EP4669456A1

EP4669456A1 - SYSTEMS AND METHODS FOR CONTINUOUS RENEWABLE HEATING OF GAS IN CHEMICAL MANUFACTURING

Info

Publication number: EP4669456A1
Application number: EP24706398.5A
Authority: EP
Inventors: Michael Edward HUCKMAN
Original assignee: SABIC Global Technologies BV
Current assignee: SABIC Global Technologies BV
Priority date: 2023-02-21
Filing date: 2024-02-19
Publication date: 2025-12-31
Also published as: WO2024175534A1; CN120981283A

Abstract

This disclosure includes systems and methods for producing chemicals without combustion of hydrocarbons in a radiant section of a furnace. A gaseous working fluid is heated by conveying the working fluid through a passage defined through a body of a stack comprising refractory bricks, at least some of which have been heated to a temperature in excess of 1500°C and, optionally, to a temperature in excess of 2000°C. The heated working fluid is then conveyed from the stack directly into a radiant section of the furnace to heat a process tube within the radiant section. The working fluid is then conveyed from the radiant section into a convection section of the furnace to provide thermal energy to one or more heat exchangers disposed within the convection section. The working fluid is then conveyed from the convection section back into the stack to reheat the working fluid.

Description

SYSTEMS AND METHODS FOR CONTINUOUS RENEWABLE HEATING OF GAS IN CHEMICAL PRODUCTION

FIELD OF DISCLOSURE

[001] The present disclosure is generally related to processes for producing heated gas and, more particularly but not by way of limitation, to processes for producing heated gas in low or no carbon chemical processes and systems powered by renewable energy.

BACKGROUND

[002] Fired heaters or combustion furnaces are utilized to burn or combust a dedicated fuel to provide heat for a variety of purposes. For example, in chemical plants a fired heater can be utilized for cracking furnaces for olefins, reforming for MeOH and NH3, heaters for dehydrogenation, and the like. To further illustrate, these furnaces may provide heat of reaction for chemical synthesis, energy to heat one or more process streams, energy to vaporize liquids (e.g., boil water used as a diluent), energy to do work (e.g., drive a compressor or pump), or energy for other process operations throughout the chemical synthesis plant. Such burning or combustion of fuels results in the production of flue gases that can be subsequently used to recover heat. However, the flue gas contains CO2, which can be harmful to the environment.

[003] Electric heaters are also utilized to provide heat in a variety of applications. Electric heaters produce heat by applying a voltage to one or more resistive element that convert the electrical current into heat energy. While electric heaters are suitable for low temperature applications, they may have issues in continuous heating of large-scale, industrial applications.

[004] Moreover, the electrification of certain components in chemical synthesis plants presents additional issues and challenges. For example, in steam cracking processes, electric furnace pyrolysis reactors may present issues or may be subject to considerations that are different than and/or not necessarily present in combustion-driven furnace pyrolysis reactors.

[005] For example, if using electricity from the power grid and/or from renewable sources, the availability and cost of electricity will vary over time. For example, electrical energy from the power grid is typically more expensive during peak consumption hours. Additionally, production of solar and wind energy varies with time of day and weather conditions — e.g., night hours and overcast time periods reduce or interrupt the generation of electricity by solar panels. Likewise, during periods when the wind is slower or non-existent, generation of electricity by wind turbines is reduced or interrupted. Additionally, utilities may offer discounts to customers that can be flexible in their consumption demands during peak hours when electricity production or grid capacity are stressed. Storing energy can shift some consumption of energy from external sources (e.g., grid, solar, wind or the like) away from hours during which energy is more expensive (e.g., peak grid hours) or of limited availability (e.g., dark hours for solar or still hours for wind). Reducing external energy needs during peak grid hours also has the added benefit of encouraging stability of the grid. Commercially, however, it is typically important for a chemical plant to maintain consistent throughput, even during periods when external energy needs are reduced — i.e., even when drawing relatively less electricity from external sources.

SUMMARY

[006] Electric heaters have been proposed to replace fired heaters in processes where the emission of carbon dioxide (CO2) is to be reduced or eliminated. However, the use of electric heaters requires for the process to be completely redesigned, which can be complicated, expensive, and introduce risk into otherwise established process systems. To illustrate, electric furnaces have no combustion production and, therefore, no flue gas. In processes that utilize the heat from the flue gas, this heat generation must now come from somewhere else. Electrifying furnaces are relatively new area in the chemical process industry and improved designs to overcome the lack of heat created via flue gas do not yet exist. The present disclosure presents systems and methods of producing chemicals in a furnace, without combusting hydrocarbons in a radiant section of the furnace.

[007] According to one embodiment, the present disclosure describes a system for the production of chemicals, for example alkenes or carbon monoxide and hydrogen from hydrocarbons. The system includes one or more stacks. Each stack has a body that defines a hollow channel extending from an inlet of the stack to an outlet of the stack and is configured or operable to heat a gaseous working fluid flowing through the hollow channel to produce a heated gaseous working fluid. The body includes one or more refractory bricks that are capable of being heated to a temperature in excess of 1500°C and, optionally, in excess of 2000°C by a power source. The system also includes a furnace having a radiant section and a convection section. The radiant section defines a hollow interior and has one or more process tubes disposed or arranged within the hollow interior. The convection section defines a convection channel extending from an inlet of the convection section to an outlet of the convection section. The inlet of the convection section is in fluid communication with the hollow interior of the radiant section and is configured to receive the gaseous working fluid from the radiant section. The convection section also includes at least one heat exchanger disposed or arranged within the convection channel and which is configured to receive thermal energy from the gaseous working fluid as it flows through the convection channel. In some configurations, the heat exchanger is capable of transferring the thermal energy to another fluid. The hollow interior of the radiant section is in direct fluid communication with the outlet of each of the stacks and is configured to receive the heated gaseous working fluid from the stacks. The outlet of the convection channel is in fluid communication with the inlet of the stack(s), such that the gaseous working fluid can be circulated sequentially: through the hollow channel of the body of the stack to be heated; through the hollow interior of the radiant section to heat the one or more process tubes; and through the convection channel to provide thermal energy to the heat exchanger(s).

[008] According to another embodiment, the present disclosure describes a process for operating a furnace of a system for the production of chemicals without combustion of hydrocarbons in a radiant section of the system. The process includes heating a gaseous working fluid by conveying the gaseous working fluid through a passage defined through a body of a stack to form a heated gaseous working fluid. The body includes one or more refractory bricks, at least some of which have been heated to a temperature in excess of 1500°C and, optionally, to a temperature in excess of 2000°C. The process also includes conveying the heated gaseous working fluid from the stack directly into a radiant section of the furnace to heat one or more process tubes disposed or arranged within the radiant section. The process also includes conveying the heated gaseous working fluid from the radiant section into a convection section of the furnace to provide thermal energy to one or more heat exchangers disposed within the convection section to form a cooled gaseous working fluid. Finally, the process includes conveying the cooled gaseous working fluid from the convection section back into the stack to reheat the cooled gaseous working fluid. In some embodiments, the one or more refractory bricks are heated by renewable energy, nonrenewable energy or a combination thereof.

[009] The term “coupled” is defined as connected, although not necessarily directly, and not necessarily mechanically; two items that are “coupled” may be unitary with each other. The terms “a” and “an” are defined as one or more unless this disclosure explicitly requires otherwise. The term “substantially” is defined as largely but not necessarily wholly what is specified (and includes what is specified; e.g., substantially 90 degrees includes 90 degrees and substantially parallel includes parallel), as understood by a person of ordinary skill in the art. In any embodiment of the present apparatuses, kits, and methods, the term “substantially” may be substituted with “within [a percentage] of’ what is specified, where the percentage includes 0.1, 1, 5, and/or 10 percent.

[0010] The terms “comprise” (and any form of comprise, such as “comprises” and “comprising”), “have” (and any form of have, such as “has” and “having”), “include” (and any form of include, such as “includes” and “including”) and “contain” (and any form of contain, such as “contains” and “containing”) are open-ended linking verbs. As a result, an apparatus or kit that “comprises,” “has,” “includes” or “contains” one or more elements possesses those one or more elements, but is not limited to possessing only those elements. Likewise, a method that “comprises,” “has,” “includes” or “contains” one or more steps possesses those one or more steps, but is not limited to possessing only those one or more steps.

[0011] Further, an apparatus, device or system that is configured in a certain way is configured in at least that way, but it can also be configured in other ways than those specifically described.

[0012] Any embodiment of any of the present apparatuses and methods can consist of or consist essentially of - rather than comprise/include/contain/have - any of the described steps, elements, and/or features. Thus, in any of the claims, the term “consisting of’ or “consisting essentially of’ can be substituted for any of the open-ended linking verbs recited above, in order to change the scope of a given claim from what it would otherwise be using the open-ended linking verb.

[0013] Details associated with the embodiments described above and others are presented below.

[0014] Some details associated with the aspects of the present disclosure are described above, and others are described below. Other implementations, advantages, and features of the present disclosure will become apparent after review of the entire application, including the Brief Description of the Drawings, Detailed Description, and the Claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The following drawings illustrate by way of example and not limitation. For the sake of brevity and clarity, every feature of a given structure is not always labeled in every figure in which that structure appears. Identical labels or reference numbers do not necessarily indicate an identical structure. Rather, the same reference number may be used to indicate a similar feature or a feature with similar functionality, as may non-identical reference numbers. Dimensioned figures are drawn to scale (unless otherwise noted), meaning the sizes of the depicted elements are accurate relative to each other for at least the embodiment depicted in the figures.

[0016] FIG. 1 depicts a front cross-sectional view of an example of one system configuration for use in the production of chemicals.

[0017] FIG. 2 depicts a front cross-sectional view of a stack of the system of FIG. 1.

[0018] FIG. 3 depicts a cutaway view of a radiant section of a furnace facing the stack of FIG.

2.

[0019] FIG. 4 depicts a front cross-sectional view of an example of another system configuration for use in the production of chemicals.

[0020] FIG. 5 depicts a front cross-sectional view of a stack of the system of FIG. 4.

[0021] FIG. 6 depicts a cutaway top view of a radiant section of a furnace and the stack of the system of FIG. 4.

[0022] FIG. 7 depicts the temperature profile of a gas travelling from an inlet of a stack to an outlet of the stack of the system of FIG. 1.

DETAILED DESCRIPTION

[0023] Embodiments of the present invention relate to continuous renewable (RE) powered furnaces. Embodiments may include ways to deliver heat from intermittent electricity RE sources, like wind and solar, at very high temperature.

[0024] RE energy (wind and solar, among others) are rising technologies for delivering carbon free power. Unfortunately, this power is intermittent - a problem in any case, but a particular problem for petrochemical operations that demand 24/7 continuous reliable power.

[0025] Heat storage is one technology area being explored as a way to bridge the intermittency gaps. When extra power is available that energy is stored as heat; when power is unavailable energy, in the form of heat, can be withdrawn. Some emerging technologies can store many MW- h of heat and some can even store at temperatures approaching 2000°C.

[0026] One way to store heat is to heat large stacks of refractory bricks using carbon free RE. These are sometimes called “rocks-in-a-box” designs. Ways to converting RE to heat are many and designs are known in the market. Devices can store RE at times when RE would be curtailed and so can heat up at low cost. Heat can be withdrawn from the device at times when RE is expensive. Most of these designs can be charged and discharged simultaneously, so can be operated to minimize electrical cost.

[0027] A proper arrangement of hot gas through the device and a bypass can allow for the system to deliver a constant temperature hot gas heating medium to the bottom of the convection section. [0028] There remains a significant technology gap for delivering this heat into petrochemical (and similar) processes. This invention may solve these heat delivery problems in a novel and effective way. In short, this invention may combine the heat storage devices with a heat delivery device that is similar to a conventional furnace. Electricity may be used to create heat in the device that is stored in a solid filled silo. Heat may be delivered by a circulating gas and the gas may be chosen to be radiatively participating (CO2, for example). The gas may be delivered into a high temperature heater at about 2000°C and at these temperatures the heat may be transferred from the gas to the process via radiant heat transfer - so it operates in a way analogous to a conventional radiant box in a furnace. The partly cooled gas leaves the radiant box where may do lower temperature heating by convection as it passes over a series of heat exchange surfaces - this lower temperature box is analogous to the convection section of conventional furnace. Once the gas is sufficiently cooled, it may be recirculated by a blower or low head compressor (these blowers have process temperature limits in the vicinity of 150°C).

[0029] Below is a list of exemplary features and the technical problems addressed by embodiments of the present invention.

• Conduits for the hot gas are a challenge because no metal can survive at these temperature. This invention may eliminate the conduit by having the heat storage device open directly into the radiant box.

• High temperature heat transfer surfaces for transferring high temperature heat convectively are almost impossible because no metal can survive at these temperatures. This invention may solve that problem by using a radiatively participating gas so that high temperature heat can be transferred by radiative heat transfer.

• Heat recovery efficiency is poor if the gas is open loop - many incumbent designs exhaust a relatively high temperature gas and lose a portion of the stored heat to the environment. This invention may solve that problem by cooling the gas in the convection banks to a temperature low enough for a blower to be able to recirculate the gas so the system is closed loop and operates at very nearly 100% efficiency.

• Process changes can be significant when high temperature heating is electrified because electric heating will not have the convection section banks found in the fired heaters that nowadays provide this heating. This invention may solve that problem.

[0030] A purpose of this invention is to combine heat storage technology with heat delivery technology in novel way that allows the power from intermittent RE sources to be delivered continuously as high temperature process heat.

[0031] Emerging heat storage technologies can deliver heat at temperatures as high as 2000°C, but there remain significant technical gaps related to delivering this high temperature heat into the process. Below are some of the key gaps and how this invention solves those problems:

• Designing a conduit to carry 2000°C gas. Most materials of construction are not capable for this purpose. This invention may solve that problem by eliminating the conduit altogether and configuring the system so that the heat storage silo opens directly into heating box.

• Convection is extremely hard at high temperatures. Generally hot gasses deliver heat by convection, but this requires a tremendous amount of heat transfer surface area. Materials of construction are very difficult to find that can survive at these temperatures. Considerable energy is burned as pressure drop. This invention may deliver high temperature heat radiatively by using a radiatively participating gas (CO2 for example), thus avoiding the difficulties associated with convection.

• Redesigning the process heat integration to compensate for the missing convection section of a conventional fired heater. This invention may solve that problem by retaining a conventional style convection section to recover heat from the partly cooled gas leaving the radiant section.

• Maximizing the fraction of stored heat ultimately delivered to the process. This invention may solve the heat loss problem by putting the hot gas (the material that delivers heat from storage to process) in a closed loop, so no or little hot gas is exhausted to the atmosphere. Cooling the gas to a reasonable temperature (somewhere ~150°C) may allow the gas to be recirculated by a blower or low-head compressor.

[0032] Some other advantages of this technology may include: • In addition to bridging intermittency gaps, this technology can reduce costs - heat can be stored when RE prices are low and heat can be drained when RE costs are high.

• Low operational risk. The process may operate very much as it did with a fired heater and so new learnings by the operational staff are minimal.

• In the case of a retrofit, process changes may be minimized and in some cases it should be possible to reuse the radiant and convection boxes from an existing fired heater.

[0033] According to one embodiment, the system includes one or more stacks or heat storage silos. Each stack or heat storage silo has a body that defines a hollow channel extending from an inlet of the stack or heat storage silo to an outlet of the stack or heat storage silo and is configured or operable to heat a gaseous working fluid flowing through the hollow channel to produce a heated gaseous working fluid.

[0034] The body of the present stacks or heat storage silos can comprise a material that is physically stable at high temperatures and adapted for thermal storage, such as firebrick, ceramic bricks, and/or other refractory materials. In some configurations, the present stacks also comprise one or more heating elements (e.g., electric heating elements). For example, the body of each stack may include a plurality of refractory bricks. In some configurations, the body may include a plurality of conductive refractory bricks that are configured to pass electric current for resistive heating and, in some configurations, a combination of such conductive refractory and non- conductive refractory bricks. In configurations that include a combination of conductive refractory bricks and non-conductive refractory bricks, the conductive refractory bricks conduct electric current to resistively convert electrical energy to thermal energy and thereby directly heat the conductive refractory bricks and indirectly heat the non-conductive refractory bricks (which are in thermal communication with the conductive refractory bricks). In some configurations, the body can be configured to operate at temperatures up to 2000°C or greater and much higher than the operating temperatures of bodies comprising just conventional electrical heating elements (e.g., Kanthal - FeCrAl alloys).

[0035] In some configurations, conductive refractory bricks include a conductive material or the refractory brick may be doped with a conductive material (e.g., metal oxide) such that electrical current will flow through the brick, but with sufficient resistance to convert electrical energy to thermal energy and thereby heat the brick for storage of thermal energy. The use of conductive refractory bricks may allow the stack to limit or omit conventional metal heating elements, such as wires or ribbons, which may be more susceptible to oxidation and other degradation when continuously operated at elevated temperatures (and may therefore be less suitable for use at temperatures comparable to those produced by conventional burners, e.g., 1500°C, 2000°C, or higher).

[0036] In some configurations, the conductive refractory bricks include, but are not limited to, doped ceramics, electrically “conductive” ceramics, carbon, graphite, metals, metal alloys and composite materials made of a ceramic material and a metallic material. Such composite materials may comprise doped or undoped ceramics. Non-limiting examples of ceramics include zirconia, chromia, titanium dioxide, magnesia, alumina, silica, niobium oxide, and molybdenum disilicide. Non-limiting examples of doped ceramics include doped silicon carbides, magnesia doped with chromium, alumina doped with chromium, chromia doped with carbon, chromia doped with magnesium. Non-limiting examples of metals include iron, chromium, tungsten, titanium, zirconium, tantalum, platinum, gold and silver. Non-limiting examples of metal alloys include stainless steel, constantan, nickel-containing alloys, cobalt-containing alloys, chromium- containing alloys, aluminum-containing alloys, titanium-containing alloys, zirconium-containing alloys, hafnium-containing alloys, niobium-containing alloys, molybdenum-containing alloys, tantalum-containing alloys, tungsten-containing alloys, tin-containing alloys, gallium-containing alloys, manganese-containing alloys, and iron-containing alloys, nickel-based superalloys, ironbased superalloys, iron-aluminum base alloys, iron-manganese-aluminum base alloys and platinum/rhodium alloy.

[0037] In still other configurations, the non-conductive refractory bricks include, but are not limited to, alumina (AI2O3), silica (SiCh), magnesia (MgO), zirconia (ZrCh), chromium oxide (CrcCh), iron oxide (Fe2O³), calcium oxide (CaO), hydrated alumina silicate and mixtures thererof. [0038] In configurations that include both conductive refractory bricks and non-conductive refractory bricks, the non-conductive refractory bricks are thermally coupled to the conductive refractory bricks to absorb the heat generated by the conductive refractory bricks to heat the body and thereby store thermal energy for later use. Both conductive and non-conductive refractory bricks can include a material having both a relatively high emissivity (e.g., 0.5 or greater, 0.7 or greater, or 0.8 or greater) for efficient emission of thermal radiation to tubes and relatively high specific heat (e.g., 400 J/kg-K or greater, 450 J/kg-K or greater, or 500 J/kg-K or greater) to increase the thermal energy the stack can temporarily “store” as thermal energy is dissipated. In some configurations, the non-conductive refractory bricks are configured to store or hold heat and may have a specific heat that is higher than the conductive refractory bricks.

[0039] The conductive refractory bricks and non-conductive refractory bricks can have any shape and may be arranged in any suitable manner. For example, the conductive and non- conductive refractory bricks may be straight (rectangular), side arch, end arch, wedge, key, flat circle, circle, splits, dome brick, skew (end/side), bull nose or jamb brick. Furthermore, the refractory bricks can be arranged in multiple layers or displaced randomly throughout the body to provide distributed heat generation within the body. In some configurations, the body includes a smaller percentage of conductive refractory bricks than non-conductive refractory bricks (e.g., a ratio of non-conductive refractory bricks to conductive refractory bricks is greater than 1.0, such as between 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2., 2.25, 2.5).

[0040] In some configurations, each stack may further include an insulating layer coupled to an exterior of the body to minimize heat dissipation from the body to an external environment. In some configurations, the insulating layer may be made of ceramic fiber, clay, alumina, silica, polycrystalline mullite, glass mat materials or mixtures thereof.

[0041] The body is configured, via the one or more heating elements (e.g., conductive refractory bricks or metallic heating elements), to receive external power (e.g., from a power source) and convert electrical energy to thermal energy that heats the material of the stack and thereby “stores” the thermal energy to be later radiatively “discharged” to heat a gaseous working fluid that is fed through the stack. This capability can allow each stack to be charged and discharged at different times, which can be particularly advantageous. For example, utilities may offer discounts to customers that can be flexible in their consumption demands during peak hours when electricity production or grid capacity are stressed. Thus, the present systems may be configured to store energy and then use this stored energy later when other energy from external sources (e.g., grid, solar, wind or the like) is more expensive (e.g., peak grid hours) or of limited availability (e.g., dark hours for solar or still hours for wind). In this way and others, the present systems can maintain operations despite temporary interruptions of power.

[0042] The power source(s) is/are generally configured to deliver electrical current to each of one or more of the stacks. For example, each power source can include or more elements or other conductors that are configured to deliver electricity to one or more conductive refractory bricks within the body of the respective stack(s). In some configurations, a power source may include a source of renewable energy such as solar, wind, geothermal, hydropower, biomass, or other renewable sources. In some configurations, a power source may include only renewable energy supplies and, in other configurations, the power source may include a combination of renewable energy and non-renewable energy supplies. In an illustrative, non-limiting example, a power source may include a plurality of solar panels and can be configured to deliver electricity to a stack during the daytime. In such an example, the present systems and stack(s) can be configured to “store” heat during the daytime and “discharge” heat during the night to continue operations until the sun rises again.

[0043] In some configurations, the working fluid may be a simulated combustion gas (SCG) with radiatively active species like CO2 or water to deliver heat by both radiation and convection. In some configurations, the SCG can be a gas comprising carbon dioxide, methane, water vapour, ozone, nitrogen oxides (e.g., nitrous oxide), chlorofluorocarbons (CFCs), halocarbons, certain organics such as volatile organic compounds, or combination thereof. In this way, the present systems may provide heat for both a radiation process and a subsequent convention process. For example, the higher the temperature of the SCG, the more radiation it will emit.

[0044] Referring to FIG. 1, there is shown a system 1 according to the present disclosure in one configuration. The system 1 generally includes stacks (or heat storage silos) 2 and 4 and furnace 6. Stacks 2 and 4 each have a body 7 that defines a hollow channel (not shown) extending from an inlet 8 of the stack to an outlet of the stack 10 and is configured or operable to receive a cooled gaseous working fluid 12 at the inlet 8, heat the cooled gaseous working fluid as it flows through the hollow channel and produce a heated gaseous working fluid 13. In some configurations, the system is closed loop (i.e., the gaseous working fluid is recirculated through the system).

[0045] The furnace 6 has a radiant section 16 and a convection section 18. The radiant section 16 defines a hollow interior and has one or more process tubes 20 disposed within the hollow interior. The hollow interior of the radiant section 16 is in direct fluid communication with the outlet 10 of each of the stack(s) 2 and 4 and is configured to receive heated working gaseous fluid 13 from the stacks 2, 4. The convection section 18 has a plurality of banks 22 (4 banks are shown in FIG. 1). The convection section 18 includes a convection channel (not shown) extending from an inlet 21 of the convection section through the plurality of banks 22 and to an outlet 23 of the convection section 18. The inlet 21 of the convection section 18 is in fluid communication with the hollow interior of the radiant section 16 and is configured to receive the heated gaseous working fluid 13 from the radiant section 16. The plurality of banks 22 are configured to receive thermal energy from the heated gaseous working fluid 13 as it flows through the convection section 18. The outlet 23 of the convection section 18 is in fluid communication with the inlet 8 of the stacks 2, 4 and discharges the cooled gaseous working fluid 12 to the inlet 8 of the stacks. As shown in FIG, 1, the gaseous working fluid can be circulated sequentially: through the hollow channel of the body of the stacks 2, 4 to be heated; through the hollow interior of the radiant section 16 to heat the process tubes 20; and through the convection channel to be cooled as it provides thermal energy to the plurality of banks 22.

[0046] In system 1, stacks 2 and 4 may be powered by renewable energy or a combination of renewable energy and non-renewable energy. The gaseous working fluid in system 1 is operable to deliver heat directly to the process tubes 20 and also indirectly by heating body 7 which reflects heat to the process tube 20. The system may be configured to circulate the gaseous working fluid in a closed loop using a blower. In some configurations, system 1 does not include a separate conduit for the circulating gaseous working fluid (i.e., the lower end of the stacks 2, 4 opens directly into the radiant section 16). For example, as shown in FIGS. 2 and 3, in one configuration each stack (with stack 4 shown) opens directly into radiant section 16 to deliver the heated gaseous working fluid 13 to the radiant section 16 via a plurality of openings 26. Also shown in FIGS 2 and 3 are the roof 16a and floor 16b of radiant section 16. Finally, the gaseous working fluid exiting the radiant section 16 is capable of providing heat to various process streams flowing through the plurality of banks 22.

[0047] Referring now to FIG. 4, there is shown another configuration of system 1. This configuration is similar to the configuration shown in FIG. 1, but instead of delivering the heated gaseous working fluid 13 into the radiant section 16 at the lower end of stacks 2, 4, the heated gaseous working fluid 13 is delivered into the radiant section 16 through floor 16b. This configuration is further shown in more detail in FIGS. 5 and 6. Heated gaseous working fluid 13 exiting the outlet of stack 4 is delivered into the radiant section 16 of the furnace 6 through a plurality of openings 26a in the floor 16b of radiant section 16 to heat process tubes 20.

[0048] FIG.7 depicts the temperature of the gaseous working fluid 72 as it travels through the stack or heat storage silo 70 from the stack’s inlet 74 to the stack outlet 76 in one configuration. In this configuration stack 70 can be broken down into a depleted zone 78a, an active heat transfer zone 78b and a fully charged zone 78c. Cooled gaseous working fluid 72 enters stack 70 at inlet 74 and first passes through the depleted zone 78a. The temperature within the depleted zone 78a may be similar to the temperature of the cooled gaseous working fluid 72. The cooled gaseous working fluid 72 then passes through the active heat transfer zone 78b. The temperature within the active heat transfer zone 78b will begin to transition from cold to hot and this is where the gaseous working fluid 72 is heated. The gaseous working fluid 72 then passes through the fully charged zone 78c where the temperature within stack 70 is at a maximum and the heated gaseous working fluid is formed.

[0049] Over the course of a heating cycle, the active heat transfer zone 78b will move from the inlet of the stack 70 to the outlet of stack 70. When the front of the active heat transfer zone 78b reaches the outlet 74, the temperature of the heated gaseous working fluid exiting stack 70 will begin to drop and this generally indicates the useful end of the heating cycle for stack 70. To maximize the amount of heat that may be recovered from stack 70 before the temperature of the heated gaseous working fluid exiting begins to drop, it’s desirable to minimize the active heat transfer zone 78b. This may be accomplished by designing stack 70 so that: i) the rate of heat transfer from stack 70 to the gaseous working fluid 70 is maximized; ii) the conduction of heat transfer through stack 70 is maximized; and iii) the aspect ratio of stock 70 (ratio of width to height) is high.

[0050] The present disclosure also provides a process for operating a furnace of a chemical production system without combustion of hydrocarbons in a radiant section of the chemical production system. In some configurations, the chemical production system may be useful in converting alkanes into alkenes or for converting methane into carbon monoxide and hydrogen.

[0051] The process generally includes heating a gaseous working fluid by conveying the gaseous working fluid through a passage defined through a body of a stack to form a heated gaseous working fluid. The body can include one or more refractory bricks, at least some of which have been heated to a temperature in excess of 1500°C and, optionally, to a temperature in excess of 2000°C. The heated gaseous working fluid is then conveyed from the stack into a radiant section of the furnace to heat a process tube disposed within the radiant section. The heated gaseous working fluid is then conveyed from the radiant section into a convection section of the furnace and provides thermal energy to one or more heat exchangers disposed within the convection section thereby forming a cooled gaseous working fluid. The cooled gaseous working fluid is then conveyed from the convection section back into the stack to reheat the cooled gaseous working fluid. In some configurations, the conveying is performed by a blower or compressor which in some configurations is disposed between the outlet of the stack and the interior of the radiant section or between the outlet of the convection section and the inlet of the stack,

* * *

[0052] The specification and examples described above and in the attached appendix provide a complete description of the structure and use of exemplary embodiments. Although certain embodiments have been described above with a certain degree of particularity, or with reference to one or more individual embodiments, those skilled in the art could make numerous alterations to the disclosed embodiments without departing from the scope of this invention. As such, the various illustrative embodiments of the present devices are not intended to be limited to the particular forms disclosed. Rather, they include all modifications and alternatives falling within the scope of the claims, and embodiments other than the one shown may include some or all of the features of the depicted embodiment. For example, components may be combined as a unitary structure, and/or connections may be substituted. Further, where appropriate, aspects of any of the examples described above may be combined with aspects of any of the other examples described to form further examples having comparable or different properties and addressing the same or different problems. Similarly, it will be understood that the benefits and advantages described above may relate to one embodiment or may relate to several embodiments.

[0053] The claims are not intended to include, and should not be interpreted to include, means- plus- or step-plus-function limitations, unless such a limitation is explicitly recited in a given claim using the phrase(s) “means for” or “step for,” respectively.

Claims

1. A system for the production of chemicals, the system comprising: one or more stacks each configured to heat a gaseous working fluid, each stack having a body that defines a hollow channel extending from an inlet to an outlet, the body comprising refractory bricks that are configured to be heated to a temperature in excess of 1500°C and, optionally, in excess of 2000°C; and a furnace having a radiant section and a convection section, the radiant section defining a hollow interior and having a process tube disposed in the interior of the radiant section, the convection section defining a convection channel extending from an inlet to an outlet, the inlet of the convection channel in fluid communication with the interior of the radiant section to receive working fluid from the radiant section, the convection section including at least one heat exchanger disposed in the convection channel and configured to receive thermal energy from the working fluid; where the interior of the radiant section is in direct fluid communication with the outlet of each of the stack(s) to receive heated working fluid from the stack(s), and the outlet of the convection channel is in fluid communication with the inlet of each of the stack(s), such that the working fluid can be circulated sequentially through the channel of the stack to be heated, into the interior of the radiant section to heat the process tube, and through the convection channel to provide thermal energy to the heat exchanger(s).

2. The system of claim 1, where a blower or compressor is not disposed between the outlet of the stack and the interior of the radiant section; and where, optionally, the radiant section shares a wall with each of the stack(s).

3. The system of any of claims 1-2, where an interior wall of the radiant section includes a material having an emissivity that is greater than or equal to 0.7, and/or an interior wall of the stack includes a material having an emissivity that is greater than or equal to 0.7.

4. The system of any of claims 1-3, where the refractory bricks comprise: conductive refractory bricks configured to receive electrical power from a power source and to convert electrical energy to thermal energy; and non-conductive refractory bricks configured to receive thermal energy from the conductive refractory bricks.

5. The system of any of claims 1-4, where the stack is free of metallic heating elements.

6. The system of any of claims 1-5, where the radiant section defines one or more inlets each in fluid communication with the outlet(s) of at least one of the stack(s), and the inlet(s) of the radiant section extend through a bottom wall of the radiant section and/or a side wall of the radiant section.

7. The system of any of claims 1-6, further comprising a blower or compressor disposed between the outlet of the convection section and the inlet of the stack, the blower or compressor configured to convey working fluid from the convection section into the stack.

8. The system of any of claims 1-7, where the one or more stacks comprise at least a first one of the stacks and a second one of the stacks.

9. A process for operating a furnace of a chemical production system without combustion of hydrocarbons in a radiant section of the system, the process comprising: heating a gaseous working fluid by conveying the working fluid through a passage defined through a body of a stack comprising refractory bricks, at least some of which have been heated to a temperature in excess of 1500°C and, optionally, to a temperature in excess of 2000°C; conveying the heated working fluid from the stack directly into a radiant section of the furnace to heat a process tube within the radiant section; conveying the working fluid from the radiant section into a convection section of the furnace to provide thermal energy to one or more heat exchangers disposed within the convection section; and conveying the working fluid from the convection section back into the stack to reheat the working fluid.

10. The process of claim 9, where at least a portion of the refractory bricks are conductive refractory bricks configured to receive electrical power from a power source and to convert electrical energy to thermal energy.

11. The process of claim 10, where at least a portion of the refractory bricks are non-conductive refractory bricks configured to receive thermal energy from the conductive refractory bricks.

12. The process of any of claims 10-11, where the conductive refractory bricks are coupled to a source of renewable power.

13. The process of any of claims 10-12, where during at least a portion of the heating step, the conductive refractory bricks are receiving either no electrical energy or are receiving electrical energy at a rate that is lower than the rate that would be required to generate thermal energy at the rate used to heat the working fluid.

14. The process of any of claims 9-13, where the working fluid comprises one or more radiatively active species, selected from a list of radiatively active species consisting of: carbon dioxide, methane, water vapour, ozone, and nitrous oxide.

15. The process of any of claims 7-14, where the working fluid is substantially free of N2 and the stack is free of metallic heating elements.