WO2025202760A1

WO2025202760A1 - A fired heater

Info

Publication number: WO2025202760A1
Application number: PCT/IB2025/051880
Authority: WO
Inventors: Mandip Kapoor; Rajesh Patel; Shilpa SINGH; Rajesh Singh; Rupam Mukherjee; Marcus Barla
Original assignee: Engineers India Ltd
Current assignee: Engineers India Ltd
Priority date: 2024-03-29
Filing date: 2025-02-21
Publication date: 2025-10-02
Anticipated expiration: 2026-09-29

Abstract

Present disclosure relates to an innovative tube configuration in the firebox which does not use any 180 degree return bend and allows the placing of a higher number of tubes on all four walls (W) of the cabin heater firebox. In this arrangement, tubes (20) are connected through 90 deg. bends and can be placed closely on all 4 walls (W) of the firebox, while being supported through vertical pipe-column supports or conventional wall tube hangers. The tubes (20) on at least one of the walls of the firebox need to be at a gentle slope and can be kept horizontal at other walls. This configuration has multiple advantages with respect to the existing fired heater tube arrangements, like placement of tubes irrespective of standard tube pitch as no 180deg. standard return bend is used, maximization of heat transfer area within a defined fire box volume, uniform heat flux & hydraulic symmetry in all passes (including odd passes).

Description

A FIRED HEATER

TECHNICAL FIELD

[0001] Present disclosure relates to process heaters. Particularly, the present disclosure relates to a cabin (box type) fired heater firebox (radiant section) that provides heat to the hydrocarbons through radiation mode.

BACKGROUND OF THE DISCLOSURE

[0002] The information in this section merely provides background information related to the present disclosure and may not constitute prior art(s) for the present disclosure.

[0003] Fired heaters are generally utilized in refineries and petrochemical industries. The fired heaters are utilized to heat hydrocarbons and other feeds for further processing, etc. The fired heater includes a plurality of burners. The plurality of burners may be utilized to heat hydrocarbons which generally flow through multiple tubes accommodated within a housing of the fired heater. The plurality of burners provides heat to the tubes so that the heat can be transferred from outside of the tubes towards inside the tubes which raises temperature of hydrocarbon flowing through the tubes. The plurality of burners may be provided at a floor / wall / roof of the housing. Further, the housing includes multiple side walls, which are utilized to support the tubes accommodated inside the housing.

[0004] Typically, the housing of the cabin fired heater includes side walls that may be oriented such as it defines a rectangular box type shape. Generally, the housing of the fired heater may be constructed such that two opposite side walls of the housing have large width, and the remaining two side walls of the housing have smaller width. The tubes of the conventional (prior art) fired heater are mainly provided with respect to the side walls having large width and the remaining side walls of the housing are kept free from tubes, these side walls remain unutilized. Further, the unutilized side walls of the fired heater require a higher thickness of the refractory linings. Furthermore, the conventional fired heater passes comprise of series of tubes connected through U- shaped (180-degree return) bends. The U-shaped bends induce significant pressure drop when the fluid flows through these connecting bends. This increases the upstream pump pressure requirement for overcoming higher pressure drop in the system resulting in higher cost and higher tube thickness erosion.

[0005] The present disclosure is directed to overcome one or more limitations stated above or any other limitations associated with the prior art.

[0006] The drawbacks/difficulties/disadvantages/limitations of the conventional techniques explained in the background section are just for exemplary purposes and the disclosure would never limit its scope only such limitations. A person skilled in the art would understand that this disclosure and below mentioned description may also solve other problems or overcome the other drawbacks/disadvantages of the conventional arts which are not explicitly captured above.

SUMMARY OF THE DISCLOSURE

[0007] The one or more shortcomings of the prior art are overcome by the configuration of a fired heater as claimed, and additional advantages are provided through the provision of the fired heater as claimed in the present disclosure. Additional features and advantages are realized through the techniques of the present disclosure. Other embodiments and aspects of the disclosure are described in detail herein and are considered a part of the claimed disclosure.

[0008] In one non-limiting embodiment of the present disclosure, a cabin type fired heater fire box (radiant section) is disclosed. The fired heater includes a housing, refractory and a tube circuit with tube supports. The housing may be defined with a plurality of sides. The tube circuit may be disposed in the housing and includes a plurality of tube passes. Further, each tube pass of the plurality of tube passes includes an inlet, an outlet, and a plurality of tube parts. The plurality of tube parts extend between the inlet and outlet, the plurality of tube parts extend close to the plurality of sides and at a gentle slope on at least one side of the plurality of sides. Furthermore, the plurality of burners may be coupled to the housing and configured to heat the tube passes. Accordingly, the fired heater is adapted to extend the tube parts of each tube pass close to each wall of the housing, thereby, enabling utilization of the earlier unutilized wall which results in extending the overall length of the tube pass, without requirement of increase in the size of the housing.

[0009] In an embodiment of the present disclosure, the plurality of tube parts extend one below or above the other between a top end and a bottom end of the housing.

[0010] In an embodiment of the present disclosure, each tube part of the plurality of tube parts may be defined with four tube sub-parts, wherein tube sub-parts may be close to the plurality of sides and at least one tube sub-part extends at a gentle slope relative to a horizontal plane.

[0011] In an embodiment of the present disclosure, each tube part of the plurality of tube parts includes a plurality of bends, wherein each bend of the plurality of bends may be positioned between each of two consecutive tube sub-parts to couple the tube sub-parts with one another. U-shaped bends (180-degree return) are not used in the present embodiment anywhere.

[0012] In an embodiment of the present disclosure, the inlet may be configured to receive fluid for circulating fluid through the plurality of tube parts and the outlet may be configured to expel the fluid from the plurality of tube parts.

[0013] In an embodiment of the present disclosure, each tube pass of the one or more tube passes may be a unitary structure.

[0014] In an embodiment of the present disclosure, a plurality of tube supports may be vertical pipe column support or through wall tube hanger support coupled to the housing, wherein each tube support of the plurality of tube supports may be defined with a supporting portion to support at least one tube part of the plurality of tube parts for supporting the one or more tube passes within the housing.

[0015] In an embodiment of the present disclosure, the plurality of sides may be defined with the plurality of walls, wherein each wall of the plurality of walls may be defined with refractory layers. [0016] In an embodiment of the present disclosure, thickness of the refractory layers defined on the plurality of walls may be uniform relative to one another.

[0017] In an embodiment of the present disclosure, the plurality of tube circuits may be oriented such that at least one tube circuit of the plurality of tube circuits may be positioned adjacent and parallel to the other tube circuits.

[0018] In an embodiment of the present disclosure, the plurality of tube passes of each tube circuit may be oriented such that at least one tube pass of the plurality of tube passes may be positioned above or below the other tube passes having the same or multiple tube sizes at lesser spacing than standard bend pitch (i.e. 2- or 3-times of tube diameter) between a top end and a bottom end of the housing allowing more number of tubes in same firebox volume.

[0019] It is to be understood that the aspects and embodiments of the disclosure described above may be used in any combination with each other. Several of the aspects and embodiments may be combined together to form a further embodiment of the disclosure.

[0020] The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

[0021] The novel features and characteristics of the disclosure are set forth in the description. The disclosure itself, however, as well as a preferred mode of use, further objectives, and advantages thereof, will best be understood by reference to the following description of an illustrative embodiment when read in conjunction with the accompanying drawings. One or more embodiments are now described, by way of example only, with reference to the accompanying drawings wherein like reference numerals represent like elements and in which: [0022] Figure 1 illustrates a perspective view of a fired heater, according to an embodiment of the present disclosure for firebox in a multiple cell multiple pass cabin type fired heater,

[0023] Figure 2 illustrates an internal view of the fired heater of Figure 1,

[0024] Figure 3 illustrates a side view of the fired heater of Figure 1,

[0025] Figure 4 illustrates a top view of the fired heater of Figure 2.

[0026] Figure 5 illustrates a perspective view of the fired heater, according to another embodiment of the present disclosure for fire box in a single cell multiple pass cabin type fired heater,

[0027] Figure 6 illustrates a front view of the fired heater of Figure 5,

[0028] Figure 7 illustrates a perspective view of the fired heater, according to the other embodiment of the present disclosure for firebox in a single cell single pass cabin type fired heater,

[0029] Figure 8 illustrates a front view of the fired heater Figure 7, and

[0030] Figure 9 illustrates a side view of the fired heater of Figure 8.

[0031] Skilled artisans will appreciate that elements in the drawings are illustrated for simplicity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the drawings may be exaggerated relative to other elements to help to improve understanding of embodiments of the present disclosure.

DETAILED DESCRIPTION

[0032] While the disclosure is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in Figures 1-9 and will be described in detail below. It should be understood, however, that it is not intended to limit the disclosure to the particular forms disclosed, but on the contrary, the disclosure is to cover all modifications, equivalents, and alternatives falling within the scope of the disclosure as defined by the appended claims.

[0033] Before describing detailed embodiments, the novelty and inventive step that are in accordance with the present disclosure reside in a fired heater. It is to be noted that a person skilled in the art can be motivated by the present disclosure and modification of the fired heater. However, such modification should be construed within the scope of the present disclosure. Accordingly, the drawings show only those specific details that are pertinent to understanding the embodiments of the present disclosure so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.

[0034] In the present disclosure, the term “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any embodiment or implementation of the present subject matter described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments.

[0035] The terms “comprises”, “comprising”, or any other variations thereof, are intended to cover a non-exclusive inclusions, such that a device that comprises a list of components does not include only those components but may include other components not expressly listed or inherent to such device. In other words, one or more elements in a device proceeded by “comprises... a” does not, without more constraints, preclude the existence of other elements or additional elements in the device.

[0036] The terms like “at least one” and “one or more” may be used interchangeably or in combination throughout the description.

[0037] Reference will now be made to the exemplary embodiments of the disclosure, as illustrated in the accompanying drawings. Wherever possible, the same numerals will be used to refer to the same or like parts. Embodiments of the disclosure are described in the following paragraphs with reference to Figures 1-9. In Figures 1-9, the same elements or elements that have the same functions are indicated by the same reference signs. [0038] Referring to Figure 1, which illustrates a perspective view of a fired heater (100). The fired heaters (100) may be utilized in process industries like refineries, petrochemical industries, etc. The fired heaters (100) may be configured to raise the temperature of hydrocarbons as per the downstream process requirements. The hydrocarbons may be residual oil, crude oil, and the like, which may be required to be at high temperatures. The fired heater (100) of the present disclosure may efficiently be utilized to raise the temperature of the hydrocarbons. The capacity of the fired heater (100) to raise temperature of the hydrocarbons depends on size of the fired heater (100). The present disclosure may be adapted to increase the capacity of fired heater (100) without increasing its overall size. For example, the fired heater (100) includes a housing (10) to accommodate the other components therein. The internal volume of the housing (10) of said fired heater (100) may be fully utilized in order to increase the capacity/efficiency without increasing the size of the housing (10).

[0039] Referring further to Figure 1, the housing (10) of the fired heater (100) includes a base (12), a roof (13), and sides (10a, 10b, 10c, lOd). The sides (10a, 10b, 10c, lOd) may be extended between the base (12) and the roof (13) and define an internal region. The sides (10a, 10b, 10c, lOd) may be defined with a plurality of walls (W). The plurality of walls (W) may be provided to retain the temperature within the internal region. Each wall of the plurality of walls includes refractory layers. The refractory layers may be configured to protect the housing (10) structure from the excessive heat. The housing (10) may include a plurality of legs (11). The plurality of legs (11) rest on a ground surface and ensure bearing load of the overall structure of the housing (10).

[0040] Referring further to Figure 1, the fired heater (100) includes a plurality of tube circuits (TC). The plurality of tube circuits (TC) may be positioned within the housing (10). The plurality of tube circuits (TC) may be supported by at least one of the base (12), the roof (13), and the sides (10a, 10b, 10c, lOd) of the housing (10). In a preferred embodiment, the tube circuits (TC) may be supported by at least one side of the sides (10a, 10b, 10c, lOd) of housing (10), without limiting the scope of the present disclosure. In an embodiment, the fired heater (100) may include a plurality of tube supports (40), as shown in Figure 7. Each tube support of the plurality of tube supports (40) may be coupled to at least one side of the sides (10a, 10b, 10c, lOd) of the housing (10). Each tube support of the plurality of tube supports (40) extends from at least one side of the sides (10a, 10b, 10c, lOd) of the housing (10) towards the tube circuit (TC) and defines a supporting portion. The supporting portion may be configured to accommodate a portion of each tube circuit of the plurality of tube circuits (TC) thereon within the housing (10).

[0041] Referring to Figure 2, in a preferred embodiment, the cabin type fired heater (100) includes two tube circuits (TC), which may be a first tube circuit (TCI) and a second tube circuit (TC2). The first tube circuit (TCI) and the second tube circuit (TC2) may be positioned adjacent and parallel to one another such that one side of the first tube circuit (TCI) may be positioned proximal to at least one side of the second tube circuit (TC2). The first tube circuit (TCI) and the second tube circuit (TC2) may be coupled to a support (S). The support (S) may be a part of the housing (10) that extends from the base (12) towards the roof (13) of the housing (10). The supports (S) may be positioned between the first tube circuit (TCI) and the second tube circuit (TC2) so that the supports (S) can hold the first tube circuit (TCI) and the second tube circuit (TC2), as shown in Figures 2, 3 and 4.

[0042] Referring to Figure 5, each tube circuit (TC) may include a plurality of tube passes (20). The plurality of tube passes (20) of each tube circuit (TC) may be oriented such that at least one tube pass of the plurality of tube passes (20) may be positioned above or below the other tube passes (20) passes having same or multiple tube sizes at lesser spacing than standard bend pitch (i.e. 2- or 3-times of tube diameter) between a top end and a bottom end of the housing (10) allowing more number of tubes in same fire box volume. The plurality of tube passes (20) may be aligned to one another. In an alternate embodiment, the plurality of tube passes (20) may be offset relative to one another, without limiting the scope of the present disclosure. In a preferred embodiment, the two or more tube passes (20), as shown in Figure 5. Said two tube passes (20) may be positioned within the housing (10). The said two tube passes (20) may be positioned adjacent and aligned to one another between the top end and the bottom end of the housing (10). Each tube pass of the said two tube passes (20) may be supported by the housing (10) through the tube supports (40), as shown in Figure 6. This configuration of the fired heater (100) aids in fully utilizing the internal volume of the housing (10). Also, this configuration of the fired heater (100) increases the overall length of the tube passes (20) without requirement in increase of the size of the housing (10) which results in increasing the overall heating capacity / efficiency of the fired heater (100).

[0043] Referring to Figure 7, which illustrates the cabin type fired heater (100) along with a single tube pass (23). Each tube pass of the plurality of tube passes (20) includes an inlet (21). The inlet (21) of each tube pass may be fluidly coupled to a hydrocarbon source and configured to receive the hydrocarbons within the respective tube pass (20). Each tube pass of the plurality of tube passes (20) includes an outlet (22). The outlet (22) of each tube pass of the plurality of tube passes (20) may be fluidly coupled to other external devices and configured to repel the heated hydrocarbons from the respective tube pass (23) towards the other external devices for different purposes.

[0044] Referring further to Figure 7, each tube pass of the plurality of tube passes (20) includes a plurality of tube parts (23). The tube parts (23) extend between the inlet (21) and the outlet (22). The tube parts (23) may be configured to allow the flow of the hydrocarbons from the inlet (21) towards the outlet (22). The tube parts (23) may be adapted such that the tube parts (23) extend close to the plurality of sides (10a, 10b, 10c, lOd) and at a gentle slope on at least one side (lOd) of the plurality of sides (10a, 10b, 10c, lOd) to expel the hydrocarbons after flowing through the tube pass. The extension of the tube parts (23) with respect to all side walls (W) of the housing (10) aids in fully utilizing the internal volume of the housing (10). Also, this configuration ensures increasing the overall length of each tube pass of the plurality of tube passes (20) without requirement of increasing the size of the housing (10).

[0045] In a preferred embodiment, each tube part of the plurality of tube parts (23) may be defined with four tube sub-parts (24a, 24b, 24c, 24d). The tube sub-parts (24a, 24b, 24c, 24d) may extend close to the plurality of sides (10a, 10b, 10c, lOd) and may extend at a gentle slope on at least one of the tube sub part relative to a horizontal plane, as shown in Figures 7 and 9. Each tube part of the plurality of tube parts (23) extends with respect to all sides (10a, 10b, 10c, lOd) of the housing (10) which results in increasing the overall length of each tube pass within the housing (10) without requirement of increasing the size of the housing (10). Accordingly, this confirmation of the tube pass ensures efficient utilization of the internal volume of the housing (10) which aids in enhancing the overall heating capacity/efficiency of the fired heater (100). [0046] In an embodiment, the plurality of tube parts (23) extend one below or above the other between the top end and the bottom end of the housing (10) at lesser spacing than standard bend pitch also, as shown in Figure 8. Accordingly, this configuration allows enhancing the number of turns of each tube pass (23) with respect to the height of the side walls of the housing (10), which aids in increasing the overall length of each tube pass of the plurality of tube passes (20) without alteration of the size of the housing (10).

[0047] Referring to Figure 8, the fired heater (100) includes a plurality of burners (30). The plurality of burners (30) may be positioned at a lower portion of the housing (10). The plurality of burners (30) may be positioned at the base (12) of the housing (10) and configured to provide heat within the housing (10). The heat provided by the burners (30) transfers to the hydrocarbons flowing through the tube passes (20) through two or more heat transfer modes such as radiation, conduction, and convection. The burners (30) may be placed in one or more rows, wherein each row may be located parallel to at least one side of the housing (10). This configuration of the fired heater (100) aids in providing heat at different portions of each tube pass uniformly.

[0048] Referring to Figure 7, each tube part of the plurality of tube parts (23) includes a plurality of bends (25). Each bend of the plurality of bends (25) may be positioned between each of two consecutive tube sub-parts. Each bend of the plurality of bends (25) may be configured to couple the tube sub-parts (24a, 24b, 24c, 24d) with one another. The bends (25) may have a structure such that when the two consecutive tube sub-parts may be coupled through the said bend, an angle of 90° may be made between said two consecutive tube sub-parts, thereby the hydrocarbons flowing through the tube parts (23) turn at 90° when it passes through the bend. Accordingly, the provision of such bends (25) in the fired heater (100) aids in reducing the pressure drop of the hydrocarbons flowing through said bends (25), thereby this structure reduces the capacity requirement of the external devices for pumping and makes the operation of raising the temperature of the hydrocarbons through the fired heater (100), economical.

[0049] In an embodiment, each tube pass of the one or more tube passes (20) may be a unitary structure. This configuration of the tube passes (20) aids in enhancing the stability of the fired heater (100). In an embodiment, thickness of the refractory layers defined on the plurality of walls may be uniform relative to one another as the tube passes (20) extend close to each wall of the plurality of housing (10). Accordingly, this configuration of the fired heater (100) aids in reducing the requirement of keeping a higher refractory thickness on account of tubes now placed on earlier unshielded walls.

[0050] In accordance with the present disclosure, the fired heater (100), as explained in the above paragraphs, efficiently utilizes the entire internal volume of the housing (10) by providing an improved structure of the tube passes (20), thereby the capacity of the fired heater (100) in terms of raising the temperature of the hydrocarbons. Further, the fired heater (100) may be adapted to reduce the pressure drop of the hydrocarbons flowing through the tube passes (20). Furthermore, the fired heater (100) of the present disclosure reduces the requirement of having higher thickness of the refractory on earlier unutilized unshielded walls. Apart from this, the fired heater (100) of the present disclosure has additional advantages, for example, the tube passes (20) may be placed irrespective of standard tube pitch, which results in maximizing the heat transfer area with more tube passes (20) without requirement of increase in the internal volume of the housing (10). Providing support to the tube passes (20) may be easy. This configuration of the fired heater (100) may be utilized with double fired heater (100) in which two or more tube passes (20) may be provided parallel to one another and have separate rows of burners (30). In this configuration, one or more vertical pipe-type supports are provided which is independent of the housing (10) and aids in modular fabrication and erection of the tube circuit (TC) resulting in better quality and faster execution.

[0051] In continuation of the above paragraph, this configuration further requires less refractory thickness for remaining two of the heater walls in prior art where tubes are placed now with less heat loss to the tune of 0.25%, which ensures a cost reduction. Further, the tube passes (20) may be covered within the plurality of walls of the housing (10), thereby the requirements of an end tube sheet (ETS) or a header box gets eliminated. Further, the placement of tube passes (20) within the housing (10) of the fired heater (100) may be easy and simple. In this configuration, the combination of multiple tube passes (20) having different tube sizes may be easily adopted. This configuration may be more flexible for thermal expansion as the tube passes (20) may freely expand or contract on the tube supports (40). The tube passes (20) including odd number of passes, may be symmetrically (i.e. from view point of pass wise uniform heating as well as hydraulic symmetry) placed within the housing (10) without any compromise in the performance of the fired heater (100). The pressure drop of the hydrocarbons flowing through the tube passes (20) reduces by approximately 15% as compared to the conventional fired heater (100). This configuration allows lower tube- to-tube pitch and packing of higher heat transfer area within the housing (10) without alteration in the size of the housing (10). As the overall length of the tube passes (20) of the fired heater (100) increases, the additional surface area of the tube passes (20) is now available, thereby the absorbed heat duty may be increased by approximately 15% to 25%. Due to a decrease in radiant flux on account of additional surface area available in this new configuration, there can be a reduction in film temperature by 20-30°F. With lower film temperatures, there shall be appreciable reduction in the rate of coking and hence longer run lengths can be achieved in the fired heater. This configuration ensures pass wise uniform distribution of radiant heat flux within the housing (10) which results in lower peak heat flux. Correspondingly, the lower peak tube pass temperature prevent the chances of heater tube failure and increases its life and reliability.

[0052] The various embodiments of the present disclosure have been described above with reference to the accompanying drawings. The present disclosure is not limited to the illustrated embodiments; rather, these embodiments are intended to fully and completely disclose the subject matter of the disclosure to those skilled in this art. In the drawings, like numbers refer to like elements throughout. The thicknesses and dimensions of some components may be exaggerated for clarity.

[0053] LIST OF REFERENCE NUMERALS

[0054] EQUIVALENTS:

The embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the description.

Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.

The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation.

Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the scope of the embodiments as described herein. Any discussion of documents, acts, materials, devices, articles and the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form a part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application. The numerical values mentioned for the various physical parameters, dimensions or quantities are only approximations and it is envisaged that the values higher/lower than the numerical values assigned to the parameters, dimensions or quantities fall within the scope of the disclosure, unless there is a statement in the specification specific to the contrary.

Claims

We Claim:

1. A fired heater (100) comprising: a housing (10) defined with a plurality of sides (10a, 10b, 10c, lOd); a plurality of tube circuits (TC) disposed in the housing (10), each tube circuit of the plurality of tube circuits (TC) comprises a plurality of tube passes (20), wherein each tube pass of the plurality of tube passes (20) comprising: an inlet (21), an outlet (22), and a plurality of tube parts (23) extending between the inlet (21) and outlet

(22), the plurality of tube parts (23) extend close to the plurality of sides (10a, 10b, 10c, lOd) and at a gentle slope on at least one side (lOd) of the plurality of sides (10a, 10b, 10c, lOd); a plurality of burners (30) coupled to the housing (10) and configured to heat the tube passes (20). The tube passes (20) including odd number of passes, are symmetrically placed (i.e. pass wise uniform heating as well as hydraulic symmetry) within the housing (10).

2. The fired heater (100) as claimed in claim 1, wherein the plurality of tube parts

(23) extend one below or above the other at lesser spacing than standard bend pitch (i.e. 2- or 3-times of tube diameter) between a top end and a bottom end of the housing (10) allowing more number of identical or different sizes of tubes in same fire box volume.

3. The fired heater (100), as claimed in claim 1, wherein each tube part of the plurality of tube parts (23) is defined with four tube sub-parts (24a, 24b, 24c, 24d), close to the plurality of sides (10a, 10b, 10c, lOd) and at least one of the tube sub-parts extend at a gentle slope, relative to a horizontal plane.

4. The fired heater (100) as claimed in claim 1, wherein each tube part of the plurality of tube parts (23) comprises a plurality of bends (25), wherein each bend of the plurality of bends (25) is positioned between each of two consecutive tube sub-parts (24a, 24b, 24c, 24d) to couple the tube sub-parts (24a, 24b, 24c, 24d) with one another.

5. The fired heater (100) as claimed in claim 1, wherein the inlet (21) is configured to receive fluid for circulating fluid through the plurality of tube parts (23) and the outlet (22) is configured to expel the fluid from the plurality of tube parts (23).

6. The fired heater (100) as claimed in claim 1, wherein each tube pass of the one or more tube passes (20) is a unitary structure.

7. The fired heater (100) as claimed in claim 1, comprising a plurality of tube supports (40) coupled to the housing (10), wherein each tube support of the plurality of tube supports (40) is defined with a supporting portion to support at least one tube part of the plurality of tube parts (23) for supporting the one or more tube passes (20) within the housing (10).

8. The fired heater (100) as claimed in claim 1, wherein the plurality of sides (10a, 10b, 10c, lOd) are defined with the plurality of walls (W), wherein each wall of the plurality of walls (W) is defined with refractory layers.

9. The fired heater (100) as claimed in claim 8, wherein thickness of the refractory layers defined on the plurality of walls are uniform relative to one another.

10. The fired heater (100) as claimed in claim 1, wherein the plurality of tube circuits (TC) are oriented such that at least one tube circuit of the plurality of tube circuits (TC) is positioned adjacent and parallel to the other tube circuits (TC) and supported with the help of vertical pipe support.

11. The fired heater (100) as claimed in claim 1, wherein the plurality of tube passes (20) of each tube circuit are oriented such that at least one tube pass of the plurality of tube passes (20) are positioned above or below to the other tube passes (20) having same or multiple tube sizes at lesser spacing than standard bend pitch (i.e. 2- or 3 -times of tube diameter) between a top end and a bottom end of the housing allowing more number of tubes in same fire box volume.