Fluidized bed gasifier ash cooling tank

Abstract

The present application discloses a fluidized bed gasification furnace ash cooling tank, which is used to cool the high-temperature ash discharged from the fluidized bed gasification furnace. It includes a main tank body, a cooling chamber is formed in the main tank body, and an ash inlet channel and an ash outlet channel are formed at the upper and lower ends of the cooling chamber respectively. The ash enters the cooling chamber from the ash inlet channel to be cooled and is finally discharged from the ash outlet channel. A partition is fixedly installed inside the main tank body, the partition includes a gathering member and a guide member, the gathering member is arranged to gradually reduce in diameter from top to bottom to tend to form a cone, and the ash is cooled on the side wall of the gathering member by the cooling liquid output from at least one first cooling liquid spraying member, and the generated ash vapor will escape along the side wall of the cooling chamber, gather at the top of the cooling chamber, and finally be discharged through at least one exhaust pipe installed on the periphery of the ash inlet channel, so as to prevent the ash vapor from entering the ash inlet channel and affecting the slag discharge of the fluidized bed gasification furnace.

Description

Technical Field

[0001] The invention belongs to the technical field related to coal chemical industry, and particularly relates to an ash cooling tank for a fluidized bed gasifier. Background Art

[0002] Clean and efficient use of coal is a major technical issue in my country's energy and environmental protection fields today, and is also one of the key technologies for the sustainable development of my country's national economy.

[0003] Coal can be gasified with a gasifying agent in a fluidized bed gasifier to produce raw coal gas. Ash is produced during the coal gasification reaction in the fluidized bed gasifier. The ash is typically discharged from the slag discharge pipe at the bottom of the gasifier and enters the expansion tube. Upon entering the expansion tube, the ash is approximately 920°C. After heat exchange in the expansion tube, the temperature drops below 900°C. The ash then enters the fluidized bed gasifier's ash cooling tank, where it continues to cool to below 400°C.

[0004] In the prior art, the slag discharge system of a fluidized bed gasifier is divided into two types: dry slag discharge and wet slag discharge. In the wet slag discharge, the ash is received in a chiller for cooling and then discharged for treatment. However, for a circulating fluidized bed gasifier, this wet slag discharge has some obvious disadvantages. For example, the coolant for wet slag discharge has a high temperature after cooling the high-temperature ash, the circulation treatment system is complex, and a large amount of calcium ions and magnesium ions in the ash will enter the coolant, making it difficult for the coolant to settle. In particular, the waste liquid generated after cooling needs to be subsequently treated, which is costly.

[0005] Compared with wet slag discharge, dry slag discharge does not produce waste liquid and is environmentally friendly. However, the ash temperature of dry slag discharge is not easy to control. If the cooling temperature is too low, saturated water will be precipitated from the ash during cooling, thereby affecting the environmental protection and efficiency of slag discharge. In addition, dry slag discharge will also generate a large amount of ash steam during cooling. The ash steam will escape and flow back into the slag discharge pipe channel of the circulating fluidized bed gasifier, affecting the slag discharge of the gasifier. Summary of the Invention

[0006] An advantage of the present invention is that it provides an ash cooling tank for a fluidized bed gasifier, which can quickly cool incoming high-temperature ash.

[0007] One advantage of the present invention is that it provides a fluidized bed gasification furnace ash cooling tank, which can accurately control the cooling temperature of the ash to ensure that no saturated water is precipitated after the ash is cooled.

[0008] Another advantage of the present invention is that it provides a fluidized bed gasification furnace ash cooling tank, in which the ash is cooled only in the area close to the side wall of the cooling chamber and generates an ash steam diversion. The ash steam will be discharged in time after escaping to the top of the cooling chamber, avoiding the ash steam affecting the slag discharge.

[0009] Another advantage of the present invention is that it provides a fluidized bed gasification furnace ash cooling tank, wherein the inner and outer walls of the main tank body form a cooling space into which coolant can be injected, thereby preventing the main tank body from overheating to ensure the safety of the main tank body, and also reducing the high temperature resistance required by the main tank body material, thereby reducing the equipment cost.

[0010] Another advantage of the present invention is that it provides a fluidized bed gasification furnace ash cooling tank, which can control the air pressure inside the main tank body to always be thirty to fifty kilopascals lower than the pressure of the steam chamber of the fluidized bed gasification furnace, so that the slag discharge in the fluidized bed gasification furnace will smoothly enter the main tank body under the action of this pressure difference, and the ash steam will also find it difficult to overcome this pressure difference and enter the ash inlet channel to affect the slag discharge in the fluidized bed gasification furnace.

[0011] To achieve at least one of the above advantages of the present invention, the present invention provides a fluidized bed gasification furnace ash cooling tank for cooling high-temperature ash discharged from the fluidized bed gasification furnace, the fluidized bed gasification furnace ash cooling tank comprising:

[0012] A main tank body, wherein an ash inlet channel and an ash outlet channel are formed at the upper and lower ends of the main tank body respectively, and a cooling chamber is formed between the ash inlet channel and the ash outlet channel;

[0013] a partition, the partition including a gathering member, the gathering member being configured in a trumpet shape and forming a communication channel, the gathering member being disposed in the middle of the cooling chamber, the gathering member forming a communication channel, and the cross-sectional diameter of the communication channel formed by the gathering member decreasing from top to bottom; the opening size of the communication channel formed by the gathering member at the upper portion is close to the cross-sectional diameter of the cooling chamber, so that the ash and ash steam entering through the ash inlet channel first pass through the communication channel;

[0014] The cross-sectional diameter of the ash inlet channel is smaller than the cross-sectional diameter of the smallest portion of the communication channel;

[0015] At least one first coolant spraying member, the first coolant spraying member includes a spraying head and a pipe, the spraying head is connected to the pipe, and the spraying head is arranged in the cooling cavity to spray coolant toward the outer side wall of the gathering member opposite to the forming of the connecting channel.

[0016] According to an embodiment of the present invention, a plurality of through holes are formed on the side wall of the retracting member, and the apertures of the through holes are set so as to prevent ash from passing through and allow cooling liquid to pass through.

[0017] According to an embodiment of the present invention, the partition comprises a guide member, wherein the guide member extends downward from the gathering member, and the guide member forms a slag discharge channel communicating with the communication channel.

[0018] According to an embodiment of the present invention, the ash inlet channel extends to a predetermined distance into the cooling chamber of the main tank body to form a dome-shaped space with the top of the main tank body.

[0019] According to one embodiment of the present invention, another first coolant spray member is installed in the dome-shaped space formed by the ash inlet channel and the top and side walls of the main tank body, a plurality of liquid spray ports are opened on the upper part of the second coolant spray member, and the second coolant spray member forms a liquid channel connected to the liquid spray ports, wherein the liquid channel passes through the main tank body.

[0020] According to one embodiment of the present invention, the fluidized bed gasification furnace ash cooling tank further includes a second coolant spraying member, which is disposed in the cooling cavity formed by the inner tank and is located below the partition.

[0021] According to an embodiment of the present invention, the main tank is equipped with at least one temperature detector and a controller, wherein the temperature detector is configured to measure the temperature of the ash before being discharged from the ash outlet channel. The controller is communicatively connected to the temperature detector.

[0022] According to one embodiment of the present invention, at least one exhaust pipe is installed on the outer periphery of the ash inlet channel on the upper part of the main tank body, and the exhaust pipe extends from the outside of the main tank body into the dome-shaped space formed by the ash inlet channel and the top and side walls of the main tank body.

[0023] According to one embodiment of the present invention, the main tank body is installed with a pressure regulating assembly and a controller, and the pressure regulating assembly includes a pressure measuring piece and at least one pressure regulating piece installed on the exhaust pipe, wherein the pressure regulating piece is connected to the exhaust pipe and is controllably connected to the controller.

[0024] According to one embodiment of the present invention, the main tank body includes an outer shell and an inner liner, wherein the inner liner forms the cooling cavity, the outer shell is arranged on the outside of the inner liner, and a cooling space is formed between the outer shell and the inner liner. At least one first channel connected to the cooling space is opened at the lower part of the outer shell, and at least one second channel connected to the cooling space is opened at the upper part of the outer shell.

[0025] Further objects and advantages of the present invention will be fully apparent from an understanding of the following description.

[0026] These and other objects, features and advantages of the present invention will be fully reflected in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A schematic diagram of the three-dimensional structure of the ash cooling tank of the fluidized bed gasification furnace according to the present invention is shown.

[0028] Figure 2 A side sectional view of the ash cooling tank of the fluidized bed gasification furnace according to the present invention is shown along the central axis AA.

[0029] Figure 3 A schematic diagram of the three-dimensional structure of the first coolant spraying member of the present invention is shown.

[0030] Figure 4 A schematic diagram of the three-dimensional structure of the second coolant spraying member of the present invention is shown. DETAILED DESCRIPTION

[0031] The following description is intended to disclose the present invention so that those skilled in the art can implement the present invention. The preferred embodiments described below are for illustrative purposes only, and those skilled in the art will readily appreciate other obvious variations. The basic principles of the present invention defined in the following description may be applied to other embodiments, variations, improvements, equivalents, and other technical solutions that do not depart from the spirit and scope of the present invention.

[0032] Those skilled in the art should understand that, in the disclosure of the present invention, the terms "longitudinal", "transverse", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like to indicate orientations or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings, which are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, the above terms should not be understood as limiting the present invention.

[0033] It is to be understood that the term "one" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of an element may be one, while in another embodiment, the number of the elements may be multiple, and the term "one" should not be understood as a limitation on the quantity.

[0034] refer to Figure 1-4 The ash cooling tank of a fluidized bed gasifier according to a preferred embodiment of the present invention will be described in detail below.

[0035] The fluidized bed gasification furnace ash cooling tank includes a main tank body 10 , a partition 20 , and at least one first cooling liquid spraying member 30 .

[0036] An ash inlet channel 101 and an ash outlet channel 102 are respectively formed at the upper and lower ends of the main tank body 10, and a cooling chamber 103 is formed between the ash inlet channel 101 and the ash outlet channel 102. The high-temperature ash discharged from the fluidized bed gasification furnace will enter the cooling chamber 103 from the ash inlet channel 101 for cooling, and finally be discharged from the ash outlet channel 102.

[0037] The partition 20 , the first coolant spraying member 30 , and the second coolant spraying member 40 are installed inside the main tank 10 .

[0038] Preferably, the main tank 10 includes an outer shell 11 and an inner liner 12, wherein the inner liner 12 forms the cooling chamber 103. The outer shell 11 is sleeved on the outer surface of the inner liner 12 to completely wrap and protect the inner liner 12.

[0039] It is worth mentioning that a cooling space 104 is formed between the outer shell 11 and the inner liner 12, at least one first channel 1101 connected to the cooling space 104 is opened at the lower part of the outer shell 11, and at least one second channel 1102 connected to the cooling space 104 is opened at the upper part of the outer shell 11.

[0040] It is particularly worth mentioning that the first channel 1101 and the second channel 1102 respectively pass through the inner liner 12 but are not connected to the cooling space 104. External cooling fluid can enter the cooling space 104 through the first channel 1101 to exchange heat with the wall of the inner liner 12, and the cooling fluid after heat exchange can be discharged through the second channel 1102.

[0041] As a variant, the external cooling fluid can also enter the cooling space 104 through the second channel 1102 to exchange heat with the wall of the inner liner 12, and the cooling fluid after heat exchange can be discharged through the first channel 1101.

[0042] It is worth mentioning that by controlling the flow rate and / or flow rate of the cooling fluid, the temperature of the inner liner 12 wall can be cooled by the cooling fluid and always maintained below 300 degrees Celsius, which not only ensures the safety of the equipment, but also reduces the high temperature resistance required by the material of the inner liner 12, thereby reducing the cost of the equipment.

[0043] The partition 20 is fixedly installed inside the main tank body 10 and includes a folding member 21. The folding member 21 is located in the middle of the cooling chamber 103. The folding member 21 is configured in a trumpet shape and forms a connecting passage 2101. The cross-sectional diameter of the connecting passage 2101 formed by the folding member 21 of the partition 20 located in the cooling chamber 103 decreases from top to bottom. In this way, the inner wall forming the connecting passage 2101 can further cool the ash vapor and increase the contact area with the ash vapor, thereby allowing the ash vapor to cool rapidly and causing the connecting passage 2101 to fall from top to bottom.

[0044] The side wall of the gathering member 21 is provided with a plurality of through-holes 2102. The apertures of the through-holes 2102 are set to prevent ash from passing through, while allowing the cooling liquid to pass through. In this way, the ash falling from above the partition 20 will be gathered by the gathering member 21 and fall from the communicating channel 2101 from top to bottom, and then from the ash. In other words, the communicating channel 2101 of the gathering member 21, due to the decreasing cross-sectional diameter from top to bottom, can also play a role in guiding the ash to fall.

[0045] It is worth mentioning that the opening size of the upper portion of the connecting channel 2101 formed by the folding member 21 is close to the cross-sectional diameter of the cooling chamber 103 , so that the ash and ash steam entering through the ash inlet channel 101 first pass through the connecting channel 2101 .

[0046] The partition 20 further includes a guide member 22, which extends downward from the gathering member 21 and forms a slag discharge channel 2201 that communicates with the communication channel 2101. As a result, after being gathered by the gathering member 21, the slag can continue to fall through the slag discharge channel 2201 and then be discharged through the slag outlet channel 102.

[0047] The first coolant spraying member 30 includes a spray head 31 and a pipe 32, wherein the spray head 31 is connected to the pipe 32. The spray head 31 is disposed in the cooling cavity 103 and sprays coolant, preferably water, toward the outer wall of the gathering member 21 opposite to the communicating channel 2101.

[0048] The pipe 32 extends to the outside of the main tank body 10 so that external cooling liquid flows into the spray head 31 through the pipe 32 and is sprayed, thereby cooling the ash in the main tank body 10 .

[0049] Specifically, a supply device for an externally supplied coolant is connected to the pipe 32 so as to continuously inject the coolant through the pipe 32 into the spray head 31. The spray head 31 has a nozzle for atomizing and spraying the injected coolant. The first coolant spraying member 30 is configured to spray the coolant toward the sidewall of the retracting member 21. After being atomized by the spraying head 31, the coolant is sprayed toward the outer wall of the retracting member 21 opposite to the connecting passage 2101. The sprayed coolant can reduce the temperature of the partition 20 through heat exchange. On the other hand, the sprayed coolant can also pass through the through-holes 2102 in the retracting member 21. The coolant that passes through can remove the cooled ash attached to the inner wall of the connecting passage 2101 from top to bottom under the action of gravity. In this way, the ash can be effectively prevented from accumulating on the retracting member 21 and clogging the through-holes 2102.

[0050] It is understood that while the coolant will exchange heat with the ash deposited on the sidewalls of the gathering member 21, thereby reducing the ash temperature, the contact between the coolant and the high-temperature ash will generate ash vapor. However, since the first coolant spraying member 30 sprays only toward the sidewalls of the gathering member 21, the ash vapor is generated only on the sidewalls of the gathering member 21. This ash vapor will dissipate upward along the sidewalls of the main tank body 10 and ultimately gather at the top of the main tank body 10.

[0051] The ash inlet channel 101 extends to a predetermined distance into the cooling chamber 103 of the main tank body 10 to form a dome-shaped space 106 with the top of the main tank body 10. It is worth mentioning that the ash inlet channel 101 is coaxially arranged with the connecting channel 2101. It is particularly worth mentioning that the cross-sectional diameter of the ash inlet channel 101 is smaller than the cross-sectional diameter of the smallest point of the connecting channel 2101. In this way, after the ash vapor escapes upward along the side wall of the main tank body 10, at least part of the ash vapor will gather in the dome-shaped space 106, and will not easily enter the ash inlet channel 101 and affect the slag discharge of the fluidized bed gasifier.

[0052] Preferably, another first coolant spraying member 30 is installed in the dome-shaped space 106 formed by the ash inlet channel 101 and the top and side walls of the main tank body 10. The coolant provided by the liquid supply device will be atomized by the first coolant spraying member 30 and sprayed from top to bottom into the dome-shaped space 106, wherein the coolant contacts the ash and exchanges heat with the ash, thereby cooling the ash vapor.

[0053] The coolant is sprayed from bottom to top by the first coolant spraying member 30 , and the ash vapor also escapes from bottom to top, thereby preventing the ash vapor from obstructing the spraying of the coolant.

[0054] The fluidized bed gasification furnace ash cooling tank further includes a second coolant spraying member 40 . The second coolant spraying member 40 is disposed in the cooling cavity 103 formed by the inner liner 12 and is located below the partition 20 .

[0055] The second coolant spray member 40 is provided with a plurality of spray ports 401 at its upper portion, and a liquid passage 402 is formed in the second coolant spray member 40 in communication with the spray ports 401. The liquid passage 402 passes through the main tank 10 and is in communication with the external liquid supply device. As a result, the coolant injected into the liquid passage 402 of the second coolant spray member 40 is sprayed upward from the spray ports 401 to further cool the ash after passing through the partition 20. Preferably, the second coolant spray member 40 is also provided with a plurality of spray ports at its lower portion.

[0056] Preferably, the second coolant spray member 40 is implemented as a cross-shaped pipe and is horizontally installed inside the main tank body 10, and the spray ports 401 are staggered on the upper part of the second coolant spray member 40 to maximize the cooling coverage of the second coolant spray member 40, so that the cooling efficiency of the second coolant spray member 40 is higher.

[0057] It can be understood that after being gathered by the partition 20, the ash will gather toward the axial center of the main tank body 10 and continue to fall. The axial center area inside the main tank body 10 will be mainly occupied by the falling ash, and the ash vapor generated by the heat exchange between the coolant sprayed by the first coolant spray part 30 and the second coolant spray part 40 and the ash will be mainly concentrated on the periphery of the ash and continue to rise. The ash vapor will escape upward through the perforation 2102 until it finally gathers at the top of the inner tank 12.

[0058] The main tank 10 is also equipped with at least one temperature sensor 50 and a controller. The temperature sensor 50 is configured to measure the temperature of the ash before it is discharged from the ash outlet passage 102. The controller is communicatively connected to the temperature sensor 50. The temperature detected by the temperature sensor 50 is transmitted to the controller, which controls the liquid supply rate of the pump body connected to the pipe 32 of the first coolant spraying member 30 and the liquid passage 402 of the second coolant spraying member 40. In addition, the controller also controls the speed of the cooling fluid entering the cooling space 104.

[0059] It can be understood that due to the mutual cooperation between the temperature sensor 50 and the controller, the temperature of the ash cooled by the cooling chamber 103 can be accurately controlled between 350 and 400 degrees Celsius when it is discharged, thereby ensuring that no saturated water precipitates from the ash.

[0060] At least one exhaust pipe 60 is installed on the outer periphery of the ash inlet channel 101 on the upper part of the main tank body 10. The exhaust pipe 60 extends from the outside of the main tank body 10 into the dome-shaped space 106 formed by the ash inlet channel 1202 and the top and side walls of the main tank body 10 to discharge the ash vapor accumulated in the dome-shaped cavity in time.

[0061] The fluidized bed gasification furnace ash cooling tank further includes a pressure regulating assembly 70 , which includes a pressure measuring piece 71 and at least one pressure regulating piece 72 installed on the exhaust pipe 60 , wherein the pressure regulating piece 72 is in communication with the exhaust pipe 60 .

[0062] Preferably, the pressure measuring element 71 is fixedly mounted on the ash inlet passage 101 to detect the pressure at the ash inlet passage 101. The controller can control the pressure regulating element 72 based on the pressure difference between the pressure measuring element 71 and the pressure in the fluidized bed, thereby adjusting the exhaust rate of the exhaust pipe 60 so that the pressure in the main tank 10 is always 30 to 50 kilopascals lower than the pressure in the steam chamber of the fluidized bed gasifier.

[0063] In this way, the slag discharge in the fluidized bed gasification furnace will smoothly pass through the ash inlet channel 101 into the cooling chamber 103 of the main tank body 10 under the action of this pressure difference, and the ash steam will find it difficult to overcome this pressure difference and enter the ash inlet channel 101 to affect the slag discharge in the fluidized bed gasification furnace.

[0064] Those skilled in the art will appreciate that the pressure measuring member 71 may be configured as a pressure sensor, and the pressure regulating member 72 may be configured as an air pump or a pressure regulating valve.

[0065] Those skilled in the art will appreciate that the embodiments of the present invention described above and shown in the accompanying drawings are intended to be illustrative only and are not intended to limit the present invention. The advantages of the present invention have been fully and effectively achieved. The functional and structural principles of the present invention have been demonstrated and illustrated in the embodiments. Any variations or modifications may be made to the embodiments of the present invention without departing from the principles described.

Claims

1. Fluidized bed gasification furnace ash cooling tank, used to cool the high-temperature ash discharged from the fluidized bed gasification furnace, characterized by: The fluidized bed gasifier ash cooling tank comprises: A main tank body, wherein an ash inlet channel and an ash outlet channel are formed at the upper and lower ends of the main tank body respectively, and a cooling chamber is formed between the ash inlet channel and the ash outlet channel; a partition, the partition including a gathering member, the gathering member being configured in a trumpet shape and forming a communication channel, the gathering member being disposed in the middle of the cooling chamber, the gathering member forming a communication channel, and the cross-sectional diameter of the communication channel formed by the gathering member decreasing from top to bottom; the opening size of the communication channel formed by the gathering member at the upper portion is close to the cross-sectional diameter of the cooling chamber, so that the ash and ash steam entering through the ash inlet channel first pass through the communication channel; The cross-sectional diameter of the ash inlet channel is smaller than the cross-sectional diameter of the smallest portion of the communication channel; at least one first coolant spraying member, the first coolant spraying member comprising a spraying head and a pipe member, the spraying head being in communication with the pipe member, the spraying head being disposed in the cooling cavity and spraying coolant toward an outer side wall of the gathering member opposite to the communicating channel; The side wall of the retracting member is provided with a plurality of through holes, wherein the apertures of the through holes are set so as to prevent ash from passing through and allow cooling liquid to pass through; The partition comprises a guide member, wherein the guide member extends downward from the gathering member, and the guide member forms a slag discharge channel communicating with the communication channel.

2. The fluidized bed gasification furnace ash cooling tank according to claim 1, characterized in that: The ash inlet channel extends into the cooling chamber of the main tank body for a predetermined distance to form a dome-shaped space with the top of the main tank body.

3. The ash cooling tank for fluidized bed gasification furnace according to claim 2, characterized in that: Another first coolant spraying member is installed in the dome-shaped space formed by the ash inlet channel and the top and side walls of the main tank body.

4. The fluidized bed gasification furnace ash cooling tank according to claim 2, characterized in that: The fluidized bed gasification furnace ash cooling tank further includes a second coolant spraying member, which is arranged in the cooling cavity formed by the inner tank and is located below the partition. A plurality of liquid spraying ports are opened on the upper part of the second coolant spraying member, and the second coolant spraying member forms a liquid passage connected to the liquid spraying ports, wherein the liquid passage passes through the main tank body.

5. The fluidized bed gasification furnace ash cooling tank according to any one of claims 1 to 4, characterized in that: The main tank body is equipped with at least one temperature detecting element and a controller. The temperature detecting element is configured to measure the temperature of the ash before being discharged from the ash outlet channel. The controller is communicatively connected to the temperature detecting element.

6. The fluidized bed gasification furnace ash cooling tank according to any one of claims 2 to 4, characterized in that: At least one exhaust pipe is installed on the upper part of the main tank body at the periphery of the ash inlet channel, and the exhaust pipe extends from the outside of the main tank body into the dome-shaped space formed by the ash inlet channel and the top and side walls of the main tank body.

7. The ash cooling tank for fluidized bed gasification furnace according to claim 6, characterized in that: The main tank body is installed with a pressure regulating assembly and a controller, wherein the pressure regulating assembly includes a pressure measuring piece and at least one pressure regulating piece installed on the exhaust pipe, wherein the pressure regulating piece is communicated with the exhaust pipe and is controllably connected to the controller.

8. The ash cooling tank for fluidized bed gasification furnace according to claim 1, characterized in that: The main tank body includes an outer shell and an inner liner, wherein the inner liner forms the cooling cavity, the outer shell is arranged on the outside of the inner liner, and a cooling space is formed between the outer shell and the inner liner. At least one first channel connected to the cooling space is opened at the lower part of the outer shell, and at least one second channel connected to the cooling space is opened at the upper part of the outer shell.

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