SE500037C2 - Method for purifying SO 7x] containing flue gases - Google Patents

Abstract

In a method for cleaning SOx-polluted flue gases from a combustion process, the flue gases are, in a gas-cleaning zone (20), passed through a gas-cleaning bed (22) of an SOx-absorbing substance which, once polluted and heated by the flue gases, is circulated out of and back to the gas-cleaning zone (20) in a circulation path which passes through a cooling zone (30), where the substance is directly contacted with a cooling medium in order to be cooled, and a separating zone (40), where sulphur pollutants are removed. The gas-cleaning bed (22) is gradually displaced into the cooling zone (30) where it instead forms a cooling bed (32) through which the cooling medium is passed. The bed is displaced through a channel (21, 50, 31) of annular cross section, such that the substance is fed as a tubular body (22, 53, 32) through the channel running through the gas-cleaning zone (20) as well as the cooling zone (30). The flue gases and the cooling medium are passed substantially radially through the bed in the gas-cleaning zone (20) and the cooling zone (30), respectively.

Description

5.00 057 10 15 20 25 30 2 the air flow, reliability and repair problems. which entails both high construction costs Secondly, the method according to SE 442 777 causes unwanted air and gas shocks that occur during the shift of the flows and which, among other things, carry fine particles from the bed material into the chimney outlet.

Thirdly, it arises in the method according to SE 442 777 problems associated with the way in which the substance in In SE 442 777 is output after some time operating granules from the beds to a separation device it is renewed / purified. such as a rotating drum, in which sulfur contaminant and dust particles are removed. After this agreement separation, the granules are returned to the bed. This solution undesirable means that even non-"pre-cooled" bedding material will be discharged from the magazine to the device, which means that heat energy goes lost. In addition, the cleaning of the bed will not be continuous. with uneven gas purification effect as a result. for the purpose of come a substantially dry flue gas purification method as on a efficiently, easily and cheaply achieves an SOX purification of flue gases from a combustion process.

The present invention has The invention also has for its object to simultaneously enable high utilization of the energy content of the fuel hold.

The invention has for its special object to provide a substantially dry flue gas purification method that avoids them problems identified above, which are associated with the purification technique of the type specified in SE 442 777.

These objects are achieved by a method according to claim 1.

According to the invention, there is thus provided a method for purification of SOX-contaminated flue gases from a combustion plant process, which method includes the following actions: 10 15 20 25 30 35 500 037 3 in a gas purification zone to allow the flue gases to pass by a substantially dry gas purification bed of an SOx absorber contaminant, to circulate such a substance, when it has been contaminated and heated by the flue gases, out and back to the gas the purification zone in a circulation path passing through a cooling zone, in which the substance is brought into direct contact with a cooling medium for cooling, and a separation zone in which sulfur pollutants are removed from the substance, that the gas purification bed is gradually shifted into the cooling zone to instead form a cooling bed in this zone, through which the refrigerant is passed, that said successive displacement of gas purification the bed from the gas purification zone to the cooling zone is provided via a tubular member extending in the direction of displacement channel for the substance, which channel passes through both gas the purification zone and the cooling zone and through which the substance is fed forward as a tubular body from an input end at the gas purification zone to a discharge end at the cooling zone, and that the flue gases and the coolant are passed radially through the bed in the gas purification zone and cooling zone, respectively. zones.

According to the invention, the gas purification bed is displaced thus successively out of the gas purification zone and into the cooling zone to instead form a cooling bed in the cooling zone, through which the refrigerant is passed. After cooling for the substance is removed from the cooling bed, through the separation zone and back to the gas purification zone. According to the invention form thus the gas purification bed and the cooling bed together one cohesive body. The channel can be, for example perforated in both the gas purification zone and the cooling zone. This tubular body, BED, for example, does not have to be circular. which thus forms a coherent can have virtually any cross section and The method according to the invention offers several advantages, among other things, a more efficient utilization and thus a lower one Eífid 037 10 15 20 25 30 35 4 consumption of the SOX absorbent, an effective whether the purifying effect of the SOX absorbent substance through that this is cooled, the possibility of recovering heat from gases, as well as a generally more rational treatment process.

Compared with purification techniques of that used in SE 442 777 given the kind can the following differences and advantages further noted: a) The requirement to use two or several separate magazines and valve mechanisms for alternating control of flue gas and air flow. Both the flue gas flow and the refrigerant flow can be continuous. This means partly a cost saving, partly increased reliability, and partly that the said air and gas shocks are avoided. b) By the cooling taking place in a gas purification zone separate cooling zone enables more efficient utilization of the energy content of the heated material. c) The degree of purification in the gas purification zone increases and becomes smoother. d) A continuous circulation of the SOx absorber the subject becomes possible.

The circulation of the SOX absorbent is performed preferably continuously or at least substantially continuously during the combustion process.

It is preferred that instead of a mechanical valve device to prevent mixing of smoke the gases and the refrigerant, use the substance itself as "materiallàs". The transfer of the substance between the gas purification zone and the cooling zone can be provided by means of a connecting channel of suitable length, which has the same or substantially the same cross-section as the tubular bed and which connects to an outlet opening with a corresponding cross section of the gas purification zone and to an inlet opening with corresponding cross section of the cooling zone. It is also conceivable 10 15 20 25 30 35 500 057 5 to completely eliminate such a connection channel and instead connect the gas purification zone directly to the cooling zone.

The refrigerant may, as is known per se SE 442 777, be air which in the cooling zone is brought to pass in direct contact with the substance and as after such heating in the cooling zone is used as combustion air in the combustion the process.

Of course, it is also possible to use it recovered heat in other ways, such as combustion air to another combustion process. It is also conceivable to use a liquid coolant The SOX absorbent may be limestone, such as dolomite, or other mineral with similar properties.

For simplicity, it is used in the following description of exemplary embodiments the term "limestone" as a non-limiting boundary examples representing the said substance, but it should be emphasized that any reference to limestone should also refer to all possible SOX absorbers substances useful in the invention.

The invention will now be described in more detail by examples, with reference to the accompanying drawings sheet which schematically explains the method according to the invention. toden.

Fig. 1 shows a flow chart for explaining the principle of the invention.

Figs. 2A, 2B and 2C show an end view, a side view and a top view of a facility for the implementation of the process in Fig. 1, in which plant the provides two separate beds.

Fig. 3 shows schematically and on an enlarged scale one modified design with two separate beds.

Fig. 4 shows schematically and on an enlarged scale one design with a common bed.

Parts with the same function generally have the same display designations in the figures.

E90 057 10 15 20 25 30 35 6 In the flow chart in Fig. 1, flue gases are fed from a non shown boiler through a channel 1 to a damper 2, which is set to direct the flue gases into a channel 3 to the treatment plant, which is generally designated 10.

After completion of purification in the treatment plant 10, is carried out the flue gases in return via a duct 4 out through a chimney at 5.

The treatment plant 10 comprises three zones: one gas purification zone 20, a cooling zone 30 and a separation zone 40.

In the embodiment shown, these three zones are arranged in mentioned order in a circulation path for limestone.

The gas purification zone 20 comprises a first container 21 containing a gas purification bed (not marked) of limestone Stone. The limestone is removed from the container 21, ie from the gas purification bed, via a bottom sealing against the flue gases valve 22. The limestone is fed into this first container 21, ie to the gas purification bed, via the feed opening 23 in the upper part of the container 21. The flue gases from the boiler is fed into the container 21 through the above-mentioned channel 3, which opens with a downwardly directed end piece 24 in the gas the purification bed in the lower part of the container 21. the gases leave the container 21, after passing through the through the gas purification bed, via one or more openings 25 at the upper part of the container 21, which openings 25 are closed to the return channel 4.

The cooling zone 30 comprises a second container 31, which is arranged below the gas purification container 21 (see also Figs. 2A and 2B) and is connected with an inlet to the bottom valve 22 for receiving limestone from the gas lower part of the bed. The one from the gas purification bed taken limestone forms a cooling bed (not marked) in it the lower part of the second container 31. Limestone from the cooling bed discharged through a bottom valve 32.

A coolant, here in the form of combustion air to the boiler, is fed by means of a fan 33 through one of the containers 31 lower part and channel 34 opening in the cooling bed. After 10 15 20 25 30 35 500 057 7 passage through the cooling bed, the air is led out through outlet 35 at the upper part of the container 31 for use as a combustion air. The bottom valve 32 seals against air leakage from the container 31 in connection with the discharge of limestone from the cooling bed.

Separation zones 40, cooling zones 30 via a channel 41, which receives limestone from includes in series a drum a screen unit 43 and a buffer container 44. the stone is transferred from the separation zone 40 to the gas ma 42, via a channel 45 to pass through the openings 23 returned to the gas purification bed in the first container 21. ' The plant 10 is illustrated on a larger scale in fig 2a-c.

The operation of the plant 10 in Figs. 1 and 2a-2c will now be described in more detail.

Hot, SOX-contaminated flue gases from combustion the process in the boiler is fed by means of a fan via 3 down in the lower part of the gas purification bed in the gas purifier 20. The polluted and hot flue gases as then in direct contact with the limestone, which absorbs the sulfur oxides with the result that on the limestone grains in the bed is deposited "shell" of contaminants. Limestone re- The effect decreases as this shell grows and in as the limestone is heated by the flue gases.

As the flue gases flow upwards through the gas bed, they encounter an increasingly cleaner and colder limestone stone, meaning that the purification effect increases gradually upwards in the gas purification bed. They finally purified and cooled flue gases are fed via the return duct 4 to the stone discharge 5.

The flue gases are continuously led into the treatment plant during combustion, and for gas purification the bed must be effective at all times, there is a continuous replacement of the limestone in this bed by removal of contaminated and heated limestone through the bottom LV! (Il 03 10 15 20 25 30 35 8 valve 22 and by filling purified and cooled limestone through the inlets 23 in the upper part of the container 21.

The discharge speed can be controlled by means of the bottom valve. It should be noted that the flue gases in the gas purification the bed is prevented from leaving the container 21 by the bottom tenventilen 22.

The limestone polluted and heated by the flue gases is then introduced by gravity holder 31 for filling the cooling bed 31. nom bottom valve 32. For cooling of in the cooling zone 30 in this container At the same time, cooled limestone is removed from the cooling bed the limestone is led air through the cooling bed in direct contact with the limestone, and the heated air is used in this embodiment as preheated combustion air to the boiler not shown.

Cooled limestone is fed from the cooling zone 30 to the separator. zone 40 in which the limestone undergoes a treatment process for separating said shell. This is done ge- by allowing the limestone to first pass the drum 42 in which the shell is broken down, and then through the sight unit in the decomposed shell is sieved away for disposal (reference numeral 46). Fig. 2b shows a screw transfer porter 47 for further transport of the landfill waste from the sight unit 43.

If necessary, new limestone is added to the circulation as shown by reference numeral 48.

With regard to the transport of limestone in circular the transmission path between zones 20, 30 and 40, the the gate from the gas purification zone 20 via the cooling zone 30 to the drum 42 with gravity. Transport from the drum 42 via the screen unit 43 to the buffer container 44, mechanization takes place. niskt. The return of purified and cooled limestone through the channel 45 is pneumatic.

The limestone thus purified is then introduced into the buffer container 44 for feed to the gas purification the bed. 10 15 20 25 30 35 500 057 9 Fig. 3 shows a variant of the embodiment in Fig. 1 and 2a-c, where the gas purification zone 20 and the cooling zone 30 have a got different design. In Fig. 3 is the gas purification bed denoted by 26 and the cooling bed by 36. Parts with corresponding functions in Fig. 1 and Fig. 3 have the same reference designations.

The first container 21 and the second container 31 upper cylindrical outer walls 21a and 31a, respectively are here perforated to allow the passage of flue gases respective cooling air. The lower parts of the containers 21 and 31 are as in Fig. 1 funnel-shaped and opens into bottom valves. 22 and 32, respectively. Furthermore, the beds 26 and 36 downward direction as in Fig. 1.

The first and the second container 21 resp. 31 i Fig. 3 is enclosed by respective annular space 27, respectively. 37, which are delimited radially outwards by a cylindrical wall 28 and 38, respectively, and radially inwardly of the perforated container walls 2la and 3la, respectively, and of tin and top walls. The polluted flue gas from the boiler led via the channel 3 to the annular space 27, and the cooling air is led to the annular space 37.

Hollow, perforated pipe sections 29 and 39, respectively extends from the top down centrally in the first container clean 2l and the second container 31. The pipe section 29 connects upwards to the channel 4 which leads away purified the flue gas from the gas purification zone 20. The pipe section 39 connects upwards to the duct 35 which dissipates heated cooling air from the cooling zone 30.

In Fig. 3, the flue gases and the cooling air thus pass radially inwards through the respective bed 26, 36 in the annular shaped upper part of the bed, to then flow upwards through the pipe section 29 and 39, respectively.

Fig. 4 shows a variant of the gas purification zone 20 and the cooling zone 30 with a single continuous bed, wherein it part forming a gas purification bed is designated 26 and it part which forms the cooling bed is designated 36. An intermediate 500 057 10 15 20 25 30 35 10 the part of the continuous bed is designated 56 and acts as a "material lock".

As in the embodiment in Fig. 3, there are annular spaces 27 and 37 for receiving the flue gases respectively tive cooling air. The flow directions are as in Fig. 3 also first radially inwards through the respective bed and out vertically, but with the difference that it the heated cooling air in Fig. 4 flows vertically downwards.

The difference from Fig. 3 lies mainly in the fact that valves 22 and 32 are missing and that the transmission of limestone from the gas purification zone 20 to the cooling zone 30 instead of is achieved by displacing the bed as a continuous modern tubular body with constant cross section. For for this purpose, an annular connecting channel 51 is used. arranged between the gas purification zone 20 and the cooling zone 30.

In the portion between the gas purification zone 20 and the cooling zone 30 the limestone bed acts as a material lock 56 which prevents the cooling air from reaching the gas purification zone 20 and, which is more important, the flue gases prevent reaching the cooling bed 36.

To amplify the latter "valve effect", they can the fans necessary for the process are placed so that the intended to drive the cooling air through the cooling bed (pre) the cooling bed 36 and the fan for the the gases are located downstream (after) the gas purification bed 26. is upstream As a result, the pressure of the flue gases in the gas purification zone 20 becomes slightly lower than the pressure of the cooling air in the cooling zone 30. I event of gas transport in any direction through material the lock 56, this will consist of air reaching the gas the purification zone 20 by overcoming the pressure drop which the material load 56 gives rise to. Also variants where the principle of material locking is combined with any mechanical valve or lock device possible.

It is also conceivable to let flue gas in Figures 3 and 4 each cooling air is transported in vertically and out horizontally.

Claims (6)

10 15 20 25 30 590 057 ll PATENT REQUIREMENTS A method of purifying SOX-contaminated flue gases from a combustion process, the method comprising the steps of: in a gas purification zone (20) passing the flue gases through a substantially dry gas purification bed of a SOX absorbing substance, and circulating such a substance, when it has been contaminated and heated by the flue gases, out from and back to the gas purification zone (20) in a circulation path passing through a cooling zone (30), in which the substance is brought into direct contact with a cooling medium to be cooled, and a separation zone (40) in which sulfur impurities are removed from the blank, characterized by: that the gas purification bed (26) is successively displaced into the cooling zone (30) to instead in this zone form a cooling bed (36), into which the cooling medium is introduced passing by said successive displacement of the gas purification bed from the gas purification zone (20) to the cooling zone (30) via a tubular channel of the blank extending in the displacement direction, which duct passes through both gas purification the zone (20) and the cooling zone (30) and through which the blank is fed as a tubular body (26, 56, 36) from an inlet end (23) at the gas purification zone (20) to an outlet end at the cooling zone (30), and that the flue gases and the cooling medium is passed radially through the bed in the gas purification zone (20) and the cooling zone (30), respectively. Method according to claim 1, characterized in that the flue gases are caused to pass radially inwards through the beds in the gas purification zone (20). 3. A method according to any one of the preceding claims, characterized in that the cross section of the annular channel and the tubular bed accommodated therein is substantially constant. 10 12 A method according to any one of the preceding claims, characterized in that the circulation of the SOX absorbent substance is carried out continuously or at least substantially continuously during the combustion process. Method according to one of the preceding claims, characterized in that the cooling medium consists of air which, after heating in the cooling zone (30), is used as preheated combustion air in the combustion process. Method according to one of the preceding claims, characterized in that the SOX absorbent substance is limestone.