according to another embodiment of the present invention.
3 is a schematic diagram of a diffuser according to an embodiment of the present invention;

Hereinafter, examples will be given in more detail so that various characteristic aspects of the present invention can be understood. In the drawings, the same or equivalent elements may be denoted by the same reference numerals, and the drawings may be exaggerated or schematically illustrated for an intuitive understanding of the features of the present invention.

In this document, unless otherwise limited or inherently unacceptable, expressions for describing the relationship between two elements, for example, expressions such as 'image' and 'connection' Of course it allows a third element to be interposed between the elements of the first and second elements. Directional indications, such as front and rear, left and right, or up and down, are only for convenience of description.

Fig. 1 shows a device for reducing harmful substances in exhaust gas for small ships according to an embodiment.

Referring to FIG. 1 , the device for reducing harmful substances is a post-treatment device connected to the exhaust line of the marine engine 1 . The processing apparatus is configured such that exhaust gas of the engine 1 is processed in the SCR module 20 through the mixer 21 and the diffuser 22 .

Upstream of the mixer 21 , an exhaust gas reducing agent, eg urea, is introduced into the exhaust gas. The urea input by the heat of the exhaust gas is converted into NH ₃ through an endothermic reaction and a hydrolysis reaction. Based on the flow direction of the exhaust gas, the upstream side corresponds to the front end, and the downstream side corresponds to the rear end.

In order to increase the NOx reduction efficiency in the SCR module 20, the conversion efficiency of urea supplied as a reducing agent to NH ₃ must be high. When the distance from the urea input point to the SCR module 20 is short, the time for the hydrolysis reaction is reduced, so that the efficiency of converting urea into NH ₃ may be reduced. According to the embodiment, the exhaust gas into which the urea is introduced is introduced into the SCR module 20 through the mixer 21 and the diffuser 22 in turn.

The mixer 21 is provided with a rotary blade for uniformly mixing NH ₃ and exhaust gas. The mixer 21 serves to help increase the NOx reduction rate in the SCR module 20 by evenly mixing NH ₃ and the exhaust gas, thereby converting efficiency between NH ₃ and NOx in the SCR module 20 can increase The residual urea introduced into the mixer 21 is converted into NH ₃ in the mixer 21 and uniformly mixed with the exhaust gas.

The diffuser 22 serves to diffuse the exhaust gas flow from the mixer 21 to improve the flow uniformity. The exhaust gas stirred with NH ₃ in the mixer 21 to form a vortex is reduced in speed in the diffuser 22 and a static pressure is increased. The diffuser 22 is designed so that the total pressure of exhaust gas at the inlet of the SCR module 20 is adjusted to a target range, and flow uniformity is ensured in the exhaust gas traveling direction and the entire area of the extension of the diffuser 22 .

The SCR module 20 reduces the reducing agent NH ₃ NOx to N ₂ and H ₂ O as shown in [Formula 1] below by a selective catalytic reaction. It is known that the NOx conversion efficiency is excellent at 250 ~ 450 °C, and reaction (b) is dominant at about 300 °C or less. As the catalyst, platinum (Pt)-based, vanadium-based (V), titanium (Ti)-based, zeolite (Zr)-based, etc. may be used, and further, TiO ₂ , W, etc. in vanadium to suppress SO ₃ production and extend catalyst life The added VOx/TiO ₂ , VOx/W/TiO ₂ catalyst may be used. Due to poor conditions such as shock and vibration generated during engine combustion, the development of a high rigidity carrier and catalyst suitable for a marine engine is required, and a catalyst and carrier to be developed in the future may also be used in the present invention.

[Formula 1]

4NO + 4NH ₃ + O ₂ → 4N ₂ + 6H ₂ O

2NO + 2NO ₂ + 4NH ₃ →4N ₂ + 6H ₂ O

2NO ₂ + NH ₃ + O ₂ → 3N ₂ + H ₂ O

In the SCR module 20, the NOx-reduced exhaust gas may be secondary treated for PM removal and the like.

FIG. 2 shows a device for reducing harmful substances in exhaust gas for small ships according to another embodiment. The same element(s) as in the previous embodiment will be briefly described or redundant description will be omitted.

In the device for reducing harmful substances of this embodiment, the exhaust gas of the engine 1 is first treated while passing through the mixer 21, the diffuser 22 and the SCR module 20, and then is secondary treated in the dust collector 30 to the outside. configured to be discharged.

An inlet line 11 is connected to the exhaust line of the engine 1 , and a reducing agent supply line 13 is connected to the inlet line 11 . For example, urea water is supplied through the reducing agent supply line 13 , and an injector 14 for directly injecting the urea water into the exhaust gas is provided at the tip of the reducing agent supply line 13 . The urea water injected from the injector 14 is mixed with the high-temperature exhaust gas, vaporized, and flows toward the SCR module 20 through the mixer 21 .

In order to increase the catalytic reaction rate in the SCR module 20 , the injection amount of urea water must be accurately controlled according to the operating conditions of the engine 1 . When the amount of urea water injection is small, the NOx reduction efficiency is lowered, and when the injection amount of NH ₃ is high, the slip phenomenon of NH ₃ into the atmosphere, that is, NH ₃ is not completely consumed in the catalytic reaction, but is released into the atmosphere. While maintaining the required level of NO _X reduction efficiency, NH ₃ slip is required to control the supply of an appropriate amount of urea water to be minimized.

The size, number, shape, rotation speed, etc. of the rotor blades of the mixer 21 are optimally designed and controlled in consideration of the flow rate, speed, temperature, etc. of the exhaust gas. If the back pressure in the mixer 21 is too large due to the shape or rotational speed of the blades, the exhaust gas flow to the SCR module 20 may be disturbed and a decrease in the output of the engine 1 may be a problem. The structure of the mixer 21 and the rotor blades is designed so that the mixing and flow uniformity of exhaust gas and NH ₃ can be maximized while minimizing the effect on the engine output.

3 schematically shows a diffuser 22 according to an embodiment.

Referring to FIG. 3 , the diffuser 22 has an inlet portion 22a and an extension portion 22b. The inlet portion 22a is a portion connected to the mixer 21, and the extension portion 22b is a section in which the diameter is gradually increased. The length of the inlet portion 22a can be reduced to a minimum if connectivity with the mixer 21 is ensured, and the inclination angle of the extension portion 22b is designed to be a gentle angle rather than a sudden change to ensure the uniformity of the flow of exhaust gas. good.

Referring back to FIG. 2 , the exhaust gas from which pollutants, mainly NOx, are primarily removed from the SCR module 20 is introduced into the dust collector 30 through the outlet line 12 to the lower side and rises to the upper portion of the dust collector 30 . Contaminants in the exhaust gas are treated secondarily.

The dust collector 30 has a filter layer for treating pollutants in the exhaust gas. The filter layer has a structure in which the DPF module 31 and the soot blower 32 are sequentially arranged from below. According to the embodiment, the DOC module 33 is additionally disposed on the sootblower 32 . The DPF module 31 , the soot blower 32 and the DOC module 33 are compactly installed in the dust collector 30 .

The DPF module 31 removes particulate matter (PM) contained in the exhaust gas by using a diesel particulate filter. The DPFs developed so far are mainly made of ceramic, and cordierite or SiC filters are the mainstream, and the removal efficiency is about 90% and the thermal durability is very good. The DPF is known as the most reliable device for removing PM among the known hazardous substance reduction devices.

Normally, the DPF device collects PM in the exhaust gas passing through the filter during engine operation, and when PM accumulates in the filter and the differential pressure between the front and rear ends of the DPF reaches a set limit, the PM is oxidized (burned) through the rear injection of fuel. It is configured to perform a playback operation. The temperature for regeneration is 500° C. or higher, preferably 600 to 650° C., and a catalyst may be used in the filter to enable regeneration at 300 to 400° C., which is near the exhaust gas temperature.

In the case of large ships, the exhaust temperature is high and DPF combustion regeneration is possible by the use of an appropriate catalytic filter. In the case of small and medium-sized ships, the temperature of the exhaust gas is about 80~400℃, and it is up to 500℃ under high load, so it is not easy to regenerate the filter by PM combustion. Therefore, in the case of a small ship, a soot blower 32 is installed at the rear end of the DPF module 31 to remove the PM accumulated in the filter of the DPF module 31 by injecting pressure air periodically or according to a predetermined logic. .

Residues such as PM in the DPF filter removed by the operation of the soot blower 32 are collected at the lower portion of the dust collector 30 . The residue collected in the lower part of the dust collector 30 may be manually removed, or a vacuum suction line for collecting the residue may be connected to the lower part of the dust collector 30 .

The DOC module 33 oxidizes and removes SOF (Soluble Organic Fraction, hydrocarbon component) in CO, HC and PM in exhaust gas using a diesel oxidation catalyst. The DOC module 33 is composed of a catalyst, a support, and a canister surrounding them, and allows the exhaust gas to be oxidized while passing through the inside of the support cell (catalyst flow path) of the honeycomb structure in which the catalyst is supported.

Embodiments of the present invention have been described above, and these embodiments will be helpful in understanding various aspects and features of the present invention. Features or elements introduced in these embodiments may be combined in various forms, and another embodiment that has not been described in this document may be presented by such a combination.

The scope of the invention to be protected is set forth in the claims. The elements recited in the claims may be variously changed and modified and replaced with equivalents without departing from the spirit or scope of the invention. Reference numerals recited in the claims, if any, are only intended to aid an easy and intuitive understanding of the claimed inventions or elements thereof, and do not limit the scope of the claimed inventions.

1: Engine 11: Inlet line
12: outlet line 13: reducing agent supply line
14: injector 20: SCR module
21: mixer 22: diffuser
30: dust collector 31: DPF module
32: sootblower 33: DOC module

Claims (2)

A device for reducing harmful substances in exhaust gas for small ships configured so that a reducing agent is injected into the exhaust gas introduced from a ship engine, and then the exhaust gas containing the reducing agent is sequentially discharged to the outside through an SCR module and a dust collector,
A diffuser is disposed at the front end of the SCR module, a mixer having rotating blades is disposed at the front end of the diffuser, and the exhaust gas and the reducing agent are mixed in the mixer and then decelerated in the diffuser to flow into the SCR module,
The dust collector includes a filter layer in which a DPF module, a soot blower and a DOC module are sequentially stacked from below, and the exhaust gas from the SCR module is configured to remove harmful substances contained in the exhaust gas while flowing upward from the bottom of the filter layer,
A device for reducing harmful substances in exhaust gas for small ships configured to remove residues in the DPF module by operating the soot blower. delete

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