FI111095B - Boiler room ventilation method e.g. for burning spent liquors of pulp industry such as black liquor recovery boiler, combustion air supplied to boiler is taken from inside of boiler room in area of lower half of height of boiler room - Google Patents

Abstract

The method involves combustion air supplied to a boiler is taken from the inside of the boiler room in the area of the lower half of the height of the boiler room. Combustion air is taken in the area of the lowest third of the height of the boiler room. An Independent claim is included for an apparatus in the ventilation of a boiler room.

Description

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Method and equipment for boiler room ventilation

The invention relates to a method according to the preamble of claim 1 for ventilation in a boiler room. The invention also relates to apparatus for boiler room ventilation of the type set forth in the preamble of claim 14.

Boiler plants burn either solid, liquid or gaseous fuel with combustion air. The boiler into which the fuel and combustion air 10 are supplied is usually located in an enclosed, open air boiler room. The boiler room is a building surrounded by a boiler, with walls and a ceiling, usually over 10 meters high, up to several tens of meters depending on the height of the boiler. A typical boiler type for process industry and power generation is one in which the heat generated by the combustion is transferred to the pipes in the walls of the boiler and to the hate water which is converted into steam. The steam produced by the boiler can be used as a source of energy and can, for example, be fed into the same plant processes where the boiler is located.

One typical boiler to which the invention is applicable is a boiler for burning pulp industry waste liquors, for example a recovery boiler.

Combustion air plays an important role in the ventilation of the boiler room. The combustion air of the boiler is usually taken from inside the boiler room, and in order to replace the amount of combustion air, it is necessary to extract the replacement air from the outside. This creates special requirements for ventilation and heating of the boiler room as the seasons change. On the other hand, for example, U.S. Patent No. 4,245,779 discloses a combustion air supply system for a residential boiler in which air is supplied to a heating pan 30 in the basement, both internally and externally. Also, European Patent Application Publication No. 281506 and Swedish Announcement Publication No. 451755 disclose a method of mixing exterior and interior air from a boiler room into combustion air. Applicant's Finnish Patent 96359, to which e.g. U.S. Patent No. 5,709,173 discloses a combustion air supply arrangement for a boiler plant 35, in which outdoor air and indoor air are mixed together for a flow of air to the combustion air duct in proportion to the boiler load and the outdoor temperature.

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The boiler room in which the combustion boiler, for example the combustion plant for pulp industry waste sludge is located, is thus a tall building, the side walls and ceiling of which insulate the boiler from the outside air. Typically, in such buildings that are substantially enclosed from the outside air, the boiler room ventilation is based on the upper combustion air intake openings, the upper exhaust air fans, the lower inlet fans, and a separate ventilation engine room where the outdoor air is heated This is also disclosed in Applicant's Finnish Patent 96359 and US Patent 5,709,173, which describes a boiler plant having a mixing section for mixing exterior combustion air and interior combustion air. In this solution, the intake air intake opening, from which the air can enter the 15 mixing sections, is also close to the roof of the boiler room. The combustion air duct to the lower part of the boiler thus extends from near the roof of the boiler room to the lower part of the boiler room. This combustion air from above the interior of the boiler room and the amount of new air corresponding to the leakage of the walls and roof are blown as the boiler operates into the 20 boiler rooms, either without direct heating or via heating devices. During the warm season, it may be necessary to remove waste heat from the process by blowing additional air into the lower part of the boiler room, which is removed from the top by blowers.

25 Long combustion air duct increases cost and space. A separate heating system is expensive and the ventilation room is expensive and bulky, for example, heating air ducts are expensive and take up space at the bottom of the boiler room, where otherwise combustion air ducts and other piping take up space. Combustion air blowers occupy space when located on the front wall of a cat-30 lan. The upper combustion air intakes help to create a chimney effect, ie high vacuum in the lower part of the boiler room. This causes problems with the operation of the doors and the danger of freezing in the lower piping. The temperature in the boiler room is uneven, ie cold at the bottom and hot at the top.

The object of the invention is to provide a new method for ventilation of a boiler room which does not suffer from the drawbacks of the prior art. The object of the invention is to provide a method by which the ventilation can be implemented more simply and adapted to the requirements of different seasons. To accomplish this purpose, the method according to the invention is essentially characterized in what is set forth in the characterizing part of the appended claim 1.

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The starting point of the invention is that the combustion air of the boiler is taken at least in part from the lower part of the boiler room. The air drawn from the lower part can be conducted in two separate streams, e.g. primary and secondary combustion air into the boiler. The air drawn from the lower part forms the largest part of the combustion air supplied to the boiler. In addition, it is possible to take up even small amounts of air, e.g. tertiary air.

This method makes the combustion air duct short, since the intake point is located much closer to the 15 combustion air supply points in the boiler than in the prior art. In addition, it is possible to take the combustion air externally to the top of the boiler room, where it descends to replace the combustion air entrained in the combustion air ducts, which, when descending downwards, warms up the waste heat of the combustion process. This is advantageous to do during the cold season of the year.

It is also possible to supply some of the combustion air to be sucked into the combustion air ducts from the outside to the lower part of the boiler room by means of blowers, and excess air is removed from the upper part of the boiler room by means of exhaust fans. This is advantageous to do during the warm season, when the air that has been warmed up by the waste heat of the incineration process is removed from the top and the bottom is not overheated.

The apparatus according to the invention, in turn, is characterized by what is stated in the characterizing part of claim 14 of the appended claims. The air intake in the combustion air duct inside the boiler room is at the bottom of the boiler room, leaving the combustion air duct short, which simplifies the structure and reduces manufacturing costs. In addition, since air conditioning can be implemented from outside to inside and out by means of blower fans and waste heat from the boiler, the air conditioning machine room can be omitted.

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The invention also makes it possible to utilize the applicant's invention disclosed in U.S. Patent No. 5,709,173, that is, combustion air can be taken directly from the outside and mixed with combustion air taken from the inside.

For other preferred embodiments, reference is made to the appended dependent claims and to the description which follows.

The invention will now be described in more detail with reference to the accompanying drawings, in which Figure 1 shows a prior art solution, Figure 2 schematically illustrates a boiler room ventilation apparatus and method according to the invention, 15 Figure 3 shows an example of boiler room airflow with an outdoor temperature with a temperature close to 0 °, and Fig. 5 shows a corresponding one when the outdoor temperature is well above zero.

Figure 1 shows a prior art air-25 boiler room replacement apparatus. It discloses the mixing of internal and external combustion air streams in the mixing section 1 according to the aforementioned U.S. Patent 5,709,173 and passing them from the upper part of the boiler room H along a long combustion air channel C to the lower part of the boiler B. The ratio of exterior to interior combustion air is controlled by control mirrors 2 and 3 at respective air intake openings 30. The combustion air channel C has a fan 4 and a heater 5 for preheating the combustion air. The combustion air supply fans 6 are located in the middle and bottom of the boiler room and the exhaust fans 7 at the top of the boiler room. In addition, the boiler plant includes a central air conditioning unit 8 with an air heater and a fan. This central air conditioning unit 35 and the corresponding air conditioning engine room can be omitted from the apparatus according to the invention. At the bottom, there are still convection heaters 9 which blow and heat the indoor air of the boiler room.

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Fig. 2 is a diagram similar to Fig. 1 showing a boiler room ventilation apparatus and method according to the invention. Boiler room H has boiler B, which in the case shown is a recovery boiler, but the invention is also applicable to other industrial and energy boilers. The combustion air from the boiler room H is drawn into the boiler at the intake point C1, from which the combustion air duct C is introduced through the fan 4 to the lower part of the boiler B. The intake point C1, from which the combustion air duct C passes for a distance directly down to the height from which it is introduced into the boiler, is located in the lower half of the internal height of the boiler room at the lower part of boiler room H. Channel C can also come directly from the side or also from the bottom to the entry height into the boiler. In the figure, the entry point Cl is within the lower third of the total height of the boiler room, i.e., at a height less than one third of the total height of the boiler room H. Because the combustion air is supplied to the boiler B from a very low position near its bottom, the length of the combustion air duct C is thus considerably shorter than in prior art solutions.

20 A boiler generally has several levels of combustion air. The figure shows the secondary air intake point C2, which is higher than the primary combustion air intake point C1. Figure 2 also have stepped-dääripalamisilma into the boiler room in the area H height of the interior of the lower half of a side below the range, the 25 intake point C2 can be adapted to the height of the boiler around the middle of the room, a room inside a boiler of the middle range i 'third of the area. From the intake point C2, the secondary combustion air is led along the downward combustion air duct C to the boiler B. The duct C may also come from the side or from below. The combustion duct 30 is inserted in the lower part of boiler B at a position higher than the primary combustion air entry point. Above the sec-combustion air intake point C2 there is still a tertiary combustion air intake point C3, from which downward the combustion air duct C introduced into the boiler B is higher than the sec-35 distal combustion air passage C.

Also, in the channels C of the secondary combustion air and the tertiary combustion air there are corresponding fans 4. The regulators for controlling the amount of combustion air in the section of channels C, which may be control dampers, are designated by reference numeral 3. In addition, FIG. , and the air is mixed to form a common combustion air flow to the boiler in mixing section 5 1. At the beginning of the exhaust air flow passage there is a control device 2 which may be a damper. The control devices 3 and 2 can be used to control the ratio of the intake air to the extract air in the secondary combustion air, and the control principle is described in more detail below.

The combustion air blowers 4 in the ducts C can respectively be placed down. For example, the fans 4 of the primary and secondary combustion air ducts C are preferably located in the lower half of the boiler room height, and the fan 4 of the tertiary combustion air ducts C is preferably located in the middle third of the boiler room height 15. At least part of the combustion air blowers 4, or preferably all, may be located on the side walls of boiler room H.

In addition, Fig. 2 shows the combustion air blowers in the lower part of the boiler room H on the side walls of the building, indicated by reference numeral 6. The blowers are located approximately in the aforementioned height ranges where the combustion air intakes C1, C2 and C3 are located. Without entry points, the building can thus be arranged on different sides of boiler B, so that part is in the lower third of the height of boiler room H and part in the middle third of its height. The air thus enters the boiler room H at the height of the lower and middle part of the building. At the top of boiler room H there are also combustion air inlets 6 and outlets 7. At least some of the inlets 6 and outlets 7 are located in the ceiling of boiler H. Inlet and outlet fans have corresponding control devices, such as dampers 30, for controlling the amount of air.

With boiler B running, combustion air is drawn from the air intake C1 at the bottom of the boiler room. The air intake point C2 of the secondary combustion air is also relatively low. The primary and secondary combustion air supplied to boiler B 35 through their own combustion air channels C together form the bulk of the combustion air supplied to boiler B. In Figure 2, both primary and secondary combustion air is taken from the lower half of the boiler room. Secondary combustion air intake may also be located upstream, e.g. in the middle third of the height of the boiler room. In all cases, air should be led to the combustion air intake points in the lower part of the boiler room to replace the combustion air drawn into the combustion air ducts C. Depending on the ambient heat state, this can be accomplished in two different ways, which will be described below.

In cold seasons, replacement air is supplied from above, i.e., the inlet fans 6 at the top of boiler room H are used. . The mixing of the air with the air in the boiler room can be ensured by providing a circular movement of the blown air around the boiler, i.e. its main flow direction is spiral instead of vertical. This can also enhance the incoming air heating from boiler B to the waste heat entering boiler room H. The circulation movement can be accomplished by directing the inlet fans 6 to supply air in the inclined direction and / or by auxiliary fans inside the boiler room. The heat of the lower part of the boiler room 20 H is ensured by the circulation air heaters 9, which also act as heaters for the boiler room when the combustion process is stopped.

During the warm season, the boiler room is prevented from overheating by also supplying 6 combustion air to the boiler room walls with inlet fans at the bottom to replace the combustion air drawn from the air intakes C1, C2 and C3. The second part of the replacement air is still supplied from above by the inlet fans 6. From the top, the warmed-up air from the process is removed from the top by the outlet fans 7, shown in Fig. 2, in the ceiling.

Figure 2 illustrates how the secondary combustion air duct can * * draw air simultaneously from both the interior air intake point C2 and from the outside of the boiler room via a wall control device 2. According to Figure 2, the primary combustion air and the tertiary combustion air are taken from the inside only, but it is possible to provide either or both of these in a similar manner with an additional duct that can supply some or all of the combustion air directly from the outside. When the combustion air 8111095 is taken directly from the outside into the combustion air duct C, there is less need to bring in replacement air from outside, thereby preventing excessive boiler room cooling during cold seasons, and even external combustion air can require even combustion air directly from outside the boiler room. The arrangement therefore provides particularly good control during the cold season, when the air supplied to the combustion air duct C can be used to regulate the air flow in the boiler room and influence its cooling.

10 The following describes the principles of ventilation in a boiler room in three different situations where the ambient temperature depends on the weather. The situations are mainly seasonal, but it may also be necessary to change or at least fine-tune the ventilation due to the daily temperature variation. The air volumes shown in Figures 3-5 are relative and are intended only to illustrate the principle of air exchange at different temperatures and not as a general design guideline. The relative unit V of air volumes is directly proportional to the normal-liquid cubic meters per unit time.

Figure 3 shows schematically the air flows of boiler room H at -18 ° C. Of the three combustion air planes, most combustion air enters the secondary combustion air duct, and in the situation of relatively severe frost in Figure 3, this maximum amount of air is taken directly from the outside and no air is drawn from the boiler room through intake point C2. Primary and tertiary combustion air in the ducts at positions C1 and C3 is replaced mainly by blowing in from the outside above these air intakes. Some of the air is also brought to the bottom of the boiler room from the side and heated. The diagram does not show leakage air. Fig. 3 further shows how a part of the inflated air (INPUT 3) can be heated (+ 15 ° C), i.e. in this case the supply air is connected to the circulating heater 9 of Fig. 2, i.e. the exiting air is inflated through the circulating air heater 9. However, also in the case of Figure 3, INPUT 3 can be blown raw from the outside.

Figure 4 shows the situation at an outdoor temperature of 0 ° C. The secondary air combustion air duct receives combustion air both directly from the outside and from boiler room H. Replacement combustion air is supplied from both the 35 9 111095 top and the bottom into the bottom of the boiler. There is thus a situation in which approximately equal amounts of replacement air are introduced by means of the upstream blowers 6 and downwards by the blowers 6 on the wall of the boiler room.

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Finally, Figure 5 shows a situation where the outdoor air temperature is + 25 ° C. All combustion air is drawn into the secondary combustion air duct from inside the boiler room via air intake C2. In the lower part of the boiler room H, more air 10 is introduced here from the side through the fans 6 than in the previous examples and it is removed by the exhaust fans 7 at the upper part of the boiler room. The replacement combustion air is also blown from the top into the boiler room.

The invention is not limited to the above embodiments, but may be modified within the scope of the inventive idea defined in the claims. The individual devices described above may be replaced by equivalent elements without changing the operation of the invention. In principle, the boiler may be a process or power generation boiler other than a recovery boiler or a similar pulp industry waste liquor boiler. Other boilers may also have several separate combustion air ducts and, at the height of the boiler, different points from which combustion air is introduced.

Claims (21)

A method of ventilating a boiler housing (H) in which combustion air is conducted to a boiler (B) for process industry or energy production from the inside of the substantially closed boiler ambient, over 10 m high boiler housing, characterized in that combustion air to be led to the boiler is taken from the inside of the boiler housing in the area of the lower half of the boiler housing (H) height. 10 Method according to claim 1, characterized in that combustion air is taken in the region of the lower third of the height of the boiler housing (H). Method according to Claim 1 or 2, characterized in that combustion air is taken into the boiler in the form of two or more combustion air flows, such as a first and a second combustion air or a first, a second and a third combustion air flow. Method according to claim 3, characterized in that the second combustion air is taken from the inside of the boiler housing (H) above the intake point (C1) for the first combustion air. Method according to claim 3 or 4, characterized in that the second combustion air to be introduced into the boiler is taken in the range of the lower half of the height of the boiler housing (H). Process according to any of claims 3-5, characterized in that the second combustion air is taken in the region of the middle third of the height of the boiler housing (H). 30 Method according to any of claims 3-6, characterized in that most of the combustion air to be taken from the inside of the boiler housing (H) is taken in the region of the two lower thirds of the height of the boiler housing (H), preferably in the area of the boiler housing (H). bottom half 35 of the boiler house height. Method according to any of the preceding claims, characterized in that replacement air is taken from outside into the upper housing of the boiler housing (H), from which it is allowed to flow downstream to one or more intake pipes. places (C1, C2, C3) for combustion air. Method according to claim 8, characterized in that the replacement air is circulated around the boiler (B) at the same time as it flows down. Method according to claim 8 or 9, characterized in that replacement air is introduced into the boiler housing also in the lower part of the boiler housing (H) and the excess air is removed from the upper part of the boiler housing. 11. A method according to claim 10, characterized in that in the lower part of the boiler house the amount of air flowing into the boiler housing (H) is changed according to the temperature of the outdoor air. Method according to any of the preceding claims, characterized in that combustion air to be conducted to the boiler is taken partly from inside and partly directly from the outside, or combustion air is taken completely directly from the outside, whereby at least another combustion air is taken at least partly from the interior of the boiler (H). ). 13. A method according to claim 12, characterized in that the ratio between the combustion air taken from inside and outside is determined at least according to the temperature of the outdoor air, so that when the temperature of the outdoor air is lower, more combustion air is taken directly from the outside. Device for ventilating a boiler housing (H) with a boiler housing (C1) for combustion air, located within the substantially closed boiler (B) of process industry or energy production, located above the boiler housing (H), characterized in that (C1) is in the region of the lower half of the height of the boiler housing (H). Device according to Claim 14, characterized in that the entry point (C1) lies in the region of the lower third of the height of the boiler housing. 15 or 1095 Device according to claim 14 or 15, characterized in that it comprises intake points (C1, C2, C3) for two or more combustion air. Device according to claim 16, characterized in that the intake point (C2) for the second combustion air is above the intake point (C1) for the first combustion air. Apparatus according to claim 16 or 17, characterized in that the intake point (C2) for the second combustion air lies in the region of the lower half of the height of the boiler housing (H). Device according to any of claims 16-18, characterized in that the intake point (C2) for the second combustion air lies in the region of the middle third of the height of the boiler housing (H). Apparatus according to any of the preceding claims 14-19, characterized in that the fans (6) or the like for the replacement air are located in the upper part of the boiler housing (H) higher than the combustion air intake points (C1, C2, C3), preferably above the boiler. (B). Apparatus according to any of the preceding claims 14-20, characterized in that at least one combustion air duct (C) is connected to a combustion air intake point (C2) and also a combustion air intake point directly from the outside.