WO1999066260A1

WO1999066260A1 - Coal, oil and gas-fired boiler system

Info

Publication number: WO1999066260A1
Application number: PCT/KR1999/000307
Authority: WO
Inventors: Sae Hwan Choi; Dong Jin Choi
Original assignee: Sae Hwan Choi; Dong Jin Choi
Priority date: 1998-06-17
Filing date: 1999-06-17
Publication date: 1999-12-23
Also published as: AU4397999A; KR20010053007A; KR19980065026A

Abstract

A coal, oil and gas-fired boiler system is disclosed. In the system, water pipes are arranged within a boiler body while being brought into surface-contact with each other, with the gaps between the pipes being filled with refractory cement and more firmly locking the pipes together. The water pipes thus effectively resist high steam and water pressures. The exhaust gas is prevented from causing environmental pollution by effectively supplying air to fuel within the combustion chamber, while forming a vortex within the combustion chamber by secondary air. The system thus achieves improved combustion efficiency. The vaporization effect of the system is improved by internal fire pipes axially arranged within each water pipe. Water within the water pipes if thus quickly heated by the flame within the fire pipes. A desulfurization unit injects powdered calcium hydroxide to the exhaust gas at an electric dust collector while burning the exhaust gas by a burner. The exhaust gas also passes through two towers wherein calcium hydroxide is supplied to the gas, thus changing carbon dioxide of the gas into calcium carbonate. The system thus discharges exhaust gas free from toxic gases into the atmosphere. The system firmly resists an exceedingly high operational pressure, improves combustion efficiency, effectively generates usable steam, and desulfurizing exhaust gas while absorption-removing other toxic gases from the exhaust gas.

Description

COAL, OIL AND GAS-FIRED BOILER SYSTEM

Technical Field

The present invention relates, in general, to fossil fuel-fired boiler systems equipped with both a desulfurization unit and a carbon dioxide (C0₂) eliminating unit and designed to selectively use inexpensive fossil fuel: coal, oil and gas as a fuel source without causing environmental pollution while providing a high degree of thermal power and, more particularly, to a coal, oil and gas-fired boiler system, with a plurality of water pipes being densely arranged in a boiler body while being brought into surface contact with each other and being firmly locked together, thus effectively resisting the high operational pressure of the boiler system, caused by a high steam pressure.

Background Art

As well known to those skilled in the art, boiler systems are equipment which burn fuel, such as fossil fuel, to generate thermal energy and convert the thermal energy into steam energy or etc., thus generating usable power.

Such boiler systems are typically classified into two types: small-scaled and large-scaled boiler systems in accordance with the scale of the systems. Such small- scaled boiler systems typically have a plurality of pipes extending in a cylindrical tank with heat passing through the pipes, thus generating desired energy. However, the small-scaled boiler systems are problematic in that there is a limitation in enlarging the capacity of the systems due to the limited size of the systems.

On the other hand, several types of large-scaled boiler systems have been proposed and used. Regardless of the types, the large-scaled boiler systems have a plurality of water pipes which are arranged on a sidewall of a firebox with water passing through the water pipes. However, such large-scaled boiler systems are problematic in that they fail to achieve a desired high degree of thermal efficiency due to their structural defects. In addition, the combustion flame at an area around the center of the firebox of said large-scaled boiler systems is not used for generating steam, but is regrettably exhausted into the atmosphere.

Such a conventional large-scaled boiler system is free from any separate combustion chamber, but an integrated firebox is defined within the total interior space of the boiler system. Within such an integrated firebox, the temperature around the upper portion is higher than that of the lower portion. Such a difference in the temperature between the upper and lower portion within the firebox makes the internal heat of the firebox fail to effectively heat the water pipes, but is exhausted into the atmosphere through a cyclone. This results in a heat loss during an operation of the system. Since the interior space of the firebox is unnecessarily large-sized, the combustion heat does not effectively circulate within the firebox, thus resulting in a reduction in the heat contact efficiency of the water pipes. This finally prevents such boiler systems from generating a desired amount of energy.

In an effort to improve the thermal efficiency of the large-scaled boiler systems, oil, calcicosis or heated sands as an additive may be injected into the firebox. However, the methods of injecting such an additive into the firebox fail to accomplish a desired combustion efficiency of the boiler systems since they result in an excessive amount of exhaust heat. Another disadvantage, experienced in the above methods of injecting the additive into the firebox, resides in that the methods form an excessive amount of toxic gases, such as suffer dioxide, carbon monoxide and carbon dioxide, in the resulting exhaust gas, thus regrettably causing an environmental pollution, particularly, air pollution.

In order to overcome the above-mentioned problems, the inventor of this invention proposed fossil fuel-fired boiler systems in Korean Utility Model Application No. 97- 22,155, applied for on Aug. 14, 1997, and in Korean Patent Application No. 98-12,010 applied for on Mar. 30, 1998.

In the above boiler systems, a combustion chamber is provided at the lower portion of a boiler body with a fuel supply unit being provided at the front portion of the boiler body for supplying fuel into said combustion chamber. Two water chambers, upper and lower water chambers, are arranged above the combustion chamber. The two water chambers communicate with each other through a plurality of water pipes. A plurality of internal fire pipes interiorly, axially and parallely extend in each of the water pipes, thus forming a multi-pipe structure in cooperation with the water pipe. The two water chambers are also connected to each other through a plurality of water circulation pipes. The objective of the water circulation pipes is to allow water to accomplish a smooth convective circulation between the two water chambers. The boiler systems also have a rooster sub- circulation pipe. A dry steam chamber, interiorly equipped with a dry steam pipe, is installed on the rooster sub-circulation pipe. Each of the boiler systems also has a steam collection and supplying unit used for collecting the steam from the dry steam chamber and supplying the steam to a turbine. The above boiler systems are rotatably held on support base units.

However, the fossil fuel-fired boiler systems, disclosed in the above Korean U. M. and Patent Applications, are problematic in that the water pipes are separately distributed and separately arranged between the two water chambers, thus having a structural defect failing to effectively resist the steam pressure and/or the water pressure during an operation of the boiler systems. Therefore, the water pipes may be easily broken. It: is thus necessary to more firmly lock the water pipes within the boiler systems.

Disclosure of the Invention

Accordingly, the present invention has been made keeping in rr.ind the above problems occurring in the prior art, and an object of the present invention is to provide a coal, oil and gas-fired boiler system, of which the water pipes are densely arranged in the system while being brought into surface contact with each other and being firmly locked to each other, the water pipes being also firmly locked to the sidewalls of the two water chambers at their ends, thus having an improved locking strength capable of effectively resisting the high operational pressure of the boiler system, caused by a high steam pressure.

In order to accomplish the above object, the present invention provides a coal, oil and gas-fired boiler system, comprising a boiler body with a combustion chamber provided at a lower portion of the boiler body, a fuel supply unit provided at a front portion of the boiler body for supplying fuel into the combustion chamber, upper and lower water chambers arranged above the combustion chamber and connected together by a plurality of first and second water pipes individually having a plurality of internal fire pipes, the fire pipes interiorly and axially extending in each of the water pipes so as to form a multi-pipe structure in cooperation with each water pipe, a plurality of water circulation pipes extending between the two water chambers and allowing water to accomplish a smooth convective circulation between the two water chambers, a dry steam chamber interiorly equipped with a dry steam pipe and installed above the upper water chamber, a steam collection and supplying unit used for collecting steam from the dry steam chamber and reheating the steam prior to supplying the steam to a turbine, an exhaust gas purifying unit connected to the boiler body, and a support base unit rotatably supporting the boiler body thereon, wherein the first and second water pipes are arranged within the boiler body while being brought into surface-contact with each other, with the fire pipes being arranged within each of the first and second water pipes, the second water pipes extending more at their both ends so as to penetrate into the two water chambers prior to being fixedly mounted to sidewalls of the two water chambers, each of the second water pipes also having a water circulation hole at a position within each of the two water chambers, thus communicating with the two water chambers.

In the above boiler system, the internal fire pipes of each of the first and second water pipes are regularly spaced apart from each other and are firmly retained at spaced positions by a plurality of spacers.

The exhaust gas purifying unit comprises a cyclone, the cyclone consisting of: a central exhaust tube vertically installed in a center of the cyclone; an external fan mounted at an external position outside a sidewall of the cyclone, with a blower tube extending from the external fan to a lower end of the central exhaust tube; a calcium hydroxide supply silo mounted to the blower tube and used for supplying calcium hydroxide into the central exhaust tube through the blower tube; and a burner provided with a flame nozzle positioned at the lower end of the central exhaust tube, the burner being used for heating exhaust gas to a high temperature. The above system further comprises: a calcium hydroxide supply unit installed under a water outlet port of a carbon dioxide dissolving tower of the exhaust gas purifying unit, the calcium hydroxide supply unit consisting of: a main casing equipped with a dispensing screw; a first hopper formed on the main casing at a position just below the water outlet port of the tower and used for introduction of water, laden with carbon dioxide and coming from the water outlet port of the tower, into the casing; a second hopper formed on the casing and used for introduction of powdered calcium hydroxide into the casing; and an outlet port formed at an outlet end of the casing and used for discharging processed water into the outside of the casing.

Brief Description of the Drawings

The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: Fig. 1 is a perspective view of a boiler body included in the boiler system in accordance with the preferred embodiment of the present invention;

Fig. 2 is a longitudinal-sectioned view of the boiler body taken along the line A-A of Fig. 1, with a desulfurization unit as an exhaust gas purifying unit being assembled with the boiler body into a boiler system according to this invention;

Fig. 3 is a cross-sectioned view taken along the line B-B of Fig. 2, showing water and fire pipe arrangement at a position between the upper and lower water chambers within the boiler body;

Fig. 4 is a cross-sectioned view taken along the line C-C of Fig. 2, showing the water and fire pipe arrangement at a position within the lower water chamber of the boiler body;

Fig. 5 is a cross-sectioned view taken along the line D-D of Fig. 2, showing an arrangement of a firebrick stack, rooster water pipes and ash removing push rods within the boiler body;

Fig. 6 is a sectional view of the desulfurization unit as an exhaust gas purifying unit included in the boiler system of this invention; and

Fig. 7 is a sectional view of the desulfurization unit taken along the line E-E of Fig. 6.

Best Mode for Carrying Out the Invention

Figs. 1 to 5 show a coal, oil and gas-fired boiler system in accordance with the preferred embodiment of the present invention. Figs. 6 and 7 show a desulfurization unit, included in the boiler system of this invention and used as an exhaust gas purifying unit for the system.

As shown in the drawings, the boiler system of this invention comprises a boiler body having two water chambers, upper and lower water chambers 40a and 40b. The two chambers 40a and 40b are arranged in upper and lower portions of a boiler body. The upper and lower water chambers 40a and 40b communicate with each other using a plurality of water pipes 41a and 41b. The first and second water pipes 41a and 41b individually have a plurality of internal fire pipes 42. The fire pipes 42 interiorly, axially and parallely extend in each of the water pipes 41a and 41b, thus forming a multi-pipe structure in cooperation with each water pipe. A dry steam chamber 50 is installed at a position above the upper water chamber 40a, while a steam tank 43 is installed in the front of the upper water chamber 40a. A combustion chamber 20 is provided at a lower position under the lower water chamber 40b, while a circulation water collection pipe 44 is arranged in the front of the lower water chamber 40b. A fuel supply unit 10 is provided at the front portion of the boiler body for supplying fuel into the combustion chamber 20. An exhaust gas purifying unit is provided in the back of the boiler body while being connected to the dry steam chamber 50. A support base unit is provided at the back of the boiler body and rotatably supports the back of said body. In a detailed description, the fuel supply unit 10 comprises two hoppers, front and rear hoppers 11a and lib, both communicating with the combustion chamber 20 as shown in Fig. 2. Each of the two hoppers 11a and lib is provided with both one fuel dispensing screw 12a, 12b and one fuel control damper 13a, 13b. The objective of the dispensing screws 12a and 12b is to feed fuel into the combustion chamber 20 while uniformly dispensing the fuel. The objective of the dampers 13a and 13b is to control the inlet amount of fuel from the two hoppers 11a and lib for the combustion chamber 20. The front hopper 11a is used for supplying limestone into the chamber 20, while the rear hopper lib is used for supplying lump coal or powdered coal into the chamber 20. A limestone passage 18b extends downwardly from the front hopper 11a, while a limestone drain port 14 is formed at the lower end of the limestone passage 18b. On the other hand, a fuel passage 18a extends downwardly from the lower end of the rear hopper lib. A shutter 15 is provided at the limestone drain port 14 for selectively opening the port 14. The shutter 15 has a rack 16 engaging with a pinion 17. The rack and pinion mechanism of the shutter 15 is automatically operated by a drive unit (not shown) , thus selectively opening or closing the limestone drain port 14 by the shutter 15. A multi-layered firebrick stack is installed across the lower portion of the combustion chamber 20 while being supported on a base plate 22 of the combustion chamber 20 using a support panel 25, thus forming an air compression chamber 26 within the combustion chamber 20 as shown in Figs. 2 and 5. The above firebrick stack is made by laying a plurality of firebricks 23 with one on top of another and by integrating the firebricks 23 into a single stack using refractory cement. Each of the firebricks 23 has a longitudinal ventilation groove 24 on its top surface. A plurality of rooster water pipes 49 are parallely arranged within the combustion chamber 20 with a predetermined regular gap allowing lump coal to pass through, but filtering off limestone. The rooster water pipes 49 are bent at their inlet ends so as to extend across the interior of the passages 18a and 18b of the two hoppers 11a and lib prior to extending to the lower portion of the lower water chamber 40b or to the circulation water collection pipe 44. In such a case, the rooster water pipes 49 inclinedly extend within the combustion chamber 20 prior to being connected to the lower water chamber 40b.

In the combustion chamber 20, a support plate column 27 is provided on each side of the lower surface of the base plate 22, with a hydraulic cylinder actuator 28 being fixedly held on the lower end of each support column 27. A transverse frame 29 is supported by the piston rods of the two actuators 28 at the outside end of each piston rod and holds a plurality of push rods 30. The push rods 30, perpendicularly extending from the transverse frame 29, are parallely and regularly arranged so as to be positioned within the gaps of the rooster water pipes 49 at the lower portion of the combustion chamber 20. Each of the push rods 30 holds an ash removing fin 31 at its outside end and pushes and moves lump coal ash on the rooster water pipes 49 to the back by the ash removing fins 31. An ash outlet door 32 is hinged to the rear portion of the rooster water pipes 49. Provided at the lower surface of the push rods 30 are rollers 33, which support the loaded weight of the rods 30 while allowing the rods 30 to be smoothly moved in opposite directions during an operation of removing lump coal ash. An ash gutter 35, provided with an ash dispensing screw 34, is installed under the ash outlet door 32. Two fans 36a and 36b are provided at a sidewall of the combustion chamber 20 for feeding pressurized air into the chamber 20. Of the two fans 36a and 36b, the lower one 36a is provided with a calcium hydroxide silo, thus being used for feeding calcium hydroxide into the combustion chamber 20 when oil is used as a fuel source. Of the two types of water pipes 41a and 41b extending between the two water chambers 40a and 40b, the second pipes 41b extend more at their both ends so as to penetrate into the chambers 40a and 40b prior to being fixedly mounted to the sidewalls of the two chambers 40a and 40b. Each of the second pipes 41b also has a water circulation hole 421 at a position within each of the two chambers 40a and 40b, thus communicating with the two chambers 40a and 40b. On the other hand, the internal fire pipes 42 of each second water pipe 41b completely pass through the two water chambers 40a and 40b prior to communicating with the combustion chamber 20 at the lower ends and with the dry steam chamber 50 at the upper ends. A plurality of water circulation pipes 45a and 45b extend between the steam tank 43 and the circulation water collection pipe 44. In the boiler system according to this invention, the water pipes 41a and 41b are densely arranged within the boiler body while being brought into surface contact with each other. The gaps between the water pipes 41a and 41b are filled with refractory cement, thus firmly locking the pipes 41a and 41b to each other. The internal fire pipes 42 of each of the water pipes 41a and 41b axially extend within each pipe 41a, 41b while being regularly spaced apart from each other and being firmly retained at the spaced positions by a plurality of spacers 411. The above spacers 411 are interiorly held on the water pipes 41a and 41b. On the lower surface of the lower water chamber 40b, a plurality of heat absorption pipes 48 are bypassed in lateral and longitudinal directions. A zigzag dry steam pipe 51, extending from the steam tank 43, passes within the dry steam chamber 50 prior to extending to a steam collection pipe 52. An ash recovery pipe 53 extends from the combustion chamber 20 to the dry steam chamber 50 at the back of the two chambers 20 and 50 as shown in Figs. 3 and 4. The objective of the above ash recovery pipe 53 is to guide both ash and unburnt powdered coal downward, which are raised up from the combustion cnamber 20 into the dry steam chamber 50 along with combustion heat, and return it to the combustion chamber 20 due to gravity.

A steam feed pipe 55 extends on the sidewall of the boiler body while extending from the steam collection pipe 52 to a steam reheating pipe 54. The steam reheating pipe 54 extends across the front portion of the combustion chamber 20 prior to being connected to a turbine (not shown) through a steam discharging pipe 56.

The support base unit is provided at the back of the boiler body and rotatably supports the back of the boiler body in a way such that the base unit effectively supports the heavy boiler body while allowing the inclination angle of the boiler body to be adjustable as desired. The support base unit comprises a frame 60 which is formed on the back of the boiler body and has a bracket 61. A base 62 is fixedly set on a support surface or the ground and is designed to effectively support the weight of the boiler body. The bracket 61 of the frame 60 is hinged to the base 62 using a pin 63, with a second hydraulic cylinder actuator 64 being connected to both the boiler body and the base 62 and rotating the boiler body around the hinged joint of the support base unit so as to adjust the inclination angle of the boiler body as desired. In the case of a large- scaled boiler body, it is preferable to use the boiler system while fixing the boiler body at an appropriately inclined position using a conventional fixing means. As shown in Figs. 2, 6 and 7, the exhaust gas purifying unit comprises a cyclone 70. The cyclone 70 is connected to an exhaust pipe 57 of the boiler body. The objective of the above cyclone 70 is to primarily filter off heavy ash from the exhaust gas and to heat the exhaust gas to a high temperature while supplying calcium hydroxide to the exhaust gas, thus changing carbon monoxide into carbon dioxide and sulfur dioxide into calcium sulfite. Two cooling water units, first and second units 80a and 80b, are orderly connected to the cyclone 70 through a gas pipe and are designed to discharge the calcium sulfite through lower outlet ports while cooling the exhaust gas to a low temperature. An electric dust collector 83 is connected to the lower portion of the second cooling water unit 80b and is used for collecting heavy metal dust and the like from the coal ash and/or calcium hydroxide. Two carbon dioxide dissolving towers 84a and 84b are orderly connected to the dust collector 83 while being parallely positioned. The two towers 84a and 84b are used for dissolving carbon dioxide of the exhaust gas in water. The exhaust gas purifying unit also comprises a calcium hydroxide supply unit 90. This unit 90 is installed under the outlet port of the second tower 84b and is used for supplying calcium hydroxide to water laden with carbon dioxide, thus changing carbon dioxide of the water into calcium carbonate and neutralizing the water prior to discharging the water into the atmosphere.

In a detailed description, a central exhaust tube 71 is vertically installed in the center of the cyclone 70, thus allowing the exhaust gas from the upper portion of the sidewall of said cyclone 70 to be whirled down around the tube 71 prior to flowing upwardly into the tube 71 from the lower end of said tube 71. An ash drain means is provided at the lower portion of the cyclone 70 for collecting the ash prior to discharging the ash from the cyclone 70, with the ash being separated from the exhaust gas due to both gravity and inertia force. The cyclone 70 is also provided with a fan unit. The fan unit has a blower tube 72 which extends from the lower end of the central exhaust tube 71 to an external fan 73. The external fan 73 is mounted at an external position outside the sidewall of the cyclone 70. A calcium hydroxide supply silo 74 is mounted to the blower tube 72 at a position outside the cyclone 70 and is used for supplying calcium hydroxide into the central exhaust tube 71 through the blower tube 72. The fan unit also has a burner 75 of which a flame nozzle 76 is positioned at the lower end of the central exhaust tube 71. The above burner 75 is used for heating the exhaust gas to a high temperature. The two cooling water units 80a and 80b is connected to each other in a way such that the sidewall of the first unit 80a is connected to the top wall of the second unit 80b through a pipe. A plurality of gas exhaust pipes 81 are vertically and parallely arranged within each of the two units 80a and 80b and allow the exhaust gas to pass through while being branched into several currents. The above gas exhaust pipes 81 are cased by a water jacket 82. The water jacket 82 is filled with water, thus cooling the exhaust gas passing through the pipes 81. The lower end portion of each unit 80a, 80b has a hopper shape, with the outlet port of the hopper-shaped lower end portion being used for discharging calcium sulfite from the unit 80a, 80b. In such a case, the calcium sulfite has been made by the neutralization process within the cyclone 70. The objective of the two cooling water units 80a and 80b is to reduce the temperature of the exhaust gas so as to allow a smooth and effective operation of the electric dust collector 83. The two carbon dioxide dissolving towers 84a and 84b, orderly connected to the dust collector 83 and connected together at the upper portion of their sidewalls. Of the two towers 84a and 84b, the first one 84a is filled with water at the lower portion, while the second one 84b temporarily contains water laden with carbon dioxide until the water is discharged from the tower 84b. Two water pumps 85a and 85b are installed outside the two towers 84a and 84b at a position around the lower portion of the towers and individually have a water supply pipe extending into the water within the first tower 84a. Two nozzle pipes 86a and 86b extend from the two water pumps 85a and 85b and are positioned upright within the two towers 84a and 84b, respectively, with the nozzles of the pipes 86a and 86b being set at the top of said pipes 86a and 86b. The two pumps 85a and 85b thus pump up water from the first tower 84a and inject pressurized water upwardly into the upper portion of the two towers 84a and 84b from the nozzles of the nozzle pipes 86a and 86b. An outlet pipe 87 extends from the sidewall of the second tower 84b. On the other hand, the calcium hydroxide supply unit 90, installed under the outlet port of the second tower 84b, comprises a horizontal main casing 91 equipped with a dispensing screw 92. Two inlet hoppers 93 and 94 are formed at the top wall of the main casing 91. Of the two hoppers 93 and 94, the first one 93 is positioned just below the outlet port of the second tower 84b and is used for introduction of water laden with carbon dioxide into the casing 91, while the second one 94 is used for introduction of powdered calcium hydroxide into the casing 91. An outlet port 95 is formed at the outlet end of the casing 91.

The operational effect of the above boiler system will be described hereinbelow.

In order to operate the boiler system with coal as a fuel source, limestone is supplied into the front hopper 11a with lump coal or powdered coal being supplied into the rear hopper lib prior to rotating the dispensing screws 13a and 13b of the two hoppers 11a and lib while controlling the fuel control dampers 13a and 13b. The coal and the limestone are introduced into the passages 18a and 18b with the rooster water pipes 49 extending across within the two passages 18a and 18b. In such a case, the coal or the fuel passes through the gaps between the rooster water pipes 49 prior to being dropped into the chamber 20. When the coal is completely dropped into the chamber 20, the coal is ignited by a pilot burner (not shown) prior to being burnt by combustion air supplied by the two fans 36a and 36. In such a case, the fans 36a and 36b primarily feed atmospheric air into the air compression chamber 26 while pressurizing the air. The pressurized air from the compression chamber 26 flows through the ventilation grooves 24 of the firebricks 23 and is injected into the combustion chamber 20. The air acts as secondary air within the combustion chamber 20, and so a vortex is formed within the chamber 20, thus allowing the coal within the chamber 20 to be almost completely burnt at a high temperature. This finally achieves an almost complete combustion of fuel. In such a case, the firebricks 23 of the stack are heated to a high temperature, and so newly dropped coal within the chamber 20 is quickly heated so as to be easily ignited. When oil or gas is used as a fuel source in place of coal, the fuel is burnt by separate burners different from the combustion of coal. In such a case, the separate burners are attached to the boiler body as positions from which the two fans 36a and 36b are removed.

The high temperature combustion heat passes through the fire pipes 42 while heating the lower water chamber 40b, thus being introduced into the dry steam chamber 50. In such a case, the combustion heat flow speed within the fire pipes 42 is increased in proportion to the activity of the combustion within the chamber 20. During such a heat circulation, the combustion heat directly heats the lower water chamber 40b in addition to both the heat absorption pipes 48 and the rooster water pipes 49, thus quickly heating water. Since the heat absorption pipes 48 are arranged on the lower water chamber 40b at a position around the combustion chamber 20, the heat absorption area of the chamber 40b is enlarged. It is thus possible to quickly heat the chamber 40b. The heating rate for the water within the pipes 41a and 41b is in propcrtion to the combustion heat flow speed within the fire pipes 42. On the other hand, the limestone does not pass through the gaps between the rooster water pipes 49, but is filtered off. The limestone, filtered off by the rooster pipes 49, move down along the inclined rooster pipes 49 within the passage 18b while being heated by surplus heat from the combustion chamber 20. When the limestone is completely heated to a desired temperature, the shutter 15 is opened, thus allowing the heated limestone to be discharged from the passage 18a through the limestone drain port 14. Water is sprayed on the heated limestone coming from the drain port 14, thus producing calcium hydroxide which is used for neutralization of sulfur dioxide and carbon dioxide.

When water is highly heated by the combustion heat from the chamber 20, the water vaporizes, thus forming steam which is moved upwardly along the water pipes 41a and 41b prior to being introduced into the upper water chamber 40a. In such a case, the water pipes 41a and 41b have a small diameter, and so the steam passes through the pipes 41a and 41b along with water. In the upper water chamber 40a, steam flows into the steam tank 43, while water returns to the lower water chamber 40b through the water circulation pipes 45a and 45b. In the dry steam chamber 50, the steam is heated while passing through the dry steam pipe 51 prior to being collected by the steam collection pipe 52. The steam is, thereafter, introduced into the steam reheating pipe 54, extending across the front portion of the combustion chamber 20, through the steam feed pipe 55. The steam is reheated within the pipe 54 prior to being supplied to a turbine (not shown) through a steam discharging pipe 56.

During such an operation of the boiler system, the highly pressurized steam applies an exceedingly high pressure tc the water pipes 41a and 41b and to the fire pipes 42. However, the water pipes 41a and 41b are firmly locked together while being brought into surface contact with each other, with the gaps between the water pipes 41a and 41b being filled with refractory cement and more firmly locking the pipes 41a and 41b together. Therefore, the water pipes 41a and 41b effectively resist such high steam and water pressures.

On the other hand, the exhaust gas or the combustion gas, introduced into the dry steam chamber 50, is discharged from the chamber 50 through the exhaust pipe 57. In such a case, the unburnt powdered coal, which is raised up from the combustion chamber 20 into the dry steam chamber 50 along with combustion heat, return downward tc the combustion chamber 20 due to gravity under the guide of the ash recovery pipe 53. It is thus possible tc completely burn the unburnt powdered coal within the combustion chamber 20.

In the combustion chamber 20, the lump coal ash is moved down along the inclined portion of the rooster pipes 49 and is finally laid on the lower portion of the pipes 49. In order to remove the lump coal ash from the combustion chamber 20, the hydraulic cylinder actuators 28 are operated to push the transverse frame 29 along with the push rods 30. The push rods 30, parallely and regularly positioned within the gaps of the rooster water pipes 49 at the lower portion of the combustion chamber 20, thus push the lump coal ash on the rooster water pipes 49 to the back by the ash removing fins 31. The lump coal ash is thus discharged from the combustion chamber 20 through the ash outlet door 32 hinged to the rear portion of the rooster water pipes 49. In such a case, the door 32 is opened when a pressure is applied from the lump coal ash to the door 32. When such a pressure is removed from the door 32, the door is closed due to gravity. The lump coal ash, coming from the door 32, is dropped into the ash gutter 35, wherein the ash dispensing screw 34 discharges the lump coal ash into the outside of the boiler body.

When changing some of the existing water pipes 41a and 41b and/or the existing fire pipes 42 with new pipes, it is primarily necessary to change the angle of the boiler body. In order to control the angle of the boiler body, the second hydraulic cylinder actuator 64, connected to both the boiler body and the base 62, is operated to rotate the boiler body around the pin 63 the base 62, thus positioning the boiler body horizontally. When the boiler body is positioned horizontally as described above, it is easy to change the pipes 41a, 41b and/or 42 with new pipes.

The exhaust gas, introduced from the dry steam chamber 5C through the pipe 57 into the cyclone 70, is whirled dovrn around the central exhaust tube 71 prior to flowing upwardly into the tube 71 so as to be exhausted from the cyclone 70. When the flowing direction of the exhaust gas is reversed within the cyclone 70, relatively heavy ash is dropped onto the lower portion of the cyclone 70 prior to being discharged from the cyclone 70. On the other hand, the exhaust gas, passing through the tube 71, is heated by the combustion heat generated by the combustion air from the external fan 73 and the flame from the nozzle 76 of the burner 75. The compounds, laden in the gas, are thus oxidized by the combustion heat, while the carbon monoxide being changed into carbon dioxide. In addition, calcium hydroxide is supplied from the calciur. hydroxide supply silo 74 into the tube 71 through the blower tube 72 of the fan 73. The calcium hydroxide chemically reacts with the sulfur dioxide, thus being neutralized into calcium sulfite. The exhaust gas, laden with the neutralized calcium sulfite is, thereafter, introduced into the two cooling water units 80a and 80b wherein the calcium sulfite is discharged from the units 80a and 80b from the outlet ports. The exhaust gas flows into the electric dust collector 83 wherein the heavy metal dust and the like from the coal ash and/or calcium hydroxide is collected. Thereafter, the exhaust gas is introduced into the water within the first carbon dioxide dissolving tower 84a prior to flowing upwardly within the tower 84a. In the first tower 84a, carbon dioxide of the exhaust gas is partially dissolved in water. On the other hand, the pump 85b repeatedly sprays pressurized water, laden with carbon dioxide, from the lower portion of the tower 84a to the gas flowing upwardly within the tower 84a, thus dissolving carbon dioxide of the gas in the water and thereby increasing the concentration of carbon dioxide in the water. The exhaust gas is, thereafter, introduced into the upper portion of the second carbon dioxide dissolving tower 84b wherein the pump 85a sprays pressurized water, laden with carbon dioxide, from the first tower 84a to the gas flowing downwardly within the second tower 84b, thus secondarily dissolving carbon dioxide of the gas in the water. The exhaust gas is, thereafter, discharged from the tower 84b into the atmosphere through the outlet pipes 87. The water, lader. with carbon dioxide, is temporarily contained in the lower portion of the first tower 84b prior to being discharged from the tower 84b into the outside of the tower S4b. In such a case, the outlet port of the tower 84b is opened or closed by a valve.

The calcium hydroxide supply unit 90, installed under the outlet port of the second tower 84b, receives water laden with carbon dioxide from the second tower 84b while supplying calcium hydroxide to the water using the motor- driven screw 92. Therefore, carbon dioxide, laden in water, is changed into calcium carbonate, and so the water is neutralized prior to being discharged into the outside of the unit 90, The exr-aust gas from the combustion chamber is almost completely neutralized while being processed as described above, thus being almost completely free from toxic. Therefore, the boiler system of this invention almost completely remove contaminants from the exhaust gas, thus being almost completely free from environmental pollution, particularly, air pollution.

Industrial Applicability

As described above, the present invention provides a coal, oil and gas-fired boiler system. In the system, a pluralit of internal fire pipes are regularly and axially arranged within a water pipe, thus reducing the internal pressure of the pipes while quickly heating water within the water pipes. In addition, the water pipes, individually having a plurality of internal fire pipes, are densely arranged in a boiler body while being brought into surface contact with each other, with the gaps between the water pipes being filled with refractory cement and more firmly locking the water pipes together. In addition, the internal fire pipes axially extend within each water pipe while being regularly spaced apart from each other and being firmly retained at the spaced positions ry a plurality of spacers. Such firmly locked water ant fire pipes thus effectively resist an exceedingly high operational pressure of the boiler system caused by a high steam pressure.

Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Claims

Claims :

1. A coal, oil and gas-fired boiler system, comprising a boiler body with a combustion chamber provided at a lower portion of the boiler body, a fuel supply unit provided at a front portion of the boiler body for supplying fuel into the combustion chamber, upper and lower water chambers arranged above said combustion chamber and connected together by a plurality of first and second water pipes individually having a plurality of internal fire pipes, said fire pipes interiorly and axially extending in each of the water pipes so as to form a multi-pipe structure in cooperation with each water pipe, a plurality of water circulation pipes extending between the two water chambers and allowing water to accomplish a smooth convective circulation between the two water chambers, a dry steam chamber interiorly equipped with a dry steam pipe and installed above said upper water chamber, a steam collection and supplying unit used for collecting steam from said dry steam chamber and reheating the steam prior to supplying the steam to a turbine, an exhaust gas purifying unit connected to said boiler body, and a support base unit rotatably supporting said boiler body thereon, wherein said first and second water pipes are arranged within the boiler body while being brought into surface-contact with each other, with the fire pipes being arranged within each of the first and second water pipes, said second water pipes extending more at their both ends so as to penetrate into the two water chambers prior to being fixedly mounted to sidewalls of said two water chambers, each of said second water pipes also having a water circulation hole at a position within each of the two water chambers, thus communicating with the two water chambers .

2. The coal, oil and gas-fired boiler system according to claim 1, wherein said internal fire pipes of each of the first and second water pipes are regularly spaced apart from each other and are firmly retained at spaced positions by a plurality of spacers.

3. The coal, oil and gas-fired boiler system according to claim 1, wherein said exhaust gas purifying unit comprises a cyclone, said cyclone consisting of: a central exhaust tube vertically installed in a center of the cyclone; an external fan mounted at an external position outside a sidewall of said cyclone, with a blower tube extending from said external fan to a lower end of said central exhaust tube; a calcium hydroxide supply silo mounted to the blower tube and used for supplying calcium hydroxide into the central exhaust tube through the blower tube; and a burner provided with a flame nozzle positioned at said lower end of the central exhaust tube, said burner being used for heating exhaust gas to a high temperature.

4. The coal, oil and gas-fired boiler system according to claim 1, further comprising: a calcium hydroxide supply unit installed under a water outlet port of a carbon dioxide dissolving tower of said exhaust gas purifying unit, said calcium hydroxide supply unit consisting of: a main casing equipped with a dispensing screw; a first hopper formed on said main casing at a position just below the water outlet port of said tower and used for introduction of water, laden with carbon dioxide and coming from the water outlet port of the tower, into the casing; a second hopper formed on the casing and used for introduction of powdered calcium hydroxide into said casing; and an outlet port formed at an outlet end of said casing and used for discharging processed water into the outside of the casing.