Pressurized type gassification apparatus

Abstract: The known pressurized type gassification apparatus, in which a gassification furnace main body (1) having a water-cooled water structure and a duct (9) having a water-cooled wall structure and containing therein a group of gas cooling heat-exchangers (4) for a produced gas of the gassification furnace main body are disposed within a pressure vessel (5), is improved in order to prevent temperature fall of a produced gas caused by natural convection of the gas within the pressure vessel and to avoid the risk of fire and explosion caused by accumulation of char within the pressure vessel. The improvements reside in that an outlet of the duct (9) and the inside of the pressure vessel (5) are communicated with each other, a partition wall (10) connecting the wall of the duct at a level higher than the communicated portion with an inner wall surface of the pressure vessel is provided, and also there are provided equalizing valves (A, B) for communicating the respective sides of the partition wall with each other when a pressure difference between the respective sides of the partition wall has become a predetermined value or larger.

Description: BACKGROUND OF THE INVENTION: Field of the Invention: The present invention relates to improvements in a pressurized type gassification apparatus, in which a gassification furnace main body having a water-cooled wall structure and a duct having a water-cooled wall structure and containing therein a group of gas cooling heat-exchangers for a produced gas of the gassification furnace main body are disposed. Description of the Prior Art: Every one of Figs. 4 to 6 illustrates a different example of a pressurized type coal gassification apparatus in the prior art. At first, Fig. 4 shows one example of such apparatus having a single-wall structure, in which reference character a designates a gassification furnace main body, character b designates a water-cooled wall, character c designates a heat insulating material, character d designates a pressure vessel, and character e designates an ash hopper. In a pressurized type gassification apparatus, since the interior of the gassification furnace main body becomes high-temperature and high-pressure, in the case of a furnace wall having a single-wall structure such as the illustrated example, in view of a structural strength it was necessary to form the furnace wall with an extremely thick wall structure. However, if the furnace wall structure is made thick, not only a cost is increased resulting in poor economy, but also there is a shortcoming that damaging of the furnace is quickened because a thermal radiation effect cannot be obtained. In this way, by merely employing a water-cooled structure it was difficult to adapt to a high-temperature and high-pressure condition of the interior of the furnace and to get a sufficient wall strength. Hence, as shown in Fig. 5, a pressurized type gassification apparatus having the so-called double-wall structure in which a gassification furnace main body is disposed within a pressure vessel, was proposed (Japanese Patent Application No. 60-48202 (1985), Laid-Open Japanese Patent Specification No. 61-207492 (1986)). This double-wall structure is constructed of a gassification furnace main body 01 and a pressure vessel 06 containing the former therein, the inner pressure of the pressure vessel 06 is maintained at a pressure equal to or a little lower than the inner pressure of the gassification furnace main body 01, and thereby the structure is adapted to a pressure difference from the outside by dispersing the high pressure within the gassification furnace main body 01 in two steps of the structure wall of the gassification furnace main body 01 and the wall of the pressure vessel 06. If such provision is made, the wall of the gassification furnace main body 01 can be made to have a thin structure, also a high thermal radiation effect can be provided by employing, for example, a water-cooled wall structure, and so, there is an advantage that a life of a gassification furnace main body can be greatly improved. However, in the case of employing such double-wall structure, it is necessitated that the pressure within the pressure vessel 06 is maintained at a certain fixed pressure in correspondence to the pressure within the gassification furnace main body 01. Therefore, in the example shown in Fig. 5, a pressurized inert gas 040 is injected to the interior of the pressure vessel 06 (the exterior of the gassification furnace main body 01). In this case, the pressure of the inert gas fed into the pressure vessel 06 must be varied in correspondence to pressure change within the gassification furnace main body 01 produced upon operation of the apparatus. Consequently, there was a shortcoming that a complicated device or equipment was necessitated for adjusting and controlling the feeding pressure of the inert gas by detecting the pressure within the furnace by means of a differential pressure gauge 041. In order to eliminate these shortcomings, a pressurized type gassification apparatus illustrated in Fig. 6 was proposed (Japanese Patent Application No. 60-221324 (1985), Laid-Open Japanese Patent Specification No. 62-81489 (1987)). In this apparatus, an interior of a pressure vessel 06 accommodating a gassification furnace main body 01 and an interior of a pressure vessel 013 accommodating a water-cooled wall 014 surrounding a heat-exchanger group 07 communicated with the interior of the gassification furnace main body 01 are communicated with each other through a balance pipe 016. And, at a slag ejection port 03 of the gassification furnace main body 01 is provided a gas sealing device 018 making use of a water seal. In addition, at an outlet of the water-cooled wall 014 is provided a gas receiver 011 mounted to the pressure vessel 013, and between the water-cooled wall 014 and the pressure vessel 013 is formed a gas passageway 036 through which a produced gas at a low temperature can freely flow in and flow out. In the apparatus shown in Fig. 6, the pressure within the pressure vessel 013 can be controlled in a self-balancing manner by allowing a low-temperature produced gas at the outlet of the water-cooled wall 014 surrounding the heat-exchanger group 07 to freely flow into the pressure vessel 013, and hence a constant pressure difference can be maintained by easily following a pressure variation within the gassification furnace main body 01. Consequently, pressure control can be achieved very economically and reliably without necessitating special pressure detector means nor control means. In addition, by providing a freed portion at the outlet of the water-cooled wall 014, a difference in thermal expansion between the water-cooled wall 014 and the pressure vessel 013 can be absorbed by this portion. Furthermore, since the sealing device 018 making use of a water seal was provided at the slag ejection port 03 of the gassification furnace main body 01, a difference in thermal expansion between the gassification furnace main body 01 and the pressure vessel 06 also can be absorbed by this water seal structure. However, the pressurized type gassification apparatus shown in Fig. 6 and described above also could not be said to be favorable in view of a performance and use of the apparatus from the following reasons, and especially with respect to an aspect of safety there was a problem, because a low-temperature gas at the outlet of the water-cooled wall can freely flow into and flow out from the pressure vessel 013 without being subjected to any restriction. That is, the gas flowed into the pressure vessel 013 fills the interior of the same vessel. And the gas coming into contact with the water-cooled wall 014 is partly heated by heat dissipated from the inside of the water-cooled wall resulting in reduction of its specific gravity, and it rises along the water-cooled wall 014. In place of the rising gas, a gas filling the upper portion falls due to difference in a specific gravity. In other words, natural convection would occur within the pressure vessel 013. Since this low-temperature gas having fallen due to natural convection passes through the gas passageway 036, mixes into a principal flow system and lowers the temperature of the produced gas, the condition of the gas fed to an apparatus in the succeeding stage becomes unstable. As this is caused by a natural convection phenomenon, it is difficult to preliminarily estimate the amount of temperature change, and it is impossible to control it. In addition, when the produced gas at the outlet of the water-cooled wall 014 flows into the pressure vessel 013 as described above, an unburnt carbon content (char) contained in the produced gas also enters into the pressure vessel. And if the char accumulates within the pressure vessel, not only it is unfaborable in view of maintenance and management of the apparatus, but also it is undesirable from the aspect of safety, because the accumulated material may ignite and may cause fire due to any circumstance and further it may become a cause of occurrence of a disaster such as explosion or the like. SUMMARY OF THE INVENTION: It is therefore one object of the present invention to provide a pressurized type gassification apparatus having a double-wall structure, in which temperature fall of a produced gas caused by occurrence of natural convection within a pressure vessel is prevented and a risk of fire and explosion caused by accumulation of char within a pressure vessel can be eliminated. According to one feature of the present invention, there is provided a pressurized type gassification apparatus, in which a gassification furnace main body having a water-cooled wall structure and a duct having a water-cooled structure and containing therein a group of gas cooling heat-exchangers for a produced gas of the gassification furnace main body are disposed within a pressure vessel, improved in that an outlet of the duct and the inside of the pressure vessel are communicated with each other, a partition wall connecting the wall of the duct at a level higher than the communicated portion with an inner wall surface of the pressure vessel is provided, a bottom portion of a space in the pressure vessel under the partition wall is formed in a conical shape by means of refractory material, and also there are provided equalizing valves for communicating the respective sides of the partition wall with each other when a pressure difference between the respective sides of the partition was has become a predetermined value or larger. According to the present invention, owing to the structural feature that a partition wall connecting the wall of the duct having a water-cooled wall structure with an inner wall surface of a pressure vessel is provided at a level higher than a communicating portion between an outlet of the duct and the pressure vessel, normally the inside of the duct having a water-cooled water structure and the inside of the pressure vessel are shut off, and so, the above-mentioned problems caused by occurrence of natural convection within a pressure vessel can be resolved. In addition, when a difference between a pressure within a gassification furnace main body and within a water-cooled wall accommodating a heat-exchanger group and a pressure within a pressure vessel containing therein the water-cooled wall has reached a certain fixed value or larger, equalizing valves are opened so as to allow communication of gas, and thereby safety of the apparatus is insured. The above-mentioned and other objects, features and advantages of the present invention will become more apparent by reference to the following description of one preferred embodiment of the invention taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS: In the accompanying drawings: Fig. 1 is a general schematic view showing one preferred embodiment of the present invention; Fig. 2 is an enlarged schematic view showing a peripheral portion of the bottom of a gas cooling heat-exchanger group in the same apparatus; Fig. 3 is a detailed partial schematic view of equalizing valves in the same peripheral portion; and Figs. 4 to 6 are schematic views respectively showing different examples of a pressurized type coal gassification apparatus in the prior art. DESCRIPTION OF THE PREFERRED EMBODIMENT: Now, the present invention will be described in greater detail with reference to Figs. 1 to 3 which illustrate one preferred embodiment of the invention. At first, referring to Fig. 1, a gassification furnace main body 1 is formed of a water-cooled wall structure having its inner surface covered by refractory material, and it is disposed within a pressure vessel 3 jointly with a slag hopper 2. On the other hand, a plurality of gas cooling heat-exchangers 4 are contained within a duct 9 having a water-cooled wall structure, and further, the duct 9 is disposed within a pressure vessel 5. These pressure vessels 3 and 5 are connected by a pressure vessel connecting pipe 7 containing a gas communication pipe 6 therein so as to form a structure for maintaining pressure balance between the respective pressure vessels. The gas communication pipe 6 communicates the interior of the gassification furnace main body 1 and the interior of the water-cooled wall duct 9 with each other. Under the gassification furnace main body 1 is disposed a slag ejection hopper 2, which is connected with the gassification furnace main body 1 via a water seal mechanism 8, so that a difference in thermal expansion caused by a temperature difference between the gassification furnace main body 1 and the pressure vessel 3 can be absorbed perfectly. On the other hand, an outlet portion of the water-cooled water duct 9 containing the gas cooling heat-exchanger group 4 therein is not directly connected with the pressure vessel 5, but is communicated with the pressure vessel 5 via a gas passageway 12 so that a low-temperature gas at the outlet of the heat-exchanger group can freely flow into and out of the pressure vessel 5. Thanks to this gas passageway 12, a difference in thermal expansion between the water-cooled wall duct 9 and the pressure vessel 5 can be absorbed, and thereby a highly reliable apparatus in which there is no fear of damaging nor breaking the gas cooling heat-exchanger group, can be constructed. This gas passageway 12 is preset so as to insure a minimum gap clearance through which gas can flow at a rate necessary for maintaining balance between the pressure in the water-cooled wall duct 9 and the pressure in the pressure vessel 5. In addition, as shown more clearly in Fig. 2, a partition wall 10 is provided so as to connect the water-cooled wall duct 9 containing the heat exchanger group therein with the inner wall surface of the pressure vessel 5 at a level higher than the above-mentioned gas flow passageway 12. Furthermore, this partition wall 10 is provided with equalizing valves A and B, which would open only in the case where a pressure difference between the respective sides of the partition wall has become a predetermined value or larger. Fig. 3 shows one example of a detailed structure of the equalizing valves A and B mounted to the partition wall 10. The equalizing valve A is constructed in such manner that it may automatically open upwards against the gravity acting upon its own weight in the case where the pressure under the partition wall 10 is higher than the pressure above the partition wall 10. The equalizing valve B is constructed in such manner that it may automatically open against the gravity acting upon a weight mounted to a valve body in the case where the pressure above the partition wall 10 is higher than the pressure under the partition wall 10. It is to be noted that the bottom portion of the space under the partition wall 10 in the pressure vessel 5 is formed in a conical shape by means of refractory material 11 for the purpose of preventing dust entered therein accompanying outflow and inflow of gas from accumulating there as much as possible. In such an apparatus, a high-temperature gas produced within the gassification furnace main body 1 has its sensible heat thermally recovered in the gas cooling heat-exchanger group 4, and it is fed as a low-temperature gas to a subsequent installation (not shown). In addition, slag would fall in the slag hopper disposed under the gassification furnace main body 1, and then it is cooled and crushed. In this preferred embodiment of the present invention, even in the event that the gas filled in the space between the pressure vessel 5 and the water-cooled wall duct 9 is heated by the dissipation heat of the water-cooled wall duct 9 and a natural convection phenomenon of the gas is generated by the change of a specific gravity of the gas within the pressure vessel 5, it would not directly influence the gas passageway 12 at the outlet portion of the heat-exchanger group because the partition wall 10 is provided, and thereby the lowering of a temperature caused by the low-temperature gas within the pressure chamber flowing into the principal flow of the produced gas, can be prevented. Furthermore, owing to the equalizing valves A and B provided on this partition wall 10, safety of the water-cooled wall duct 9 and the pressure vessel 5 can be insured. More particularly, as described above the equalizing valves A and B are provided for the purpose of maintaining the pressure difference between the inside of the water-cooled wall duct 9 and the inside of the pressure vessel 5 at a certain constant balanced pressure difference which insures safety of the apparatus, and in the event that the pressure difference has exceeded this balanced pressure difference and has become an abnormal value, either one of the equalizing valves A and B would automatically open and the pressure difference would be returned to a normal value. The above-described equalizing valves A and B would have their appropriate specifications determined after a tolerable pressure difference has been calculated taking into consideration a structural strength and an operating condition of the pressurized type gassification apparatus. In addition, the equalizing valves are necessitated to be formed in such structure that a fine granular char component contained in the gas filling the inside of the pressure vessel 5 may hardly accumulate thereon. Furthermore, if the equalizing valves A and B are designed under the consideration that they can aut omatically maintain the pressure within the pressure vessel at an appropriate value even upon start and stop of the pressurized type gassification apparatus and upon variation of a load, safety and reliability of the apparatus can be further improved. Specifically, they are designed so as to operate at a pressure difference of 50 - 600 mm water column taking into account a pressure difference between the upper side and the lower side of the partition wall, an operational aperture area and an own weight of the equalizing valve and a compressive strength of the water-cooled wall duct and the pressure vessel. As described above, in the illustrated embodiment, owing to the provision of the partition wall 10 provided with the equalizing valves A and B within the pressure vessel 5, the problems in the performance and utilization of the pressurized type gassification apparatus generated as a result of a natural convection phenomenon of the gas within the pressure vessel 5, can be resolved, and safety and reliability of the apparatus are also improved. As will be apparent from the detailed description of one preferred embodiment above, according to the present invention, in a pressurized type gassification apparatus having a double-wall structure, in which a gassification furnace main body having a water-cooled wall structure and a duct having a water-cooled wall structure and containing therein a group of gas cooling heat-exchangers for a produced gas of the same gassification furnace main body are disposed within a pressure vessel, problems in the performance and utilization of the apparatus such as temperature lowering of a produced gas which occurred in the prior art as a result of natural convection of the gas within the pressure vessel and a risk of fire and explosion resulted from accumulation of char within the pressure vessel, can be resolved, and an apparatus having high safety and reliability can be provided.

Claims: A pressurized type gassification apparatus, in which a gassification furnace main body (1) having a water-colled wall structure and a duct (9) having a water-cooled wall structure and containing therein a group of gas cooling heat-exchangers (4) for a produced gas of said gassification furnace main body are disposed within a pressure vessel (5); wherein an outlet of said duct (9) and the inside of said pressure vessel (5) are communicated with each other, characterized by a partition wall (10) connecting the wall of said duct (9) at a level higher than said communicated portion with an inner wall surface of said pressure vessel (5), a bottom portion of a space in the pressure vessel (5) under the partition wall (10) being formed in a conical shape by means of refractory material (11), and equalizing valves (A, B) for communicating the respective sides of said partition wall (10) with each other when a pressure difference between the respective sides of said partition wall (10) has become a predetermined value or larger. A pressurized type gassification apparatus as claimed in Claim 1, characterized in that said equalizing valves are provided in multiple, among which one or a plurality of equalizing valves are constructed so as to communicate the respective sides of said partition wall when a pressure on one side of said partition wall has become higher than a pressure on the other side thereof by a predetermined value or larger, and the remaining equalizing valves are constructed so as to communicate the respective sides of said partition wall when the pressure on the other side of said partition wall has become higher than the pressure on said one side thereof by the predetermined or larger. A pressurized type gassification apparatus as claimed in Claim 1, characterized in that an outlet side of said duct having a water-cooled wall structure is communicated with the inside of said pressure vessel (5) via a gas passageway (12).

Inventors: AKIYAMA HIROSHI C O NAGASAKI S, KOGA YOSHITAKA C O NAGASAKI SH, OGAWA KIICHIRO C O MITSUBISHI, TAKAKI MITSUHARU C O NAGASAKI, AKIYAMA, HIROSHI, C/O NAGASAKI SHIPYARD ENGINE, KOGA, YOSHITAKA, C/O NAGASAKI SHIPYARD ENGINE, OGAWA, KIICHIRO, C/O MITSUBISHI JUKOGYO K.K., TAKAKI, MITSUHARU, C/O NAGASAKI SHIPYARD ENGINE
Applicants: MITSUBISHI HEAVY IND LTD, MITSUBISHI JUKOGYO KABUSHIKI KAISHA
Application year: 1991
Main classification: C10J3
IPC codes: C10J3