Boiler Unit

Abstract

The invention is concerned with an integrated unit comprising a unitary boiler and gas cleaning apparatus. Preferably the integrated unit comprises a boiler unit, and gas cleaning apparatus, the integrated unit has a reaction unit and further comprises a radiant zone connected to the reaction unit, the radiant zone being connected to a convection zone. The integrated unit further comprises a heat exchange means encircling at least one of the radiant zone and the convection zone, and gas cleaning means is preferably provided around at least a part of the heat exchange means. The reaction unit may comprise a fluid bed boiler, gasifier or pyrolytic chamber and wherein fuel is burned completely; burned under pyrolytic conditions; or is gasified. The heat exchange means may comprise an annular heat exchange chamber and the gas cleaning means may be provided in an annular gas cleaning chamber encircling the heat exchange chamber.

Claims

1. (canceled)

2. An integrated unit comprising a boiler unit, and gas cleaning apparatus, the integrated unit having a reaction unit and further comprising a radiant zone connected to the reaction unit, the radiant zone being connected to a convection zone, the integrated unit further comprising a heat exchange means encircling at least one of the radiant zone and the convection zone, and gas cleaning means being provided around at least a part of the heat exchange means.

3. An integrated unit according to claim 1 wherein the reaction unit comprises a fluid bed boiler, gasifier or pyrolytic chamber and wherein fuel is burned completely; burned under pyrolytic conditions; or is gasified.

4. An integrated unit according to claim 1 wherein the heat exchange means comprises an annular heat exchange chamber.

5. An integrated unit according to claim 4 wherein the gas cleaning means is provided in an annular gas cleaning chamber encircling the heat exchange chamber.

6. An integrated unit according to claim 5 wherein the gas cleaning means comprises an array of bag filters in the gas cleaning chamber and wherein the bag filter comprises at least one of: fabric; ceramic and metal material.

7. An integrated unit according to claim 6 wherein the heat exchange chamber and the gas cleaning chamber are arranged such that the flow of the gases is directly towards and in line with the bag filters and wherein the gas cleaning chamber comprises a number of sub chambers and wherein optionally the sub-chambers are fluidly separated.

8. An integrated unit according to claim 7 wherein a supply of pressurised air can be applied to a downstream side of the bag filters.

9. An integrated unit according to claim 8 arranged to apply pressurised air in a pulse and wherein the pulse is applied to each sub-chamber sequentially and optionally the boiler remains in operation.

10. An integrated unit according to claim 5 wherein a sorbent can be injected into the gas cleaning chamber.

11. An integrated unit according to claim 5 wherein waste material can be removed from a base of the gas cleaning chamber.

12. An integrated unit according to claim 1 wherein the gas cleaning chamber comprises a moving floor.

13. An integrated unit according to claim 12 wherein the moving floor comprises a rotating floor having at least one paddle extending between an inner band and an outer band and wherein the or each paddle is arranged to move waste particulate towards an open section.

14. An integrated unit according to claim 1 wherein the radiant zone is positioned above the reaction unit.

15. An integrated unit according to claim 12 wherein the convection zone is in free fluid communication with the radiant zone.

16. An integrated unit according to claim 5 wherein at least one wall of the annular chamber is formed by at least one helically wound heat exchange tube.

17. An integrated unit according to claim 16 wherein the at least one wall also defines at least a portion of the radiant zone and the convection zone.

18. An integrated unit according to claim 4 wherein the heat exchange chamber comprises an economiser and an evaporator.

19. An integrated unit according to claim 1 wherein a chimney is centrally located above the radiant and convection zones.

20. An integrated unit according to claim 1 having a footprint comprising that of a fluid bed boiler.

21. An integrated unit comprising a boiler unit, and gas cleaning apparatus, the integrated unit comprising a radiant zone connected to the boiler, the radiant zone being connected to a reaction unit, the integrated unit further comprising a heat exchange means encircling at least one of the radiant zone and the convection zone, and gas cleaning means being provided around at least a part of the heat exchange means and wherein the heat exchange chamber and the gas cleaning chamber are arranged such that the flow of the gases is directly towards and in line with gas cleaning means and wherein the gas cleaning chamber comprises a number of sub chambers.

Description

[0064] The invention will now be described by way of example only with reference to the accompanying figures in which:

[0065] FIG. 1 is a perspective view of an integrated boiler and gas cleaning unit in accordance with the inventions;

[0066] FIG. 2 is a plan view of the unit of FIG. 1;

[0067] FIG. 3 is a sectional view along the line A-A of FIG. 2;

[0068] FIG. 4 is a schematic view of a bag filter; and

[0069] FIG. 5 is an enlarged view of the area in circle B in FIG. 2

[0070] FIG. 6 is a schematic view of an alternative arrangement;

[0071] FIG. 7 is a plan view of the embodiment of FIG. 6;

[0072] FIG. 8 is a section across the upper portion of the gas cleaning chamber; and

[0073] FIG. 9 is a cross-section of a portion of the integrated unit along the line A-A of FIG. 6;

[0074] FIG. 1 is a perspective view of an integrated unit 1 comprising a boiler unit 2 and gas cleaning apparatus in accordance with the present invention. The boiler unit 2 comprises a fluid bed boiler 4 providing a reaction unit having a combustion zone 6. A cylindrical assemblage 8 is provided above the fluid bed boiler and contains therein a radiant zone 10 and a convection zone 12 encircled by a heat exchange means 14. A gas cleaning means 16 is provided around the heat exchange means 14 and the whole assemblage is contained within a cylindrical shell 18. An upper portion 20 of the shell tapers inwardly to an outlet 22 which in use is connected to a chimney 24.

[0075] A plan view of the integrated unit is shown in FIG. 2. The upper portion 20 of the shell can be seen to be divided into segments 26. The outlet 28 from the upper portion is located over the radiation and convection chambers. Gases flowing into the upper portion of the shell flow out of the outlet 22 into the chimney 24. A substantially even radial distribution of gases flows into the chimney. An access door 30 is also provided in the upper section of the shell.

[0076] The integrated unit will now be described further in relation to a cross-section view along the line A-A in FIG. 2.

[0077] The integrated unit has a base 32 comprising a fluid bed boiler. The fluid bed comprises a number of sparge tubes 34 which are provided a bed of sand 36. A primary air fan is connected to the sparge tubes. The sparge tubes 36 are arranged to be spaced across the fluidised bed and run substantially parallel to one another. A waste outlet 38 is provided at the bottom of the fluidised bed to allow ash and other waste products to be removed from the fluidised bed periodically. A waste hopper 40 or other means of removing waste material is provided below the waste outlet. Waste is removed from the fluidised bed periodically. The frequency of removal is typically once a shift or once a day. The frequency may be varied according to the quantity of fuel used and the quality of fuel used.

[0078] As is the case in a typical fluidised bed burner a burner 42 is provided for initiation of combustion. Typically combustion may be initiated at approximately 600 C. and a working temperature of around 800 C. to 900 C may be achieved.

[0079] A feed chute 44 is provided which delivers fuel material to the fluidised bed. The fuel material may be waste material such as landfill or may be a biomass. Alternative fuels may be used such as, for example, coal.

[0080] The fuel material is delivered to the fluid bed burner from an outlet 46 above the fluid bed. Fuel falls from the feed chute towards the fluidised bed. Typically around 40% combustion of fuel occurs in the fluidised bed. Pollutants such as tramp metal or inert material that are not combusted fall through the fluidised bed and can be removed from the waste outlet as described above.

[0081] Secondary air is delivered to the combustion zone of the reaction unit by means of an air supply connected to a manifold 48. The manifold 48 delivers air to a mid-to upper portion 50 of the combustion zone. The air may comprise a mixture of oxygen and other gases. A composition of the air may be controlled so that the supply of oxygen in the air is optimised such that substantially complete combustion of fuel can occur in the combustion zone. Typically up to 60% of the combustion can occur around the manifold outlets. With significant combustion of fuel occurring in the upper portion of the combustion zone it has been found that the temperature in the upper portion of the combustion zone can reach between 1200 C. and 1300 C. As described below this temperature may be controlled in use to be lower than 1200 C. Typically the temperature in the upper portion of the combustion zone is controlled to be about 900 C.

[0082] Gases from the combustion zone 6 of the reaction unit pass upwardly into the cylindrical assemblage 8 which is located above the fluid bed boiler and is sealed thereto. The cylindrical assemblage 8 comprises an axially extending radiant zone 10 and an aligned and axially extending convection zone 12. The radiant zone and the convection zone are mutually aligned and the radiant zone 10 extends continuously into the convection zone 12. The radiant and convection zones are defined by helically wound heat exchange coils 52 which define a radiant chamber and a convection chamber. Gases from the combustion zone can pass freely into the radiant chamber and thence into the convection chamber.

[0083] It will be appreciated that the boiler may be operated under pyrolytic conditions. In other embodiments the boiler can be arranged to produce synthetic gas. In some embodiments the boiler may be arranged to operate in a gasification mode.

[0084] The radiant zone 10 acts as a cold black body and draws heat from the upper part of the combustion zone 6. The radiant zone controls the temperature in the upper portion of the combustion zone 6. The radiant chamber is defined by helically wound heat exchange coils 52 through which water at a cooler temperature than the gases is passed and heat energy is transferred between gases in the radiant chamber and water in the heat exchange coils.

[0085] Gases from the combustion zone may typically reside in the radiant zone 10 for a period of time which is sufficient that the particles are held at a temperature of greater than 850 C. for at least two seconds. Accordingly, the fuel supplied to the combustion zone of the reaction unit is held at a temperature of greater than 850 C. for at least two seconds. The fuel is desirably completely combusted and unwanted pollutants such as hydrocarbons, dioxins and furans are preferably completely combusted and destroyed. Accordingly, the fuel material is completely combusted as required by the waste incineration directive. Gases flow from the radiant chamber into the convection chamber, which as referred to above, is also defined by helically wound heat exchange tubes 52. Cooler water flowing through the heat exchange tubes extracts further heat from the gases flowing through the convection chamber. Typically gases exiting from the convection chamber preferably have a temperature which has been lowered to about 870 C.

[0086] An insulating cap 54 is provided across the top of the convection chamber defining a radially extending passage over an upper portion of the helically wound heat exchange tubes. Gases from the convection chamber are deflected by the insulating cap 54 and pass radially outwardly from the radiant chamber before being deflected into the convective heat exchange means, which comprises an annular heat exchange chamber 14 arranged around the radiant and convection chambers. In this embodiment an inner wall 56 of the heat exchange chamber is defined by the helically wound heat exchange tubes 52 which surround the radiant and convection chambers. An outer wall 58 of the annular heat exchange chamber 14 is defined at least in part by further helically wound heat exchange tubes.

[0087] The heat exchange chamber comprises an evaporator section 60 and an economiser section 62. The evaporator section 60 contains a number of circumferentially extending heat exchange tubes 64 which contain pressurised water at a pressure of about 22 bargauge.

[0088] The economiser section 62 preferably contains a further set of circumferentially extending heat exchange tubes 66. The further set of circumferentially extending heat exchange tubes 66 also contains pressurised water which may typically be at a pressure of from 5 to 70 bargauge.

[0089] The hot gases flow around the circumferentially extending heat exchange tubes in the evaporator section 60 and the economiser section 62. The hot waste gases flow downwardly through the heat exchange chamber 14. The hot waste gases typically enter the evaporator section at around 850 C. to 860 C. The waste gases lose heat and energy in the heat exchanger chamber and exit from the economiser section at a temperature of approximately 150 C. Gases exiting from the heat exchange chamber are deflected by a flow reverser 68 formed in a base section such that a direction of flow of the gases is reversed and the gases flow upwardly into a gas cleaning chamber which is provided around the heat exchange means. The base section also comprises an injection means (not shown) arranged to inject sorbent materials into the gas flow. The sorbent material typically comprises at least one of sodium bicarbonate, activated carbon, and lime. Other sorbent materials may be utilised by the skilled person instead of or in addition to the sorbents referred to above. The sorbent materials are used to remove unwanted pollutants such as sulphur and chlorine from the gases. The sorbent materials are selected to react with the unwanted pollutants and to remove pollutants from the gas stream by binding sulphur and chlorine into a powder form.

[0090] The base section comprises at least one waste removal means. In this embodiment the waste removal means comprises a rotating floor having an inner band 70 and an outer band 72 which are arranged to be rotatable around the radiant chamber. The inner and outer bands are arranged to rotate around the circumference of the base section. Floor spacing plates 74 are provided between the inner and outer bands. These floor plates can rotate on passing over a waste removal device (not shown). As the floor plates rotate any waste material on the floor plate passes through the operable section and is deposited into a waste hopper located below the waste removal device such as a rotary valve air lock. The waste hopper can be transported from a location below the base section in order to remove waste material via the rotary valve air lock.

[0091] A paddle 73 is provided extending between the inner and outer bands. The paddle is arranged to move waste particulate material from below the filter bags and into the openable section such that the waste particulate material is deposition on the waste removal device.

[0092] As described above gases exiting from the heat exchange chamber have the direction of flow reversed and pass upwardly into the gas cleaning chamber which is provided in an annular chamber extending around the heat exchange chamber. Bag filters 76 are provided in the gas cleaning chamber and these are arranged to hang vertically in the annular chamber. The bag filters 76 are arranged to be substantially parallel with one another and also arranged such that a number of bag filters extend across from an inner side of the annular chamber to the outer side. A number of bag filters are arranged radially in each segment of the annular chamber. The bag filters are arranged in the gas cleaning chamber such that the flow of gases is directly towards and in line with the bag filters. The gases flow substantially parallel to the orientation of the bag filters.

[0093] Each bag filter 76 comprises a fabric material is arranged over a steel cage. Typically each bag filter is about 10 cm in diameter. This is the steel cage supports the fabric material of the bag filter against the flow of gases. Over time particulate material in the gases is removed from the airflow by the bag filters. Such particulate material may comprise ash as a combustion product from the fuel. The particulate material may also comprise sorbent material which has been injected into the gas flow stream. The sorbent material is carried by the gas flow towards the bag filters. As the sorbent material is carried in the gas flow in the gas cleaning chamber sorbent material is able to react with pollutants in the gases. Both sorbent material which has reacted with pollutants and the sorbent material which has not reacted with pollutants is retained on an upstream side of the bag filters. Further gases passing through the bag filters are forced to pass through the sorbent material retained in the upstream side and so further absorption of pollutants can occur.

[0094] It will be appreciated that the bag filter may comprise a ceramic fibre. In other embodiments filter can be formed of a wire mesh. The wire mesh can be fine wires meshed together. In some cases the metal may be platinum. Platinum can have an additional benefit of acting as catalyst for the removal of organic compounds from the gas. The platinum wire may assist in the removal of carbon monoxide from the exhaust gases.

[0095] Gases passing through the bag filter are clean and do not contain pollutants such as sulphur and chlorine, furans or dioxins etc. and have also been cleaned of any ash or particulate material typically down to 1.0 microns. It has been found that the gasses meet the legal requirements for clean air such as are specified in the Integrated Pollution Prevention Control (IPPC) directive.

[0096] Gases exiting from the gas cleaning chamber 16 passed into a radial chamber 78 and are directed radially inwardly. The outlet 22 is placed at the centre of the radial chamber 78 and an induced draught fan 80 is provided in the outlet to draw gases from the radial chamber and to direct them to the chimney 24. The chimney is not shown but is a conventional chimney.

[0097] Bag filter cleaning means (not shown) are provided in the upper portion of the shell. The bag filter cleaning means typically comprises a pressurised air supply and the manifold connecting the as supplied to each bag filter. As required in the course of operation, pressurised vessels can be pulsed into the bag filters in a reverse direction, so dislodging any particulate material on the upstream side of the bag filters. Typically the pressurised air supply is at 2 to 5 bargauge and is pulsed in order to dislodge the particulate material from the upstream side of the bag filters. A control means also provided to control the supply of air to the bag filters for cleaning purposes. The pulse air is supplied to bag filters in a section of an arc. Remaining sections of the gas cleaning chamber operate in a normal fashion. Cleaning of the bag filters may operate sporadically or continuously. The section of the gas cleaning apparatus which is being cleaned is rotated around the annulus. A pressurised air supply manifold is provided in the upper portion. Solenoid valves control supply of the pressurised air to the bag filters.

[0098] The access door 30 is provided in the upper portion of the shell to allow access to the air supply manifolds and valves and to allow the bag filters to be replaced as required or to be serviced.

[0099] In an alternative embodiment illustrated in FIG. 6 the boiler and heat exchange chambers are arranged as before. The gases exit from the gas cleaning chamber in a centrally located outlet 100 and are then directed into a duct 102. The duct 102 is arranged perpendicular to the outlet duct 100. The duct 102 delivers the exhaust gases to a testing and measuring device located within the duct. The measuring device is arranged to measure species in the exhaust gases. Pollution species that may be measured include chlorides, hydrochlorides, sulphides, sulphur dioxides; nitrogen oxides and particulate material. Other species may also be monitored. Regulations specify the amount of pollutant that may be in the gases. According to present requirements the gases are arranged to travel in a straight line in the duct for a specified distance before entering the measuring device. It is understood that flow in a straight line for the specified distance leads to linear flow.

[0100] Exhaust gases flow from the measuring device flow to a return duct 105 and to a chimney 107. In alternative arrangements the exhaust gases may be returned to a vent that is laterally located.

[0101] FIG. 7 is a plan view of the embodiment of FIG. 6. The upper section 20 is arranged above the bag cleaning chamber and the duct 102 extends from the exhaust outlet 100 from the gas cleaning chamber.

[0102] As is best seen in FIG. 8 in the alternative arrangement the gas cleaning chambers 106 is divided into sub-chambers 108. Each sub-chamber 108 comprises an section of the annular gas cleaning chamber 106. Each sub chamber 108 comprises an arc of approximately 60 of the annular chamber 106. A first sub chamber 110 does not contain any bag filters. The remaining five sub-chambers 112 each have a number of rows 114 of bag filters 116. A baffle 118 is provided at a top end of the five sub-chambers 112 and the baffle controls 118 flow of gas from the sub-chambers 112 to the first sub chamber 110 towards the outlet 120 into the duct 102. When the baffle 120 from a sub chamber 112 is closed gases do not flow through the respective sub-chamber 112 and the gases in the respective sub-chamber 112 are stagnant.

[0103] Pressurised air is supplied to an outer manifold 122. The pressurised air is fluidly connected to a number of inner manifolds 124 each of which is arranged to be able to supply the pressurised air to the bag filters 116. Valves are provided in each inner manifold to control a flow of pressurised pulse air to the bag filters 116. A controller is arranged to control the supply of air from the outer manifold to the bag filters 116.

[0104] The baffle 118 controls a flow of air from an upper chamber above the gas cleaning chamber towards the measuring device and the chimney. Closing the baffle stops flow from the upper portion of the sub chambers towards the first sub chamber and into the outlet and duct to the measuring device. Exhaust gases tend to follow the course of least resistance and the flow of exhaust gases moves to flow through the sub chambers in respect of which the respective baffle remains open.

[0105] In the cleaning process one sub-chamber 112 is closed at a time. Once the respective baffle 118 is closed the gases are not drawn through the closed sub chamber and gas flow on the immediately upstream side of the bag filter becomes stagnant. A particular advantage of the arrangement is that the boiler and gas cleaning apparatus can continue to be used while one of the bag cleaning sub-chambers is closed and the bag filters cleaned. The bag filters in the sub-chambers can be cleaned on a sequential arrangement. This contrasts with conventional boilers and gas cleaning arrangements in which the boiler and gas cleaning apparatus have to be suspended while cleaning of the bag filters is carried out.

[0106] In the cleaning process the pulsed air is controlled to be suppled from the outer manifold 122 and into the inner manifolds 114. A controller located remotely, is arranged to apply the pulsed air to the bag filters 116. Particulate material collected on the upstream side of the bag filters is displaced by the pulsed air and falls from the bag filter 116 and onto the rotatable floor located at the base of the gas cleaning chamber to be removed.

[0107] FIG. 9 is a cross section along the line A-A in FIG. 7. The boiler arrangement and the heat exchange apparatus is the same as in FIG. 3. In this embodiment the gases flow from the boiler 130 and into the radiant chamber 132 and then into the heat exchange chamber 134. Gases from the heat exchange chamber 134 flow to the base 136 of the heat exchange chamber and then upwardly into the annular gas cleaning chamber. Gases flowing through the gas cleaning chamber pass through the bag filters 116. Particulate material collects on the upstream side of the bag filters. When the cleaning process is carried out pulsed air passing through the bag filters dislodges the particulate material which falls to the rotatable moving floor 138.

[0108] Downstream of the bag filters 116 the gases flow through the respective baffle 118 into the first sub-chamber 110 through the baffle and into the duct 102. The side ducting 102 carries gases to a testing device 104 which is compatible with standard testing requirements. The testing device is arranged after a section of straight ducting such that the gas flow is considered to be laminar on entry to the testing device. Downstream of the testing device the gases flow through a return valve 105 and is discharged into the chimney 107.

[0109] The controller is arranged to clean each of the sub-chambers sequentially. An important aspect is that the bag filters are cleaned while the boiler is operating and that it is not necessary to stop or interrupt the operation of the boiler.