阅读说明：本技术 从气体混合物流中除去气体的方法和装置 (Method and apparatus for removing gas from gas mixture stream ) 是由 克拉斯·英奇 彼得·弗兰岑 卡尔·佩特鲁斯·哈格马克 于 2020-03-04 设计创作，主要内容包括：一种从气体混合物流中除去气体的方法和装置。在气体混合物流(106)中引入第一液体(82),以蒸发冷却所述气体混合物并使其饱和。提供第二液体(84)的小液滴,所述小液滴能够吸附并溶解所述气体和所述小液滴的尺寸小到不会被重力沉降并大到足以被离心分离。将小液滴喷射到所述气体混合物流中,以将所述气体吸附和溶解到所述液滴中；以及从所述气体混合物流中离心分离所述小液滴。(A method and apparatus for removing gas from a gas mixture stream. A first liquid (82) is introduced into the gas mixture stream (106) to evaporatively cool and saturate the gas mixture. Providing small droplets of a second liquid (84) that are capable of adsorbing and dissolving the gas and the small droplets are of a size small enough not to be gravitationally settled and large enough to be centrifuged. Spraying small droplets into the gas mixture stream to adsorb and dissolve the gas into the droplets; and centrifuging the droplets from the gas mixture stream.)

1. A method of removing gas from a gas mixture stream, characterized in that

Introducing a first liquid into the stream of the gaseous mixture to evaporatively cool and saturate the gaseous mixture;

providing droplets of a second liquid, said droplets being capable of dissolving said gas and said droplets being of a size small enough not to be gravitationally settled and large enough to be centrifuged;

injecting the small droplets into the gas mixture stream to adsorb and dissolve the gas into the droplets; and

centrifuging the droplets from the gas mixture stream.

2. The method of claim 1, comprising introducing the first liquid by spraying small droplets of the first liquid into the stream of gas mixture.

3. The method of claim 2, comprising forming small droplets of the first liquid by atomization.

4. The method of claim 3, comprising generating the first liquid atomization by pressurized air using a two-fluid nozzle or by high pressure liquid injection using a single-fluid nozzle.

5. A method according to claim 4, comprising forming small droplets of the second liquid by atomisation.

6. The method of claim 5, comprising generating the second liquid atomization by pressurized air using a two-fluid nozzle or by high pressure liquid injection using a single-fluid nozzle.

7. A method according to any one of claims 2 to 6, comprising controlling the droplet size of the first and second liquids to vary between 20 μm and 200 μm, typically about 50 μm.

8. A method according to any one of claims 2 to 7, comprising injecting droplets of the second liquid into the gas mixture stream downstream of the injection of droplets of the first liquid.

9. The method of any one of claims 2-8, comprising ejecting droplets of the second liquid co-currently with the gas mixture stream.

10. A method according to any one of the preceding claims, wherein the first liquid is water and the second liquid is an aqueous alkaline solution.

11. A process according to any one of the preceding claims, wherein the gas mixture is a combustion exhaust gas and the gas to be removed is a sulphur oxide containing gas.

12. A process according to any one of the preceding claims, wherein the gas mixture is an exhaust gas stream from a marine diesel engine and the gas to be removed is a sulphur oxide containing gas.

13. A device (10) for insertion into an exhaust gas flow passage of an exhaust gas conduit (104) for performing the method of claim 10, comprising:

a nozzle (32, 42) for water and an aqueous alkaline solution;

at least one centrifugal separator (52) located downstream of the nozzle in the gas mixture stream;

the nozzle includes:

at least one water nozzle (32); and

at least one atomizing nozzle (42) located downstream of the at least one water spray nozzle (32) in the gas mixture stream for producing droplets of the aqueous alkaline solution.

14. The apparatus (10) of claim 13, wherein the exhaust pipe (104) is an exhaust pipe of a marine diesel engine.

15. The device according to claim 13 or 14, wherein the nozzle (32, 42) is a single fluid nozzle or a two fluid nozzle.

16. The apparatus of any one of claims 13-15, wherein the at least one nozzle (42) is oriented to spray co-currently with the gas mixture stream and the at least one nozzle (32) is oriented to spray counter-currently with the gas mixture stream.

17. Device according to any one of claims 13 to 17, comprising a control and drive unit (80) able to control the size of the droplets during operation according to the engine load.

Technical Field

The present invention relates to a method for removing gas from a gas mixture stream.

The invention also relates to a device for carrying out the method.

Background

Existing systems for reducing sulfur oxides (SOx), such as sulfur dioxide, in marine diesel engine exhaust gases are based primarily on various types of scrubbers. For this reason, wet scrubbers are most commonly used, wherein an aerosol of an alkaline solution, such as sodium hydroxide (NaOH), is sprayed into the scrubber in a so-called closed-loop system to react it with sulfur oxides to form, for example, water-soluble salts or other disposable reaction products. This is often the case when the ship is in a port or the alkalinity of the sea water is insufficient. In case the seawater itself has sufficient alkalinity, a so-called open system may be used at sea, in which seawater aerosol is added to react with sulfur oxides in the exhaust gas, thereby removing them.

These scrubber systems require a large amount of exhaust gas spray water to transport the sulfur oxides into the aerosol droplets, which must be very large and the exhaust gas flow must be very slow to enable gravity deposition of the droplets against the gas flow in the scrubber. This in turn makes the device very large.

To improve these systems, the compact system forming the basis of the present invention and disclosed in WO2018/231105a1 proposes to inject an aerosol at high pressure into the exhaust gas stream and to separate the liquid droplets from the gas stream using centrifugal techniques. It is thus possible to use a smaller amount of water to obtain very small droplets, which have a larger total surface area and which are able to react quickly with sulphur dioxide. The amount of water that needs to be sprayed is only about 2.5% to 5% of the amount of water required by prior systems while maintaining the separation effect.

Disclosure of Invention

The object of the present invention is to further improve the prior art methods and devices in general, and in particular the method and device disclosed in WO2018/231105a1, to better meet the new emission requirements, i.e. the emissions correspond to not more than 0.1% of the sulphur in diesel fuel.

In one aspect of the invention, the method comprises:

introducing a first liquid into the stream of the gaseous mixture to evaporatively cool and saturate the gaseous mixture;

providing droplets of a second liquid, said droplets being capable of dissolving said gas and said droplets being of a size small enough not to be gravitationally settled and large enough to be centrifuged;

injecting the droplets into the gas mixture stream to dissolve the gas into the droplets; and

centrifuging the droplets from the gas mixture stream.

While the present invention may be generally practiced in various applications for removing gases from a gas mixture stream, the present disclosure specifically exemplifies use for removing sulfur dioxide from combustion exhaust gases such as the marine diesel engines described above. Examples of such applications can be found in the following documents:

EP2499091, EP2747877, US8444942, EP2298957, EP1524023, WO2016/062731 and EP 3393625.

Supplying the liquid in two steps has the following general and specific application advantages:

the initial step of introducing the first liquid (e.g., water) results in evaporation and saturation, the evaporation saturating and cooling the hot (e.g., 300-. It is important that during the step of introducing the first liquid, evaporation and saturation keep the droplets of the second liquid unchanged in size. Otherwise, as in the single spraying step of WO2018/231105a1, water would continue to evaporate from the droplets with cooling, after which the droplet size could not be controlled. Therefore, the saturation in the step of introducing water effectively prevents the evaporation of the liquid droplets introduced in the spraying step. Cooling is also advantageous in conventional centrifugal separators which cannot withstand excessive heat.

Since the droplet size of the second liquid is small enough not to be gravitationally settled and large enough to be centrifuged, they are safely entrained by the flow of gas mixture and move forward and are separated from the flow of gas mixture in the centrifuging step.

The first liquid may be introduced by spraying small droplets of the first liquid into the stream of gas mixture. The small droplets provide rapid cooling and eventual saturation.

Small droplets of the first liquid may be formed by atomizing pressurized air using a two-fluid nozzle, or by high pressure liquid injection using a single-fluid nozzle. A two-fluid nozzle may be advantageous to produce very small droplets to cool as quickly as possible.

Small droplets of the second liquid may also be formed by atomizing pressurized air using a two-fluid nozzle, or by high pressure liquid spraying using a single-fluid nozzle. Single fluid nozzles are advantageous for producing more droplets per unit time, which in turn may require a smaller number of nozzles.

Atomization of the liquid will produce an aerosol with small droplets to provide a large total surface area, so that the reaction time of the first and second liquids is short, little or no slowing of a given flow rate is required, especially for exhaust gas streams of diesel engines, rapid evaporation of water and saturation is obtained in the first step, and the sulphur oxides are neutralized using the base in the droplets, so that the system can also be kept very compact.

By creating atomization with pressurized air, the droplet size can be controlled by varying the flow rates of the air and the aqueous alkaline solution.

The size of the droplets can also be controlled by varying only the pressure of the pressurized air. The droplet size can be controlled in this way when the atomizing nozzle and the flow rate of the alkaline solution have been determined.

The size can be controlled to vary between about 20-200 μm, typically about 50 μm. Further smaller droplets in the gas stream may pass through in an undesirable mannerAnd (5) separating. This size is understood more formally as the size of the medium-sized droplets. E.g. of medium size d_v50The diameter of the drop representing 50% of the drop volume is greater than d_v50。d_v50A typical distribution equal to 50 μm contains droplets of 20-130 μm (10% by volume of the droplets having a diameter smaller than 20 μm and 90% by volume of the droplets having a diameter smaller than 130 μm).

Droplets of a second liquid may be injected into the gas mixture stream downstream of the injection of the first liquid. Thereby, the gas mixture stream can be saturated sufficiently in a given time.

Aerosol droplets may be injected co-currently with the exhaust gas stream.

The first liquid may be water and the second liquid may be an aqueous alkaline solution.

The gas mixture may be combustion exhaust gas and the gas to be removed may be a gas containing sulfur oxides.

In particular, the gas mixture may be an exhaust gas stream from a marine diesel engine, and the gas to be removed may be a sulfur oxide containing gas.

The device for carrying out the method according to the invention is inserted into the exhaust gas flow channel of an exhaust gas duct for carrying out the above method, comprising nozzles for water and an aqueous alkaline solution; and at least one centrifugal separator located downstream of the nozzle of the gas mixture stream; the nozzles include at least one water nozzle, and at least one atomizing nozzle, located downstream of the at least one water nozzle in the gas mixture stream, for producing droplets of the alkaline solution.

The exhaust pipe may be an exhaust pipe of a marine diesel engine.

In one embodiment, the at least one atomizing nozzle is a two-fluid (alkaline solution and pressurized air) nozzle, although atomization can also be performed by a single-fluid high-pressure nozzle. Such nozzles, which have not been used in the prior art, can be selected and controlled to achieve the desired droplet size.

The device may further comprise a control and drive unit capable of controlling the droplet size during operation in dependence on the engine load.

Other features and advantages of the invention will be apparent from the claims and the detailed description that follows.

Drawings

FIG. 1 is a schematic diagram illustrating an exemplary apparatus for treating exhaust gas from a marine diesel engine.

The drawings are generally exemplary, and thus, the scale, orientation, dimensions, etc. of interrelated components may not correspond to an actual device.

Components having interrelated functions may be referred to by the same numeral.

Detailed Description

In the following detailed description, the invention is implemented on a marine installation, although the invention may be implemented in other fields of processing gases.

The marine device 10 in fig. 1 is schematically shown inserted into the exhaust gas flow channel of the exhaust pipe 104 of the large diesel propulsion engine 102 of the marine vessel 100. Diesel fuel, which may be used in engines 102 in the megawatt range, typically contains significant amounts of sulfur that is converted to sulfur oxides (SOx), such as SO in the exhaust gas stream 106₂。

In general, the apparatus 10 for reducing these sulfur oxides can be considered to consist of a continuously zoned injection section 20 and a centrifugal separation section 50 forming the exhaust gas duct 106. The injection fluid is supplied to the nozzles 32, 42 of the injection section 20 by a drive and control unit 80.

The injection section 20 is serially divided into a water injection section 30 and an alkaline solution injection section 40 having respective nozzles 32 and 42 in sequence, the nozzles 32 and 42 may be arranged singly or in one or more circular arrays around the exhaust gas stream. The water may be seawater 82 and an alkaline solution 84, such as sodium hydroxide (NaOH), may contain seawater.

As shown in dashed lines in fig. 1, the nozzles 32 in the water jet section 30 may be of a single fluid type, e.g., capable of utilizing the kinetic energy of pressurized water to break it up into droplets and eject the droplets into the exhaust gas stream 106. The water droplets cool the exhaust stream and evaporate in the exhaust stream, saturating the exhaust stream with water vapor. However, they may also be of the two-fluid (two-phase) type, as indicated by the solid line in fig. 1.

Although the nozzles 42 of the alkaline solution injection section 40 shown in dashed lines in fig. 1 may also be of a single fluid type, in the embodiment shown in solid lines the nozzles 42 are shown as of a two-fluid (two-phase) type, capable of atomizing a stream of liquid alkaline solution 84 into an aerosol of small droplets using pressurized air/compressed air and injecting the aerosol into the vapor-saturated exhaust stream 106. The lower region of the large circled solid line of fig. 1 shows an external mixing type two-fluid atomization nozzle 42, but other types of two-fluid atomization nozzles may be used.

Since the exhaust stream is already saturated with steam, the droplets of the alkaline solution will retain their size. In the droplets, the alkaline solution in the droplets reacts with the acidic sulfur oxide and neutralizes the salt and water. The reaction may occur and be completed 62 in a reaction chamber 62, the reaction chamber 62 forming an interior space that extends through the separator section 50 and almost to above the alkaline solution injection section 40.

The separation section 50 has a plurality of centrifugal separators 52. As can be seen in the enlarged circular upper region of fig. 1, each separator 52 has a rotor 54, which rotor 54 has a stack of narrowly spaced conical separation discs 56 which project into a reaction chamber 62. The separator may also be of a more basic type, having radial wings in the rotor instead of conical discs (not shown). Each separator 52 is of the counter-flow type, i.e. the exhaust gas flow passes radially inwards (arrows P) through the spaces between the discs 56, resisting the pumping effect created by the rotating rotor 52. Such a rotor-type centrifugal separator 52 for centrifugal separation of solid and/or liquid particles from a gas stream, such as crankcase gas, is known per se, for example from WO2012/052243 a 1.

Each separator rotor 54 is further equipped with a fan 64 that rotates with the rotor 54. The fan 64 is located in the chamber 58, the chamber 58 being separated from and enclosing a separation section 68 of the reaction chamber 62 for enhancing the flow of the cleaning gas from the gas outlet 60 of the rotor 52 to the chamber 58 and further to the cleaning exhaust gas outlet 70. Alternatively, a common fan (not shown) may be arranged upstream or downstream of the reaction chamber 62, rather than providing a separate fan 64 for each separator 52, the reaction chamber 62 being used to feed a mixture of exhaust gas, water and reaction products through the stacked discs of the rotor 54 and to discharge the gas with a reduced content of sulphur oxides to the exhaust gas outlet 70. The separator rotor 54 is driven by a single motor 72 or by a common motor and belt drive (not shown), similar to that shown in figure 2 of WO2012/052243 a 1. In the reaction chamber 62 there is at least one outlet 74 for discharging reaction products and liquid separated by the separator rotor 54. Different separator devices similar to the above description and usable in the present invention are described in detail in the initially mentioned document WO2018/231105a 1.

The control and drive unit 80 is shown by way of example and in a simplified manner. The control and drive unit 80 operates and is briefly configured as follows: pumps 88 draw and pressurize the seawater and alkaline solution from respective sources 82 and 84. The compressor 86 draws in and pressurizes ambient air that may be temporarily stored in the accumulator 92. Valves 90 distribute the respective pressurized fluids to nozzles 32 and 42. The regulator 94 maintains a set point for pressure and/or flow. The settings of the valve 90 and the regulator 94 are controlled by a control unit 96. The settings for controlling the droplet size, such as the settings for liquid and air pressure, are controlled by the exhaust gas flow rate in accordance with the engine load changes during operation of the vessel 100. The exhaust gas flow is detected by a flow sensor 108 in the exhaust pipe 102.

The unit 80 may be specifically configured to control the size of the droplets produced by the atomizing nozzles 42 by varying the rate of air and liquid flow through a selected type of atomizing nozzle 42 in a known manner. Only the air pressure needs to be changed when the atomizing nozzle type and the liquid flow rate are given.

The foregoing detailed description has been given primarily for clearness of understanding and no unnecessary limitations are to be understood therefrom. Modifications will be apparent to those skilled in the art upon reading this disclosure, and may be made without departing from the spirit of the invention or the scope of the appended claims.