阅读说明：本技术 用于将硫燃烧生成二氧化硫的方法和设备 (Process and apparatus for combustion of sulfur to sulfur dioxide ) 是由 K-H·道姆 H·施托希 S·布劳纳 于 2018-07-30 设计创作，主要内容包括：本发明描述了一种用于硫燃烧的反应器。反应器壁(23)形成对称的基底区域b,至少两个燃烧器(2,2’)分别利用燃烧器保持装置(22)来安装。所有燃烧器保持装置(22)相对于彼此具有相同的距离,每个燃烧器保持装置(22)相对于基底区域b的中心点z具有相同的距离。至少一个燃烧器保持装置(22’)布置成使得在运行期间燃烧器(2’)的火焰相对于中心轴线a成0°至45°之间的角度α,中心轴线a定义为燃烧器保持装置(22’)和中心点z之间的最短连接。(A reactor for the combustion of sulfur is described. The reactor wall (23) forms a symmetrical base region b, and at least two burners (2,2') are each mounted by means of burner retaining devices (22). All burner holding devices (22) have the same distance with respect to each other, and each burner holding device (22) has the same distance with respect to the center point z of the base area b. The at least one burner holding device (22') is arranged such that during operation the flame of the burner (2') is at an angle a between 0 ° and 45 ° with respect to a central axis a, which is defined as the shortest connection between the burner holding device (22') and the central point z.)

1. A reactor for the combustion of sulfur, the reactor wall (23) forming a symmetrical base area b, at least two burners (2,2') each being mounted with burner holding means (22), all burner holding means (22) having the same distance to each other, each burner holding means (22) having the same distance to a centre point z of the base area b, characterized in that at least one burner holding means (22') is arranged such that during operation the flame of a burner (2') is at an angle α between 0 ° and 45 ° to a centre axis a, which centre axis a is defined as the shortest connection between a burner holding means (22') and the centre point z.

2. The reactor according to claim 1, wherein the base region b is square or circular.

3. Reactor according to any of the preceding claims, characterized in that the base area b is a polygon having at least six sides and the number of sides is a multiple of the number of burners (2, 2').

4. A reactor according to any of the preceding claims, characterized in that at least three burners (2,2') are provided.

5. Reactor according to any of the preceding claims, characterized in that the reactor has a first zone where heat is transferred via radiation at the waste heat boiler and a second zone where heat is transferred via convection.

6. Reactor according to any of the preceding claims, characterized in that the reactor wall is at least partially designed as a membrane wall (24).

7. Reactor according to any of the preceding claims, characterized in that the reactor has two heat exchangers (6,15), between which two heat exchangers (6,15) additional oxygen is introduced or an additional burner (2 ") is provided.

8. Reactor according to any of the preceding claims, characterized in that at least one control unit is provided, which adjusts the burner holding device (22') over a range of angles a based on the measured temperature so that the heat distribution is as uniform as possible, the adjustment being based on a stored experimentally determined matrix.

9. A process for the combustion of sulfur, wherein sulfur is combusted in at least two burners which are mounted on a reactor wall, characterized in that at least one burner is arranged with respect to its flame direction such that the flame direction is at an angle α with respect to the axis a of the shortest connection between the burner holding means and the centre point z of the base area b defined by the reactor wall.

Technical Field

The invention relates to a reactor for the combustion of sulfur, the reactor walls forming a symmetrical base area (b), at least two burners being mounted with burner holding means, respectively, all burner holding means having the same distance relative to each other, each burner holding means having the same distance relative to the centre point (z) of the base area (b).

Background

Processes for the manufacture of sulfuric acid have been well known for decades. By this method, sulfur is combusted to sulfur dioxide (SO)₂) Then further oxidized into sulfur trioxide (SO) by heterogeneous catalytic reaction₃). Absorbing the generated sulfur trioxide in concentrated sulfuric acid, adding water, and finally converting into sulfuric acid (H)₂SO₄). The source of oxygen for sulfur combustion can be air or oxygen-enriched air, or pure oxygen.

In particular, liquid sulfur is conveyed via a line to at least one burner where it is mixed with an oxygen-containing gas (e.g., air) conveyed via a line into the burner. The burners flame a furnace, which is typically lined with multiple layers of refractory bricks. In the furnace, a gas containing SO2 is formed according to the reaction of adiabatic combustion:

S+O₂→SO₂；ΔH～-297kJ/mol

in the known process, oxidation of sulphur takes place in a furnace, the sulphur being sprayed into the furnace or atomized by other means, for example by means of nozzles or special burners, as can be found for example in EP 2627949.

Due to the droplet size and the mainstream combustion temperature, a certain residence time is required for complete evaporation and subsequent oxidation of the droplets. The reaction is therefore limited only by mass transfer phenomena, which is why it is important to have a complete mixing of the sulphur and oxygen fed to the reactor.

In general, the adiabatic combustion temperature of 1,000 ℃ or higher is a result determined by the ratio of sulfur to combustion air. In addition, standard sulfur combustion units employ a Waste Heat Boiler (WHB) to recover excess energy from the system. Typically, a fire tube boiler is installed downstream of the furnace to cool the combustion gases to typical values between 400 and 500 ℃ while generating high pressure steam.

Generally, when using fire tube boilers, the capacity of the apparatus of the described method is limited for two reasons.

First, the gas temperature is limited to about 1200 ℃ since the hot tube plate (gas inlet side of the waste heat boiler) cannot withstand higher temperatures without the risk of local material overheating. Hot gas is fed through the pipeline and high pressure water/steam is present at the shell side. At very large equipment sizes, this also results in very large diameters of the outer shell of the fire tube boiler; therefore, the mechanical design requires very large wall thicknesses of the shell and tubesheet due to steam pressure.

In this case, moreover, it is particularly important to use a relatively high steam pressure. At typical large equipment sizes of 5,000mtpd (metric tons/day), the fire tube design cannot accommodate any substantial further increase in steam pressure from the current typical 65 bar to, for example, 100 bar. However, since product steam is preferred for feeding to the steam turbine generator, a higher steam pressure is required, as this provides the advantage of improved thermal efficiency.

Secondly, for sulphur burners it can be said that they are generally horizontal vessels lined with multiple layers of refractory material. The quality and design of the refractory material depends on the operating conditions, such as adiabatic combustion temperature. Generally, the required specific volumetric heat rate is in the range of 300,000 to 3,000,000kcal/m³The furnace volume.

In the case of very large plant capacities, the furnace size can become very large. In this case, the design is potentially not sustainable due to limitations in the reduced integrity of the brick lining at larger furnace diameters, particularly in terms of increased circumferential compressive stresses and/or horizontal cylindrical instability. Furthermore, the length of the furnace is also limited in terms of brick lining, as differential thermal expansion and compensation thereof become more and more difficult. High specific heat rates can minimize problems by reducing furnace size, but also places limitations on the homogeneous/uniform distribution of atomized sulfur and the required thorough mixing of gases.

Although large plant output capacities can be achieved with multiple parallel furnace and waste heat boiler units, a significantly larger single unit will be required in the future to reduce capital costs and increase energy efficiency.

Disclosure of Invention

It is therefore an object of the present invention to provide an arrangement of burners, furnaces and associated waste heat boilers, so as to enable almost unlimited plant capacity.

The above object is achieved by a device having the features according to claim 1.

The reactor is conceived as a water-tube type waste heat boiler, characterized in that high-pressure water/steam is circulated inside the wall-tubes (as opposed to a fire-tube type boiler). It is also preferred to combust the sulphur with a suitable proportion of air to achieve an adiabatic combustion temperature of 1500 to 2000 ℃, which is significantly higher compared to conventional arrangements. At the same time, the total flow of combustion gases will become smaller, so that the size/diameter of the vessel/reactor is significantly reduced. Thus, the lower part of the waste heat boiler does not comprise convection surfaces, but the walls are only exposed to radiation. Once the raw combustion gas temperature is reduced (based on the heat transfer by radiation to the walls), the upper part of the waste heat boiler will also contain convective heat transfer surfaces, while the walls will extend over the entire length of the vessel.

Such a reactor for sulfur combustion comprises walls forming a symmetrical plan view area/base area. In the reactor, at least two burners are each mounted with a burner holding device. The burner holding devices are mounted symmetrically to each other on the wall of the combustion chamber. The distance between each burner holding device is the same. Furthermore, the distance of each burner holding device from the center of the combustion base area should be the same.

The decisive factor is that at least one of the burner holding devices is designed to be deliberately adjustable such that the associated flame is at an angle α with respect to the transverse center point axis, which is between 0 ° and 45 °, preferably between 2 ° and 15 °. The central axis is the axis forming the direct connection between the centre of the burner retaining means and the centre of the base area.

Thus, the burner can be deliberately adjusted such that the hottest point of the combustion chamber is no longer located in the center of the substrate area. However, it is important to establish an asymmetric temperature distribution within the reactor with respect to the center of the substrate region. This asymmetric temperature distribution results in a gas flow that promotes better mixing of the gases on the one hand but also better heat dissipation to downstream convection surfaces on the other hand. It is therefore also possible to design and build a sulphur combustion system without any brick-lined furnace and to replace the conventional fire-tube boiler with a water-tube boiler. Such a combustion reactor is suitable for unlimited equipment size, is designed essentially as a water tube boiler known in the industry, and incorporates a plurality of burners. This concept is more specific to power plants with greater heat capacity and operating pressure. Therefore, the limiting factors discussed above are ignored.

The preferred design of the invention is to design the reactor base as a square or a circle, which ensures the simplest possible design and thus the simplest possible and most economical manufacture.

Another advantage is that: the base area is a polygon having at least six sides, the number of sides being the same as or a multiple of the number of burners, preferably multiplied by one or two, in order to ensure a symmetrical distribution of burners, with equal distances between the burner arrangements. It is particularly preferred that the number of sides corresponds to the number of burners. This particular design enables a modular design.

It is also preferred to have at least three burners. The increased number of burners can further increase the plant capacity.

Another advantageous design of the invention provides a so-called convection zone above/around the combustion zone, where the heat transfer in the lower part is dominated by radiation and the gas flow is further mixed. This reliably prevents thermal backflow.

Furthermore, it is advantageous if the wall is at least partially designed as a membrane wall. The membrane wall is a wall made of a tube, at least partially enclosing the combustion chamber. A heat transfer medium (e.g., a water/steam mixture) may be conveyed through the tubes. In summary, the reactor wall is an integral part of a waste heat boiler of the water-tube type, consisting of a plurality of preferably vertical tubes, which contain the water/steam mixture of the circulating water inside the waste heat boiler, with welded fins on each opposite side of the tubes, in order to connect (weld) to adjacent tubes, thus forming a membrane wall structure.

In order to withstand the high gas temperatures and to protect the furnace components, the interior of the membrane wall housing can be covered with a thin layer of refractory castable. This not only protects the walls (and bottom) from unwanted contact with unevaporated sulphur droplets, but the cooled walls also significantly reduce the internal surface temperature of the refractory, making it suitable for use with castable materials. No separate horizontal or vertical furnace is required. The height of the combustion section (i.e. the pouring protection) is determined by the residence time required for the complete evaporation of the sulphur droplets. Thus, the downstream convective heat transfer section is not exposed to unvaporized sulfur.

The disadvantages of burner installations in separate brick lined furnaces are: once the equipment is tripped or temporarily taken off-line, the burner must be removed from the furnace, i.e., otherwise the burner is exposed to hot furnace radiation without cooling, which can result in mechanical damage or deformation of the burner rotor or conventional nozzle. Therefore, removing the burner is time critical.

By means of the invention, the surface temperature and thus the residual radiation after a shutdown are considerably lower/smaller than in the case of the refractory measures of conventional individual furnaces without or by using a castable cooled by the wall of the film. Once combustion stops, the combustion chamber cools down quickly, eventually approaching film temperature. The traditional furnace temperature of about 1600 ℃ is compared with the temperature of the membrane wall (the castable can be added according to specific conditions) lower than about 500 ℃. Therefore, it is no longer necessary to quickly remove the burner from the furnace.

It is also advantageous that the reactor is completely designed with membrane walls in order to remove a large amount of heat from the system via radiation at an early stage. Preferably, the outer shell of the furnace and the downstream convection boiler elements are designed as an integral continuous full length membrane wall, with water/steam being circulated through the vertical boiler tubes to provide cooling for the internals.

The inner diameter of the reactor is designed to be larger than the combustion flame length, thus making itself perfectly suited for the side arrangement of the sulfur burner, even with much smaller acid plant sizes compared to the above 5,000mtpd capacity, but preferably for greater plant capacity.

Typically, one heat exchanger designed as a convection heat zone is installed in the reactor downstream of the combustor section. However, it is also preferred to use two such heat exchangers. Between two such heat exchangers, additional oxygen injection measures or additional burners may be provided. Thus, a portion of the combustion may be relocated, which may also provide a more uniform heat distribution.

By the arrangement of the two-stage combustion system, the reactor will enable the first combustion unit stage to operate in a sub-stoichiometric range (with respect to oxygen) and thus not prone to the formation of nitrogen oxides. The latter are undesirable impurities because they are at least partially absorbed by the acid.

Another special design of the invention envisages the provision of at least one control unit which adjusts the burner over the range of angle α on the basis of the measured temperature in order to make the heat distribution as uniform as possible, wherein the adjustment is made on the basis of a stored experimentally determined matrix.

It is particularly preferred to carry out the temperature measurement in the heat exchanger, so that, in practice, a relatively large heat distribution can be transmitted owing to the already reduced temperature. This solution can be carried out both on the base area of the heat exchanger and along the entire flow-direction path, preferably in all three dimensions.

Finally, the invention also comprises a process for the combustion of sulfur having the features of claim 8.

In this process, sulfur is burned with at least two burners. These burners are mounted on the combustion chamber wall, which defines a plane of symmetry. The flame direction of the burner can be deliberately adjusted via the respective burner mounting means such that the angle α is between 0 ° and 45 °, preferably between 2 ° and 15 °, with respect to the axis of the shortest connection between the burner means and the center of the substrate region defined by the combustion chamber wall.

In summary, the present invention provides the following advantages:

1. there is no furnace size limitation, i.e. no separate furnace.

2. The reactor membrane wall can be used on the basis of good sulfur atomization, thus minimizing the risk of sulfur droplets hitting the membrane wall. Thus, the castable coating can be omitted; or for security reasons, a castable coating may be installed, although at a low risk.

3. There is no expansion difference between the furnace and the waste heat boiler and the interface stress is smaller with a brick-liner-free design.

4. An almost unlimited number of burners can be arranged around the furnace/waste heat boiler and therefore there is no limitation in the size capacity of the plant in terms of sulfur combustion.

5. The steam pressure of the waste heat boiler is almost not limited, and thus the thermal efficiency can be remarkably improved.

6. The shape of the furnace/reactor and waste heat boiler may be circular or, for example, square/hexagonal/octagonal, depending on manufacturing preferences and internal process gas pressure.

7. High SO of combustion gases can be achieved when oxygen-enriched air is used at concentrations well in excess of the ambient air limit of 20.9% oxygen content₂And (4) concentration.

Drawings

Further features, advantages and possible applications of the invention can be derived from the following description of exemplary embodiments and the accompanying drawings. All features described and/or illustrated herein form the subject matter of the invention, either individually or in any desired combination, however they may be combined in any claim or when referring back to the preceding claim.

The figures show schematically:

figure 1a shows schematically a first arrangement known in the industry for the combustion of sulphur, comprising a brick lined vertical combustion chamber (4), which is connected to a waste heat boiler located at the top of the combustion chamber,

FIG. 1b schematically shows a second arrangement, conventional, popular and known in the industry, for the combustion of sulphur, comprising a brick lined horizontal combustion chamber (4), which is connected sideways to a waste heat boiler (6),

fig. 1c schematically shows a third conventional and industrially known arrangement for the combustion of sulphur, comprising 2 or more brick lined horizontal combustion chambers (4) and a single brick lined central vertical collection chamber (4') connected to a waste heat boiler (6),

fig. 2a schematically shows a first embodiment burner arrangement for sulfur combustion according to the invention, without a separate combustion chamber, the oxygen supply for sulfur combustion can be air or oxygen-enriched air,

FIG. 2b schematically shows a second embodiment of a burner arrangement for sulfur combustion according to the present invention, without a separate combustion chamber, using oxygen-enriched air or pure oxygen, with which arrangement and by recycling the gas cooled at the waste heat boiler (6) and subsequently further cooling in a heat exchanger, e.g. an economizer (11), a high SO of the gas can be achieved₂The concentration can reach 100% (volume percentage),

FIG. 2c schematically shows a third embodiment burner arrangement for sulfur combustion according to the present invention, without a separate combustion chamber, such that the sulfur combustion is sub-stoichiometric with respect to oxygen, thus resulting in less formation of nitrogen oxides, wherein an appropriate amount of oxygen (air or oxygen-enriched air) is added to complete the remainder of S₂Before the oxidation of the gas, unoxidized S will be contained at the waste heat boiler (6)₂The combustion products of the gas are cooled to typically 550 c and then an additional heat exchanger, such as a boiler element.

Fig. 2d schematically shows a fifth embodiment burner arrangement for sulphur combustion according to the invention, without a separate combustion chamber, the sulphur burner (2,2 ") being arranged for two-stage combustion, the first (lower) combustion gas being intercooled by means of a waste heat boiler (6) and the gas being finally cooled (15) after the second (upper) sulphur combustion. Also, oxygen may be supplied by means of air or oxygen-enriched air.

Fig. 3 schematically shows a burner arrangement according to the invention, in this case arranged in a cylindrical reactor shape.

Detailed Description

Figure 1a shows a possible design of a reactor for the combustion of sulphur. Liquid sulfur is introduced into the burner 2 via line 1, 1'. An oxygen-like gas, typically air, is fed into the burner 2 via lines 3, 3'. The sulphur is burned in a vertical combustion chamber 4 with a brick lining 5.

The generated heat is then conducted into the heat exchanger 6. The sulphur dioxide produced is discharged via line 7.

Fig. 1b essentially corresponds to this design, wherein the horizontal combustion chamber 4 is arranged here on the side of the heat exchanger 6 of the waste heat boiler.

Fig. 1c shows an arrangement with a central vertical collection chamber 4' and two horizontal combustion chambers 4 arranged symmetrically relative thereto, followed by a waste heat boiler 6.

Contrary to the above, the subject of the invention is to omit a separate sulfur burner or sulfur combustion chamber, while the burner directly blows the flame into the lower hollow of the membrane wall water tube boiler. The lower void of the waste heat boiler is the radiant chamber (high temperature), while the upper part of the boiler contains the convection section.

Fig. 2a shows a somewhat more complex structure which can only be achieved by adjusting the burner 2 according to the invention. Likewise, sulfur is fed to combustor 2 via lines 1,1', and air or oxygen-enriched air is fed via lines 3, 3'.

The decisive factors are: there is no brick lined combustion chamber 4, but the burner 2 is arranged in the same housing as the waste heat boiler and its associated heat exchanger.

The design essentially corresponds to that of fig. 2b, in which fig. 2b part of the generated sulphur dioxide is first fed via line 7 and line 10 to the heat exchanger 11, then to the compressor 12 and finally recycled via line 16 to lines 3 and 3'. Such recirculation of cooled gas can be used to achieve higher SO₂Concentrations of up to 100% by volume.

Figure 2c shows a configuration in which air or oxygen-enriched air is introduced into the system above the first heat exchanger 6 via lines 13 and 14, and combustion is then completed. A second heat exchanger 15 is located above the gas/air input. Thus, a secondary combustion is provided, arranged in the same full length membrane shell. Anoxic substoichiometric combustion is applied to the low-sulfur burner 2 SO that SO is contained₂Also contains gaseous unburnt sulfur S₂Typically, it is cooled to 550 to 700 ℃ at the heat exchanger 6 before the air/oxygen-enriched air is added. By addition of air, S₂Subsequent complete oxidation of the gas to SO₂. Thus, not only the combustion temperature of the first combustion stage is kept low, but also the formation of nitrogen oxides is prevented/reduced due to the limited oxygen content.

Fig. 2d shows alternatively the arrangement of two further burners 2 "and corresponding sulfur supply lines 1". Thus, both combustion temperatures, i.e. the first and second stages, can be kept at a low level and both low NOx values and a higher SO of the total combustion gas can be achieved₂And (4) concentration.

Fig. 3 shows a burner arrangement according to the invention. The burner wall 23 forms a base region with a centre point z. The burner retaining means 22 are mounted on the wall 23, each burner 22 being mounted at the same distance from all other burners 22.

The central axis a is defined as the shortest connection from the burner mounting device 22 to the centre point z. At least one of the burner retaining means 22 is arranged such that the burner flame is angled with respect to the central axis during operation by an angle α.

At least a part of the reactor wall 23 is provided with a tube 25 as membrane wall 24.

This arrangement causes all of the combustion air and combustion gases to circulate/rotate, thereby improving the uniformity of mixing and flow of the gases as they enter the downstream convection section. As a result, the heat transfer in the region near the burner 2 is dominated by radiation, whereas a convection region is established above/downstream the radiation region.

The angle of inclination a may vary from zero degrees or a few degrees to a larger value, for example 15. It is clear that the present concept can be applied to membrane walls of all other shapes.

List of reference numerals

1,1' line

2,2' burner

3,3' line

4,4' combustion chamber

5 burner

6 heat exchanger

7 pipeline

9,10 pipeline

11 heat exchanger

12 compressor

13,14 pipeline

15 heat exchanger

16 pipeline

22,22' burner holding device

23 reactor wall

24 membrane wall

25 tube

a center line

b area of substrate

z center point

Angle alpha