The present invention relates to an industrial chimney having improved durability. More in particular, the present invention relates to industrial chimneys for discharging flue gas into the atmosphere, typically power plant chimneys, with an inner lining of a cellular glass block system that is attached to the inside wall of the chimney with an adhesive, and that are less maintenance-prone.

Industrial chimneys are tall up to several hundred meters and slender upright structures, which are used to discharge waste/flue gases derived from industrial processes, at higher elevation with sufficient exit velocity such that the gases and suspended solids (ash) are dispersed into the atmosphere. Generally they are circular in cross section.

Power plants are examples of industrial systems, wherein a wide range of fuels (coal, oil, petroleum coke, lignite, biofuels) is converted into power. The flue gasses of the combustion processes are discharged via one or more chimneys.

To protect the chimney against aggressive components of the flue gas, in particular if the chimney is prepared from concrete, a lining must be applied on the inside. The lining must have excellent chemical resistance, temperature resistance, resistance to extreme thermal cycles from hot to cold and vice versa, high resilience and durability. For this purpose closed-cell glass blocks may be used.

Borosilicate closed-cell glass blocks have been used as chimney lining system. The borosilicate closed-cell glass blocks may be applied on a substrate (steel, concrete or brickwork; e.g., inner wall of a chimney) by way of a primer (depending on the nature of the substrate) and an adhesive. Indeed, linings made of (borosilicate) closed-cell glass blocks have excellent chemical resistance, temperature resistance, resistance to extreme thermal cycles from hot to cold and vice versa; high resilience and durability.

Such linings are applied in new chimneys, but also in existing chimneys. For instance PENNGUARD™ linings are provided by Hadek with a full 10 year warranty.

The adhesives that are used for such linings tend to be slightly permeable by liquid vapour, subject to pressure, temperature and composition of flue gasses. Due to the chemically aggressive compounds in the flue gas, permeation has a negative effect on the service life of the lining and the chimney construction's life.

Improvements in the service life of this lining are highly desirable, thereby decreasing the need for maintenance and/or repair to the chimney. Surprisingly, such an improvement has now been found.

Accordingly, the invention provides an industrial chimney for discharging a flue gas into the atmosphere, the chimney comprising a substrate defining an upright flow channel having an inlet and an outlet at its upper end, the substrate being provided with an inner lining comprising closed-cell glass blocks, attached to said substrate with use of an adhesive and optionally a primer, wherein the flow through area of the upright flow channel is increased in size in an upper part of the flow channel in the direction of the outlet.

The industrial chimney according to the invention comprises a substrate, also known as shell. An inner lining made of closed-cell glass blocks, is clad to the interior wall of the substrate using a suitable adhesive and optionally a primer. The substrate with its inner lining defines an upright flow channel having an inlet, typically in a lower section of the chimney, for receiving the gas to be discharged, and an outlet at its upper end for discharging the flue gas into the atmosphere. The flow channel has a flow through area perpendicular to the longitudinal (upright) axis of the flow channel.

According to the invention the flow channel has an upper part of which the flow through area is larger than the flow through area of an adjacent lower section of the flow channel. Thus the flow through area is not constant over the entire length of the flow channel. Preferably the flow through area of this upper part gradually increases towards and up to the outlet at the upper end. E.g. the upper part may have an inverted frustoconical shape or a bell mouth shape . The increased flow through area prevents the occurrence of substantial

overpressure in the flow channel, even under worst conditions, while maintaining a sufficient flow rate of the flue gas for effectively dispersing the flue gas in the atmosphere. By inhibiting (local) overpressure permeation of the aggressive flue gas into the adhesive is reduced or effectively eliminated, thereby increasing the durability of the lining and consequently its service life. Without wishing to be bound to any theory, below a more detailed explanation is presented.

It is well established that chimneys for power plants can be built economically by applying a glass block lining system to the inside of a e.g., reinforced concrete chimney, avoiding the use of any internal flue. The method of construction is typically by slip form of the reinforced concrete chimney, similar to the construction of any other chimney. It is however less well known that in many power plant chimneys, the volume of flue gas creates overpressure in the chimney. This overpressure creates a negative effect on organic components of the lining systems, i.e., the adhesive and optionally primer, if used, that are permeable at certain temperatures and pressures. Glass block linings are permeable through their joints. It has been witnessed in select cases that this can have a negative effect on the service life of the lining, which has to exceed 30 years, increasing the need for maintenance and/or repair to the chimney.

Surprisingly, it has been found that an elegant solution in order to extend the service life is to reduce the negative effect of pressure conditions on the organic components of the lining systems. Permeation can be described with Fick's First law. This approximation tells us that:

(1 ) increased pressure increases permeation rate, and

(2) increased thickness reduces permeation rate.

Up to now permeation could only be reduced by increasing the thickness of the applied adhesive layer (typical between 3 mm and 60 mm). However, in specific cases full permeation of the lining cannot be completely ruled out in case of positive pressure and long periods of continuous service life.

The normal route of decreasing pressure, widening the flow channel diameter, would have a negative effect on the flue gas velocity and the space required to construct such an increased diameter chimney.

Nonetheless, the present inventors continued to explore this unlikely path to solve the issue of failure in the adhesive system and came up with an elegant, alternative solution.

When a chimney is constructed with an upright flow channel having a flow through area that increases in size in the upper part thereof, the inventors realized that they can decrease the overpressure over the total chimney height, as the under-pressure is increased. In other words, the upper part of the flow channel having an increased flow through area eliminates overpressure and prevents the permeation of water and acid into the organic components and thus increases the lifetime of the lining and chimney and reduces maintenance thereof. Additionally this expanding upper part increases the natural draft of the chimney. This in turn may result in less auxiliary power being consumed by the power plant in particular its (final pump or fan in the flue gas system, thus reducing the fuel consumption of the power plant per produced MWh.

It is not necessary per se that the upper part having a flow through area that increases in size is provided with a cell glass block lining as described above, but advantageously it is. The dimensions of the upper part of the upright flow channel can be easily determined by the person skilled in the art. Generally the upper part will be in the upper half of the chimney length.

The angle vis-a-vis the inner periphery of the upper part or its tangent at the transition position and the longitudinal axis of the flow channel may be anywhere up to 60° in case of a linear, curved or a hyperbolical increasing upper part. More preferably, the angle is 45° or less, more preferably 30° or less, more preferably in the range of 4-10°, in particular between 6 and 8° for reason of maintaining appropriate flow conditions and preventing turbulence..

The height of the upper part is relative to the height of the entire chimney. Obviously, this part should not adversely affect the stability of the chimney construction nor impact adversely the flow behaviour of the flue gas. Typically the height of the upper part is 25 metres or less. Typically, the industrial chimneys according to the invention are between 50 and 400 meters high, preferably from 100-175 metres high. Although the general shape of the cross section (flow through area) of the flow channel, such as square, rectangular, elliptical is not critical, typically the flow through area will be circular with diameters ranging from 3 meter to 15 metres, preferably 4-10 metres, at the beginning (lower end) of the upper part.

The chimney is preferably a power plant chimney.

The substrate of the chimney can be steel, brick or concrete, preferably concrete, more preferably reinforced concrete. For instance, the chimney may be formed by slip forming or jump forming.

Borosilicate closed-cell blocks work best, although alternative closed-cell glass blocks may be used. The PENNGUARD™ lining system is a preferred embodiment.

The present invention addresses the issue of permeation into the organic components of the inner lining, in particular into the adhesive. Preferably an acid resistant adhesive is used. Any adhesive known in the art for this application may be used. Examples of suitable adhesives comprise silicone based adhesives and polymer asphalt adhesives such as urethane asphalt adhesives.

The use of a primer is optional, depending on the substrate, nature of the lining blocks and also depending on the adhesive used. For reinforced concrete chimneys preferably a primer is used. Suitable primers comprise among others epoxy primers.

The present invention also relates to a process for the construction of the industrial chimney as discussed above. This process comprises the steps of

(a) providing a lower section of a substrate defining an upright flow channel; which is provided with an inner lining comprising closed-cell glass blocks, attached to said substrate with use of an adhesive and optionally a primer;

(b) constructing a top section from a substrate, which defines the upper part of the upright flow channel; wherein the flow through area of the upright flow channel increases in size in the upper part of the upright flow channel in the direction of the outlet.,

The present invention may be applied in new chimneys, but also in existing chimneys. For instance in step a) the top of an existing chimney having a substrate and inner lining may be removed and replaced with an expanding upper part as explained above. In that case only the top section of the substrate is rebuilt and advantageously provided with the lining system of optional primer, adhesive and closed-cell glass blocks, thereby establishing the upper part of the flow channel having an increased size of its flow through area towards the outlet. In other words, this embodiment is a method of extending the lifetime of the inner lining of an already existing chimney by applying an upper part as described above.

The chimney of the present invention may also be built directly with an upper part according to the invention. The substrate is erected or constructed. The inside of the substrate may then be treated with a primer. Next the closed-cell glass blocks may be applied with the (acid resistant) adhesive, at least the lower section up to said upper part. The present invention therefore also comprises a process for the construction of new chimneys, as well as a process for the refurbishing of existing chimneys.

The present invention is also directed to the use of the new chimney, for the purpose of reducing the fuel consumption of a power plant per produced MWh. It has appeared that the power consumption used for the (final) pump/fan in the flue gas treatment system can be substantially reduced by application of the upper part to the chimney.

Finally, the invention resides in an industrial plant for performing a process resulting in a flue gas to be discharged, comprising an industrial chimney as discussed above. A preferred embodiment thereof is a power plant for converting a fuel into electricity.

The invention is illustrated by the attached drawing, wherein.

Fig. 1 shows an embodiment of the industrial chimney of the present invention,

Fig. 2 shows a detail of the embodiment of Fig. 1 ;

Fig. 3 a)-d) illustrate an embodiment of a prior art industrial chimney , as well as the pressure in view of the height in the flow channel thereof; and.

Fig. 4 a)-d) illustrate the embodiment of Fig. 1 , as well as the pressure in view of the height in the flow channel thereof.

In Fig. 1 an embodiment of an industrial chimney 10 is shown. The chimney 10 has an upright configuration defining an upright (vertical) flow channel 12.. An inlet 14 for introducing flue gas derived from an industrial plant 13, such as a power plant, into the flow channel 12 is provided near the lower end 15. An outlet 16 at the upper end 18 of the chimney 10 discharges the flue gas from the flow channel 12 into the atmosphere. The flow direction of the flue gas is represented by arrows A. The chimney 10 comprises a lower section 20 from the bottom end 15 up to transition 22. In this lower section 20 the flow channel 12 has a constant flow through area. From this transition 22 up to the outlet 16 the flow through area increases gradually. This upper section from transition 22 up to outlet 16 is indicated by numeral 24. In the embodiment shown having a circular cross section of the flow channel, the diameter thereof increases linearly as a function of the height.

Fig. 2 shows details of the construction of the embodiment of Fig. 1. An outer substrate 26 e.g. made from reinforced concrete, is provided at its inner surface 28 with a primer layer 30, to which borosilicate closed cell glass blocks 32 are fixed using adhesive 34.

The angle a between the sloping surface of the blocks 32 which delimit an upper part 36 of the flow channel 12 having a gradually increasing flow through area and the longitudinal vertical axis of the flow channel is approximately 8°. The part of the substrate below transition 22 is indicated as lower section 40, while the part above the transition is top section 42. Fig. 3 a) shows an embodiment of a prior art chimney 1 10 having an inlet 1 14 and outlet 116 and flow channel 1 12. The lining (not shown) thereof is of a configuration similar to that shown in Fig. 2. Fig. 3 b) shows the pressure in the channel 112 as function of the height h under optimal conditions , showing a linear decreasing course towards the outlet 1 16. Fig. 3 d) shows the pressure in worst conditions, from which it appears that over the full length of the chimney a positive pressure is present at the lining. Fig. 3c) represents common conditions..

Fig. 4 a)-d) represent the embodiment of an industrial chimney of Fig. 1 according to the invention and the prevailing pressures under the same conditions as Fig. 3 b)-d)..

From comparing Fig. 3 and Fig. 4 it appears that providing an upper part 36 having an increasing flow through area of the flow channel 12 under optimal conditions (Fig. 3 b); Fig. 4 b)) the under-pressure is increased in the chimney according to the invention. Under common conditions (Fig. 3 c); Fig. 4 c)) there is overpressure in the prior art chimney, while in the chimney according to the invention under-pressure is present. Although under worst conditions (Fig. 3 d); Fig. 4 d)) there is overpressure in both chimneys, the net pressure in the chimney according to the invention is still negative and the maximum overpressure is reduced. Thus under all circumstances the chimney according to the invention offers an increased lifetime of the inner lining.